Engineering tunable bio-inspired polymeric coatings for amphiphobic fibrous materials

NASA Astrophysics Data System (ADS)

Oyola-Reynoso, Stephanie

Chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolysable moieties in the presence of physisorbed water. In the following chapters, we demonstrate that using alkyltrichlorosilanes (trivalent [3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound polymeric particles. We infer that the presence of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane, prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2-201.4 g/m2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from 70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, cardboard houses can be rendered self-cleaning or tolerant to surface running water. Each of the chapters below supports the mechanism via a series of applications, material characterization, and/or, smart engineering.

Relationship between Surface Modifications of Nanoparticle and Invasion into Suspension Cells

NASA Astrophysics Data System (ADS)

Matsui, Y.; Sakai, N.; Tsuda, A.; Yoneda, M.

2011-07-01

Nanomaterials have a variety of properties for each material. There is little information available on which kinds of material properties have effects on toxicity and kinetics. This paper presents that a relationship between material properties and hazard data by undertaking a bibliographical survey at first. With respect to cytotoxicity, it probably depends mainly on the particle volume dose and to a certain degree on particle solubility. It can be concluded from these results that there is a relationship between material properties and hazard data. Many activities involving nano risk are occurring all over the world. Secondly, we assayed actually for cellular uptake of three kinds of Quantum dots (15 nm, 5.5×1012 particles/ml) to demonstrate our result of bibliographical survey. Three different surface modification quantum dots (non-modification, -COOH, -NH3) were mixed with floating Jurkat cells in each. After thirty minute, we washed these cells three times and detected fluorescence by flow cytometer. Almost all the carboxylate particles invaded a cell, about 60% aminated them also invaded and few non-modification particles were taken up. Nanomaterials are often very broadly categorized and named based upon their basic material composition or product shape. Our results confirm that we have to examine which physical-chemical properties affect some adverse effects for each nanomaterial.

Influence of nano alumina coating on the flexural bond strength between zirconia and resin cement

PubMed Central

Mumcu, Emre; Şen, Murat

2018-01-01

PURPOSE The purpose of this in vitro study is to examine the effects of a nano-structured alumina coating on the adhesion between resin cements and zirconia ceramics using a four-point bending test. MATERIALS AND METHODS 100 pairs of zirconium bar specimens were prepared with dimensions of 25 mm × 2 mm × 5 mm and cementation surfaces of 5 mm × 2 mm. The samples were divided into 5 groups of 20 pairs each. The groups are as follows: Group I (C) – Control with no surface modification, Group II (APA) – airborne-particle-abrasion with 110 µm high-purity aluminum oxide (Al2O3) particles, Group III (ROC) – airborne-particle-abrasion with 110 µm silica modified aluminum oxide (Al2O3 + SiO2) particles, Group IV (TCS) – tribochemical silica coated with Al2O3 particles, and Group V (AlC) – nano alumina coating. The surface modifications were assessed on two samples selected from each group by atomic force microscopy and scanning electron microscopy. The samples were cemented with two different self-adhesive resin cements. The bending bond strength was evaluated by mechanical testing. RESULTS According to the ANOVA results, surface treatments, different cement types, and their interactions were statistically significant (P<.05). The highest flexural bond strengths were obtained in nanostructured alumina coated zirconia surfaces (50.4 MPa) and the lowest values were obtained in the control group (12.00 MPa), both of which were cemented using a self-adhesive resin cement. CONCLUSION The surface modifications tested in the current study affected the surface roughness and flexural bond strength of zirconia. The nano alumina coating method significantly increased the flexural bond strength of zirconia ceramics. PMID:29503713

Modeling the Effect of Surface Modification of Gold Nanoparticles Irradiated with 60Co on the Secondary Particles Emission Spectrum

NASA Astrophysics Data System (ADS)

Belousov, A. V.; Morozov, V. N.; Krusanov, G. A.; Kolyvanova, M. A.; Chernyaev, A. P.; Shtil, A. A.

2018-03-01

The Monte Carlo method (computer simulation) is used to construct a physical model of secondary particles emission induced by the simulated irradiation of a gold nanoparticle with 60Co. It is demonstrated that the modification of the nanoparticle surface with polyethylene glycol affects the spectrum of secondary electrons produced in a nanoparticle and leaving it and its shell. The model takes into account the size and the chemical composition of the shell and provides an opportunity to design antitumor radiosensitizers based on gold nanoparticles.

Enhancement in electrical conductivity of pastes containing submicron Ag-coated Cu filler with palmitic acid surface modification

NASA Astrophysics Data System (ADS)

Choi, Eun Byeol; Lee, Jong-Hyun

2017-09-01

The fabrication and applied use of submicron Ag-coated Cu (Cu@Ag) particles as a filler material for epoxy-based conductive pastes having the advantages of a lower material cost and antioxidation behavior were studied. Submicron Cu@Ag particles were successfully prepared and surface-modified using palmitic acid. Diffuse reflectance infrared Fourier transform spectroscopy and thermogravimetric differential scanning calorimetry results indicated the formation of an organic layer by the chemical interaction between the Cu@Ag surface and palmitic acid and the survival of the organic layer after treatment at 160 °C for 3 h in air. The printed pastes containing both commercial micron Cu@Ag flakes and the fabricated submicron Cu@Ag particles showed a greatly reduced electrical resistivity (4.68 × 10-4 Ω cm) after surface modification compared to an initial value of 1.85 × 10-3 Ω cm when cured.

Photo-ionization and modification of nanoparticles on transparent substrates by ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Komolov, Vladimir; Li, Hao; Yu, Qingsong; Przhibel'skii, Sergey; Smirnov, Dmitry

2011-02-01

The objective of this combined experimental and theoretical research is to study the dynamics and mechanisms of nanoparticle interaction with ultrashort laser pulses and related modifications of substrate surface. For the experimental effort, metal (gold), dielectric (SiO2) and dielectric with metal coating (about 30 nm thick) spherical nanoparticles deposited on glass substrate are utilized. Size of the particles varies from 20 to 200 nm. Density of the particles varies from low (mean inter-particle distance 100 nm) to high (mean inter-particle distance less than 1 nm). The nanoparticle assemblies and the corresponding empty substrate surfaces are irradiated with single 130-fs laser pulses at wavelength 775 nm and different levels of laser fluence. Large diameter of laser spot (0.5-2 mm) provides gradient variations of laser intensity over the spot and allows observing different laser-nanoparticle interactions. The interactions vary from total removal of the nanoparticles in the center of laser spot to gentle modification of their size and shape and totally non-destructive interaction. The removed particles frequently form specific sub-micrometer-size pits on the substrate surface at their locations. The experimental effort is supported by simulations of the nanoparticle interactions with high-intensity ultrashort laser pulse. The simulation employs specific modification of the molecular dynamics approach applied to model the processes of non-thermal particle ablation following laser-induced electron emission. This technique delivers various characteristics of the ablation plume from a single nanoparticle including energy and speed distribution of emitted ions, variations of particle size and overall dynamics of its ablation. The considered geometry includes single isolated particle as well a single particle on a flat substrate that corresponds to the experimental conditions. The simulations confirm existence of the different regimes of laser-nanoparticle interactions depending on laser intensity and wavelength. In particular, implantation of ions departing from the nanoparticles towards the substrate is predicted.

Synthesis and characterization of Ni doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Tamgadge, Y. S.; Gedam, P. P.; Ganorkar, R. P.; Mahure, M. A.; Pahurkar, V. G.; Muley, G. G.

2018-05-01

In this paper, we present synthesis of L-valine assisted surface modification of Ni doped ZnO nanoparticles (NPs) using chemical precipitation method. Samples were calcined at 500oC for 2h. Uncalcined and calcined samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) spectroscopy. Ni doped ZnO NPs with average particle size of 8 nm have been successfully obtained using L-valine as surface modifying agent. Increase in the particle size was observed after the calcination. XRD and TEM studies confirmed the purity, surface morphology and hexagonal wurtzite crystal structure of ZnO NPs. UV-vis spectroscopy indicated the blue shift of excitons absorption wavelength and surface modification by L-valine.

Surface modification of Cu metal particles by the chemical reaction between the surface oxide layer and a halogen surfactant

NASA Astrophysics Data System (ADS)

Yokoyama, Shun; Takahashi, Hideyuki; Itoh, Takashi; Motomiya, Kenichi; Tohji, Kazuyuki

2014-01-01

Surface oxides on small (2-5 μm) copper metal particles can be removed by chemical reaction with tris(2,3-dibromopropyl) isocyanurate (TIC) in diethylene glycol mono-n-hexyl ether (DGHE) solution under mild conditions where metal particles are not damaged. Surface oxides convert to copper bromide species and subsequently dissolve into the solvent. It was found that resultant surface species are resistant to re-oxidation due to remaining surface bromides. This finding opens up a possibility to create microclines based on cheap copper nanoparticles.

Ammonia modification for flotation separation of polycarbonate and polystyrene waste plastics.

PubMed

Wang, Chong-Qing; Wang, Hui; Gu, Guo-Hua; Lin, Qing-Quan; Zhang, Ling-Ling; Huang, Luo-Luo; Zhao, Jun-Yao

2016-05-01

A promising method, ammonia modification, was developed for flotation separation of polycarbonate (PC) and polystyrene (PS) waste plastics. Ammonia modification has little effect on flotation behavior of PS, while it changes significantly that of PC. The PC recovery in the floated product drops from 100% to 3.17% when modification time is 13min and then rises to 100% after longer modification. The mechanism of ammonia modification was studied by contact angle, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements. Contact angle of PC indicates the decline of PC recovery in the floated product is ascribed to an increase in surface wettability. FT-IR and XPS spectra suggest that ammonia modification causes chemical reactions occurred on PC surface. Flotation behavior of ammonia-modified PC and PS was investigated with respect to flotation time, frother concentration and particle sizes. Flotation separation of PC and PS waste plastics was conducted based on the flotation behavior of single plastic. PC and PS mixtures with different particle sizes are separated efficiently, implying that the technology possesses superior applicability to particle sizes of plastics. The purity of PS and PC is up to 99.53% and 98.21%, respectively, and the recovery of PS and PC is larger than 92.06%. A reliable, cheap and effective process is proposed for separation of PC and PS waste plastics. Copyright © 2016 Elsevier Ltd. All rights reserved.

A bio-enabled maximally mild layer-by-layer Kapton surface modification approach for the fabrication of all-inkjet-printed flexible electronic devices

PubMed Central

Fang, Yunnan; Hester, Jimmy G. D.; Su, Wenjing; Chow, Justin H.; Sitaraman, Suresh K.; Tentzeris, Manos M.

2016-01-01

A bio-enabled, environmentally-friendly, and maximally mild layer-by-layer approach has been developed to surface modify inherently hydrophobic Kapton HN substrates to allow for great printability of both water- and organic solvent-based inks thus facilitating the full-inkjet-printing of flexible electronic devices. Different from the traditional Kapton surface modification approaches which are structure-compromising and use harsh conditions to target, and oxidize and/or remove part of, the surface polyimide of Kapton, the present Kapton surface modification approach targeted the surface electric charges borne by its additive particles, and was not only the first to utilize environmentally-friendly clinical biomolecules to build up a thin film of protamine-heparin complex on Kapton, but also the first to be conducted under minimally destructive and maximally mild conditions. Besides, for electrically charged ink particles, the present surface modification method can enhance the uniformity of the inkjet-printed films by reducing the “coffee ring effect”. As a proof-of-concept demonstration, reduced graphene oxide-based gas sensors, which were flexible, ultra-lightweight, and miniature-sized, were fully-inkjet-printed on surface modified Kapton HN films and tested for their sensitivity to dimethyl methylphosphonate (a nerve agent simulant). Such fabricated sensors survived a Scotch-tape peel test and were found insensitive to repeated bending to a small 0.5 cm radius. PMID:28008987

A bio-enabled maximally mild layer-by-layer Kapton surface modification approach for the fabrication of all-inkjet-printed flexible electronic devices

NASA Astrophysics Data System (ADS)

Fang, Yunnan; Hester, Jimmy G. D.; Su, Wenjing; Chow, Justin H.; Sitaraman, Suresh K.; Tentzeris, Manos M.

2016-12-01

A bio-enabled, environmentally-friendly, and maximally mild layer-by-layer approach has been developed to surface modify inherently hydrophobic Kapton HN substrates to allow for great printability of both water- and organic solvent-based inks thus facilitating the full-inkjet-printing of flexible electronic devices. Different from the traditional Kapton surface modification approaches which are structure-compromising and use harsh conditions to target, and oxidize and/or remove part of, the surface polyimide of Kapton, the present Kapton surface modification approach targeted the surface electric charges borne by its additive particles, and was not only the first to utilize environmentally-friendly clinical biomolecules to build up a thin film of protamine-heparin complex on Kapton, but also the first to be conducted under minimally destructive and maximally mild conditions. Besides, for electrically charged ink particles, the present surface modification method can enhance the uniformity of the inkjet-printed films by reducing the “coffee ring effect”. As a proof-of-concept demonstration, reduced graphene oxide-based gas sensors, which were flexible, ultra-lightweight, and miniature-sized, were fully-inkjet-printed on surface modified Kapton HN films and tested for their sensitivity to dimethyl methylphosphonate (a nerve agent simulant). Such fabricated sensors survived a Scotch-tape peel test and were found insensitive to repeated bending to a small 0.5 cm radius.

Effects of the surface modification of silver nanoparticles on the surface-enhanced Raman spectroscopy of methylene blue for borohydride-reduced silver colloid

NASA Astrophysics Data System (ADS)

Dong, Xiao; Gu, Huaimin; Kang, Jian; Yuan, Xiaojuan; Wu, Jiwei

2010-12-01

The paper further investigated the relationship between the modification of the surface chemistry and the enhancement mechanisms of borohydride-reduced silver particles (BRSC). The bands of residual ions die down while the anomalous bands increase gradually with the increasing of the concentration of Cl - and Br -. It means the residual ions are displaced gradually by the added Cl - or Br - and the two halides can lead to the aggregation of the BRSC to a certain extent. However, the most strongly binding anions - I -, cannot cause any aggregation of silver particles. From the detection of methylene blue (MB), the relationship between the modification of silver surface chemistry and the enhancement mechanisms was discussed. Chloride gives the greatest enhancement while the iodide gives the lowest enhancement among the different kinds of anions. There are also some anomalous bands in the SERS spectra of MB, and these anomalous bands were given rational explanation in this paper.

Surface modification of calcined kaolin with toluene diisocyanate based on high energy ball milling

NASA Astrophysics Data System (ADS)

Yuan, Yongbing; Chen, Hongling; Lin, Jinbin; Ji, Yan

2013-11-01

The surface of calcined kaolin particle was modified with toluene diisocyanate (TDI) by using high energy ball milling. The prepared hybrids were characterized by FT-IR, MAS NMR, thermal analysis (TGA-DSC), static water contact angle (CA), apparent viscosity and transmission electron microscopy (TEM). FT-IR and MAS NMR spectra demonstrated that TDI molecules were chemically anchored to kaolin surface after modification. The results of thermal analysis showed that the maximum grafting ratio reached up to 446.61% when the mass ratio of TDI/kaolin was 0.5:1.0, and CA measurements revealed that the resultant hybrids exhibited strong hydrophobicity (148.82°). Apparent viscosity and TEM were employed to examine the dispersion properties of blank and modified kaolin particles in poly (dimenthylsiloxane) matrix. The results illustrated that the dispersion stability depended strongly on the grafting ratio of TDI, neither too low nor too high achieved uniform and stable dispersion, and the favorable grafting ratio was obtained when the mass ratio of TDI/kaolin was 0.2:1.0. Further modification of TDI/kaolin (mass ration of TDI/kaolin, 1.0:1.0) particles with bis(aminopropyl)-terminated-poly(dimethylsiloxane) (APS) was also investigated. TEM evidenced that the dispersion properties of the obtained TDI/APS/kaolin particles were remarkably improved in octamethyl cyclotetrasiloxane compared with the original TDI/kaolin particles.

Recruiting physisorbed water in surface polymerization for bio-inspired materials of tunable hydrophobicity

DOE PAGES

Oyola-Reynoso, S.; Tevis, I. D.; Chen, J.; ...

2016-08-18

Here, chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolyzable moieties in the presence of physisorbed water. In this report, we demonstrated that using alkyltrichlorosilanes (trivalent [i.e., 3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound particles. We infer that the presencemore » of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2–201.4 g m –2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from ~70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student's t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, paper-based houses can be rendered self-cleaning or tolerant to surface running water. In another application, we demonstrated that the felicitous choice of architectural design allows for the hydrophobic paper to be used for water harvesting.« less

Coating agents affected toward magnetite nanoparticles properties

NASA Astrophysics Data System (ADS)

Petcharoen, Karat; Sirivat, Anuvat

2012-02-01

Magnetite nanoparticles --MNPs-- are innovative materials used in biological and medical applications. They respond to magnetic field through the superparamagnetic behavior at room temperature. In this study, the MNPs were synthesized via the chemical co-precipitation method using various coating agents. Fatty acids, found naturally in the animal fats, can be used as a coating agent. Oleic acid and hexanoic acid were chosen as the surface modification agents to study the improvement in the suspension of MNPs in water and the magnetite properties. Suspension stability, particle size, and electrical conductivity of MNPs are critically affected by the modification process. The well-dispersed MNPs in water can be improved by the surface modification and the oleic acid coated MNPs possess excellent suspension stability over 1 week. The particle size of MNPs increases up to 40 nm using oleic acid coated MNPs. The electrical conductivity of the smallest particle size is 1.3x10-3 S/cm, which is 5 times higher than that of the largest particle, suggesting potential applications as a biomedical material under both of the electrical and magnetic fields.

Inversion of particle-stabilized emulsions of partially miscible liquids by mild drying of modified silica particles.

PubMed

White, Kathryn A; Schofield, Andrew B; Wormald, Philip; Tavacoli, Joseph W; Binks, Bernard P; Clegg, Paul S

2011-07-01

Using a system of modified silica particles and mixtures of water and 2,6-lutidine to form particle-stabilized emulsions, we show that subtle alterations to the hydration of the particle surface can cause major shifts in emulsion structure. We use fluorescence confocal microscopy, solid state nuclear magnetic resonance (NMR) and thermo-gravimetric analysis (TGA) to explore this sensitivity, along with other shifts caused by modifications to the silica surface chemistry. The silica particles are prepared by a variant of the Stöber procedure and are modified by the inclusion of 3-(aminopropyl)triethoxysilane and the dye fluorescein isothiocyanate. Treatment prior to emulsification consists of gently drying the particles under carefully controlled conditions. In mixtures of water and 2,6-lutidine of critical composition, the particles stabilize droplet emulsions and bijels. Decreasing particle hydration yields an inversion of the emulsions from lutidine-in-water (L/W) to water-in-lutidine (W/L), with bijels forming around inversion. So dependent is the emulsion behavior on particle hydration that microscopic differences in drying within a particle sample can cause differences in the wetting behavior of that sample, which helps to stabilize multiple emulsions. The formation of bijels at emulsion inversion is also crucially dependent on the surface modification of the silica. Copyright © 2011 Elsevier Inc. All rights reserved.

Surface engineering of nanoparticles in suspension for particle based bio-sensing

PubMed Central

Sen, Tapas; Bruce, Ian J.

2012-01-01

Surface activation of nanoparticles in suspension using amino organosilane has been carried out via strict control of a particle surface ad-layer of water using a simple but efficient protocol ‘Tri-phasic Reverse Emulsion’ (TPRE). This approach produced thin and ordered layers of particle surface functional groups which allowed the efficient conjugation of biomolecules. When used in bio-sensing applications, the resultant conjugates were highly efficient in the hybrid capture of complementary oligonucleotides and the detection of food borne microorganism. TPRE overcomes a number of fundamental problems associated with the surface modification of particles in aqueous suspension viz. particle aggregation, density and organization of resultant surface functional groups by controlling surface condensation of the aminosilane. The approach has potential for application in areas as diverse as nanomedicine, to food technology and industrial catalysis. PMID:22872809

Surface Modification of Melamine-Formaldehyde (MF-R) Macroparticles in Complex Plasma

NASA Astrophysics Data System (ADS)

Semenov, A. V.; Pergament, A. L.; Scherbina, A. I.; Pikalev, A. A.

2018-04-01

The surface modification of melamine-formaldehyde (MF-R) macroparticles (4.12 ± 0.09 μm in diameter) in dc glow discharges in neon, argon, and an argon-oxygen mixture (90% Ar, 10% O2) was studied experimentally. The macroparticles were treated in the discharge plasma for 10, 20, 40, and 60 min. The macroparticles were placed in ordered plasma-dust structures and then extracted from them. The results of atomic force microscopy of the surface profile are presented. Quantitative data on destruction of the surface layer and aspects of its modification are discussed. The amount of substance removed from the particle surface for the exposure time was calculated using the fractal analysis method.

Dopamine Polymerization in Liquid Marbles: A General Route to Janus Particle Synthesis.

PubMed

Sheng, Yifeng; Sun, Guanqing; Ngai, To

2016-04-05

Coating a liquid with a particle shell not only renders a droplet superhydrophobic but also isolates a well-confined microenvironment for miniaturized chemical processes. Previously, we have demonstrated that particles at the liquid marble interface provide an ideal platform for the site-selective modification of superhydrophobic particles. However, the need for a special chemical reaction limits their potential use for the fabrication of Janus particles with various properties. Herein, we combine the employment of liquid marbles as microreactors with the remarkable adhesive ability of polydopamine to develop a general route for the synthesis of Janus particles from micrometer-sized superhydrophobic particles. We demonstrate that dopamine polymerization and deposition inside liquid marbles could be used for the selective surface modification of microsized silica particles, resulting in the formation of Janus particles. Moreover, it is possible to manipulate the Janus balance of the particles via the addition of surfactants and/or organic solvents to tune the interfacial energy. More importantly, owing to the many functional groups in polydopamine, we show that versatile strategies could be introduced to use these partially polydopamine-coated silica particles as platforms for further modification, including nanoparticle immobilization, metal ion chelation and reduction, as well as for chemical reactions. Given the flexibility in the choice of cores and the modification strategies, this developed method is distinctive in its high universality, good controllability, and great practicability.

To alloy or not to alloy? Cr modified Pt/C cathode catalysts for PEM fuel cells.

PubMed

Wells, Peter P; Qian, Yangdong; King, Colin R; Wiltshire, Richard J K; Crabb, Eleanor M; Smart, Lesley E; Thompsett, David; Russell, Andrea E

2008-01-01

The cathode electrocatalysts for proton exchange membrane (PEM) fuel cells are commonly platinum and platinum based alloy nanoparticles dispersed on a carbon support. Control over the particle size and composition has, historically, been attained empirically, making systematic studies of the effects of various structural parameters difficult. The controlled surface modification methodology used in this work has enabled the controlled modification of carbon supported Pt nanoparticles by Cr so as to yield nanoalloy particles with defined compositions. Subsequent heat treatment in 5% H2 in N2 resulted in the formation of a distinct Pt3Cr alloy phase which was either restricted to the surface of the particles or present throughout the bulk of the particle structure. Measurement of the oxygen reduction activity of the catalysts was accomplished using the rotating thin film electrode method and the activities obtained were related to the structure of the nanoalloy catalyst particles, largely determined using Cr K edge and Pt L3 edge XAS.

Laser Surface Treatment and Modification of Aluminum Alloy Matrix Composites

NASA Astrophysics Data System (ADS)

Abbass, Muna Khethier

2018-02-01

The present work aimed to study the laser surface treatment and modification of Al-4.0%Cu-1.0%Mg alloy matrix composite reinforced with 10%SiC particles produced by stir casting. The specimens of the base alloy and composite were irradiated with an Nd:YAG laser of 1000 mJ, 1064 nm and 3 Hz . Dry wear test using the pin-on -disc technique at different sliding times (5-30 min) at a constant applied load and sliding speed were performed before and after laser treatment. Micro hardness and wear resistance were increased for all samples after laser hardening treatment. The improvement of these properties is explained by microstructural homogenization and grain refinement of the laser treated surface. Modification and refinement of SiC particles and grain refinement in the microstructure of the aluminum alloy matrix (α-Al) were observed by optical and SEM micrographs. The highest increase in hardness was 21.4% and 26.2% for the base alloy and composite sample respectively.

Some modification of cellulose nanocrystals for functional Pickering emulsions

PubMed Central

Saidane, Dorra; Perrin, Emilie; Cherhal, Fanch; Guellec, Florian

2016-01-01

Cellulose nanocrystals (CNCs) are negatively charged colloidal particles well known to form highly stable surfactant-free Pickering emulsions. These particles can vary in surface charge density depending on their preparation by acid hydrolysis or applying post-treatments. CNCs with three different surface charge densities were prepared corresponding to 0.08, 0.16 and 0.64 e nm−2, respectively. Post-treatment might also increase the surface charge density. The well-known TEMPO-mediated oxidation substitutes C6-hydroxyl groups by C6-carboxyl groups on the surface. We report that these different modified CNCs lead to stable oil-in-water emulsions. TEMPO-oxidized CNC might be the basis of further modifications. It is shown that they can, for example, lead to hydrophobic CNCs with a simple method using quaternary ammonium salts that allow producing inverse water-in-oil emulsions. Different from CNC modification before emulsification, modification can be carried out on the droplets after emulsification. This way allows preparing functional capsules according to the layer-by-layer process. As a result, it is demonstrated here the large range of use of these biobased rod-like nanoparticles, extending therefore their potential use to highly sophisticated formulations. This article is part of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’. PMID:27298429

Nanoscale Surface Modifications of Orthopaedic Implants: State of the Art and Perspectives

PubMed Central

Staruch, RMT; Griffin, MF; Butler, PEM

2016-01-01

Background: Orthopaedic implants such as the total hip or total knee replacement are examples of surgical interventions with postoperative success rates of over 90% at 10 years. Implant failure is associated with wear particles and pain that requires surgical revision. Improving the implant - bone surface interface is a key area for biomaterial research for future clinical applications. Current implants utilise mechanical, chemical or physical methods for surface modification. Methods: A review of all literature concerning the nanoscale surface modification of orthopaedic implant technology was conducted. Results: The techniques and fabrication methods of nanoscale surface modifications are discussed in detail, including benefits and potential pitfalls. Future directions for nanoscale surface technology are explored. Conclusion: Future understanding of the role of mechanical cues and protein adsorption will enable greater flexibility in surface control. The aim of this review is to investigate and summarise the current concepts and future directions for controlling the implant nanosurface to improve interactions. PMID:28217214

Microscale surface modifications for heat transfer enhancement.

PubMed

Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C

2013-10-09

In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.

Surface modification of ultra thin PES-zeolite using thermal annealing to increase flux and rejection of produced water treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kusworo, T. D., E-mail: tdkusworo@che.undip.ac.id; Widayat,; Pradini, A. W.

2015-12-29

Membrane technology is an alternative of water treatment based on filtration that is being developed. Surface Modification using heat treatment has been investigated to improve the performance of ultra thin PES-Zeolite nanocomposite membrane for produced water treatment from Pertamina Balongan. Two types of membranes with surface modification and without modification were prepared to study the effect of surface modification on its permeation properties. Asymmetric ultra thin PES-Zeolite nanocomposite membrane for produced water treatment was casted using the dry/wet phase inversion technique from dope solutions containing polyethersulfone, N-methyl-2-pyrrolidone (NMP) as a solvent and zeolite as a filler. Experimental results showed thatmore » the heat treatment at near glass transition temperature was increase the rejection of COD, Turbidity and ion Ca{sup 2+}. The better adherence of zeolite particles in the polymer matrix combined with formation of charge transfer complexes (CTCs) and cross-linking might be the main factors to enhance the percent of rejection. Field emission scanning electron microscopy (FESEM) micrographs showed that the selective layer and the substructure of PES-zeolite membrane became denser and more compact after the heat treatment. The FESEM micrographs also showed that the heat treatment was increased the adherence of zeolite particle and polymer. Membranes treated at 180 °C for 15 seconds indicated increase the rejection and small decrease in flux for produced water treatment.« less

Preparation of almost dispersant-free colloidal silica with superb dispersiblility in organic solvents and monomers

NASA Astrophysics Data System (ADS)

Huang, Feng-Hsi; Chang, Chao-Ching; Oyang, Tai-Yueh; Chen, Ching-Chung; Cheng, Liao-Ping

2011-09-01

Surface modification of silica nanoparticles synthesized by the sol-gel process was performed using coupling agents, 3-(trimethoxysilyl) propyl methacrylate (MSMA) and/or trimethyethoxylsilane (TMES). The chemical structures of the formed particles were analyzed by means of Fourier Transform Infrared Spectroscopy (FTIR) and solid-state Si-Nuclear Magnetic Resonance (Si-NMR), and the particle sizes were determined by Transmission Electron Microscopy (TEM) imaging. The latter results indicate that such surface modifications can effectively lessen the serious aggregation being common to pure silica nanoparticles. In some cases, separate particles of ca. 5-10 nm dia. could be obtained, when both MSMA and TMES were employed during the modification process. Dynamic light scattering method was adopted to examine the stability of the prepared silica sols during a long-term storage. It was found that the aggregation phenomenon can essentially be eliminated in case that the surface of silica contained sufficient amount of TMES moiety. Vacuum distillation was used to remove the volatile components such as methanol, ethanol, and water from the silica sol. The condensed product, containing 2 wt% residual solvent, appeared as a uniform transparent paste-like material, which can be dispersed in common organic solvents and monomers within a few seconds.

The carbonaceous sorbent based on the secondary silica-containing material from oil extraction industry

NASA Astrophysics Data System (ADS)

Starostina, I. V.; Stolyarov, D. V.; Anichina, Ya N.; Porozhnyuk, E. V.

2018-01-01

The object of research in this work is the silica-containing waste of oil extraction industry - the waste kieselghur (diatomite) sludge from precoat filtering units, used for the purification of vegetable oils from organic impurities. As a result of the thermal modification of the sludge, which contains up to 70% of organic impurities, a finely-dispersed low-porous carbonaceous mineral sorption material is formed. The modification of the sludge particles surface causes the substantial alteration of its physical, chemical, adsorption and structural properties - the organic matter is charred, the particle size is reduced, and on the surface of diatomite particles a carbon layer is formed, which deposits in macropores and partially occludes them. The amount of mesopores is increased, along with the specific surface of the obtained product. The optimal temperature of sludge modification is 500°C. The synthesized carbonaceous material can be used as an adsorbing agent for the purification of wastewater from heavy metal ions. The sorption capacity of Cu2+ ions amounted to 14.2 mg·g-1 and for Ni2+ ions - 17.0 mg·g-1. The obtained values exceed the sorption capacity values of the initial kieselghur, used as a filtering charge, for the researched metal ions.

Surface-coated fly ash used as filler in biodegradable poly(vinyl alcohol) composite films: Part 1—The modification process

NASA Astrophysics Data System (ADS)

Nath, D. C. D.; Bandyopadhyay, S.; Gupta, S.; Yu, A.; Blackburn, D.; White, C.

2010-02-01

The surfaces of fly ash (FA) particles were modified by surfactant, sodium lauryl sulphate (SLS) and used in fabrication of composite films with polyvinyl alcohol (PVA). Both unmodified fly ash (FA) and modified fly ash (SLS-FA) samples were examined using a range of analytical tools including X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The distribution patterns of SLS-FA particles were shifted to the higher regions compared to FA by adding 1.2-4.2 μm in the ranges between 2 and 25 μm, whereas the modification process reduced the size of the particles over 25 μm due to grinding during the activation process. The increased 1.2-4.2 μm in average can be considered the thickness of the surfactant on the SLS-FA surface. On the oxides based chemical analysis by XRF, the compositions were almost unchanged. SEM and TEM were visualised the irregular sizes morphology mostly spherical of the particles, although it is impossible to capture the images of exactly same particles in modified and unmodified forms. The composite films reinforced with SLS-FA showed 33% higher strength than those of FA filled films. The enhancement of tensile strength attributed from the level of physical bonding between SLS-FA and PVA surfaces.

Wrinkling Non-Spherical Particles and Its Application in Cell Attachment Promotion

NASA Astrophysics Data System (ADS)

Li, Minggan; Joung, Dehi; Hughes, Bethany; Waldman, Stephen D.; Kozinski, Janusz A.; Hwang, Dae Kun

2016-07-01

Surface wrinkled particles are ubiquitous in nature and present in different sizes and shapes, such as plant pollens and peppercorn seeds. These natural wrinkles provide the particles with advanced functions to survive and thrive in nature. In this work, by combining flow lithography and plasma treatment, we have developed a simple method that can rapidly create wrinkled non-spherical particles, mimicking the surface textures in nature. Due to the oxygen inhibition in flow lithography, the non-spherical particles synthesized in a microfluidic channel are covered by a partially cured polymer (PCP) layer. When exposed to plasma treatment, this PCP layer rapidly buckles, forming surface-wrinkled particles. We designed and fabricated various particles with desired shapes and sizes. The surfaces of these shapes were tuned to created wrinkle morphologies by controlling UV exposure time and the washing process. We further demonstrated that wrinkles on the particles significantly promoted cell attachment without any chemical modification, potentially providing a new route for cell attachment for various biomedical applications.

Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications

NASA Astrophysics Data System (ADS)

Kobayashi, Yoshio; Nagasu, Ryoko; Shibuya, Kyosuke; Nakagawa, Tomohiko; Kubota, Yohsuke; Gonda, Kohsuke; Ohuchi, Noriaki

2014-08-01

This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol-gel process. The sol-gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2-NH2). Surface modification of the Au/SiO2-NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2-NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.

Morphology of ejected particles and impact sites on intercepting substrates following exit-surface laser damage with nanosecond pulses in silica

DOE PAGES

Demos, Stavros G.; Negres, Raluca A.

2016-09-08

A volume of superheated material reaching localized temperatures of the order of 1 eV and pressures of the order of 10 GPa is generated following laser-induced damage (breakdown) on the surface of transparent dielectric materials using nanosecond pulses. This leads to material ejection and the formation of a crater. To elucidate the material behaviors involved, we examined the morphologies of the ejected particles and found distinctive features that support their classification into different types. The different morphologies arise from the difference in the structure and physical properties (such as the dynamic viscosity and presence of instabilities) of the superheated andmore » surrounding affected material at the time of ejection of each individual particle. In addition, the temperature and kinetic energy of a subset of the ejected particles were found to be sufficient to initiate irreversible modification on the intercepting silica substrates. Finally, the modifications observed are associated with mechanical damage and fusion of melted particles on the collector substrate.« less

Charged particle modification of ices in the Saturnian and Jovian systems

NASA Technical Reports Server (NTRS)

Johnson, R. E.; Barton, L. A.; Boring, J. W.; Jesser, W. A.; Brown, W. L.

1985-01-01

The modification by ion bombardment of the surfaces of icy objects in the Saturnian and Jovian systems is discussed. Chemical changes in ices are induced by breaking of bonds and by implantation of incident ions. Long-term irradiation by fast ions produces physical changes such as increasing the surface reflectivity and ability to scatter light. On large satellites, molecules which are ejected by ion bombardment are redistributed across the surfaces of large satellites. For small satellites and ring particles bombarded by ions, such as those of Saturn, most or all of the sputtered material is lost to space, forming a neutral torus in the locale of the satellite orbits and rings and supplying ions to the magnetosphere. Noting the existence of such a torus, the sputter erosion and possible stabilization of the E-ring of Saturn is discussed.

Modifying Silicates for Better Dispersion in Nanocomposites

NASA Technical Reports Server (NTRS)

Campbell, Sandi

2005-01-01

An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces, the co-ion exchange strengthens the polymer/silicate interface and ensures irreversible separation of the silicate layers. One way in which it does this is to essentially tether one amine of each diamine molecule to a silicate surface, leaving the second amine free for reaction with monomers during the synthesis of a polymer. In addition, the incorporation of alkyl ammonium ions into the galleries at low concentration helps to keep low the melt viscosity of the oligomer formed during synthesis of the polymer and associated processing - a consideration that is particularly important in the case of a highly cross-linked, thermosetting polymer. Because of the chemical bonding between the surface-modifying amines and the monomers, even when the alkyl ammonium ions become degraded at high processing temperature, the silicate layers do not aggregate and, hence, nanometer-level dispersion is maintained.

Surface-functionalized polymethacrylic acid based hydrogel microparticles for oral drug delivery.

PubMed

Sajeesh, S; Bouchemal, K; Sharma, C P; Vauthier, C

2010-02-01

Aim of the present work was to develop novel thiol-functionalized hydrogel microparticles based on poly(methacrylic acid)-chitosan-poly(ethylene glycol) (PCP) for oral drug delivery applications. PCP microparticles were prepared by a modified ionic gelation process in aqueous medium. Thiol modification of surface carboxylic acid groups of PCP micro particles was carried out by coupling l-cysteine with a water-soluble carbodiimide. Ellman's method was adopted to quantify the sulfhydryl groups, and dynamic light-scattering technique was used to measure the average particle size. Cytotoxicity of the modified particles was evaluated on Caco 2 cells by MTT assay. Effect of thiol modification on permeability of paracellular marker fluorescence dextran (FD4) was evaluated on Caco 2 cell monolayers and freshly excised rat intestinal tissue with an Ussing chamber set-up. Mucoadhesion experiments were carried out by an ex vivo bioadhesion method with excised rat intestinal tissue. The average size of the PCP microparticles was increased after thiol modification. Thiolated microparticles significantly improved the paracellular permeability of FD4 across Caco 2 cell monolayers, with no sign of toxicity. However, the efficacy of thiolated system remained low when permeation experiments were carried out across excised intestinal membrane. This was attributed to the high adhesion of the thiolated particles on the gut mucosa. Nevertheless, it can be concluded that surface thiolation is an interesting strategy to improve paracellular permeability of hydrophilic macromolecules. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Surface Modification of Zirconia Substrate by Calcium Phosphate Particles Using Sol-Gel Method.

PubMed

Jin, So Dam; Um, Sang Cheol; Lee, Jong Kook

2015-08-01

Surface modification with a biphasic composition of hydroxyapatite (HA) and tricalcium phosphate (TCP) was performed on a zirconia substrate using a sol-gel method. An initial calcium phosphate sol was prepared by mixing a solution of Ca(NO3)2 · 4H20 and (C2H5O)3P(O), while both porous and dense zirconia were used as substrates. The sol-gel coating was performed using a spin coater. The coated porous zirconia substrate was re-sintered at 1350 °C 2 h, while coated dense zirconia substrate was heat-treated at 750 °C 1 h. The microstructure of the resultant HA/TCP coatings was found to be dependent on the type of zirconia substrate used. With porous zirconia as a starting substrate, numerous isolated calcium phosphate particles (TCP and HA) were uniformly dispersed on the surface, and the particle size and covered area were dependent on the viscosity of the calcium phosphate sol. Conversely, when dense zirconia was used as a starting substrate, a thick film of nano-sized HA particles was obtained after heat treatment, however, substantial agglomeration and cracking was also observed.

Manipulating surface wettability and oil absorbency of diatomite depending on processing and ambient conditions

NASA Astrophysics Data System (ADS)

Özen, İlhan; Şimşek, Süleyman; Okyay, Gamze

2015-03-01

In this study, a diatomite sample, which is a natural inorganic mineral with inherently high water and oil absorption capacity, was subjected to grinding before surface modification. Afterwards, the diatomite surface was modified via facile methods using a fluorocarbon (FC) chemical and stearic acid (SA) in addition to the sol-gel fluorosilanization (FS) process. The water and oil wettability, and oil absorbency properties of the unmodified and modified diatomites were investigated in addition to diatomite characterizations such as chemical content, surface area, particle size distribution, morphology, and modification efficiency. It was revealed that the wettability was changed completely depending on the surface modification agent and the media used, while the oil absorbency property surprisingly did not change. On the other hand, the oil absorbency was worsened by the grinding process, whereas the wettability was not affected.

DNA-magnetic Particle Binding Analysis by Dynamic and Electrophoretic Light Scattering.

PubMed

Haddad, Yazan; Dostalova, Simona; Kudr, Jiri; Zitka, Ondrej; Heger, Zbynek; Adam, Vojtech

2017-11-09

Isolation of DNA using magnetic particles is a field of high importance in biotechnology and molecular biology research. This protocol describes the evaluation of DNA-magnetic particles binding via dynamic light scattering (DLS) and electrophoretic light scattering (ELS). Analysis by DLS provides valuable information on the physicochemical properties of particles including particle size, polydispersity, and zeta potential. The latter describes the surface charge of the particle which plays major role in electrostatic binding of materials such as DNA. Here, a comparative analysis exploits three chemical modifications of nanoparticles and microparticles and their effects on DNA binding and elution. Chemical modifications by branched polyethylenimine, tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane are investigated. Since DNA exhibits a negative charge, it is expected that zeta potential of particle surface will decrease upon binding of DNA. Forming of clusters should also affect particle size. In order to investigate the efficiency of these particles in isolation and elution of DNA, the particles are mixed with DNA in low pH (~6), high ionic strength and dehydration environment. Particles are washed on magnet and then DNA is eluted by Tris-HCl buffer (pH = 8). DNA copy number is estimated using quantitative polymerase chain reaction (PCR). Zeta potential, particle size, polydispersity and quantitative PCR data are evaluated and compared. DLS is an insightful and supporting method of analysis that adds a new perspective to the process of screening of particles for DNA isolation.

Sol–gel synthesis of MCM-41 silicas and selective vapor-phase modification of their surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roik, N.V., E-mail: roik_nadya@ukr.net; Belyakova, L.A.

2013-11-15

Silica particles with uniform hexagonal mesopore architecture were synthesized by template directed sol–gel condensation of tetraethoxysilane or mixture of tetraethoxysilane and (3-chloropropyl)triethoxysilane in a water–ethanol–ammonia solution. Selective functionalization of exterior surface of parent materials was carried out by postsynthetic treatment of template-filled MCM-41 and Cl-MCM-41 with vapors of (3-chloropropyl)triethoxysilane and 1,2-ethylenediamine in vacuum. The chemical composition of obtained mesoporous silicas was estimated by IR spectroscopy and chemical analysis of surface products of reactions. Characteristics of porous structure of resulting materials were determined from the data of X-ray, low-temperature nitrogen ad-desorption and transmission electron microscopy measurements. Obtained results confirm invariability ofmore » highly ordered mesoporous structure of MCM-41 and Cl-MCM-41 after their selective postsynthetic modification in vapor phase. It was proved that proposed method of vapor-phase functionalization of template-filled starting materials is not accompanied by dissolution of the template and chemical modification of pores surface. This provides preferential localization of grafted functional groups onto the exterior surface of mesoporous silicas. - Graphical abstract: Sol–gel synthesis and postsynthetic chemical modification of template-filled MCM-41 and Cl-MCM-41 with (3-chloropropyl)triethoxysilane and 1,2-ethylenediamine in vapor phase. Display Omitted - Highlights: • Synthesis of MCM-41 silica by template directed sol–gel condensation. • Selective vapor-phase functionalization of template-filled silica particles. • Preferential localization of grafted groups onto the exterior surface of mesoporous silicas.« less

Structure of Hydrophobically Modified Phytoglycogen Nanoparticles

NASA Astrophysics Data System (ADS)

Atkinson, John; Nickels, Jonathan; Dutcher, John; Katsaras, John

Phytoglycogen is a highly branched, polysaccharide nanoparticle produced by some varieties of plants including sweet corn. These particles are attractive candidates for cosmetic, industrial and biomedical applications. Many of these applications result from phytoglycogen's unique interaction with water: (1) high solubility; (2) low viscosity and high stability in aqueous dispersions; and (3) a remarkable capacity to sequester and retain water. Neutron scattering measurements of native phytoglycogen revealed that the particles have uniform size, uniform radial particle density, and a high level of hydration. Hydrophobically modifying the outer surface of the hydrophilic nanoparticles opens up new applications in food and biomedicine, such as solubilizing and stabilizing bioactive compounds. One such modification is octenyl succinate anhydride (OSA), where the hydrophobicity can be tuned by adjusting the degree of substitution. I will present the results of small angle neutron scattering (SANS) measurements of aqueous dispersions of OSA-modified phytoglycogen with two different degrees of modification. Contrast series SANS measurements have yielded information about the radial density profile, providing insight into the nature of the chemical modification of the particles.

Assessment of potential positive effects of nZVI surface modification and concentration levels on TCE dechlorination in the presence of competing strong oxidants, using an experimental design.

PubMed

Kaifas, Delphine; Malleret, Laure; Kumar, Naresh; Fétimi, Wafa; Claeys-Bruno, Magalie; Sergent, Michelle; Doumenq, Pierre

2014-05-15

Nanoscale zero-valent iron (nZVI) particles are efficient for the remediation of aquifers polluted by trichloroethylene (TCE). But for on-site applications, their reactivity can be affected by the presence of common inorganic co-pollutants, which are equally reduced by nZVI particles. The aim of this study was to assess the potential positive effects of nZVI surface modification and concentration level on TCE removal in the concomitant presence of two strong oxidants, i.e., Cr(VI) and NO3(-). A design of experiments, testing four factors (i.e. nZVI concentration, nZVI surface modification, Cr(VI) concentration and NO3(-) concentration), was used to select the best trials for the identification of the main effects of the factors and of the factors interactions. The effects of these factors were studied by measuring the following responses: TCE removal rates at different times, degradation kinetic rates, and the transformation products formed. As expected, TCE degradation was delayed or inhibited in most of the experiments, due to the presence of inorganics. The negative effects of co-pollutants can be palliated by combining surface modification with a slight increase in nZVI concentration. Encouragingly, complete TCE removal was achieved for some given experimental conditions. Noteworthily, nZVI surface modification was found to promote the efficient degradation of TCE. When degradation occurred, TCE was mainly transformed into innocuous non-chlorinated transformation products, while hazardous chlorinated transformation products accounted for a small percentage of the mass-balance. Copyright © 2014 Elsevier B.V. All rights reserved.

[Preparation and catalytic activity of surface-modification CNTs/TiO2 composite photocatalysts].

PubMed

Wang, Huan-Ying; Li, Wen-Jun; Chang, Zhi-Dong; Zhou, Hua-Lei; Guo, Hui-Chao

2011-09-01

A novel kind of carbon nanotubes/titanium dioxide (CNTs/TiO2) composite photocatalyst was prepared by a modified sol-gel method in which the nanoscaled TiO2 particles were uniformly deposited on the CNTs modified with poly(vinyl pyrrolidone) (PVP). The composites were characterized by a range of analytical techniques including high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show the successful covering of the CNTs with PVP, forming core-shell structure. The nanoscaled TiO2 particles were uniformly deposited on the surface of CNTs reducing the bare CNTs which avoid losing the absorption and scattering of photons. The combination of CNTs and TiO2 particles imply the enhanced interactions between the CNTs and TiO2 interface which possibly becomes heterojunction. The composites become mesoporous crystalline TiO2 (anatase) clusters after annealing at 500 degrees C, and the surface area increases obviously. The photocatalytic activities of surface modification CNTs/TiO2 (smCNTs/TiO2) composites are extremely enhanced from the results of the photodegradation of methylene blue (MB).

Sol–gel method as a way of carbonyl iron powder surface modification for interaction improvement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Małecki, P., E-mail: pawel.malecki@pwr.edu.pl; Kolman, K.; Pigłowski, J.

2015-03-15

This article presents a method for modification of carbonyl iron particles’ surface (CIP), (d{sub 50}=4–9 µm) by silica coatings obtained using the sol–gel method. Reaction parameters were determined to obtain dry magnetic powder with homogeneous silica coatings without further processing and without any by-product in the solid or liquid phase. This approach is new among the commonly used methods of silica coating of iron particles. No attempt has been made to cover a carbonyl iron surface by silica in a waste-free method, up to date. In the current work two different silica core/shell structures were made by the sol–gel process,more » based on different silica precursors: tetraethoxy-silane (TEOS) and tetramethoxy-silane (TMOS). The dependence between the synthesis procedure and thickness of silica shell covering carbonyl iron particles has been described. Surface morphology of the modified magnetic particles and the coating thickness were characterized with the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Determination of the physicochemical structure of the obtained materials was performed by the energy-dispersive X-ray spectroscope (EDS), and the infrared technique (IR). The surface composition was analyzed using X-ray photoelectron spectroscopy (XPS). Additionally, distribution of particle size was measured using light microscopy. The new, efficient process of covering micro-size CIP with a nanometric silica layer was shown. Results of a performed analysis confirm the effectiveness of the presented method. - Highlights: • Proper covering CIP by sol–gel silica layer avoids agglomeration. • A new solid waste-free method of CIP coating is proposed. • Examination of the properties of modified CIP in depends on washing process. • Coatings on CIP particles doesn’t change the magnetic properties of particles.« less

Improved rubber nanofillers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyle, T. J.

2012-03-01

During this task, Silane functionalized TiO2 and HK3Ti4O4(SiO4)3 were sent to Goodyear (GY) for testing. These materials were characterized based on their interaction with the model elastomer, squalene. The Van der Waals interactions and Hamaker Constants for ZnO particles in squalene and rubber materials were characterized and it was determined that a 10-20 nm spacing was necessary between primary filler particles to maintain a stable nanocomposite. Contact angle measurements on the ZnO and ZnO-silane materials indicated that the solvent should wet the particles, and solvophobic attractions should not be present. These studies showed that the surface modification with sulfosilane couplingmore » agents was successful, and high levels of dispersion of the particles remained possible. Further, a novel surface charging phenomenon where negative surface charging is developed in the squalene environment was observed and corroborated by measurements of particle size and of the surface modified materials in squalene. This impacts the dispersion of the particles according to the traditional colloidal interpretation of electrostatic repulsive forces between particles. Additionally, thin nanocomposite fibers were developed using electrospinning. The size and shape of the oxides did not change during the electrospinning process, although the shape of the fiber and the distribution of the particles, particularly for ZnO, was not ideal. There was an obvious increase in elastic modulus and hardness from the addition of the oxides, but differentiating the oxides, and particularly the surfactants, was difficult. The A-1289 lead to the greatest dispersion of the filler particles, while the A-1589 and the NXT produced clustered particle aggregates. This agrees with previous study of these materials in low molecular weight squalene solvent studies reported earlier. The behavior of the nanoparticle ZnO and the microparticle silica is different as well, with the ZnO being contained within the elastomer, and the SiO2 forming monolayers at the surface of the elastomer. The dynamic mechanical analysis did not show clear trends between the surface modification and the aggregate structure. In the silica particles, the NXT led to the least particle interaction, followed by the A-1289 and highest particle interaction found for the A-1589. For the nanosized ZnO, the best dispersion was found for the A-1589, with both the A-1289 and NXT exhibiting frequency dependent responses.« less

[Chemical modification on the surface of nano-particles of ZnO and its characterization].

PubMed

Yu, Hai-yin; Du, Jun; Gu, Jia-shan; Guan, Ming-yun; Wu, Zheng-cui; Ling, Qing; Sun, Yi-min

2004-02-01

After nano-particles (ZnO) had been encapsulated by a kind of water-soluble cellulose Hydoxyl-Propyl-Methyl Cellulose (HPMC), then methyl methacrylate was grafted onto the surface of them. Thus the surface of nano-ZnO had been successfully modified. FTIR, DTA and TEM were utilized to confirm the results. FTIR shows that HPMC was adsorbed onto the surface of ZnO, and PMMA was also grafted onto its surface, DTA says that the heat stability of HPMC, HPMC-g-PMMA and ZnO/HPMC-g-PMMA increased greatly, TEM photo demonstrates that polymer adhered onto the surface of nano-ZnO which was encapsulated by a layer of film-like polymer.

Improvement of β-TCP/PLLA biodegradable material by surface modification with stearic acid.

PubMed

Ma, Fengcang; Chen, Sai; Liu, Ping; Geng, Fang; Li, Wei; Liu, Xinkuan; He, Daihua; Pan, Deng

2016-05-01

Poly-L-lactide (PLLA) is a biodegradable polymer and used widely. Incorporation of beta tricalcium phosphate (β-TCP) into PLLA can enhance its osteoinductive properties. But the interfacial layer between β-TCP particles with PLLA matrix is easy to be destroyed due to inferior interfacial compatibility of the organic/inorganic material. In this work, a method of β-TCP surface modification with stearic acid was investigated to improve the β-TCP/PLLA biomaterial. The effects of surface modification on the β-TCP were investigated by FTIR, XPS, TGA and CA. It was found that the stearic acid reacted with β-TCP and oxhydryl was formed during the surface modification. Hydrophilicity of untreated or modified β-TCP/PLLA composite was increased by the addition of 10 wt.% β-TCP, but it decreased as the addition amount increased from 10 wt.% to 20 wt.%. Two models were suggested to describe the effect of β-TCP concentration on CA of the composites. Mechanical properties of β-TCP/PLLA composites were tested by bending and tensile tests. Fractures of the composites after mechanical test were observed by SEM. It was found that surface modification with stearic acid improved bending and tensile strengths of the β-TCP/PLLA composites obviously. The SEM results indicated that surface modification decreased the probability of interface debonding between fillers and matrix under load. Copyright © 2016 Elsevier B.V. All rights reserved.

Easy on-demand single-pass self-assembly and modification to fabricate gold@graphene-based anti-inflammatory nanoplatforms

NASA Astrophysics Data System (ADS)

Byeon, Jeong Hoon; Park, Jae Hong

2016-10-01

Zwitterionic chitosan (ZC) was modified by fully (both for lateral dimension and thickness) nanodimensional gold-graphene oxide (Au@GO) flakes under visible light and the potential of the resulting materials as biomedical nanoplatforms was investigated. Fully nanodimensional GO flakes floating in nitrogen gas were incorporated with Au nanoparticles to form Au@GO nanoflakes, and the Au@GO was then incorporated with ZC droplets to form the Au@GO-ZC hybrid nanoparticles. The collected particles were exposed to visible light to induce the photocatalytic activity of the Au@GO nanoflakes towards the ZC derivatives. The visible-light-exposed particles show different chemical and surface properties from the unexposed particles, while there were no significant differences in cytotoxicity and macrophage inflammatory protein production. This work suggests that incorporating fully nanodimensional Au@GO flakes with ZC is a suitable technique for ambient photo-modification of the chitosans’ surface property without significant changes in size and shape and increases in cytotoxicity and inflammatory response.

A novel DNA nanosensor based on CdSe/ZnS quantum dots and synthesized Fe3O4 magnetic nanoparticles.

PubMed

Hushiarian, Roozbeh; Yusof, Nor Azah; Abdullah, Abdul Halim; Ahmad, Shahrul Ainliah Alang; Dutse, Sabo Wada

2014-04-09

Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.

Flotation separation of polyvinyl chloride and polyethylene terephthalate plastics combined with surface modification for recycling.

PubMed

Wang, Chongqing; Wang, Hui; Fu, Jiangang; Zhang, Lingling; Luo, Chengcheng; Liu, Younian

2015-11-01

Surface modification with potassium permanganate (KMnO4) solution was developed for separation of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) waste plastics. The floatability of PVC decreases with increasing of KMnO4 concentration, treatment time, temperature and stirring rate, while that of PET is unaffected. Fourier transform infrared (FT-IR) analysis confirms that mechanism of surface modification may be due to oxidization reactions occurred on PVC surface. The optimum conditions are KMnO4 concentration 1.25 mM/L, treatment time 50 min, temperature 60°C, stirring rate 300 r/min, frother concentration 17.5 g/L and flotation time 1 min. PVC and PET with different particle sizes were separated efficiently through two-stage flotation. Additionally, after ultrasonic assisted surface modification, separation of PVC and PET with different mass ratios was obtained efficiently through one-stage flotation. The purity and the recovery of the obtained products after flotation separation are up to 99.30% and 99.73%, respectively. A flotation process was designed for flotation separation of PVC and PET plastics combined with surface modification. This study provides technical insights into physical separation of plastic wastes for recycling industry. Copyright © 2015 Elsevier Ltd. All rights reserved.

Copper Modified Magnetic Bimetallic Nano-catalysts Ligand Regulated Catalytic Activity

EPA Science Inventory

Postsynthetic modification of magnetic nano ferrites (Fe3O4) has been accomplished by anchoring glutathione and dopamine on the surface. The Cu nano particles immobilized over these surfaces were investigated for the coupling and cyclo addition reactions. The Fe3O4-DOPA-Cu (na...

[Comperative study of implant surface characteristics].

PubMed

Katona, Bernadett; Daróczi, Lajos; Jenei, Attila; Bakó, József; Hegedus, Csaba

2013-12-01

The osseointegration between the implant and its' bone environment is very important. The implants shall meet the following requirements: biocompatibility, rigidity, resistance against corrosion and technical producibility. In our present study surface morphology and material characteristics of different implants (Denti Bone Level, Denti Zirconium C, Bionika CorticaL, Straumann SLA, Straumann SLA Active, Dentsply Ankylos and Biotech Kontact implant) were investigated with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The possible surface alterations caused by the manufacturing technology were also investigated. During grit-blasting the implants' surface is blasted with hard ceramic particles (titanium oxide, alumina, calcium phosphate). Properties of blasting material are critical because the osseointegration of dental implants should not be hampered. The physical and chemical features of blasting particles could importantly affect the produced surfaces of implants. Titanium surfaces with micro pits are created after immersion in mixtures of strong acids. On surfaces after dual acid-etching procedures the crosslinking between fibrin and osteogenetic cells could be enhanced therefore bone formation could be directly facilitated on the surface of the implant. Nowadays there are a number of surface modification techniques available. These can be used as a single method or in combination with each other. The effect of the two most commonly used surface modifications (acid-etching and grit-blasting) on different implants are demonstrated in our investigation.

Meletin sustained-release gliadin nanoparticles prepared via solvent surface modification on blending electrospraying

NASA Astrophysics Data System (ADS)

Yang, Yao-Yao; Zhang, Man; Liu, Zhe-Peng; Wang, Ke; Yu, Deng-Guang

2018-03-01

Almost all electrospraying processes are carried out under an air-solution interface, thereby overlooking the potential influence of an additional solvent surface modification between air and the working solution. A pure solvent was explored to temporarily and dynamically surround the solutions utilized for blending electrospraying, which contained a guest drug meletin and a protein drug carrier gliadin. The new modified processes created protein-based medicated nanoparticles (P2) with higher quality than their counterparts (P1) from blending processes, as demonstrated by the SEM and TEM images. Although the particles from the two processes were similar (nanocomposites), and the particles P1 were larger than P2, the later provided a better meletin sustained-release profile than the former. This finding was verified by the smaller initial burst release, longer sustained-release time period, and shorter late leveling-off stage. These unanticipated results were attributed to the rounder surface, the more uniform size distribution, and the smaller total surface area of particles P2 than P1. The microformation mechanism of the modified coaxial process was suggested. The protocols reported here paved a new way for the development of new kinds of functional nanoparticles by modifying the interfaces of working fluids during electrospraying.

Multistep synthesis on SU-8: combining microfabrication and solid-phase chemistry on a single material.

PubMed

Cavalli, Gabriel; Banu, Shahanara; Ranasinghe, Rohan T; Broder, Graham R; Martins, Hugo F P; Neylon, Cameron; Morgan, Hywel; Bradley, Mark; Roach, Peter L

2007-01-01

SU-8 is an epoxy-novolac resin and a well-established negative photoresist for microfabrication and microengineering. The photopolymerized resist is an extremely highly crosslinked polymer showing outstanding chemical and physical robustness with residual surface epoxy groups amenable for chemical functionalization. In this paper we describe, for the first time, the preparation and surface modification of SU-8 particles shaped as microbars, the attachment of appropriate linkers, and the successful application of these particles to multistep solid-phase synthesis leading to oligonucleotides and peptides attached in an unambiguous manner to the support surface.

The effect of surface-bulk potential difference on the kinetics of intercalation in core-shell active cathode particles

NASA Astrophysics Data System (ADS)

Kazemiabnavi, Saeed; Malik, Rahul; Orvananos, Bernardo; Abdellahi, Aziz; Ceder, Gerbrand; Thornton, Katsuyo

2018-04-01

Surface modification of active cathode particles is commonly observed in battery research as either a surface phase evolving during the cycling process, or intentionally engineered to improve capacity retention, rate capability, and/or thermal stability of the cathode material. Here, a continuum-scale model is developed to simulate the galvanostatic charge/discharge of a cathode particle with core-shell heterostructure. The particle is assumed to be comprised of a core material encapsulated by a thin layer of a second phase that has a different open-circuit voltage. The effect of the potential difference between the surface and bulk phases (Ω) on the kinetics of lithium intercalation and the galvanostatic charge/discharge profiles is studied at different values of Ω, C-rates, and exchange current densities. The difference between the Li chemical potential in the surface and bulk phases of the cathode particle results in a concentration difference between these two phases. This leads to a charge/discharge asymmetry in the galvanostatic voltage profiles, causing a decrease in the accessible capacity of the particle. These effects are more significant at higher magnitudes of surface-bulk potential difference. The proposed model provides detailed insight into the kinetics and voltage behavior of the intercalation/de-intercalation processes in core-shell heterostructure cathode particles.

Surface modification of bioactive glass nanoparticles and the mechanical and biological properties of poly(L-lactide) composites.

PubMed

Liu, Aixue; Hong, Zhongkui; Zhuang, Xiuli; Chen, Xuesi; Cui, Yang; Liu, Yi; Jing, Xiabin

2008-07-01

Novel bioactive glass (BG) nanoparticles/poly(L-lactide) (PLLA) composites were prepared as promising bone-repairing materials. The BG nanoparticles (Si:P:Ca=29:13:58 weight ratio) of about 40nm diameter were prepared via the sol-gel method. In order to improve the phase compatibility between the polymer and the inorganic phase, PLLA (M(n)=9700Da) was linked to the surface of the BG particles by diisocyanate. The grafting ratio of PLLA was in the vicinity of 20 wt.%. The grafting modification could improve the tensile strength, tensile modulus and impact energy of the composites by increasing the phase compatibility. When the filler loading reached around 4 wt.%, the tensile strength of the composite increased from 56.7 to 69.2MPa for the pure PLLA, and the impact strength energy increased from 15.8 to 18.0 kJ m(-2). The morphology of the tensile fracture surface of the composite showed surface-grafted bioactive glass particles (g-BG) to be dispersed homogeneously in the PLLA matrix. An in vitro bioactivity test showed that, compared to pure PLLA scaffold, the BG/PLLA nanocomposite demonstrated a greater capability to induce the formation of an apatite layer on the scaffold surface. The results of marrow stromal cell culture revealed that the composites containing either BG or g-BG particles have much better biocompatibility compared to pure PLLA material.

Effect of inductively coupled plasma surface treatment on silica gel and mesoporous MCM-41 particles

NASA Astrophysics Data System (ADS)

J, A. JUAREZ-MORENO; U, CHACON-ARGAEZ; J, BARRON-ZAMBRANO; C, CARRERA-FIGUEIRAS; P, QUINTANA-OWEN; W, TALAVERA-PECH; Y, PEREZ-PADILLA; A, AVILA-ORTEGA

2018-06-01

Silica gel and MCM-41 synthesized mesoporous materials were treated with either oxygen (O2), hexamethyldisiloxane (HMDSO) and organic vapors like ethanol (EtOH), and acrylonitrile (AN) inductive plasma. The radiofrequency power for the modification was fixed to 120 W and 30 min, assuring a high degree of organic ionization energy in the plasma. The surface properties were studied by infrared spectroscopy (FTIR), scanning electron microscopy, x-ray photoelectron spectroscopy and dynamic light scattering technique was used for characterizing size distributions. When the silica and MCM-41 particles were modified by AN and HMDSO plasma gases, the surface morphology of the particles was changed, presenting another color, size or shape. In contrast, the treatments of oxygen and EtOH did not affect the surface morphology of both particles, but increased the oxygen content at the surface bigger than the AN and HMDSO plasma treatments. In this study, we investigated the influence of different plasma treatments on changes in morphology and the chemical composition of the modified particles which render them a possible new adsorbent for utilization in sorptive extraction techniques for polar compounds.

Colloid Surface Chemistry Critically Affects Multiple Particle Tracking Measurements of Biomaterials

PubMed Central

Valentine, M. T.; Perlman, Z. E.; Gardel, M. L.; Shin, J. H.; Matsudaira, P.; Mitchison, T. J.; Weitz, D. A.

2004-01-01

Characterization of the properties of complex biomaterials using microrheological techniques has the promise of providing fundamental insights into their biomechanical functions; however, precise interpretations of such measurements are hindered by inadequate characterization of the interactions between tracers and the networks they probe. We here show that colloid surface chemistry can profoundly affect multiple particle tracking measurements of networks of fibrin, entangled F-actin solutions, and networks of cross-linked F-actin. We present a simple protocol to render the surface of colloidal probe particles protein-resistant by grafting short amine-terminated methoxy-poly(ethylene glycol) to the surface of carboxylated microspheres. We demonstrate that these poly(ethylene glycol)-coated tracers adsorb significantly less protein than particles coated with bovine serum albumin or unmodified probe particles. We establish that varying particle surface chemistry selectively tunes the sensitivity of the particles to different physical properties of their microenvironments. Specifically, particles that are weakly bound to a heterogeneous network are sensitive to changes in network stiffness, whereas protein-resistant tracers measure changes in the viscosity of the fluid and in the network microstructure. We demonstrate experimentally that two-particle microrheology analysis significantly reduces differences arising from tracer surface chemistry, indicating that modifications of network properties near the particle do not introduce large-scale heterogeneities. Our results establish that controlling colloid-protein interactions is crucial to the successful application of multiple particle tracking techniques to reconstituted protein networks, cytoplasm, and cells. PMID:15189896

Electrophoresis in ice surface grooves for probing protein affinity to a specific plane of ice crystal.

PubMed

Inagawa, Arinori; Okada, Yusuke; Okada, Tetsuo

2018-06-01

Channel-like grooves are formed on the surface of frozen aqueous sucrose. They are filled with a freeze concentrated solution (FCS) and act as an efficient size-tunable separation field for micro and nanoparticles. The width of the channel can be easily varied by changing the temperature. Because the channel width decreases with decreasing temperature, particles become immobilized due to physical interference from the ice wall when the temperature reaches a threshold point specific to the particle size. Surface modification of particles can add a factor of chemical interaction between the particles and ice walls. In this study, anti-freeze proteins (AFPs) are anchored on 1µm-polystyrene (PS) particles, and their behavior in the surface grooves on the ice is studied. The threshold temperature is an effective criterion for evaluating chemical interactions between particles and ice walls. The AFP binding on 1µm PS particles lowers the threshold temperature by 2.5°C, indicating interactions between AFPs on the PS particles and the ice wall. Because the AFPs studied here show selectivity towards the prism plane, it is critical that the prism plane of the ice crystal is in contact with the FCS in the surface grooves. Copyright © 2017 Elsevier B.V. All rights reserved.

Long-circulating Janus nanoparticles made by electrohydrodynamic co-jetting for systemic drug delivery applications.

PubMed

Rahmani, Sahar; Villa, Carlos H; Dishman, Acacia F; Grabowski, Marika E; Pan, Daniel C; Durmaz, Hakan; Misra, Asish C; Colón-Meléndez, Laura; Solomon, Michael J; Muzykantov, Vladimir R; Lahann, Joerg

2015-01-01

Nanoparticles with controlled physical properties have been widely used for controlled release applications. In addition to shape, the anisotropic nature of the particles can be an important design criterion to ensure selective surface modification or independent release of combinations of drugs. Electrohydrodynamic (EHD) co-jetting is used for the fabrication of uniform anisotropic nanoparticles with individual compartments and initial physicochemical and biological characterization is reported. EHD co-jetting is used to create nanoparticles, which are characterized at each stage with scanning electron microscopy (SEM), structured illumination microscopy (SIM), dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). Surface immobilization techniques are used to incorporate polyethylene glycol (PEG) and I(125) radiolabels into the nanoparticles. Particles are injected in mice and the particle distribution after 1, 4 and 24 hours is assessed. Nanoparticles with an average diameter of 105.7 nm are prepared by EHD co-jetting. The particles contain functional chemical groups for further surface modification and radiolabeling. The density of PEG molecules attached to the surface of nanoparticles is determined to range between 0.02 and 6.04 ligands per square nanometer. A significant fraction of the nanoparticles (1.2% injected dose per mass of organ) circulates in the blood after 24 h. EHD co-jetting is a versatile method for the fabrication of nanoparticles for drug delivery. Circulation of the nanoparticles for 24 h is a pre-requisite for subsequent studies to explore defined targeting of the nanoparticles to a specific anatomic site.

Erythrocyte membrane-camouflaged polymeric nanoparticles as a biomimetic delivery platform

PubMed Central

Hu, Che-Ming J.; Zhang, Li; Aryal, Santosh; Cheung, Connie; Fang, Ronnie H.; Zhang, Liangfang

2011-01-01

Efforts to extend nanoparticle residence time in vivo have inspired many strategies in particle surface modifications to bypass macrophage uptake and systemic clearance. Here we report a top-down biomimetic approach in particle functionalization by coating biodegradable polymeric nanoparticles with natural erythrocyte membranes, including both membrane lipids and associated membrane proteins for long-circulating cargo delivery. The structure, size and surface zeta potential, and protein contents of the erythrocyte membrane-coated nanoparticles were verified using transmission electron microscopy, dynamic light scattering, and gel electrophoresis, respectively. Mice injections with fluorophore-loaded nanoparticles revealed superior circulation half-life by the erythrocyte-mimicking nanoparticles as compared to control particles coated with the state-of-the-art synthetic stealth materials. Biodistribution study revealed significant particle retention in the blood 72 h following the particle injection. The translocation of natural cellular membranes, their associated proteins, and the corresponding functionalities to the surface of synthetic particles represents a unique approach in nanoparticle functionalization. PMID:21690347

Stratospheric aerosol modification by supersonic transport operations with climate implications

NASA Technical Reports Server (NTRS)

Toon, O. B.; Turco, R. P.; Pollack, J. B.; Whitten, R. C.; Poppoff, I. G.; Hamill, P.

1980-01-01

The potential effects on stratospheric aerosois of supersonic transport emissions of sulfur dioxide gas and submicron size soot granules are estimated. An interactive particle-gas model of the stratospheric aerosol is used to compute particle changes due to exhaust emissions, and an accurate radiation transport model is used to compute the attendant surface temperature changes. It is shown that a fleet of several hundred supersonic aircraft, operating daily at 20 km, could produce about a 20% increase in the concentration of large particles in the stratosphere. Aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K.

[Study on process and principle of lactose grinding modification to decrease hygroscopic of Rhodiolae Crenulatae Radix et Rhizoma extract].

PubMed

Zhang, Ding-Kun; Zhang, Fang; Lin, Jun-Zhi; Han, Li; Wu, Zhen-Feng; Yang, Ying-Guang; Yang, Ming

2014-04-01

In this paper, Rhodiolae Crenulatae Radix et Rhizoma extract,with high hygroscopic,was selected as research model, while lactose was selected as modifiers to study the effect of the grinding modification method on the hygroscopic. Subsequently, particle size distribution, scannin electron microscopy, infrared spectroscopy and surface properties were adopted for a phase analysis. The results showed that the modified extract, prepared by Rhodiolae Crenulatae Radix et Rhizoma extract grinding 5 min with the same amount of lactose UP2, which hygroscopic initial velocity, acceleration, and critical relative humidity moisture were less than that of Rhodiolae Crenulatae Radix et Rhizoma extract and the mixture dramatically. In addition, compared with the mixture, the size distribution of modified extract was much less, the microstructure was also difference, while the infrared spectroscopy and surface properties were similar with that of lactose. It is the main principle that lactose particle adhered to the surface of Rhodiolae Crenulatae Radix et Rhizoma extract after grinding mofication to decress the moisture obviously.

RF plasma based selective modification of hydrophilic regions on super hydrophobic surface

NASA Astrophysics Data System (ADS)

Lee, Jaehyun; Hwang, Sangyeon; Cho, Dae-Hyun; Hong, Jungwoo; Shin, Jennifer H.; Byun, Doyoung

2017-02-01

Selective modification and regional alterations of the surface property have gained a great deal of attention to many engineers. In this paper, we present a simple, a cost-effective, and amendable reforming method for disparate patterns of hydrophilic regions on super-hydrophobic surfaces. Uniform super-hydrophobic layer (Contact angle; CA > 150°, root mean square (RMS) roughness ∼0.28 nm) can be formed using the atmospheric radio frequency (RF) plasma on top of the selective hydrophilic (CA ∼ 70°, RMS roughness ∼0.34 nm) patterns imprinted by electrohydrodynamic (EHD) jet printing technology with polar alcohols (butyl carbitol or ethanol). The wettability of the modified surface was investigated qualitatively utilizing scanning electron microscopy (SEM), atomic force microscopy (AFM), and wavelength scanning interferometer (WSI). Secondary ion mass spectroscopy (SIMS) analysis showed that the alcohol addiction reaction changed the types of radicals on the super-hydrophobic surface. The wettability was found to depend sensitively on chemical radicals on the surface, not on surface morphology (particle size and surface roughness). Furthermore, three different kinds of representative hydrophilic samples (polystyrene nano-particle aqueous solution, Salmonella bacteria medium, and poly(3,4-ethylenediocythiophene) ink) were tested for uniform deposition onto the desired hydrophilic regions. This simple strategy would have broad applications in various research fields that require selective deposition of target materials.

Chemical modification of M13 bacteriophage and its application in cancer cell imaging.

PubMed

Li, Kai; Chen, Yi; Li, Siqi; Nguyen, Huong Giang; Niu, Zhongwei; You, Shaojin; Mello, Charlene M; Lu, Xiaobing; Wang, Qian

2010-07-21

The M13 bacteriophage has been demonstrated to be a robust scaffold for bionanomaterial development. In this paper, we report on the chemical modifications of three kinds of reactive groups, i.e., the amino groups of lysine residues or N-terminal, the carboxylic acid groups of aspartic acid or glutamic acid residues, and the phenol group of tyrosine residues, on M13 surface. The reactivity of each group was identified through conjugation with small fluorescent molecules. Furthermore, the regioselectivity of each reaction was investigated by HPLC-MS-MS. By optimizing the reaction condition, hundreds of fluorescent moieties could be attached to create a highly fluorescent M13 bacteriophage. In addition, cancer cell targeting motifs such as folic acid could also be conjugated onto the M13 surface. Therefore, dual-modified M13 particles with folic acid and fluorescent molecules were synthesized via the selective modification of two kinds of reactive groups. Such dual-modified M13 particles showed very good binding affinity to human KB cancer cells, which demonstrated the potential applications of M13 bacteriophage in bioimaging and drug delivery.

Spectroscopic studies of conformational changes of β-lactoglobulin adsorbed on gold nanoparticle surfaces.

PubMed

Winuprasith, Thunnalin; Suphantharika, Manop; McClements, David Julian; He, Lili

2014-02-15

In this work, we investigated the conformational changes of a globular protein (β-lactoglobulin, β-lg) coated on the surface of 200 nm gold nanoparticles (GNPs) using a number of analytical techniques: dynamic light scattering (DLS); particle electrophoresis (ζ-potential); localized surface plasmon resonance (LSPR) spectroscopy; transmission electron microscopy (TEM); and surface-enhanced Raman scattering (SERS). The β-lg (pH 3) concentration had a pronounced effect on the aggregation and surface charge of β-lg-coated GNPs. The surface charge of GNPs changed from negative to positive as increasing amounts of β-lg molecule were added, indicating that the globular protein molecules adsorbed to the surfaces of the particles. Extensive particle aggregation occurred when β-lg did not saturate the GNP surfaces, which was attributed to electrostatic bridging flocculation. Modifications in LSPR and SERS spectra after addition of β-lg to the GNP suspensions supported the adsorption of β-lg to the particle surfaces. Moreover, SERS highlighted the importance of a number of specific molecular groups in the binding interaction, and suggested conformational changes of the globular protein after adsorption. This research provides useful information for characterizing and understanding the interactions between globular proteins and colloidal particles. Copyright © 2013 Elsevier Inc. All rights reserved.

Tough and Reinforced Polypropylene/Kaolin Composites using Modified Kaolin

NASA Astrophysics Data System (ADS)

Yao, J. L.; Zhu, H. X.; Qi, Y. B.; Guo, M. J.; Hu, Q.; Gao, L.

2018-05-01

Polypropylene (PP)/kaolin composites have been prepared by filling modified kaolin with diethylenetriaminepentaacetic acid (DTPA) into the PP matrix. The surface modification of kaolin particles effectively improves the compatibility between kaolin and PP matrix. It is conducive for uniform dispersion of inorganic particles in the matrix, and enhances the mechanical performance of the composites. Compared with plain kaolin, the mechanical properties of the modified composites exhibit higher tensile strength, bending strength, impact strength and melt index simultaneously. The DTPA modification of kaolin overall enhances the mechanical properties of PP composites. It meets the requirements in various applications, and makes the modified experiment interesting in modern teaching.

A study on the preparation of floating photocatalyst supported by hollow TiO2 and its performance

NASA Astrophysics Data System (ADS)

Wang, Jingang; He, Bin; Kong, Xiang Z.

2015-02-01

This research used hollow glass microspheres (HGMS) as carrier and polystyrene (PSt) as template. PSt was loaded on HGMS surface through the modification by silane coupler. Next, amorphous titanium dioxide (TiO2) produced through tetrabutyl titanate (TBT) hydrolysis precipitated on PSt surface, forming HGMS/PSt/TiO2 particles. Lastly, using the calcinations method, this research obtained anatase TiO2, eliminated PSt, and ultimately acquired composite particles with hollow TiO2 loaded on HGMS surface (HGMSHT). SEM results presented that hollow TiO2 was compact on HGMS surface and a multilayer network structure was formed. The specific surface area of HGMSHT particles was 26 m2/g, which was much larger than that of HGMS/TiO2 (HGMST) composite particles (5.6 m2/g) through direct TBT hydrolysis. Results of catalytic degradation experiment with Rhodamine B and phenol under UV light and sunlight demonstrated that due to larger TiO2 load capacity and specific surface area, the catalytic activity of HGMSHT composite particles was significantly more desirable than that of HGMST, and the catalyst presented satisfactory stability.

Surface modification of malachite with ethanediamine and its effect on sulfidization flotation

NASA Astrophysics Data System (ADS)

Feng, Qicheng; Zhao, Wenjuan; Wen, Shuming

2018-04-01

Ethanediamine was used to modify the mineral surface of malachite to improve its sulfidization and flotation behavior. The activation mechanism was investigated by adsorption experiments, X-ray photoelectron spectroscopy (XPS) analysis, and zeta potential measurements. Microflotation experiments showed that the flotation recovery of malachite was enhanced after the pretreatment of the mineral particles with ethanediamine prior to the addition of Na2S. Adsorption tests revealed that numerous sulfide ion species in the pulp solution were transferred onto the mineral surface through the formation of more copper sulfide species. This finding was confirmed by the results of the XPS measurements. Ethanediamine modification not only increased the contents of copper sulfide species on the malachite surface but also enhanced the reactivity of the sulfidization products. During sulfidization, Cu(II) species on the mineral surface were reduced into Cu(I) species, and the percentages of S22- and Sn2- relative to the total S increased after modification, resulting in increased surface hydrophobicity. The results of zeta potential measurements showed that the ethanediamine-modified mineral surface adsorbed with more sulfide ion species was advantageous to the attachment of xanthate species, thereby improving malachite floatability. The proposed ethanediamine modification followed by sulfidization xanthate flotation exhibits potential for industrial application.

Influences of surface modification of nano-silica by silane coupling agents on the thermal and frictional properties of cyanate ester resin

NASA Astrophysics Data System (ADS)

Chuang, Wang; Geng-sheng, Jiao; Lei, Peng; Bao-lin, Zhu; Ke-zhi, Li; Jun-long, Wang

2018-06-01

The surface of nano-silicon dioxide (nano-SiO2) particles was modified by small molecular coupling agent KH-560 and macromolecular coupling agent SEA-171, respectively, to change the surface activity and structure. The modified nano-SiO2 was then used for reinforcing cyanate ester resin (CE). Influences of the content of nano-SiO2 and the interfacial structure over the thermal and frictional properties of nano-SiO2/CE composites were investigated. The mechanism of the surface modification of silicon dioxide by KH-560 and SEA-171 was discussed. The experimental results show that the addition of coupling agents increased the interfacial bonding between nano-SiO2 particles and the CE resin so that the heat resistance and friction properties of the composites were improved. After surface treatment of nano-SiO2 by SEA-171, the thermal decomposition temperature of the 3.0 wt% nano-SiO2/CE composites increased nearly by 75 °C and the frictional coefficient was reduced by 25% compared with that of the pure CE, and the wear resistance increased by 77%.

Electrochemical performance of LiCoO 2 cathodes by surface modification using lanthanum aluminum garnet

NASA Astrophysics Data System (ADS)

Lu, Cheng-Zhang; Chen, Jin-Ming; Cho, Yung-Da; Hsu, Wen-Hsiang; Muralidharan, P.; Fey, George Ting-Kuo

LiCoO 2 particles were coated with various wt.% of lanthanum aluminum garnets (3LaAlO 3:Al 2O 3) by an in situ sol-gel process, followed by calcination at 1123 K for 12 h in air. X-ray diffraction (XRD) patterns confirmed the formation of a 3LaAlO 3:Al 2O 3 compound and the in situ sol-gel process synthesized 3LaAlO 3:Al 2O 3-coated LiCoO 2 was a single-phase hexagonal α-NaFeO 2-type structure of the core material without any modification. Scanning electron microscope (SEM) images revealed a modification of the surface of the cathode particles. Transmission electron microscope (TEM) images exposed that the surface of the core material was coated with a uniform compact layer of 3LaAlO 3:Al 2O 3, which had an average thickness of 40 nm. Galvanostatic cycling studies demonstrated that the 1.0 wt.% 3LaAlO 3:Al 2O 3-coated LiCoO 2 cathode showed excellent cycle stability of 182 cycles, which was much higher than the 38 cycles sustained by the pristine LiCoO 2 cathode material when it was charged at 4.4 V.

Study of Perfluorophosphonic Acid Surface Modifications on Zinc Oxide Nanoparticles.

PubMed

Quiñones, Rosalynn; Shoup, Deben; Behnke, Grayce; Peck, Cynthia; Agarwal, Sushant; Gupta, Rakesh K; Fagan, Jonathan W; Mueller, Karl T; Iuliucci, Robbie J; Wang, Qiang

2017-11-28

In this study, perfluorinated phosphonic acid modifications were utilized to modify zinc oxide (ZnO) nanoparticles because they create a more stable surface due to the electronegativity of the perfluoro head group. Specifically, 12-pentafluorophenoxydodecylphosphonic acid, 2,3,4,5,6-pentafluorobenzylphosphonic acid, and (1H,1H,2H,2H-perfluorododecyl)phosphonic acid have been used to form thin films on the nanoparticle surfaces. The modified nanoparticles were then characterized using infrared spectroscopy, X-ray photoelectron spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. Dynamic light scattering and scanning electron microscopy-energy dispersive X-ray spectroscopy were utilized to determine the particle size of the nanoparticles before and after modification, and to analyze the film coverage on the ZnO surfaces, respectively. Zeta potential measurements were obtained to determine the stability of the ZnO nanoparticles. It was shown that the surface charge increased as the alkyl chain length increases. This study shows that modifying the ZnO nanoparticles with perfluorinated groups increases the stability of the phosphonic acids adsorbed on the surfaces. Thermogravimetric analysis was used to distinguish between chemically and physically bound films on the modified nanoparticles. The higher weight loss for 12-pentafluorophenoxydodecylphosphonic acid and (1H,1H,2H,2H-perfluorododecyl)phosphonic acid modifications corresponds to a higher surface concentration of the modifications, and, ideally, higher surface coverage. While previous studies have shown how phosphonic acids interact with the surfaces of ZnO, the aim of this study was to understand how the perfluorinated groups can tune the surface properties of the nanoparticles.

Repetitive heterocoagulation of oppositely charged particles for enhancement of magnetic nanoparticle loading into monodisperse silica particles.

PubMed

Matsumoto, Hideki; Nagao, Daisuke; Konno, Mikio

2010-03-16

Oppositely charged particles were repetitively heterocoagulated to fabricate highly monodisperse magnetic silica particles with high loading of magnetic nanoparticles. Positively charged magnetic nanoparticles prepared by surface modification with N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TSA) were used to heterocoagulate with silica particles under basic conditions to give rise to negative silica surface charge and prevent the oxidation of the magnetic nanoparticles. The resultant particles of silica core homogeneously coated with the magnetic nanoparticles were further coated with thin silica layer with sodium silicate in order to enhance colloidal stability and avoid desorption of the magnetic nanoparticles from the silica cores. Five repetitions of the heterocoagulation and the silica coating could increase saturation magnetization of the magnetic silica particles to 27.7 emu/g, keeping the coefficient of variation of particle sizes (C(V)) less than 6.5%. Highly homogeneous loading of the magnetic component was confirmed by measuring Fe-to-Si atomic ratios of individual particles with energy dispersive X-ray spectroscopy.

Morphology and texture of particles along the Spirit rover traverse from sol 450 to sol 745

NASA Astrophysics Data System (ADS)

Yingst, R. A.; Crumpler, L.; Farrand, W. H.; Li, R.; Cabrol, N. A.; Neakrase, L. D.

2008-12-01

We quantified and classified the shape, roundness, size, and texture of 935 loose surface particles along the Spirit rover traverse from sols 450-745 to assess origin, transport, and other alteration mechanisms that altered particles during and after formation. Variation in particle morphologic parameters along traverse is consistent with crossing mapped geologic unit boundaries. Texture is divided into four types: vesicular, smooth and flat-faceted, rough and flat-faceted, and very rough. Sphericity and roundness are intermediate and low, respectively, comparable to particles moved by high-energy transport or to crushed particles. This indicates intermittent, high-energy emplacement or modification of a single lithology, rather than systematic, continuous low-energy abrasion or wear over time. Comparison with particle morphology at other Mars landing sites is consistent with the hypothesis that no secondary systematic transport or wide-scale chemical alteration was active at a significant enough level to alter macromorphology. In particular, particle morphology at the Mars Pathfinder site shows stronger evidence of abrasion than along the Spirit traverse, suggesting Mars Pathfinder particles have undergone abrasion processes that particles in this study area have not. Additionally, morphology indices have correlation coefficients near zero, indicating that a fluvial transport mechanism is likely not responsible for morphology. Morphology and texture are instead related to origin and composition rather than subsequent modification. Morphology and texture support a volcanic origin, possibly without modification, but most likely altered primarily by ballistic impact, implying that the Spirit landing site and traverse may be utilized in the future as a standard site for characterization of impact-derived morphology.

Development of viral nanoparticles for efficient intracellular delivery

NASA Astrophysics Data System (ADS)

Wu, Zhuojun; Chen, Kevin; Yildiz, Ibrahim; Dirksen, Anouk; Fischer, Rainer; Dawson, Philip E.; Steinmetz, Nicole F.

2012-05-01

Viral nanoparticles (VNPs) based on plant viruses such as Cowpea mosaic virus (CPMV) can be used for a broad range of biomedical applications because they present a robust scaffold that allows functionalization by chemical conjugation and genetic modification, thereby offering an efficient drug delivery platform that can target specific cells and tissues. VNPs such as CPMV show natural affinity to cells; however, cellular uptake is inefficient. Here we show that chemical modification of the CPMV surface with a highly reactive, specific and UV-traceable hydrazone linker allows bioconjugation of polyarginine (R5) cell penetrating peptides (CPPs), which can overcome these limitations. The resulting CPMV-R5 particles were taken up into a human cervical cancer cell line (HeLa) more efficiently than native particles. Uptake efficiency was dependent on the density of R5 peptides on the surface of the VNP; particles displaying 40 R5 peptides per CPMV (denoted as CPMV-R5H) interact strongly with the plasma membrane and are taken up into the cells via an energy-dependent mechanism whereas particles displaying 10 R5 peptides per CPMV (CPMV-R5L) are only slowly taken up. The fate of CPMV-R5 versus native CPMV particles within cells was evaluated in a co-localization time course study. It was indicated that the intracellular localization of CPMV-R5 and CPMV differs; CPMV remains trapped in Lamp-1 positive endolysosomes over long time frames; in contrast, 30-50% of the CPMV-R5 particles transitioned from the endosome into other cellular vesicles or compartments. Our data provide the groundwork for the development of efficient drug delivery formulations based on CPMV-R5.Viral nanoparticles (VNPs) based on plant viruses such as Cowpea mosaic virus (CPMV) can be used for a broad range of biomedical applications because they present a robust scaffold that allows functionalization by chemical conjugation and genetic modification, thereby offering an efficient drug delivery platform that can target specific cells and tissues. VNPs such as CPMV show natural affinity to cells; however, cellular uptake is inefficient. Here we show that chemical modification of the CPMV surface with a highly reactive, specific and UV-traceable hydrazone linker allows bioconjugation of polyarginine (R5) cell penetrating peptides (CPPs), which can overcome these limitations. The resulting CPMV-R5 particles were taken up into a human cervical cancer cell line (HeLa) more efficiently than native particles. Uptake efficiency was dependent on the density of R5 peptides on the surface of the VNP; particles displaying 40 R5 peptides per CPMV (denoted as CPMV-R5H) interact strongly with the plasma membrane and are taken up into the cells via an energy-dependent mechanism whereas particles displaying 10 R5 peptides per CPMV (CPMV-R5L) are only slowly taken up. The fate of CPMV-R5 versus native CPMV particles within cells was evaluated in a co-localization time course study. It was indicated that the intracellular localization of CPMV-R5 and CPMV differs; CPMV remains trapped in Lamp-1 positive endolysosomes over long time frames; in contrast, 30-50% of the CPMV-R5 particles transitioned from the endosome into other cellular vesicles or compartments. Our data provide the groundwork for the development of efficient drug delivery formulations based on CPMV-R5. Electronic supplementary information (ESI) available: Experimental details and additional supporting data. See DOI: 10.1039/c2nr30366c

Effect of stearic acid modified HAp nanoparticles in different solvents on the properties of Pickering emulsions and HAp/PLLA composites.

PubMed

Zhang, Ming; Wang, Ai-Juan; Li, Jun-Ming; Song, Na

2017-10-01

Stearic acid (Sa) was used to modify the surface properties of hydroxyapatite (HAp) in different solvents (water, ethanol or dichloromethane(CH 2 Cl 2 )). Effect of different solvents on the properties of HAp particles (activation ratio, grafting ratio, chemical properties), emulsion properties (emulsion stability, emulsion type, droplet morphology) as well as the cured materials (morphology, average pore size) were studied. FT-IR and XPS results confirmed the interaction occurred between stearic acid and HAp particles. Stable O/W and W/O type Pickering emulsions were prepared using unmodified and Sa modified HAp nanoparticles respectively, which indicated a catastrophic inversion of the Pickering emulsion happened possibly because of the enhanced hydrophobicity of HAp particles after surface modification. Porous materials with different structures and pore sizes were obtained using Pickering emulsion as the template via in situ evaporation solvent method. The results indicated the microstructures of cured samples are different form each other when HAp was surface modified in different solvents. HAp particles fabricated using ethanol as solvent has higher activation ratio and grafting ratio. Pickering emulsion with higher stability and cured porous materials with uniform morphology were obtained compared with samples prepared using water and CH 2 Cl 2 as solvents. In conclusion, surface modification of HAp in different solvents played a very important role for its stabilized Pickering emulsion as well as the microstructure of cured samples. It is better to use ethanol as the solvent for Sa modified HAp particles, which could increase the stability of Pickering emulsion and obtain cured samples with uniform pore size. Copyright © 2017 Elsevier B.V. All rights reserved.

Chemical surface modification of polycrystalline platinum thin-films to promote preferential chemisorption of n-hexane, piperidine, and cyclohexane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, V.; Schwank, J.; Gland, J.

In this study, hard/soft Lewis acid-base (HSAB) principles are used to modify a thin-polycrystalline platinum film to promote preferential chemisorption of molecules such as piperidine, n-hexane, and cyclohexane. Specifically, the particle size and electron density distribution of the platinum surface is modified using thermal treatment and co-adsorption of electro-positive and negative species. These studies are conducted in an ultra-high vacuum chamber. The platinum surface is characterized, before and after modification protocols, using a variety of in-situ and ex-situ techniques. These include temperature programmed desorption (TPD), both resistance change and work function measurements, and both X-ray photoelectron spectroscopy and diffraction.

Surface modification to waveguides

DOEpatents

Timberlake, John R.; Ruzic, David N.; Moore, Richard L.; Cohen, Samuel A.; Manos, Dennis M.

1983-01-01

A method of treating the interior surfaces of a waveguide to improve power transmission comprising the steps of mechanically polishing to remove surface protrusions; electropolishing to remove embedded particles; ultrasonically cleaning to remove any residue; coating the interior waveguide surfaces with an alkyd resin solution or electrophoretically depositing carbon lamp black suspended in an alkyd resin solution to form a 1.mu. to 5.mu. thick film; vacuum pyrolyzing the film to form a uniform adherent carbon coating.

Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Wei; Nallathamby, Prakash D.; Foster, Carmen M.; Morrell-Falvey, Jennifer L.; Mortensen, Ninell P.; Doktycz, Mitchel J.; Gu, Baohua; Retterer, Scott T.

2013-10-01

A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or ``free'' surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or ``free'' surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems. Electronic supplementary information (ESI) available: Cell culture preparation for dose/response imaging experiments. See DOI: 10.1039/c3nr02639f

Highly selective creation of hydrophilic micro-craters on super hydrophobic surface using electrohydrodynamic jet printing

NASA Astrophysics Data System (ADS)

Lee, Jaehyun; Hwang, Sangyeon; Prasetyo, Fariza Dian; Nguyen, Vu Dat; Hong, Jungwoo; Shin, Jennifer H.; Byun, Doyoung

2014-11-01

Selective surface modification is considered as an alternative to conventional printing techniques in high resolution patterning. Here, we present fabrication of hydrophilic patterns on the super hydrophobic surface, which makes structure on the hydrophilic region. The super hydrophobic surface is able to be chemically changed to hydrophilic with alcohols. As a consecutive process, electrohydrodynamic (EHD) jet printing was utilized to fabricate local hydrophilic craters with 30-200 μm sizes. 3 kinds of target liquids were deposited well on hydrophilic region; PEDOT (poly 3,4 ethylenediocythiophene), polystyrene nano-particles, and salmonella bacteria medium. Additionally, qualitative analysis were presented for modification mechanism and surface properties on super hydrophobic/hydrophilic by analysis of surface energy with contact angle, SEM (scanning electron microscopy) image, and SIMS (secondary ion mass spectroscopy) analysis. This new simple modification method provides possibility to be utilizing in bio-patterning engineering such as cell culturing microchip and lab on a chip. This research was supported by the Basi Science Research Program through the National Research Foundation of Korea (NRF) (Grand Number: 2014-023284).

Size-dependent reactivity of diamond nanoparticles.

PubMed

Williams, Oliver A; Hees, Jakob; Dieker, Christel; Jäger, Wolfgang; Kirste, Lutz; Nebel, Christoph E

2010-08-24

Photonic active diamond nanoparticles attract increasing attention from a wide community for applications in drug delivery and monitoring experiments as they do not bleach or blink over extended periods of time. To be utilized, the size of these diamond nanoparticles needs to be around 4 nm. Cluster formation is therefore the major problem. In this paper we introduce a new technique to modify the surface of particles with hydrogen, which prevents cluster formation in buffer solution and which is a perfect starting condition for chemical surface modifications. By annealing aggregated nanodiamond powder in hydrogen gas, the large (>100 nm) aggregates are broken down into their core ( approximately 4 nm) particles. Dispersion of these particles into water via high power ultrasound and high speed centrifugation, results in a monodisperse nanodiamond colloid, with exceptional long time stability in a wide range of pH, and with high positive zeta potential (>60 mV). The large change in zeta potential resulting from this gas treatment demonstrates that nanodiamond particle surfaces are able to react with molecular hydrogen at relatively low temperatures, a phenomenon not witnessed with larger (20 nm) diamond particles or bulk diamond surfaces.

Photocatalytic reduction of heavy metal ions on derivatized titanium dioxide nano-particle surface studied by XAFS

NASA Astrophysics Data System (ADS)

Chen, Lin X.; Rajh, Tijana; Mićić, Olga Wang, Zhiyu; Tiede, David M.; Thurnauer, Marion

1997-12-01

Photoreduction of heavy metal ions, Cu 2- and Hg 2+, on TiO 2 nano-particle surfaces, has been investigated by XAFS measurements. The effects of TiO 2 surface modification reagents on the reaction efficiency have been studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01 M Cu 2+ and TiO 2 nano-particles. Fifty percent of the adsorbed Cu 2+ has been reduced to Cu 0 after 1-h illumination with a UV-enhanced xenon lamp. Photoreduction of Hg 2+ on TiO 2 colloid surfaces was also investigated without and with thiolactic acid (TLA). In this case, the photoreduction efficiency for Hg 2+ was lowered. Structures of metal ion surroundings in various complexes as well as their role in photoreduction of metal ions are discussed.

Long-circulating Janus nanoparticles made by electrohydrodynamic co-jetting for systemic drug delivery applications

PubMed Central

Rahmani, Sahar; Villa, Carlos H.; Dishman, Acacia F.; Grabowski, Marika E.; Pan, Daniel C.; Durmaz, Hakan; Misra, Asish C; Colón-Meléndez, Laura; Solomon, Michael J.; Muzykantov, Vladimir R.; Lahann, Joerg

2016-01-01

Background Nanoparticles with controlled physical properties have been widely used for controlled release applications. In addition to shape, the anisotropic nature of the particles can be an important design criterion to ensure selective surface modification or independent release of combinations of drugs. Purpose Electrohydrodynamic (EHD) co-jetting is used for the fabrication of uniform anisotropic nanoparticles with individual compartments and initial physicochemical and biological characterization is reported. Methods EHD co-jetting is used to create nanoparticles, which are characterized at each stage with scanning electron microscopy (SEM), structured illumination microscopy (SIM), dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). Surface immobilization techniques are used to incorporate polyethylene glycol (PEG) and I125 radiolabels into the nanoparticles. Particles are injected in mice and the particle distribution after 1, 4 and 24 hours is assessed. Results and discussion Nanoparticles with an average diameter of 105.7 nm are prepared by EHD co-jetting. The particles contain functional chemical groups for further surface modification and radiolabeling. The density of PEG molecules attached to the surface of nanoparticles is determined to range between 0.02 and 6.04 ligands per square nanometer. A significant fraction of the nanoparticles (1.2% injected dose per mass of organ) circulates in the blood after 24 h. Conclusion EHD co-jetting is a versatile method for the fabrication of nanoparticles for drug delivery. Circulation of the nanoparticles for 24 h is a pre-requisite for subsequent studies to explore defined targeting of the nanoparticles to a specific anatomic site. PMID:26453170

Facile Preparation of a Robust and Durable Superhydrophobic Coating Using Biodegradable Lignin-Coated Cellulose Nanocrystal Particles

PubMed Central

Huang, Jingda; Lyu, Shaoyi

2017-01-01

It is a challenge for a superhydrophobic coating to overcome the poor robustness and the rough surface structure that is usually built using inorganic particles that are difficult to degrade. In this study, a robust superhydrophobic coating is facilely prepared by using commercial biodegradable lignin-coated cellulose nanocrystal (L-CNC) particles after hydrophobic modification to build rough surface structures, and by choosing two different adhesives (double-sided tape and quick-setting epoxy) to support adhesion between the L-CNC particles and the substrates. In addition to excellent self-cleaning and water repellence properties, the resulting coatings show outstanding mechanical strength and durability against sandpaper abrasion, finger-wipe, knife-scratch, water jet, UV radiation, high temperature, and acidic and alkali solutions, possessing a wide application prospect. PMID:28906449

A nonviral DNA delivery system based on surface modified silica-nanoparticles can efficiently transfect cells in vitro.

PubMed

Kneuer, C; Sameti, M; Bakowsky, U; Schiestel, T; Schirra, H; Schmidt, H; Lehr, C M

2000-01-01

Diverse polycationic polymers have been used as nonviral transfection agents. Here we report the ability of colloidal silica particles with covalently attached cationic surface modifications to transfect plasmid DNA in vitro and make an attempt to describe the structure of the resulting transfection complexes. In analogy to the terms lipoplex and polyplex, we propose to describe the nanoparticle-DNA complexes by the term "nanoplex". Three batches, Si10E, Si100E, and Si26H, sized between 10 and 100 nm and with zeta potentials ranging from +7 to +31 mV at pH 7.4 were evaluated. The galactosidase expression plasmid DNA pCMVbeta was immobilized on the particle surface and efficiently transfected Cos-1 cells. The transfection activity was accompanied by very low cytotoxicity, with LD(50) values in the milligrams per milliliter range. The most active batch, Si26H, was produced by modification of commercially available silica particles with N-(6-aminohexyl)-3-aminopropyltrimethoxysilane, yielding spherical nanoparticles with a mean diameter of 26 nm and a zeta potential of +31 mV at pH 7.4. Complexes of Si26H and pCMVbeta plasmid DNA formed at w/w ratios of 10 were most effective in promoting transfection of Cos-1 cells in the absence of serum. At this ratio, >90% of the DNA was associated with the particles, yielding nanoplexes with a net negative surface charge. When the transfection medium was supplemented with 10% serum, maximum gene expression was observed at a w/w ratio of 30, at which the resulting particle-DNA complexes possessed a positive surface charge. Transfection was strongly increased in the presence of 100 microM chloroquine in the incubation medium and reached approximately 30% of the efficiency of a 60 kDa polyethylenimine. In contrast to polyethylenimine, no toxicity was observed at the concentrations required. Atomic force microscopy of Si26H-DNA complexes revealed a spaghetti-meatball-like structure. The surface of complexes prepared at a w/w ratio of 30 was dominated by particles half-spheres. Complex sizes correlated well with those determined previously by dynamic light scattering.

Simple fabrication of antireflective silicon subwavelength structure with self-cleaning properties.

PubMed

Kim, Bo-Soon; Ju, Won-Ki; Lee, Min-Woo; Lee, Cheon; Lee, Seung-Gol; Beom-Hoan, O

2013-05-01

A subwavelength structure (SWS) was formed via a simple chemical wet etching using a gold (Au) catalyst. Single nano-sized Au particles were fabricated by metallic self-aggregation. The deposition and thermal annealing of the thin metallic film were carried out. Thermal annealing of a thin metallic film enables the creation of metal nano particles by isolating them from each other by means of the self-aggregation of the metal. After annealing, the samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When silicon (Si) was etched for 2 minutes using the Au nano particles, the reflectance was decreased almost 0% over the entire wavelength range from 300 to 1300 nm due to its deep and steeply double tapered structure. When given varying incident angle degrees from 30 degrees to 60 degrees, the reflectance was also maintained at less than 3%. Following this, the etched silicon was treated with a plasma-polymerized fluorocarbon (PPFC) film of about 5 nm using an ICP reactor for surface modification. The result of this surface treatment, the contact angle increased significantly from 27.5 degrees to 139.3 degrees. The surface modification was successful and maintained almost 0% reflectance because of the thin film deposition.

Fabrication and characterization of a novel hydrophobic CaCO3 grafted by hydroxylated poly(vinyl chloride) chains

NASA Astrophysics Data System (ADS)

Bao, Lixia; Yang, Simei; Luo, Xin; Lei, Jingxin; Cao, Qiue; Wang, Jiliang

2015-12-01

The hydroxylated PVC (PVC-OH) was successfully synthesized by a suspension polymerization of vinyl chloride (VC), butyl acrylate (BA) and hydroxyethyl acrylate (HEA). Novel hydrophobic CaCO3 was then prepared by a urethane formation reaction between methylene diphenyl diisocyanate (MDI) and the sbnd OH groups both in the PVC-OH chains and on the surface of pristine CaCO3 particles. The effect of the PVC-OH content on the grafting ratio of treated CaCO3 particles was extensively investigated. Combining the result of Fourier transform infrared (FTIR) with that of water contact angle, it can be concluded that the hydrophobicity of CaCO3 had been efficiently improved by the PVC-OH segments grafted on the surface of CaCO3 particles. X-ray diffraction (XRD), thermal gravity analysis (TGA), scanning electron microscope (SEM) and transmission electron microscope (TEM) were also used to study crystalline behaviors, thermal stability and surface morphology of the modified CaCO3 particles, respectively. The change of specific surface area implying surface modification was investigated as well.

Modification of surface properties of copper-refractory metal alloys

DOEpatents

Verhoeven, John D.; Gibson, Edwin D.

1993-10-12

The surface properties of copper-refractory metal (CU-RF) alloy bodies are modified by heat treatments which cause the refractory metal to form a coating on the exterior surfaces of the alloy body. The alloys have a copper matrix with particles or dendrites of the refractory metal dispersed therein, which may be niobium, vanadium, tantalum, chromium, molybdenum, or tungsten. The surface properties of the bodies are changed from those of copper to that of the refractory metal.

Surface modification to waveguides

DOEpatents

Timberlake, J.R.; Ruzic, D.N.; Moore, R.L.; Cohen, S.A.; Manos, D.M.

1982-06-16

A method is described for treating the interior surfaces of a waveguide to improve power transmission comprising the steps of mechanically polishing to remove surface protrusions; electropolishing to remove embedded particles; ultrasonically cleaning to remove any residue; coating the interior waveguide surfaces with an alkyd resin solution or electrophoretically depositing carbon lamp black suspended in an alkyd resin solution to form a 1..mu.. to 5..mu.. thick film; vacuum pyrolyzing the film to form a uniform adherent carbon coating.

Porous ceramic membrane with superhydrophobic and superoleophilic surface for reclaiming oil from oily water

NASA Astrophysics Data System (ADS)

Su, Changhong; Xu, Youqian; Zhang, Wei; Liu, Yang; Li, Jun

2012-01-01

A porous ceramic tube with superhydrophobic and superoleophilic surface was fabricated by sol-gel and then surface modification with polyurethane-polydimethysiloxane, and an oil-water separator based on the porous ceramic tube was erected to characterize superhydrophobic and superoleophilic surface's separation efficiency and velocity when being used to reclaim oil from oily water and complex oily water containing clay particle. The separator is fit for reclaiming oil from oily water.

Surface modification of lactose inhalation blends by moisture.

PubMed

Watling, C P; Elliott, J A; Scruton, C; Cameron, R E

2010-05-31

We present an investigation of the effects of relative humidity (RH) on lactose powders during storage, with the aims of determining the humidity conditions under which lactose inhalation blends are stable, and characterising the surface changes that occur as a result of water condensation. Lactose inhalation powders manufactured by milling and sieving were stored in environments of RH from 32% to 100% (at room temperature) and changes in surface properties were observed using BET nitrogen adsorption, environmental scanning electron microscopy and laser diffraction particle size analysis. We found that the specific surface area of all lactose powders decreased during storage, with the rate of decrease and final drop being larger at higher RH (ranging from a 62% decrease at 100% RH to a 34% decrease at 32% RH, at room temperature). The specific surface area decrease corresponded to a reduction in the volume of fine particles (<5 microm) in the blend. Two effects were found to contribute to the decrease in specific surface area: the smoothing of coarse particles, attributed to the surface fine particles undergoing deliquescence due to their enhanced solubility by the Kelvin effect (i.e. due to their greater curvature and consequently greater surface energy), and solid bridging between fine particles in agglomerates, such that loose fine particles disappeared from the powder blend, having bonded with coarser particles. These changes in particle properties resulting from moisture exposure are expected to influence the fine particle fraction of drug released from the powder blends, and the observation that lactose inhalation blends were unstable even at 32% RH could potentially be a concern for the pharmaceutical industry. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Method and Apparatus for the Quantification of Particulate Adhesion Forces on Various Substrates

NASA Technical Reports Server (NTRS)

Wohl, Christopher J.; Atkins, Brad M.; Connell, John W.

2011-01-01

Mitigation strategies for lunar dust adhesion have typically been limited to qualitative analysis. This technical memorandum describes the generation and operation of an adhesion testing device capable of quantitative assessment of adhesion forces between particulates and substrates. An aerosolization technique is described to coat a surface with a monolayer of particulates. Agitation of this surface, via sonication, causes particles to dislodge and be gravitationally fed into an optical particle counter. Experimentally determined adhesion force values are compared to forces calculated from van der Waals interactions and are used to calculate the work of adhesion using Johnson-Kendall-Roberts (JKR) theory. Preliminary results indicate that a reduction in surface energy and available surface area, through topographical modification, improve mitigation of particulate adhesion.

Studies of Itokawa's Surface Exposure by Measurements of Cosmic-ray Produced Nuclides

NASA Technical Reports Server (NTRS)

Caffee, M. W.; Nishiizumi, K.; Tsuchiyama, A.; Uesugi, M.; Zolensky, M. E.

2014-01-01

We plan to investigate the evolutionary history of surface materials from 25143 Itokawa, the Hayabusa samples. Our studies are based on the measurement of nuclides produced in asteroidal surface materials by cosmic rays. Cosmogenic radionuclides are used to determine the duration and nature of the exposure of materials to energetic particles. Our goals are to understand both the fundamental processes on the asteroidal surface and the evolutionary history of its surface materials. They are also key to understanding the history of Itokawa's surface and asteroid-meteoroid evolutionary dynamics. To achieve our key goals, in particular reconstructing the evolutionary histories of the asteroidal surface, we proposed: (1) characterizing Itokawa particles using SXCT, SXRD, and FE-SEM without modification of the sample; (2) embedding each particle in acrylic resin, then slicing a small corner with an ultra-microtome and examining it using super-STEM and SIMS for characterizing surface morphology, space weathering, and oxygen three-isotope analysis; and finally (3) measuring small amounts of cosmogenic radionuclides (104-105 atoms) in Hayabusa samples by AMS. However, we have to modify our plan due to unexpected situation.

Biofunctionalization of silica-coated magnetic particles mediated by a peptide

NASA Astrophysics Data System (ADS)

Care, Andrew; Chi, Fei; Bergquist, Peter L.; Sunna, Anwar

2014-08-01

A linker peptide sequence with affinity to silica-containing materials was fused to Streptococcus protein G', an antibody-binding protein. This recombinant fusion protein, linker-protein G (LPG) was produced in E. coli and exhibited strong affinity to silica-coated magnetic particles and was able to bind to them at different pHs, indicating a true pH-independent binding. LPG was used as an anchorage point for the oriented immobilization of antibodies onto the surface of the particles. These particle-bound "LPG-Antibody complexes" mediated the binding and recovery of different cell types (e.g., human stem cells, Legionella, Cryptosporidium and Giardia), enabling their rapid and simple visualization and identification. This strategy was used also for the efficient capture of Cryptosporidium oocysts from water samples. These results demonstrate that LPG can mediate the direct biofunctionalization of silica-coated magnetic particles without the need for complex surface chemical modification.

Novel surface modification of polymer-based separation media controlling separation selectivity, retentivity and generation of electroosmotic flow.

PubMed

Hosoya, Ken; Kubo, Takuya; Takahashi, Katsuo; Ikegami, Tohru; Tanaka, Nobuo

2002-12-06

Uniformly sized packing materials based on synthetic polymer particles for high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) have been prepared from polymerization mixtures containing methacrylic acid (MAA) as a functional monomer and by using a novel surface modification method. This "dispersion method" affords effectively modified separation media. Both the amount of MAA utilized in the preparation and reaction time affect the selectivity of chromatographic separation in both the HPLC and the CEC mode and electroosmotic flow. This detailed study revealed that the dispersion method effectively modified internal surface of macroporous separation media and, based on the amount of MAA introduced, exclusion mechanism for the separation of certain solutes could be observed.

Copolyimide Surface Modifying Agents for Particle Adhesion Mitigation

NASA Technical Reports Server (NTRS)

Wohl, Christopher J.; Connell, John W.

2011-01-01

Marine biofouling, insect adhesion on aircraft surfaces, microbial contamination of sterile environments, and particle contamination all present unique challenges for which researchers have adopted an array of mitigation strategies. Particulate contamination is of interest to NASA regarding exploration of the Moon, Mars, asteroids, etc.1 Lunar dust compromised seals, clogged filters, abraded visors and space suit surfaces, and was a significant health concern during the Apollo missions.2 Consequently, NASA has instituted a multi-faceted approach to address dust including use of sacrificial surfaces, active mitigation requiring the use of an external energy source, and passive mitigation utilizing materials with an intrinsic resistance to surface contamination. One passive mitigation strategy is modification of a material s surface energy either chemically or topographically. The focus of this paper is the synthesis and evaluation of novel copolyimide materials with surface modifying agents (SMA, oxetanes) enabling controlled variation of surface chemical composition.

Surface confined ionic liquid as a stationary phase for HPLC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Qian; Baker, Gary A; Baker, Sheila N

Trimethoxysilane ionosilane derivatives of room temperature ionic liquids based on alkylimidazolium bromides were synthesized for attachment to silica support material. The derivatives 1-methyl-3-(trimethoxysilylpropyl)imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl)imidazolium bromide were used to modify the surface of 3 {micro}m diameter silica particles to act as the stationary phase for HPLC. The modified particles were characterized by thermogravimetric analysis (TGA) and {sup 13}C and {sup 29}Si NMR spectroscopies. The surface modification procedure rendered particles with a surface coverage of 0.84 {micro}mol m{sup -2} for the alkylimidazolium bromide. The ionic liquid moiety was predominantly attached to the silica surface through two siloxane bonds of themore » ionosilane derivative (63%). Columns packed with the modified silica material were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic carboxylic acids as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic interaction, and other electrostatic interactions.« less

Surface and capillary forces encountered by zinc sulfide microspheres in aqueous electrolyte.

PubMed

Gillies, Graeme; Kappl, Michael; Butt, Hans-Jürgen

2005-06-21

The colloid probe technique was used to investigate the interactions between individual zinc sulfide (ZnS) microspheres and an air bubble in electrolyte solution. Incorporation of zinc ions into the electrolyte solution overcomes the disproportionate zinc ion dissolution and mimics high-volume-fraction conditions common in flotation. Determined interaction forces revealed a distinct lack of long-ranged hydrophobic forces, indicated by the presence of a DLVO repulsion prior to particle engulfment. Single microsphere contact angles were determined from particle-bubble interactions. Contact angles increased with decreasing radii and with surface oxidation. Surface modification by the absorption of copper and subsequently potassium O-ethyldithiocarbonate (KED) reduced repulsive forces and strongly increased contact angles.

Adhesion force interactions between cyclopentane hydrate and physically and chemically modified surfaces.

PubMed

Aman, Zachary M; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

2014-12-07

Interfacial interactions between liquid-solid and solid-solid phases/surfaces are of fundamental importance to the formation of hydrate deposits in oil and gas pipelines. This work establishes the effect of five categories of physical and chemical modification to steel on clathrate hydrate adhesive force: oleamide, graphite, citric acid ester, nonanedithiol, and Rain-X anti-wetting agent. Hydrate adhesive forces were measured using a micromechanical force apparatus, under both dry and water-wet surface conditions. The results show that the graphite coating reduced hydrate-steel adhesion force by 79%, due to an increase in the water wetting angle from 42 ± 8° to 154 ± 7°. Two chemical surface coatings (nonanedithiol and the citric acid ester) induced rapid hydrate growth in the hydrate particles; nonanedithiol increased hydrate adhesive force by 49% from the baseline, while the citric acid ester coating reduced hydrate adhesion force by 98%. This result suggests that crystal growth may enable a strong adhesive pathway between hydrate and other crystalline structures, however this effect may be negated in cases where water-hydrocarbon interfacial tension is minimised. When a liquid water droplet was placed on the modified steel surfaces, the graphite and citric acid ester became less effective at reducing adhesive force. In pipelines containing a free water phase wetting the steel surface, chemical or physical surface modifications alone may be insufficient to eliminate hydrate deposition risk. In further tests, the citric acid ester reduced hydrate cohesive forces by 50%, suggesting mild activity as a hybrid anti-agglomerant suppressing both hydrate deposition and particle agglomeration. These results demonstrate a new capability to develop polyfunctional surfactants, which simultaneously limit the capability for hydrate particles to aggregate and deposit on the pipeline wall.

A new setup for the investigation of swift heavy ion induced particle emission and surface modifications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meinerzhagen, F.; Breuer, L.; Bukowska, H.

2016-01-15

The irradiation with fast ions with kinetic energies of >10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations, which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion, and neutral mass spectrometry, as well as low energy electron diffraction undermore » ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany. Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup, particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator.« less

Unraveling atomic-level self-organization at the plasma-material interface

NASA Astrophysics Data System (ADS)

Allain, J. P.; Shetty, A.

2017-07-01

The intrinsic dynamic interactions at the plasma-material interface and critical role of irradiation-driven mechanisms at the atomic scale during exposure to energetic particles require a priori the use of in situ surface characterization techniques. Characterization of ‘active’ surfaces during modification at atomic-scale levels is becoming more important as advances in processing modalities are limited by an understanding of the behavior of these surfaces under realistic environmental conditions. Self-organization from exposure to non-equilibrium and thermalized plasmas enable dramatic control of surface morphology, topography, composition, chemistry and structure yielding the ability to tune material properties with an unprecedented level of control. Deciphering self-organization mechanisms of nanoscale morphology (e.g. nanodots, ripples) and composition on a variety of materials including: compound semiconductors, semiconductors, ceramics, polymers and polycrystalline metals via low-energy ion-beam assisted plasma irradiation are critical to manipulate functionality in nanostructured systems. By operating at ultra-low energies near the damage threshold, irradiation-driven defect engineering can be optimized and surface-driven mechanisms controlled. Tunability of optical, electronic, magnetic and bioactive properties is realized by reaching metastable phases controlled by atomic-scale irradiation-driven mechanisms elucidated by novel in situ diagnosis coupled to atomistic-level computational tools. Emphasis will be made on tailored surface modification from plasma-enhanced environments on particle-surface interactions and their subsequent modification of hard and soft matter interfaces. In this review, we examine current trends towards in situ and in operando surface and sub-surface characterization to unravel atomic-scale mechanisms at the plasma-material interface. This work will emphasize on recent advances in the field of plasma and ion-induced nanopatterning and nanostructuring as well as ultra-thin film deposition. Future outlook will examine the critical role of complementary surface-sensitive techniques and trends towards advances in both in situ and in operando tooling.

Thermo-mechanical characterization of siliconized E-glass fiber/hematite particles reinforced epoxy resin hybrid composite

NASA Astrophysics Data System (ADS)

V. R., Arun prakash; Rajadurai, A.

2016-10-01

In this present work hybrid polymer (epoxy) matrix composite has been strengthened with surface modified E-glass fiber and iron(III) oxide particles with varying size. The particle sizes of 200 nm and <100 nm has been prepared by high energy ball milling and sol-gel methods respectively. To enhance better dispersion of particles and improve adhesion of fibers and fillers with epoxy matrix surface modification process has been done on both fiber and filler by an amino functional silane 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized iron(III) oxide particles were characterized by XRD and FTIR spectroscopy analysis. Fixed quantity of surface treated 15 vol% E-glass fiber was laid along with 0.5 and 1.0 vol% of iron(III) oxide particles into the matrix to fabricate hybrid composites. The composites were cured by an aliphatic hardener Triethylenetetramine (TETA). Effectiveness of surface modified particles and fibers addition into the resin matrix were revealed by mechanical testing like tensile testing, flexural testing, impact testing, inter laminar shear strength and hardness. Thermal behavior of composites was evaluated by TGA, DSC and thermal conductivity (Lee's disc). The scanning electron microscopy was employed to found shape and size of iron(III) oxide particles adhesion quality of fiber with epoxy matrix. Good dispersion of fillers in matrix was achieved with surface modifier APTMS. Tensile, flexural, impact and inter laminar shear strength of composites was improved by reinforcing surface modified fiber and filler. Thermal stability of epoxy resin was improved when surface modified fiber was reinforced along with hard hematite particles. Thermal conductivity of epoxy increased with increase of hematite content in epoxy matrix.

Development of Advanced Coatings for Laser Modifications Through Process and Materials Simulation

NASA Astrophysics Data System (ADS)

Martukanitz, R. P.; Babu, S. S.

2004-06-01

A simulation-based system is currently being constructed to aid in the development of advanced coating systems for laser cladding and surface alloying. The system employs loosely coupled material and process models that allow rapid determination of material compatibility over a wide range of processing conditions. The primary emphasis is on the development and identification of composite coatings for improved wear and corrosion resistance. The material model utilizes computational thermodynamics and kinetic analysis to establish phase stability and extent of diffusional reactions that may result from the thermal response of the material during virtual processing. The process model is used to develop accurate thermal histories associated with the laser surface modification process and provides critical input for the non-isothermal materials simulations. These techniques were utilized to design a laser surface modification experiment that utilized the addition of stainless steel alloy 431 and TiC produced using argon and argon and nitrogen shielding. The deposits representing alloy 431 and TiC powder produced in argon resulted in microstructures retaining some TiC particles and an increase in hardness when compared to deposits produced using only the 431 powder. Laser deposits representing alloy 431 and TiC powder produced with a mixture of argon and nitrogen shielding gas resulted in microstructures retaining some TiC particles, as well as fine precipitates of Ti(CN) formed during cooling and a further increase in hardness of the deposit.

Affinity Electrophoresis Using Ligands Attached To Polymers

NASA Technical Reports Server (NTRS)

Van Alstine, James M.; Snyder, Robert S.; Harris, J. M.; Brooks, D. E.

1990-01-01

In new technique, reduction of electrophoretic mobilities by addition of polyethylene glycol to ligands increases electrophoretic separabilities. In immuno-affinity electrophoresis, modification of ligands extends specificity of electrophoretic separation to particles having surface electric-charge structures otherwise making them electrophoretically inseparable. Modification of antibodies by polyethylene glycol greatly reduces ability to aggregate while enhancing ability to affect electrophoretic mobilities of cells. In hydrophobic-affinity electrophoresis, addition of polyethylene glycol reduces tendency toward aggregation of cells or macromolecules.

Effect of crystal habits on the surface energy and cohesion of crystalline powders.

PubMed

Shah, Umang V; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Gamble, John F; Tobyn, Michael J; Heng, Jerry Y Y

2014-09-10

The role of surface properties, influenced by particle processing, in particle-particle interactions (powder cohesion) is investigated in this study. Wetting behaviour of mefenamic acid was found to be anisotropic by sessile drop contact angle measurements on macroscopic (>1cm) single crystals, with variations in contact angle of water from 56.3° to 92.0°. This is attributed to variations in surface chemical functionality at specific facets, and confirmed using X-ray photoelectron spectroscopy (XPS). Using a finite dilution inverse gas chromatography (FD-IGC) approach, the surface energy heterogeneity of powders was determined. The surface energy profile of different mefenamic acid crystal habits was directly related to the relative exposure of different crystal facets. Cohesion, determined by a uniaxial compression test, was also found to relate to surface energy of the powders. By employing a surface modification (silanisation) approach, the contribution from crystal shape from surface area and surface energy was decoupled. By "normalising" contribution from surface energy and surface area, needle shaped crystals were found to be ∼2.5× more cohesive compared to elongated plates or hexagonal cuboid shapes crystals. Copyright © 2014. Published by Elsevier B.V.

The impact of size on particulate vaccine adjuvants.

PubMed

Shah, Ruchi R; O'Hagan, Derek T; Amiji, Mansoor M; Brito, Luis A

2014-12-01

Particulate adjuvants have been successful at inducing increased immune responses against many poorly immunogenic antigens. However, the mechanism of action of these adjuvants often remains unclear. As more potential vaccine targets are emerging, it is becoming necessary to broaden our knowledge on the factors involved in generating potent immune responses to recombinant antigens with adjuvants. While composition of adjuvants is integral in defining the overall performance of an adjuvant, some physical parameters such as particle size, surface charge and surface modification may also contribute to the potency. In this review, we will try to highlight the role of particle size in controlling the immune responses to adjuvanted vaccines, with a focus on insoluble aluminum salts, oil-in-water emulsions, polymeric particles and liposomes.

Surface Plasmon Resonance Evaluation of Colloidal Metal Aerogel Filters

NASA Technical Reports Server (NTRS)

Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

1997-01-01

We have fabricated aerogels containing gold, silver, and platinum nanoparticles for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to porous or heterogeneous media. Specifically, we apply the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs further modification for aggregated or surfactant modified systems. Additionally, the kinetics suggest that collective particle interactions in coagulated clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

Modification and investigation of silica particles as a foam stabilizer

NASA Astrophysics Data System (ADS)

Zhu, Qian; Zhou, Hua-lei; Song, Ying-xiao; Chang, Zhi-dong; Li, Wen-jun

2017-02-01

As a solid foam stabilizer, spherical silica particles with diameters ranging from 150 to 190 nm were prepared via an improved Stöber method and were subsequently modified using three different silane coupling agents to attain the optimum surface hydrophobicity of the particles. Fourier transform infrared (FTIR) spectra and the measured contact angles were used to characterize the surface properties of the prepared particles. The foam stability was investigated by the foam drainage half-life and the expansion viscoelastic modulus of the liquid film. The results demonstrate that all of the modified silica nanoparticles effectively improve the foam stability. The surface hydrophobicity of the modified particles is found to be a key factor influencing the foam stability. The optimum contact angle of the particles lies in the approximate range from 50° to 55°. The modifier molecular structure used can also influence the stabilizing foam property of the solid particles. The foam system stabilized by (CH3)2SiCl2-modified silica particles exhibits the highest stability; its drainage half-life at maximum increases by 27% compared to that of the blank foam system and is substantially greater than those of the foam systems stabilized by KH570- and KH550-modified particles.

Identification of the functional groups on the surface of nanoparticles formed in photonucleation of aldehydes generated during forest fire events

NASA Astrophysics Data System (ADS)

Dultsev, Fedor N.; Mik, Ivan A.; Dubtsov, Sergei N.; Dultseva, Galina G.

2014-11-01

We describe the new procedure developed to determine the functional groups on the surface of nanoparticles formed in photonucleation of furfural, one of the aldehydes generated during forest fire events. The procedure is based on the detection of nanoparticle rupture from chemically modified surface of the quartz crystal microbalance oscillating in the thickness shear mode under voltage sweep. The rupture force is determined from the voltage at which the rupture occurs. It depends on particle mass and on the affinity of the surface functional groups of the particle to the groups that are present on the modified QCM surface. It was demonstrated with the amine modification of the surface that the nanoparticles formed in furfural photonucleation contain carbonyl and carboxyl groups. The applicability of the method for the investigation of functional groups on the surface of the nanoparticles of atmospheric aerosol is demonstrated.

Reduction of calcium flux from the extracellular region and endoplasmic reticulum by amorphous nano-silica particles owing to carboxy group addition on their surface.

PubMed

Onodera, Akira; Yayama, Katsutoshi; Morosawa, Hideto; Ishii, Yukina; Tsutsumi, Yasuo; Kawai, Yuichi

2017-03-01

Several studies have reported that amorphous nano-silica particles (nano-SPs) modulate calcium flux, although the mechanism remains incompletely understood. We thus analyzed the relationship between calcium flux and particle surface properties and determined the calcium flux route. Treatment of Balb/c 3T3 fibroblasts with nano-SPs with a diameter of 70 nm (nSP70) increased cytosolic calcium concentration, but that with SPs with a diameter of 300 or 1000 nm did not. Surface modification of nSP70 with a carboxy group also did not modulate calcium flux. Pretreatment with a general calcium entry blocker almost completely suppressed calcium flux by nSP70. Preconditioning by emptying the endoplasmic reticulum (ER) calcium stores slightly suppressed calcium flux by nSP70. These results indicate that nSP70 mainly modulates calcium flux across plasma membrane calcium channels, with subsequent activation of the ER calcium pump, and that the potential of calcium flux by nano-SPs is determined by the particle surface charge.

Poly(organo phosphazene) nanoparticles surface modified with poly(ethylene oxide).

PubMed

Vandorpe, J; Schacht, E; Stolnik, S; Garnett, M C; Davies, M C; Illum, L; Davis, S S

1996-10-05

The use of biodegradable derivatives of poly(organo phosphazenes) for the preparation of nanoparticles and their surface modification with the novel poly(ethylene oxide) derivative of poly(organo phosphazene) has been assessed using a range of in vitro characterization methods. The nanoparticles were produced by the precipitation solvent evaporation method from the derivative co-substituted with phenylalanine and glycine ethyl ester side groups. A reduction in particle size to less than 200 nm was achieved by an increase in pH of the preparation medium. The formation (and colloidal stability) of these nanoparticles seems to be controlled by two opposite effects: attractive hydrophobic interactions between phenylalanine ester groups and electrostatic repulsions arising from the carboxyl groups formed due to (partial) hydrolysis of the ester bond(s) at the high pH of the preparation medium. The poly[(glycine ethyl ester)phosphazene] derivative containing 5000-Da poly(ethylene oxide) as 5% of the side groups was used for the surface modification of nanoparticles. Adsorbed onto the particles, the polymer produced a thick coating layer of approximately 35 nm. The coated nanoparticles exhibited reduced surface negative potential and improved colloidal stability toward electrolyte-induced flocculation, relative to the uncoated system. However, the steric stabilization provided was less effective than that of a Poloxamine 908 coating. This difference in effectiveness of the steric stabilization might indicate that, although both the stabilizing polymers possess a 5000-Da poly(ethylene oxide) moiety, there is a difference in the arrangements of these poly(ethylene oxide) chains at the particle surface. (c) 1996 John Wiley & Sons, Inc.

Smoothed Particle Hydrodynamics: A consistent model for interfacial multiphase fluid flow simulations

NASA Astrophysics Data System (ADS)

Krimi, Abdelkader; Rezoug, Mehdi; Khelladi, Sofiane; Nogueira, Xesús; Deligant, Michael; Ramírez, Luis

2018-04-01

In this work, a consistent Smoothed Particle Hydrodynamics (SPH) model to deal with interfacial multiphase fluid flows simulation is proposed. A modification to the Continuum Stress Surface formulation (CSS) [1] to enhance the stability near the fluid interface is developed in the framework of the SPH method. A non-conservative first-order consistency operator is used to compute the divergence of stress surface tensor. This formulation benefits of all the advantages of the one proposed by Adami et al. [2] and, in addition, it can be applied to more than two phases fluid flow simulations. Moreover, the generalized wall boundary conditions [3] are modified in order to be well adapted to multiphase fluid flows with different density and viscosity. In order to allow the application of this technique to wall-bounded multiphase flows, a modification of generalized wall boundary conditions is presented here for using the SPH method. In this work we also present a particle redistribution strategy as an extension of the damping technique presented in [3] to smooth the initial transient phase of gravitational multiphase fluid flow simulations. Several computational tests are investigated to show the accuracy, convergence and applicability of the proposed SPH interfacial multiphase model.

Surface modification of poly(D,L-lactic acid) scaffolds for orthopedic applications: a biocompatible, nondestructive route via diazonium chemistry.

PubMed

Mahjoubi, Hesameddin; Kinsella, Joseph M; Murshed, Monzur; Cerruti, Marta

2014-07-09

Scaffolds made with synthetic polymers such as polyesters are commonly used in bone tissue engineering. However, their hydrophobicity and the lack of specific functionalities make their surface not ideal for cell adhesion and growth. Surface modification of these materials is thus crucial to enhance the scaffold's integration in the body. Different surface modification techniques have been developed to improve scaffold biocompatibility. Here we show that diazonium chemistry can be used to modify the outer and inner surfaces of three-dimensional poly(D,L-lactic acid) (PDLLA) scaffolds with phosphonate groups, using a simple two-step method. By changing reaction time and impregnation procedure, we were able to tune the concentration of phosphonate groups present on the scaffolds, without degrading the PDLLA matrix. To test the effectiveness of this modification, we immersed the scaffolds in simulated body fluid, and characterized them with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman, and infrared spectroscopy. Our results showed that a layer of hydroxyapatite particles was formed on all scaffolds after 2 and 4 weeks of immersion; however, the precipitation was faster and in larger amounts on the phosphonate-modified than on the bare PDLLA scaffolds. Both osteogenic MC3T3-E1 and chondrogenic ATDC5 cell lines showed increased cell viability/metabolic activity when grown on a phosphonated PDLLA surface in comparison to a control PDLLA surface. Also, more calcium-containing minerals were deposited by cultures grown on phosphonated PDLLA, thus showing the pro-mineralization properties of the proposed modification. This work introduces diazonium chemistry as a simple and biocompatible technique to modify scaffold surfaces, allowing to covalently and homogeneously bind a number of functional groups without degrading the scaffold's polymeric matrix.

Electron-emission-induced cooling of boundary region in fusion devices

NASA Astrophysics Data System (ADS)

Mishra, Sanjay K.; Avinash, K.; Kaw, Predhiman; Kaw

2014-12-01

In this brief communication we have explored whether the electron emission from the boundary region surfaces (or from additional fine structured dust particles/droplets of some benign material put purposely in the area surrounding the surfaces) can act as an efficient cooling mechanism for boundary region surfaces/dust electrons and hence the lattice. In order to estimate the contribution of this cooling process a simple kinetic model based on charge flux balance and associated energetics has been established. Along with some additional sophistication like suitable choice of material and modification in the work function via surface coating, the estimates show that it is possible to keep the temperature of the plate/particles well within the critical limit, i.e. melting/sublimation point for the desired regime of incident heat flux.

Modelling of multi-vortex convection of fine alloying components in the molten pool under the laser radiation

NASA Astrophysics Data System (ADS)

Gurin, A. M.; Kovalev, O. B.

2013-06-01

The work is devoted to the mathematical modelling and numerical solution of the problems of conjugate micro-convection, which arises under the laser radiation action in the metal melt with surface-active refractory disperse components added for the modification, hardening, and doping of the treated surface. A multi-vortex structure of the melt flow has been obtained, the number of vortices in which depends on the surface tension variation, on the temperature and power of laser radiation. Special attention is paid to the numerical modelling of the behavior in the melt of the substrate of disperse admixture consisting of the tungsten carbide particles. The role of microconvection in the distribution of powder particles in the surface layer of the substrate after its cooling is shown.

In vitro bioactivity investigations of Ti-15Mo alloy after electrochemical surface modification.

PubMed

Kazek-Kęsik, Alicja; Kuna, Karolina; Dec, Weronika; Widziołek, Magdalena; Tylko, Grzegorz; Osyczka, Anna M; Simka, Wojciech

2016-07-01

Titanium and its aluminum and vanadium-free alloys have especially great potential for medical applications. Electrochemical surface modification improves their surface bioactivity and stimulates osseointegration process. In this work, the effect of plasma electrolytic oxidation of the β-type alloy Ti-15Mo surface on its bioactivity is presented. Bioactivity of the modified alloy was investigated by immersion in simulated body fluid (SBF). Biocompatibility of the modified alloys were tested using human bone marrow stromal cells (hBMSC) and wild intestinal strains (DV/A, DV/B, DV/I/1) of Desulfovibrio desulfuricans bacteria. The particles of apatite were formed on the anodized samples. Human BMSC cells adhered well on all the examined surfaces and expressed ALP, collagen, and produced mineralized matrix as determined after 10 and 21 days of culture. When the samples were inoculated with D. desulfuricans bacteria, only single bacteria were visible on selected samples. There were no obvious changes in surface morphology among samples. Colonization and bacterial biofilm formation was observed on as-ground sample. In conclusion, the surface modification improved the Ti-15Mo alloy bioactivity and biocompatibility and protected surface against colonization of the bacteria. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 903-913, 2016. © 2015 Wiley Periodicals, Inc.

Simple route for nano-hydroxyapatite properties expansion.

PubMed

Rojas, L; Olmedo, H; García-Piñeres, A J; Silveira, C; Tasic, L; Fraga, F; Montero, M L

2015-10-20

Simple surface modification of nano-hydroxyapatite, through acid-basic reactions, allows expanding the properties of this material. Introduction of organic groups such as hydrophobic alkyl chains, carboxylic acid, and amide or amine basic groups on the hydroxyapatite surface systematically change the polarity, surface area, and reactivity of hydroxyapatite without modifying its phase. Physical and chemical properties of the new derivative particles were analyzed. The biocompatibility of modified Nano-Hap on Raw 264.7 cells was also assessed.

Single-step fabrication of electrodes with controlled nanostructured surface roughness using optically-induced electrodeposition

NASA Astrophysics Data System (ADS)

Liu, N.; Li, M.; Liu, L.; Yang, Y.; Mai, J.; Pu, H.; Sun, Y.; Li, W. J.

2018-02-01

The customized fabrication of microelectrodes from gold nanoparticles (AuNPs) has attracted much attention due to their numerous applications in chemistry and biomedical engineering, such as for surface-enhanced Raman spectroscopy (SERS) and as catalyst sites for electrochemistry. Herein, we present a novel optically-induced electrodeposition (OED) method for rapidly fabricating gold electrodes which are also surface-modified with nanoparticles in one single step. The electrodeposition mechanism, with respect to the applied AC voltage signal and the elapsed deposition time, on the resulting morphology and particle sizes was investigated. The results from SEM and AFM analysis demonstrated that 80-200 nm gold particles can be formed on the surface of the gold electrodes. Simultaneously, both the size of the nanoparticles and the roughness of the fabricated electrodes can be regulated by the deposition time. Compared to state-of-the-art methods for fabricating microelectrodes with AuNPs, such as nano-seed-mediated growth and conventional electrodeposition, this OED technique has several advantages including: (1) electrode fabrication and surface modification using nanoparticles are completed in a single step, eliminating the need for prefabricating micro electrodes; (2) the patterning of electrodes is defined using a digitally-customized, projected optical image rather than using fixed physical masks; and (3) both the fabrication and surface modification processes are rapid, and the entire fabrication process only requires less than 6 s.

Synthesis, Characterization, Topographical Modification, and Surface Properties of Copoly(Imide Siloxane)s

NASA Technical Reports Server (NTRS)

Wohl, Christopher J.; Atkins, Brad M.; Belcher, Marcus A.; Connell, John W.

2012-01-01

Novel copoly(imide siloxane)s were synthesized from commercially available aminopropyl terminated siloxane oligomers, aromatic dianhydrides, and diamines. This synthetic approach produced copolymers with well-defined siloxane blocks linked with imide units in a random fashion. The copoly(amide acid)s were characterized by solution viscosity and subsequently used to cast thin films followed by thermal imidization in an inert atmosphere. Thin films were characterized using contact angle goniometry, attenuated total reflection Fourier transform infrared spectroscopy, confocal and optical microscopy, and tensile testing. Adhesion of micronsized particles was determined quantitatively using a sonication device. The polydimethylsiloxane (PDMS) moieties lowered the copolymer surface energy due to migration of siloxane moieties to the film s surface, resulting in a notable reduction in particle adhesion. A further reduction in particle adhesion was achieved by introducing topographical features on a scale of several to tens of microns by a laser ablation technique.

The influence of ionic strength and organic compounds on nanoparticle TiO2 (n-TiO2) aggregation.

PubMed

Lee, Jaewoong; Bartelt-Hunt, Shannon L; Li, Yusong; Gilrein, Erica Jeanne

2016-07-01

This study investigated the aggregation of n-TiO2 in the presence of humic acid (HA) and/or 17β-estradiol (E2) under high ionic strength conditions simulating levels detected in landfill leachate. Aggregation of n-TiO2 was strongly influenced by ionic strength as well as ionic valence in that divalent cations (Ca(2+)) were more effective than monovalent (Na(+)) at the surface modification. HA or E2 enhanced aggregation of n-TiO2 in 20 mM CaCl2, however little aggregation was observed in 100 mM NaCl. Similarly, we observed only the increased aggregation of n-TiO2 in the presence of HA/E2. These results showed the critical role of particles' surface charges on the aggregation behaviors of n-TiO2 that HA plays more significantly than E2. However, the slightly increased zeta potential and aggregation of n-TiO2 in the combination of HA and E2 at both 20 mM CaCl2 and 100 mM NaCl means that E2 has influenced on the surface modification of n-TiO2 by adsorption. Based on the aggregation of n-TiO2 under high ionic strength with HA and/or E2, we simulated the mobility of aggregated n-TiO2 in porous media. As a result, we observed that the mobility distance of aggregated n-TiO2 was dramatically influenced by the surface modification with both HA and/or E2 between particles and media. Furthermore, larger mobility distance was observed with larger aggregation of n-TiO2 particles that can be explained by clean bed filtration (CFT) theory. Copyright © 2016 Elsevier Ltd. All rights reserved.

Melting of SiC powders preplaced duplex stainless steel using TIG welding

NASA Astrophysics Data System (ADS)

Maleque, M. A.; Afiq, M.

2018-01-01

TIG torch welding technique is a conventional melting technique for the cladding of metallic materials. Duplex stainless steels (DSS) show decrease in performance under aggressive environment which may lead to unanticipated failure due to poor surface properties. In this research, surface modification is done by using TIG torch method where silicon carbide (SiC) particles are fused into DSS substrate in order to form a new intermetallic compound at the surface. The effect of particle size, feed rate of SiC preplacement, energy input and shielding gas flow rate on surface topography, microstructure, microstructure and hardness are investigated. Deepest melt pool (1.237 mm) is produced via TIG torch with highest energy input of 1080 J/mm. Observations of surface topography shows rippling marks which confirms that re-solidification process has taken place. Melt microstructure consist of dendritic and globular carbides precipitate as well as partially melted silicon carbides (SiC) particles. Micro hardness recorded at value ranging from 316 HV0.5 to 1277 HV0.5 which shows increment from base hardness of 260 HV0.5kgf. The analyzed result showed that incorporation of silicon carbide particles via TIG Torch method increase the hardness of DSS.

Effect of surface modifications on the bond strength of zirconia ceramic with resin cement resin.

PubMed

Hallmann, Lubica; Ulmer, Peter; Lehmann, Frank; Wille, Sebastian; Polonskyi, Oleksander; Johannes, Martina; Köbel, Stefan; Trottenberg, Thomas; Bornholdt, Sven; Haase, Fabian; Kersten, Holger; Kern, Matthias

2016-05-01

Purpose of this in vitro study was to evaluate the effect of surface modifications on the tensile bond strength between zirconia ceramic and resin. Zirconia ceramic surfaces were treated with 150-μm abrasive alumina particles, 150-μm abrasive zirconia particles, argon-ion bombardment, gas plasma, and piranha solution (H2SO4:H2O2=3:1). In addition, slip casting surfaces were examined. Untreated surfaces were used as the control group. Tensile bond strengths (TBS) were measured after water storage for 3 days or 150 days with additional 37,500 thermal cycling for artificial aging. Statistical analyses were performed with 1-way and 3-way ANOVA, followed by comparison of means with the Tukey HSD test. After storage in distilled water for three days at 37 °C, the highest mean tensile bond strengths (TBS) were observed for zirconia ceramic surfaces abraded with 150-μm abrasive alumina particles (TBS(AAP)=37.3 MPa, TBS(CAAP)=40.4 MPa), and 150-μm abrasive zirconia particles (TBS(AZP)=34.8 MPa, TBS(CAZP)=35.8 MPa). Also a high TBS was observed for specimens treated with argon-ion bombardment (TBS(BAI)=37.8 MPa). After 150 days of storage, specimens abraded with 150-μm abrasive alumina particles and 150-μm abrasive zirconia particles revealed high TBS (TBS(AAP)=37.6 MPa, TBS(CAAP)=33.0 MPa, TBS(AZP)=22.1 MPa and TBS(CAZP)=22.8 MPa). A high TBS was observed also for specimens prepared with slip casting (TBS(SC)=30.0 MPa). A decrease of TBS was observed for control specimens (TBS(UNT)=12.5 MPa, TBS(CUNT)=9.0 MPa), specimens treated with argon-ion bombardment (TBS(BAI)=10.3 MPa) and gas plasma (TBS(GP)=11.0 MPa). A decrease of TBS was observed also for specimens treated with piranha solution (TBS(PS)=3.9 MPa, TBS(CPS)=4.1 MPa). A significant difference in TBS after three days storage was observed for specimens treated with different methods (p<0.001). Thermal cycling significantly reduced TBS for all groups (p<0.001) excluding groups: AAP(p>0.05), CAAP(p>0.05) and SC(p>0.05). However, the failure patterns of debonded specimens prepared with 150-μm abrasive zirconia particles were 96.7% cohesive. Treatment of zirconia ceramic surfaces with abrasive zirconia particles is a promising method to increase the tensile bond strength without significant damage of the ceramic surface itself. An alternative promising method is slip casting. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Patchy micelles based on coassembly of block copolymer chains and block copolymer brushes on silica particles.

PubMed

Zhu, Shuzhe; Li, Zhan-Wei; Zhao, Hanying

2015-04-14

Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation.

Recent development, applications, and perspectives of mesoporous silica particles in medicine and biotechnology.

PubMed

Pasqua, Luigi; Cundari, Sante; Ceresa, Cecilia; Cavaletti, Guido

2009-01-01

Mesoporous silica particles (MSP) are a new development in nanotechnology. Covalent modification of the surface of the silica is possible both on the internal pore and on the external particle surface. It allows the design of functional nanostructured materials with properties of organic, biological and inorganic components. Research and development are ongoing on the MSP, which have applications in catalysis, drug delivery and imaging. The most recent and interesting advancements in size, morphology control and surface functionalization of MSP have enhanced the biocompatibility of these materials with high surface areas and pore volumes. In the last 5 years several reports have demonstrated that MSP can be efficiently internalized using in vitro and animal models. The functionalization of MSP with organic moieties or other nanostructures brings controlled release and molecular recognition capabilities to these mesoporous materials for drug/gene delivery and sensing applications, respectively. Herein, we review recent research progress on the design of functional MSP materials with various mechanisms of targeting and controlled release.

Photocatalytic reduction of heavy metal ions on derivatized titanium dioxide nano-particle surface studied by XAFS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, L. X.; Rajh, T.; Micic, O.

1997-01-01

Photoreduction of heavy metal ions, Cu{sup 2-} and Hg{sup 2+}, on TiO{sup 2} nano-particle surfaces, has been investigated by XAFS measurements. The effects of TiO{sup 2} surface modification reagents on the reaction efficiency have been studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01 M Cu{sup 2+} and TiO{sup 2} nano-particles. Fifty percent of the adsorbed Cu{sup 2+} has been reduced to Cu{sup 0} after 1-h illumination with a UV-enhanced xenon lamp. Photoreduction of Hg{sup 2+} on TiO{sup 2} colloid surfaces was also investigated without and with thiolactic acid (TLA).more » In this case, the photoreduction efficiency for Hg{sup 2+} was lowered. Structures of metal ion surroundings in various complexes as well as their role in photoreduction of metal ions are discussed.« less

A Co-Precursor Approach Coupled with a Supercritical Modification Method for Constructing Highly Transparent and Superhydrophobic Polymethylsilsesquioxane Aerogels.

PubMed

Lei, Chaoshuai; Li, Junning; Sun, Chencheng; Yang, Hailong; Xia, Tao; Hu, Zijun; Zhang, Yue

2018-03-30

Polymethylsilsesquioxane (PMSQ) aerogels obtained from methyltrimethoxysilane (MTMS) are well-known high-performance porous materials. Highly transparent and hydrophobic PMSQ aerogel would play an important role in transparent vacuum insulation panels. Herein, the co-precursor approach and supercritical modification method were developed to prepare the PMSQ aerogels with high transparency and superhydrophobicity. Firstly, benefiting from the introduction of tetramethoxysilane (TMOS) in the precursor, the pore structure became more uniform and the particle size was decreased. As the TMOS content increased, the light transmittance increased gradually from 54.0% to 81.2%, whereas the contact angle of water droplet decreased from 141° to 99.9°, ascribed to the increase of hydroxyl groups on the skeleton surface. Hence, the supercritical modification method utilizing hexamethyldisilazane was also introduced to enhance the hydrophobic methyl groups on the aerogel's surface. As a result, the obtained aerogels revealed superhydrophobicity with a contact angle of 155°. Meanwhile, the developed surface modification method did not lead to any significant changes in the pore structure resulting in the superhydrophobic aerogel with a high transparency of 77.2%. The proposed co-precursor approach and supercritical modification method provide a new horizon in the fabrication of highly transparent and superhydrophobic PMSQ aerogels.

Modification of narrow ablating capillaries under the influence of multiple femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Gubin, K. V.; Lotov, K. V.; Trunov, V. I.; Pestryakov, E. V.

2016-09-01

Powerful femtosecond laser pulses that propagate through narrow ablating capillaries cause modification of capillary walls, which is studied experimentally and theoretically. At low intensities, the laser-induced periodic surface structures and porous coating composed of sub-micron particles appear on the walls. At higher intensities, the surface is covered by deposited droplets of the size up to 10 μm. In both cases, the ablated material forms a solid plug that completely blocks the capillary after several hundreds or thousands of pulses. The suggested theoretical model indicates that the plug formation is a universal effect. It must take place in any narrow tube subject to ablation under the action of short laser pulses.

Milling induced amorphisation and recrystallization of α-lactose monohydrate.

PubMed

Badal Tejedor, Maria; Pazesh, Samaneh; Nordgren, Niklas; Schuleit, Michael; Rutland, Mark W; Alderborn, Göran; Millqvist-Fureby, Anna

2018-02-15

Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the α-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed α-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between unprocessed α-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spray-dried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanoparticle modification by weak polyelectrolytes for pH-sensitive pickering emulsions.

PubMed

Haase, Martin F; Grigoriev, Dmitry; Moehwald, Helmuth; Tiersch, Brigitte; Shchukin, Dmitry G

2011-01-04

The affinity of weak polyelectrolyte coated oxide particles to the oil-water interface can be controlled by the degree of dissociation and the thickness of the weak polyelectrolyte layer. Thereby the oil in water (o/w) emulsification ability of the particles can be enabled. We selected the weak polyacid poly(methacrylic acid sodium salt) and the weak polybase poly(allylamine hydrochloride) for the surface modification of oppositely charged alumina and silica colloids, respectively. The isoelectric point and the pH range of colloidal stability of both particle-polyelectrolyte composites depend on the thickness of the weak polyelectrolyte layer. The pH-dependent wettability of a weak polyelectrolyte-coated oxide surface is characterized by contact angle measurements. The o/w emulsification properties of both particles for the nonpolar oil dodecane and the more polar oil diethylphthalate are investigated by measurements of the droplet size distributions. Highly stable emulsions can be obtained when the degree of dissociation of the weak polyelectrolyte is below 80%. Here the average droplet size depends on the degree of dissociation, and a minimum can be found when 15 to 45% of the monomer units are dissociated. The thickness of the adsorbed polyelectrolyte layer strongly influences the droplet size of dodecane/water emulsion droplets but has a less pronounced impact on the diethylphthalate/water droplets. We explain the dependency of the droplet size on the emulsion pH value and the polyelectrolyte coating thickness with arguments based on the particle-wetting properties, the particle aggregation state, and the oil phase polarity. Cryo-SEM visualization shows that the regularity of the densely packed particles on the oil-water interface correlates with the degree of dissociation of the corresponding polyelectrolyte.

Silica nanoparticles carrying boron-containing polymer brushes

NASA Astrophysics Data System (ADS)

Brozek, Eric M.; Mollard, Alexis H.; Zharov, Ilya

2014-05-01

A new class of surface-modified silica nanoparticles has been developed for potential applications in boron neutron capture therapy. Sub-50 nm silica particles were synthesized using a modified Stöber method and used in surface-initiated atom transfer radical polymerization of two biocompatible polymers, poly(2-(hydroxyethyl)methacrylate) and poly(2-(methacryloyloxy)ethyl succinate). The carboxylic acid and hydroxyl functionalities of the polymeric side chains were functionalized with carboranyl clusters in high yields. The resulting particles were characterized using DLS, TEM, solution 1H NMR, solid state 11B NMR and thermogravimetric analysis. The particles contain between 13 and 18 % of boron atoms by weight, which would provide a high amount of 10B nuclides for BNCT, while the polymer chains are suitable for further modification with cell targeting ligands.

Combined Embedding of N/F-Doping and CaCO3 Surface Modification in the TiO2 Photoanode for Dye-Sensitized Solar Cells.

PubMed

Park, Su Kyung; Yun, Tae Kwan; Bae, Jae Young

2016-03-01

N/F-doping and CaCO3 surface modification was carried out in TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect of the N/F doped TiO2 and the CaCO3 coating showed a great increase of the short-circuit current (J(sc)), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 7.00% of a commercial TiO2 photoelectrode to 7.90% of an uncoated N/F-doped electrode, and to 9.09% of a N/F-doped and CaCO3 surface modified electrode. An enhanced photoresponse in N/F-doped TiO2 nanoparticles generate more photo-excited electrons, as supported by measured UV-Vis diffuse reflectance spectra. A successive CaCO3 surface modification then forms a barrier on the surface of the N/F-doped TiO2 particles; the higher basicity of the CaCO3 modified TiO2 facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.

A Chemical-Adsorption Strategy to Enhance the Reaction Kinetics of Lithium-Rich Layered Cathodes via Double-Shell Surface Modification.

PubMed

Guo, Lichao; Li, Jiajun; Cao, Tingting; Wang, Huayu; Zhao, Naiqin; He, Fang; Shi, Chunsheng; He, Chunnian; Liu, Enzuo

2016-09-21

Sluggish surface reaction kinetics hinders the power density of Li-ion battery. Thus, various surface modification techniques have been applied to enhance the electronic/ionic transfer kinetics. However, it is challenging to obtain a continuous and uniform surface modification layer on the prime particles with structure integration at the interface. Instead of classic physical-adsorption/deposition techniques, we propose a novel chemical-adsorption strategy to synthesize double-shell modified lithium-rich layered cathodes with enhanced mass transfer kinetics. On the basis of experimental measurement and first-principles calculation, MoO2S2 ions are proved to joint the layered phase via chemical bonding. Specifically, the Mo-O or Mo-S bonds can flexibly rotate to bond with the cations in the layered phase, leading to the good compatibility between the thiomolybdate adsorption layer and layered cathode. Followed by annealing treatment, the lithium-excess-spinel inner shell forms under the thiomolybdate adsorption layer and functions as favorable pathways for lithium and electron. Meanwhile, the nanothick MoO3-x(SO4)x outer shell protects the transition metal from dissolution and restrains electrolyte decomposition. The double-shell modified sample delivers an enhanced discharge capacity almost twice as much as that of the unmodified one at 1 A g(-1) after 100 cycles, demonstrating the superiority of the surface modification based on chemical adsorption.

PREFACE Surface Modifications of Diamond and Related Materials (Session D, E-MRS Spring Meeting)

NASA Astrophysics Data System (ADS)

Nebel, Christoph E.

2010-11-01

This special issue contains selected papers which were presented at the E-MRS Symposium BIOMATERIALS, SENSORS & SURFACES, D: 'Surface modifications of diamond and related materials' which was held on 7-9 June 2010 in Strasbourg (France). With about 54 oral and poster presentations given from teams all over the world it was a very interesting, dense and lively meeting. The symposium focused on chemical modifications applied to graft surfaces of diamond, nano-diamond particles, diamond-like carbon, graphene, graphite and carbon nano-tubes with linker molecular layers for realization of bio-sensors, bio-markers, separation techniques, and switchable chemical links. Presented techniques span spontaneous bonding to photo-chemical attachment, electrochemical modifications, to Suzuki-coupling of aryl molecules. Special attention was drawn to mechanisms driving bonding kinetics such as electron transfer reactions, hydrogen cleavage reactions by nucleophilic molecules and growths schemas which vary from correlated two-dimensional chain reactions to three-dimensional cross polymerization. Hydrogen terminations, surface defects, surface roughness and atomic arrangements of surface carbon atoms were of interest to elucidate bonding mechanisms. In addition, bonding stability, either of linker molecules or of complex functionalized surfaces with DNA, proteins and enzymes was discussed by several speakers as well as details of the electronic interfaces between solid transducers and bio-layers. Here the characterization of surface and interface defect densities, of Fermi level pinning and of electron transfer rates was a major topic. Miniaturization of sensor area and application of new detection schemas was discussed. Diamond nano-particles which are increasingly used as biomarkers in drug delivery experiments also attracted attention. The organizers express our gratitude to the international members of the scientific committee who actively contributed to ensure an attractive program in proposing invited speakers. Finally, our symposium would not have been successful without the strong involvement and implication of the EMRS headquarter especially P Siffert, T Lippert, S Schoeffter and C Kocher. They will all find here our sincere thanks. Christoph E Nebel (Chair) Fraunhofer-Institute for Applied Solid State Physics (IAF), Germany Takako Nakamura National Institute of Advanced Industrial Science and Technology (AIST), Japan Philippe Bergonzo CEA-LIST, France John Foord University of Oxford, United Kingdom Kian-Ping Loh National University of Singapore, Singapore

Characterization of Nanoparticle Aggregation in Biologically Relevant Fluids

NASA Astrophysics Data System (ADS)

McEnnis, Kathleen; Lahann, Joerg

Nanoparticles (NPs) are often studied as drug delivery vehicles, but little is known about their behavior in blood once injected into animal models. If the NPs aggregate in blood, they will be shunted to the liver or spleen instead of reaching the intended target. The use of animals for these experiments is costly and raises ethical questions. Typically dynamic light scattering (DLS) is used to analyze aggregation behavior, but DLS cannot be used because the components of blood also scatter light. As an alternative, a method of analyzing NPs in biologically relevant fluids such as blood plasma has been developed using nanoparticle tracking analysis (NTA) with fluorescent filters. In this work, NTA was used to analyze the aggregation behavior of fluorescent polystyrene NPs with different surface modifications in blood plasma. It was expected that different surface chemistries on the particles will change the aggregation behavior. The effect of the surface modifications was investigated by quantifying the percentage of NPs in aggregates after addition to blood plasma. The use of this characterization method will allow for better understanding of particle behavior in the body, and potential problems, specifically aggregation, can be addressed before investing in in vivo studies.

Method for chemical surface modification of fumed silica particles

DOEpatents

Grabbe, Alexis; Michalske, Terry Arthur; Smith, William Larry

1999-01-01

Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

Hydrothermal modification and recycling of nonmetallic particles from waste print circuit boards.

PubMed

Gao, Xuehua; Li, Qisheng; Qiu, Jun

2018-04-01

Nonmetallic particles recycled from waste print circuit boards (NPRPs) were modified by a hydrothermal treatment method and the catalysts, solvents, temperature and time were investigated, which affected the modification effect of NPRPs. The mild hydrothermal treatment method does not need high temperature, and would not cause secondary pollution. Further, the modified NPRPs were used as the raw materials for the epoxy resin and glass fibers/epoxy resin composites, which were prepared by pouring and hot-pressing method. The mechanical properties and morphology of the composites were discussed. The results showed that relative intensity of the hydroxyl bonds on the surface of NPRPs increased 58.9% after modification. The mechanical tests revealed that both flexural and impact properties of the composites can be significantly improved by adding the modified NPRPs. Particularly, the maximum increment of flexural strength, flexural modulus and impact strength of the epoxy matrix composites with 30% modified NPRPs is 40.1%, 80.0% and 79.0%, respectively. Hydrothermal treatment can modify surface of NPRPs successfully and modified NPRPs can not only improve the properties of the composites, but also reduce the production cost of the composites and environmental pollution. Thus, we develop a new way to recycle nonmetallic materials of waste print circuit boards and the highest level of waste material recycling with the raw materials-products-raw materials closed cycle can be realized through the hydrothermal modification and reuse of NPRPs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Volume Labeling with Alexa-Fluor Dyes and Surface Functionalization of Highly Sensitive Fluorescent SiO2 Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei; Foster, Carmen M; Morrell-Falvey, Jennifer L

2013-01-01

A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and amore » polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or free surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.« less

Paramagnetic iron-doped hydroxyapatite nanoparticles with improved metal sorption properties. A bioorganic substrates-mediated synthesis.

PubMed

Mercado, D Fabio; Magnacca, Giuliana; Malandrino, Mery; Rubert, Aldo; Montoneri, Enzo; Celi, Luisella; Bianco Prevot, Alessandra; Gonzalez, Mónica C

2014-03-26

This paper describes the synthesis of paramegnetic iron-containing hydroxyapatite nanoparticles and their increased Cu(2+) sorbent capacity when using Ca(2+) complexes of soluble bioorganic substrates from urban wastes as synthesis precursors. A thorough characterization of the particles by TEM, XRD, FTIR spectroscopy, specific surface area, TGA, XPS, and DLS indicates that loss of crystallinity, a higher specific area, an increased surface oxygen content, and formation of surface iron phases strongly enhance Cu(2+) adsorption capacity of hydroxyapatite-based materials. However, the major effect of the surface and morphologycal modifications is the size diminution of the aggregates formed in aqueous solutions leading to an increased effective surface available for Cu(2+) adsorption. Maximum sorption values of 550-850 mg Cu(2+) per gram of particles suspended in an aqueous solution at pH 7 were determined, almost 10 times the maximum values observed for hydroxyapatite nanoparticles suspensions under the same conditions.

Tailoring MCM-41 mesoporous silica particles through modified sol-gel process for gas separation

NASA Astrophysics Data System (ADS)

Sang, Wong Yean; Ching, Oh Pei

2017-10-01

Mobil Composition of Matter-41 (MCM-41) is recognized as a potential filler to enhance permeability of mixed matrix membrane (MMM). However, the required loading for available micron-sized MCM-41 was considerably high in order to achieve desired separation performance. In this work, reduced-size MCM-41 was synthesized to minimize filler loading, improve surface modification and enhance polymer-filler compatibility during membrane fabrication. The effect of reaction condition, stirring rate and type of post-synthesis washing solution used on particle diameter of resultant MCM-41 were investigated. It was found that MCM-41 produced at room temperature condition yield particles with smaller diameter, higher specific surface area and enhanced mesopore structure. Increase of stirring rate up to 500 rpm during synthesis also reduced the particle diameter. In addition, replacing water with methanol as the post-synthesis washing solution to remove bromide ions from the precipitate was able to further reduce the particle size by inhibiting polycondensation reaction.

Optical trapping/modification of nano-(micro)particles by gradient and photorefractive forces during laser illumination

NASA Astrophysics Data System (ADS)

Kukhtarev, N.; Kukhtareva, T.; Okafor, F.

2010-08-01

In this paper we describe photo-induced trapping/redistribution of silver nano-(micro) particles near the surface of photorefractive crystal LiNbO3:Fe. This type of optical trapping is due to combined forces of direct gradient-force trapping and asymmetric photorefractive forces of electro-phoresis and dielectro-phoresis. The silver nanoparticles were produced through extracellular biosynthesis on exposure to the fungus, Fusarium oxysporum (FO) and to the plant extracts. Pulsed and CW visible laser radiation lead to significant modification of nanoparticle clusters. This study indicates that extracellular biosynthesis can constitute a possible viable alternative method for the production of nanoparticles. In addition, the theoretical modeling of asymmetric photorefractive electric field grating has been presented and compared with the experimental results.

Influence of Roughness-Induced Slip on Colloid Transport: Experimental and Modelling Insights

NASA Astrophysics Data System (ADS)

Rasmuson, J. A.; Johnson, W. P.

2017-12-01

A limitation of classic colloid filtration theory is that it applies only to smooth surfaces, yet most natural surfaces present some degree of nano- to micro-scale roughness. A large volume of research has been dedicated to understanding the effects of roughness on particle attachment at the nano-scale since these interactions dictate field scale transport behavior. It has been previously demonstrated that roughness imposes a finite slip vector at the surface that causes particles to experience higher near-surface velocities than would be expected over a smooth surface. Slip near a rough surface can affect two primary mechanisms of particle attenuation: 1) interception of the surface (finding a landing spot) and 2) arrest on the surface (sticking the landing). However, a clear designation on how slip affects particle transport near rough surfaces is missing. The goal of this study was to provide a guide for the height of the slip layer and contact surface in reference to the mean-plane for rough surfaces. Direct observation was used to measure near-surface velocities of particles translating near surfaces of varying roughness spanning three orders of magnitude. The influence of roughness on particle transport was investigated using computational fluid dynamics (CFD) modeling with rough surfaces measured with atomic force microscopy (AFM). The CFD and experimental results were used to calibrate a Lagrangian particle transport model that utilizes simple modifications to the flow field for a smooth surface using statistically based roughness parameters. Advantages of the Lagrangian model are significantly decreased computation times and applicability to a wide range of natural surfaces without explicitly simulating individual asperities. The results suggest that the no-slip boundary should be placed at the bottom of the maximum asperity valleys, and that the contact surface should be placed at the root mean square (RMS) roughness above the mean plane. Collector surfaces with the greatest RMS roughness had the highest sensitivity to the placement of the contact surface. These findings highlight the need for accurate and representative AFM measurements and have important implications for future transport models.

Flotation and flocculation chemistry of coal and oxidized coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somasundaran, P.

1990-01-01

The objective of this research project is to understand the fundamentals involved in the flotation and flocculation of coal and oxidized coals and elucidate mechanisms by which surface interactions between coal and various reagents enhance coal beneficiation. An understanding of the nature of the heterogeneity of coal surfaces arising from the intrinsic distribution of chemical moieties is fundamental to the elucidation of mechanism of coal surface modification and its role in interfacial processes such as flotation, flocculation and agglomeration. A new approach for determining the distribution in surface properties of coal particles was developed in this study and various techniquesmore » capable of providing such information were identified. Distributions in surface energy, contact angle and wettability were obtained using novel techniques such as centrifugal immersion and film flotation. Changes in these distributions upon oxidation and surface modifications were monitored and discussed. An approach to the modelling of coal surface site distributions based on thermodynamic information obtained from gas adsorption and immersion calorimetry is proposed. Polyacrylamide and dodecane was used to alter the coal surface. Methanol adsorption was also studied. 62 figs.« less

Removal of dissolved and colloidal silica

DOEpatents

Midkiff, William S.

2002-01-01

Small amorphous silica particles are used to provide a relatively large surface area upon which silica will preferentially adsorb, thereby preventing or substantially reducing scaling caused by deposition of silica on evaporative cooling tower components, especially heat exchange surfaces. The silica spheres are contacted by the cooling tower water in a sidestream reactor, then separated using gravity separation, microfiltration, vacuum filtration, or other suitable separation technology. Cooling tower modifications for implementing the invention process have been designed.

Investigation of γ-(2,3-Epoxypropoxy)propyltrimethoxy Silane Surface Modified Layered Double Hydroxides Improving UV Ageing Resistance of Asphalt.

PubMed

Zhang, Canlin; Yu, Jianying; Xue, Lihui; Sun, Yubin

2017-01-19

γ-(2,3-Epoxypropoxy)propyltrimethoxy silane surface modified layered double hydroxides (KH560-LDHs) were prepared and used to improve the ultraviolet ageing resistance of asphalt. The results of X-ray photoelectron spectrometry (XPS) indicated that KH560 has been successfully grafted onto the surface of LDHs. The agglomeration of LDHs particles notably reduced after KH560 surface modification according to scanning electron microscopy (SEM), which implied that the KH560 surface modification was helpful to promote the dispersibility of LDHs in asphalt. Then, the influence of KH560-LDHs and LDHs on the physical and rheological properties of asphalt before and after UV ageing was thoroughly investigated. The storage stability test showed that the difference in softening point (Δ S ) of LDHs modified asphalt decreased from 0.6 °C to 0.2 °C at an LDHs content of 1% after KH560 surface modification, and the tendency became more pronounced with the increase of LDH content, indicating that KH560 surface modification could improve the stability of LDHs in asphalt. After UV ageing, the viscous modulus ( G'' ) of asphalt significantly reduced, and correspondingly, the elastic modulus ( G' ) and rutting factor ( G */sin δ) rapidly increased. Moreover, the asphaltene increased and the amount of "bee-like" structures of the asphalt decreased. Compared with LDHs, KH560-LDHs obviously restrained performance deterioration of the asphalt, and helped to relieve the variation of the chemical compositions and morphology of asphalt, which suggested that the improvement of KH560-LDHs on UV ageing resistance of asphalt was superior to LDHs.

Super-Hydrophobic Surface Prepared by Lanthanide Oxide Ceramic Deposition Through PS-PVD Process

NASA Astrophysics Data System (ADS)

Li, Jie; Li, Cheng-Xin; Chen, Qing-Yu; Gao, Jiu-Tao; Wang, Jun; Yang, Guan-Jun; Li, Chang-Jiu

2017-02-01

Super-hydrophobic surface has received widespread attention in recent years. Both the surface morphology and chemical composition have significant impact on hydrophobic performance. A novel super-hydrophobic surface based on plasma spray-vapor deposition was introduced in the present paper. Samaria-doped ceria, which has been proved as an intrinsic hydrophobic material, was used as feedstock material. Additionally, in order to investigate the influence of surface free energy on the hydrophobicity, chemical modification by low surface free energy materials including stearic acid and 1,1,2,2-tetrahydroperfluorodecyltrimethoxysilane (FAS) was used on coating surface. Scanning electron microscopy and Fourier transform infrared spectroscopy were employed to characterize the coating surface. The results show that the obtained surface has a hierarchical structure composed by island-like structures agglomerated with angular-like sub-micrometer-sized particles. Moreover, with the surface free energy decreases, the hydrophobic property of the surface improves gradually. The water contact angle of the as-sprayed coating surface increases from 110° to 148° after modification by stearic acid and up to 154° by FAS. Furthermore, the resultant surface with super-hydrophobicity exhibits an excellent stability.

PEG-stabilized core-shell surface-imprinted nanoparticles.

PubMed

Moczko, Ewa; Guerreiro, Antonio; Piletska, Elena; Piletsky, Sergey

2013-08-06

Here we present a simple technique to produce target-specific molecularly imprinted polymeric nanoparticles (MIP NPs) and their surface modification in order to prevent the aggregation process that is ever-present in most nanomaterial suspensions/dispersions. Specifically, we studied the influence of surface modification of MIP NPs with polymerizable poly(ethylene glycol) on their degree of stability in water, in phosphate buffer, and in the presence of serum proteins. Grafting a polymer shell on the surface of nanoparticles decreases the surface energy, enhances the polarity, and as a result improves the dispersibility, storage, and colloidal stability as compared to those of core (unmodified) particles. Because of the unique solid-phase approach used for synthesis, the binding sites of MIP NPs are protected during grafting, and the recognition properties of nanoparticles are not affected. These results are significant for developing nanomaterials with selective molecular recognition, increased biocompatibility, and stability in solution. Materials synthesized this way have the potential to be used in a variety of technological fields, including in vivo applications such as drug delivery and imaging.

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Yang; Piper, Daniela M.; Gu, Meng

Surface modification of silicon nanoparticle via molecular layer deposition (MLD) has been recently proved to be an effective way for dramatically enhancing the cyclic performance in lithium ion batteries. However, the fundamental mechanism as how this thin layer of coating function is not known, which is even complicated by the inevitable presence of native oxide of several nanometers on the silicon nanoparticle. Using in-situ TEM, we probed in detail the structural and chemical evolution of both uncoated and coated silicon particles upon cyclic lithiation/delithation. We discovered that upon initial lithiation, the native oxide layer converts to crystalline Li2O islands, whichmore » essentially increases the impedance on the particle, resulting in ineffective lithiation/delithiation, and therefore low coulombic efficiency. In contrast, the alucone MLD coated particles show extremely fast, thorough and highly reversible lithiation behaviors, which are clarified to be associated with the mechanical flexibility and fast Li+/e- conductivity of the alucone coating. Surprisingly, the alucone MLD coating process chemically changes the silicon surface, essentially removing the native oxide layer and therefore mitigates side reaction and detrimental effects of the native oxide. This study provides a vivid picture of how the MLD coating works to enhance the coulombic efficiency and preserve capacity and clarifies the role of the native oxide on silicon nanoparticles during cyclic lithiation and delithiation. More broadly, this work also demonstrated that the effect of the subtle chemical modification of the surface during the coating process may be of equal importance as the coating layer itself.« less

Formation of grafted surface layers on silicon dioxide particles and their investigation by means of thermoprogrammed oxidation

NASA Astrophysics Data System (ADS)

Aleksandrova, E. O.; Novichkov, R. V.; Olenin, A. Yu.; Zuev, B. K.

2017-03-01

Silica nanoparticles are obtained according to the Stober-Fink-Bohn method, and their surfaces are chemically modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane. It is estimated that sols of porous silica nanoparticles (average sizes, 50-200 nm) form during primary chemical process; the average size of the particles can be increased to 400-500 nm by consecutive growth. Oxythermography (thermoprogrammed oxidation) measurements reveal a stepped dependence between the content of organic substance of nanoparticles and the duration of chemical modification reaction exists. It is concluded that this could be due to the formation of dense shell (or shells) as a result of sols aging between the cycles of growth; such shells impose diffusive restrictions when molecules penetrate into the pores of the internal volume of the particles.

Monitoring solute interactions with poly(ethylene oxide)-modified colloidal silica nanoparticles via fluorescence anisotropy decay.

PubMed

Tleugabulova, Dina; Duft, Andy M; Brook, Michael A; Brennan, John D

2004-01-06

The fluorescence-based nanosize metrology approach, proposed recently by Geddes and Birch (Geddes, C. D.; Birch, D. J. S. J. Non-Cryst. Solids 2000, 270, 191), was used to characterize the extent of binding of a fluorescent cationic solute, rhodamine 6G (R6G), to the surface of silica particles after modification of the surface with the hydrophilic polymer poly(ethylene oxide) (PEO) of various molecular weights. The measurement of the rotational dynamics of R6G in PEO solutions showed the absence of strong interactions between R6G and PEO chains in water and the ability of the dye to sense the presence of polymer clusters in 30 wt % solutions. Time-resolved anisotropy decays of polymer-modified Ludox provided direct evidence for distribution of the dye between bound and free states, with the bound dye showing two decay components: a nanosecond decay component that is consistent with local motions of bound probes and a residual anisotropy component due to slow rotation of large silica particles. The data showed that the dye was strongly adsorbed to unmodified silica nanoparticles, to the extent that less than 1% of the dye was present in the surrounding aqueous solution. Addition of PEO blocked the adsorption of the dye to a significant degree, with up to 50% of the probe being present in the aqueous solution for Ludox samples containing 30 wt % of low molecular weight PEO. The addition of such agents also decreased the value and increased the fractional contribution of the nanosecond rotational correlation time, suggesting that polymer adsorption altered the degree of local motion of the bound probe. Atomic force microscopy imaging studies provided no evidence for a change in the particle size upon surface modification but did suggest interparticle aggregation after polymer adsorption. Thus, this redistribution of the probe is interpreted as being due to coverage of particles with the polymer, resulting in lower adsorption of R6G to the silica. The data clearly show the power of time-resolved fluorescence anisotropy decay measurements for probing the modification of silica surfaces and suggest that this method should prove useful in characterization of new chromatographic stationary phases and nanocomposite materials.

Numerical investigation of melting and solidification processes in modified surface layers of metal at induction heating

NASA Astrophysics Data System (ADS)

Shchukin, V. G.; Popov, V. N.

2017-10-01

One of the perspective ways to improve the operational properties of parts of machines during induction treatment of their surfaces is the modification of the melt by specially prepared nanoscale particles of refractory compounds (carbides, nitrides, carbonitrides, etc.). This approach allows us to increase the number of crystallization centers and to refine the structural components of the solidified metal. The resulting high dispersity and homogeneity of crystalline grains favorably affect the quality of the treated surfaces. 3D numerical simulation of thermophysical processes in the modification of the surface layer of metal in a moving substrate was carried out. It is assumed that the surface of the substrate is covered with a layer of specially prepared nanoscale particles of a refractory compound, which, upon penetration into the melt, are uniformly distributed in it. The possibility of applying a high-frequency electromagnetic field of high power for heating and melting of a metal (iron) for the purpose of its subsequent modification is investigated. The distribution of electromagnetic energy in the metal is described by empirical formulas. Melting of the metal is considered in the Stefan approximation, and upon solidification it is assumed that all nanoparticles serve as centers for volume-sequential crystallization. Calculations were carried out with the following parameters: specific power p0 = 35 and 40 kW/cm2 at frequency f = 440 and 1200 kHz, the substrate velocity V = 0.5-2.5 cm/s, the nanoparticles' size is 50 nm and concentration Np = 2.0 . 109 cm-3. Based on the results obtained in a quasi-stationary formulation, the distribution of the temperature field, the dimensions of the melting and crystallization zones, the change in the solid fraction in the two-phase zone, the area of the treated substrate surface, depending on the speed of its movement and induction heating characteristics were estimated.

A coating of silane modified silica nanoparticles on PET substrate film for inkjet printing

NASA Astrophysics Data System (ADS)

Wu, J.; Liu, L.; Jiang, B.; Hu, Z.; Wang, X. Q.; Huang, Y. D.; Lin, D. R.; Zhang, Q. H.

2012-04-01

The paper aims to design nanoporous coatings for inkjet printing and study its microstructure influence on the ink absorption. In the present work, two inkjet materials were prepared: one with unmodified nano-SiO2 (S_1), the other with silica coupling agent modified nano-SiO2 (S_2). The surface characteristic changing after modification was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM). Wetting with contact angles was determined by the dynamic contact angle analysis test (DCAT). Through measurements, the dispersion of modified nano-SiO2 particles in the coating was superior to the dispersion of unmodified nano-SiO2 particles, surface roughness value (Ra) of S_1 was significantly higher than that of S_2, dynamic contact angle of S_2 is smaller than that of S_1 and ink droplet absorption in S_2 was much faster than in S_1. These results also reveal that the modification method is effective and offers a potential way to fabricate inkjet material with the advantages of microstructure and ink absorption over traditional methods.

Surface modification of upconverting nanoparticles by layer-by-layer assembled polyelectrolytes and metal ions.

PubMed

Palo, Emilia; Salomäki, Mikko; Lastusaari, Mika

2017-12-15

Modificating and protecting the upconversion luminescence nanoparticles is important for their potential in various applications. In this work we demonstrate successful coating of the nanoparticles by a simple layer-by-layer method using negatively charged polyelectrolytes and neodymium ions. The layer fabrication conditions such as number of the bilayers, solution concentrations and selected polyelectrolytes were studied to find the most suitable conditions for the process. The bilayers were characterized and the presence of the desired components was studied and confirmed by various methods. In addition, the upconversion luminescence of the bilayered nanoparticles was studied to see the effect of the surface modification on the overall intensity. It was observed that with selected deposition concentrations the bilayer successfully shielded the particle resulting in stronger upconversion luminescence. The layer-by-layer method offers multiple possibilities to control the bilayer growth even further and thus gives promises that the use of upconverting nanoparticles in applications could become even easier with less modification steps in the future. Copyright © 2017 Elsevier Inc. All rights reserved.

[Improvement of powder flowability and hygroscopicity of traditional Chinese medicine extract by surface coating modification technology].

PubMed

Zeng, Rong-Gui; Jiang, Qie-Ying; Liao, Zheng-Gen; Zhao, Guo-Wei; Luo, Yun; Luo, Juan; Lv, Dan

2016-06-01

To study the improvement of powder flowability and hygroscopicity of traditional Chinese medicine extract by surface coating modification technology. The 1% hydrophobic silica nanoparticles were used as surface modifier, and andrographis extract powder was taken as a model drug. Three different techniques were used for coating model drugs, with angle of repose, compressibility, flat angle and cohesion as the comprehensive evaluation indexes for the powder flowability. The powder particle size and the size distribution were measured by Mastersizer 2000. FEI scanning electron microscope was used to observe the surface morphology and structure of the powder. The percentage of Si element on the powder surface was measured by energy dispersive spectrometer. The hygroscopicity of powder was determined by Chinese pharmacopoeia method. All of the three techniques can improve the flowability of powder extract. In particular, hygroscopicity of extract powder can also be improved by dispersion and then high-speed mixing, which can produce a higher percentage of Si element on the powder surface. The improvement principle may be correlated with a modifier adhered to the powder surface. Copyright© by the Chinese Pharmaceutical Association.

Influence of surface morphology on the immersion mode ice nucleation efficiency of hematite particles

NASA Astrophysics Data System (ADS)

Hiranuma, N.; Hoffmann, N.; Kiselev, A.; Dreyer, A.; Zhang, K.; Kulkarni, G.; Koop, T.; Möhler, O.

2014-03-01

In this paper, the effect of the morphological modification of aerosol particles with respect to heterogeneous ice nucleation is comprehensively investigated for laboratory-generated hematite particles as a model substrate for atmospheric dust particles. The surface-area-scaled ice nucleation efficiencies of monodisperse cubic hematite particles and milled hematite particles were measured with a series of expansion cooling experiments using the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud simulation chamber. Complementary offline characterization of physico-chemical properties of both hematite subsets were also carried out with scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, dynamic light scattering (DLS), and an electro-kinetic particle charge detector to further constrain droplet-freezing measurements of hematite particles. Additionally, an empirical parameterization derived from our laboratory measurements was implemented in the single-column version of the Community Atmospheric Model version 5 (CAM5) to investigate the model sensitivity in simulated ice crystal number concentration on different ice nucleation efficiencies. From an experimental perspective, our results show that the immersion mode ice nucleation efficiency of milled hematite particles is almost an order of magnitude higher at -35.2 °C < T < -33.5 °C than that of the cubic hematite particles, indicating a substantial effect of morphological irregularities on immersion mode freezing. Our modeling results similarly show that the increased droplet-freezing rates of milled hematite particles lead to about one order magnitude higher ice crystal number in the upper troposphere than cubic hematite particles. Overall, our results suggest that the surface irregularities and associated active sites lead to greater ice activation through droplet freezing.

The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size

PubMed Central

Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

2016-01-01

Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of −0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process. PMID:27104527

The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size.

PubMed

Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

2016-04-20

Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of -0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process.

Modification of titanium surfaces by adding antibiotic-loaded PHB spheres and PEG for biomedical applications.

PubMed

Rodríguez-Contreras, Alejandra; Marqués-Calvo, María Soledad; Gil, Francisco Javier; Manero, José María

2016-08-01

Novel researches are focused on the prevention and management of post-operative infections. To avoid this common complication of implant surgery, it is preferable to use new biomaterials with antibacterial properties. Therefore, the aim of this work is to develop a method of combining the antibacterial properties of antibiotic-loaded poly(3-hydroxybutyrate) (PHB) nano- and micro-spheres and poly(ethylene glycol) (PEG) as an antifouling agent, with titanium (Ti), as the base material for implants, in order to obtain surfaces with antibacterial activity. The Ti surfaces were linked to both PHB particles and PEG by a covalent bond. This attachment was carried out by firstly activating the surfaces with either Oxygen plasma or Sodium hydroxide. Further functionalization of the activated surfaces with different alkoxysilanes allows the reaction with PHB particles and PEG. The study confirms that the Ti surfaces achieved the antibacterial properties by combining the antibiotic-loaded PHB spheres, and PEG as an antifouling agent.

Fluorescence-encoded gold nanoparticles: library design and modulation of cellular uptake into dendritic cells.

PubMed

Rodriguez-Lorenzo, Laura; Fytianos, Kleanthis; Blank, Fabian; von Garnier, Christophe; Rothen-Rutishauser, Barbara; Petri-Fink, Alke

2014-04-09

In order to harness the unique properties of nanoparticles for novel clinical applications and to modulate their uptake into specific immune cells we designed a new library of homo- and hetero-functional fluorescence-encoded gold nanoparticles (Au-NPs) using different poly(vinyl alcohol) and poly(ethylene glycol)-based polymers for particle coating and stabilization. The encoded particles were fully characterized by UV-Vis and fluorescence spectroscopy, zeta potential and dynamic light scattering. The uptake by human monocyte derived dendritic cells in vitro was studied by confocal laser scanning microscopy and quantified by fluorescence-activated cell sorting and inductively coupled plasma atomic emission spectroscopy. We show how the chemical modification of particle surfaces, for instance by attaching fluorescent dyes, can conceal fundamental particle properties and modulate cellular uptake. In order to mask the influence of fluorescent dyes on cellular uptake while still exploiting its fluorescence for detection, we have created hetero-functionalized Au-NPs, which again show typical particle dependent cellular interactions. Our study clearly prove that the thorough characterization of nanoparticles at each modification step in the engineering process is absolutely essential and that it can be necessary to make substantial adjustments of the particles in order to obtain reliable cellular uptake data, which truly reflects particle properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes.

PubMed

Akhmetshina, Alsu A; Davletbaeva, Ilsiya M; Grebenschikova, Ekaterina S; Sazanova, Tatyana S; Petukhov, Anton N; Atlaskin, Artem A; Razov, Evgeny N; Zaripov, Ilnaz I; Martins, Carla F; Neves, Luísa A; Vorotyntsev, Ilya V

2015-12-30

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf₂N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N₂, NH₃, H₂S, and CO₂ gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF₆] and [emim][Tf₂N]. The modification of SILMs by nanosize silica particles leads to an increase of NH₃ separation relatively to CO₂ or H₂S.

Nanostructure and surface activation of mayenite (12CaO·7Al2O3) ceramics via femtosecond laser irradiation in solvents

NASA Astrophysics Data System (ADS)

Visbal, Heidy; Hirano, Minami; Omura, Takuya; Shimizu, Masahiro; Takaishi, Taigo; Hirao, Kazuyuki

2017-07-01

Mayenite (12CaO·7Al2O3) is a highly interesting functional material due to the wide variety of its possible future applications. In this study, we used femtosecond laser irradiation in several solvents with varying polarities to increase the specific surface area of 12CaO·7Al2O3 ceramics and reduce their particle size without any structural degradation or loss of crystallinity. We observed that when femtosecond laser irradiation was applied to solvents bearing hydroxyl groups, a smaller particle size was obtained with the particle size decreasing as the polarity of the solvent increased. Using infrared spectroscopy, we confirmed the presence of hydroxyl and carbonyl surface functional groups at the surface of 12CaO·7Al2O3 ceramics after femtosecond laser irradiation. This is attributed to the direct chemical bonds breaking of the solvent via multiphoton ionization and/or tunneling ionization, followed by the Coulomb explosion and the subsequent production of ions that are adsorbed on the surfaces of 12CaO·7Al2O3 ceramics. Femtosecond laser irradiation in polar solvents with hydroxyl groups can reduce the particle size and increase the specific surface area without degradation or loss of crystallinity of 12CaO·7Al2O3 ceramics. Additionally, this method can be used for the surface modification and introduction of functional groups on the 12CaO·7Al2O3 ceramics surface.

The photocatalytic and cytotoxic effects of titanium dioxide particles used in sunscreen

NASA Astrophysics Data System (ADS)

Rampaul, Ashti

Titanium dioxide nanoparticles are used in sunscreens to reflect UV radiation from the skin. However, titanium dioxide as anatase and rutile crystal forms is a well-known photocatalyst. The nanoparticles are surface coated with inert inorganic oxides such as silica and alumina or organics such as organosilanes or silicone polymers and more recently, have been doped with manganese oxide. These modifications to the titanium dioxide particles are purported to prevent the production of harmful reactive oxygen species. A range of sunscreens was tested with crystal form and modification type identified via XRD, Raman Spectroscopy, XPS and SSNMR. The particle modification and crystal form determined whether the particles were inert or rapidly degraded methylene blue dye, and killed or protected cultured human epithelium cells. Novel solid state Electron Paramagnetic Resonance analysis showed that the greatest amount of superoxide anions was formed during UVA irradiation of the mixed anatase and rutile crystal forms coated with an organosilane. These particles also degraded methylene blue at a similar rate to Degussa P25, a standard uncoated titanium dioxide powder and produced an increase in UVA induced apoptosis of human keratinocytes. Double Stranded Breaks were observed extensively in cells exposed to UVA irradiated mixed anatase and rutile titanium dioxide with organosilane. A new apoptotic-like cell death mechanism may have been recognised during the UVA irradiation of animal and human cells in the presence of titanium dioxide. This research concludes that mixed anatase and rutile crystal forms of titanium dioxide coated with organosilane or dimethicone may not be safe to use in sunscreen lotions. A less harmful alternative for sunscreen formulations is the manganese doped rutile particles or the alumina coated rutile powders, both of which exhibited a protective effect on cultured epithelial cells.

Enhanced assembly and colloidal stabilization of primate erythroparvovirus 1 virus-like particles for improved surface engineering.

PubMed

Sánchez-Rodríguez, Sandra Paola; Morán-García, Areli del Carmen; Bolonduro, Olurotimi; Dordick, Jonathan S; Bustos-Jaimes, Ismael

2016-04-15

Virus-like particles (VLPs) are the product of the self-assembly, either in vivo or in vitro, of structural components of viral capsids. These particles are excellent scaffolds for surface display of biomolecules that can be used in vaccine development and tissue-specific drug delivery. Surface engineering of VLPs requires structural stability and chemical reactivity. Herein, we report the enhanced assembly, colloidal stabilization and fluorescent labeling of primate erythroparvovirus 1 (PE1V), generally referred to as parvovirus B19. In vitro assembly of the VP2 protein of PE1V produces VLPs, which are prone to flocculate and hence undergo limited chemical modification by thiol-specific reagents like the fluorogenic monobromobimane (mBBr). We determined that the addition of 0.2M l-arginine during the assembly process produced an increased yield of soluble VLPs with good dispersion stability. Fluorescent labeling of VLPs suspended in phosphate buffered saline (PBS) added with 0.2M l-Arg was achieved in significantly shorter times than the flocculated VLPs assembled in only PBS buffer. Finally, to demonstrate the potential application of this approach, mBBr-labeled VLPs were successfully used to tag human hepatoma HepG2 cells. This new method for assembly and labeling PE1V VLPs eases its applications and provides insights on the manipulation of this biomaterial for further developments. Application of virus-derived biomaterials sometimes requires surface modification for diverse purposes, including enhanced cell-specific interaction, the inclusion of luminescent probes for bioimaging, or the incorporation of catalytic properties for the production of enzyme nanocarriers. In this research, we reported for the first time the colloidal stabilization of the primate erythroparvovirus 1 (PE1V) virus-like particles (VLPs). Also, we report the chemical modification of the natural Cys residues located on the surface of these VLPs with a fluorescent probe, as well as its application for tagging hepatoma cells in vitro. Keeping in mind that PE1V is a human pathogen, virus-host interactions already exist in human cells, and they can be exploited for therapeutic and research aims. This study will impact on the speed in which the scientific community will be able to manipulate PE1V VLPs for diverse purposes. Additionally, this study may provide insights on the colloidal properties of these VLPs as well as in the effect of different protein additives used for protein stabilization. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via "Click" Reaction.

PubMed

Hollingsworth, Javoris V; Bhupathiraju, N V S Dinesh K; Sun, Jirun; Lochner, Eric; Vicente, M Graça H; Russo, Paul S

2016-01-13

A facile approach using click chemistry is demonstrated for immobilization of metalloporphyrins onto the surface of silica-coated iron oxide particles. Oleic-acid stabilized iron oxide nanocrystals were prepared by thermal decomposition of iron(III) acetylacetonate. Their crystallinity, morphology, and superparamagnetism were determined using X-ray diffraction, transmission electron microscopy, and a superconducting quantum interference device. Monodisperse core-shell particles were produced in the silica-coating of iron oxide via microemulsion synthesis. Surface modification of these particles was performed in two steps, which included the reaction of silica-coated iron oxide particles with 3-bromopropyltrichlorosilane, followed by azido-functionalization with sodium azide. Monoalkylated porphyrins were prepared using the Williamson ether synthesis of commercially available tetra(4-hydroxyphenyl) porphyrin with propargyl bromide in the presence of a base. (1)H NMR and matrix-assisted laser desorption ionization confirmed the identity of the compounds. The prepared monoalkyne porphyrins were zinc-metalated prior to their introduction to azide-functionalized, silica-coated iron oxide particles in the click reaction. X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to characterize the surface chemistry after each step in the reaction. In addition, particle size was determined using dynamic light scattering and microscopy. The presented methodology is versatile and can be extended to other photoreactive systems, such as phthalocyanines and boron-dipyrromethane, which may lead to new materials for optical, photonic, and biological applications.

Colloids with high-definition surface structures

PubMed Central

Chen, Hsien-Yeh; Rouillard, Jean-Marie; Gulari, Erdogan; Lahann, Joerg

2007-01-01

Compared with the well equipped arsenal of surface modification methods for flat surfaces, techniques that are applicable to curved, colloidal surfaces are still in their infancy. This technological gap exists because spin-coating techniques used in traditional photolithographic processes are not applicable to the curved surfaces of spherical objects. By replacing spin-coated photoresist with a vapor-deposited, photodefinable polymer coating, we have now fabricated microstructured colloids with a wide range of surface patterns, including asymmetric and chiral surface structures, that so far were typically reserved for flat substrates. This high-throughput method can yield surface-structured colloidal particles at a rate of ≈107 to 108 particles per operator per day. Equipped with spatially defined binding pockets, microstructured colloids can engage in programmable interactions, which can lead to directed self-assembly. The ability to create a wide range of colloids with both simple and complex surface patterns may contribute to the genesis of previously unknown colloidal structures and may have important technological implications in a range of different applications, including photonic and phononic materials or chemical sensors. PMID:17592149

Bromelain Surface Modification Increases the Diffusion of Silica Nanoparticles in the Tumor Extracellular Matrix

PubMed Central

2015-01-01

Tumor extracellular matrix (ECM) represents a major obstacle to the diffusion of therapeutics and drug delivery systems in cancer parenchyma. This biological barrier limits the efficacy of promising therapeutic approaches including the delivery of siRNA or agents intended for thermoablation. After extravasation due to the enhanced penetration and retention effect of tumor vasculature, typical nanotherapeutics are unable to reach the nonvascularized and anoxic regions deep within cancer parenchyma. Here, we developed a simple method to provide mesoporous silica nanoparticles (MSN) with a proteolytic surface. To this extent, we chose to conjugate MSN to Bromelain (Br–MSN), a crude enzymatic complex, purified from pineapple stems, that belongs to the peptidase papain family. This surface modification increased particle uptake in endothelial, macrophage, and cancer cell lines with minimal impact on cellular viability. Most importantly Br–MSN showed an increased ability to digest and diffuse in tumor ECM in vitro and in vivo. PMID:25119793

Bromelain surface modification increases the diffusion of silica nanoparticles in the tumor extracellular matrix.

PubMed

Parodi, Alessandro; Haddix, Seth G; Taghipour, Nima; Scaria, Shilpa; Taraballi, Francesca; Cevenini, Armando; Yazdi, Iman K; Corbo, Claudia; Palomba, Roberto; Khaled, Sm Z; Martinez, Jonathan O; Brown, Brandon S; Isenhart, Lucas; Tasciotti, Ennio

2014-10-28

Tumor extracellular matrix (ECM) represents a major obstacle to the diffusion of therapeutics and drug delivery systems in cancer parenchyma. This biological barrier limits the efficacy of promising therapeutic approaches including the delivery of siRNA or agents intended for thermoablation. After extravasation due to the enhanced penetration and retention effect of tumor vasculature, typical nanotherapeutics are unable to reach the nonvascularized and anoxic regions deep within cancer parenchyma. Here, we developed a simple method to provide mesoporous silica nanoparticles (MSN) with a proteolytic surface. To this extent, we chose to conjugate MSN to Bromelain (Br-MSN), a crude enzymatic complex, purified from pineapple stems, that belongs to the peptidase papain family. This surface modification increased particle uptake in endothelial, macrophage, and cancer cell lines with minimal impact on cellular viability. Most importantly Br-MSN showed an increased ability to digest and diffuse in tumor ECM in vitro and in vivo.

Modification, calibration, and performance of the Ultra-High Sensitivity Aerosol Spectrometer for particle size distribution and volatility measurements during the Atmospheric Tomography Mission (ATom) airborne campaign

NASA Astrophysics Data System (ADS)

Kupc, Agnieszka; Williamson, Christina; Wagner, Nicholas L.; Richardson, Mathews; Brock, Charles A.

2018-01-01

Atmospheric aerosol is a key component of the chemistry and climate of the Earth's atmosphere. Accurate measurement of the concentration of atmospheric particles as a function of their size is fundamental to investigations of particle microphysics, optical characteristics, and chemical processes. We describe the modification, calibration, and performance of two commercially available, Ultra-High Sensitivity Aerosol Spectrometers (UHSASs) as used on the NASA DC-8 aircraft during the Atmospheric Tomography Mission (ATom). To avoid sample flow issues related to pressure variations during aircraft altitude changes, we installed a laminar flow meter on each instrument to measure sample flow directly at the inlet as well as flow controllers to maintain constant volumetric sheath flows. In addition, we added a compact thermodenuder operating at 300 °C to the inlet line of one of the instruments. With these modifications, the instruments are capable of making accurate (ranging from 7 % for Dp < 0.07 µm to 1 % for Dp > 0.13 µm), precise (< ±1.2 %), and continuous (1 Hz) measurements of size-resolved particle number concentration over the diameter range of 0.063-1.0 µm at ambient pressures of > 1000 to 225 hPa, while simultaneously providing information on particle volatility.We assessed the effect of uncertainty in the refractive index (n) of ambient particles that are sized by the UHSAS assuming the refractive index of ammonium sulfate (n = 1.52). For calibration particles with n between 1.44 and 1.58, the UHSAS diameter varies by +4/-10 % relative to ammonium sulfate. This diameter uncertainty associated with the range of refractive indices (i.e., particle composition) translates to aerosol surface area and volume uncertainties of +8.4/-17.8 and +12.4/-27.5 %, respectively. In addition to sizing uncertainty, low counting statistics can lead to uncertainties of < 20 % for aerosol surface area and < 30 % for volume with 10 s time resolution. The UHSAS reduction in counting efficiency was corrected for concentrations > 1000 cm-3.Examples of thermodenuded and non-thermodenuded aerosol number and volume size distributions as well as propagated uncertainties are shown for several cases encountered during the ATom project. Uncertainties in particle number concentration were limited by counting statistics, especially in the tropical upper troposphere where accumulation-mode concentrations were sometimes < 20 cm-3 (counting rates ˜ 5 Hz) at standard temperature and pressure.

Modeling of ultra-small lipid nanoparticle surface charge for targeting glioblastoma.

PubMed

Mendes, Maria; Miranda, Ana; Cova, Tânia; Gonçalves, Lídia; Almeida, António J; Sousa, João J; do Vale, Maria L C; Marques, Eduardo F; Pais, Alberto; Vitorino, Carla

2018-05-30

Surface modification of ultra-small nanostructured lipid carriers (usNLC) via introduction of a positive charge is hypothesized to prompt site-specific drug delivery for glioblastoma multiforme (GBM) treatment. A more effective interaction with negatively charged lipid bilayers, including the blood-brain barrier (BBB), will facilitate the nanoparticle access to the brain. For this purpose, usNLC with a particle size of 43.82 ± 0.03 nm and a polydispersity index of 0.224 were developed following a Quality by Design approach. Monomeric and gemini surfactants, either with conventional headgroups or serine-based ones, were tested for the surface modification, and the respective safety and efficacy to target GBM evaluated. A comprehensive in silico-in vitro approach is also provided based on molecular dynamics simulations and cytotoxicity studies. Overall, monomeric serine-derived surfactants displayed the best performance, considering altogether particle size, zeta potential, cytotoxic profile and cell uptake. Although conventional surfactants were able to produce usNLC with suitable physicochemical properties and cell uptake, their use is discouraged due to their high cytotoxicity. This study suggests that monomeric serine-derived surfactants are promising agents for developing nanosystems aiming at brain drug delivery. Copyright © 2018 Elsevier B.V. All rights reserved.

CALCINATION AND SINTERING MODELS FOR APPLICATION TO HIGH-TEMPERATURE, SHORT-TIME SULFATION OF CALCIUM-BASED SORBENTS

EPA Science Inventory

To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the rate of calcination of CaCO3 or Ca(OH)2 is described by an empirical modification of the shrinking-core model. The physical model depicts particle decomposi...

Plasma polymer-functionalized silica particles for heavy metals removal.

PubMed

Akhavan, Behnam; Jarvis, Karyn; Majewski, Peter

2015-02-25

Highly negatively charged particles were fabricated via an innovative plasma-assisted approach for the removal of heavy metal ions. Thiophene plasma polymerization was used to deposit sulfur-rich films onto silica particles followed by the introduction of oxidized sulfur functionalities, such as sulfonate and sulfonic acid, via water-plasma treatments. Surface chemistry analyses were conducted by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Electrokinetic measurements quantified the zeta potentials and isoelectric points (IEPs) of modified particles and indicated significant decreases of zeta potentials and IEPs upon plasma modification of particles. Plasma polymerized thiophene-coated particles treated with water plasma for 10 min exhibited an IEP of less than 3.5. The effectiveness of developed surfaces in the adsorption of heavy metal ions was demonstrated through copper (Cu) and zinc (Zn) removal experiments. The removal of metal ions was examined through changing initial pH of solution, removal time, and mass of particles. Increasing the water plasma treatment time to 20 min significantly increased the metal removal efficiency (MRE) of modified particles, whereas further increasing the plasma treatment time reduced the MRE due to the influence of an ablation mechanism. The developed particulate surfaces were capable of removing more than 96.7% of both Cu and Zn ions in 1 h. The combination of plasma polymerization and oxidative plasma treatment is an effective method for the fabrication of new adsorbents for the removal of heavy metals.

Oleate-based hydrothermal preparation of CoFe2O4 nanoparticles, and their magnetic properties with respect to particle size and surface coating

NASA Astrophysics Data System (ADS)

Repko, Anton; Vejpravová, Jana; Vacková, Taťana; Zákutná, Dominika; Nižňanský, Daniel

2015-09-01

We present a facile and high-yield synthesis of cobalt ferrite nanoparticles by hydrothermal hydrolysis of Co-Fe oleate in the presence of pentanol/octanol/toluene and water at 180 or 220 °C. The particle size (6-10 nm) was controlled by the composition of the organic solvent and temperature. Magnetic properties were then investigated with respect to the particle size and surface modification with citric acid or titanium dioxide (leading to hydrophilic particles). The as-prepared hydrophobic nanoparticles (coated by oleic acid) had a minimum inter-particle distance of 2.5 nm. Their apparent blocking temperature (estimated as a maximum of the zero-field-cooled magnetization) was 180 K, 280 K and 330 K for the particles with size of 6, 9 and 10.5 nm, respectively. Replacement of oleic acid on the surface by citric acid decreased inter-particle distance to less than 1 nm, and increased blocking temperature by ca. 10 K. On the other hand, coating with titanium dioxide, supported by nitrilotri(methylphosphonic acid), caused increase of the particle spacing, and lowering of the blocking temperature by ca. 20 K. The CoFe2O4@TiO2 nanoparticles were sufficiently stable in water, methanol and ethanol. The particles were also investigated by Mössbauer spectroscopy and alternating-current (AC) susceptibility measurements, and their analysis with Vögel-Fulcher and power law. Effect of different particle coating and dipolar interactions on the magnetic properties is discussed.

Radiolytic stability of gibbsite and boehmite with adsorbed water

NASA Astrophysics Data System (ADS)

Huestis, Patricia; Pearce, Carolyn I.; Zhang, X.; N'Diaye, Alpha T.; Rosso, Kevin M.; LaVerne, Jay A.

2018-04-01

Aluminum oxyhydroxide (boehmite, AlOOH) and aluminum hydroxide (gibbsite, Al(OH)3) powders with adsorbed water were irradiated with γ-rays and 5 MeV He ions (α-particles) in order to determine overall radiation stability and chemical modification to the surface. No variation in overall phase or crystallinity due to radiolysis was observed with X-ray diffraction (XRD) and Raman spectroscopy for doses up to 2 MGy with γ-rays and 175 MGy with α-particles. Temperature programed desorption (TPD) of the water from the surface to the gas phase indicated that the water was chemisorbed and strongly bound. Water adsorption sites are of similar energy for both gibbsite and boehmite. Observation of the water adsorbed on the surface of gibbsite and boehmite with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed broad peaks at 3100-3600 cm-1 due to OH stretching that slowly decreased on heating to 500 °C, which corresponds well with the water vapor evolution observed with TPD. Both materials were found to be amorphous following heating to 500 °C. X-ray photoelectron spectroscopy (XPS) indicated surface reduction of Al(III) to Al metal on radiolysis with α-particles. Complete loss of chemisorbed water and the formation of bulk O atoms was observed following radiolysis with α-particles.

Radiolytic stability of gibbsite and boehmite with adsorbed water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huestis, Patricia; Pearce, Carolyn I.; Zhang, X.

Aluminum oxyhydroxide (boehmite, AlOOH) and aluminum hydroxide (gibbsite, Al(OH)3) powders with adsorbed water were irradiated with -rays and 5 MeV He ions (α-particles) in order to determine overall radiation stability and chemical modification to the surface. No variation in overall phase or crystallinity due to radiolysis was observed with X-ray diffraction (XRD) and Raman spectroscopy for doses up to 2 MGy with -rays and 175 MGy with α-particles. Temperature programed desorption (TPD) of the water from the surface to the gas phase indicated that the water was chemisorbed and strongly bound. Water adsorption sites are of similar energy for bothmore » gibbsite and boehmite. Observation of the water adsorbed on the surface of gibbsite and boehmite with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed broad peaks at 3100-3600 cm-1 due to OH stretching that slowly decreased on heating to 500oC, which corresponds well with the water vapor evolution observed with TPD. Both materials were found to be amorphous following heating to 500oC. X-ray photoelectron spectroscopy (XPS) indicated surface reduction of Al(III) to Al metal on radiolysis with α-particles. Complete loss of chemisorbed water and the formation of bulk O atoms was observed following radiolysis with α-particles.« less

Foraging on the potential energy surface: a swarm intelligence-based optimizer for molecular geometry.

PubMed

Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D; Sebastiani, Daniel

2012-11-21

We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials.

Foraging on the potential energy surface: A swarm intelligence-based optimizer for molecular geometry

NASA Astrophysics Data System (ADS)

Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D.; Sebastiani, Daniel

2012-11-01

We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials.

From fly ash waste slurry to functional adsorbent for valuable rare earth ion separation: An ingenious combination process involving modification, dewatering and grafting.

PubMed

Zhou, Qi; Luo, Tiantian; Yang, Heng; Liang, Cheng; Jing, Luru; Luo, Wenjun

2018-03-01

Acid extracting aluminum from fly ash would produce pestilent secondary fly ash slurry with strong acidity, high content of Cl - and residual Al 3+ that is difficult to be further used. In order to achieve the zero emission, a potential integrated treatment process for reutilization was proposed in this paper. By intelligent use of residual Al 3+ in sludge as catalyst, hydrophobic modification of solid particle was taken with fatty acid via a heterogeneous esterification at normal temperature. Due to the solvophobic force, moisture content of its filter cake was 36.46%, which reduced 11.14% compared with the unmodified one, hydrophobicity scale can achieve 100% with modifier accounting for only 0.8% of solid content and the Cl - concentrations decreased from 20 to 0.102 g/L in wash liquor, thus greatly saving water for washing and energy for drying. Subsequently, based on the appearance of hydrocarbon chains on particle surface, a high-efficiency ultraviolet-induced grafting polymerization was implemented to fabricate density polyacrylic acid decorated fly ash particles from the surface "CH" sites, the resultant composite was proved to efficiently separate valuable rare-earth Gd 3+ from wastewater with outstanding adsorption and regeneration performance, hence bringing high added-value utilization for these hazardous waste. Copyright © 2017 Elsevier Inc. All rights reserved.

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes

PubMed Central

Akhmetshina, Alsu A.; Davletbaeva, Ilsiya M.; Grebenschikova, Ekaterina S.; Sazanova, Tatyana S.; Petukhov, Anton N.; Atlaskin, Artem A.; Razov, Evgeny N.; Zaripov, Ilnaz I.; Martins, Carla F.; Neves, Luísa A.; Vorotyntsev, Ilya V.

2015-01-01

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S. PMID:26729177

On the mobility of iron particles embedded in elastomeric silicone matrix

NASA Astrophysics Data System (ADS)

Rabindranath, R.; Böse, H.

2013-02-01

In this contribution the rheological and magnetorheological properties of different polydimethylsiloxane (PDMS) based magnetorheological elastomers (MRE) are presented and discussed. In order to investigate the mobility of the iron particles with respect to the rheological characteristics, the iron particles were silanized with vinyltrimethoxysilane to enable a reaction between the modified particle and the cross-linking agent of the silicone elastomer. In addition, the vinyl-functionalized particles were further modified by the coupling of the superficial vinyl groups with a long-chain hydride terminated PDMS, which enables a reaction pathway with the vinyl terminated PDMS. On the other hand, the iron particles were treated with surfactants such as fatty acids, calcium and aluminum soaps, respectively, prior to vulcanization in order to increase the mobility of the iron particles in the elastomeric matrix. It was found, that both, the modification with the long-chain hydride terminated PDMS as well as the treatment with surfactants lead to an increase of the storage modulus G', the loss modulus G" and the loss factor tan δ in the magnetic field. It is concluded that both modifications, the coupling with long-chain hydride terminated PDMS as well as the treatment with surfactants, provide a greater mobility of the iron particles and hence a greater friction represented by the increase of the loss factor tan δ. Consequently it is assumed that untreated iron particles are less mobile in the rubber matrix due to covalent bonding with the silicone components, most likely due to the reaction of the hydroxyl groups on the metal surface with the silane groups of the cross-linking agent.

Development of a High Efficiency Dry Powder Inhaler: Effects of Capsule Chamber Design and Inhaler Surface Modifications

PubMed Central

Behara, Srinivas R.B.; Farkas, Dale R.; Hindle, Michael; Longest, P. Worth

2013-01-01

Purpose The objective of this study was to explore the performance of a high efficiency dry powder inhaler (DPI) intended for excipient enhanced growth (EEG) aerosol delivery based on changes to the capsule orientation and surface modifications of the capsule and device. Methods DPIs were constructed by combining newly designed capsule chambers (CC) with a previously developed three-dimensional (3D) rod array for particle deagglomeration and a previously optimized EEG formulation. The new CCs oriented the capsule perpendicular to the incoming airflow and were analyzed for different air inlets at a constant pressure drop across the device. Modifications to the inhaler and capsule surfaces included use of metal dispersion rods and surface coatings. Aerosolization performance of the new DPIs was evaluated and compared with commercial devices. Results The proposed capsule orientation and motion pattern increased capsule vibrational frequency and reduced the aerosol MMAD compared with commercial/modified DPIs. The use of metal rods in the 3D array further improved inhaler performance. Coating the inhaler and capsule with PTFE significantly increased emitted dose (ED) from the optimized DPI. Conclusions High efficiency performance is achieved for EEG delivery with the optimized DPI device and formulation combination producing an aerosol with MMAD < 1.5 µm, FPF<5µm/ED > 90%, and ED > 80%. PMID:23949304

Effects of content and surface hydrophobic modification of BaTiO3 on the cooling properties of ASA (acrylonitrile-styrene-acrylate copolymer)

NASA Astrophysics Data System (ADS)

Xiang, Bo; Zhang, Jun

2018-01-01

For the field of cool material, barium titanate (BaTiO3, BT) is still a new member that needs to be further studied. Herein, the effects of both content and surface hydrophobic modification of BT on the cooling properties of acrylonitrile-styrene-acrylate copolymer (ASA) were detailedly investigated, aiming to fabricate composited cool material. Butyl acrylate (BA) was employed to convert the surface of BT from hydrophilic to hydrophobic. The addition of unmodified BT could significantly improve the solar reflectance of ASA, especially when the addition amount is 3 vol%, the near infrared (NIR) reflectance increased from 22.02 to 72.60%. However, serious agglomeration occurred when the addition amount increased to 5 vol% and therefore led to a relatively smaller increase in solar reflectance and an obvious decline in impact strength. After surface hydrophobic modification, the modified BT (M-BT) presented better dispersibility in ASA matrix, which contributed to the improvement of both solar reflectance and impact strength. In addition, the temperature test provided a more sufficient and intuitive way to evaluate the cooling effect of the composited cool materials, and a significant decrease (over 10 °C) could be achieved in the temperature test when M-BT particles were introduced.

Enhancing the Hydrophilicity and Cell Attachment of 3D Printed PCL/Graphene Scaffolds for Bone Tissue Engineering

PubMed Central

Wang, Weiguang; Caetano, Guilherme; Ambler, William Stephen; Blaker, Jonny James; Frade, Marco Andrey; Mandal, Parthasarathi; Diver, Carl; Bártolo, Paulo

2016-01-01

Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes, as well as surface treatment. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion-based additive manufacturing system to produce poly(ε-caprolactone) (PCL)/pristine graphene scaffolds for bone tissue applications and the influence of chemical surface modification on their biological behaviour. Scaffolds with the same architecture but different concentrations of pristine graphene were evaluated from surface property and biological points of view. Results show that the addition of pristine graphene had a positive impact on cell viability and proliferation, and that surface modification leads to improved cell response. PMID:28774112

Enhancing the Hydrophilicity and Cell Attachment of 3D Printed PCL/Graphene Scaffolds for Bone Tissue Engineering.

PubMed

Wang, Weiguang; Caetano, Guilherme; Ambler, William Stephen; Blaker, Jonny James; Frade, Marco Andrey; Mandal, Parthasarathi; Diver, Carl; Bártolo, Paulo

2016-12-07

Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes, as well as surface treatment. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion-based additive manufacturing system to produce poly( ε -caprolactone) (PCL)/pristine graphene scaffolds for bone tissue applications and the influence of chemical surface modification on their biological behaviour. Scaffolds with the same architecture but different concentrations of pristine graphene were evaluated from surface property and biological points of view. Results show that the addition of pristine graphene had a positive impact on cell viability and proliferation, and that surface modification leads to improved cell response.

PEG-Stabilized Core–Shell Surface-Imprinted Nanoparticles

PubMed Central

Moczko, Ewa; Guerreiro, Antonio; Piletska, Elena; Piletsky, Sergey

2016-01-01

Here we present a simple technique to produce target-specific molecularly imprinted polymeric nanoparticles (MIP NPs) and their surface modification in order to prevent the aggregation process that is ever-present in most nanomaterial suspensions/dispersions. Specifically, we studied the influence of surface modification of MIP NPs with polymerizable poly(ethylene glycol) on their degree of stability in water, in phosphate buffer, and in the presence of serum proteins. Grafting a polymer shell on the surface of nanoparticles decreases the surface energy, enhances the polarity, and as a result improves the dispersibility, storage, and colloidal stability as compared to those of core (unmodified) particles. Because of the unique solid-phase approach used for synthesis, the binding sites of MIP NPs are protected during grafting, and the recognition properties of nanoparticles are not affected. These results are significant for developing nanomaterials with selective molecular recognition, increased biocompatibility, and stability in solution. Materials synthesized this way have the potential to be used in a variety of technological fields, including in vivo applications such as drug delivery and imaging. PMID:23855734

Development of Ultra-High Molecular Weight Polyethylene (UHMWPE) Coating by Cold Spray Technique

NASA Astrophysics Data System (ADS)

Ravi, Kesavan; Ichikawa, Yuji; Deplancke, Tiana; Ogawa, Kazuhiro; Lame, Olivier; Cavaille, Jean-Yves

2015-08-01

Ultra-high molecular weight polyethylene or UHMWPE is an extremely difficult material to coat with, as it is rubbery and chemically very inert. The Cold Spray process appears to be a promising alternative processing technique but polymers are in general difficult to deposit using this method. So, attempts to develop UHMWPE coatings were made using a downstream injection cold spray technique incorporating a few modifications. A conventional cold spray machine yielded only a few deposited particles of UHMWPE on the substrate surface, but with some modifications in the nozzle geometry (especially the length and inner geometry) a thin coating of 45 μm on Al substrate was obtained. Moreover, experiments with the addition of fumed nano-alumina to the feedstock yielded a coating of 1-4 mm thickness on Al and polypropylene substrates. UHMWPE was seen to be melt crystallized during the coating formation, as can be seen from the differential calorimetry curves. Influence of nano-ceramic particles was explained by observing the creation of a bridge bond between UHMWPE particles.

Selectively-etched nanochannel electrophoretic and electrochemical devices

DOEpatents

Surh, Michael P.; Wilson, William D.; Barbee, Jr., Troy W.; Lane, Stephen M.

2004-11-16

Nanochannel electrophoretic and electrochemical devices having selectively-etched nanolaminates located in the fluid transport channel. The normally flat surfaces of the nanolaminate having exposed conductive (metal) stripes are selectively-etched to form trenches and baffles. The modifications of the prior utilized flat exposed surfaces increase the amount of exposed metal to facilitate electrochemical redox reaction or control the exposure of the metal surfaces to analytes of large size. These etched areas variously increase the sensitivity of electrochemical detection devices to low concentrations of analyte, improve the plug flow characteristic of the channel, and allow additional discrimination of the colloidal particles during cyclic voltammetry.

Selectively-etched nanochannel electrophoretic and electrochemical devices

DOEpatents

Surh, Michael P [Livermore, CA; Wilson, William D [Pleasanton, CA; Barbee, Jr., Troy W.; Lane, Stephen M [Oakland, CA

2006-06-27

Nanochannel electrophoretic and electrochemical devices having selectively-etched nanolaminates located in the fluid transport channel. The normally flat surfaces of the nanolaminate having exposed conductive (metal) stripes are selectively-etched to form trenches and baffles. The modifications of the prior utilized flat exposed surfaces increase the amount of exposed metal to facilitate electrochemical redox reaction or control the exposure of the metal surfaces to analytes of large size. These etched areas variously increase the sensitivity of electrochemical detection devices to low concentrations of analyte, improve the plug flow characteristic of the channel, and allow additional discrimination of the colloidal particles during cyclic voltammetry.

Effect of pH and leucine concentration on aerosolization properties of carrier-free formulations of levofloxacin.

PubMed

Barazesh, Ahmadreza; Gilani, Kambiz; Rouini, Mohammadreza; Barghi, Mohammad Ali

2018-06-15

The aim of this study was to evaluate the effect of leucine at different pH values preferred for inhalation on particle characteristics and aerosolization performance of spray dried carrier-free formulations of levofloxacin. A full factorial design was applied to optimize the formulation containing levofloxacin with or without leucine in different pH values and the optimum condition was determined. Particle size and morphology, crystallinity state, electrostatic charge and surface composition of the particles were determined. Aerodynamic properties of the powders were also assessed by an Andersen cascade impactor after aerosolization through an Aerolizer® at an air flow rate of 60 L/min. The pH of initial solution affected various physical properties of the drug containing particles and hence their in vitro deposition. The profound effect of pH was on water content, electrostatic charge and surface composition of the particles. The negative effect of water content on in vitro deposition of the drug was covered by preferred surface accumulation of leucine at pH 6. Optimum formulation which obtained by co-spray drying of the drug with 21.79% leucine at pH 5.98 presented a fine particle fraction equal to 54.38. In conclusion, changing pH of the initial solution influenced the effect of leucine on aerosolization of levofloxacine spray dried particles by modification of their physical properties. Copyright © 2018 Elsevier B.V. All rights reserved.

Differential effect of hydroxyapatite nano-particle versus nano-rod decorated titanium micro-surface on osseointegration.

PubMed

Bai, Long; Liu, Yanlian; Du, Zhibin; Weng, Zeming; Yao, Wei; Zhang, Xiangyu; Huang, Xiaobo; Yao, Xiaohong; Crawford, Ross; Hang, Ruiqiang; Huang, Di; Tang, Bin; Xiao, Yin

2018-06-15

Coating materials applied for intraosseous implants must be optimized to stimulate osseointegration. Osseointegration is a temporal and spatial physiological process that not only requires interactions between osteogenesis and angiogenesis but also necessitates a favorable immune microenvironment. It is now well-documented that hierarchical nano-micro surface structures promote the long-term stability of implants, the interactions between nano-micro structure and the immune response are largely unknown. Here, we report the effects of microporous titanium (Ti) surfaces coated with nano-hydroxyapatite (HA) produced by micro-arc oxidation and steam-hydrothermal treatment (SHT) on multiple cell behavior and osseointegration. By altering the processing time of SHT it was possible to shift HA structures from nano-particles to nano-rods on the microporous Ti surfaces. Ti surfaces coated with HA nano-particles were found to modulate the inflammatory response resulting in an osteoimmune microenvironment more favorable for osteo-/angio-genesis, most likely via the activation of certain key signaling pathways (TGF-β, OPG/RANKL, and VEGF). By contrast, Ti surfaces coated with nano-rod shaped HA particles had a negative impact on osteo-/angio-genesis and osteoimmunomodulation. In vivo results further demonstrated that Ti implant surfaces decorated with HA nano-particles can stimulate new bone formation and osseointegration with enhanced interaction between osteocytes and implant surfaces. This study demonstrated that Ti implants with micro-surfaces coated with nano-particle shaped HA have a positive impact on osseointegration. Osteo-/angio-genesis are of importance during osteointegration of the implants. Recent advances unravel that immune response of macrophages and its manipulated osteoimmunomodulation also exerts a pivotal role to determine the fate of the implant. Surface nano-micro modification has evidenced to be efficient to influence osteogenesis, however, little is known links nano-microstructured surface to immune response, as well the osteoimmunomodulation. This study demonstrates that the nano-particles decorated micro-surface, compared with the nano-rods decorated micro-surface enables osteogenesis and angiogenesis concurrently that has not been investigated previously. This study also unravels that the immune response of macrophages can be manipulated by the nano-micro surface, especially the nano-dimension matters, leading to a differential effect on osteointegration. The additional knowledge obtained from this study may provide foundation and reference for future design of the coating materials for implantable materials. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Scalable imprinting of shape-specific polymeric nanocarriers using a release layer of switchable water solubility.

PubMed

Agarwal, Rachit; Singh, Vikramjit; Jurney, Patrick; Shi, Li; Sreenivasan, S V; Roy, Krishnendu

2012-03-27

There is increasing interest in fabricating shape-specific polymeric nano- and microparticles for efficient delivery of drugs and imaging agents. The size and shape of these particles could significantly influence their transport properties and play an important role in in vivo biodistribution, targeting, and cellular uptake. Nanoimprint lithography methods, such as jet-and-flash imprint lithography (J-FIL), provide versatile top-down processes to fabricate shape-specific, biocompatible nanoscale hydrogels that can deliver therapeutic and diagnostic molecules in response to disease-specific cues. However, the key challenges in top-down fabrication of such nanocarriers are scalable imprinting with biological and biocompatible materials, ease of particle-surface modification using both aqueous and organic chemistry as well as simple yet biocompatible harvesting. Here we report that a biopolymer-based sacrificial release layer in combination with improved nanocarrier-material formulation can address these challenges. The sacrificial layer improves scalability and ease of imprint-surface modification due to its switchable solubility through simple ion exchange between monovalent and divalent cations. This process enables large-scale bionanoimprinting and efficient, one-step harvesting of hydrogel nanoparticles in both water- and organic-based imprint solutions. © 2012 American Chemical Society

Optimization of amino group density on surfaces of titanium dioxide nanoparticles covalently bonded to a silicone substrate for antibacterial and cell adhesion activities.

PubMed

Okada, Masahiro; Yasuda, Shoji; Kimura, Tsuyoshi; Iwasaki, Mitsunobu; Ito, Seishiro; Kishida, Akio; Furuzono, Tsutomu

2006-01-01

A composite consisting of titanium dioxide (TiO2) particle, the surface of which was modified with amino groups, and a silicone substrate through covalent bonding at their interface was developed, and antibacterial and cell adhesion activities of the composite were evaluated. The density of the amino groups on the TiO2 particle surface was controlled by the reaction time of the modification reaction. The degradation rate of CH3CHO in the presence of the TiO2 particles under UV irradiation decreased with an increase in the amino group density on the TiO2 surface. On the other hand, the number of L929 cells adhering on the TiO2/silicone composite increased with an increase in the amino group density. From the above two results, the optimum density of amino groups for both photoreactivity and cell adhesiveness was estimated to be 2.0-4.0 molecules/nm2. The optimum amino group-modified TiO2/silicone composite sheet (amino group density, 3.0 molecules/nm2) showed an effective antibacterial activity for Escherichia coli bacteria under UV irradiation. (c) 2005 Wiley Periodicals, Inc

Surfactant adsorption and aggregate structure of silica nanoparticles: a versatile stratagem for the regulation of particle size and surface modification

NASA Astrophysics Data System (ADS)

Chaudhary, Savita; Rohilla, Deepak; Mehta, S. K.

2014-03-01

The area of silica nanoparticles is incredibly polygonal. Silica particles have aroused exceptional deliberation in bio-analysis due to great progress in particular arenas, for instance, biocompatibility, unique properties of modifiable pore size and organization, huge facade areas and pore volumes, manageable morphology and amendable surfaces, elevated chemical and thermal stability. Currently, silica nanoparticles participate in crucial utilities in daily trade rationales such as power storage, chemical and genetic sensors, groceries dispensation and catalysis. Herein, the size-dependent interfacial relation of anionic silica nanoparticles with twelve altered categories of cationic surfactants has been carried out in terms of the physical chemical facets of colloid and interface science. The current analysis endeavours to investigate the virtual consequences of different surfactants through the development of the objective composite materials. The nanoparticle size controls, the surface-to-volume ratio and surface bend relating to its interaction with surfactant will also be addressed in this work. More importantly, the simulated stratagem developed in this work can be lengthened to formulate core-shell nanostructures with functional nanoparticles encapsulated in silica particles, making this approach valuable and extensively pertinent for employing sophisticated materials for catalysis and drug delivery.

Modification of Pawlow's thermodynamical model for the melting of small single-component particles

NASA Astrophysics Data System (ADS)

Barybin, Anatoly; Shapovalov, Victor

2011-02-01

A new approach to the melting of small particles is proposed to modify the known Pawlow's model by taking into account the transfer of material from solid spherical particles to liquid ones through a gas phase. Thermodynamical analysis gives rise to a differential equation for the melting point Tm involving such size-dependent and temperature-dependent parameters of a material as the surface tensions σs(l ), molar heat of fusion ΔHm and molar volumes vs(l ). Solution of this equation has shown that all the limiting cases for size-independent situations coincide with results known in the literature and our analysis of size-dependent situations gives results close to the experimental data previously obtained by other authors for some metallic particles.

A polymeric fastener can easily functionalize liposome surfaces with gadolinium for enhanced magnetic resonance imaging.

PubMed

Smith, Cartney E; Shkumatov, Artem; Withers, Sarah G; Yang, Binxia; Glockner, James F; Misra, Sanjay; Roy, Edward J; Wong, Chun-Ho; Zimmerman, Steven C; Kong, Hyunjoon

2013-11-26

Common methods of loading magnetic resonance imaging (MRI) contrast agents into nanoparticles often suffer from challenges related to particle formation, complex chemical modification/purification steps, and reduced contrast efficiency. This study presents a simple, yet advanced process to address these issues by loading gadolinium, an MRI contrast agent, exclusively on a liposome surface using a polymeric fastener. The fastener, so named for its ability to physically link the two functional components together, consisted of chitosan substituted with diethylenetriaminepentaacetic acid (DTPA) to chelate gadolinium, as well as octadecyl chains to stabilize the modified chitosan on the liposome surface. The assembly strategy, mimicking the mechanisms by which viruses and proteins naturally anchor to a cell, provided greater T1 relaxivity than liposomes loaded with gadolinium in both the interior and outer leaflet. Gadolinium-coated liposomes were ultimately evaluated in vivo using murine ischemia models to highlight the diagnostic capability of the system. Taken together, this process decouples particle assembly and functionalization and, therefore, has considerable potential to enhance imaging quality while alleviating many of the difficulties associated with multifunctional particle fabrication.

Effect of casein and inulin addition on physico-chemical characteristics of low fat camel dairy cream.

PubMed

Ziaeifar, Leila; Labbafi Mazrae Shahi, Mohsen; Salami, Maryam; Askari, Gholam R

2018-05-21

The effect of the addition of the camel casein fraction on some physico-chemical properties of low fat camel milk cream was studied. Oil-in-water emulsions, 25, 30, and 35 (w/w) fat, were prepared using inulin, camel skim milk, milk fat and variable percentages of casein (1, 2, and 3% w/w). The droplet size, ζ-potential, surface protein concentration, viscosity and surface tension of low fat dairy creams was measured. Cream containing 2% (w/w) casein had better stability. The modifications in physico-chemical properties appeared to be driven by changes in particle size distribution caused by droplet aggregation. The cream containing 2% casein leads to a gradual decrease in droplet size, as the particle size decreased, apparent viscosity increased. When casein concentration increased, ζ-potential decreased due to combination of c terminal (negative charge) with the surface of fat particles but steric repulsion improved textural properties. Cream with 30% fat and 2% casein had the best result. Copyright © 2018 Elsevier B.V. All rights reserved.

A Polymeric Fastener can Easily Functionalize Liposome Surfaces with Gadolinium for Enhanced Magnetic Resonance Imaging

PubMed Central

Smith, Cartney E.; Shkumatov, Artem; Withers, Sarah G.; Glockner, James F.; Misra, Sanjay; Roy, Edward J.; Wong, Chun-Ho; Zimmerman, Steven C.; Kong, Hyunjoon

2013-01-01

Common methods of loading magnetic resonance imaging (MRI) contrast agents into nanoparticles often suffer from challenges related to particle formation, complex chemical modification/purification steps, and reduced contrast efficiency. This study presents a simple, yet advanced process to address these issues by loading gadolinium, an MRI contrast agent, exclusively on a liposome surface using a polymeric fastener. The fastener, so named for its ability to physically link the two functional components together, consisted of chitosan substituted with diethylenetriaminepentaacetic acid (DTPA) to chelate gadolinium, as well as octadecyl chains to stabilize the modified chitosan on the liposome surface. The assembly strategy, mimicking the mechanisms by which viruses and proteins naturally anchor to a cell, provided greater T1 relaxivity than liposomes loaded with gadolinium in both the interior and outer leaflet. Gadolinium-coated liposomes were ultimately evaluated in vivo using murine ischemia models to highlight the diagnostic capability of the system. Taken together, this process decouples particle assembly and functionalization, and therefore has considerable potential to enhance imaging quality while alleviating many of the difficulties associated with multifunctional particle fabrication. PMID:24083377

How do energetic ions damage metallic surfaces?

DOE PAGES

Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

2015-02-20

Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films withmore » (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.« less

The toxicity of plastic nanoparticles to green algae as influenced by surface modification, medium hardness and cellular adsorption.

PubMed

Nolte, Tom M; Hartmann, Nanna B; Kleijn, J Mieke; Garnæs, Jørgen; van de Meent, Dik; Jan Hendriks, A; Baun, Anders

2017-02-01

To investigate processes possibly underlying accumulation and ecological effects of plastic nano-particles we have characterized their interaction with the cell wall of green algae. More specifically, we have investigated the influence of particle surface functionality and water hardness (Ca 2+ concentration) on particle adsorption to algae cell walls. Polystyrene nanoparticles with different functional groups (non-functionalized, -COOH and -NH 2 ) as well as coated (starch and PEG) gold nanoparticles were applied in these studies. Depletion measurements and atomic force microscopy (AFM) showed that adsorption of neutral and positively charged plastic nanoparticles onto the cell wall of P. subcapitata was stronger than that of negatively charged plastic particles. Results indicated that binding affinity is a function of both inter-particle and particle-cell wall interactions which are in turn influenced by the medium hardness and particle concentration. Physicochemical modelling using DLVO theory was used to interpret the experimental data, using also values for interfacial surface free energies. Our study shows that material properties and medium conditions play a crucial role in the rate and state of nanoparticle bio-adsorption for green algae. The results show that the toxicity of nanoparticles can be better described and assessed by using appropriate dose metrics including material properties, complexation/agglomeration behavior and cellular attachment and adsorption. The applied methodology provides an efficient and feasible approach for evaluating potential accumulation and hazardous effects of nanoparticles to algae caused by particle interactions with the algae cell walls. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction.

PubMed

Rahnama, H; Sattarzadeh, A; Kazemi, F; Ahmadi, N; Sanjarian, F; Zand, Z

2016-11-15

Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe3O4 nano-particle surface utilizing SiO2 and TiO2 layer as Fe3O4/SiO2 and Fe3O4/SiO2/TiO2 and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe3O4 nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe3O4 coated by SiO2 or SiO2/TiO2 were higher than the naked Fe3O4 nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe3O4/SiO2/TiO2 as a new MNP for separation of DNA molecules from biological sources. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of thickness and surface modifications on flexural strength of monolithic zirconia.

PubMed

Ozer, Fusun; Naden, Andrew; Turp, Volkan; Mante, Francis; Sen, Deniz; Blatz, Markus B

2017-10-14

A recommended minimum thickness for monolithic zirconia restorations has not been reported. Assessing a proper thickness that has the necessary load-bearing capacity but also conserves dental hard tissues is essential. The purpose of this in vitro study was to evaluate the effect of thickness and surface modifications on monolithic zirconia after simulated masticatory stresses. Monolithic zirconia disks (10 mm in diameter) were fabricated with 1.3 mm and 0.8 mm thicknesses. For each thickness, 21 disks were fabricated. The specimens of each group were further divided into 3 subgroups (n=7) according to the surface treatments applied: untreated (control), airborne-particle abrasion with 50-μm Al 2 O 3 particles at a pressure of 400 kPa at 10 mm, and grinding with a diamond rotary instrument followed by polishing. The biaxial flexure strength was determined by using a piston-on-3-balls technique in a universal testing machine. Flexural loading was applied with a 1.4-mm diameter steel cylinder, centered on the disk, at a crosshead speed of 0.5 mm/min until fracture occurred. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed. The data were statistically analyzed with 2-way ANOVA, Tamhane T2, 1-way ANOVA, and Student t tests (α=.05). The 1.3-mm specimens had significantly higher flexural strength than the 0.8-mm specimens (P<.05). Airborne-particle abrasion significantly increased the flexural strength (P<.05). Grinding and polishing did not affect the flexural strength of the specimens (P>.05). The mean flexural strength of 0.8-mm and 1.3-mm thick monolithic zirconia was greater than reported masticatory forces. Airborne-particle abrasion increased the flexural strength of monolithic zirconia. Grinding did not affect flexural strength if subsequently polished. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Laser-induced asymmetric faceting and growth of a nano-protrusion on a tungsten tip

NASA Astrophysics Data System (ADS)

Yanagisawa, Hirofumi; Zadin, Vahur; Kunze, Karsten; Hafner, Christian; Aabloo, Alvo; Kim, Dong Eon; Kling, Matthias F.; Djurabekova, Flyura; Osterwalder, Jürg; Wuensch, Walter

2016-12-01

Irradiation of a sharp tungsten tip by a femtosecond laser and exposed to a strong DC electric field led to reproducible surface modifications. By a combination of field emission microscopy and scanning electron microscopy, we observed asymmetric surface faceting with sub-ten nanometer high steps. The presence of faceted features mainly on the laser-exposed side implies that the surface modification was driven by a laser-induced transient temperature rise on a scale of a couple of picoseconds in the tungsten tip apex. Moreover, we identified the formation of a nano-tip a few nanometers high located at one of the corners of a faceted plateau. The results of simulations emulating the experimental conditions are consistent with the experimental observations. The presented technique would be a new method to fabricate a nano-tip especially for generating coherent electron pulses. The features may also help to explain the origin of enhanced field emission, which leads to vacuum arcs, in high electric field devices such as radio-frequency particle accelerators.

Cellular Binding of Anionic Nanoparticles is Inhibited by Serum Proteins Independent of Nanoparticle Composition.

PubMed

Fleischer, Candace C; Kumar, Umesh; Payne, Christine K

2013-09-01

Nanoparticles used in biological applications encounter a complex mixture of extracellular proteins. Adsorption of these proteins on the nanoparticle surface results in the formation of a "protein corona," which can dominate the interaction of the nanoparticle with the cellular environment. The goal of this research was to determine how nanoparticle composition and surface modification affect the cellular binding of protein-nanoparticle complexes. We examined the cellular binding of a collection of commonly used anionic nanoparticles: quantum dots, colloidal gold nanoparticles, and low-density lipoprotein particles, in the presence and absence of extracellular proteins. These experiments have the advantage of comparing different nanoparticles under identical conditions. Using a combination of fluorescence and dark field microscopy, flow cytometry, and spectroscopy, we find that cellular binding of these anionic nanoparticles is inhibited by serum proteins independent of nanoparticle composition or surface modification. We expect these results will aid in the design of nanoparticles for in vivo applications.

Physicochemical characterization of engineered nanoparticles under physiological conditions: effect of culture media components and particle surface coating.

PubMed

Fatisson, Julien; Quevedo, Ivan R; Wilkinson, Kevin J; Tufenkji, Nathalie

2012-03-01

The use of engineered nanoparticles (ENPs) in commercial products has increased substantially over the last few years. Some research has been conducted in order to determine whether or not such materials are cytotoxic, but questions remain regarding the role that physiological media and sera constituents play in ENP aggregation or stabilization. In this study, several characterization methods were used to evaluate the particle size and surface potential of 6 ENPs suspended in a number of culture media and in the presence of different culture media constituents. Dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS) were employed for size determinations. Results were interpreted on the basis of ENP surface potentials evaluated from particle electrophoretic mobilities (EPM). Measurements made after 24h of incubation at 37°C showed that the cell culture medium constituents had only moderate impact on the physicochemical properties of the ENP, although incubation in bovine serum albumin destabilized the colloidal system. In contrast, most of the serum proteins increased colloidal stabilization. Moreover, the type of ENP surface modification played a significant role in ENP behavior whereby the complexity of interactions between the ENPs and the medium components generally decreased with increasing complexity of the particle surface. This investigation emphasizes the importance of ENP characterization under conditions that are representative of cell culture media or physiological conditions for improved assessments of nanoparticle cytotoxicity. Copyright © 2011 Elsevier B.V. All rights reserved.

Impact of metal matrix composite on the evolution and erosion performance characteristics of non lubricated-dry abrasive degradation of ternary composite coating for refineries system

NASA Astrophysics Data System (ADS)

Anawe, Paul Apeye Lucky; Fayomi, Ojo Sunday Isaac

2018-06-01

The application of rational design principles and process in electrodeposition can eliminate many engineering catastrophes related to corrosion and micromechanical failure in service. This has led to appreciate the need of surface modification on component for enhance life span. Admixed Zn-30Al-13Ti-chloride composite bath was electrolytically prepared and successfully deposited on UNS G10150 mild steel substrate by zinc dual anode deposition processes within an interval of applied current density, particle concentration and constant time. The codeposition of Zn-Al-Ti coating was studied in the presence of other bath ingredient. The effect of deposition current and particle concentration on structural property, adhesion behaviour, ideal crystal orientation, surface topography and electrochemical properties of Zn-Al-Ti alloy coating series on mild steel were analytically examined. The wear stability of the developed composite materials was examined via sliding reciprocating rig. The structural integrity was examined with scanning electron microscope equipped with EDS, X-ray diffraction; Atomic force microscope, dura scan micro-hardness tester and 3 μ metrohm Potentiostat/galvanostat. Interestingly the induced activity of the Zn-Al-Ti chloride composite alloy results into excellent structural modification and stable crystal precipitation within the structural interface as a result of Zn3Al, Zn2Ti and ZnAl3Ti2 intermetallic phase. The obtained results showed that the introduction of Ti particles in the presence of other bath additive in the plating bath mostly modified the surface and brings an increase in the microhardness, corrosion resistance and reduce wear deformation of Zn-Al-Ti chloride composite alloy.

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

PubMed Central

Elvington, Mark C.; Taylor-Pashow, Kathryn M. L.; Tosten, Michael H.; Hobbs, David T.

2016-01-01

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150 nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide. PMID:26967828

Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harnisch, Jennifer Anne

2001-01-01

The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performancemore » both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol (BHT) SAMs. BHT chemisorbs to the gold surface in a previously unprecedented planar fashion. Carbon and gold substrates can be chemically altered by several methodologies resulting in new surface properties. The development of modification protocols and their application in the analytical arena is considered herein.« less

Covalent Immobilization of (-)-Riboflavin on Polymer Functionalized Silica Particles: Application in the Photocatalytic E→Z Isomerization of Polarized Alkenes.

PubMed

Metternich, Jan B; Sagebiel, Sven; Lückener, Anne; Lamping, Sebastian; Ravoo, Bart Jan; Gilmour, Ryan

2018-03-20

The covalent immobilization of the biomimetic, photo-organocatalyst (-)-riboflavin on silica micro- and nanoparticles via atom transfer radical polymerization (ATRP) is disclosed. Given the effectiveness of (-)-riboflavin as a versatile, environmentally benign photocatalyst, an immobilization strategy based on acrylate-linker modification of the catalyst core and controlled polymerization on initiator pre-functionalized silica particles has been developed. Validation of this approach is demonstrated in the E→Z isomerization of a benchmark cinnamonitrile (Z/E up to 88:12) with 0.97 mol % catalyst loading. Characterization of the immobilized photocatalyst supports covalent embedding of the catalyst in the polymeric brushes on the silica particle surface. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Noble Metal Immersion Spectroscopy of Silica Alcogels and Aerogels

NASA Technical Reports Server (NTRS)

Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

1998-01-01

We have fabricated aerogels containing gold and silver nanoparticles for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to porous or heterogeneous media. Specifically, we apply the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs further modification for aggregated or surfactant modified systems. Additionally, the kinetics suggest that collective particle interactions in coagulated clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

Superhydrophobic surfaces using selected zinc oxide microrod growth on ink-jetted patterns.

PubMed

Myint, Myo Tay Zar; Kitsomboonloha, Rungrot; Baruah, Sunandan; Dutta, Joydeep

2011-02-15

The synthesis and properties of superhydrophobic surfaces based on binary surface topography made of zinc oxide (ZnO) microrod-decorated micropatterns are reported. ZnO is intrinsically hydrophilic but can be utilized to create hydrophobic surfaces by creating artificial roughness via microstructuring. Micron scale patterns consisting of nanocrystalline ZnO seed particles were applied to glass substrates with a modified ink-jet printer. Microrods were then grown on the patterns by a hydrothermal process without any further chemical modification. Water contact angle (WCA)(1) up to 153° was achieved. Different micro array patterned surfaces with varying response of static contact angle or sessile droplet analysis are reported. Copyright © 2010 Elsevier Inc. All rights reserved.

Investigations into the mechanism of material removal and surface modification at atomic scale on stainless steel using molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Ranjan, Prabhat; Balasubramaniam, R.; Jain, V. K.

2018-06-01

A molecular dynamics simulation (MDS) has been carried out to investigate the material removal phenomenon of chemo-mechanical magnetorheological finishing (CMMRF) process. To understand the role of chemical assisted mechanical abrasion in CMMRF process, material removal phenomenon is subdivided into three different stages. In the first stage, new atomic bonds viz. Fe-O-Si is created on the surface of the workpiece (stainless steel). The second stage deals with the rupture of parent bonds like Fe-Fe on the workpiece. In the final stage, removal of material from the surface in the form of dislodged debris (cluster of atoms) takes place. Effects of process parameters like abrasive particles, depth of penetration and initial surface condition on finishing force, potential energy (towards secondary phenomenon such as chemical instability of the finished surface) and material removal at atomic scale have been investigated. It was observed that the type of abrasive particle is one of the important parameters to produce atomically smooth surface. Experiments were also conducted as per the MDS to generate defect-free and sub-nanometre-level finished surface (Ra value better than 0.2 nm). The experimental results reasonably agree well with the simulation results.

Thermoresponsive magnetic nano-biosensors for rapid measurements of inorganic arsenic and cadmium.

PubMed

Siddiki, Mohammad Shohel Rana; Shimoaoki, Shun; Ueda, Shunsaku; Maeda, Isamu

2012-10-18

Green fluorescent protein-tagged sensor proteins, ArsR-GFP and CadC-GFP, have been produced as biosensors for simple and low-cost quantification of As(III) or Cd(II). In this study, the sensor protein-promoter DNA complexes were reconstructed on the surfaces of magnetic particles of different sizes. After the surface modification all the particles could be attracted by magnets, and released different amounts of GFP-tagged protein, according to the metal concentrations within 5 min, which caused significant increases in fluorescence. A detection limit of 1 µg/L for As(III) and Cd(II) in purified water was obtained only with the nanoparticles exhibiting enough magnetization after heat treatment for 1 min. Therefore, thermoresponsive magnetic nano-biosensors offer great advantages of rapidity and sensitivity for the measurement of the toxic metals in drinking water.

Influence of Surface Modifications on the Spatiotemporal Microdistribution of Quantum Dots In Vivo.

PubMed

Nekolla, Katharina; Kick, Kerstin; Sellner, Sabine; Mildner, Karina; Zahler, Stefan; Zeuschner, Dagmar; Krombach, Fritz; Rehberg, Markus

2016-05-01

For biomedical applications of nanoconstructs, it is a general prerequisite to efficiently reach the desired target site. In this regard, it is crucial to determine the spatiotemporal distribution of nanomaterials at the microscopic tissue level. Therefore, the effect of different surface modifications on the distribution of microinjected quantum dots (QDs) in mouse skeletal muscle tissue has been investigated. In vivo real-time fluorescence microscopy and particle tracking reveal that carboxyl QDs preferentially attach to components of the extracellular matrix (ECM), whereas QDs coated with polyethylene glycol (PEG) show little interaction with tissue constituents. Transmission electron microscopy elucidates that carboxyl QDs adhere to collagen fibers as well as basement membranes, a type of ECM located on the basolateral side of blood vessel walls. Moreover, carboxyl QDs have been found in endothelial junctions as well as in caveolae of endothelial cells, enabling them to translocate into the vessel lumen. The in vivo QD distribution is confirmed by in vitro experiments. The data suggest that ECM components act as a selective barrier depending on QD surface modification. For future biomedical applications, such as targeting of blood vessel walls, the findings of this study offer design criteria for nanoconstructs that meet the requirements of the respective application. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative analysis of Hedgehog gradient formation using an inducible expression system

PubMed Central

Su, Vivian F; Jones, Kelly A; Brodsky, Michael; The, Inge

2007-01-01

Background The Hedgehog (Hh) family of secreted growth factors are morphogens that act in development to direct growth and patterning. Mutations in human Hh and other Hh pathway components have been linked to human diseases. Analysis of Hh distribution during development indicates that cholesterol modification and receptor mediated endocytosis affect the range of Hh signaling and the cellular localization of Hh. Results We have used an inducible, cell type-specific expression system to characterize the three-dimensional distribution of newly synthesized, GFP-tagged Hh in the developing Drosophila wing. Following induction of Hh-GFP expression in posterior producing cells, punctate structures containing Hh-GFP were observed in the anterior target cells. The distance of these particles from the expressing cells was quantified to determine the shape of the Hh gradient at different time points following induction. The majority of cholesterol-modified Hh-GFP was found associated with cells near the anterior/posterior (A/P) boundary, which express high levels of Hh target genes. Without cholesterol, the Hh gradient was flatter, with a lower percentage of particles near the source and a greater maximum distance. Inhibition of Dynamin-dependent endocytosis blocked formation of intracellular Hh particles, but did not prevent movement of newly synthesized Hh to the apical or basolateral surfaces of target cells. In the absence of both cholesterol and endocytosis, Hh particles accumulated in the extracellular space. Staining for the Hh receptor Ptc revealed four categories of Hh particles: cytoplasmic with and without Ptc, and cell surface with and without Ptc. Interestingly, mainly cholesterol-modified Hh is detected in the cytoplasmic particles lacking Ptc. Conclusion We have developed a system to quantitatively analyze Hh distribution during gradient formation. We directly demonstrate that inhibition of Dynamin-dependent endocytosis is not required for movement of Hh across target cells, indicating that transcytosis is not required for Hh gradient formation. The localization of Hh in these cells suggests that Hh normally moves across both apical and basolateral regions of the target cells. We also conclude that cholesterol modification is required for formation of a specific subset of Hh particles that are both cytoplasmic and not associated with the receptor Ptc. PMID:17484784

Quantitative analysis of Hedgehog gradient formation using an inducible expression system.

PubMed

Su, Vivian F; Jones, Kelly A; Brodsky, Michael; The, Inge

2007-05-07

The Hedgehog (Hh) family of secreted growth factors are morphogens that act in development to direct growth and patterning. Mutations in human Hh and other Hh pathway components have been linked to human diseases. Analysis of Hh distribution during development indicates that cholesterol modification and receptor mediated endocytosis affect the range of Hh signaling and the cellular localization of Hh. We have used an inducible, cell type-specific expression system to characterize the three-dimensional distribution of newly synthesized, GFP-tagged Hh in the developing Drosophila wing. Following induction of Hh-GFP expression in posterior producing cells, punctate structures containing Hh-GFP were observed in the anterior target cells. The distance of these particles from the expressing cells was quantified to determine the shape of the Hh gradient at different time points following induction. The majority of cholesterol-modified Hh-GFP was found associated with cells near the anterior/posterior (A/P) boundary, which express high levels of Hh target genes. Without cholesterol, the Hh gradient was flatter, with a lower percentage of particles near the source and a greater maximum distance. Inhibition of Dynamin-dependent endocytosis blocked formation of intracellular Hh particles, but did not prevent movement of newly synthesized Hh to the apical or basolateral surfaces of target cells. In the absence of both cholesterol and endocytosis, Hh particles accumulated in the extracellular space. Staining for the Hh receptor Ptc revealed four categories of Hh particles: cytoplasmic with and without Ptc, and cell surface with and without Ptc. Interestingly, mainly cholesterol-modified Hh is detected in the cytoplasmic particles lacking Ptc. We have developed a system to quantitatively analyze Hh distribution during gradient formation. We directly demonstrate that inhibition of Dynamin-dependent endocytosis is not required for movement of Hh across target cells, indicating that transcytosis is not required for Hh gradient formation. The localization of Hh in these cells suggests that Hh normally moves across both apical and basolateral regions of the target cells. We also conclude that cholesterol modification is required for formation of a specific subset of Hh particles that are both cytoplasmic and not associated with the receptor Ptc.

A review on the application of inorganic nano-structured materials in the modification of textiles: focus on anti-microbial properties.

PubMed

Dastjerdi, Roya; Montazer, Majid

2010-08-01

Textiles can provide a suitable substrate to grow micro-organisms especially at appropriate humidity and temperature in contact to human body. Recently, increasing public concern about hygiene has been driving many investigations for anti-microbial modification of textiles. However, using many anti-microbial agents has been avoided because of their possible harmful or toxic effects. Application of inorganic nano-particles and their nano-composites would be a good alternative. This review paper has focused on the properties and applications of inorganic nano-structured materials with good anti-microbial activity potential for textile modification. The discussed nano-structured anti-microbial agents include TiO(2) nano-particles, metallic and non-metallic TiO(2) nano-composites, titania nanotubes (TNTs), silver nano-particles, silver-based nano-structured materials, gold nano-particles, zinc oxide nano-particles and nano-rods, copper nano-particles, carbon nanotubes (CNTs), nano-clay and its modified forms, gallium, liposomes loaded nano-particles, metallic and inorganic dendrimers nano-composite, nano-capsules and cyclodextrins containing nano-particles. This review is also concerned with the application methods for the modification of textiles using nano-structured materials. Copyright 2010 Elsevier B.V. All rights reserved.

A Method for Molecular Dynamics on Curved Surfaces

PubMed Central

Paquay, Stefan; Kusters, Remy

2016-01-01

Dynamics simulations of constrained particles can greatly aid in understanding the temporal and spatial evolution of biological processes such as lateral transport along membranes and self-assembly of viruses. Most theoretical efforts in the field of diffusive transport have focused on solving the diffusion equation on curved surfaces, for which it is not tractable to incorporate particle interactions even though these play a crucial role in crowded systems. We show here that it is possible to take such interactions into account by combining standard constraint algorithms with the classical velocity Verlet scheme to perform molecular dynamics simulations of particles constrained to an arbitrarily curved surface. Furthermore, unlike Brownian dynamics schemes in local coordinates, our method is based on Cartesian coordinates, allowing for the reuse of many other standard tools without modifications, including parallelization through domain decomposition. We show that by applying the schemes to the Langevin equation for various surfaces, we obtain confined Brownian motion, which has direct applications to many biological and physical problems. Finally we present two practical examples that highlight the applicability of the method: 1) the influence of crowding and shape on the lateral diffusion of proteins in curved membranes; and 2) the self-assembly of a coarse-grained virus capsid protein model. PMID:27028633

A Method for Molecular Dynamics on Curved Surfaces

NASA Astrophysics Data System (ADS)

Paquay, Stefan; Kusters, Remy

2016-03-01

Dynamics simulations of constrained particles can greatly aid in understanding the temporal and spatial evolution of biological processes such as lateral transport along membranes and self-assembly of viruses. Most theoretical efforts in the field of diffusive transport have focussed on solving the diffusion equation on curved surfaces, for which it is not tractable to incorporate particle interactions even though these play a crucial role in crowded systems. We show here that it is possible to combine standard constraint algorithms with the classical velocity Verlet scheme to perform molecular dynamics simulations of particles constrained to an arbitrarily curved surface, in which such interactions can be taken into account. Furthermore, unlike Brownian dynamics schemes in local coordinates, our method is based on Cartesian coordinates allowing for the reuse of many other standard tools without modifications, including parallelisation through domain decomposition. We show that by applying the schemes to the Langevin equation for various surfaces, confined Brownian motion is obtained, which has direct applications to many biological and physical problems. Finally we present two practical examples that highlight the applicability of the method: (i) the influence of crowding and shape on the lateral diffusion of proteins in curved membranes and (ii) the self-assembly of a coarse-grained virus capsid protein model.

Synthesis of silica-polymer core-shell nanoparticles by reversible addition-fragmentation chain transfer polymerization.

PubMed

Moraes, John; Ohno, Kohji; Maschmeyer, Thomas; Perrier, Sébastien

2013-10-14

Hybrid nanoparticles hold great promise for a range of applications such as drug-delivery vectors or colloidal crystal self-assemblies. The challenge of preparing highly monodisperse particles for these applications has recently been overcome by using living radical polymerization techniques. In particular, the use of reversible addition-fragmentation chain transfer (RAFT), initiated from silica surfaces, yields well-defined particles from a range of precursor monomers resulting in nanoparticles of tailored sizes that are accessible via the rational selection of polymerization conditions. Furthermore, using RAFT allows post-polymerization modification to afford multifunctional, monodisperse, nanostructures under mild and non-stringent reaction conditions.

Utilizing copper(I) catalyzed azide-alkyne Huisgen 1,3-dipolar cycloaddition for the surface modification of colloidal particles with electroactive and emissive moieties

NASA Astrophysics Data System (ADS)

Rungta, Parul

The development of charge-transporting and fluorescing colloidal particles that can be directly printed into electroluminescent devices may result in a broad impact on the use of electrical energy for illumination. The objective of this work was to design and synthesize electroactive & fluorescing colloidal particles; establish their optical, electronic, and thermodynamic properties; and transition them into a device format for potential applications. The original intended application of this work was to build "better" colloidally-based organic light emitting devices (OLEDs) by creating functional particles with superior electrical and optical performance relative to commercially available technologies, but through the course of the research, the particles that were developed were found to be better suited for medical applications. Nonetheless, the global objective envisioned at the onset of this research was consistent with its final outcomes. The research tasks pursued to accomplish this global objective included: (1) The design and synthesis of electroactive moieties and their conversion into organic light emitting devices; An electron-transporting monomer was synthesized that was structurally & energetically similar to the small molecule 2-biphenyl-4-yl-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD). The monomer was copolymerized with 2-(9H-carbazol-9-yl)ethyl 2-methylacrylate (CE) and the resulting copolymer was utilized in OLEDs which employed fluorescent coumarin 6 (C6) or phosphorescent tris(2-phenylpyridine)iridium(III) [Ir(ppy)3] emitters. The copolymer devices exhibited a mean luminance of ca. 400 and 3,552 cd/m2 with the C6 and Ir(ppy)3 emitters, that were stable with thermal aging at temperatures ranging from 23°C to 130°C. Comparable poly(9-vinyl-9H-carbazole)/tBu-PBD blend devices exhibited more pronounced variations in performance with thermal aging. (2) The surface-modification of colloids with electroactive & fluorescing moieties via "click" chemistry; Aqueous-phase 83 nm poly(propargyl acrylate) (PA) nanoparticles were surface-functionalized with sparingly water soluble fluorescent moieties through a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) (i.e., "click" transformation) to produce fluoroprobes with a large Stokes shift. For moieties which could not achieve extensive surface coverage on the particles utilizing a standard click transformation procedure, the presence of beta-cyclodextrin (beta-CD) during the transformation enhanced the grafting density onto the particles. For an oxadiazole containing molecule (AO), an azide-modified coumarin 6 (AD1) and a polyethylene glycol modified naphthalimide-based emitter (AD2), respectively, an 84%, 17% and 5% increase in the grafting densities were observed, when the transformation was performed in the presence of beta-CD. In contrast, a carbazolyl-containing moiety (AC) exhibited a slight retardation in the final grafting density when beta-CD was employed. Photoluminescence studies indicated that AC & AO when attached to the particles form an exciplex. An efficient energy transfer from the exciplex to the surface attached AD2 resulted in a total Stokes shift of 180 nm for the modified particles. (3) The synthesis and characterization of near-infrared (NIR) emitting particles for potential applications in cancer therapy. PA particles were surface modified through the "click" transformation of an azide-terminated indocyanine green (azICG), an NIR emitter, and poly(ethylene glycol) (azPEG) chains of various molecular weights. The placement of azICG onto the surface of the particles allowed for the chromophores to complex with bovine serum albumin (BSA) when dispersed in PBS that resulted in an enhancement of the dye emission. In addition, the inclusion of azPEG with the chromophores onto the particle surface resulted in a synergistic nine-fold enhancement of the fluorescence intensity, with azPEGs of increasing molecular weight amplifying the response. Preliminary photodynamic therapy (PDT) studies with human liver carcinoma cells (HepG2) combined with the modified particles indicated that a minor exposure of 780 nm radiation resulted in a statistically significant reduction in cell growth.

[Surface modification of dental alumina ceramic with silica coating].

PubMed

Xie, Hai-Feng; Zhang, Fei-Min; Wang, Xiao-Zu; Xia, Yang

2006-12-01

To make silica coating through sol-gel process, and to evaluate the wettability of dental alumina ceramic with or without coating. Silica coating was prepared with colloidal silica sol on In-Ceram alumina ceramic surface which had been treated with air particle abrasion. Coating gel after heat treatment was observed with atomic force microscope (AFM), and was analyzed by infrared spectrum (IR) with gel without sintered as control. Contact angles of oleic acid to be finished, sandblasted and coated ceramic surface of were measured. AFM pictures showed that some parts of nano-particles in coating gel conglomerated after heat treatment. It can be seen from the IR picture that bending vibration absorption kurtosis of Si-OH also vanished after heat treatment. Among contact angles of three treated surface, the ones on polished surface were the biggest (P = 0.000, P = 0.000), and sandblasting+silica coating surface the smallest (P = 0.000, P = 0.003). Silica coating can be made with sol-gel process successfully. Heat treatment may reinforce Si-O-Si net structure of coating gel. Wettability of dental alumina ceramic with silica coating is higher than with sandblasting and polishing.

Effect of detonation nanodiamonds on phagocyte activity.

PubMed

Karpukhin, Alexey V; Avkhacheva, Nadezhda V; Yakovlev, Ruslan Yu; Kulakova, Inna I; Yashin, Valeriy A; Lisichkin, Georgiy V; Safronova, Valentina G

2011-07-01

Detonation ND (nanodiamond) holds much promise for biological studies and medical applications. Properties like size of particles, inclination for modification of their surface and unambiguous biocompatibility are crucial. Of prime importance is interaction between ND and immune cells, which supervise foreign intrusion into an organism and eliminate it. Neutrophils are more reactive in inflammatory response implementing cytotoxical arsenal including ROS (reactive oxygen species). The aim of the work was to estimate the ability of two ND samples (produced by Diamond Center and PlasmaChem) to keep the vitality of neutrophils from the inflammatory site. The ability of cells to generate ROS in the presence of ND particles is considered as indicating their biocompatibility. IR spectra and size of particles in the samples were characterized. Acid modification of ND was carried out to get the luminescent form. In the biological aspect, ND demonstrated up or down action, depending on the concentration, time and conditions of activation of cells. Weak action of ND in whole blood was obtained possibly owing to the ND adsorbed plasma proteins, which mask active functional groups to interact with the cell membrane. ND did not influence the viability of isolated inflammatory neutrophils in low and moderate concentrations and suppressed it in high concentrations (≥1 g/l). Addition of ND to the cell suspension initiated concentration-dependent reaction to produce ROS similar to respiratory burst. ND up-regulated response to bacterial formylpeptide, but up- and down-modified (low or high concentrations, accordingly) response to such bacterial agents as OZ (opsonized zymosan), which neutrophils swallow up by oxygen-dependent phagocytosis. Localization of the particles on the cell surface as into the cells was identified by monitoring the intrinsic fluorescence of oxidized ND. The various mechanisms that could account for penetration of ND particles into the cell are discussed. Common conclusion concerns compatibility of ND with living neutrophils from inflammatory site and their normal functioning for infection safeguard.

Lead and cadmium sorption mechanisms on magnetically modified biochars.

PubMed

Trakal, Lukáš; Veselská, Veronika; Šafařík, Ivo; Vítková, Martina; Číhalová, Sylva; Komárek, Michael

2016-03-01

This paper discusses Cd(II) and Pb(II) sorption efficiency of biochars modified by impregnation with magnetic particles. All selected biochar characteristics were significantly affected after the modification. More specifically, the cation exchange capacity increased after the modification, except for grape stalk biochar. However, the changes in the pH value, PZC, and BET surface after modification process were less pronounced. The metal loading rate was also significantly improved, especially for Cd(II) sorption on/in nut shield and plum stone biochars (10- and 16-times increase, respectively). The results indicated that cation exchange (as a metal sorption mechanism) was strengthened after Fe oxide impregnation, which limited the desorbed amount of tested metals. In contrast, the magnetization of grape stalk biochar reduced Pb(II) sorption in comparison with that of pristine biochar. Magnetic modification is, therefore, more efficient for biochars with well-developed structure and for more mobile metals, such as Cd(II). Copyright © 2015 Elsevier Ltd. All rights reserved.

Hydrophilicity, photocatalytic activity and stability of tetraethyl orthosilicate modified TiO2 film on glazed ceramic surface

NASA Astrophysics Data System (ADS)

Zhang, Peng; Tian, Jie; Xu, Ruifen; Ma, Guojun

2013-02-01

A new, simple, and low-cost method has been developed to enhance the surface properties of TiO2 film. Degussa P25-TiO2 nanoparticles were modified by tetraethyl orthosilicate (TEOS) on glazed ceramic tiles. Effects of tetraethyl orthosilicate modification on microstructure, crystal structure, hydrophilicity, photocatalytic activity and stability of the film were investigated. The obtained results showed that P25-TiO2/TEOS particles exhibited better dispersion, higher surface area, bigger surface roughness and smaller particle size comparing to pure P25-TiO2 particles, which resulted in better hydrophilicity after 10 days in a dark place and higher photocatalytic activity under visible light irradiation. 68% of Rhodamine B was degraded by P25-TiO2/TEOS film in 25 h with the light intensity of 5000 ± 500 lx, and degradation rate reached to 82% with the light intensity of 10,000 ± 1000 lx. Furthermore, two fundamentally different systems, in which the films recycle for repetitive degradation after soaked in dye solution and for discoloration after depositing dye on the surfaces, respectively, were measured to confirm that P25-TiO2/TEOS film showed excellently stable performances. Therefore the P25-TiO2/TEOS film we obtained has good washing resistance and would be a promising candidate for practical applications.

Micro-PIV/LIF measurements on electrokinetically-driven flow in surface modified microchannels

NASA Astrophysics Data System (ADS)

Ichiyanagi, Mitsuhisa; Sasaki, Seiichi; Sato, Yohei; Hishida, Koichi

2009-04-01

Effects of surface modification patterning on flow characteristics were investigated experimentally by measuring electroosmotic flow velocities, which were obtained by micron-resolution particle image velocimetry using a confocal microscope. The depth-wise velocity was evaluated by using the continuity equation and the velocity data. The microchannel was composed of a poly(dimethylsiloxane) chip and a borosilicate cover-glass plate. Surface modification patterns were fabricated by modifying octadecyltrichlorosilane (OTS) on the glass surface. OTS can decrease the electroosmotic flow velocity compared to the velocity in the glass microchannel. For the surface charge varying parallel to the electric field, the depth-wise velocity was generated at the boundary area between OTS and the glass surfaces. For the surface charge varying perpendicular to the electric field, the depth-wise velocity did not form because the surface charge did not vary in the stream-wise direction. The surface charge pattern with the oblique stripes yielded a three-dimensional flow in a microchannel. Furthermore, the oblique patterning was applied to a mixing flow field in a T-shaped microchannel, and mixing efficiencies were evaluated from heterogeneity degree of fluorescent dye intensity, which was obtained by laser-induced fluorescence. It was found that the angle of the oblique stripes is an important factor to promote the span-wise and depth-wise momentum transport and contributes to the mixing flow in a microchannel.

New chemical approach to obtain dense layer phosphate-based ionic conductor coating on negative electrode material surface: Synthesis way, outgassing and improvement of C-rate capability

NASA Astrophysics Data System (ADS)

Fleutot, Benoit; Davoisne, Carine; Gachot, Grégory; Cavalaglio, Sébastien; Grugeon, Sylvie; Viallet, Virginie

2017-04-01

Li4Ti5O12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li3PO4 coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li3PO4 coated Li4Ti5O12 is improved at high C-rate by the surface modification (improvement of 30 mAh g-1 at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies.

Redox properties of undoped 5 nm diamond nanoparticles.

PubMed

Holt, Katherine B; Ziegler, Christoph; Caruana, Daren J; Zang, Jianbing; Millán-Barrios, Enrique J; Hu, Jingping; Foord, John S

2008-01-14

This paper demonstrates the promoting effects of 5 nm undoped detonation diamond nanoparticles on redox reactions in solution. An enhancement in faradaic current for the redox couples Ru(NH(3))(6)(3+/2+) and Fe(CN)(6)(4-/3-) was observed for a gold electrode modified with a drop-coated layer of nanodiamond (ND), in comparison to the bare gold electrode. The ND layer was also found to promote oxygen reduction. Surface modification of the ND powders by heating in air or in a hydrogen flow resulted in oxygenated and hydrogenated forms of the ND, respectively. Oxygenated ND was found to exhibit the greatest electrochemical activity and hydrogenated ND the least. Differential pulse voltammetry of electrode-immobilised ND layers in the absence of solution redox species revealed oxidation and reduction peaks that could be attributed to direct electron transfer (ET) reactions of the ND particles themselves. It is hypothesised that ND consists of an insulating sp(3) diamond core with a surface that has significant delocalised pi character due to unsatisfied surface atoms and C[double bond, length as m-dash]O bond formation. At the nanoscale surface properties of the particles dominate over those of the bulk, allowing ET to occur between these essentially insulating particles and a redox species in solution or an underlying electrode. We speculate that reversible reduction of the ND may occur via electron injection into available surface states at well-defined reduction potentials and allow the ND particles to act as a source and sink of electrons for the promotion of solution redox reactions.

Adenovirus Particles that Display the Plasmodium falciparum Circumsporozoite Protein NANP Repeat Induce Sporozoite-Neutralizing Antibodies in Mice

PubMed Central

Palma, Christopher; Overstreet, Michael G.; Guedon, Jean-Marc; Hoiczyk, Egbert; Ward, Cameron; Karen, Kasey A.; Zavala, Fidel; Ketner, Gary

2011-01-01

Adenovirus particles can be engineered to display exogenous peptides on their surfaces by modification of viral capsid proteins, and particles that display pathogen-derived peptides can induce protective immunity. We constructed viable recombinant adenoviruses that display B-cell epitopes from the Plasmodium falciparum circumsporozoite protein (PfCSP) in the major adenovirus capsid protein, hexon. Recombinants induced high-titer antibodies against CSP when injected intraperitoneally into mice. Serum obtained from immunized mice recognized both recombinant PfCSP protein and P. falciparum sporozoites, and neutralized P. falciparum sporozoites in vitro. Replicating adenovirus vaccines have provided economical protection against adenovirus disease for over three decades. The recombinants described here may provide a path to an affordable malaria vaccine in the developing world. PMID:21199707

Deuterium retention and surface modification of tungsten macrobrush samples exposed in FTU Tokamak

NASA Astrophysics Data System (ADS)

Maddaluno, G.; Giacomi, G.; Rufoloni, A.; Verdini, L.

2007-06-01

The effect of discrete structures such as macrobrush or castellated surfaces on power handling and deuterium retention of plasma facing components is to be assessed since such geometrical configurations are needed for increasing the lifetime of the armour to heat-sink joint. Four small macrobrush W and W + 1%La2O3 samples have been exposed in the Frascati Tokamak Upgrade (FTU) scrape-off layer up to the last closed flux surface by means of the Sample Introduction System. FTU is an all metal machine with no carbon source inside vacuum vessel; it exhibits ITER relevant energy and particle fluxes on the plasma facing components. Here, results on morphological surface changes (SEM), chemical composition (EDX) and deuterium retention (TDS) are reported.

Rice Starch Particle Interactions at Air/Aqueous Interfaces—Effect of Particle Hydrophobicity and Solution Ionic Strength

PubMed Central

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film. PMID:29868551

Rice Starch Particle Interactions at Air/Aqueous Interfaces-Effect of Particle Hydrophobicity and Solution Ionic Strength.

PubMed

McNamee, Cathy E; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film.

Rice starch particle interactions at air/aqueous interfaces– effect of particle hydrophobicity and solution ionic strength

NASA Astrophysics Data System (ADS)

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-05-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e. the natural particle found inside the plant, at air/aqueous interfaces and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film.

A generalized transport-velocity formulation for smoothed particle hydrodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chi; Hu, Xiangyu Y., E-mail: xiangyu.hu@tum.de; Adams, Nikolaus A.

The standard smoothed particle hydrodynamics (SPH) method suffers from tensile instability. In fluid-dynamics simulations this instability leads to particle clumping and void regions when negative pressure occurs. In solid-dynamics simulations, it results in unphysical structure fragmentation. In this work the transport-velocity formulation of Adami et al. (2013) is generalized for providing a solution of this long-standing problem. Other than imposing a global background pressure, a variable background pressure is used to modify the particle transport velocity and eliminate the tensile instability completely. Furthermore, such a modification is localized by defining a shortened smoothing length. The generalized formulation is suitable formore » fluid and solid materials with and without free surfaces. The results of extensive numerical tests on both fluid and solid dynamics problems indicate that the new method provides a unified approach for multi-physics SPH simulations.« less

Colloidal Stability in Asymmetric Electrolytes: Modifications of the Schulze-Hardy Rule.

PubMed

Trefalt, Gregor; Szilagyi, Istvan; Téllez, Gabriel; Borkovec, Michal

2017-02-21

The Schulze-Hardy rule suggests a strong dependence of the critical coagulation concentration (CCC) on the ionic valence. This rule is addressed theoretically and confronted with recent experimental results. The commonly presented derivation of this rule assumes symmetric electrolytes and highly charged particles. Both assumptions are incorrect. Symmetric electrolytes containing multivalent ions are hardly soluble, and experiments are normally carried out with the well-soluble salts of asymmetric electrolytes containing monovalent and multivalent ions. In this situation, however, the behavior is completely different whether the multivalent ions represent the counterions or co-ions. When these ions represent the counterions, meaning that the multivalent ions have the opposite sign than the charge of the particle, they adsorb strongly to the particles. Thereby, they progressively reduce the magnitude of the surface charge with increasing valence. In fact, this dependence of the charge density on the counterion valence is mainly responsible for the decrease of the CCC with the valence. In the co-ion case, where the multivalent ions have the same sign as the charge of the particle, the multivalent ions are repelled from the particles, and the surfaces remain highly charged. In this case, the inverse Schulze-Hardy rule normally applies, whereby the CCC varies inversely proportional to the co-ion valence.

Uniform Surface Modification of 3D Bioglass®-Based Scaffolds with Mesoporous Silica Particles (MCM-41) for Enhancing Drug Delivery Capability

PubMed Central

Boccardi, Elena; Philippart, Anahí; Juhasz-Bortuzzo, Judith A.; Beltrán, Ana M.; Novajra, Giorgia; Vitale-Brovarone, Chiara; Spiecker, Erdmann; Boccaccini, Aldo R.

2015-01-01

The design and characterization of a new family of multifunctional scaffolds based on bioactive glass (BG) of 45S5 composition for bone tissue engineering and drug delivery applications are presented. These BG-based scaffolds are developed via a replication method of polyurethane packaging foam. In order to increase the therapeutic functionality, the scaffolds were coated with mesoporous silica particles (MCM-41), which act as an in situ drug delivery system. These sub-micron spheres are characterized by large surface area and pore volume with a narrow pore diameter distribution. The solution used for the synthesis of the silica mesoporous particles was designed to obtain a high-ordered mesoporous structure and spherical shape – both are key factors for achieving the desired controlled drug release. The MCM-41 particles were synthesized directly inside the BG-based scaffolds, and the drug-release capability of this combined system was evaluated. Moreover, the effect of MCM-41 particle coating on the bioactivity of the BG-based scaffolds was assessed. The results indicate that it is possible to obtain a multifunctional scaffold system characterized by high and interconnected porosity, high bioactivity, and sustained drug delivery capability. PMID:26594642

Modification of Structure and Tribological Properties of the Surface Layer of Metal-Ceramic Composite under Electron Irradiation in the Plasmas of Inert Gases

NASA Astrophysics Data System (ADS)

Ovcharenko, V. E.; Ivanov, K. V.; Mohovikov, A. A.; Yu, B.; Xu, Yu; Zhong, L.

2018-01-01

Metal-ceramic composites are the main materials for high-load parts in tribomechanical systems. Modern approaches to extend the operation life of tribomechanical systems are based on increasing the strength and tribological properties of the surface layer having 100 to 200 microns in depth. The essential improvement of the properties occurs when high dispersed structure is formed in the surface layer using high-energy processing. As a result of the dispersed structure formation the more uniform distribution of elastic stresses takes place under mechanical or thermal action, the energy of stress concentrators emergence significantly increases and the probability of internal defects formation reduces. The promising method to form the dispersed structure in the surface layer is pulse electron irradiation in the plasmas of inert gases combining electron irradiation and ion bombardment in one process. The present work reports upon the effect of pulse electron irradiation in plasmas of different inert gases with different atomic mass and ionization energy on the structure and tribological properties of the surface layer of TiC/(Ni-Cr) metal-ceramic composite with the volume ratio of the component being 50:50. It is experimentally shown that high-dispersed heterophase structure with a fraction of nanosized particles is formed during the irradiation. Electron microscopy study reveals that refining of the initial coarse TiC particles occurs via their dissolution in the molten metal binder followed by the precipitation of secondary fine particles in the interparticle layers of the binder. The depth of modified layer and the fraction of nanosized particles increase when the atomic number of the plasma gas increases and ionization energy decreases. The wear resistance of metal-ceramic composite improves in accordance to the formation of nanocrystalline structure in the surface layer.

Study of the coalescence/splash threshold of droplet impact on liquid films and its relevance in assessing airborne particle release.

PubMed

Motzkus, C; Gensdarmes, F; Géhin, E

2011-10-15

Impingement of droplets on surfaces occurs in many industrial and natural processes. The study of droplet break-up is fundamental in order to determine the potential sources of airborne contamination for scenarios of hazardous liquid falls such as dripping. There are very few data in the literature describing the case of impact of millimetre-size droplets. The purposes of this work were to study experimentally particle emission during the impact of droplets on a liquid film and to assess the use of coalescence/splash relations to predict airborne particle release. The results are described using dimensionless numbers taking into account the inertial, viscosity and surface tension forces. Experiments were carried out for Weber numbers between 62 and 1754 and for Ohnesorge numbers between 2.0×10(-3) and 1.5×10(-2). New results on coalescence/splash thresholds are obtained using highly sensitive aerosol measurement and allow a prediction concerning the presence or absence of airborne particles according to a threshold relation. Moreover, we propose a modification of the Cossali et al.'s relation in order to describe the coalescence/prompt splash threshold. Copyright © 2011 Elsevier Inc. All rights reserved.

Review on Nano zerovalent Iron (nZVI): From Modification to Environmental Applications

NASA Astrophysics Data System (ADS)

Chen, Xing; Ji, Dandan; Wang, Xiqing; Zang, Lihua

2017-01-01

Nanoscale zero-valent iron (nZVI), with its reductive potentials and wide availability, offers degradative remediation of environmental contaminants. Although nZVI particles were successfully used in wastewater treatment, there are still some drawbacks associated with the process and needs to be addressed. For example, magnetic attraction between nanoiron particles causes the rapid aggregation of particles. In addition, nZVI are more prone to react with dissolved oxygen and oxygen-rich compounds. Meantimes, nZVI could exert some degree of toxicity towards microbial species, and the effects of nZVI at the cellular and community levels are progressively being elucidated. To overcome these problems, nZVI particles were immobilized in or on suitable solid supports, and also to expand the effective pH range of the Fenton reaction. Therefore, refer to the new trends is very important when selecting nZVI for the treatment of various matrices. This review also identifies problems that may occurs a result of changes in the physicochemical properties of nZVI due to their modification (e.g. other metal doping, coating the surface, or deposition on the support). Toxicity studies suggest that cellmembrane disruption and oxidative stress through the generation of Fe2+ and reactive oxygen species by nZVI are the main mechanisms contributing to nZVI cytotoxicity. This review highlights the application of nano-zero valent iron in treating refractory compounds.

Surface modification of polypropylene based particle foams

NASA Astrophysics Data System (ADS)

Schreier, P.; Trassl, C.; Altstädt, V.

2014-05-01

This paper deals with the modification of the surface properties of expanded polypropylene (EPP). EPP is a semi-hard to soft elastic thermoplastic foam. The characteristic surface of EPP shows process-related steam nozzle imprints and gussets. Therefore EPP does not satisfy the quality requirements for visible automotive applications. In order to meet these demands, plastic surfaces are usually enhanced with functional or decorative coatings, e.g. textiles, plastic films or paint. The coating of plastics with low surface energies such as PP often leads to adhesion problems by reason of the missing polar and functional groups. This paper gives an evaluation of activation and pre-treatment methods of EPP, with the aim to identify the most suitable pre-treatment method. For this purpose five typical surface treatment methods - flame treatment, corona, fluorination, atmospheric and low-pressure plasma - were performed on EPP samples. As a comparison criterion the maximum increase in the adhesion force between a polyurethane-based coating and the modified EPP substrate was selected. Moreover the influence of the selected pre-treatment method on the increase in the total surface energy and its polar component was investigated by the drop shape analysis method. The results showed that the contact angle measurement is a suitable method to determine the polar and disperse fractions of the surface tension of EPP. Furthermore, all performed methods increased the adhesion of EPP.

Effect of nanodiamond modification of siloxane surfaces on stem cell behaviour

NASA Astrophysics Data System (ADS)

Keremidarska, M.; Hikov, T.; Radeva, E.; Pramatarova, L.; Krasteva, N.

2014-12-01

Mesenchymal stem cells (MSCs) hold a great promise for use in many cell therapies and tissue engineering due to their remarkable potential to replicate indefinitely and differentiate into various cell types. Many efforts have been put to study the factors controlling stem cell differentiation. However, still little knowledge has been gained to what extent biomaterials properties influence stem cell adhesion, growth and differentiation. Research utilizing bone marrow-derived MSCs has concentrated on development of specific materials which can enhance specific differentiation of stem cells e.g. osteogenic and chondrogenic. In the present work we have modified an organosilane, hexamethyldisiloxane (HMDS) with detonation nanodiamond (DND) particles aiming to improve adhesion, growth and osteodifferentiation of rat mesenchymal stem cells. HMDS/DND films were deposited on cover glass using two approaches: premixing of both compounds, followed by plasma polymerization (PP) and PP of HMDS followed by plasma deposition of DND particles. We did not observe however an increase in rMSCs adhesion and growth on DND-modified PPHMDS surfaces compared to unmodified PPHMDS. When we studied alkaline phosphatase (ALP) activity, which is a major sign for early osteodifferentiation, we found the highest ALP activity on the PPHMDS/DND material, prepared by consequent deposition while on the other composite material ALP activity was the lowest. These results suggested that DND-modified materials were able to control osteodifferention in MSCs depending on the deposition approach. Modification of HMDS with DND particles by consequent plasma deposition seems to be a promising approach to produce biomaterials capable to guide stem cell differentiation toward osteoblasts and thus to be used in bone tissue engineering.

Enhancement of catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol through interfacial modification with heteropolymolybdates

NASA Astrophysics Data System (ADS)

Barczuk, Piotr J.; Lewera, Adam; Miecznikowski, Krzysztof; Zurowski, Artur; Kulesza, Pawel J.

As evidenced from the increase of electrocatalytic currents measured under voltammetric and chronoamperometric conditions, the activity of bimetallic Pt-Ru and Pt-Sn nanoparticles towards oxidation of ethanol is increased by modification of their surfaces with ultra-thin films of phosphododecamolybdic acid (H 3PMo 12O 40). The enhancement effect has been most pronounced in a case of heteropolymolybdate-modified carbon-supported Pt-Sn catalysts. Independent high-resolution XPS measurements indicate the ability of heteropolymolybdates to stabilize tin (in bimetallic Pt-Sn particles) at higher oxidation states (presumably as tin oxo species). The overall activation effect may also be ascribed to changes in the morphology of catalytic films following modification with heteropolymolybdates. Presence of the polyoxometallate is also likely to increase of the interfacial population of reactive oxo groups in the vicinity of platinum centers.

Extensive Chemical Modifications in the Primary Protein Structure of IgG1 Subvisible Particles Are Necessary for Breaking Immune Tolerance.

PubMed

Boll, Björn; Bessa, Juliana; Folzer, Emilien; Ríos Quiroz, Anacelia; Schmidt, Roland; Bulau, Patrick; Finkler, Christof; Mahler, Hanns-Christian; Huwyler, Jörg; Iglesias, Antonio; Koulov, Atanas V

2017-04-03

A current concern with the use of therapeutic proteins is the likely presence of aggregates and submicrometer, subvisible, and visible particles. It has been proposed that aggregates and particles may lead to unwanted increases in the immune response with a possible impact on safety or efficacy. The aim of this study was thus to evaluate the ability of subvisible particles of a therapeutic antibody to break immune tolerance in an IgG1 transgenic mouse model and to understand the particle attributes that might play a role in this process. We investigated the immunogenic properties of subvisible particles (unfractionated, mixed populations, and well-defined particle size fractions) using a transgenic mouse model expressing a mini-repertoire of human IgG1 (hIgG1 tg). Immunization with proteinaceous subvisible particles generated by artificial stress conditions demonstrated that only subvisible particles bearing very extensive chemical modifications within the primary amino acid structure could break immune tolerance in the hIgG1 transgenic mouse model. Protein particles exhibiting low levels of chemical modification were not immunogenic in this model.

Enhanced hydrolysis of cellulose hydrogels by morphological modification.

PubMed

Alfassi, Gilad; Rein, Dmitry M; Cohen, Yachin

2017-11-01

Cellulose is one of the most abundant bio-renewable materials on earth, yet the potential of cellulosic bio-fuels is not fully exploited, primarily due to the high costs of conversion. Hydrogel particles of regenerated cellulose constitute a useful substrate for enzymatic hydrolysis, due to their porous and amorphous structure. This article describes the influence of several structural aspects of the cellulose hydrogel on its hydrolysis. The hydrogel density was shown to be directly proportional to the cellulose concentration in the initial solution, thus affecting its hydrolysis rate. Using high-resolution scanning electron microscopy, we show that the hydrogel particles in aqueous suspension exhibit a dense external surface layer and a more porous internal network. Elimination of the external surface layer accelerated the hydrolysis rate by up to sixfold and rendered the process nearly independent of cellulose concentration. These findings may be of practical relevance to saccharification processing costs, by reducing required solvent quantities and enzyme load.

Thermoresponsive Magnetic Nano-Biosensors for Rapid Measurements of Inorganic Arsenic and Cadmium

PubMed Central

Siddiki, Mohammad Shohel Rana; Shimoaoki, Shun; Ueda, Shunsaku; Maeda, Isamu

2012-01-01

Green fluorescent protein-tagged sensor proteins, ArsR-GFP and CadC-GFP, have been produced as biosensors for simple and low-cost quantification of As(III) or Cd(II). In this study, the sensor protein-promoter DNA complexes were reconstructed on the surfaces of magnetic particles of different sizes. After the surface modification all the particles could be attracted by magnets, and released different amounts of GFP-tagged protein, according to the metal concentrations within 5 min, which caused significant increases in fluorescence. A detection limit of 1 μg/L for As(III) and Cd(II) in purified water was obtained only with the nanoparticles exhibiting enough magnetization after heat treatment for 1 min. Therefore, thermoresponsive magnetic nano-biosensors offer great advantages of rapidity and sensitivity for the measurement of the toxic metals in drinking water. PMID:23202034

Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

PubMed

Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

2007-09-25

The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors

NASA Astrophysics Data System (ADS)

Mazur, Mykola; Barras, Alexandre; Kuncser, Victor; Galatanu, Andrei; Zaitzev, Vladimir; Turcheniuk, Kostiantyn V.; Woisel, Patrice; Lyskawa, Joel; Laure, William; Siriwardena, Aloysius; Boukherroub, Rabah; Szunerits, Sabine

2013-03-01

The synthesis of multifunctional magnetic nanoparticles (MF-MPs) is one of the most active research areas in advanced materials as their multifunctional surfaces allow conjugation of biological and chemical molecules, thus making it possible to achieve target-specific diagnostic in parallel to therapeutics. We report here a simple strategy to integrate in a one-step reaction several reactive sites onto the particles. The preparation of MF-MPs is based on their simultaneous modification with differently functionalized dopamine derivatives using simple solution chemistry. The formed MF-MPs show comparable magnetic properties to those of naked nanoparticles with almost unaltered particle size of around 25 nm. The different termini, amine, azide and maleimide functions, enable further functionalization of MF-MPs by the grafting-on approach. Michael addition, Cu(i) catalyzed « click » chemistry and amidation reactions are performed on the MF-MPs integrating subsequently 6-(ferrocenyl)-hexanethiol, horseradish peroxidase (HRP) and mannose.

Use of lectin-functionalized particles for oral immunotherapy

PubMed Central

Diesner, Susanne C; Wang, Xue-Yan; Jensen-Jarolim, Erika; Untersmayr, Eva; Gabor, Franz

2013-01-01

Immunotherapy, in recent times, has found its application in a variety of immunologically mediated diseases. Oral immunotherapy may not only increase patient compliance but may, in particular, also induce both systemic as well as mucosal immune responses, due to mucosal application of active agents. To improve the bioavailability and to trigger strong immunological responses, recent research projects focused on the encapsulation of drugs and antigens into polymer particles. These particles protect the loaded antigen from the harsh conditions in the GI tract. Furthermore, modification of the surface of particles by the use of lectins, such as Aleuria aurantia lectin, wheatgerm agglutinin or Ulex europaeus-I, enhances the binding to epithelial cells, in particular to membranous cells, of the mucosa-associated lymphoid tissue. Membranous cell-specific targeting leads to an improved transepithelial transport of the particle carriers. Thus, enhanced uptake and presentation of the encapsulated antigen by antigen-presenting cells favor strong systemic, but also local, mucosal immune responses. PMID:22834202

Isolation of N-linked glycopeptides by hydrazine-functionalized magnetic particles.

PubMed

Sun, Shisheng; Yang, Ganglong; Wang, Ting; Wang, Qinzhe; Chen, Chao; Li, Zheng

2010-04-01

We introduce a novel combination of magnetic particles with hydrazine chemistry, dubbed as hydrazine-functionalized magnetic particles (HFMP) for isolation of glycopeptides. Four methods have been developed and compared for the production of HFMP by hydrazine modification of the surface of the carboxyl and epoxy-silanized magnetic particles, respectively. The evaluation of the capability and specificity of HFMP as well as the optimization of the coupling condition for capturing of glycoproteins were systematically investigated. The results showed that HFMP prepared by adipic dihydrazide functionalization from carboxyl-silanized magnetic particles (HFCA) displayed the maximum capture capacity and isolated efficiency for glycoprotein. When measured with glycoproteins, the capacity of the HFCA (1 g) for coupling bovine fetuin was 130 +/- 5.3 mg. The capability of this method was also confirmed by successful isolation of all formerly glycosylated peptides from standard glycoproteins and identification of their glycosylation sites, which demonstrated the feasibility of the HFCA as an alternative solid support for isolation of glycoproteins/glycopeptides.

Effect of Be Modification on the Oxide Bifilms and Tensile Strength Reliability of Al-Si-Mg Alloys Containing Excess Fe

NASA Astrophysics Data System (ADS)

Asadian Nozari, M.; Taghiabadi, R.; Karimzadeh, M.; Ghoncheh, M. H.

2018-03-01

The effect of oxide bifilms and Be modification (0.2 wt pct) on the tensile strength reliability of the as-cast and T6 heat-treated Al-9Si-0.35Mg-1.5Fe alloy was investigated using Weibull analysis. For this purpose, the density of oxide bifilms in the molten alloy was intentionally increased by surface agitation. According to the results, Be modifies the β-Al5FeSi particles to the less harmful α-Fe compounds and substantially decreases the bifilm density in the castings leading to improved tensile properties and higher reliability. Moreover, the beneficial effect of Be was found to be more in the samples containing higher amounts of bifilms. For instance, in the heat-treated condition, Be increased the Weibull modulus of the non-agitated and surface-agitated samples by 4 and 94 pct, respectively. This improvement can be attributed to the strengthening effect of Be on the young surface oxides so that they resist more against rupture when melt is subjected to the surface turbulence. The reduced pressure test and fractography investigations also confirmed the reduction of bifilm density and bifilm-related defects in Be-modified samples.

Effect of Be Modification on the Oxide Bifilms and Tensile Strength Reliability of Al-Si-Mg Alloys Containing Excess Fe

NASA Astrophysics Data System (ADS)

Asadian Nozari, M.; Taghiabadi, R.; Karimzadeh, M.; Ghoncheh, M. H.

2018-06-01

The effect of oxide bifilms and Be modification (0.2 wt pct) on the tensile strength reliability of the as-cast and T6 heat-treated Al-9Si-0.35Mg-1.5Fe alloy was investigated using Weibull analysis. For this purpose, the density of oxide bifilms in the molten alloy was intentionally increased by surface agitation. According to the results, Be modifies the β-Al5FeSi particles to the less harmful α-Fe compounds and substantially decreases the bifilm density in the castings leading to improved tensile properties and higher reliability. Moreover, the beneficial effect of Be was found to be more in the samples containing higher amounts of bifilms. For instance, in the heat-treated condition, Be increased the Weibull modulus of the non-agitated and surface-agitated samples by 4 and 94 pct, respectively. This improvement can be attributed to the strengthening effect of Be on the young surface oxides so that they resist more against rupture when melt is subjected to the surface turbulence. The reduced pressure test and fractography investigations also confirmed the reduction of bifilm density and bifilm-related defects in Be-modified samples.

Copoly(imide siloxane) Abhesive Materials with Varied Siloxane Oligomer Length

NASA Technical Reports Server (NTRS)

Wohl, Christoper J.; Atkins, Brad M.; Lin, Yi; Belcher, Marcus A.; Connell, John W.

2010-01-01

In this work, low surface energy copoly(imide siloxane)s were synthesized with various siloxane segment lengths. Characterization of these materials revealed that domain formation of the low surface energy component within the matrix was more prevalent for longer siloxane segments as indicated by increased opacity, decreased mechanical properties, and variation of the Tg. Incorporation of siloxanes lowered the polymer s surface energy as indicated by water contact angle values. Topographical modification of these materials by laser ablation patterning further reduced the surface energy, even generating superhydrophobic surfaces. Combined, the contact angle data and particle adhesion testing indicated that copoly(imide siloxane) materials may provide greater mitigation to particulate adhesion than polyimide materials alone. These enhanced surface properties for abhesive applications did result in a reduction of the tensile moduli of the copolymers. It is possible that lower siloxane loading levels would result in retention of the mechanical properties of the polyimide while still affording abhesive surface properties. This hypothesis is currently being investigated. Laser ablation patterning offers further reduction in particle retention as the available surface area for particle adhesion is reduced. Pattern variation and size dependencies are currently being evaluated. For the purposes of lunar dust adhesion mitigation, it is likely that this approach, termed passive due to the lack of input from an external energy source, would not be sufficient to mitigate surface contamination or clean contaminated surfaces for some lunar applications. It is feasible to combine these materials with active mitigation strategies - methods that utilize input from external energy sources - would broaden the applicability of such materials for abhesive purposes. Collaborative efforts along these lines have been initiated with researchers at NASA Kennedy Space Center where experiments are being conducted involving a series of embedded electrodes within polymeric matrices.

Improvement of charge separation in TiO{sub 2} by its modification with different tungsten compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tryba, B., E-mail: beata.tryba@zut.edu.pl; Tygielska, M.; Grzeskowiak, M.

2016-04-15

Highlights: • Ammonium m-tungstate doped to TiO{sub 2} highly improved charge separation in TiO{sub 2}. • Negative electrokinetic potential of TiO{sub 2} facilitates holes migration to its surface. • Fast migration of holes to TiO{sub 2} surfaces increased yield of OH radicals formation. • Adsorption of dyes on photocatalyst increased its decomposition under visible light. - Abstract: Three different tungsten precursors were used for TiO{sub 2} modification: H{sub 2}WO{sub 4}, WO{sub 2}, and ammonium m-tungstate. It was proved that modification of TiO{sub 2} with tungsten compounds enhanced its photocatalytic activity through the improvement of charge separation. This effect was obtainedmore » by coating of TiO{sub 2} particles with tungsten compound, which changed their surficial electrokinetical potential from positive onto negative. The most efficient tungsten compound, which caused enhanced separation of free carriers was ammonium m-tungstate (AMT). Two dyes with different ionic potential were used for the photocatalytic decomposition. It appeared that cationic dye—Methylene Blue was highly adsorbed on the negatively charged surface of TiO{sub 2} modified by AMT and decomposed, however this photocatalyst was quickly deactivated whereas anionic dye—acid red was better adsorbed on the less acidic surface of TiO{sub 2} and was rapidly decomposed with almost the same rate in the five following cycles.« less

Modeling of single film bubble and numerical study of the plateau structure in foam system

NASA Astrophysics Data System (ADS)

Sun, Zhong-guo; Ni, Ni; Sun, Yi-jie; Xi, Guang

2018-02-01

The single-film bubble has a special geometry with a certain amount of gas shrouded by a thin layer of liquid film under the surface tension force both on the inside and outside surfaces of the bubble. Based on the mesh-less moving particle semi-implicit (MPS) method, a single-film double-gas-liquid-interface surface tension (SDST) model is established for the single-film bubble, which characteristically has totally two gas-liquid interfaces on both sides of the film. Within this framework, the conventional surface free energy surface tension model is improved by using a higher order potential energy equation between particles, and the modification results in higher accuracy and better symmetry properties. The complex interface movement in the oscillation process of the single-film bubble is numerically captured, as well as typical flow phenomena and deformation characteristics of the liquid film. In addition, the basic behaviors of the coalescence and connection process between two and even three single-film bubbles are studied, and the cases with bubbles of different sizes are also included. Furthermore, the classic plateau structure in the foam system is reproduced and numerically proved to be in the steady state for multi-bubble connections.

Modifications to particles as they move through landscapes: connecting soils and sediments

NASA Astrophysics Data System (ADS)

Owens, Philip N.

2016-04-01

In many areas of the world, soils are eroded leading to the movement of particles towards the global ocean. Along this journey, there are modifications to these particles and we tend to refer to this altered material as sediment in recognition that such material may no longer be fully reflective of its source. These modifications are brought about by physical, chemical and biological processes, and by the inclusion of additional sources of material, such as channel banks. The degree of modification is partly a function of the inherent properties of the original soil material but also reflects landscape type, and the temporal and spatial scales of investigation. This presentation will consider the changes in particles between soil profiles and sediment transported in river systems, drawing on examples from studies in Canada and beyond. It is hoped that by understanding the transformation of such material we can predict better its movement and impacts.

Quantum mechanics of a constrained particle

NASA Astrophysics Data System (ADS)

da Costa, R. C. T.

1981-04-01

The motion of a particle rigidly bounded to a surface is discussed, considering the Schrödinger equation of a free particle constrained to move, by the action of an external potential, in an infinitely thin sheet of the ordinary three-dimensional space. Contrary to what seems to be the general belief expressed in the literature, this limiting process gives a perfectly well-defined result, provided that we take some simple precautions in the definition of the potentials and wave functions. It can then be shown that the wave function splits into two parts: the normal part, which contains the infinite energies required by the uncertainty principle, and a tangent part which contains "surface potentials" depending both on the Gaussian and mean curvatures. An immediate consequence of these results is the existence of different quantum mechanical properties for two isometric surfaces, as can be seen from the bound state which appears along the edge of a folded (but not stretched) plane. The fact that this surface potential is not a bending invariant (cannot be expressed as a function of the components of the metric tensor and their derivatives) is also interesting from the more general point of view of the quantum mechanics in curved spaces, since it can never be obtained from the classical Lagrangian of an a priori constrained particle without substantial modifications in the usual quantization procedures. Similar calculations are also presented for the case of a particle bounded to a curve. The properties of the constraining spatial potential, necessary to a meaningful limiting process, are discussed in some detail, and, as expected, the resulting Schrödinger equation contains a "linear potential" which is a function of the curvature.

Study of magnetic nanoparticles and overcoatings for biological applications including a sensor device

NASA Astrophysics Data System (ADS)

Grancharov, Stephanie G.

I. A general introduction to the field of nanomaterials is presented, highlighting their special attributes and characteristics. Nanoparticles in general are discussed with respect to their structure, form and properties. Magnetic particles in particular are highlighted, especially the iron oxides. The importance and interest of integrating these materials with biological media is discussed, with emphasis on transferring particles from one medium to another, and subsequent modification of surfaces with different types of materials. II. A general route to making magnetic iron oxide nanoparticles is explained, both as maghemite and magnetite, including properties of the particles and characterization. A novel method of producing magnetite particles without a ligand is then presented, with subsequent characterization and properties described. III. Attempts to coat iron oxide nanoparticles with a view to creating biofunctional magnetic nanoparticles are presented, using a gold overcoating method. Methods of synthesis and characterization are examined, with unique problems to core-shell structures analyzed. IV. Solubility of nanoparticles in both aqueous and organic media is discussed and examined. The subsequent functionalization of the surface of maghemite and magnetite nanoparticles with a variety of biomaterials including block copolypeptides, phospholipids and carboxydextran is then presented. These methods are integral to the use of magnetic nanoparticles in biological applications, and therefore their properties are examined once tailored with these molecules. V. A new type of magnetic nanoparticle sensor-type device is described. This device integrates bio-and DNA-functionalized nanoparticles with conjugate functionalized silicon dioxide surfaces. These techniques to pattern particles to a surface are then incorporated into a device with a magnetic tunnel junction, which measures magnetoresistance in the presence of an external magnetic field. This configuration thereby introduces a new way to detect magnetic nanoparticles via their magnetic properties after conjugation via biological entities.

Methods of preparation and modification of advanced zero-valent iron nanoparticles, their properties and application in water treatment technologies

NASA Astrophysics Data System (ADS)

Filip, Jan; Kašlík, Josef; Medřík, Ivo; Petala, Eleni; Zbořil, Radek; Slunský, Jan; Černík, Miroslav; Stavělová, Monika

2014-05-01

Zero-valent iron nanoparticles are commonly used in modern water treatment technologies. Compared to conventionally-used macroscopic iron or iron microparticles, the using of nanoparticles has the advantages given mainly by their generally large specific surface area (it drives their high reactivity and/or sorption capacity), small dimensions (it allows their migration e.g. in ground water), and particular physical and chemical properties. Following the applications of zero-valent iron particles in various pilot tests, there arose several critical suggestions for improvements of used nanomaterials and for development of new generation of reactive nanomaterials. In the presentation, the methods of zero-valent iron nanoparticles synthesis will be summarized with a special attention paid to the thermally-induced solid-state reaction allowing preparation of zero-valent iron nanoparticles in an industrial scale. Moreover, the method of thermal reduction of iron-oxide precursors enables to finely tune the critical parameters (mainly particle size and morphology, specific surface area, surface chemistry of nanoparticles etc.) of resulting zero-valet iron nanoparticles. The most important trends of advanced nanoparticles development will be discussed: (i) surface modification of nanomaterilas, (ii) development of nanocomposites and (iii) development of materials for combined reductive-sorption technologies. Laboratory testing of zero-valent iron nanoparticles reactivity and migration will be presented and compared with the field observations: the advanced zero-valent iron nanoparticles were used for groundwater treatment at the locality contaminated by chlorinated hydrocarbons (VC, DCE, TCE and PCE) and reacted nanoparticles were extracted from the sediments for their fate assessment. The authors gratefully acknowledge the support by the Technology Agency of the Czech Republic "Competence Centres" (project No. TE01020218) and the EU FP7 (project NANOREM).

Influence of Pre-Sintered Zirconia Surface Conditioning on Shear Bond Strength to Resin Cement

PubMed Central

Sawada, Tomofumi; Spintzyk, Sebastian; Schille, Christine; Zöldföldi, Judit; Paterakis, Angelos; Schweizer, Ernst; Stephan, Ingrid; Rupp, Frank; Geis-Gerstorfer, Jürgen

2016-01-01

This study analyzed the shear bond strength (SBS) of resin composite on zirconia surface to which a specific conditioner was applied before sintering. After sintering of either conditioner-coated or uncoated specimens, both groups were divided into three subgroups by their respective surface modifications (n = 10 per group): no further treatment; etched with hydrofluoric acid; and sandblasted with 50 µm Al2O3 particles. Surfaces were characterized by measuring different surface roughness parameters (e.g., Ra and Rmax) and water contact angles. Half of the specimens underwent thermocycling (10,000 cycles, 5–55 °C) after self-adhesive resin cement build-up. The SBSs were measured using a universal testing machine, and the failure modes were analyzed by microscopy. Data were analyzed by nonparametric and parametric tests followed by post-hoc comparisons (α = 0.05). Conditioner-coated specimens increased both surface roughness and hydrophilicity (p < 0.01). In the non-thermocycled condition, sandblasted surfaces showed higher SBSs than other modifications, irrespective of conditioner application (p < 0.05). Adhesive fractures were commonly observed in the specimens. Thermocycling favored debonding and decreased SBSs. However, conditioner-coated specimens upon sandblasting showed the highest SBS (p < 0.05) and mixed fractures were partially observed. The combination of conditioner application before sintering and sandblasting after sintering showed the highest shear bond strength and indicated improvements concerning the failure mode. PMID:28773641

Improvement of the overall performances of LiMn{sub 2}O{sub 4} via surface-modification by polypyrrole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ting; Wang, Wan; Zhu, Ding

2015-11-15

Graphical abstract: Polypyrrole(PPy) film has improved the rate performance of LiMn{sub 2}O{sub 4} efficiently due to its excellent conductivity. PPy@LiMn{sub 2}O{sub 4} could provide more energy under the higher power than pristine LMO. - Highlights: • The PPy layer on the surface of LMO particles hasn’t been studied in LiMn{sub 2}O{sub 4} so far. • The solvent in the synthesis process of PPy@LMO is absolute ethyl alcohol. • The differences of surface-modification between the PPy and PI for LMO. • The analyses of rate performances are through specific power. - Abstract: Polypyrrole (PPy) is an excellent conductive polymer and themore » study on its utilization in the surface modification of the LiMn{sub 2}O{sub 4} (LMO) is few. In this work, the structure, morphology and electrochemical performance of surface-modified LiMn{sub 2}O{sub 4} composites with PPy and polyimides (PI) were discussed. The crystal structure, chemical bonds and morphology were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Moreover, the specific power and cycling performance were tested at room and high (55 °C) temperature. The PPy@LMO (surface-modified LMO composites with PPy) shows better performances than the pristine LMO. The addition of PPy not only weakens the corrosion caused by electrolyte, but also improves the discharge capacity at higher rates. The charge transfer resistance of the PPy@LMO is much lower than that of the pristine LMO after cycling.« less

Morphological specializations of the buccal cavity in relation to the food and feeding habit of a carp Cirrhinus mrigala: a scanning electron microscopic investigation.

PubMed

Yashpal, Madhu; Kumari, Usha; Mittal, Swati; Mittal, Ajay Kumar

2009-06-01

The buccal cavity of an herbivorous fish, Cirrhinus mrigala, was investigated by scanning electron microscopy to determine its surface ultrastructure. The buccal cavity shows significant adaptive modifications in relation to food and feeding ecology of the fish. The buccal cavity of the fish is of modest size and limited capacity, which is considered an adaptation with respect to the small-sized food items primarily consumed by the fish that could be accommodated in a small space. Modification of surface epithelial cells, on the upper jaw, into characteristic structures-the unculi-is considered an adaptation to browse or scrap, to grasp food materials, e.g., algal felts, and to protect the epithelial surface against abrasions, likely to occur during their characteristic feeding behavior. Differentiation of the highly specialized lamellar organ on the anterior region of the palate could be an adaptation playing a significant role in the selection, retention, and sorting out of palatable food particles from the unpalatable items ingested by the fish. The filamentous epithelial projections and the lingulate epithelial projections on the palatal organ in the posterior region of the palate are considered to serve a critical function in final selection, handling, maneuvering, and propelling the food particles toward the esophagus. The abundance of different categories of taste buds in the buccal cavity suggests that gustation is well developed and the fish is highly responsive in the evaluation and the selection of the preferred palatable food items. The secretions of mucous cells in the buccal cavity are associated with multiple functions-particle entrapment, lubrication of the buccal epithelium and food particles to assist smooth passage of food, and to protect the epithelium from possible abrasion. These morphological characteristics ensure efficient working of the buccal cavity in the assessment of the quality and palatability of ingested food, their retention and transport toward the esophagus. Such an adaptation may be essential in conducting the function most basic to the survival of the individuals and species-feeding.

Modification, characterization and investigations of key factors controlling the transport of modified nano zero-valent iron (nZVI) in porous media.

PubMed

Saha, Amal Krishna; Sinha, Alok; Pasupuleti, Srinivas

2018-01-25

Enhancement of nano zero-valent iron (nZVI) stability and transport in the subsurface environment is important for in situ degradation of contaminants. Various biodegradable dispersants (poly (acrylic acid) (PAA), Tween 20 and Reetha Extracts) have been tested to evaluate their effectiveness in this regard. Application of dispersants during the synthesis of nZVI have positively affected the reduction in particle size. The transport capacity in terms of fraction elution at different pore water velocities and collector grain size (filter media) was analyzed using correlation equation for the filtration model by Rajagopalan and Tien (RT model). At a surfactant concentration of 5% for PAA, Tween 20 and Reetha (Sapindus trifoliata) extracts, the lowest particle size and the highest zeta potential achieved are 8.67 nm and -55.29 mV, 75.24 nm and -62.68 mV, 61.6 nm and -37.82 mV, respectively. The trend of colloidal stability by The Derjaguin-Landau-Verwey-Overbeek (DLVO) Theory model for PAA and Reetha applied concentration was 3% > 4% > 5% > 2% > 1% > 0%. For Tween 20, modified nZVI particle shows a higher repulsive force with increasing Tween 20 concentration. Results indicated that some mechanisms such as aggregation, ripening and surface modification with different carrier pore water velocities had a considerable impact on nZVI retention in porous media. The results indicate that natural surfactant like Reetha extracts exhibits an alternative potential capacity for nZVI modification in comparison with synthetic surfactants (PAA and Tween 20).

Improving Dielectric Properties of PVDF Composites by Employing Surface Modified Strong Polarized BaTiO₃ Particles Derived by Molten Salt Method.

PubMed

Fu, Jing; Hou, Yudong; Zheng, Mupeng; Wei, Qiaoyi; Zhu, Mankang; Yan, Hui

2015-11-11

BaTiO3/polyvinylidene fluoride (BT/PVDF) is the extensive reported composite material for application in modern electric devices. However, there still exists some obstacles prohibiting the further improvement of dielectric performance, such as poor interfacial compatibility and low dielectric constant. Therefore, in depth study of the size dependent polarization and surface modification of BT particle is of technological importance in developing high performance BT/PVDF composites. Here, a facile molten-salt synthetic method has been applied to prepare different grain sized BT particles through tailoring the calcination temperature. The size dependent spontaneous polarizationof BT particle was thoroughly investigated by theoretical calculation based on powder X-ray diffraction Rietveld refinement data. The results revealed that 600 nm sized BT particles possess the strong polarization, ascribing to the ferroelectric size effect. Furthermore, the surface of optimal BT particles has been modified by water-soluble polyvinylprrolidone (PVP) agent, and the coated particles exhibited fine core-shell structure and homogeneous dispersion in the PVDF matrix. The dielectric constant of the resulted composites increased significantly, especially, the prepared composite with 40 vol % BT loading exhibited the largest dielectric constant (65, 25 °C, 1 kHz) compared with the literature values of BT/PVDF at the same concentration of filler. Moreover, the energy storage density of the composites with tailored structure was largely enhanced at the low electric field, showing promising application as dielectric material in energy storage device. Our work suggested that introduction of strong polarized ferroelectric particles with optimal size and construction of core-shell structured coated fillers by PVP in the PVDF matrix are efficacious in improving dielectric performance of composites. The demonstrated approach can also be applied to the design and preparation of other polymers-based nanocomposites filled with ferroelectric particles to achieve desirable dielectric properties.

Modification of zeolite 4A for use as an adsorbent for glyphosate and as an antibacterial agent for water.

PubMed

Zavareh, Siamak; Farrokhzad, Zahra; Darvishi, Farshad

2018-07-15

The aim of this work was to design a low cost adsorbent for efficient and selective removal of glyphosate from water at neutral pH conditions. For this purpose, zeolite 4A, a locally abundant and cheap mineral material, was ion-exchanged with Cu 2+ to produce Cu-zeolite 4A. The FTIR results revealed that the modification has no important effect on chemical structure of zeolite 4A. After modification, highly crystalline zeolite 4A was converted to amorphous Cu-zeolite 4A according to XRD studies. The SEM images showed spherical-like particles with porous surfaces for Cu-zeolite 4A compared to cubic particles with smooth surfaces for zeolite 4A. Adsorption equilibrium data were well fitted with non-linear forms of Langmuir, Freundlich and Temkin isotherms. The maximum adsorption capacity for Cu-zeolite 4A was calculated to be 112.7 mg g -1 based on the Langmuir model. The adsorption of glyphosate by the modified adsorbent had fast kinetics fitted both pseudo-first-order and pseudo-second-order models. A mechanism based on chemical adsorption was proposed for the removal process. The modified adsorbent had a good selectivity to glyphosate over natural waters common cations and anions. It also showed desired regeneration ability as an important feature for practical uses. The potential use of the developed material as antibacterial agent for water disinfection filters was also investigated by MIC method. Relatively strong antibacterial activity was observed for Cu-zeolite 4A against Gram-positive and Gram-negative model bacteria while zeolite 4A had no antibacterial properties. No release of Cu 2+ to aqueous solutions was detected as unique feature of the developed material. Copyright © 2018 Elsevier Inc. All rights reserved.

Mesoporous inorganic nanoscale particles for drug adsorption and controlled release.

PubMed

Cavallaro, Giuseppe; Lazzara, Giuseppe; Fakhrullin, Rawil

2018-03-01

The review provides an overview of the mesoporous inorganic particles employed as drug delivery systems for controlled and sustained release of drugs. We have classified promising nanomaterials for drug delivery on the basis of their natural or synthetic origin. Nanoclays are available in different morphologies (nanotubes, nanoplates and nanofibers) and they are typically available at low cost from natural resources. The surface chemistry of nanoclays is versatile for targeted modifications to control loading and release properties. Synthetic nanomaterials (imogolite, laponite and mesoporous silica) present the advantages of well-established purity and availability with size features that are finely controlled. Both nanoclays and inorganic synthetic nanoparticles can be functionalized forming organic/inorganic architectures with stimuli-responsive features.

Packing of nonoverlapping cubic particles: Computational algorithms and microstructural characteristics

NASA Astrophysics Data System (ADS)

Malmir, Hessam; Sahimi, Muhammad; Tabar, M. Reza Rahimi

2016-12-01

Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO2 sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir et al., Sci. Rep. 6, 35024 (2016), 10.1038/srep35024]. A modification of the random sequential addition (RSA) algorithm has been developed to generate such packings, and a variety of microstructural descriptors, including the radial distribution function, the face-normal correlation function, two-point probability and cluster functions, the lineal-path function, the pore-size distribution function, and surface-surface and surface-void correlation functions, have been computed, along with the specific surface and mean chord length of the packings. The results indicate the existence of both spatial and orientational long-range order as the the packing density increases. The maximum packing fraction achievable with the RSA method is about 0.57, which represents the limit for a structure similar to liquid crystals.

Restricted access magnetic materials prepared by dual surface modification for selective extraction of therapeutic drugs from biological fluids

NASA Astrophysics Data System (ADS)

Wang, Yu; Wang, Yuxia; Chen, Lei; Wan, Qian-Hong

2012-02-01

Magnetic porous particles with dual functionality have been prepared by a two-step procedure and evaluated as novel restricted access materials for extraction of therapeutic agents from biological fluids. The magnetic silica particles served as scaffolds were first modified with diol groups, which were then converted to octadecyl esters through reaction with stearoyl chloride. In the second step, the octadecyl esters on the exterior surface were hydrolyzed by the action of lipase to yield magnetic particles with hydrophobic reversed-phase ligands on the inner surface and biocompatible diol groups on the outer surface. The restricted access behavior of the resulting materials was confirmed by differential binding of small molecules such as methotrexate (MTX), leucovorin (LV) and folic acid (FA) relative to bovine serum albumin. While MTX, LV and FA were all bound to the magnetic particles with high affinity, the adsorption of the protein was markedly reduced due to size exclusion effect. The utility of the magnetic particles for sample preparation was tested in solid-phase extraction of MTX, LV and FA from spiked human serum and the effects of the SPE conditions on the recovery of the analytes were systematically studied. Moreover, the magnetic particle-based sample preparation procedure coupled with reversed-phase liquid chromatography analysis was validated in terms of specificity, linearity and reproducibility. The method was shown to be free from interference of endogenous compounds and linear over the concentration range of 0.5-10 μg/mL for the three drugs studied. The limits of detection for the three drugs in serum were in the range of 0.160-0.302 μg/mL. Reproducibility expressed as the RSD of the recovery for ten replicated extractions at three different concentrations was found to be less than 8.93%. With a unique combination of surface functionality with magnetic cores, the restricted access magnetic particles may be adapted in automated and high throughput protocols for routine analysis of a large volume of clinical samples.

Supracolloidal Architectures Self-Assembled in Microdroplets.

PubMed

Xu, Xuejiao; Tian, Feng; Liu, Xin; Parker, Richard M; Lan, Yang; Wu, Yuchao; Yu, Ziyi; Scherman, Oren A; Abell, Chris

2015-10-26

We demonstrate a novel method for the formation of a library of structured colloidal assemblies by exploiting the supramolecular heteroternary host-guest interaction between cucurbit[8]uril (CB[8]) and methyl viologen- and naphthalene-functionalised particles. The approach is dependent upon compartmentalisation in microdroplets generated by a microfluidic platform. Though the distribution of colloidal particles encapsulated within each microdroplet followed a Poisson distribution, tuning the concentration of the initial colloidal particle suspensions provided some level of control over the structure of the formed colloidal assemblies. This ability to direct the assembly of complementarily-functionalised colloids through a supramolecular interaction, without the need for complex modification of the colloidal surface or external stimuli, presents an exciting new approach towards the design of structured colloidal materials with the potential to produce many challenging structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Particle-in-Cell laser-plasma simulation on Xeon Phi coprocessors

NASA Astrophysics Data System (ADS)

Surmin, I. A.; Bastrakov, S. I.; Efimenko, E. S.; Gonoskov, A. A.; Korzhimanov, A. V.; Meyerov, I. B.

2016-05-01

This paper concerns the development of a high-performance implementation of the Particle-in-Cell method for plasma simulation on Intel Xeon Phi coprocessors. We discuss the suitability of the method for Xeon Phi architecture and present our experience in the porting and optimization of the existing parallel Particle-in-Cell code PICADOR. Direct porting without code modification gives performance on Xeon Phi close to that of an 8-core CPU on a benchmark problem with 50 particles per cell. We demonstrate step-by-step optimization techniques, such as improving data locality, enhancing parallelization efficiency and vectorization leading to an overall 4.2 × speedup on CPU and 7.5 × on Xeon Phi compared to the baseline version. The optimized version achieves 16.9 ns per particle update on an Intel Xeon E5-2660 CPU and 9.3 ns per particle update on an Intel Xeon Phi 5110P. For a real problem of laser ion acceleration in targets with surface grating, where a large number of macroparticles per cell is required, the speedup of Xeon Phi compared to CPU is 1.6 ×.

Phase composition and fine structure of 0.18C-1Cr-3Ni-1Mo-Fe steel after plasma-electrolytic treatment

NASA Astrophysics Data System (ADS)

Popova, Natalya; Bayatanova, Lyayla; Nikonenko, Elena; Skakov, Mazhyn; Kozlov, Eduard

2017-01-01

The paper presents the transmission electron microscopy (TEM) investigation of 0.18C-1Cr-3Mn-1Mo- Fe steel specimens to study phase transitions and modification of fine structure after plasma-electrolytic treatment (carbonitriding at 850°C during 5 min). TEM investigations involve two points: on the specimen surface and at ˜40 µm distance from it. The experiments show that the structure in the original state is a mixture consisting of ferrite and perlite grains. Carbonitriding results in a considerable modification of the quality and quantity of steel structure. Thus, on the surface, α-phase is represented by lamellar martensite, while at ˜40 µm depth - by massive and lamellar martensite tempered at low and high temperatures. Moreover, on the subsurface of the martensite plates' boundaries retained austenite layers are observed, while inside plates the particles of alloyed cementite, carbonitrides of M23(C,N)6, M2C0.61N0.39, M6,2C3,5N0,3, M(C,N)2, Cr12Fe32Mo7Ni7 types, and β-graphite are present. In the specimen at the depth of ˜40 µm, retained austenite layers are observed on the boundaries of martensite laths and plates, while inside plates only the particles of alloyed cementite and M23(C,N)6 carbonitride are formed.

Synergistic effect of cationic and anionic surfactants for the modification of Ca-montmorillonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zepeng, E-mail: zhangzp@cugb.edu.cn; Zhang, Jichu; Liao, Libing, E-mail: bliao@cugb.edu.cn

2013-05-15

Highlights: ► The basal spacing of MMT–CTAB–SDS reaches 5.30 nm. ► MMT–CTAB–SDS shows perfect dispersion property and excellent heat resistance. ► SDS helped to improve the heat resistance and decrease the surface energy of the MMT–CTAB–SDS particles. - Abstract: The synergistic effect of cationic surfactant (CTAB) and anionic surfactant (SDS) for the modification of Ca-montmorillonite (Ca-MMT) has been developed, and the novel cation–anion modified organomontmorillonite (MMT–CTAB–SDS) was prepared. X-ray diffraction (XRD) analysis indicates that the interlayer spacing of montmorillonite was well expanded by the intercalation of CTAB and SDS and the basal spacing increased from 1.54 nm (Ca-MMT) to 5.30more » nm (MMT–CTAB–SDS). Thermogravimetric analysis (TG) showed that the MMT–CTAB–SDS displayed excellent heat resistance. Scanning electron microscopy (SEM) analysis proved that the MMT–CTAB–SDS exhibited excellent dispersion property and the plates with few silicate layers can be observed. Contact angle tests indicated that the hydrophilicity of MMT–CTAB–SDS was lower than that of Ca-MMT and higher than that of MMT–CTAB. It was verified that SDS contributed to expanding the interlayer space, further improved the heat resistance of the MMT–CTAB and decreased the surface energy of the MMT–CTAB–SDS particles.« less

Preparation of Superhydrophobic Film on Ti Substrate and Its Anticorrosion Property

PubMed Central

Zhu, Min; Tang, Wenchuan; Huang, Luyao; Zhang, Dawei; Du, Cuiwei; Yu, Gaohong; Chen, Ming; Chowwanonthapunya, Thee

2017-01-01

Superhydrophobic films were fabricated on a titanium substrate with or without anodizing by using a self-assembling method. Firstly, the pretreatments of mechanical polishing/anodizing or mechanical polishing only were conducted, respectively. Subsequently, the preparation of polydopamine film layer, deposition of nano-silver particles, and post modification of 1H,1H,2H,2H-perfluorodecanethiol were performed on the surface of the pretreated substrate. The surface morphologies, compositions, wettability, and corrosion resistance of the films were investigated with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), water contact angle measurements, and electrochemical tests, respectively. Meanwhile, the effect of the deposition time in the silver nitrate solution on the hydrophobicity of the specimen surface was investigated. The result showed that with the increase of deposition time, the hydrophobic property enhanced gradually. The surface deposited for 7 h exhibited an optimum hydrophobic effect, which was characterized with a large water contact angle (WCA) of 154°, and the surface was rather rough and covered by a relatively uniform layer of micro-nano silver particles. The excellent hydrophobicity was attributed to a rough stratified microstructure along with the low surface energy. The electrochemical measurements showed that the existence of the superhydrophobic film can effectively enhance the corrosion resistance of Ti samples. PMID:28772987

Surface functionalized SiO2 nanoparticles with cationic polymers via the combination of mussel inspired chemistry and surface initiated atom transfer radical polymerization: Characterization and enhanced removal of organic dye.

PubMed

Huang, Qiang; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Zeng, Guangjian; Huang, Hongye; Jiang, Ruming; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

2017-08-01

Monodispersed SiO 2 particles functionalized with cationic polymers poly-((3-acrylamidopropyl)trimethylammonium chloride) (PAPTCl) were prepared using mussel inspired surface modification strategy and surface initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, X-ray photoelectron spectroscopy, and zeta potential were employed to characterize these SiO 2 samples. The adsorption performance of the functionalized SiO 2 (donated as SiO 2 -PDA-PAPTCl) towards anionic organic dye Congo red (CR) was investigated to evaluate their potential environmental applications. We demonstrated that the surface of SiO 2 particles can be successfully functionalized with cationic PAPTCl. The adsorption capability of as-prepared SiO 2 was found to increases from 28.70 and 106.65mg/g after surface grafted with cationic polymers. The significant enhancement in the adsorption capability of SiO 2 -PDA-PAPTCl is mainly attributed to the introduction of cationic polymers. More importantly, this strategy is expected to be promising for fabrication of many other functional polymer nanocomposites for environmental applications due to the universality of mussel inspired chemistry and well designability and good monomer adaptability of SI-ATRP. Copyright © 2017 Elsevier Inc. All rights reserved.

Preparation of Superhydrophobic Film on Ti Substrate and Its Anticorrosion Property.

PubMed

Zhu, Min; Tang, Wenchuan; Huang, Luyao; Zhang, Dawei; Du, Cuiwei; Yu, Gaohong; Chen, Ming; Chowwanonthapunya, Thee

2017-06-08

Superhydrophobic films were fabricated on a titanium substrate with or without anodizing by using a self-assembling method. Firstly, the pretreatments of mechanical polishing/anodizing or mechanical polishing only were conducted, respectively. Subsequently, the preparation of polydopamine film layer, deposition of nano-silver particles, and post modification of 1H,1H,2H,2H-perfluorodecanethiol were performed on the surface of the pretreated substrate. The surface morphologies, compositions, wettability, and corrosion resistance of the films were investigated with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), water contact angle measurements, and electrochemical tests, respectively. Meanwhile, the effect of the deposition time in the silver nitrate solution on the hydrophobicity of the specimen surface was investigated. The result showed that with the increase of deposition time, the hydrophobic property enhanced gradually. The surface deposited for 7 h exhibited an optimum hydrophobic effect, which was characterized with a large water contact angle (WCA) of 154°, and the surface was rather rough and covered by a relatively uniform layer of micro-nano silver particles. The excellent hydrophobicity was attributed to a rough stratified microstructure along with the low surface energy. The electrochemical measurements showed that the existence of the superhydrophobic film can effectively enhance the corrosion resistance of Ti samples.

Guided self-assembly of nanostructured titanium oxide

NASA Astrophysics Data System (ADS)

Wang, Baoxiang; Rozynek, Zbigniew; Fossum, Jon Otto; Knudsen, Kenneth D.; Yu, Yingda

2012-02-01

A series of nanostructured titanium oxide particles were synthesized by a simple wet chemical method and characterized by means of small-angle x-ray scattering (SAXS)/wide-angle x-ray scattering (WAXS), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), thermal analysis, and rheometry. Tetrabutyl titanate (TBT) and ethylene glycol (EG) can be combined to form either TiOx nanowires or smooth nanorods, and the molar ratio of TBT:EG determines which of these is obtained. Therefore, TiOx nanorods with a highly rough surface can be obtained by hydrolysis of TBT with the addition of cetyl-trimethyl-ammonium bromide (CTAB) as surfactant in an EG solution. Furthermore, TiOx nanorods with two sharp ends can be obtained by hydrolysis of TBT with the addition of salt (LiCl) in an EG solution. The AFM results show that the TiOx nanorods with rough surfaces are formed by the self-assembly of TiOx nanospheres. The electrorheological (ER) effect was investigated using a suspension of titanium oxide nanowires or nanorods dispersed in silicone oil. Oil suspensions of titanium oxide nanowires or nanorods exhibit a dramatic reorganization when submitted to a strong DC electric field and the particles aggregate to form chain-like structures along the direction of applied electric field. Two-dimensional SAXS images from chains of anisotropically shaped particles exhibit a marked asymmetry in the SAXS patterns, reflecting the preferential self-assembly of the particles in the field. The suspension of rough TiOx nanorods shows stronger ER properties than that of the other nanostructured TiOx particles. We find that the particle surface roughness plays an important role in modification of the dielectric properties and in the enhancement of the ER effect.

Guided self-assembly of nanostructured titanium oxide.

PubMed

Wang, Baoxiang; Rozynek, Zbigniew; Fossum, Jon Otto; Knudsen, Kenneth D; Yu, Yingda

2012-02-24

A series of nanostructured titanium oxide particles were synthesized by a simple wet chemical method and characterized by means of small-angle x-ray scattering (SAXS)/wide-angle x-ray scattering (WAXS), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), thermal analysis, and rheometry. Tetrabutyl titanate (TBT) and ethylene glycol (EG) can be combined to form either TiO(x) nanowires or smooth nanorods, and the molar ratio of TBT:EG determines which of these is obtained. Therefore, TiO(x) nanorods with a highly rough surface can be obtained by hydrolysis of TBT with the addition of cetyl-trimethyl-ammonium bromide (CTAB) as surfactant in an EG solution. Furthermore, TiO(x) nanorods with two sharp ends can be obtained by hydrolysis of TBT with the addition of salt (LiCl) in an EG solution. The AFM results show that the TiO(x) nanorods with rough surfaces are formed by the self-assembly of TiO(x) nanospheres. The electrorheological (ER) effect was investigated using a suspension of titanium oxide nanowires or nanorods dispersed in silicone oil. Oil suspensions of titanium oxide nanowires or nanorods exhibit a dramatic reorganization when submitted to a strong DC electric field and the particles aggregate to form chain-like structures along the direction of applied electric field. Two-dimensional SAXS images from chains of anisotropically shaped particles exhibit a marked asymmetry in the SAXS patterns, reflecting the preferential self-assembly of the particles in the field. The suspension of rough TiO(x) nanorods shows stronger ER properties than that of the other nanostructured TiO(x) particles. We find that the particle surface roughness plays an important role in modification of the dielectric properties and in the enhancement of the ER effect.

Textile Functionalization and Its Effects on the Release of Silver Nanoparticles into Artificial Sweat.

PubMed

Wagener, Sandra; Dommershausen, Nils; Jungnickel, Harald; Laux, Peter; Mitrano, Denise; Nowack, Bernd; Schneider, Gregor; Luch, Andreas

2016-06-07

This study addresses the release of total silver (Ag) and silver nanoparticles (Ag-NPs) from textiles into artificial sweat, particularly considering the functionalization technology used in textile finishing. Migration experiments were conducted for four commercially available textiles and for six laboratory-prepared textiles. Two among these lab-prepared textiles represent materials in which Ag-NPs were embedded within the textile fibers (composites), whereas the other lab-prepared textiles contain Ag particles on the respective fiber surfaces (coatings). The results indicate a smaller release of total Ag from composites in comparison to surface-coated textiles. The particulate fraction determined within the artificial sweat was negligible for most textiles, meaning that the majority of the released Ag is present as dissolved Ag. It is also relevant to note that nanotextiles do not release more particulate Ag than conventional Ag textiles. The results rather indicate that the functionalization type is the most important parameter affecting the migration. Furthermore, after measuring different Ag-NP types in their pristine form with inductively coupled plasma mass spectrometry in the single particle mode, there is evidence that particle modifications, like surface coating, may also influence the dissolution behavior of the Ag-NPs in the sweat solutions. These factors are important when discussing the likelihood of consumer exposure.

Bonding Strength Properties of Adhesively-Timber Joint with Thixotropic and Room Temperature Cured Epoxy Based Adhesive Reinforced with Nano- and Micro-particles

NASA Astrophysics Data System (ADS)

Ahmad, Z.; Ansell, M. P.; Smedley, D.

2011-02-01

This research work is concerned with in situ bonded-in timber connection using pultruded rod; where the manufacturing of such joint requires adhesive which can produce thick glue-lines and does not allow any use of pressure and heat. Four types of thixotropic (for ease application) and room temperature cured epoxy based were used namely CB10TSS (regarded as standards adhesive), Nanopox (modification of CB10TSS with addition of nanosilica), Albipox (modification of CB10TSS with addition of liquid rubber) and Timberset (an epoxy-based adhesive with addition of micro-size ceramic particles). The quality of the adhesive bonds was accessed using block shear test in accordance with ASTM D905. The bond strength depends on how good the adhesive wet the timber surface. Therefore the viscosity and contact angle was also measured. The nano- and microfiller additions increased the bond strength significantly. The viscosity correlates well with contact angle measurements where lower viscosities are associated with lower contact angles. However contact angle contradicts with measured strength and wettability.

Thermal and colloidal behavior of amine-treated clays: the role of amphiphilic organic cation concentration.

PubMed

Marras, S I; Tsimpliaraki, A; Zuburtikudis, I; Panayiotou, C

2007-11-15

The modification of sodium montmorillonite (NaMMT) through the insertion of amphiphilic hexadecylammonium cations into the clay's interlayer spaces has been studied. Alkylammonium concentrations equivalent to 0.15-3.00 times the cation exchange capacity of the clay were used. The conformation of the surfactant cations in the confined space of the silicate galleries was investigated by X-ray diffraction analysis and scanning electron microscopy, while the organoclay's thermal stability was examined by thermogravimetric analysis. The clay's surface properties induced by the ion-exchange process were followed by measurements of the mineral's zeta potential as a function of pH and surfactant concentration, while the coagulation rates of organoclay suspensions in water and in chloroform were examined using dynamic light scattering. All the results are consistent with showing that the overall characteristics and thus the behavior of the modified MMT particles strongly depend on the alkylammonium surfactant concentration used in the modification process. This, however, has very important implications for any attempt to incorporate the organomodified MMT particles into different media for various applications such as polymer nanocomposite preparation.

Efficient silver modification of TiO2 nanotubes with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Huang, Jing; Ding, Lei; Xi, Yaoning; Shi, Liang; Su, Ge; Gao, Rongjie; Wang, Wei; Dong, Bohua; Cao, Lixin

2018-06-01

In this paper, Ag(CH3NH2)2+, Ag(NH3)2+ and Ag+ with different radii have been used as silver sources to find out the distribution of Ag ions on the H-TNT surface, which is critical to the final performance. The influence of this distribution on visible photocatalytic activity is further studied. The results indicate that, when Ag+ used as silver source with low concentration, these small sized silver ions mainly distribute on interlayer spacing of H-TNT. After heat-treatment and photo-reduction, the generated silver nanoparticles uniformly embed in the anatase TiO2 nanotube walls, and bring large interfacial area between Ag particles and TiO2 nanotubes. The separation effect of photogenerated electron-hole pair in TiO2 is enhanced by Ag particles, and achieves the best at 0.15 g/L, much higher than P25, TiO2/0, Ag-N@TiO2 and Ag-C-N@TiO2. This paper provides new ideas for the modification of TiO2 nanotubes.

Research of Adhesion Bonds Between Gas-Thermal Coating and Pre-Modified Base

NASA Astrophysics Data System (ADS)

Kovalevskaya, Z.; Zaitsev, K.; Klimenov, V.

2016-08-01

Nature of adhesive bonds between gas-thermal nickel alloy coating and carbon steel base was examined using laser profilometry, optical metallography, transmission and scanning electron microscopy. The steel surface was plastically pre-deformed by an ultrasonic tool. Proved that ultrasound pre-treatment modifies the steel surface. Increase of dislocation density and formation of sub micro-structure are base elements of surface modification. While using high-speed gas-flame, plasma and detonation modes of coatings, surface activation occurs and durable adhesion is formed. Ultrasonic pre-treatment of base material is effective when sprayed particles and base material interact through physical-chemical bond formation. Before applying high-speed gas flame and plasma sprayed coatings, authors recommend ultrasonic pretreatment, which creates periodic wavy topography with a stroke of 250 microns on the steel surface. Before applying detonation sprayed coatings, authors recommend ultrasound pretreatment that create modified surface with a uniform micro-topography.

Surface modification of ZnO nanorods with Hamilton receptors.

PubMed

Zeininger, Lukas; Klaumünzer, Martin; Peukert, Wolfgang; Hirsch, Andreas

2015-04-13

A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. Synthesized zinc oxide nanorods [ZnO] were used for surface functionalization. The wet-chemical functionalization procedure towards monolayer-grafted particles [ZnO-HR] is described and a detailed characterization study is presented. In addition, the detection of specific cyanurate molecules is demonstrated. The hybrid structures [ZnO-HR-CA] were stable towards agglomeration and exhibited enhanced dispersability in apolar solvents. This observation, in combination with several spectroscopic experiments gave evidence of the highly directional supramolecular recognition at the surface of nanoparticles.

Saturn's satellites - Near-infrared spectrophotometry (0.65-2.5 microns) of the leading and trailing sides and compositional implications

NASA Technical Reports Server (NTRS)

Steele, A.; Clark, R. N.; Brown, R. H.; Owensby, P. D.

1984-01-01

Water ice absorptions at 2.0, 1.5, and 1.25 microns are noted in near-IR spectra of Tethys, Dione, Rhea, Iapetus, and Hyperion, and the weak 1.04-micron ice absorption, which is detected for Rhea and Dione, is studied to establish band depth upper limits. The leading-trailing side 1.04-micron ice band depth differences on Saturn's satellites are similar to those for the Galilean satellites, indicating possible surface modification by magnetospheric charged particle bombardment. Limits are obtained for the amounts of particulates, trapped gases, and ammonium hydroxide on the surface. With the exception of the dark side of Iapetus, the surfaces of all of Saturn's satellites are nearly pure ice water.

Surface Modification of Intraocular Lenses

PubMed Central

Huang, Qi; Cheng, George Pak-Man; Chiu, Kin; Wang, Gui-Qin

2016-01-01

Objective: This paper aimed to review the current literature on the surface modification of intraocular lenses (IOLs). Data Sources: All articles about surface modification of IOLs published up to 2015 were identified through a literature search on both PubMed and ScienceDirect. Study Selection: The articles on the surface modification of IOLs were included, but those on design modification and surface coating were excluded. Results: Technology of surface modification included plasma, ion beam, layer-by-layer self-assembly, ultraviolet radiation, and ozone. The main molecules introduced into IOLs surface were poly (ethylene glycol), polyhedral oligomeric silsesquioxane, 2-methacryloyloxyethyl phosphorylcholine, TiO2, heparin, F-heparin, titanium, titanium nitride, vinyl pyrrolidone, and inhibitors of cytokines. The surface modification either resulted in a more hydrophobic lens, a more hydrophilic lens, or a lens with a hydrophilic anterior and hydrophobic posterior surface. Advances in research regarding surface modification of IOLs had led to a better biocompatibility in both in vitro and animal experiments. Conclusion: The surface modification is an efficient, convenient, economic and promising method to improve the biocompatibility of IOLs. PMID:26830993

Improvement of flow and bulk density of pharmaceutical powders using surface modification.

PubMed

Jallo, Laila J; Ghoroi, Chinmay; Gurumurthy, Lakxmi; Patel, Utsav; Davé, Rajesh N

2012-02-28

Improvement in flow and bulk density, the two most important properties that determine the ease with which pharmaceutical powders can be handled, stored and processed, is done through surface modification. A limited design of experiment was conducted to establish a standardized dry coating procedure that limits the extent of powder attrition, while providing the most consistent improvement in angle of repose (AOR). The magnetically assisted impaction coating (MAIC) was considered as a model dry-coater for pharmaceutical powders; ibuprofen, acetaminophen, and ascorbic acid. Dry coated drug powders were characterized by AOR, particle size as a function of dispersion pressure, particle size distribution, conditioned bulk density (CBD), Carr index (CI), flow function coefficient (FFC), cohesion coefficient using different instruments, including a shear cell in the Freeman FT4 powder rheometer, and Hansen flowability index. Substantial improvement was observed in all the measured properties after dry coating relative to the uncoated powders, such that each powder moved from a poorer to a better flow classification and showed improved dispersion. The material intrinsic property such as cohesion, plotted as a function of particle size, gave a trend similar to those of bulk flow properties, AOR and CI. Property improvement is also illustrated in a phase map of inverse cohesion (or FFC) as a function of bulk density, which also indicated a significant positive shift due to dry coating. It is hoped that such phase maps are useful in manufacturing decisions regarding the need for dry coating, which will allow moving from wet granulation to roller compaction or to direct compression based formulations. Copyright © 2011 Elsevier B.V. All rights reserved.

Layer by Layer, Nano-particle "Only" Surface Modification of Filtration Membranes

NASA Astrophysics Data System (ADS)

Escobar-Ferrand, Luis

Layer by Layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for the modification of polymeric micro and ultrafiltration (MF/UF) membranes to produce thin film composites (TFC) with potential nanofiltration (NF) and reverse osmosis (RO) capabilities.. A variety of porous substrate membranes with different membrane surface characteristics are employed, but exhibiting in common that wicking of water does not readily occur into the pore structure, including polycarbonate track etched (PCTE), polyethersulfone (PES) and sulfonated PES (SPEES) MF/UF membranes. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those reported by Lee et al. Appropriate selection of the pH's for anionic and cationic particle deposition enables the construction of nanoparticle only layers 100--1200 nm in thickness atop the original membrane substrates. The surface layer thickness varies monotonically with the number of bilayers (anionic/cationic deposition cycles) as expected. The deposition process is optimized to eliminate drying induced cracking and to improve mechanical durability via thickness control and post-deposition hydro-thermal treatment. The hydrodynamic permeability of these TFC membranes is measured to evaluate their performance under typical NF operating conditions using dead-end permeation experiments and their performance compared quantitatively with realistic hydrodynamic models, with favorable results. For track etched polycarbonate MF substrates, surface modification causes a permeability reduction of approximately two orders of magnitude with respect to the bare substrates, to values comparable to those for typical commercial NF membranes. Good quantitative agreement with hydrodynamic models with no adjustable parameters was also established for this case, providing indirect confirmation that the LbL deposited surface layers are largely defect (crack) free. Imaging of our TFC membranes after permeation tests confirmed that no significant mechanical damage resulted, indicating integrity and robustness of the LbL deposited surface layers in typical applications. The selectivity of these novel TFC membranes was also tested using standard "rejection" tests normally used to characterize NF and RO membranes for their capabilities in typical applications, such as water softening or desalination. We report the dextran standards molecular weight "cut-off" (MWCO) using mixed dextrans from 1.5 to 500 KDa in dead-end stir cells, and the percentage of rejection of standard bivalent and monovalent salt solutions using steady cross flow permeation experiments. The results confirm rejection of at least 60% of even the smallest dextrans, an estimated dextran MWCO of 20 KDa, and rejection of 10% and 20% for monovalent (NaCl) and bivalent (MgSO4) salts, respectively, for all the TFC membranes studied, while the unmodified membranes showed no rejection capability at all. The work supports that nanoparticle based LbL surface modification of MF/UF membranes can produce filtration quality media for important water purification applications, such as nanofiltration (NF) softening processes, natural organic matter (NOM) elimination and possibly reverse osmosis (RO) desalination.

Tunable geometry of bacterial inclusion bodies as substrate materials for tissue engineering

NASA Astrophysics Data System (ADS)

García-Fruitós, Elena; Seras-Franzoso, Joaquín; Vazquez, Esther; Villaverde, Antonio

2010-05-01

A spectrum of materials for biomedical applications is produced in bacteria, and some of them, such as metals or polyhydroxyalkanoates, are straightforwardly obtained as particulate entities. We have explored the biofabrication process of bacterial inclusion bodies, particulate proteinaceous materials (ranging from 50 to 500 nm in diameter) recently recognized as suitable for surface topographical modification and tissue engineering. Inclusion bodies have been widely described as spherical or pseudo-spherical particles with only minor morphological variability, mostly restricted to their size. Here we have identified a cellular gene in Escherichia coli (clpP) that controls the in vivo fabrication process of inclusion bodies. In the absence of the encoded protease, the dynamics of protein deposition is perturbed, resulting in unusual tear-shaped particles with enhanced surface-volume ratios. This fact modifies the ability of inclusion bodies to promote mammalian cell attachment and differentiation upon surface decoration. The implications of the genetic control of inclusion body geometry are discussed in the context of their biological fabrication and regarding the biomedical potential of these protein clusters in regenerative medicine.

Direct Observation of Double Hydrogen Transfer via Quantum Tunneling in a Single Porphycene Molecule on a Ag(110) Surface.

PubMed

Koch, Matthias; Pagan, Mark; Persson, Mats; Gawinkowski, Sylwester; Waluk, Jacek; Kumagai, Takashi

2017-09-13

Quantum tunneling of hydrogen atoms (or protons) plays a crucial role in many chemical and biological reactions. Although tunneling of a single particle has been examined extensively in various one-dimensional potentials, many-particle tunneling in high-dimensional potential energy surfaces remains poorly understood. Here we present a direct observation of a double hydrogen atom transfer (tautomerization) within a single porphycene molecule on a Ag(110) surface using a cryogenic scanning tunneling microscope (STM). The tautomerization rates are temperature independent below ∼10 K, and a large kinetic isotope effect (KIE) is observed upon substituting the transferred hydrogen atoms by deuterium, indicating that the process is governed by tunneling. The observed KIE for three isotopologues and density functional theory calculations reveal that a stepwise transfer mechanism is dominant in the tautomerization. It is also found that the tautomerization rate is increased by vibrational excitation via an inelastic electron tunneling process. Moreover, the STM tip can be used to manipulate the tunneling dynamics through modification of the potential landscape.

Improved sample management in the cylindrical-tube microelectrophoresis method

NASA Technical Reports Server (NTRS)

Smolka, A. J. K.

1980-01-01

A modification to an analytical microelectrophoresis system is described that improves the manipulation of the sample particles and fluid. The apparatus modification and improved operational procedure should yield more accurate measurements of particle mobilities and permit less skilled operators to use the apparatus.

High pulse number thermal shock tests on tungsten with steady state particle background

NASA Astrophysics Data System (ADS)

Wirtz, M.; Kreter, A.; Linke, J.; Loewenhoff, Th; Pintsuk, G.; Sergienko, G.; Steudel, I.; Unterberg, B.; Wessel, E.

2017-12-01

Thermal fatigue of metallic materials, which will be exposed to severe environmental conditions e.g. plasma facing materials in future fusion reactors, is an important issue in order to predict the life time of complete wall components. Therefore experiments in the linear plasma device PSI-2 were performed to investigate the synergistic effects of high pulse number thermal shock events (L = 0.38 GW m-2, Δt = 0.5 ms) and stationary D/He (6%) plasma particle background on the thermal fatigue behavior of tungsten. Similar to experiments with pure thermal loads, the induced microstructural and surface modifications such as recrystallization and roughening as well as crack formation become more pronounced with increasing number of thermal shock events. However, the amount of damage significantly increases for synergistic loads showing severe surface roughening, plastic deformation and erosion resulting from the degradation of the mechanical properties caused by bombardment and diffusion of D/He to the surface and the bulk of the material. Additionally, D/He induced blistering and bubble formation were observed for all tested samples, which could change the thermal and mechanical properties of near surface regions.

Nylon surface modification: 2. Nylon-supported composite films.

PubMed

Herrera-Alonso, Margarita; McCarthy, Thomas J; Jia, Xinqiao

2006-02-14

We have developed techniques for the introduction of reactive functional groups to nylon surfaces via site-specific reactions targeting at the naturally abundant amide repeating units on the surface. In this report, we describe the fabrication of nylon-supported composite surfaces using the most efficient modification methods we have developed. N-Alkylation with (3-glycidoxypropyl)triethoxysilane (GPTES) in the presence of potassium tert-butoxide (t-BuOK) leads to surfaces with silica-like reactivity. Subsequent chemical vapor deposition using tetrachlorosilane (SiCl4) and water results in composite films with a thin layer of silica, which was made hydrophobic by reaction with a fluorinated silane reagent. Reduction of the amide groups with borane-THF (BH3-THF) complex leads to a 69% conversion of surface amides to the corresponding secondary amine groups. Alginate was chosen as the model polyelectrolyte for the introduction of a hydrated surface layer. Because of the strong electrostatic interaction between alginate and the amine-enriched nylon surfaces, the adsorption is fast and concentration-independent (within the concentration range studied). The polysaccharide coats the surface homogeneously, without the formation of large aggregates. The amine surfaces obtained by reduction with BH3-THF ((BH3-THF)nylon-NH) and by alkylation with 2-bromoethylamine hydrobromide (BEA-HBr, (EBA-HBr)nylon-NH2) were also used to study gold deposition through electroless plating. Immobilization of a negatively charged metal complex (AuCl4(-)) was achieved through electrostatic interaction. Gold particles disperse preferentially in the bulk of (EBA-HBr)nylon-NH2 films, while they remain confined to the outer surface layer of (BH3-THF)nylon-NH films.

Quantitative characterization of collagen in the fibrotic capsule surrounding implanted polymeric microparticles through second harmonic generation imaging

DOE PAGES

Akilbekova, Dana; Bratlie, Kaitlin M.; Abraham, Thomas

2015-06-30

The collagenous capsule formed around an implant will ultimately determine the nature of its in vivo fate. To provide a better understanding of how surface modifications can alter the collagen orientation and composition in the fibrotic capsule, we used second harmonic generation (SHG) microscopy to evaluate collagen organization and structure generated in mice subcutaneously injected with chemically functionalized polystyrene particles. SHG is sensitive to the orientation of a molecule, making it a powerful tool for measuring the alignment of collagen fibers. Additionally, SHG arises from the second order susceptibility of the interrogated molecule in response to the electric field. Variationmore » in these tensor components distinguishes different molecular sources of SHG, providing collagen type specificity. Here, we demonstrated the ability of SHG to differentiate collagen type I and type III quantitatively and used this method to examine fibrous capsules of implanted polystyrene particles. Data presented in this work shows a wide range of collagen fiber orientations and collagen compositions in response to surface functionalized polystyrene particles. Dimethylamino functionalized particles were able to form a thin collagenous matrix resembling healthy skin. These findings have the potential to improve the fundamental understanding of how material properties influence collagen organization and composition quantitatively.« less

Quantitative Characterization of Collagen in the Fibrotic Capsule Surrounding Implanted Polymeric Microparticles through Second Harmonic Generation Imaging.

PubMed

Akilbekova, Dana; Bratlie, Kaitlin M

2015-01-01

The collagenous capsule formed around an implant will ultimately determine the nature of its in vivo fate. To provide a better understanding of how surface modifications can alter the collagen orientation and composition in the fibrotic capsule, we used second harmonic generation (SHG) microscopy to evaluate collagen organization and structure generated in mice subcutaneously injected with chemically functionalized polystyrene particles. SHG is sensitive to the orientation of a molecule, making it a powerful tool for measuring the alignment of collagen fibers. Additionally, SHG arises from the second order susceptibility of the interrogated molecule in response to the electric field. Variation in these tensor components distinguishes different molecular sources of SHG, providing collagen type specificity. Here, we demonstrated the ability of SHG to differentiate collagen type I and type III quantitatively and used this method to examine fibrous capsules of implanted polystyrene particles. Data presented in this work shows a wide range of collagen fiber orientations and collagen compositions in response to surface functionalized polystyrene particles. Dimethylamino functionalized particles were able to form a thin collagenous matrix resembling healthy skin. These findings have the potential to improve the fundamental understanding of how material properties influence collagen organization and composition quantitatively.

Quantitative Characterization of Collagen in the Fibrotic Capsule Surrounding Implanted Polymeric Microparticles through Second Harmonic Generation Imaging

PubMed Central

Akilbekova, Dana; Bratlie, Kaitlin M.

2015-01-01

The collagenous capsule formed around an implant will ultimately determine the nature of its in vivo fate. To provide a better understanding of how surface modifications can alter the collagen orientation and composition in the fibrotic capsule, we used second harmonic generation (SHG) microscopy to evaluate collagen organization and structure generated in mice subcutaneously injected with chemically functionalized polystyrene particles. SHG is sensitive to the orientation of a molecule, making it a powerful tool for measuring the alignment of collagen fibers. Additionally, SHG arises from the second order susceptibility of the interrogated molecule in response to the electric field. Variation in these tensor components distinguishes different molecular sources of SHG, providing collagen type specificity. Here, we demonstrated the ability of SHG to differentiate collagen type I and type III quantitatively and used this method to examine fibrous capsules of implanted polystyrene particles. Data presented in this work shows a wide range of collagen fiber orientations and collagen compositions in response to surface functionalized polystyrene particles. Dimethylamino functionalized particles were able to form a thin collagenous matrix resembling healthy skin. These findings have the potential to improve the fundamental understanding of how material properties influence collagen organization and composition quantitatively. PMID:26125551

Effect of amine functionalization of spherical MCM-41 and SBA-15 on controlled drug release

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szegedi, A., E-mail: szegedi@chemres.h; Popova, M.; Goshev, I.

2011-05-15

MCM-41 and SBA-15 silica materials with spherical morphology and different particle sizes were synthesized and modified by post-synthesis method with 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, were carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N{sub 2} physisorption, thermal analysis, elemental analysis and FT-IR spectroscopy. Surface modification with amino groups resulted in high degree of ibuprofen loading and slow rate of release for MCM-41, whereas it was the opposite for SBA-15. The adsorbed drug content and the delivery rate can be predetermined by the choicemore » of mesoporous material with the appropriate structural characteristics and surface functionality. -- Graphical Abstract: Ibuprofen delivery from the parent and amino-modified spherical MCM-41 materials with 100 nm (small) and 500 nm (large) particle sizes. Display Omitted Highlights: {yields} Spherical type MCM-41 and SBA-15 with different particle sizes were modified by APTES. {yields} Adsorption and release rate of ibuprofen were compared. {yields} High degree of ibuprofen loading, slow release rate for MCM-41, the opposite for SBA-15. {yields} MCM-41 with 100 nm particles was more stable and showed slower release rate« less

Quantitative characterization of collagen in the fibrotic capsule surrounding implanted polymeric microparticles through second harmonic generation imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akilbekova, Dana; Bratlie, Kaitlin M.; Abraham, Thomas

The collagenous capsule formed around an implant will ultimately determine the nature of its in vivo fate. To provide a better understanding of how surface modifications can alter the collagen orientation and composition in the fibrotic capsule, we used second harmonic generation (SHG) microscopy to evaluate collagen organization and structure generated in mice subcutaneously injected with chemically functionalized polystyrene particles. SHG is sensitive to the orientation of a molecule, making it a powerful tool for measuring the alignment of collagen fibers. Additionally, SHG arises from the second order susceptibility of the interrogated molecule in response to the electric field. Variationmore » in these tensor components distinguishes different molecular sources of SHG, providing collagen type specificity. Here, we demonstrated the ability of SHG to differentiate collagen type I and type III quantitatively and used this method to examine fibrous capsules of implanted polystyrene particles. Data presented in this work shows a wide range of collagen fiber orientations and collagen compositions in response to surface functionalized polystyrene particles. Dimethylamino functionalized particles were able to form a thin collagenous matrix resembling healthy skin. These findings have the potential to improve the fundamental understanding of how material properties influence collagen organization and composition quantitatively.« less

Erosion, Transportation, and Deposition on Outer Solar System Satellites: Landform Evolution Modeling Studies

NASA Technical Reports Server (NTRS)

Moore, Jeffrey Morgan; Howard, Alan D.; Schenk, Paul M.

2013-01-01

Mass movement and landform degradation reduces topographic relief by moving surface materials to a lower gravitational potential. In addition to the obvious role of gravity, abrasive mechanical erosion plays a role, often in combination with the lowering of cohesion, which allows disaggregation of the relief-forming material. The identification of specific landform types associated with mass movement and landform degradation provides information about local sediment particle size and abundance and transportation processes. Generally, mass movements can be classified in terms of the particle sizes of the transported material and the speed the material moved during transport. Most degradation on outer planet satellites appears consistent with sliding or slumping, impact erosion, and regolith evolution. Some satellites, such as Callisto and perhaps Hyperion and Iapetus, have an appearance that implies that some additional process is at work, most likely sublimation-driven landform modification and mass wasting. A variant on this process is thermally driven frost segregation as seen on all three icy Galilean satellites and perhaps elsewhere. Titan is unique among outer planet satellites in that Aeolian and fluvial processes also operate to erode, transport, and deposit material. We will evaluate the sequence and extent of various landform-modifying erosional and volatile redistribution processes that have shaped these icy satellites using a 3-D model that simulates the following surface and subsurface processes: 1) sublimation and re-condensation of volatiles; 2) development of refractory lag deposits; 3) disaggregation and downward sloughing of surficial material; 4) radiative heating/cooling of the surface (including reflection, emission, and shadowing by other surface elements); 5) thermal diffusion; and 6) vapor diffusion. The model will provide explicit simulations of landform development and thusly predicts the topographic and volatile evolution of the surface and final landscape form as constrained by DEMs. We have also simulated fluvial and lacustrine modification of icy satellites landscapes to evaluate the degree to which fluvial erosion of representative initial landscapes can replicate the present Titan landscape.

Surface modification and deuterium retention in reduced-activation steels under low-energy deuterium plasma exposure. Part I: undamaged steels

NASA Astrophysics Data System (ADS)

Ogorodnikova, O. V.; Zhou, Z.; Sugiyama, K.; Balden, M.; Gasparyan, Yu.; Efimov, V.

2017-03-01

In this paper, reduced-activation ferritic/martensitic (RAFM) steels including Eurofer (9Cr) and oxide dispersion strengthening (ODS) steels by the addition of Y2O3 particles with different amounts of Cr, namely, (9-16)Cr were exposed to low energy deuterium (D) plasma (~20-200 eV per D) up to a fluence of 2.9  ×  1025 D m-2 in the temperature range from 290 K to 700 K. The depth profile of D in steels was measured up to 8 µm depth by nuclear reaction analysis (NRA) and the total retained amount of D in those materials was determined by thermal desorption spectroscopy (TDS). It was found that the D retention in ODS steels is higher compared to Eurofer due to the much higher density of fine dispersoids and finer grain size. This work shows that in addition to the sintering temperature and time, the type, size and concentration of the doping particles have an enormous effect on the increase in the D retention. The D retention in undamaged ODS steels strongly depends on the Cr content: ODS with 12Cr has a minimum and the D retention in the case of ODS with (14-16)Cr is higher compared to (9-12)Cr. The replacing of Ti by Al in ODS-14Cr steels reduces the D retention. The formation of nano-structure surface roughness enriched in W or Ta due to combination of preferential sputtering of light elements and radiation-induced segregation was observed at incident D ion energy of 200 eV for both Eurofer and ODS steels. Both the surface roughness and the eroded layer enhance with increasing the temperature. The surface modifications result in a reduction of the D retention near the surface due to increasing the desorption flux and can reduce the overall D retention.

Physicochemical properties and oral bioavailability of ursolic acid nanoparticles using supercritical anti-solvent (SAS) process.

PubMed

Yang, Lei; Sun, Zhen; Zu, Yuangang; Zhao, Chunjian; Sun, Xiaowei; Zhang, Zhonghua; Zhang, Lin

2012-05-01

The objective of the study was to prepare ursolic acid (UA) nanoparticles using the supercritical anti-solvent (SAS) process and evaluate its physicochemical properties and oral bioavailability. The effects of four process variables, pressure, temperature, drug concentration and drug solution flow rate, on drug particle formation during SAS process, were investigated. Particles with mean particle size ranging from 139.2±19.7 to 1039.8±65.2nm were obtained by varying the process parameters. The UA was characterised by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, specific surface area, dissolution test and bioavailability test. It was concluded that physicochemical properties and bioavailability of crystalline UA could be improved by physical modification, such as particle size reduction and generation of amorphous state using SAS process. Further, SAS process was a powerful methodology for improving the physicochemical properties and bioavailability of UA. Copyright © 2011 Elsevier Ltd. All rights reserved.

Self-assembled monolayers improve protein distribution on holey carbon cryo-EM supports

PubMed Central

Meyerson, Joel R.; Rao, Prashant; Kumar, Janesh; Chittori, Sagar; Banerjee, Soojay; Pierson, Jason; Mayer, Mark L.; Subramaniam, Sriram

2014-01-01

Poor partitioning of macromolecules into the holes of holey carbon support grids frequently limits structural determination by single particle cryo-electron microscopy (cryo-EM). Here, we present a method to deposit, on gold-coated carbon grids, a self-assembled monolayer whose surface properties can be controlled by chemical modification. We demonstrate the utility of this approach to drive partitioning of ionotropic glutamate receptors into the holes, thereby enabling 3D structural analysis using cryo-EM methods. PMID:25403871

Toughening of thermosetting polyimides

NASA Technical Reports Server (NTRS)

Gollob, D. S.; Mandell, J. F.; Mcgarry, F. J.

1979-01-01

Work directed toward increasing the resistance to crack propagation of thermoset polyimides is described. Rubber modification and Teflon microfiber impregnation techniques for increasing fracture toughness are investigated. Unmodified Kerimid 601 has a fracture surface work value of 0.20 in-lbs/sq in. Dispersed particles of amine terminated butadiene acrylonitrile liquid rubber or of silicone rubber do not raise this value much. By contrast, 5 percent of well fibrillated Teflon produces an eight-fold increase in fracture toughness. Further process improvements should increase this factor to 20-30.

International Conference on Surface Modification of Metals by Ion Beams Held in Riva Del Garda, Italy on 12-16 September 1988 (Final Program and Abstracts)

DTIC Science & Technology

1988-09-16

Precipitates in Carbon Steel by Low Dose alpha- particle bombard- mento, .M.M. Ramos. L. Amaral, M. Behar. A Vas- quez, G. Marest and F.C. Zawislak...planted martensitic low carbon steel (C - 0.2 wt%). The characteriza- tion of the precipitates is done via Conversion Electron Mbssbauer technique (CEMS... PHASE TRANSFORMATIONS OF A NITROGEN IMPLANTED AUSTENITIC STAINLESS STEEL (XO CrNITI 189) by R. Leutenecker Fraunhofer-Institut for

Electrophoretic characterization of aldehyde-fixed red blood cells, kidney cells, lynphocytes and chamber coatings

NASA Technical Reports Server (NTRS)

1976-01-01

Ground-based electrokinetic data on the electrophoresis flight experiment to be flown on the Apollo-Soyuz Test Project experiment MA-011 are stipulated. Aldehyde-fixed red blood cells, embryonic kidney cells and lymphocytes were evaluated by analytical particle electrophoresis. The results which aided in the interpretation of the final analysis of the MA-011 experiment are documented. The electrophoresis chamber surface modifications, the buffer, and the material used in the column system are also discussed.

Iron oxide nanoparticles stabilized with dendritic polyglycerols as selective MRI contrast agents

NASA Astrophysics Data System (ADS)

Nordmeyer, Daniel; Stumpf, Patrick; Gröger, Dominic; Hofmann, Andreas; Enders, Sven; Riese, Sebastian B.; Dernedde, Jens; Taupitz, Matthias; Rauch, Ursula; Haag, Rainer; Rühl, Eckart; Graf, Christina

2014-07-01

Monodisperse small iron oxide nanoparticles functionalized with dendritic polyglycerol (dPG) or dendritic polyglycerol sulfate (dPGS) are prepared. They are highly stable in aqueous solutions as well as physiological media. In particular, oleic acid capped iron oxide particles (core diameter = 11 +/- 1 nm) were modified by a ligand exchange process in a one pot synthesis with dPG and dPGS bearing phosphonate as anchor groups. Dynamic light scattering measurements performed in water and different biological media demonstrate that the hydrodynamic diameter of the particles is only slightly increased by the ligand exchange process resulting in a final diameter of less than 30 nm and that the particles are stable in these media. It is also revealed by magnetic resonance studies that their magnetic relaxivity is reduced by the surface modification but it is still sufficient for high contrast magnetic resonance imaging (MRI). Additionally, incubation of dPGS functionalized iron oxide nanoparticles with human umbilical vein endothelial cells showed a 50% survival at 85 nM (concentration of nanoparticles). Surface plasmon resonance (SPR) studies demonstrate that the dPGS functionalized iron oxide nanoparticles inhibit L-selectin ligand binding whereas the particles containing only dPG do not show this effect. Experiments in a flow chamber with human myelogenous leukemia cells confirmed L-selectin inhibition of the dPGS functionalized iron oxide nanoparticles and with that the L-selectin mediated leukocyte adhesion. These results indicate that dPGS functionalized iron oxide nanoparticles are a promising contrast agent for inflamed tissue probed by MRI.Monodisperse small iron oxide nanoparticles functionalized with dendritic polyglycerol (dPG) or dendritic polyglycerol sulfate (dPGS) are prepared. They are highly stable in aqueous solutions as well as physiological media. In particular, oleic acid capped iron oxide particles (core diameter = 11 +/- 1 nm) were modified by a ligand exchange process in a one pot synthesis with dPG and dPGS bearing phosphonate as anchor groups. Dynamic light scattering measurements performed in water and different biological media demonstrate that the hydrodynamic diameter of the particles is only slightly increased by the ligand exchange process resulting in a final diameter of less than 30 nm and that the particles are stable in these media. It is also revealed by magnetic resonance studies that their magnetic relaxivity is reduced by the surface modification but it is still sufficient for high contrast magnetic resonance imaging (MRI). Additionally, incubation of dPGS functionalized iron oxide nanoparticles with human umbilical vein endothelial cells showed a 50% survival at 85 nM (concentration of nanoparticles). Surface plasmon resonance (SPR) studies demonstrate that the dPGS functionalized iron oxide nanoparticles inhibit L-selectin ligand binding whereas the particles containing only dPG do not show this effect. Experiments in a flow chamber with human myelogenous leukemia cells confirmed L-selectin inhibition of the dPGS functionalized iron oxide nanoparticles and with that the L-selectin mediated leukocyte adhesion. These results indicate that dPGS functionalized iron oxide nanoparticles are a promising contrast agent for inflamed tissue probed by MRI. Electronic supplementary information (ESI) available: A detailed description of the synthesis of the ligands as well as the preparation and functionalization of the iron oxide nanoparticles including their physico-chemical characterization are presented. Further, details of the cell experiments and the SPR experiments are given. Two representative movies are provided showing leukocyte rolling on the ligand coated surface of the flow chamber. See DOI: 10.1039/c3nr04793h

The behavior of MC3T3-E1 cells on chitosan/poly-L-lysine composite films: effect of nanotopography, surface chemistry, and wettability.

PubMed

Zheng, Zhenhuan; Zhang, Ling; Kong, Lijun; Wang, Aijun; Gong, Yandao; Zhang, Xiufang

2009-05-01

In the present work, a series of composite films were produced from chitosan/poly-L-lysine blend solutions. The surface topography, chemistry, and wettability of composite films were characterized by atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle assay, respectively. For all composite films, blending with poly-L-lysine induced changes in surface chemistry and wettability. Interestingly, it was also found that increasing poly-L-lysine weight fraction in blend solutions could result in different nanoscaled surface topographic features, which displayed particle-, granule-, or fiber-dominant morphologies. MC3T3-E1 osteoblast-like cells were cultured on all composite films to evaluate the effects of surface nanotopography, chemistry, and wettability on cell behavior. The observations indicated that MC3T3-E1 cell behavior was affected by surface topography, chemistry, and wettability simultaneously and that cells showed strong responses to surface topography. On fiber-dominant surface, cells fully spread with obvious cytoskeleton organization and exhibited significantly higher level of adhesion and proliferation compared with particle- or granule-dominant surfaces. Furthermore, fiber-dominant surface also induced greater expression of mature osteogenic marker osteocalcin and higher mineralization based on RT-PCR and von Kossa staining. The results suggest that topographic modification of chitosan substratum at the nanoscale may be exploited in regulating cell behavior for its applications in tissue engineering.

Preparation of modified waterworks sludge particles as adsorbent to enhance coagulation of slightly polluted source water.

PubMed

Chen, Wei; Gao, Xiaohong; Xu, Hang; Wang, Kang; Chen, Taoyuan

2017-08-01

Without treatment, waterworks sludge is ineffective as an adsorbent. In this study, raw waterworks sludge was used as the raw material to prepare modified sludge particles through high-temperature calcination and alkali modification. The feasibility of using a combination of modified particles and polyaluminum chloride (PAC) as a coagulant for treatment of slightly polluted source water was also investigated. The composition, structure, and surface properties of the modified particles were characterized, and their capabilities for removing ammonia nitrogen and turbidity were determined. The results indicate that the optimal preparation conditions for the modified sludge particles were achieved by preparing the particles with a roasting temperature of 483.12 °C, a roasting time of 3.32 h, and a lye concentration of 3.75%. Furthermore, enhanced coagulation is strengthened with the addition of modified sludge particles, which is reflected by reduction of the required PAC dose and enhancement of the removal efficiency of ammonia nitrogen and turbidity by over 80 and 93%, respectively. Additional factors such as pH, temperature, dose, and dosing sequence were also evaluated. The optimum doses of modified particles and PAC were 40 and 15 mg/L, respectively, and adding modified particles at the same time as or prior to adding PAC improves removal efficiency.

Copper circuit patterning on polymer using selective surface modification and electroless plating

NASA Astrophysics Data System (ADS)

Park, Sang Jin; Ko, Tae-Jun; Yoon, Juil; Moon, Myoung-Woon; Oh, Kyu Hwan; Han, Jun Hyun

2017-02-01

We have examined a potential new and simple method for patterning a copper circuit on PET substrate by copper electroless plating, without the pretreatment steps (i.e., sensitization and activation) for electroless plating as well as the etching processes of conventional circuit patterning. A patterned mask coated with a catalyst material, Ag, for the reduction of Cu ions, is placed on a PET substrate. Subsequent oxygen plasma treatment of the PET substrate covered with the mask promotes the selective generation of anisotropic pillar- or hair-like nanostructures coated with co-deposited nanoparticles of the catalyst material on PET. After oxygen plasma treatment, a Cu circuit is well formed just by dipping the plasma-treated PET into a Cu electroless plating solution. By increasing the oxygen gas pressure in the chamber, the height of the nanostructures increases and the Ag catalyst particles are coated on not only the top but also the side surfaces of the nanostructures. Strong mechanical interlocking between the Cu circuit and PET substrate is produced by the large surface area of the nanostructures, and enhances peel strength. Results indicate this new simple two step (plasma surface modification and pretreatment-free electroless plating) method can be used to produce a flexible Cu circuit with good adhesion.

Oxidative and cytotoxic stress induced by inorganic granular and fibrous particles.

PubMed

Helmig, Simone; Walter, Dirk; Putzier, Julia; Maxeiner, Hagen; Wenzel, Sibylle; Schneider, Joachim

2018-06-01

The hazards of granular and fibrous particles have been associated with the generation of reactive oxygen species (ROS), which in turn is often associated with physicochemical properties exhibited by these particles. In the present study, the ability of various types of fibrous and granular dusts to generate oxidative stress, and their cytotoxicity, was investigated. Biopersistent granular dusts employed in the present study included micro‑ and nanosized titanium dioxide with rutile or anatase crystal structure modifications. Additionally, glass fibres, chrysotile and crocidolite asbestos representative of fibrous dust were selected. Detailed characterisation of particles was performed using scanning electron microscopy, and the effect of exposure to these particles on cell viability and intracellular ROS generation was assessed by PrestoBlue and 2',7'‑dichlorofluorescein assays, respectively. A549 human lung epithelial adenocarcinoma cells were exposed to increasing concentrations (0.1‑10 µg/cm2) of particles and fibres for 24 h. Subsequently, the gene expression of X‑linked inhibitor of apoptosis (XIAP), superoxide dismutase (SOD)1 and SOD2 were analysed by reverse transcription‑quantitative polymerase chain reaction. All investigated granular particles induce ROS production in A549 lung carcinoma cells within 24 h. Hematite increased ROS production in a dose‑dependent manner. A concentration of >1 µg/cm2 TiO2 na with its disordered surface, demonstrated the greatest ability to generate ROS. Therefore, the crystalline surface structure of the particle may be considered as a determinant of the extent of ROS induction by the particle. Fibrous particle compared with granular particles were associated with a lower ability to generate ROS. Glass fibres did not significantly increase ROS production in A549 cells, but elevated gene expression of SOD2 was observed. The results demonstrated that in general, the ability of particles to generate ROS depends on their number and crystal phase. Therefore, the present study helps to understand the cause of particle toxicity.

In-line three-dimensional holography of nanocrystalline objects at atomic resolution

PubMed Central

Chen, F.-R.; Van Dyck, D.; Kisielowski, C.

2016-01-01

Resolution and sensitivity of the latest generation aberration-corrected transmission electron microscopes allow the vast majority of single atoms to be imaged with sub-Ångstrom resolution and their locations determined in an image plane with a precision that exceeds the 1.9-pm wavelength of 300 kV electrons. Such unprecedented performance allows expansion of electron microscopic investigations with atomic resolution into the third dimension. Here we report a general tomographic method to recover the three-dimensional shape of a crystalline particle from high-resolution images of a single projection without the need for sample rotation. The method is compatible with low dose rate electron microscopy, which improves on signal quality, while minimizing electron beam-induced structure modifications even for small particles or surfaces. We apply it to germanium, gold and magnesium oxide particles, and achieve a depth resolution of 1–2 Å, which is smaller than inter-atomic distances. PMID:26887849

Sequential and simultaneous thermal and particle exposure of tungsten

NASA Astrophysics Data System (ADS)

Steudel, I.; Huber, A.; Kreter, A.; Linke, J.; Sergienko, G.; Unterberg, B.; Wirtz, M.

2016-02-01

The broad array of expected loading conditions in a fusion reactor such as ITER necessitates high requirements on the plasma facing materials (PFMs). Tungsten, the PFM for the divertor region, the most affected part of the in-vessel components, must thus sustain severe, distinct exposure conditions. Accordingly, comprehensive experiments investigating sequential and simultaneous thermal and particle loads were performed on double forged pure tungsten, not only to investigate whether the thermal and particle loads cause damage but also if the sequence of exposure maintains an influence. The exposed specimens showed various kinds of damage such as roughening, blistering, and cracking at a base temperature where tungsten could be ductile enough to compensate the induced stresses exclusively by plastic deformation (Pintsuk et al 2011 J. Nucl. Mater. 417 481-6). It was found out that hydrogen has an adverse effect on the material performance and the loading sequence on the surface modification.

Liquid-liquid interfacial nanoparticle assemblies

DOEpatents

Emrick, Todd S [South Deerfield, MA; Russell, Thomas P [Amherst, MA; Dinsmore, Anthony [Amherst, MA; Skaff, Habib [Amherst, MA; Lin, Yao [Amherst, MA

2008-12-30

Self-assembly of nanoparticles at the interface between two fluids, and methods to control such self-assembly process, e.g., the surface density of particles assembling at the interface; to utilize the assembled nanoparticles and their ligands in fabrication of capsules, where the elastic properties of the capsules can be varied from soft to tough; to develop capsules with well-defined porosities for ultimate use as delivery systems; and to develop chemistries whereby multiple ligands or ligands with multiple functionalities can be attached to the nanoparticles to promote the interfacial segregation and assembly of the nanoparticles. Certain embodiments use cadmium selenide (CdSe) nanoparticles, since the photoluminescence of the particles provides a convenient means by which the spatial location and organization of the particles can be probed. However, the systems and methodologies presented here are general and can, with suitable modification of the chemistries, be adapted to any type of nanoparticle.

Deaggregation, Modification, and Developing Applications for Detonation Nanodiamond

NASA Astrophysics Data System (ADS)

Mochalin, Vadym

2017-06-01

Nanodiamond powder (ND) is one of the most promising materials for advanced composites and biomedical applications. It is also a commercial precursor for carbon nanoonions - material for high power micrometer size supercapacitors and potentially, Li-ion batteries. ND is produced by detonation of explosives with negative oxygen balance in a closed chamber, where extremely high pressures and temperatures develop during detonation. ND consists of diamond particles of 5 nm diameter, combining fully accessible large surface and rich and tailorable surface chemistry. ND has unique properties including optical, electrical, thermal, and mechanical, and is biocompatible and non-toxic. Due to numerous surface functional groups, ND has catalytic and electrochemical activity. Several techniques have been proposed for ND deaggregation based on milling with costly ceramic microbeads, leaving difficult to remove contaminations in the resulting ND suspension. We have recently discovered a novel, green technique for ND deaggregation using sonication in aqueous sodium chloride slurry. Upon completion of the process sodium chloride can be easily washed out with water leaving behind no contaminants and yielding stable single-digit ND colloids. Modification and development of applications for ND in composites, drug delivery, biomedical imaging, etc., will be also discussed.

Spectroscopic investigation of nitrogen-functionalized carbon materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Kevin N.; Christensen, Steven T.; Nordlund, Dennis

2016-04-07

Carbon materials are used in a diverse set of applications ranging from pharmaceuticals to catalysis. Nitrogen modification of carbon powders has shown to be an effective method for enhancing both surface and bulk properties of as-received material for a number of applications. Unfortunately, control of the nitrogen modification process is challenging and can limit the effectiveness and reproducibility of N-doped materials. Additionally, the assignment of functional groups to specific moieties on the surface of nitrogen-modified carbon materials is not straightforward. Herein, we complete an in-depth analysis of functional groups present at the surface of ion-implanted Vulcan and Graphitic Vulcan throughmore » the use of X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS). Our results show that regardless of the initial starting materials used, nitrogen ion implantation conditions can be tuned to increase the amount of nitrogen incorporation and to obtain both similar and reproducible final distributions of nitrogen functional groups. The development of a well-controlled/reproducible nitrogen implantation pathway opens the door for carbon supported catalyst architectures to have improved numbers of nucleation sites, decreased particle size, and enhanced catalyst-support interactions.« less

Surface functionalization of WS2 fullerene-like nanoparticles.

PubMed

Shahar, Chen; Zbaida, David; Rapoport, Lev; Cohen, Hagai; Bendikov, Tatyana; Tannous, Johny; Dassenoy, Fabrice; Tenne, Reshef

2010-03-16

WS(2) belongs to a family of layered metal dichalcogenide compounds that are known to form cylindrical (inorganic nanotubes-INT) and polyhedral nanostructures--onion or nested fullerene-like (IF) particles. The outermost layers of these IF nanoparticles can be peeled under shear stress, thus IF nanoparticles have been studied for their use as solid lubricants. However, the IF nanoparticles tend to agglomerate, presumably because of surface structural defects induced by elastic strain and curvature, a fact that has a deleterious effect on their tribological properties. In the present work, chemical modification of the IF-WS(2) surface with alkyl-silane molecules is reported. The surface-modified IF nanoparticles display improved dispersion in oil-based suspensions. The alkyl-silane coating reduces the IF-WS(2) nanoparticles' tendency to agglomerate and consequently improves the long-term tribological behavior of oil formulated with the IF additive.

Synthesis and enhanced humidity detection response of nanoscale Au-particle-decorated ZnS spheres

PubMed Central

2014-01-01

We successfully prepared Au-nanoparticle-decorated ZnS (ZnS-Au) spheres by sputtering Au ultrathin films on surfaces of hydrothermally synthesized ZnS spheres and subsequently postannealed the samples in a high-vacuum atmosphere. The Au nanoparticles were distributed on ZnS surfaces without substantial aggregation. The Au nanoparticle diameter range was 5 to 10 nm. Structural information showed that the surface of the annealed ZnS-Au spheres became more irregular and rough. A humidity sensor constructed using the Au-nanoparticle-decorated ZnS spheres demonstrated a substantially improved response to the cyclic change in humidity from 11% relative humidity (RH) to 33% to 95% RH at room temperature. The improved response was associated with the enhanced efficiency of water molecule adsorption onto the surfaces of the ZnS because of the surface modification of the ZnS spheres through noble-metal nanoparticle decoration. PMID:25520595

High Power Diode Laser-Treated HP-HVOF and Twin Wire Arc-Sprayed Coatings for Fossil Fuel Power Plants

NASA Astrophysics Data System (ADS)

Mann, B. S.

2013-08-01

This article deals with high power diode laser (HPDL) surface modification of twin wire arc-sprayed (TWAS) and high pressure high velocity oxy-fuel (HP-HVOF) coatings to combat solid particle erosion occurring in fossil fuel power plants. To overcome solid particle impact wear above 673 K, Cr3C2-NiCr-, Cr3C2-CoNiCrAlY-, and WC-CrC-Ni-based HVOF coatings are used. WC-CoCr-based HVOF coatings are generally used below 673 K. Twin wire arc (TWA) spraying of Tafa 140 MXC and SHS 7170 cored wires is used for a wide range of applications for a temperature up to 1073 K. Laser surface modification of high chromium stainless steels for steam valve components and LPST blades is carried out regularly. TWA spraying using SHS 7170 cored wire, HP-HVOF coating using WC-CoCr powder, Ti6Al4V alloy, and high chromium stainless steels (X20Cr13, AISI 410, X10CrNiMoV1222, 13Cr4Ni, 17Cr4Ni) were selected in the present study. Using robotically controlled parameters, HPDL surface treatments of TWAS-coated high strength X10CrNiMoV1222 stainless steel and HP-HVOF-coated AISI 410 stainless steel samples were carried out and these were compared with HPDL-treated high chromium stainless steels and titanium alloy for high energy particle impact wear (HEPIW) resistance. The HPDL surface treatment of the coatings has improved the HEPIW resistance manifold. The improvement in HPDL-treated stainless steels and titanium alloys is marginal and it is not comparable with that of HPDL-treated coatings. These coatings were also compared with "as-sprayed" coatings for fracture toughness, microhardness, microstructure, and phase analyses. The HEPIW resistance has a strong relationship with the product of fracture toughness and microhardness of the HPDL-treated HP-HVOF and TWAS SHS 7170 coatings. This development opens up a possibility of using HPDL surface treatments in specialized areas where the problem of HEPIW is very severe. The HEPIW resistance of HPDL-treated high chromium stainless steels and titanium alloys, HPDL-treated TWAS SHS 7170 and HP-HVOF coatings, and their micrographs and X-ray diffraction analysis is reported in this article.

Comparison of The Effect of Implant Abutment Surface Modifications on Retention of Implant-Supported Restoration with A Polymer Based Cement

PubMed Central

Sahu, Nabaprakash; Lakshmi, Namratha; Azhagarasan, N.S.; Agnihotri, Yoshaskam; Rajan, Manoj; Hariharan, Ramasubramanian

2014-01-01

Background: In cement-retained implant-supported restoration it is important to gain adequate retention of definitive restoration as well as retrievability of prosthesis. The surface of the abutment, alloy of the restoration and the type of cement used influences the retention of the restoration. There is a need to analyze the influence of surface modifications of abutments on the retentive capabilities of provisional implant cements. Purpose of study: To compare the effect of implant abutment surface modifications on retention of implant-supported restoration cemented with polymer based cement. Materials and method: Thirty solid titanium implant abutments (ADIN), 8mm height, were divided into 3 groups. Ten abutments with retentive grooves (Group I) as supplied by the manufacturer, Ten abutments milled to 20 taper circumferentially (Group II), and Ten abutments milled and air-abraded with 110 μm aluminum oxide (Group III) were used in this study. Ni-Cr coping were casted for each abutment and polymer based cement was used to secure them to the respective abutments. Using a universal testing machine at a crosshead speed of 0.5 cm/minute, tensile bond strength was recorded (N). Results: Mean tensile bond strength of Group I, II and III were found to be 408.3, 159.9 and 743.8 Newton respectively. The values were statistically different from each other (p<0.001). Conclusion: Abutments with milled and sandblasted surface provide the highest retention followed by abutments with retentive grooves and then by abutments with milled surface when cast copings were cemented to implant abutments with polymer based cement. Clinical implications: Retention of restoration depends on the surface of the abutment as well as the luting agents used. Incorporation of retentive grooves or particle abrasion can enhance retention especially in situation of short clinical crown. PMID:24596785

Harnessing of radio frequency discharge for production of biologically compatible coatings for ophthalmology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullin, I.Sh.; Bragin, V.E.; Bykanov, A.N.

Gas discharge plasma modification of polymer materials and metals is one of the known physical approaches for improving of materials biocompatibility in ophthalmology and surgery. The surface treatment in RF discharges can be effectively realized in the discharge afterglow and in the discharge region itself too. This modification method is more convenient and produces more uniform surfaces in comparison with other discharge types. The carried out experiments and published up to now results show that interaction of UV radiation, fluxes of ions, electrons and metastable particles with material`s surface changes chemical composition and surface structure. The exerting of these agentsmore » on the sample surface produces the following effects. There are processes of physical and plasma-chemical surface etching producing effective surface cleaning of different types of contaminations. It may be surface contaminations by hydrocarbons because of preliminary surface contacts with biological or physical bodies. It may be surface contaminations caused by characteristic properties of chemical technology too. There is a surface layer with thickness from some angstroms up to few hundreds of angstroms. The chemical content and structure of this layer is distinguished from the bulk polymer properties. The presence of such {open_quotes}technological{close_quotes} contaminations produces the layer of material substantially differing from the base polymer. The basic layer physical and chemical properties for example, gas permeation rate may substantially differ from the base polymer. Attempts to clean the surface from these contaminations by chemical methods (solutions) have not been successful and produced contaminations of more deep polymer layers. So the plasma cleaning is the most profitable method of polymer treatment for removing the surface contaminations. The improving of wettability occurs during this stage of treatment.« less

Electrochemical surface modification of titanium in dentistry.

PubMed

Kim, Kyo-Han; Ramaswamy, Narayanan

2009-01-01

Titanium and its alloys have good biocompatibility with body cells and tissues and are widely used for implant applications. However, clinical procedures place more stringent and tough requirements on the titanium surface necessitating artificial surface treatments. Among the many methods of titanium surface modification, electrochemical techniques are simple and cheap. Anodic oxidation is the anodic electrochemical technique while electrophoretic and cathodic depositions are the cathodic electrochemical techniques. By anodic oxidation it is possible to obtain desired roughness, porosity and chemical composition of the oxide. Anodic oxidation at high voltages can improve the crystallinity of the oxide. The chief advantage of this technique is doping of the coating of the bath constituents and incorporation of these elements improves the properties of the oxide. Electrophoretic deposition uses hydroxyapatite (HA) powders dispersed in a suitable solvent at a particular pH. Under these operating conditions these particles acquire positive charge and coatings are obtained on the cathodic titanium by applying an external electric field. These coatings require a post-sintering treatment to improve the coating properties. Cathodic deposition is another type of electrochemical method where HA is formed in situ from an electrolyte containing calcium and phosphate ions. It is also possible to alter structure and/or chemistry of the obtained deposit. Nano-grained HA has higher surface energy and greater biological activity and therefore emphasis is being laid to produce these coatings by cathodic deposition.

Epithelial Microvilli Establish an Electrostatic Barrier to Microbial Adhesion

PubMed Central

Bennett, Kaila M.; Walker, Sharon L.

2014-01-01

Microvilli are membrane extensions on the apical surface of polarized epithelia, such as intestinal enterocytes and tubule and duct epithelia. One notable exception in mucosal epithelia is M cells, which are specialized for capturing luminal microbial particles; M cells display a unique apical membrane lacking microvilli. Based on studies of M cell uptake under different ionic conditions, we hypothesized that microvilli may augment the mucosal barrier by providing an increased surface charge density from the increased membrane surface and associated glycoproteins. Thus, electrostatic charges may repel microbes from epithelial cells bearing microvilli, while M cells are more susceptible to microbial adhesion. To test the role of microvilli in bacterial adhesion and uptake, we developed polarized intestinal epithelial cells with reduced microvilli (“microvillus-minus,” or MVM) but retaining normal tight junctions. When tested for interactions with microbial particles in suspension, MVM cells showed greatly enhanced adhesion and uptake of particles compared to microvillus-positive cells. This preference showed a linear relationship to bacterial surface charge, suggesting that microvilli resist binding of microbes by using electrostatic repulsion. Moreover, this predicts that pathogen modification of electrostatic forces may contribute directly to virulence. Accordingly, the effacement effector protein Tir from enterohemorrhagic Escherichia coli O157:H7 expressed in epithelial cells induced a loss of microvilli with consequent enhanced microbial binding. These results provide a new context for microvillus function in the host-pathogen relationship, based on electrostatic interactions. PMID:24778113

Emulsions Stabilized by Chitosan-Modified Silica Nanoparticles: pH Control of Structure-Property Relations.

PubMed

Alison, Lauriane; Demirörs, Ahmet F; Tervoort, Elena; Teleki, Alexandra; Vermant, Jan; Studart, Andre R

2018-05-29

In food-grade emulsions, particles with an appropriate surface modification can be used to replace surfactants and potentially enhance the stability of emulsions. During the life cycle of products based on such emulsions, they can be exposed to a broad range of pH conditions and hence it is crucial to understand how pH changes affect stability of emulsions stabilized by particles. Here, we report on a comprehensive study of the stability, microstructure, and macroscopic behavior of pH-controlled oil-in-water emulsions containing silica nanoparticles modified with chitosan, a food-grade polycation. We found that the modified colloidal particles used as stabilizers behave differently depending on the pH, resulting in unique emulsion structures at multiple length scales. Our findings are rationalized in terms of the different emulsion stabilization mechanisms involved, which are determined by the pH-dependent charges and interactions between the colloidal building blocks of the system. At pH 4, the silica particles are partially hydrophobized through chitosan modification, favoring their adsorption at the oil-water interface and the formation of Pickering emulsions. At pH 5.5, the particles become attractive and the emulsion is stabilized by a network of agglomerated particles formed between the droplets. Finally, chitosan aggregates form at pH 9 and these act as the emulsion stabilizers under alkaline conditions. These insights have important implications for the processing and use of particle-stabilized emulsions. On one hand, changes in pH can lead to undesired macroscopic phase separation or coalescence of oil droplets. On the other hand, the pH effect on emulsion behavior can be harnessed in industrial processing, either to tune their flow response by altering the pH between processing stages or to produce pH-responsive emulsions that enhance the functionality of the emulsified end products.

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

PubMed Central

Pandey, Shivendra; Gultepe, Evin; Gracias, David H.

2013-01-01

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize. In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 μm to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices. PMID:23407436

Preparation and Investigation of Foaming Amphiphilic Fluorinated Nanoparticles for Enhanced Oil Recovery.

PubMed

Wang, Keliang; Wang, Gang; Lu, Chunjing; Pei, Cuiying; Wang, Ying

2017-12-08

Amphiphilic nanoparticles have attracted increasing interest as Pickering emulsifiers owing to the combined advantages of both traditional surfactants and homogeneous particles. Here, foaming amphiphilic fluorinated nanoparticles were prepared for enhanced oil recovery by the toposelective surface modification method. The structure and properties of amphiphilic nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, a laser diffraction method, fluorescence microscopy, a pendant drop tensiometer, and foamscan. It was found that the amphiphilic fluorinated nanoparticles exhibited significant interfacial activity at the air-water interface and generated stabilized aqueous foams against coalescence and drainage even in the absence of surfactants. When the particle concentration reached 0.6 wt %, the adsorption of the amphiphilic nanoparticles at the interface was saturated and the equilibrium surface tension dropped to around 32.7 mN/m. When the particle concentration reached 0.4 wt %, the Gibbs stability criterion was fulfilled. The amphiphilic nanoparticles foam system has a better plugging capacity and enhanced oil recovery capacity. The results obtained provide fundamental insights into the understanding of the self-assembly behavior and foam properties of amphiphilic fluorinated nanoparticles and further demonstrate the future potential of the amphiphilic nanoparticles used as colloid surfactants for enhanced oil recovery applications.

Preparation and Investigation of Foaming Amphiphilic Fluorinated Nanoparticles for Enhanced Oil Recovery

PubMed Central

Wang, Keliang; Lu, Chunjing; Pei, Cuiying; Wang, Ying

2017-01-01

Amphiphilic nanoparticles have attracted increasing interest as Pickering emulsifiers owing to the combined advantages of both traditional surfactants and homogeneous particles. Here, foaming amphiphilic fluorinated nanoparticles were prepared for enhanced oil recovery by the toposelective surface modification method. The structure and properties of amphiphilic nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, a laser diffraction method, fluorescence microscopy, a pendant drop tensiometer, and foamscan. It was found that the amphiphilic fluorinated nanoparticles exhibited significant interfacial activity at the air–water interface and generated stabilized aqueous foams against coalescence and drainage even in the absence of surfactants. When the particle concentration reached 0.6 wt %, the adsorption of the amphiphilic nanoparticles at the interface was saturated and the equilibrium surface tension dropped to around 32.7 mN/m. When the particle concentration reached 0.4 wt %, the Gibbs stability criterion was fulfilled. The amphiphilic nanoparticles foam system has a better plugging capacity and enhanced oil recovery capacity. The results obtained provide fundamental insights into the understanding of the self-assembly behavior and foam properties of amphiphilic fluorinated nanoparticles and further demonstrate the future potential of the amphiphilic nanoparticles used as colloid surfactants for enhanced oil recovery applications. PMID:29292747

Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

PubMed

Zhao, Xiaohong; Zhang, Yanjuan; Hu, Huayu; Huang, Zuqiang; Yang, Mei; Chen, Dong; Huang, Kai; Huang, Aimin; Qin, Xingzhen; Feng, Zhenfei

2016-10-01

Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin. Copyright © 2016 Elsevier B.V. All rights reserved.

Bypassing adverse injection reactions to nanoparticles through shape modification and attachment to erythrocytes

NASA Astrophysics Data System (ADS)

Wibroe, Peter Popp; Anselmo, Aaron C.; Nilsson, Per H.; Sarode, Apoorva; Gupta, Vivek; Urbanics, Rudolf; Szebeni, Janos; Hunter, Alan Christy; Mitragotri, Samir; Mollnes, Tom Eirik; Moghimi, Seyed Moein

2017-07-01

Intravenously injected nanopharmaceuticals, including PEGylated nanoparticles, induce adverse cardiopulmonary reactions in sensitive human subjects, and these reactions are highly reproducible in pigs. Although the underlying mechanisms are poorly understood, roles for both the complement system and reactive macrophages have been implicated. Here, we show the dominance and importance of robust pulmonary intravascular macrophage clearance of nanoparticles in mediating adverse cardiopulmonary distress in pigs irrespective of complement activation. Specifically, we show that delaying particle recognition by macrophages within the first few minutes of injection overcomes adverse reactions in pigs using two independent approaches. First, we changed the particle geometry from a spherical shape (which triggers cardiopulmonary distress) to either rod- or disk-shape morphology. Second, we physically adhered spheres to the surface of erythrocytes. These strategies, which are distinct from commonly leveraged stealth engineering approaches such as nanoparticle surface functionalization with poly(ethylene glycol) and/or immunological modulators, prevent robust macrophage recognition, resulting in the reduction or mitigation of adverse cardiopulmonary distress associated with nanopharmaceutical administration.

A new powder production route for transparent spinel windows: powder synthesis and window properties

NASA Astrophysics Data System (ADS)

Cook, Ronald; Kochis, Michael; Reimanis, Ivar; Kleebe, Hans-Joachim

2005-05-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. The new powder production method allows fine control over the starting particle size, size distribution, purity and stoichiometry. The new process involves formation of a boehmite sol-gel from the hydrolysis of aluminum alkoxides followed by surface modification of the boehmite nanoparticles using carboxylic acids. The resulting surface modified boehmite nanoparticles can then be metal exchanged at room temperature with magnesium acetylacetonate to make a precursor powder that is readily transformed into pure phase spinel.

Climatic modification by CO2, H2O, and aerosol

NASA Technical Reports Server (NTRS)

Rasool, I.

1972-01-01

Research is reported on the effects of increasing the CO2, aerosols, and water content of the atmosphere on the surface temperature and climatology. An atmospheric model is described with the incoming solar radiation for a planetary albedo of 33 percent, surface temperature of 288 K, relative humidity of 75 percent, cloud cover of 48 percent, CO2 of 0.3 parts per thousand, and aerosol density of two million per square centimeter. The results show that if the CO2 increases by a factor of 1000 or more, the total pressure of the atmosphere increases, and the earth may become as hot as Venus. It is also shown that as the amount of dust particles in the atmosphere increases, the solar radiation decreases, and the surface temperature lowers.

A new approach for crystallization of copper(ii) oxide hollow nanostructures with superior catalytic and magnetic response

NASA Astrophysics Data System (ADS)

Singh, Inderjeet; Landfester, Katharina; Chandra, Amreesh; Muñoz-Espí, Rafael

2015-11-01

We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism.We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism. Electronic supplementary information (ESI) available: Associated structural and morphological analysis, XPS characterization, BET surface area, catalytic measurements, recycle tests of the catalyst, and magnetic characterizations. See DOI: 10.1039/c5nr05579b

A Survey of Plasmas and Their Applications

NASA Technical Reports Server (NTRS)

Eastman, Timothy E.; Grabbe, C. (Editor)

2006-01-01

Plasmas are everywhere and relevant to everyone. We bath in a sea of photons, quanta of electromagnetic radiation, whose sources (natural and artificial) are dominantly plasma-based (stars, fluorescent lights, arc lamps.. .). Plasma surface modification and materials processing contribute increasingly to a wide array of modern artifacts; e.g., tiny plasma discharge elements constitute the pixel arrays of plasma televisions and plasma processing provides roughly one-third of the steps to produce semiconductors, essential elements of our networking and computing infrastructure. Finally, plasmas are central to many cutting edge technologies with high potential (compact high-energy particle accelerators; plasma-enhanced waste processors; high tolerance surface preparation and multifuel preprocessors for transportation systems; fusion for energy production).

Optoelectronic investigation of nanodiamond interactions with human blood

NASA Astrophysics Data System (ADS)

Ficek, M.; Wróbel, M. S.; Wasowicz, M.; Jedrzejewska-Szczerska, M.

2016-03-01

We present optoelectronic investigation of in vitro interactions of whole human blood with different nanodiamond biomarkers. Plasmo-chemical modifications of detonation nanodiamond particles gives the possibility for controlling their surface for biological applications. Optical investigations reveal the biological activity of nanodiamonds in blood dependent on its surface termination. We compare different types of nanodiamonds: commercial non-modified detonation nanodiamonds, and nanodiamonds modified by MW PACVD method with H2-termination, and chemically modified nanodiamond with O2-termination. The absorption spectra, and optical microscope investigations were conducted. The results indicate haemocompatibility of non-modified detonation nanodiamond as well as modified nanodiamonds, which enables their application for drug delivery, as well as sensing applications.

Surface modification effects on defect-related photoluminescence in colloidal CdS quantum dots.

PubMed

Lee, TaeGi; Shimura, Kunio; Kim, DaeGwi

2018-05-03

We investigated the effects of surface modification on the defect-related photoluminescence (PL) band in colloidal CdS quantum dots (QDs). A size-selective photoetching process and a surface modification technique with a Cd(OH)2 layer enabled the preparation of size-controlled CdS QDs with high PL efficiency. The Stokes shift of the defect-related PL band before and after the surface modification was ∼1.0 eV and ∼0.63 eV, respectively. This difference in the Stokes shifts suggests that the origin of the defect-related PL band was changed by the surface modification. Analysis by X-ray photoelectron spectroscopy revealed that the surface of the CdS QDs before and after the surface modification was S rich and Cd rich, respectively. These results suggest that Cd-vacancy acceptors and S-vacancy donors affect PL processes in CdS QDs before and after the surface modification, respectively.

Structural and Functional Properties of Soy Protein Isolates Modified by Soy Soluble Polysaccharides.

PubMed

Xu, Yan-Teng; Liu, Ling-Ling

2016-09-28

Aiming to achieve the modification to soy protein isolate (SPI) by soy soluble polysaccharides (SSPS), electrically driven complex systems were first established in the environment of pH 3.0, and then reconstituted SPI particles with different SPI-SSPS ratios were obtained under freeze-drying process. Through this treatment, the structures of SPI particles were partly unfolded and adsorbed SSPS mainly via hydrophobic interactions and hydrogen bonding with larger particle sizes. The adherence of SSPS decreased the surface hydrophobicity of reconstituted SPI particles, but exerted not much influence on the emulsifying and foaming activities and increased the corresponding stabilities due to enhancing the unfolded extent of structure and improving the conformation flexibility. Reconstituted SPI-SSPS particles might rearrange and link each other due to the presence of SSPS on the air-water interface to better stabilize these systems. At SPI-SSPS ratio of 10:1, lower temperature was required to form gels with lower gel intensity and porous structure. The findings provide a further comprehension to the relationship between structures and functional properties of SPI modified by SSPS and the feasibility of applying these reconstituted particles to needed areas.

New concepts in ionospheric modification. Final report, 15 April 1986-30 September 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banks, P.M.; Fraser-Smith, A.C.; Gilchrist, B.E.

1987-04-01

This report considers the ionospheric modification that can be produced by energetic charged-particle and photon beams, which are emitted from a platform or vehicle (spacecraft or rockets) located in the ionosphere. The various beams considered include (1) charged-particle beams composed of low-, moderate-, and high-energy electrons, (2) beams of ions and plasma, and (3) photon beams of soft x rays and extreme-ultraviolet radiation. Briefly considered, in addition to the beam topics, is the ionospheric modification produced by the release of neutral gas of high molecular weight from a rapidly moving vehicle such as the Space Shuttle Orbiter. When a rankingmore » is made in terms of the new information that may be obtained, the scale of the modification that may be produced, and the availability of beam sources, ionospheric modification by means of relativistic electron beams appears particularly promising. However, all the methods have their own distinctive features that could make their use desirable under particular circumstances. The modification produced by means of beams of soft x rays, for example, is not strongly dependent on the beam's direction relative to the earth's magnetic field, and thus modification can be produced in regions inaccessible to a charged-particle beam from the same vehicle.« less

Kinetic of antigent-antibody reactions with scattering method

NASA Astrophysics Data System (ADS)

Bilyi, Olexander I.; Kiselyov, Yevgen M.; Novikov, Volodymyr P.

2001-07-01

The immune reactions of interaction antigen-antibody represent specific effect of an antigene with an antibody, which outcome are the complex immune aggregates forming precipitate in case of a soluble antigene, or agglutinate in case of a corpuscular antigene. Immunological methods which uses in the quality of carrier protein latex's polymeric microspheresis, gained name and method latex agglutination. Polymeric microspheresis have the array of advantages before biological carries, which consist in the opportunity of the variation of attributes surface and size microspheresis in the broad band of meanings with the preservation of narrow distribution particles behind measurements, the putting of functional groups, necessary for bunch with ligand on stage their synthesis, in ragidity at storage. The quantitative evaluation of parameters of a response of interaction antigen-antibody in immunology is possible by optical methods on a measurement of a modification of intensity of a light stream of a solution in an outcome of a course of a reaction. Concentration of immune complexes determine both on slacking a taking place stream of light, and on a modification of intensity of a stream of light scattering suspended particles in a solution. The process light scattering by colloidal aggregates are formed from suspension microspheresis with adsorbed on their surface protein is described. In report the physics principle of registration immune reaction by light scattering methods is concerned. The results of the effectiveness latex's preparation created on basis of the polymeric carries is described.

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Surface oxide removal by a XeCl laser for decontamination

NASA Astrophysics Data System (ADS)

Sentis, M. L.; Delaporte, Ph; Marine, W.; Uteza, O.

2000-06-01

The laser ablation performed with an automated excimer XeCl laser unit is used for large surface cleaning. The study focuses on metal surfaces that are oxidised and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The unit contains an XeCl laser, the beam delivery system, the particle collection cell, and the system for real-time control of cleaning processes. The interaction of laser radiation with a surface is considered, in particular, the surface damage caused by cleaning radiation. The beam delivery system consists of an optical fibre bundle of 5 m long and allows delivering 150 W at 308 nm for laser surface cleaning. The cleaning process is controlled by analysing in real time the plasma electric field evolution. The system permits the cleaning of 2 to 6 m2 h-1 of oxides with only slight substrate modifications.

An Impact Ejecta Behavior Model for Small, Irregular Bodies

NASA Technical Reports Server (NTRS)

Richardson, J. E.; Melosh, H. J.; Greenberg, R.

2003-01-01

In recent years, spacecraft observations of asteroids 951 Gaspra, 243 Ida, 253 Mathilde, and 433 Eros have shown the overriding dominance of impact processes with regard to the structure and surface morphology of these small, irregular bodies. In particular, impact ejecta play an important role in regolith formation, ranging from small particles to large blocks, as well as surface feature modification and obscuration. To investigate these processes, a numerical model has been developed based upon the impact ejecta scaling laws provided by Housen, Schmidt, and Holsapple, and modified to more properly simulate the late-stage ejection velocities and ejecta plume shape changes (ejection angle variations) shown in impact cratering experiments. A target strength parameter has also been added to allow the simulation of strength-dominated cratering events in addition to the more familiar gravity-dominated cratering events. The result is a dynamical simulation which models -- via tracer particles -- the ejecta plume behavior, ejecta blanket placement, and impact crater area resulting from a specified impact on an irregularly shaped target body, which is modeled in 3-dimensional polygon fashion. This target body can be placed in a simple rotation state about one of its principal axes, with the impact site and projectile/target parameters selected by the user. The gravitational force from the irregular target body (on each tracer particle) is determined using the polygonized surface (polyhedron) gravity technique developed by Werner.

Advances in Mineral Dust Source Composition Measurement with Imaging Spectroscopy at the Salton Sea, CA

NASA Astrophysics Data System (ADS)

Green, R. O.; Realmuto, V. J.; Thompson, D. R.; Mahowald, N. M.; Pérez García-Pando, C.; Miller, R. L.; Clark, R. N.; Swayze, G. A.; Okin, G. S.

2015-12-01

Mineral dust emitted from the Earth's surface is a principal contributor to direct radiative forcing over the arid regions, where shifts in climate have a significant impact on agriculture, precipitation, and desert encroachment around the globe. Dust particles contribute to both positive and negative forcing, depending on the composition of the particles. Particle composition is a function of the surface mineralogy of dust source regions, but poor knowledge of surface mineralogy on regional to global scales limits the skill of Earth System models to predict shifts in regional climate around the globe. Earth System models include the source, emission, transport and deposition phases of the dust cycle. In addition to direct radiative forcing contributions, mineral dust impacts include indirect radiative forcing, modification of the albedo and melting rates of snow and ice, kinetics of tropospheric photochemistry, formation and deposition of acidic aerosols, supply of nutrients to aquatic and terrestrial ecosystems, and impact on human health and safety. We demonstrate the ability to map mineral dust source composition in the Salton Sea dust source region with imaging spectroscopy measurements acquired as part of the NASA HyspIRI preparatory airborne campaign. These new spectroscopically derived compositional measurements provide a six orders of magnitude improvement over current atlases for this dust source region and provide a pathfinder example for a remote measurement approach to address this critical dust composition gap for global Earth System models.

Characterization of Surface Modification of Polyethersulfone Membrane

USDA-ARS?s Scientific Manuscript database

Surface modification of polyethersulfone (PES) membrane surface using UV/ozone-treated grafting and interfacial polymerization on membrane surface was investigated in order to improve the resistance of membrane surface to protein adsorption. These methods of surface modification were compared in te...

Dispersion of ceria nanoparticles on γ-alumina surface functionalized using long chain carboxylic acids

NASA Astrophysics Data System (ADS)

Ledwa, Karolina Anna; Kępiński, Leszek

2017-04-01

Dispersion and stability of nanoparticles on a support is determined by the interaction between these phases. In case of hydrophobic nanoparticles (e.g. synthesized by reverse microemulsion method) the interaction with hydrophilic support (e.g. γ-Al2O3) is weak and agglomeration as well as poor resistance to sintering may cause problems. The bonding of the particles to the support may be effectively strengthened by proper modification of the support, e.g. by adsorption of hydrophobic compounds on its surface. In this work decanoic, myristic, stearic and oleic acid were used for the first time to cover γ-Al2O3 surface in order to enhance the dispersion of ceria nanoparticles deposited afterward by impregnation on such support. TGA and FTIR methods revealed that at monolayer coverage (1.1-2.5 molecules per nm2) the acid molecules are firmly bounded to the alumina surface. Morphology, textural properties, phase composition and reducibility of the CeO2/γ-Al2O3 samples were investigated using TEM, SEM, BET, XRD and H2-TPR methods. It has been shown that deposition of CeO2 nanoparticles on γ-Al2O3 surface covered with all studied acids enhances its dispersion, stability and reducibility. The most effective modification of the γ-Al2O3 surface was obtained at loading of 2.3 molecules of decanoic acid per nm2 of the support.

Equilibrium Conditions of Sediment Suspending Flows on Earth, Mars and Titan

NASA Astrophysics Data System (ADS)

Amy, L. A.; Dorrell, R. M.

2016-12-01

Sediment entrainment, erosion and deposition by liquid water on Earth is one of the key processes controlling planetary surface evolution. Similar modification of planetary surfaces by liquids associated with a volatile cycle are also inferred to have occurred on other planets (e.g., water on Mars and methane-ethane on Titan). Here we explore conditions for equilibrium flow - the threshold between net sediment erosion and deposition - on different planets. We use a new theoretical model for particle erosion-suspension-deposition: this model shows a better fit to empirical data than comparative suspension criterions (e.g., Rouse Number) since it takes into account both flow competence and capacity, and particle size distribution effects. Shear stresses required to initially entrain sediment and maintain equilibrium flow vary significantly, being several times lower on Mars and more than ten times lower on Titan resulting principally from lower gravities. On all planets it is harder to maintain equilibrium flow as sediment mixtures become poorer sorted (higher shear stresses are needed as standard deviation increases). In comparison to large differences in critical shear stresses, critical slopes for equilibrium flow are similar for planets. Compared to Earth, equilibrium slopes on Mars should be slightly lower whilst those on Titan will be higher or lower for organic and ice particle systems, respectively. Particle size distribution has a similar, order of magnitude effect, on equilibrium slope on each planet. The results highlight that whilst reduced gravity on Titan and Mars significantly decreases the bed shear stress required for particle transport, it also proportionally effects the bed shear stress of moving fluid, such that similar slope gradients are required for equilibrium flow; minor variations in equilibrium slopes are related to differences in the particle-fluid density contrasts as well as fluid viscosities. These results help explain why planetary surfaces share striking similarities in their present or past landscapes and shows that particle size distribution is critical to sediment transport dynamics. Interestingly, particle distribution may vary between planets depending on the particle compositions and weathering regimes, imposing differences in equilibrium conditions.

Ambient observations of hygroscopic growth factor and f(RH) below 1: Case studies from surface and airborne measurements

NASA Astrophysics Data System (ADS)

Shingler, Taylor; Sorooshian, Armin; Ortega, Amber; Crosbie, Ewan; Wonaschütz, Anna; Perring, Anne E.; Beyersdorf, Andreas; Ziemba, Luke; Jimenez, Jose L.; Campuzano-Jost, Pedro; Mikoviny, Tomas; Wisthaler, Armin; Russell, Lynn M.

2016-11-01

This study reports a detailed set of ambient observations of optical/physical shrinking of particles from exposure to water vapor with consistency across different instruments and regions. Data have been utilized from (i) a shipboard humidified tandem differential mobility analyzer during the Eastern Pacific Emitted Aerosol Cloud Experiment in 2011, (ii) multiple instruments on the NASA DC-8 research aircraft during the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys in 2013, and (iii) the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe during ambient measurements in Tucson, Arizona, during summer 2014 and winter 2015. Hygroscopic growth factor (ratio of humidified-to-dry diameter, GF = Dp,wet/Dp,dry) and f(RH) (ratio of humidified-to-dry scattering coefficients) values below 1 were observed across the range of relative humidity (RH) investigated (75-95%). A commonality of observations of GF and f(RH) below 1 in these experiments was the presence of particles enriched with carbonaceous matter, especially from biomass burning. Evidence of externally mixed aerosol, and thus multiple GFs with at least one GF < 1, was observed concurrently with f(RH) < 1 during smoke periods. Possible mechanisms responsible for observed shrinkage are discussed and include particle restructuring, volatilization effects, and refractive index modifications due to aqueous processing resulting in optical size modification. To further investigate ambient observations of GFs and f(RH) values less than 1, it is recommended to add an optional prehumidification bypass module to hygroscopicity instruments, to preemptively collapse particles prior to controlled RH measurements.

Self-standing elastomeric composites based on lithium ferrites and their dielectric behavior

NASA Astrophysics Data System (ADS)

Soreto Teixeira, S.; Graça, M. P. F.; Dionisio, M.; Ilcíkova, M.; Mosnacek, J.; Spitalsky, Z.; Krupa, I.; Costa, L. C.

2014-12-01

Lithium ferrite (LiFe5O8) is an attractive material for technological applications due to its physical properties, which are significantly dependent on the preparation method and raw materials. In this work, LiFe5O8 crystallites were obtained by controlled heat-treatment process at 1100 °C, of a homogeneous mixture of Li2O-Fe2O3 powders, prepared by wet ball-milling and using lithium and iron nitrates as raw materials. The main goal was the preparation of a flexible and self-standing tick composite film by embedding lithium ferrite particles in a polymeric matrix, taking advantage of the good mechanical properties of the polymer and of the electrical and dielectric properties of the ferrite. The selected polymer matrix was styrene-b-isoprene-b-styrene copolymer. To prepare the composites, the lithium ferrite particles were chemically modified in order to functionalize their surface. To analyse the influence of the particles surface modification, different composites were made, with modified and unmodified particles. The structure of the obtained composites was studied by FTIR, XRD, TGA, and DSC techniques. The dielectric properties were analysed, in the frequency range between 10 Hz and 1 MHz and in function of temperature in the range between -73 °C and 127 °C. These properties were related with the structure and concentration of the particles in the matrix network. The composites with the modified particles present higher dielectric constant, maintaining values of loss tangent sufficiently low (<10-2) that can be considered interesting for technological applications.

Enhanced photovoltaic properties in dye sensitized solar cells by surface treatment of SnO2 photoanodes

PubMed Central

Basu, Kaustubh; Benetti, Daniele; Zhao, Haiguang; Jin, Lei; Vetrone, Fiorenzo; Vomiero, Alberto; Rosei, Federico

2016-01-01

We report the fabrication and testing of dye sensitized solar cells (DSSC) based on tin oxide (SnO2) particles of average size ~20 nm. Fluorine-doped tin oxide (FTO) conducting glass substrates were treated with TiOx or TiCl4 precursor solutions to create a blocking layer before tape casting the SnO2 mesoporous anode. In addition, SnO2 photoelectrodes were treated with the same precursor solutions to deposit a TiO2 passivating layer covering the SnO2 particles. We found that the modification enhances the short circuit current, open-circuit voltage and fill factor, leading to nearly 2-fold increase in power conversion efficiency, from 1.48% without any treatment, to 2.85% achieved with TiCl4 treatment. The superior photovoltaic performance of the DSSCs assembled with modified photoanode is attributed to enhanced electron lifetime and suppression of electron recombination to the electrolyte, as confirmed by electrochemical impedance spectroscopy (EIS) carried out under dark condition. These results indicate that modification of the FTO and SnO2 anode by titania can play a major role in maximizing the photo conversion efficiency. PMID:26988622

Characterization of the interactions between protein and carbon black.

PubMed

Chen, Tzu-Tao; Chuang, Kai-Jen; Chiang, Ling-Ling; Chen, Chun-Chao; Yeh, Chi-Tai; Wang, Liang-Shun; Gregory, Clive; Jones, Tim; BéruBé, Kelly; Lee, Chun-Nin; Chuang, Hsiao-Chi; Cheng, Tsun-Jen

2014-01-15

A considerable amount of studies have been conducted to investigate the interactions of biological fluids with nanoparticle surfaces, which exhibit a high affinity for proteins and particles. However, the mechanisms underlying these interactions have not been elucidated, particularly as they relate to human health. Using bovine serum albumin (BSA) and mice bronchoalveolar lavage fluid (BALF) as models for protein-particle conjugates, we characterized the physicochemical modifications of carbon blacks (CB) with 23nm or 65nm in diameter after protein treatment. Adsorbed BALF-containing proteins were quantified and identified by pathways, biological analyses and protein classification. Significant modifications of the physicochemistry of CB were induced by the addition of BSA. Enzyme modulators and hydrolase predominately interacted with CB, with protein-to-CB interactions that were associated with the coagulation pathways. Additionally, our results revealed that an acute-phase response could be activated by these proteins. With regard to human health, the present study revealed that the CB can react with proteins (∼55kDa and 70kDa) after inhalation and may modify the functional structures of lung proteins, leading to the activation of acute-inflammatory responses in the lungs. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of Nanoparticle Surface on the HPLC Elution Profile of Liposomal Nanoparticles.

PubMed

Itoh, Naoki; Yamamoto, Eiichi; Santa, Tomofumi; Funatsu, Takashi; Kato, Masaru

2016-06-01

Nanoparticles have been used in diverse areas, and even broader applications are expected in the future. Since surface modification can influence the configuration and toxicity of nanoparticles, a rapid screening method is important to ensure nanoparticle quality. We examined the effect of the nanoparticle surface morphology on the HPLC elution profile using two types of 100-nm liposomal nanoparticles (AmBisome(Ⓡ) and DOXIL(Ⓡ)). These 100-nm-sized nanoparticles eluted before the holdup time (about 4 min), even when a column packed with particles with a relatively large pore size (30 nm) was used. The elution time of the nanoparticles increased with pegylation of the nanoparticles and protein adsorption to the nanoparticles; however, the nanoparticles still eluted before the holdup time. The results of this study indicate that HPLC is a suitable tool for rapid evaluation of the surface of liposomal nanoparticles.

Quasi-one-dimensional arrangement of silver nanoparticles templated by cellulose microfibrils.

PubMed

Wu, Min; Kuga, Shigenori; Huang, Yong

2008-09-16

We demonstrate a simple, facile approach to the deposition of silver nanoparticles on the surface of cellulose microfibrils with a quasi-one-dimensional arrangement. The process involves the generation of aldehyde groups by oxidizing the surface of cellulose microfibrils and then the assembly of silver nanoparticles on the surface by means of the silver mirror reaction. The linear nature of the microfibrils and the relatively uniform surface chemical modification result in a uniform linear distribution of silver particles along the microfibrils. The effects of various reaction parameters, such as the reaction time for the reduction process and employed starting materials, have been investigated by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy. Additionally, the products were examined for their electric current-voltage characteristics, the results showing that these materials had an electric conductivity of approximately 5 S/cm, being different from either the oxidated cellulose or bulk silver materials by many orders of magnitude.

Stabilization of gold nanoparticles by 6-mercaptopurine monolayers. Effects of the solvent properties.

PubMed

Viudez, Alfonso J; Madueño, Rafael; Pineda, Teresa; Blázquez, Manuel

2006-09-14

6-Mercaptopurine-coated gold nanoparticles (6MP-AuNPs) have been prepared by modification of the nanoparticle surface with 6MP upon displacement of the protective layer of citrate anions. The modification has been studied by UV-vis and FTIR spectroscopies. A study of the stability of these 6MP-AuNPs in aqueous solutions as a function of ionic strength and pH has shown the importance of the charges on the stabilization. The protonation of N9 of the 6MP molecules brings about a sudden flocculation phenomenon. However, the flocculation is reversible upon changing the pH to values where the molecules become newly charged. Evidence of the competence between the interaction of capping solvent molecules and the attractive forces between particles is also shown in this paper.

Casein-Coated Fe5C2 Nanoparticles with Superior r2 Relaxivity for Liver-Specific Magnetic Resonance Imaging.

PubMed

Cowger, Taku A; Tang, Wei; Zhen, Zipeng; Hu, Kai; Rink, David E; Todd, Trever J; Wang, Geoffrey D; Zhang, Weizhong; Chen, Hongmin; Xie, Jin

2015-01-01

Iron oxide nanoparticles have been extensively used as T2 contrast agents for liver-specific magnetic resonance imaging (MRI). The applications, however, have been limited by their mediocre magnetism and r2 relaxivity. Recent studies show that Fe5C2 nanoparticles can be prepared by high temperature thermal decomposition. The resulting nanoparticles possess strong and air stable magnetism, suggesting their potential as a novel type of T2 contrast agent. To this end, we improve the synthetic and surface modification methods of Fe5C2 nanoparticles, and investigated the impact of size and coating on their performances for liver MRI. Specifically, we prepared 5, 14, and 22 nm Fe5C2 nanoparticles and engineered their surface by: 1) ligand addition with phospholipids, 2) ligand exchange with zwitterion-dopamine-sulfonate (ZDS), and 3) protein adsorption with casein. It was found that the size and surface coating have varied levels of impact on the particles' hydrodynamic size, viability, uptake by macrophages, and r2 relaxivity. Interestingly, while phospholipid- and ZDS-coated Fe5C2 nanoparticles showed comparable r2, the casein coating led to an r2 enhancement by more than 2 fold. In particular, casein coated 22 nm Fe5C2 nanoparticle show a striking r2 of 973 mM(-1)s(-1), which is one of the highest among all of the T2 contrast agents reported to date. Small animal studies confirmed the advantage of Fe5C2 nanoparticles over iron oxide nanoparticles in inducing hypointensities on T2-weighted MR images, and the particles caused little toxicity to the host. The improvements are important for transforming Fe5C2 nanoparticles into a new class of MRI contrast agents. The observations also shed light on protein-based surface modification as a means to modulate contrast ability of magnetic nanoparticles.

Evolution of Elemental Composition and Morphology in Fusion Reactor's First Wall

NASA Astrophysics Data System (ADS)

Kim, Yong W.

2007-11-01

Forcing of a multi-element alloy by a gradient field can modify the spatial profile of its elemental composition. The gradient field may be in the imposed temperature or the flux of impinging particles. In a fusion device, both scenarios apply. The consequences must be well understood because they change the thermal transport properties as well as the strength, corrosion and wear characteristics of the first wall materials. Given the large number of directions material evolution can take, new robust methods of near-surface composition analyses are needed. This paper presents a new measurement methodology and requisite instrumentation, which can provide measures of local elemental composition and transport properties simultaneously by time-resolved spectroscopy of laser-produced plasma (LPP) plume emissions from the specimen surfaces. The studies to date show that the composition profiles can be modified thermally in a reproducible manner; disparate thermal transport of constituent atoms can incur modifications of near-surface composition profiles.[Y.W. Kim, Int. J. Thermophysics 28, 732 (2007)] Also, disparate fluxes of fuel particles, fusion products and impurities force the first walls in myriad ways. Repetitive application of the LPP analysis can resolve the near-surface composition profile as well as transport properties over several microns with depth resolutions to 20 nm. Work supported in part by NSF-DMR.

Direct Functionalization of an Acid-Terminated Nanodiamond with Azide: Enabling Access to 4-Substituted-1,2,3-Triazole-Functionalized Particles

DOE PAGES

Kennedy, Zachary C.; Barrett, Christopher A.; Warner, Marvin G.

2017-03-01

Azides on the periphery of nanodiamond materials (ND) are of great utility because they have been shown to undergo Cu-catalyzed and Cu-free cycloaddition reactions with structurally diverse alkynes, affording particles tailored for applications in biology and materials science. However, current methods employed to access ND featuring azide groups typically require either harsh pretreatment procedures or multiple synthesis steps and use surface linking groups that may be susceptible to undesirable cleavage. Here in this paper we demonstrate an alternative single-step approach to producing linker-free, azide-functionalized ND. Our method was applied to low-cost, detonation-derived ND powders where surface carbonyl groups undergo silver-mediatedmore » decarboxylation and radical substitution with azide. ND with directly grafted azide groups were then treated with a variety of aliphatic, aromatic, and fluorescent alkynes to afford 1-(ND)-4-substituted-1,2,3-triazole materials under standard copper-catalyzed cycloaddition conditions. Surface modification steps were verified by characteristic infrared absorptions and elemental analyses. High loadings of triazole surface groups (up to 0.85 mmol g –1) were obtained as determined from thermogravimetric analysis. The azidation procedure disclosed is envisioned to become a valuable initial transformation in numerous future applications of ND.« less

Barrier coated drug layered particles for enhanced performance of amorphous solid dispersion dosage form.

PubMed

Puri, Vibha; Dantuluri, Ajay K; Bansal, Arvind K

2012-01-01

Amorphous solid dispersions (ASDs) may entail tailor-made dosage form design to exploit their solubility advantage. Surface phenomena dominated the performance of amorphous celecoxib solid dispersion (ACSD) comprising of amorphous celecoxib (A-CLB), polyvinylpyrrolidone, and meglumine (7:2:1, w/w). ACSD cohesive interfacial interactions hindered its capsule dosage form dissolution (Puri V, Dhantuluri AK, Bansal AK 2011. J Pharm Sci 100:2460-2468). Furthermore, ACSD underwent significant devitrification under environmental stress. In the present study, enthalpy relaxation studies revealed its free surface to contribute to molecular mobility. Based on all these observations, barrier coated amorphous CLB solid dispersion layered particles (ADLP) were developed by Wurster process, using microcrystalline cellulose as substrate and polyvinyl alcohol (PVA), inulin, and polyvinyl acetate phthalate (PVAP) as coating excipients. Capsule formulations of barrier coated-ADLP could achieve rapid dispersibility and high drug release. Evaluation under varying temperature and RH conditions suggested the crystallization inhibitory efficiency in order of inulin < PVA ≈ PVAP; however, under only temperature treatment, crystallization inhibition increased with increase in T(g) of the coating material. Simulated studies using DSC evidenced drug-polymer mixing at the interface as a potential mechanism for surface stabilization. In conclusion, surface modification yielded a fast dispersing robust high drug load ASD based dosage form. Copyright © 2011 Wiley-Liss, Inc.

Advanced Electrodes for High Power Li-ion Batteries.

PubMed

Zaghib, Karim; Mauger, Alain; Groult, Henri; Goodenough, John B; Julien, Christian M

2013-03-15

While little success has been obtained over the past few years in attempts to increase the capacity of Li-ion batteries, significant improvement in the power density has been achieved, opening the route to new applications, from hybrid electric vehicles to high-power electronics and regulation of the intermittency problem of electric energy supply on smart grids. This success has been achieved not only by decreasing the size of the active particles of the electrodes to few tens of nanometers, but also by surface modification and the synthesis of new multi-composite particles. It is the aim of this work to review the different approaches that have been successful to obtain Li-ion batteries with improved high-rate performance and to discuss how these results prefigure further improvement in the near future.

Effective holographic recordings in the photopolymer nanocomposites with functionalized silica nanoparticle and polyurethane matrix

NASA Astrophysics Data System (ADS)

Han, Samsook; Lee, Muncheul; Kim, Byung Kyu

2011-11-01

Effective holographic nanocomposites were developed by the surface-functionalized silica nanoparticles and two acrylate monomers/polyurethane (PU) matrix polymer. The functionalization was done with silane compounds carrying long alkyl chain or vinyl group. We evaluated the holographic nanocomposite films by the diffraction efficiency, volume shrinkage, optical loss, and the film morphology. It was found that acrylate monomers/PU system gave higher diffraction efficiency than those of two monomers due to the high refractive index mismatch between the acrylate-rich and PU-rich regions. With the modification of silica particle, up to 35% of particle loading was possible to give a maximum diffraction efficiency of 93.6% for a film of 20 μm in thickness, along with improved refractive index modulation and the sensitivity.

Formulation of poorly water-soluble Gemfibrozil applying power ultrasound.

PubMed

Ambrus, R; Naghipour Amirzadi, N; Aigner, Z; Szabó-Révész, P

2012-03-01

The dissolution properties of a drug and its release from the dosage form have a basic impact on its bioavailability. Solubility problems are a major challenge for the pharmaceutical industry as concerns the development of new pharmaceutical products. Formulation problems may possibly be overcome by modification of particle size and morphology. The application of power ultrasound is a novel possibility in drug formulation. This article reports on solvent diffusion and melt emulsification, as new methods supplemented with drying in the field of sonocrystallization of poorly water-soluble Gemfibrozil. During thermoanalytical characterization, a modified structure was detected. The specific surface area of the drug was increased following particle size reduction and the poor wettability properties could also be improved. The dissolution rate was therefore significantly increased. Copyright © 2011 Elsevier B.V. All rights reserved.

Microstructural and surface modifications and hydroxyapatite coating of Ti-6Al-4V triply periodic minimal surface lattices fabricated by selective laser melting.

PubMed

Yan, Chunze; Hao, Liang; Hussein, Ahmed; Wei, Qingsong; Shi, Yusheng

2017-06-01

Ti-6Al-4V Gyroid triply periodic minimal surface (TPMS) lattices were manufactured by selective laser melting (SLM). The as-built Ti-6Al-4V lattices exhibit an out-of-equilibrium microstructure with very fine α' martensitic laths. When subjected to the heat treatment of 1050°C for 4h followed by furnace cooling, the lattices show a homogenous and equilibrium lamellar α+β microstructure with less dislocation and crystallographic defects compared with the as-built α' martensite. The as-built lattices present very rough strut surfaces bonded with plenty of partially melted metal particles. The sand blasting nearly removed all the bonded metal particles, but created many tiny cracks. The HCl etching eliminated these tiny cracks, and subsequent NaOH etching resulted in many small and shallow micro-pits and develops a sodium titanate hydrogel layer on the surfaces of the lattices. When soaked in simulated body fluid (SBF), the Ti-6Al-4V TPMS lattices were covered with a compact and homogeneous biomimetic hydroxyapatite (HA) layer. This work proposes a new method for making Ti-6Al-4V TPMS lattices with a homogenous and equilibrium microstructure and biomimetic HA coating, which show both tough and bioactive characteristics and can be promising materials usable as bone substitutes. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of hematite nanoparticles synthesized via two different pathways

NASA Astrophysics Data System (ADS)

Das, Soumya; Hendry, M. Jim

2014-08-01

Hematite is one of the most common and thermodynamically stable iron oxides found in both natural and anthropogenic systems. Owing to its ubiquity, stability, moderate specific surface area, and ability to sequester metals and metalloids from aquatic systems, it has been the subject of a large number of adsorption studies published during the past few decades. Although preparation techniques are known to affect the surface morphology of hematite nanoparticles, the effects of aging under environmentally relevant conditions have yet to be tested with respect to surface morphology, surface area, and adsorptive capacity. We prepared hematite via two different pathways and aged it under highly alkaline conditions encountered in many mill tailings settings. Crystal habits and morphologies of the hematite nanoparticles were analyzed via scanning electron microscopy and transmission electron microscopy. X-ray diffraction, Raman spectroscopy, and Brunauer-Emmett-Teller surface area analyses were also conducted on the hematite nanoparticles before and after aging. The hematite synthesized via an Fe(III) salt solution (average particle size 37 nm) was morphologically and structurally different from the hematite synthesized via ferrihydrite aging (average particle size 144 nm). Overall, our data demonstrate that the crystallinity of hematite produced via ferrihydrite transformation is susceptible to morphological alterations/modifications. In contrast, the hematite formed via hydrolysis of an Fe(III) salt solution remains very stable in terms of structure, size, and morphology even under extreme experimental conditions.

Versatile Surface Functionalization of Metal-Organic Frameworks through Direct Metal Coordination with a Phenolic Lipid Enables Diverse Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Wei; Xiang, Guolei; Shang, Jin

Here, a novel strategy for the versatile functionalization of the external surface of metal-organic frameworks (MOFs) has been developed based on the direct coordination of a phenolic-inspired lipid molecule DPGG (1,2-dipalmitoyl-sn-glycero-3-galloyl) with metal nodes/sites surrounding MOF surface. X-ray diffraction and Argon sorption analysis prove that the modified MOF particles retain their structural integrity and porosity after surface modification. Density functional theory calculations reveal that strong chelation strength between the metal sites and the galloyl head group of DPGG is the basic prerequisite for successful coating. Due to the pH-responsive nature of metal-phenol complexation, the modification process is reversible by simplemore » washing in weak acidic water, showing an excellent regeneration ability for water-stable MOFs. Moreover, the colloidal stability of the modified MOFs in the nonpolar solvent allows them to be further organized into 2 dimensional MOF or MOF/polymer monolayers by evaporation-induced interfacial assembly conducted on an air/water interface. Lastly, the easy fusion of a second functional layer onto DPGG-modified MOF cores, enabled a series of MOF-based functional nanoarchitectures, such as MOFs encapsulated within hybrid supported lipid bilayers (so-called protocells), polyhedral core-shell structures, hybrid lipid-modified-plasmonic vesicles and multicomponent supraparticles with target functionalities, to be generated. for a wide range of applications.« less

Targeted partial surface modification with nano-SiO2@Li2CoPO4F as high-voltage cathode material for LIBs

NASA Astrophysics Data System (ADS)

Chang, Caiyun; Huang, Zhipeng; Tian, Runsai; Jiang, Xinyu; Li, Chunsheng; Feng, Jijun

2017-10-01

Tuning whole/partial surface modification on cathode material with oxide material is a sought-after method to enhance the electrochemical performance in power storage field. Herein, nano-SiO2 targeted partial surface modified high voltage cathode material Li2CoPO4F has been successfully fabricated via a facile self-assembly process in silica dispersion at ambient temperature. With the aid of polar -OH groups attracted on the surface of SiO2 micelles, the nano-SiO2 preferentially nestle up along the borders and boundaries of Li2CoPO4F particles, where protection should be deployed with emphasis against the undesirable interactions between materials and electrolytes. Compared with pristine Li2CoPO4F, the SiO2 selectively modified Li2CoPO4F cathode materials, especially LCPF-3S, exhibit desirable electrochemical performances with higher discharge capacity, more outstanding cycle stability and favorable rate capability without any additional carbon involved. The greatly enhanced electrochemical properties can be attributed to the improved lithium-ion diffusion kinetics and structure tolerance during repeated lithiation/delithiation process. Such findings reveal a great potential of nano-SiO2 modified Li2CoPO4F as high energy cathode material for lithium ion batteries.

Preparation and Surface Property of Fluoroalkyl End-Capped Vinyltrimethoxysilane Oligomer/Talc Composite-Encapsulated Organic Compounds: Application for the Separation of Oil and Water.

PubMed

Oikawa, Yuri; Saito, Tomoya; Yamada, Satoshi; Sugiya, Masashi; Sawada, Hideo

2015-07-01

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R(F)-(CH2-CHSi(OMe)3)n-R(F); n = 2, 3; R(F) = CF(CF3)OC3F7 (R(F)-VM oligomer)] can undergo the sol-gel reaction in the presence of talc particles under alkaline conditions at room temperature to provide the corresponding fluorinated oligomeric silica/talc nanocomposites (RF-VM-SiO2/Talc). A variety of guest molecules such as 2-hydroxy-4-methoxybenzophenone (HMB), bisphenol A (BPA), bisphenol AF, 3-(hydroxysilyl)-1-propanesulfonic acid (THSP), and perfluoro-2-methyl-3-oxahexanoic acid (R(F)-COOH) are effectively encapsulated into the R(F)-VM-SiO2/Talc composite cores to afford the corresponding fluorinated nanocomposites-encapsulated these guest molecules. The R(F)-VM-SiO2/Talc composites encapsulated low molecular weight aromatic compounds such as HMB and BPA can exhibit a superoleophilic-superhydrophobic characteristic on the surfaces; however, the R(F)-VM-SiO2/Talc composite-encapsulated THSP and R(F)-COOH exhibit a superoleophobic-superhydrophilic characteristic on the modified surfaces. In these nanocomposites, the R(F)-VM-SiO2/Talc/THSP composites are applicable to the surface modification of polyester fabric, and the modified polyester fabric possessing a superoleophobic-superhydrophilic characteristic on the surface can be used for the membrane for oil (dodecane)/water separation. In addition, the R(F)-VM-SiO2/Talc composites-encapsulated micrometer-size controlled cross-linked polystyrene particles can be also prepared under similar conditions, and the obtained composite white-colored particle powders are applied to the packing material for the column chromatography to separate water-in-oil (W/O) emulsion.

Core/shell silicon/polyaniline particles via in-flight plasma-induced polymerization

NASA Astrophysics Data System (ADS)

Yasar-Inceoglu, Ozgul; Zhong, Lanlan; Mangolini, Lorenzo

2015-08-01

Although silicon nanoparticles have potential applications in many relevant fields, there is often the need for post-processing steps to tune the property of the nanomaterial and to optimize it for targeted applications. In particular surface modification is generally necessary to both tune dispersibility of the particles in desired solvents to achieve optimal coating conditions, and to interface the particles with other materials to realize functional heterostructures. In this contribution we discuss the realization of core/shell silicon/polymer nanoparticles realized using a plasma-initiated in-flight polymerization process. Silicon particles are produced in a non-thermal plasma reactor using silane as a precursor. After synthesis they are aerodynamically injected into a second plasma reactor into which aniline vapor is introduced. The second plasma initiates the polymerization reactor leading to the formation of a 3-4 nm thick polymer shell surrounding the silicon core. The role of processing conditions on the properties of the polymeric shell is discussed. Preliminary results on the testing of this material as an anode for lithium ion batteries are presented.

Toughening mechanisms in interfacially modified HDPE/thermoplastic starch blends.

PubMed

Taguet, Aurélie; Bureau, Martin N; Huneault, Michel A; Favis, Basil D

2014-12-19

The mechanical behavior of polymer blends containing 80 wt% of HDPE and 20 wt% of TPS and compatibilized with HDPE-g-MA grafted copolymer was investigated. Unmodified HDPE/TPS blends exhibit high fracture resistance, however, the interfacial modification of those blends by addition of HDPE-g-MA leads to a dramatic drop in fracture resistance. The compatibilization of HDPE/TPS blends increases the surface area of TPS particles by decreasing their size. It was postulated that the addition of HDPE-g-MA induces a reaction between maleic anhydride and hydroxyl groups of the glycerol leading to a decrease of the glycerol content in the TPS phase. This phenomenon increases the stiffness of the modified TPS particles and stiffer TPS particles leading to an important reduction in toughness and plastic deformation, as measured by the EWF method. It is shown that the main toughening mechanism in HDPE/TPS blends is shear-yielding. This article demonstrates that stiff, low diameter TPS particles reduce shear band formation and consequently decrease the resistance to crack propagation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Enhanced corrosion resistance and cytocompatibility of biodegradable Mg alloys by introduction of Mg(OH)2 particles into poly (L-lactic acid) coating

PubMed Central

Shi, Yong-juan; Pei, Jia; Zhang, Jian; Niu, Jia-lin; Zhang, Hua; Guo, Sheng-rong; Li, Zhong-hua; Yuan, Guang-yin

2017-01-01

A strategy of suppressing the fast degradation behaviour of Mg-based biomaterials by the introduction of one of Mg degradation products Mg(OH)2 was proposed according to the following degradation mechanism, Mg + 2H2O ⇋ Mg(OH)2 + H2↑. Specifically, Mg(OH)2 submicron particles were mixed into poly (L-lactic acid) (PLLA) to synthesize a composite coating onto hydrofluoric acid-pretreated Mg-Nd-Zn-Zr alloy. The in vitro degradation investigations showed that the addition of Mg(OH)2 particles not only slowed down the corrosion of Mg matrix, but also retarded the formation of gas pockets underneath the polymer coating. Correspondingly, cytocompatibility results exhibited significant improvement of proliferation of endothelial cells, and further insights was gained into the mechanisms how the introduction of Mg(OH)2 particles into PLLA coating affected the magnesium alloy degradation and cytocompatibility. The present study provided a promising surface modification strategy to tailor the degradation behaviour of Mg-based biomaterials. PMID:28150751

Interfacial Properties of High-Density Lipoprotein-like Lipid Droplets with Different Lipid and Apolipoprotein A-I Compositions

PubMed Central

Koivuniemi, Artturi; Sysi-Aho, Marko; Orešič, Matej; Ollila, Samuli

2013-01-01

The surface properties of high-density lipoproteins (HDLs) are important because different enzymes bind and carry out their functions at the surface of HDL particles during metabolic processes. However, the surface properties of HDL and other lipoproteins are poorly known because they cannot be directly measured for nanoscale particles with contemporary experimental methods. In this work, we carried out coarse-grained molecular dynamics simulations to study the concentration of core lipids in the surface monolayer and the interfacial tension of droplets resembling HDL particles. We simulated lipid droplets composed of different amounts of phospholipids, cholesterol esters (CEs), triglycerides (TGs), and apolipoprotein A-Is. Our results reveal that the amount of TGs in the vicinity of water molecules in the phospholipid monolayer is 25–50% higher compared to the amount of CEs in a lipid droplet with a mixed core of an equal amount of TG and CE. In addition, the correlation time for the exchange of molecules between the core and the monolayer is significantly longer for TGs compared to CEs. This suggests that the chemical potential of TG is lower in the vicinity of aqueous phase but the free-energy barrier for the translocation between the monolayer and the core is higher compared to CEs. From the point of view of enzymatic modification, this indicates that TG molecules are more accessible from the aqueous phase. Further, our results point out that CE molecules decrease the interfacial tension of HDL-like lipid droplets whereas TG keeps it constant while the amount of phospholipids varies. PMID:23708359

Modification process optimization, characterization and adsorption property of granular fir-based activated carbon

NASA Astrophysics Data System (ADS)

Chen, Congjin; Li, Xin; Tong, Zhangfa; Li, Yue; Li, Mingfei

2014-10-01

Granular fir-based activated carbon (GFAC) was modified with H2O2, and orthogonal array experimental design method was used to optimize the process. The properties of the original and modified GFAC were characterized by N2 adsorption-desorption isotherms, Brunauer-Emmett-Teller (BET) equation, Barett-Joyner-Halenda (BJH) equation, field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FT-IR) analysis, etc. When 10.00 g of GFAC with particle size of 0.25-0.85 mm was modified by 150.0 ml of aqueous H2O2 solution, the optimized conditions were found to be as follows: aqueous H2O2 solution concentration 1.0 mol·l-1, modification temperature 30.0 °C, modification time 4.0 h. Modified under the optimized conditions, decolonization of caramel, methylene blue adsorption, phenol adsorption and iodine number of the modified GFAC increased by 500.0%, 59.7%, 32.5%, and 15.1%, respectively. The original and optimally modified GFAC exhibited adsorption isotherms of hybrid Type I-IV isotherms with H4 hysteresis. BET surface area, micropore area, total pore volume, micropore volume, and microporosity of the modified GFAC increased by 7.33%, 11.25%, 3.89%, 14.23%, 9.91%, respectively. Whereas the average pore width decreased by 3.16%. In addition, the amount of surface oxygen groups (such as carbonyl or carboxyl) increased in the modified GFAC.

Surface Modification of Biomaterials: A Quest for Blood Compatibility

PubMed Central

de Mel, Achala; Cousins, Brian G.; Seifalian, Alexander M.

2012-01-01

Cardiovascular implants must resist thrombosis and intimal hyperplasia to maintain patency. These implants when in contact with blood face a challenge to oppose the natural coagulation process that becomes activated. Surface protein adsorption and their relevant 3D confirmation greatly determine the degree of blood compatibility. A great deal of research efforts are attributed towards realising such a surface, which comprise of a range of methods on surface modification. Surface modification methods can be broadly categorized as physicochemical modifications and biological modifications. These modifications aim to modulate platelet responses directly through modulation of thrombogenic proteins or by inducing antithrombogenic biomolecules that can be biofunctionalised onto surfaces or through inducing an active endothelium. Nanotechnology is recognising a great role in such surface modification of cardiovascular implants through biofunctionalisation of polymers and peptides in nanocomposites and through nanofabrication of polymers which will pave the way for finding a closer blood match through haemostasis when developing cardiovascular implants with a greater degree of patency. PMID:22693509

Novel "anchor modification" of polymeric biomaterial surfaces by the utilization of cyclodextrin inclusion complex supramolecules.

PubMed

Zhao, Xiaobin; Courtney, James M

2009-07-01

In this article, a novel approach for the surface modification of polymeric biomaterials by the utilization of supramolecules was studied. The supramolecules selected were cyclodextrin inclusion complexes (CICs). The biomaterial selected for surface modification was plasticized poly (vinyl chloride) (PVC-P). Results indicate that when the CICs were blended into PVC-P, they tend to migrate and "anchor" on the surface to achieve a remarkable protein-resistant surface, with improved blood compatibility. In comparison with a physical mixture of cyclodextrins and a "guest" molecule, such as poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO and PPO-PEO-PPO for PVC-P modification, CICs modified PVC-P are more consistent in processing and achieve reproducible surface characteristics. Based on this study, a novel "anchor modification" was proposed regarding CICs modified surface. This "anchor modification" is likely to reduce plasticizer extraction from PVC-P and also can be utilized for the modification of polymers other than PVC-P.

Thermodynamic and Dynamic Aspects of Ice Nucleation

NASA Technical Reports Server (NTRS)

Barahona, Donifan

2018-01-01

It is known that ice nucleating particles (INP) immersed within supercooled droplets promote the formation of ice. Common theoretical models used to represent this process assume that the immersed particle lowers the work of ice nucleation without significantly affecting the dynamics of water in the vicinity of the particle. This is contrary to evidence showing that immersed surfaces significantly affect the viscosity and diffusivity of vicinal water. To study how this may affect ice formation this work introduces a model linking the ice nucleation rate to the modification of the dynamics and thermodynamics of vicinal water by immersed particles. It is shown that INP that significantly reduce the work of ice nucleation also pose strong limitations to the growth of the nascent ice germs. This leads to the onset of a new ice nucleation regime, called spinodal ice nucleation, where the dynamics of ice germ growth instead of the ice germ size determines the nucleation rate. Nucleation in this regime is characterized by an enhanced sensitivity to particle area and cooling rate. Comparison of the predicted ice nucleation rate against experimental measurements for a diverse set of species relevant to cloud formation suggests that spinodal ice nucleation may be common in nature.

Tapered microelectrode array system for dielectrophoretically filtration: fabrication, characterization, and simulation study

NASA Astrophysics Data System (ADS)

Buyong, Muhamad Ramdzan; Larki, Farhad; Takamura, Yuzuru; Majlis, Burhanuddin Yeop

2017-10-01

This paper presents the fabrication, characterization, and simulation of microelectrode arrays system with tapered profile having an aluminum surface for dielectrophoresis (DEP)-based manipulation of particles. The proposed structure demonstrates more effective electric field gradient compared with its counterpart with untapered profile. Therefore, according to the asymmetric distribution of the electric field in the active region of microelectrode, it produces more effective particle manipulation. The tapered aluminum microelectrode array (TAMA) fabrication process uses a state-of-the-art technique in the formation of the resist's taper profile. The performance of TAMA with various sidewall profile angles (5 deg to 90 deg) was analyzed through finite-element method numerical simulations to offer a better understanding of the origin of the sidewall profile effect. The ability of capturing and manipulating of the device was examined through modification of the Clausius-Mossotti factor and cross-over frequency (f). The fabricated system has been particularly implemented for filtration of particles with a desired diameter from a mixture of particles with three different diameters in an aqueous medium. The microelectrode system with tapered side wall profile offers a more efficient platform for particle manipulation and sensing applications compared with the conventional microelectrode systems.

Surface Modification of Li-Rich Cathode Materials for Lithium-Ion Batteries with a PEDOT:PSS Conducting Polymer.

PubMed

Wu, Feng; Liu, Jianrui; Li, Li; Zhang, Xiaoxiao; Luo, Rui; Ye, Yusheng; Chen, Renjie

2016-09-07

Composites of lithium-rich Li1.2Ni0.2Mn0.6O2 and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) are synthesized through coprecipitation followed by a wet coating method. In the resulting samples, the amorphous conductive polymer films on the surface of the Li1.2Ni0.2Mn0.6O2 particles are 5-20 nm thick. The electrochemical properties of Li1.2Ni0.2Mn0.6O2 are obviously enhanced after PSS coating. The composite sample with an optimal 3 wt % coating exhibits rate capability and cycling properties that are better than those of Li1.2Ni0.2Mn0.6O2, with an excellent initial discharge capacity of 286.5 mA h g(-1) at a current density of 0.1 C and a discharge capacity that remained at 146.9 mA h g(-1) at 1 C after 100 cycles. The improved performances are ascribed to the high conductivity of the PSS coating layer, which can improve the conductivity of the composite material. The PSS layer also suppresses the formation and growth of a solid electrolyte interface. Surface modification with PSS is a feasible approach for improving the comprehensive properties of cathode materials.

Effect of surface modification on photoluminescence properties of Y3Al5O12:Ce3+, Gd3+ nano-phosphors.

PubMed

Li, Jie; Zhao, Junfu; Zhou, Hefeng; Liang, Jian; Liu, Xuguang; Xu, Bingshe

2011-04-01

In this study, a series of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors were prepared using a simply wet chemical process with polyvinyl pyrrolidone as a modifier. The crystal and bonding structures of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors prepared with different weight percentages of polyvinyl pyrrolidone were characterized by X-ray diffractometry and infrared spectrometry. The decomposition process of dried precursor gel with adding 1.37 wt% polyvinyl pyrrolidone was investigated by differential thermal and thermogravimetric analysis. The effect of surface modification on photoluminescence properties for the samples was studied. The results show that the steric hindrance effect of polyvinyl pyrrolidone leads to high dispersion and good crystallinity of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors prepared with adding a proper weight percentages of polyvinyl pyrrolidone. Adding polyvinyl pyrrolidone is beneficial for the photoluminescence enhancement of the samples, which is attributed to the promotion of the incorporation of Ce(3+) and Gd(3+) into the Y(3)Al(5)O(12) nanocrystal and the surface passivation of the nano-particles by the polyvinyl pyrrolidone molecules. Copyright © 2011 Elsevier B.V. All rights reserved.

The effect of polymer surface modification on polymer-protein interaction via interfacial polymerization and hydrophilic polymer grafting

USDA-ARS?s Scientific Manuscript database

Protein membrane separation is prone to fouling on the membrane surface resulting from protein adsorption onto the surface. Surface modification of synthetic membranes is one way to reduce fouling. We investigated surface modification of polyethersulfone (PES) as a way of improving hydrophilicity ...

On the impact of snow cover on daytime pollution dispersion

NASA Astrophysics Data System (ADS)

Segal, M.; Garratt, J. R.; Pielke, R. A.; Hildebrand, P.; Rogers, F. A.; Cramer, J.; Schanot, A.

A preliminary evaluation of the impact of snow cover on daytime pollutant dispersion conditions is made by using conceptual, scaling, and observational analyses. For uniform snow cover and synoptically unperturbed sunny conditions, observations indicate a considerate suppression of the surface sensible heat flux, the turbulence, and the development of the daytime atmospheric boundary layer (ABL) when compared to snow-free conditions. However, under conditions of non-uniform snow cover, as in urban areas, or associated with vegetated areas or bare ground patches, a milder effect on pollutant dispersion conditions would be expected. Observed concentrations of atmospheric particles within the ABL, and surface pollutant concentrations in urban areas, reflect the impact of snow cover on the modification of ABL characteristics.

Aptamer functionalized noble metal particles for bioanalytical and biomedical applications

NASA Astrophysics Data System (ADS)

Yasun, Emir

Noble metal particles, especially gold (Au) and silver (Ag) have been exploited in a broad range of biological applications due to their unique intrinsic features that depend on their physical appearance or optoelectronic properties, which can be tuned with the change in the size or shape of those particles. Thus, this tunability enables gold nanoparticles (AuNPs) to be used in biomedical diagnostic and therapeutical applications. In photothermal therapy applications, nanomaterials, which can absorb efficiently in NIR region, are utilized since the healthy tissue or cells can't absorb at this spectral region. Among AuNPs, gold nanorods (AuNRs) are one of the best candidates for hyperthermia therapy of cancer cells with their high absorption cross-sections and tunable absorption maxima in NIR region. When this unique optical property is combined with the specificity against cancer cells utilized by aptamer conjugations, AuNRs become to be one of the most important nanoparticles employed in both cancer cell sensing and therapy. However, one drawback of AuNRs is having the surfactant CTAB on their surface, which can cause nonspecificity and cytotoxicity. In this research, the side effects of CTAB are passivated by BSA modification, where the nonspecificity and cytotoxicity are dramatically decreased prior to the NIR treatment. Recognition of changes in the rare cancer protein abundances can lead the early diagnosis of cancer, so capturing these low abundance proteins has a great significance. In this research, firstly, aptamer conjugated AuNRs were used to capture 1ng of a-thrombin effectively from plasma samples as model system. Then both aptamer conjugated AuNRs and silver microspheres (SMSs) are used to capture the biomarker proteins of a colon cancer cell line, DLD-1. Gold and silver surfaces can easily be modified through thiolate chemistry, compared to the tedious modification steps for the magnetic particles, so more aptamer immobilization can be achieved for AuNRs and SMSs, which can increase the possibility of binding to the target protein. Furthermore, SMSs offer a novel separation method, gravitational separation owing to their heavy nature. In this way, there is no need for an external stimuli to separate the captured proteins and protein isolation can take only seconds.

Fluorescence imaging of the nanoparticles modified with indocyanine green

NASA Astrophysics Data System (ADS)

Gareev, K. G.; Babikova, K. Y.; Postnov, V. N.; Naumisheva, E. B.; Korolev, D. V.

2017-11-01

The comparative research of silica, the magnetite and magnetite-silica nanoparticles modified with fluorescent dyes using gas-phase and liquid-phase methods was conducted. At the content of fluorescent dye comparable in size a particular spectrophotometric method, nanoparticles with fluorescein have up to 1000 times larger overall luminous efficiency. It is revealed that magnetic nanoparticles are characterized by a smaller light efficiency in comparison with silica particles, at the same time particles of a magnetite are most effective at modification with fluorescein, and magnetite-silica particles - at modification with indocyanine green.

Surface modification of graphene oxide nanosheets by protamine sulfate/sodium alginate for anti-cancer drug delivery application

NASA Astrophysics Data System (ADS)

Xie, Meng; Zhang, Feng; Liu, Lijiao; Zhang, Yanan; Li, Yeping; Li, Huaming; Xie, Jimin

2018-05-01

In order to improve the efficiency of anticancer drug delivery, a graphene oxide (GO) based drug delivery system modificated by natural peptide protamine sulfate (PRM) and sodium alginate (SA) was established via electrostatic attraction at each step of adsorption based on layer-by-layer self-assembly. The nanocomposites were then loaded with anticancer drug doxorubicin hydrochloride (DOX) to estimate the feasibility as drug carriers. The nanocomposites loaded with DOX revealed a remarkable pH-sensitive drug release property. The modification with protamine sulfate and sodium alginate could not only impart the nanocomposites an improved dispersibility and stability under physiological pH, but also suppress the protein adhesion. Due to the high water dispersibility and the small particle size, GO-PRM/SA nanocomposites were able to be uptaken by MCF-7 cells. It was found that GO-PRM/SA nanocomposites exhibited no obvious cytotoxicity towards MCF-7 cells, while GO-PRM/SA-DOX exhibited better cytotoxicity than GO-DOX. Therefore, the GO-PRM/SA nanocomposites were feasible as drug delivery vehicles.

In-line three-dimensional holography of nanocrystalline objects at atomic resolution

DOE PAGES

Chen, F. -R.; Van Dyck, D.; Kisielowski, C.

2016-02-18

We report that resolution and sensitivity of the latest generation aberration-corrected transmission electron microscopes allow the vast majority of single atoms to be imaged with sub-Ångstrom resolution and their locations determined in an image plane with a precision that exceeds the 1.9-pm wavelength of 300 kV electrons. Such unprecedented performance allows expansion of electron microscopic investigations with atomic resolution into the third dimension. Here we show a general tomographic method to recover the three-dimensional shape of a crystalline particle from high-resolution images of a single projection without the need for sample rotation. The method is compatible with low dose ratemore » electron microscopy, which improves on signal quality, while minimizing electron beam-induced structure modifications even for small particles or surfaces. Lastly, we apply it to germanium, gold and magnesium oxide particles, and achieve a depth resolution of 1–2 Å, which is smaller than inter-atomic distances.« less

Polypyrrole Coated Cellulosic Substrate Modified by Copper Oxide as Electrode for Nitrate Electroreduction

NASA Astrophysics Data System (ADS)

Hamam, A.; Oukil, D.; Dib, A.; Hammache, H.; Makhloufi, L.; Saidani, B.

2015-08-01

The aim of this work is to synthesize polypyrrole (PPy) films on nonconducting cellulosic substrate and modified by copper oxide particles for use in the nitrate electroreduction process. Firstly, the chemical polymerization of polypyrrole onto cellulosic substrate is conducted by using FeCl3 as an oxidant and pyrrole as monomer. The thickness and topography of the different PPy films obtained were estimated using a profilometer apparatus. The electrochemical reactivity of the obtained electrodes was tested by voltamperometry technique and electrochemical impedance spectroscopy. Secondly, the modification of the PPy film surface by incorporation of copper oxide particles is conducted by applying a galvanostatic procedure from a CuCl2 solution. The SEM, EDX and XRD analysis showed the presence of CuO particles in the polymer films with dimensions less than 50 nm. From cyclic voltamperometry experiments, the composite activity for the nitrate electroreduction reaction was evaluated and the peak of nitrate reduction is found to vary linearly with initial nitrate concentration.

The role of nanocrystalline binder metallic coating into WC after additive manufacturing

NASA Astrophysics Data System (ADS)

Cavaleiro, A. J.; Fernandes, C. M.; Farinha, A. R.; Gestel, C. V.; Jhabvala, J.; Boillat, E.; Senos, A. M. R.; Vieira, M. T.

2018-01-01

Tungsten carbide with microsized particle powders are commonly used embedded in a tough binder metal. The application of these composites is not limited to cutting tools, WC based material has been increasingly used in gaskets and other mechanical parts with complex geometries. Consequently, additive manufacturing processes as Selective Laser Sintering (SLS) might be the solution to overcome some of the manufacturing problems. However, the use of SLS leads to resolve the problems resulting from difference of physical properties between tungsten carbide and the metallic binder, such as laser absorbance and thermal conductivity. In this work, an original approach of powder surface modification was considered to prepare WC-metal composite powders and overcome these constraints, consisting on the sputter-coating of the WC particle surfaces with a nanocrystalline thin film of metallic binder material (stainless steel). The coating improves the thermal behavior and rheology of the WC particles and, at the same time, ensures a binder homogenous distribution. The feasibility of the SLS technology as manufacturing process for WC powder sputter-coated with 13 wt% stainless steel AISI 304L was explored with different laser power and scanning speed parameters. The SLS layers were characterized regarding elemental distribution, phase composition and morphology, and the results are discussed emphasizing the role of the coating on the consolidation process.

A study on the fabrication of superhydrophobic iron surfaces by chemical etching and galvanic replacement methods and their anti-icing properties

NASA Astrophysics Data System (ADS)

Li, Kunquan; Zeng, Xingrong; Li, Hongqiang; Lai, Xuejun

2015-08-01

Hierarchical structures on iron surfaces were constructed by means of chemical etching by hydrochloric acid (HCl) solution or the galvanic replacement by silver nitrate (AgNO3) solution. The superhydrophobic iron surfaces were successfully prepared by subsequent hydrophobic modification with stearic acid. The superhydrophobic iron surfaces were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and water contact angle (WCA). The effects of reactive concentration and time on the microstructure and the wetting behavior were investigated. In addition, the anti-icing properties of the superhydrophobic iron surfaces were also studied. The FTIR study showed that the stearic acid was chemically bonded onto the iron surface. With the HCl concentration increase from 4 mol/L to 8 mol/L, the iron surface became rougher with a WCA ranging from 127° to 152°. The AgNO3 concentration had little effect on the wetting behavior, but a high AgNO3 concentration caused Ag particle aggregates to transform from flower-like formations into dendritic crystals, owing to the preferential growth direction of the Ag particles. Compared with the etching method, the galvanic replacement method on the iron surface more favorably created roughness required for achieving superhydrophobicity. The superhydrophobic iron surface showed excellent anti-icing properties in comparison with the untreated iron. The icing time of water droplets on the superhydrophobic surface was delayed to 500 s, which was longer than that of 295 s for untreated iron. Meanwhile, the superhydrophobic iron surface maintained superhydrophobicity after 10 icing and de-icing cycles in cold conditions.

Self-standing elastomeric composites based on lithium ferrites and their dielectric behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soreto Teixeira, S.; Graça, M. P. F.; Costa, L. C.

2014-12-14

Lithium ferrite (LiFe{sub 5}O{sub 8}) is an attractive material for technological applications due to its physical properties, which are significantly dependent on the preparation method and raw materials. In this work, LiFe{sub 5}O{sub 8} crystallites were obtained by controlled heat-treatment process at 1100 °C, of a homogeneous mixture of Li{sub 2}O-Fe{sub 2}O{sub 3} powders, prepared by wet ball-milling and using lithium and iron nitrates as raw materials. The main goal was the preparation of a flexible and self-standing tick composite film by embedding lithium ferrite particles in a polymeric matrix, taking advantage of the good mechanical properties of the polymer andmore » of the electrical and dielectric properties of the ferrite. The selected polymer matrix was styrene-b-isoprene-b-styrene copolymer. To prepare the composites, the lithium ferrite particles were chemically modified in order to functionalize their surface. To analyse the influence of the particles surface modification, different composites were made, with modified and unmodified particles. The structure of the obtained composites was studied by FTIR, XRD, TGA, and DSC techniques. The dielectric properties were analysed, in the frequency range between 10 Hz and 1 MHz and in function of temperature in the range between −73 °C and 127 °C. These properties were related with the structure and concentration of the particles in the matrix network. The composites with the modified particles present higher dielectric constant, maintaining values of loss tangent sufficiently low (<10{sup −2}) that can be considered interesting for technological applications.« less

Nose-to-Brain Delivery: Investigation of the Transport of Nanoparticles with Different Surface Characteristics and Sizes in Excised Porcine Olfactory Epithelium.

PubMed

Mistry, Alpesh; Stolnik, Snjezana; Illum, Lisbeth

2015-08-03

The ability to deliver therapeutically relevant amounts of drugs directly from the nasal cavity to the central nervous system to treat neurological diseases is dependent on the availability of efficient drug delivery systems. Increased delivery and/or therapeutic effect has been shown for drugs encapsulated in nanoparticles; however, the factors governing the transport of the drugs and/or the nanoparticles from the nasal cavity to the brain are not clear. The present study evaluates the potential transport of nanoparticles across the olfactory epithelium in relation to nanoparticle characteristics. Model systems, 20, 100, and 200 nm fluorescent carboxylated polystyrene (PS) nanoparticles that were nonmodified or surface modified with polysorbate 80 (P80-PS) or chitosan (C-PS), were assessed for transport across excised porcine olfactory epithelium mounted in a vertical Franz diffusion cell. Assessment of the nanoparticle content in the donor chamber of the diffusion cell, accompanied by fluorescence microscopy of dismounted tissues, revealed a loss of nanoparticle content from the donor suspension and their association with the excised tissue, depending on the surface properties and particle size. Chitosan surface modification of PS nanoparticles resulted in the highest tissue association among the tested systems, with the associated nanoparticles primarily located in the mucus, whereas the polysorbate 80-modified nanoparticles showed some penetration into the epithelial cell layer. Assessment of the bioelectrical properties, metabolic activity, and histology of the excised olfactory epithelium showed that C-PS nanoparticles applied in pH 6.0 buffer produced a damaging effect on the epithelial cell layer in a size-dependent manner, with fine 20 nm sized nanoparticles causing substantial tissue damage relative to that with the 100 and 200 nm counterparts. Although histology showed that the olfactory tissue was affected by the application of citrate buffer that was augmented by addition of chitosan in solution, this was not reflected in the bioelectrical parameters and the metabolic activity of the tissue. Regarding transport across the excised olfactory tissue, none of the nanoparticle systems tested, irrespective of particle size or surface modification, was transported across the epithelium to appear in measurable amounts in the receiver chamber.

Palladium-zinc catalysts on mesoporous titania prepared by colloid synthesis. II. Synthesis and characterization of PdZn/TiO2 coating on inner surface of fused silica capillary

NASA Astrophysics Data System (ADS)

Okhlopkova, Lyudmila B.; Kerzhentsev, Michail A.; Tuzikov, Fedor V.; Larichev, Yurii V.; Ismagilov, Zinfer R.

2012-09-01

Nanoparticle-doped mesoporous titania coating was synthesized by incorporation of PdZn nanoparticles into TiO2 sol followed by dip coating of the sol on inner surface of fused silica capillary. Monodispersed PdZn bimetallic colloidal particles with average particle diameters of approximately 2 nm have been prepared by an ethylene glycol reduction of ZnCl2 and Pd(CH3COO)2 in the presence of polyvinylpyrrolidone. The textural properties, surface structure, chemical composition, and morphology of the samples were investigated by means of N2 sorption measurements, TEM, and X-ray diffraction. PdZn/TiO2 coating has been further analyzed by quantitative analysis of the SAXS data in combination with the density contrast method, providing direct structural-dispersion information about the active component and support. Calcination conditions suitable for surfactant removal have been optimized to obtain PdZn/TiO2 coatings with required metal particle size and composition. The high dispersion and chemical composition of the nanoparticles embedded in mesoporous titania coating have been retained with no modification after thermal treatment in vacuum at 300 °C. Results suggest how porous structure of the PdZn coating may be fine-tuned to improve the accessibility of the pores to reactants. The control of the pore size in the range of 4.9-6.8 nm of the mesoporous titania was achieved by adding co-surfactants, such as n-butanol.

Surface modification of PLGA nanoparticles by carbopol to enhance mucoadhesion and cell internalization.

PubMed

Surassmo, Suvimol; Saengkrit, Nattika; Ruktanonchai, Uracha Rungsardthong; Suktham, Kunat; Woramongkolchai, Noppawan; Wutikhun, Tuksadon; Puttipipatkhachorn, Satit

2015-06-01

Mucoadhesive poly (lactic-co-glycolic acid) (PLGA) nanoparticles having a modified shell-matrix derived from polyvinyl alcohol (PVA) and Carbopol (CP), a biodegradable polymer coating, to improve the adhesion and cell transfection properties were developed. The optimum formulations utilized a CP concentration in the range of 0.05-0.2%w/v, and were formed using modified emulsion-solvent evaporation technique. The resulting CP-PLGA nanoparticles were characterized in terms of their physical and chemical properties. The absorbed CP on the PLGA shell-matrix was found to affect the particle size and surface charge, with 0.05% CP giving rise to smooth spherical particles (0.05CP-PLGA) with the smallest size (285.90 nm), and strong negative surface charge (-25.70 mV). The introduction of CP results in an enhancement of the mucoadhesion between CP-PLGA nanoparticles and mucin particles. In vitro cell internalization studies highlighted the potential of 0.05CP-PLGA nanoparticles for transfection into SiHa cells, with uptake being time dependent. Additionally, cytotoxicity studies of CP-PLGA nanoparticles against SiHa cancer cells indicated that low concentrations of the nanoparticles were non-toxic to cells (cell viability >80%). From the various formulations studied, 0.05CP-PLGA nanoparticles proved to be the optimum model carrier having the required mucoadhesive profile and could be an alternative therapeutic efficacy carrier for targeted mucosal drug delivery systems with biodegradable polymer. Copyright © 2015 Elsevier B.V. All rights reserved.

Polystyrene Core-Silica Shell Particles with Defined Nanoarchitectures as a Versatile Platform for Suspension Array Technology.

PubMed

Sarma, Dominik; Gawlitza, Kornelia; Rurack, Knut

2016-04-19

The need for rapid and high-throughput screening in analytical laboratories has led to significant growth in interest in suspension array technologies (SATs), especially with regard to cytometric assays targeting a low to medium number of analytes. Such SAT or bead-based assays rely on spherical objects that constitute the analytical platform. Usually, functionalized polymer or silica (SiO2) microbeads are used which each have distinct advantages and drawbacks. In this paper, we present a straightforward synthetic route to highly monodisperse SiO2-coated polystyrene core-shell (CS) beads for SAT with controllable architectures from smooth to raspberry- and multilayer-like shells by varying the molecular weight of poly(vinylpyrrolidone) (PVP), which was used as the stabilizer of the cores. The combination of both organic polymer core and a structurally controlled inorganic SiO2 shell in one hybrid particle holds great promises for flexible next-generation design of the spherical platform. The particles were characterized by electron microscopy (SEM, T-SEM, and TEM), thermogravimetry, flow cytometry, and nitrogen adsorption/desorption, offering comprehensive information on the composition, size, structure, and surface area. All particles show ideal cytometric detection patterns and facile handling due to the hybrid structure. The beads are endowed with straightforward modification possibilities through the defined SiO2 shells. We successfully implemented the particles in fluorometric SAT model assays, illustrating the benefits of tailored surface area which is readily available for small-molecule anchoring. Very promising assay performance was shown for DNA hybridization assays with quantification limits down to 8 fmol.

Strongly correlated surface states

NASA Astrophysics Data System (ADS)

Alexandrov, Victor A.

Everything has an edge. However trivial, this phrase has dominated theoretical condensed matter in the past half a decade. Prior to that, questions involving the edge considered to be more of an engineering problem rather than a one of fundamental science: it seemed self-evident that every edge is different. However, recent advances proved that many surface properties enjoy a certain universality, and moreover, are 'topologically' protected. In this thesis I discuss a selected range of problems that bring together topological properties of surface states and strong interactions. Strong interactions alone can lead to a wide spectrum of emergent phenomena: from high temperature superconductivity to unconventional magnetic ordering; interactions can change the properties of particles, from heavy electrons to fractional charges. It is a unique challenge to bring these two topics together. The thesis begins by describing a family of methods and models with interactions so high that electrons effectively disappear as particles and new bound states arise. By invoking the AdS/CFT correspondence we can mimic the physical systems of interest as living on the surface of a higher dimensional universe with a black hole. In a specific example we investigate the properties of the surface states and find helical spin structure of emerged particles. The thesis proceeds from helical particles on the surface of black hole to a surface of samarium hexaboride: an f-electron material with localized magnetic moments at every site. Interactions between electrons in the bulk lead to insulating behavior, but the surfaces found to be conducting. This observation motivated an extensive research: weather the origin of conduction is of a topological nature. Among our main results, we confirm theoretically the topological properties of SmB6; introduce a new framework to address similar questions for this type of insulators, called Kondo insulators. Most notably we introduce the idea of Kondo band banding (KBB): a modification of edges and their properties due to interactions. We study (chapter 5) a simplified 1D Kondo model, showing that the topology of its ground state is unstable to KBB. Chapter 6 expands the study to 3D: we argue that not only KBB preserves the topology but it could also explain the experimentally observed anomalously high Fermi velocity at the surface as the case of large KBB effect.

He ion irradiation effects on multiwalled carbon nanotubes structure

NASA Astrophysics Data System (ADS)

Elsehly, Emad M.; Chechenin, Nikolay G.; Makunin, Alexey V.; Shemukhin, Andrey A.; Motaweh, Hussien A.

2017-03-01

Samples of multi-walled carbon nanotubes (MWNTs) were irradiated with 80 keV He ions. Scanning electron microscopy (SEM) inspection showed that the average outer diameters of the tube decreased as a result of ion irradiation. The samples were also characterized using Raman spectrometry by analysis of the intensity of main bands in the spectra of virgin and irradiated MWNT samples. Modifications of the disorder mode (D-band) and the tangential mode (G-band) were studied as a function of irradiation fluences. Raman spectra showed that as the fluence increases, the MWNTs first show disorder due to the produced defects, and then amorphization under still higher fluence of ion irradiation. Thermal and athermal mechanisms of the radiation induced MWNTs modifications are discussed. Contribution to the Topical Issue "Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces", edited by A.N. Grum-Grzhimailo, E.V. Gryzlova, Yu V. Popov, and A.V. Solov'yov.

An In Situ Method for Sizing Insoluble Residues in Precipitation and Other Aqueous Samples

PubMed Central

Axson, Jessica L.; Creamean, Jessie M.; Bondy, Amy L.; Capracotta, Sonja S.; Warner, Katy Y.; Ault, Andrew P.

2015-01-01

Particles are frequently incorporated into clouds or precipitation, influencing climate by acting as cloud condensation or ice nuclei, taking up coatings during cloud processing, and removing species through wet deposition. Many of these particles, particularly ice nuclei, can remain suspended within cloud droplets/crystals as insoluble residues. While previous studies have measured the soluble or bulk mass of species within clouds and precipitation, no studies to date have determined the number concentration and size distribution of insoluble residues in precipitation or cloud water using in situ methods. Herein, for the first time we demonstrate that Nanoparticle Tracking Analysis (NTA) is a powerful in situ method for determining the total number concentration, number size distribution, and surface area distribution of insoluble residues in precipitation, both of rain and melted snow. The method uses 500 μL or less of liquid sample and does not require sample modification. Number concentrations for the insoluble residues in aqueous precipitation samples ranged from 2.0–3.0(±0.3)×108 particles cm−3, while surface area ranged from 1.8(±0.7)–3.2(±1.0)×107 μm2 cm−3. Number size distributions peaked between 133–150 nm, with both single and multi-modal character, while surface area distributions peaked between 173–270 nm. Comparison with electron microscopy of particles up to 10 μm show that, by number, > 97% residues are <1 μm in diameter, the upper limit of the NTA. The range of concentration and distribution properties indicates that insoluble residue properties vary with ambient aerosol concentrations, cloud microphysics, and meteorological dynamics. NTA has great potential for studying the role that insoluble residues play in critical atmospheric processes. PMID:25705069

Lignosulfonate-stabilized selenium nanoparticles and their deposition on spherical silica.

PubMed

Modrzejewska-Sikorska, Anna; Konował, Emilia; Klapiszewski, Łukasz; Nowaczyk, Grzegorz; Jurga, Stefan; Jesionowski, Teofil; Milczarek, Grzegorz

2017-10-01

We report a novel room-temperature synthesis of selenium nanoparticles, which for the first time uses lignosulfonate as a stabilizer. Various lignosulfonates obtained both from hardwood and softwood were tested. Selenium oxide was used as the precursor of zero-valent selenium. Three different reducers were tested - sodium borohydride, hydrazine and ascorbic acid - and the latter proved most effective in terms of the particle size and stability of the final colloid. The lignosulfonate-stabilized selenium nanoparticles had a negative zeta potential, dependent on pH, which for some lignosulfonates reached -50mV, indicating the excellent stability of the colloid. When spherical silica particles were introduced to the synthesis mixture, selenium nanoparticles were deposited on their surface. Additionally, star-like structures consisting of sharp selenium needles with silica cores were observed. After drying, the selenium-functionalized silica had a grey metallic hue. The method reported here is simple and cost-effective, and can be used for the preparation of large quantities of selenium colloids or the surface modification of other materials with selenium. Copyright © 2017 Elsevier B.V. All rights reserved.

Oral Delivery of DMAB-Modified Docetaxel-Loaded PLGA-TPGS Nanoparticles for Cancer Chemotherapy

NASA Astrophysics Data System (ADS)

Chen, Hongbo; Zheng, Yi; Tian, Ge; Tian, Yan; Zeng, Xiaowei; Liu, Gan; Liu, Kexin; Li, Lei; Li, Zhen; Mei, Lin; Huang, Laiqiang

2011-12-01

Three types of nanoparticle formulation from biodegradable PLGA-TPGS random copolymer were developed in this research for oral administration of anticancer drugs, which include DMAB-modified PLGA nanoparticles, unmodified PLGA-TPGS nanoparticles and DMAB-modified PLGA-TPGS nanoparticles. Firstly, the PLGA-TPGS random copolymer was synthesized and characterized. DMAB was used to increase retention time at the cell surface, thus increasing the chances of particle uptake and improving oral drug bioavailability. Nanoparticles were found to be of spherical shape with an average particle diameter of around 250 nm. The surface charge of PLGA-TPGS nanoparticles was changed to positive after DMAB modification. The results also showed that the DMAB-modified PLGA-TPGS nanoparticles have significantly higher level of the cellular uptake than that of DMAB-modified PLGA nanoparticles and unmodified PLGA-TPGS nanoparticles. In vitro, cytotoxicity experiment showed advantages of the DMAB-modified PLGA-TPGS nanoparticle formulation over commercial Taxotere® in terms of cytotoxicity against MCF-7 cells. In conclusion, oral chemotherapy by DMAB-modified PLGA-TPGS nanoparticle formulation is an attractive and promising treatment option for patients.

Co-processing as a tool to improve aqueous dispersibility of cellulose ethers.

PubMed

Sharma, Payal; Modi, Sameer R; Bansal, Arvind K

2015-01-01

Cellulose ethers are important materials with numerous applications in pharmaceutical industry. They are widely employed as stabilizers and viscosity enhancers for dispersed systems, binders in granulation process and as film formers for tablets. These polymers, however, exhibit challenge during preparation of their aqueous dispersions. Rapid hydration of their surfaces causes formation of a gel that prevents water from reaching the inner core of the particle. Moreover, the surfaces of these particles become sticky, thus leading to agglomeration, eventually reducing their dispersion kinetics. Numerous procedures have been tested to improve dispersibility of cellulose ethers. These include the use of cross-linking agents, alteration in the synthesis process, adjustment of water content of cellulose ether, modification by attaching hydrophobic substituents and co-processing using various excipients. Among these, co-processing has provided the most encouraging results. This review focuses on the molecular mechanisms responsible for the poor dispersibility of cellulose ethers and the role of co-processing technologies in overcoming the challenge. An attempt has been made to highlight various co-processing techniques and specific role of excipients used for co-processing.

High Power Particle Beams and Pulsed Power for Industrial Applications

NASA Astrophysics Data System (ADS)

Bluhm, Hansjoachim; An, Wladimir; Engelko, Wladimir; Giese, Harald; Frey, Wolfgang; Heinzel, Annette; Hoppé, Peter; Mueller, Georg; Schultheiss, Christoph; Singer, Josef; Strässner, Ralf; Strauß, Dirk; Weisenburger, Alfons; Zimmermann, Fritz

2002-12-01

Several industrial scale projects with economic and ecologic potential are presently emanating from research and development in the fields of high power particle beams and pulsed power in Europe. Material surface modifications with large area pulsed electron beams are used to protect high temperature gas turbine blades and steel structures in Pb/Bi cooled accelerator driven nuclear reactor systems against oxidation and corrosion respectively. Channel spark electron beams are applied to deposit bio-compatible or bio-active layers on medical implants. Cell membranes are perforated with strong pulsed electric fields to extract nutritive substances or raw materials from the cells and to kill bacteria for sterilization of liquids. Eletrodynamic fragmentation devices are developed to reutilize concrete aggregates for the production of high quality secondary concrete. All activities have a large potential to contribute to a more sustainable economy.

Backscattered helium spectroscopy in the helium ion microscope: Principles, resolution and applications

NASA Astrophysics Data System (ADS)

van Gastel, R.; Hlawacek, G.; Dutta, S.; Poelsema, B.

2015-02-01

We demonstrate the possibilities and limitations for microstructure characterization using backscattered particles from a sharply focused helium ion beam. The interaction of helium ions with matter enables the imaging, spectroscopic characterization, as well as the nanometer scale modification of samples. The contrast that is seen in helium ion microscopy (HIM) images differs from that in scanning electron microscopy (SEM) and is generally a result of the higher surface sensitivity of the method. It allows, for instance, a much better visualization of low-Z materials as a result of the small secondary electron escape depth. However, the same differences in beam interaction that give HIM an edge over other imaging techniques, also impose limitations for spectroscopic applications using backscattered particles. Here we quantify those limitations and discuss opportunities to further improve the technique.

Smart and Fragrant Garment via Surface Modification of Cotton Fabric With Cinnamon Oil/Stimuli Responsive PNIPAAm/Chitosan Nano Hydrogels.

PubMed

Bashari, Azadeh; Hemmatinejad, Nahid; Pourjavadi, Ali

2017-09-01

This paper deals with obtaining aromatherapic textiles via applying stimuli-responsive poly N-isopropyl acryl amide (PNIPAAm) /chitosan (PNCS) nano hydrogels containing cinnamon oil on cotton fabric and looks into the treated fabric characteristics as an antibacterial and temperature/pH responsive fabric. The semi-batch surfactant-free dispersion polymerization method was proposed to the synthesis of PNCS nano particles. The incorporation of modified β -cyclodextrin ( β -CD) into the PNCS nanohydrogel was performed in order to prepare a hydrophobic(cinnamon oil) carrier embedded in stimuli-responsive nanohydrogel. The β -CD postloading process of cinnamon oil in to the hydrogel nano particles was performed via ultrasonic bath and exhaustion methods. The antibacterial activity of the treated fabrics at different temperatures demonstrated the preparing new functional bio-antibacterial fabrics with temperature responsiveness.

Modification of jet-like correlations in Pb-Au collisions at 158A GeV/c

NASA Astrophysics Data System (ADS)

Ceres Collaboration; Adamová, D.; Agakichiev, G.; Antończyk, D.; Appelshäuser, H.; Belaga, V.; Bielčíková, J.; Braun-Munzinger, P.; Busch, O.; Cherlin, A.; Damjanović, S.; Dietel, T.; Dietrich, L.; Drees, A.; Dubitzky, W.; Esumi, S. I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glässel, P.; Holeczek, J.; Kalisky, M.; Kniege, S.; Kushpil, V.; Maas, A.; Marín, A.; Milošević, J.; Milov, A.; Miśkowiec, D.; Panebrattsev, Yu.; Petchenova, O.; Petráček, V.; Pfeiffer, A.; Płoskoń, M.; Rak, J.; Ravinovich, I.; Rehak, P.; Sako, H.; Schmitz, W.; Schuchmann, S.; Sedykh, S.; Shimansky, S.; Stachel, J.; Šumbera, M.; Tilsner, H.; Tserruya, I.; Wessels, J. P.; Wienold, T.; Wurm, J. P.; Xie, W.; Yurevich, S.; Yurevich, V.

2009-07-01

Results of a two-particle correlation analysis of high-p charged particles in Pb-Au collisions at 158A GeV/c are presented. The data have been recorded by the CERES experiment at the CERN-SPS. The correlations are studied as function of transverse momentum, particle charge and collision centrality. We observe a jet-like structure in the vicinity of a high-p trigger particle and a broad back-to-back distribution. The yields of associated particles per trigger show a strong dependence on the trigger/associate charge combination. A comparison to PYTHIA confirms the jet-like pattern at the near-side but suggests a strong modification at the away-side, implying significant energy transfer of the hard-scattered parton to the medium.

Modifications of exposure to ambient particulate matter: Tackling bias in using ambient concentration as surrogate with particle infiltration factor and ambient exposure factor.

PubMed

Shi, Shanshan; Chen, Chen; Zhao, Bin

2017-01-01

Numerous epidemiological studies explored health risks attributed to outdoor particle pollution. However, a number of these studies routinely utilized ambient concentration as a surrogate for personal exposure to ambient particles. This simplification ignored the difference between indoor and outdoor concentrations of outdoor originated particles and may bias the estimate of particle-health associations. Intending to avoid the bias, particle infiltration factor (F inf ), which describes the penetration of outdoor particles in indoor environment, and ambient exposure factor (α), which represents the fraction of outdoor particles people are truly exposed to, are utilized as modification factors to modify outdoor particle concentration. In this study, the probabilistic distributions of annually-averaged and seasonally-averaged F inf and α were assessed for residences and residents in Beijing. F inf of a single residence and α of an individual was estimated based on the mechanisms governing particle outdoor-to-indoor migration and human time-activity pattern. With this as the core deterministic model, probabilistic distributions of F inf and α were estimated via Monte Carlo Simulation. Annually-averaged F inf of PM 2.5 and PM 10 for residences in Beijing tended to be log-normally distributed as lnN(-0.74,0.14) and lnN(-0.94,0.15) with geometric mean value as 0.47 and 0.39, respectively. Annually-averaged α of PM 2.5 and PM 10 for Beijing residents also tended to be log-normally distributed as lnN(-0.59,0.12) and lnN(-0.73,0.13) with geometric mean value as 0.55 and 0.48, respectively. As for seasonally-averaged results, F inf and α of PM 2.5 and PM 10 were largest in summer and smallest in winter. The obvious difference between these modification factors and unity suggested that modifications of ambient particle concentration need to be considered in epidemiological studies to avoid misclassifications of personal exposure to ambient particles. Moreover, considering the inter-individual difference of F inf and α may lead to a brand new perspective of particle-health associations in further epidemiological study. Copyright © 2016 Elsevier Ltd. All rights reserved.

Variation of the chemical reactivity of Thermus thermophilus HB8 ribosomal proteins as a function of pH.

PubMed

Running, William E; Reilly, James P

2010-10-01

Ribosomes occupy a central position in cellular metabolism, converting stored genetic information into active cellular machinery. Ribosomal proteins modulate both the intrinsic function of the ribosome and its interaction with other cellular complexes, such as chaperonins or the signal recognition particle. Chemical modification of proteins combined with mass spectrometric detection of the extent and position of covalent modifications is a rapid, sensitive method for the study of protein structure and flexibility. By altering the pH of the solution, we have induced non-denaturing changes in the structure of bacterial ribosomal proteins and detected these conformational changes by covalent labeling. Changes in ribosomal protein modification across a pH range from 6.6 to 8.3 are unique to each protein, and correlate with their structural environment in the ribosome. Lysine residues whose extent of modification increases as a function of increasing pH are on the surface of proteins, but in close proximity either to glutamate and aspartate residues, or to rRNA backbone phosphates. Increasing pH disrupts tertiary and quaternary interactions mediated by hydrogen bonding or ionic interactions, and regions of protein structure whose conformations are sensitive to these changes are of potential importance in modulating the flexibility of the ribosome or its interaction with other cellular complexes.

Plasmonic Library Based on Substrate-Supported Gradiential Plasmonic Arrays

PubMed Central

2014-01-01

We present a versatile approach to produce macroscopic, substrate-supported arrays of plasmonic nanoparticles with well-defined interparticle spacing and a continuous particle size gradient. The arrays thus present a “plasmonic library” of locally noncoupling plasmonic particles of different sizes, which can serve as a platform for future combinatorial screening of size effects. The structures were prepared by substrate assembly of gold-core/poly(N-isopropylacrylamide)-shell particles and subsequent post-modification. Coupling of the localized surface plasmon resonance (LSPR) could be avoided since the polymer shell separates the encapsulated gold cores. To produce a particle array with a broad range of well-defined but laterally distinguishable particle sizes, the substrate was dip-coated in a growth solution, which resulted in an overgrowth of the gold cores controlled by the local exposure time. The kinetics was quantitatively analyzed and found to be diffusion rate controlled, allowing for precise tuning of particle size by adjusting the withdrawal speed. We determined the kinetics of the overgrowth process, investigated the LSPRs along the gradient by UV–vis extinction spectroscopy, and compared the spectroscopic results to the predictions from Mie theory, indicating the absence of local interparticle coupling. We finally discuss potential applications of these substrate-supported plasmonic particle libraries and perspectives toward extending the concept from size to composition variation and screening of plasmonic coupling effects. PMID:25137554

Surface-Modified Nanocarriers for Nose-to-Brain Delivery: From Bioadhesion to Targeting

PubMed Central

Clementino, Adryana; Buttini, Francesca; Colombo, Gaia; Pescina, Silvia; Stanisçuaski Guterres, Silvia; Nicoli, Sara

2018-01-01

In the field of nasal drug delivery, nose-to-brain delivery is among the most fascinating applications, directly targeting the central nervous system, bypassing the blood brain barrier. Its benefits include dose lowering and direct brain distribution of potent drugs, ultimately reducing systemic side effects. Recently, nasal administration of insulin showed promising results in clinical trials for the treatment of Alzheimer’s disease. Nanomedicines could further contribute to making nose-to-brain delivery a reality. While not disregarding the need for devices enabling a formulation deposition in the nose’s upper part, surface modification of nanomedicines appears the key strategy to optimize drug delivery from the nasal cavity to the brain. In this review, nanomedicine delivery based on particle engineering exploiting surface electrostatic charges, mucoadhesive polymers, or chemical moieties targeting the nasal epithelium will be discussed and critically evaluated in relation to nose-to-brain delivery. PMID:29543755

Water-repellent coatings prepared by modification of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Chakradhar, R. P. S.; Dinesh Kumar, V.

Superhydrophobic coatings with a static water contact angle (WCA) > 150° were prepared by modifying ZnO nanoparticles with stearic acid (ZnO@SA). ZnO nanoparticles of size ˜14 nm were prepared by solution combustion method. X-ray diffraction (XRD) studies reveal that as prepared ZnO has hexagonal wurtzite structure whereas the modified coatings convert to zinc stearate. Field emission scanning electron micrographs (FE-SEM) show the dual morphology of the coatings exhibiting both particles and flakes. The flakes are highly fluffy in nature with voids and nanopores. Fourier transformed infrared (FTIR) spectrum shows the stearate ion co-ordinates with Zn2+ in the bidentate form. The surface properties such as surface free energy (γp) and work of adhesion (W) of the unmodified and modified ZnO coatings have been evaluated. The electron paramagnetic resonance (EPR) spectroscopy reveals that surface defects play a major role in the wetting behavior.

Functionalization of vertically aligned carbon nanotubes.

PubMed

Van Hooijdonk, Eloise; Bittencourt, Carla; Snyders, Rony; Colomer, Jean-François

2013-01-01

This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs). The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers) to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs.

Functionalization of vertically aligned carbon nanotubes

PubMed Central

Snyders, Rony; Colomer, Jean-François

2013-01-01

Summary This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs). The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers) to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs. PMID:23504581

Biosynthesis, characterisation and antimicrobial activity of silver nanoparticles using Hibiscus rosa-sinensis petals extracts.

PubMed

Nayak, Debasis; Ashe, Sarbani; Rauta, Pradipta Ranjan; Nayak, Bismita

2015-10-01

Green synthesis of metallic nanoparticles has lured the world from the chemical and physical approaches owing to its rapid, non-hazardous and economic aspect of production mechanism. In this study, silver nanoparticles (AgNPs) were synthesised using petal extracts of Hibiscus rosa-sinensis. The AgNPs displayed characteristic surface plasmon resonance peak at around 421 nm having a mean particle size of 76.25±0.17 nm and carried a charge of -41±0.2 mV. The X-ray diffraction patterns displayed typical peaks of face centred cubic crystalline silver. The surface morphology was characterised by scanning electron microscopy and atomic force microscopy. Fourier transform infrared spectroscopy studies confirmed the surface modifications of the functional groups for the synthesis of AgNPs. Furthermore, the synthesised AgNPs displayed proficient antimicrobial activity against pathogenic strains of Vibrio cholerae, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus.

Selective depression of titanaugite in the ilmenite flotation with carboxymethyl starch

NASA Astrophysics Data System (ADS)

Meng, Qingyou; Yuan, Zhitao; Yu, Li; Xu, Yuankai; Du, Yusheng; Zhang, Chen

2018-05-01

In order to intensify the flotation separation of ilmenite from titanaugite, surface modification of mineral particles was carried out using carboxymethyl starch (CMS) by microflotation experiments, zeta potential measurements, Fourier transform infrared (FTIR) and atomic force microscopy (AFM) analysis. Microflotation results showed that CMS was a selective depressant, and it effectively enhanced the floatability difference between ilmenite and titanaugite in the pH range from 6.0 to 10.0. As it was revealed by the zeta potential, FTIR and AFM analysis, the CMS adsorption occurred onto mineral surfaces through chemisorption and hydrogen bonding, while CMS exhibited a stronger interaction with titanaugite than ilmenite. After that, the CMS adsorption impeded the adsorption of sodium oleate collector on titanaugite surfaces, giving rise to a concomitant decrease in the floatability of titanaugite. These findings exhibit great potential for CMS application in the selective flotation of ilmenite.

a Study of Dynamic Powder Consolidation Based on a Particle-Level Mathematical Model.

NASA Astrophysics Data System (ADS)

Williamson, Richard L.

A mathematical model is developed to investigate the effects of large amplitude shock waves on powder materials during dynamic consolidation. The model is constructed at the particle level, focusing on a region containing a few powder particles and the surrounding interstices. The general equations of continuum mechanics are solved over this region, using initial and boundary conditions appropriate for the consolidation process. Closure of the equation system is obtained using an analytical equation of state; relations are included to account for solid to liquid phase changes. An elastic, perfectly-plastic constitutive law, specifically modified to describe material behavior at high-strain-rates, is applied to the solid materials. To reduce complexity, the model is restricted to two dimensions, therefore individual particles are approximated as infinitely long cylinders rather than spheres. The equation system is solved using standard finite-difference numerical techniques. It is demonstrated that for typical consolidation conditions, energy diffusion mechanisms are insignificant during the rapid densification phase of consolidation. Using type 304 stainless steel powder material, the particle-level model is used to investigate the mechanisms responsible for particle surface heating and metallurgical bonding during consolidation. It is demonstrated that energy deposition near particle surfaces results both from rapid particle deformation during interstitial filling and large localized impacts occurring at the final instant of interstitial closure; particle interior regions remain at sufficiently low temperatures to avoid microstructural modification. Nonuniform metallurgical bonding is predicted around the particle periphery, ranging from complete fusion to mechanical abutment. Simulation results are used to investigate the detailed wave propagation phenomena at the particle level, providing an improved understanding of this complex behavior. A variety of parametric studies are conducted including investigations of the effects of stress wave amplitude and rise time, the role of interstitial gases during consolidation, and various geometric aspects including the importance of initial void fraction. The model is applied to a metal matrix composite system to investigate the consolidation of mixtures of differing materials; results of a two-dimensional experiment are included. Available experimental data are compared with simulation results. In general, very good agreement between simulation results and data is obtained.

Tunable Pickering Emulsions with Environmentally Responsive Hairy Silica Nanoparticles.

PubMed

Liu, Min; Chen, Xiaoli; Yang, Zongpeng; Xu, Zhou; Hong, Liangzhi; Ngai, To

2016-11-30

Surface modification of the nanoparticles using surface anchoring of amphiphilic polymers offers considerable scope for the design of a wide range of brush-coated hybrid nanoparticles with tunable surface wettability that may serve as new class of efficient Pickering emulsifiers. In the present study, we prepared mixed polymer brush-coated nanoparticles by grafting ABC miktoarm star terpolymers consisting of poly(ethylene glycol), polystyrene, and poly[(3-triisopropyloxysilyl)propyl methacrylate] (μ-PEG-b-PS-b-PIPSMA) on the surface of silica nanoparticles. The wettability of the as-prepared nanoparticles can be precisely tuned by a change of solvent or host-guest complexation. 1 H NMR result confirmed that such wettability change is due to the reorganization of the polymer chain at the grafted layer. We show that this behavior can be used for stabilization and switching between water-in-oil (W/O) and oil-in-water (O/W) emulsions. For hairy particles initially dispersed in oil, W/O emulsions were always obtained with collapsed PEG chains and mobile PS chains at the grafted layer. However, initially dispersing the hairy particles in water resulted in O/W emulsions with collapsed PS chains and mobile PEG chains. When a good solvent for both PS and PEG blocks such as toluene was used, W/O emulsions were always obtained no matter where the hairy particles were dispersed. The wettability of the mixed polymer brush-coated silica particles can also be tuned by host-guest complexation between PEG block and α-CD. More importantly, our result showed that surprisingly the resultant mixed brush-coated hairy nanoparticles can be employed for the one-step production of O/W/O multiple emulsions that are not attainable from conventional Pickering emulsifiers. The functionalized hairy silica nanoparticles at the oil-water interface can be further linked together utilizing poly(acrylic acid) as the reversible linker to form supramolecular colloidosomes, which show pH-dependent release of cargo.

Highly selective isolation and purification of heme proteins in biological samples using multifunctional magnetic nanospheres.

PubMed

Liu, Yating; Li, Yan; Wei, Yun

2014-12-01

Magnetic particles with suitable surface modification are capable of binding proteins selectively, and magnetic separations have advantages of rapidity, convenience, and high selectivity. In this paper, new magnetic nanoparticles modified with imidazolium ionic liquid (Fe3O4 @SiO2 @ILs) were successfully fabricated. N-Methylimidazolium was immobilized onto silica-coated magnetic nanoparticles via γ-chloropropyl modification as a magnetic nanoadsorbent for heme protein separation. The particle size was about 90 nm without significant aggregation during the preparation process. Hemoglobin as one of heme proteins used in this experiment was compared with other nonheme proteins. It has been found that the magnetic nanoparticles can be used for more rapid, efficient, and specific adsorption of hemoglobin with a binding capacity as high as 5.78 mg/mg. In comparison with other adsorption materials of proteins in the previous reports, Fe3 O4 @SiO2 @ILs magnetic nanoparticles exhibit the excellent performance in isolation of heme proteins with higher binding capacity and selectivity. In addition, a short separation time makes the functionalized nanoparticles suitable for purifying unstable proteins, as well as having other potential applications in a variety of biomedical fields. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic light emitting diode with surface modification layer

DOEpatents

Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

2017-09-12

An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

Influence of multiple-passes on microstructure and mechanical properties of Al-Mg/SiC surface composites fabricated via underwater friction stir processing

NASA Astrophysics Data System (ADS)

Srivastava, Manu; Rathee, Sandeep; Maheshwari, Sachin; Siddiquee, Arshad Noor

2018-06-01

Friction stir processing (FSP) is a relatively newly developed solid-state process involving surface modifications for fabricating metal matrix surface composites. Obtaining metal matrix nano-composites with uniform dispersion of reinforcement particles via FSP route is an intricate task to accomplish. In this work, AA5059/SiC nano surface composites (SCs) were developed. Effect of multiple FSP passes and SiC addition on microstructure and mechanical properties of fabricated SCs during underwater condition was investigated. Results reflected that the average microhardness value of base metal (BM) increases from 85 Hv to 159 Hv in stir zone of four pass underwater friction stir processed (FSPed) SC. Highest ultimate tensile strength (UTS) achieved during four pass FSPed sample was 377 MPa that is higher than UTS of BM (321 MPa) and four pass FSPed sample developed at ambient air FSP conditions (347 MPa). An appreciably narrower heat affected zone is obtained owing to fast cooling and reduced heat conduction during underwater FSP, amounting to higher UTS as compared to BM and SC at ambient conditions. Thus, it can be concluded that surrounding medium and number of FSP passes have significant impact on mechanical properties of fabricated SCs. Analysis of microstructures and distribution of SiC particles in fabricated SCs were studied by optical microscope and FESEM respectively and found in good corroboration with the mechanical properties.

Rapid and extensive debromination of decabromodiphenyl ether by smectite clay-templated subnanoscale zero-valent iron.

PubMed

Yu, Kai; Gu, Cheng; Boyd, Stephen A; Liu, Cun; Sun, Cheng; Teppen, Brian J; Li, Hui

2012-08-21

Subnanoscale zerovalent iron (ZVI) synthesized using smectite clay as a template was utilized to investigate reduction of decabromodiphenyl ether (DBDE). The results revealed that DBDE was rapidly debrominated by the prepared smectite-templated ZVI with a reaction rate 10 times greater than that by conventionally prepared nanoscale ZVI. This enhanced reduction is plausibly attributed to the smaller-sized smectite-templated ZVI clusters (∼0.5 nm) vs that of the conventional nanoscale ZVI (∼40 nm). The degradation of DBDE occurred in a stepwise debromination manner. Pentabromodiphenyl ethers were the terminal products in an alkaline suspension (pH 9.6) of smectite-templated ZVI, whereas di-, tri-, and tetrabromodiphenyl ethers formed at the neutral pH. The presence of tetrahydrofuran (THF) as a cosolvent at large volume fractions (e.g., >70%) in water reduced the debromination rates due to enhanced aggregation of clay particles and/or diminished adsorption of DBDE to smectite surfaces. Modification of clay surfaces with tetramethylammonium (TMA) attenuated the colsovent effect on the aggregation of clay particles, resulting in enhanced debromination rates. Smectite clay provides an ideal template to form subnanoscale ZVI, which demonstrated superior debromination reactivity with DBDE compared with other known forms of ZVIs. The ability to modify the nature of smectite clay surface by cation exchange reaction utilizing organic cations can be harnessed to create surface properties compatible with various contaminated sites.

Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Owen, Jonathan; Park, Jungwon; Trudeau, Paul-Emile

Chemical modification of nanocrystal surfaces is fundamentally important to their assembly, their implementation in biology and medicine, and greatly impacts their electrical and optical properties. However, it remains a major challenge owing to a lack of analytical tools to directly determine nanoparticle surface structure. Early nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) studies of CdSe nanocrystals prepared in tri-n-octylphosphine oxide (1) and tri-n-octylphosphine (2), suggested these coordinating solvents are datively bound to the particle surface. However, assigning the broad NMR resonances of surface-bound ligands is complicated by significant concentrations of phosphorus-containing impurities in commercial sources of 1, andmore » XPS provides only limited information about the nature of the phosphorus containing molecules in the sample. More recent reports have shown the surface ligands of CdSe nanocrystals prepared in technical grade 1, and in the presence of alkylphosphonic acids, include phosphonic and phosphinic acids. These studies do not, however, distinguish whether these ligands are bound datively, as neutral, L-type ligands, or by X-type interaction of an anionic phosphonate/phosphinate moiety with a surface Cd{sup 2+} ion. Answering this question would help clarify why ligand exchange with such particles does not proceed generally as expected based on a L-type ligand model. By using reagents with reactive silicon-chalcogen and silicon-chlorine bonds to cleave the ligands from the nanocrystal surface, we show that our CdSe and CdSe/ZnS core-shell nanocrystal surfaces are likely terminated by X-type binding of alkylphosphonate ligands to a layer of Cd{sup 2+}/Zn{sup 2+} ions, rather than by dative interactions. Further, we provide spectroscopic evidence that 1 and 2 are not coordinated to our purified nanocrystals.« less

Can soil drying affect the sorption of pesticides in soil?

NASA Astrophysics Data System (ADS)

Chaplain, Véronique; Saint, Philippe; Mamy, Laure; Barriuso, Enrique

2010-05-01

The sorption of pesticides in soils mainly controls their further dispersion into the environment. Sorption is usually related to the physico-chemical properties of molecules but it also depends on the hydrophobic features of soils. However, the hydrophobicity of soils changes with wetting and drying cycles and this can be enhanced with climate change. The objective of this study was to measure by using controlled artificial soils the influence of the hydrophobic characteristic of soils on the retention of a model pesticide. Artificial soils consisted in silica particles covered by synthetic cationic polymers. Polymers were characterized by the molar ratio of monomers bearing an alkyl chain of 12C. Two polymers were used, with 20 and 80 % ratios, and the same degree of polymerization. In addition, porous and non-porous particles were used to study the accessibility notion and to measure the influence of diffusion on pesticide sorption kinetics. Lindane was chosen as model molecule because its adsorption is supposed mainly due to hydrophobic interactions. Results on polymers adsorption on silica showed that it was governed by electrostatic interactions, without any dependency of the hydrophobic ratio. Polymers covered the entire surface of porous particles. Kinetic measurements showed that lindane sorption was slowed in porous particles due to the molecular diffusion inside the microporosity. The adsorption of lindane on covered silica particles corresponded to a partition mechanism described by linear isotherms. The slope was determined by the hydrophobic ratio of polymers: the sorption of lindane was highest in the most hydrophobic artificial soil. As a result, modification in soil hydrophobicity, that can happen with climate change, might affect the sorption and the fate of pesticides. However additional experiments are needed to confirm these first results. Such artificial soils should be used as reference materials to compare the reactivity of pesticides, to identify the main adsorption mechanisms, and to study the effect of modifications in soil physico-chemical properties on the fate of pesticides.

Impact of laser-contaminant interaction on the performance of the protective capping layer of 1w high-reflection mirror coatings

DOE PAGES

Qiu, S. R.; Norton, M. A.; Raman, R. N.; ...

2015-10-02

In this paper, high dielectric constant multilayer coatings are commonly used on high-reflection mirrors for high-peak-power laser systems because of their high laser-damage resistance. However, surface contaminants often lead to damage upon laser exposure, thus limiting the mirror’s lifetime and performance. One plausible approach to improve the overall mirror resistance against laser damage, including that induced by laser-contaminant coupling, is to coat the multilayers with a thin protective capping (absentee) layer on top of the multilayer coatings. An understanding of the underlying mechanism by which laser-particle interaction leads to capping layer damage is important for the rational design and selectionmore » of capping materials of high-reflection multilayer coatings. In this paper, we examine the responses of two candidate capping layer materials, made of SiO 2 and Al 2O 3, over silica-hafnia multilayer coatings. These are exposed to a single oblique shot of a 1053 nm laser beam (fluence ~10 J/cm 2, pulse length 14 ns), in the presence of Ti particles on the surface. We find that the two capping layers show markedly different responses to the laser-particle interaction. The Al 2O 3 cap layer exhibits severe damage, with the capping layer becoming completely delaminated at the particle locations. The SiO 2 capping layer, on the other hand, is only mildly modified by a shallow depression. Combining the observations with optical modeling and thermal/mechanical calculations, we argue that a high-temperature thermal field from plasma generated by the laser-particle interaction above a critical fluence is responsible for the surface modification of each capping layer. The great difference in damage behavior is mainly attributed to the large disparity in the thermal expansion coefficient of the two capping materials, with that of Al 2O 3 layer being about 15 times greater than that of SiO 2.« less

Impact of laser-contaminant interaction on the performance of the protective capping layer of 1w high-reflection mirror coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiu, S. R.; Norton, M. A.; Raman, R. N.

In this paper, high dielectric constant multilayer coatings are commonly used on high-reflection mirrors for high-peak-power laser systems because of their high laser-damage resistance. However, surface contaminants often lead to damage upon laser exposure, thus limiting the mirror’s lifetime and performance. One plausible approach to improve the overall mirror resistance against laser damage, including that induced by laser-contaminant coupling, is to coat the multilayers with a thin protective capping (absentee) layer on top of the multilayer coatings. An understanding of the underlying mechanism by which laser-particle interaction leads to capping layer damage is important for the rational design and selectionmore » of capping materials of high-reflection multilayer coatings. In this paper, we examine the responses of two candidate capping layer materials, made of SiO 2 and Al 2O 3, over silica-hafnia multilayer coatings. These are exposed to a single oblique shot of a 1053 nm laser beam (fluence ~10 J/cm 2, pulse length 14 ns), in the presence of Ti particles on the surface. We find that the two capping layers show markedly different responses to the laser-particle interaction. The Al 2O 3 cap layer exhibits severe damage, with the capping layer becoming completely delaminated at the particle locations. The SiO 2 capping layer, on the other hand, is only mildly modified by a shallow depression. Combining the observations with optical modeling and thermal/mechanical calculations, we argue that a high-temperature thermal field from plasma generated by the laser-particle interaction above a critical fluence is responsible for the surface modification of each capping layer. The great difference in damage behavior is mainly attributed to the large disparity in the thermal expansion coefficient of the two capping materials, with that of Al 2O 3 layer being about 15 times greater than that of SiO 2.« less

Modification of Roberts' Theory for Rocket Exhaust Plumes Eroding Lunar Soil

NASA Technical Reports Server (NTRS)

Metzger, Philip T.; Lane, John E.; Immer, Christopher D.

2008-01-01

Roberts' model of lunar soil erosion beneath a landing rocket has been updated in several ways to predict the effects of future lunar landings. The model predicts, among other things, the number of divots that would result on surrounding hardware due to the impact of high velocity particulates, the amount and depth of surface material removed, the volume of ejected soil, its velocity, and the distance the particles travel on the Moon. The results are compared against measured results from the Apollo program and predictions are made for mitigating the spray around a future lunar outpost.

Generic approach for synthesizing asymmetric nanoparticles and nanoassemblies

DOEpatents

Sun, Yugang; Hu, Yongxing

2015-05-26

A generic route for synthesis of asymmetric nanostructures. This approach utilizes submicron magnetic particles (Fe.sub.3O.sub.4--SiO.sub.2) as recyclable solid substrates for the assembly of asymmetric nanostructures and purification of the final product. Importantly, an additional SiO.sub.2 layer is employed as a mediation layer to allow for selective modification of target nanoparticles. The partially patched nanoparticles are used as building blocks for different kinds of complex asymmetric nanostructures that cannot be fabricated by conventional approaches. The potential applications such as ultra-sensitive substrates for surface enhanced Raman scattering (SERS) have been included.

Prospects for spinel-stabilized, high-capacity lithium-ion battery cathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Croy, Jason R.; Park, Joong Sun; Shin, Youngho

Herein we report early results on efforts to optimize the electrochemical performance of a cathode composed of a lithium- and manganese-rich “layered-layered-spinel” material for lithium-ion battery applications. Pre-pilot scale synthesis leads to improved particle properties compared with lab-scale efforts, resulting in high capacities (≳200 mAh/g) and good energy densities (>700 Wh/kg) in tests with lithium-ion cells. Subsequent surface modifications give further improvements in rate capabilities and high-voltage stability. These results bode well for advances in the performance of this class of lithium- and manganese-rich cathode materials.

Prospects for spinel-stabilized, high-capacity lithium-ion battery cathodes

DOE PAGES

Croy, Jason R.; Park, Joong Sun; Shin, Youngho; ...

2016-10-13

Herein we report early results on efforts to optimize the electrochemical performance of a cathode composed of a lithium- and manganese-rich “layered-layered-spinel” material for lithium-ion battery applications. Pre-pilot scale synthesis leads to improved particle properties compared with lab-scale efforts, resulting in high capacities (≳200 mAh/g) and good energy densities (>700 Wh/kg) in tests with lithium-ion cells. Subsequent surface modifications give further improvements in rate capabilities and high-voltage stability. These results bode well for advances in the performance of this class of lithium- and manganese-rich cathode materials.

Nanogold as NEMS platform: past, present, and future

NASA Astrophysics Data System (ADS)

Cornejo-Monroy, Delfino; Acosta-Torres, Laura S.; Castaño, Victor M.

2012-06-01

Gold has been a biomedical material since ancient times. We shall review the historical uses of gold, in different forms as well as the properties of this metal, which make it very attractive for MEMS and NEMS applications. In particular, we will discuss the synthesis and physic-chemical characteristics of nano particles of gold, emphasizing the role of surface modification, which enables the nano gold to act as a true nano reactor or a nano platform to develop various functions at the nanoscale. Finally, we will describe the use of nano gold for drug targeting and disease detection.

Investigations into the behaviour of Plasma surrounding Pulsars: DYMPHNA3D

NASA Astrophysics Data System (ADS)

Rochford, Ronan; Mc Donald, John; Shearer, Andy

2011-08-01

We report on a new 3D fully relativistic, modular, parallel and scalable Particle-In-Cell (PIC) code currently being developed at the Computational Astrophysics Laboratory in the National University of Ireland, Galway and its initial test applications to the plasma distribution in the vicinity of a rapidly rotating neutron star. We find that Plasma remains confined by trapping surfaces close to the star as opposed to propagating to a significant portion of the light-cylinder distance as predicted in this early work. We discuss planned future modifications and applications of the developed code.

Quantification of electrical field-induced flow reversal in a microchannel.

PubMed

Pirat, C; Naso, A; van der Wouden, E J; Gardeniers, J G E; Lohse, D; van den Berg, A

2008-06-01

We characterize the electroosmotic flow in a microchannel with field effect flow control. High resolution measurements of the flow velocity, performed by micro particle image velocimetry, evidence the flow reversal induced by a local modification of the surface charge due to the presence of the gate. The shape of the microchannel cross-section is accurately extracted from these measurements. Experimental velocity profiles show a quantitative agreement with numerical results accounting for this exact shape. Analytical predictions assuming a rectangular cross-section are found to give a reasonable estimate of the velocity far enough from the walls.

Carbonyl iron powder surface modification of magnetorheological elastomers for vibration absorbing application

NASA Astrophysics Data System (ADS)

Chen, Dong; Yu, Miao; Zhu, Mi; Qi, Song; Fu, Jie

2016-11-01

With excellent characteristic of magnetic-control stiffness, magnetorheological elastomer (MRE) is well suited as a spring element of vibration absorber. To improve the vibration attenuation performance of MRE vibration absorbers, this paper expects to improve the mechanical strength and reduce the loss factor of MRE by interface modification. The surface of carbonyl iron powder (CIP) was modified with silica coating by a simple and convenient approach. Several MRE samples, with different proportions of modified CIPs were fabricated under a constant magnetic field. The morphology and composition of modified CIP were characterized by scanning electron microscope and Fourier transform infrared spectra. The results indicated that the modified CIPs were coated with uniform and continuous silica, which can make a better combination between particle and matrix. The tensile strength, magnetorheological properties and the damping properties of the MRE samples were tested by material testing machine and rheometer. The experimental results demonstrated that the loss factor of the MRE which incorporated with modified CIPs decreased markedly, and the tensile strength of such material has been much improved, at the same time this kind of MRE kept high MR effect. It is expected that this MRE material will meet the requirements of vibration absorber.

M13 bacteriophage display framework that allows sortase-mediated modification of surface-accessible phage proteins.

PubMed

Hess, Gaelen T; Cragnolini, Juan J; Popp, Maximilian W; Allen, Mark A; Dougan, Stephanie K; Spooner, Eric; Ploegh, Hidde L; Belcher, Angela M; Guimaraes, Carla P

2012-07-18

We exploit bacterial sortases to attach a variety of moieties to the capsid proteins of M13 bacteriophage. We show that pIII, pIX, and pVIII can be functionalized with entities ranging from small molecules (e.g., fluorophores, biotin) to correctly folded proteins (e.g., GFP, antibodies, streptavidin) in a site-specific manner, and with yields that surpass those of any reported using phage display technology. A case in point is modification of pVIII. While a phage vector limits the size of the insert into pVIII to a few amino acids, a phagemid system limits the number of copies actually displayed at the surface of M13. Using sortase-based reactions, a 100-fold increase in the efficiency of display of GFP onto pVIII is achieved. Taking advantage of orthogonal sortases, we can simultaneously target two distinct capsid proteins in the same phage particle and maintain excellent specificity of labeling. As demonstrated in this work, this is a simple and effective method for creating a variety of structures, thus expanding the use of M13 for materials science applications and as a biological tool.

An M13 bacteriophage display framework that allows sortase-mediated modification of surface-accessible phage proteins

PubMed Central

Hess, Gaelen T.; Cragnolini, Juan J.; Popp, Maximilian W.; Allen, Mark A.; Dougan, Stephanie K.; Spooner, Eric; Ploegh, Hidde L.; Belcher, Angela M.; Guimaraes, Carla P.

2013-01-01

We exploit bacterial sortases to attach a variety of moieties to the capsid proteins of M13 bacteriophage. We show that pIII, pIX, and pVIII can be functionalized with entities ranging from small molecules (e.g., fluorophores, biotin) to correctly folded proteins (e.g., GFP, antibodies, streptavidin) in a site-specific manner, and with yields that surpass those of any reported using phage display technology. A case in point is modification of pVIII. While a phage vector limits the size of the insert into pVIII to a few amino acids, a phagemid system limits the number of copies actually displayed at the surface of M13. Using sortase-based reactions, a 100-fold increase in the efficiency of display of GFP onto pVIII is achieved. Taking advantage of orthogonal sortases, we can simultaneously target two distinct capsid proteins in the same phage particle and maintain excellent specificity of labeling. As demonstrated in this work, this is a simple and effective method for creating a variety of structures, thus expanding the use of M13 for materials science applications and as a biological tool. PMID:22759232

Friction Stir Processing of Particle Reinforced Composite Materials

PubMed Central

Gan, Yong X.; Solomon, Daniel; Reinbolt, Michael

2010-01-01

The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned.

Design and synthesis of magnetic nanoparticles with gold shells for single particle optical tracking

NASA Astrophysics Data System (ADS)

Lim, Jitkang

The design, synthesis, and characterization of iron oxide core, gold shell nanoparticles are studied in this thesis. Firstly, nanoparticles with 18 +/- 1.7 nm diameter iron oxide cores with ˜5 nm thick gold shells were synthesized via a new seed-mediated electroless deposition method. The nanoparticles were superparamagnetic at room temperature and could be reversibly collected by a permanent magnet. These nanoparticles displayed a sharp localized surface plasmon resonance peak at 605 nm, as predicted by scattering theory, and their large scattering cross-section allowed them to be individually resolved in darkfield optical microscopy while undergoing Brownian motion in aqueous suspension. Later, commercially available 38 +/- 3.8 nm diameter spherical iron oxide nanoparticles (from Ocean Nanotech, Inc) were employed to make core-shell particles. These particles were decorated with cationic poly(diallyldimethylammonium chloride) (PDDA) which further promotes the attachment of small gold clusters. After gold seeding, the average hydrodynamic diameter of the core-shell particles is 172 +/- 65.9 nm. The magnetophoretic motion of these particles was guided by a piece of magnetized mu-metal. Individual particle trajectories were observed by darkfield optical microscopy. The typical magnetophoretic velocity achieved was within the range of 1--10 mum/sec. Random walk analysis performed on these particles while undergoing Brownian motion confirmed that individual particles were indeed being imaged. The particle size variation within the observed sample obtained through random walk analysis was within the size distribution obtained by dynamic light scattering. When the current to the solenoid used to magnetize the mu-metal was turned off, all the collected core-shell particles were readily redispersed by diffusion back into the surrounding environment. A Peclet number analysis was performed to probe the convective motion of nanospheres and nanorods under the influence of magnetophoresis and diffusion. Under most circumstances, magnetophoretic behavior dominates diffusion for nanorods, as the magnetic field lines tend to align the magnetic moment along the rod axis. The synthesis and dispersion of fluorophore-tagged nanorods are described. Fluorescence microscopy was employed to image the nanorod motion in a magnetic field gradient. The preliminary experimental data are consistent with the Peclet number analysis. Lastly, the colloidal stability of iron oxide core, gold shell nanoparticles in high ionic strength media was investigated. Such particles are sufficiently charged to be stable against flocculation without modification in low ionic strength media, but they require surface modification to be stably dispersed in elevated ionic strength media that are appropriate for biotechnological applications. Dynamic light scattering and ultraviolet-visible spectrophotometry were used to monitor the colloidal stability of core-shell particles in pH 7.4, 150 mM ionic strength phosphate buffered saline (PBS). While uncoated particles flocculated immediately upon being introduced into PBS, core-shell particles with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than five days in PBS. Adsorbed dextran allowed flocculation that was limited to the formation of small clusters, while poly(ethylene glycol) homopolymers ranging in molecular weight from 6,000 to 100,000 were ineffective steric stabilizers. The effectiveness of adsorbed Pluronic copolymers as steric stabilizers was interpreted in terms of the measured adsorbed layer thickness and extended DLVO theory predictions of the interparticle interactions.

Improving sedimentation stability of magnetorheological fluids using an organic molecular particle coating

NASA Astrophysics Data System (ADS)

Cheng, Haibin; Wang, Ming; Liu, Chaosheng; Wereley, Norman M.

2018-07-01

A key goal for implementation of magnetorheological fluids (MRFs) is to minimize sedimentation or to increase suspension stability. In this study, a series of MRF samples were synthesized by suspending carbonyl iron particles (CIPs), which had different organic molecules and auxiliaries grafted onto their surface, in silicone oil. The magnetorheology of these MRF samples was measured using a magneto-rheometer, and their sedimentation behaviors were quantitatively evaluated using a thermal conductivity sedimentation measurement method. The effect of these coatings on the stability of the MRFs was analyzed. Results show that all of the MRFs exhibit good MR effects and that the surface modification does not greatly weaken the MR effect. Suspension stability was substantially improved by grafting organic molecular structures onto the surface of the CIPs, and the sedimentation rate was influenced by the organic molecule structure. Compared to the uncoated CIPs, when the organic molecule was changed from octyl acyl ethylenediamine triacetate (C7H15COED3A) to lauryl acyl ethylenediamine triacetate (C11H23COED3A) and stearyl acyl ethylenediamine triacetate (C17H35COED3A), the sedimentation rate decreased by 53.9% to 64.2% and 75.1%, respectively. The mechanisms of how organic molecular structure affects the stability of MRFs are discussed.

Characterization of silica particles modified with γ-methacryloxypropyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Jiang, Jun; Wang, Wang; Shen, Haiying; Wang, Jiamin; Cao, Jinzhen

2017-03-01

The surface of hydrophilic silica particles was modified with different concentrations (2, 4, 6, 8 and 10%) of γ-methacryloxypropyltrimethoxysilane (MPTS). The hydrophobicity and hygroscopicity of unmodified and modified silica were investigated through water contact angle (WCA) tests and dynamic vapor sorption (DVS) method, respectively. The results showed that the surface properties of silica were closely related with the MPTS concentration. Within the range of MPTS concentration applied, 8% MPTS modified silica showed the least aggregation. With the increasing MPTS concentration, the WCAs on modified silica film increased correspondingly, and finally exceeded 90° at 6% and 8% concentrations. The equilibrium moisture contents (EMCs) of modified silica also decreased with the increasing MPTS concentration. The improvement on hydrophobicity can be correlated with the reduction of residual hydroxyl groups (-OH) on modified silica. The self-condensation of MPTS began to occur at concentrations higher than 4%, especially at 8%. Owing to this effect, the modified silica with 8% MPTS showed a slightly higher EMC than 6% MPTS within low relative humidity (RH) range up to 40%. At a higher RH ranging from 40 to 90%, 8% group showed the lowest EMCs because of its highest hydrophobicity and low specific surface area. A mechanism concerning the MPTS modification of silica was also proposed in this study based on the research results.

Enhanced antibacterial activity and biocompatibility of zinc-incorporated organic-inorganic nanocomposite coatings via electrophoretic deposition.

PubMed

Huang, Pin; Ma, Kena; Cai, Xinjie; Huang, Dan; Yang, Xu; Ran, Jiabing; Wang, Fushi; Jiang, Tao

2017-12-01

Increased use of reconstruction procedures in orthopedics has improved the life of patients undergoing surgery. However, surgical site infection remains a major challenge. Efforts were made to fabricate antibacterial surfaces with good biocompatibility. This present study aimed to fabricate zinc-incorporated chitosan/gelatin (CS/G) nanocomposite coatings on the titanium substrates via electrophoretic deposition (EPD). Physicochemical characterization confirmed that zinc was successfully deposited in a metallic oxide/salt complex status. Transmission electron microscopic (TEM) results observed formation of core-shell nanosized particles released from the coatings. The selected-area electron diffraction (SAED) pattern of the particles presented faces of ZnO with organic background. Mechanical tests showed improved tensile and shear bond strength between substrates and zinc-incorporated coating surfaces. Zinc-incorporated CS/G coatings presented antibacterial abilities against both Gram-negative E. coli and Gram-positive S. aureus in a concentration-dependent manner. The generation of ZnO/Zn 2+ complex in the coatings may contribute to bacteria inhibition. In vitro study demonstrated that appropriate concentration of zinc could promote proliferative and osteogenic activities of rat bone marrow stromal cells. The present study suggested that zinc-incorporated CS/G coating was a promising candidate for surface modification of biomedical materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Apparently enhanced magnetization of Cu(I)-modified γ-Fe2O3 based nanoparticles

NASA Astrophysics Data System (ADS)

Qiu, Xiaoyan; He, Zhenghong; Mao, Hong; Zhang, Ting; Lin, Yueqiang; Liu, Xiaodong; Li, Decai; Meng, Xiangshen; Li, Jian

2017-11-01

Using a chemically induced transition method in FeCl2 solution, γ-Fe2O3 based magnetic nanoparticles, in which γ-Fe2O3 crystallites were coated with FeCl3ṡ6H2O, were prepared. During the synthesis of the γ-Fe2O3 nanoparticles Cu(I) modification of the particles was attempted. According to the results from both magnetization measurements and structural characterization, it was judged that a magnetic silent "dead layer", which can be attributed to spin disorder in the surface of the γ-Fe2O3 crystallites due to breaking of the crystal symmetry, existed in the unmodified particles. For the Cu(I)-modified sample, the CuCl thin layer on the γ-Fe2O3 crystallites incurred the crystal symmetry to reduce the spin disorder, which "awakened" the "dead layer" on the surface of the γ-Fe2O3 crystallites, enhancing the apparent magnetization of the Cu(I)-modified nanoparticles. It was determined that the surface spin disorder of the magnetic crystallite could be related to the coating layer on the crystallite, and can be modified by altering the coating layer to enhance the effective magnetization of the magnetic nanoparticles.

Development of stable low-electroosmotic mobility coatings. [for use in electrophoresis systems in space

NASA Technical Reports Server (NTRS)

Vanderhoff, J. W.; Micale, F. J.

1979-01-01

Long-time rinsings of the Z6040-methlycellulose coating used successfully on the ASTP MA=011 experiment indicate the permanency of this coating is inadequate for continuous flowing systems. Two approaches are described for developing coatings which are stable under continuous fluid movement and which exhibit finite and predictable electroosmotic mobility values while being effective on different types of surfaces, such as glass, plastics, and ceramic alumina, such as is currently used as the electrophoresis channel in the GE-SPAR-CPE apparatus. The surface charge modification of polystyrene latex, especially by protein absorption, to be used as model materials for ground-based electrophoresis experiments, and the preliminary work directed towards the seeded polymerization of large-particle-size monodisperse latexes in a microgravity environment are discussed.

Ligand exchange and MIP-based paraoxon memories onto QCM sensor

NASA Astrophysics Data System (ADS)

Birlik Özkütük, Ebru; Emir Diltemiz, Sibel; Özalp, Elif; Uzun, Lokman; Ersöz, Arzu

2015-04-01

In this study, we have aimed to prepare quartz crystal microbalance (QCM) sensor using paraoxon-imprinted particles. Firstly, methacryloyl antipyrine (MAAP)-based metal-chelate-coordinated pre-complex has been prepared and used for paraoxon templation. Then, paraoxon-imprinted nanofilms were formed on QCM sensor after modification of the gold surfaces with allyl mercaptan. By this way, specific and selective memories, which depend on metal-chelate interactions between Eu(III) ions and template, for paraoxon molecules have been obtained on the electrode surface. QCM sensor has characterized using AFM and ellipsometer. The detection limit and the affinity constant have found to be 0.09 μM and 5.71 × 103 M-1 for MAAP-Eu paraoxon-based nanofilm, respectively. The specificity of the QCM sensor has shown using parathion as a competitor molecule.

Synthesis of Silver Polymer Nanocomposites and Their Antibacterial Activity

NASA Astrophysics Data System (ADS)

Gavade, Chaitali; Shah, Sunil; Singh, N. L.

2011-07-01

PVA (Polyvinyl Alcohol) silver nanocomposites of different sizes were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and amine hydrazine as a reducing agent. The formation of the silver nanoparticles was noticed using UV- visible absorption spectroscopy. The UV-visible spectroscopy revealed the formation of silver nanoparticles by exhibiting the surface plasmon resonance. The bactericidal activity due to silver release from the surface was determined by the modification of conventional diffusion method. Salmonella typhimurium, Serratia sps and Shigella sps were used as test bacteria which are gram-negative type bacteria. Effect of the different sizes of silver nano particles on antibacterial efficiency was discussed. Zones of inhibition were measured after 24 hours of incubation at 37 °C which gave 20 mm radius for high concentration of silver nanoparticles.

Helical plant viral nanoparticles-bioinspired synthesis of nanomaterials and nanostructures.

PubMed

Narayanan, Kannan Badri; Han, Sung Soo

2017-05-19

Viral nanotechnology is revolutionizing the biomimetic and bioinspired synthesis of novel nanomaterials. Bottom-up nanofabrication by self-assembly of individual molecular components of elongated viral nanoparticles (VNPs) and virus-like particles (VLPs) has resulted in the production of superior materials and structures in the nano(bio)technological fields. Viral capsids are attractive materials, because of their symmetry, monodispersity, and polyvalency. Helical VNPs/VLPs are unique prefabricated nanoscaffolds with large surface area to volume ratios and high aspect ratios, and enable the construction of exquisite supramolecular nanostructures. This review discusses the genetic and chemical modifications of outer, inner, and interface surfaces of a viral protein cage that will almost certainly lead to the development of superior next-generation targeted drug delivery and imaging systems, biosensors, energy storage and optoelectronic devices, therapeutics, and catalysts.

Modification of silicon nitride surfaces with GOPES and APTES for antibody immobilization: computational and experimental studies

NASA Astrophysics Data System (ADS)

Dien To, Thien; Nguyen, Anh Tuan; Nhat Thanh Phan, Khoa; Thu Thi Truong, An; Doan, Tin Chanh Duc; Mau Dang, Chien

2015-12-01

Chemical modification of silicon nitride (SiN) surfaces by silanization has been widely studied especially with 3-(aminopropyl)triethoxysilane (APTES) and 3-(glycidyloxypropyl) dimethylethoxysilane (GOPES). However few reports performed the experimental and computational studies together. In this study, surface modification of SiN surfaces with GOPES and APTES covalently bound with glutaraldehyde (GTA) was investigated for antibody immobilization. The monoclonal anti-cytokeratin-FITC (MACF) antibody was immobilized on the modified SiN surfaces. The modified surfaces were characterized by water contact angle measurements, atomic force microscopy and fluorescence microscopy. The FITC-fluorescent label indicated the existence of MACF antibody on the SiN surfaces and the efficiency of the silanization reaction. Absorption of APTES and GOPES on the oxidized SiN surfaces was computationally modeled and calculated by Materials Studio software. The computational and experimental results showed that modification of the SiN surfaces with APTES and GTA was more effective than the modification with GOPES.

Laser surface modification of Ti and TiC coatings on magnesium alloy

NASA Astrophysics Data System (ADS)

Kim, J. M.; Lee, S. G.; Park, J. S.; Kim, H. G.

2014-12-01

In order to enhance the surface properties of magnesium alloy, a highly intense laser surface melting process following plasma spraying of Ti or TiC on AZ31 alloy were employed. When laser surface melting was applied to Ti coated magnesium alloy, the formation of fine Ti particle dispersed surface layer on the substrate occurred. The corrosion potential of the AZ31 alloy with Ti dispersed surface was significantly increased in 3.5 wt % NaCl solution. Additionally, an improved hardness was observed for the laser treated specimens as compared to the untreated AZ31 alloy. Laser melting process following plasma thermal deposition was also applied for obtaining in situ TiC coating layer on AZ31 alloy. The TiC coating layer could be successfully formed via in situ reaction between pure titanium and carbon powders. Incomplete TiC formation was observed in the plasma sprayed specimen, while completely transformed TiC layer was found after post laser melting process. It was also confirmed that the laser post treatment induced enhanced adhesion strength between the coating and the substrate.

Improving dissolution and oral bioavailability of pranlukast hemihydrate by particle surface modification with surfactants and homogenization

PubMed Central

Ha, Eun-Sol; Baek, In-hwan; Yoo, Jin-Wook; Jung, Yunjin; Kim, Min-Soo

2015-01-01

The present study was carried out to develop an oral formulation of pranlukast hemihydrate with improved dissolution and oral bioavailability using a surface-modified microparticle. Based on solubility measurements, surface-modified pranlukast hemihydrate microparticles were manufactured using the spray-drying method with hydroxypropylmethyl cellulose, sucrose laurate, and water and without the use of an organic solvent. The hydrophilicity of the surface-modified pranlukast hemihydrate microparticle increased, leading to enhanced dissolution and oral bioavailability of pranlukast hemihydrate without a change in crystallinity. The surface-modified microparticles with an hydroxypropylmethyl cellulose/sucrose laurate ratio of 1:2 showed rapid dissolution of up to 85% within 30 minutes in dissolution medium (pH 6.8) and oral bioavailability higher than that of the commercial product, with approximately 2.5-fold and 3.9-fold increases in area under the curve (AUC0→12 h) and peak plasma concentration, respectively. Therefore, the surface-modified microparticle is an effective oral drug delivery system for the poorly water-soluble therapeutic pranlukast hemihydrate. PMID:26150699

Antimicrobial activity of transition metal acid MoO(3) prevents microbial growth on material surfaces.

PubMed

Zollfrank, Cordt; Gutbrod, Kai; Wechsler, Peter; Guggenbichler, Josef Peter

2012-01-01

Serious infectious complications of patients in healthcare settings are often transmitted by materials and devices colonised by microorganisms (nosocomial infections). Current strategies to generate material surfaces with an antimicrobial activity suffer from the consumption of the antimicrobial agent and emerging multidrug-resistant pathogens amongst others. Consequently, materials surfaces exhibiting a permanent antimicrobial activity without the risk of generating resistant microorganisms are desirable. This publication reports on the extraordinary efficient antimicrobial properties of transition metal acids such as molybdic acid (H(2)MoO(4)), which is based on molybdenum trioxide (MoO(3)). The modification of various materials (e.g. polymers, metals) with MoO(3) particles or sol-gel derived coatings showed that the modified materials surfaces were practically free of microorganisms six hours after contamination with infectious agents. The antimicrobial activity is based on the formation of an acidic surface deteriorating cell growth and proliferation. The application of transition metal acids as antimicrobial surface agents is an innovative approach to prevent the dissemination of microorganisms in healthcare units and public environments. Copyright © 2011 Elsevier B.V. All rights reserved.

Novel microstructural growth in the surface of Inconel 625 by the addition of SiC under electron beam melting

NASA Astrophysics Data System (ADS)

Ahmad, M.; Ali, G.; Ahmed, Ejaz; Haq, M. A.; Akhter, J. I.

2011-06-01

Electron beam melting is being used to modify the microstructure of the surfaces of materials due to its ability to cause localized melting and supercooling of the melt. This article presents an experimental study on the surface modification of Ni-based superalloy (Inconel 625) reinforced with SiC ceramic particles under electron beam melting. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques have been applied to characterize the resulted microstructure. The results revealed growth of novel structures like wire, rod, tubular, pyramid, bamboo and tweezers type morphologies in the modified surface. In addition to that fibrous like structure was also observed. Formation of thin carbon sheet has been found at the regions of decomposed SiC. Electron beam modified surface of Inconel 625 alloy has been hardened twice as compared to the as-received samples. Surface hardening effect may be attributed to both the formation of the novel structures as well as the introduction of Si and C atom in the lattice of Inconel 625 alloy.

Morphology and inhibition performance of Ag thin film as antimicrobial coating deposited by RF-PVD on 316 L stainless steel

NASA Astrophysics Data System (ADS)

Purniawan, A.; Khrisna, Y. S. A.; Rasyida, A.; Atmono, T. M.

2018-04-01

Foreign body related infection (FBRIs) is caused by forming biofilm of bacterial colony of medical equipment surfaces. In many cases, the FBRIs is still happened on the surface after medical sterilization process has been performed. In order to avoid the case, surface modification by antimicrobial coating was used. In this work, we present silver (Ag) thin film on 316 L stainless steel substrate surface was deposited using Radio Frequency Sputtering PVD (RF-PVD). The morphology of Ag thin film were characterized using SEM-EDX. Surface roughness of the thin film was measured by AFM. In addition, Kirby Bauer Test in Escherichia coli (E. coli) was conducted in order to evaluate the inhibition performance of the Ag thin film antimicrobial coating. Based on SEM and AFM results show that the particle size is increased from 523 nm to 708 nm and surface roughness from 9 to 20 nm for deposition time 10 minutes to 20 minutes, respectively. In addition, the inhibition layer of the coating is about 29 mm.

Surface Structure as a Foundation of Nanotechnology

NASA Astrophysics Data System (ADS)

Robinson, Ian

2007-03-01

The three generations of synchrotron sources achieved to date, parasitic, dedicated and undulator-based, have each time revolutionized the field of X-ray diffraction. Surface structure determination, demonstrated (but very difficult) already with Coolidge tube sources, benefited from the enormous flux gain in the first generation, such as SSRL. Dedicated 2nd-generation sources, such as NSLS, allowed in-situ surface preparation and reliable steady beams to be available when a surface was ready to measure. Third generation sources, such as APS, enormously improved the brightness, hence coherence, and thus allowed access to the surfaces of nanoparticles. This talk will illustrate how these technological advances led to two significant scientific breakthroughs. The concept of crystal truncation rods (CTR) led to new views of how the surface is a modification of, but still an extension of the bulk crystal structure. The development of lensless coherent x-ray diffraction (CXD) imaging has allowed access to the structure of nanocrystalline materials by three-dimensional phase mapping of the particle interiors. The structural principles of these new nano materials are being investigated at present using these new methods.

Surface modification to prevent oxide scale spallation

DOEpatents

Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A

2013-07-16

A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

Hayabusa2 Sampler: Collection of Asteroidal Surface Material

NASA Astrophysics Data System (ADS)

Sawada, Hirotaka; Okazaki, Ryuji; Tachibana, Shogo; Sakamoto, Kanako; Takano, Yoshinori; Okamoto, Chisato; Yano, Hajime; Miura, Yayoi; Abe, Masanao; Hasegawa, Sunao; Noguchi, Takaaki

2017-07-01

Japan Aerospace Exploration Agency (JAXA) launched the asteroid exploration probe "Hayabusa2" in December 3rd, 2014, following the 1st Hayabusa mission. With technological and scientific improvements from the Hayabusa probe, we plan to visit the C-type asteroid 162137 Ryugu (1999 JU3), and to sample surface materials of the C-type asteroid that is likely to be different from the S-type asteroid Itokawa and contain more pristine materials, including organic matter and/or hydrated minerals, than S-type asteroids. We developed the Hayabusa2 sampler to collect a minimum of 100 mg of surface samples including several mm-sized particles at three surface locations without any severe terrestrial contamination. The basic configuration of the sampler design is mainly as same as the 1st Hayabusa (Yano et al. in Science, 312(5778):1350-1353, 2006), with several minor but important modifications based on lessons learned from the Hayabusa to fulfill the scientific requirements and to raise the scientific value of the returned samples.

Uptake and bio-reactivity of polystyrene nanoparticles is affected by surface modifications, ageing and LPS adsorption: in vitro studies on neural tissue cells

NASA Astrophysics Data System (ADS)

Murali, Kumarasamy; Kenesei, Kata; Li, Yang; Demeter, Kornél; Környei, Zsuzsanna; Madarász, Emilia

2015-02-01

Because of their capacity of crossing an intact blood-brain barrier and reaching the brain through an injured barrier or via the nasal epithelium, nanoparticles have been considered as vehicles to deliver drugs and as contrast materials for brain imaging. The potential neurotoxicity of nanoparticles, however, is not fully explored. Using particles with a biologically inert polystyrene core material, we investigated the role of the chemical composition of particle surfaces in the in vitro interaction with different neural cell types. PS NPs within a size-range of 45-70 nm influenced the metabolic activity of cells depending on the cell-type, but caused toxicity only at extremely high particle concentrations. Neurons did not internalize particles, while microglial cells ingested a large amount of carboxylated but almost no PEGylated NPs. PEGylation reduced the protein adsorption, toxicity and cellular uptake of NPs. After storage (shelf-life >6 months), the toxicity and cellular uptake of NPs increased. The altered biological activity of ``aged'' NPs was due to particle aggregation and due to the adsorption of bioactive compounds on NP surfaces. Aggregation by increasing the size and sedimentation velocity of NPs results in increased cell-targeted NP doses. The ready endotoxin adsorption which cannot be prevented by PEG coating, can render the particles toxic. The age-dependent changes in otherwise harmless NPs could be the important sources for variability in the effects of NPs, and could explain the contradictory data obtained with ``identical'' NPs.Because of their capacity of crossing an intact blood-brain barrier and reaching the brain through an injured barrier or via the nasal epithelium, nanoparticles have been considered as vehicles to deliver drugs and as contrast materials for brain imaging. The potential neurotoxicity of nanoparticles, however, is not fully explored. Using particles with a biologically inert polystyrene core material, we investigated the role of the chemical composition of particle surfaces in the in vitro interaction with different neural cell types. PS NPs within a size-range of 45-70 nm influenced the metabolic activity of cells depending on the cell-type, but caused toxicity only at extremely high particle concentrations. Neurons did not internalize particles, while microglial cells ingested a large amount of carboxylated but almost no PEGylated NPs. PEGylation reduced the protein adsorption, toxicity and cellular uptake of NPs. After storage (shelf-life >6 months), the toxicity and cellular uptake of NPs increased. The altered biological activity of ``aged'' NPs was due to particle aggregation and due to the adsorption of bioactive compounds on NP surfaces. Aggregation by increasing the size and sedimentation velocity of NPs results in increased cell-targeted NP doses. The ready endotoxin adsorption which cannot be prevented by PEG coating, can render the particles toxic. The age-dependent changes in otherwise harmless NPs could be the important sources for variability in the effects of NPs, and could explain the contradictory data obtained with ``identical'' NPs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06849a

Influence of alumina coating on characteristics and effects of SiO2 nanoparticles in algal growth inhibition assays at various pH and organic matter contents.

PubMed

Van Hoecke, Karen; De Schamphelaere, Karel A C; Ramirez-Garcia, Sonia; Van der Meeren, Paul; Smagghe, Guy; Janssen, Colin R

2011-08-01

Silica nanoparticles (NPs) belong to the industrially most important NP types. In a previous study it was shown that amorphous SiO(2) NPs of 12.5 and 27.0 nm are stable in algal growth inhibition assays and that their ecotoxic effects are related to NP surface area. Here, it was hypothesized and demonstrated that an alumina coating completely alters the particle-particle, particle-test medium and particle-algae interactions of SiO(2) NPs. Therefore, stability and surface characteristics, dissolution, nutrient adsorption and effects on algal growth rate of both alumina coated SiO(2) NPs and bare SiO(2) NPs in OECD algal test medium as a function of pH (6.0-8.6) and natural organic matter (NOM) contents (0-12 mg C/l) were investigated. Alumina coated SiO(2) NPs aggregated in all media and adsorbed phosphate depending on pH and NOM concentration. On the other hand, no aggregation or nutrient adsorption was observed for the bare SiO(2) NPs. Due to their positive surface charge, alumina coated SiO(2) NPs agglomerated with Pseudokirchneriella subcapitata. Consequently, algal cell density measurements based on cell counts were unreliable and hence fluorescent detection of extracted chlorophyll was the preferred method. Alumina coated SiO(2) NPs showed lower toxicity than bare SiO(2) NPs at concentrations ≥46 mg/l, except at pH 6.0. At low concentrations, no clear pH effect was observed for alumina coated SiO(2) NPs, while at higher concentrations phosphate deficiency could have contributed to the higher toxicity of those particles at pH 6.0-6.8 compared to higher pH values. Bare SiO(2) NPs were not toxic at pH 6.0 up to 220 mg/l. Addition of NOM decreased toxicity of both particles. For SiO(2) NPs the 48 h 20% effect concentration of 21.8 mg/l increased 2.6-21 fold and a linear relationship was observed between NOM concentration and effective concentrations. No effect was observed for alumina coated SiO(2) NPs in presence of NOM up to 1000 mg/l. All experiments point out that the alumina coating completely altered NP interactions. Due to the difference in surface composition the SiO(2) NPs, which had the smallest surface area, were more toxic to the alga than the alumina coated SiO(2) NPs. Hence, surface modification can dominate the effect of surface area on toxicity. Copyright © 2011 Elsevier Ltd. All rights reserved.

Amphiphilic semi-interpenetrating polymer networks using pulverized rubber

NASA Astrophysics Data System (ADS)

Shahidi, Nima

Scrap rubber materials provide a significant challenge to either reuse or safe disposal. Every year, millions of tires are discarded to landfills in the United States, consuming a staggering amount of land space, creating a high risk for large fires, breeding mosquitoes that spread diseases, and wasting the planet's natural resources. This situation cannot be sustained. The challenge of reusing scrap rubber materials is mainly due to the crosslinked structure of vulcanized rubber that prevent them from melting and further processing for reuse. The most feasible recycling approach is believed to be a process in which the vulcanized rubber is first pulverized into a fine powder and then incorporated into new products. The production of fine rubber particles is generally accomplished through the use of a cryogenic process that is costly. Therefore, development of a cost effective technology that utilizes a large quantity of the scrap rubber materials to produce high value added materials is an essential element in maintaining a sustainable solution to rubber recycling. In this research, a cost effective pulverization process, solid state shear extrusion (SSSE), was modified and used for continuous pulverization of the rubber into fine particles. In the modified SSSE process, pulverization takes place at high compressive shear forces and a controlled temperature. Furthermore, an innovative particle modification process was developed to enhance the chemical structure and surface properties of the rubber particles for manufacturing of high value added products. Modification of rubber particles was accomplished through the polymerization of a hydrophilic monomer mixture within the intermolecular structure of the hydrophobic rubber particles. The resulting composite particles are considered as amphiphilic particulate phase semi-interpenetrating polymer networks (PPSIPNs). The modified rubber particles are water dispersible and suitable for use in a variety of aqueous media applications such as additives to waterborne emulsions. This innovative process for the first time opened up the application of rubber particles in aqueous media. The kinetics of polymerization reaction of hydrophilic monomer mixture within the rubber particles was investigated based on the assumption of partitioning of acrylic acid monomer in the hydrophobic rubber particles. The produced PPSIPNs were used as additives to waterborne emulsions and the mechanical and physical properties of the prepared coatings were examined. It was observed that the PPSIPNs could be added in high quantities with an improvement in adhesion, enhancement of the impact strength, and hardness of the coatings. This approach aims to develop environmentally benign products from scrap rubber materials.

Atmospheric pressure plasma jet's characterization and surface wettability driven by neon transformer

NASA Astrophysics Data System (ADS)

Elfa, R. R.; Nafarizal, N.; Ahmad, M. K.; Sahdan, M. Z.; Soon, C. F.

2017-03-01

Atmospheric pressure plasma driven by Neon transformer power supply argon is presented in this paper. Atmospheric pressure plasma system has attracted researcher interest over low pressure plasma as it provides a flexibility process, cost-efficient, portable device and vacuum-free device. Besides, another golden key of this system is the wide promising application in the field of work cover from industrial and engineering to medical. However, there are still numbers of fundamental investigation that are necessary such as device configuration, gas configuration and its effect. Dielectric barrier discharge which is also known as atmospheric pressure plasma discharge is created when there is gas ionization process occur which enhance the movement of atom and electron and provide energetic particles. These energetic particles can provide modification and cleaning property to the sample surface due to the bombardment of the high reactive ion and radicals to the sample surface. In order to develop atmospheric pressure plasma discharge, a high voltage and high frequency power supply is needed. In this work, we used a neon transformer power supply as the power supply. The flow of the Ar is feed into 10 mm cylinder quartz tube with different treatment time in order to investigate the effect of the plasma discharge. The analysis of each treatment time is presented by optical emission spectroscopy (OES) and water contact angle (WCA) measurement. The increase of gas treatment time shows increases intensity of reactive Ar and reduces the angle of water droplets in water contact angle. Treatment time of 20 s microslide glass surface shows that the plasma needle discharges have modified the sample surface from hydrophilic surface to superhydrophilic surface. Thus, this leads to another interesting application in reducing sample surface adhesion to optimize productivity in the industry of paintings, semiconductor and more.

Rubber particle proteins REF1 and SRPP1 interact differently with native lipids extracted from Hevea brasiliensis latex.

PubMed

Wadeesirisak, Kanthida; Castano, Sabine; Berthelot, Karine; Vaysse, Laurent; Bonfils, Frédéric; Peruch, Frédéric; Rattanaporn, Kittipong; Liengprayoon, Siriluck; Lecomte, Sophie; Bottier, Céline

2017-02-01

Rubber particle membranes from the Hevea latex contain predominantly two proteins, REF1 and SRPP1 involved in poly(cis-1,4-isoprene) synthesis or rubber quality. The repartition of both proteins on the small or large rubber particles seems to differ, but their role in the irreversible coagulation of the rubber particle is still unknown. In this study we highlighted the different modes of interactions of both recombinant proteins with different classes of lipids extracted from Hevea brasiliensis latex, and defined as phospholipids (PL), glycolipids (GL) and neutral lipids (NL). We combined two biophysical methods, polarization modulated-infrared reflection adsorption spectroscopy (PM-IRRAS) and ellipsometry to elucidate their interactions with monolayers of each class of lipids. REF1 and SRPP1 interactions with native lipids are clearly different; SRPP1 interacts mostly in surface with PL, GL or NL, without modification of its structure. In contrast REF1 inserts deeply in the lipid monolayers with all lipid classes. With NL, REF1 is even able to switch from α-helice conformation to β-sheet structure, as in its aggregated form (amyloid form). Interaction between REF1 and NL may therefore have a specific role in the irreversible coagulation of rubber particles. Copyright © 2016 Elsevier B.V. All rights reserved.

Peptide-controlled access to the interior surface of empty virus nanoparticles.

PubMed

Sainsbury, Frank; Saunders, Keith; Aljabali, Alaa A A; Evans, David J; Lomonossoff, George P

2011-11-04

The structure of Cowpea mosaic virus (CPMV) is known to high resolution, thereby enabling the rational use of the particles in diverse applications, from vaccine design to nanotechnology. A recently devised method for the production of empty virus-like particles (eVLPs) has opened up new possibilities for CPMV capsid-based technologies, such as internal mineralisation of the particle. We have investigated the role of the carboxyl (C) terminus of the small coat (S) protein in controlling access to the interior of CPMV eVLPs by determining the efficiency of internal mineralisation. The presence of the C-terminal 24-amino acid peptide of the S protein was found to inhibit internal mineralisation, an effect that could be eliminated by enzymatic removal of this region. We have also demonstrated the amenability of the C terminus to genetic modification. Substitution with six histidine residues generated stable particles and facilitated external mineralisation by cobalt. These findings demonstrate consistent internal and external mineralisation of CPMV, and will aid the further exploration and development of the use of eVLPs for bionanotechnological and medical applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modification of Ag nanoparticles on the surface of SrTiO3 particles and resultant influence on photoreduction of CO2

NASA Astrophysics Data System (ADS)

Shao, Kunjuan; Wang, Yanjie; Iqbal, Muzaffar; Lin, Lin; Wang, Kai; Zhang, Xuehua; He, Meng; He, Tao

2018-03-01

Modification of a wide-bandgap semiconductor with noble metals that can exhibit surface plasmon effect is an effective approach to make it responsive to the visible light. In this work, a series of cubic and all-edge-truncated SrTiO3 with and without thermal pretreatment in air are modified by Ag nanoparticles via photodeposition method. The crystal structure, morphology, loading amount of Ag nanoparticles, and optical properties of the obtained Ag-SrTiO3 nanomaterials are well characterized by powder X-ray diffraction, scanning microscope, transmission electron microscope, energy disperse X-ray spectroscopy, ICP-MS and UV-vis diffuse-reflection spectroscopy. The loading amount and size of the Ag nanoparticles can be controlled to some extent by tuning the photodeposition time via growth-dissolution mechanism. The Ag nanoparticles are inclined to deposit on different locations on the surface of cubic and truncated SrTiO3 with and without thermal pretreatment. The resultant SrTiO3 modified by Ag nanoparticles exhibits visible light activity for photocatalytic reduction of CO2, which is closely related to the oxygen vacancy induced by thermal pretreatment, size and amount of Ag nanoparticles. Accordingly, there is an optimized photodeposition time for the synthesis of the photocatalyst that exhibits the highest photocatalytic activity.

Adhesion, Growth, and Maturation of Vascular Smooth Muscle Cells on Low-Density Polyethylene Grafted with Bioactive Substances

PubMed Central

Parizek, Martin; Slepickova Kasalkova, Nikola; Bacakova, Lucie; Bacakova, Marketa; Lisa, Vera; Svorcik, Vaclav

2013-01-01

The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar+ plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted. PMID:23586032

Adhesion, growth, and maturation of vascular smooth muscle cells on low-density polyethylene grafted with bioactive substances.

PubMed

Parizek, Martin; Slepickova Kasalkova, Nikola; Bacakova, Lucie; Svindrych, Zdenek; Slepicka, Petr; Bacakova, Marketa; Lisa, Vera; Svorcik, Vaclav

2013-01-01

The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar(+) plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted.

Investigation on electrical surface modification of waste to energy ash for possible use as an electrode material in microbial fuel cells.

PubMed

Webster, Megan; Lee, Hae Yang; Pepa, Kristi; Winkler, Nathan; Kretzschmar, Ilona; Castaldi, Marco J

2018-03-01

With the world population expected to reach 8.5 billion by 2030, demand for access to electricity and clean water will grow at unprecedented rates. Municipal solid waste combusted at waste to energy (WtE) facilities decreases waste volume and recovers energy, but yields ash as a byproduct, the beneficial uses of which are actively being investigated. Ash is intrinsically hydrophobic, highly oxidized, and exhibits high melting points and low conductivities. The research presented here explores the potential of ash to be used as an electrode material for a microbial fuel cell (MFC). This application requires increased conductivity and hydrophilicity, and a lowered melting point. Three ash samples were investigated. By applying an electric potential in the range 50-125 V across the ash in the presence of water, several key property changes were observed: lower melting point, a color change within the ash, evidence of changes in surface morphologies of ash particles, and completely wetting water-ash contact angles. We analyzed this system using a variety of analytical techniques including sector field inductively coupled plasma mass spectrometry, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and tensiometry. Ability to make such surface modifications and significant property changes could allow ash to become useful in an application such as an electrode material for a MFC.

Nanoniobia modification of CdS photoanode for an efficient and stable photoelectrochemical cell.

PubMed

Pareek, Alka; Paik, Pradip; Borse, Pramod H

2014-12-30

Herein we report the surface modification of a CdS film by niobia nanoparticles via thioglycerol as an organic linker and thus fabricate an efficient and a stable photoanode for a photoelectrochemical (PEC) cell. We have synthesized three differenly sized (∼3, ∼6 ,and ∼9 nm) niobia nanoparticles by a hydrothermal synthesis approach and have further investigated the particle-size-dependent PEC performance of the nanoparticle-modified CdS photoanode. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirm the formation of Nb2O5 nanoparticles that are prepared via decomposition of the niobium peroxo complex during the hydrothermal reaction and reveal the presence of surface OH(-) groups over niobia nanoparticles that impart a high catalytic property to a material. The nano-Nb2O5-modified photoanode displayed a 23-fold higher power conversion efficiency compared to that of CdS. This modified structure increases the open circuit voltage (OCV) from 0.65 to 0.77 V, which is attributed to the nano-Nb2O5-induced surface passivation effect over bare CdS. Linking of nanoparticles on the CdS surface improves the photocorrosion stability of the CdS photoanode for even longer than 4 h in contrast to the tens of minutes for the base CdS surface. The uniform coverage of the CdS photoanode surface by niobia nanoparticles is thus found to be the controlling parameter for achieving a higher PEC performance and stability of the photoanode. This finding directed us to design an improved CdS photoanode for efficient and prolonged PEC hydrogen generation from a PEC cell.

The recognition and interpretation of micro-particle impacts on space craft surfaces

NASA Astrophysics Data System (ADS)

Kearsley, Anton

Modern analysis instruments now allow the rapid examination of returned spacecraft surfaces, enabling the location and identification of impact features, and the attribution of their impactor origins. This paper describes application of novel electron, ion and micro-X-ray Fluorescence techniques to impacts on diverse compositions of substrate, including solar cell glass, poly-sulfone and fluoro-polymer-impregnated glass fibre composites, multilayer insulation foils, aluminium and titanium alloys. Examples will include two generations of solar cells and stiffener materials from the Hubble Space Telescope (HST), Beta-cloth from the NASA Mir-Trek cover blanket, aluminised Kapton foils from the Japanese Space Flyer Unit (SFU) and the European Retrievable Carrier (EuReCa), Al-alloy plates from the Long Duration Exposure Facility (LDEF), Al foils from the NASA Stardust mission, Al-alloy and Zinc orthotitanate (ZOT) painted alloy plate from HST, and titanium alloys from a re-entered titanium pressure tank. Each type of spacecraft surface poses unique problems of analysis, especially in the recognition of extraneous signatures from the impacting particle, especially if a complex chemical composition is already present in the target. For example, solar cells provide an excellent capture and analysis medium for monitoring fluxes of micrometre-scale orbital debris from solid rocket motor firings in low Earth orbit. However, they provide a hard and dense capture medium upon which substantial modification of the impactor may occur, making the precise identification of micrometeoroid components difficult. Unfortunately, extensive spallation by larger (> 100 micrometre) particle impacts on the thin and brittle structure of solar cells also usually results in complete loss of impactor signature. Although thick alloy surfaces may prevent complete impact penetration, the analysis of particle residues within their deep concavity has proven difficult, until the recent introduction of new high-efficiency energy dispersive X-ray (EDX) detectors. Along with Particle Induced X-ray Emission and micro-XRF imaging systems, the new EDX detectors allow recognition of subtle trace quantities of residue from even millimetre-scale craters and thin foil penetrations. Data from these differing substrates and techniques need to be integrated if we are to fully document micro-particle populations from the wide range of natural (cometary and asteroidal, i.e. micrometeoroid) and artificial (i.e. orbital debris) sources.

Synthesis, surface modification and characterisation of biocompatible magnetic iron oxide nanoparticles for biomedical applications.

PubMed

Mahdavi, Mahnaz; Ahmad, Mansor Bin; Haron, Md Jelas; Namvar, Farideh; Nadi, Behzad; Rahman, Mohamad Zaki Ab; Amin, Jamileh

2013-06-27

Superparamagnetic iron oxide nanoparticles (MNPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. These applications required that the MNPs such as iron oxide Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) having high magnetization values and particle size smaller than 100 nm. This paper reports the experimental detail for preparation of monodisperse oleic acid (OA)-coated Fe₃O₄ MNPs by chemical co-precipitation method to determine the optimum pH, initial temperature and stirring speed in order to obtain the MNPs with small particle size and size distribution that is needed for biomedical applications. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence spectrometry (EDXRF), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). The results show that the particle size as well as the magnetization of the MNPs was very much dependent on pH, initial temperature of Fe²⁺ and Fe³⁺ solutions and steering speed. The monodisperse Fe₃O₄ MNPs coated with oleic acid with size of 7.8 ± 1.9 nm were successfully prepared at optimum pH 11, initial temperature of 45°C and at stirring rate of 800 rpm. FTIR and XRD data reveal that the oleic acid molecules were adsorbed on the magnetic nanoparticles by chemisorption. Analyses of TEM show the oleic acid provided the Fe₃O₄ particles with better dispersibility. The synthesized Fe₃O₄ nanoparticles exhibited superparamagnetic behavior and the saturation magnetization of the Fe₃O₄ nanoparticles increased with the particle size.

Synthesis, characterization and application of Lagerstroemia speciosa embedded magnetic nanoparticle for Cr(VI) adsorption from aqueous solution.

PubMed

Srivastava, Shalini; Agrawal, Shashi Bhushan; Mondal, Monoj Kumar

2017-05-01

Lagerstroemia speciosa bark (LB) embedded magnetic nanoparticles were prepared by co-precipitation of Fe 2+ and Fe 3+ salt solution with ammonia and LB for Cr(VI) removal from aqueous solution. The native LB, magnetic nanoparticle (MNP), L. speciosa embedded magnetic nanoparticle (MNPLB) and Cr(VI) adsorbed MNPLB particles were characterized by SEM-EDX, TEM, BET-surface area, FT-IR, XRD and TGA methods. TEM analysis confirmed nearly spherical shape of MNP with an average diameter of 8.76nm and the surface modification did not result in the phase change of MNP as established by XRD analysis, while led to the formation of secondary particles of MNPLB with diameter of 18.54nm. Characterization results revealed covalent binding between the hydroxyl group of MNP and carboxyl group of LB particles and further confirmed its physico-chemical nature favorable for Cr(VI) adsorption. The Cr(VI) adsorption on to MNPLB particle as an adsorbent was tested under different contact time, initial Cr(VI) concentration, adsorbent dose, initial pH, temperature and agitation speed. The results of the equilibrium and kinetics of adsorption were well described by Langmuir isotherm and pseudo-second-order model, respectively. The thermodynamic parameters suggest spontaneous and endothermic nature of Cr(VI) adsorption onto MNPLB. The maximum adsorption capacity for MNPLB was calculated to be 434.78mg/g and these particles even after Cr(VI) adsorption were collected effortlessly from the aqueous solution by a magnet. The desorption of Cr(VI)-adsorbed MNPLB was found to be more than 93.72% with spent MNPLB depicting eleven successive adsorption-desorption cycles. Copyright © 2016. Published by Elsevier B.V.

Radiopacifier Particle Size Impacts the Physical Properties of Tricalcium Silicate–based Cements

PubMed Central

Saghiri, Mohammad Ali; Gutmann, James L.; Orangi, Jafar; Asatourian, Armen; Sheibani, Nader

2016-01-01

Introduction The aim of this study was to evaluate the impact of radiopaque additive, bismuth oxide, particle size on the physical properties, and radiopacity of tricalcium silicate–based cements. Methods Six types of tricalcium silicate cement (CSC) including CSC without bismuth oxide, CSC + 10% (wt%) regular bismuth oxide (particle size 10 μm), CSC + 20% regular bismuth oxide (simulating white mineral trioxide aggregate [WMTA]) as a control, CSC + 10% nano bismuth oxide (particle size 50–80 nm), CSC + 20% nano-size bismuth oxide, and nano WMTA (a nano modification of WMTA comprising nanoparticles in the range of 40–100 nm) were prepared. Twenty-four samples from each group were divided into 4 groups and subjected to push-out, surface microhardness, radiopacity, and compressive strength tests. Data were analyzed by 1-way analysis of variance with the post hoc Tukey test. Results The push-out and compressive strength of CSC without bismuth oxide and CSC with 10% and 20% nano bismuth oxide were significantly higher than CSC with 10% or 20% regular bismuth oxide (P < .05). The surface micro-hardness of CSC without bismuth oxide and CSC with 10% regular bismuth oxide had the lowest values (P < .05). The lowest radiopacity values were seen in CSC without bismuth oxide and CSC with 10% nano bismuth oxide (P < .05). Nano WMTA samples showed the highest values for all tested properties (P < .05) except for radiopacity. Conclusions The addition of 20% nano bismuth oxide enhanced the physical properties of CSC without any significant changes in radiopacity. Regular particle-size bismuth oxide reduced the physical properties of CSC material for tested parameters. PMID:25492489

Effective reduction in the nanoparticle sizes of NiO obtained via the pyrolysis of nickel malonate precursor modified using oleylamine surfactant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lontio Fomekong, Roussin, E-mail: lonforou@yahoo.fr; Institut de la Matière Condensée et des Nanosciences, Université Catholique de Louvain, Croix du Sud 1, 1348 Louvain-La-Neuve; Ngolui Lambi, John

2016-09-15

Nickel oxide nanoparticles were synthesized via thermal decomposition of two precursors, the first, a simple nickel malonate and the second, a nickel malonate modified by oleylamine, a surfactant, both having been synthesized by precipitation. While FTIR, TGA and ToF-SIMS were used to characterize the two precursors and to show the presence of oleylamine in the modified precursor, XRD, SEM, TEM and BET were employed to investigate the structure, the morphology and the specific surface area of the decomposition products obtained after pyrolysis. The results showed that the modification of nickel malonate by oleylamine was effective. The XRD results, which showedmore » a cubic structure for the NiO obtained, suggest with SEM an important particle size reduction (at least 54%) when oleylamine was used to modify the nickel malonate precursor. The SEM images also showed a well-defined spherical nanoparticle morphology in both cases, not affected by the presence of oleylamine. The TEM also confirmed the reduction of particle size and their spherical nature but at the same time showed that, in the presence of oleylamine, there was no agglomeration resulting in a more uniform particle size distribution. The specific surface area of the NiO obtained by the oleylamine-modified precursor was 4.7 times larger than that obtained with the regular precursor. This again confirms the particle size reduction. - Highlights: • Nickel malonate precursor has been synthesized by precipitation method. • This precursor was successfully modified by a surfactant (oleylamine). • NiO was identified as the decomposition products of the previous precursors. • Oleylamine has provoked around 54% of particle size reduction of the NiO.« less

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica.

PubMed

Ji, Yazhou; Caskey, Christopher; Richards, Ryan M

2015-07-09

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

PubMed Central

Ji, Yazhou; Caskey, Christopher; Richards, Ryan M.

2015-01-01

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability. PMID:26274058

Reinforcement with alumina particles at the interface region of AA6101-T6 and AA1350 alloys during friction stir welding

NASA Astrophysics Data System (ADS)

Ashok Kumar, R.; Thansekhar, M. R.

2018-04-01

This paper deals the combinational effect of friction stir welding and friction stir processing on dissimilar AA6101-T6 and AA1350 aluminium alloys. For that, alumina particles are reinforced at interface region of AA6101-T6 and AA1350 aluminium alloys. Friction Stir Welding and Friction Stir Processing are done simultaneously for various sizes of groove. To analyze the welding quality and surface modifications, mechanical, wear and microstructural tests are carried out. Among these, smallest groove of 0.5 mm width and 1 mm depth reveals highest tensile and bending strengths and largest groove of 2 mm width and 3 mm depth gives maximum hardness and wear resistance. Taguchi technique shows that groove width is most influencing parameter. Developed second order models with interaction predict the responses with minimum error.

Mass transport through vertically aligned large diameter MWCNT embedded in parylene

PubMed Central

Krishnakumar, P; Tiwari, P B; Staples, S; Luo, T; Darici, Y; He, J; Lindsay, SM

2013-01-01

We have fabricated porous membranes using a parylene encapsulated vertically aligned forest of multi-walled carbon nanotube (MWCNT, about 7nm inner diameter). The transport of charged particles in electrolyte through these membranes was studied by applying electric field and pressure. Under an electric field in the range of 4.4×104 V/m, electrophoresis instead of electroomosis is found to be the main mechanism for ion transport. Small molecules and 5 nm gold nanoparticles can be driven through the membranes by an electric field. However, small biomolecules, like DNA oligomers, cannot. Due to the weak electric driving force, the interactions between charged particles and the hydrophobic CNT inner surface play important roles in the transport, leading to enhanced selectivity for small molecules. Simple chemical modification on the CNT ends also induces an obvious effect on the translocation of single strand DNA oligomer and gold nanoparticle under a modest pressure (<294 Pa). PMID:23064678

Particle creation and reheating in a braneworld inflationary scenario

NASA Astrophysics Data System (ADS)

Bilić, Neven; Domazet, Silvije; Djordjevic, Goran S.

2017-10-01

We study the cosmological particle creation in the tachyon inflation based on the D-brane dynamics in the Randall-Sundrum (RSII) model extended to include matter in the bulk. The presence of matter modifies the warp factor which results in two effects: a modification of the RSII cosmology and a modification of the tachyon potential. Besides, a string theory D-brane supports among other fields a U(1) gauge field reflecting open strings attached to the brane. We demonstrate how the interaction of the tachyon with the U(1) gauge field drives cosmological creation of massless particles and estimate the resulting reheating at the end of inflation.

Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in √{sNN} = 5.02 TeVp + Pb collisions measured by the ATLAS experiment

NASA Astrophysics Data System (ADS)

Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.; Abeloos, B.; Aben, R.; Abouzeid, O. S.; Abraham, N. L.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Affolder, A. A.; Agatonovic-Jovin, T.; Agricola, J.; Aguilar-Saavedra, J. A.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allen, B. W.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alstaty, M.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M. G.; Amadio, B. T.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anders, J. K.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonelli, M.; Antonov, A.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Armitage, L. J.; Arnaez, O.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Artz, S.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Augsten, K.; Avolio, G.; Axen, B.; Ayoub, M. K.; Azuelos, G.; Baak, M. A.; Baas, A. E.; Baca, M. J.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Baines, J. T.; Baker, O. K.; Baldin, E. M.; Balek, P.; Balestri, T.; Balli, F.; Balunas, W. K.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Barak, L.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barklow, T.; Barlow, N.; Barnes, S. L.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barranco Navarro, L.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Basalaev, A.; Bassalat, A.; Bates, R. L.; Batista, S. J.; Batley, J. R.; Battaglia, M.; Bauce, M.; Bauer, F.; Bawa, H. S.; Beacham, J. B.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, M.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bednyakov, V. A.; Bedognetti, M.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, J. K.; Belanger-Champagne, C.; Bell, A. S.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Belyaev, N. L.; Benary, O.; Benchekroun, D.; Bender, M.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez, J.; Benjamin, D. P.; Bensinger, J. R.; Bentvelsen, S.; Beresford, L.; Beretta, M.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Beringer, J.; Berlendis, S.; Bernard, N. R.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Berta, P.; Bertella, C.; Bertoli, G.; Bertolucci, F.; Bertram, I. A.; Bertsche, C.; Bertsche, D.; Besjes, G. J.; Bessidskaia Bylund, O.; Bessner, M.; Besson, N.; Betancourt, C.; Bethke, S.; Bevan, A. J.; Bhimji, W.; Bianchi, R. M.; Bianchini, L.; Bianco, M.; Biebel, O.; Biedermann, D.; Bielski, R.; Biesuz, N. V.; Biglietti, M.; Bilbao de Mendizabal, J.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biondi, S.; Bjergaard, D. M.; Black, C. W.; Black, J. E.; Black, K. M.; Blackburn, D.; Blair, R. E.; Blanchard, J.-B.; Blanco, J. E.; Blazek, T.; Bloch, I.; Blocker, C.; Blum, W.; Blumenschein, U.; Blunier, S.; Bobbink, G. J.; Bobrovnikov, V. S.; Bocchetta, S. S.; Bocci, A.; Bock, C.; Boehler, M.; Boerner, D.; Bogaerts, J. A.; Bogavac, D.; Bogdanchikov, A. G.; Bohm, C.; Boisvert, V.; Bokan, P.; Bold, T.; Boldyrev, A. S.; Bomben, M.; Bona, M.; Boonekamp, M.; Borisov, A.; Borissov, G.; Bortfeldt, J.; Bortoletto, D.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Bossio Sola, J. D.; Boudreau, J.; Bouffard, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Boutle, S. K.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bracinik, J.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Breaden Madden, W. D.; Brendlinger, K.; Brennan, A. J.; Brenner, L.; Brenner, R.; Bressler, S.; Bristow, T. M.; Britton, D.; Britzger, D.; Brochu, F. M.; Brock, I.; Brock, R.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brosamer, J.; Brost, E.; Broughton, J. H.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Bruni, A.; Bruni, G.; Brunt, Bh; Bruschi, M.; Bruscino, N.; Bryant, P.; Bryngemark, L.; Buanes, T.; Buat, Q.; Buchholz, P.; Buckley, A. G.; Budagov, I. A.; Buehrer, F.; Bugge, M. K.; Bulekov, O.; Bullock, D.; Burckhart, H.; Burdin, S.; Burgard, C. D.; Burghgrave, B.; Burka, K.; Burke, S.; Burmeister, I.; Busato, E.; Büscher, D.; Büscher, V.; Bussey, P.; Butler, J. M.; Buttar, C. M.; Butterworth, J. M.; Butti, P.; Buttinger, W.; Buzatu, A.; Buzykaev, A. R.; Cabrera Urbán, S.; Caforio, D.; Cairo, V. M.; Cakir, O.; Calace, N.; Calafiura, P.; Calandri, A.; Calderini, G.; Calfayan, P.; Caloba, L. P.; Calvet, D.; Calvet, S.; Calvet, T. P.; Camacho Toro, R.; Camarda, S.; Camarri, P.; Cameron, D.; Caminal Armadans, R.; Camincher, C.; Campana, S.; Campanelli, M.; Camplani, A.; Campoverde, A.; Canale, V.; Canepa, A.; Cano Bret, M.; Cantero, J.; Cantrill, R.; Cao, T.; Capeans Garrido, M. D. M.; Caprini, I.; Caprini, M.; Capua, M.; Caputo, R.; Carbone, R. M.; Cardarelli, R.; Cardillo, F.; Carli, I.; Carli, T.; Carlino, G.; Carminati, L.; Caron, S.; Carquin, E.; Carrillo-Montoya, G. D.; Carter, J. R.; Carvalho, J.; Casadei, D.; Casado, M. P.; Casolino, M.; Casper, D. W.; Castaneda-Miranda, E.; Castelijn, R.; Castelli, A.; Castillo Gimenez, V.; Castro, N. F.; Catinaccio, A.; Catmore, J. R.; Cattai, A.; Caudron, J.; Cavaliere, V.; Cavallaro, E.; Cavalli, D.; Cavalli-Sforza, M.; Cavasinni, V.; Ceradini, F.; Cerda Alberich, L.; Cerio, B. C.; Cerqueira, A. S.; Cerri, A.; Cerrito, L.; Cerutti, F.; Cerv, M.; Cervelli, A.; Cetin, S. A.; Chafaq, A.; Chakraborty, D.; Chan, S. K.; Chan, Y. L.; Chang, P.; Chapman, J. D.; Charlton, D. G.; Chatterjee, A.; Chau, C. C.; Chavez Barajas, C. A.; Che, S.; Cheatham, S.; Chegwidden, A.; Chekanov, S.; Chekulaev, S. V.; Chelkov, G. A.; Chelstowska, M. A.; Chen, C.; Chen, H.; Chen, K.; Chen, S.; Chen, S.; Chen, X.; Chen, Y.; Cheng, H. C.; Cheng, H. J.; Cheng, Y.; Cheplakov, A.; Cheremushkina, E.; Cherkaoui El Moursli, R.; Chernyatin, V.; Cheu, E.; Chevalier, L.; Chiarella, V.; Chiarelli, G.; Chiodini, G.; Chisholm, A. S.; Chitan, A.; Chizhov, M. V.; Choi, K.; Chomont, A. R.; Chouridou, S.; Chow, B. K. B.; Christodoulou, V.; Chromek-Burckhart, D.; Chudoba, J.; Chuinard, A. J.; Chwastowski, J. J.; Chytka, L.; Ciapetti, G.; Ciftci, A. K.; Cinca, D.; Cindro, V.; Cioara, I. A.; Ciocio, A.; Cirotto, F.; Citron, Z. H.; Citterio, M.; Ciubancan, M.; Clark, A.; Clark, B. L.; Clark, M. R.; Clark, P. J.; Clarke, R. N.; Clement, C.; Coadou, Y.; Cobal, M.; Coccaro, A.; Cochran, J.; Coffey, L.; Colasurdo, L.; Cole, B.; Colijn, A. P.; Collot, J.; Colombo, T.; Compostella, G.; Conde Muiño, P.; Coniavitis, E.; Connell, S. H.; Connelly, I. A.; Consorti, V.; Constantinescu, S.; Conti, G.; Conventi, F.; Cooke, M.; Cooper, B. D.; Cooper-Sarkar, A. M.; Cormier, K. J. R.; Cornelissen, T.; Corradi, M.; Corriveau, F.; Corso-Radu, A.; Cortes-Gonzalez, A.; Cortiana, G.; Costa, G.; Costa, M. J.; Costanzo, D.; Cottin, G.; Cowan, G.; Cox, B. E.; Cranmer, K.; Crawley, S. J.; Cree, G.; Crépé-Renaudin, S.; Crescioli, F.; Cribbs, W. 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L.; Massa, I.; Massa, L.; Mastrandrea, P.; Mastroberardino, A.; Masubuchi, T.; Mättig, P.; Mattmann, J.; Maurer, J.; Maxfield, S. J.; Maximov, D. A.; Mazini, R.; Mazza, S. M.; Mc Fadden, N. C.; Mc Goldrick, G.; Mc Kee, S. P.; McCarn, A.; McCarthy, R. L.; McCarthy, T. G.; McClymont, L. I.; McDonald, E. F.; McFarlane, K. W.; McFayden, J. A.; McHedlidze, G.; McMahon, S. J.; McPherson, R. A.; Medinnis, M.; Meehan, S.; Mehlhase, S.; Mehta, A.; Meier, K.; Meineck, C.; Meirose, B.; Melini, D.; Mellado Garcia, B. R.; Melo, M.; Meloni, F.; Mengarelli, A.; Menke, S.; Meoni, E.; Mergelmeyer, S.; Mermod, P.; Merola, L.; Meroni, C.; Merritt, F. S.; Messina, A.; Metcalfe, J.; Mete, A. S.; Meyer, C.; Meyer, C.; Meyer, J.-P.; Meyer, J.; Meyer Zu Theenhausen, H.; Miano, F.; Middleton, R. P.; Miglioranzi, S.; Mijović, L.; Mikenberg, G.; Mikestikova, M.; Mikuž, M.; Milesi, M.; Milic, A.; Miller, D. W.; Mills, C.; Milov, A.; Milstead, D. A.; Minaenko, A. A.; Minami, Y.; Minashvili, I. A.; Mincer, A. I.; Mindur, B.; Mineev, M.; Ming, Y.; Mir, L. M.; Mistry, K. P.; Mitani, T.; Mitrevski, J.; Mitsou, V. A.; Miucci, A.; Miyagawa, P. S.; Mjörnmark, J. U.; Moa, T.; Mochizuki, K.; Mohapatra, S.; Molander, S.; Moles-Valls, R.; Monden, R.; Mondragon, M. C.; Mönig, K.; Monk, J.; Monnier, E.; Montalbano, A.; Montejo Berlingen, J.; Monticelli, F.; Monzani, S.; Moore, R. W.; Morange, N.; Moreno, D.; Moreno Llácer, M.; Morettini, P.; Mori, D.; Mori, T.; Morii, M.; Morinaga, M.; Morisbak, V.; Moritz, S.; Morley, A. K.; Mornacchi, G.; Morris, J. D.; Mortensen, S. S.; Morvaj, L.; Mosidze, M.; Moss, J.; Motohashi, K.; Mount, R.; Mountricha, E.; Mouraviev, S. V.; Moyse, E. J. W.; Muanza, S.; Mudd, R. D.; Mueller, F.; Mueller, J.; Mueller, R. S. P.; Mueller, T.; Muenstermann, D.; Mullen, P.; Mullier, G. A.; Munoz Sanchez, F. J.; Murillo Quijada, J. A.; Murray, W. J.; Musheghyan, H.; Muškinja, M.; Myagkov, A. G.; Myska, M.; Nachman, B. P.; Nackenhorst, O.; Nagai, K.; Nagai, R.; Nagano, K.; Nagasaka, Y.; Nagata, K.; Nagel, M.; Nagy, E.; Nairz, A. M.; Nakahama, Y.; Nakamura, K.; Nakamura, T.; Nakano, I.; Namasivayam, H.; Naranjo Garcia, R. F.; Narayan, R.; Narrias Villar, D. I.; Naryshkin, I.; Naumann, T.; Navarro, G.; Nayyar, R.; Neal, H. A.; Nechaeva, P. Yu.; Neep, T. J.; Nef, P. D.; Negri, A.; Negrini, M.; Nektarijevic, S.; Nellist, C.; Nelson, A.; Nemecek, S.; Nemethy, P.; Nepomuceno, A. A.; Nessi, M.; Neubauer, M. S.; Neumann, M.; Neves, R. M.; Nevski, P.; Newman, P. R.; Nguyen, D. H.; Nguyen Manh, T.; Nickerson, R. B.; Nicolaidou, R.; Nielsen, J.; Nikiforov, A.; Nikolaenko, V.; Nikolic-Audit, I.; Nikolopoulos, K.; Nilsen, J. K.; Nilsson, P.; Ninomiya, Y.; Nisati, A.; Nisius, R.; Nobe, T.; Nodulman, L.; Nomachi, M.; Nomidis, I.; Nooney, T.; Norberg, S.; Nordberg, M.; Norjoharuddeen, N.; Novgorodova, O.; Nowak, S.; Nozaki, M.; Nozka, L.; Ntekas, K.; Nurse, E.; Nuti, F.; O'Grady, F.; O'Neil, D. C.; O'Rourke, A. 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D.; Papageorgiou, K.; Paramonov, A.; Paredes Hernandez, D.; Parker, A. J.; Parker, M. A.; Parker, K. A.; Parodi, F.; Parsons, J. A.; Parzefall, U.; Pascuzzi, V. R.; Pasqualucci, E.; Passaggio, S.; Pastore, Fr.; Pásztor, G.; Pataraia, S.; Pater, J. R.; Pauly, T.; Pearce, J.; Pearson, B.; Pedersen, L. E.; Pedersen, M.; Pedraza Lopez, S.; Pedro, R.; Peleganchuk, S. V.; Pelikan, D.; Penc, O.; Peng, C.; Peng, H.; Penwell, J.; Peralva, B. S.; Perego, M. M.; Perepelitsa, D. V.; Perez Codina, E.; Perini, L.; Pernegger, H.; Perrella, S.; Peschke, R.; Peshekhonov, V. D.; Peters, K.; Peters, R. F. Y.; Petersen, B. A.; Petersen, T. C.; Petit, E.; Petridis, A.; Petridou, C.; Petroff, P.; Petrolo, E.; Petrov, M.; Petrucci, F.; Pettersson, N. E.; Peyaud, A.; Pezoa, R.; Phillips, P. W.; Piacquadio, G.; Pianori, E.; Picazio, A.; Piccaro, E.; Piccinini, M.; Pickering, M. A.; Piegaia, R.; Pilcher, J. E.; Pilkington, A. D.; Pin, A. W. J.; Pinamonti, M.; Pinfold, J. L.; Pingel, A.; Pires, S.; Pirumov, H.; Pitt, M.; Plazak, L.; Pleier, M.-A.; Pleskot, V.; Plotnikova, E.; Plucinski, P.; Pluth, D.; Poettgen, R.; Poggioli, L.; Pohl, D.; Polesello, G.; Poley, A.; Policicchio, A.; Polifka, R.; Polini, A.; Pollard, C. S.; Polychronakos, V.; Pommès, K.; Pontecorvo, L.; Pope, B. G.; Popeneciu, G. A.; Popovic, D. S.; Poppleton, A.; Pospisil, S.; Potamianos, K.; Potrap, I. N.; Potter, C. J.; Potter, C. T.; Poulard, G.; Poveda, J.; Pozdnyakov, V.; Pozo Astigarraga, M. E.; Pralavorio, P.; Pranko, A.; Prell, S.; Price, D.; Price, L. E.; Primavera, M.; Prince, S.; Proissl, M.; Prokofiev, K.; Prokoshin, F.; Protopopescu, S.; Proudfoot, J.; Przybycien, M.; Puddu, D.; Puldon, D.; Purohit, M.; Puzo, P.; Qian, J.; Qin, G.; Qin, Y.; Quadt, A.; Quayle, W. B.; Queitsch-Maitland, M.; Quilty, D.; Raddum, S.; Radeka, V.; Radescu, V.; Radhakrishnan, S. K.; Radloff, P.; Rados, P.; Ragusa, F.; Rahal, G.; Raine, J. A.; Rajagopalan, S.; Rammensee, M.; Rangel-Smith, C.; Ratti, M. G.; Rauscher, F.; Rave, S.; Ravenscroft, T.; Ravinovich, I.; Raymond, M.; Read, A. L.; Readioff, N. P.; Reale, M.; Rebuzzi, D. M.; Redelbach, A.; Redlinger, G.; Reece, R.; Reeves, K.; Rehnisch, L.; Reichert, J.; Reisin, H.; Rembser, C.; Ren, H.; Rescigno, M.; Resconi, S.; Rezanova, O. L.; Reznicek, P.; Rezvani, R.; Richter, R.; Richter, S.; Richter-Was, E.; Ricken, O.; Ridel, M.; Rieck, P.; Riegel, C. J.; Rieger, J.; Rifki, O.; Rijssenbeek, M.; Rimoldi, A.; Rimoldi, M.; Rinaldi, L.; Ristić, B.; Ritsch, E.; Riu, I.; Rizatdinova, F.; Rizvi, E.; Rizzi, C.; Robertson, S. H.; Robichaud-Veronneau, A.; Robinson, D.; Robinson, J. E. M.; Robson, A.; Roda, C.; Rodina, Y.; Rodriguez Perez, A.; Rodriguez Rodriguez, D.; Roe, S.; Rogan, C. S.; Røhne, O.; Romaniouk, A.; Romano, M.; Romano Saez, S. M.; Romero Adam, E.; Rompotis, N.; Ronzani, M.; Roos, L.; Ros, E.; Rosati, S.; Rosbach, K.; Rose, P.; Rosenthal, O.; Rosien, N.-A.; Rossetti, V.; Rossi, E.; Rossi, L. P.; Rosten, J. H. N.; Rosten, R.; Rotaru, M.; Roth, I.; Rothberg, J.; Rousseau, D.; Royon, C. R.; Rozanov, A.; Rozen, Y.; Ruan, X.; Rubbo, F.; Rudolph, M. S.; Rühr, F.; Ruiz-Martinez, A.; Rurikova, Z.; Rusakovich, N. A.; Ruschke, A.; Russell, H. L.; Rutherfoord, J. P.; Ruthmann, N.; Ryabov, Y. F.; Rybar, M.; Rybkin, G.; Ryu, S.; Ryzhov, A.; Rzehorz, G. F.; Saavedra, A. F.; Sabato, G.; Sacerdoti, S.; Sadrozinski, H. F.-W.; Sadykov, R.; Safai Tehrani, F.; Saha, P.; Sahinsoy, M.; Saimpert, M.; Saito, T.; Sakamoto, H.; Sakurai, Y.; Salamanna, G.; Salamon, A.; Salazar Loyola, J. E.; Salek, D.; Sales de Bruin, P. H.; Salihagic, D.; Salnikov, A.; Salt, J.; Salvatore, D.; Salvatore, F.; Salvucci, A.; Salzburger, A.; Sammel, D.; Sampsonidis, D.; Sanchez, A.; Sánchez, J.; Sanchez Martinez, V.; Sandaker, H.; Sandbach, R. L.; Sander, H. G.; Sandhoff, M.; Sandoval, C.; Sandstroem, R.; Sankey, D. P. C.; Sannino, M.; Sansoni, A.; Santoni, C.; Santonico, R.; Santos, H.; Santoyo Castillo, I.; Sapp, K.; Sapronov, A.; Saraiva, J. G.; Sarrazin, B.; Sasaki, O.; Sasaki, Y.; Sato, K.; Sauvage, G.; Sauvan, E.; Savage, G.; Savard, P.; Sawyer, C.; Sawyer, L.; Saxon, J.; Sbarra, C.; Sbrizzi, A.; Scanlon, T.; Scannicchio, D. A.; Scarcella, M.; Scarfone, V.; Schaarschmidt, J.; Schacht, P.; Schachtner, B. M.; Schaefer, D.; Schaefer, R.; Schaeffer, J.; Schaepe, S.; Schaetzel, S.; Schäfer, U.; Schaffer, A. C.; Schaile, D.; Schamberger, R. D.; Scharf, V.; Schegelsky, V. A.; Scheirich, D.; Schernau, M.; Schiavi, C.; Schier, S.; Schillo, C.; Schioppa, M.; Schlenker, S.; Schmidt-Sommerfeld, K. R.; Schmieden, K.; Schmitt, C.; Schmitt, S.; Schmitz, S.; Schneider, B.; Schnoor, U.; Schoeffel, L.; Schoening, A.; Schoenrock, B. D.; Schopf, E.; Schott, M.; Schovancova, J.; Schramm, S.; Schreyer, M.; Schuh, N.; Schultens, M. J.; Schultz-Coulon, H.-C.; Schulz, H.; Schumacher, M.; Schumm, B. A.; Schune, Ph.; Schwartzman, A.; Schwarz, T. A.; Schwegler, Ph.; Schweiger, H.; Schwemling, Ph.; Schwienhorst, R.; Schwindling, J.; Schwindt, T.; Sciolla, G.; Scuri, F.; Scutti, F.; Searcy, J.; Seema, P.; Seidel, S. C.; Seiden, A.; Seifert, F.; Seixas, J. M.; Sekhniaidze, G.; Sekhon, K.; Sekula, S. J.; Seliverstov, D. M.; Semprini-Cesari, N.; Serfon, C.; Serin, L.; Serkin, L.; Sessa, M.; Seuster, R.; Severini, H.; Sfiligoj, T.; Sforza, F.; Sfyrla, A.; Shabalina, E.; Shaikh, N. W.; Shan, L. Y.; Shang, R.; Shank, J. T.; Shapiro, M.; Shatalov, P. B.; Shaw, K.; Shaw, S. M.; Shcherbakova, A.; Shehu, C. Y.; Sherwood, P.; Shi, L.; Shimizu, S.; Shimmin, C. O.; Shimojima, M.; Shiyakova, M.; Shmeleva, A.; Shoaleh Saadi, D.; Shochet, M. J.; Shojaii, S.; Shrestha, S.; Shulga, E.; Shupe, M. A.; Sicho, P.; Sickles, A. M.; Sidebo, P. E.; Sidiropoulou, O.; Sidorov, D.; Sidoti, A.; Siegert, F.; Sijacki, Dj.; Silva, J.; Silverstein, S. B.; Simak, V.; Simard, O.; Simic, Lj.; Simion, S.; Simioni, E.; Simmons, B.; Simon, D.; Simon, M.; Sinervo, P.; Sinev, N. B.; Sioli, M.; Siragusa, G.; Sivoklokov, S. Yu.; Sjölin, J.; Sjursen, T. B.; Skinner, M. B.; Skottowe, H. P.; Skubic, P.; Slater, M.; Slavicek, T.; Slawinska, M.; Sliwa, K.; Slovak, R.; Smakhtin, V.; Smart, B. H.; Smestad, L.; Smiesko, J.; Smirnov, S. Yu.; Smirnov, Y.; Smirnova, L. N.; Smirnova, O.; Smith, M. N. K.; Smith, R. W.; Smizanska, M.; Smolek, K.; Snesarev, A. A.; Snyder, S.; Sobie, R.; Socher, F.; Soffer, A.; Soh, D. A.; Sokhrannyi, G.; Solans Sanchez, C. A.; Solar, M.; Soldatov, E. Yu.; Soldevila, U.; Solodkov, A. A.; Soloshenko, A.; Solovyanov, O. V.; Solovyev, V.; Sommer, P.; Son, H.; Song, H. Y.; Sood, A.; Sopczak, A.; Sopko, V.; Sorin, V.; Sosa, D.; Sotiropoulou, C. L.; Soualah, R.; Soukharev, A. M.; South, D.; Sowden, B. C.; Spagnolo, S.; Spalla, M.; Spangenberg, M.; Spanò, F.; Sperlich, D.; Spettel, F.; Spighi, R.; Spigo, G.; Spiller, L. A.; Spousta, M.; St. Denis, R. D.; Stabile, A.; Stamen, R.; Stamm, S.; Stanecka, E.; Stanek, R. W.; Stanescu, C.; Stanescu-Bellu, M.; Stanitzki, M. M.; Stapnes, S.; Starchenko, E. A.; Stark, G. H.; Stark, J.; Staroba, P.; Starovoitov, P.; Stärz, S.; Staszewski, R.; Steinberg, P.; Stelzer, B.; Stelzer, H. J.; Stelzer-Chilton, O.; Stenzel, H.; Stewart, G. A.; Stillings, J. A.; Stockton, M. C.; Stoebe, M.; Stoicea, G.; Stolte, P.; Stonjek, S.; Stradling, A. R.; Straessner, A.; Stramaglia, M. E.; Strandberg, J.; Strandberg, S.; Strandlie, A.; Strauss, M.; Strizenec, P.; Ströhmer, R.; Strom, D. M.; Stroynowski, R.; Strubig, A.; Stucci, S. A.; Stugu, B.; Styles, N. A.; Su, D.; Su, J.; Subramaniam, R.; Suchek, S.; Sugaya, Y.; Suk, M.; Sulin, V. V.; Sultansoy, S.; Sumida, T.; Sun, S.; Sun, X.; Sundermann, J. E.; Suruliz, K.; Susinno, G.; Sutton, M. R.; Suzuki, S.; Svatos, M.; Swiatlowski, M.; Sykora, I.; Sykora, T.; Ta, D.; Taccini, C.; Tackmann, K.; Taenzer, J.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takai, H.; Takashima, R.; Takeshita, T.; Takubo, Y.; Talby, M.; Talyshev, A. A.; Tan, K. G.; Tanaka, J.; Tanaka, R.; Tanaka, S.; Tannenwald, B. B.; Tapia Araya, S.; Tapprogge, S.; Tarem, S.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tashiro, T.; Tassi, E.; Tavares Delgado, A.; Tayalati, Y.; Taylor, A. C.; Taylor, G. N.; Taylor, P. T. E.; Taylor, W.; Teischinger, F. A.; Teixeira-Dias, P.; Temming, K. K.; Temple, D.; Ten Kate, H.; Teng, P. K.; Teoh, J. J.; Tepel, F.; Terada, S.; Terashi, K.; Terron, J.; Terzo, S.; Testa, M.; Teuscher, R. J.; Theveneaux-Pelzer, T.; Thomas, J. P.; Thomas-Wilsker, J.; Thompson, E. N.; Thompson, P. D.; Thompson, A. S.; Thomsen, L. A.; Thomson, E.; Thomson, M.; Tibbetts, M. J.; Ticse Torres, R. E.; Tikhomirov, V. O.; Tikhonov, Yu. A.; Timoshenko, S.; Tipton, P.; Tisserant, S.; Todome, K.; Todorov, T.; Todorova-Nova, S.; Tojo, J.; Tokár, S.; Tokushuku, K.; Tolley, E.; Tomlinson, L.; Tomoto, M.; Tompkins, L.; Toms, K.; Tong, B.; Torrence, E.; Torres, H.; Torró Pastor, E.; Toth, J.; Touchard, F.; Tovey, D. R.; Trefzger, T.; Tricoli, A.; Trigger, I. M.; Trincaz-Duvoid, S.; Tripiana, M. F.; Trischuk, W.; Trocmé, B.; Trofymov, A.; Troncon, C.; Trottier-McDonald, M.; Trovatelli, M.; Truong, L.; Trzebinski, M.; Trzupek, A.; Tseng, J. C.-L.; Tsiareshka, P. V.; Tsipolitis, G.; Tsirintanis, N.; Tsiskaridze, S.; Tsiskaridze, V.; Tskhadadze, E. G.; Tsui, K. M.; Tsukerman, I. I.; Tsulaia, V.; Tsuno, S.; Tsybychev, D.; Tudorache, A.; Tudorache, V.; Tuna, A. N.; Tupputi, S. A.; Turchikhin, S.; Turecek, D.; Turgeman, D.; Turra, R.; Turvey, A. J.; Tuts, P. M.; Tyndel, M.; Ucchielli, G.; Ueda, I.; Ueno, R.; Ughetto, M.; Ukegawa, F.; Unal, G.; Undrus, A.; Unel, G.; Ungaro, F. C.; Unno, Y.; Unverdorben, C.; Urban, J.; Urquijo, P.; Urrejola, P.; Usai, G.; Usanova, A.; Vacavant, L.; Vacek, V.; Vachon, B.; Valderanis, C.; Valdes Santurio, E.; Valencic, N.; Valentinetti, S.; Valero, A.; Valery, L.; Valkar, S.; Vallecorsa, S.; Valls Ferrer, J. A.; van den Wollenberg, W.; van der Deijl, P. C.; van der Geer, R.; van der Graaf, H.; van Eldik, N.; van Gemmeren, P.; van Nieuwkoop, J.; van Vulpen, I.; van Woerden, M. C.; Vanadia, M.; Vandelli, W.; Vanguri, R.; Vaniachine, A.; Vankov, P.; Vardanyan, G.; Vari, R.; Varnes, E. W.; Varol, T.; Varouchas, D.; Vartapetian, A.; Varvell, K. E.; Vasquez, J. G.; Vazeille, F.; Vazquez Schroeder, T.; Veatch, J.; Veloce, L. M.; Veloso, F.; Veneziano, S.; Ventura, A.; Venturi, M.; Venturi, N.; Venturini, A.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J. C.; Vest, A.; Vetterli, M. C.; Viazlo, O.; Vichou, I.; Vickey, T.; Vickey Boeriu, O. E.; Viehhauser, G. H. A.; Viel, S.; Vigani, L.; Vigne, R.; Villa, M.; Villaplana Perez, M.; Vilucchi, E.; Vincter, M. G.; Vinogradov, V. B.; Vittori, C.; Vivarelli, I.; Vlachos, S.; Vlasak, M.; Vogel, M.; Vokac, P.; Volpi, G.; Volpi, M.; von der Schmitt, H.; von Toerne, E.; Vorobel, V.; Vorobev, K.; Vos, M.; Voss, R.; Vossebeld, J. H.; Vranjes, N.; Vranjes Milosavljevic, M.; Vrba, V.; Vreeswijk, M.; Vuillermet, R.; Vukotic, I.; Vykydal, Z.; Wagner, P.; Wagner, W.; Wahlberg, H.; Wahrmund, S.; Wakabayashi, J.; Walder, J.; Walker, R.; Walkowiak, W.; Wallangen, V.; Wang, C.; Wang, C.; Wang, F.; Wang, H.; Wang, H.; Wang, J.; Wang, J.; Wang, K.; Wang, R.; Wang, S. M.; Wang, T.; Wang, T.; Wang, W.; Wang, X.; Wanotayaroj, C.; Warburton, A.; Ward, C. P.; Wardrope, D. R.; Washbrook, A.; Watkins, P. M.; Watson, A. T.; Watson, M. F.; Watts, G.; Watts, S.; Waugh, B. M.; Webb, S.; Weber, M. S.; Weber, S. W.; Webster, J. S.; Weidberg, A. R.; Weinert, B.; Weingarten, J.; Weiser, C.; Weits, H.; Wells, P. S.; Wenaus, T.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Wessels, M.; Wetter, J.; Whalen, K.; Whallon, N. L.; Wharton, A. M.; White, A.; White, M. J.; White, R.; Whiteson, D.; Wickens, F. J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik-Fuchs, L. A. M.; Wildauer, A.; Wilk, F.; Wilkens, H. G.; Williams, H. H.; Williams, S.; Willis, C.; Willocq, S.; Wilson, J. A.; Wingerter-Seez, I.; Winklmeier, F.; Winston, O. J.; Winter, B. T.; Wittgen, M.; Wittkowski, J.; Wollstadt, S. J.; Wolter, M. W.; Wolters, H.; Wosiek, B. K.; Wotschack, J.; Woudstra, M. J.; Wozniak, K. W.; Wu, M.; Wu, M.; Wu, S. L.; Wu, X.; Wu, Y.; Wyatt, T. R.; Wynne, B. M.; Xella, S.; Xu, D.; Xu, L.; Yabsley, B.; Yacoob, S.; Yakabe, R.; Yamaguchi, D.; Yamaguchi, Y.; Yamamoto, A.; Yamamoto, S.; Yamanaka, T.; Yamauchi, K.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, H.; Yang, Y.; Yang, Z.; Yao, W.-M.; Yap, Y. C.; Yasu, Y.; Yatsenko, E.; Yau Wong, K. H.; Ye, J.; Ye, S.; Yeletskikh, I.; Yen, A. L.; Yildirim, E.; Yorita, K.; Yoshida, R.; Yoshihara, K.; Young, C.; Young, C. J. S.; Youssef, S.; Yu, D. R.; Yu, J.; Yu, J. M.; Yu, J.; Yuan, L.; Yuen, S. P. Y.; Yusuff, I.; Zabinski, B.; Zaidan, R.; Zaitsev, A. M.; Zakharchuk, N.; Zalieckas, J.; Zaman, A.; Zambito, S.; Zanello, L.; Zanzi, D.; Zeitnitz, C.; Zeman, M.; Zemla, A.; Zeng, J. C.; Zeng, Q.; Zengel, K.; Zenin, O.; Ženiš, T.; Zerwas, D.; Zhang, D.; Zhang, F.; Zhang, G.; Zhang, H.; Zhang, J.; Zhang, L.; Zhang, R.; Zhang, R.; Zhang, X.; Zhang, Z.; Zhao, X.; Zhao, Y.; Zhao, Z.; Zhemchugov, A.; Zhong, J.; Zhou, B.; Zhou, C.; Zhou, L.; Zhou, L.; Zhou, M.; Zhou, N.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhukov, K.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, S.; Zinonos, Z.; Zinser, M.; Ziolkowski, M.; Živković, L.; Zobernig, G.; Zoccoli, A.; Zur Nedden, M.; Zurzolo, G.; Zwalinski, L.; Atlas Collaboration

2016-12-01

Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p + Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of √{sNN} = 5.02TeV. Charged particles are reconstructed over pseudorapidity | η | < 2.3 and transverse momentum between 0.1 GeV and 22 GeV in a dataset corresponding to an integrated luminosity of 1 μb-1. The results are presented in the form of charged-particle nuclear modification factors, where the p + Pb charged-particle multiplicities are compared between central and peripheral p + Pb collisions as well as to charged-particle cross sections measured in pp collisions. The p + Pb collision centrality is characterized by the total transverse energy measured in - 4.9 < η < - 3.1, which is in the direction of the outgoing lead beam. Three different estimations of the number of nucleons participating in the p + Pb collision are carried out using the Glauber model and two Glauber-Gribov colour-fluctuation extensions to the Glauber model. The values of the nuclear modification factors are found to vary significantly as a function of rapidity and transverse momentum. A broad peak is observed for all centralities and rapidities in the nuclear modification factors for charged-particle transverse momentum values around 3 GeV. The magnitude of the peak increases for more central collisions as well as rapidity ranges closer to the direction of the outgoing lead nucleus.

Simultaneous Sterilization With Surface Modification Of Plastic Bottle By Plasma-Based Ion Implantation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakudo, N.; Ikenaga, N.; Ikeda, F.

2011-01-07

Dry sterilization of polymeric material is developed. The technique utilizes the plasma-based ion implantation which is same as for surface modification of polymers. Experimental data for sterilization are obtained by using spores of Bacillus subtilis as samples. On the other hand we previously showed that the surface modification enhanced the gas barrier characteristics of plastic bottles. Comparing the implantation conditions for the sterilization experiment with those for the surface modification, we find that both sterilization and surface modification are simultaneously performed in a certain range of implantation conditions. This implies that the present bottling system for plastic vessels will bemore » simplified and streamlined by excluding the toxic peroxide water that has been used in the traditional sterilization processes.« less

Laser surface modification of Yttria Stabilized Zirconia (YSZ) thermal barrier coating on AISI H13 tool steel substrate

NASA Astrophysics Data System (ADS)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2018-03-01

This paper presents laser surface modification of plasma sprayed yttria stabilized zirconia (YSZ) coating to seal porosity defect. Laser surface modification on plasma sprayed YSZ was conducted using 300W JK300HPS Nd: YAG laser at different operating parameters. Parameters varied were laser power and pulse frequency with constant residence time. The coating thickness was measured using IM7000 inverted optical microscope and surface roughness was analysed using two-dimensional Mitutoyo Surface Roughness Tester. Surface roughness of laser surface modification of YSZ H-13 tool steel decreased significantly with increasing laser power and decreasing pulse frequency. The re-melted YSZ coating showed higher hardness properties compared to as-sprayed coating surface. These findings were significant to enhance thermal barrier coating surface integrity for dies in semi-solid processing.

Metal-Coated Cenospheres Obtained via Magnetron Sputter Coating: A New Precursor for Syntactic Foams

NASA Astrophysics Data System (ADS)

Shishkin, A.; Hussainova, I.; Kozlov, V.; Lisnanskis, M.; Leroy, P.; Lehmhus, D.

2018-05-01

Syntactic foams (SFs) and metal matrix syntactic foams (MMSFs) represent an advanced type of metal matrix composites (MMCs) based on hollow microspheres as particulate reinforcement. In general, SF and MMSFs allow tailoring of properties through choice of matrix, reinforcement, and volume fraction of the latter. A further handle for property adjustment is surface modification of the reinforcing particles. The present study introduces cenospheres for use as filler material in SF and MMSFs and as lightweight filler with electromagnetic interference shielding properties in civil engineering, which have been surface coated by means of physical vapor deposition, namely vibration-assisted sputter coating using a magnetron sputtering system. Altogether four types of such cenosphere-based composite powders (CPs) with an original particle size range of 50-125 µm (average particle size d50 75 µm) were studied. Surface films deposited on these were composed of Cu, stainless steel, Ti, and Ti-TiN double layers. For Cu coatings, the deposited metal film thickness was shown to be dependent on the sputtering energy. Scanning electron microscope backscattering images revealed nonporous films uniform in thickness directly after sputtering. Film thickness varied between 0.15 µm and 2.5 µm, depending on coating material and sputtering parameters. From these materials, samples were produced without addition of metal powders, exhibiting metal contents as low as 8-10 wt.% based on the coating alone. Obtained samples had an apparent density of 1.1-1.9 g/cm3 and compressive strengths ranging from 22 MPa to 135 MPa.

A Review of Particle Swarm Optimization

NASA Astrophysics Data System (ADS)

Jain, N. K.; Nangia, Uma; Jain, Jyoti

2018-03-01

This paper presents an overview of the research progress in Particle Swarm Optimization (PSO) during 1995-2017. Fifty two papers have been reviewed. They have been categorized into nine categories based on various aspects. This technique has attracted many researchers because of its simplicity which led to many improvements and modifications of the basic PSO. Some researchers carried out the hybridization of PSO with other evolutionary techniques. This paper discusses the progress of PSO, its improvements, modifications and applications.

Effect of liquid epoxidized natural rubber (LENR) on mechanical properties and morphology of natural rubber/high density polyethylene/mengkuang fiber (NR/HDPE/MK) bio-composite

NASA Astrophysics Data System (ADS)

Piah, Mohd Razi Mat; Baharum, Azizah

2016-11-01

The use of mengkuang fiber (MK) fibers in NR/HDPE (40/60) blend was studied via surface modification of fiber. The MK fiber was pre-washed with 5%wt/v sodium hydroxide solution prior to treatment with liquid epoxidized natural rubber (LENR). The concentration of LENR were varied from 5%-20%wt in toluene. The effects of LENR concentrations were studied in terms of mechanical properties and morphology formed. Melt-blending was performed using an internal mixer (Haake Rheomix 600). The processing parameters identified were 135°C temperature, 45 rpm rotor speed, 12 minutes processing time and at 20%wt MK fiber loading. The optimum LENR treatment concentration was obtained at 5%wt with tensile strength, tensile modulus, and impact strength of 10.3 MPa, 414.2 MPa and 14.4 kJ/m2 respectively. The tensile modulus of LENR-treated MK fiber filled NR/HDPE bio-composite has shown enhancement up to 16.7% higher than untreated MK fiber. The tensile and impact strength were decreased with increasing LENR concentration due to the broken of MK fibers to smaller particles and adhered to each other. FESEM micrographs confirmed the formation of fiber-fiber agglomeration in NR/HDPE blends. The optical microscope analysis shows MK fibers is shorter than original fiber lengths after NaOH-LENR surface modification. The internal bonding forces of MK fiber seems to be weaker than external force exerted on it, therefore, the MK fiber has broken to smaller particles and reduced the mechanical properties of NR/HDPE/MK(20%) bio-composite.

High-throughput profiling of nanoparticle-protein interactions by fluorescamine labeling.

PubMed

Ashby, Jonathan; Duan, Yaokai; Ligans, Erik; Tamsi, Michael; Zhong, Wenwan

2015-02-17

A rapid, high throughput fluorescence assay was designed to screen interactions between proteins and nanoparticles. The assay employs fluorescamine, a primary-amine specific fluorogenic dye, to label proteins. Because fluorescamine could specifically target the surface amines on proteins, a conformational change of the protein upon interaction with nanoparticles will result in a change in fluorescence. In the present study, the assay was applied to test the interactions between a selection of proteins and nanoparticles made of polystyrene, silica, or iron oxide. The particles were also different in their hydrodynamic diameter, synthesis procedure, or surface modification. Significant labeling differences were detected when the same protein incubated with different particles. Principal component analysis (PCA) on the collected fluorescence profiles revealed clear grouping effects of the particles based on their properties. The results prove that fluorescamine labeling is capable of detecting protein-nanoparticle interactions, and the resulting fluorescence profile is sensitive to differences in nanoparticle's physical properties. The assay can be carried out in a high-throughput manner, and is rapid with low operation cost. Thus, it is well suited for evaluating interactions between a larger number of proteins and nanoparticles. Such assessment can help to improve our understanding on the molecular basis that governs the biological behaviors of nanomaterials. It will also be useful for initial examination of the bioactivity and reproducibility of nanomaterials employed in biomedical fields.

Experimental benchmark of kinetic simulations of capacitively coupled plasmas in molecular gases

NASA Astrophysics Data System (ADS)

Donkó, Z.; Derzsi, A.; Korolov, I.; Hartmann, P.; Brandt, S.; Schulze, J.; Berger, B.; Koepke, M.; Bruneau, B.; Johnson, E.; Lafleur, T.; Booth, J.-P.; Gibson, A. R.; O'Connell, D.; Gans, T.

2018-01-01

We discuss the origin of uncertainties in the results of numerical simulations of low-temperature plasma sources, focusing on capacitively coupled plasmas. These sources can be operated in various gases/gas mixtures, over a wide domain of excitation frequency, voltage, and gas pressure. At low pressures, the non-equilibrium character of the charged particle transport prevails and particle-based simulations become the primary tools for their numerical description. The particle-in-cell method, complemented with Monte Carlo type description of collision processes, is a well-established approach for this purpose. Codes based on this technique have been developed by several authors/groups, and have been benchmarked with each other in some cases. Such benchmarking demonstrates the correctness of the codes, but the underlying physical model remains unvalidated. This is a key point, as this model should ideally account for all important plasma chemical reactions as well as for the plasma-surface interaction via including specific surface reaction coefficients (electron yields, sticking coefficients, etc). In order to test the models rigorously, comparison with experimental ‘benchmark data’ is necessary. Examples will be given regarding the studies of electron power absorption modes in O2, and CF4-Ar discharges, as well as on the effect of modifications of the parameters of certain elementary processes on the computed discharge characteristics in O2 capacitively coupled plasmas.

Structures of ribonucleoprotein particle modification enzymes

PubMed Central

Liang, Bo; Li, Hong

2016-01-01

Small nucleolar and Cajal body ribonucleoprotein particles (RNPs) are required for the maturation of ribosomes and spliceosomes. They consist of small nucleolar RNA or Cajal body RNA combined with partner proteins and represent the most complex RNA modification enzymes. Recent advances in structure and function studies have revealed detailed information regarding ribonucleoprotein assembly and substrate binding. These enzymes form intertwined RNA–protein assemblies that facilitate reversible binding of the large ribosomal RNA or small nuclear RNA. These revelations explain the specificity among the components in enzyme assembly and substrate modification. The multiple conformations of individual components and those of complete RNPs suggest a dynamic assembly process and justify the requirement of many assembly factors in vivo. PMID:21108865

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zonghai; Amine, Khalil; Belharouak, Ilias

An active material for an electrochemical device wherein a surface of the active material is modified by a surface modification agent, wherein the surface modification agent is an organometallic compound.

Uptake and transfection with polymeric nanoparticles are dependent on polymer end-group structure, but largely independent of nanoparticle physical and chemical properties

PubMed Central

Sunshine, Joel C.; Peng, Daniel Y.; Green, Jordan J.

2012-01-01

Development of non-viral particles for gene delivery requires a greater understanding of the properties that enable gene delivery particles to overcome the numerous barriers to intracellular DNA delivery. Linear poly(beta-amino) esters (PBAE) have shown substantial promise for gene delivery, but the mechanism behind their effectiveness is not well quantified with respect to these barriers. In this study, we synthesized, characterized, and evaluated for gene delivery an array of linear PBAEs that differed by small changes along the backbone, side chain, and end-group of the polymers. We examined particle size and surface charge, polymer molecular weight, polymer degradation rate, buffering capacity, cellular uptake, transfection, and cytotoxicity of nanoparticles formulated with these polymers. Significantly, this is the first study that has quantified how small differential structural changes to polymers of this class modulate buffering capacity and polymer degradation rate and relates these findings to gene delivery efficacy. All polymers formed positively charged (zeta potential 21–29 mV) nanosized articles (~ 150 nm). The polymers hydrolytically degraded quickly in physiological conditions, with half-lives ranging from 90 minutes to 6 hours depending on polymer structure. The PBAE buffering capacities in the relevant pH range (pH 5.1 – 7.4) varied from 34% to 95% protonable amines, and on a per mass basis, PBAEs buffered 1.4–4.6 mmol H+/g. When compared to 25 kDa branched polyethyleneimine (PEI), PBAEs buffer significantly fewer protons/mass, as PEI buffers 6.2 mmol H+/g over the same range. However, due to the relatively low cytotoxicity of PBAEs, higher polymer mass can be used to form particles than with PEI and total buffering capacity of PBAE-based particles significantly exceeds that of PEI. Uptake into COS-7 cells ranged from 0% to 95% of cells and transfection ranged from 0% to 93% of cells, depending on the base polymer structure and the end-modifications examined. Five polymers achieved higher uptake and transfection efficacy with less toxicity than branched-PEI control. Surprisingly, acrylate-terminated base polymers were dramatically less efficacious than their end-capped versions, both in terms of uptake (1–3% for acrylate, 75–94% for end-capped) and transfection efficacy (0–1% vs. 20–89%), even though there are minimal differences between acrylate and end-capped polymers in terms of DNA retardation in gel electrophoresis, particle size, zeta potential, and cytotoxicity. These studies further elucidate the role of polymer structure for gene delivery and highlight that small molecule end-group modification of a linear polymer can be critical for cellular uptake in a manner that is largely independent of polymer/DNA binding, particle size, and particle surface charge. PMID:22970908

Surface modification of porous titanium with rice husk as space holder

NASA Astrophysics Data System (ADS)

Wang, Xinsheng; Hou, Junjian; Liu, Yanpei

2018-06-01

Porous titanium was characterized after its surface modification by acid and alkali solution immersion. The results show that the acid surface treatment caused the emergence of flocculent sodium titanate and induced apatite formation. The surface modification of porous titanium promotes biological activation, and the application of porous titanium is also improved as an implant material because of the existence of C and Si.

Modifications of the optical properties for DAM-ADC nuclear track detector exposed to alpha particles

NASA Astrophysics Data System (ADS)

Rammah, Y. S.; Awad, E. M.

2018-05-01

Modifications of the optical properties of diallyl maleate-allyl diglycol carbonate (DAM-ADC) nuclear detector induced by alpha particles are described. DAM-ADC samples were irradiated perpendicularly by thin 241Am disk source that emits alpha particles with 5.48 MeV. The optical absorption has been measured using the ultraviolet-visible (UV-1100) spectroscopy. It was found that DAM-ADC polymer shows substantial modifications in its optical characteristics upon irradiated with alpha particles with different energies. The optical energy band gap (Egap) for the detector was calculated for the direct and the indirect allowed transitions in K-space using two approaches (Tauc's model and absorption spectrum fitting (ASF) method). Urbach's energy (Ea), number of carbon atoms per conjugated length (N), number of carbon atoms per cluster (M), and refractive index (n) for the present samples were determined. Results reveal that the values of energy gap in direct transition are greater than those of indirect, before and after irradiation. (Egap), (Ea), (N), (M), and (n) of the present samples are changed significantly with irradiation time and value of alpha energy. Results reflect the possibility of using DAM-ADC polymer track detectors to estimate alpha particle energies using the variation of the absorbance.

High reactive sulphide chemically supported on silica surface to prepare functional nanoparticle

NASA Astrophysics Data System (ADS)

Chen, Lijuan; Guo, Xiaohui; Jia, Zhixin; Tang, Yuhan; Wu, Lianghui; Luo, Yuanfang; Jia, Demin

2018-06-01

A solid-phase preparation method was applied to obtain a novel, green and effective functional nanoparticle, silica-supported sulfur monochloride (silica-s-S2Cl2), by the chemical reaction between chlorine atom and silicon hydroxyl on the silica surface. Through this chemical reaction, silica surface supported with high content of sulfur, and the functional nanoparticles can not only vulcanize the rubber instead of sulfur or other vulcanizing agent with high performance, but also improve the filler-rubber interaction as a modifier due to the improved modification effect. 29Si NMR, Raman spectroscopy, Element analysis and TGA confirm that the sulfur monochloride is chemically bonded on the silica surface. Cure properties measurement, morphology of filler dispersion, mechanical properties measurement, immobilized polymer layer and oxidation induction time increment together show that the novel vulcanizing agent silica-s-S2Cl2 instead of sulfur in rubber vulcanization gives rise to significant improvement in the crosslinking density and the interfacial adhesion between silica particles and the rubber matrix, which is on account of the promoted vulcanizing on the functional silica nanoparticles surface with the supported sulfur.

Surface modification and stability of detonation nanodiamonds in microwave gas discharge plasma

NASA Astrophysics Data System (ADS)

Stanishevsky, Andrei V.; Walock, Michael J.; Catledge, Shane A.

2015-12-01

Detonation nanodiamonds (DND), with low hydrogen content, were exposed to microwave plasma generated in pure H2, N2, and O2 gases and their mixtures, and investigated using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Raman, and X-ray photoelectron spectroscopies. Considerable alteration of the DND surface was observed under the plasma conditions for all used gases, but the diamond structure of the DND particle core was preserved in most cases. The stabilizing effect of H2 in H2/N2 and H2/O2 binary gas plasmas on the DND structure and the temperature-dependent formation of various CNHx surface groups in N2 and H2/N2 plasmas were observed and discussed for the first time. DND surface oxidation and etching were the main effects of O2 plasma, whereas the N2 plasma led to DND surfaces rich in amide groups below 1073 K and nitrile groups at higher temperatures. Noticeable graphitization of the DND core structure was detected only in N2 plasma when the substrate temperature was above 1103 K.

Shape Modification and Size Classification of Microcrystalline Graphite Powder as Anode Material for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Wang, Cong; Gai, Guosheng; Yang, Yufen

2018-03-01

Natural microcrystalline graphite (MCG) composed of many crystallites is a promising new anode material for lithium-ion batteries (LiBs) and has received considerable attention from researchers. MCG with narrow particle size distribution and high sphericity exhibits excellent electrochemical performance. A nonaddition process to prepare natural MCG as a high-performance LiB anode material is described. First, raw MCG was broken into smaller particles using a pulverization system. Then, the particles were modified into near-spherical shape using a particle shape modification system. Finally, the particle size distribution was narrowed using a centrifugal rotor classification system. The products with uniform hemispherical shape and narrow size distribution had mean particle size of approximately 9 μm, 10 μm, 15 μm, and 20 μm. Additionally, the innovative pilot experimental process increased the product yield of the raw material. Finally, the electrochemical performance of the prepared MCG was tested, revealing high reversible capacity and good cyclability.

Surface modification of medical implant materials with hydrophilic polymers for enhanced biocompatibility and delivery of therapeutic agents

NASA Astrophysics Data System (ADS)

Urbaniak, Daniel J.

2004-11-01

In the research reported here, the surface modification of medical grade poly(dimethyl siloxane), polyetherurethane, and stainless steel through gamma-radiation grafting of hydrophilic polymers was investigated. Emphasis was placed on developing improved and simplified surface modification methods that produce more stable and more bioacceptible hydrophilic graft surfaces. As a result of this research, new surface modification techniques were developed that yield significantly improved surface stability unachievable using previous surface modification techniques. The surface modification of poly(dimethyl siloxane) with hydrophilic polymers was carried out using gamma radiation initiated graft polymerization. The addition of alkali metal hydroxides afforded a unique way to enhance the grafting of N-vinyl-2 pyrrolidone, dimethylacryamide, 2-methacryloyloxyethyl phosphoryl choline, N,N-dimethyl-N-(methacryloyloxyethyl)-N-(3-sulfopropyl)-ammonium-betaine, N,N-dimethyl-N-(methacrylamidopropyl)-N-(3-sulfopropyl)-ammonium-betaine, and copolymers thereof to silicones. Ethanolamine was found to further enhance the grafting of some hydrophilic polymers to silicone. The resulting hydrophilic surface grafts were resistant to hydrophobic surface rearrangement. This process overcomes previous problems inherent in silicone surface modification. The technique was also found to moderately enhance the grafting of hydrophilic monomers to polyetherurethane and to 316-L stainless steel. The surface modification of 316-L stainless steel was further enhanced by treating the substrates with a chromium III methacrylate bonding agent prior to irradiation. The coatings were evaluated for their potential use as depots for delivering therapeutic agents. The release of ofloxacin from surface-modified poly(dimethyl siloxane) and dexamethasone from surface-modified 316-L stainless steel was evaluated by in-vitro experiments. Therapeutic levels of drugs were released from surface-modified specimens via a burst effect. Improved surface characterization methods were another aspect of this research. New nanomechanical testing techniques were developed and used to evaluate the viscoelastic surface mechanical properties of low modulus surface-modified specimens. Dynamic nanoindentation characterization techniques were designed to measure the storage modulus and loss modulus of compliant viscoelastic substrate surfaces. The results of these experiments were compared with modulus data obtained by conventional dynamic mechanical spectroscopy. Nanoscratch testing methods were also developed that qualitatively compared the abrasion resistance of surface-modified substrates. (Abstract shortened by UMI.)

Recombinant Expression of Tandem-HBc Virus-Like Particles (VLPs).

PubMed

Stephen, Sam L; Beales, Lucy; Peyret, Hadrien; Roe, Amy; Stonehouse, Nicola J; Rowlands, David J

2018-01-01

The hepatitis B virus (HBV) core protein (HBc) has formed the building block for virus-like particle (VLP) production for more than 30 years. The ease of production of the protein, the robust ability of the core monomers to dimerize and assemble into intact core particles, and the strong immune responses they elicit when presenting antigenic epitopes all demonstrate its promise for vaccine development (reviewed in Pumpens and Grens (Intervirology 44: 98-114, 2001)). HBc has been modified in a number of ways in attempts to expand its potential as a novel vaccine platform. The HBc protein is predominantly α-helical in structure and folds to form an L-shaped molecule. The structural subunit of the HBc particle is a dimer of monomeric HBc proteins which together form an inverted T-shaped structure. In the assembled HBc particle the four-helix bundle formed at each dimer interface appears at the surface as a prominent "spike." The tips of the "spikes" are the preferred sites for the insertion of foreign sequences for vaccine purposes as they are the most highly exposed regions of the assembled particles. In the tandem-core modification two copies of the HBc protein are covalently linked by a flexible amino acid sequence which allows the fused dimer to fold correctly and assemble into HBc particles. The advantage of the modified structure is that the assembly of the dimeric subunits is defined and not formed by random association. This facilitates the introduction of single, larger sequences at the tip of each surface "spike," thus overcoming the conformational clashes contingent on insertion of large structures into monomeric HBc proteins.Differences in inserted sequences influence the assembly characteristics of the modified proteins, and it is important to optimize the design of each novel construct to maximize efficiency of assembly into regular VLPs. In addition to optimization of the construct, the expression system used can also influence the ability of recombinant structures to assemble into regular isometric particles. Here, we describe the production of recombinant tandem-core particles in bacterial, yeast and plant expression systems.

Evaluation of surface, microstructure and phase modifications on various tungsten grades induced by pulsed plasma loading

NASA Astrophysics Data System (ADS)

Vilémová, M.; Pala, Z.; Jäger, A.; Matějíček, J.; Chernyshova, M.; Kowalska-Strzęciwilk, E.; Tonarová, D.; Gribkov, V. A.

2016-03-01

Progress in the field of nuclear fusion requires the development of a new generation of tungsten materials that are expected to meet specific property, lifetime and safety requirements. Pursuing this goal, the new materials must be properly tested in a wide range of conditions including cases where material is brought to the molten stage, such as with large fusion plasma instabilities. In this study, two prospective candidates from the family of dispersion strengthened (DS) tungsten materials, i.e., W-1%Y2O3 and W-2.5%TiC, were subjected to extreme heat loading exerted by the deuterium plasma generator PF6. The study focuses on the interaction of the tungsten matrix with the dispersed particles during material melting. The materials underwent significant changes in microstructure and phase content. Among the most serious was the loss of TiC particles and void formation in W-2.5%TiC and phase change of polymorphic Y2O3 particles in W-1% Y2O3.

Optofluidic control of axonal guidance

NASA Astrophysics Data System (ADS)

Gu, Ling; Ordonez, Simon; Black, Bryan; Mohanty, Samarendra K.

2013-03-01

Significant efforts are being made for control on axonal guidance due to its importance in nerve regeneration and in the formation of functional neuronal circuitry in-vitro. These include several physical (topographic modification, optical force, and electric field), chemical (surface functionalization cues) and hybrid (electro-chemical, photochemical etc) methods. Here, we report comparison of the effect of linear flow versus microfluidic flow produced by an opticallydriven micromotor in guiding retinal ganglion axons. A circularly polarized laser tweezers was used to hold, position and spin birefringent calcite particle near growth cone, which in turn resulted in microfluidic flow. The flow rate and resulting shear-force on axons could be controlled by a varying the power of the laser tweezers beam. The calcite particles were placed separately in one chamber and single particle was transported through microfluidic channel to another chamber containing the retina explant. In presence of flow, the turning of axons was found to strongly correlate with the direction of flow. Turning angle as high as 90° was achieved. Optofluidic-manipulation can be applied to other types of mammalian neurons and also can be extended to stimulate mechano-sensing neurons.

Surface modification of acetaminophen particles by atomic layer deposition.

PubMed

Kääriäinen, Tommi O; Kemell, Marianna; Vehkamäki, Marko; Kääriäinen, Marja-Leena; Correia, Alexandra; Santos, Hélder A; Bimbo, Luis M; Hirvonen, Jouni; Hoppu, Pekka; George, Steven M; Cameron, David C; Ritala, Mikko; Leskelä, Markku

2017-06-15

Active pharmaceutical ingredients (APIs) are predominantly organic solid powders. Due to their bulk properties many APIs require processing to improve pharmaceutical formulation and manufacturing in the preparation for various drug dosage forms. Improved powder flow and protection of the APIs are often anticipated characteristics in pharmaceutical manufacturing. In this work, we have modified acetaminophen particles with atomic layer deposition (ALD) by conformal nanometer scale coatings in a one-step coating process. According to the results, ALD, utilizing common chemistries for Al 2 O 3 , TiO 2 and ZnO, is shown to be a promising coating method for solid pharmaceutical powders. Acetaminophen does not undergo degradation during the ALD coating process and maintains its stable polymorphic structure. Acetaminophen with nanometer scale ALD coatings shows slowed drug release. ALD TiO 2 coated acetaminophen particles show cytocompatibility whereas those coated with thicker ZnO coatings exhibit the most cytotoxicity among the ALD materials under study when assessed in vitro by their effect on intestinal Caco-2 cells. Copyright © 2017 Elsevier B.V. All rights reserved.