Science.gov

Sample records for nano silica morphology

  1. Alteration of Cell Morphology with Nano- and Micro-Topographical Surface on Closed-Packed Silica Nanobeads.

    PubMed

    Park, Jeong Su; Lee, Dahyun; Park, Ji Yeon; Lee, Hyo Jin; Kim, Jin-Seok; Lee, Jin Seok

    2016-06-01

    The nanotopological cues are emerging field of in vivo study, because it stimulates alteration of cell morphology and cell behavior such as adhesion, proliferation, differentiation, apoptosis and migration. However, it has not studies nanosurface affected cancer cell behavior, therefore, in this study, we determined that effects the silica nanobeads used as nanotopological tools on cancer cells. For synthesis of silica beads, we made it using stober method and basic amino acid (L-arginine) instead of NH4OH. We carried out rubbing beads to obtain the monolayer silica beads and it used as nanotopological cues for fabrication. It was induced changing cell morphology at 1DIV in group-II (SB-450 and SB-570). However, it was maintained in group-I (SB-118, SB-230) and group-III (SB-1450) like control. Therefore, we separated type-I and type-II surface along with area of cell adhesion and morphology. The characteristic of type-II surface was long distance between contact points, resulting in increase of tension to cells. We found that the morphology rounded up by type-II surface at 1DIV. We described that the nanosurface-induced mechanical tension is associated with alteration of morphology, thus the silica nanobeads used as nanotopological tools for cancer research.

  2. Alteration of Cell Morphology with Nano- and Micro-Topographical Surface on Closed-Packed Silica Nanobeads.

    PubMed

    Park, Jeong Su; Lee, Dahyun; Park, Ji Yeon; Lee, Hyo Jin; Kim, Jin-Seok; Lee, Jin Seok

    2016-06-01

    The nanotopological cues are emerging field of in vivo study, because it stimulates alteration of cell morphology and cell behavior such as adhesion, proliferation, differentiation, apoptosis and migration. However, it has not studies nanosurface affected cancer cell behavior, therefore, in this study, we determined that effects the silica nanobeads used as nanotopological tools on cancer cells. For synthesis of silica beads, we made it using stober method and basic amino acid (L-arginine) instead of NH4OH. We carried out rubbing beads to obtain the monolayer silica beads and it used as nanotopological cues for fabrication. It was induced changing cell morphology at 1DIV in group-II (SB-450 and SB-570). However, it was maintained in group-I (SB-118, SB-230) and group-III (SB-1450) like control. Therefore, we separated type-I and type-II surface along with area of cell adhesion and morphology. The characteristic of type-II surface was long distance between contact points, resulting in increase of tension to cells. We found that the morphology rounded up by type-II surface at 1DIV. We described that the nanosurface-induced mechanical tension is associated with alteration of morphology, thus the silica nanobeads used as nanotopological tools for cancer research. PMID:27427740

  3. Dopamine-induced silica-polydopamine hybrids with controllable morphology.

    PubMed

    Ho, Chia-Che; Ding, Shinn-Jyh

    2014-04-01

    Novel silica-polydopamine hybrids, with controllable morphology, are facilely fabricated in an emulsion system consisting of tetraethyl orthosilicate, dopamine, water, and NaOH under weakly basic conditions (pH 8.5-10). An increase in initial pH favors the formation of nano-structured spherical silica-PDA hybrids from a flocculated structure.

  4. Silica hollow spheres with nano-macroholes like diatomaceous earth.

    PubMed

    Fujiwara, Masahiro; Shiokawa, Kumi; Sakakura, Ikuko; Nakahara, Yoshiko

    2006-12-01

    Artificial synthesis of hollow cell walls of diatoms is an ultimate target of nanomaterial science. The addition of some water-soluble polymers such as sodium polymethacrylate to a solution of water/oil/water emulsion system, which is an essential step of the simple synthetic procedure of silica hollow spheres (microcapsules), led to the formation of silica hollow spheres with nano-macroholes (>100 nm) in their shell walls, the morphologies of which are analogous to those of diatom earth.

  5. Action of colloidal silica films on different nano-composites

    NASA Astrophysics Data System (ADS)

    Abdalla, S.; Al-Marzouki, F.; Obaid, A.; Gamal, S.

    Nano-composite films have been the subject of extensive work to develop the energy-storage efficiency of electrostatic capacitors. Factors such as polymer purity, nano-particles size, and film morphology drastically affect the electrostatic efficiency of the dielectric material that form an insulating film between conductive electrodes of a capacitor. This in turn affects the energy storage performance of the capacitor. In the present work, we have studied the dielectric properties of 4 high pure amorphous polymer films: polymethylmethacrylate (PMMA), polystyrene, polyimide and poly-4-vinylpyridine. Comparison between the dielectric properties of these polymers has revealed that the higher break down performance is a character of polyimide PI and PMMA. Also, our experimental data shows that adding colloidal silica to PMMA and PI leads to a net decrease in the dielectric properties compared to the pure polymer.

  6. Acrylic coatings exhibiting improved hardness, solvent resistance and glossiness by using silica nano-composites

    NASA Astrophysics Data System (ADS)

    Dashtizadeh, Ahmad; Abdouss, Majid; Mahdavi, Hossein; Khorassani, Manuchehr

    2011-01-01

    To prepare nano-composite emulsion acrylic resins with improved surface hardness and solvent resistance, nano-silica particles were treated with surfactants. The monomers of methyl methacrylate/butylacrylate were co-polymerized on the surface of dispersed silica particles. Several emulsions with different silica contents and copolymer mole fractions were prepared. Finally the emulsions were modified to water-based acrylic coatings and improved properties such as surface hardness, solvent resistance and glossiness were determined. The study of coatings was directed to find the improved resin by optimum surface properties. Size distribution and morphology of latexes were characterized by Fourier transform infrared spectroscopy, dynamic light scattering, transmission electron microscopy and scanning electron microscopy. The glass transition temperature of nano-composites was measured and discussed its relation with silica contents, monomer mole fractions and improved properties of coatings. The optimum pendulum hardness of coatings was on 0.46 methyl methacrylate mole fraction and 120 g silica content. An increase in pendulum hardness of nano-composites with the addition of modified silica was observed. DLS and TEM studies indicate that silica particles were dispersed homogenously through the polymer matrix.

  7. Performance of concrete incorporating colloidal nano-silica

    NASA Astrophysics Data System (ADS)

    Zeidan, Mohamed Sabry

    Nanotechnology, as one of the most modern fields of science, has great market potential and economic impact. The need for research in the field of nanotechnology is continuously on the rise. During the last few decades, nanotechnology was developing rapidly into many fields of applied sciences, engineering and industrial applications, especially through studies of physics, chemistry, medicine and fundamental material science. These new developments may be attributed to the fact that material properties and performance can be significantly improved and controlled through nano-scale processes and nano-structures. This research program aims at 1) further understanding the behavior of cementitious materials when amended on the nano-scale level and 2) exploring the effect of this enhancement on the microstructure of cement matrix. This study may be considered as an important step towards better understanding the use of nano-silica in concrete. The main goal of the study is to investigate the effect of using colloidal nano-silica on properties of concrete, including mechanical properties, durability, transport properties, and microstructure. The experimental program that was conducted included a laboratory investigation of concrete mixtures in which nano-silica was added to cement or to a combination of cement and Class F fly ash. Various ratios of nano-silica were used in concrete mixtures to examine the extent and types of improvements that could be imparted to concrete. The conducted experimental program assessed these improvements in terms of reactivity, mechanical properties, and durability of the mixtures under investigation. Advanced testing techniques---including mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM)---were used to investigate the effect of nano-silica on the microstructure of the tested mixtures. In addition, the effect of nano-silica on the alkali-silica reaction (ASR) was examined using various techniques, including testing

  8. Engineering the synthesis of silica-gold nano-urchin particles using continuous synthesis

    NASA Astrophysics Data System (ADS)

    Sebastian, Víctor; Lee, Seung-Kon; Jensen, Klavs F.

    2014-10-01

    Compared to freestanding nanoparticles, supported nanostructures typically show better mechanical stability as well as ease of handling. Unique shapes such as core-shells, raspberries and crescents have been developed on supported materials to gain improved chemical and optical properties along with versatility and tunability. We report the formation of hyper-branched gold structures on silica particles, silica-gold nano-urchin (SGNU) particles. Kinetic control of crystallization, fast mass transfer as well as a bumped surface morphology of the silica particles are important factors for the growth of gold branches on the silica support. Using a microfluidic platform, continuous synthesis of SGNUs is achieved with increased reaction rate (less than 12 min of residence time), better controllability and reproducibility than that obtained in batch synthesis. The hyper-branched gold structures display surface-enhanced Raman scattering (SERS).Compared to freestanding nanoparticles, supported nanostructures typically show better mechanical stability as well as ease of handling. Unique shapes such as core-shells, raspberries and crescents have been developed on supported materials to gain improved chemical and optical properties along with versatility and tunability. We report the formation of hyper-branched gold structures on silica particles, silica-gold nano-urchin (SGNU) particles. Kinetic control of crystallization, fast mass transfer as well as a bumped surface morphology of the silica particles are important factors for the growth of gold branches on the silica support. Using a microfluidic platform, continuous synthesis of SGNUs is achieved with increased reaction rate (less than 12 min of residence time), better controllability and reproducibility than that obtained in batch synthesis. The hyper-branched gold structures display surface-enhanced Raman scattering (SERS). Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04021j

  9. Comparison of dielectric properties of polydimethylsiloxane (PDMS) grafted polyacrylates/nano alumina and nano silica composites

    NASA Astrophysics Data System (ADS)

    Murudkar, Vrishali V.; Gaonkar, Amita A.; Deshpande, V. D.; Mhaske, S. T.

    2016-05-01

    Polydimethylsiloxane possess very poor mechanical properties. However, typically the initial modulus and durability of material is low and to improve this aspect a reinforcement phase is required. For the composite to be effective the filler must be with large aspect ratio i.e. with large surface area to volume ratio. Nano alumina (Al2O3) and nano silica (SiO2) are materials of choice for nanocomposite design. Grafted Polydimethylsiloxane (G-PDMS) and nano alumina and nano Silica composites have been prepared, by solvent casting method. FTIR study reveals that there is bonding overlap in G-PDMS/SiO2 nano composites. In dielectric study, it is observed that G-PDMS/SiO2 nano composites were more conducting in nature than G-PDMS/ Al2O3 nano composites. G-PDMS/ Al2O3 nano composites showed enhanced dielectric constant and less loss of energy than G-PDMS/SiO2 nano composites.

  10. Thick multilayered (silica/gold) dipole nano-antenna.

    PubMed

    Khaleque, Abdul; Mironov, Evgeny G; Liu, Liming; Hattori, Haroldo T

    2015-12-01

    Nano-antennas are the optical equivalent of antennas that are used to transmit and receive information at radio frequencies. These antennas have been used in different applications in photonics such as optical imaging, particle manipulation, bio-sensing, and improvement of the performance of solar cells. In this article we study composite nano-antennas made of alternating layers of silica and gold. We show that a 50% filling factor leads to a 2.0 times increase in the electric-field enhancement factor when compared with a pure-gold antenna. PMID:26836661

  11. Effect of catalyst concentration on size, morphology and optical properties of silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Arora, Ekta; Ritu, Kumar, Sacheen; Kumar, Dinesh

    2016-05-01

    Today, nanomaterials play a key role in various fields such as electronics, aerospace, pharmaceuticals and biomedical because of their unique physical, chemical and biological properties which are different from bulk materials. Nano sized silica particles have gained the prominent position in scientific research and have wide applications. The sol-gel method is the best method to synthesize silica nanoparticles because of its potential to produce monodispersed with narrow size distribution at mild conditions. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate (TEOS) in ethanol act as solvent. The synthesized nanoparticles were characterized by Field Emission Scanning electron Microscope (FE-SEM), UV Spectrometer. The smallest size of silica particles is around 150nm examined by using FE-SEM. The optical properties and band structure was analyzed using UV-visible spectroscopy which is found to be increase by reducing the size of particles. Concentration effect of catalyst on the size, morphology and optical properties were analyzed.

  12. Pore morphology study of silica aerogels

    SciTech Connect

    Hua, D.W.; Anderson, J.; Haereid, S.; Smith, D.M.

    1994-12-31

    Silica aerogels have numerous properties which suggest applications such as ultra high efficiency thermal insulation. These properties relate directly to the aerogel`s pore size distribution. The micro and meso pore size ranges can be investigated by normal small angle x-ray scattering and possibly, nitrogen adsorption. However, the measurement of larger pores (> 250 {angstrom}) is more difficult. Due to their limited mechanical strength, mercury porosimetry and nitrogen condensation can disrupt the gel structure and electron microscopy provides only limited large scale structure information. The use of small angle light scattering techniques seems to have promise, the only hurdle is that aerogels exhibit significant multiple scattering. This can be avoided if one observes the gels in the wet stage since the structure of the aerogel should be very similar to the wet gel (as the result of supercritical drying). Thus, if one can match the refractive index, the morphology can be probed. The combination of certain alcoholic solvents fit this index matching criteria. Preliminary results for the gel network (micron range) and primary particle structure (manometer) are reported by using small angle light scattering and ultra-small angle x-ray scattering. The effects on structure over the length scale range of <1 nm to >5 {mu}m under different conditions (precursors, pH, etc.) are presented. The change in structure of an aerogel during isostatic compaction to 228 MPa (to simulate drying from wetting solvents) are also discussed.

  13. Conductive polyurethane composites containing polyaniline-coated nano-silica.

    PubMed

    Liu, Bo-Tau; Syu, Jhan-Rong; Wang, De-Hua

    2013-03-01

    In this study, we used 1.2-Aminopropyltriethoxysilane (APTS) as a coupling agent to synthesize silica-polyaniline (PANI) core-shell nanoparticles. The core-shell nanoparticles and PANI oligomers were reacted with isocyanates to prepare the conductive polyurethane (PU)-PANI-silica nanocomposites. The core-shell-nanoparticle structure shows significant enhancement on electrical properties of the conductive nanocomposites even though only 0.0755-wt.% PANI was coated on the nano-silica. The surface resistance of the nanocomposite containing 5 wt.% PANI can reduce to ~10(8) Ω/sq, lowering two orders in contrast to the nanocomposite without the core-shell structure. In comparison with the neat PU, tensile strength and elongation of the nanocomposite containing silica-PANI core-shell nanoparticles can increase 3.1 and 3.8 times, respectively. We suspect that the extraordinary enhancement of electrical and mechanical properties may result from the fact that contact probability among PANI moieties and chemical bonding between particles and PU matrix increase due to the PANI coated on the surface of silica. PMID:23261334

  14. The use of Reactive Ion Etching for obtaining “free” silica nano test tubes

    NASA Astrophysics Data System (ADS)

    Buyukserin, Fatih; Martin, Charles R.

    2010-10-01

    Silica nano test tubes are one-dimensional inorganic nanostructures with several biotechnological applications including biosensing, magnetic resonance imaging, and targeted cancer therapeutics. They are generally prepared by sol-gel deposition of silica to nanoporous alumina templates. Preparing samples composed of isolated free silica nano test tubes can be a challenging process due to the conformal coating of silica on the template. This causes the formation of a top-surface silica layer which laterally connects the nano test tubes. Herein, we detailed the use of Reactive Ion Etching to remove this top-surface silica layer which yields free silica nano test tubes with template dissolution. Compared with the mechanical polishing approach, Reactive Ion Etching treatment allows a fine manipulation ability of the surface material at the nanoscale level. When used excessively, Reactive Ion Etching causes an orifice closing phenomenon that may be employed to create novel one-dimensional nanocapsules.

  15. New insight into mesoporous silica for nano metal-organic framework.

    PubMed

    Kondo, Atsushi; Takanashi, Shinji; Maeda, Kazuyuki

    2012-10-15

    A micropore- and mesopore-integrated material was synthesized by using a mesoporous silica and a metal-organic framework (MOF). The composite was composed of nano MOF crystals and mesoporous silica showing high porosity based on the intrinsic micropores of MOF and mesopores of mesoporous silica and additional pore spaces that should be from the void between nano MOF crystals. The composite shows higher adsorption rate of ethanol at 303 K than that of the bulk MOF.

  16. Species-specific polyamines from diatoms control silica morphology

    NASA Astrophysics Data System (ADS)

    Kröger, Nils; Deutzmann, Rainer; Bergsdorf, Christian; Sumper, Manfred

    2000-12-01

    Biomineralizing organisms use organic molecules to generate species-specific mineral patterns. Here, we describe the chemical structure of long-chain polyamines (up to 20 repeated units), which represent the main organic constituent of diatom biosilica. These substances are the longest polyamine chains found in nature and induce rapid silica precipitation from a silicic acid solution. Each diatom is equipped with a species-specific set of polyamines and silica-precipitating proteins, which are termed silaffins. Different morphologies of precipitating silica can be generated by polyamines of different chain lengths as well as by a synergistic action of long-chain polyamines and silaffins.

  17. Use of polypropylene fibers coated with nano-silica particles into a cementitious mortar

    NASA Astrophysics Data System (ADS)

    Coppola, B.; Di Maio, L.; Scarfato, P.; Incarnato, L.

    2015-12-01

    Fiber reinforced cementitious composite (FRCC) materials have been widely used during last decades in order to overcome some of traditional cementitious materials issues: brittle behaviour, fire resistance, cover spalling, impact strength. For composite materials, fiber/matrix bond plays an important role because by increasing fiber/matrix interactions is possible to increase the behaviour of the entire material. In this study, in order to improve fiber to matrix adhesion, two chemical treatments of polypropylene fibers were investigated: alkaline hydrolysis and nano-silica sol-gel particles deposition. Treatmtents effect on fibers morphology and mechanical properties was investigated by scanning electron microscopy (SEM) and tensile tests. SEM investigations report the presence of spherical nano-silica particles on fiber surface, in the case of sol-gel process, while alkaline hydrolysis leads to an increase of fibers roughness. Both treatments have negligible influence on fibers mechanical properties confirming the possibility of their use in a cementitious mortar. Pullout tests were carried out considering three embedded length of fibers in mortar samples (10, 20 and 30 mm, respectively) showing an increase of pullout energy for treated fibers. The influence on fiber reinforced mortar mechanical properties was investigated by three-point flexural tests on prismatic specimens considering two fibers length (15 and 30 mm) and two fibers volume fractions (0.50 and 1.00 %). A general increase of flexural strength over the reference mix was achieved and an overall better behaviour is recognizable for mortars containing treated fibers.

  18. Use of polypropylene fibers coated with nano-silica particles into a cementitious mortar

    SciTech Connect

    Coppola, B. Di Maio, L.; Scarfato, P.; Incarnato, L.

    2015-12-17

    Fiber reinforced cementitious composite (FRCC) materials have been widely used during last decades in order to overcome some of traditional cementitious materials issues: brittle behaviour, fire resistance, cover spalling, impact strength. For composite materials, fiber/matrix bond plays an important role because by increasing fiber/matrix interactions is possible to increase the behaviour of the entire material. In this study, in order to improve fiber to matrix adhesion, two chemical treatments of polypropylene fibers were investigated: alkaline hydrolysis and nano-silica sol-gel particles deposition. Treatmtents effect on fibers morphology and mechanical properties was investigated by scanning electron microscopy (SEM) and tensile tests. SEM investigations report the presence of spherical nano-silica particles on fiber surface, in the case of sol-gel process, while alkaline hydrolysis leads to an increase of fibers roughness. Both treatments have negligible influence on fibers mechanical properties confirming the possibility of their use in a cementitious mortar. Pullout tests were carried out considering three embedded length of fibers in mortar samples (10, 20 and 30 mm, respectively) showing an increase of pullout energy for treated fibers. The influence on fiber reinforced mortar mechanical properties was investigated by three-point flexural tests on prismatic specimens considering two fibers length (15 and 30 mm) and two fibers volume fractions (0.50 and 1.00 %). A general increase of flexural strength over the reference mix was achieved and an overall better behaviour is recognizable for mortars containing treated fibers.

  19. Development of construction materials using nano-silica and aggregates recycled from construction and demolition waste.

    PubMed

    Mukharjee, Bibhuti Bhusan; Barai, Sudhirkumar V

    2015-06-01

    The present work addresses the development of novel construction materials utilising commercial grade nano-silica and recycled aggregates retrieved from construction and demolition waste. For this, experimental work has been carried out to examine the influence of nano-silica and recycled aggregates on compressive strength, modulus of elasticity, water absorption, density and volume of voids of concrete. Fully natural and recycled aggregate concrete mixes are designed by replacing cement with three levels (0.75%, 1.5% and 3%) of nano-silica. The results of the present investigation depict that improvement in early days compressive strength is achieved with the incorporation of nano-silica in addition to the restoration of reduction in compressive strength of recycled aggregate concrete mixes caused owing to the replacement of natural aggregates by recycled aggregates. Moreover, the increase in water absorption and volume of voids with a reduction of bulk density was detected with the incorporation of recycled aggregates in place of natural aggregates. However, enhancement in density and reduction in water absorption and volume of voids of recycled aggregate concrete resulted from the addition of nano-silica. In addition, the results of the study reveal that nano-silica has no significant effect on elastic modulus of concrete. PMID:25986048

  20. Development of construction materials using nano-silica and aggregates recycled from construction and demolition waste.

    PubMed

    Mukharjee, Bibhuti Bhusan; Barai, Sudhirkumar V

    2015-06-01

    The present work addresses the development of novel construction materials utilising commercial grade nano-silica and recycled aggregates retrieved from construction and demolition waste. For this, experimental work has been carried out to examine the influence of nano-silica and recycled aggregates on compressive strength, modulus of elasticity, water absorption, density and volume of voids of concrete. Fully natural and recycled aggregate concrete mixes are designed by replacing cement with three levels (0.75%, 1.5% and 3%) of nano-silica. The results of the present investigation depict that improvement in early days compressive strength is achieved with the incorporation of nano-silica in addition to the restoration of reduction in compressive strength of recycled aggregate concrete mixes caused owing to the replacement of natural aggregates by recycled aggregates. Moreover, the increase in water absorption and volume of voids with a reduction of bulk density was detected with the incorporation of recycled aggregates in place of natural aggregates. However, enhancement in density and reduction in water absorption and volume of voids of recycled aggregate concrete resulted from the addition of nano-silica. In addition, the results of the study reveal that nano-silica has no significant effect on elastic modulus of concrete.

  1. Vital roles of nano silica in synthetic based mud for high temperature drilling operation

    NASA Astrophysics Data System (ADS)

    Yusof, Muhammad Aslam Md; Hanafi, Nor Hazimastura

    2015-07-01

    At high temperature drilling, chemicals degradation occurs which reduce the effectiveness of the drilling fluid. There is a potential that by using nano sized particles which have thermal stability up to 2500°F to be used as a stabilizer to withstand the harsh condition. Therefore, this project aims to identify the performance of synthetic-based mud (SBM) with nano silica for high temperature drilling operation. A conventional SBM performance has been compared with additional percentages of nano silica. 20% and 40% of nano silica out of fluid loss weight has been added into the SBM and analyzed the rheological properties and other drilling fluid properties. The conventional SBM formulation has lost some amount of weighting material or solids in the mud and has been replaced by lighter and smaller size of nanoparticles. It has reduced the rheological properties of the mud but the gelation formed by nano silica material has given higher gel strength. Also, nano silica potentially plugs the porous media, resulted in lower filtration loss measurement and thinner mud cake ranged 20% to 50% respectively.

  2. Morphological characterization of silica obtained by calcination of methacrylic and epoxy - silica hybrid systems

    NASA Astrophysics Data System (ADS)

    Tescione, F.; Lionetto, F.; Corcione, C. Esposito; Buonocore, G. G.; Striani, R.; Lavorgna, M.; Frigione, M.

    2016-05-01

    The work is addressed to investigating the potentiality of calcination of organic-inorganic (O-I) hybrids as a feasible approach to produce silica particles, at mild temperature conditions and with tailored morphology. Two different innovative hybrid systems were obtained through sol-gel process with a siloxane content ranging from 6 to 26wt%. The two O-I hybrids differed for i) the organic matrix (methacrylic or epoxy), ii) its crosslinking mechanism (photopolymerization for methacrylic systems or thermal cold-cure for epoxy systems) and iii) the rate ratio between sol-gel and crosslinking reactions. Different characterization techniques were used to understand the effect of composition and curing method on the morphology of the silica obtained from O-I hybrids after calcination in air. The results confirm the morphology and properties of silica particles in terms of surface and porosity may be tailored over a wide range by varying the composition and nature of organic and inorganic precursors of hybrids.

  3. Probabilistic modeling of the flows and environmental risks of nano-silica.

    PubMed

    Wang, Yan; Kalinina, Anna; Sun, Tianyin; Nowack, Bernd

    2016-03-01

    Nano-silica, the engineered nanomaterial with one of the largest production volumes, has a wide range of applications in consumer products and industry. This study aimed to quantify the exposure of nano-silica to the environment and to assess its risk to surface waters. Concentrations were calculated for four environmental (air, soil, surface water, sediments) and two technical compartments (wastewater, solid waste) for the EU and Switzerland using probabilistic material flow modeling. The corresponding median concentration in surface water is predicted to be 0.12 μg/l in the EU (0.053-3.3 μg/l, 15/85% quantiles). The concentrations in sediments in the complete sedimentation scenario were found to be the largest among all environmental compartments, with a median annual increase of 0.43 mg/kg · y in the EU (0.19-12 mg/kg · y, 15/85% quantiles). Moreover, probabilistic species sensitivity distributions (PSSD) were computed and the risk of nano-silica in surface waters was quantified by comparing the predicted environmental concentration (PEC) with the predicted no-effect concentration (PNEC) distribution, which was derived from the cumulative PSSD. This assessment suggests that nano-silica currently poses no risk to aquatic organisms in surface waters. Further investigations are needed to assess the risk of nano-silica in other environmental compartments, which is currently not possible due to a lack of ecotoxicological data. PMID:26745294

  4. Luminescence, absorption and morphology studies of laser-damage sites in silica glasses and coatings

    NASA Astrophysics Data System (ADS)

    Gallais, Laurent; Capoulade, Jeremie; Wagner, Frank; Krol, Helene; Natoli, Jean-Yves; Commandre, Mireille; Kurbanov, Saidislam

    2005-12-01

    The analysis of modifications induced by laser damage in optical materials is important for understanding the damage process. In this work, we study the morphological and structural modifications induced by a nano-second pulsed laser (355 and 1064nm) on fused silica samples (Suprasil, Herasil) and silica thin films (deposited by IP, IAD, EBD, IAD). The morphological changes are analyzed using optical microscopy, optical 3D surface profiler. The absorption modifications are measured by photothermal microscopy with a micronic resolution. Luminescence (excited at 244nm) mappings are also performed on damage sites and the luminescence spectra analyzed. Based on these measurements, we study the different laser damage step that we have identified: initiation by absorbing nanoscale defects, heating of the defect and the surrounding matrix, modification of the surrounding material that becomes absorbing, and macroscopic damage at final. We identify and spatially resolve several kinds of defects induced by catastrophic breakdown and we also discuss the observed structural changes on damage sites, taking into account the physical processes involved.

  5. Morphological Control of Multifunctional Mesoporous Silica Nanomaterials for Catalysis Applications

    SciTech Connect

    Huh, Seong

    2004-12-19

    I found an efficient method to control the morphology of the organically monofunctionalized mesoporous silica materials by introducing different types of organoalkoxysilanes in a base-catalyzed co-condensation reaction. The monofunctionalized materials exhibit different particle morphologies relative to the pure MCM-41 material. The concentration dependence of the morphology is a critical factor to determine the final particle shape. A proposed mechanism of the shape evolution is also offered. After understanding the role of organoalkoxysilanes in producing various well-shaped nanomaterials, I also obtained a series of bifunctional mesoporous silica materials with certain particle morphology. A series of bifunctional mesoporous silica nanospheres (MSNs) whose physicochemical properties was investigated via solid state NMR techniques and Cu2+ adsorption capacity tests, The ratio of two different organic groups inside of mesopores of these MSNs could be fine-tuned. These MSNs serve as a useful model system to study substrate selectivity in catalytic reactions and sorption phenomena. For example, the Cu2+ adsorption capacity of these materials was dictated by the chemical nature of the mesopores generated by the different organic functional groups. An investigation of the substrate selectivity of the bifunctionalized MSNs in a competitive nitroaldol reaction using an equimolar amount of two competing 4-nitrobenzaldehyde derivatives was performed. Shape-controlled bifunctional MSNs were employed as the catalysts. The properties of the MSNs were investigated using various spectroscopic methods and electron microscopy. The more hydrophobic the surface organic groups are, the higher the ratio of hydrophobic final product. This is the first example to demonstrate the selection of substrate using physicochemical nature of the mesopore surface other than the conventional shape selection in zeolite systems. I also created a cooperative dual catalyst

  6. Size-dependent toxicity of silica nano-particles to Chlorella kessleri.

    PubMed

    Fujiwara, Kitao; Suematsu, Hitoshi; Kiyomiya, Emiko; Aoki, Motohide; Sato, Mamiko; Moritoki, Nobuko

    2008-08-01

    SiO(2) nano-particles were found to exhibit size-dependent toxicity toward the alga, Chlorella kessleri. Small SiO(2) nano-particles exhibit stronger toxicity: 50% inhibitory concentrations (IC(50)) value for 5 nm = 0.8 +/- 0.6%, 26 nm = 7.1 +/- 2.8%, and 78 nm = 9.1 +/- 4.7%. Enlargement of the cell body was observed by flow cytometry, which is due to the presence of structures that obstructed cell division. Optical and transmission microscopes were used to observe coagulated cells with incomplete division. Although the physiological effect of SiO(2) nano-particles was not clear, SiO(2) nano-particles are toxic, at least for algae in aquatic media. Under the transmission electron microscope, several amorphous structures appeared in the cells that were exposed to 5-nm silica nano-particles. PMID:18584432

  7. Enhancement of impact strength of poly (methyl methacrylate) with surface fine-tuned nano-silica

    NASA Astrophysics Data System (ADS)

    Wen, Bin; Dong, Yixiao; Wu, Lili; Long, Chao; Zhang, Chaocan

    2015-07-01

    Highly dispersible nanoparticles in organic solvent always receive wide interests due to their compatibility with polymer materials. This paper reported a kind of isopropanol alcohol silica dispersion which obtained using a method of azeotropic distillation. The isopropanol alcohol dispersed silica (IPADS) were treated with coupling agents to fine-tune their surface properties. Polymethyl methacrylate (PMMA) was then used as a research object to test the compatibility between IPADS and polymer. UV-vis spectra indicate that IPADS would reach its high compatibility with PMMA if coupling with trimethoxypropylsilane (PTMS). Followed experiments on PMMA proved that the high compatibility can prominently enhance the impact strength about 30%. The results may provide reference both for nano-silica modification and better understanding of nano-enhanced materials.

  8. Self-Assembled Silica Nano-Composite Polymer Electrolytes: Synthesis, Rheology & Electrochemistry

    SciTech Connect

    Khan, Saad A.: Fedkiw Peter S.; Baker, Gregory L.

    2007-01-24

    The ultimate objectives of this research are to understand the principles underpinning nano-composite polymer electrolytes (CPEs) and facilitate development of novel CPEs that are low-cost, have high conductivities, large Li+ transference numbers, improved electrolyte-electrode interfacial stability, yield long cycle life, exhibit mechanical stability and are easily processable. Our approach is to use nanoparticulate silica fillers to formulate novel composite electrolytes consisting of surface-modified fumed silica nano-particles in polyethylene oxides (PEO) in the presence of lithium salts. We intend to design single-ion conducting silica nanoparticles which provide CPEs with high Li+ transference numbers. We also will develop low-Mw (molecular weight), high-Mw and crosslinked PEO electrolytes with tunable properties in terms of conductivity, transference number, interfacial stability, processability and mechanical strength

  9. Controllable synthesis of hollow mesoporous silica spheres and application as support of nano-gold

    SciTech Connect

    Wang, Tao; Ma, Weihua Shangguan, Junnan; Jiang, Wei; Zhong, Qin

    2014-07-01

    Hollow silica spheres with mesoporous structure were synthesized by sol–gel/emulsion method. In the process, the surfactant, cetyltrimethylammonium bromide (CTAB) was used to stabilize the oil droplet and also used as structure direct agent. The diameter of the hollow silica spheres, ranging from 895 nm to 157 nm, can be controlled by changing the ratio of ethanol to water and the concentration of the surfactant as well. The shell thickness of the spheres decreased when the ratio of ethanol to water decreased. The proposed mechanism of the formation of silica spheres could elucidate the experimental results well. Furthermore, the resultant hollow mesoporous silica spheres were then employed as support of nano-gold which was used to catalyze the isomerization reaction of propylene oxide to produce allyl alcohol. - Graphical abstract: It is the schematic mechanism for the formation of hollow mesoporous silica spheres. - Highlights: • The formation mechanism of the hollow spheres is proposed. • The isomerization of propylene oxide can be catalyzed by the nano-gold/SiO{sub 2}. • The hollow silica spheres can be prepared controllably.

  10. Functional role of cationic surfactant to control the nano size of silica powder

    NASA Astrophysics Data System (ADS)

    Singh, L. P.; Bhattacharyya, S. K.; Mishra, G.; Ahalawat, S.

    2011-09-01

    Preparation of dispersed, amorphous, spherical silica nanoparticles using cationic surfactant as organic template, tetraethoxysilane (TEOS) as silica precursor and ammonia as catalyst has been carried out using sol gel process. The aim of the present study was to evaluate the simultaneous effects of cationic surfactant on the textural and structural properties of silica nanoparticles. We used a series of the cationic surfactants, dodecytrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) to evaluate the effects of the chain length of cationic surfactant on the grain size of silica nanoparticles. The size of silica nanoparticles can be finely tuned in the range ~50-100 nm by changing the chain length of cationic surfactant. Decreasing the particle size of silica nano particles resulted in increase in chain length of cationic surfactant. Further, these silica nanoparticles are incorporated with cement paste to evaluate the beneficial effect on mechanical properties of cement. Synthesized silica nanoparticles were analyzed using scanning electron microscopy (SEM), 29Si MAS NMR, powder X-ray diffraction techniques (XRD) and IR studies.

  11. Effect of nano-silica spheres template on CO2 capture of exchange resin-based nanoporous carbons.

    PubMed

    Meng, Long-Yue; Park, Soo-Jin

    2013-01-01

    In this work, a nanoporous carbon-based adsorbent with a higher specific surface area was directly prepared from polystyrene-based cation exchange resin (PCER) by carbonization of a mixture of nano-silica spheres. The silica/PCER composites were carbonized at 1173 K with different silica/PCER ratios. The effects of nano-silica spheres content on the pore structures of nanoporous carbons were investigated by N2 full isotherms. The CO2 capture capacity was measured by CO2 isothermal adsorption at 298 K and 1 bar. From the results, it was found that the nano-silica spheres/PCER ratio had a major influence on the CO2 capture capacity and the textural properties of the prepared nanoporous carbons. The specific surface area and total pore volume, as well as the pore size of the nanoporous carbons increased with increasing silica/PCER ratio. PMID:23646745

  12. Zwitterion-stabilized silica nanoparticles: toward nonstick nano.

    PubMed

    Estephan, Zaki G; Jaber, Jad A; Schlenoff, Joseph B

    2010-11-16

    Using a short-chain zwitterionic organosiloxane, silica nanoparticles were stabilized against aggregation by high ionic strength and/or proteins. Turbidimetry and dynamic light scattering showed that "zwitterated" nanoparticles did not exhibit a significant increase in hydrodynamic radius. When challenged with 3 M NaCl or 50% fetal bovine serum, aggregation was inhibited for at least 24 h, longer with mild heat treatment, which produced nanoparticles with zero net surface charge. These findings suggest "zwitteration" of silica-capped nanoparticles provides excellent stability for in vivo circulation diagnostics and therapies. PMID:20942453

  13. Antimicrobial activity of silica coated silicon nano-tubes (SCSNT) and silica coated silicon nano-particles (SCSNP) synthesized by gas phase condensation.

    PubMed

    Tank, Chiti; Raman, Sujatha; Karan, Sujoy; Gosavi, Suresh; Lalla, Niranjan P; Sathe, Vasant; Berndt, Richard; Gade, W N; Bhoraskar, S V; Mathe, Vikas L

    2013-06-01

    Silica-coated, silicon nanotubes (SCSNTs) and silica-coated, silicon nanoparticles (SCSNPs) have been synthesized by catalyst-free single-step gas phase condensation using the arc plasma process. Transmission electron microscopy and scanning tunneling microscopy showed that SCSNTs exhibited a wall thickness of less than 1 nm, with an average diameter of 14 nm and a length of several 100 nm. Both nano-structures had a high specific surface area. The present study has demonstrated cheaper, resistance-free and effective antibacterial activity in silica-coated silicon nano-structures, each for two Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) was estimated, using the optical densitometric technique, and by determining colony-forming units. The MIC was found to range in the order of micrograms, which is comparable to the reported MIC of metal oxides for these bacteria. SCSNTs were found to be more effective in limiting the growth of multidrug-resistant Staphylococcus aureus over SCSNPs at 10 μg/ml (IC 50 = 100 μg/ml).

  14. Silica fertilization and nano-MnO₂ amendment on bacterial community composition in high arsenic paddy soils.

    PubMed

    Shao, Jihai; He, Yaxian; Zhang, Huiling; Chen, Anwei; Lei, Ming; Chen, Junfeng; Peng, Liang; Gu, Ji-Dong

    2016-03-01

    Silica fertilization and nano-MnO2 amendment are reported as useful approaches in lowering the accumulation of arsenic in rice grains, but the effects of silica fertilization or nano-MnO2 amendment on microbial community in the paddy soils containing high concentration of arsenic are still unknown. In order to elucidate this question, the structures and composition of microbial community in the paddy soils, in response to silica fertilization and nano-MnO2 amendment, were investigated using pyrosequencing technique. The results indicated that Proteobacteria, Chloroflexi, and Acidobacteria were the main dominating phyla in these paddy soils. A decrease in the relative abundance of Chloroflexi and Cyanobacteria, but an increase in the relative abundance of Acidobacteria was observed after silica fertilization and nano-MnO2 amendment. The changes of Acidobacteria, Chloroflexi, and Cyanobacteria were strongly correlated with pH and the concentration of bioavailable arsenic in the paddy soils. The α-diversity of bacteria in the paddy soils increased in response to silica fertilization at low amendment level, but decreased under silica or nano-MnO2 amendment at high amendment level. Results of β-diversity analysis indicated that the microbial communities in the control treatment shared more similarity with that of those received low level of nano-MnO2 amendment, and the two silica fertilization treatments also shared more similarity with each other. PMID:26563550

  15. Silica fertilization and nano-MnO₂ amendment on bacterial community composition in high arsenic paddy soils.

    PubMed

    Shao, Jihai; He, Yaxian; Zhang, Huiling; Chen, Anwei; Lei, Ming; Chen, Junfeng; Peng, Liang; Gu, Ji-Dong

    2016-03-01

    Silica fertilization and nano-MnO2 amendment are reported as useful approaches in lowering the accumulation of arsenic in rice grains, but the effects of silica fertilization or nano-MnO2 amendment on microbial community in the paddy soils containing high concentration of arsenic are still unknown. In order to elucidate this question, the structures and composition of microbial community in the paddy soils, in response to silica fertilization and nano-MnO2 amendment, were investigated using pyrosequencing technique. The results indicated that Proteobacteria, Chloroflexi, and Acidobacteria were the main dominating phyla in these paddy soils. A decrease in the relative abundance of Chloroflexi and Cyanobacteria, but an increase in the relative abundance of Acidobacteria was observed after silica fertilization and nano-MnO2 amendment. The changes of Acidobacteria, Chloroflexi, and Cyanobacteria were strongly correlated with pH and the concentration of bioavailable arsenic in the paddy soils. The α-diversity of bacteria in the paddy soils increased in response to silica fertilization at low amendment level, but decreased under silica or nano-MnO2 amendment at high amendment level. Results of β-diversity analysis indicated that the microbial communities in the control treatment shared more similarity with that of those received low level of nano-MnO2 amendment, and the two silica fertilization treatments also shared more similarity with each other.

  16. Electrodeposition of macroporous nickel coating by employing nano-silica as template.

    PubMed

    Xu, Lijian; Chen, Baizhen; Du, Jingjing

    2012-09-01

    A novel method of preparing the macrporous nickel coating was described. The macrporous nickel coating was fabricated by employing nano-silica as the template. The effects of technological conditions and the concentration of the additives on the surface quality of coating were investigated, the nano-silica was characterized transmission electron microscopy (TEM) and laser particle size analyzer, and the macrporous nickel coating was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results showed that nano-silica particles were about 100 nm, the optimal technological conditions of electrodepositing nickel were that the cathode current density was 12 A/dm2, the temperature was 30 degrees C and the pH value was 2.0, the concentration of lauryl sodium sulfate was 0.15 g/L and the concentration of glucide was 3 g/L, the macrporous nickel coating was obtained when the adding nano-SiO2 content in the electroplating bath was 6 g/L and its structure was crystalline.

  17. Micro-nano hierarchical superhydrophobic electrospray-synthesized silica layers.

    PubMed

    Kim, Ji-Yeong; Kim, Eun-Kyeong; Kim, Sang Sub

    2013-02-15

    This paper reports the preparation of superhydrophobic SiO(2) layers with a micro-nano hierarchical surface structure. SiO(2) layers, which were rough on the microscale, were prepared using an electrospraying method combined with a sol-gel chemical route. To create a nanoscale structure, the surface of the SiO(2) layers was coated with Au nanoparticles using an ultraviolet-enhanced chemical reduction process, resulting in a micro-nano hierarchical surface structure. A subsequent fluorination treatment with a solution containing trichloro(1H,1H,2H,2H-perfluorooctyl)silane resulted in fluorination of the micro-nano hierarchical SiO(2) layers. The resulting SiO(2) layers showed outstanding repellency toward a range of liquid droplets, for example, a water-repellency of 170°. The surface fraction and work of adhesion of the fluorinated, micro-nano hierarchical SiO(2) layers were estimated using the Cassie-Baxter and Young-Dupre equations, respectively. The long-term durability and ultraviolet resistance of the superhydrophobic SiO(2) layers prepared in this study highlight their potential in a range of practical applications.

  18. Tennis core strings of polyamide-6 modified by surface-capped nano-silica

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Yi, Hongling; Lin, Heng; Zheng, Baicun

    2013-01-01

    A new method that modified silica nanoparticles were infused into PA6 is to produce tennis core string through a melt-extrusion process. The idea was to produce a highly strong and elastic tennis core string of PA6, utilizing the interactions between modified silica and polymer. The effects of surface-capped nano-silica on the strength and elongation of tennis core string were studied. It has been observed that with the infusion of silica nanoparticles modified by γ-glycidoxypropyltrimethoxysilane (GPS), the stress at breaking and E-modulus of tennis core string is enhanced by 46.24% and 15.17% comparing with neat PA6 with changeless elongation at breaking at a critical concentration. The source of this improvement has been traced to the produced strong covalent bond and hydrogen bond between epoxy groups and-COOH and-NH2 in polyamide. Besides, compared with kinds of others strings of previous research results, tennis core string added nano-silica modified by γ-glycidoxypropyltrimethoxysilane (GPS) has a strength at breaking at 352.43 MPa exceeding the natural gut string, the polyvinylidene fluoride (PVDF), Monofil string and integrated nylon string by 42.05%, 4.49% and 9.38%, respectively. Meanwhile, tennis core string of polyamide modified by surface-capped nanosilica (PGMNS) has a higher elastic ratio at 0.15 than the other four strings.

  19. Synthesis of nano grade hollow silica sphere via a soft template method.

    PubMed

    Tsai, Ming-Shyong; Li, Miao Ju; Yen, Fu-Hsu

    2008-06-01

    The nano grade hollow silica sphere (HSS) was synthesized by a novel soft template method. We found that the precipitate of aluminate had a porous structure that could be the soft template for HSS. After mixing the colloidal silica with the aluminate precipitate, the bubble trapped in this porous structure could form the nano grade HSS. The aluminate precipitate was removed by adjusting the pH of the slurry to approximately 1. The outside diameter, the specific surface, and the mean pore size diameter of the forming HSS were 60-90 nm, 571 m2/g, and 3 nm, respectively. The formed HSS was collected by modifying the surface with Si(OCH3)3CHCH2 (VTMO) and then filtrating the precipitated gel in the n-butanol and ethanol solvent system.

  20. Molecular Dynamics Study on the Particle Dispersion Mechanism of Polyamide-imide/Silica Nano-composite Materials

    NASA Astrophysics Data System (ADS)

    Kikuchi, Hideyuki; Iwasaki, Tomio; Hanawa, Hidehito; Honda, Yuki

    We studied the particle dispersion mechanism of polyamide-imide/silica nano-composite material by using molecular-dynamics simulation technique based on Newtonian dynamics and quantum mechanics. In simulations, adhesive fracture energies at the interfaces between silica and solvents were calculated, and Brownian motions of silica particles were simulated to clarify dispersion properties. The simulation results showed that the colloidal state of silica was maintained by covering the silica surface with a new low hygroscopicity solvent and that the chemical structure of polymer contributed to the dispersion of silica. It is found that the results obtained from molecular dynamics agree well with those obtained by experiments, and that molecular-dynamics simulation technique will become very useful for the development of nano-composite materials in the future.

  1. Stability and geometry of silica nano-ribbons (SNRs): a first-principles study.

    PubMed

    Fang, C M; van Blaaderen, A; van Huis, M A

    2016-08-21

    Silica based materials are attractive because of their versatility and their unique structures and properties, which have led to numerous applications of silica in a range of fields. Recently, various low-dimensional silica materials have been synthesized experimentally. Here we present a first-principles study on the geometry and stability of novel low-dimensional silica nano-ribbons (SNRs) using density-functional theory (DFT) with van der Waals interactions (optB88-vdW). SNRs of various widths with different surface groups, and with the geometry of hexagonal rings and squares, were taken into consideration. An atomically flat ribbon with mixing squares and rings is also included. The calculations showed high stability for the single layer and bilayer silica ribbons, both containing hexagonal rings. The calculations also revealed a high flexibility of silica chains. The local structure and chemical bonding were carefully analyzed. Electronic band structure calculations showed an insulating nature of the SNRs with energy gaps of about 5.0 to 6.0 eV, which are determined by nonbonding and anti-bonding O 2p states. PMID:27436792

  2. Synthesis and characterization of guar gum templated hybrid nano silica.

    PubMed

    Singh, V; Singh, S K; Pandey, S; Sanghi, R

    2011-08-01

    The objective of the present study was the fabrication of green adsorbent hybrids for which native guar gum was used as template to polymerize tetraethoxysilane. The properties and performances of the hybrids could be tailored by using varying molecular sizes of the partially depolymerized guar gum templates of various molecular sizes as control. Zn(II) uptake from aqueous solution was used as a criterion for evaluating the adsorbent efficiency. The optimum material (H4) in terms of maximum Zn(II) uptake, was obtained when the template size used was 375 kDa at a calcination temperature of 700°C. H4 was also evaluated for Ca(II), Mg(II), Cd(II) and Hg(II) adsorption. To explore the other applicability areas, the hybrids have been extensively characterized using FTIR, XRD, TGA-DTA, PL, SEM, TEM and BET analyses. H4 was found to be as efficient as previously reported vinyl modified-silica nanohybrids. It had a high surface area (264 m(2)/g) with silica nanoparticles in the size range of 90-140 nm. Being thermally very stable and photoluminescent, the material can be potentially used for many biological, medical and environmental applications.

  3. Effect of nano-silica filler on the uniform packaging of white light emitting diodes.

    PubMed

    Hyeon, Deok Jae; Kim, Tea Hoon; Park, Lee Soon

    2013-09-01

    The packaging process of white light-emitting diodes (WLEDs) take a relatively long time, even when utilizing an automated dispensing system. Therefore the silicone-based packaging formulation and control of rheology during the packaging of LEDs are very important. The effect of phosphor settling during the curing state of LED packaging has been reported. In this work we studied the effect of phosphor paste on the dispensing stage of the WLEDs packaging process utilizing nanosilica particles as viscosity modifiers. With nano-silica in the silicone resin the sedimentation of YAG phosphor particles were effectively blocked and a uniform distribution of YAG phosphor in the cured silicon resin could be achieved. We also examined the incorporation of red quantum dots (QDs) to improve the color rendering index of the WLEDs with the aid of nano-silica as a rheological additive. The application of nano-silica in the layer-by-layer type encapsulation of red QDs was found to be effective in WLEDs packaging, which improved the color rendering index with warm white emission. PMID:24205584

  4. Nano-Web Cobalt Modified Silica Nanoparticles Catalysts for Water Oxidation and MB Oxidative Degradation.

    PubMed

    Wang, Li; Chen, Qiuyun; Li, Chenghao; Fang, Fang

    2016-05-01

    Dioxygen generating materials, using water as oxygen source, can be used as catalysts in hypoxic environments. Cobalt(II) modified silica (SiO2@NPCo) nanoparticles were synthesized through coordination of cobalt(II) ions with nitrogen atoms from 2-acetylpyridine modified silica (SiO2@NP). The SiO2@NPCo nanoparticles further reacted with 1,3,5-benzenetricarboxylic acids, forming porous nano-web nanoparticles (SiO2@NPCoCOOH). The synthesized SiO2@NPCoCOOH nanoparticles were demonstrated as better white LED light driven photochemical catalysts for oxidation of water than individual nanoparticles (SiO2@NPCo). Moreover, the SiO2@NPCoCOOH/water system could decrease the content of methylene blue (MB) in solution and therefore, the nanoweb cobalt(II) modified silica nanoparticles can be environmentally friendly catalysts for oxidative degradation of MB, using water as the oxygen source. PMID:27483932

  5. Nano-Web Cobalt Modified Silica Nanoparticles Catalysts for Water Oxidation and MB Oxidative Degradation.

    PubMed

    Wang, Li; Chen, Qiuyun; Li, Chenghao; Fang, Fang

    2016-05-01

    Dioxygen generating materials, using water as oxygen source, can be used as catalysts in hypoxic environments. Cobalt(II) modified silica (SiO2@NPCo) nanoparticles were synthesized through coordination of cobalt(II) ions with nitrogen atoms from 2-acetylpyridine modified silica (SiO2@NP). The SiO2@NPCo nanoparticles further reacted with 1,3,5-benzenetricarboxylic acids, forming porous nano-web nanoparticles (SiO2@NPCoCOOH). The synthesized SiO2@NPCoCOOH nanoparticles were demonstrated as better white LED light driven photochemical catalysts for oxidation of water than individual nanoparticles (SiO2@NPCo). Moreover, the SiO2@NPCoCOOH/water system could decrease the content of methylene blue (MB) in solution and therefore, the nanoweb cobalt(II) modified silica nanoparticles can be environmentally friendly catalysts for oxidative degradation of MB, using water as the oxygen source.

  6. Controlling the nano-bio interface to build collagen-silica self-assembled networks

    NASA Astrophysics Data System (ADS)

    Aimé, Carole; Mosser, Gervaise; Pembouong, Gaëlle; Bouteiller, Laurent; Coradin, Thibaud

    2012-10-01

    Bio-hybrid networks are designed based on the self-assembly of surface-engineered collagen-silica nanoparticles. Collagen triple helices can be confined on the surface of sulfonate-modified silica particles in a controlled manner. This gives rise to hybrid building blocks with well-defined diameters and surface potentials. Taking advantage of the self-assembling properties of collagen, collagen-silica networks are further built-up in solution. The structural and specific recognition properties of the collagen fibrils are well-preserved within the hybrid assembly. A combination of calorimetry, dynamic light scattering, zetametry and microscopy studies indicates that network formation occurs via a surface-mediated mechanism where pre-organization of the protein chains on the particle surface favors the fibrillogenesis process. These results enlighten the importance of the nano-bio interface on the formation and properties of self-assembled bionanocomposites.Bio-hybrid networks are designed based on the self-assembly of surface-engineered collagen-silica nanoparticles. Collagen triple helices can be confined on the surface of sulfonate-modified silica particles in a controlled manner. This gives rise to hybrid building blocks with well-defined diameters and surface potentials. Taking advantage of the self-assembling properties of collagen, collagen-silica networks are further built-up in solution. The structural and specific recognition properties of the collagen fibrils are well-preserved within the hybrid assembly. A combination of calorimetry, dynamic light scattering, zetametry and microscopy studies indicates that network formation occurs via a surface-mediated mechanism where pre-organization of the protein chains on the particle surface favors the fibrillogenesis process. These results enlighten the importance of the nano-bio interface on the formation and properties of self-assembled bionanocomposites. Electronic supplementary information (ESI) available: XPS

  7. Synthesis and characterization of a multimode stationary phase: Congo red derivatized silica in nano-flow HPLC.

    PubMed

    Zhang, Yi; Zhang, Yan; Wang, Guan; Chen, Wujuan; He, Pingang; Wang, Qingjiang

    2016-02-01

    A novel Congo red (CR) derivatized silica stationary phase was prepared and packed into a fused silica capillary tube for nano-flow HPLC. A variety of analytes including poly-aromatic hydrocarbons, parabens, acids, sulfonamides, bases, and nucleosides were successfully separated using the CR. In comparison with commercial ODS columns, this new stationary phase has a different separation mechanism (hydrophobically-assisted ion-exchange), which was evident in the separation of benzoic acid derivatives and sulfonamides. The successful application of CR-bonded silica stationary phase in the HILIC and PALC modes demonstrates the effectiveness of this potential chromatographic material in nano flow HPLC.

  8. Synthesis and characterization of a multimode stationary phase: Congo red derivatized silica in nano-flow HPLC.

    PubMed

    Zhang, Yi; Zhang, Yan; Wang, Guan; Chen, Wujuan; He, Pingang; Wang, Qingjiang

    2016-02-01

    A novel Congo red (CR) derivatized silica stationary phase was prepared and packed into a fused silica capillary tube for nano-flow HPLC. A variety of analytes including poly-aromatic hydrocarbons, parabens, acids, sulfonamides, bases, and nucleosides were successfully separated using the CR. In comparison with commercial ODS columns, this new stationary phase has a different separation mechanism (hydrophobically-assisted ion-exchange), which was evident in the separation of benzoic acid derivatives and sulfonamides. The successful application of CR-bonded silica stationary phase in the HILIC and PALC modes demonstrates the effectiveness of this potential chromatographic material in nano flow HPLC. PMID:26646316

  9. Critical review of the safety assessment of nano-structured silica additives in food.

    PubMed

    Winkler, Hans Christian; Suter, Mark; Naegeli, Hanspeter

    2016-01-01

    The development of nano-materials is viewed as one of the most important technological advances of the 21st century and new applications of nano-sized particles in the production, processing, packaging or storage of food are expected to emerge soon. This trend of growing commercialization of engineered nano-particles as part of modern diet will substantially increase oral exposure. Contrary to the proven benefits of nano-materials, however, possible adverse health effects have generally received less attention. This problem is very well illustrated by nano-structured synthetic amorphous silica (SAS), which is a common food additive since several decades although the relevant risk assessment has never been satisfactorily completed. A no observed adverse effect level of 2500 mg SAS particles/kg body weight per day was derived from the only available long-term administration study in rodents. However, extrapolation to a safe daily intake for humans is problematic due to limitations of this chronic animal study and knowledge gaps as to possible local intestinal effects of SAS particles, primarily on the gut-associated lymphoid system. This uncertainty is aggravated by digestion experiments indicating that dietary SAS particles preserve their nano-sized structure when reaching the intestinal lumen. An important aspect is whether food-borne particles like SAS alter the function of dendritic cells that, embedded in the intestinal mucosa, act as first-line sentinels of foreign materials. We conclude that nano-particles do not represent a completely new threat and that most potential risks can be assessed following procedures established for conventional chemical hazards. However, specific properties of food-borne nano-particles should be further examined and, for that purpose, in vitro tests with decision-making cells of the immune system are needed to complement existing in vivo studies. PMID:27287345

  10. Critical review of the safety assessment of nano-structured silica additives in food.

    PubMed

    Winkler, Hans Christian; Suter, Mark; Naegeli, Hanspeter

    2016-06-10

    The development of nano-materials is viewed as one of the most important technological advances of the 21st century and new applications of nano-sized particles in the production, processing, packaging or storage of food are expected to emerge soon. This trend of growing commercialization of engineered nano-particles as part of modern diet will substantially increase oral exposure. Contrary to the proven benefits of nano-materials, however, possible adverse health effects have generally received less attention. This problem is very well illustrated by nano-structured synthetic amorphous silica (SAS), which is a common food additive since several decades although the relevant risk assessment has never been satisfactorily completed. A no observed adverse effect level of 2500 mg SAS particles/kg body weight per day was derived from the only available long-term administration study in rodents. However, extrapolation to a safe daily intake for humans is problematic due to limitations of this chronic animal study and knowledge gaps as to possible local intestinal effects of SAS particles, primarily on the gut-associated lymphoid system. This uncertainty is aggravated by digestion experiments indicating that dietary SAS particles preserve their nano-sized structure when reaching the intestinal lumen. An important aspect is whether food-borne particles like SAS alter the function of dendritic cells that, embedded in the intestinal mucosa, act as first-line sentinels of foreign materials. We conclude that nano-particles do not represent a completely new threat and that most potential risks can be assessed following procedures established for conventional chemical hazards. However, specific properties of food-borne nano-particles should be further examined and, for that purpose, in vitro tests with decision-making cells of the immune system are needed to complement existing in vivo studies.

  11. Poly(vinyl alcohol)/silica nanocomposites: morphology and thermal degradation kinetics.

    PubMed

    Peng, Zheng; Kong, Ling Xue; Li, Si-Dong; Spiridonov, Pavel

    2006-12-01

    The morphology of self-assembled poly(vinyl alcohol)/silica (PVA/SiO2) nanocomposites is investigated with atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the SiO2 nanoparticles are homogenously distributed throughout the PVA matrix in a form of spherical nano-cluster. The average size of the SiO2 clusters is below 50 nm at the low contents (SiO2 < or =5 5 wt%), while particle aggregations are clearly observed and their average size markedly increases to 110 nm when 10 wt% SiO2 is loaded. The thermogravimetric analysis (TGA) shows that the nanocomposite significantly outperforms the pure PVA in the thermal resistance. By using a multi-heating-rate method, the thermal degradation kinetics of the nanocomposite with a SiO2 content of 5 wt% is compared to the PVA host. The reaction activation energy (E) of the nanocomposite, similar to the pure PVA, is divided into two main stages corresponding to two degradation steps. However, at a given degradation temperature, the nanocomposite presents much lower reaction velocity constants (k), while its E is 20 kJ/mol higher than that of the PVA host. PMID:17256356

  12. Super-amphiphilic surface of nano silica/polyurethane hybrid coated PET film via a plasma treatment.

    PubMed

    Bui, Van-Tien; Liu, Xuyan; Ko, Seung Hyeon; Choi, Ho-Suk

    2015-09-01

    This study first reports the fabrication of a super-amphiphilic surface using PET films with a silica-polyurethane hybrid top-coat layer through a non-thermal, one-atmospheric-pressure plasma treatment. This surface displays contact angle close to zero with both aqueous and oily liquids, which has attracted enormous attention for a wide-range of practical applications. We systematically investigated the influence of the plasma treatment time on the wetting behavior of the silica-polyurethane coated PET surface. The changes in morphology and chemical composition of PET surfaces before and after a plasma treatment were analyzed. In order to gain an insight into the formation of a super-amphiphilic PET surface and optimize the conditions under which super-amphiphilicity can be realized, we used a hemi-wicking action as a theoretical model and experimentally verified it through determining the critical angle. We also proposed a guide for designing a nano-sphere patterned PDMS surface which can generate super-wetting properties after a plasma treatment.

  13. Preparation of monodisperse polystyrene/silica core-shell nano-composite abrasive with controllable size and its chemical mechanical polishing performance on copper

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Wang, Haibo; Zhang, Zefang; Qin, Fei; Liu, Weili; Song, Zhitang

    2011-11-01

    Monodisperse silica-coated polystyrene (PS) nano-composite abrasives with controllable size were prepared via a two-step process. Monodisperse positively charged PS colloids were synthesized via polymerization of styrene by using a cationic initiator. In the subsequent coating process, silica formed shell on the surfaces of core PS particles via the ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane. Neither centrifugation/water wash/redispersion cycle process nor surface modification or addition surfactant was needed in the whole process. The morphology of the abrasives was characterized by scanning electron microscope. Transmission electron microscope and energy dispersive X-ray analysis results indicated that silica layer was successfully coated onto the surfaces of PS particles. Composite abrasive has a core-shell structure and smooth surface. The chemical mechanical polishing performances of the composite abrasive and conventional colloidal silica abrasive on blanket copper wafers were investigated. The root mean square roughness decreases from 4.27 nm to 0.56 nm using composite abrasive. The PS/SiO2 core-shell composite abrasives exhibited little higher material removal rate than silica abrasives.

  14. Surface modification to produce hydrophobic nano-silica particles using sodium dodecyl sulfate as a modifier

    NASA Astrophysics Data System (ADS)

    Qiao, Bing; Liang, Yong; Wang, Ting-Jie; Jiang, Yanping

    2016-02-01

    Hydrophobic silica particles were prepared using the surfactant sodium dodecyl sulfate (SDS) as a modifier by a new route comprising three processes, namely, aqueous mixing, spray drying and thermal treatment. Since SDS dissolves in water, this route is free of an organic solvent and gave a perfect dispersion of SDS, that is, there was excellent contact between SDS and silica particles in the modification reaction. The hydrophobicity of the modified surface was verified by the contact angle of the nano-sized silica particles, which was 107°. The SDS grafting density reached 1.82 nm-2, which is near the highest value in the literature. The optimal parameters of the SDS/SiO2 ratio in the aqueous phase, process temperature and time of thermal treatment were determined to be 20%, 200 °C and 30 min, respectively. The grafting mechanism was studied by comparing the modification with that on same sized TiO2 particles, which indicated that the protons of the Brønsted acid sites on the surface of SiO2 reacted with SDS to give a carbocation which then formed a Si-O-C structure. This work showed that the hydrophilic surface of silica can be modified to be a hydrophobic surface by using a water soluble modifier SDS in a new modification route.

  15. Synthesis of nano-forsterite powder by making use of natural silica sand

    NASA Astrophysics Data System (ADS)

    Nurbaiti, Upik; Suud, Fikriyatul Azizah; Darminto, Triwikantoro, Zainuri, Mochamad; Pratapa, Suminar

    2016-02-01

    Nano-forsterite powder with natural silica sand and magnesium powder as the raw materials have been succesfully synthesized. The silica sand was purified followed by a coprecipitation process to obtain colloidal silica. The magnesium powder was dissolved in a chloric acid solution to obtain MgCl2 solution. The nanoforsterite powder was synthesised using a sol-gel method which included the mixing the colloidal silica and the MgCl2 solution with various aging and filtering processes. The samples were dried at 100 °C using a hot plate and then the dried powders were calcinated at 900 °C for 2 hours. The samples were characetised for their elements and phase compositions using X-ray Flourescence (XRF) and X-ray Diffraction (XRD) methods, respectively. The diffraction data were qualitatively analyzed using Match!2 software and quantitatively using Rietica software. The crystallite size was verified using Transmission Electron Microscopy (TEM). Results of XRD data analysis showed that the forsterite content reached up to 90.5% wt. The TEM average crystallite size was approximately 53(6) nm.

  16. Effects of material morphology on the phototoxicity of nano-TiO2 to bacteria.

    PubMed

    Tong, Tiezheng; Shereef, Anas; Wu, Jinsong; Binh, Chu Thi Thanh; Kelly, John J; Gaillard, Jean-François; Gray, Kimberly A

    2013-01-01

    Nanostructured titania (nano-TiO2) is produced in diverse shapes, but it remains largely unknown how tuning the morphology of nano-TiO2 may alter its toxicity. Herein, we show that material morphology plays a critical role in regulating the phototoxicity of nano-TiO2 to bacteria. Low-dimensional nano-TiO2, including nanotubes, nanorods, and nanosheets, were synthesized hydrothermally, and their effects on the bacterial viability of Escherichia coli and Aeromonas hydrophila were compared to spherical nanostructures (anatase nanospheres and P25). Results reveal that TiO2 nanotubes and nanosheets are less phototoxic than their rod- and sphere-shape counterparts under simulated solar irradiation. None of the tested nano-TiO2 shows toxicity in the dark. In contrast to their diminished phototoxicity, however, TiO2 nanotubes and nanosheets exhibit comparable or even higher photoactivity than other nanostructures. Observations by scanning transmission electron microscopy suggest that material morphology influences nano-TiO2 phototoxicity by governing how nano-TiO2 particles align at the bacterial cell surface. Overall, when comparing materials with different morphologies and dimensionality, nano-TiO2 phototoxicity is not a simple function of photocatalytic reactivity or ROS production. Instead, we propose that the evaluation of nano-TiO2 phototoxicity encompasses a three-pronged approach, involving the intrinsic photoactivity, aggregation of nano-TiO2, and the nano-TiO2/bacteria surface interactions.

  17. Morphological and electronic properties of ultrathin crystalline silica epilayers on a Mo(112) substrate

    NASA Astrophysics Data System (ADS)

    Schroeder, T.; Giorgi, J. B.; Bäumer, M.; Freund, H.-J.

    2002-10-01

    Ultrathin crystalline silica layers grown on a Mo(112) substrate have been shown to be a useful silica model oxide support in surface science model catalyst studies. As the oxide support material plays an important role in the catalytic process, a multitechnique surface science study is presented to characterize the morphological and electronic properties of the heteroepitaxial system SiO2/Mo(112). The long-range order of the silica epilayer which grows commensurate with a c(2×2) surface unit mesh on the Mo(112) substrate is studied by low-energy electron diffraction (LEED). The defect structure of the silica epilayer is characterized in a spot profile analysis (SPA)-LEED study. Antiphase domain boundaries split the silica epilayer into an array of silica crystal grains whose average size and shape is determined. Aiming to prepare flat silica surfaces, the change in the surface roughness with progress in the film preparation is monitored in a combined SPA-LEED and scanning tunneling microscopy (STM) study and seen to influence also the Si-O stretching frequency in the infrared-reflection-absorption spectroscopy spectra. In STM images of the final silica film an average surface roughness of about 1 Å is detected. It is possible to visualize the silica film unit cell periodicity. A combined anger electron spectroscopy and ultraviolet photoelectron spectroscopy valence band study confirms the silica film stoichiometry and the growth of a 4:2 coordinated silica polymorph on the Mo(112) surface. These various surface science studies allow us to propose models for the growth and structure of the silica epilayer on the Mo(112) surface.

  18. Contamination resistant antireflection nano-textures in fused silica for laser optics

    NASA Astrophysics Data System (ADS)

    Hobbs, Douglas S.; MacLeod, Bruce D.; Sabatino, Ernest; Britten, Jerald A.; Stolz, Christopher J.

    2013-11-01

    Anti-reflecting (AR) surface relief nano-textures have been integrated with fused silica diffraction gratings to demonstrate the potential of stable diffractive 3ω beam samplers with increased energy to target at the National Ignition Facility (NIF). TelAztec's AR texturing process was used to etch Random-type AR (RAR) microstructures in sub-scale NIF Grating Debris Shields consisting of large pitch, shallow line gratings. This superposition yielded the desired ~3.5% increase in zero-order transmission uniformly over the full aperture without compromising the grating function. Another fused silica window fabricated with RAR nano-textures in both faces for a 3ω (351nm) transmission of 99.5%, was subjected to capillary condensation tests to evaluate the resistance of the RAR texture to the adsorption of organic compounds. It was found that for a one day exposure time to a surrogate suite of organic contaminants, the RAR textured fused silica surfaces adsorbed less than one fourth the amount of organic contaminants found on a NIF baseline hardened sol-gel AR coated optic. In two additional exposure cycles, further RAR process refinement reduced the amount of adsorbed organics to a level nearly 200 times below the current NIF baseline. Significantly, the 3ω transmission of the RAR textured window remained unchanged after all three exposure cycles, whereas the sol-gel coated windows showed losses up to 4.9% for the highest contaminant concentration. Large beam pulsed laser damage testing of RAR textured fused silica windows was conducted with the Optical Sciences Laser (OSL) at NIF. The RAR sample damage resistance was found to be equivalent to the current NIF baseline - even after multiple aggressive chemical cleaning cycles. Lastly, a series of RAR textured and sol-gel AR coated windows were subjected to commercial 3ω pulsed laser damage testing at Quantel. The results indicate an average RAR damage threshold of 26 J/cm2, a level about 80% of the two NIF fused

  19. Mesoporous Nano-Silica Serves as the Degradation Inhibitor in Polymer Dielectrics

    PubMed Central

    Yang, Yang; Hu, Jun; He, Jinliang

    2016-01-01

    A new generation of nano-additives for robust high performance nanodielectrics is proposed. It is demonstrated for the first time that mesoporous material could act as “degradation inhibitor” for polymer dielectrics to sequestrate the electrical degradation products then restrain the electrical aging process especially under high temperature conditions, which is superior to the existing additives of nanodielectrics except further increasing the dielectric strength. Polyethylenimine (PEI) loaded nano-scaled mesoporous silica MCM-41 (nano-MS) is doped into the dielectric matrix to prepare the PP/MCM-41-PEI nanocomposites. PEI provides the amines to capture the electrical degradation products while the MCM-41 brackets afford large adsorption surface, bring down the activating temperature of the absorbent then enhance the absorptive capacity. The electrical aging tests confirm the contribution of the mesoporous structure to electrical aging resistance and FT-IR analysis of the electrical degraded regions demonstrates the chemical absorption especially under high temperature conditions. Take the experimental data as examples, extending the aging durability and dielectric strength of polymer dielectrics by 5 times and 16%, respectively, can have substantial commercial significance in energy storage, power electronics and power transmission areas. PMID:27338622

  20. Mesoporous Nano-Silica Serves as the Degradation Inhibitor in Polymer Dielectrics.

    PubMed

    Yang, Yang; Hu, Jun; He, Jinliang

    2016-06-24

    A new generation of nano-additives for robust high performance nanodielectrics is proposed. It is demonstrated for the first time that mesoporous material could act as "degradation inhibitor" for polymer dielectrics to sequestrate the electrical degradation products then restrain the electrical aging process especially under high temperature conditions, which is superior to the existing additives of nanodielectrics except further increasing the dielectric strength. Polyethylenimine (PEI) loaded nano-scaled mesoporous silica MCM-41 (nano-MS) is doped into the dielectric matrix to prepare the PP/MCM-41-PEI nanocomposites. PEI provides the amines to capture the electrical degradation products while the MCM-41 brackets afford large adsorption surface, bring down the activating temperature of the absorbent then enhance the absorptive capacity. The electrical aging tests confirm the contribution of the mesoporous structure to electrical aging resistance and FT-IR analysis of the electrical degraded regions demonstrates the chemical absorption especially under high temperature conditions. Take the experimental data as examples, extending the aging durability and dielectric strength of polymer dielectrics by 5 times and 16%, respectively, can have substantial commercial significance in energy storage, power electronics and power transmission areas.

  1. Mesoporous Nano-Silica Serves as the Degradation Inhibitor in Polymer Dielectrics

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Hu, Jun; He, Jinliang

    2016-06-01

    A new generation of nano-additives for robust high performance nanodielectrics is proposed. It is demonstrated for the first time that mesoporous material could act as “degradation inhibitor” for polymer dielectrics to sequestrate the electrical degradation products then restrain the electrical aging process especially under high temperature conditions, which is superior to the existing additives of nanodielectrics except further increasing the dielectric strength. Polyethylenimine (PEI) loaded nano-scaled mesoporous silica MCM-41 (nano-MS) is doped into the dielectric matrix to prepare the PP/MCM-41-PEI nanocomposites. PEI provides the amines to capture the electrical degradation products while the MCM-41 brackets afford large adsorption surface, bring down the activating temperature of the absorbent then enhance the absorptive capacity. The electrical aging tests confirm the contribution of the mesoporous structure to electrical aging resistance and FT-IR analysis of the electrical degraded regions demonstrates the chemical absorption especially under high temperature conditions. Take the experimental data as examples, extending the aging durability and dielectric strength of polymer dielectrics by 5 times and 16%, respectively, can have substantial commercial significance in energy storage, power electronics and power transmission areas.

  2. Mesoporous Nano-Silica Serves as the Degradation Inhibitor in Polymer Dielectrics.

    PubMed

    Yang, Yang; Hu, Jun; He, Jinliang

    2016-01-01

    A new generation of nano-additives for robust high performance nanodielectrics is proposed. It is demonstrated for the first time that mesoporous material could act as "degradation inhibitor" for polymer dielectrics to sequestrate the electrical degradation products then restrain the electrical aging process especially under high temperature conditions, which is superior to the existing additives of nanodielectrics except further increasing the dielectric strength. Polyethylenimine (PEI) loaded nano-scaled mesoporous silica MCM-41 (nano-MS) is doped into the dielectric matrix to prepare the PP/MCM-41-PEI nanocomposites. PEI provides the amines to capture the electrical degradation products while the MCM-41 brackets afford large adsorption surface, bring down the activating temperature of the absorbent then enhance the absorptive capacity. The electrical aging tests confirm the contribution of the mesoporous structure to electrical aging resistance and FT-IR analysis of the electrical degraded regions demonstrates the chemical absorption especially under high temperature conditions. Take the experimental data as examples, extending the aging durability and dielectric strength of polymer dielectrics by 5 times and 16%, respectively, can have substantial commercial significance in energy storage, power electronics and power transmission areas. PMID:27338622

  3. Morphology and Optical Properties of Bare and Silica Coated Hybrid Silver Nanoparticles.

    PubMed

    Ghimire, Sushant; Lebek, Werner; Godehardt, Reinhold; Lee, Wan In; Adhikari, Rameshwar

    2016-05-01

    Owing to their wide applications in the field of optoelectronics, photonics, catalysis, and medicine; plasmonic metal nanoparticles are attaining considerable interest nowadays. The optical properties of these metal nanoparticles depend upon their size, shape, and surrounding medium. The present work studies the morphology and optical properties of bare silver nanoparticles and silica coated hybrid silver nanoparticles. Aqueous phase mediated synthesis and water-in-oil microemulsion mediated synthesis are two different wet chemical routes employed for nanosynthesis. Direct coating of silica is performed in water-in-oil microemulsion on pre-synthesized silver nanoparticles using tetraethyl orthosilicate as silica precursor. This study shows that using different wet chemical routes the size of the synthesized nanoparticles could be tuned. In addition, using reverse micelles as nanoreactors, the thickness of the silica shell around the core silver nanoparticles could be significantly controlled. Further, the optical properties of silver nanoparticles could be adjusted through the size and the surface coating. PMID:27483900

  4. Preparation of superhydrophobic and transparent micro-nano hybrid coatings from polymethylhydroxysiloxane and silica ormosil aerogels

    NASA Astrophysics Data System (ADS)

    Nagappan, Saravanan; Park, Jin Joo; Park, Sung Soo; Ha, Chang-Sik

    2014-12-01

    Superhydrophobic and transparent polymethylhydroxysiloxane (PMHOS)/silica ormosil aerogel hybrids were prepared successfully by mixing of PMHOS with various weight percentages of silica ormosil aerogels (as synthesized from methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS) precursors) in separate seal perfume glass vials. The hybrids were spin coated on glass substrate at 1000 rpm for 60 seconds and used for further analysis. The surface morphology and chemical compositions of the hybrids were analyzed by high resolution scanning electron microscopy, high resolution transmission electron microscopy, atomic force spectroscopy, adsorption and desorption isotherm, and X-ray photoelectron spectroscopy. The transparency, thermal decomposition and static contact angle (SCA) of each sample were measured by UV-Visible spectrophotometer, TGA and drop shape analysis system, respectively. The spin coated substrates showed good superhydrophobic properties, thermal stability as well as transparency on the glass substrates.

  5. Amorphous Silica- and Carbon- rich nano-templated surfaces as model interstellar dust surfaces for laboratory astrochemistry

    NASA Astrophysics Data System (ADS)

    Pascual, Natalia; Dawes, Anita; González-Posada, Fernando; Thompson, Neil; Chakarov, Dinko; Mason, Nigel J.; Fraser, Helen Jane

    2015-08-01

    Experimental studies on surface astrochemistry are vital to our understanding of chemical evolution in the interstellar medium (ISM). Laboratory surface-astrochemists have recently begun to study chemical reactions on interstellar dust-grain mimics, ranging from graphite, HOPG and graphene (representative of PAHs or large C-grains in the ISM) to amorphous olivine (representative of silicate dust) and ablated meteoritic samples (representative of interplanetary dust). These pioneering experiments show that the nature of the surface fundamentally affects processes at the substrate surface, substrate-ice interface, and ice over-layer. What these experiments are still lacking is the ability to account for effects arising from the discrete nano-scale of ISM grains, which might include changes to electronic structure, optical properties and surface-kinetics in comparison to bulk materials. The question arises: to what extent are the chemical and optical properties of interstellar ices affected by the size, morphology and material of the underlying ISM dust?We have designed, fabricated and characterised a set of nano-structured surfaces, where nanoparticles, representative of ISM grains, are adhered to an underlying support substrate. Here we will show the nanoparticles that have been manufactured from fused-silica (FS), glassy carbon (GC) and amorphous-C (aC). Our optical characterisation data shows that the nanostructured surfaces have different absorption cross-sections and significant scattering in comparison to the support substrates, which has implications for the energetic processing of icy ISM dust. We have been able to study how water-ice growth differs on the nanoparticles in comparison to the “flat” substrates, indicating increased ice amorphicity when nanoparticles are present, and on C-rich surfaces, compared to Si-rich particles. These data will be discussed in the context of interstellar water-ice features.

  6. Interfacial Structure of Composites of Poly(m-xylylen adipamide) and Silica Nano-Particles

    NASA Astrophysics Data System (ADS)

    Achiwa, Osamu; Kyogoku, Yoshitaka; Matsuda, Yasuhiro; Tasaka, Shigeru

    2012-10-01

    Interfacial structure of composites of poly(m-xylylen adipamide) (MXD6) and silica nano-particles (SNPs) was investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and infrared (IR) spectroscopy. In the DSC curves of the composites, changes in specific heat similar to a glass transition behavior (sub-Tg) were detected at 0-40 °C, and sub-Tg decreased with the increase in the weight fraction of SNPs. Crystallization temperature (Tc) decreased, and XRD peaks became sharper with the increase in the weight fraction of SNPs. The IR spectra suggest that the hydrogen bonds between MXD6 chains were weakened by the addition of SNPs.

  7. Strong and bioactive composites containing nano-silica-fused whiskers for bone repair.

    PubMed

    Xu, Hockin H K; Smith, Douglas T; Simon, Carl G

    2004-08-01

    Self-hardening calcium phosphate cement (CPC) sets to form hydroxyapatite with high osteoconductivity, but its brittleness and low strength limit its use to only non-stress bearing locations. Previous studies developed bioactive composites containing hydroxyapatite fillers in Bis-GMA-based composites for bone repair applications, and they possessed higher strength values. However, these strengths were still lower than the strength of cortical bone. The aim of this study was to develop strong and bioactive composites by combining CPC fillers with nano-silica-fused whiskers in a resin matrix, and to characterize the mechanical properties and cell response. Silica particles were fused to silicon carbide whiskers to roughen the whisker surfaces for enhanced retention in the matrix. Mass ratios of whisker:CPC of 1:2, 1:1 and 2:1 were incorporated into a Bis-GMA-based resin and hardened by two-part chemical curing. Composite with only CPC fillers without whiskers served as a control. The specimens were tested using three-point flexure and nano-indentation. Composites with whisker:CPC ratios of 2:1 and 1:1 had flexural strengths (mean+/-SD; n=9) of (164+/-14) MPa and (139+/-22) MPa, respectively, nearly 3 times higher than (54+/-5) MPa of the control containing only CPC fillers (p<0.05). The strength of the new whisker-CPC composites was 3 times higher than the strength achieved in previous studies for conventional bioactive composites containing hydroxyapatite particles in Bis-GMA-based resins. The mechanical properties of the CPC-whisker composites nearly matched those of cortical bone and trabecular bone. Osteoblast-like cell adhesion, proliferation and viability were equivalent on the non-whisker control containing only CPC fillers, on the whisker composite at whisker:CPC of 1:1, and on the tissue culture polystyrene control, suggesting that the new CPC-whisker composite was non-cytotoxic.

  8. Morphology And Microstructure in Fused Silica Induced By High Fluence Ultraviolet 3omega (355 Nm) Laser Pulses

    SciTech Connect

    Wong, J.; Ferriera, J.L.; Lindsey, E.F.; Haupt, D.L.; Hutcheon, I.D.; Kinney, J.H.

    2007-08-08

    The morphology and microstructure induced in high quality fused silica by UV (355 nm) laser pulses at high fluence (10-45 J/cm{sup 2}) have been investigated using a suite of microscopic and spectroscopic tools. The laser beam has a near-Gaussian profile with a 1/e{sup 2} diameter of 0.98 mm at the sample plane and a pulse length FWHM (full width at half maximum) of 7.5 ns. The damage craters consist of a molten core region (thermal explosion), surrounded by a near concentric region of fractured material. The latter arises from propagation of lateral cracks induced by the laser-generated shock waves, which also compact the crater wall, {approx} 10 {micro}m thick and {approx} 20% higher in density. The size of the damage crater varies with laser fluence, number of pulses, and laser irradiation history. In the compaction layer, there is no detectable change in the Si/O stoichiometry to within {+-} 1.6% and no crystalline nano-particles of Si were observed. Micro- (1-10 {micro}m) and nano- (20-200 nm) cracks are found, however. A lower valence Si{sup 3+} species on the top 2-3 nm of the compaction layer is evident from the Si 2p XPS. The results are used to construct a physical model of the damage crater and to gain critical insight into laser damage process.

  9. Mixed surfactants-directed the mesoporous silica materials with various morphologies and structures

    SciTech Connect

    Lin Huiming; Qu Fengyu; Wu Xiang; Xue Ming; Zhu Guangshan; Qiu Shilun

    2011-06-15

    A new mixed surfactants system using alkyl carboxylic acids and quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl] urea] (PEPU) as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures, including flakes, regular spheres, nanoparticles, and tube-spheres. The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials. The structure and property of the surfactant and the cationic polymer determined the formation of mesoporous silica, and also had a signification influence on the morphology and structure of the final materials. To further explore the possible formation mechanism of these mesoporous materials, zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. In addition, the structure, morphology, and porosity of these materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N{sub 2} adsorption-desorption measurements. - Graphical abstract: A new mixed surfactants system using alkyl carboxylic acids and PEPU as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures. Highlights: {yields}A new mixed surfactants system induced the mesoporous silica materials with various morphologies and structure. > It is a development of the type S{sup -}N{sup +}I{sup -} route of the mesoporous formation. > Zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. > The property and amount of surfactant and polymer determined the formation of the mesoporous materials.

  10. Femtosecond versus picosecond laser machining of nano-gratings and micro-channels in silica glass.

    PubMed

    Corbari, Costantino; Champion, Audrey; Gecevičius, Mindaugas; Beresna, Martynas; Bellouard, Yves; Kazansky, Peter G

    2013-02-25

    The ability of 8 picosecond pulse lasers for three dimensional direct-writing in the bulk of transparent dielectrics is assessed through a comparative study with a femtosecond laser delivering 600 fs pulses. The comparison addresses two main applications: the fabrication of birefringent optical elements and two-step machining by laser exposure and post-processing by chemical etching. Formation of self-organized nano-gratings in glass by ps-pulses is demonstrated. Differential etching between ps-laser exposed regions and unexposed silica is observed. Despite attaining values of retardance (>100 nm) and etching rate (2 μm/min) similar to fs pulses, ps pulses are found unsuitable for bulk machining in silica glass primarily due to the build-up of a stress field causing scattering, cracks and non-homogeneous etching. Additionally, we show that the so-called "quill-effect", that is the dependence of the laser damage from the direction of writing, occurs also for ps-pulse laser machining. Finally, an opposite dependence of the retardance from the intra-pulse distance is observed for fs- and ps-laser direct writing.

  11. Fiber Bragg grating filter using evaporated induced self assembly of silica nano particles

    NASA Astrophysics Data System (ADS)

    Hammarling, Krister; Zhang, Renyung; Manuilskiy, Anatoliy; Nilsson, Hans-Erik

    2014-03-01

    In the present work we conduct a study of fiber filters produced by evaporation of silica particles upon a MM-fiber core. A band filter was designed and theoretically verified using a 2D Comsol simulation model of a 3D problem, and calculated in the frequency domain in respect to refractive index. The fiber filters were fabricated by stripping and chemically etching the middle part of an MM-fiber until the core was exposed. A mono layer of silica nano particles were evaporated on the core using an Evaporation Induced Self-Assembly (EISA) method. The experimental results indicated a broader bandwidth than indicated by the simulations which can be explained by the mismatch in the particle size distributions, uneven particle packing and finally by effects from multiple mode angles. Thus, there are several closely connected Bragg wavelengths that build up the broader bandwidth. The experimental part shows that it is possible by narrowing the particle size distributing and better control of the particle packing, the filter effectiveness can be greatly improved.

  12. Morphology controlling method for amorphous silica nanoparticles and jellyfish-like nanowires and their luminescence properties.

    PubMed

    Liu, Haitao; Huang, Zhaohui; Huang, Juntong; Xu, Song; Fang, Minghao; Liu, Yan-Gai; Wu, Xiaowen; Zhang, Shaowei

    2016-01-01

    Uniform silica nanoparticles and jellyfish-like nanowires were synthesized by a chemical vapour deposition method on Si substrates treated without and with Ni(NO3)2, using silicon powder as the source material. Composition and structural characterization using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and fourier-transform infrared spectroscopy showed that the as-prepared products were silica nanoparticles and nanowires which have amorphous structures. The form of nanoparticles should be related to gas-phase nucleation procedure. The growth of the nanowires was in accordance with vapour-liquid-solid mechanism, followed by Ostwald ripening to form the jellyfish-like morphology. Photoluminescence and cathodoluminescence measurements showed that the silica products excited by different light sources show different luminescence properties. The emission spectra of both silica nanoparticles and nanowires are due to the neutral oxygen vacancies (≡Si-Si≡). The as-synthesized silica with controlled morphology can find potential applications in future nanodevices with tailorable photoelectric properties. PMID:26940294

  13. Morphology controlling method for amorphous silica nanoparticles and jellyfish-like nanowires and their luminescence properties

    PubMed Central

    Liu, Haitao; Huang, Zhaohui; Huang, Juntong; Xu, Song; Fang, Minghao; Liu, Yan-gai; Wu, Xiaowen; Zhang, Shaowei

    2016-01-01

    Uniform silica nanoparticles and jellyfish-like nanowires were synthesized by a chemical vapour deposition method on Si substrates treated without and with Ni(NO3)2, using silicon powder as the source material. Composition and structural characterization using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and fourier-transform infrared spectroscopy showed that the as-prepared products were silica nanoparticles and nanowires which have amorphous structures. The form of nanoparticles should be related to gas-phase nucleation procedure. The growth of the nanowires was in accordance with vapour-liquid-solid mechanism, followed by Ostwald ripening to form the jellyfish-like morphology. Photoluminescence and cathodoluminescence measurements showed that the silica products excited by different light sources show different luminescence properties. The emission spectra of both silica nanoparticles and nanowires are due to the neutral oxygen vacancies (≡Si-Si≡). The as-synthesized silica with controlled morphology can find potential applications in future nanodevices with tailorable photoelectric properties. PMID:26940294

  14. Morphology controlling method for amorphous silica nanoparticles and jellyfish-like nanowires and their luminescence properties.

    PubMed

    Liu, Haitao; Huang, Zhaohui; Huang, Juntong; Xu, Song; Fang, Minghao; Liu, Yan-Gai; Wu, Xiaowen; Zhang, Shaowei

    2016-03-04

    Uniform silica nanoparticles and jellyfish-like nanowires were synthesized by a chemical vapour deposition method on Si substrates treated without and with Ni(NO3)2, using silicon powder as the source material. Composition and structural characterization using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and fourier-transform infrared spectroscopy showed that the as-prepared products were silica nanoparticles and nanowires which have amorphous structures. The form of nanoparticles should be related to gas-phase nucleation procedure. The growth of the nanowires was in accordance with vapour-liquid-solid mechanism, followed by Ostwald ripening to form the jellyfish-like morphology. Photoluminescence and cathodoluminescence measurements showed that the silica products excited by different light sources show different luminescence properties. The emission spectra of both silica nanoparticles and nanowires are due to the neutral oxygen vacancies (≡Si-Si≡). The as-synthesized silica with controlled morphology can find potential applications in future nanodevices with tailorable photoelectric properties.

  15. Morphology controlling method for amorphous silica nanoparticles and jellyfish-like nanowires and their luminescence properties

    NASA Astrophysics Data System (ADS)

    Liu, Haitao; Huang, Zhaohui; Huang, Juntong; Xu, Song; Fang, Minghao; Liu, Yan-Gai; Wu, Xiaowen; Zhang, Shaowei

    2016-03-01

    Uniform silica nanoparticles and jellyfish-like nanowires were synthesized by a chemical vapour deposition method on Si substrates treated without and with Ni(NO3)2, using silicon powder as the source material. Composition and structural characterization using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and fourier-transform infrared spectroscopy showed that the as-prepared products were silica nanoparticles and nanowires which have amorphous structures. The form of nanoparticles should be related to gas-phase nucleation procedure. The growth of the nanowires was in accordance with vapour-liquid-solid mechanism, followed by Ostwald ripening to form the jellyfish-like morphology. Photoluminescence and cathodoluminescence measurements showed that the silica products excited by different light sources show different luminescence properties. The emission spectra of both silica nanoparticles and nanowires are due to the neutral oxygen vacancies (≡Si-Si≡). The as-synthesized silica with controlled morphology can find potential applications in future nanodevices with tailorable photoelectric properties.

  16. Automated oligonucleotide solid-phase synthesis on nanosized silica particles using nano-on-micro assembled particle supports.

    PubMed

    Farre, Carole; Lansalot, Muriel; Bazzi, Rana; Roux, Stéphane; Marquette, Christophe A; Catanante, Gaëlle; Blum, Loïc J; Charvet, Nicolas; Louis, Cédric; Chaix, Carole

    2010-04-01

    This article describes an original strategy to enable solid-phase oligodeoxyribonucleotide (ODN) synthesis on nanosized silica particles. It consists of the reversible immobilization of silica nanoparticles (NPs) on micrometric silica beads. The resulting assemblies, called nano-on-micro (NOM) systems, are well adapted to ODN synthesis in an automated instrument. First, NPs are derivatized with OH functions. For NOM assembly preparation, these functions react with the silanols of the microbeads under specific experimental conditions. Furthermore, OH groups allow ODN synthesis on the nanoparticles via phosphoramidite chemistry. The stability of the NOM assemblies during ODN solid-phase synthesis is confirmed by scanning and transmission electron microscopy (SEM and TEM, respectively), together with dynamic light scattering analyses. Then, the release of ODN-functionalized nanoparticles is performed under mild conditions (1% NH(4)OH in water, 1 h, 60 degrees C). Our technique provides silica nanoparticles well functionalized with oligonucleotides, as demonstrated by hybridization experiments conducted with the cDNA target.

  17. Biodegradation of 2,4-dinitrophenol with laccase immobilized on nano-porous silica beads

    PubMed Central

    2013-01-01

    Many organic hazardous pollutants, including 2,4-dinitrophenol (2,4-DNP), which are water soluble, toxic, and not easily biodegradable make concerns for environmental pollution worldwide. In the present study, degradation of nitrophenols-contained effluents by using laccase immobilized on the nano-porous silica beads was evaluated. 2,4-DNP was selected as the main constituent of industrial effluents containing nitrophenols. The performance of the system was characterized as a function of pH, contact time, temperature, pollutant, and mediator concentrations. The laccase-silica beads were employed in a mixed-batch reactor to determine the degradation efficiency after 12 h of enzyme treatment. The obtained data showed that the immobilized laccase degraded more than 90% of 2,4-DNP within 12 h treatment. The immobilization process improved the activity and sustainability of laccase for degradation of the pollutant. Temperatures more than 50°C reduced the enzyme activity to about 60%. However, pH and the mediator concentration could not affect the enzyme activity. The degradation kinetic was in accordance with a Michaelis–Menten equation with Vmax and Km obtained as 0.25–0.38 μmoles/min and 0.13–0.017 mM, respectively. The stability of the immobilized enzyme was maintained for more than 85% of its initial activity after 30 days. Based on the results, it can be concluded that high resistibility and reusability of immobilized laccase on CPC-silica beads make it considerable choice for wastewater treatment. PMID:23547870

  18. Dehydration of Glycerin to Acrolein Over Heteropolyacid Nano-Catalysts Supported on Silica-Alumina.

    PubMed

    Kang, Tae Hun; Choi, Jung Ho; Choi, Jun Seon; Song, In Kyu

    2015-10-01

    A series of H3PW12O40 nano-catalysts supported on silica-alumina (XH3PW12O40/SA (X = 10, 15, 20, 25, and 30)) with different H3PW12O40 content (X, wt%) were prepared, and they were applied to the dehydration of glycerin to acrolein. The effect of H3PW12O40 content on the physicochemical properties and catalytic activities of XH3PW12O40/SA nano-catalysts was investigated. Surface area and pore volume of XH3PW12O40/SA catalysts decreased with increasing H3PW12O40 content. Formation of H3PW12O40 aggregates was observed in the catalysts with high H3PW12O40 loading. Brønsted acidity of the catalysts showed a volcano-shaped trend with respect to H3PW12O40 content. It was revealed that yield for acrolein increased with increasing Brønsted acidity of XH3PW12O40/SA catalysts. Brønsted acidity of XH3PW12O40/SA catalysts served as a crucial factor determining the catalytic performance in the dehydration of glycerin. Among the catalysts tested, 25H3PW12O40/SA catalyst with the largest Brønsted acidity showed the best catalytic performance. PMID:26726511

  19. Dehydration of Glycerin to Acrolein Over Heteropolyacid Nano-Catalysts Supported on Silica-Alumina.

    PubMed

    Kang, Tae Hun; Choi, Jung Ho; Choi, Jun Seon; Song, In Kyu

    2015-10-01

    A series of H3PW12O40 nano-catalysts supported on silica-alumina (XH3PW12O40/SA (X = 10, 15, 20, 25, and 30)) with different H3PW12O40 content (X, wt%) were prepared, and they were applied to the dehydration of glycerin to acrolein. The effect of H3PW12O40 content on the physicochemical properties and catalytic activities of XH3PW12O40/SA nano-catalysts was investigated. Surface area and pore volume of XH3PW12O40/SA catalysts decreased with increasing H3PW12O40 content. Formation of H3PW12O40 aggregates was observed in the catalysts with high H3PW12O40 loading. Brønsted acidity of the catalysts showed a volcano-shaped trend with respect to H3PW12O40 content. It was revealed that yield for acrolein increased with increasing Brønsted acidity of XH3PW12O40/SA catalysts. Brønsted acidity of XH3PW12O40/SA catalysts served as a crucial factor determining the catalytic performance in the dehydration of glycerin. Among the catalysts tested, 25H3PW12O40/SA catalyst with the largest Brønsted acidity showed the best catalytic performance.

  20. Concentration gradient induced morphology evolution of silica nanostructure growth on photoresist-derived carbon micropatterns

    PubMed Central

    2012-01-01

    The evolution of silica nanostructure morphology induced by local Si vapor source concentration gradient has been investigated by a smart design of experiments. Silica nanostructure or their assemblies with different morphologies are obtained on photoresist-derived three-dimensional carbon microelectrode array. At a temperature of 1,000°C, rope-, feather-, and octopus-like nanowire assemblies can be obtained along with the Si vapor source concentration gradient flow. While at 950°C, stringlike assemblies, bamboo-like nanostructures with large joints, and hollow structures with smaller sizes can be obtained along with the Si vapor source concentration gradient flow. Both vapor–liquid-solid and vapor-quasiliquid-solid growth mechanisms have been applied to explain the diverse morphologies involving branching, connecting, and batch growth behaviors. The present approach offers a potential method for precise design and controlled synthesis of nanostructures with different features. PMID:22938090

  1. Concentration gradient induced morphology evolution of silica nanostructure growth on photoresist-derived carbon micropatterns

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Shi, Tielin; Xi, Shuang; Lai, Wuxing; Liu, Shiyuan; Li, Xiaoping; Tang, Zirong

    2012-09-01

    The evolution of silica nanostructure morphology induced by local Si vapor source concentration gradient has been investigated by a smart design of experiments. Silica nanostructure or their assemblies with different morphologies are obtained on photoresist-derived three-dimensional carbon microelectrode array. At a temperature of 1,000°C, rope-, feather-, and octopus-like nanowire assemblies can be obtained along with the Si vapor source concentration gradient flow. While at 950°C, stringlike assemblies, bamboo-like nanostructures with large joints, and hollow structures with smaller sizes can be obtained along with the Si vapor source concentration gradient flow. Both vapor-liquid-solid and vapor-quasiliquid-solid growth mechanisms have been applied to explain the diverse morphologies involving branching, connecting, and batch growth behaviors. The present approach offers a potential method for precise design and controlled synthesis of nanostructures with different features.

  2. Influence of Environmental Factors on the Adsorption Capacity and Thermal Conductivity of Silica Nano-Porous Materials.

    PubMed

    Zhang, Hu; Gu, Wei; Li, Ming-Jia; Fang, Wen-Zhen; Li, Zeng-Yao; Tao, Wen-Quan

    2015-04-01

    In this work, the influence of temperature and humidity environment on the water vapor adsorption capacity and effective thermal conductivity of silica nano-porous material is conducted within a relative humidity range from 15% to 90% at 25 °C, 40 °C and 55 °C, respectively. The experiment results show that both the temperature and relative humidity have significant influence on the adsorption capacity and effective thermal conductivity of silica nano-porous materials. The adsorption capacity and effective thermal conductivity increase with humidity because of the increases of water vapor concentration. The effective thermal conductivity increases linearly with adsorption saturation capacity at constant temperature. Because adsorption process is exothermic reaction, the increasing temperature is not conducive to the adsorption. But the effective thermal conductivity increases with the increment of temperature at the same water uptake because of the increment of water thermal conductivity with temperature Geometric models and unit cell structure are adopted to predict the effective thermal conductivity and comparisons with the experimental result are made, and for the case of moist silica nano-porous materials with high porosity no quantitative agreement is found. It is believed that the adsorbed water will fill in the nano-pores and gap and form lots of short cuts, leading to a significant reduction of the thermal resistance.

  3. Further Insight into the Definite Morphology and Formation Mechanism of Mesoporous Silica KCC-1.

    PubMed

    Febriyanti, E; Suendo, V; Mukti, R R; Prasetyo, A; Arifin, A F; Akbar, M A; Triwahyono, S; Marsih, I N; Ismunandar

    2016-06-14

    The unique three-dimensional pore structure of KCC-1 has attracted significant attention and has proven to be different compared to other conventional mesoporous silica such as the MCM-41 family, SBA-15, or even MSN nanoparticles. In this research, we carefully examine the morphology of KCC-1 to define more appropriate nomenclature. We also propose a formation mechanism of KCC-1 based on our experimental evidence. Herein, the KCC-1 morphology was interpreted mainly on the basis of compiling all observation and information taken from SEM and TEM images. Further analysis on TEM images was carried out. The gray value intensity profile was derived from TEM images in order to determine the specific pattern of this unique morphology that is found to be clearly different from that of other types of porous spherical-like morphologies. On the basis of these results, the KCC-1 morphology would be more appropriately reclassified as bicontinuous concentric lamellar morphology. Some physical characteristics such as the origin of emulsion, electrical conductivity, and the local structure of water molecules in the KCC-1 emulsion were disclosed to reveal the formation mechanism of KCC-1. The origin of the KCC-1 emulsion was characterized by the observation of the Tyndall effect, conductometry to determine the critical micelle concentration, and Raman spectroscopy. In addition, the morphological evolution study during KCC-1 synthesis completes the portrait of the formation of mesoporous silica KCC-1. PMID:27120557

  4. Comparison of Nanoparticle Exposures Between Fumed and Sol-gel Nano-silica Manufacturing Facilities

    PubMed Central

    OH, Sewan; KIM, Boowook; KIM, Hyunwook

    2014-01-01

    Silica nanoparticles (SNPs) are widely used all around the world and it is necessary to evaluate appropriate risk management measures. An initial step in this process is to assess worker exposures in their current situation. The objective of this study was to compare concentrations and morphologic characteristics of fumed (FS) and sol-gel silica nanoparticles (SS) in two manufacturing facilities. The number concentration (NC) and particle size were measured by a real-time instrument. Airborne nanoparticles were subsequently analyzed using a TEM/EDS. SNPs were discharged into the air only during the packing process, which was the last manufacturing step in both the manufacturing facilities studied. In the FS packing process, the geometric mean (GM) NC in the personal samples was 57,000 particles/cm3. The geometric mean diameter (GMD) measured by the SMPS was 64 nm. Due to the high-temperature formation process, the particles exhibited a sintering coagulation. In the SS packing process that includes a manual jet mill operation, the GM NC was calculated to be 72,000 particles/cm3 with an assumption of 1,000,000 particles/cm3 when the upper limit is exceeded (5% of total measure). The particles from SS process had a spherical-shaped morphology with GMD measured by SMPS of 94 nm. PMID:24583511

  5. Additive-induced morphological tuning of self-assembled silica-barium carbonate crystal aggregates

    NASA Astrophysics Data System (ADS)

    Kellermeier, Matthias; Glaab, Fabian; Carnerup, Anna M.; Drechsler, Markus; Gossler, Benjamin; Hyde, Stephen T.; Kunz, Werner

    2009-04-01

    Crystallisation of barium carbonate from alkaline silica solutions results in the formation of extraordinary micron-scale architectures exhibiting non-crystallographic curved shapes, such as helical filaments and worm-like braids. These so-called "silica biomorphs" consist of a textured assembly of uniform elongated witherite nanocrystallites, which is occasionally sheathed by a skin of amorphous silica. Although great efforts have been devoted to clarifying the physical origin of these fascinating materials, to date little is known about the processes underlying the observed self-organisation. Herein, we describe the effect of two selected additives, a cationic surfactant and a cationic polymer, on the morphology of the forming crystal aggregates, and relate changes to experiments conducted in the absence of additives. Minor amounts of both substances are shown to exert a significant influence on the growth process, leading to the formation of predominantly flower-like spherulitic aggregates. The observed effects are discussed in terms of feasible morphogenesis pathways. Based on the assumption of a template membrane steering biomorph formation, it is proposed that the two additives are capable of performing specific bridging functions promoting the aggregation of colloidal silica which constitutes the membrane. Morphological changes are tentatively ascribed to varying colloid coordination effecting distinct membrane curvatures.

  6. Reducing Logistics Footprints and Replenishment Demands: Nano-engineered Silica Aerogels a Proven Method for Water Treatment

    SciTech Connect

    Daily, W; Coleman, S; Love, A; Reynolds, J; O'Brien, K; Gammon, S

    2004-09-22

    Rapid deployment and the use of objective force aggressively reduce logistic footprints and replenishment demands. Maneuver Sustainment requires that Future Combat Systems be equipped with water systems that are lightweight, have small footprints, and are highly adaptable to a variety of environments. Technologies employed in these settings must be able to meet these demands. Lawrence Livermore National Laboratory has designed and previously field tested nano-engineered materials for the treatment of water. These materials have been either based on silica aerogel materials or consist of composites of these aerogels with granular activated carbon (GAC). Recent tests have proven successful for the removal of contaminants including uranium, hexavalent chromium, and arsenic. Silica aerogels were evaluated for their ability to purify water that had been spiked with the nerve agent VX (O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate). These results demonstrated that silica aerogels were able to remove the VX from the supply water and were nearly 30 times more adsorbent than GAC. This performance could result in REDUCING CHANGEOUT FREQUENCY BY A FACTOR OF 30 or DECREASING the VOLUME of adsorbent BY A FACTOR OF 30; thereby significantly reducing logistic footprints and replenishment demands. The use of the nano-engineered Silica Aerogel/GAC composites would provide a water purification technology that meets the needs of Future Combat Systems.

  7. Monodisperse hollow silica nanospheres for nano insulation materials: synthesis, characterization, and life cycle assessment.

    PubMed

    Gao, Tao; Jelle, Bjørn Petter; Sandberg, Linn Ingunn C; Gustavsen, Arild

    2013-02-01

    The application of manufactured nanomaterials provides not only advantages resulting from their unique properties but also disadvantages derived from the high energy use and CO(2) burden related to their manufacture, operation, and disposal. It is therefore important to understand the trade-offs of process economics of nanomaterial production and their associated environmental footprints in order to strengthen the existing advantages while counteracting disadvantages. This work reports the synthesis, characterization, and life cycle assessment (LCA) of a new type of superinsulating materials, nano insulation materials (NIMs), which are made of hollow silica nanospheres (HSNSs) and have great flexibility in modifying their properties by tuning the corresponding structural parameters. The as-prepared HSNSs in this work have a typical inner pore diameter of about 150 nm and a shell thickness of about 10-15 nm and exhibit a reduced thermal conductivity of about 0.02 W/(m K) because of their size-dependent thermal conduction at the nanometer scale. The energy and raw material consumption related to the synthesis of HSNSs have been analyzed by the LCA method. The results indicate that the recycle of chemicals, up-scaling production, and use of environmentally friendly materials can greatly affect the process of environmental footprints. New synthesis routes for NIMs with improved thermal performance and energy and environmental features are also recommended on the basis of the LCA study.

  8. Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media.

    PubMed

    Yang, Zhangmei; Qiu, Xinhong; Fang, Zhanqiang; Pokeung, Tsang

    2015-01-01

    Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through sand. However, the agglomeration of nano zero-valent iron (NZVI) particles limits the migration distance, which inhibits their usefulness. In the study described herein, NZVI supported by mesoporous silica microspheres covered with FeOOH (SiO2@FeOOH@Fe) was synthesized, and its mobility was demonstrated on the basis of transport in porous media. Degradation of decabromodiphenyl ether (BDE209) was more efficient by SiO2@FeOOH@Fe than by 'bare' NZVI. Breakthrough curves and mass recovery showed the mobility of SiO2@FeOOH@Fe in granular media was better than that of bare NZVI. It increased greatly in the presence of natural organic matter (NOM) and decreased when high Ca2+ and Mg2+ concentrations were encountered. Analysis of the transport data on the basis of filtration theory showed diffusion to be the main mechanism for particle removal in silicon sand. Increasing the NOM may decrease agglomeration of the grains of sand, which has a positive effect on the mobility of SiO2@FeOOH@Fe. Presumably, increasing the concentrations of Ca2+ and Mg2+ compresses the diffuse double layer of SiO2@FeOOH@Fe, resulting in a reduction of mobility.

  9. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    SciTech Connect

    Zhang, Jinyu; Zhou, Guowei Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d{sub 100}), and cell parameter (a{sub 0}) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d{sub 100} and a{sub 0} continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%. - Graphical abstract: Curved rod-shaped mesoporous silica can be obtained at low and the highest PVP concentration, while straight rod-shaped mesoporous silica can be obtained at higher PVP concentration. - Highlights: • Mesoporous silica with morphology evolution from CRMS to SRMS were prepared. • Effects of PVP molecular weight and concentration on silica morphology were studied. • A possible mechanism for the formation of morphology evolution SiO{sub 2} was proposed. • Esterification of lauric acid with 1-butanol catalyzed by immobilized PPL.

  10. Nuclear nano-morphology markers of histologically normal cells detect the "field effect" of breast cancer.

    PubMed

    Bista, Rajan K; Wang, Pin; Bhargava, Rohit; Uttam, Shikhar; Hartman, Douglas J; Brand, Randall E; Liu, Yang

    2012-08-01

    Accurate detection of breast malignancy from histologically normal cells ("field effect") has significant clinical implications in a broad base of breast cancer management, such as high-risk lesion management, personalized risk assessment, breast tumor recurrence, and tumor margin management. More accurate and clinically applicable tools to detect markers characteristic of breast cancer "field effect" that are able to guide the clinical management are urgently needed. We have recently developed a novel optical microscope, spatial-domain low-coherence quantitative phase microscopy, which extracts the nanoscale structural characteristics of cell nuclei (i.e., nuclear nano-morphology markers), using standard histology slides. In this proof-of-concept study, we present the use of these highly sensitive nuclear nano-morphology markers to identify breast malignancy from histologically normal cells. We investigated the nano-morphology markers from 154 patients with a broad spectrum of breast pathology entities, including normal breast tissue, non-proliferative benign lesions, proliferative lesions (without and with atypia), "malignant-adjacent" normal tissue, and invasive carcinoma. Our results show that the nuclear nano-morphology markers of "malignant-adjacent" normal tissue can detect the presence of invasive breast carcinoma with high accuracy and do not reflect normal aging. Further, we found that a progressive change in nuclear nano-morphology markers that parallel breast cancer risk, suggesting its potential use for risk stratification. These novel nano-morphology markers that detect breast cancerous changes from nanoscale structural characteristics of histologically normal cells could potentially benefit the diagnosis, risk assessment, prognosis, prevention, and treatment of breast cancer.

  11. Linking CO2 Sorption Performance to Polymer Morphology in Aminopolymer/Silica Composites through Neutron Scattering.

    PubMed

    Holewinski, Adam; Sakwa-Novak, Miles A; Jones, Christopher W

    2015-09-16

    Composites of poly(ethylenimine) (PEI) and mesoporous silica are effective, reversible adsorbents for CO2, both from flue gas and in direct air-capture applications. The morphology of the PEI within the silica can strongly impact the overall carbon capture efficiency and rate of saturation. Here, we directly probe the spatial distribution of the supported polymer through small-angle neutron scattering (SANS). Combined with textural characterization from physisorption analysis, the data indicate that PEI first forms a thin conformal coating on the pore walls, but all additional polymer aggregates into plug(s) that grow along the pore axis. This model is consistent with observed trends in amine-efficiency (CO2/N binding ratio) and pore size distributions, and points to a trade-off between achieving high chemical accessibility of the amine binding sites, which are inaccessible when they strongly interact with the silica, and high accessibility for mass transport, which can be hampered by diffusion through PEI plugs. We illustrate this design principle by demonstrating higher CO2 capacity and uptake rate for PEI supported in a hydrophobically modified silica, which exhibits repulsive interactions with the PEI, freeing up binding sites.

  12. Structural, Morphological and Antibacterial Investigation of Ag-Impregnated Sol-Gel-Derived 45S5 NanoBioglass Systems.

    PubMed

    Durgalakshmi, D; Balakumar, S; Raja, C Ashok; George, Rani P; Mudali, U Kamachi

    2015-06-01

    An increasing percentage of ageing population requires 30-year survivability of orthopedic devices that is not possible with the current bioinert materials, having a maximum of 15-year survivability. To satisfy this growing need, a shift is needed from replacement of tissues to regeneration of tissues. This is highly possible through the use of silica-bioactive glasses. However, a failure of implant can occur due to infections even by using such materials. Advances in using silver for antibacterial applications have been commercialized. However, higher concentrations of silver also lead to toxic effects. In this study, nanoBioglass 45S5 (NBG) and Ag-NBG were synthesized by using sol-gel method followed by solution-phase method, respectively. The bioactive crystals such as Na2Ca2Si3O9, CaCO3, and AgPO3, very much needed in the field of bone tissue engineering and in antibacterial strategies, were obtained in the NBG Matrix. The morphological investigation of NBG with 1 mM Ag+ concentrations shows the nanospikes arrangement of size 30-40 nm with spherical porous structure of size 10-20 nm, which supports the formation of collagen molecular fibrils on the surface of NBG matrices and enhances osseointegration. Both gram-positive and gram-negative strains show higher antibacterial activity for nanoBioglass with 1 mM Ag+ concentration. PMID:26369040

  13. Morphology and structure of particles produced by femtosecond laser ablation of fused silica

    NASA Astrophysics Data System (ADS)

    Sharma, S. P.; Oliveira, V.; Vilar, Rui

    2016-04-01

    The aim of the present work was to study the morphology and structure of the nanoparticles produced by femtosecond laser ablation of fused silica. Ultrashort laser pulses of 1030 nm wavelength and 550 fs duration were tightly focused by a high numerical aperture microscope objective at the surface of fused silica samples while scanning the sample in relation to the stationary laser beam. Laser tracks were created with pulse energies in the range 5-100 μJ, resulting in ablation debris of different morphologies. The debris were examined by scanning and transmission electron microscopy for their morphology and crystal structure in relation to the incident laser pulse energy. Ejected particles with sizes ranging from a few nanometers to a few microns were found. Their morphologies can be broadly classified into three categories: very fine round nanoparticles with diameters lower than 20 nm, nanoparticles with intermediate sizes between 50 and 200 nm, and big irregular particles with typical size between 0.5 and 1.5 μm. The fine nanoparticles of the first category are predominantly observed at higher pulse energies and tend to aggregate to form web-like and arborescent-like structures. The nanoparticles with intermediate sizes are observed for all pulse energies used and may appear isolated or aggregated in clusters. Finally, the larger irregular particles of the third category are observed for all energies and appear normally isolated.

  14. Kinetically-controlled template-free synthesis of hollow silica micro-/nanostructures with unusual morphologies

    NASA Astrophysics Data System (ADS)

    Zhang, An-Qi; Li, Hui-Jun; Qian, Dong-Jin; Chen, Meng

    2014-04-01

    We report a kinetically-controlled template-free room-temperature production of hollow silica materials with various novel morphologies, including tubes, crutches, ribbons, bundles and bells. The obtained products, which grew in a well-controlled manner, were monodispersed in shape and size. The role of ammonia, sodium citrate, polyvinylpyrrolidone, chloroauric acid and NaCl in shape control is discussed in detail. The oriented growth of these micro-/nanostructures directed by reverse micelles followed a solution-solution-solid (SSS) mechanism, similar to the classic vapor-liquid-solid mechanism. The evolution processes of silica rods, tubes, crutches, bundles and bells were recorded using transmission electron microscopy to prove the SSS mechanism.

  15. Resolving the morphology of niobium carbonitride nano-precipitates in steel using atom probe tomography.

    PubMed

    Breen, Andrew J; Xie, Kelvin Y; Moody, Michael P; Gault, Baptiste; Yen, Hung-Wei; Wong, Christopher C; Cairney, Julie M; Ringer, Simon P

    2014-08-01

    Atom probe is a powerful technique for studying the composition of nano-precipitates, but their morphology within the reconstructed data is distorted due to the so-called local magnification effect. A new technique has been developed to mitigate this limitation by characterizing the distribution of the surrounding matrix atoms, rather than those contained within the nano-precipitates themselves. A comprehensive chemical analysis enables further information on size and chemistry to be obtained. The method enables new insight into the morphology and chemistry of niobium carbonitride nano-precipitates within ferrite for a series of Nb-microalloyed ultra-thin cast strip steels. The results are supported by complementary high-resolution transmission electron microscopy.

  16. Glutaraldehyde-chitosan and poly (vinyl alcohol) blends, and fluorescence of their nano-silica composite films.

    PubMed

    Hu, Huawen; Xin, John H; Hu, Hong; Chan, Allan; He, Liang

    2013-01-01

    In this study, a commercial chitosan cross-linked with glutaraldehyde (GA-chitosan) having the autofluorescent property was effectively blended with a poly (vinyl alcohol) (PVA) matrix, in the formation of a transparent and fluorescent blend film. The fluorescent efficiency of the film was enhanced with red-shifted emission band by increasing the concentrations of the GA-chitosan and decreasing the PVA crystallinity. It was found that the incorporation of silica nanoparticles could further decrease the PVA crystallinity, enhance the fluorescent efficiency, and largely redshift the emission band, as compared with the neat GA-chitosan-PVA blend film. This fluorescent property could be finely tuned by careful doping of the silica nanoparticles and change of the PVA crystallinity. These phenomena could be reasonably explained by high extent of isolation of the fluorophores, increase of the stiffness of the fluorescent conjugated planar structure, and further decrease of the PVA crystallinity. In addition, the introduction of the nano-silica could improve the water and heat resistances of the GA-chitosan-PVA based silica nanocomposites. PMID:23044137

  17. In vitro comet and micronucleus assays do not predict morphological transforming effects of silica particles in Syrian Hamster Embryo cells.

    PubMed

    Darne, Christian; Coulais, Catherine; Terzetti, Francine; Fontana, Caroline; Binet, Stéphane; Gaté, Laurent; Guichard, Yves

    2016-01-15

    Crystalline silica particles and asbestos have both been classified as carcinogenic by the International Agency for Research on Cancer (IARC). However, because of the limited data available, amorphous silica was not classifiable. In vitro, the carcinogenic potential of natural crystalline and amorphous silica particles has been revealed by the Syrian Hamster Embryo (SHE) cell transformation assay. On the other hand, the genotoxic potential of those substances has not been investigated in SHE cells. And yet, genotoxicity assays are commonly used for hazard evaluation and they are often used as in vitro assays of reference to predict a possible carcinogenic potential. The main objective of this study was to compare the genotoxic potential and the carcinogenic potential of different crystalline and amorphous silica particles in SHE cells. Three silica samples of different crystallinity were used: natural amorphous silica, partially crystallized silica and quartz silica particles. Their genotoxicity were tested through the in vitro micronucleus assay and the comet assay in SHE, and their carcinogenic potential through the SHE transformation assay. In addition, silica samples were also tested with the same genotoxicity assays in V79 hamster-lung cells, a common in vitro model for particle exposure. Results obtained in the micronucleus and the comet assays show that none of the silica was capable of inducing genotoxic effects in SHE cells and only the amorphous silica induced genotoxic effects in V79 cells. However in the SHE cell transformation assays, the partially crystallized and quartz silica were able to induce morphological cell transformation. Together, these data suggest that, in vitro, the short-term genotoxic assays alone are not sufficient to predict the hazard and the carcinogenic potential of this type of particles; SHE transformation assay appears a more reliable tool for this purpose and should be included in the "in vitro battery assays" for hazard

  18. Uptake of silica covered Quantum Dots into living cells: Long term vitality and morphology study on hyaluronic acid biomaterials.

    PubMed

    D'Amico, Michele; Fiorica, Calogero; Palumbo, Fabio Salvatore; Militello, Valeria; Leone, Maurizio; Dubertret, Benoit; Pitarresi, Giovanna; Giammona, Gaetano

    2016-10-01

    Quantum Dots (QDs) are promising very bright and stable fluorescent probes for optical studies in the biological field but water solubility and possible metal bio-contamination need to be addressed. In this work, a simple silica-QD hybrid system is prepared and the uptake in bovine chondrocytes living cells without any functionalization of the external protective silica shield is demonstrated. Moreover, long term treated cells vitality (up to 14days) and the transfer of silica-QDs to the next cell generations are here reported. Confocal fluorescence microscopy was also used to determine the morphology of the so labelled cells and the relative silica-QDs distribution. Finally, we employ silica-QD stained chondrocytes to characterize, as proof of concept, hydrogels obtained from an amphiphilic derivative of hyaluronic acid (HA-EDA-C18) functionalized with different amounts of the RGD peptide. PMID:27287118

  19. Uptake of silica covered Quantum Dots into living cells: Long term vitality and morphology study on hyaluronic acid biomaterials.

    PubMed

    D'Amico, Michele; Fiorica, Calogero; Palumbo, Fabio Salvatore; Militello, Valeria; Leone, Maurizio; Dubertret, Benoit; Pitarresi, Giovanna; Giammona, Gaetano

    2016-10-01

    Quantum Dots (QDs) are promising very bright and stable fluorescent probes for optical studies in the biological field but water solubility and possible metal bio-contamination need to be addressed. In this work, a simple silica-QD hybrid system is prepared and the uptake in bovine chondrocytes living cells without any functionalization of the external protective silica shield is demonstrated. Moreover, long term treated cells vitality (up to 14days) and the transfer of silica-QDs to the next cell generations are here reported. Confocal fluorescence microscopy was also used to determine the morphology of the so labelled cells and the relative silica-QDs distribution. Finally, we employ silica-QD stained chondrocytes to characterize, as proof of concept, hydrogels obtained from an amphiphilic derivative of hyaluronic acid (HA-EDA-C18) functionalized with different amounts of the RGD peptide.

  20. Biocompatible mesoporous silica nanoparticles with different morphologies for animal cell membrane penetration

    SciTech Connect

    Trewyn, B.; Nieweg, J.; Zhao, Y,; Lin, V.

    2007-11-24

    Two MCM-41 type, fluorescein-labeled mesoporous silica nanomaterials (MSNs) consisting of spherical and tube-shaped particles were synthesized and characterized. Both materials have hexagonally arranged mesopores with high surface area (>950 m{sup 2}/g) and a narrow distribution of pore diameters. The cellular uptake efficiency and kinetics of both MSNs were measured in a cancer cell line (CHO) and a noncancerous cell line (fibroblasts) by flow cytometry and fluorescence confocal microscopy. The correlation between the particle morphology and aggregation of MSNs to the effectiveness of cellular uptake was investigated. We envision that our study on the morphology dependent endocytosis of MSNs would lead to future developments of efficient transmembrane nanodevices for intracellular sensing and gene/drug delivery.

  1. Two-dimensional "nano-ring and nano-crystal" morphologies in Langmuir monolayer of phthalocyaninato nickel complexes.

    PubMed

    Liu, Qingyun; Liu, Hongguo; Bian, Yongzhong; Wang, Xueying; Chen, Yanli; Jiang, Jianzhuang; Li, Xiyou

    2006-08-01

    Three 1,8,15,22-tetrasubstituted phthalocyaninato nickel complexes Ni[Pc(alpha-OR)(4)] [H(2)Pc(alpha-OC(5)H(11))(4) = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(7)H(15))(4) = 1,8,15,22-tetrakis(2,4-dimethyl-3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(10)H(7))(4) = 1,8,15,22-tetrakis(2-naphthyloxy)phthalocyanine] (1-3) have been prepared by treating the corresponding metal-free phthalocyanines H(2)Pc(alpha-OR)(4) with Ni(acac)(2)2H(2)O in refluxing n-pentanol. Structures of the Langmuir monolayers of these compounds at different temperature have been investigated. Compound 1 formed nano-ring structures with the outer diameter of 70-150 nm and inner diameter of 50 nm at 25.0 degrees C while 2 and 3 formed round particles. This difference can be ascribed to the different substituents at alpha position. The morphologies of the aggregates of 1 in monolayers have been found to change with temperature. Decreasing in temperature induced the formation of regular quadrate crystals. UV-vis absorption spectra revealed strong intermolecular interactions in the nano-ring aggregates. Polarized UV-vis absorption spectra suggest a titled orientation with respect to the surface of substrate for phthalocyanine macrocycles in the nano-ring aggregates.

  2. Covalent Immobilization and Characterization of a Novel Pullulanase from Fontibacillus sp. Strain DSHK 107 onto Florisil® and Nano-silica for Pullulan Hydrolysis.

    PubMed

    Alagöz, Dilek; Yildirim, Deniz; Güvenmez, Hatice Korkmaz; Sihay, Damla; Tükel, S Seyhan

    2016-08-01

    A novel pullulanase partially purified from Fontibacillus sp. was covalently immobilized on Florisil® and nano-silica through both glutaraldehyde and (3-glycidyloxypropyl)trimethoxysilane spacer arms. The pullulanase immobilized on Florisil® and nano-silica through glutaraldehyde spacer arm showed 85 and 190 % activity of its free form, respectively, whereas no activity was observed when it was immobilized on the same supports through (3-glycidyloxypropyl)trimethoxysilane spacer arm. The maximum working pHs of both the immobilized pullulanases on Florisil® and nano-silica through glutaraldehyde spacer arm were determined as 5.0; however, the maximum working pH of the free pullulanase was pH 6.0. The maximum temperatures of all the pullulanase preparations were determined as 35 °C. The apparent K m values were 1.49, 1.54, and 0.59 mg/mL pullunan, respectively, for the free and immobilized pullulanases on Florisil® and nano-silica. The corresponding apparent V max values were 0.59, 1.53, and 1.57 U mg prot.(-1) min.(-1). Thermal stability of pullulanases immobilized on Florisil® and nano-silica was enhanced 6.5- and 15.6-folds, respectively at 35 °C and 6.6- and 16.0-folds, respectively, at 50 °C. The pullulanases immobilized on Florisil® and nano-silica protected 71 and 90 % of their initial activities after 10 reuses.

  3. A new high-throughput method utilizing porous silica-based nano-composites for the determination of partition coefficients of drug candidates.

    PubMed

    Yu, Chih H; Tam, Kin; Tsang, Shik C

    2011-09-01

    We show that highly porous silica-based nanoparticles prepared via micro-emulsion and sol-gel techniques are stable colloids in aqueous solution. By incorporating a magnetic core into the porous silica nano-composite, it is found that the material can be rapidly separated (precipitated) upon exposure to an external magnetic field. Alternatively, the porous silica nanoparticles without magnetic cores can be equally separated from solution by applying a high-speed centrifugation. Using these silica-based nanostructures a new high-throughput method for the determination of partition coefficient for water/n-octanol is hereby described. First, a tiny quantity of n-octanol phase is pre-absorbed in the porous silica nano-composite colloids, which allows an establishment of interface at nano-scale between the adsorbed n-octanol with the bulk aqueous phase. Organic compounds added to the mixture can therefore undergo a rapid partition between the two phases. The concentration of drug compound in the supernatant in a small vial can be determined by UV-visible absorption spectroscopy. With the adaptation of a robotic liquid handler, a high-throughput technology for the determination of partition coefficients of drug candidates can be employed for drug screening in the industry based on these nano-separation skills. The experimental results clearly suggest that this new method can provide partition coefficient values of potential drug candidates comparable to the conventional shake-flask method but requires much shorter analytical time and lesser quantity of chemicals.

  4. Preparation, characterization and luminescent properties of dense nano-silica hybrids loaded with 1,8-naphthalic anhydride.

    PubMed

    Wang, Jinpeng; Sun, Jihong; Li, Yuzhen; Wang, Feng

    2014-03-01

    Novel luminescent dense nano-silica hybrid materials (DNSS) modified with different amounts of (3-aminopropyl)triethoxysilane (APTES) and 1,8-naphthalic anhydride (NA) were successfully synthesized via two steps combined with post-grafting methods. Powder X-ray diffraction (XRD), N2-sorption analysis, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), photoluminescence (PL) spectroscopy and elemental analysis, as well as time-resolved decays were employed to characterize the resultant hybrid materials. The results revealed that luminescent organic molecules had been successfully loaded onto the amine-modified surface of nano-silica spheres. In addition, their fluorescence intensity and characteristic peak of emission spectra changed with increasing amount of APTES and NA additive. In particular, the characteristic peak showed a red shift from 390 to 450 nm, however, this was inconsistent with results calculated on the basis of the elemental analysis data, most probably because of the dispersion behaviors of NA molecules from the aggregating to the monolayer state. These observations demonstrated the existence of a quantum confinement effectiveness of NA-DNSS samples, and therefore a possible mechanism was put forward.

  5. Structures and dielectric properties of thin polyimide films with nano-foam morphology

    NASA Astrophysics Data System (ADS)

    Cha, H. J.; Hedrick, J.; DiPietro, R. A.; Blume, T.; Beyers, R.; Yoon, D. Y.

    1996-04-01

    Thin polyimide films with dispersed nano-foam morphology have been prepared for the purpose of obtaining low dielectric polymer insulators for microelectronic applications. They were obtained by utilizing micro phase-separated triblock copolymers where the thermally stable polyimide matrix component was derived from pyromellitic dianhydride (PMDA) with 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3F) and a thermally labile poly(propylene oxide)(PO) component comprised the outside block of the ABA triblock architecture. TEM studies show that the initial irregular nanoscale phase-separated morphology of polyimide triblock copolymers are mostly maintained in the final nano-foam films upon thermal decomposition of the dispersed PO component. The nano-foam polyimide films exhibit significantly lower dielectric constants ɛ' (e.g., 2.3 at 19% porosity) as compared with ɛ'≊2.9 for the homopolymer, as predicted by Maxwell-Garnett theory, with the nano-pore structures remaining stable at 350 °C.

  6. Study of the effect of nano surface morphology on the stain-resistant property of ceramic tiles

    NASA Astrophysics Data System (ADS)

    Pan, S. P.; Hung, J. K.; Liu, Y. T.

    2014-03-01

    In this study, six types of commercially available ceramic tiles, including nano-structured ceramic tiles and regular ceramic tiles, were selected to investigate the effect of surface morphology on their stain-resistant property. The stain-resistant efficiencies of various ceramic tiles with nano-size surface were measured in order to determine the appropriate method for testing ceramic tiles with nano-structure surface.

  7. Effect of resin infiltration on the thermal and mechanical properties of nano-sized silica-based thermal insulation.

    PubMed

    Lee, Jae Chun; Kim, Yun-Il; Lee, Dong-Hun; Kim, Won-Jun; Park, Sung; Lee, Dong Bok

    2011-08-01

    Several kinds of nano-sized silica-based thermal insulation were prepared by dry processing of mixtures consisting of fumed silica, ceramic fiber, and a SiC opacifier. Infiltration of phenolic resin solution into the insulation, followed by hot-pressing, was attempted to improve the mechanical strength of the insulation. More than 22% resin content was necessary to increase the strength of the insulation by a factor of two or more. The structural integrity of the resin-infiltrated samples could be maintained, even after resin burn-out, presumably due to reinforcement from ceramic fibers. For all temperature ranges and similar sample bulk density values, the thermal conductivities of the samples after resin burn-out were consistently higher than those of the samples obtained from the dry process. Mercury intrusion curves indicated that the median size of the nanopores formed by primary silica aggregates in the samples after resin burn-out is consistently larger than that of the sample without resin infiltration.

  8. The influence of molybdenum disulfide nanoplatelets on the dispersion of nano silica in natural rubber composites

    NASA Astrophysics Data System (ADS)

    Weng, Peijin; Wei, Qiuyan; Tang, Zhenghai; Lin, Tengfei; Guo, Baochun

    2015-12-01

    The dispersion of nanofiller in polymer composites is critical in governing the ultimate performances. Present study aimed to improve the dispersion of silica in elastomeric materials based on natural rubber (NR) composites using the nanoplatelets of molybdenum disulfide (MoS2), a graphene-like layered inorganic. NR latex was co-coagulated with MoS2 suspension to form NR/MoS2 compounds (1∼5 phr). Then silica (30 phr) was incorporated into NR/MoS2 compounds, followed by curing with sulfur, to obtained NR/MoS2/silica composites. The dispersion state of silica in the composites was examined by TEM and the effects of MoS2 on the performance of the composites were investigated. It was found that a small amount of MoS2 nanoplatelets significantly improved the silica dispersion. Consequently, the static and dynamic mechanical properties of the crosslinked natural rubber materials were greatly enhanced. The improved dispersion of silica is associated with charge transfer interaction, giving rise to electrostatic repulsion among silica.

  9. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    NASA Astrophysics Data System (ADS)

    Zhang, Jinyu; Zhou, Guowei; Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d100), and cell parameter (a0) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d100 and a0 continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%.

  10. Cetuximab-modified mesoporous silica nano-medicine specifically targets EGFR-mutant lung cancer and overcomes drug resistance.

    PubMed

    Wang, Yuetong; Huang, Hsin-Yi; Yang, Liu; Zhang, Zhanxia; Ji, Hongbin

    2016-01-01

    Drug resistance to tyrosine kinase inhibitor (TKI) is the main obstacle for efficient treatment of epidermal growth factor receptor (EGFR)-mutant lung cancer patients. Here we design a cetuximab-capped mesoporous silica nanoparticle (MP-SiO2 NP) as the drug carrier to specifically target EGFR-mutant lung cancer cells and efficiently release loaded drugs including doxorubicin and gefitinib. This innovative nano-medicine can specifically target lung cancer cells with high EGFR expression rather than those with low EGFR level. Treatment of a gefitinib-resistant cell line derived from PC9 cell (PC9-DR) with the gefitinib-loaded cetuximab-capped MP-SiO2 NP showed a significant inhibition of cell growth. Moreover, this nano-medicine successfully suppressed the progression of PC9-DR xenograft tumors. This tumor suppression was due to the endocytosis of large amount of nano-medicine and the effective gefitinib release induced by high glutathione (GSH) level in PC9-DR cells. Collectively, our study provides a novel approach to overcome EGFR-TKI resistance using cetuximab modified MP-SiO2 NP, which holds strong potential for effective management of EGFR-mutant lung cancer. PMID:27151505

  11. Refractive index detection range adjustable liquid-core fiber optic sensor based on surface plasmon resonance and a nano-porous silica coating

    NASA Astrophysics Data System (ADS)

    Chen, Yuzhi; Li, Xuejin; Zhou, Huasheng; Hong, Xueming; Geng, Youfu

    2016-09-01

    A liquid-core fiber optic surface plasmon resonance sensor with an adjustable nano-porous silica coating is first presented in this paper. By adjusting the refractive index of the nano-porous silica coating, the sensor can be used in different refractive index detection ranges. A low refractive index interval of 1.33-1.34 and a high refractive index interval of 1.42-1.44 are taken as examples to be investigated. Results show that our sensor works well in these two intervals by using appropriate nano-porous silica coatings. The highest sensitivities of the low and high refractive index intervals are obtained to be 5840 nm/RIU and 5120 nm/RIU, respectively. In addition, the sensing performances and the working wavelengths can be adjusted to meet different working requirements by changing the refractive index of the nano-porous silica coating. We also take the single mode incidence cases to explain the effects of different single incident light modes on the sensing performances.

  12. Refractive index detection range adjustable liquid-core fiber optic sensor based on surface plasmon resonance and a nano-porous silica coating

    NASA Astrophysics Data System (ADS)

    Chen, Yuzhi; Li, Xuejin; Zhou, Huasheng; Hong, Xueming; Geng, Youfu

    2016-09-01

    A liquid-core fiber optic surface plasmon resonance sensor with an adjustable nano-porous silica coating is first presented in this paper. By adjusting the refractive index of the nano-porous silica coating, the sensor can be used in different refractive index detection ranges. A low refractive index interval of 1.33–1.34 and a high refractive index interval of 1.42–1.44 are taken as examples to be investigated. Results show that our sensor works well in these two intervals by using appropriate nano-porous silica coatings. The highest sensitivities of the low and high refractive index intervals are obtained to be 5840 nm/RIU and 5120 nm/RIU, respectively. In addition, the sensing performances and the working wavelengths can be adjusted to meet different working requirements by changing the refractive index of the nano-porous silica coating. We also take the single mode incidence cases to explain the effects of different single incident light modes on the sensing performances.

  13. Synthesis of organic-inorganic hybrid sols with nano silica particles and organoalkoxysilanes for transparent and high-thermal-resistance coating films using sol-gel reaction.

    PubMed

    Na, Moonkyong; Park, Hoyyul; Ahn, Myeongsang; Lee, Hyeonhwa; Chung, Ildoo

    2010-10-01

    Organic-inorganic hybrid sols were synthesized from nano silica particles dispersed in water and from organoalkoxysilanes, using the sol-gel reaction. This work focuses on the effects of the three multifunctional organoalkoxysilanes dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), and tetramethoxysilane (TMOS) to form a transparent and high-thermal-resistance coating film. The stability of the hybrid sol was evaluated as a function of the reaction time for 10 d through the variation of the viscosity. The viscosity of the silica/DMDMS and silica/MTMS sol was slightly increased for 10 d. The multifunctional organoalkoxysilanes formed dense silica networks through hydrolysis and condensation reaction, which enhanced the thermal resistance of the coating films. No thermal degradation of the silica/DMDMS sample occurred up to 600 degrees C, and none of the silica/MTMS and silica/TMOS samples occurred either up to 700 degrees C. The organic-inorganic hybrid sols were coated on the glass substrate using a spin-coating procedure. The organic-inorganic hybrid sols formed flat coating films without cracks. The transmittance of the hybrid sol coating films using MTMS and DMDMS was shown to be over 90%. The transmittance of the silica/TMOS sol coating film reacted for 10 d abruptly decreased due to faster gelation. The silica/DMDMS and silica/MTMS hybrid sols formed smooth coating films while the surface roughness of the silica/TMOS coating film markedly increased when the hybrid sol reacted for 10 d. The increase of the surface roughness of the silica/TMOS coating film can be attributed to the degradation of the stability of the hybrid sol and to the loss of transmittance of the coating film. It was confirmed in this study that the use of organic-inorganic hybrid sol can yield transparent and high-thermal-resistance coating films.

  14. Nano rough micron patterned titanium for directing osteoblast morphology and adhesion.

    PubMed

    Puckett, Sabrina; Pareta, Rajesh; Webster, Thomas J

    2008-01-01

    Previous studies have demonstrated greater functions ofosteoblasts (bone-forming cells) on nanophase compared with conventional metals. Nanophase metals possess a biologically inspired nanostructured surface that mimics the dimensions of constituent components in bone, including collagen and hydroxyapatite. Not only do these components possess dimensions on the nanoscale, they are aligned in a parallel manner creating a defined orientation in bone. To date, research has yet to evaluate the effect that organized nanosurface features can have on the interaction of osteoblasts with material surfaces. Therefore, to determine if surface orientation of features can mediate osteoblast adhesion and morphology, this study investigated osteoblast function on patterned titanium substrates containing alternating regions of micron rough and nano rough surfaces prepared by novel electron beam evaporation techniques. This study was also interested in determining whether or not the size of the patterned regions had an effect on osteoblast behavior and alignment. Results indicated early controlled osteoblast alignment on these patterned materials as well as greater osteoblast adhesion on the nano rough regions of these patterned substrates. Interestingly, decreasing the width of the nano rough regions (from 80 microm to 22 microm) on these patterned substrates resulted in a decreased number of osteoblasts adhering to these areas. Changes in the width of the nano rough regions also resulted in changes in osteoblast morphology, thus, suggesting there is an optimal pattern dimension that osteoblasts prefer. In summary, results of this study provided evidence that aligned nanophase metal features on the surface of titanium improved early osteoblast functions (morphology and adhesion) promising for their long term functions, criteria necessary to improve orthopedic implant efficacy.

  15. Assessment of angiogenesis in osseointegration of a silica-collagen biomaterial using 3D-nano-CT.

    PubMed

    Alt, Volker; Kögelmaier, Daniela Vera; Lips, Katrin S; Witt, Vera; Pacholke, Sabine; Heiss, Christian; Kampschulte, Marian; Heinemann, Sascha; Hanke, Thomas; Thormann, Ulrich; Schnettler, Reinhard; Langheinrich, Alexander C

    2011-10-01

    Bony integration of biomaterials is a complex process in which angiogenesis plays a crucial role. We evaluated micro- and nano-CT imaging to demonstrate and quantify neovascularization in bony integration of a biomaterial and to give an image based estimation for the needed resolution for imaging angiogenesis in an animal model of femora defect healing. In 8 rats 5mm full-size defects were created at the left femur that was filled with silica-collagen bone substitute material and internally fixed with plate osteosynthesis. After 6 weeks the femora were infused in situ with Microfil, harvested and scanned for micro-CT (9 μm)(3) and nano-CT (3 μm)(3) imaging. Using those 3D images, the newly formed blood vessels in the area of the biomaterial were assessed and the total vascular volume fraction, the volume of the bone substitute material and the volume of the bone defect were quantitatively characterized. Results were complemented by histology. Differences were statistically assessed using (ANOVA). High-resolution nano-CT demonstrated new blood vessel formation surrounding the biomaterial in all animals at capillary level. Immunohistochemistry confirmed the newly formed blood vessels surrounding the bone substitute material. The mean vascular volume fraction (VVF) around the implant was calculated to be 3.01 ± 0.4%. The VVF was inversely correlated with the volume of the bone substitute material (r=0.8) but not with the dimension of the fracture zone (r=0.3). Nano-CT imaging is feasible for quantitative analysis of angiogenesis during bony integration of biomaterials and a promising tool in this context for the future. PMID:21723963

  16. Interactions of neurons with topographic nano cues affect branching morphology mimicking neuron-neuron interactions.

    PubMed

    Baranes, Koby; Kollmar, Davida; Chejanovsky, Nathan; Sharoni, Amos; Shefi, Orit

    2012-08-01

    We study the effect of topographic nano-cues on neuronal growth-morphology using invertebrate neurons in culture. We use photolithography to fabricate substrates with repeatable line-pattern ridges of nano-scale heights of 10-150 nm. We plate leech neurons atop the patterned-substrates and compare their growth pattern to neurons plated atop non-patterned substrates. The model system allows us the analysis of single neurite-single ridge interactions. The use of high resolution electron microscopy reveals small filopodia processes that attach to the line-pattern ridges. These fine processes, that cannot be detected in light microscopy, add anchoring sites onto the side of the ridges, thus additional physical support. These interactions of the neuronal process dominantly affect the neuronal growth direction. We analyze the response of the entire neuronal branching tree to the patterned substrates and find significant effect on the growth patterns compared to non-patterned substrates. Moreover, interactions with the nano-cues trigger a growth strategy similarly to interactions with other neuronal cells, as reflected in their morphometric parameters. The number of branches and the number of neurites originating from the soma decrease following the interaction demonstrating a tendency to a more simplified neuronal branching tree. The effect of the nano-cues on the neuronal function deserves further investigation and will strengthen our understanding of the interplay between function and form.

  17. Effect of morphology and solvent on two-photon absorption of nano zinc oxide

    SciTech Connect

    Kavitha, M.K.; Haripadmam, P.C.; Gopinath, Pramod; Krishnan, Bindu; John, Honey

    2013-05-15

    Highlights: ► ZnO nanospheres and triangular structures synthesis by novel precipitation technique. ► The effect of precursor concentration on the size and shape of nano ZnO. ► Open aperture Z-scan measurements of the ZnO nanoparticle dispersions. ► Nanospheres exhibit higher two photon absorption coefficient than triangular nanostructures. ► Nanospheres dispersed in water exhibit higher two photon absorption coefficient than its dispersion in 2-propanol. - Abstract: In this paper, we report the effect of morphology and solvent on the two-photon absorption of nano zinc oxide. Zinc oxide nanoparticles in two different morphologies like nanospheres and triangular nanostructures are synthesized by novel precipitation technique and their two-photon absorption coefficient is measured using open aperture Z-scan technique. Experimental results show that the zinc oxide nanospheres exhibit higher two-photon absorption coefficient than the zinc oxide triangular nanostructures. The zinc oxide nanospheres dispersed in water exhibit higher two-photon absorption coefficient than that of its dispersion in 2-propanol. The zinc oxide nanospheres dispersed in water shows a decrease in two-photon absorption coefficient with an increase in on-axis irradiance. The result confirms the dependence of shape and solvent on the two-photon absorption of nano zinc oxide.

  18. Morphologies of laser-induced damage in hafnia-silica multilayer mirror and polarizer coatings

    SciTech Connect

    Genin, F.Y.; Stolz, C.J.

    1996-08-01

    Hafnium-silica multilayer mirrors and polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The mirrors and polarizers were coated for operation at 1053 nm at 45{degree} and at Brewster`s angle (56{degree}), respectively. They were tested with a single 3-ns laser pulse. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies were found: pits, flatbottom pits, scalds, and delaminates. The pits and flat bottom pits (<30{mu}m dia) were detected at lower fluences (as low as 5 J/cm{sup 2}). The pits seemed to result from ejection of nodular defects by causing local enhancement of the electric field. Scalds and delaminates could be observed at higher fluences (above 13 J/cm{sup 2}) and seemed to result from the formation of plasmas on the surface. These damage types often originated at pits and were less than 300 {mu}m diameter; their size increased almost linearly with fluence. Finally, effects of the damage on the beam (reflectivity degradation and phase modulations) were measured.

  19. Nano-silica fabricated with silver nanoparticles: antifouling adsorbent for efficient dye removal, effective water disinfection and biofouling control

    NASA Astrophysics Data System (ADS)

    Das, Sujoy K.; Khan, Md. Motiar R.; Parandhaman, T.; Laffir, Fathima; Guha, Arun K.; Sekaran, G.; Mandal, Asit Baran

    2013-05-01

    A nano-silica-AgNPs composite material is proposed as a novel antifouling adsorbent for cost-effective and ecofriendly water purification. Fabrication of well-dispersed AgNPs on the nano-silica surface, designated as NSAgNP, has been achieved through protein mediated reduction of silver ions at ambient temperature for development of sustainable nanotechnology. The coated proteins on AgNPs led to the formation of stable NSAgNP and protected the AgNPs from oxidation and other ions commonly present in water. The NSAgNP exhibited excellent dye adsorption capacity both in single and multicomponent systems, and demonstrated satisfactory tolerance against variations in pH and dye concentration. The adsorption mainly occurred through electrostatic interaction, though π-π interaction and pore diffusion also contributed to the process. Moreover, the NSAgNP showed long-term antibacterial activity against both planktonic cells and biofilms of Gram-negative Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity of AgNPs retarded the initial attachment of bacteria on NSAgNP and thus significantly improved the antifouling properties of the nanomaterial, which further inhibited biofilm formation. Scanning electron and fluorescence microscopic studies revealed that cell death occurred due to irreversible damage of the cell membrane upon electrostatic interaction of positively charged NSAgNP with the negatively charged bacterial cell membrane. The high adsorption capacity, reusability, good tolerance, removal of multicomponent dyes and E. coli from the simulated contaminated water and antifouling properties of NSAgNP will provide new opportunities to develop cost-effective and ecofriendly water purification processes.A nano-silica-AgNPs composite material is proposed as a novel antifouling adsorbent for cost-effective and ecofriendly water purification. Fabrication of well-dispersed AgNPs on the nano-silica surface, designated as NSAgNP, has been achieved through

  20. Preparation of magnetic nano-composite: barium hexaferrite loaded in the ordered meso-porous silica matrix (MCM-41).

    PubMed

    Emamian, H R; Honarbakhsh-Raouf, A; Ataie, A

    2010-04-01

    In this work a magnetic nano-composite was synthesized by modified incorporation of iron-barium complex into ordered meso-porous silica (MCM-41) as a matrix. The MCM-41 was synthesized by silylation treatment which was accompanied by pH adjusting. Low angle XRD patterns of both annealed MCM-41 and resulted composite exhibited the characteristic reflection of high quality hexagonal meso-structures. TEM image of the composite material revealed that the hexagonal ordered meso-structure host material was not affected by wet impregnation and subsequent calcination in order to incorporate with barium hexaferrite. Also, TEM images accompanied by EDS analysis confirmed the formation of second phase consists of barium and iron ions inside the MCM-41 channels. The resulted composite material showed a super-paramagnetic nature at room temperature.

  1. Nano-silica fabricated with silver nanoparticles: antifouling adsorbent for efficient dye removal, effective water disinfection and biofouling control.

    PubMed

    Das, Sujoy K; Khan, Md Motiar R; Parandhaman, T; Laffir, Fathima; Guha, Arun K; Sekaran, G; Mandal, Asit Baran

    2013-06-21

    A nano-silica-AgNPs composite material is proposed as a novel antifouling adsorbent for cost-effective and ecofriendly water purification. Fabrication of well-dispersed AgNPs on the nano-silica surface, designated as NSAgNP, has been achieved through protein mediated reduction of silver ions at ambient temperature for development of sustainable nanotechnology. The coated proteins on AgNPs led to the formation of stable NSAgNP and protected the AgNPs from oxidation and other ions commonly present in water. The NSAgNP exhibited excellent dye adsorption capacity both in single and multicomponent systems, and demonstrated satisfactory tolerance against variations in pH and dye concentration. The adsorption mainly occurred through electrostatic interaction, though π-π interaction and pore diffusion also contributed to the process. Moreover, the NSAgNP showed long-term antibacterial activity against both planktonic cells and biofilms of Gram-negative Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity of AgNPs retarded the initial attachment of bacteria on NSAgNP and thus significantly improved the antifouling properties of the nanomaterial, which further inhibited biofilm formation. Scanning electron and fluorescence microscopic studies revealed that cell death occurred due to irreversible damage of the cell membrane upon electrostatic interaction of positively charged NSAgNP with the negatively charged bacterial cell membrane. The high adsorption capacity, reusability, good tolerance, removal of multicomponent dyes and E. coli from the simulated contaminated water and antifouling properties of NSAgNP will provide new opportunities to develop cost-effective and ecofriendly water purification processes.

  2. Facile fabrication of nano-structured silica hybrid film with superhydrophobicity by one-step VAFS approach

    NASA Astrophysics Data System (ADS)

    Jia, Yi; Yue, Renliang; Liu, Gang; Yang, Jie; Ni, Yong; Wu, Xiaofeng; Chen, Yunfa

    2013-01-01

    Here we report a novel one-step vapor-fed aerosol flame synthesis (VAFS) method to attain silica hybrid film with superhydrophobicity on normal glass and other engineering material substrates using hexamethyldisiloxane (HMDSO) as precursor. The deposited nano-structured silica films represent excellent superhydrophobicity with contact angle larger than 150° and sliding angle below 5°, without any surface modification or other post treatments. SEM photographs proved that flame-made SiO2 nanoparticles formed dual-scale surface roughness on the substrates. It was confirmed by FTIR and XPS that the in situ formed organic fragments on the particle surface as species like (CH3)xSiO2-x/2 (x = 1, 2, 3) which progressively lowered the surface energy of fabricated films. Thus, these combined dual-scale roughness and lowered surface energy cooperatively produced superhydrophobic films. IR camera had been used to monitor the real-time flame temperature. It is found that the inert dilution gas inflow played a critical role in attaining superhydrophobicity due to its cooling and anti-oxidation effect. This method is facile and scalable for diverse substrates, without any requirement of complex equipments and multiple processing steps. It may contribute to the industrial fabrication of superhydrophobic films.

  3. Morphology controllable nano-sheet polypyrrole-graphene composites for high-rate supercapacitor.

    PubMed

    Zhu, Jianbo; Xu, Youlong; Wang, Jie; Wang, Jingping; Bai, Yang; Du, Xianfeng

    2015-08-14

    Polypyrrole is a promising candidate for supercapacitor electrode materials due to its high capacitance and low cost. However, the major bottlenecks restricting its application are its poor rate capability and cycling stability. Herein, we control the morphology of polypyrrole-graphene composites by adjusting the graphene content, causing the typical "cauliflower" morphology of polypyrrole to gradually turn into the homogeneous nano-sheet morphology of these composites. The composites consequently exhibit good thermal stability, high protonation level (37.4%), high electronic conductivity (625.3 S m(-1)), and fast relaxation time (0.22 s). These remarkable characteristics afford a high capacitance of 255.7 F g(-1) at 0.2 A g(-1), still retaining a capacitance of 199.6 F g(-1) at 25.6 A g(-1). In addition, high capacitance retention of up to 93% is observed after 1000 cycles testing at different current densities of 0.2, 1.6, 6.4, 12.8 and 25.6 A g(-1), indicating high stability. The composite's excellent electrochemical performance is mainly attributed to its nano-sheet structure and high electronic conductivity, providing unobstructed pathways for the fast diffusion and exchange of ions/electrons. PMID:26165718

  4. Photothermal investigation of the laser-induced modification of a single gold nano-particle in a silica film

    NASA Astrophysics Data System (ADS)

    Bertussi, B.; Natoli, J.-Y.; Commandre, M.; Rullier, J.-L.; Bonneau, F.; Combis, P.; Bouchut, P.

    2005-10-01

    Absorbing defects are believed to induce thermal effects that lead to laser damage, but the correlation between defect absorption and damage has not been clearly demonstrated. A model system consisting of a thin-film of silica containing gold nano-particles serving as nano-scale absorbing defects is investigated. For this purpose, a photothermal microscope coupled with a pulsed Nd:YAG laser allow us to follow the evolution of gold inclusion absorption before and after laser irradiation, without repositioning the sample. The "pre-damage" threshold had been defined previously as the laser fluence causing localized modification of the defect absorption without any surface modification. Thanks to the high sensitivity of photothermal microscopy, we find this threshold to be sevenfold less than that for the appearance of surface cracks. Numerical simulations are performed to evaluate the thermal evolution of the inclusion as a function of the laser fluence. From the comparison of experimental and theoretical results, we observe that the pre-damage threshold is closely linked to the melting of the metallic inclusion. Furthermore, the effect of repetitive shots on the evolution of gold inclusion absorption is examined experimentally and discussed.

  5. MMS6 protein regulates crystal morphology during nano-sized magnetite biomineralization in vivo.

    PubMed

    Tanaka, Masayoshi; Mazuyama, Eri; Arakaki, Atsushi; Matsunaga, Tadashi

    2011-02-25

    Biomineralization, the process by which minerals are deposited by organisms, has attracted considerable attention because this mechanism has shown great potential to inspire bottom-up material syntheses. To understand the mechanism for morphological regulation that occurs during biomineralization, many regulatory proteins have been isolated from various biominerals. However, the molecular mechanisms that regulate the morphology of biominerals remain unclear because there is a lack of in vivo evidence. Magnetotactic bacteria synthesize intracellular magnetosomes that comprise membrane-enveloped single crystalline magnetite (Fe(3)O(4)). These nano-sized magnetite crystals (<100 nm) are bacterial species dependent in shape and size. Mms6 is a protein that is tightly associated with magnetite crystals. Based on in vitro experiments, this protein was first implicated in morphological regulation during nano-sized magnetite biomineralization. In this study, we analyzed the mms6 gene deletion mutant (Δmms6) of Magnetospirillum magneticum (M. magneticum) AMB-1. Surprisingly, the Δmms6 strain was found to synthesize the smaller magnetite crystals with uncommon crystal faces, while the wild-type and complementation strains synthesized highly ordered cubo-octahedral crystals. Furthermore, deletion of mms6 gene led to drastic changes in the profiles of the proteins tightly bound to magnetite crystals. It was found that Mms6 plays a role in the in vivo regulation of the crystal structure to impart the cubo-octahedral morphology to the crystals during biomineralization in magnetotactic bacteria. Magnetotactic bacteria synthesize magnetite crystals under ambient conditions via a highly controlled morphological regulation system that uses biological molecules.

  6. The effect of ultrasonication on the size and morphology of iron oxide - chitosan nano and microparticles

    NASA Astrophysics Data System (ADS)

    Akın, Deniz; Yakar, Arzu; Gündüz, Ufuk

    2013-12-01

    The aim of this study is to synthesize magnetic Fe3O4-chitosan nano and microparticles (Fe3O4-CPs) by suspension cross-linking and ionic gelation methods and investigate the effect of ultrasonication on the size, morphology and magnetic properties. The synthesized particles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and vibrating sample magnetometry (VSM). The results showed that the ultrasonication decreased the mean particle diameter and enhanced magnetic properties of Fe3O4-CPs due to the Fe3O4 content.

  7. The effect of ultrasonication on the size and morphology of iron oxide - chitosan nano and microparticles

    SciTech Connect

    Akın, Deniz; Yakar, Arzu; Gündüz, Ufuk

    2013-12-16

    The aim of this study is to synthesize magnetic Fe{sub 3}O{sub 4}-chitosan nano and microparticles (Fe{sub 3}O{sub 4}-CPs) by suspension cross-linking and ionic gelation methods and investigate the effect of ultrasonication on the size, morphology and magnetic properties. The synthesized particles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and vibrating sample magnetometry (VSM). The results showed that the ultrasonication decreased the mean particle diameter and enhanced magnetic properties of Fe{sub 3}O{sub 4}-CPs due to the Fe{sub 3}O{sub 4} content.

  8. Local coordination and dynamics of a protic ammonium based ionic liquid immobilized in nano-porous silica micro-particles probed by Raman and NMR spectroscopy.

    PubMed

    Garaga, Mounesha N; Persson, Michael; Yaghini, Negin; Martinelli, Anna

    2016-03-01

    Room temperature ionic liquids confined in a solid material, for example, nano-porous silica, are particularly propitious for energy related applications. The aim of this study is to probe the molecular interactions established between the protic ionic liquid diethylmethylammonium methanesulfonate (DEMA-OMs) and silica, where the latter consists of nano-porous micro-particles with pores in the size range of 10 nm. The changes in the local coordination and transport properties induced by the nano-confinement of the ionic liquid are investigated by a combination of Raman and solid-state NMR spectroscopy. In particular, one-dimensional (1D) (1)H and (29)Si and two-dimensional (2D) (29)Si{(1)H} HETOCR solid-state NMR are combined to identify the sites of interaction at the silica-ionic liquid interface. Pulsed field gradient (PFG) NMR experiments are performed to estimate the self-diffusion of both bulk and nano-confined DEMA-OMs. Complementary information on the overall coordination and interaction scheme is achieved by Raman spectroscopy. All these advanced experimental techniques are revealed to be crucial to differentiate between ionic liquid molecules residing in the inter- or intra-particle domains.

  9. A new high-throughput method utilizing porous silica-based nano-composites for the determination of partition coefficients of drug candidates.

    PubMed

    Yu, Chih H; Tam, Kin; Tsang, Shik C

    2011-09-01

    We show that highly porous silica-based nanoparticles prepared via micro-emulsion and sol-gel techniques are stable colloids in aqueous solution. By incorporating a magnetic core into the porous silica nano-composite, it is found that the material can be rapidly separated (precipitated) upon exposure to an external magnetic field. Alternatively, the porous silica nanoparticles without magnetic cores can be equally separated from solution by applying a high-speed centrifugation. Using these silica-based nanostructures a new high-throughput method for the determination of partition coefficient for water/n-octanol is hereby described. First, a tiny quantity of n-octanol phase is pre-absorbed in the porous silica nano-composite colloids, which allows an establishment of interface at nano-scale between the adsorbed n-octanol with the bulk aqueous phase. Organic compounds added to the mixture can therefore undergo a rapid partition between the two phases. The concentration of drug compound in the supernatant in a small vial can be determined by UV-visible absorption spectroscopy. With the adaptation of a robotic liquid handler, a high-throughput technology for the determination of partition coefficients of drug candidates can be employed for drug screening in the industry based on these nano-separation skills. The experimental results clearly suggest that this new method can provide partition coefficient values of potential drug candidates comparable to the conventional shake-flask method but requires much shorter analytical time and lesser quantity of chemicals. PMID:21780284

  10. Silica xerogel-chitosan nano-hybrids for use as drug eluting bone replacement.

    PubMed

    Lee, Eun-Jung; Jun, Shin-Hee; Kim, Hyoun-Ee; Kim, Hae-Won; Koh, Young-Hag; Jang, Jun-Hyeog

    2010-01-01

    Silica xerogel-chitosan hybrids containing vancomycin were fabricated by the sol-gel process at room temperature and their potential as a drug eluting bone replacement was evaluated in terms of their mechanical properties and drug release behaviors. Regardless of the content of chitosan, all of the prepared hybrids had a uniform mesoporous structure, which would allow the effectual loading of vancomycin. As the content of chitosan was increased, the strength, strain to failure, and work of fracture of the hybrids were significantly enhanced, while the elastic modulus was decreased. These changes in the mechanical properties were mainly attributed to the mitigation of the brittleness of the silica xerogel through its hybridization with the flexible chitosan phase. In addition, the initial burst-effect was remarkably reduced by increasing the content of chitosan. The hybrids with more than 30% chitosan could release the vancomycin for an extended period of time in a controlled manner.

  11. Alendronate decorated nano hydroxyapatite in mesoporous silica: Cytotoxicity and osteogenic properties

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Liu, Weiqiang; She, Zhending; Wu, Hongkai; Shi, Xuetao

    2011-09-01

    Mesoporous silica is a promising drug delivery vehicle due to its large surface area and order porous structure. Hydroxyapatite-modified mesoporous silica materials (MSH) have been developed, and the cytotoxicity of MSH and unmodified mesoporous silica (HMS) has also been studied in this work. The results indicated that MSH exhibited lower cytotoxicity than HMS. The drug release property of MSH was also investigated in this paper. Alendronate (AL) was laden into MSH and HMS, respectively. MSH exhibited long release period lasting over 30 days with a weak burst release in the first 5 days; however, the AL release period of HMS was just 5 days with a remarkable burst release. In addition, the osteogenic commitment induced in human marrow mesenchymal stem cells (MSCs) by MSH-alendronate (MSH-AL) was also investigated, and the osteogenesis of MSCs was evaluated by alkaline phosphatase (ALP) assay. The osteogenesis of MSCs induced by MSH-AL is comparable to that induced by the osteogenic medium. Taken together, MSH can be severed as potential bone repair materials with lower cytotoxicity.

  12. Effects of Nano-CeO2 with Different Nanocrystal Morphologies on Cytotoxicity in HepG2 Cells

    PubMed Central

    Wang, Lili; Ai, Wenchao; Zhai, Yanwu; Li, Haishan; Zhou, Kebin; Chen, Huiming

    2015-01-01

    Cerium oxide nanoparticles (nano-CeO2) have been reported to cause damage and apoptosis in human primary hepatocytes. Here, we compared the toxicity of three types of nano-CeO2 with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) in human hepatocellular carcinoma cells (HepG2). The cells were treated with the nano-CeO2 at various concentrations (6.25, 12.5, 25, 50, 100 μg/mL). The crystal structure, size and morphology of nano-CeO2 were investigated by X-ray diffractometry and transmission electron microscopy. The specific surface area was detected using the Brunauer, Emmet and Teller method. The cellular morphological and internal structure were observed by microscopy; apoptotic alterations were measured using flow cytometry; nuclear DNA, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and glutathione (GSH) in HepG2 cells were measured using high content screening technology. The scavenging ability of hydroxyl free radicals and the redox properties of the nano-CeO2 were measured by square-wave voltammetry and temperature-programmed-reduction methods. All three types of nano-CeO2 entered the HepG2 cells, localized in the lysosome and cytoplasm, altered cellular shape, and caused cytotoxicity. The nano-CeO2 with smaller specific surface areas induced more apoptosis, caused an increase in MMP, ROS and GSH, and lowered the cell’s ability to scavenge hydroxyl free radicals and antioxidants. In this work, our data demonstrated that compared with cube-like and octahedron-like nano-CeO2, the rod-like nano-CeO2 has lowest toxicity to HepG2 cells owing to its larger specific surface areas. PMID:26404340

  13. Effects of Nano-CeO₂ with Different Nanocrystal Morphologies on Cytotoxicity in HepG2 Cells.

    PubMed

    Wang, Lili; Ai, Wenchao; Zhai, Yanwu; Li, Haishan; Zhou, Kebin; Chen, Huiming

    2015-09-02

    Cerium oxide nanoparticles (nano-CeO₂) have been reported to cause damage and apoptosis in human primary hepatocytes. Here, we compared the toxicity of three types of nano-CeO₂ with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) in human hepatocellular carcinoma cells (HepG2). The cells were treated with the nano-CeO₂ at various concentrations (6.25, 12.5, 25, 50, 100 μg/mL). The crystal structure, size and morphology of nano-CeO₂ were investigated by X-ray diffractometry and transmission electron microscopy. The specific surface area was detected using the Brunauer, Emmet and Teller method. The cellular morphological and internal structure were observed by microscopy; apoptotic alterations were measured using flow cytometry; nuclear DNA, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and glutathione (GSH) in HepG2 cells were measured using high content screening technology. The scavenging ability of hydroxyl free radicals and the redox properties of the nano-CeO₂ were measured by square-wave voltammetry and temperature-programmed-reduction methods. All three types of nano-CeO₂ entered the HepG2 cells, localized in the lysosome and cytoplasm, altered cellular shape, and caused cytotoxicity. The nano-CeO₂ with smaller specific surface areas induced more apoptosis, caused an increase in MMP, ROS and GSH, and lowered the cell's ability to scavenge hydroxyl free radicals and antioxidants. In this work, our data demonstrated that compared with cube-like and octahedron-like nano-CeO₂, the rod-like nano-CeO₂ has lowest toxicity to HepG2 cells owing to its larger specific surface areas.

  14. Study of blend composition of nano silica under the influence of neutron flux

    NASA Astrophysics Data System (ADS)

    Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan

    2014-08-01

    Nano SiO2 compound with 160 m2/g specific surface area and 20 nm sizes has been irradiated continuously with neutron flux up to 20 hours in various periods in TRIGA Mark II type research reactor. The initial activities of different type radionuclides defined in the result of eight day activity analysis changes between wide range of 1,5 kBq- 1,5GBq. In the result of activity analysis carried out after the irradiation, the element content of 0,5% mixture existing in nano SiO2 compound has been defined with radionuclides of relevant element. It has been defined percentage amounts of elements in blend composition according to the performed activities.

  15. Nano-Structured Mesoporous Silica Wires with Intra-Wire Lamellae via Evaporation-Induced Self-Assembly in Space-Confined Channels

    SciTech Connect

    Hu, Michael Z.; Shi, Donglu; Blom, Douglas Allen

    2014-04-06

    Evaporation-induced self-assembly (EISA) of silica sol-gel ethanol-water solution mixtures with block-copolymer were studied inside uniform micro/nano channels. Nano-structured mesoporous silica wires, with various intra-wire self-assembly structures including lamellae, were prepared via EISA process but in space-confined channels with the diameter ranging from 50 nm to 200 nm. Membranes made of anodized aluminum oxide (AAO) and track-etched polycarbonate (EPC) were utilized as the arrays of space-confined channels (i.e., 50, 100, and 200-nm EPC and 200-nm AAO) for infiltration and drying of mixture solutions; these substrate membranes were submerged in mixture solutions consisting of a silica precursor, a structure-directing agent, ethanol, and water. After the substrate channels were filled with the solution under vacuum impregnation, the membrane was removed from the solution and dried in air. The silica precursor used was tetra-ethyl othosilicate (TEOS), and the structure-directing agent employed was triblock copolymer Pluronic-123 (P123). It was found that the formation of the mesoporous nanostructures in silica wires within uniform channels were significantly affected by the synthesis conditions including (1) pre-assemble TEOS aging time, (2) the evaporation rate during the vacuum impregnation, and (3) the air-dry temperature. The obtained intra-wire structures, including 2D-hexagonal rods and lamellae, were studied by scanning transmission electron microscopy (STEM). A steric hindrance effect seems to explain well the observed polymer-silica mesophase formation tailored by TEOS aging time. The evaporation effect, air-drying effect, and AAO-vs-EPC substrate effect on the mesoporous structure of the formed silica wires were also presented and discussed.

  16. Preparation of nano-hydroxyapatite particles with different morphology and their response to highly malignant melanoma cells in vitro

    NASA Astrophysics Data System (ADS)

    Li, Bo; Guo, Bo; Fan, Hongsong; Zhang, Xingdong

    2008-11-01

    To investigate the effects of nano-hydroxyapatite (HA) particles with different morphology on highly malignant melanoma cells, three kinds of HA particles with different morphology were synthesized and co-cultured with highly malignant melanoma cells using phosphate-buffered saline (PBS) as control. A precipitation method with or without citric acid addition as surfactant was used to produce rod-like hydroxyapatite (HA) particles with nano- and micron size, respectively, and a novel oil-in-water emulsion method was employed to prepare ellipse-like nano-HA particles. Particle morphology and size distribution of the as prepared HA powders were characterized by transmission electron microscope (TEM) and dynamic light scattering technique. The nano- and micron HA particles with different morphology were co-cultured with highly malignant melanoma cells. Immunofluorescence analysis and MTT assay were employed to evaluate morphological change of nucleolus and proliferation of tumour cells, respectively. To compare the effects of HA particles on cell response, the PBS without HA particles was used as control. The experiment results indicated that particle nanoscale effect rather than particle morphology of HA was more effective for the inhibition on highly malignant melanoma cells proliferation.

  17. Investigation of nuclear nano-morphology marker as a biomarker for cancer risk assessment using a mouse model

    NASA Astrophysics Data System (ADS)

    Bista, Rajan K.; Uttam, Shikhar; Hartman, Douglas J.; Qiu, Wei; Yu, Jian; Zhang, Lin; Brand, Randall E.; Liu, Yang

    2012-06-01

    The development of accurate and clinically applicable tools to assess cancer risk is essential to define candidates to undergo screening for early-stage cancers at a curable stage or provide a novel method to monitor chemoprevention treatments. With the use of our recently developed optical technology--spatial-domain low-coherence quantitative phase microscopy (SL-QPM), we have derived a novel optical biomarker characterized by structure-derived optical path length (OPL) properties from the cell nucleus on the standard histology and cytology specimens, which quantifies the nano-structural alterations within the cell nucleus at the nanoscale sensitivity, referred to as nano-morphology marker. The aim of this study is to evaluate the feasibility of the nuclear nano-morphology marker from histologically normal cells, extracted directly from the standard histology specimens, to detect early-stage carcinogenesis, assess cancer risk, and monitor the effect of chemopreventive treatment. We used a well-established mouse model of spontaneous carcinogenesis--ApcMin mice, which develop multiple intestinal adenomas (Min) due to a germline mutation in the adenomatous polyposis coli (Apc) gene. We found that the nuclear nano-morphology marker quantified by OPL detects the development of carcinogenesis from histologically normal intestinal epithelial cells, even at an early pre-adenomatous stage (six weeks). It also exhibits a good temporal correlation with the small intestine that parallels the development of carcinogenesis and cancer risk. To further assess its ability to monitor the efficacy of chemopreventive agents, we used an established chemopreventive agent, sulindac. The nuclear nano-morphology marker is reversed toward normal after a prolonged treatment. Therefore, our proof-of-concept study establishes the feasibility of the SL-QPM derived nuclear nano-morphology marker OPL as a promising, simple and clinically applicable biomarker for cancer risk assessment and

  18. Photoluminescence from low thermal budget silicon nano-crystals in silica.

    PubMed

    Soubane, Driss; Quitoriano, Nathaniel J

    2015-07-24

    We have developed a novel method to fabricate Si nanocrystals in a silica matrix with a considerably reduced thermal budget using pulsed laser deposition. Normally, Si nanocrystals are formed through phase separation by annealing a Si-rich SiO2 film at 1100 °C; we show Si nanocrystal formation in as-deposited films at 550 °C. We suggest the mechanism for this is through surface diffusion during deposition. We also show the ability to vary the size of these nanocrystals by adjusting the deposition conditions and can increase their size through annealing. If the nanocrystals are small they have excellent photoluminescence properties however larger nanocrystals have poor luminescence.

  19. Controlled deposition of functionalized silica coated zinc oxide nano-assemblies at the air/water interface for blood cancer detection.

    PubMed

    Pandey, Chandra Mouli; Dewan, Srishti; Chawla, Seema; Yadav, Birendra Kumar; Sumana, Gajjala; Malhotra, Bansi Dhar

    2016-09-21

    We report results of the studies relating to controlled deposition of the amino-functionalized silica-coated zinc oxide (Am-Si@ZnO) nano-assemblies onto an indium tin oxide (ITO) coated glass substrate using Langmuir-Blodgett (LB) technique. The monolayers have been deposited by transferring the spread solution of Am-Si@ZnO stearic acid prepared in chloroform at the air-water interface, at optimized pressure (16 mN/m), concentration (10 mg/ml) and temperature (23 °C). The high-resolution transmission electron microscopic studies of the Am-Si@ZnO nanocomposite reveal that the nanoparticles have a microscopic structure comprising of hexagonal assemblies of ZnO with typical dimensions of 30 nm. The surface morphology of the LB multilayer observed by scanning electron microscopy shows uniform surface of the Am-Si@ZnO film in the nanometer range (<80 nm). These electrodes have been utilized for chronic myelogenous leukemia (CML) detection by covalently immobilizing the amino-terminated oligonucleotide probe sequence via glutaraldehyde as a crosslinker. The response studies of these fabricated electrodes carried out using electrochemical impedance spectroscopy show that this Am-Si@ZnO LB film based nucleic acid sensor exhibits a linear response to complementary DNA (10(-6)-10(-16) M) with a detection limit of 1 × 10(-16) M. This fabricated platform is validated with clinical samples of CML positive patients and the results demonstrate its immense potential for clinical diagnosis. PMID:27590542

  20. MicroSPE-nanoLC-ESI-MS/MS Using 10-μm-i.d. Silica-Based Monolithic Columns for Proteomics

    SciTech Connect

    Luo, Quanzhou; Page, Jason S.; Tang, Keqi; Smith, Richard D.

    2007-01-01

    Silica-based monolithic narrow bore capillary columns (25 cm x 10 µm i.d.) with an integrated nanoESI emitter has been developed to provide high quality and robust microSPE-nanoLC-ESI-MS analyses. The integrated nanoESI emitter adds no dead volume to the LC separation, allowing stable electrospray performance to be obtained at flow rates of ~10 nL/min. In an initial application we identified 5510 unique peptides covering 1443 distinct Shewanella oneidensis proteins from a 300 ng tryptic digest sample in a single 4-h LC-MS/MS analysis using a linear ion trap MS (LTQ). We found the use of an integrated monolithic ESI emitter provided enhanced resistance to clogging and good run-to-run reproducibility.

  1. AEM and HREM evaluation of carbon nanostructures in silica aerogels

    SciTech Connect

    Song, X.Y.; Cao, W.; Hunt, A.J.

    1994-04-01

    Nanostructured carbon has been deposited in silica aerogels by chemical vapor infiltration using acetylene or ferrocene at moderate temperatures. Using analytical electron microscopy and high-resolution electron microscopy, we have observed various carbon rings and nanotubes in the silica aerogel-based carbon composite. Both X-ray microanalysis and nano-probe diffraction techniques have been used to confirm the presence of those carbon nanostructures. Morphologies and structural properties of the carbon nanotubes and rings have also been examined in detail.

  2. Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica.

    PubMed

    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.

  3. Self-cleaning behavior in polyurethane/silica coatings via formation of a hierarchical packed morphology of nanoparticles

    NASA Astrophysics Data System (ADS)

    Hejazi, Iman; Mir Mohamad Sadeghi, Gity; Seyfi, Javad; Jafari, Seyed-Hassan; Khonakdar, Hossein Ali

    2016-04-01

    In the current research, a hierarchical morphology comprising of packed assembly of nanoparticles was induced in thermoplastic polyurethane (TPU)/silica nanocomposite coatings in order to achieve self-cleaning behavior. Moderately hydrophilic behavior of TPU hinders its transforming to a superhydrophobic material. In the presented method, a very thin layer of silica nanoparticles is applied to the surface of TPU sheets under elevated temperature and pressure. As temperature and pressure of the process remain unchanged, processing time was considered as a main variable. Based on scanning electron microscopy and confocal microscopy results, it was found that at a certain processing time, nanoparticles can form an utterly packed morphology leading to a self-cleaning behavior. Once the process was prolonged, TPU macromolecules found the chance to migrate onto the coating's top layer due to the enhanced mobility of chains at high temperature. This observation was further proved by X-ray photoelectron spectroscopy analysis and cross-sectional morphology. The presented method has promising potentials in transforming intrinsically hydrophilic polymers into superhydrophobic materials with self-cleaning behavior.

  4. Bioresponsive carbon nano-gated multifunctional mesoporous silica for cancer theranostics

    NASA Astrophysics Data System (ADS)

    Prasad, Rajendra; Aiyer, Sandhya; Chauhan, Deepak S.; Srivastava, Rohit; Selvaraj, Kaliaperumal

    2016-02-01

    Designing bioresponsive nanocarriers for controlled and efficient intracellular drug release for cancer therapy is a major thrust area in nanomedicine. With recent recognition by the US FDA as a safe material for human trials, mesoporous silica nanoparticles (MSNPs) are being extensively explored as promising theranostic agents. Green fluorescent carbon quantum dots (CQDs), though known as possible alternatives for their more toxic and relatively less efficient predecessors, are less known as gate keepers for drug release control. We report for the first time an efficient bioresponse of CQDs when judiciously designed using glutathione cleavable (redox responsive) disulphide bonds. When the anticancer drug doxorubicin loaded MSNPs are capped with these CQDs, they display promising drug release control on exposure to a mimicked intracellular cancer environment. Their dual functionality is well established with good control on preventing the premature release and exceptional bio-imaging of HeLa cancer cells. Fluorescence images prove selective targeting of HeLa cells by overexpression of folate receptors from the surface functionalised folic acid ligand. Extensive characterisation using XRD, TEM, BET analysis, drug loading tests, drug release kinetics, MTT assay and fluoroscence cell imaging helps in understanding the multifunctionalities of the successful design, extending its scope with exciting prospects towards non-invasive targeted drug delivery and bio-imaging for effective cancer diagnosis and treatment.Designing bioresponsive nanocarriers for controlled and efficient intracellular drug release for cancer therapy is a major thrust area in nanomedicine. With recent recognition by the US FDA as a safe material for human trials, mesoporous silica nanoparticles (MSNPs) are being extensively explored as promising theranostic agents. Green fluorescent carbon quantum dots (CQDs), though known as possible alternatives for their more toxic and relatively less efficient

  5. Spontaneous gradual accumulation of hexagonally-aligned nano-silica on gold nanoparticles embedded in stabilized zirconia: a pathway from catalytic to NH3-sensing performance

    NASA Astrophysics Data System (ADS)

    Plashnitsa, Vladimir V.; Elumalai, Perumal; Fujio, Yuki; Kawaguchi, Toshikazu; Miura, Norio

    2011-05-01

    The present study highlights the influence of nano-impurities on the catalytic/sensing performance of nano-structured Au sensing-electrodes (SEs) housed in a quartz reactor and operated at high temperature over a long period of time. The planar sensor, made from a nano-structured Au-SE on a polished-polycrystalline (pp) yttria-stabilized zirconia (YSZ) substrate exhibited initially negligible electromotive force (emf) response to each of the examined gases (CO, CH4, C3H8, C3H6, NOx and NH3; 400 ppm each) at 700 °C in the presence of 5 vol.% oxygen and 5 vol.% water vapor. Such a poor emf response was attributed to the excellent gas-phase oxidation/reduction ability of Au nanoparticles embedded in the YSZ substrate at high temperature. The response of the planar sensor made up of nano-structured Au-SE was monitored for about 75 days at 700 °C. As a result of this long-term monitoring, we detected the appearance of highly sensitive and selective NH3 gas-sensing properties after 45-75 days of sensor operation. Detailed observation of the morphology and composition of the as-fabricated nano-structured Au-SE after 75 days operation at 700 °C revealed the gradual accumulation of hexagonally-aligned SiO2 nano-impurities on the surface of the Au nanoparticles. The NH3 sensing mechanism of the YSZ-based sensor using the spontaneously-formed composite (nano-Au + nano-SiO2)-SE is therefore proposed to be based on a strong acid-base interaction between gaseous NH3 and SiO2 nano-impurities, followed by spillover of adsorbed NH3 towards the nano-Au/pp-YSZ interface.

  6. Spontaneous gradual accumulation of hexagonally-aligned nano-silica on gold nanoparticles embedded in stabilized zirconia: a pathway from catalytic to NH3-sensing performance.

    PubMed

    Plashnitsa, Vladimir V; Elumalai, Perumal; Fujio, Yuki; Kawaguchi, Toshikazu; Miura, Norio

    2011-05-01

    The present study highlights the influence of nano-impurities on the catalytic/sensing performance of nano-structured Au sensing-electrodes (SEs) housed in a quartz reactor and operated at high temperature over a long period of time. The planar sensor, made from a nano-structured Au-SE on a polished-polycrystalline (pp) yttria-stabilized zirconia (YSZ) substrate exhibited initially negligible electromotive force (emf) response to each of the examined gases (CO, CH(4), C(3)H(8), C(3)H(6), NO(x) and NH(3); 400 ppm each) at 700 °C in the presence of 5 vol.% oxygen and 5 vol.% water vapor. Such a poor emf response was attributed to the excellent gas-phase oxidation/reduction ability of Au nanoparticles embedded in the YSZ substrate at high temperature. The response of the planar sensor made up of nano-structured Au-SE was monitored for about 75 days at 700 °C. As a result of this long-term monitoring, we detected the appearance of highly sensitive and selective NH(3) gas-sensing properties after 45-75 days of sensor operation. Detailed observation of the morphology and composition of the as-fabricated nano-structured Au-SE after 75 days operation at 700 °C revealed the gradual accumulation of hexagonally-aligned SiO(2) nano-impurities on the surface of the Au nanoparticles. The NH(3) sensing mechanism of the YSZ-based sensor using the spontaneously-formed composite (nano-Au + nano-SiO(2))-SE is therefore proposed to be based on a strong acid-base interaction between gaseous NH(3) and SiO(2) nano-impurities, followed by spillover of adsorbed NH(3) towards the nano-Au/pp-YSZ interface.

  7. Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Li, Bin; Zhang, Qin-Jian; Shi, Yan-Chao; Li, Jia-Jun; Li, Hong; Lu, Fan-Xiu; Chen, Guang-Chao

    2014-08-01

    A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and Raman spectra, respectively. The nanocrystalline grains are averagely with 80 nm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses (100) dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

  8. Effect of nano-alumina concentration on the mechanical, rheological, barrier and morphological properties of guar gum.

    PubMed

    Savvashe, Prashant; Kadam, Pravin; Mhaske, Shashank

    2016-04-01

    In this work, nano-alumina was utilized as a reinforcing agent for guar gum, with an aim to improve its performance properties; especially, mechanical and barrier i.e. water vapor transmission rate (WVTR). Films were prepared by the process of solution casting. Concentration of nano-alumina was varied as 0, 1, 3, 5 and 7 parts per hundred parts of resin (phr) in guar gum. The prepared pristine and guar gum/alumina nano-composite films were characterized for mechanical, puncture, x-ray diffraction, barrier, rheological and morphological properties. Tensile strength, Young's modulus, puncture strength, viscosity and crystallinity increased; whereas, WVTR, elongation at break (%) and damping factor decreased with increased concentration of nano-alumina in guar gum. However, optimized improvement in the performance properties were determined for 5 phr nano-alumina loaded guar gum polymer matrix, attributed to its better dispersion and interaction into the guar gum polymer chains due to the hydrophilic nature of both the materials. Above 5 phr concentration nano-alumina started forming aggregates, as evident from scanning electron microscopy. PMID:27413221

  9. Effect of nano-alumina concentration on the mechanical, rheological, barrier and morphological properties of guar gum.

    PubMed

    Savvashe, Prashant; Kadam, Pravin; Mhaske, Shashank

    2016-04-01

    In this work, nano-alumina was utilized as a reinforcing agent for guar gum, with an aim to improve its performance properties; especially, mechanical and barrier i.e. water vapor transmission rate (WVTR). Films were prepared by the process of solution casting. Concentration of nano-alumina was varied as 0, 1, 3, 5 and 7 parts per hundred parts of resin (phr) in guar gum. The prepared pristine and guar gum/alumina nano-composite films were characterized for mechanical, puncture, x-ray diffraction, barrier, rheological and morphological properties. Tensile strength, Young's modulus, puncture strength, viscosity and crystallinity increased; whereas, WVTR, elongation at break (%) and damping factor decreased with increased concentration of nano-alumina in guar gum. However, optimized improvement in the performance properties were determined for 5 phr nano-alumina loaded guar gum polymer matrix, attributed to its better dispersion and interaction into the guar gum polymer chains due to the hydrophilic nature of both the materials. Above 5 phr concentration nano-alumina started forming aggregates, as evident from scanning electron microscopy.

  10. Morphologies and wetting properties of copper film with 3D porous micro-nano hierarchical structure prepared by electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Wang, Hongbin; Wang, Ning; Hang, Tao; Li, Ming

    2016-05-01

    Three-dimensional porous micro-nano hierarchical structure Cu films were prepared by electrochemical deposition with the Hydrogen bubble dynamic template. The morphologies of the deposited films characterized by Scanning Electronic Microscopy (SEM) exhibit a porous micro-nano hierarchical structure, which consists of three levels in different size scales, namely the honeycomb-like microstructure, the dendritic substructure and the nano particles. Besides, the factors which influenced the microscopic morphology were studied, including the deposition time and the additive Ethylene diamine. By measuring the water contact angle, the porous copper films were found to be super-hydrophobic. The maximum of the contact angles could reach as high as 162.1°. An empirical correlation between morphologies and wetting properties was revealed for the first time. The pore diameter increased simultaneously with the deposition time while the contact angle decreased. The mechanism was illustrated by two classical models. Such super-hydrophobic three-dimensional hierarchical micro-nano structure is expected to have practical application in industry.

  11. Effect of content of chiral selector and pore size of core-shell type silica support on the performance of amylose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phases in nano-liquid chromatography and capillary electrochromatography.

    PubMed

    Rocchi, Silvia; Fanali, Salvatore; Farkas, Tivadar; Chankvetadze, Bezhan

    2014-10-10

    In this study the separation performance of various chiral stationary phases (CSPs) made of polysaccharide-based chiral selectors coated onto superficially porous (core-shell or fused-core) silica supports were evaluated. The CSPs obtained by coating of various amounts of chiral selector (1-5%) onto supports of various pore size (100 and 300 Å) were studied. Their evaluation was pursued in both chiral nano-liquid chromatography (nano-LC) and chiral capillary electrochromatography (CEC). Among the goals of this study was to re-examine our previous unexpected finding of better performance of superficially porous CSP under CEC conditions compared to nano-LC conditions for a new set of chiral compounds, as well as to study the effect of varying the chiral selector content and nominal pore size of supporting silica on the performance of core-shell silica-based polysaccharide-type CSPs. Based on the results of this study it can be seen that CSPs based on superficially porous silica can successfully be used for the separation of enantiomers in both nano-LC and CEC mode. Only a slight advantage of CEC over nano-LC mode was observed in this study from the viewpoint of plate numbers, especially at higher mobile phase flow rates. It must also be noted that the optimal theoretical plate height is still too high and further optimization of superficially porous CSPs is necessary for both nano-LC and CEC applications.

  12. XAFS Study on Nano-Sized Metal Catalyst Prepared by a Photo-Assisted Deposition Using Ti-Containing Mesoporous Silica Thin Film Photocatalyst

    SciTech Connect

    Shimada, Makoto; Nishio, Shinichiro; Shimizu, Toshiaki; Mori, Kohsuke; Ohmichi, Tetsutaro; Katayama, Iwao; Yamashita, Hiromi

    2007-02-02

    Transparent Ti-containing mesoporous silica (TMS) thin films can be prepared on quartz plates using the spin-coating sol-gel method. These thin films have performed super-hydrophilic surface property. Using a photo-assisted deposition (PAD) method, nano-sized Pt metal can be highly deposited on TMS thin films under UV-light irradiation. XAFS measurement indicates that TMS thin films contain isolated and tetrahedrally coordinated Ti-oxide moieties in the frameworks and nano-sized Pt particles can be highly deposited on the photo-excited Ti species in TMS thin films. Measurement of contact angle of droplet water showed that the surface property of Pt/TMS thin film is also hydrophilic as comparable to that of original TMS thin film.

  13. Combined exposure to nano-silica and lead induced potentiation of oxidative stress and DNA damage in human lung epithelial cells.

    PubMed

    Lu, Chun-Feng; Yuan, Xiao-Yan; Li, Li-Zhong; Zhou, Wei; Zhao, Jun; Wang, Yi-Mei; Peng, Shuang-Qing

    2015-12-01

    Growing evidence has confirmed that exposure to ambient particulate matters (PM) is associated with increased morbidity and mortality of cardiovascular and pulmonary diseases. Ambient PM is a complex mixture of particles and air pollutants. Harmful effects of PM are specifically associated with ultrafine particles (UFPs) that can adsorb high concentrations of toxic air pollutants and are easily inhaled into the lungs. However, combined effects of UFPs and air pollutants on human health remain unclear. In the present study, we elucidated the combined toxicity of silica nanoparticles (nano-SiO2), a typical UFP, and lead acetate (Pb), a typical air pollutant. Lung adenocarcinoma A549 cells were exposed to nano-SiO2 and Pb alone or their combination, and their combined toxicity was investigated by focusing on cellular oxidative stress and DNA damage. Factorial analyses were performed to determine the potential interactions between nano-SiO2 and Pb. Our results showed that exposure of A549 cells to a modest cytotoxic concentration of Pb alone induced oxidative stress, as evidenced by elevated reactive oxygen species generation and lipid peroxidation, and reduced glutathione content and superoxide dismutase and glutathione peroxidase activities. In addition, exposure of A549 cells to Pb alone induced DNA damage, as evaluated by alkaline comet assay. Exposure of A549 cells to non-cytotoxic concentration of nano-SiO2 did not induce cellular oxidative stress and DNA damage. However, exposure to the combination of nano-SiO2 and Pb potentiated oxidative stress and DNA damage in A549 cells. Factorial analyses indicated that the potentiation of combined toxicity of nano-SiO2 and Pb was induced by additive or synergistic interactions.

  14. Effects of electrolytes and surfactants on the morphology and stability of advanced silver nano-materials

    SciTech Connect

    Obaid, Abdullah Yousif; AL-Thabaiti, Shaeel Ahmed; El-Mossalamy, E.H.; Hussain, Javed Ijaz; Khan, Zaheer

    2013-03-15

    Highlights: ► Stoichiometric ratio of S{sub 2}O{sub 3}{sup 2−} and Ag{sup +} ions are responsible to the formation of prefect transparent yellow colored silver sol. ► Higher S{sub 2}O{sub 3}{sup 2−} concentrations has damping effect. ► Head group of the surfactants and nature of the electrolytes have significant effect on the stability of silver nanoparticles. - Abstract: The impact of electrolytes, stabilizing and/or capping agents on morphology of colloidal silver nano-materials (AgNPs) has been studied spectroscopically. Sodium thiosulfate acts as reducing-, stabilizing- and damping-agents. Stoichiometric ratios of S{sub 2}O{sub 3}{sup 2−} and Ag{sup +} ions were responsible to the formation stable and prefect transparent dark yellow colored AgNPs. The S{sub 2}O{sub 3}{sup 2−}-stabilized AgNPs were significantly more stable in inorganic electrolytes (NaNO{sub 3}, Na{sub 2}SO{sub 4}, Na{sub 2}CO{sub 3} and KBr). S{sub 2}O{sub 3}{sup 2−} is adsorbed more strongly than the used other anions. The addition of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) has significant effects on the absorbance of S{sub 2}O{sub 3}{sup 2−}-stabilized AgNPs which can be rationalized in terms of electrostatic attraction and repulsion between the adsorbed S{sub 2}O{sub 3}{sup 2−} ions on to the surface of AgNPs and cationic and/or anionic head groups of used surfactants, respectively. Transmission electron microscopy images suggest that AgNPs are polydispersed, spherical and exhibiting an interesting irregular morphology.

  15. Electrical and morphological properties of magnetocaloric nano ZnNi ferrite

    NASA Astrophysics Data System (ADS)

    Hemeda, O. M.; Mostafa, Nasser Y.; Abd Elkader, Omar H.; Hemeda, D. M.; Tawfik, A.; Mostafa, M.

    2015-11-01

    A series of Zn1-xNixFe2O4 nano ferrite (with x=0, 0.2, 0.4, 0.6, 0.8, and 1) compositions were synthesized using the combustion technique. The powder samples were characterized by XRD. The X-ray analysis showed that the samples were single phase spinel cubic structure. The AC resistivity decreases by increasing the frequency from 1 kHz to 10 kHz. As the frequency of the applied field increases the hopping of charge carrier also increase, thereby decreasing the resistivity. A shift in dielectric maximum is observed toward higher temperature with increasing the Ni content from 536 K to 560 K at 1 kHz. The HRTEM (high resolution TEM) images of four compositions have lattice spacing which confirms the crystalline nature of the samples. The surface morphology SEM of the sample consists of some grains with relatively homogenies distribution with an average size varying from 0.85 to 0.92 μm. The values for entropy change in this work are still small but are significally higher than the values that have been reported for iron oxide nanoparticle. The magnetic entropy change was calculated from measurements of M (H, T) where H is the magnetic field and T is the temperature. The maximum value of entropy change (∆S) obtained near Curie temperature which makes these material candidates for magnetocaloric applications.

  16. Effect of hydroxyapatite nano-particles on morphology, rheology and thermal behavior of poly(caprolactone)/chitosan blends.

    PubMed

    Ghorbani, Fereshte Mohammad; Kaffashi, Babak; Shokrollahi, Parvin; Akhlaghi, Shahin; Hedenqvist, Mikael S

    2016-02-01

    The effect of hydroxyapatite nano-particles (nHA) on morphology, and rheological and thermal properties of PCL/chitosan blends was investigated. The tendency of nHA to reside in the submicron-dispersed chitosan phase is determined using SEM and AFM images. The presence of electrostatic interaction between amide sites of chitosan and ionic groups on the nHA surface was proved by FTIR. It is shown that the chitosan phase is thermodynamically more favorable for the nano-particles to reside than the PCL phase. Lack of implementation of Cox-Merz theory for this system shows that the polymer-nano-particle network is destructed by the flow. Results from dynamic rheological measurements and Zener fractional model show that the presence of nHA increases the shear moduli and relaxation time of the PCL/chitosan blends. DSC measurements showed that nHA nano-particles are responsible for the increase in melting and crystallization characteristics of the PCL/chitosan blends. Based on thermogravimetric analysis, the PCL/chitosan/nHA nano-composites exhibited a greater thermal stability compared to the nHA-free blends.

  17. Effects of hierarchical micro/nano-topographies on the morphology, proliferation and differentiation of osteoblast-like cells.

    PubMed

    Huang, Qianli; Elkhooly, Tarek A; Liu, Xujie; Zhang, Ranran; Yang, Xing; Shen, Zhijian; Feng, Qingling

    2016-09-01

    Coating the surfaces of titanium-based implants with appropriate hierarchical micro/nano-topographies resembling the structure of natural bone significantly enhances their biological performance. However, the relationship between nanostructures surfaces and their effects on modulating cellular response is not clearly understood. Moreover, it is not clear whether the surface chemistry or topography is the main factor on modulating cellular behavior, because the commonly used surface modification techniques for titanium-based implants simultaneously modify surface topography and chemistry. The aim of this study is to investigate osteoblast-like cell adhesion, proliferation and differentiation on hierarchical micro/nano-topographies with similar surface chemistry but different nano-scale features. Micro-arc oxidation and post hydrothermal treatment were employed to fabricate micro/nano-topographies on titanium. According to the morphological features, they were classified as microcrater (micro-topography), nanoplate (hierarchical topography with nanoplates) and nanoleaf (hierarchical topography with nanoleaves). The response of osteoblast like cells (SaOS-2) was studied on each surface after sputtering with a thin layer of gold (Au) to minimize the influence of surface chemistry. The morphological evaluation after histochemical staining revealed that the adherent cells were polygonal-shaped on microcrater surface, roundish on nanoplate surface and elongated on nanoleaf surface. Additionally, compared to microcrater surface, nanoplate surface slowed down cell proliferation and exhibited no enhancement on cell differentiation. However, nanoleaf surface supported cell proliferation and promoted cell differentiation. The results indicate that tuning morphological features of nanostructures on micro-topography can serve as a promising strategy to specifically modulate cellular response, such as cell morphology, proliferation, differentiation and mineralization.

  18. Fabrication of Functional Nano-objects through RAFT Dispersion Polymerization and Influences of Morphology on Drug Delivery.

    PubMed

    Qiu, Liang; Xu, Chao-Ran; Zhong, Feng; Hong, Chun-Yan; Pan, Cai-Yuan

    2016-07-20

    To study the influence of self-assembled morphologies on drug delivery, four different nano-objects, spheres, nanorods, nanowires, and vesicles having aldehdye-based polymer as core, were successfully prepared via alcoholic RAFT dispersion polymerization of p-(methacryloxyethoxy)benzaldehyde (MAEBA) using poly((N,N'-dimethylamino)ethyl methacrylate) (PDMAEMA) as a macro chain transfer agent (macro-CTA) for the first time. The morphologies and sizes of the four nano-objects were characterized by TEM and DLS, and the spheres with average diameter (D) of 70 nm, the nanorods with D of 19 nm and length of 140 nm, and the vesicles with D of 137 nm were used in the subsequent cellular internalization, in vitro release, and intracellular release of the drug. The anticancer drug doxorubicin (DOX) was conjugated onto the core polymers of nano-objects through condensation reaction between aldehyde groups of the PMAEBA with primary amine groups in the DOX. Because the aromatic imine is stable under neutral conditions, but is decomposed in a weakly acidic solution, in vitro release of the DOX from the DOX-loaded nano-objects was investigated in the different acidic solutions. All of the block copolymer nano-objects show very low cytotoxicity to HeLa cells up to the concentration of 1.2 mg/mL, but the DOX-loaded nano-objects reveal different cell viability and their IC50s increase as the following order: nanorods-DOX < vesicles-DOX < spheres-DOX. The IC50 of nanowires-DOX is the biggest among the four nano-objects owing to their too large size to be internalized. Endocytosis tests demonstrate that the internalization of vesicles-DOX by the HeLa cells is faster than that of the nanorods-DOX, and the spheres-DOX are the slowest to internalize among the studied nano-objects. Relatively more nanorods localized in the acidic organelles of the HeLa cells lead to faster intracellular release of the DOX, so the IC50 of nanorods is lower than that of the vesicles-DOX.

  19. The Effect of HF/NH4F Etching on the Morphology of Surface Fractures on Fused Silica

    SciTech Connect

    Wong, L; Suratwala, T; Feit, M D; Miller, P E; Steele, R A

    2008-04-03

    The effects of HF/NH{sub 4}F, wet chemical etching on the morphology of individual surface fractures (indentations, scratches) and of an ensemble of surface fractures (ground surfaces) on fused silica glass has been characterized. For the individual surface fractures, a series of static or dynamic (sliding) Vickers and Brinnell indenters were used to create radial, lateral, Hertzian cone and trailing indentation fractures on a set of polished fused silica substrates which were subsequently etched. After short etch times, the visibility of both surface and subsurface cracks is significantly enhanced when observed by optical microscopy. This is attributed to the removal of the polishing-induced Bielby layer and the increased width of the cracks following etching allowing for greater optical scatter at the fracture interface. The removal of material during etching was found to be isotropic except in areas where the etchant has difficulty penetrating or in areas that exhibit significant plastic deformation/densification. Isolated fractures continue to etch, but will never be completely removed since the bottom and top of the crack both etch at the same rate. The etching behavior of ensembles of closely spaced cracks, such as those produced during grinding, has also been characterized. This was done using a second set of fused silica samples that were ground using either fixed or loose abrasives. The resulting samples were etched and both the etch rate and the morphology of the surfaces were monitored as a function of time. Etching results in the formation of a series of open cracks or cusps, each corresponding to the individual fractures originally on the surface of the substrate. During extended etching, the individual cusps coalesce with one another, providing a means of reducing the depth of subsurface damage and the peak-to-valley roughness. In addition, the material removal rate of the ground surfaces was found to scale with the surface area of the cracks as a

  20. Use of a Novel Sub-2 µm Silica Hydride Vancomycin Stationary Phase in Nano-Liquid Chromatography. II. Separation of Derivatized Amino Acid Enantiomers.

    PubMed

    Rocchi, Silvia; Fanali, Chiara; Fanali, Salvatore

    2015-11-01

    A novel vancomycin silica hydride stationary phase was synthesized and the particles of 1.8 µm were packed into fused silica capillaries of 75 µm internal diameter (I.D.). The chiral stationary phase (CSP) was tested for the separation of some derivatized amino acid enantiomers by using nano-liquid chromatography (nano-LC). Some experimental parameters such as the type and the content of organic modifier, the pH, and the concentration of the buffer added to the mobile phase were modified and the effect on enantioselectivity, retention time, and enantioresolution factor was studied. The separation of selected dansyl amino acids (Dns-AAs), e.g., Asp, Glu, Leu, and Phe in their enantiomers was initially achieved utilizing a mobile phase containing 85% (v/v) methanol (MeOH) and formate buffer measuring the enantioresolution factor and enantioselectivity in the range 1.74-4.17 and 1.39-1.59, respectively. Better results were obtained employing a more polar organic solvent as acetonitrile (ACN) in the mobile phase. Optimum results (Rs 1.41-6.09 and α 1.28-2.36) were obtained using a mobile phase containing formate buffer pH 2.5/water/MeOH/ACN 6:19:12.5:62.5 (v/v/v/v) in isocratic elution mode at flow rate of 130 nL/min.

  1. [Co-delivery of paclitaxel and cyclosporine by a novel liposome-silica hybrid nano-carrier for anti-tumor therapy via oral route].

    PubMed

    Deng, Li; Su, Ting-Ting; Huang, Xing-Liang; Wang, Ya-Hua; Li, Chong

    2014-01-01

    In this study, we developed a novel liposome-silica hybrid nano-carrier for tumor combination therapy via oral route, using paclitaxel and cyclosporine as a model drug pair. Optimization of the preparation of the drug-loading formulation and characterization of its physicochemical parameters and drug release profile were performed in vitro. Then in vivo pharmacodynamics and pharmacokinetics studies were performed. The results showed that the obtained formulation has a small particle size (mean diameter of 100.2 +/- 15.2 nm), a homogeneous distribution [the polydispersity index was (0.251 +/- 0.018)] and high encapsulation efficiency (90.15 +/- 2.47) % and (80.64 +/- 3.52) % for paclitaxel and cyclosporine respectively with a mild and easy preparation process. A sequential drug release trend of cyclosporine prior to palictaxel was observed. The liposome-silica hybrid nano-carrier showed good biocompatibility in vivo and co-delivery of cyclosporine and paclitaxel significantly enhanced the oral absorption of paclitaxel with improved anti-tumor efficacy, suggesting a promising approach for multi-drug therapy against tumor and other serious diseases via oral route. PMID:24783515

  2. Surface analysis and anti-graffiti behavior of a weathered polyurethane-based coating embedded with hydrophobic nano silica

    NASA Astrophysics Data System (ADS)

    Rabea, A. Mohammad; Mohseni, M.; Mirabedini, S. M.; Tabatabaei, M. Hashemi

    2012-03-01

    In this study, a permanent anti-graffiti polyurethane coating was prepared using concomitant loading of an OH-functional silicone modified polyacrylate additive ranging from 2 to 15 mol% and hydrophobic silica nanoparticles from 1 to 5 wt%. UV-visible spectroscopy, contact angle measurement and dynamic mechanical thermal analysis (DMTA) analysis were conducted on selected samples to study the weathering performance of samples containing various amounts of silica nanoparticles before and after accelerated weathering conditions. The results showed that higher amounts of additive had inferior effects on the anti-graffiti performance of the coating samples after exposure. However, silica nanoparticles could positively affect the anti-graffiti performance against ageing cycles. This improvement was attributed to lower degradation of samples containing silica nanoparticles and barrier property of nanoparticles against graffiti penetration. The presence of silica nanoparticles did not have any significant effect on the surface free energy of the samples prior and after ageing.

  3. Optimization of pore structure and particle morphology of mesoporous silica for antibody adsorption for use in affinity chromatography

    NASA Astrophysics Data System (ADS)

    Hikosaka, Ryouichi; Nagata, Fukue; Tomita, Masahiro; Kato, Katsuya

    2016-10-01

    Antibodies have received significant attention for use as antibody drugs, because they bind the objective protein (antigen) via antigen-antibody reactions. Recently, many reports have appeared on various monoclonal antibodies that recognize a single antigen. In this study, monoclonal antibodies are used as adsorbates on mesoporous silica (MPS) for affinity chromatography. MPS has high surface area and large pore volume; moreover, pore diameter, pore structure, and particle morphology are relatively easy to tune by adjusting the conditions of synthesis. The pore structure (two-dimensional (2D) hexagonal and three-dimensional cubic) and particle morphology (spherical and polyhedral) of MPS are optimized for use in a monoclonal antibody/MPS composite. When anti-IgG (one of the monoclonal antibodies) adsorbs on the MPS material and IgG (antigen) binds to anti-IgG/MPS composites, MCM-41p with a 2D-hexagonal pore structure and polyhedral particle morphology has the highest IgG binding efficiency. In addition, the antibody/MPS composites remain stable in chaotropic and low-pH solutions and can be cycled at least five times without decreasing IgG elution. In purification and removal tests, the use of the antibody/MPS composites allows only the objective protein from protein mixtures to be bound and eluted.

  4. Properties and Osteogenicity of Two Calcium Sulfate Materials with Micro or Nano Morphology.

    PubMed

    Zhang, Chunli; Li, Zhonghai; Li, Qihong; Han, Liwei; Zhu, Jialiang; Bai, Yulong; Ge, Cheng; Zhao, Yantao; Zhong, Hongbin

    2016-03-01

    Calcium sulfate dihydrate (CaSO4 x 2H2O, CSD) was widely used as the artificial bone graft. In this study, two kinds of CSD materials were characterized with XRD, TG/DTA, FT-IR, and SEM. They were both composed of CSD. Spherical shape particles were observed for nano-CSD with diameters of 52-300 nm. The micro-CSD were thin sheet particles with dimensions of 5-10 μm. At 56 days post-implantation in vivo, nano-CSD had good tissue compatibility. A frequently used bioactive material DBM, which was the combination of nano-CSD (nano-CSD-DBM) and micro-CSD (micro-CSD-DBM) in a 1:1 weight ratio separately. Composite materials were implanted in intramuscular pockets in nude mouse model. New bone mineralization could be both observed in the surgery site. Collagen I was also widely distributed by immunohistochemistry assay. And new bone area of nano-CSD-DBM was 28 ± 4.6% at 4 weeks post-operation. But new bone area of micro-CSD-DBM was 16 ± 3.7% (less than nano-CSD-DBM). Nano-CSD showed increased degradation rate with obvious anginogenicity. And nano-CSD-DBM showed more excellent bone induction property as bone substitute implant.

  5. Silica Supported Ceria Nanoparticles: A Hybrid Nanostructure To Increase Stability And Surface Reactivity Of Nano-crystalline Ceria

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Varga, Tamas; Thevuthasan, Suntharampillai

    2014-01-21

    The mixed oxidation state (3+/4+) of ceria nanoparticles of smaller sizes make them attractive materials for their catalytic antioxidant biological properties. However the unmodified smaller ceria nanoparticles are limited in their use due to particles agglomeration and reduced surface chemical reactivity in the solutions used to disperse the nanoparticles. This work describes an effort to stabilize small ceria nanoparticles, retaining their desired activity, on a larger stable silica support. The ceria nanoparticles attached to silica was synthesized by a solution synthesis technique in which the surface functional groups of silica nanoparticles were found to be essential for the formation of smaller ceria nanoparticles. The surface chemical and vibrational spectroscopy analysis revealed cerium–silicate (Ce-O-Si) covalent bond linkage between silica and cerium oxide nanoparticles. The colloidal properties (agglomerate particle size and suspension stability) of ceria attached to silica was significantly improved due to inherent physico-chemical characteristics of silica against random collision and gravitation settling as opposed to unmodified ceria nanoparticles in solution. The bio-catalytic activity of ceria nanoparticles in the 3+ oxidation state was not found to be limited by attachment to the silica support as measured by free radical scavenging activity in different biological media conditions.

  6. Synthesis and Characterization of Ordered Mesoporous Silica with Controlled Macroscopic Morphology for Membrane Applications

    NASA Astrophysics Data System (ADS)

    Stohlman, Olive R.

    2011-12-01

    Ordered mesoporous materials have tunable pore sizes between 2 and 50 nm and are characterized by ordered pore structures and high surface areas (~1000 m2/g). This makes them particularly favorable for a number of membrane applications such as protein separation, polymer extrusion, nanowire fabrication and membrane reactors. These membranes can be fabricated as top-layers on macroporous supports or as embedded membranes in a dense matrix. The first part of the work deals with the hydrothermal synthesis and water-vapor/oxygen separation properties of supported MCM-48 and a new Al-MCM-48 type membrane for potential use in air conditioning systems. Knudsen-type permeation is observed in these membranes. The combined effect of capillary condensation and the aluminosilicate matrix resulted in the highest separation factor (142) in Al-MCM-48 membranes, with a water vapor permeance of 6x10 -8mol/m2·Pa·s. The second part focuses on synthesis of embedded mesoporous silica membranes with helically ordered pores by a novel Counter Diffusion Self-Assembly (CDSA) method. This method is an extension of the interfacial synthesis method for fiber synthesis using tetrabutylorthosilicate (TBOS) and cetyltrimethylammonium bromide (CTAB) as the silica source and surfactant respectively. The initial part of this study determined the effect of TBOS height and humidity on fiber formation. From this study, the range of TBOS heights for best microscopic and macroscopic ordering were established. Next, the CDSA method was used to successfully synthesize membranes, which were characterized to have good support plugging and an ordered pore structure. Factors that influence membrane synthesis and plug microstructure were determined. SEM studies revealed the presence of gaps between the plugs and support pores, which occur due to shrinking of the plug on drying. Development of a novel liquid deposition method to seal these defects constituted the last part of this work. Post sealing, excess

  7. Anion-controlled morphologies and spectral features of cyanine-based nanoGUMBOS - an improved photosensitizer

    NASA Astrophysics Data System (ADS)

    Jordan, Atiya N.; Das, Susmita; Siraj, Noureen; de Rooy, Sergio L.; Li, Min; El-Zahab, Bilal; Chandler, Lin; Baker, Gary A.; Warner, Isiah M.

    2012-07-01

    The ability to control the morphologies and spectral properties of organic low-dimensional nanomaterials is of paramount importance. The research reported herein demonstrates a template-free approach to tailored morphological and optical properties for a novel class of pseudoisocyanine (PIC)-based fluorescent organic nanoparticles derived from a group of uniform materials based on organic salts (GUMBOS). The synthesized nanoscale PIC-based particles (termed nanoGUMBOS), [PIC][NTf2] and [PIC][BETI], exhibit interesting adaptability as a function of the associated anion. The diamond-shaped nanostructures of [PIC][NTf2] and [PIC][BETI] nanorods exhibit enhanced fluorescence quantum yields relative to the parent compound, [PIC][I]. As supported by fluorescence lifetime measurements, these enhanced spectral properties can be attributed to differences in molecular self-assembly ordering (e.g., H- vs. J-aggregation) and restricted molecular rotation leading to reduced twisted intramolecular charge transfer in the nanoGUMBOS. The electrochemical properties of the PIC-based GUMBOS suggest their potential use in dye-sensitized solar cells.The ability to control the morphologies and spectral properties of organic low-dimensional nanomaterials is of paramount importance. The research reported herein demonstrates a template-free approach to tailored morphological and optical properties for a novel class of pseudoisocyanine (PIC)-based fluorescent organic nanoparticles derived from a group of uniform materials based on organic salts (GUMBOS). The synthesized nanoscale PIC-based particles (termed nanoGUMBOS), [PIC][NTf2] and [PIC][BETI], exhibit interesting adaptability as a function of the associated anion. The diamond-shaped nanostructures of [PIC][NTf2] and [PIC][BETI] nanorods exhibit enhanced fluorescence quantum yields relative to the parent compound, [PIC][I]. As supported by fluorescence lifetime measurements, these enhanced spectral properties can be attributed to

  8. Synthesis of silver nanoparticles deposited on silica by γ-irradiation and preparation of PE/Ag nano compound masterbatches

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Kim Lan; Trinh Nguyen, Thuy Ai; Phu Dang, Van; Duy Nguyen, Ngoc; Le, Anh Quoc; Hien Nguyen, Quoc

    2013-12-01

    Silver nanoparticles (AgNPs) deposited on silica were synthesized by gamma Co-60 irradiation of Ag+ dispersion in silica/ethanol/water mixture (9/80/20:w/v/v). The reduction of Ag+ is occurred by hydrated electron (e-aq) and hydrogen atom (H•) generated during radiolysis of ethanol/water. The conversion doses (Ag+ → Ag0) were determined by UV-Vis spectroscopy. The synthesized AgNPs/silica were characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD), which showed the size of AgNPs to be in the range of 5-40 nm for Ag+ concentrations from 5 to 20 mM. Masterbatches of PE/AgNPs/silica compound with silver content from 250 to 1000 mg kg-1 were also prepared. These masterbatches can be suitably used for various applications such as antimicrobial food containers and packing films, etc.

  9. Growing gold fractal nano-structures and studying changes in their morphology as a function of film growth rate

    NASA Astrophysics Data System (ADS)

    Banerjee, Amit; Banerjee, S. S.

    2016-10-01

    We investigate the formation of fractal like nano-structures on free standing gold films grown via surfactant mediated thin film growth process. We determine these structures to be confined within the first few monolayers of the thin film. Their chemical composition is identical to that of the Au film, although their density is different from the surrounding film. We observe changes in the morphology of these fractal structures by controlling the film growth rate, which spans across three orders of magnitude. From our study, we quantify the morphological changes in the fractal structure via a roundness parameter and we suggest an empirical relation between the roundness parameter and the growth rate. The study shows an inverse relationship between the roundness parameter and the growth rate and also that the fractal to compact morphological transition is continuous.

  10. Formation of Silica/Graphene Oxide Hybrid Nano Films by Layer-by-Layer Self-Assembly and Biomimetic Silicification.

    PubMed

    Yang, Sung Ho

    2015-02-01

    Silica/graphene oxide hybrid thin films were formed by layer-by-layer self-assembly and biomimetic silicification, and the thickness and structure of hybrid thin films were finely controlled at the nanometer scale, by tuning number of the layer-by-layer process. The physical properties of thin films were characterized by infrared spectroscopy, atomic force microscopy, and scanning electron microscopy. In addition, silica/graphene oxide hybrid thin films were successfully utilized for cell culture platforms.

  11. Effect of morphology of dispersed nano-CeO2 on far infrared emission property of natural tourmaline.

    PubMed

    Zhu, Dongbin; Xu, Anping; Liang, Jinsheng

    2011-11-01

    Dispersed nano-CeO2 successfully grew on the surface of natural tourmaline powders by a precipitation method. The results of Fourier transform infrared spectroscopy (FTIR) showed that CeO2 (111) nanospots could apparently enhance the far infrared emission property of tourmaline in relation to CeO2 nanoparticles. This is the first report regarding the effect of the morphology of nano-CeO2 on the far infrared emission property of natural tourmaline. The results of the characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) showed that CeO2 (111) nanospots have much more chemisorbed oxygen than CeO2 nanoparticles, which is beneficial to the unit cell volume shrinkage of tourmaline, thus increasing its far infrared emissivity. PMID:22413254

  12. Effect of morphology of dispersed nano-CeO2 on far infrared emission property of natural tourmaline.

    PubMed

    Zhu, Dongbin; Xu, Anping; Liang, Jinsheng

    2011-11-01

    Dispersed nano-CeO2 successfully grew on the surface of natural tourmaline powders by a precipitation method. The results of Fourier transform infrared spectroscopy (FTIR) showed that CeO2 (111) nanospots could apparently enhance the far infrared emission property of tourmaline in relation to CeO2 nanoparticles. This is the first report regarding the effect of the morphology of nano-CeO2 on the far infrared emission property of natural tourmaline. The results of the characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) showed that CeO2 (111) nanospots have much more chemisorbed oxygen than CeO2 nanoparticles, which is beneficial to the unit cell volume shrinkage of tourmaline, thus increasing its far infrared emissivity.

  13. Morphological and cytohistochemical evaluation of renal effects of cadmium-doped silica nanoparticles given intratracheally to rat

    NASA Astrophysics Data System (ADS)

    Coccini, T.; Roda, E.; Barni, S.; Manzo, L.

    2013-04-01

    Renal morphological parameters were determined in rats intratracheally instilled with model cadmium-containing silica nanoparticles (Cd-SiNPs, 1mg/rat), also exploring whether their potential modifications would be associated with toxicogenomic changes. Cd-SiNP effects, evaluated 7 and 30 days post-exposure, were assessed by (i) histopathology (Haematoxylin/Eosin Staining), (ii) characterization of apoptotic features by TUNEL staining. Data were compared with those obtained by CdCl2 (400μg/rat), SiNPs (600μg/rat), 0.1 ml saline. Area-specific cell apoptosis was observed in all treatment groups: cortex and inner medulla were the most affected regions. Apoptotic changes were apparent at 7 days post-exposure in both areas, and were still observable in inner medulla 30 days after treatment. Increase in apoptotic frequency was more pronounced in Cd-SiNP-treated animals compared to either CdCl2 or SiNPs. Histological findings showed comparable alterations in the renal glomerular (cortex) architecture occurring in all treatment groups at both time-points considered. The glomeruli appeared often collapsed, showing condensed, packed mesangial and endothelial cells. Oedematous haemorrhagic glomeruli were also observed in Cd-SiNPs-treated animals. Bare SiNPs caused morphological and apoptotic changes without modifying the renal gene expression profile. These findings support the concept that multiple assays and an integrated testing strategy should be recommended to characterize toxicological responses to nanoparticles in mammalian systems.

  14. Silica-coated upconversion lanthanide nanoparticles: The effect of crystal design on morphology, structure and optical properties

    PubMed Central

    Kostiv, Uliana; Šlouf, Miroslav; Macková, Hana; Zhigunov, Alexander; Engstová, Hana; Smolková, Katarína; Ježek, Petr

    2015-01-01

    Summary NaYF4:Yb3+/Er3+ nanoparticles were synthesized by thermal decomposition of lanthanide trifluoroacetates using oleylamine (OM) as both solvent and surface binding ligand. The effect of reaction temperature and time on the properties of the particles was investigated. The nanoparticles were characterized by transmission electron microscopy (TEM), electron diffraction (ED), energy dispersive spectroscopy (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), elemental analysis and X-ray diffraction (XRD) to determine morphology, size, polydispersity, crystal structure and elemental composition of the nanocrystals. TEM microscopy revealed that the morphology of the nanoparticles could be fine-tuned by modifying of the synthetic conditions. A cubic-to-hexagonal phase transition of the NaYF4:Yb3+/Er3+ nanoparticles at temperatures above 300 °C was confirmed by both ED and XRD. Upconversion luminescence under excitation at 980 nm was observed in the luminescence spectra of OM–NaYF4:Yb3+/Er3+ nanoparticles. Finally, the OM–NaYF4:Yb3+/Er3+ nanoparticles were coated with a silica shell to enable further functionalization and increase biocompatibility and stability in aqueous media, preventing particle aggregation. PMID:26734520

  15. Ultrasound-assisted/biosurfactant-templated size-tunable synthesis of nano-calcium sulfate with controllable crystal morphology.

    PubMed

    Hazra, Chinmay; Bari, Sarang; Kundu, Debasree; Chaudhari, Ambalal; Mishra, Satyendra; Chatterjee, Aniruddha

    2014-05-01

    Nano-sized crystals of alpha calcium sulfate hemihydrate (α-HH) with considerable morphology-dependent properties find promising applications in the clinical fields as a cementitious material. Towards this end, ultrasound-assisted rhamnolipid and surfactin biosurfactant-template route is explored to control the morphology and aspect ratio of nano-CaSO4 by adjusting the mass ratio of rhamnolipid/H2O, surfactin/H2O and rhamnolipid/surfactin. The change in the molar ratio of [SO4(2-)]:[Ca(2+)] results in modification in variable morphology and size of nano-CaSO4 including long, short rods and nanoplates. With increase in the rhamnolipid/H2O ratio from 1.3 to 4.5, the crystal length decreases from 3 μm to 600 nm with the corresponding aspect ratio reduced sharply from 10 to 3. Similarly, the crystal morphology gradually changes from submicrometer-sized long rod to hexagonal plate, and then plate-like appearance with increase in surfactin concentration. The preferential adsorption of rhamnolipid on the side facets and surfactin on the top facets contributes to the morphology control. The process using 50% amplitude with a power input of 45.5 W was found to be the most ideal as observed from the high yields and lower average l/w aspect ratio, leading to more than 94% energy savings as compared to that utilized by the conventional process. As a morphology and crystal habit modifier, effects of Mg(2+) and K(+) ions on α-HH growth were investigated to find an optimal composition of solution for α-HH preparation. Mg(2+) ions apparently show an accelerating effect on the α-HH growth; however, the nucleation of α-HH is probably retarded by K(+) ions. Thus, the present work is a simple, versatile, highly efficient approach to controlling the morphology of α-HH and thereby, offers more opportunities for α-HH multiple applications.

  16. Facile fabrication of a lotus-effect composite coating via wrapping silica with polyurethane

    NASA Astrophysics Data System (ADS)

    Su, Changhong

    2010-01-01

    A lotus-effect coating was fabricated by wrapping micro-silica and nano-silica with polyurethane (PU) and subsequent spraying. The coating shows the similar self-cleaning property as lotus leaves: the contact angle is as large as 168° and the sliding angle is as low as 0.5°. Surface morphology of the coating was studied with scanning electron microscopy and atomic force microscopy. The composite coating shows the similar structure as lotus leaves.

  17. Characterization of the Morphology and Rapid Expansion of Swellable Organically Modified Silica

    NASA Astrophysics Data System (ADS)

    Christman, Lilianna E.; Logue, Amanda; Edmiston, Paul L.; Lehman, Susan Y.

    2011-03-01

    Swellable organically modified silica (SOMS) is a novel sol-gel derived material.~ SOMS is hydrophobic and selectively absorbs non-polar liquids and immediately swells 5 to 6 times upon absorption.~ SOMS can be used to remove organic contaminants from water; the contaminant can then be recovered and the SOMS reused.~ We have investigated the SOMS swelling behavior of neat organic liquids usng macroscopic measurements of the force exerted during expansion and through atomic force microscopy (AFM) of the surface. ~A powdered SOMS sample was placed in a cylinder with an adjustable piston.~ Solvent percolated into the cylinder and the piston gradually moved to allow expansion while measuring the force using a load cell.~ During expansion the SOMS exerted forces up to 150 N per gram of material.~ AFM shows the surface of the SOMS is textured with cauliflower-like features.~ In unswollen SOMS, these globules have length scales of a few hundred nanometers, while for SOMS swollen in a solvent the features expand to several micrometers.

  18. Silica-Supported Titania-Zirconia Nanocomposites: Structural and Morphological Characteristics in Different Media.

    PubMed

    Sulym, Iryna; Goncharuk, Olena; Sternik, Dariusz; Skwarek, Ewa; Derylo-Marczewska, Anna; Janusz, Wladyslaw; Gun'ko, Vladimir M

    2016-12-01

    A series of TiO2-ZrO2/SiO2 nanocomposites were synthesized using a liquid-phase method and characterized by various techniques, namely, nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy, and photon correlation spectroscopy (PCS). It was revealed that the component ratio and calcination temperature affect the phase composition of nanocomposites. Composites TiZrSi1 (TiO2:ZrO2:SiO2 = 3:10:87) and TiZrSi2 (10:10:80) calcined at 1100 °С demonstrate the presence of t-ZrO2 crystallites in TiZrSi1 and ZrTiO4 phase in TiZrSi2. The samples calcined at 550 °С were amorphous as it was found from XRD data. According to the Raman spectra, the bands specific for anatase are observed in TiZrSi2. According to XPS data, Zr and Ti are in the highest oxidation state (+4). Textural analysis shows that initial silica is mainly meso/macroporous, but composites are mainly macroporous. The particle size distributions in aqueous media showed a tendency of increasing particle size with increasing TiO2 content in the composites.

  19. Silica-Supported Titania-Zirconia Nanocomposites: Structural and Morphological Characteristics in Different Media

    NASA Astrophysics Data System (ADS)

    Sulym, Iryna; Goncharuk, Olena; Sternik, Dariusz; Skwarek, Ewa; Derylo-Marczewska, Anna; Janusz, Wladyslaw; Gun'ko, Vladimir M.

    2016-02-01

    A series of TiO2-ZrO2/SiO2 nanocomposites were synthesized using a liquid-phase method and characterized by various techniques, namely, nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy, and photon correlation spectroscopy (PCS). It was revealed that the component ratio and calcination temperature affect the phase composition of nanocomposites. Composites TiZrSi1 (TiO2:ZrO2:SiO2 = 3:10:87) and TiZrSi2 (10:10:80) calcined at 1100 °C demonstrate the presence of t-ZrO2 crystallites in TiZrSi1 and ZrTiO4 phase in TiZrSi2. The samples calcined at 550 °C were amorphous as it was found from XRD data. According to the Raman spectra, the bands specific for anatase are observed in TiZrSi2. According to XPS data, Zr and Ti are in the highest oxidation state (+4). Textural analysis shows that initial silica is mainly meso/macroporous, but composites are mainly macroporous. The particle size distributions in aqueous media showed a tendency of increasing particle size with increasing TiO2 content in the composites.

  20. The influence of nano silica particles on gamma-irradiation ageing of elastomers based on chlorosulphonated polyethylene and acrylonitrile butadiene rubber

    NASA Astrophysics Data System (ADS)

    Marković, G.; Marinović-Cincović, M.; Tanasić, Lj.; Jovanović, V.; Samaržija-Jovanović, S.; Vukić, N.; Budinski-Simendić, J.

    2011-12-01

    The goal of this work was to study gamma irradiation ageing of rubber blends based on acrylonitrile butadiene rubber (NBR) and chlorosulphonated polyethylene rubber (CSM) reinforced by silica nano particles. The NBR/CSM compounds (50: 50, w/w) filled with different content of filler (0-100 phr) were crosslinked by sulfur. The vulcanization characteristics were assessed using the rheometer with an oscillating disk. The vulcanizates were prepared in a hydraulic press. The obtained materials were exposed to the different irradiation doses (100, 200, 300 and 400 kGy). The mechanical properties (hardness, modulus at 100% elongation, tensile strength and elongation at break) and swelling numbers were assessed before and after gamma irradiation ageing.

  1. 'Nano' Morphology and Element Signatures of Early Life on Earth: A New Tool for Assessing Biogenicity

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Mostefaoui, S.; Meibom, A.; Selo, M.; McKay, D. S.; Robert, F.

    2006-01-01

    The relatively young technology of NanoSIMS is unlocking an exciting new level of information from organic matter in ancient sediments. We are using this technique to characterize Proterozoic organic material that is clearly biogenic as a guide for interpreting controversial organic structures in either terrestrial or extraterrestrial samples. NanoSIMS is secondary ion mass spectrometry for trace element and isotope analysis at sub-micron resolution. In 2005, Robert et al. [1] combined NanoSIMS element maps with optical microscopic imagery in an effort to develop a new method for assessing biogenicity of Precambrian structures. The ability of NanoSIMS to map simultaneously the distribution of organic elements with a 50 nm spatial resolution provides new biologic markers that could help define the timing of life s development on Earth. The current study corroborates the work of Robert et al. and builds on their study by using NanoSIMS to map C, N (as CN), S, Si and O of both excellently preserved microfossils and less well preserved, non-descript organics in Proterozoic chert from the ca. 0.8 Ga Bitter Springs Formation of Australia.

  2. Mechanical and Morphological Properties of Polypropylene/Nano α-Al2O3 Composites

    PubMed Central

    Mirjalili, F.; Chuah, L.; Salahi, E.

    2014-01-01

    A nanocomposite containing polypropylene (PP) and nano α-Al2O3 particles was prepared using a Haake internal mixer. Mechanical tests, such as tensile and flexural tests, showed that mechanical properties of the composite were enhanced by addition of nano α-Al2O3 particles and dispersant agent to the polymer. Tensile strength was approximately ∼16% higher than pure PP by increasing the nano α-Al2O3 loading from 1 to 4 wt% into the PP matrix. The results of flexural analysis indicated that the maximum values of flexural strength and flexural modulus for nanocomposite without dispersant were 50.5 and 1954 MPa and for nanocomposite with dispersant were 55.88 MPa and 2818 MPa, respectively. However, higher concentration of nano α-Al2O3 loading resulted in reduction of those mechanical properties that could be due to agglomeration of nano α-Al2O3 particles. Transmission and scanning electron microscopic observations of the nanocomposites also showed that fracture surface became rougher by increasing the content of filler loading from 1 to 4% wt. PMID:24688421

  3. Organization of research team for nano-associated safety assessment in effort to study nanotoxicology of zinc oxide and silica nanoparticles.

    PubMed

    Kim, Yu-Ri; Park, Sung Ha; Lee, Jong-Kwon; Jeong, Jayoung; Kim, Ja Hei; Meang, Eun-Ho; Yoon, Tae Hyun; Lim, Seok Tae; Oh, Jae-Min; An, Seong Soo A; Kim, Meyoung-Kon

    2014-01-01

    Currently, products made with nanomaterials are used widely, especially in biology, bio-technologies, and medical areas. However, limited investigations on potential toxicities of nanomaterials are available. Hence, diverse and systemic toxicological data with new methods for nanomaterials are needed. In order to investigate the nanotoxicology of nanoparticles (NPs), the Research Team for Nano-Associated Safety Assessment (RT-NASA) was organized in three parts and launched. Each part focused on different contents of research directions: investigators in part I were responsible for the efficient management and international cooperation on nano-safety studies; investigators in part II performed the toxicity evaluations on target organs such as assessment of genotoxicity, immunotoxicity, or skin penetration; and investigators in part III evaluated the toxicokinetics of NPs with newly developed techniques for toxicokinetic analyses and methods for estimating nanotoxicity. The RT-NASA study was carried out in six steps: need assessment, physicochemical property, toxicity evaluation, toxicokinetics, peer review, and risk communication. During the need assessment step, consumer responses were analyzed based on sex, age, education level, and household income. Different sizes of zinc oxide and silica NPs were purchased and coated with citrate, L-serine, and L-arginine in order to modify surface charges (eight different NPs), and each of the NPs were characterized by various techniques, for example, zeta potentials, scanning electron microscopy, and transmission electron microscopy. Evaluation of the "no observed adverse effect level" and systemic toxicities of all NPs were performed by thorough evaluation steps and the toxicokinetics step, which included in vivo studies with zinc oxide and silica NPs. A peer review committee was organized to evaluate and verify the reliability of toxicity tests, and the risk communication step was also needed to convey the current findings

  4. An investigation on morphology and mechanical properties of HDPE/nanoclay/nanoCaCO3 ternary nanocomposites

    NASA Astrophysics Data System (ADS)

    Garmabi, Hamid; Tabari, Seyed Emad Alavi; Javadi, Azizeh; Behrouzi, Hormoz; Hosseini, Gholamabbas

    2016-03-01

    Ternary Nanocomposites of high-density polyethylene (HDPE) containing two types of nano particles, a layered organoclay (Closite 15A) and a spherical nano Calcium Carbonate (CaCO3), with various compositions were prepared using melt mixing. Maleic anhydride grafted polyethylene (MA-g-PE) was used to enhance the dispersion of nanofillers and better interface adhesion. Three different levels of nanoclay (1, 3, 5 wt. %), CaCO3 (6, 8, 10 wt. %) and MA-g-PE (3, 6, 9 wt. %) were used. The mixing was done in two steps: First a concentrated masterbatch of nanoparticles in HPDE and MA-g-PE was prepared using an internal mixer and then melt-mixing of nanocomposites was done in a lab scale co-rotating twin screw extruder. The morphology of samples was studied using Scanning Electron Microscopy (SEM) and mechanical properties were evaluated using tensile and impact tests. According to the SEM micrographs, nanofillers were well dispersed in the HDPE matrix and XRD patterns showed the intercalation of nanoclay layers too. Generally using the layered nanoclay can enhance the tensile modulus while the use of spherical nano CaCO3 results into improved toughness. It was found that co-incorporation of these two types of nanofillers, leads to improve the stiffness and minimize the reduction of impact strength, simultaneously.

  5. Double layer approach to create durable superhydrophobicity on cotton fabric using nano silica and auxiliary non fluorinated materials

    NASA Astrophysics Data System (ADS)

    Manatunga, Danushika Charyangi; de Silva, Rohini M.; de Silva, K. M. Nalin

    2016-01-01

    Creation of differential superhydrophobicity by applying different non-fluorinated hydrophobization agents on a cotton fabric roughened with silica nanoparticles was studied. Cotton fabric surface has been functionalized with silica nanoparticles and further hydrophobized with different hydrophobic agents such as hexadecyltrimethoxy silane (HDTMS), stearic acid (SA), triethoxyoctyl silane (OTES) and hybrid mixtures of HDTMS/SA and HDTMS/OTES. The cotton fabrics before and after the treatment were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). The wetting behavior of cotton samples was investigated by water contact angle (WCA) measurement, water uptake, water repellency and soil repellency testing. The treated fabrics exhibited excellent water repellency and high water contact angles (WCA). When the mixture of two hydrophobization agents such as HDTMS/OTES and HDTMS/SA is used, the water contact angle has increased (145°-160°) compared to systems containing HDTMS, OTES, SA alone (130°-140°). It was also noted that this fabricated double layer (silica + hydrophobization agent) was robust even after applying harsh washing conditions and there is an excellent anti-soiling effect observed over different stains. Therefore superhydrophobic cotton surfaces with high WCA and soil repellency could be obtained with silica and mixture of hydrophobization agents which are cost effective and environmentally friendly when compared with the fluorosilane treatment.

  6. Removal of hexavalent chromium in soil and groundwater by supported nano zero-valent iron on silica fume.

    PubMed

    Li, Yongchao; Jin, Zhaohui; Li, Tielong; Li, Shujing

    2011-01-01

    Silica fume supported-Fe(0) nanoparticles (SF-Fe(0)) were prepared using commercial silica fume as a support. The feasibility of using this SF-Fe(0) for reductive immobilization of Cr(VI) was investigated through batch tests. Compared with unsupported Fe(0), SF-Fe(0) was significantly more active in Cr(VI) removal especially in 84 wt% silica fume loading. Silica fume had also been found to inhibit the formation of Fe(III)/Cr(III) precipitation on Fe nanoparticles' surface, which was increasing the deactivation resistance of iron. Cr(VI) was removed through physical adsorption of Cr(VI) onto the SF-Fe(0) surface and subsequent reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) could be expressed by pseudo first-order reaction kinetics. The rate constant increased with the increase in iron loading but decreased with the increase in initial Cr(VI) concentration. Furthermore, column tests showed that the SF-Fe(0) could be readily transported in model soil.

  7. Anion-controlled morphologies and spectral features of cyanine-based nanoGUMBOS--an improved photosensitizer.

    PubMed

    Jordan, Atiya N; Das, Susmita; Siraj, Noureen; de Rooy, Sergio L; Li, Min; El-Zahab, Bilal; Chandler, Lin; Baker, Gary A; Warner, Isiah M

    2012-08-21

    The ability to control the morphologies and spectral properties of organic low-dimensional nanomaterials is of paramount importance. The research reported herein demonstrates a template-free approach to tailored morphological and optical properties for a novel class of pseudoisocyanine (PIC)-based fluorescent organic nanoparticles derived from a group of uniform materials based on organic salts (GUMBOS). The synthesized nanoscale PIC-based particles (termed nanoGUMBOS), [PIC][NTf(2)] and [PIC][BETI], exhibit interesting adaptability as a function of the associated anion. The diamond-shaped nanostructures of [PIC][NTf(2)] and [PIC][BETI] nanorods exhibit enhanced fluorescence quantum yields relative to the parent compound, [PIC][I]. As supported by fluorescence lifetime measurements, these enhanced spectral properties can be attributed to differences in molecular self-assembly ordering (e.g., H- vs. J-aggregation) and restricted molecular rotation leading to reduced twisted intramolecular charge transfer in the nanoGUMBOS. The electrochemical properties of the PIC-based GUMBOS suggest their potential use in dye-sensitized solar cells.

  8. Synthesis and characterization of Pt nanoparticles with different morphologies in mesoporous silica SBA-15 for methanol oxidation reaction.

    PubMed

    Chen, C S; Lai, Y T; Chen, T C; Chen, C H; Lee, J F; Hsu, C W; Kao, H M

    2014-11-01

    Mesoporous SBA-15 silica materials functionalized with and without carboxylic acid groups were used to effectively control the morphology of Pt crystals, and the materials thus obtained were applied to methanol oxidation reactions. The Pt particles aggregated to form long spheroids inside the channels in pure SBA-15. When carboxylic acid groups were utilized, the SBA-15(-COOH) material facilitated the formation of higher Pt surface area, smaller Pt nanoparticles and nearly spherical shape due to the strong interaction between Pt(4+) ions and carboxylic acid on SBA-15. The Pt(4+) ions on the SBA-15(-COOH) material can be directly transformed to reduced Pt particles during calcination. The methanol oxidation activity on a Pt surface is strongly dependent on the shape of Pt particles. The near-spherical Pt nanoparticles on the SBA-15(-COOH) exhibited higher catalytic activity during methanol oxidation than Pt catalysts on unmodified SBA-15. The near-spherical Pt particles on the SBA-15(-COOH) contained large numbers of terrace sites on their surfaces, which led to high efficiency during methanol oxidation.

  9. Photoinduced charge generation rates in soluble P3HT : PCBM nano-aggregates predict the solvent-dependent film morphology

    NASA Astrophysics Data System (ADS)

    Roy, Palas; Jha, Ajay; Dasgupta, Jyotishman

    2016-01-01

    The device efficiency of bulk heterojunction (BHJ) solar cells is critically dependent on the nano-morphology of the solution-processed polymer : fullerene blend. Active control on blend morphology can only emanate from a detailed understanding of solution structures during the film casting process. Here we use photoinduced charge transfer (CT) rates to probe the effective length scale of the pre-formed solution structures and their energy disorder arising from a mixture of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in three different organic solvents. The observed solvent-dependent ultrafast biphasic rise of the transient polaron state in solution along with changes detected in the C&z.dbd;C stretching frequency of bound PCBM provides direct evidence for film-like P3HT : PCBM interfaces in solution. Using the diffusive component of the charge transfer rate, we deduce ~3-times larger functional nano-domain size in toluene than in chlorobenzene thereby correctly predicting the relative polymer nanofiber widths observed in annealed films. We thus provide first experimental evidence for the postulated polymer : fullerene : solvent ternary phase that seeds the eventual morphology in spin-cast films. Our work motivates the design of new chemical additives to tune the grain size of the evolving polymer : fullerene domains within the solution phase.The device efficiency of bulk heterojunction (BHJ) solar cells is critically dependent on the nano-morphology of the solution-processed polymer : fullerene blend. Active control on blend morphology can only emanate from a detailed understanding of solution structures during the film casting process. Here we use photoinduced charge transfer (CT) rates to probe the effective length scale of the pre-formed solution structures and their energy disorder arising from a mixture of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in three

  10. Profoundly improving flow properties of a cohesive cellulose powder by surface coating with nano-silica through comilling.

    PubMed

    Chattoraj, Sayantan; Shi, Limin; Sun, Changquan Calvin

    2011-11-01

    Poor flow properties hinder the easy handling of powders during industrial-scale processing. In this work, we show that powder flow can be substantially improved by reducing the cohesion of powders by coating them with nanosized guest particles. We further show that comilling is an efficient process for nanocoating. We have systematically investigated the effects of total number of comilling cycles (10-70 cycles) and silica loading (0-1.0 wt %) on the flow behavior of a highly cohesive and poorly flowing grade of microcrystalline cellulose powder (Avicel PH105). Optimum flow enhancement has been achieved with 1.0 wt % silica loading at 40 comilling cycles. The flow properties of nanocoated Avicel PH105 are comparable to those of Avicel PH102, which exhibits adequate flowability for processing on a high-speed tablet press. Comilling is fast and suitable for continuous processing. It shows potential for addressing industrial powder handling problems caused by poor powder flow properties.

  11. Impact of dissolved silica on arsenite removal by nano-particulate FeS and FeS-coated sand.

    PubMed

    Han, Young-Soo; Demond, Avery H; Hayes, Kim F

    2013-07-01

    This work evaluated the inhibitory effect of dissolved silica on arsenite adsorption to nanoparticulate FeS (NP-FeS) or mackinawite and FeS-coated sand (CS-FeS) sorbents. Arsenite retention by the NP-FeS solid was not affected by dissolved silicate over a wide range in pH, in contrast to the known inhibitory effect of dissolved silica on As(III) uptake by Fe-(hydr)oxide systems. However, some inhibition was observed in CS-FeS system at pH 9. This latter result is attributed to the co-existence of both FeS and small amounts of Fe-(hydr)oxide phases on the sand surface. Given the ubiquitous presence of dissolved Si in groundwater, FeS-based sorbents may have an advantage for As retention compared to those based on Fe-(hydr)oxides in reducing subsurface environments.

  12. Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

    NASA Astrophysics Data System (ADS)

    Kapoor, Seema; Batra, Uma; Kohli, Suchita

    2011-12-01

    Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 °C and sintered to different temperatures (200 °C, 400 °C, 600 °C, 800 °C, 1000 °C and 1200 °C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 °C to 1000 °C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 °C without any additional phase other than HAP, whereas peak of β-TCP (tricalcium phosphate) was observed at 1200 °C. Photomicrograph of

  13. Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

    SciTech Connect

    Kapoor, Seema; Batra, Uma; Kohli, Suchita

    2011-12-12

    Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 deg. C and sintered to different temperatures (200 deg. C, 400 deg. C, 600 deg. C, 800 deg. C, 1000 deg. C and 1200 deg. C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 deg. C to 1000 deg. C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 deg. C without any additional phase other than HAP, whereas peak of {beta}-TCP (tricalcium phosphate) was observed

  14. Detection of high-silica lava flows and lava morphology at the Alarcon Rise, Gulf of California, Mexico using automated classification of the morphological-compositional relationship in AUV multibeam bathymetry and sonar backscatter

    NASA Astrophysics Data System (ADS)

    Maschmeyer, C.; White, S. M.; Dreyer, B. M.; Clague, D. A.

    2015-12-01

    An automated compositional classification by adaptive neuro-fuzzy inference system (ANFIS) was developed to study volcanic processes that create high-silica lava at oceanic ridges. The objective of this research is to determine the existence of a relationship between lava morphology and composition. Researchers from the Monterey Bay Aquarium Research Institute (MBARI) recorded morphologic observations and collected samples for geochemical analysis during ROV dives at the Alarcon Rise in 2012 and 2015. The Alarcon Rise is a unique spreading ridge environment where composition ranges from basaltic to rhyolitic, making it an ideal location to examine the compositional-morphologic relationship of lava flows. Preliminary interpretation of field data indicates that high-silica lavas are typically associated with 3-5 m, blocky pillows at the heavily faulted north end of the Alarcon. Visual analysis of multibeam bathymetry and side-scan sonar backscatter from MBARI AUV D. Allen B. and gridded at 1 m suggests that lava flow morphology (pillow, lobate, sheet) can be distinguished by seafloor roughness. Bathymetric products used by ANFIS to quantify the morphologic-compositional relationship were slope, aspect, and bathymetric position index (BPI, a measure of local height relative to the adjacent terrain). Sonar backscatter intensity is influenced by surface roughness and previously used to distinguish lava morphology. Gray-level co-occurrence matrices (GLCM) were applied to backscatter to create edge-detection filters that recognized faults and fissures. Input data are slope, aspect, bathymetric value, BPI at 100 m scale, BPI at 500 m scale, backscatter intensity, and the first principle component of backscatter GLCM. After lava morphology was classified on the Alarcon Rise map, another classification was completed to detect locations of high-silica lava. Application of an expert classifier like ANFIS to distinguish lava composition may become an important tool in oceanic

  15. Synthesis of nano Cu2O on cotton: morphological, physical, biological and optical sensing characterizations.

    PubMed

    Sedighi, Ali; Montazer, Majid; Samadi, Nasrin

    2014-09-22

    In this paper, Cu2O nanoparticles were in situ synthesized on cotton fabric through a new simple and cost-effective chemical reduction method using copper sulfate, sodium hydroxide and ammonia. Cotton fabric participates as a reducing agent in reduction of copper sulfate and facilitates synthesis of cuprous oxide in nano-scale as a stabilizer. The produced cotton/nano Cu2O composite were characterized by X-ray diffraction, scanning electron microscopy and Energy-dispersive X-ray spectroscopy. Interaction of Cu2O with cotton fabric in addition to alteration of cotton functional groups were studied by Fourier transforms infrared spectroscopy. The intermediate solution, copper-amine complex, was analyzed by ultraviolet-visible spectroscopy. The mechanical properties of the cotton/nano Cu2O composite were studied using Instron indicated a higher tensile strain. The antibacterial activity of the fabric samples showed considerable behavior against S. aureus and E. coli. Further, the treated fabric became highly hydrophobic and sensed ammonia and hydrogen peroxide chromatically. PMID:24906783

  16. Synthesis of nano Cu2O on cotton: morphological, physical, biological and optical sensing characterizations.

    PubMed

    Sedighi, Ali; Montazer, Majid; Samadi, Nasrin

    2014-09-22

    In this paper, Cu2O nanoparticles were in situ synthesized on cotton fabric through a new simple and cost-effective chemical reduction method using copper sulfate, sodium hydroxide and ammonia. Cotton fabric participates as a reducing agent in reduction of copper sulfate and facilitates synthesis of cuprous oxide in nano-scale as a stabilizer. The produced cotton/nano Cu2O composite were characterized by X-ray diffraction, scanning electron microscopy and Energy-dispersive X-ray spectroscopy. Interaction of Cu2O with cotton fabric in addition to alteration of cotton functional groups were studied by Fourier transforms infrared spectroscopy. The intermediate solution, copper-amine complex, was analyzed by ultraviolet-visible spectroscopy. The mechanical properties of the cotton/nano Cu2O composite were studied using Instron indicated a higher tensile strain. The antibacterial activity of the fabric samples showed considerable behavior against S. aureus and E. coli. Further, the treated fabric became highly hydrophobic and sensed ammonia and hydrogen peroxide chromatically.

  17. Fabrication of silica nanostructures with a microwave assisted direct patterning process

    NASA Astrophysics Data System (ADS)

    Shin, Ju-Hyeon; Go, Bit-Na; Choi, Je-Hong; Kim, Jin-Seoung; Jung, Gun-Young; Kim, Heetae; Lee, Heon

    2014-06-01

    Silica nanostructures were fabricated on glass substrate using a microwave assisted direct patterning (MADP) process, which is a variety of soft lithography. During the MADP process using polydimethylsiloxane (PDMS), mold and microwave heating are performed simultaneously. Blanket thin film and micro- to nano-sized structures, including moth-eye patterns of SiO2, which consisted of coalesced silica nanoparticles, were formed on glass substrates from SiO2 nano-particle dispersed solutions with varied microwave heating time. Optical properties and surface morphologies of micro-sized hemisphere, nano-sized pillar, moth-eye and 50 nm sized line/space silica patterns were measured using UV-vis and a scanning electron microscope. X-ray diffraction analysis of SiO2 thin films with and without microwave heating was also carried out.

  18. Comparison of the morphology of alkali–silica gel formed in limestones in concrete affected by the so-called alkali–carbonate reaction (ACR) and alkali–silica reaction (ASR)

    SciTech Connect

    Grattan-Bellew, P.E.; Chan, Gordon

    2013-05-15

    The morphology of alkali–silica gel formed in dolomitic limestone affected by the so-called alkali–carbonate reaction (ACR) is compared to that formed in a siliceous limestone affected by alkali–silica reaction (ASR). The particle of dolomitic limestone was extracted from the experimental sidewalk in Kingston, Ontario, Canada that was badly cracked due to ACR. The siliceous limestone particle was extracted from a core taken from a highway structure in Quebec, affected by ASR. Both cores exhibited marked reaction rims around limestone particles. The aggregate particles were polished and given a light gold coating in preparation for examination in a scanning electron microscope. The gel in the ACR aggregate formed stringers between the calcite crystals in the matrix of the rock, whereas gel in ASR concrete formed a thick layer on top of the calcite crystals, that are of the same size as in the ACR aggregate.

  19. In vitro osteoblast-like cell proliferation on nano-hydroxyapatite coatings with different morphologies on a titanium-niobium shape memory alloy.

    PubMed

    Xiong, Jianyu; Li, Yuncang; Hodgson, Peter D; Wen, Cui'e

    2010-12-01

    The morphology of nanomaterials significantly affects their physical, chemical, and biological properties. In the present study, nano-hydroxyapatite coatings with different morphologies were produced on the surface of a titanium-niobium shape memory alloy via a hydrothermal process. The effect of the nano-hydroxyapatite coatings on the in vitro proliferation of SaOS-2 osteoblast-like cells was investigated. Factors including crystallinity, surface micro-roughness, and surface energy of the nano-hydroxyapatite coatings were discussed. Results show that in vitro proliferation of the osteoblast-like cells was significantly enhanced on the nano-hydroxyapatite-coated titanium-niobium alloy compared to the titanium-niobium alloy without coating. The cell numbers on the nano-hydroxyapatite-coated titanium-niobium alloy changed consistently with the surface energy of the hydroxyapatite coatings. This study suggests that surface energy as a characteristic parameter influencing the in vitro proliferation of osteoblast-like cells was predominant over the crystallinity and surface micro-roughness of the nano-hydroxyapatite coatings.

  20. In vitro osteoblast-like cell proliferation on nano-hydroxyapatite coatings with different morphologies on a titanium-niobium shape memory alloy.

    PubMed

    Xiong, Jianyu; Li, Yuncang; Hodgson, Peter D; Wen, Cui'e

    2010-12-01

    The morphology of nanomaterials significantly affects their physical, chemical, and biological properties. In the present study, nano-hydroxyapatite coatings with different morphologies were produced on the surface of a titanium-niobium shape memory alloy via a hydrothermal process. The effect of the nano-hydroxyapatite coatings on the in vitro proliferation of SaOS-2 osteoblast-like cells was investigated. Factors including crystallinity, surface micro-roughness, and surface energy of the nano-hydroxyapatite coatings were discussed. Results show that in vitro proliferation of the osteoblast-like cells was significantly enhanced on the nano-hydroxyapatite-coated titanium-niobium alloy compared to the titanium-niobium alloy without coating. The cell numbers on the nano-hydroxyapatite-coated titanium-niobium alloy changed consistently with the surface energy of the hydroxyapatite coatings. This study suggests that surface energy as a characteristic parameter influencing the in vitro proliferation of osteoblast-like cells was predominant over the crystallinity and surface micro-roughness of the nano-hydroxyapatite coatings. PMID:20725978

  1. Development and characterization of silica and titania based nano structured materials for the removal of indoor and outdoor air pollutants

    NASA Astrophysics Data System (ADS)

    Peiris, Thelge Manindu Nirasha

    Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized

  2. Structural, morphological and optical properties of PEDOT:PSS/QDs nano-composite films prepared by spin-casting

    NASA Astrophysics Data System (ADS)

    Najeeb, Mansoor Ani; Abdullah, Shahino Mah; Aziz, Fakhra; Ahmad, Zubair; Rafique, Saqib; Wageh, S.; Al-Ghamdi, Ahmed A.; Sulaiman, Khaulah; Touati, Farid; Shakoor, R. A.; Al-Thani, N. J.

    2016-09-01

    This paper describes the structural, morphological and optical properties of the nano-composite of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and quantum dots (QDs). The ZnSe and CdSe QDs have been synthesized, with the aid of Mercaptoacetic acid (MAA), by a colloidal method with an average size of ~5 to 7 nm. QDs have been embedded in PEDOT:PSS using a simple solution processing approach and has been deposited as thin films by spin coating technique. The QDs embedded PEDOT:PSS enhances the light absorption spectra of samples, prominently in terms of absorption intensity which may consequently improve sensitivity of the optoelectronic devices.

  3. Comparative investigation of CuFe2O4 nano and microstructures for structural, morphological, optical and magnetic properties

    NASA Astrophysics Data System (ADS)

    Raja, G.; Gopinath, S.; Raj, R. Azhagu; Shukla, Arun K.; Alhoshan, Mansour S.; Sivakumar, K.

    2016-09-01

    CuFe2O4 nanocrystals were synthesized by the sol-gel method (SGM) and microwave method (MM) by using sucrose as a fuel. The structural, morphological, optical and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). The XRD results confirmed the formation of cubic phase CuFe2O4. The formation of CuFe2O4 nano and microstructures were confirmed by HR-SEM. Photoluminescence emissions were determined by PL spectra, respectively. The relatively high saturation magnetization (78.22 emu/g) of CuFe2O4-MM shows that it is ferromagnetic and low saturation magnetization (35.98 emu/g) of CuFe2O4O-SGM confirms the super paramagnetic behavior.

  4. Adsorbate-driven morphological changes on Cu(111) nano-pits

    SciTech Connect

    Mudiyanselage, K.; Xu, F.; Hoffmann, F. M.; Hrbek, J.; Waluyo, I.; Boscoboinik, J. A.; Stacchiola, D. J.

    2014-12-09

    Adsorbate-driven morphological changes of pitted-Cu(111) surfaces have been investigated following the adsorption and desorption of CO and H. The morphology of the pitted-Cu(111) surfaces, prepared by Ar+ sputtering, exposed a few atomic layers deep nested hexagonal pits of diameters from 8 to 38 nm with steep step bundles. The roughness of pitted-Cu(111) surfaces can be healed by heating to 450-500 K in vacuum. Adsorption of CO on the pitted-Cu(111) surface leads to two infrared peaks at 2089-2090 and 2101-2105 cm-1 for CO adsorbed on under-coordinated sites in addition to the peak at 2071 cm-1 for CO adsorbed on atop sites of the close-packed Cu(111) surface. CO adsorbed on under-coordinated sites is thermally more stable than that of atop Cu(111) sites. Annealing of the CO-covered surface from 100 to 300 K leads to minor changes of the surface morphology. In contrast, annealing of a H covered surface to 300 K creates a smooth Cu(111) surface as deduced from infrared data of adsorbed CO and scanning tunnelling microscopy (STM) imaging. The observation of significant adsorbate-driven morphological changes with H is attributed to its stronger modification of the Cu(111) surface by the formation of a sub-surface hydride with a hexagonal structure, which relaxes into the healed Cu(111) surface upon hydrogen desorption. These morphological changes occur ~150 K below the temperature required for healing of the pitted-Cu(111) surface by annealing in vacuum. In contrast, the adsorption of CO, which only interacts with the top-most Cu layer and desorbs by 160 K, does not significantly change the morphology of the pitted-Cu(111) surface.

  5. Adsorbate-driven morphological changes on Cu(111) nano-pits

    DOE PAGES

    Mudiyanselage, K.; Xu, F.; Hoffmann, F. M.; Hrbek, J.; Waluyo, I.; Boscoboinik, J. A.; Stacchiola, D. J.

    2014-12-09

    Adsorbate-driven morphological changes of pitted-Cu(111) surfaces have been investigated following the adsorption and desorption of CO and H. The morphology of the pitted-Cu(111) surfaces, prepared by Ar+ sputtering, exposed a few atomic layers deep nested hexagonal pits of diameters from 8 to 38 nm with steep step bundles. The roughness of pitted-Cu(111) surfaces can be healed by heating to 450-500 K in vacuum. Adsorption of CO on the pitted-Cu(111) surface leads to two infrared peaks at 2089-2090 and 2101-2105 cm-1 for CO adsorbed on under-coordinated sites in addition to the peak at 2071 cm-1 for CO adsorbed on atop sitesmore » of the close-packed Cu(111) surface. CO adsorbed on under-coordinated sites is thermally more stable than that of atop Cu(111) sites. Annealing of the CO-covered surface from 100 to 300 K leads to minor changes of the surface morphology. In contrast, annealing of a H covered surface to 300 K creates a smooth Cu(111) surface as deduced from infrared data of adsorbed CO and scanning tunnelling microscopy (STM) imaging. The observation of significant adsorbate-driven morphological changes with H is attributed to its stronger modification of the Cu(111) surface by the formation of a sub-surface hydride with a hexagonal structure, which relaxes into the healed Cu(111) surface upon hydrogen desorption. These morphological changes occur ~150 K below the temperature required for healing of the pitted-Cu(111) surface by annealing in vacuum. In contrast, the adsorption of CO, which only interacts with the top-most Cu layer and desorbs by 160 K, does not significantly change the morphology of the pitted-Cu(111) surface.« less

  6. Peptide-Decorated Gold Nanoparticles as Functional Nano-Capping Agent of Mesoporous Silica Container for Targeting Drug Delivery.

    PubMed

    Chen, Ganchao; Xie, Yusheng; Peltier, Raoul; Lei, Haipeng; Wang, Ping; Chen, Jun; Hu, Yi; Wang, Feng; Yao, Xi; Sun, Hongyan

    2016-05-11

    A stimuli-responsive drug delivery system (DDS) with bioactive surface is constructed by end-capping mesoporous silica nanoparticles (MSNs) with functional peptide-coated gold nanoparticles (GNPs). MSNs are first functionalized with acid-labile α-amide-β-carboxyl groups to carry negative charges, and then capped with positively charged GNPs that are decorated with oligo-lysine-containing peptide. The resulting hybrid delivery system exhibits endo/lysosomal pH triggered drug release, and the incorporation of RGD peptide facilitates targeting delivery to αvβ3 integrin overexpressing cancer cells. The system can serve as a platform for preparing diversified multifunctional nanocomposites using various functional inorganic nanoparticles and bioactive peptides. PMID:27102225

  7. Peptide-Decorated Gold Nanoparticles as Functional Nano-Capping Agent of Mesoporous Silica Container for Targeting Drug Delivery.

    PubMed

    Chen, Ganchao; Xie, Yusheng; Peltier, Raoul; Lei, Haipeng; Wang, Ping; Chen, Jun; Hu, Yi; Wang, Feng; Yao, Xi; Sun, Hongyan

    2016-05-11

    A stimuli-responsive drug delivery system (DDS) with bioactive surface is constructed by end-capping mesoporous silica nanoparticles (MSNs) with functional peptide-coated gold nanoparticles (GNPs). MSNs are first functionalized with acid-labile α-amide-β-carboxyl groups to carry negative charges, and then capped with positively charged GNPs that are decorated with oligo-lysine-containing peptide. The resulting hybrid delivery system exhibits endo/lysosomal pH triggered drug release, and the incorporation of RGD peptide facilitates targeting delivery to αvβ3 integrin overexpressing cancer cells. The system can serve as a platform for preparing diversified multifunctional nanocomposites using various functional inorganic nanoparticles and bioactive peptides.

  8. The Surface Morphology and Optical Properties of Refined Glasses with Inorganic Nano-molecules

    NASA Astrophysics Data System (ADS)

    Drajewicz, Marcin; Pytel, Maciej; Rokicki, Paweł; Góral, Marek

    2015-05-01

    New refining technology of soda-calcium-silicon glass surfaces with inorganic compounds nano-molecules has been presented in the study. In order to determine modification of the glass surface SEM observation and EDX analysis have been carried out. The UV-VIS, photo-elasticity and ellipsometry examinations were carried out on glass samples. The results of investigations that have been conducted show that refining process of the glass surface by use of nanopowder inorganic compounds deposited electrostatically on glass surface provides forming of very thin (about 50 nm) surface layers [1]. This method of surface modification improves physical and chemical glass properties. In this paper results of microhardness test of refined glass were also presented.

  9. Structural, morphological, magnetic and dielectric characterization of nano-phased antimony doped manganese zinc ferrites

    NASA Astrophysics Data System (ADS)

    Sridhar, Ch. S. L. N.; Lakshmi, Ch. S.; Govindraj, G.; Bangarraju, S.; Satyanarayana, L.; Potukuchi, D. M.

    2016-05-01

    Nano-phased doped Mn-Zn ferrites, viz., Mn0.5-x/2Zn0.5-x/2SbXFe2O4 for x=0 to 0.3 (in steps of 0.05) prepared by hydrothermal method are characterized by X-ray diffraction, Infrared and scanning electron microscopy. XRD and SEM infer the growth of nano-crystalline cubic and hematite (α-Fe2O3) phase structures. IR reveals the ferrite phase abundance and metal ion replacement with dopant. Decreasing trend of lattice constant with dopant reflects the preferential replacement of Fe3+ions by Sb5+ion. Doping is found to cause for the decrease (i.e., 46-14 nm) of grain size. An overall trend of decreasing saturation magnetization is observed with doping. Low magnetization is attributed to the diamagnetic nature of dopant, abundance of hematite (α-Fe2O3) phase, non-stoichiometry and low temperature (800 °C) sintering conditions. Increasing Yafet-Kittel angle reflects surface spin canting to pronounce lower Ms. Lower coercivity is observed for x≤0.1, while a large Hc results for higher concentrations. High ac resistivity (~106 ohm-cm) and low dielectric loss factor (tan δ~10-2-10-3) are witnessed. Resistivity is explained on the base of a transformation in the Metal Cation-to-Oxide anion bond configuration and blockade of conductivity path. Retarded hopping (between adjacent B-sites) of carriers across the grain boundaries is addressed. Relatively higher resistivity and low dielectric loss in Sbdoped Mn-Zn ferrite systems pronounce their utility in high frequency applications.

  10. Simultaneous Determination of Se and Te in Ores by HG-AFS After Online Preconcentration with Nano-TiO2 Immobilized on Silica Gel.

    PubMed

    Zhou, Jing-rong; Deng, Dong-yan; Huang, Ke; Tian, Yun-fei; Hou, Xian-deng

    2015-09-01

    A simple, sensitive and interference-free method was established for simultaneous determination of trace selenium and tellurium in ore samples by HG-AFS, by using nano-TiO2 immobilized on a silica gel packed microcolumn for online preconcentration. Selenium and tellurium were selectively adsorbed to the microcolumn in acidic condition and then completely eluted with 2% (m/v) NaOH solution. The experimental conditions for hydride generation, adsorption, elution and potential interference were investigated in detail. Under the optimum conditions, the detection limits of selenium and tellurium by the proposed method with 180 s sampling time were 4.0 and 3.6 ng · L(-1), with sensitivity enhancement of 20- and 13-fold compared to conventional hydride generation method, respectively. The relative standard deviation (RSD, n=5) of this method for 1 μg · L(-1) Se(IV) and Te(IV) were 0.7% and 2.3%, respectively. This method was applied to determination of selenium and tellurium in several ore samples. PMID:26669138

  11. Bimodal porous silica microspheres decorated with polydopamine nano-particles for the adsorption of methylene blue in fixed-bed columns.

    PubMed

    Ataei-Germi, Taher; Nematollahzadeh, Ali

    2016-05-15

    Bimodal meso/macro-porous silica microspheres (MSM) were synthesized by a modified sol-emulsion-gel method and then the surface was coated with polydopamine (PDA) nano-particles of 39nm in size. Focusing on the encouraging properties of the synthesized adsorbent, such as high specific surface area (612.3m(2)g(-1), because of mesopores), fast mass transfer (0.9-2.67×10(-3)mLmin(-1)mg, because of macropores), and abundant "adhesive" functional groups of PDA, it was used for the removal of methylene blue (MB) from aqueous solution in a fixed-bed column. The effect of different parameters such as pH, initial concentration, and flow rate was studied. The results revealed that an appropriate sorption condition is an alkaline solution of MB (e.g., pH 10) at low flow rate (less than 5mLmin(-1)). Furthermore, the compatibility of the experimental data with mathematical models such as Thomas and Adams-Bohart was investigated. Both of the models showed a good agreement with the experimental data (R(2)=0.9954-0.9994), and could be applied for the prediction of the column properties and breakthrough curves. Regeneration of the column was performed by using HCl solution with a concentration of 0.1M as an eluent. PMID:26943002

  12. Synthesis of polymer nano-brushes by self-seeding method and study of various morphologies by AFM

    NASA Astrophysics Data System (ADS)

    Agbolaghi, S.; Abbaspoor, S.; Abbasi, F.

    2016-11-01

    Polymer brushes due to their high sensitivity to environmental changes are the best and newest means for developing the responsive materials. Polymer nano-brushes consisting various surface morphologies and uniformly distributed amorphous grafted chains were synthesized via single-crystal growth procedure. Poly(ethylene glycol)- b-polystyrene (PEG- b-PS) and poly(ethylene glycol)- b-poly(methyl methacrylate) (PEG- b-PMMA) block copolymers were prepared by atom transfer radical polymerization (ATRP). On the basis of various height differences, phase regions were detectable through atomic force microscopy (AFM NanoscopeIII). The novelty of this work is developing and characterizing the random and intermediate single-co-crystals. Besides, some other sorts of brush-covered single crystals like homo-brush and matrix-dispersed mixed-brushes were involved just for comparing the distinct morphologies. The intermediate (neither matrix-dispersed nor random) single-co-crystals were detectable through their thickness fluctuations in AFM height profiles. On the contrary, the random single-co-crystals were verified through comparing with their corresponding homopolymer and homo-brush single crystals. The growth fronts of (120), (240), (200) and (040) were detected by electron diffraction of transmission electron microscope.

  13. Effect of Electrophoresis on the Efficiency of Graphite-Nano-TiO2 Modified Silica Sol-Gel Electrode.

    PubMed

    Hejazi, Mohammad Saeid; Majidi, Mir Reza; Gholizadeh, Sima; Hamidi-Asl, Ezat; Turner, Anthony P F; Golabi, Seyed Mahdi

    2015-05-01

    Electrophoresis treatment was used to improve the function of a nano-TiO2 modified sol-gel electrode. Electrodes were prepared using TiO2 nanoparticles and fine graphite powder and then treated by electrophoresis. The developed electrode was employed for the detection of lactate dehydrogenase (LDH) by following the decrease in the immobilised lactate peak current due to its LDH-mediated enzymatic oxidation. Detection was realised using square wave voltammetry (SWV). Experiments showed that the positive and negative heads of the electrophoresis-treated electrode displayed different activities, with the positive head response being remarkably improved. Parameters affecting the electrode response, such as applied potential value, electrophoresis time and percentage of TiO2, were investigated and optimised. The improved performance was dependent on TiO2 concentration as well as electrophoresis voltage and time. The prepared sensor, under optimised conditions, displayed a detection limit of 0.0073 U/μl for LDH.

  14. Effects of silica nanoparticles on copper nanowire dispersions in aqueous PVA solutions

    NASA Astrophysics Data System (ADS)

    Lee, Seung Hak; Song, Hyeong Yong; Hyun, Kyu

    2016-05-01

    In this study, the effects of adding silica nanoparticles to PVA/CuNW suspensions were investigated rheologically, in particular, by small and large amplitude oscillatory shear (SAOS and LAOS) test. Interesting, the SAOS test showed the complex viscosities of CuNW/silica based PVA matrix were smaller than those of PVA/CuNW without silica. These phenomena show that nano-sized silica affects the dispersion of CuNW in aqueous PVA, which suggests small particles can prevent CuNW aggregation. Nonlinearity (third relative intensity ≡ I 3/1) was calculated from LAOS test results using Fourier Transform rheology (FT-rheology) and nonlinear linear viscoelastic ratio (NLR) value was calculated using the nonlinear parameter Q and complex modulus G*. Nonlinearity ( I 3/1) results showed more CuNW aggregation in PVA/CuNW without silica than in PVA/CuNW with silica. NLR (= [ Q 0( ϕ)/ Q 0(0)]/[ G*( ϕ)/ G*(0)]) results revealed an optimum concentration ratio of silica to CuNW to achieve a well-dispersed state. Degree of dispersion was assessed through the simple optical method. SAOS and LAOS test, and dried film morphologies showed nano-sized silica can improve CuNW dispersion in aqueous PVA solutions.

  15. Aggregate morphology of nano-TiO2: role of primary particle size, solution chemistry, and organic matter.

    PubMed

    Chowdhury, Indranil; Walker, Sharon L; Mylon, Steven E

    2013-01-01

    A systematic investigation was conducted to understand the role of aquatic conditions on the aggregate morphology of nano-TiO2, and the subsequent impact on their fate in the environment. In this study, three distinctly sized TiO2 nanoparticles (6, 13, and 23 nm) that had been synthesized with flame spray pyrolysis were employed. Nanoparticle aggregate morphology was measured using static light scattering (SLS) over a wide range of solution chemistry, and in the presence of natural organic matter (NOM). Results showed that primary nanoparticle size can significantly affect the fractal dimension of stable aggregates. A linear relationship was observed between surface areas of primary nanoparticles and fractal dimension indicating that smaller primary nanoparticles can form more compact aggregate in the aquatic environment. The pH, ionic strength, and ion valence also influenced the aggregate morphology of TNPs. Increased pH resulted a decrease in fractal dimension, whereas higher ionic strength resulted increased fractal dimension particularly for monovalent ions. When NOM was present, aggregate fractal dimension was also affected, which was also notably dependent on solution chemistry. Fractal dimension of aggregate increase for 6 nm system in the presence of NOM, whereas a drop in fractal dimension was observed for 13 nm and 23 nm aggregates. This effect was most profound for aggregates comprised of the smallest primary particles suggesting that interactions of NOM with smaller primary nanoparticles are more significant than those with larger ones. The findings from this study will be helpful for the prediction of nanoparticle aggregate fate in the aquatic environment. PMID:24592445

  16. Performance improvement of lithium manganese phosphate by controllable morphology tailoring with acid-engaged nano engineering.

    PubMed

    Guo, Hui; Wu, Chunyang; Liao, Longhuan; Xie, Jian; Zhang, Shichao; Zhu, Peiyi; Cao, Gaoshao; Zhao, Xinbing

    2015-01-20

    Olivine-type lithium manganese phosphate (LiMnPO4) has been considered as a promising cathode for next-generation Li-ion batteries. Preparation of high-performance LiMnPO4 still remains a great challenge because of its intrinsically low Li-ion/electronic conductivity. In this work, significant performance enhancement of LiMnPO4 has been realized by a controllable acid-engaged morphology tailoring from large spindles into small plates. We find that acidity plays a critical role in altering the morphology of the LiMnPO4 crystals. We also find that size decrease and plate-like morphology are beneficial for the performance improvement of LiMnPO4. Among the plate-like samples, the one with the smallest size shows the best electrochemical performance. After carbon coating, it can deliver high discharge capacities of 104.0 mAh g(-1) at 10 C and 85.0 mAh g(-1) at 20 C. After 200 cycles at 1 C, it can still maintain a high discharge capacity of 106.4 mAh g(-1), showing attractive applications in high-power and high-energy Li-ion batteries.

  17. The filler-rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties.

    PubMed

    Tadiello, L; D'Arienzo, M; Di Credico, B; Hanel, T; Matejka, L; Mauri, M; Morazzoni, F; Simonutti, R; Spirkova, M; Scotti, R

    2015-05-28

    Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber. PMID:25899456

  18. Ball milling synthesis of silica nanoparticle from rice husk ash for drug delivery application.

    PubMed

    Salavati-Niasari, Masoud; Javidi, Jaber; Dadkhah, Mahnaz

    2013-07-01

    Silica nanoparticles were synthesized from rice husk ash at room temperature by using high energy planetary ball mill. The milling time and mill rotational speed were varied in four levels. The morphology of the synthesized powders was investigated by the FE-SEM and TEM image as well as XRD patterns. The results have revealed that the nano-sized amorphous silica particles are formed after about 6 h ball milling and they are spherical in shape. The average particle size of the silica powders is found to be around 70 nm which decreases with increasing ball milling time or mill rotational speed. The as-synthesized silica nanoparticles were subsequently employed as drug carrier to investigate in vitro release behavior of Penicillin-G in simulated body fluid. UV-Vis spectroscopy was used to determine the amount of Penicillin-G released from the carrier. Penicillin-G release profile from silica nanoparticles exhibited a delayed release effect. PMID:22931308

  19. From nano to micro: topographical scale and its impact on cell adhesion, morphology and contact guidance

    NASA Astrophysics Data System (ADS)

    Nguyen, Anh Tuan; Sathe, Sharvari R.; Yim, Evelyn K. F.

    2016-05-01

    Topography, among other physical factors such as substrate stiffness and extracellular forces, is known to have a great influence on cell behaviours. Optimization of topographical features, in particular topographical dimensions ranging from nanoscale to microscale, is the key strategy to obtain the best cellular performance for various applications in tissue engineering and regenerative medicine. In this review, we provide a comprehensive survey on the significance of sizes of topography and their impacts on cell adhesion, morphology and alignment, and neurite guidance. Also recent works mimicking the hierarchical structure of natural extracellular matrix by combining both nanoscale and microscale topographies are highlighted.

  20. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles.

    PubMed

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-12-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.

  1. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles.

    PubMed

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-12-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation. PMID:27206644

  2. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles

    NASA Astrophysics Data System (ADS)

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-05-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.

  3. Morphology of Nano and Micro Fiber Structures in Ultrafine Particles Filtration

    NASA Astrophysics Data System (ADS)

    Kimmer, Dusan; Vincent, Ivo; Fenyk, Jan; Petras, David; Zatloukal, Martin; Sambaer, Wannes; Zdimal, Vladimir

    2011-07-01

    Selected procedures permitting to prepare homogeneous nanofibre structures of the desired morphology by employing a suitable combination of variables during the electrospinning process are presented. A comparison (at the same pressure drop) was made of filtration capabilities of planar polyurethane nanostructures formed exclusively by nanofibres, space polycarbonate nanostructures having bead spacers, structures formed by a combination of polymethyl methacrylate micro- and nanofibres and polypropylene meltblown microstructures, through which ultrafine particles of ammonium sulphate 20-400 nm in size were filtered. The structures studied were described using a new digital image analysis technique based on black and white images obtained by scanning electron microscopy. More voluminous structures modified with distance microspheres and having a greater thickness and mass per square area of the material, i.e. structures possessing better mechanical properties, demanded so much in nanostructures, enable preparation of filters having approximately the same free volume fraction as flat nanofibre filters but an increased effective fibre surface area, changed pore size morphology and, consequently, a higher filter quality.

  4. Morphology of Nano and Micro Fiber Structures in Ultrafine Particles Filtration

    SciTech Connect

    Kimmer, Dusan; Vincent, Ivo; Fenyk, Jan; Petras, David; Zatloukal, Martin; Sambaer, Wannes; Zdimal, Vladimir

    2011-07-15

    Selected procedures permitting to prepare homogeneous nanofibre structures of the desired morphology by employing a suitable combination of variables during the electrospinning process are presented. A comparison (at the same pressure drop) was made of filtration capabilities of planar polyurethane nanostructures formed exclusively by nanofibres, space polycarbonate nanostructures having bead spacers, structures formed by a combination of polymethyl methacrylate micro- and nanofibres and polypropylene meltblown microstructures, through which ultrafine particles of ammonium sulphate 20-400 nm in size were filtered. The structures studied were described using a new digital image analysis technique based on black and white images obtained by scanning electron microscopy. More voluminous structures modified with distance microspheres and having a greater thickness and mass per square area of the material, i.e. structures possessing better mechanical properties, demanded so much in nanostructures, enable preparation of filters having approximately the same free volume fraction as flat nanofibre filters but an increased effective fibre surface area, changed pore size morphology and, consequently, a higher filter quality.

  5. Plasma enhanced chemical vapour deposition of silica onto Ti: Analysis of surface chemistry, morphology and functional hydroxyl groups

    PubMed Central

    Szili, Endre J.; Kumar, Sunil; Smart, Roger St. C.; Lowe, Rachel; Saiz, Eduardo; Voelcker, Nicolas H.

    2009-01-01

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO2, showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups. PMID:19809536

  6. Morphology-controlled synthesis of Ag{sub 3}PO{sub 4} nano/microcrystals and their antibacterial properties

    SciTech Connect

    Wu, Aiping; Tian, Chungui; Chang, Wei; Hong, Yu; Zhang, Qi; Qu, Yang; Fu, Honggang

    2013-09-01

    Graphical abstract: The Ag{sub 3}PO{sub 4} with rhombic dodecahedral, spherical and small size particles were controllable fabricated just by changing the types of the solvent. The materials possess good antibacterial properties toward different kinds of bacteria. - Highlights: • The Ag{sub 3}PO{sub 4} with three morphologies were controllable fabricated. • The Ag{sub 3}PO{sub 4} as-prepared possess obvious antibacterial properties in the dark. • The antibacterial ability of Ag{sub 3}PO{sub 4} could be greatly improved under the visible light irradiation. - Abstract: We reported the controllable fabrication of Ag{sub 3}PO{sub 4} nano/microcrystals through a simple solution-based precipitation reaction. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and infrared spectroscopy. The results indicated that the Ag{sub 3}PO{sub 4} crystals with three different morphology, including the rhombic dodecahedron of 500 nm, the sphere of 100 nm and the particles with small-size of 20 nm, could be obtained in the solvents of water, ethylene glycol (EG) and dimethyl sulfoxide (DMSO). The antibacterial assay showed that all samples possess obvious antibacterial properties. In addition, the Ag{sub 3}PO{sub 4} with small size of 20 nm showed better activity due to their high specific surface areas. Notably, we have found that the antibacterial ability of Ag{sub 3}PO{sub 4} could be greatly improved under the visible light irradiation, which are superior to that in the dark and commercial streptomycin.

  7. Morphological Characterisation of Unstained and Intact Tissue Micro-architecture by X-ray Computed Micro- and Nano-Tomography

    PubMed Central

    Walton, Lucy A.; Bradley, Robert S.; Withers, Philip J.; Newton, Victoria L.; Watson, Rachel E. B.; Austin, Clare; Sherratt, Michael J.

    2015-01-01

    Characterisation and quantification of tissue structures is limited by sectioning-induced artefacts and by the difficulties of visualising and segmenting 3D volumes. Here we demonstrate that, even in the absence of X-ray contrast agents, X-ray computed microtomography (microCT) and nanotomography (nanoCT) can circumvent these problems by rapidly resolving compositionally discrete 3D tissue regions (such as the collagen-rich adventitia and elastin-rich lamellae in intact rat arteries) which in turn can be segmented due to their different X-ray opacities and morphologies. We then establish, using X-ray tomograms of both unpressurised and pressurised arteries that intra-luminal pressure not only increases lumen cross-sectional area and straightens medial elastic lamellae but also induces profound remodelling of the adventitial layer. Finally we apply microCT to another human organ (skin) to visualise the cell-rich epidermis and extracellular matrix-rich dermis and to show that conventional histological and immunohistochemical staining protocols are compatible with prior X-ray exposure. As a consequence we suggest that microCT could be combined with optical microscopy to characterise the 3D structure and composition of archival paraffin embedded biological materials and of mechanically stressed dynamic tissues such as the heart, lungs and tendons. PMID:25975937

  8. Morphological Characterisation of Unstained and Intact Tissue Micro-architecture by X-ray Computed Micro- and Nano-Tomography.

    PubMed

    Walton, Lucy A; Bradley, Robert S; Withers, Philip J; Newton, Victoria L; Watson, Rachel E B; Austin, Clare; Sherratt, Michael J

    2015-05-15

    Characterisation and quantification of tissue structures is limited by sectioning-induced artefacts and by the difficulties of visualising and segmenting 3D volumes. Here we demonstrate that, even in the absence of X-ray contrast agents, X-ray computed microtomography (microCT) and nanotomography (nanoCT) can circumvent these problems by rapidly resolving compositionally discrete 3D tissue regions (such as the collagen-rich adventitia and elastin-rich lamellae in intact rat arteries) which in turn can be segmented due to their different X-ray opacities and morphologies. We then establish, using X-ray tomograms of both unpressurised and pressurised arteries that intra-luminal pressure not only increases lumen cross-sectional area and straightens medial elastic lamellae but also induces profound remodelling of the adventitial layer. Finally we apply microCT to another human organ (skin) to visualise the cell-rich epidermis and extracellular matrix-rich dermis and to show that conventional histological and immunohistochemical staining protocols are compatible with prior X-ray exposure. As a consequence we suggest that microCT could be combined with optical microscopy to characterise the 3D structure and composition of archival paraffin embedded biological materials and of mechanically stressed dynamic tissues such as the heart, lungs and tendons.

  9. Morphological Characterisation of Unstained and Intact Tissue Micro-architecture by X-ray Computed Micro- and Nano-Tomography.

    PubMed

    Walton, Lucy A; Bradley, Robert S; Withers, Philip J; Newton, Victoria L; Watson, Rachel E B; Austin, Clare; Sherratt, Michael J

    2015-01-01

    Characterisation and quantification of tissue structures is limited by sectioning-induced artefacts and by the difficulties of visualising and segmenting 3D volumes. Here we demonstrate that, even in the absence of X-ray contrast agents, X-ray computed microtomography (microCT) and nanotomography (nanoCT) can circumvent these problems by rapidly resolving compositionally discrete 3D tissue regions (such as the collagen-rich adventitia and elastin-rich lamellae in intact rat arteries) which in turn can be segmented due to their different X-ray opacities and morphologies. We then establish, using X-ray tomograms of both unpressurised and pressurised arteries that intra-luminal pressure not only increases lumen cross-sectional area and straightens medial elastic lamellae but also induces profound remodelling of the adventitial layer. Finally we apply microCT to another human organ (skin) to visualise the cell-rich epidermis and extracellular matrix-rich dermis and to show that conventional histological and immunohistochemical staining protocols are compatible with prior X-ray exposure. As a consequence we suggest that microCT could be combined with optical microscopy to characterise the 3D structure and composition of archival paraffin embedded biological materials and of mechanically stressed dynamic tissues such as the heart, lungs and tendons. PMID:25975937

  10. Morphology evolution, magnetic and microwave absorption properties of nano/submicrometre iron particles obtained at different reduced temperatures

    NASA Astrophysics Data System (ADS)

    Fan, Xi'an; Guan, Jianguo; Wang, Wei; Tong, Guoxiu

    2009-04-01

    Nano/submicrometre iron particles were prepared by a hydrogen reduction method in a fluidized bed furnace using α-FeOOH nanorods as precursors. The effect of the reducing temperature (T) on the microstructure, static magnetic properties, microwave electromagnetic parameters and microwave absorption properties of the resultant iron particles was investigated. When T increases from 450 to 650 °C, the as-obtained iron particles show an obvious morphology evolution from anisotropic nanorods to isotropic submicrometre polyhedra. As a result, the saturation magnetization, the complex permittivity and the real permeability all increase, while the coercivity and the imaginary permeability decrease due to the reducing surface effect and shape anisotropy. Nanocomposites containing 30 wt% iron nanorods obtained at 450 °C show a minimal reflection loss (RL) as low as -36.8 dB at 14.1 GHz and an absorption band with RL under -10 dB from 11.6 to 17.0 GHz when the thickness is 1.5 mm, suggesting that they are promising as a strong absorption, thin and lightweight microwave absorber.

  11. Sintering effects on structure, morphology, and electrical properties of sol-gel synthesized, nano-crystalline erbium oxide

    NASA Astrophysics Data System (ADS)

    Bakhsh, Allah; Maqsood, Asghari

    2012-12-01

    The nano-crystalline erbium oxide powder was synthesized through the sol-gel technique. The effect of sintering temperature from 250°C to 1400°C on structure, morphology, and electrical properties was studied. The results were compared with the microcrystalline erbium oxide purchased from the market. The synthesized erbium oxide showed fiber like nanostructures. Dielectric properties at different sintering temperatures were measured in the frequency range 100 Hz to 5MHz. The synthesized erbium oxide had the highest dielectric constant at 650°C. The behavior of the dissipation factor tan δ for sol-gel synthesized material was distinct from that of the purchased material; it was higher at low frequencies and then decreased with the increase in frequency. The synthesized material sintered at different temperatures exhibited a similar sort of frequency-dependent response for permittivity (ɛ) and resistivity ( ρ). This was in accordance with Koop's theory of dielectrics. For the microcrystalline material, frequency dependence of permittivity and resistivity was not uniform. The results showed that sol-gel synthesized erbium oxide could be a good candidate for high-k applications.

  12. Morphological Characterisation of Unstained and Intact Tissue Micro-architecture by X-ray Computed Micro- and Nano-Tomography

    NASA Astrophysics Data System (ADS)

    Walton, Lucy A.; Bradley, Robert S.; Withers, Philip J.; Newton, Victoria L.; Watson, Rachel E. B.; Austin, Clare; Sherratt, Michael J.

    2015-05-01

    Characterisation and quantification of tissue structures is limited by sectioning-induced artefacts and by the difficulties of visualising and segmenting 3D volumes. Here we demonstrate that, even in the absence of X-ray contrast agents, X-ray computed microtomography (microCT) and nanotomography (nanoCT) can circumvent these problems by rapidly resolving compositionally discrete 3D tissue regions (such as the collagen-rich adventitia and elastin-rich lamellae in intact rat arteries) which in turn can be segmented due to their different X-ray opacities and morphologies. We then establish, using X-ray tomograms of both unpressurised and pressurised arteries that intra-luminal pressure not only increases lumen cross-sectional area and straightens medial elastic lamellae but also induces profound remodelling of the adventitial layer. Finally we apply microCT to another human organ (skin) to visualise the cell-rich epidermis and extracellular matrix-rich dermis and to show that conventional histological and immunohistochemical staining protocols are compatible with prior X-ray exposure. As a consequence we suggest that microCT could be combined with optical microscopy to characterise the 3D structure and composition of archival paraffin embedded biological materials and of mechanically stressed dynamic tissues such as the heart, lungs and tendons.

  13. Silane effects on the surface morphology and abrasion resistance of transparent SiO2/UV-curable resin nano-composites

    NASA Astrophysics Data System (ADS)

    Hsiang, Hsing-I.; Chang, Yu-Lun; Chen, Chi-Yu; Yen, Fu-Su

    2011-02-01

    Transparent ultraviolet curable nano-composite coatings consisting of nano-sized SiO2 and acrylate resin have been developed to improve the abrasion resistance of organic polymers. The nano-sized SiO2 particles were surface-modified using various amounts of 3-methacryloxypropyltrimethoxysilane. The 3-methacryloxypropyltrimethoxysilane concentration effects on the surface morphology and abrasion resistance of the transparent SiO2/ultraviolet-curable resin nano-composites were investigated using scanning electron microscopy, atomic force microscopy, and ultraviolet-visible spectrophotometer. The results showed that as the 3-methacryloxypropyltrimethoxysilane/SiO2 weight ratio increased from 0.2 to 0.6, the dispersion, compatibility and cross-linking density between the 3-methacryloxypropyltrimethoxysilane-modified SiO2 particles and acrylate resin were improved, leading to an increase in abrasion resistance. However, as the 3-methacryloxypropyltrimethoxysilane/SiO2 weight ratio was increased to 1.5, the additional 3-methacryloxypropyltrimethoxysilane may exceed that needed to fill the pores with the probability of SiO2 nano-particles existing on the coating surface was lower than that for samples with a 3-methacryloxypropyltrimethoxysilane/SiO2 weight ratio of 0.6. This produced a decrease in abrasion resistance.

  14. Hydrothermal synthesis and luminescent properties of SrF2 and SrF2:Ln3+ (Ln = Eu, Ce, Tb) nano-assembly with controllable morphology.

    PubMed

    Sun, Yuanping; Jia, Peiyun

    2014-05-01

    SrF2 and SrF2:Ln3+ (Ln = Eu, Ce, Tb) nano-assemblies with controllable size and morphology have been successfully prepared via a facile hydrothermal process. X-ray diffraction, scanning electron microscopy, and photoluminescence spectrum were used to characterize the samples. The experimental results indicate that chelating reagent and acidity play important roles in the formation of micro-crystals with uniform size and peculiar morphology. As-obtained SrF2:Eu3+ and SrF2:Ce3+, SrF2:Tb3+ samples show red, ultraviolet and green emission under the irradiation of ultraviolet.

  15. Transfer of silica-coated magnetic (Fe3O4) nanoparticles through food: a molecular and morphological study in zebrafish.

    PubMed

    Piccinetti, Chiara Carla; Montis, Costanza; Bonini, Massimo; Laurà, Rosaria; Guerrera, Maria Cristina; Radaelli, Giuseppe; Vianello, Fabio; Santinelli, Veronica; Maradonna, Francesca; Nozzi, Valentina; Miccoli, Andrea; Olivotto, Ike

    2014-12-01

    The increasing use of magnetic iron oxide nanoparticles (NPs) in biomedical applications has prompted extensive investigation of their interactions with biological systems also through animal models. A variety of toxic effects have been detected in NP-exposed fish and fish embryos, including oxidative stress and associated changes, such as lipid oxidation, apoptosis, and gene expression alterations. The main exposure route for fish is through food and the food web. This study was devised to investigate the effects of silica-coated NP administration through food in zebrafish (ZF, Danio rerio). Silica-coated magnetic NPs were administered to ZF through feed (zooplankton) from day 1 to 15 posthatching (ph). Larvae were examined 6 and 15 days ph and adults 3 and 6 months ph. A multidisciplinary approach, including morphometric examination; light, transmission electron, and confocal microscopy; inductively coupled plasma emission spectrometry; and real-time polymerase chain reaction, was applied to detect NP accumulation, structural and ultrastructural damage, and activation of detoxification processes in larvae and adults. Our findings document that the silica-coated NPs: (1) do not induce toxicity in ZF, (2) are excreted through feces, and (3) do not activate detoxification processes or promote tissue/cell injury.

  16. A multifunctional role of trialkylbenzenes for the preparation of aqueous colloidal mesostructured/mesoporous silica nanoparticles with controlled pore size, particle diameter, and morphology

    NASA Astrophysics Data System (ADS)

    Yamada, Hironori; Ujiie, Hiroto; Urata, Chihiro; Yamamoto, Eisuke; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2015-11-01

    Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size and higher hydrophobicity of TIPB than TMB induce the incorporation of TIPB into micelles without the structural change. When TMB was used as TAB, the pore size of CMSS was also enlarged while the mesostructure and particle morphology were varied. Interestingly, when tetramethoxysilane and TIPB were used, CMSS with a very small particle diameter (20 nm) with concave surfaces and large mesopores were obtained, which may strongly be related to the initial nucleation of CMSS. A judicious choice of TAB and Si sources is quite important to control the mesostructure, size of mesopores, particle diameter, and morphology.Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size

  17. A study on the tensile properties of silicone rubber/polypropylene fibers/silica hybrid nanocomposites.

    PubMed

    Ziraki, Sahar; Zebarjad, Seyed Mojtaba; Hadianfard, Mohammad Jafar

    2016-04-01

    Metacarpophalangeal joint implants have been usually made of silicone rubber. In the current study, silica nano particles and polypropylene fibers were added to silicone rubber to improve silicone properties. The effect of the addition of silica nano particles and polypropylene fibers on the tensile behavior of the resultant composites were investigated. Composite samples with different content of PP fibers and Silica nano particles (i. e. 0, 1 and 2wt%) as well as the hybrid composite of silicone rubber with 1wt% SiO2 and 1wt% PP fiber were prepared. Tensile tests were done at constant cross head speed. To study the body fluid effect on the mechanical properties of silicone rubber composites, samples soaked in simulated body fluid (SBF) at 37°C were also tested. The morphology of the samples were studied by scanning electron microscope. Results of analysis revealed that an increase in PP fibers and silica nano particles content to 2wt%, increases the tensile strength of silicone rubber of about 75% and 42% respectively. It was found out that the strength of the samples decreases after being soaked in simulated body fluid, though composites with PP fibers as the reinforcement showed less property degradation. PMID:26874087

  18. Synthesis of manganese incorporated hierarchical mesoporous silica nanosphere with fibrous morphology by facile one-pot approach for efficient catalytic ozonation.

    PubMed

    Afzal, Shahzad; Quan, Xie; Chen, Shuo; Wang, Jing; Muhammad, Dost

    2016-11-15

    Manganese incorporated fibrous silica nanosphere (MnOx-0.013/KCC-1) was synthesized by one step hydrothermal method for the first time and its catalytic activity for ozonation of oxalic acid was studied. For comparison, manganese loaded MCM-41 (MnOx-0.013/MCM-41) was prepared by impregnation method. Various characterizations showed that the morphological, structural and textural properties of MnOx-0.013/KCC-1 were well preserved. Ozonation and catalytic ozonation by MnOx-0.013/KCC-1 and MnOx-0.013/MCM-41 led to 4, 85 and 60% reduction in TOC respectively. Furthermore, 0.05 and 1.2mgL(-1) leaching of Mn was detected from MnOx-0.013/KCC-1 and MnOx-0.013/MCM-41, which are approximately 2.0 and 42.0% of the total Mn present in MnOx-0.013/KCC-1 and MnOx-0.013/MCM-41 respectively. The high catalytic activity was attributed to the generation of hydroxyl radical. Surface hydroxyl groups investigated by using phosphates and ATR-FTIR were believed to be the active sites. Our proposed method of synthesis can be generalized for the synthesis of other metal oxides incorporated fibrous silica for environmental catalysis and other catalytic reactions.

  19. Synthesis of manganese incorporated hierarchical mesoporous silica nanosphere with fibrous morphology by facile one-pot approach for efficient catalytic ozonation.

    PubMed

    Afzal, Shahzad; Quan, Xie; Chen, Shuo; Wang, Jing; Muhammad, Dost

    2016-11-15

    Manganese incorporated fibrous silica nanosphere (MnOx-0.013/KCC-1) was synthesized by one step hydrothermal method for the first time and its catalytic activity for ozonation of oxalic acid was studied. For comparison, manganese loaded MCM-41 (MnOx-0.013/MCM-41) was prepared by impregnation method. Various characterizations showed that the morphological, structural and textural properties of MnOx-0.013/KCC-1 were well preserved. Ozonation and catalytic ozonation by MnOx-0.013/KCC-1 and MnOx-0.013/MCM-41 led to 4, 85 and 60% reduction in TOC respectively. Furthermore, 0.05 and 1.2mgL(-1) leaching of Mn was detected from MnOx-0.013/KCC-1 and MnOx-0.013/MCM-41, which are approximately 2.0 and 42.0% of the total Mn present in MnOx-0.013/KCC-1 and MnOx-0.013/MCM-41 respectively. The high catalytic activity was attributed to the generation of hydroxyl radical. Surface hydroxyl groups investigated by using phosphates and ATR-FTIR were believed to be the active sites. Our proposed method of synthesis can be generalized for the synthesis of other metal oxides incorporated fibrous silica for environmental catalysis and other catalytic reactions. PMID:27434734

  20. 3D Non-destructive morphological analysis of a solid oxide fuel cell anode using full-field X-ray nano-tomography

    NASA Astrophysics Data System (ADS)

    Karen Chen-Wiegart, Yu-chen; Cronin, J. Scott; Yuan, Qingxi; Yakal-Kremski, Kyle J.; Barnett, Scott A.; Wang, Jun

    2012-11-01

    An accurate 3D morphological analysis is critically needed to study the process-structure-property relationship in many application fields such as battery electrodes, fuel cells and porous materials for sensing and actuating. Here we present the application of a newly developed full field X-ray nano-scale transmission microscopy (TXM) imaging for a non-destructive, comprehensive 3D morphology analysis of a porous Ni-YSZ solid oxide fuel cell anode. A unique combination of improved 3D resolution and large analyzed volume (˜3600 μm3) yields structural data with excellent statistical accuracy. 3D morphological parameters quantified include phase volume fractions, surface and interfacial area densities, phase size distribution, directional connectivity, tortuosity, and electrochemically active triple phase boundary density. A prediction of electrochemical anode polarization resistance based on this microstructural data yielded good agreement with a measured anode resistance via electrochemical impedance spectroscopy. The Mclachlan model is used to estimate the anode electrical conductivity.

  1. Surface modification of nano-silica on the ligament advanced reinforcement system for accelerated bone formation: primary human osteoblasts testing in vitro and animal testing in vivo.

    PubMed

    Li, Mengmeng; Wang, Shiwen; Jiang, Jia; Sun, Jiashu; Li, Yuzhuo; Huang, Deyong; Long, Yun-Ze; Zheng, Wenfu; Chen, Shiyi; Jiang, Xingyu

    2015-05-01

    The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ∼21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction.

  2. Surface modification of nano-silica on the ligament advanced reinforcement system for accelerated bone formation: primary human osteoblasts testing in vitro and animal testing in vivo

    NASA Astrophysics Data System (ADS)

    Li, Mengmeng; Wang, Shiwen; Jiang, Jia; Sun, Jiashu; Li, Yuzhuo; Huang, Deyong; Long, Yun-Ze; Zheng, Wenfu; Chen, Shiyi; Jiang, Xingyu

    2015-04-01

    The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ~21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction.The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ~21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01439e

  3. Photoinduced charge generation rates in soluble P3HT : PCBM nano-aggregates predict the solvent-dependent film morphology.

    PubMed

    Roy, Palas; Jha, Ajay; Dasgupta, Jyotishman

    2016-02-01

    The device efficiency of bulk heterojunction (BHJ) solar cells is critically dependent on the nano-morphology of the solution-processed polymer : fullerene blend. Active control on blend morphology can only emanate from a detailed understanding of solution structures during the film casting process. Here we use photoinduced charge transfer (CT) rates to probe the effective length scale of the pre-formed solution structures and their energy disorder arising from a mixture of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in three different organic solvents. The observed solvent-dependent ultrafast biphasic rise of the transient polaron state in solution along with changes detected in the C=C stretching frequency of bound PCBM provides direct evidence for film-like P3HT : PCBM interfaces in solution. Using the diffusive component of the charge transfer rate, we deduce ∼3-times larger functional nano-domain size in toluene than in chlorobenzene thereby correctly predicting the relative polymer nanofiber widths observed in annealed films. We thus provide first experimental evidence for the postulated polymer : fullerene : solvent ternary phase that seeds the eventual morphology in spin-cast films. Our work motivates the design of new chemical additives to tune the grain size of the evolving polymer : fullerene domains within the solution phase. PMID:26763690

  4. Addition of P3HT-grafted Silica nanoparticles improves bulk-heterojunction morphology in P3HT-PCBM blends

    PubMed Central

    Garg, Mohit; Padmanabhan, Venkat

    2016-01-01

    We present molecular dynamics simulations of a ternary blend of P3HT, PCBM and P3HT-grafted silica nanoparticles (SiNP) for applications in polymer-based solar cells. Using coarse-grained models, we study the effect of SiNP on the spatial arrangement of PCBM in P3HT. Our results suggest that addition of SiNP not only alters the morphology of PCBM clusters but also improves the crystallinity of P3HT. We exploit the property of grafted SiNP to self-assemble into a variety of anisotropic structures and the tendency of PCBM to preferentially adhere to SiNP surface, due to favorable interactions, to achieve morphologies with desirable characteristics for the active layer, including domain size, crystallinity of P3HT, and elimination of isolated islands of PCBM. As the concentration of SiNP increases, the number of isolated PCBM molecules decreases, which in turn improves the crystallinity of P3HT domains. We also observe that by tuning the grafting parameters of SiNP, it is possible to achieve structures ranging from cylindrical to sheets to highly interconnected network of strings. The changes brought about by addition of SiNP shows a promising potential to improve the performance of these materials when used as active layers in organic photovoltaics. PMID:27628895

  5. Addition of P3HT-grafted Silica nanoparticles improves bulk-heterojunction morphology in P3HT-PCBM blends

    NASA Astrophysics Data System (ADS)

    Garg, Mohit; Padmanabhan, Venkat

    2016-09-01

    We present molecular dynamics simulations of a ternary blend of P3HT, PCBM and P3HT-grafted silica nanoparticles (SiNP) for applications in polymer-based solar cells. Using coarse-grained models, we study the effect of SiNP on the spatial arrangement of PCBM in P3HT. Our results suggest that addition of SiNP not only alters the morphology of PCBM clusters but also improves the crystallinity of P3HT. We exploit the property of grafted SiNP to self-assemble into a variety of anisotropic structures and the tendency of PCBM to preferentially adhere to SiNP surface, due to favorable interactions, to achieve morphologies with desirable characteristics for the active layer, including domain size, crystallinity of P3HT, and elimination of isolated islands of PCBM. As the concentration of SiNP increases, the number of isolated PCBM molecules decreases, which in turn improves the crystallinity of P3HT domains. We also observe that by tuning the grafting parameters of SiNP, it is possible to achieve structures ranging from cylindrical to sheets to highly interconnected network of strings. The changes brought about by addition of SiNP shows a promising potential to improve the performance of these materials when used as active layers in organic photovoltaics.

  6. Addition of P3HT-grafted Silica nanoparticles improves bulk-heterojunction morphology in P3HT-PCBM blends.

    PubMed

    Garg, Mohit; Padmanabhan, Venkat

    2016-01-01

    We present molecular dynamics simulations of a ternary blend of P3HT, PCBM and P3HT-grafted silica nanoparticles (SiNP) for applications in polymer-based solar cells. Using coarse-grained models, we study the effect of SiNP on the spatial arrangement of PCBM in P3HT. Our results suggest that addition of SiNP not only alters the morphology of PCBM clusters but also improves the crystallinity of P3HT. We exploit the property of grafted SiNP to self-assemble into a variety of anisotropic structures and the tendency of PCBM to preferentially adhere to SiNP surface, due to favorable interactions, to achieve morphologies with desirable characteristics for the active layer, including domain size, crystallinity of P3HT, and elimination of isolated islands of PCBM. As the concentration of SiNP increases, the number of isolated PCBM molecules decreases, which in turn improves the crystallinity of P3HT domains. We also observe that by tuning the grafting parameters of SiNP, it is possible to achieve structures ranging from cylindrical to sheets to highly interconnected network of strings. The changes brought about by addition of SiNP shows a promising potential to improve the performance of these materials when used as active layers in organic photovoltaics. PMID:27628895

  7. Core-shell-structured silica/polyacrylate particles prepared by Pickering emulsion: influence of the nucleation model on particle interfacial organization and emulsion stability

    PubMed Central

    2014-01-01

    This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO2 composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO2 composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles. PMID:25313299

  8. Morphology of ejected debris from laser super-heated fused silica following exit surface laser-induced damage

    NASA Astrophysics Data System (ADS)

    Demos, Stavros G.; Negres, Raluca A.; Raman, Rajesh N.; Feit, Michael D.; Manes, Kenneth R.; Rubenchik, Alexander M.

    2015-11-01

    Laser induced damage (breakdown) initiated on the exit surface of transparent dielectric materials using nanosecond pulses creates a volume of superheated material reaching localized temperatures on the order of 1 eV and pressures on the order of 10 GPa or larger. This leads to material ejection and the formation of a crater. The volume of this superheated material depends largely on the laser parameters such as fluence and pulse duration. To elucidate the material behaviors involved, we examined the morphologies of the ejected superheated material particles and found distinctive morphologies. We hypothesize that these morphologies arise from the difference in the structure and physical properties (such as the dynamic viscosity and presence of instabilities) of the superheated material at the time of ejection of each individual particle. Some of the ejected particles are on the order of 1 µm in diameter and appear as "droplets". Another subgroup appears to have stretched, foam-like structure that can be described as material globules interconnected via smaller in diameter columns. Such particles often contain nanometer size fibers attached on their surface. In other cases, only the globules have been preserved suggesting that they may be associated with a collapsed foam structure under the dynamic pressure as it traverses in air. These distinct features originate in the structure of the superheated material during volume boiling just prior to the ejection of the particles.

  9. STEM characterization on silica nanowires with new mesopore structures by space-confined self-assembly within nano-scale channels

    SciTech Connect

    Lai, Peng; Hu, Michael Z.; Shi, Donglu; Blom, Douglas Allen

    2008-01-01

    Critical channel diameters were found (below which space confinement takes effect, leading to more uniform and ordered mesopore structures) in the study of evaporation-induced coassembly of triblock-copolymer (P123) and silica molecular precursors (TEOS, tetraethyl orthosilicate) by employing channels in anodized aluminum oxide (AAO, 13 200 nm channel diameter) and in track-etched polycarbonate (EPC, 10 80 nm channel diameter) and for the first time we have observed a new mesopore structure (i.e., packed hollow spheres) in silica nanowires formed in AAO channels with diameters from 30 to 80 nm.

  10. SIZE AND DENSITY ESTIMATION FROM IMPACT TRACK MORPHOLOGY IN SILICA AEROGEL: APPLICATION TO DUST FROM COMET 81P/WILD 2

    SciTech Connect

    Niimi, Rei; Tsuchiyama, Akira; Kadono, Toshihiko; Okudaira, Kyoko; Hasegawa, Sunao; Tabata, Makoto; Watanabe, Takayuki; Yagishita, Masahito; Machii, Nagisa; Nakamura, Akiko M.; Uesugi, Kentaro; Takeuchi, Akihisa; Nakano, Tsukasa

    2012-01-01

    A large number of cometary dust particles were captured with low-density silica aerogel during the NASA Stardust mission. The dust particles penetrated into the aerogel and formed various track shapes. To estimate the properties of the dust particles, such as density and size, based on the morphology of the tracks, we carried out systematic experiments testing impacts into low-density aerogel at 6 km s{sup -1} using projectiles of various sizes and densities. We found that the maximum track diameter and the ratio of the track length to the maximum track diameter in aerogel are good indicators of projectile size and density, respectively. Based on these results, we estimated the size and density of individual dust particles from comet 81P/Wild 2. The average density of the 'fluffy' dust particles and the bulk density of all dust particles were obtained as 0.35 {+-} 0.07 and 0.49 {+-} 0.18 g cm{sup -3}, respectively. These statistical data provided the content of monolithic and coarse grains in the Stardust particles, {approx}30 wt%. Combining this result with some mid-infrared observational data, we found that the content of crystalline silicates is {approx}50 wt% or more of non-volatile material.

  11. The structure, morphology, and the metal-enhanced fluorescence of nano-Ag/ZnO core-shell structure

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Ding, Yanli; Peng, Xiang; Zhou, Mingtao; Liang, Xiaoyan; Min, Jiahua; Wang, Linjun; Shi, Weimin

    2014-09-01

    Nano-polyc rystalline silver (Ag) particles with the diameter of 60 nm were synthesized by the reducing agent sodium citrate. An amorphous zinc oxide (ZnO) shell layer was then coated on the surface of silver particles using wet chemical method. The Ag/ZnO core-shell structure was characterized by scanning electron microscope, transmission electron microscopy, ultraviolet-visible spectroscopy and fluorescence (FL) measurement. The results showed that nano-Ag/ZnO core-shell particles with an average diameter of ~100 nm were prepared successfully, and the FL intensity of Rhodamine 6G (R6G) mixed with Ag/ZnO nanoparticle was 53 % greater than that of the same amount of R6G without any nanoparticles, which may be related to the effect of surface plasmon resonance.

  12. The structure, morphology, and the metal-enhanced fluorescence of nano-Ag/ZnO core-shell structure

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Ding, Yanli; Peng, Xiang; Zhou, Mingtao; Liang, Xiaoyan; Min, Jiahua; Wang, Linjun; Shi, Weimin

    2015-06-01

    Nano-polyc rystalline silver (Ag) particles with the diameter of 60 nm were synthesized by the reducing agent sodium citrate. An amorphous zinc oxide (ZnO) shell layer was then coated on the surface of silver particles using wet chemical method. The Ag/ZnO core-shell structure was characterized by scanning electron microscope, transmission electron microscopy, ultraviolet-visible spectroscopy and fluorescence (FL) measurement. The results showed that nano-Ag/ZnO core-shell particles with an average diameter of ~100 nm were prepared successfully, and the FL intensity of Rhodamine 6G (R6G) mixed with Ag/ZnO nanoparticle was 53 % greater than that of the same amount of R6G without any nanoparticles, which may be related to the effect of surface plasmon resonance.

  13. Effect of molecular weight of poly(epsilon-caprolactone) on interpenetrating network structure, apatite-forming ability, and degradability of poly(epsilon-caprolactone)/silica nano-hybrid materials.

    PubMed

    Rhee, Sang-Hoon

    2003-05-01

    The effect of molecular weight of poly(epsilon-caprolactone) (PCL) on the bioactivity of a PCL/silica nano-hybrid containing calcium salt was investigated. Two hybrids were prepared with low and high molecular weight PCLs, respectively, through a sol-gel method. Their bioactivities were evaluated using a simulated body fluid (SBF), which had almost the same ion concentrations with human blood plasma. Fast and uniform nucleation and growth of the apatite crystals were observed to occur all through the hybrid surface when low molecular weight PCL was used, while slow and random nucleation and growth of the apatite crystals were observed to occur when high molecular weight PCL was used, after soaking for 3 days in the SBF. This phenomenon was explained in terms of the distribution and dispersion of silica phase in the hybrid and the ionic activity product of the apatite in the SBF, which were dependent on the free volume and degradation rate of non-bioactive PCL phase, respectively.

  14. Microwave-assisted combustion synthesis of nano iron oxide/iron-coated activated carbon, anthracite, cellulose fiber, and silica, with arsenic adsorption studies

    EPA Science Inventory

    Combustion synthesis of iron oxide/iron coated carbons such as activated carbon, anthracite, cellulose fiber and silica is described. The reactions were carried out in alumina crucibles using a Panasonic kitchen microwave with inverter technology, and the reaction process was com...

  15. Morphology Controllable Synthesis of ScF3:Er3+, Yb3+ Nano/Sub-Microncrystals by Hydrothermal/Solvothermal Process.

    PubMed

    Han, Lili; Li, Hua; Ci, Zhipeng; Wang, Yuhua

    2016-04-01

    In this paper, red phosphors Yb3+-Er3+ co-doped ScF3 nano/microcrystals were successfully prepared by a facile hydrothermal/solvothermal route using the sodium dodecyl benzene sulfonate (SDBS) as the surfactant. The structure, morphologies and up-conversion (UC) photoluminescence properties of the as-prepared products were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectra, respectively. The SEM images show that the obtained samples are the uniform cubic and cuboid crystals. With the increase of the surfactant SDBS or the change in the solvent types, the sample change their size from nanometer to submicron. Upon the 980 nm laser diode excitation, the ScF3:Era+, Yb3+ nanocrystals exhibit red emission which can be assigned to the characteristic 4F9/2/4I15/2 transition of Er3+. In order to understand the emission mechanisms of ScF3:ErS+, Yb3+ nanocrystals, the dependence of UC luminescence intensity on the 980 nm excitation power was measured, suggesting that the UC phenomenon results from a two-photon process. Meanwhile, the emission intensities of the YbS+-Er3+ codoped ScF3 nano/sub-micro crystals with different solution composition show an obvious change under the 980 nm laser excitation. Therefore, the phosphors Yb3+-Er3+ co-doped ScF3 possibly have a potential application in the biological applications.

  16. Morphology Controllable Synthesis of ScF3:Er3+, Yb3+ Nano/Sub-Microncrystals by Hydrothermal/Solvothermal Process.

    PubMed

    Han, Lili; Li, Hua; Ci, Zhipeng; Wang, Yuhua

    2016-04-01

    In this paper, red phosphors Yb3+-Er3+ co-doped ScF3 nano/microcrystals were successfully prepared by a facile hydrothermal/solvothermal route using the sodium dodecyl benzene sulfonate (SDBS) as the surfactant. The structure, morphologies and up-conversion (UC) photoluminescence properties of the as-prepared products were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectra, respectively. The SEM images show that the obtained samples are the uniform cubic and cuboid crystals. With the increase of the surfactant SDBS or the change in the solvent types, the sample change their size from nanometer to submicron. Upon the 980 nm laser diode excitation, the ScF3:Era+, Yb3+ nanocrystals exhibit red emission which can be assigned to the characteristic 4F9/2/4I15/2 transition of Er3+. In order to understand the emission mechanisms of ScF3:ErS+, Yb3+ nanocrystals, the dependence of UC luminescence intensity on the 980 nm excitation power was measured, suggesting that the UC phenomenon results from a two-photon process. Meanwhile, the emission intensities of the YbS+-Er3+ codoped ScF3 nano/sub-micro crystals with different solution composition show an obvious change under the 980 nm laser excitation. Therefore, the phosphors Yb3+-Er3+ co-doped ScF3 possibly have a potential application in the biological applications. PMID:27451694

  17. Solvothermal synthesis and tunable luminescence of Tb{sup 3+}, Eu{sup 3+} codoped YF{sub 3} nano- and micro-crystals with uniform morphologies

    SciTech Connect

    Tian, Yue; Chen, Baojiu; Li, Xiangping; Zhang, Jinsu; Tian, Bining; Sun, Jiashi; Cheng, Lihong; Zhong, Haiyang; Zhong, Hua; Hua, Ruinian

    2012-12-15

    Tb{sup 3+}, Eu{sup 3+} codoped YF{sub 3} nano- and micro-crystals with the morphologies of ellipsoid-like nanoplate, spindle, sandwich-structural rhombus and nanoaggregate were synthesized through a solvothermal method. The morphologies of the prepared products can be tailored by controlling the volume ratio of ethylene glycol (EG) to H{sub 2}O, solvent type or the reaction time. A possible formation mechanism of the sandwich-structural rhombus like YF{sub 3} phosphor was proposed. The emitting colors of YF{sub 3}:Tb{sup 3+},Eu{sup 3+} phosphors can be easily tuned from yellowish green, yellow to orange by increasing Eu{sup 3+} concentration. The energy transfer from Tb{sup 3+} to Eu{sup 3+} in YF{sub 3} phosphors was studied. It was found that the interaction type between Tb{sup 3+} and Eu{sup 3+} is electric dipole-dipole interaction. - Graphical abstract: Sandwich-structural rhombus like YF{sub 3}:Tb{sup 3+}, Eu{sup 3+} phosphors were synthesized through a solvothermal process. The formation mechanism of the sandwich-structural rhombus like YF{sub 3}:Tb{sup 3+}, Eu{sup 3+} phosphors was studied. Highlights: Black-Right-Pointing-Pointer YF{sub 3} nano- and micro-crystals were synthesized through solvothermal route. Black-Right-Pointing-Pointer A formation mechanism of the sandwich-structural rhombus like YF{sub 3} was proposed. Black-Right-Pointing-Pointer The emitting colors of YF{sub 3}:Tb{sup 3+},Eu{sup 3+} phosphors can be tuned. Black-Right-Pointing-Pointer Energy transfer from Tb{sup 3+} to Eu{sup 3+} is confirmed as electric dipole-dipole interaction.

  18. Nano-Ag complexes prepared by γ-radiolysis and their structures and physical properties

    NASA Astrophysics Data System (ADS)

    Kim, Hwa-Jung; Choi, Seong-Ho; Park, Hae-Jun

    2012-10-01

    In this study, nano-silver (nano-Ag) complexes showing different properties have been synthesized as follows. Polypyrrolidone (PVP)-stabilized silver colloids (NAg), nano-Ag bound to silica (SiO2) (NSS), and nano-Ag bound to a complex of SiO2 and polyaniline (PANI) (NSSPAI) were prepared via γ-irradiation at room temperature. NAg and NSS used PVP as a colloidal stabilizer, while NSSPAI did not use PVP as a colloidal stabilizer. Interesting bonding properties occurred in the nano-Ag complex and anticipated structural changes were clearly shown through a surface analysis of x-ray photoelectron spectroscopy (XPS). The morphologies by field emission-scanning electron microscopy (FE-SEM) analysis showed that nano-Ag complexes have various particle sizes ranging from 10 to 30 nm. NSS (average, 10 nm) and NSSPAI (average, 30 nm) showed a uniformly spherical shape and size, while NAg did not. From the reflection peaks in the x-ray diffraction (XRD) patterns, surface crystallinity of the nano-Ag complexes was indicated to be in the same degree as that of NSSPAI>NSS>NAg. Also, in the contact angle (CA) determination, surface hydrophobicity of NSSPAI was stronger than those of NSS and NAg, relatively. The different nano-Ag complexes prepared by γ-irradiation can be applicable in various industry fields due to the increase in specific property.

  19. In-situ synthesis of Au nano particles of co-existing morphologies in liquid crystalline matrix

    NASA Astrophysics Data System (ADS)

    Dan, Kaustabh; Datta, Alokmay

    2015-06-01

    The present study describes the in-situ synthesis of Au nano particles (Au-NP) in the room temperature nematic liquid crystalline (LC) substance MBBA (N-4 methoxybenzylidene 4 butylaniline) without any external reducing or stabilizing agents. UV-Visible absorption and fluorescence spectroscopy clearly show formation of Au-NP within the LC matrix through the plasmon resonance peak for the NPs and EDAX measurements confirm this formation. Transmission electron Microscopy shows co-existence of spherical and prismatic NPs. FTIR spectroscopy shows a considerable shift in the C=N stretch band pointing to the location of the growth centre of the NPs. Polarization microscopy data indicates a definite phase ordering and texture transformation from Nematic to highly ordered smectic mesophase.

  20. In-situ synthesis of Au nano particles of co-existing morphologies in liquid crystalline matrix

    SciTech Connect

    Dan, Kaustabh Datta, Alokmay

    2015-06-24

    The present study describes the in-situ synthesis of Au nano particles (Au-NP) in the room temperature nematic liquid crystalline (LC) substance MBBA (N-4 methoxybenzylidene 4 butylaniline) without any external reducing or stabilizing agents. UV-Visible absorption and fluorescence spectroscopy clearly show formation of Au-NP within the LC matrix through the plasmon resonance peak for the NPs and EDAX measurements confirm this formation. Transmission electron Microscopy shows co-existence of spherical and prismatic NPs. FTIR spectroscopy shows a considerable shift in the C=N stretch band pointing to the location of the growth centre of the NPs. Polarization microscopy data indicates a definite phase ordering and texture transformation from Nematic to highly ordered smectic mesophase.

  1. Solar absorptance of copper-cobalt oxide thin film coatings with nano-size, grain-like morphology: Optimization and synchrotron radiation XPS studies

    NASA Astrophysics Data System (ADS)

    Amri, Amun; Duan, XiaoFei; Yin, Chun-Yang; Jiang, Zhong-Tao; Rahman, M. Mahbubur; Pryor, Trevor

    2013-06-01

    Copper-cobalt oxides thin films had been successfully coated on reflective aluminium substrates via a facile sol-gel dip-coating method for solar absorptance study. The optimum absorptance in the range of solar radiation is needed for further optimum design of this material for selective solar absorber application. Field emission scanning electron microscopy was used to characterize the surface morphology of the coating whereby nano-size, grain-like morphology was observed. Synchrotron radiation X-ray photoelectron spectroscopy was employed to analyze the electronic structure of the coated surface showing that the (i) oxygen consisted of lattice, surface and subsurface oxygen, (ii) copper consisted of octahedral and tetrahedral Cu+, as well as octahedral and paramagnetic Cu2+ oxidation states, and (iii) cobalt consisted of tetrahedral and paramagnetic Co(II), octahedral Co(III) as well as mixed Co(II,III) oxidation states. In order to optimize the solar absorptance of the coatings, relevant parameters such as concentrations of cobalt and copper, copper/cobalt concentration ratios and dip-speed were investigated. The optimal coating with α = 83.4% was produced using 0.25 M copper acetate and 0.25 M cobalt chloride (Cu/Co ratio = 1) with dip-speed 120 mm/min (four cycles). The operational simplicity of the dip-coating system indicated that it could be extended for coating of other mixed metal oxides as well.

  2. Effects of dip-coating speed and annealing temperature on structural, morphological and optical properties of sol-gel nano-structured TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Touam, Tahar; Atoui, Mohamed; Hadjoub, Ilhem; Chelouche, Azeddine; Boudine, Boubekeur; Fischer, Alexis; Boudrioua, Azzedine; Doghmane, Abdellaziz

    2014-09-01

    We reported material characterization of the nano-structured TiO2 thin films prepared by the sol-gel dip-coating process on glass substrates. The dependence of the structural, morphological and optical properties of the synthesized films on the fabrication parameters such as withdrawal velocity and annealing temperature were investigated by the techniques of X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible spectrophotometry. The results indicate that for the TiO2 films annealed at 500 °C there exhibits (1 0 1) XRD peak corresponding to the anatase phase of TiO2. The latter is consistent with the recorded Raman signal observed at 142 cm-1 (Eg mode) and 391 cm-1 (B1g mode), respectively. From the analyses made on the SEM micrographs and AFM images, it was revealed that the morphology and surface roughness of the thin films would depend on the withdrawal speed and the heat treatment temperature. The UV-visible spectroscopy analyses show that all the films were transparent in the visible region with an average transmittance of more than 70%. With an increase on the dip-coating speed from 1 cm/min to 3 cm/min, we observed a spectral red shift of the absorption edge from 3.76 eV to 3.71 eV, indicating a decrease in the bandgap energy (Eg) of the films.

  3. Morphology control and multicolor up-conversion luminescence of GdOF:Yb3+/Er3+, Tm3+, Ho3+ nano/submicrocrystals.

    PubMed

    Zhang, Yang; Li, Xuejiao; Kang, Xiaojiao; Hou, Zhiyao; Lin, Jun

    2014-06-14

    In this paper, well defined GdOF:Yb(3+)/Er(3+), Tm(3+), Ho(3+) nano/submicrocrystals with multiform morphologies were prepared via the urea-based precipitation method without using any surfactants. The morphologies of the GdOF products, including spindles and spheres with different sizes (30-550 nm), could be easily modulated by changing the fluorine sources, and the possible formation mechanism has been presented. XRD, FT-IR, SEM, TEM, as well as up-conversion (UC) photoluminescence spectra were used to characterize the prepared samples. Under 980 nm NIR excitation, the relative emission intensities and emission colors of Yb(3+)/Er(3+), Yb(3+)/Tm(3+) and Yb(3+)/Ho(3+) doped GdOF could be precisely adjusted over a wide range by tuning the Yb(3+) doping concentration. The strategies for color tuning of UC emission proposed in the current system may be helpful to achieve efficient multicolor luminescence under 980 nm laser excitation. In addition, the corresponding UC mechanisms in the co-doping GdOF systems were analyzed in detail based on the emission spectra and the plot of luminescence intensity to pump power.

  4. Silica Fillers for elastomer Reinforement

    SciTech Connect

    Kohls, D.J.; Schaefer, D.W.

    2012-09-10

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  5. Morphology and orientational behavior of silica-coated spindle-type hematite particles in a magnetic field probed by small-angle X-ray scattering.

    PubMed

    Reufer, Mathias; Dietsch, Hervé; Gasser, Urs; Hirt, Ann; Menzel, Andreas; Schurtenberger, Peter

    2010-04-15

    Form factor and magnetic properties of silica-coated spindle-type hematite nanoparticles are determined from SAXS measurements with applied magnetic field and magnetometry measurements. The particle size, polydispersity and porosity are determined using a core-shell model for the form factor. The particles are found to align with their long axis perpendicular to the applied field. The orientational order is determined from the SAXS data and compared to the orientational order obtained from magnetometry. The direct access to both, the orientational order of the particles, and the magnetic moments allow one to determine the magnetic properties of the individual spindle-type hematite particles. We study the influence of the silica coating on the magnetic properties and find a fundamentally different behavior of silica-coated particles. The silica coating reduces the effective magnetic moment of the particles. This effect is enhanced with field strength and can be explained by superparamagnetic relaxation in the highly porous particles.

  6. Nanoporous TiO2 nanoparticle assemblies with mesoscale morphologies: nano-cabbage versus sea-anemone

    NASA Astrophysics Data System (ADS)

    Darbandi, Masih; Gebre, Tesfaye; Mitchell, Lucas; Erwin, William; Bardhan, Rizia; Levan, M. Douglas; Mochena, Mogus D.; Dickerson, James H.

    2014-05-01

    We report the novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies. Constituent nanoparticles evolved into multifaceted assemblies, exhibiting excellent crystallinity and enhanced photocatalytic activity compared with commercial TiO2. Such materials could be exploited for applications, like organic pollutant degradation.We report the novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies. Constituent nanoparticles evolved into multifaceted assemblies, exhibiting excellent crystallinity and enhanced photocatalytic activity compared with commercial TiO2. Such materials could be exploited for applications, like organic pollutant degradation. Electronic supplementary information (ESI) available: Synthesis and characterization procedures, TEM/XRD of samples prepared at different temperature and water content, table of nitrogen adsorption-desorption values of different samples. See DOI: 10.1039/c3nr06154j

  7. Nano-morphology induced additional surface plasmon resonance enhancement of SERS sensitivity in Ag/GaN nanowall network

    NASA Astrophysics Data System (ADS)

    Sharvani, S.; Upadhayaya, Kishor; Kumari, Gayatri; Narayana, Chandrabhas; Shivaprasad, S. M.

    2015-11-01

    The GaN nanowall network, formed by opening the screw dislocations by kinetically controlled MBE growth, possesses a large surface and high conductivity. Sharp apexed nanowalls show higher surface electron concentration in the band-tail states, in comparison to blunt apexed nanowalls. Uncapped silver nanoparticles are vapor deposited on the blunt and sharp GaN nanowall networks to study the morphological dependence of band-edge plasmon-coupling. Surface enhanced Raman spectroscopy studies performed with a rhodamine 6G analyte on these two configurations clearly show that the sharp nanowall morphology with smaller Ag nanoparticles shows higher enhancement of the Raman signal. A very large enhancement factor of 2.8 × 107 and a very low limit of detection of 10-10 M is observed, which is attributed to the surface plasmon resonance owing to the high surface electron concentration on the GaN nanowall in addition to that of the Ag nanoparticles. The significantly higher sensitivity with same-sized Ag nanoparticles confirms the unconventional role of morphology-dependent surface charge carrier concentration of GaN nanowalls in the enhancement of Raman signals.

  8. Nano-morphology induced additional surface plasmon resonance enhancement of SERS sensitivity in Ag/GaN nanowall network.

    PubMed

    Sharvani, S; Upadhayaya, Kishor; Kumari, Gayatri; Narayana, Chandrabhas; Shivaprasad, S M

    2015-11-20

    The GaN nanowall network, formed by opening the screw dislocations by kinetically controlled MBE growth, possesses a large surface and high conductivity. Sharp apexed nanowalls show higher surface electron concentration in the band-tail states, in comparison to blunt apexed nanowalls. Uncapped silver nanoparticles are vapor deposited on the blunt and sharp GaN nanowall networks to study the morphological dependence of band-edge plasmon-coupling. Surface enhanced Raman spectroscopy studies performed with a rhodamine 6G analyte on these two configurations clearly show that the sharp nanowall morphology with smaller Ag nanoparticles shows higher enhancement of the Raman signal. A very large enhancement factor of 2.8 × 10(7) and a very low limit of detection of 10(-10) M is observed, which is attributed to the surface plasmon resonance owing to the high surface electron concentration on the GaN nanowall in addition to that of the Ag nanoparticles. The significantly higher sensitivity with same-sized Ag nanoparticles confirms the unconventional role of morphology-dependent surface charge carrier concentration of GaN nanowalls in the enhancement of Raman signals. PMID:26502004

  9. Multiscale Micro-Nano Nested Structures: Engineered Surface Morphology for Efficient Light Escaping in Organic Light-Emitting Diodes.

    PubMed

    Zhou, Lei; Dong, Xiaoxuan; Zhou, Yun; Su, Wenming; Chen, Xiaolian; Zhu, Yufu; Shen, Su

    2015-12-01

    Various micro-to-nanometer scale structures are extremely attractive for light escaping in organic light-emitting diodes. To develop and optimize such structures, an innovative approach was demonstrated for the first time to fabricate multiscale micro-nano nested structures by photolithography with a well-designed mask pattern followed by a controllable thermal reflow process. The experimental and theoretical characterizations verify that these unique nested structures hold the capability of light concentration, noticeable low haze, and efficient antireflection. As a proof-of-concept, the incorporation of this pattern onto the glass substrate efficiently facilitates light escaping from the device, resulting in current efficiency 1.60 times and external quantum efficiency 1.63 times that of a control flat device, respectively. Moreover, compared to a hexagonally arranged microlens array and quasi-random biomimetic moth eye nanostructures, the nested structures proposed here can magically tune the spatial emission profile to comply with the Lambertian radiation pattern. Hence, this novel structure is expected to be of great potential in related ubiquitous optoelectronic applications and provide scientific inspiration to other novel multiscale micro-nanostructure research.

  10. Inducing an Order–Order Morphological Transition via Chemical Degradation of Amphiphilic Diblock Copolymer Nano-Objects

    PubMed Central

    2016-01-01

    The disulfide-based cyclic monomer, 3-methylidene-1,9-dioxa-5,12,13-trithiacyclopentadecane-2,8-dione (MTC), is statistically copolymerized with 2-hydroxypropyl methacrylate to form a range of diblock copolymer nano-objects via reversible addition–fragmentation chain transfer (RAFT) polymerization. Poly(glycerol monomethacrylate) (PGMA) is employed as the hydrophilic stabilizer block in this aqueous polymerization-induced self-assembly (PISA) formulation, which affords pure spheres, worms or vesicles depending on the target degree of polymerization for the core-forming block. When relatively low levels (<1 mol %) of MTC are incorporated, high monomer conversions (>99%) are achieved and high blocking efficiencies are observed, as judged by 1H NMR spectroscopy and gel permeation chromatography (GPC), respectively. However, the side reactions that are known to occur when cyclic allylic sulfides such as MTC are statistically copolymerized with methacrylic comonomers lead to relatively broad molecular weight distributions. Nevertheless, the worm-like nanoparticles obtained via PISA can be successfully transformed into spherical nanoparticles by addition of excess tris(2-carboxyethyl)phosphine (TCEP) at pH 8–9. Surprisingly, DLS and TEM studies indicate that the time scale needed for this order–order transition is significantly longer than that required for cleavage of the disulfide bonds located in the worm cores indicated by GPC analysis. This reductive degradation pathway may enable the use of these chemically degradable nanoparticles in biomedical applications, such as drug delivery systems and responsive biomaterials. PMID:27228898

  11. In-situ growth of porous alumino-silicates and fabrication of nano-porous membranes

    NASA Astrophysics Data System (ADS)

    Kodumuri, Pradeep

    2009-12-01

    Feasibility of depositing continuous films of nano-porous alumino-silicates, primarily zeolites and MCM-41, on metallic and non-metallic substrates was examined with an aim to develop membranes for separation of gaseous mixtures and also for application as hydrogen storage material. Mesoporous silica was deposited in-side the pores of these nano-porous disks with an aim to develop membranes for selective separations. Our study involves supported zeolite film growth on substrates using in-situ hydrothermal synthesis. Faujasite, Silicalite and Mesoporous silica have been grown on various metallic and non-metallic supports. Metallic substrates used for film growth included anodized titanium, sodium hydroxide treated Titanium, Anodized aluminum, and sintered copper. A non-metallic substrate used was nano-porous aluminum oxide. Zeolite film growth was characterized using Scanning Electron Microscope (AMRAY 1820) and High Resolution Transmission electron microscope. Silicalite was found to grow uniformly on all the substrates to form a uniform and closely packed film. Faujasite tends to grow in the form of individual particles which do not inter-grow like silicalite to form a continuous film. Mesoporous silica was found to grow uniformly on anodized aluminum compared to growth on sintered copper and anodized titanium. Mesoporous silica growth on AnodiscRTM was found to cover more than half the surface of the substrate. Commercially obtained AnodiscRTM was found to have cylindrical channels of the pore branching into each other and since we needed pore channels of uniform dimension for Mesoporous silica growth, we have fabricated nano-porous alumina with uniform pore channels. Nano-porous alumina membranes containing uniform distribution of through thickness cylindrical pore channels were fabricated using anodization of aluminum disks. Free-standing nano-porous alumina membranes were used as templates for electro-deposition in order to fabricate nickel and palladium nano

  12. "Gray Areas": Silica gels, amorphous silica and cryptocrystalline silica on fault surfaces

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Kirkpatrick, J. D.; White, J. C.; Faber, C.; Caine, J. S.

    2012-12-01

    Silica gels, in the form of their solid-phase equivalents, are widely found in brittle fault zones and are commonly associated with mineral deposits. High- to moderate-velocity rotary friction experiments have produced silica gels on sliding surfaces coeval with dramatic slip weakening. In light of the latter, silica gel formation has been proposed as a potential mechanism of slip weakening during earthquakes in the shallow crust. However, low velocity sliding experiments have also produced significant amounts of amorphous material distributed throughout slipping layers, and dramatic weakening is not observed. Comparison of the products of laboratory experiments to geological examples is complicated by the diagenesis and lithification of silica gels. They may form hydrous and amorphous solids, hydrous crystalline solids, or dehydrate to quartz. In addition, the abundance and style of occurrence of these products in faults suggest that there are multiple origins for silica gels in faults. We review the mechanisms by which silica gels may form in fault zones and describe the solidification, crystallization and dehydration evolution of the silica. Analytical transmission electron microscope (TEM) observations of slip-surface silica deposits from the Corona Fault, San Francisco, the Dixie Valley Fault, Nevada, and the Olive Fault, Namibia typify the nano- to micro-structural evolution of the fault surface silica layers. We suggest criteria for identifying these materials in natural fault rocks. Some of these gels may form by comminution and hydrolization of silica-rich wall rocks, as has been observed in high-velocity experiments (Corona Fault). Others may form by depressurization and boiling of aqueous fluids, probably during fault valving (Olive Fault). Silica saturated hydrothermal fluids released during faulting may contribute in some cases (Dixie Valley Fault). Regardless of the mechanism of gel formation, the dramatic rheological weakening observed in friction

  13. Immobilization of Fusarium verticillioides fungus on nano-silica (NSi-Fus): a novel and efficient biosorbent for water treatment and solid phase extraction of Mg(II) and Ca(II).

    PubMed

    Mahmoud, Mohamed E; Yakout, Amr A; Abdel-Aal, Hany; Osman, Maher M

    2013-04-01

    Biosorption and water treatment of Mg(II) and Ca(II) hardness was designed via surface loading of heat inactivated Fusarium verticillioides fungus (Fus) on nano-silica (NSi) for developing the (NSi-Fus) as a novel biosorbent. Surface characterization was confirmed by FT-IR and SEM analysis. The (NSi), (Fus) and (NSi-Fus) sorbents were investigated for removal of Mg(II) and Ca(II) by using the batch equilibrium technique under the influence of solution pH, contact time, sorbent dosage, initial metal concentration and interfering ion. The maximum magnesium capacity values were identified as 600.0, 933.3 and 1000.0 μmole g(-1) while, the maximum calcium values were 1066.7, 1800.0 and 1333.3 μmole g(-1) for (NSi), (Fus) and (NSi-Fus), respectively. Sorption equilibria were established in ∼20 min and the data were well described by both Langmuir and Freundlich models. The potential applications of these biosorbents for water-softening and extraction of magnesium and calcium from sea water samples were successfully accomplished. PMID:23517902

  14. Creation of freestanding wrinkled nano-films with desired deformation properties by controlling the surface morphology of a sacrificial layer

    NASA Astrophysics Data System (ADS)

    Hirakata, Hiroyuki; Maruyama, Tomohiro; Yonezu, Akio; Minoshima, Kohji

    2013-05-01

    Various wrinkle patterns can be formed due to the buckling of a stiff thin film on a compliant substrate. However, most wrinkled films previously reported were fixed on a large deformable substrate and thereby the potential deformability of the film was mechanically constrained by the substrate. In this study, we developed a technique for forming various wrinkled structures on the surface of a sacrificial resin layer. Since the sacrificial layer can be subsequently removed with a solvent, freestanding wrinkled films are created using the sacrificial layer. We found that a wrinkled structure is formed on the surface of the layer by applying a compressive strain to the resin layer at the appropriate moment during the hardening process. The wrinkle pattern depends on the curing time and the timing of the straining in two in-plane orthogonal directions. In addition to conventional stripe and labyrinth patterns by simple uniaxial and equi-biaxial strains, respectively, it was found that independent biaxial strains induce interesting structures, such as an orthogonally ordered wrinkle pattern and a nonsymmetrical buckling structure, in which the stripe array produced by the first straining remains and many finer wrinkles appear in each stripe by the second straining in the orthogonal direction. We conducted tensile experiments for 300-nm-thick freestanding Cu films having these wrinkled structures. The wrinkled nano-films have a variety of mechanical properties: the stripe structure has extremely high deformability (more than 10% strain) and reversibility, the labyrinth structure shows planar isotropic deformation, and the nonsymmetrical buckling structure has an anisotropic modulus and strength. Finite element analysis on the wrinkle structures revealed that the local stress concentration dominates the fracture limits.

  15. Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

    PubMed Central

    Lechner, Carolin C.; Becker, Christian F. W.

    2015-01-01

    Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed. PMID:26295401

  16. Seeded Growth of Highly Luminescent CdSe/CdS Nano-Heterostructures with Rod and Tetrapod Morphologies

    SciTech Connect

    Talapin, Dmitri; Talapin, Dmitri V.; Nelson, James H.; Shevchenko, Elena V.; Aloni, Shaul; Sadtler, Bryce; Alivisatos, A. Paul

    2007-08-09

    We have demonstrated that seeded growth of nanocrystals offers a convenient way to design nanoheterostructures with complex shapes and morphologies by changing the crystalline structure of the seed. By using Use nanocrystals with wurtzite and zinc blende structure as seeds for growth of US nanorods, we synthesized CdSe/CdS heterostructure nanorods and nanotetrapods, respectively. Both of these structures showed excellent luminescentproperties, combining high photoluminescence efficiency (similar to 80 and similar to 50percent for nanorods and nanotetrapods, correspondingly), giant extinction coefficients (similar to 2 x 10(7) and similar to 1.5 x 10(8) M-1 cm (-1) at 350 nm for nanorods and nanotetrapods, correspondingly), and efficient energy transfer from the US arms into the emitting CdSe Core.

  17. A facile processing way of silica needle arrays with tunable orientation by tube arrays fabrication and etching method

    SciTech Connect

    Zhu Mingwei; Gao Haigen; Li Hongwei; Xu Jiao; Chen Yanfeng

    2010-03-15

    A simple method to fabricate silica micro/nano-needle arrays (SNAs) is presented based on tube-etching mechanism. Using silica fibers as templates, highly aligned and free-standing needle arrays are created over large area by simple processes of polymer infiltration, cutting, chemical etching and polymer removal. Their sizes and orientations can be arbitrarily and precisely tuned by simply selecting fiber sizes and the cutting directions, respectively. This technique enables the needle arrays with special morphology to be fabricated in a greatly facile way, thereby offers them the potentials in various applications, such as optic, energy harvesting, sensors, etc. As a demonstration, the super hydrophobic property of PDMS treated SNAs is examined. - Graphical abstract: Silica needle arrays are fabricated by tube arrays fabrication and etching method. They show super hydrophobic property after being treated with PDMS.

  18. Temperature-Responsive Poly(ɛ-caprolactone) Cell Culture Platform with Dynamically Tunable Nano-Roughness and Elasticity for Control of Myoblast Morphology

    PubMed Central

    Uto, Koichiro; Ebara, Mitsuhiro; Aoyagi, Takao

    2014-01-01

    We developed a dynamic cell culture platform with dynamically tunable nano-roughness and elasticity. Temperature-responsive poly(ɛ-caprolactone) (PCL) films were successfully prepared by crosslinking linear and tetra-branched PCL macromonomers. By optimizing the mixing ratios, the crystal-amorphous transition temperature (Tm) of the crosslinked film was adjusted to the biological relevant temperature (~33 °C). While the crosslinked films are relatively stiff (50 MPa) below the Tm, they suddenly become soft (1 MPa) above the Tm. Correspondingly, roughness of the surface was decreased from 63.4–12.4 nm. It is noted that the surface wettability was independent of temperature. To investigate the role of dynamic surface roughness and elasticity on cell adhesion, cells were seeded on PCL films at 32 °C. Interestingly, spread myoblasts on the film became rounded when temperature was suddenly increased to 37 °C, while significant changes in cell morphology were not observed for fibroblasts. These results indicate that cells can sense dynamic changes in the surrounding environment but the sensitivity depends on cell types. PMID:24451135

  19. Temperature-responsive poly(ε-caprolactone) cell culture platform with dynamically tunable nano-roughness and elasticity for control of myoblast morphology.

    PubMed

    Uto, Koichiro; Ebara, Mitsuhiro; Aoyagi, Takao

    2014-01-01

    We developed a dynamic cell culture platform with dynamically tunable nano-roughness and elasticity. Temperature-responsive poly(ε-caprolactone) (PCL) films were successfully prepared by crosslinking linear and tetra-branched PCL macromonomers. By optimizing the mixing ratios, the crystal-amorphous transition temperature (Tm) of the crosslinked film was adjusted to the biological relevant temperature (~33 °C). While the crosslinked films are relatively stiff (50 MPa) below the Tm, they suddenly become soft (1 MPa) above the Tm. Correspondingly, roughness of the surface was decreased from 63.4-12.4 nm. It is noted that the surface wettability was independent of temperature. To investigate the role of dynamic surface roughness and elasticity on cell adhesion, cells were seeded on PCL films at 32 °C. Interestingly, spread myoblasts on the film became rounded when temperature was suddenly increased to 37 °C, while significant changes in cell morphology were not observed for fibroblasts. These results indicate that cells can sense dynamic changes in the surrounding environment but the sensitivity depends on cell types.

  20. Controlling morphology and crystallite size of Cu(In{sub 0.7}Ga{sub 0.3})Se{sub 2} nano-crystals synthesized using a heating-up method

    SciTech Connect

    Hsu, Wei-Hsiang; Hsiang, Hsing-I; Chia, Chih-Ta; Yen, Fu-Su

    2013-12-15

    CuIn{sub 0.7}Ga{sub 0.3}Se{sub 2}(CIGS) nano-crystals were successfully synthesized via a heating-up process. The non-coordinating solvent (1-octadecene) and selenium/cations ratio effects on the crystalline phase and crystallite size of CIGS nano-crystallites were investigated. It was observed that the CIGS nano-crystallite morphology changed from sheet into spherical shape as the amount of 1-octadecene addition was increased. CIGS nano-crystals were obtained in 9–20 nm sizes as the selenium/cations ratio increased. These results suggest that the monomer reactivity in the solution can be adjusted by changing the solvent type and selenium/cations ratio, hence affecting the crystallite size and distribution. - Graphical abstract: CuIn{sub 0.7}Ga{sub 0.3}Se{sub 2}(CIGS) nano-crystals were successfully synthesized via a heating-up process in this study. The super-saturation in the solution can be adjusted by changing the OLA/ODE ratio and selenium/cation ratio.

  1. Structure, morphology and optical properties of undoped and MN-doped ZnO(1-x)Sx nano-powders prepared by precipitation method

    NASA Astrophysics Data System (ADS)

    Dejene, F. B.; Onani, M. O.; Koao, L. F.; Wako, A. H.; Motloung, S. V.; Yihunie, M. T.

    2016-01-01

    The undoped and Mn-doped ZnO(1-x)Sx nano-powders were successfully synthesized by precipitation method without using any capping agent. Its structure, morphology, elemental analysis, optical and luminescence properties were determined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy (UV) and photoluminescence spectroscopy (PL). A typical SEM image of the un-doped ZnO(1-x)Sx nanoparticles exhibit flake like structures that changes to nearly spherical particles with Mn-doping. The XRD of undoped and Mn doped ZnO(1-x)Sx pattern reveals the formation of a product indexed to the hexagonal wurtzite phase of ZnS. The nanopowders have crystallite sizes estimated from XRD measurements were in the range of 10-20 nm. All the samples showed absorption maximum of ZnO(1-x)Sx at 271 nm and high transmittance in UV and visible region, respectively. The undoped ZnO(1-x)Sx nanoparticles show strong room-temperature photoluminescence with four emission bands centering at 338 nm, 384 nm, 448 nm and 705 nm that may originate to the impurity of ZnO(1-x)Sx, existence of oxide related defects. The calculated bandgap of the nanocrystalline ZnO(1-x)Sx showed a blue-shift with respect to the Mn-doping. The PL spectra of the Mn-doped samples exhibit a strong orange emission at around 594 nm attributed to the 4T1-6A1 transition of the Mn2+ ions.

  2. RAFT aqueous dispersion polymerization yields poly(ethylene glycol)-based diblock copolymer nano-objects with predictable single phase morphologies.

    PubMed

    Warren, Nicholas J; Mykhaylyk, Oleksandr O; Mahmood, Daniel; Ryan, Anthony J; Armes, Steven P

    2014-01-22

    A poly(ethylene glycol) (PEG) macromolecular chain transfer agent (macro-CTA) is prepared in high yield (>95%) with 97% dithiobenzoate chain-end functionality in a three-step synthesis starting from a monohydroxy PEG113 precursor. This PEG113-dithiobenzoate is then used for the reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). Polymerizations conducted under optimized conditions at 50 °C led to high conversions as judged by (1)H NMR spectroscopy and relatively low diblock copolymer polydispersities (M(w)/M(n) < 1.25) as judged by GPC. The latter technique also indicated good blocking efficiencies, since there was minimal PEG113 macro-CTA contamination. Systematic variation of the mean degree of polymerization of the core-forming PHPMA block allowed PEG113-PHPMA(x) diblock copolymer spheres, worms, or vesicles to be prepared at up to 17.5% w/w solids, as judged by dynamic light scattering and transmission electron microscopy studies. Small-angle X-ray scattering (SAXS) analysis revealed that more exotic oligolamellar vesicles were observed at 20% w/w solids when targeting highly asymmetric diblock compositions. Detailed analysis of SAXS curves indicated that the mean number of membranes per oligolamellar vesicle is approximately three. A PEG113-PHPMA(x) phase diagram was constructed to enable the reproducible targeting of pure phases, as opposed to mixed morphologies (e.g., spheres plus worms or worms plus vesicles). This new RAFT PISA formulation is expected to be important for the rational and efficient synthesis of a wide range of biocompatible, thermo-responsive PEGylated diblock copolymer nano-objects for various biomedical applications. PMID:24400622

  3. Nanoscale morphology for high hydrophobicity of a hard sol gel thin film

    NASA Astrophysics Data System (ADS)

    Wu, Y. L.; Chen, Z.; Zeng, X. T.

    2008-08-01

    It is challenging to obtain a hydrophobic smooth coating with high optical and mechanical properties at the same time because the hydrophobic additives are soft in nature resulting in reduced hardness and durability. This paper reports a durable hydrophobic transparent coating on glass fabricated by sol-gel technology and a low volume medium pressure (LVMP) spray process. The sol-gel formula consists of a pre-linked hydrophobic nano-cluster from hydroxyl-terminated polydimethylsiloxane, titanium tetraisopropoxide and a silica-based sol-gel matrix with silica hard fillers. Polydimethylsiloxane (PDMS) is uniformly distributed throughout the coating layer providing durable hydrophobic property. Mechanical properties are achieved by the hard matrix and hard fillers with the nano-structures. Due to the surface nano-morphology, a high degree of hydrophobicity was maintained with only 10 vol.% PDMS, while the hardness and abrasion resistance of the coatings were not significantly compromised. Chemical analyses by FTIR confirmed the uniform distribution of the PDMS and surface morphology analyses by atomic force microscopy (AFM) displayed the nano-surface structures that enhanced the hydrophobicity. The special surface nanostructures can be quantified using surface Kurtosis and ratio between asperity peak height to distance between peaks. The LVMP process influences the spray droplet size resulting in different surface structures.

  4. Surface studies on superhydrophobic and oleophobic polydimethylsiloxane-silica nanocomposite coating system

    NASA Astrophysics Data System (ADS)

    Basu, Bharathibai J.; Dinesh Kumar, V.; Anandan, C.

    2012-11-01

    Superhydrophobic and oleophobic polydimethylsiloxane (PDMS)-silica nanocomposite double layer coating was fabricated by applying a thin layer of low surface energy fluoroalkyl silane (FAS) as topcoat. The coatings exhibited WCA of 158-160° and stable oleophobic property with oil CA of 79°. The surface morphology was characterized by field emission scanning electron microscopy (FESEM) and surface chemical composition was determined by energy dispersive X-ray spectrometery (EDX) and X-ray photoelectron spectroscopy (XPS). FESEM images of the coatings showed micro-nano binary structure. The improved oleophobicity was attributed to the combined effect of low surface energy of FAS and roughness created by the random distribution of silica aggregates. This is a facile, cost-effective method to obtain superhydrophobic and oleophobic surfaces on larger area of various substrates.

  5. Nano-structured surface plasmon resonance sensor for sensitivity enhancement

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Ho; Kim, Hyo-Sop; Kim, Jin-Ho; Choi, Sung-Wook; Cho, Yong-Jin

    2008-08-01

    A new nano-structured SPR sensor was devised to improve its sensitivity. Nano-scaled silica particles were used as the template to fabricate nano-structure. The surface of the silica particles was modified with thiol group and a single layer of the modified silica particles was attached on the gold or silver thin film using Langmuir-Blodgett (LB) method. Thereafter, gold or silver was coated on the template by an e-beam evaporator. Finally, the nano-structured surface with basin-like shape was obtained after removing the silica particles by sonication. Applying the new developed SPR sensor to a model food of alcoholic beverage, the sensitivities for the gold and silver nano-structured sensors, respectively, had 95% and 126% higher than the conventional one.

  6. Spark Plasma Sintering and Multi-scale Characterization of Mesoporous Silica Disks

    NASA Astrophysics Data System (ADS)

    Maheshwari, Harsh

    Oil from shale and tight formations has helped the United States produce close to 10 million barrels of oil per day, a 40-year high. Well characterized sintered nano materials will serve as calibration materials for understanding important thermodynamic and flow properties of fluids in similar formations. To this effect, sintered mesoporous silica monoliths containing micro- and nano-porosity are characterized across multiple length scales at various processing temperatures using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers hardness tests, and Brunauer-Emmett-Teller (BET) gas adsorption measurements. Results show that the mesoporosity in raw SBA-15 silica powders can be retained during spark-plasma sintering (SPS) up to 850 ºC which is lower than those achieved by conventional sintering techniques (>1050 ºC). Details of micro- and meso-porosity were revealed by studying the internal structure through SEM and in-situ TEM tomography of the sintered specimens in comparison to the pristine silica powder. The microporosity is retained up to 950°C under the same pressure, and the degree of microporosity increases when the mesopores collapse due to individual nanoparticle shrinkage. In situ TEM characterization of mesoporosity in the absence of applied pressure reveal pore collapse above 1050°C, which is considerably above the temperatures observed under applied pressures during SPS processing. The degree of microporosity, obtained under different processing conditions, is correlated to the mechanical properties, available surface area and pore morphology. In spite of the unique synthesis process, sintered mesoporous silica satisfies the Ryshkewitch relationship -- the correlation of mechanical properties to porosity. Subsequently, in-situ TEM nanoindentation was conducted to investigate the mechanical properties of individual mesoporous silica nanoparticles. The ability to control the micro- and meso-porosity of these

  7. Synthesis and Characterization of Bionanoparticle-Silica Composites and Mesoporous Silica with Large Pores

    SciTech Connect

    Niu, Z.; Yang, L.; Kabisatpathy, S.; He, J.; Lee, A.; Ron, J.; Sikha, G.; Popov, B.N.; Emrick, T.; Russell, T. P.; Wang. Q.

    2009-03-24

    A sol-gel process has been developed to incorporate bionanoparticles, such as turnip yellow mosaic virus, cowpea mosaic virus, tobacco mosaic virus, and ferritin into silica, while maintaining the integrity and morphology of the particles. The structures of the resulting materials were characterized by transmission electron microscopy, small angle X-ray scattering, and N{sub 2} adsorption-desorption analysis. The results show that the shape and surface morphology of the bionanoparticles are largely preserved after being embedded into silica. After removal of the bionanoparticles by calcination, mesoporous silica with monodisperse pores, having the shape and surface morphology of the bionanoparticles replicated inside the silica, was produced,. This study is expected to lead to both functional composite materials and mesoporous silica with structurally well-defined large pores.

  8. Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

    PubMed

    Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

    2016-02-01

    This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used. PMID:27433652

  9. Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

    PubMed

    Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

    2016-02-01

    This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

  10. Enhancing plasma peptide MALDI-TOF-MS profiling by mesoporous silica assisted crystallization.

    PubMed

    Terracciano, Rosa; Casadonte, Francesca; Pasqua, Luigi; Candeloro, Patrizio; Di Fabrizio, Enzo; Urbani, Andrea; Savino, Rocco

    2010-02-15

    Promising profiling techniques based on new material/solid phase extraction for capturing "molecular signatures" from body fluids are being coupled to MALDI-TOF-MS. Sample preparation significantly influences spectrum quality in this ionization method. Mesoporous silica beads (MSB), by the means of nano-sized porous channels with high surface area, enable harvesting of peptides from plasma and serum excluding large size proteins. We have investigated the morphology of a sample slurry, developed as a new tool for plasma peptides enrichment based on mesoporous materials. Our study highlights a correlation between crystals morphology and enhanced performances in MALDI-TOF-MS analysis. This is the first report which correlates the increase in signal intensity with crystal formation in samples preparations which make use of various kinds of slurries for the analysis of samples clinically relevant like human plasma.

  11. Synchrotron X-ray phase nano-tomography-based analysis of the lacunar-canalicular network morphology and its relation to the strains experienced by osteocytes in situ as predicted by case-specific finite element analysis.

    PubMed

    Varga, Peter; Hesse, Bernhard; Langer, Max; Schrof, Susanne; Männicke, Nils; Suhonen, Heikki; Pacureanu, Alexandra; Pahr, Dieter; Peyrin, Françoise; Raum, Kay

    2015-04-01

    Osteocytes are hypothesized to regulate bone remodeling guided by both biological and mechanical stimuli. Morphology of the lacunar-canalicular network of osteocytes has been hypothesized to be strongly related to the level of mechanical loading and to various bone diseases. Finite element modeling could help to better understand the mechanosensation process by predicting the physiological strain environment. The aims of this study were to (i) quantify the lacunar-canalicular morphology in the cortex of the human femur; (ii) predict the in situ local deformations around and in osteocytes by means of case-specific finite element models; and (iii) investigate the potential relationship between morphology and deformations. Human femoral cortical bone samples were imaged using synchrotron X-ray phase nano-tomography with 50 nm voxel size. Rectangular volumes of interest were selected to contain single osteocyte lacunae and the surrounding matrix. Lacunar-canalicular morphology was quantified and the cell geometry was artificially reconstructed based on a priori assumptions. Finite element models of the volumes of interest were generated, containing the extracellular matrix, osteocyte and peri-cellular matrix, and subjected to uniaxial compression. The morphological analysis revealed that canalicular number was dictated by lacunar size, that the spacing of canaliculi fell within a narrow range, suggesting that these pores are well distributed throughout the bone matrix and indicated the trend that lacunae at the outer osteon boundary were less elongated than others. No apparent relationship was found between the morphological parameters and the predicted strains. The globally applied strain was amplified locally by factors up to 10 and up to 70 in the extracellular matrix and the in cells, respectively. Cell deformations were localized mainly at the body-dendrite junctions, with magnitudes reaching the in vitro stimulatory threshold reported for osteocytes.

  12. Nanoscale control of silica particle formation via silk-silica fusion proteins for bone regeneration.

    PubMed

    Mieszawska, Aneta J; Nadkarni, Lauren D; Perry, Carole C; Kaplan, David L

    2010-10-26

    The biomimetic design of silk/silica fusion proteins was carried out, combining the self assembling domains of spider dragline silk (Nephila clavipes) and silaffin derived R5 peptide of Cylindrotheca fusiformis that is responsible for silica mineralization. Genetic engineering was used to generate the protein-based biomaterials incorporating the physical properties of both components. With genetic control over the nanodomain sizes and chemistry, as well as modification of synthetic conditions for silica formation, controlled mineralized silk films with different silica morphologies and distributions were successfully generated; generating 3D porous networks, clustered silica nanoparticles (SNPs), or single SNPs. Silk serves as the organic scaffolding to control the material stability and multiprocessing makes silk/silica biomaterials suitable for different tissue regenerative applications. The influence of these new silk-silica composite systems on osteogenesis was evaluated with human mesenchymal stem cells (hMSCs) subjected to osteogenic differentiation. hMSCs adhered, proliferated, and differentiated towards osteogenic lineages on the silk/silica films. The presence of the silica in the silk films influenced osteogenic gene expression, with the upregulation of alkaline phosphatase (ALP), bone sialoprotein (BSP), and collagen type 1 (Col 1) markers. Evidence for early bone formation as calcium deposits was observed on silk films with silica. These results indicate the potential utility of these new silk/silica systems towards bone regeneration. PMID:20976116

  13. Synthesis and Characterisation of Nano Lanthana

    NASA Astrophysics Data System (ADS)

    Moothedan, Marymol; Sherly, K. B.

    2011-10-01

    Nano sized oxide materials have gained an immense importance due to their unque electrical and magnetic properties. Nano Lanthana has various applications in solide oxide fuel cells, catalytic exhaust gas converters, magnetic data storage, water treatment and also as a nano catalyst. The performance of the nano Lanthana depends on the particle size, morphology, crystalline nature etc which in tern depends on the method of preparation and pre-treatment conditions. In this study nano Lanthana was prepared by using the natural polymer Starch as the template. The effect of reaction condition and concentration of starch on the formation, particle size, crystalline nature, and morphology of nano lanthana was also investigated. The phase composition, crystallinine character and particle size were obtained from XRD. The surface morphology of the prepared sample was investigated by SEM. Elemental analysis using SEM-EDAX confirmed the stochiometry of the sample..

  14. Silica reusable surface insulation

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Smith, M.; Leiser, D. B. (Inventor)

    1976-01-01

    A reusable silica surface insulation material is provided by bonding amorphous silica fibers with colloidal silica at an elevated temperature. The surface insulation is ordinarily manufactured in the form of blocks (i.e., tiles).

  15. Size- and structure-dependent toxicity of silica particulates

    NASA Astrophysics Data System (ADS)

    Hanada, Sanshiro; Miyaoi, Kenichi; Hoshino, Akiyoshi; Inasawa, Susumu; Yamaguchi, Yukio; Yamamoto, Kenji

    2011-03-01

    Nano- and micro-particulates firmly attach with the surface of various biological systems. In some chronic pulmonary disease such as asbestosis and silicosis, causative particulates will induce chronic inflammatory disorder, followed by poor prognosis diseases. However, nano- and micro-scale specific toxicity of silica particulates is not well examined enough to recognize the risk of nano- and micro-particulates from the clinical aspect. To clarify the effect of the size and structure of silica particulates on the cellular damage and the biological response, we assessed the cytotoxicity of the various kinds of silica particles including amorphous and crystalline silica, in mouse alveolar macrophage culture, focusing on the fibrotic and inflammatory response. Our study showed that the cytotoxicity, which depends on the particle size and surface area, is correlated with their inflammatory response. By contrast, production of TGF-β, which is one of the fibrotic agents in lung, by addition of crystal silica was much higher than that of amorphous silica. We conclude that fibrosis and inflammation are induced at different phases and that the size- and structure-differences of silica particulates affect the both biological responses, caused by surface activity, radical species, and so on.

  16. Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

    NASA Astrophysics Data System (ADS)

    Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

    2016-05-01

    Silica/polyaniline (PANI) core–shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core–shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

  17. Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

    NASA Astrophysics Data System (ADS)

    Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

    2016-05-01

    Silica/polyaniline (PANI) core-shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core-shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

  18. PREFACE: Nano- and microfluidics Nano- and microfluidics

    NASA Astrophysics Data System (ADS)

    Jacobs, Karin

    2011-05-01

    , Uhlmann et al and articles to be published in a later issue by Bäumchen and Jacobs, Walz et al). Moreover, simulations accounted for these new phenomena (see articles in this issue by Leonforte et al, Hyväaluoma et al, Varnik et al, Chelakkot et al, Litvinov et al and the article to be published in a later issue by Boettcher et al), since commercial software packages typically override these special yet fundamentally new conditions. For future applications, the know-how can be used, for instance, to manipulate particles or molecules in microfluidic systems (see articles in this issue by Nottebrock et al, Straube, Uhlmann et al and the article to be published in a later issue by Boettcher et al). The articles have been divided into four subsections: 'Probing the boundary condition', 'Flow over or in special geometries', 'Soft objects in fluid flow' and 'Manipulating flow'. Many articles, however, cover more than only one aspect and could easily be listed under one of the other subsections. Three articles, two listed in the section 'Probing the boundary condition' and one listed in 'Manipulating flow', could not be included and will be published in a later issue (Bäumchen and Jacobs, Walz et al, Boettcher et al). The collection of studies gives a comprehensive overview of what has been achieved to 'bridge the gap between molecular motion and continuum flow', which was the mission of the programme and which will now form a sound platform for continuative studies. References [1] Bowtell D D 1999 Nature Genet. 21 25 [2] Lion N et al 2003 Electrophoresis 24 3533 [3] Weston A D and Hood L 2004 J. Proteome Res. 3 179 [4] Li D 2004 Microfluidics Nanofluidics 1 1 Nano- and microfluidics contents Impact of slippage on the morphology and stability of a dewetting rim Andreas Münch and Barbara Wagner Nanoscale discontinuities at the boundary of flowing liquids: a look into structure Max Wolff, Philipp Gutfreund, Adrian Rühm, Bulent Akgun and Hartmut Zabel Capillary waves of

  19. Large-scale and highly efficient synthesis of micro- and nano-fibers with controlled fiber morphology by centrifugal jet spinning for tissue regeneration

    NASA Astrophysics Data System (ADS)

    Ren, Liyun; Pandit, Vaibhav; Elkin, Joshua; Denman, Tyler; Cooper, James A.; Kotha, Shiva P.

    2013-02-01

    PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min-1. During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation.PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a

  20. Large-scale and highly efficient synthesis of micro- and nano-fibers with controlled fiber morphology by centrifugal jet spinning for tissue regeneration.

    PubMed

    Ren, Liyun; Pandit, Vaibhav; Elkin, Joshua; Denman, Tyler; Cooper, James A; Kotha, Shiva P

    2013-03-21

    PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min(-1). During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation.

  1. Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er(3+)/Yb(3+) nano-crystalline phosphor.

    PubMed

    Joshi, C; Dwivedi, A; Rai, S B

    2014-08-14

    Infrared-to-visible upconverting rare earths Er(3+)/Yb(3+) co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532 nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555 K under 976 nm laser excitation. PMID:24751781

  2. Annealing variation of the morphology, elemental composition, stiffness and elastic modulus of the self assembled Ag nano structures on clean undoped Si(100) under ambient conditions

    NASA Astrophysics Data System (ADS)

    Pautz, Matthew; Buchheit, Joshua; Parks, Jeffery; Senevirathne, Indrajith

    2010-03-01

    Understanding self assembly of Ag nanostructures on surface support is interesting due to various possible plasmonic and catalytic applications. It can be hypothesized that the mechanical strength and elemental composition of these nanostructures also vary with temperature variations. Out layer oxidation resulting from ambient exposure gives complex characteristics for these nanostructures. RT(300K) Magnetron sputter deposited Ag, on clean, undoped Si(100) was studied under ambient conditions by contact mode and non contact mode Atomic Force Microscopy (AFM) and Scanning Electron Microcopy (SEM). Surface elemental composition on the deposited system was measured with Energy Dispersive X ray Spectroscopy (EDX). Self assembled Ag nano structures on Si were observed to have ˜60nm in width and ˜10nm in height. Annealing at 373K and above they ripen into bigger structures of ˜400nm length. At different annealing stages O, Si and Ag concentrations were measured using EDX. Surface stiffness and elasticity at each stage were measured using force curve method via nano indentation using contact mode AFM.

  3. The formation of helical mesoporous silica nanotubes

    NASA Astrophysics Data System (ADS)

    Wan, Xiaobing; Pei, Xianfeng; Zhao, Huanyu; Chen, Yuanli; Guo, Yongmin; Li, Baozong; Hanabusa, Kenji; Yang, Yonggang

    2008-08-01

    Three chiral cationic gelators were synthesized. They can form translucent hydrogels in pure water. These hydrogels become highly viscous liquids under strong stirring. Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of these gelators as templates. The mechanism of the formation of this hierarchical nanostructure was studied using transmission electron microscopy at different reaction times. The results indicated that there are some interactions between the silica source and the gelator. The morphologies of the self-assemblies of gelators changed gradually during the sol-gel transcription process. It seems that the silica source directed the organic self-assemblies into helical nanostructures.

  4. Laser Surface Treatment of Silica Sol-gel Coating to Produce Nanocrystalline Structure

    NASA Astrophysics Data System (ADS)

    Razavi, R. Shoja; Gordani, Gh.; Hojjati, A.

    2011-12-01

    In this study two methods of laser and furnace sintering are used to prepare nanocrystalline structure of silica sol-gel coating on glass substrate. In laser sintering method, an Nd:YAG pulsed laser with a laser pulse energy of 1 J used to sinter the silica sol-gel coating. To evaluate the surface morphology and microstructural analysis, XRD and SEM were used. The optical properties of coatings were examined by UV/VIS spectroscopy. The results indicated that the laser sintered coating was denser than the furnace sintered coating. No porosity and cracks were detected on the surface of laser sintered coating. Using Scherer mathematical equation, it was shown that the grain size of laser sintered coating is well within nano size range. The uniformity of nanocrystalline structure clearly improved the reflection of incident beam from the laser sintered coating. This was mainly due to increase in grain boundary regions which in turn can cause some the wavelength of the incident beam to be transmitted from silica coatings.

  5. Development of vapor deposited silica sol-gel particles for use as a bioactive materials system.

    PubMed

    Snyder, Katherine L; Holmes, Hallie R; VanWagner, Michael J; Hartman, Natalie J; Rajachar, Rupak M

    2013-06-01

    Silica-based sol-gel and bioglass materials are used in a variety of biomedical applications including the surface modification of orthopedic implants and tissue engineering scaffolds. In this work, a simple system for vapor depositing silica sol-gel nano- and micro-particles onto substrates using nebulizer technology has been developed and characterized. Particle morphology, size distribution, and degradation can easily be controlled through key formulation and manufacturing parameters including water:alkoxide molar ratio, pH, deposition time, and substrate character. These particles can be used as a means to rapidly modify substrate surface properties, including surface hydrophobicity (contact angle changes >15°) and roughness (RMS roughness changes of up to 300 nm), creating unique surface topography. Ions (calcium and phosphate) were successfully incorporated into particles, and induced apatitie-like mineral formation upon exposure to simulated body fluid Preosteoblasts (MC3T3) cultured with these particles showed up to twice the adhesivity within 48 h when compared to controls, potentially indicating an increase in cell proliferation, with the effect likely due to both the modified substrate properties as well as the release of silica ions. This novel method has the potential to be used with implants and tissue engineering materials to influence cell behavior including attachment, proliferation, and differentiation via cell-material interactions to promote osteogenesis.

  6. Modelling nano-clusters and nucleation.

    PubMed

    Catlow, C Richard A; Bromley, Stefan T; Hamad, Said; Mora-Fonz, Miguel; Sokol, Alexey A; Woodley, Scott M

    2010-01-28

    We review the growing role of computational techniques in modelling the structures and properties of nano-particulate oxides and sulphides. We describe the main methods employed, including those based on both electronic structure and interatomic potential approaches. Particular attention is paid to the techniques used in searching for global minima in the energy landscape defined by the nano-particle cluster. We summarise applications to the widely studied ZnO and ZnS systems, to silica nanochemistry and to group IV oxides including TiO(2). We also consider the special case of silica cluster chemistry in solution and its importance in understanding the hydrothermal synthesis of microporous materials. The work summarised, together with related experimental studies, demonstrates a rich and varied nano-cluster chemistry for these materials.

  7. Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica.

    PubMed

    Bansal, Vipul; Ahmad, Absar; Sastry, Murali

    2006-11-01

    Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.

  8. Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica.

    PubMed

    Bansal, Vipul; Ahmad, Absar; Sastry, Murali

    2006-11-01

    Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials. PMID:17061888

  9. Measurements of BET Surface Area on Silica Nanosprings

    SciTech Connect

    Karkamkar, Abhijeet J.

    2008-09-01

    Nitrogen adsorption desorption isotherm for Silica nanosprings (GoNano2) samples deposited on substrate. The isotherm was obtained at 77 K using liquid N2 bath. The area of the substrate is 16 cm2. The amount of the sample is 0.44 mg/cm2. Amount of silica nanosprings= 7.04 mg. There is no indication of substantial micro or mesoporosity in the sample based on the nature of the isotherm. Eleven point BET surface area was measured. Nine points plotted. Goodness if fit R= 0.9992. BET surface area for silica nanosprings= 262 cm2/g

  10. Magnetic Silica-Supported Ruthenium Nanoparticles: An Efficient Catalyst for Transfer Hydrogenation of Carbonyl Compounds

    EPA Science Inventory

    One-pot synthesis of ruthenium nanoparticles on magnetic silica is described which involve the in situ generation of magnetic silica (Fe3O4@ SiO2) and ruthenium nano particles immobilization; the hydration of nitriles and transfer hydrogenation of carbonyl compounds occurs in hi...

  11. The effects of sodium dodecyl sulfate and sodium saccharin on morphology, hardness and wear behavior of Cr-WC nano composite coatings

    NASA Astrophysics Data System (ADS)

    Rezaei-Sameti, M.; Nadali, S.; Falahatpisheh, A.; Rakhshi, M.

    2013-04-01

    The effects of sodium saccharin and sodium dodecyl sulfate (SDS) additives on the amount of incorporated tungsten carbide (WC) particles and morphology of the coatings are investigated. The structure and morphology of the coatings are determined by scanning electron microscopy techniques (SEM). The hardness and tribological behavior of the coatings are studied by micro hardness and pin on disk methods. The experimental results show that with the addition of sodium saccharin and SDS the amount of WC particles in the coating decreases and the size of WC agglomerates reduces. The average size of WC particles is 70 nm. On the other hand the wear resistances of the coatings increase and the optimum wear resistance is 1 g/L.

  12. Two-dimensional self-assemblies of silica nanoparticles formed using the "bubble deposition technique".

    PubMed

    Zhang, Xinfeng; Tang, Guolei; Yang, Shihe; Benattar, Jean-Jacques

    2010-11-16

    Two-dimensional silica nanoparticle assemblies were obtained by deposition of bubble made from a surfactant solution containing nanoparticles onto hydrophobic silicon substrate. The morphologies of the nanoparticle assemblies can be finely controlled by several experimental parameters, including surfactant concentration, nanoparticle concentration, and deposition time. Monolayer of nanoparticles with surface coverage of about 100% can be obtained under appropriate conditions. The method can also be applied to another hydrophobic substrate, HMDS (hexamethyldisilazane)-modified silicon substrate. Furthermore, it can be applied directly to lithography patterned substrates, meaning a high compatibility with the well-developed conventional top-down approaches to nanodevices. This bubble deposition technique is expected to be a promising method in the field of nano-object assembly and organization and has great application potentials.

  13. A biomimetic nano hybrid coating based on the lotus effect and its anti-biofouling behaviors

    NASA Astrophysics Data System (ADS)

    Li, Jiang; Wang, Guoqing; Meng, Qinghua; Ding, Chunhua; Jiang, Hong; Fang, Yongzeng

    2014-10-01

    To develop an environmentally friendly anti-biofouling coating in virtue of bionics, a block copolymer containing fluorine (Coplm_F) of low surface energy was prepared by copolymerization. The Ag-loaded mesoporous silica (Ag@SBA) acting as a controlled-release antifoulant was prepared from the mesoporous silica (SBA-15). The nano hybrid coating (Ag@SBA/Coplm_F) composing of the Coplm_F and Ag@SBA was to biomimetically simulate the lotus microstructure. The concentration of fluorine element on surface was analyzed by the energy dispersive spectroscopy (EDS) and found rising to 1.45% after hybridation, which could be explained by the driving effect of SBA-15 via the hydrogen bond. This nanoscale morphology of the hybrid coating was measured and found highly semblable to the microstructure of the lotus surface. The contact angle was determined as 151° which confirmed the superhydrophobicity and lotus effect. The adhesion behaviors of Pseudomonas fluorescens, Diatoms, and Chlorella on the surface of the nano hybrid coating (Ag@SBA/Coplm_F) were studied and good effects of anti-biofouling were observed.

  14. Impact of the excitation source and plasmonic material on cylindrical active coated nano-particles.

    PubMed

    Arslanagic, Samel; Liu, Yan; Malureanu, Radu; Ziolkowski, Richard W

    2011-01-01

    Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper) are employed and compared for the nano-shell layers.

  15. Cucurbit[8]uril as building block for facile fabrication of well-defined organic crystalline nano-objects with multiple morphologies and compositions.

    PubMed

    An, Qi; Dong, Cheng; Zhu, Wei; Tao, Cheng-An; Yang, Haowei; Wang, Yingxia; Li, Guangtao

    2012-02-20

    Cucurbit[n]urils (CB[n]) have great potential in material and medical applications due to their advantageous molecular recognition properties. Despite organic microcrystals being highly desirable in materials science and the medical industry, CB[n]-based micro- and nanocrystals have not been reported. A facile and efficient approach for producing CB[8]-based organic crystals with well-defined micro- and nanostructures is described, based on the unique host-guest chemistry of CB[8] macrocycle with small guest molecules. The described strategy allows fabrication of micro- and nanocrystals with multiple morphologies and compositions by simply adjusting the preparation conditions and the type of guest molecules. The mechanisms for the formation of the micro/nanocrystals are studied, and morphology-dependent optical and thermal properties typical of organic micro/nanocrystals are described. Additionally, attractive potentials of the prepared microcrystals are shown upon storing small molecules, and in optical applications. The molecular recognition abilities of CB[8] are highlighted in both its preparation process and potential application.

  16. The Effect of Nano-Morphology Modification Using an Amphiphilic Polymer on the Proton Conductivity of Composite Membrane for a Polymer Membrane-Based Fuel Cell.

    PubMed

    Roh, Sung-Hee; Rho, Seon-Gyun; Kim, Sang-Chai; Kim, Ju-Young; Jung, Ho-Young

    2016-02-01

    The effect of morphology modification using an amphiphilic polymer on the proton conductivity of composite membrane for a polymer membrane-based fuel cell was investigated. The proton conductivity of each composite membrane was analyzed by the electrochemical impedance spectroscopy (EIS). The morphological change was confirmed by scanning electron microscope (SEM). In the composite membrane, the proton conductive component was sulfonated poly(ether ether ketone) (sPEEK), while the nonconductive component was poly(vinylidenedifluoride) and the amphiphilic polymer as a compatibilizer was urethane acrylate non-ionomer (UAN). UAN as a compatibilizer improved the interfacial stability between sPEEK and PVdF polymers, even though two polymers were apparently immiscible. The homogeneous distribution of sPEEK and PVdF domains in the composite membrane was obtained with the introduction of UAN due to the amphiphilicity. Therefore, it was found that the proton conductivity of the composite membrane increased with the incorporation of UAN as a compatibilizer. PMID:27433736

  17. Formation of asymmetrical structured silica controlled by a phase separation process and implication for biosilicification.

    PubMed

    Shi, Jia-Yuan; Yao, Qi-Zhi; Li, Xi-Ming; Zhou, Gen-Tao; Fu, Sheng-Quan

    2013-01-01

    Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification.

  18. Formation of Asymmetrical Structured Silica Controlled by a Phase Separation Process and Implication for Biosilicification

    PubMed Central

    Shi, Jia-Yuan; Yao, Qi-Zhi; Li, Xi-Ming; Zhou, Gen-Tao; Fu, Sheng-Quan

    2013-01-01

    Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification. PMID:23585878

  19. Opaline Silica Occurrences in the Columbia Hills of Mars: A Case Study in the Hunt for Biosignatures

    NASA Astrophysics Data System (ADS)

    Ruff, S. W.; Farmer, J. D.

    2016-05-01

    Microbially mediated silica sinter deposits of El Tatio in the Atacama Desert of Chile have remarkably similar morphologic and spectral characteristics as those of silica deposits adjacent to Home Plate in the Columbia Hills of Mars.

  20. Conversion of geothermal waste to commercial products including silica

    DOEpatents

    Premuzic, Eugene T.; Lin, Mow S.

    2003-01-01

    A process for the treatment of geothermal residue includes contacting the pigmented amorphous silica-containing component with a depigmenting reagent one or more times to depigment the silica and produce a mixture containing depigmented amorphous silica and depigmenting reagent containing pigment material; separating the depigmented amorphous silica and from the depigmenting reagent to yield depigmented amorphous silica. Before or after the depigmenting contacting, the geothermal residue or depigmented silica can be treated with a metal solubilizing agent to produce another mixture containing pigmented or unpigmented amorphous silica-containing component and a solubilized metal-containing component; separating these components from each other to produce an amorphous silica product substantially devoid of metals and at least partially devoid of pigment. The amorphous silica product can be neutralized and thereafter dried at a temperature from about 25.degree. C. to 300.degree. C. The morphology of the silica product can be varied through the process conditions including sequence contacting steps, pH of depigmenting reagent, neutralization and drying conditions to tailor the amorphous silica for commercial use in products including filler for paint, paper, rubber and polymers, and chromatographic material.

  1. Multifunctional mesoporous silica catalyst

    DOEpatents

    Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

    2015-03-31

    The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

  2. What Is Crystalline Silica?

    MedlinePlus

    ... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

  3. Silica extraction from geothermal water

    DOEpatents

    Bourcier, William L; Bruton, Carol J

    2014-09-23

    A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

  4. FracMAP: A user-interactive package for performing simulation and orientation-specific morphology analysis of fractal-like solid nano-agglomerates

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Rajan K.; Garro, Mark A.; Chancellor, Shammah; Herald, Christopher; Moosmüller, Hans

    2009-08-01

    Computer simulation techniques have found extensive use in establishing empirical relationships between three-dimensional (3d) and two-dimensional (2d) projected properties of particles produced by the process of growth through the agglomeration of smaller particles (monomers). In this paper, we describe a package, FracMAP, that has been written to simulate 3d quasi-fractal agglomerates and create their 2d pixelated projection images by restricting them to stable orientations as commonly encountered for quasi-fractal agglomerates collected on filter media for electron microscopy. Resulting 2d images are analyzed for their projected morphological properties. Program summaryProgram title: FracMAP Catalogue identifier: AEDD_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDD_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4722 No. of bytes in distributed program, including test data, etc.: 27 229 Distribution format: tar.gz Programming language: C++ Computer: PC Operating system: Windows, Linux RAM: 2.0 Megabytes Classification: 7.7 Nature of problem: Solving for a suitable fractal agglomerate construction under constraints of typical morphological parameters. Solution method: Monte Carlo approximation. Restrictions: Problem complexity is not representative of run-time, since Monte Carlo iterations are of a constant complexity. Additional comments: The distribution file contains two versions of the FracMAP code, one for Windows and one for Linux. Running time: 1 hour for a fractal agglomerate of size 25 on a single processor.

  5. Integrated lithography to prepare periodic arrays of nano-objects

    NASA Astrophysics Data System (ADS)

    Sipos, Áron; Szalai, Anikó; Csete, Mária

    2013-08-01

    We present an integrated lithography method to prepare versatile nano-objects with variable shape and nano-scaled substructure, in wavelength-scaled periodic arrays with arbitrary symmetry. The idea is to illuminate colloid sphere monolayers by polarized beams possessing periodic lateral intensity modulations. Finite element method was applied to determine the effects of the wavelength, polarization and angle of incidence of the incoming beam, and to predict the characteristics of nano-objects, which can be fabricated on thin metal layer covered substrates due to the near-field enhancement under silica colloid spheres. The inter-object distance is controlled by varying the relative orientation of the periodic intensity modulation with respect to the silica colloid sphere monolayer. It is shown that illuminating silica colloid sphere monolayers by two interfering beams, linear patterns made of elliptical holes appear in case of linear polarization, while circularly polarized beams result in co-existent rounded objects, as more circular nano-holes and nano-crescents. The size of the nano-objects and their sub-structure is determined by the spheres diameter and by the wavelength. We present various complex plasmonic patterns made of versatile nano-objects that can be uniquely fabricated applying the inherent symmetry breaking possibilities in the integrated lithography method.

  6. New non-toxic transition metal nanocomplexes and Zn complex-silica xerogel nanohybrid: Synthesis, spectral studies, antibacterial, and antitumor activities

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy; Saif, M.; Nabeel, Asmaa I.; Shokry, R.

    2016-08-01

    A new chromone Schiff base and its complexes of Cu(II), Ni(II), Co(II), Fe(III), Zn(II), Cd(II), and UO2(VI) as well as Zn(II) complex-silica xerogel nanohybrid were successfully prepared in a nano domain with crystalline or amorphous structures. Structures of the Schiff base and its complexes were investigated by elemental and thermal analyses, IR, 1H NMR, electronic, ESR, mass spectra, XRD, and TEM, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data revealed that the Schiff base ligand behaves as a monobasic tridentate ligand. The coordination sites with metal ions are γ-pyrone oxygen, azomethine nitrogen, and oxygen of the carboxylic group. The metal complexes exhibited octahedral geometry, except Cu(II) complex, which has a square planar geometry and UO2(VI) complex, in which uranium ion is hepta-coordinated. Transmission electron microscope (TEM) analysis showed that Ni(II) and Zn(II) complexes have aggregated spheres and rod morphologies, respectively. TEM images of Zn(II) complex-silica xerogel nanohybrid showed a nanosheet morphology with 46 nm average size and confirmed that the complex was uniformly distributed into the silica pores. The obtained nanocomplexes were tested as antimicrobial and antitumor agents. The results showed that Zn(II) nanocomplex and Zn(II) complex-silica xerogel nanohybrid have high activity. The toxicity test on mice showed that Zn(II) complex and Zn(II) complex-silica xerogel nanohybrid have lower toxicity than cisplatin.

  7. Physicochemical characterizations of nano-palm oil fuel ash

    SciTech Connect

    Rajak, Mohd Azrul Abdul; Majid, Zaiton Abdul; Ismail, Mohammad

    2015-07-22

    Palm Oil Fuel Ash (POFA) is known as a good supplementary cementing material due to its siliceous-rich content. The application of nanotechnology in the pozzolanic materials could invent new functions in the efficiency of physical and chemical properties of materials. Thus, the present study aims to generate nano-sized POFA and characterize the physicochemical properties of nano-palm oil fuel ash (nPOFA). The nPOFA was prepared by mechanically grinding micro POFA using a high intensity ball milling for 6 hours. The physicochemical properties of nPOFA were characterized via X-Ray Fluoresence (XRF), Scanning Emission microscopy- Energy Dispersive X-Ray (SEM-EDX), Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD). The particle size of nPOFA acquired from TEM analysis was in the range of 20 nm to 90 nm, while the average crystallite size calculated from XRD diffractogram was 61.5 nm. The resulting nPOFA has a BET surface area of 145.35 m{sup 2}/g, which is more than 85% increment in surface area compared to micro-sized POFA. The morphology and elemental studies showed the presence of spherical as well as irregularly shaped and fine nPOFA particles contains with high silicon content. The presence of α-quartz as the major phase of the nPOFA was identified through XRD analysis. The study concludes that nPOFA has the potential as a supplementary cementing material due to the high silica content, high surface area and the unique behaviors of nano-structured particles.

  8. Physicochemical characterizations of nano-palm oil fuel ash

    NASA Astrophysics Data System (ADS)

    Rajak, Mohd Azrul Abdul; Majid, Zaiton Abdul; Ismail, Mohammad

    2015-07-01

    Palm Oil Fuel Ash (POFA) is known as a good supplementary cementing material due to its siliceous-rich content. The application of nanotechnology in the pozzolanic materials could invent new functions in the efficiency of physical and chemical properties of materials. Thus, the present study aims to generate nano-sized POFA and characterize the physicochemical properties of nano-palm oil fuel ash (nPOFA). The nPOFA was prepared by mechanically grinding micro POFA using a high intensity ball milling for 6 hours. The physicochemical properties of nPOFA were characterized via X-Ray Fluoresence (XRF), Scanning Emission microscopy- Energy Dispersive X-Ray (SEM-EDX), Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD). The particle size of nPOFA acquired from TEM analysis was in the range of 20 nm to 90 nm, while the average crystallite size calculated from XRD diffractogram was 61.5 nm. The resulting nPOFA has a BET surface area of 145.35 m2/g, which is more than 85% increment in surface area compared to micro-sized POFA. The morphology and elemental studies showed the presence of spherical as well as irregularly shaped and fine nPOFA particles contains with high silicon content. The presence of α-quartz as the major phase of the nPOFA was identified through XRD analysis. The study concludes that nPOFA has the potential as a supplementary cementing material due to the high silica content, high surface area and the unique behaviors of nano-structured particles.

  9. Detailed investigation of the influence of the process parameters on the nano-morphology of Ag deposited on SiC by radio-frequency sputtering

    NASA Astrophysics Data System (ADS)

    Ruffino, F.; Grimaldi, M. G.

    2011-08-01

    In this work, a detailed study of the influence of the synthesis parameters (deposition time t and emission current I) on the morphological properties of Ag nanoparticles sputter-deposited on silicon carbide is carried out. Using the atomic force microscopy technique, we analyzed the evolution of several structural characteristics as a function both of t and I: the length and width of the Ag nanoparticles, the number of nanoparticles per unit area, the nanoparticles' fraction of the covered area, and the roughness of the resulting Ag film. Using consolidated theoretical frameworks and fitting approaches, the relations between such quantities and the process parameters t and I were established. In particular, the application of the interrupted coalescence model allowed us to evaluate the critical mean island diameter for the partial coalescence process; the dynamic scaling theories of growing interfaces lead, instead, to the determination of the dynamic scaling, growth, and roughness exponents (the values of which suggest a conservative growth process of the islands in which the atomic surface diffusion plays a key role). Finally, the Avrami approach to the study of the evolution of the fraction of area covered by the Ag islands allowed us to evaluate the Avrami exponent.

  10. A study of the influence of micro and nano phase morphology on the mechanical properties of a rubber-modified epoxy resin

    NASA Astrophysics Data System (ADS)

    Russell, Bobby Glenn

    Epoxy resins are thermosets with extraordinary adhesion; high strength; good resistance to creep, heat, and chemicals; and they have low shrinkage. Conversely, these polymers are brittle, they are sensitive to moisture, and they exhibit poor toughness. To improve their toughness, they are often modified by introducing dispersed rubber particles in the primary phase. In this study, the epoxy resin was modified with carboxyl-terminated butadiene acrylonitrile (CTBN), liquid-reactive rubbers. The initiator concentration, percent acrylonitrile in the CTBN rubber, and cure temperatures were altered to give varying materials properties. Statistical analysis of the morphology data showed that the percentage of rubber acrylonitrile had an effect on both the rubber particle size and volume fraction. The cure temperature had an effect on the rubber particle volume and modulus. Plots of the rubber particle size, volume fraction, and modulus versus bulk elastic storage modulus and fracture toughness revealed that rubber particle size had no effect on bulk properties, volume fraction and rubber particle modulus had an effect on both the bulk storage elastic modulus and fracture toughness.

  11. Sonochemical synthesis of silica particles and their size control

    NASA Astrophysics Data System (ADS)

    Kim, Hwa-Min; Lee, Chang-Hyun; Kim, Bonghwan

    2016-09-01

    Using an ultrasound-assisted sol-gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  12. How Nano Are Nanocomposites

    SciTech Connect

    Schaefer, Dale W.; Justice, Ryan S.

    2010-10-22

    Composite materials loaded with nanometer-sized reinforcing fillers are widely believed to have the potential to push polymer mechanical properties to extreme values. Realization of anticipated properties, however, has proven elusive. The analysis presented here traces this shortfall to the large-scale morphology of the filler as determined by small-angle X-ray scattering, light scattering, and electron imaging. We examine elastomeric, thermoplastic, and thermoset composites loaded with a variety of nanoscale reinforcing fillers such as precipitated silica, carbon nanotubes (single and multiwalled), and layered silicates. The conclusion is that large-scale disorder is ubiquitous in nanocomposites regardless of the level of dispersion, leading to substantial reduction of mechanical properties (modulus) compared to predictions based on idealized filler morphology.

  13. Self-assembly of nanoporous silica shapes: Synthesis, morphogenesis, and applications

    NASA Astrophysics Data System (ADS)

    Kievsky, Yaroslav

    Increasing interest in nanotechnologies and biocomplexity has created the need to understand the morphogenesis of complex self-assembled shapes, which either exist in nature or can be synthesized for a specific purpose. The material obtained as a result of liquid crystal templating (hexagonal mesostructured silica, e.g., so-called MCM-41) features large variety of complex micron size shapes and sizes. This is a good test system for investigation of the morphogenesis of the nanoporous silicas. Such material is of great interest to industry since it features highly uniform nanosize porosity, and consequently, can be functionalized by putting various substances inside the pores. While the synthesis of this material is relatively well elaborated and its chemistry is understood, the mechanisms responsible for the overall morphogenesis of silica nanoporous shapes require further investigation. This is the main goal of the present work. The basic hypothesis was that the complex morphology of the shapes is a result of relaxation of mechanical stresses which appear due to differential polymerization of silica precursor. Such a difference occurs due to difference in time required to assembly different layers of the shapes, as a result of the age distinction between the older inner parts of the shapes and the younger outer layers. The main goals of this work are to elaborate quantitatively the theory of morphogenesis of self-assembled nanoporous silica shapes, to develop experimental recipes of synthesis of specific shapes in controlled way, to predict and synthesize new shapes suitable for specific applications. Important insights of this research open a new area of controlled synthesis of nanoporous silica shapes, contribute a new way of thinking about templated synthesis of hierarchical materials over size scales which has never been seen in solid state chemistry. The results of this work have an impact in such areas as development of new shapes as templates for

  14. Electrical and morphological characterization of transfer-printed Au/Ti/TiOx/p+-Si nano- and microstructures with plasma-grown titanium oxide layers

    NASA Astrophysics Data System (ADS)

    Weiler, Benedikt; Nagel, Robin; Albes, Tim; Haeberle, Tobias; Gagliardi, Alessio; Lugli, Paolo

    2016-04-01

    Highly-ordered, sub-70 nm-MOS-junctions of Au/Ti/TiOx/p+-Si were efficiently and reliably fabricated by nanotransfer-printing (nTP) over large areas and their functionality was investigated with respect to their application as MOS-devices. First, we used a temperature-enhanced nTP process and integrated the plasma-oxidation of a nm-thin titanium film being e-beam evaporated directly on the stamp before the printing step without affecting the p+-Si substrate. Second, morphological investigations (scanning electron microscopy) of the nanostructures confirm the reliable transfer of Au/Ti/TiOx-pillars of 50 nm, 75 nm, and 100 nm size of superior quality on p+-Si by our transfer protocol. Third, the fabricated nanodevices are also characterized electrically by conductive AFM. Fourth, the results are compared to probe station measurements on identically processed, i.e., transfer-printed μm-MOS-structures including a systematic investigation of the oxide formation. The jV-characteristics of these MOS-junctions demonstrate the electrical functionality as plasma-grown tunneling oxides and the effectivity of the transfer-printing process for their large-scale fabrication. Next, our findings are supported by fits to the jV-curves of the plasma-grown titanium oxide by kinetic-Monte-Carlo simulations. These fits allowed us to determine the dominant conduction mechanisms, the material parameters of the oxides and, in particular, a calibration of the thickness depending on applied plasma time and power. Finally, also a relative dielectric permittivity of 12 was found for such plasma-grown TiOx-layers.

  15. Optimization, Yield Studies and Morphology of WO3Nano-Wires Synthesized by Laser Pyrolysis in C2H2and O2Ambients—Validation of a New Growth Mechanism

    PubMed Central

    2008-01-01

    Laser pyrolysis has been used to synthesize WO3nanostructures. Spherical nano-particles were obtained when acetylene was used to carry the precursor droplet, whereas thin films were obtained at high flow-rates of oxygen carrier gas. In both environments WO3nano-wires appear only after thermal annealing of the as-deposited powders and films. Samples produced under oxygen carrier gas in the laser pyrolysis system gave a higher yield of WO3nano-wires after annealing than the samples which were run under acetylene carrier gas. Alongside the targeted nano-wires, the acetylene-ran samples showed trace amounts of multi-walled carbon nano-tubes; such carbon nano-tubes are not seen in the oxygen-processed WO3nano-wires. The solid–vapour–solid (SVS) mechanism [B. Mwakikunga et al., J. Nanosci. Nanotechnol., 2008] was found to be the possible mechanism that explains the manner of growth of the nano-wires. This model, based on the theory from basic statistical mechanics has herein been validated by length-diameter data for the produced WO3nano-wires.

  16. Relationship between amorphous silica and precious metal in quartz veins

    NASA Astrophysics Data System (ADS)

    Harrichhausen, N.; Rowe, C. D.; Board, W. S.; Greig, C. J.

    2015-12-01

    Super-saturation of silica is common in fault fluids, due to pressure changes associated with fracture, fault slip, or temperature gradients in hydrothermal systems. These mechanisms lead to precipitation of amorphous silica, which will recrystallize to quartz under typical geologic conditions. These conditions may also promote the saturation of precious metals, such as gold, and the precipitation of nanoparticles. Previous experiments show that charged nanoparticles of gold can attach to the surface of amorphous silica nanoparticles. Thus, gold and silica may be transported as a colloid influencing mineralization textures during amorphous silica recrystallization to quartz. This may enrich quartz vein hosted gold deposits, but the instability of hydrous silica during subsequent deformation means that the microstructural record of precipitation of gold is lost. We investigate a recent, shallow auriferous hydrothermal system at Dixie Valley, Nevada to reveal the nano- to micro-scale relationships between gold and silica in fresh veins. Fault slip surfaces at Dixie Valley exhibit layers of amorphous silica with partial recrystallization to quartz. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) show amorphous silica can contain a few wt. % gold while areas recrystallized to quartz are barren. At the Jurassic Brucejack deposit in British Columbia, Canada we observe the cryptocrystalline quartz textures that may indicate recrystallization from amorphous silica within quartz-carbonate veins containing high grade gold. Comb quartz within syntaxial veins, vugs, and coating breccia clasts indicate structural dilation. Vein geometry is investigated to determine relative importance of fault slip in creating dilational sites. By comparing quartz-carbonate veins from the Dixie Valley to Brucejack, we can determine whether amorphous silica formed in different environments show similar potential to affect precious metal mineralization.

  17. Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

    SciTech Connect

    Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D; Elhadj, S; Yang, S T

    2009-10-30

    Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.

  18. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  19. Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd2+, Cu2+ and Hg2+ ions in water and some foodstuff samples.

    PubMed

    Afkhami, Abbas; Soltani-Felehgari, Farzaneh; Madrakian, Tayyebeh; Ghaedi, Hamed; Rezaeivala, Majid

    2013-04-10

    A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N'-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, -1.100 V vs. Ag/AgCl; deposition time, 60s; resting time, 10s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL(-1) for the determination of Cd(2+), Cu(2+) and Hg(2+), respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd(2+), Cu(2+) and Hg(2+). Furthermore, the present method was applied to the determination of Cd(2+), Cu(2+) and Hg(2+) in water and some foodstuff samples.

  20. Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd2+, Cu2+ and Hg2+ ions in water and some foodstuff samples.

    PubMed

    Afkhami, Abbas; Soltani-Felehgari, Farzaneh; Madrakian, Tayyebeh; Ghaedi, Hamed; Rezaeivala, Majid

    2013-04-10

    A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N'-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, -1.100 V vs. Ag/AgCl; deposition time, 60s; resting time, 10s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL(-1) for the determination of Cd(2+), Cu(2+) and Hg(2+), respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd(2+), Cu(2+) and Hg(2+). Furthermore, the present method was applied to the determination of Cd(2+), Cu(2+) and Hg(2+) in water and some foodstuff samples. PMID:23522108

  1. Interactions of silica surfaces

    SciTech Connect

    Vigil, G.; Xu, Z.; Steinberg, S.; Israelachvili, J. . Dept. of Chemical and Nuclear Engineering and Materials Dept.)

    1994-07-01

    Adhesion, friction, and colloidal forces in air and aqueous salt solutions have been measured between various silica surfaces prepared by depositing amorphous but highly smooth silica films on mica. The results show four interesting and interrelated phenomena: (i) the adhesion of silica surfaces in air increases slowly with contact time, especially in humid air where the contacting surfaces become separated by an [approximately]20-[angstrom]-thick layer of hydrated silica or silica gel; (ii) the friction of two silica surfaces exhibits large sticking or stiction spikes, whose magnitude increases in the presence of water and when the surfaces are kept in contact longer before sliding; (iii) the non-DLVO repulsion commonly seen at short range (<40 A) between silica surfaces immersed in aqueous solutions is monotonically repulsive, with no oscillatory component, and is quite unlike theoretical expectations and previous measurements of forces due to solvent structure; (iv) dynamic contact angle measurements reveal time-dependent effects which cannot be due to a fixed surface chemical heterogeneity or roughness. The results indicate that silica surfaces undergo slow structural and chemical changes during interactions with water and with each other. More specifically, the authors propose that the unusual interfacial and colloidal properties of silica are due, not to hydration effects, but to the presence of an [approximately]10-[angstrom]-thick gel-like layer of protruding silanol and silicilic acid groups that grow on the surfaces in the presence of water. These protruding groups react chemically (sinter) with similar groups located on an opposing surface and give rise to the unusual time-dependent adhesion, friction, and non-DLVO forces observed. The proposed mechanism in terms of a surface layer of silica gel is consistent with the known surface chemistry of silica and accounts for the results reported and for other unusual surface and colloidal properties of silica.

  2. Silica, silicosis, and cancer

    SciTech Connect

    Goldsmith, D.F.; Winn, D.M.; Shy, C.M.

    1986-01-01

    These proceedings collect papers on occupational exposure. Topics include: measurement of silica dust, mortality in granite workers, effects of quartz in coal mine dust, pneumoconiosis, and lung cancer.

  3. Biocompatibility Assessment of Si-based Nano- and Micro-particles

    PubMed Central

    Jaganathan, Hamsa; Godin, Biana

    2012-01-01

    Silicon is one of the most abundant chemical elements found on the Earth. Due to its unique chemical and physical properties, silicon based materials and their oxides (e.g. silica) have been used in several industries such as building and construction, electronics, food industry, consumer products and biomedical engineering/medicine. This review summarizes studies on effects of silicon and silica nano- and micro-particles on cells and organs following four main exposure routes, namely, intravenous, pulmonary, dermal and oral. Further, possible genotoxic effects of silica based nanoparticles are discussed. The review concludes with an outlook on improving and standardizing biocompatibility assessment for nano- and micro-particles. PMID:22634160

  4. The properties of Portland cement-limestone-silica fume mortars

    SciTech Connect

    Zelic, J.; Krstulovic, R.; Tkalcec, E.; Krolo, P.

    2000-01-01

    This work has studied the influence of the combined action of silica fume and limestone or strength development, porosity, pore structure and morphological features in the system where 15 wt% of cement was substituted by finely ground limestone. Silica fume was added in amounts of 0, 2, 5, 8, 11 and 15 wt% on a cement basis, respectively. It has been established that limestone addition considerably increases the total porosity of mortars. However, if introduced together with silica fume up to 8 wt% of silica, porosity decreases. More than 8 wt% of silica increases the porosity again. The cement mortar containing 8 wt% of silica fume shows the highest compressive strength, the minimum value of the total porosity, and its pore size distribution curve shows a discontinuous pore structure. Limestone is taken up to the system and reacts with aluminate and ferrite phases from cement. Approximately 5 wt% is available for reaction after 120 days hydration of mortars containing no silica fume. The quantity of limestone incorporated is affected by the silica fume content. The replacement of Portland cement by 15 wt% of silica fume causes reduction both in the amount of cement and in the free CH content available for limestone chemical activity, and in this condition limestone acts only as a filler addition.

  5. Preparation of monodisperse porous silica particles using poly(glycidyl methacrylate) microspheres as a template.

    PubMed

    Grama, S; Horák, D

    2015-01-01

    Monodisperse macroporous poly(glycidyl methacrylate) (PGMA) microspheres were used as a template for preparing porous silica particles. The starting polymer microspheres that were 9.3 microm in size were synthesized by multistep swelling polymerization using a modified Ugelstad technique. Subsequently, silica (SiO2) was deposited on the surface and inside the PGMA microspheres to produce poly(glycidyl methacrylate)-silica hybrid particles (PGMA-SiO2). Upon calcination of the PGMA-SiO2 microspheres, porous silica particles were formed. The morphology, particle size, polydispersity and inner structure of the silica microspheres were investigated by scanning and transmission electron microscopy. Thermogravimetric analysis and dynamic adsorption of nitrogen determined the amount of silica formed and its specific surface area. Compared with the starting PGMA microspheres, the size of the porous silica particles decreased by up to 30%. These porous silica microspheres are promising for chromatography and biomedical applications. PMID:26447591

  6. Preparation of monodisperse porous silica particles using poly(glycidyl methacrylate) microspheres as a template.

    PubMed

    Grama, S; Horák, D

    2015-01-01

    Monodisperse macroporous poly(glycidyl methacrylate) (PGMA) microspheres were used as a template for preparing porous silica particles. The starting polymer microspheres that were 9.3 microm in size were synthesized by multistep swelling polymerization using a modified Ugelstad technique. Subsequently, silica (SiO2) was deposited on the surface and inside the PGMA microspheres to produce poly(glycidyl methacrylate)-silica hybrid particles (PGMA-SiO2). Upon calcination of the PGMA-SiO2 microspheres, porous silica particles were formed. The morphology, particle size, polydispersity and inner structure of the silica microspheres were investigated by scanning and transmission electron microscopy. Thermogravimetric analysis and dynamic adsorption of nitrogen determined the amount of silica formed and its specific surface area. Compared with the starting PGMA microspheres, the size of the porous silica particles decreased by up to 30%. These porous silica microspheres are promising for chromatography and biomedical applications.

  7. Chitosan-silica hybrid porous membranes.

    PubMed

    Pandis, Christos; Madeira, Sara; Matos, Joana; Kyritsis, Apostolos; Mano, João F; Ribelles, José Luis Gómez

    2014-09-01

    Chitosan-silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol-gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol-gel reactions took place with Tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) acting as silica precursors. GPTMS served also as a coupling agent between the free amino groups of chitosan and the silica network. The morphology study of the composite revealed that the silica phase appears as a layer covering the chitosan membrane pore walls. The mechanical properties of the hybrids were characterized by means of compressive stress-strain measurements. By immersion in water the hybrids exhibit an increase in elastic modulus up to two orders of magnitude. PMID:25063153

  8. Silica-metal core-shell nanostructures.

    PubMed

    Jankiewicz, B J; Jamiola, D; Choma, J; Jaroniec, M

    2012-01-15

    Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed

  9. Silica, Silicosis, and Autoimmunity

    PubMed Central

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  10. Synthesis and new structure shaping mechanism of silica particles formed at high pH

    SciTech Connect

    Zhang, Henan; Zhao, Yu; Akins, Daniel L.

    2012-10-15

    For the sol-gel synthesis of silica particles under high pH catalytic conditions (pH>12) in water/ethanol solvent, we have deduced that the competing dynamics of chemical etching and sol-gel process can explain the types of silica particles formed and their morphologies. We have demonstrated that emulsion droplets that are generated by adding tetraethyl orthosilicate (TEOS) to a water-ethanol solution serve as soft templates for hollow spherical silica (1-2 {mu}m). And if the emulsion is converted by the sol-gel process, one finds that suspended solid silica spheres of diameter of {approx}900 nm are formed. Moreover, several other factors are found to play fundamental roles in determining the final morphologies of silica particles, such as by variation of the pH (in our case, using OH{sup -}) to a level where condensation dominates; by changing the volume ratios of water/ethanol; and using an emulsifier (specifically, CTAB) - Graphical abstract: 'Local chemical etching' and sol-gel process have been proposed to interpret the control of morphologies of silica particles through varying initial pHs in syntheses. Highlights: Black-Right-Pointing-Pointer Different initial pHs in our syntheses provides morphological control of silica particles. Black-Right-Pointing-Pointer 'Local chemical etching' and sol-gel process describes the formation of silica spheres. Black-Right-Pointing-Pointer The formation of emulsions generates hollow silica particles.

  11. Ion-shaping of embedded gold hollow nanoshells into vertically aligned prolate morphologies

    NASA Astrophysics Data System (ADS)

    Coulon, Pierre-Eugéne; Amici, Julia; Clochard, Marie-Claude; Khomenkov, Vladimir; Dufour, Christian; Monnet, Isabelle; Grygiel, Clara; Perruchas, Sandrine; Ulysse, Christian; Largeau, Ludovic; Rizza, Giancarlo

    2016-02-01

    Ion beam shaping is a novel technique with which one can shape nano-structures that are embedded in a matrix, while simultaneously imposing their orientation in space. In this work, we demonstrate that the ion-shaping technique can be implemented successfully to engineer the morphology of hollow metallic spherical particles embedded within a silica matrix. The outer diameter of these particles ranges between 20 and 60 nm and their shell thickness between 3 and 14 nm. Samples have been irradiated with 74 MeV Kr ions at room temperature and for increasing fluences up to 3.8 × 1014 cm-2. In parallel, the experimental results have been theoretically simulated by using a three-dimensional code based on the thermal-spike model. These calculations show that the particles undergo a partial melting during the ion impact, and that the amount of molten phase is maximal when the impact is off-center, hitting only one hemisphere of the hollow nano-particle. We suggest a deformation scenario which differs from the one that is generally proposed for solid nano-particles. Finally, these functional materials can be seen as building blocks for the fabrication of nanodevices with really three-dimensional architecture.

  12. Ion-shaping of embedded gold hollow nanoshells into vertically aligned prolate morphologies.

    PubMed

    Coulon, Pierre-Eugéne; Amici, Julia; Clochard, Marie-Claude; Khomenkov, Vladimir; Dufour, Christian; Monnet, Isabelle; Grygiel, Clara; Perruchas, Sandrine; Ulysse, Christian; Largeau, Ludovic; Rizza, Giancarlo

    2016-01-01

    Ion beam shaping is a novel technique with which one can shape nano-structures that are embedded in a matrix, while simultaneously imposing their orientation in space. In this work, we demonstrate that the ion-shaping technique can be implemented successfully to engineer the morphology of hollow metallic spherical particles embedded within a silica matrix. The outer diameter of these particles ranges between 20 and 60 nm and their shell thickness between 3 and 14 nm. Samples have been irradiated with 74 MeV Kr ions at room temperature and for increasing fluences up to 3.8 × 10(14) cm(-2). In parallel, the experimental results have been theoretically simulated by using a three-dimensional code based on the thermal-spike model. These calculations show that the particles undergo a partial melting during the ion impact, and that the amount of molten phase is maximal when the impact is off-center, hitting only one hemisphere of the hollow nano-particle. We suggest a deformation scenario which differs from the one that is generally proposed for solid nano-particles. Finally, these functional materials can be seen as building blocks for the fabrication of nanodevices with really three-dimensional architecture.

  13. Ion-shaping of embedded gold hollow nanoshells into vertically aligned prolate morphologies

    PubMed Central

    Coulon, Pierre-Eugéne; Amici, Julia; Clochard, Marie-Claude; Khomenkov, Vladimir; Dufour, Christian; Monnet, Isabelle; Grygiel, Clara; Perruchas, Sandrine; Ulysse, Christian; Largeau, Ludovic; Rizza, Giancarlo

    2016-01-01

    Ion beam shaping is a novel technique with which one can shape nano-structures that are embedded in a matrix, while simultaneously imposing their orientation in space. In this work, we demonstrate that the ion-shaping technique can be implemented successfully to engineer the morphology of hollow metallic spherical particles embedded within a silica matrix. The outer diameter of these particles ranges between 20 and 60 nm and their shell thickness between 3 and 14 nm. Samples have been irradiated with 74 MeV Kr ions at room temperature and for increasing fluences up to 3.8 × 1014 cm−2. In parallel, the experimental results have been theoretically simulated by using a three-dimensional code based on the thermal-spike model. These calculations show that the particles undergo a partial melting during the ion impact, and that the amount of molten phase is maximal when the impact is off-center, hitting only one hemisphere of the hollow nano-particle. We suggest a deformation scenario which differs from the one that is generally proposed for solid nano-particles. Finally, these functional materials can be seen as building blocks for the fabrication of nanodevices with really three-dimensional architecture. PMID:26883992

  14. Ion-shaping of embedded gold hollow nanoshells into vertically aligned prolate morphologies.

    PubMed

    Coulon, Pierre-Eugéne; Amici, Julia; Clochard, Marie-Claude; Khomenkov, Vladimir; Dufour, Christian; Monnet, Isabelle; Grygiel, Clara; Perruchas, Sandrine; Ulysse, Christian; Largeau, Ludovic; Rizza, Giancarlo

    2016-01-01

    Ion beam shaping is a novel technique with which one can shape nano-structures that are embedded in a matrix, while simultaneously imposing their orientation in space. In this work, we demonstrate that the ion-shaping technique can be implemented successfully to engineer the morphology of hollow metallic spherical particles embedded within a silica matrix. The outer diameter of these particles ranges between 20 and 60 nm and their shell thickness between 3 and 14 nm. Samples have been irradiated with 74 MeV Kr ions at room temperature and for increasing fluences up to 3.8 × 10(14) cm(-2). In parallel, the experimental results have been theoretically simulated by using a three-dimensional code based on the thermal-spike model. These calculations show that the particles undergo a partial melting during the ion impact, and that the amount of molten phase is maximal when the impact is off-center, hitting only one hemisphere of the hollow nano-particle. We suggest a deformation scenario which differs from the one that is generally proposed for solid nano-particles. Finally, these functional materials can be seen as building blocks for the fabrication of nanodevices with really three-dimensional architecture. PMID:26883992

  15. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  16. Silica Synthesis by Sponges: Unanticipated Molecular Mechanism

    NASA Astrophysics Data System (ADS)

    Morse, D. E.; Weaver, J. C.

    2001-12-01

    substitutions of specific amino acid sidechains, in conjunction with computer-assisted molecular modeling and biomimetic synthesis, allowed us to probe the determinants of catalytic activity and confirm the identification of the amino acid sidechains required for hydrolysis of the silicon alkoxides. If, as suggested by the data of others, silicic acid is conjugated with organic moieties after its transport into the cell, the catalytic mechanism described here may be important in biosilicification by sponges. As is often the case, we have been better able to answer mechanistic questions about "how" silica can be formed biologically, than "why" the diversity of structures is elaborated. Studies of spicule formation during cellular regeneration in Tethya aurantia reveal that synthesis of the larger silica needles (megascleres) and smaller starburst-shaped microscleres may be independently regulated, presumably at the genetic level. The spatial segregation of these morphologically-distinct spicule types within the sponge further suggests an adaptive significance of the different skeletal elements.

  17. Electrochemical Sensors: Functionalized Silica

    SciTech Connect

    Fryxell, Glen E.; Lin, Yuehe; Yantasee, Wassana

    2009-03-24

    This chapter summarizes recent devellopment of electrochemical sensors based on functionlized mesoporous silica materials. The nanomatrials based sensors have been developed for sensitive and selective enrironmental detection of toxic heavy metal and uranium ions.

  18. Synthesis of silica vesicles with controlled entrance size for high loading, sustained release, and cellular delivery of therapeutical proteins.

    PubMed

    Zhang, Jun; Karmakar, Surajit; Yu, Meihua; Mitter, Neena; Zou, Jin; Yu, Chengzhong

    2014-12-29

    A rationally designed two-step synthesis of silica vesicles is developed with the formation of vesicular structure in the first step and fine control over the entrance size by tuning the temperature in the second step. The silica vesicles have a uniform size of ≈50 nm with excellent cellular uptake performance. When the entrance size is equal to the wall thickness, silica vesicles after hydrophobic modification show the highest loading amount (563 mg/g) towards Ribonuclease A with a sustained release behavior. Consequently, the silica vesicles are excellent nano-carriers for cellular delivery applications of therapeutical biomolecules. PMID:25060135

  19. Nano-technology and nano-toxicology

    PubMed Central

    Maynard, Robert L.

    2012-01-01

    Rapid developments in nano-technology are likely to confer significant benefits on mankind. But, as with perhaps all new technologies, these benefits are likely to be accompanied by risks, perhaps by new risks. Nano-toxicology is developing in parallel with nano-technology and seeks to define the hazards and risks associated with nano-materials: only when risks have been identified they can be controlled. This article discusses the reasons for concern about the potential effects on health of exposure to nano-materials and relates these to the evidence of the effects on health of the ambient aerosol. A number of hypotheses are proposed and the dangers of adopting unsubstantiated hypotheses are stressed. Nano-toxicology presents many challenges and will need substantial financial support if it is to develop at a rate sufficient to cope with developments in nano-technology. PMID:22662021

  20. Crystalline Silica Primer

    USGS Publications Warehouse

    ,

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  1. PATCHY SILICA-COATED SILVER NANOWIRES AS SERS SUBSTRATES

    SciTech Connect

    Murph, S.; Murphy, C.

    2013-03-29

    We report a class of core-shell nanomaterials that can be used as efficient surface-enhancement Raman scattering (SERS) substrates. The core consists of silver nanowires, prepared through a chemical reduction process, that are used to capture 4- mercaptobenzoic acid (4-MBA), a model analyte. The shell was prepared through a modified Stöber method and consists of patchy or full silica coats. The formation of silica coats was monitored via transmission electron microscopy, UV-visible spectroscopy and phase-analysis light scattering for measuring effective surface charge. Surprisingly, the patchy silica coated silver nanowires are better SERS substrate than silver nanowires; nanomolar concentration of 4-MBA can be detected. In addition, “nano-matryoshka” configurations were used to quantitate/explore the effect of the electromagnetic field at the tips of the nanowire (“hot spots”) in the Raman scattering experiment.

  2. Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

    PubMed

    Borges, Endler M

    2015-04-01

    Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed.

  3. Modifying Si-based consolidants through the addition of colloidal nano-particles

    NASA Astrophysics Data System (ADS)

    Ksinopoulou, E.; Bakolas, A.; Moropoulou, A.

    2016-04-01

    The modification of silicon-based stone consolidants has been the subject of many scientific studies aiming to overcome the commonly reported drawbacks of these materials, such as the tendency to shrink and crack during drying. The addition of nano-particle dispersions into silica matrix has been found to enhance their effectiveness in several ways. Objective of the current research was to study the preparation of particle-modified consolidants (PMC), consisting of an ethyl silicate matrix (TEOS) loaded with colloidal silica (SiO2) nano-particles and oxide titania (TiO2) particles. The effect of the polyacrylic acid on the dispersion stability was also investigated, by varying its concentration into PMC samples. The prepared materials were allowed to dry in two different relative humidity environments and then evaluated based on their stability in the sol phase, the aggregation sizes, determined through dynamic light scattering, the % solids content and their morphological characteristics, observed via scanning electron microscopy (SEM-EDAX). Mercury intrusion porosimetry was also applied to investigate the microstructural characteristics and differences between the prepared consolidants. Significant role in the final form of the material is played by both the initial molar ratios in the mixtures, as well as the conditions where the drying and aging takes place. Based on the results, the three-component PMCs appear to be promising in stone consolidation, as they show a reduction in cracking and shrinkage during drying and a more porous network, compared with the siliceous material, or the two-component TEOS-SiO2 formulation.

  4. Processing pathway dependence of amorphous silica nanoparticle toxicity - colloidal versus pyrolytic

    PubMed Central

    Zhang, Haiyuan; Dunphy, Darren R.; Jiang, Xingmao; Meng, Huan; Sun, Bingbing; Tarn, Derrick; Xue, Min; Wang, Xiang; Lin, Sijie; Ji, Zhaoxia; Li, Ruibin; Garcia, Fred L.; Yang, Jing; Kirk, Martin L.; Xia, Tian; Zink, Jeffrey I; Nel, Andre; Brinker, C. Jeffrey

    2012-01-01

    We have developed structure/toxicity relationships for amorphous silica nanoparticles (NPs) synthesized through low temperature, colloidal (e.g. Stöber silica) or high temperature pyrolysis (e.g. fumed silica) routes. Through combined spectroscopic and physical analyses, we have determined the state of aggregation, hydroxyl concentration, relative proportion of strained and unstrained siloxane rings, and potential to generate hydroxyl radicals for Stöber and fumed silica NPs with comparable primary particle sizes (16-nm in diameter). Based on erythrocyte hemolytic assays and assessment of the viability and ATP levels in epithelial and macrophage cells, we discovered for fumed silica an important toxicity relationship to post-synthesis thermal annealing or environmental exposure, whereas colloidal silicas were essentially non-toxic under identical treatment conditions. Specifically, we find for fumed silica a positive correlation of toxicity with hydroxyl concentration and its potential to generate reactive oxygen species (ROS) and cause red blood cell hemolysis. We propose fumed silica toxicity stems from its intrinsic population of strained three-membered rings (3MRs) along with its chain-like aggregation and hydroxyl content. Hydrogen-bonding and electrostatic interactions of the silanol surfaces of fumed silica aggregates with the extracellular plasma membrane cause membrane perturbations sensed by the Nalp3 inflammasome, whose subsequent activation leads to secretion of the cytokine IL-1β. Hydroxyl radicals generated by the strained 3MRs in fumed silica but largely absent in colloidal silicas may contribute to the inflammasome activation. Formation of colloidal silica into aggregates mimicking those of fumed silica had no effect on cell viability or hemolysis. This study emphasizes that not all amorphous silica is created equal and that the unusual toxicity of fumed silica compared to colloidal silica derives from its framework and surface chemistry along

  5. Characterization of Vapor Deposited Nano Structured Membranes

    SciTech Connect

    Jankowski, A; Cherepy, N; Ferreira, J; Hayes, J

    2004-03-25

    The vapor deposition methods of planar magnetron sputtering and electron-beam evaporation are used to synthesize materials with nano structured morphological features that have ultra-high surface areas with continuous open porosity at the nano scale. These nano structured membranes are used in a variety of fuel cells to provide electrode and catalytic functions. Specifically, stand alone and composite nickel electrodes for use in thin film solid-oxide, and molten carbonate fuel cells are formed by sputter deposition and electron bean evaporation, respectively. Also, a potentially high-performance catalyst material for the direct reformation of hydrocarbon fuels at low temperatures is deposited as a nano structure by the reactive sputtering of a copper-zinc alloy using a partial pressure of oxygen at an elevated substrate temperature.

  6. Phosphorylated nano-diamond/ Polyimide Nanocomposites

    NASA Astrophysics Data System (ADS)

    Beyler-Çiǧil, Asli; Çakmakçi, Emrah; Vezir Kahraman, Memet

    2014-08-01

    In this study, a novel route to synthesize polyimide (PI)/phosphorylated nanodiamond films with improved thermal and mechanical properties was developed. Surface phosphorylation of nano-diamond was performed in dichloromethane. Phosphorylation dramatically enhanced the thermal stability of nano-diamond. Poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized with 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydianiline (4,4'-ODA) in the solution of N,N- dimethylformamide (DMF). Pure BTDA-ODA polyimide films and phosphorylated nanodiamond containing BTDA-ODA PI films were prepared. The PAA displayed good compatibility with phosphorylated nano-diamond. The morphology of the polyimide (PI)/phosphorylated nano-diamond was characterized by scanning electron microscopy (SEM). Chemical structure of polyimide and polyimide (PI)/phosphorylated nano-diamond was characterized by FTIR. SEM and FTIR results showed that the phosphorylated nano-diamond was successfully prepared. Thermal properties of the polyimide (PI)/phosphorylated nanodiamond was characterized by thermogravimetric analysis (TGA). TGA results showed that the thermal stability of (PI)/phosphorylated nano-diamond film was increased.

  7. Gold nanostructure-integrated silica-on-silicon waveguide for the detection of antibiotics in milk and milk products

    NASA Astrophysics Data System (ADS)

    Ozhikandathil, Jayan; Badilescu, Simona; Packirisamy, Muthukumaran

    2012-10-01

    Antibiotics are extensively used in veterinary medicine for the treatment of infectious diseases. The use of antibiotics for the treatment of animals used for food production raised the concern of the public and a rapid screening method became necessary. A novel approach of detection of antibiotics in milk is reported in this work by using an immunoassay format and the Localized Surface Plasmon Resonance property of gold. An antibiotic from the penicillin family that is, ampicillin is used for testing. Gold nanostructures deposited on a glass substrate by a novel convective assembly method were heat-treated to form a nanoisland morphology. The Au nanostructures were functionalized and the corresponding antibody was absorbed from a solution. Solutions with known concentrations of antigen (antibiotics) were subsequently added and the spectral changes were monitored step by step. The Au LSPR band corresponding to the nano-island structure was found to be suitable for the detection of the antibody antigen interaction. The detection of the ampicillin was successfully demonstrated with the gold nano-islands deposited on glass substrate. This process was subsequently adapted for the integration of gold nanostructures on the silica-on-silicon waveguide for the purpose of detecting antibiotics.

  8. Growth of hydroxyapatite nanoparticles on silica gels.

    PubMed

    Rivera-Muñoz, E M; Huirache-Acuña, R; Velázquez, R; Alonso-Núñez, G; Eguía-Eguía, S

    2011-06-01

    Synthetic, hydroxyapatite nanoparticles were grown on the surface of silica gels. The synthesis of those nanoparticles was obtained by immersing silica gels in a simulated body fluid (SBF) at 37 degrees C. The SBF was replaced every week to keep constant the Ca and P ion concentration and subsequent growth of hydroxyapatite was evaluated after 1-6 weeks of total soaking time in SBF. Hydroxyapatite nanoparticles were observed by scanning electron microscopy (SEM) on the surface of silica gel samples and confirmed by energy dispersive X-ray spectroscopy (EDS), Fourier Transform Infra Red Spectroscopy (FTIR) and powder X-ray Diffractometry (XRD) analysis. These particles show a regular shape and uniform size every week, keeping within the nanoscale always. Both the size and morphology of hydroxyapatite nanoparticles obtained are the result of the use of different chemical additives in the synthesis of silica gels, since they affect the liquid-to-solid interface, and the growth could correspond to a diffusion limited aggregation (DLA) process. A more detailed analysis, with higher magnifications, showed that hydroxyapatite nanoparticles are not solid spheres, showing a branched texture and their size depends on the scale and resolution of the measure instrument. PMID:21770224

  9. Zinc oxide nanostructures confined in porous silicas.

    PubMed

    Coasne, Benoit; Mezy, Aude; Pellenq, R J M; Ravot, D; Tedenac, J C

    2009-02-18

    We report on molecular simulations of zinc oxide nanostructures obtained within silica nanopores of diameter D = 1.6 nm and D = 3.2 nm. Both the effects of confinement (by varying the pore size) and degree of pore filling on the structure of the nanomaterial are addressed. Two complementary approaches are adopted: 1) the stability of the three crystalline phases of ZnO (wurtzite, rocksalt, and blende) in the silica nanopores is studied, and 2) ZnO nanostructures are obtained by slowly cooling down a homogeneous liquid phase confined in the silica pores. None of the ideal nanostructures (wurtzite, rocksalt, blende) retains the ideal structure of the initial crystal when confined within the silica pores. Only the structure starting from the ideal wurtzite nanocrystal remains significantly crystalline after relaxation, as revealed by the marked peaks in the pair correlation functions for this system. The morphology and degree of cristallinity of the structures are found to depend on the parameters involved in the synthesis (pore size, filling density). Nanograin boundaries are observed between domains of different crystal structures. Reminiscent features of the bulk behavior, such as faceting of the nanostructures, are also observed when the system size becomes large. We show that the use of nanopores as a template imposes that the confined particles exhibit neutral (basal) surfaces. These predictions provide a guide to experiments on semiconductor nanoparticles.

  10. Nanoindentation of heterogeneous carbonaceous films containing Ni nano-crystals.

    PubMed

    Richter, A; Czerwosz, E; Dłuzewski, P; Kozłowski, M; Nowicki, M

    2009-01-01

    Composite films of nano-size nickel grains embedded in a carbonaceous matrix are synthesized by a PVD process of C(60) fullerenes and Ni acetate. The morphology of the nano-composite films is characterized by TEM, selected area electron diffraction, chemical analysis and AFM. Correlations with deposition parameters and typical structure changes are found. The mechanical properties are analyzed by nanoindentation. The load-displacement charts show typical pop-ins correlated with the heterogeneous nano-structure. The depth dependent hardness and indentation modulus vary according to the nano-composite structure and reflect the changes of the mechanical properties in the film.

  11. From matrix nano- and micro-phase tougheners to composite macro-properties.

    PubMed

    Kinloch, A J; Taylor, A C; Techapaitoon, M; Teo, W S; Sprenger, S

    2016-07-13

    In this paper, firstly, the morphology and toughness of a range of bulk epoxy polymers, which incorporate a second phase of well-dispersed silica nanoparticles and/or rubber microparticles, have been determined. Secondly, the macro-properties of natural-fibre reinforced-plastic (NFRP) composites based upon these epoxy polymers have been ascertained, using (i) unidirectional flax fibres or (ii) regenerated-cellulose fibres in the architecture of a plain-woven fabric. Thirdly, the toughening mechanisms which are induced in these materials by the presence of the silica nanoparticles, the rubber microparticles and the natural fibres have been identified. Finally, the values of the toughness of the bulk epoxy polymers and corresponding NFRPs have been quantitatively modelled. The increased toughness recorded for the bulk epoxy polymer due to the presence of the silica nanoparticles and/or rubber microparticles was indeed typically transferred to the NFRP composites when using such epoxies as the matrices for the fibres. Thus, the important role that may be played by modifications to the epoxy matrices in order to increase the toughness of the composites was very clearly demonstrated by these results. However, notwithstanding, the toughening mechanisms induced by the fibres were essentially responsible for the very high toughnesses of the NFRP composites, compared with the bulk epoxy polymers. The modelling studies successfully predicted the values of toughness of the bulk epoxy polymers and of the NFRP composites. These studies also quantified the extent to which each toughening mechanism, induced by the second-phase nano- and microparticles and the natural fibres, contributed to the overall values of toughness of the materials. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242298

  12. From matrix nano- and micro-phase tougheners to composite macro-properties.

    PubMed

    Kinloch, A J; Taylor, A C; Techapaitoon, M; Teo, W S; Sprenger, S

    2016-07-13

    In this paper, firstly, the morphology and toughness of a range of bulk epoxy polymers, which incorporate a second phase of well-dispersed silica nanoparticles and/or rubber microparticles, have been determined. Secondly, the macro-properties of natural-fibre reinforced-plastic (NFRP) composites based upon these epoxy polymers have been ascertained, using (i) unidirectional flax fibres or (ii) regenerated-cellulose fibres in the architecture of a plain-woven fabric. Thirdly, the toughening mechanisms which are induced in these materials by the presence of the silica nanoparticles, the rubber microparticles and the natural fibres have been identified. Finally, the values of the toughness of the bulk epoxy polymers and corresponding NFRPs have been quantitatively modelled. The increased toughness recorded for the bulk epoxy polymer due to the presence of the silica nanoparticles and/or rubber microparticles was indeed typically transferred to the NFRP composites when using such epoxies as the matrices for the fibres. Thus, the important role that may be played by modifications to the epoxy matrices in order to increase the toughness of the composites was very clearly demonstrated by these results. However, notwithstanding, the toughening mechanisms induced by the fibres were essentially responsible for the very high toughnesses of the NFRP composites, compared with the bulk epoxy polymers. The modelling studies successfully predicted the values of toughness of the bulk epoxy polymers and of the NFRP composites. These studies also quantified the extent to which each toughening mechanism, induced by the second-phase nano- and microparticles and the natural fibres, contributed to the overall values of toughness of the materials. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

  13. Kinetics of silica polymerization

    SciTech Connect

    Weres, O.; Yee, A.; Tsao, L.

    1980-05-01

    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  14. New porous polycaprolactone-silica composites for bone regeneration.

    PubMed

    Plazas Bonilla, Clara E; Trujillo, Sara; Demirdögen, Bermali; Perilla, Jairo E; Murat Elcin, Y; Gómez Ribelles, José L

    2014-07-01

    Polycaprolactone porous membranes were obtained by freeze extraction of dioxane from polycaprolactone-dioxane solid solutions. Porosities as high as 90% with interconnected structures were obtained by this technique. A silica phase was synthesized inside the pores of the polymer membrane by sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica precursor and catalyzed in acidic and basic conditions. Two different morphologies of the inorganic phase were obtained depending on the type of catalyst. In acid catalyzed sol-gel reaction, a homogeneous layer of silica was deposited on the pores, and discrete microspheres were synthesized on the pore walls when a basic catalyst was used. The morphology of the inorganic phase influenced the mechanical and thermal behavior, as well as the hydrophilic character of the composites. Bioactivity of the porous materials was tested in vitro by measuring the deposition of hydroxyapatite on the surfaces of the porous composite membranes. Polycaprolactone/silica composites revealed a superior bioactivity performance compared with that of the pure polymer; evidenced by the characteristic cauliflower structures on the material surface, increase in weight and Ca/P ratio of the hydroxyapatite layer. Also, the acid catalyzed composites presented better bioactivity than the base catalyzed composites, evidencing the importance in the morphology of the silica phase.

  15. Highly aspherical silica nanoshells by templating tubular liposomes

    PubMed Central

    Tan, Grace; Xu, Peng; He, Jibao; Lawson, Louise; McPherson, Gary L.

    2010-01-01

    A dual-lipid liposome system consisting of a phospholipid and a skin ceramide extruded though a 100 nm membrane yields novel tubular and helical liposomes. These liposomes were used as templates to generate highly aspherical silica nanocapsules with length to diameter aspect ratios exceeding 10. Many of these nanocapsules have the morphology of a bulbous end attached to a long tip, mimicking microneedles attached to a reservoir. The fidelity of helical liposomes is transcribed to the silicas and the long tips indicate helically entwined left-handed silica structures. The silica coating is expected to protect and stabilize the internal contents of the liposomes, as well as enable surface functionalization for applications in drug or targeted delivery. PMID:20352059

  16. Incorporation of terbium(III) ion into mesoporous silica particles

    NASA Astrophysics Data System (ADS)

    Kataoka, Takuya; Wang, Liyin; Kobayashi, Kouhei; Nishikawa, Masami; Tagaya, Motohiro

    2016-10-01

    Terbium(III)-doped mesoporous silicas were synthesized, and the states of terbium ions in the silica frameworks were investigated. The mesopores were preserved upon doping at terbium ion molar concentrations relative to (Si+Tb) up to 15 mol %, indicating the interaction of terbium ions with Si-O bonds. Significant morphological changes of the particles were observed with increasing the doping concentration. The shapes of the photoluminescence spectra due to the transitions of 5D4 → 7F6 and 5D4 → 7F5 were indicative of the presence of terbium ions in the silica matrix, and the quantum efficiency (2.1-2.8%) and lifetime (1.6-1.9 ms) decreased with increasing the doping concentration up to 15 mol %. Therefore, the terbium ions are considered to be located inside the amorphous silica frameworks, where they electrostatically interact with the O atoms of silanol and siloxane groups.

  17. Patterned silica films using microphase separation of a block copolymer

    NASA Astrophysics Data System (ADS)

    Kataoka, Sho; Takeuchi, Yasutaka; Endo, Akira

    2014-11-01

    Block copolymers exhibit various nanoscale ordered morphologies induced by microphase separation. Here, we present a method for providing two types of patterned silica films on Si wafer substrates simply by shifting the phase equilibrium of a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-P4VP). In this method, siloxane is adsorbed onto poly(4-vinylpyridine) blocks of PS-P4VP whose structure varies with solvent polarity and is calcined to remove the block copolymer. Siloxane is in a dispersed phase with toluene as a solvent resulting in silica nanoparticle arrays, while siloxane is in a continuous phase with N, N-dimethylformamide (DMF) resulting in silica films with ordered mesopores. Since the pore size of silica films prepared in DMF is approximately 20 nm, the film has the ability to serve as a support for enzymes such as laccase.

  18. Silica in alkaline brines

    USGS Publications Warehouse

    Jones, B.F.; Rettig, S.L.; Eugster, H.P.

    1967-01-01

    Analysis of sodium carbonate-bicarbonate brines from closed basins in volcanic terranes of Oregon and Kenya reveals silica contents of up to 2700 parts per million at pH's higher than 10. These high concentrations of SiO 2 can be attributed to reaction of waters with silicates, and subsequent evaporative concentration accompanied by a rise in pH. Supersaturation with respect to amorphous silica may occur and persist for brines that are out of contact with silicate muds and undersaturated with respect to trona; correlation of SiO2 with concentration of Na and total CO2 support this interpretation. Addition of moredilute waters to alkaline brines may lower the pH and cause inorganic precipitation of substantial amounts of silica.

  19. Silica Precipitation and Lithium Sorption

    SciTech Connect

    Jay Renew

    2015-09-20

    This file contains silica precipitation and lithium sorption data from the project. The silica removal data is corrected from the previous submission. The previous submission did not take into account the limit of detection of the ICP-MS procedure.

  20. Temperature and moisture dependence of dielectric constant for silica aerogels

    SciTech Connect

    Hrubesh, L.H., LLNL

    1997-03-01

    The dielectric constants of silica aerogels are among the lowest measured for any solid material. The silica aerogels also exhibit low thermal expansion and are thermally stable to temperatures exceeding 500{degrees}C. However, due to the open porosity and large surface areas for aerogels, their dielectric constants are strongly affected by moisture and temperature. This paper presents data for the dielectric constants of silica aerogels as a function of moisture content at 25{degrees}C, and as a function of temperature, for temperatures in the range from 25{degrees}C to 450{degrees}C. Dielectric constant data are also given for silica aerogels that are heat treated in dry nitrogen at 500{degrees}C, then cooled to 25{degrees}C for measurements in dry air. All measurements are made on bulk aerogel spheres at 22GHz microwave frequency, using a cavity perturbation method. The results of the dependence found here for bulk materials can be inferred to apply also to thin films of silica aerogels having similar nano-structures and densities.

  1. Multipod-like silica/polystyrene clusters

    NASA Astrophysics Data System (ADS)

    Désert, Anthony; Morele, Jérémy; Taveau, Jean-Christophe; Lambert, Olivier; Lansalot, Muriel; Bourgeat-Lami, Elodie; Thill, Antoine; Spalla, Olivier; Belloni, Luc; Ravaine, Serge; Duguet, Etienne

    2016-03-01

    Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the history of the cluster growth and the final composition of the cluster mixture. Finally, using the model as a predictive tool and varying the extra experimental conditions, e.g. the composition of the surfactant mixture and the styrene concentration, result in trapping other cluster morphologies, such as tripods.Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the

  2. Water evaporation in silica colloidal deposits.

    PubMed

    Peixinho, Jorge; Lefèvre, Grégory; Coudert, François-Xavier; Hurisse, Olivier

    2013-10-15

    The results of an experimental study on the evaporation and boiling of water confined in the pores of deposits made of mono-dispersed silica colloidal micro-spheres are reported. The deposits are studied using scanning electron microscopy, adsorption of nitrogen, and adsorption of water through attenuated total reflection-infrared spectroscopy. The evaporation is characterized using differential scanning calorimetry and thermal gravimetric analysis. Optical microscopy is used to observe the patterns on the deposits after evaporation. When heating at a constant rate and above boiling temperature, the release of water out of the deposits is a two step process. The first step is due to the evaporation and boiling of the surrounding and bulk water and the second is due to the desorption of water from the pores. Additional experiments on the evaporation of water from membranes having cylindrical pores and of heptane from silica deposits suggest that the second step is due to the morphology of the deposits.

  3. Perylene-labeled silica nanoparticles: synthesis and characterization of three novel silica nanoparticle species for live-cell imaging.

    PubMed

    Blechinger, Julia; Herrmann, Rudolf; Kiener, Daniel; García-García, F Javier; Scheu, Christina; Reller, Armin; Bräuchle, Christoph

    2010-11-01

    The increasing exposure of humans to nanoscaled particles requires well-defined systems that enable the investigation of the toxicity of nanoparticles on the cellular level. To facilitate this, surface-labeled silica nanoparticles, nanoparticles with a labeled core and a silica shell, and a labeled nanoparticle network-all designed for live-cell imaging-are synthesized. The nanoparticles are functionalized with perylene derivatives. For this purpose, two different perylene species containing one or two reactive silica functionalities are prepared. The nanoparticles are studied by transmission electron microscopy, widefield and confocal fluorescence microscopy, as well as by fluorescence spectroscopy in combination with fluorescence anisotropy, in order to characterize the size and morphology of the nanoparticles and to prove the success and homogeneity of the labeling. Using spinning-disc confocal measurements, silica nanoparticles are demonstrated to be taken up by HeLa cells, and they are clearly detectable inside the cytoplasm of the cells.

  4. Evaluating Dimethyldiethoxysilane for use in Polyurethane Crosslinked Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Randall, Jason P.; Meador, Mary Ann B.; Jana, Sadhan C.

    2008-01-01

    Silica aerogels are highly porous materials which exhibit exceptionally low density and thermal conductivity. Their "pearl necklace" nanostructure, however, is inherently weak; most silica aerogels are brittle and fragile. The strength of aerogels can be improved by employing an additional crosslinking step using isocyanates. In this work, dimethyldiethoxysilane (DMDES) is evaluated for use in the silane backbone of polyurethane crosslinked aerogels. Approximately half of the resulting aerogels exhibited a core/shell morphology of hard crosslinked aerogel surrounding a softer, uncrosslinked center. Solid state NMR and scanning electron microscopy results indicate the DMDES incorporated itself as a conformal coating around the outside of the secondary silica particles, in much the same manner as isocyanate crosslinking. Response surface curves were generated from compression data, indicating levels of reinforcement comparable to that in previous literature, despite the core/shell morphology.

  5. Fire effects on silica fractionation

    NASA Astrophysics Data System (ADS)

    Unzué-Belmonte, Dácil; Schaller, Jörg; Vandevenne, Floor; Barao, Lúcia; Struyf, Eric; Meire, Patrick

    2015-04-01

    Fire events are expected to increase due to climate change, both in number and intensity Effects range from changes in soil biogeochemistry up to the whole ecosystem functioning and morphology. While N, P and C cycling have received quite some attention, little attention was paid to fire effects on the biogeochemical Si cycle and the consequences after a fire event. The Si cycle is a globally important biogeochemical cycle, with strong connections to other biogeochemical cycles, including C. Dissolved silica is taken up by plants to form protective structures called phytoliths, which become a part of the soil and contribute strongly to soil Si cycling upon litter burial. Different silica fractions are found in soils, with phytoliths among the most easily soluble, especially compared to silicate minerals. A whole set of secondary non-biogenic fractions exist, that also have a high reactivity (adsorbed Si, reactive secondary minerals…). Biogenic and other pedogenic secondary Si stocks form an important filter between weathering of mineral silicates and eventual transport of dissolved Si to rivers and the coastal zone. We used a new method to analyze the different reactive fractions of silica in the litter layer of 3 ecosystems after different fire treatments. Using a continuous extraction of Si and Al in 0.5M NaOH at 85°C, biogenic and non-biogenic alkaline reactive Si fractions can be separated based on their Si/Al ratios and their reactivity. We analyzed the silica fractionation after two burning treatments (no heating, 350°C and 550°C) from three types of litter (spruce forest, beech forest and Sphagnum peat). Reactive Si from litter of spruce and beech forest was purely biogenic, based on the observed Si/Al ratio. Beech litter (~2.2 % BSi) had two different biogenic silica pools, one reactive and one more refractory. Spruce litter (~1.5% BSi) showed only one fraction of biogenic Si. There was negligible biogenic Si present in the peat samples (<0.1%). While

  6. Survey of food-grade silica dioxide nanomaterial occurrence, characterization, human gut impacts and fate across its lifecycle.

    PubMed

    Yang, Yu; Faust, James J; Schoepf, Jared; Hristovski, Kiril; Capco, David G; Herckes, Pierre; Westerhoff, Paul

    2016-09-15

    There is increasing recognition of the importance of transformations in nanomaterials across their lifecycle, yet few quantitative examples exist. We examined food-grade silicon dioxide (SiO2) nanomaterials from its source (bulk material providers), occurrence in food products, impacts on human gastrointestinal tract during consumption, and fate at wastewater treatment plants. Based upon XRD, XPS and TEM analysis, pure SiO2 present in multiple food-grade stock SiO2 exhibited consistent morphologies as agglomerates, ranging in size from below 100nm to >500nm, with all primary particle size in the range of 9-26nm and were most likely amorphous SiO2 based upon high resolution TEM. Ten of 14 targeted foods purchased in the USA contained SiO2 of the same morphology and size as the pristine bulk food-grade SiO2, at levels of 2 to 200mg Si per serving size. A dissolution study of pristine SiO2 showed up to 7% of the dissolution of the silica, but the un-dissolved SiO2 maintained the same morphology as the pristine SiO2. Across a realistic exposure range, pristine SiO2 exhibited adverse dose-response relationships on a cell model (microvilli) of the human gastro-intestinal tract, association onto microvilli and evidence that SiO2 lead to production of reactive oxygen species (ROS). We also observed accumulation of amorphous nano-SiO2 on bioflocs in tests using lab-cultured activated sludge and sewage sludges from a full-scale wastewater treatment plant (WWTP). Nano-scale SiO2 of the same size and morphology as pristine food-grade SiO2 was observed in raw sewage at a WWTP, but we identified non-agglomerated individual SiO2 particles with an average diameter of 21.5±4.7nm in treated effluent from the WWTP. This study demonstrates an approach to track nanomaterials from source-to-sink and establishes a baseline occurrence of nano-scale SiO2 in foods and WWTPs.

  7. Epoxy Grout With Silica Thickener

    NASA Technical Reports Server (NTRS)

    Mcclung, C. E.

    1984-01-01

    Grout cures quickly, even in presence of hydraulic oil. Grout is mixture of aggregate particles, finely-divided silica, epoxy resin, and triethylenetetramine curing agent, with mixture containing about 85 percent silica and aggregate particle sand 15 percent resin and curing agent. Silica is thickening agent and keeps grout from sagging.

  8. Preparing hydroxyapatite-silicon composite suspensions with homogeneous distribution of multi-walled carbon nano-tubes for electrophoretic coating of NiTi bone implant and their effect on the surface morphology

    NASA Astrophysics Data System (ADS)

    Khalili, Vida; Khalil-Allafi, Jafar; Xia, Wei; Parsa, Alireza B.; Frenzel, Jan; Somsen, Christoph; Eggeler, Gunther

    2016-03-01

    Preparing a stable suspension is a main step towards the electrophoretically depositing of homogeneous and dense composite coatings on NiTi for its biomedical application. In the present study, different composite suspensions of hydroxyapatite, silicon and multi-walled carbon nano-tubes were prepared using n-butanol and triethanolamine as media and dispersing agent, respectively. Multi-walled carbon nanotubes were first functionalized in the nitric acid vapor for 15 h at 175 °C, and then mixed into suspensions. Thermal desorption spectroscopy profiles indicate the formation of functional groups on multi-walled carbon nano-tubes. An excellent suspension stability can be achieved for different amounts of triethanolamine. The amount of triethanolamine can be increased by adding a second component to a stable hydroxyapatite suspension due to an electrostatic interaction between components in suspension. The stability of composite suspension is less than that of the hydroxyapatite suspension, due to density differences, which under the gravitational force promote the demixing. The scanning electron microscopy images of the coatings surface show that more dense coatings are developed on NiTi substrate using electrophoretic deposition and sintering at 850 °C in the simultaneous presence of silicon and multi-walled carbon nanotubes in the hydroxyapatite coatings. The atomic force microscopy results of the coatings surface represent that composite coatings of hydroxyapatite-20 wt.% silicon and hydroxyapatite-20 wt.% silicon-1 wt.% multi-walled carbon nano-tubes with low zeta potential have rougher surfaces.

  9. Nanohybrids from nanotubular J-aggregates and transparent silica nanoshells.

    PubMed

    Qiao, Yan; Polzer, Frank; Kirmse, Holm; Kirstein, Stefan; Rabe, Jürgen P

    2015-08-01

    Organic-inorganic nanohybrids have been synthesized by in situ coating supramolecular nanotubular J-aggregates with helically wound silica ribbons, reflecting the J-aggregates' superstructure. The J-aggregates retain their morphology and optical properties in the nanohybrids, and display improved stability against elevated temperatures, chemical ambient and photo-bleaching. PMID:26121136

  10. Cascade enzymatic catalysis in poly(acrylic acid) brushes-nanospherical silica for glucose detection.

    PubMed

    Zhao, Yan; Wang, Ying; Zhang, Xiaobin; Kong, Rongmei; Xia, Lian; Qu, Fengli

    2016-08-01

    The ultrasensitive monitoring of glucose with a fast and accurate method is significant in potential therapeutics and optimizes protein biosynthesis. Incorporation of enzyme into matrix is considered as promising candidates for constructing highly sensitive glucose-responsive systems. In this study, three-dimensional poly(acrylic acid) brushes-nanospherical silica (PAA-nano silica) with high amplification capability and stability were used to covalently immobilize bienzymes for cascade enzymatic catalysis. The major advantages of PAA-nano silica-bienzyme co-incorporation is that the enzymes are proximity distribution, and such close confinement both minimized the diffusion of intermediates among the enzymes in the consecutive reaction and improve the utilization efficiency of enzymes, thereby enhancing the overall reaction efficiency and specificity. Thus, this present bienzymatic biosensor shows robust signal amplification and ultrasensitivity of glucose-responsive properties with a detection limit of 0.04μM. PMID:27216683

  11. Scratch and abrasion properties of polyurethane-based micro- and nano-hybrid obturation materials.

    PubMed

    Estevez, Miriam; Rodriguez, J Rogelio; Vargas, Susana; Guerra, J A; Brostow, Witold; Lobland, Haley E Hagg

    2013-06-01

    Polyurethane-based micro- and nano-hybrid composites were produced with controlled porosity to be used as obturation materials. In addition to hydroxyapatite (HAp) micro-particles in the composites, two different ceramics particle types were also added: alumina micro-particles and silica nano-particles. Particles of different sizes provide the materials with improved mechanical properties: the use of micro- and nano-particles produces a better packing because the nano-particles fill the interstitial space left by the micro-particles, rendering an improvement in the mechanical properties. The silica and alumina particles provide the materials with appropriate abrasion and scratching properties, while the HAp provides the required bio-acceptance. The polymeric matrix was a mono-component solvent-free polyurethane. The porosity was selected by controlling the chemical reaction.

  12. Preparation and characterization of silica nanoparticulate polyacrylonitrile composite and porous nanofibers

    NASA Astrophysics Data System (ADS)

    Ji, Liwen; Saquing, Carl; Khan, Saad A.; Zhang, Xiangwu

    2008-02-01

    In this study, polyacrylonitrile (PAN) composite nanofibers containing different amounts of silica nanoparticulates have been obtained via electrospinning. The surface morphology, thermal properties and crystal structure of PAN/silica nanofibers are characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results indicate that the addition of silica nanoparticulates affects the structure and properties of the nanofibers. In addition to PAN/silica composite nanofibers, porous PAN nanofibers have been prepared by selective removal of the silica component from PAN/silica composite nanofibers using hydrofluoric (HF) acid. ATR-FTIR and thermal gravimetric analysis (TGA) experiments validate the removal of silica nanoparticulates by HF acid, whereas SEM and TEM results reveal that the porous nanofibers obtained from composite fibers with higher silica contents exhibited more nonuniform surface morphology. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers made from PAN/silica (5 wt%) composite precursors is higher than that of pure nonporous PAN nanofibers.

  13. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

    NASA Astrophysics Data System (ADS)

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

    2015-02-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate.

  14. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

    PubMed Central

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

  15. Formation of nano-phase hydroxyapatite film on TiO2 nano-network.

    PubMed

    Lee, Kang; Ko, Yeong-Mu; Choe, Han-Cheol; Kim, Byung-Hoon

    2012-01-01

    Nano- and micro-phase HA film formed on TiO2 nano-network surface by simple electrochemical treatment. The range of lateral pore size of the network specimen was about 10-120 nm on Ti surface by anodized in 5 M NaOH solution at 0.3 A for 10 min. Nano-network TiO2 surface were formed by this anodization step which acted as templates and anchorage for growth of the HA during subsequent pulsed electrochemical deposition process at 85 degrees C. The phase and morphologies of deposits HA were influenced by the electrolyte concentration. The nano needle-like precipitates formed under low SBF concentration were identified to be HA crystals orientated parallel to the c-axis direction. Increasing electrolyte concentration, needle-like deposits transferred to the plate-like and micro plate like precipitates in the case of high SBF concentration.

  16. Origin of optical bistability and hysteretic reflectivity on account of nonlinearity at optically induced gallium silica interface

    NASA Astrophysics Data System (ADS)

    Sharma, Arvind; Nagar, A. K.

    2016-05-01

    The origin of optical bistability and hysterectic reflectivity on account of nonlinearity at optically induced Gallium silica interface has been investigated. Assuming the wave to be incident from the gallium nano particle layer side at gallium silica interface. The coupling between incident and reflected waves has shown nonlinear effects on Snell's law and Fresnel law. Effect of these nonlinear processes optical bistability and hysterectic reflectivity theoretically has been investigated. Theoretical results obtained are consistent with the available experimental results.

  17. Entrapping quercetin in silica/polyethylene glycol hybrid materials: Chemical characterization and biocompatibility.

    PubMed

    Catauro, Michelina; Bollino, Flavia; Nocera, Paola; Piccolella, Simona; Pacifico, Severina

    2016-11-01

    Sol-gel synthesis was exploited to entrap quercetin, a natural occurring antioxidant polyphenol, in silica-based hybrid materials, which differed in their polyethylene glycol (PEG) content (6, 12, 24 and 50wt%). The materials obtained, whose nano-composite nature was ascertained by Scanning Electron Microscopy (SEM), were chemically characterized by Fourier Transform InfraRed (FT-IR) and UV-Vis spectroscopies. The results prove that a reaction between the polymer and the drug occurred. Bioactivity tests showed their ability to induce hydroxyapatite nucleation on the sample surfaces. The direct contact method was applied to screen the cytotoxicity of the synthetized materials towards fibroblast NIH 3T3 cells, commonly used for in vitro biocompatibility studies, and three nervous system cell lines (neuroblastoma SH-SY5Y, glioma U251, and pheochromocytoma PC12 cell lines), adopted as models in oxidative stress related studies. Using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay NIH 3T3 proliferation was assessed and the morphology was not compromised by direct exposure to the materials. Analogously, PC-12, and U-251 cell lines were not affected by new materials. SH-SY5Y appeared to be the most sensitive cell line with cytotoxic effects of 20-35%.

  18. Entrapping quercetin in silica/polyethylene glycol hybrid materials: Chemical characterization and biocompatibility.

    PubMed

    Catauro, Michelina; Bollino, Flavia; Nocera, Paola; Piccolella, Simona; Pacifico, Severina

    2016-11-01

    Sol-gel synthesis was exploited to entrap quercetin, a natural occurring antioxidant polyphenol, in silica-based hybrid materials, which differed in their polyethylene glycol (PEG) content (6, 12, 24 and 50wt%). The materials obtained, whose nano-composite nature was ascertained by Scanning Electron Microscopy (SEM), were chemically characterized by Fourier Transform InfraRed (FT-IR) and UV-Vis spectroscopies. The results prove that a reaction between the polymer and the drug occurred. Bioactivity tests showed their ability to induce hydroxyapatite nucleation on the sample surfaces. The direct contact method was applied to screen the cytotoxicity of the synthetized materials towards fibroblast NIH 3T3 cells, commonly used for in vitro biocompatibility studies, and three nervous system cell lines (neuroblastoma SH-SY5Y, glioma U251, and pheochromocytoma PC12 cell lines), adopted as models in oxidative stress related studies. Using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay NIH 3T3 proliferation was assessed and the morphology was not compromised by direct exposure to the materials. Analogously, PC-12, and U-251 cell lines were not affected by new materials. SH-SY5Y appeared to be the most sensitive cell line with cytotoxic effects of 20-35%. PMID:27524014

  19. Biomineralization regulation by nano-sized features in silk fibroin proteins: synthesis of water-dispersible nano-hydroxyapatite.

    PubMed

    Huang, Xiaowei; Liu, Xi; Liu, Shanshan; Zhang, Aili; Lu, Qiang; Kaplan, David L; Zhu, Hesun

    2014-11-01

    In the present study, silk fibroin (SF) was used as a template to prepare nano-hydroxyapatite (nano-HA) via a biomineralization process. We observed that the content of SF affected both the morphology and water dispersibility of nano-HA particles. Scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), zetasizer, and Fourier transform infrared spectroscopy (FTIR) were used to examine nano-HA particle features including the surface morphology, aggregation performance, and crystallization. Rod-like nano-HA particles with desired water dispersibility were achieved when the ratio of SF/HA (calculated) was above 7:3. SEM, TEM, and zeta potential results revealed that nano-HA particles were enclosed by the SF which formed a negative charge layer preventing the aggregation of HA nanoparticles in aqueous solution. Moreover, the nano-HA particles were able to re-disperse in water without precipitation for two weeks at room temperature, 60°C, and 90°C. Our work suggested a facile and effective approach of designing water-dispersible nano-HA particles which may have wide potential application in tissue engineering especially bone regeneration.

  20. Synthesis of microforsterite using derived-amorphous-silica of silica sands

    NASA Astrophysics Data System (ADS)

    Nurbaiti, Upik; Triwikantoro, Zainuri, Mochamad; Pratapa, Suminar

    2016-04-01

    Synthesis of microforsterite (Mg2SiO4) has been successfully done by a simple method benefiting of the local silica sands from Tanah Laut, Indonesia. The starting material was amorphous silica powder which was processed using coprecipitation method from the sands. The silica powder was obtained from a series of stages of the purification process of the sands, namely magnetic separation, grinding and soaking with HCl. The microforsterite synthesis followed the reaction of stoichiometric mole ratio mixing of 1:2 of the amorphous silica and MgO powders with 3 wt% addion of PVA as a catalyst.The mixture was calcined at temperatures between 1150-1400°C with 4 hours holding time. XRD data showed that calcination at a temperature of 1150°C for 4 hours was optimum where the weight fraction of forsterite can reach as much as 93 wt% with MgO as the secondary phase and without MgSiO3. SEM photograph of the microforsterite showed tapered morphology with a relatively homogeneous distribution.

  1. Plackett-Burman experimental design for bacterial cellulose-silica composites synthesis.

    PubMed

    Guzun, Anicuta Stoica; Stroescu, Marta; Jinga, Sorin Ion; Voicu, Georgeta; Grumezescu, Alexandru Mihai; Holban, Alina Maria

    2014-09-01

    Bacterial cellulose-silica hybrid composites were prepared starting from wet bacterial cellulose (BC) membranes using Stöber reaction. The structure and surface morphology of hybrid composites were examined by FTIR and SEM. The SEM pictures revealed that the silica particles are attached to BC fibrils and are well dispersed in the BC matrix. The influence of silica particles upon BC crystallinity was studied using XRD analysis. Thermogravimetric (TG) analysis showed that the composites are stable up to 300°C. A Plackett-Burman design was applied in order to investigate the influence of process parameters upon silica particle sizes and silica content of BC-silica composites. The statistical model predicted that it is possible for silica particles size to vary the synthesis parameters in order to obtain silica particles deposed on BC membranes in the range from 34.5 to 500 nm, the significant parameters being ammonia concentration, reaction time and temperature. The silica content also varies depending on process parameters, the statistical model predicting that the most influential parameters are water-tetraethoxysilane (TEOS) ratio and reaction temperature. The antimicrobial behavior on Staphylococcus aureus of BC-silica composites functionalized with usnic acid (UA) was also studied, in order to create improved surfaces with antiadherence and anti-biofilm properties.

  2. Mesoporous silica nanotubes hybrid membranes for functional nanofiltration

    NASA Astrophysics Data System (ADS)

    El-Safty, Sherif A.; Shahat, Ahmed; Mekawy, Moataz; Nguyen, Hoa; Warkocki, Wojciech; Ohnuma, Masato

    2010-09-01

    The development of nanofiltration systems would greatly assist in the production of well-defined particles and biomolecules with unique properties. We report a direct, simple synthesis of hexagonal silica nanotubes (NTs), which vertically aligned inside anodic alumina membranes (AAM) by means of a direct templating method of microemulsion phases with cationic surfactants. The direct approach was used as soft templates for predicting ordered assemblies of surfactant/silica composites through strong interactions within AAM pockets. Thus, densely packed NTs were successfully formed in the entirety of the AAM channels. These silica NTs were coated with layers of organic moieties to create a powerful technique for the ultrafine filtration. The resulting modified-silica NTs were chemically robust and showed affinity toward the transport of small molecular particles. The rigid silica NTs inside AAM channels had a pore diameter of <= 4 nm and were used as ultrafine filtration systems for noble metal nanoparticles (NM NPs) and semiconductor nanocrystals (SC NCs) fabricated with a wide range of sizes (1.0-50 nm) and spherical/pyramidal morphologies. Moreover, the silica NTs hybrid membranes were also found to be suitable for separation of biomolecules such as cytochrome c (CytC). Importantly, this nanofilter design retains high nanofiltration efficiency of NM NPs, SC NCs and biomolecules after a number of reuse cycles. Such retention is crucial in industrial applications.

  3. Investigating the role of surface micro/nano structure in cell adhesion behavior of superhydrophobic polypropylene/nanosilica surfaces.

    PubMed

    Hejazi, Iman; Seyfi, Javad; Hejazi, Ehsan; Sadeghi, Gity Mir Mohamad; Jafari, Seyed Hassan; Khonakdar, Hossein Ali

    2015-03-01

    The main aim of the current study was to investigate the effects of different topographical features on the biological performance of polypropylene (PP)/silica coatings. To this end, a novel method including combined use of nanoparticles and non-solvent was used for preparation of superhydrophobic PP coatings. The proposed method led to a much more homogeneous appearance with a better adhesion to the glass substrate. Moreover, a notable reduction was observed in the required contents of nanoparticles (100-20 wt% with respect to the polymer) and non-solvent (35.5-9 vol%) for achieving superhydrophobicity. Surface composition and morphology of the coatings were also investigated via X-ray photoelectron spectroscopy and scanning electron microscopy. Based on both qualitative and quantitative evaluations, it was found that the superhydrophobic coatings with only nano-scale roughness strongly prevented adhesion and proliferation of 4T1 mouse mammary tumor cells as compared to the superhydrophobic surfaces with micro-scale structure. Such results demonstrate that the cell behavior could be controlled onto the polymer and nanocomposite-based surfaces via tuning the surface micro/nano structure.

  4. Viscoelasticity of silica gels

    SciTech Connect

    Scherer, G.W.

    1995-12-01

    The response of silica gels to mechanical loads depends on the properties of the solid phase and the permeability of the network. Understanding this behavior is essential for modeling of stresses developed during drying or heating of gels. The permeability and the mechanical properties are readily determined from a simple beam-bending experiment, by measuring the load relaxation that occurs at constant deflection. Load decay results from movement of the liquid within the network; in addition, there may be viscoelastic relaxation of the network itself. Silica gel is viscoelastic in chemically aggressive media, but in inert liquids (such as ethanol or acetone) it is elastic. Experiments show that the viscoelastic relaxation time decreases as the concentration and pH of the water in the pore liquid increase. During drying, the permeability decreases and the viscosity increases, both exhibiting a power-law dependence on density of the gel network.

  5. Surface patterns in drying films of silica colloidal dispersions.

    PubMed

    Boulogne, F; Giorgiutti-Dauphiné, F; Pauchard, L

    2015-01-01

    We report an experimental study on the drying of silica colloidal dispersions. Here we focus on surface instability occurring in a drying paste phase before crack formation which affects the final film quality. Observations at macroscopic and microscopic scales reveal the occurrence of instability, and the morphology of the film surface. Furthermore, we show that the addition of adsorbing polymers on silica particles can be used to suppress the instability under particular conditions of molecular weight and concentration. We relate this suppression to the increase of the paste elastic modulus.

  6. "Nano" Scale Biosignatures and the Search for Extraterrestrial Life

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Robert, F.; Meibom, A.; Mostefaoui, S.; Selo, M.; Walter, M. R.; Sugitani, K.; Allwood, A.; Mimura, K.; Gibson, E. K.

    2008-01-01

    A critical step in the search for remnants of potential life forms on other planets lies in our ability to recognize indigenous fragments of ancient microbes preserved in some of Earth's oldest rocks. To this end, we are building a database of nano-scale chemical and morphological characteristics of some of Earth's oldest organic microfossils. We are primarily using the new technology of Nano-Secondary ion mass spectrometry (NanoSIMS) which provides in-situ, nano-scale elemental analysis of trace quantities of organic residues. The initial step was to characterize element composition of well-preserved, organic microfossils from the late Proterozoic (0.8 Ga) Bitter Springs Formation of Australia. Results from that work provide morphologic detail and nitrogen/carbon ratios that appear to reflect the well-established biological origin of these 0.8 Ga fossils.

  7. Silica Foams for Fire Prevention and Firefighting.

    PubMed

    Vinogradov, Alexander V; Kuprin, D S; Abduragimov, I M; Kuprin, G N; Serebriyakov, Evgeniy; Vinogradov, Vladimir V

    2016-01-13

    We report the new development of fire-extinguishing agents employing the latest technology of fighting and preventing fires. The in situ technology of fighting fires and explosions involves using large-scale ultrafast-gelated foams, which possess new properties and unique characteristics, in particular, exceptional thermal stability, mechanical durability, and full biocompatibility. We provide a detailed description of the physicochemical processes of silica foam formation at the molecular level and functional comparison with current fire-extinguishing and fire-fighting agents. The new method allows to produce controllable gelation silica hybrid foams in the range from 2 to 30 s up to 100 Pa·s viscosity. Chemical structure and hierarchical morphology obtained by scanning electron microscopy and transmission electron microscopy images develop thermal insulation capabilities of the foams, reaching a specific heat value of more than 2.5 kJ/(kg·°C). The produced foam consists of organized silica nanoparticles as determined by X-ray photoelectron spectroscopy and X-ray diffraction analysis with a narrow particle size distribution of ∼10-20 nm. As a result of fire-extinguishing tests, it is shown that the extinguishing efficiency exhibited by silica-based sol-gel foams is almost 50 times higher than that for ordinary water and 15 times better than that for state-of-the-art firefighting agent aqueous film forming foam. The biodegradation index determined by the time of the induction period was only 3 d, while even for conventional foaming agents this index is several times higher.

  8. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  9. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  10. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  11. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  12. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  13. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  14. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  15. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  16. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and... GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of...

  17. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  18. Enzyme-modified nanoparticles using biomimetically synthesized silica.

    PubMed

    Zamora, Patricia; Narváez, Arántzazu; Domínguez, Elena

    2009-09-01

    The entrapment of enzymes within biomimetic silica nanoparticles offers unique and simple immobilization protocols that merge the stability of proteins confined in solid phases with the high loading and reduced diffusion limitations inherent to nano-sized structures. Herein, we report on the biomimetic silica entrapment of chemically derivatized horseradish peroxidase for amperometric sensing applications. Scanning electron microscopy shows evidence of the formation of enzyme-modified nanospheres using poly(ethylenimine) as a template for silicic acid condensation. When these nanospheres are directly deposited on graphite electrodes, chemically modified anionic peroxidase shows direct electron transfer at 0 mV vs Ag|AgCl. Microgravimetric measurements as well as SEM images demonstrate that negatively charged peroxidase is also entrapped when silica precipitates at gold electrodes are modified with a self-assembled monolayer of poly(ethylenimine). Electrostatic interactions may play a crucial role for efficient enzyme entrapment and silica condensation at the PEI template monolayer. The in-situ biomimetically synthesized peroxidase nanospheres are catalytically active, enabling direct bioelectrocatalysis at 0 mV vs Ag|AgCl with long-term stability.

  19. The Developmental Toxicity of Complex Silica-Embedded Nickel Nanoparticles Is Determined by Their Physicochemical Properties

    PubMed Central

    Mahoney, Sharlee; Najera, Michelle; Bai, Qing; Burton, Edward A.; Veser, Götz

    2016-01-01

    Complex engineered nanomaterials (CENs) are a rapidly developing class of structurally and compositionally complex materials that are expected to dominate the next generation of functional nanomaterials. The development of methods enabling rapid assessment of the toxicity risk associated with this type of nanomaterial is therefore critically important. We evaluated the toxicity of three differently structured nickel-silica nanomaterials as prototypical CENs: simple, surface-deposited Ni-SiO2 and hollow and non-hollow core-shell Ni@SiO2 materials (i.e., ~1–2 nm Ni nanoparticles embedded into porous silica shells with and without a central cavity, respectively). Zebrafish embryos were exposed to these CENs, and morphological (survival and malformations) and physiological (larval motility) endpoints were coupled with thorough characterization of physiochemical characteristics (including agglomeration, settling and nickel ion dissolution) to determine how toxicity differed between these CENs and equivalent quantities of Ni2+ salt (based on total Ni). Exposure to Ni2+ ions strongly compromised zebrafish larva viability, and surviving larvae showed severe malformations. In contrast, exposure to the equivalent amount of Ni CEN did not result in these abnormalities. Interestingly, exposure to Ni-SiO2 and hollow Ni@SiO2 provoked abnormalities of zebrafish larval motor function, indicating developmental toxicity, while non-hollow Ni@SiO2 showed no toxicity. Correlating these observations with physicochemical characterization of the CENs suggests that the toxicity of the Ni-SiO2 and hollow Ni@SiO2 material may result partly from an increased effective exposure at the bottom of the well due to rapid settling. Overall, our data suggest that embedding nickel NPs in a porous silica matrix may be a straightforward way to mitigate their toxicity without compromising their functional properties. At the same time, our results also indicate that it is critical to consider

  20. The Developmental Toxicity of Complex Silica-Embedded Nickel Nanoparticles Is Determined by Their Physicochemical Properties.

    PubMed

    Mahoney, Sharlee; Najera, Michelle; Bai, Qing; Burton, Edward A; Veser, Götz

    2016-01-01

    Complex engineered nanomaterials (CENs) are a rapidly developing class of structurally and compositionally complex materials that are expected to dominate the next generation of functional nanomaterials. The development of methods enabling rapid assessment of the toxicity risk associated with this type of nanomaterial is therefore critically important. We evaluated the toxicity of three differently structured nickel-silica nanomaterials as prototypical CENs: simple, surface-deposited Ni-SiO2 and hollow and non-hollow core-shell Ni@SiO2 materials (i.e., ~1-2 nm Ni nanoparticles embedded into porous silica shells with and without a central cavity, respectively). Zebrafish embryos were exposed to these CENs, and morphological (survival and malformations) and physiological (larval motility) endpoints were coupled with thorough characterization of physiochemical characteristics (including agglomeration, settling and nickel ion dissolution) to determine how toxicity differed between these CENs and equivalent quantities of Ni2+ salt (based on total Ni). Exposure to Ni2+ ions strongly compromised zebrafish larva viability, and surviving larvae showed severe malformations. In contrast, exposure to the equivalent amount of Ni CEN did not result in these abnormalities. Interestingly, exposure to Ni-SiO2 and hollow Ni@SiO2 provoked abnormalities of zebrafish larval motor function, indicating developmental toxicity, while non-hollow Ni@SiO2 showed no toxicity. Correlating these observations with physicochemical characterization of the CENs suggests that the toxicity of the Ni-SiO2 and hollow Ni@SiO2 material may result partly from an increased effective exposure at the bottom of the well due to rapid settling. Overall, our data suggest that embedding nickel NPs in a porous silica matrix may be a straightforward way to mitigate their toxicity without compromising their functional properties. At the same time, our results also indicate that it is critical to consider modification

  1. New support for high-performance liquid chromatography based on silica coated with alumina particles.

    PubMed

    Silveira, José Leandro R; Dib, Samia R; Faria, Anizio M

    2014-01-01

    A new material based on silica coated with alumina nanoparticles was proposed for use as a chromatographic support for reversed-phase high-performance liquid chromatography. Alumina nanoparticles were synthesized by a sol-gel process in reversed micelles composed of sodium bis(2-ethylhexyl)sulfosuccinate, and the support material was formed by the self-assembly of alumina layers on silica spheres. Spectroscopic and (29)Si nuclear magnetic resonance results showed evidence of chemical bonds between the alumina nanoparticles and the silica spheres, while morphological characterizations showed that the aluminized silica maintained the morphological properties of silica desired for chromatographic purposes after alumina incorporation. Stability studies indicated that bare silica showed high dissolution (~83%), while the aluminized silica remained practically unchanged (99%) after passing one liter of the alkaline mobile phase, indicating high stability under alkaline conditions. The C18 bonded aluminized silica phase showed great potential for use in high-performance liquid chromatography to separate basic molecules in the reversed-phase mode.

  2. Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Patel, Binay S.

    Epoxies are widely used as underfill resins throughout the microelectronics industry to mechanically couple and protect various components of flip-chip assemblies. Generally rigid materials largely surround underfill resins. Improving the mechanical and thermal properties of epoxy resins to better match those of their rigid counterparts can help extend the service lifetime of flip-chip assemblies. Recently, researchers have demonstrated that silica nanoparticles are effective toughening agents for lightly-crosslinked epoxies. Improvements in the fracture toughness of silica-filled epoxy nanocomposites have primarily been attributed to two toughening mechanisms: particle debonding with subsequent void growth and matrix shear banding. Various attempts have been made to model the contribution of these toughening mechanisms to the overall fracture energy observed in silica-filled epoxy nanocomposites. However, disparities still exist between experimental and modeled fracture energy results. In this dissertation, the thermal, rheological and mechanical behavior of eight different types of silica-filled epoxy nanocomposites was investigated. Each nanocomposite consisted of up to 10 vol% of silica nanoparticles with particle sizes ranging from 20 nm to 200 nm, with a variety of surface treatments and particle structures. Fractographical analysis was conducted with new experimental approaches in order to accurately identify morphological evidence for each proposed toughening mechanism. Overall, three major insights into the fracture behavior of real world silica-filled epoxy nanocomposites were established. First, microcracking was observed as an essential toughening mechanism in silica-filled epoxy nanocomposites. Microcracking was observed on the surface and subsurface of fractured samples in each type of silica-filled epoxy nanocomposite. The additional toughening contribution of microcracking to overall fracture energy yielded excellent agreement between experimental

  3. Liver injury induced by thirty- and fifty-nanometer-diameter silica nanoparticles.

    PubMed

    Isoda, Katsuhiro; Tetsuka, Eriko; Shimizu, Yoshimi; Saitoh, Kanae; Ishida, Isao; Tezuka, Masakatsu

    2013-01-01

    Nano-size silica material is a promising reagent for disease diagnosis, cosmetics, and the food industry. For the successful application of nanoparticle materials in bioscience, evaluation of nano-size material toxicity is important. We previously found that nano-size silica particles caused acute liver failure in mice. However, the hepatotoxicity of nanosilica particles with the diameter of 70 nm or less is unknown. Here, we investigated the relationship between particle size and toxicity using nanosilica particles with diameters of 30, 50, and 70 nm (SP30, SP50, and SP70, respectively). We observed dose-dependent increases in hepatic injury following administration of SP50 and SP30, with SP30 causing greater acute liver injury than that seen with SP50. Smaller silica nanoparticles induced liver injury even at proportionally lower dose levels. Furthermore, we investigated the combinatorial toxicity of SP30 in the presence of chemically induced liver injury (including that caused by carbon tetrachloride, paraquat, cisplatin, and acetaminophen). We observed that particles of the smallest size tested (SP30) synergized with chemical substances in causing liver injury. These data suggest that the size (diameter) of the silica nanoparticles affects the severity of nanoparticle-induced liver injury, a finding that will be useful for future investigations in nanotechnology and nanotoxicology.

  4. The world ocean silica cycle.

    PubMed

    Tréguer, Paul J; De La Rocha, Christina L

    2013-01-01

    Over the past few decades, we have realized that the silica cycle is strongly intertwined with other major biogeochemical cycles, like those of carbon and nitrogen, and as such is intimately related to marine primary production, the efficiency of carbon export to the deep sea, and the inventory of carbon dioxide in the atmosphere. For nearly 20 years, the marine silica budget compiled by Tréguer et al. (1995) , with its exploration of reservoirs, processes, sources, and sinks in the silica cycle, has provided context and information fundamental to study of the silica cycle. Today, the budget needs revisiting to incorporate advances that have notably changed estimates of river and groundwater inputs to the ocean of dissolved silicon and easily dissolvable amorphous silica, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, reverse weathering removal fluxes, and outputs of biogenic silica (especially on ocean margins and in the form of nondiatomaceous biogenic silica). The resulting budget recognizes significantly higher input and output fluxes and notes that the recycling of silicon occurs mostly at the sediment-water interface and not during the sinking of silica particles through deep waters.

  5. Gold nanorods-silica Janus nanoparticles for theranostics

    NASA Astrophysics Data System (ADS)

    Wang, Ying-Shuai; Shao, Dan; Zhang, Lu; Zhang, Xu-Lin; Li, Jing; Feng, Jing; Xia, Hong; Huo, Qi-Sheng; Dong, Wen-Fei; Sun, Hong-Bo

    2015-04-01

    A multi-functional gold nanorods-mesoporous silica Janus nanoparticles (NPs) were fabricated by a facile and mild strategy. These Janus NPs not only exhibit small shift of the local surface plasmon resonance wavelength but also have high potential for drug loading and low cytotoxicity. More importantly, the Janus nano-composites could efficiently deliver the imaging agents or drugs into liver cancer cells, at the same time the Janus NPs have good effect on photothermal, which indicate that the unique Janus NPs could be a promising candidate of theranostic system for combined photothermo-/chemo-cancer therapy.

  6. Evaluation the pozzolanic reactivity of sonochemically fabricated nano natural pozzolan.

    PubMed

    Askarinejad, Azadeh; Pourkhorshidi, Ali Reza; Parhizkar, Tayebeh

    2012-01-01

    Natural pozzolans are appropriate supplementary cementitious materials in cement and concrete industry. A simple sonochemical method was developed to synthesize nanostructures of natural pozzolan. Chemical composition, crystallinity, morphology and reactivity of the natural pozzolan samples were compared before and after the sonochemical process, by using powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermal Gravimetry and Differential Thermal Analysis (TG/DTA). Compressive strength tests were performed to evaluate the properties of blended cements incorporating nano natural pozzolan. Under optimized conditions, the nano natural pozzolans showed a superior reactivity as compared with the bulk natural pozzolan. Also higher compressive strength was obtained for the cement specimen incorporating nano natural pozzolan.

  7. Effect of neutron flux, temperature and frequency on the permittivity of nanocrystalline silica

    NASA Astrophysics Data System (ADS)

    Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan

    2014-08-01

    In the work nano silica has been irradiated by 2×1013 cm-2s-1 neutron flux at different times up to 20 h. The temperature and frequency dependencies of real and imaginary parts of dielectric constant of the nanomaterial exposed to neutron flux influence and initial state has been comparatively analyzed. From analysis results it has been revealed that the permittivity of nano SiO2 increases in general tendency with influence of neutron flux. The mutual dependence of the real and imaginary parts of dielectric constant of nano SiO2 particles has been reviewed. From the cases similar to Cole-Cole diagrams existing in the dependencies it has been revealed that the value of the relaxation period is compatible with polarization of the nano particles. It has been observed an increase in polarization with increase of influence period of neutron flux. Mechanisms of all effects observed in the experiments have been given.

  8. Nucleation of polystyrene latex particles in the presence of gamma-methacryloxypropyltrimethoxysilane: functionalized silica particles.

    PubMed

    Bourgeat-Lami, Elodie; Insulaire, Mickaelle; Reculusa, Stéphane; Perro, Adeline; Ravaine, Serge; Duguet, Etienne

    2006-02-01

    Silica/polystyrene nanocomposite particles with different morphologies were synthesized through emulsion polymerization of styrene in the presence of silica particles previously modified by gamma-methacryloxypropyltrimethoxysilane (MPS). Grafting of the silane molecule was performed by direct addition of MPS to the aqueous silica suspension in the presence of an anionic surfactant under basic conditions. The MPS grafting density on the silica surface was determined using the depletion method and plotted against the initial MPS concentration. The influence of the MPS grafting density, the silica particles size and concentration and the nature of the surfactant on the polymerization kinetics and the particles morphology was investigated. When the polymerization was performed in the presence of an anionic surfactant, transmission electron microscopy images showed the formation of polymer spheres around silica for MPS grafting densities lower than typically 1 micromole x m(-2) while the conversion versus time curves indicated a strong acceleration effect under such conditions. In contrast, polymerizations performed in the presence of a larger amount of MPS moieties or in the presence of a non ionic emulsifier resulted in the formation of "excentered" core-shell morphologies and lower polymerization rates. The paper identifies the parameters that allow to control particles morphology and polymerization kinetics and describes the mechanism of formation of the nanocomposite colloids.

  9. One-step synthesis of hydrophobic mesoporous silica and its application in nonylphenol adsorption

    NASA Astrophysics Data System (ADS)

    Zhao, Yanling; Song, Jinliang; Wu, Dong; Tang, Tao; Sun, Yuhan

    2015-11-01

    Highly CH3-functionalized mesoporous silica with nearly spherical morphology was synthesized under acidic conditions by co-condensation of two different silica precursors polymethylhydrosiloxane (PMHS) and tetraethoxysilane (TEOS) in the presence of triblock copolymer P123 as template. XRD, N2 adsorption-desorption, HRTEM, SEM and 29Si MAS NMR were used to identify its highly-ordered mesopore array structure, nearly spherical particle morphology and CH3 functionalization of the as-synthesized material. The resulting hydrophobic mesoporous silica possessed regular mesochannel arrays, indicating that the introduction of PMHS had little impact on the formation of an ordered mesostructure. Also, PMHS played an important role in morphology control and organic functionalization, ensuring nearly spherical particle morphology and high CH3 functionalization degree of the obtained mesoporous silica material. As compared with pristine mesoporous silica SBA-15, the hydrophobic mesoporous silica showed the higher adsorption performance when they were used as adsorbents to remove organic pollutant nonylphenol at a very low concentration from aqueous solution.

  10. Nucleation of polystyrene latex particles in the presence of gamma-methacryloxypropyltrimethoxysilane: functionalized silica particles.

    PubMed

    Bourgeat-Lami, Elodie; Insulaire, Mickaelle; Reculusa, Stéphane; Perro, Adeline; Ravaine, Serge; Duguet, Etienne

    2006-02-01

    Silica/polystyrene nanocomposite particles with different morphologies were synthesized through emulsion polymerization of styrene in the presence of silica particles previously modified by gamma-methacryloxypropyltrimethoxysilane (MPS). Grafting of the silane molecule was performed by direct addition of MPS to the aqueous silica suspension in the presence of an anionic surfactant under basic conditions. The MPS grafting density on the silica surface was determined using the depletion method and plotted against the initial MPS concentration. The influence of the MPS grafting density, the silica particles size and concentration and the nature of the surfactant on the polymerization kinetics and the particles morphology was investigated. When the polymerization was performed in the presence of an anionic surfactant, transmission electron microscopy images showed the formation of polymer spheres around silica for MPS grafting densities lower than typically 1 micromole x m(-2) while the conversion versus time curves indicated a strong acceleration effect under such conditions. In contrast, polymerizations performed in the presence of a larger amount of MPS moieties or in the presence of a non ionic emulsifier resulted in the formation of "excentered" core-shell morphologies and lower polymerization rates. The paper identifies the parameters that allow to control particles morphology and polymerization kinetics and describes the mechanism of formation of the nanocomposite colloids. PMID:16573042

  11. Amine-functionalized magnetic mesoporous silica nanoparticles for DNA separation

    NASA Astrophysics Data System (ADS)

    Sheng, Wei; Wei, Wei; Li, Junjian; Qi, Xiaoliang; Zuo, Gancheng; Chen, Qi; Pan, Xihao; Dong, Wei

    2016-11-01

    We report a modified approach for the functionalized magnetic mesoporous silica nanoparticles (MMSN) using polymer microspheres incorporated with magnetic nanoparticles in the presence of cetyltrimethylammonium bromide (CTAB) and the core-shell magnetic silica nanoparticles (MSN). These particles were functionalized with amino groups via the addition of aminosilane directly to the particle sol. We then evaluate their DNA separation abilities and find the capacity of DNA binding significantly increased (210.22 μg/mg) compared with normal magnetic silica spheres (138.44 μg/mg) by using an ultraviolet and visible spectrophotometer (UV). The morphologies, magnetic properties, particle size, pore size, core-shell structure and Zeta potential are characterized by Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), Transmission electron microscopy (TEM), Powder X-ray diffraction (XRD), and dynamic light scattering (DLS). This work demonstrates that our MMSN own an excellent potential application in bioseparation and drug delivery.

  12. Structure/property relationships of polymers containing hybrid nano-filler: Polyhedral oligomeric silsesquioxanes (POSS)

    NASA Astrophysics Data System (ADS)

    Geng, Haiping

    Polyhedral Oligomeric Silsesquioxane (POSS) is a three-dimensional structurally well-defined cage-like molecule represented by formula (RSiO 1.5)n (n = 6, 8, 10 or higher, R is an organic group). POSS macromers have an inorganic silica-like core, which is surrounded by organic groups, and the physical size of the POSS cage is about 1.5 nm. Because of their hybrid nature and nanometer-scale feature, as shown in this study, POSS macromers were dispersed in a molecular level into polymeric systems by blending, in effect achieved POSS/Polymer nano-blends. The POSS macromers used in this work were cubic-caged POSS macromers bearing different organic corner groups. Polystyrene (PS) and polydimethyl siloxane (PDMS) were used as model polymers. The investigations involved in this work include two parts. In the first part, the microstructures and thermal properties of the POSS macromers were investigated by using X-ray diffractometer, Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). In the second part, the morphologies of POSS/Polymer blends were examined using Transmission Electronic Microscopy (TEM), and X-ray diffractometer. Their thermal and rheological properties were studied with DSC, TGA, and Rheometer. The results of this work showed that different corner groups on the POSS cage affected the morphological structures and properties of the POSS macromers. The higher the degree of the symmetry and regularity of the POSS macromers and the smaller the size of the corner groups, the more ordered the POSS macromers. The POSS macromers with functionalities, which may undergo chemical cross-linking reactions, possessed high thermal stabilities. The morphology studies of POSS/PS and POSS/PDMS blends showed that depending on the attached organic groups on the POSS cages, the structures of the polymer matrix and the composition of the blends, the morphologies of the POSS/polymer blends ranged from complete separation to homogeneous dispersion in

  13. Synthesis of nano-textured biocompatible scaffolds from chicken eggshells

    NASA Astrophysics Data System (ADS)

    Asghar, Waseem; Kim, Young-Tae; Ilyas, Azhar; Sankaran, Jeyantt; Wan, Yuan; Iqbal, Samir M.

    2012-11-01

    Cell adhesion, morphology and growth are influenced by surface topography at nano and micrometer scales. Nano-textured surfaces are prepared using photolithography, plasma etching and long polymer chemical etching which are cost prohibitive and require specialized equipment. This article demonstrates a simple approach to synthesize nano-textured scaffolds from chicken eggshells. Varieties of pattern are made on the eggshells like micro-needle forests and nanopores, giving very uniform nano-textures to the surfaces. The surfaces are characterized for chemical composition and crystal phase. The novel patterns are transferred to PDMS surfaces and the nano-textured PDMS surfaces are used to study the effect of texturing on human fibroblast cell growth and attachment. The effects of surface topographies, along with laminin coating on cell cultures, are also studied. We find an exciting phenomenon that the initial seeding density of the fibroblast cells affects the influence of the nano-texturing on cell growth. These nano-textured surfaces give 16 times more fibroblast growth when compared to flat PDMS surfaces. The novel nano-textured patterns also double the laminin adsorption on PDMS.

  14. Sustainable nano-catalysis

    EPA Science Inventory

    A novel nano-catalyst system which bridges the homogenous and heterogeneous system is described that is cheaper, easily accessible (sustainable) and requires no need of catalyst filtration during the work-up. Because of its nano-size, i.e. high surface area, the contact between r...

  15. Interfacial engineering for silica nanocapsules.

    PubMed

    Wibowo, David; Hui, Yue; Middelberg, Anton P J; Zhao, Chun-Xia

    2016-10-01

    Silica nanocapsules have attracted significant interest due to their core-shell hierarchical structure. The core domain allows the encapsulation of various functional components such as drugs, fluorescent and magnetic nanoparticles for applications in drug delivery, imaging and sensing, and the silica shell with its unique properties including biocompatibility, chemical and physical stability, and surface-chemistry tailorability provides a protection layer for the encapsulated cargo. Therefore, significant effort has been directed to synthesize silica nanocapsules with engineered properties, including size, composition and surface functionality, for various applications. This review provides a comprehensive overview of emerging methods for the manufacture of silica nanocapsules, with a special emphasis on different interfacial engineering strategies. The review starts with an introduction of various manufacturing approaches of silica nanocapsules highlighting surface engineering of the core template nanomaterials (solid nanoparticles, liquid droplets, and gas bubbles) using chemicals or biomolecules which are able to direct nucleation and growth of silica at the boundary of two-phase interfaces (solid-liquid, liquid-liquid, and gas-liquid). Next, surface functionalization of silica nanocapsules is presented. Furthermore, strategies and challenges of encapsulating active molecules (pre-loading and post-loading approaches) in these capsular systems are critically discussed. Finally, applications of silica nanocapsules in controlled release, imaging, and theranostics are reviewed. PMID:27522646

  16. Silica-induced apoptosis in alveolar and granulomatous cells in vivo.

    PubMed Central

    Leigh, J; Wang, H; Bonin, A; Peters, M; Ruan, X

    1997-01-01

    Silica is a toxicant that can stimulate cells to produce various cellular products such as free radicals, cytokines, and growth factors. Silica and its induced substances may induce apoptosis to regulate the evolution of silica-induced inflammation and fibrosis. To examine this hypothesis, groups of Wistar male rats were intratracheally instilled with different doses of Min-U-Sil 5 silica (Silica, Berkeley Springs, WV). Ten days after the instillation, we obtained cells by bronchoalveolar lavage and placed them on slides by cytospin preparation. The slides were stained with Diff-Quik (Lab Aids, Sydney, NSW, Australia) and examined under oil immersion. A substantial number of cells with apoptotic features were identified in all silica-instilled rats and the apoptosis was confirmed by agarose gel electrophoresis. The number of apoptotic cells was clearly related to silica dosage. Engulfment of apoptotic cells by macrophages was also noted. Neutrophil influx in silica-instilled rats could be saturated with the increase of silica dosage and the number of macrophages in different dose groups changed in parallel with the proportion of apoptotic cells. Fifty-six days after instillation, morphologically apoptotic cells could be identified in granulomatous cells of lung tissue from silica-instilled rats. We conclude that intratracheal instillation of silica could induce apoptosis in both alveolar and granulomatous cells, and the apoptotic change and subsequent engulfment by macrophages might play a role in the evolution of silica-induced effects. Images Figure 1. Figure 3. Figure 4. Figure 5. Figure 7. Figure 8. PMID:9400731

  17. A Giant Reconstruction of α-quartz (0001) Interpreted as Three Domains of Nano Dauphine Twins

    PubMed Central

    Eder, S. D.; Fladischer, K.; Yeandel, S. R.; Lelarge, A.; Parker, S. C.; Søndergård, E.; Holst, B.

    2015-01-01

    Silica (SiO2) is one of the most common materials on Earth. The crystalline form α-quartz is the stable silica polymorph at ambient conditions although metastable forms exist. α-quartz is a piezoelectric material, it can be produced artificially and is widely used for example in electronics and the biosciences. Despite the many application areas, the atomic surface structures of silica polymorphs are neither well understood nor well characterized. Here we present measurements of α-quartz (0001). Helium Atom Scattering combined with Atomic Force Microscopy reveals a giant reconstruction consisting of 5.55 ± 0.07 nm wide ribbons, oriented 10.4° ± 0.8° relative to the bulk unit cell. The ribbons, with the aid of atomistic modelling, can be explained as a self-organised pattern of nano Dauphine twins (nano electrical twins). PMID:26446516

  18. Visualisation of morphological interaction of diamond and silver nanoparticles with Salmonella Enteritidis and Listeria monocytogenes.

    PubMed

    Sawosz, Ewa; Chwalibog, André; Mitura, Katarzyna; Mitura, Stanisław; Szeliga, Jacek; Niemiec, Tomasz; Rupiewicz, Marlena; Grodzik, Marta; Sokołowska, Aleksandra

    2011-09-01

    Currently, medicine intensively searches for methods to transport drugs to a target (sick) point within the body. The objective of the present investigation was to evaluate morphological characteristics of the assembles of silver or diamond nanoparticles with Salmonella Enteritidis (G-) or Listeria monocytogenes (G+), to reveal possibilities of constructing nanoparticle-bacteria vehicles. Diamond nanoparticles (nano-D) were produced by the detonation method. Hydrocolloids of silver nanoparticles (nano-Ag) were produced by electric non-explosive patented method. Hydrocolloids of nanoparticles (200 microl) were added to bacteria suspension (200 microl) in the following order: nano-D + Salmonella E.; nano-D + Listeria monocytogenes; nano-Ag + Salmonella E; nano-Ag + Listeria monocytogenes. Samples were inspected by transmission electron microscopy. Visualisation of nanoparticles and bacteria interaction showed harmful effects of both nanoparticles on bacteria morphology. The most spectacular effect of nano-D were strong links between nano-D packages and the flagella of Salmonella E. Nano-Ag were closely attached to Listeria monocytogenes but not to Salmonella E. There was no evidence of entering nano-Ag inside Listeria monocytogenes but smaller particles were placed inside Salmonella E. The ability of nano-D to attach to the flagella and the ability of nano-Ag to penetrate inside bacteria cells can be utilized to design nano-bacteria vehicles, being carriers for active substances attached to nanoparticles. PMID:22097468

  19. Novel nanocomposites from spider silk–silica fusion (chimeric) proteins

    PubMed Central

    Wong Po Foo, Cheryl; Patwardhan, Siddharth V.; Belton, David J.; Kitchel, Brandon; Anastasiades, Daphne; Huang, Jia; Naik, Rajesh R.; Perry, Carole C.; Kaplan, David L.

    2006-01-01

    Silica skeletal architectures in diatoms are characterized by remarkable morphological and nanostructural details. Silk proteins from spiders and silkworms form strong and intricate self-assembling fibrous biomaterials in nature. We combined the features of silk with biosilica through the design, synthesis, and characterization of a novel family of chimeric proteins for subsequent use in model materials forming reactions. The domains from the major ampullate spidroin 1 (MaSp1) protein of Nephila clavipes spider dragline silk provide control over structural and morphological details because it can be self-assembled through diverse processing methods including film casting and fiber electrospinning. Biosilica nanostructures in diatoms are formed in aqueous ambient conditions at neutral pH and low temperatures. The R5 peptide derived from the silaffin protein of Cylindrotheca fusiformis induces and regulates silica precipitation in the chimeric protein designs under similar ambient conditions. Whereas mineralization reactions performed in the presence of R5 peptide alone form silica particles with a size distribution of 0.5–10 μm in diameter, reactions performed in the presence of the new fusion proteins generate nanocomposite materials containing silica particles with a narrower size distribution of 0.5–2 μm in diameter. Furthermore, we demonstrate that composite morphology and structure could be regulated by controlling processing conditions to produce films and fibers. These results suggest that the chimeric protein provides new options for processing and control over silica particle sizes, important benefits for biomedical and specialty materials, particularly in light of the all aqueous processing and the nanocomposite features of these new materials. PMID:16769898

  20. Controlled growth and gas sorption properties of IRMOF-3 nano/microcrystals.

    PubMed

    Yang, Ji-Min; Liu, Qing; Kang, Yan-Shang; Sun, Wei-Yin

    2014-11-28

    IRMOF-3 nano/microcrystals with controllable morphologies and sizes were successfully obtained by a simple solvothermal method. The shape evolution of IRMOF-3 crystals from cube to truncated cube, cuboctahedron, truncated octahedron and finally to octahedron was achieved by adjusting the amount of surfactant. The surfaces of the IRMOF-3 nano/microstructures are affected by the reaction temperature, and the nano/microparticles show shape-dependent sorption properties.

  1. EDITORIAL: Nano-enhanced! Nano-enhanced!

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2010-08-01

    advantages of ZnO nanowires for field emission devices has been greater control over the electronic properties. Alternative morphologies of ZnO nanostructures have also been explored for field emission enhancements, such as urchin structures, which provide field enhancement factors of 1239, but with the additional benefit of greater stability [3]. Theoretical investigations to understand the mechanisms behind these field enhancements have also grown increasingly more sophisticated, through both analytical techniques and finite theorems. Results from a comparison of these two approaches in the form of Mie theory and the finite element method, using a dipole oscillator as the excitation source, were reported recently by researchers from Duke University, USA [4]. The work found excellent agreement in terms of amplitude, plasmon resonance peak position and full width at half-maximum. These field enhancements lend themselves to a range of technological applications, such as the demonstrated potential of plasmonic interactions in DNA sensing arrays [5]. As well as plasmon resonances, Bragg diffraction in nanoparticles also has the potential to provide enhanced system responses. Researchers in Taiwan have shown enhancements in the acceptance angle as well as the photoresponsivity of n-ZnO/p-si photodiodes with the use of a monolayer of silica nanoparticles [6]. In this issue, researchers in Italy and Japan report work on enhancing the cathodoluminescence from SiC-based systems. They investigate the role of a shell of amorphous silica in core/shell 3C-SiC/SiO2 nanowires and observe a shell-induced enhancement of the SiC near-band-edge emission, which is attributed to carrier diffusion from the shell to the core, promoted by the alignment of the SiO2 and SiC bands in a type I quantum well [7]. Their research is another demonstration of how nanostructures provide enhancements to system responses through a wide range of mechanisms, a breadth of creativity that is mirrored in the

  2. Superhydrophobicity on transparent fluorinated ethylene propylene films with nano-protrusion morphology by Ar + O{sub 2} plasma etching: Study of the degradation in hydrophobicity after exposure to the environment

    SciTech Connect

    Gupta, Nitant; Kavya, M. V.; Singh, Yogesh R. G.; Jyothi, J.; Barshilia, Harish C.

    2013-10-28

    Fluorinated ethylene propylene (FEP) films were made superhydrophobic by Ar + O{sub 2} plasma etching process. Field emission scanning electron microscopy and atomic force microscopy studies of the plasma-treated FEP samples detected the presence of uniformly distributed nano-protrusions exhibiting a low surface roughness necessary for maintaining the transparency of the samples. In fact, optical transmittance measurements showed an improvement in the transparency of FEP samples after plasma treatment. The X-ray photoelectron spectroscopic analysis showed the presence of –CF{sub x}–O–CF{sub x}– (x = 1, 2, or 3) linkages in both untreated and plasma-treated samples which explains the hydrophilic nature (contact angle below 90{sup ∘}) of the untreated sample. Fourier transform infrared spectroscopy showed no changes in the bulk properties of the plasma-treated samples. Moreover, exposure to the environment caused the surfaces to lose their superhydrophobic property in an indefinite amount of time. This has been further studied through a water immersion experiment and explained through the wetting state transition from Cassie state to Wenzel state.

  3. Electrochemical strain microscopy of silica glasses

    NASA Astrophysics Data System (ADS)

    Proksch, R.

    2014-08-01

    Piezoresponse Force Microscopy and Electrochemical Strain Microscopy (ESM) are two related techniques that have had considerable success in nano-scale probing of functional material properties. Both measure the strain of the sample in response to a localized electric field beneath a sharp conductive tip. In this work, a collection of commercially available glass samples were measured with a variety of Si cantilevers coated with different conductive metals. In some cases, these glasses showed significant hysteresis loops, similar in appearance to those measured on ferroelectric materials with spontaneous permanent electric dipoles. The magnitude of the electrochemical strain and hysteresis correlated well with the molar percentage of sodium in the glass material, with high sodium (soda-lime) glass showing large hysteresis and fused silica (pure SiO2) showing essentially no hysteresis. The "elephant-ear" shape of the hysteresis loops correlated well with it originating from relaxation behavior—an interpretation verified by observing the temperature dependent relaxation of the ESM response. Cation mobility in a disordered glass should have a low diffusion constant. To evaluate this diffusion constant, the temperature of the glass was varied between room temperature to ˜200 °C. Vanishing hysteresis as the temperature increased was associated with a decrease in the relaxation time of the electrochemical response. The hysteretic behavior changed drastically in this temperature range, consistent with bound surface water playing a large role in the relaxation. This demonstrates the ability of ESM to differentiate cationic concentrations in a range of silica glasses. In addition, since glass is a common sample substrate for, this provides some clear guidance for avoiding unwanted substrate crosstalk effects in piezoresponse and electrochemical strain response measurements.

  4. Physical properties of carboxymethyl cellulose based nano-biocomposites with Graphene nano-platelets.

    PubMed

    Ebrahimzadeh, Saba; Ghanbarzadeh, Babak; Hamishehkar, Hamed

    2016-03-01

    Carboxymethyl cellulose (CMC) based bio-nanocomposite filled with graphene nano-platelets (GNPs) was prepared using casting technique. The morphology, thermal, light barrier, water vapor permeability (WVP), contact angle, moisture absorption and mechanical properties of the resulted bio-nanocomposites were investigated. The results indicated with addition of 0.5% w/w GNPs to polymer matrix, ultimate tensile strength (UTS) decreased from 7.74 MPa (in the pure film) to 5.69 MPa however, strain to break (SB) increased from 12.49% to 19.87%. The GNPs caused to reducing of light transmission and increasing of the water repelling nature of nano-biocomposites. However, it had not effect on melting point of CMC based nano-biocomposites.

  5. Synthesis of antireflective silica coatings through the synergy of polypeptide layer-by-layer assemblies and biomineralization

    NASA Astrophysics Data System (ADS)

    Lee, Yung-Lun; Lin, Ting-Xuan; Hsu, Feng-Ming; Jan, Jeng-Shiung

    2016-01-01

    We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting more than 6% increase in transmittance in the near UV/visible spectral range can be obtained at an optimized refractive index, thickness, and surface roughness. The abrasion test showed that the silica coatings exhibited sufficient structural durability due to continuous silica nanostructures and low surface roughness. This study demonstrated that nanostructured thin films can be synthesized for AR coatings using the synergy between the LbL assembly technique and biomineralization.We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting

  6. Crystallized alkali-silica gel in concrete from the late 1890s

    SciTech Connect

    Peterson, Karl . E-mail: cee@mtu.edu; Gress, David . E-mail: dlgress@unh.edu; Van Dam, Tom . E-mail: cee@mtu.edu; Sutter, Lawrence . E-mail: cee@mtu.edu

    2006-08-15

    The Elon Farnsworth Battery, a concrete structure completed in 1898, is in an advanced state of disrepair. To investigate the potential for rehabilitation, cores were extracted from the battery. Petrographic examination revealed abundant deposits of alkali silica reaction products in cracks associated with the quartz rich metasedimentary coarse aggregate. The products of the alkali silica reaction are variable in composition and morphology, including both amorphous and crystalline phases. The crystalline alkali silica reaction products are characterized by quantitative X-ray energy dispersive spectrometry (EDX) and X-ray diffraction (XRD). The broad extent of the reactivity is likely due to elevated alkali levels in the cements used.

  7. Effect of silica nanoparticles on reinforcement of poly(phenylene ether) based thermoplastic elastomer.

    PubMed

    Gupta, Samik; Maiti, Parnasree; Krishnamoorthy, Kumar; Krishnamurthy, Raja; Menon, Ashok; Bhowmick, Anil K

    2008-04-01

    Reinforcement of a novel poly(phenylene ether) (PPE) based thermoplastic elastomer (TPE), i.e., styrene-ethylene-butylene-styrene (SEBS)/ethylene vinyl acetate (EVA) and PPE-polystyrene (PS), was studied to develop a reinforced thermoplastic elastomer or thermoplastic vulcanizate (TPV). An effort was made to reinforce selectively the elastomeric dispersed phase of EVA by silica nanoparticles and silica sol-gel precursors, like alkoxy orthosilanes, using twin-screw extrusion and injection molding processes. Improvement of tensile strength and percent elongation at break was observed both with silica nanoparticles and tetraethoxy orthosilane (TEOS). Addition of TEOS transformed the dispersed EVA lamellar morphology into semispherical domains as a consequence of possible crosslinking. Soxhlet extraction was done on the silica and TEOS reinforced materials. The insoluble residues collected from both the silica and TEOS reinforced samples were analyzed in detail using both morphological and spectroscopic studies. This extensive study also provided an in-depth conceptual understanding of the PPE based TPE behavior upon reinforcement with silica nanoparticles and silica sol-gel precursors and the effect of reinforcement on recycling behavior.

  8. Characterisation of silica derived from rice husk (Muar, Johor, Malaysia) decomposition at different temperatures

    NASA Astrophysics Data System (ADS)

    Azmi, M. A.; Ismail, N. A. A.; Rizamarhaiza, M.; W. M. Hasif. A. A., K.; Taib, H.

    2016-07-01

    Rice husk was thermally decomposed to yield powder composed of silica (SiO2). Temperatures of 700°C and 1000°C were chosen as the decomposition temperatures. X-Ray Diffraction (XRD), X-Ray Florescence (XRF), Fourier Transform Infrared (FTIR), and Field Emission Scanning Electron Microscope (FESEM) analyses were conducted on a synthetic silica powder (SS-SiO2) and the rice husk ash as for the comparative characterisation study. XRD analyses clearly indicated that the decomposed rice husk yielded silica of different nature which are Crystalline Rice Husk Silica (C-RHSiO2) and Amorphous Rice Husk Silica (A-RHSiO2). Moreover, it was found that SS-SiO2 was of Quartz phase, C-RHSiO2 was of Trydimite and Cristobalite. Through XRF detection, the highest SiO2 purity was detected in SS-SiO2 followed by C-RHSiO2 and A-RHSiO2 with purity percentages of 99.60%, 82.30% and 86.30% respectively. FTIR results clearly indicated silica (SiO2) bonding 1056, 1064, 1047, 777, 790 and 798 cm-1) increased as the crystallinity silica increased. The Cristobalite phase was detected in C-RH SiO2 at the wavelength of 620 cm-1. Morphological features as observed by FESEM analyses confirmed that, SS-SiO2 and C-RH SiO2 showed prominent coarse granular morphology.

  9. Nanocharacterization of bio-silica using atomic force and ultrasonic force microscopy

    NASA Astrophysics Data System (ADS)

    Gill, Vinaypreet S.; Hallinan, Kevin P.; Brar, N. S.

    2005-04-01

    Nanotechnology has become central to our research efforts to fabricate relatively smaller size devices, which are more versatile than their older and larger predecessors. Silica is a very important material in this regard. Recently, a new biomimetically inspired path to silica production has been demonstrated. This processing technique was inspired from biological organisms, such as marine diatoms, which produce silica at ambient conditions and almost neutral ph with beautiful control over location and structure. Recently, several researchers have demonstrated that positional control of silica formed could be achieved by application of an electric field to locate charged enzymes responsible for the bio catalytic condensation of silica from solution. Secondly, chemical and physical controls of silica structural morphology were achievable. Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) techniques are employed for the first time to provide both substantially improved resolution of the morphology and relative measurement of the modulus of elasticity of the structures. In particular, these measurements reveal the positive impact of a shear flow field present during the silica formation on both the "ordering" of the structure and the mechanical properties.

  10. Effect of composition on thermal conductivity of silica insulation media.

    PubMed

    Park, Sung; Kwon, Young-Pil; Kwon, Hyuk-Chon; Lee, Hae-Weon; Lee, Jae Chun

    2008-10-01

    Nano-sized fumed silica-based insulation media were prepared by adding TiO2 powders and ceramic fibers as opacifiers and structural integrity improvers, respectively. The high temperature thermal conductivities of the fumed silica-based insulation media were investigated using different types of TiO2 opacifier and by varying its content. The opacifying effects of nanostructured TiO2 powders produced by homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial TiO2 powder. The nanostructured HPPLT TiO2 powder with a mean particle size of 1.8 microm was more effective to reduce radiative heat transfer than the commercial one with a similar mean particle size. The insulation samples with the HPPLT TiO2 powder showed about 46% lower thermal conductivity at temperatures of about 820 degrees C than those with the commercial one. This interesting result might be due to the more effective radiation scattering efficiency of the nanostructured HPPLT TiO2 powder which has better gap filling and coating capability in nano-sized composite compacts.

  11. Fabrication of nano structural biphasic materials from phosphogypsum waste and their in vitro applications

    SciTech Connect

    Mohamed, Khaled R.; Mousa, Sahar M.; El Bassyouni, Gehan T.

    2014-02-01

    Graphical abstract: (a) Schema of the process, (b) TEM of nano particles of biphasic materials and (c) SEM of post-immersion. - Highlights: • Ratio of HA and β-TCP phases were controlled by thermal treatment. • HA partially decomposed into β-TCP with other bioactive phases. • Calcined HA at 900 °C is the best for the bioactivity behavior. - Abstract: In this study, a novel process of preparing biphasic calcium phosphate (BCP) is proposed. Also its bioactivity for the utilization of the prepared BCP as a biomaterial is studied. A mixture of calcium hydroxyapatite (HAP) and tricalcium phosphate (β-TCP) could be obtained by thermal treatment of HAP which was previously prepared from phosphogypsum (PG) waste. The chemical and phase composition, morphology and particle size of prepared samples was characterized by X-ray diffraction (XRD), Infrared spectroscopy (IR), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The bioactivity was investigated by soaking of the calcined samples in simulated body fluid (SBF). Results confirmed that the calcination temperatures played an important role in the formation of calcium phosphate (CP) materials. XRD results indicated that HAP was partially decomposed into β-TCP. The in vitro data confirmed that the calcined HAP forming BCP besides other phases such as pyrophosphate and silica are bioactive materials. Therefore, BCP will be used as good biomaterials for medical applications.

  12. PREFACE: International Conference on Structural Nano Composites (NANOSTRUC 2012)

    NASA Astrophysics Data System (ADS)

    Njuguna, James

    2012-09-01

    Dear Colleagues It is a great pleasure to welcome you to NanoStruc2012 at Cranfield University. The purpose of the 2012 International Conference on Structural Nano Composites (NanoStruc2012) is to promote activities in various areas of materials and structures by providing a forum for exchange of ideas, presentation of technical achievements and discussion of future directions. NanoStruc brings together an international community of experts to discuss the state-of-the-art, new research results, perspectives of future developments, and innovative applications relevant to structural materials, engineering structures, nanocomposites, modelling and simulations, and their related application areas. The conference is split in 7 panel sessions, Metallic Nanocomposites and Coatings, Silica based Nanocomposites, safty of Nanomaterials, Carboin based Nanocomposites, Multscale Modelling, Bio materials and Application of Nanomaterials. All accepted Papers will be published in the IOP Conference Series: Materials Science and Engineering (MSE), and included in the NanoStruc online digital library. The abstracts will be indexed in Scopus, Compedex, Inspec, INIS (International Nuclear Information System), Chemical Abstracts, NASA Astrophysics Data System and Polymer Library. Before ending this message, I would like to acknowledge the hard work, professional skills and efficiency of the team which ensured the general organisation. As a conclusion, I would like to Welcome you to the Nanostruc2012 and wish you a stimulating Conference and a wonderful time. On behalf of the scientific committee, Signature James Njuguna Conference Chair The PDF of this preface also contains committee listings and associates logos.

  13. Biomimetic synthesis of raspberry-like hybrid polymer-silica core-shell nanoparticles by templating colloidal particles with hairy polyamine shell.

    PubMed

    Pi, Mengwei; Yang, Tingting; Yuan, Jianjun; Fujii, Syuji; Kakigi, Yuichi; Nakamura, Yoshinobu; Cheng, Shiyuan

    2010-07-01

    The nanoparticles composed of polystyrene core and poly[2-(diethylamino)ethyl methacrylate] (PDEA) hairy shell were used as colloidal templates for in situ silica mineralization, allowing the well-controlled synthesis of hybrid silica core-shell nanoparticles with raspberry-like morphology and hollow silica nanoparticles by subsequent calcination. Silica deposition was performed by simply stirring a mixture of the polymeric core-shell particles in isopropanol, tetramethyl orthosilicate (TMOS) and water at 25 degrees C for 2.5h. No experimental evidence was found for nontemplated silica formation, which indicated that silica deposition occurred exclusively in the PDEA shell and formed PDEA-silica hybrid shell. The resulting hybrid silica core-shell particles were characterized by transmission electron microscopy (TEM), thermogravimetry, aqueous electrophoresis, and X-ray photoelectron spectroscopy. TEM studies indicated that the hybrid particles have well-defined core-shell structure with raspberry morphology after silica deposition. We found that the surface nanostructure of hybrid nanoparticles and the composition distribution of PDEA-silica hybrid shell could be well controlled by adjusting the silicification conditions. These new hybrid core-shell nanoparticles and hollow silica nanoparticles would have potential applications for high-performance coatings, encapsulation and delivery of active organic molecules.

  14. Biomimetic synthesis of raspberry-like hybrid polymer-silica core-shell nanoparticles by templating colloidal particles with hairy polyamine shell.

    PubMed

    Pi, Mengwei; Yang, Tingting; Yuan, Jianjun; Fujii, Syuji; Kakigi, Yuichi; Nakamura, Yoshinobu; Cheng, Shiyuan

    2010-07-01

    The nanoparticles composed of polystyrene core and poly[2-(diethylamino)ethyl methacrylate] (PDEA) hairy shell were used as colloidal templates for in situ silica mineralization, allowing the well-controlled synthesis of hybrid silica core-shell nanoparticles with raspberry-like morphology and hollow silica nanoparticles by subsequent calcination. Silica deposition was performed by simply stirring a mixture of the polymeric core-shell particles in isopropanol, tetramethyl orthosilicate (TMOS) and water at 25 degrees C for 2.5h. No experimental evidence was found for nontemplated silica formation, which indicated that silica deposition occurred exclusively in the PDEA shell and formed PDEA-silica hybrid shell. The resulting hybrid silica core-shell particles were characterized by transmission electron microscopy (TEM), thermogravimetry, aqueous electrophoresis, and X-ray photoelectron spectroscopy. TEM studies indicated that the hybrid particles have well-defined core-shell structure with raspberry morphology after silica deposition. We found that the surface nanostructure of hybrid nanoparticles and the composition distribution of PDEA-silica hybrid shell could be well controlled by adjusting the silicification conditions. These new hybrid core-shell nanoparticles and hollow silica nanoparticles would have potential applications for high-performance coatings, encapsulation and delivery of active organic molecules. PMID:20347275

  15. Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels

    NASA Technical Reports Server (NTRS)

    Ou, Danny; Stepanian, Christopher J.; Hu, Xiangjun

    2010-01-01

    Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression . an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum- insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.) A silica/polymer aerogel of the present type could be characterized, somewhat more precisely, as consisting of multiply bonded, linear polymer reinforcements within a silica aerogel matrix. Thus far, several different polymethacrylates (PMAs) have been incorporated into aerogel networks to increase resistance to crushing and to improve other mechanical properties while minimally affecting thermal conductivity and density. The polymethacrylate phases are strongly linked into the silica aerogel networks in these materials. Unlike in other organic/inorganic blended aerogels, the inorganic and organic phases are chemically bonded to each other, by both covalent and hydrogen bonds. In the process for making a silica/polymer alloy aerogel, the covalent bonds are introduced by prepolymerization of the methacrylate monomer with trimethoxysilylpropylmethacrylate, which serves as a phase cross-linker in that it contains both organic and inorganic monomer functional groups and hence acts as a connector between the organic and inorganic phases. Hydrogen bonds are formed between the silanol groups of the inorganic phase and the

  16. A new anion-exchange/hydrophobic monolith as stationary phase for nano liquid chromatography of small organic molecules and inorganic anions.

    PubMed

    Aydoğan, Cemil

    2015-05-01

    In this study, an anion-exchange/hydrophobic polymethacrylate-based stationary phase was prepared for nano-liquid chromatography of small organic molecules and inorganic anions. The stationary phase was synthesized by in situ polymerization of 3-chloro-2-hydroxypropylmethacrylate and ethylene dimethacrylate inside silanized 100 μm i.d. fused silica capillary. The porogen mixture consisted of toluene and dodecanol. The pore size distrubution profiles of the resulting monolith were determined by mercury intrusion porosimetry and the morphology of the prepared monolith was investigated by scanning electron microscope. Good permeability, stability and column efficiency were observed on the monolithic column with nano flow. The produced monolithic column, which contains reactive chloro groups, was then modified by reaction with N,N-dimethyl-N-dodecylamine to obtain an anion-exchange/hydrophobic monolithic stationary phase. The functionalized monolith contained ionizable amine groups and hydrophobic groups that are useful of anion-exchange/hydrophobic mixed-mode chromatography. The final monolithic column performance with respect to anion-exchange and hydrophobic interactions was assesed by the separation of alkylbenzene derivatives, phenolic compounds and inorganic anions, respectively. Theoretical plate numbers up to 23,000 plates/m were successfully achieved in the separation of inorganic anions.

  17. Nano-structural characteristics and optical properties of silver chiral nano-flower sculptured thin films

    NASA Astrophysics Data System (ADS)

    Savaloni, Hadi; Haydari-Nasab, Fatemh; Malmir, Mariam

    2011-08-01

    Silver chiral nano-flowers with 3-, 4- and 5-fold symmetry were produced using oblique angle deposition method in conjunction with the rotation of sample holder with different speeds at different sectors of each revolution corresponding to symmetry order of the acquired nano-flower. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), were employed to obtain morphology and nano-structure of the films. Optical characteristics of silver chiral nano-flower thin films were obtained using single beam spectrophotometer with both s- and p-polarization incident light at 30° and 70° incidence angles and at different azimuthal angles ( φ). Optical spectra showed both TM (TDM (transverse dipole mode) and TQM (transverse quadruple mode)) and LM (longitudinal mode) Plasmon resonance peaks. For 3- and 4-fold symmetry chiral nano-flowers the s-polarization extinction spectra obtained at different azimuthal angles did not show significant change in the Plasmon peak position while 5-fold symmetry chiral nano-flower showed a completely different behavior, which may be the result of increased surface anisotropy, so when the φ angle is changed the s-polarization response from the surface can change more significantly than that for lower symmetries. In general, for 3-, 4- and 5-fold symmetry chiral nano-flowers a sharp peak at lower wavelengths (<450 nm) is observed in the s-polarization spectra, while in addition to this peak a broad peak at longer wavelengths (i.e., LM) observed in the p-polarization spectra, which is more dominant for 70° incidence angle.

  18. Highly ordered poly(thiophene)s prepared in mesoporous silica nanoparticles.

    PubMed

    Seo, Seogjae; Kim, Jeonghun; Kim, Byeonggwan; Vinu, Ajayan; Kim, Eunkyoung

    2011-05-01

    Nanostructured PEDOT was synthesized using mesoporous silica as a nano-template. The polymerization of thiophene monomers was performed with an oxidant and mesoporous silica nanoparticles. The silica particles took essential role in absorbing monomers and oxidant molecules, and growth of polymers inside their pores. As prepared polymer/silica composite was treated with HF solution to remove silica template to result in 1D wire structure and mesh type porous 3D structures from SBA-15 and KIT-6 template, respectively. The average size of the poly(thiophene) wires was 10 15 nm, which was matched well to the pores size of the silica templates, as determined from an electron microscopy. At optimized condition, the room temperature electrical conductivities of the PEDOT grown from SBA-15 and KIT-6 template were similar as 1.1 and 1.0 S/cm, respectively. However, the evolution of the PEDOT conductivity versus temperature was different depending on the templates. These results gave a unique chance to tailor made 3 dimensional structure as well as properties of conductive polymer. PMID:21780498

  19. Time and frequency dependent rheology of reactive silica gels.

    PubMed

    Wang, Miao; Winter, H Henning; Auernhammer, Günter K

    2014-01-01

    In a mixture of sodium silicate and low concentrated sulfuric acid, nano-sized silica particles grow and may aggregate to a system spanning gel network. We studied the influence of the finite solubility of silica at high pH on the mechanical properties of the gel with classical and piezo-rheometers. Direct preparation of the gel sample in the rheometer cell avoided any pre-shear of the gel structure during the filling of the rheometer. The storage modulus of the gel grew logarithmically with time with two distinct growth laws. The system passes the gel point very quickly but still shows relaxation at low frequency, typically below 6 rad/s. We attribute this as a sign of structural rearrangements due to the finite solubility of silica at high pH. The reaction equilibrium between bond formation and dissolution maintains a relatively large bond dissolution rate, which leads to a finite life time of the bonds and behavior similar to physical gels. This interpretation is also compatible with the logarithmic time dependence of the storage modulus. The frequency dependence was more pronounced for lower water concentrations, higher temperatures and shorter reaction times. With two relaxation models (the modified Cole-Cole model and the empirical Baumgaertel-Schausberger-Winter model) we deduced characteristic times from the experimental data. Both models approximately described the data and resulted in similar relaxation times.

  20. Hierarchical Micro-Nano Coatings by Painting

    NASA Astrophysics Data System (ADS)

    Kirveslahti, Anna; Korhonen, Tuulia; Suvanto, Mika; Pakkanen, Tapani A.

    2016-03-01

    In this paper, the wettability properties of coatings with hierarchical surface structures and low surface energy were studied. Hierarchically structured coatings were produced by using hydrophobic fumed silica nanoparticles and polytetrafluoroethylene (PTFE) microparticles as additives in polyester (PES) and polyvinyldifluoride (PVDF). These particles created hierarchical micro-nano structures on the paint surfaces and lowered or supported the already low surface energy of the paint. Two standard application techniques for paint application were employed and the presented coatings are suitable for mass production and use in large surface areas. By regulating the particle concentrations, it was possible to modify wettability properties gradually. Highly hydrophobic surfaces were achieved with the highest contact angle of 165∘. Dynamic contact angle measurements were carried out for a set of selected samples and low hysteresis was obtained. Produced coatings possessed long lasting durability in the air and in underwater conditions.

  1. Underivatized oxysterols and nanoLC-ESI-MS: A mismatch.

    PubMed

    Roberg-Larsen, Hanne; Vesterdal, Caroline; Wilson, Steven Ray; Lundanes, Elsa

    2015-07-01

    Due to their non-charged character, liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) measurements of oxysterols are often performed after derivatization with e.g. charged Girard reagents. However, derivatization reactions are time-consuming and may require numerous steps to remove excess reagent. In addition, extensive sample handling can be associated with cholesterol autoxidation, resulting in analyte artifacts and hence false positives. Nano scale liquid chromatography in combination with electrospray-mass spectrometry (nanoLC-ESI-MS) is a powerful tool for analyzing limited samples, due to substantially increased sensitivity compared to conventional LC-ESI-MS. The signal enhancement may compensate for the poor ionization of the oxysterols; hence we have explored the possibility to quantify oxysterols without derivatization using nanoLC-ESI-MS. Non-derivatized oxysterols and nanoLC were however not compatible, due to persistent and large carry-over. This was attributed to the extended contribution of surface to volume ratio in such miniaturized systems and interactions with the materials of the nanoLC instrumentation (e.g. adsorption to the fused silica tubing). Two contemporary MS instruments (Q-Exactive™ hybrid quadrupole-Orbitrap and TSQ Quantiva™ triple quadrupole) were used. However, both the MS and MS/MS spectra of non-derivatized oxysterols were ambiguous and/or unrepeatable for both of the instruments employed. Derivatizing oxysterols is more cumbersome, but provides more selective and reliable results, and Girard derivatization+nanoLC-ESI-MS continues to be our recommended choice for measuring oxysterols in very limited samples. These investigations also indicate that extra care should be taken to remove lipids prior to nanoLC of other analytes, as adsorbed oxysterols, etc. can compromise analysis.

  2. Nano-composite materials

    DOEpatents

    Lee, Se-Hee; Tracy, C. Edwin; Pitts, J. Roland

    2010-05-25

    Nano-composite materials are disclosed. An exemplary method of producing a nano-composite material may comprise co-sputtering a transition metal and a refractory metal in a reactive atmosphere. The method may also comprise co-depositing a transition metal and a refractory metal composite structure on a substrate. The method may further comprise thermally annealing the deposited transition metal and refractory metal composite structure in a reactive atmosphere.

  3. Nano/micro-scaled La(1,3,5-BTC)(H{sub 2}O){sub 6} coordination polymer: Facile morphology-controlled fabrication and color-tunable photoluminescence properties by co-doping Eu{sup 3+},Tb{sup 3+}

    SciTech Connect

    Liu Kai; Zheng Yuhua; Jia Guang; Yang Mei; Song Yanhua; Guo Ning; You Hongpeng

    2010-10-15

    Nano/micro-sized coordination polymer La(1,3,5-BTC)(H{sub 2}O){sub 6} with controllable morphologies have been successfully prepared on a large scale via a simple solution phase method at room temperature. By rationally adjusting the synthetic parameters such as concentration, molar ratio of reactants, surfactant, and solvent, the La(1,3,5-BTC)(H{sub 2}O){sub 6} with 3D flowerlike, wheatearlike, spherical, sheaflike, taillike, bundlelike hierarchical architectures, and 1D nanorods can be selectively prepared. More interestingly, the photoluminescence color of codoped Eu{sup 3+} and Tb{sup 3+} lanthanum 1,3,5-benzenetricarboxylate phosphors can be easily tuned from red, orange, yellow, green-yellow to green by changing co-doping concentration of activator ions, making the material has potential applications in building minioptoelectronic devices, biomedicine, and color display fields. - Graphical abstract: La(1,3,5-BTC)(H{sub 2}O){sub 6} with 3D flowerlike, wheatearlike, spherical, sheaflike, taillike, bundlelike architectures, and 1D nanorods were selectively prepared; color-tunable photoluminescence from red to green was also realized by co-doping Eu{sup 3+} and Tb{sup 3+}.

  4. Tomography and optical properties of silver nano-inukshuk

    SciTech Connect

    Ghosh, Tanmay; Das, Pabitra; Ghosh, Tapas; Satpati, Biswarup

    2015-06-24

    Following a simple dip-and-rinse galvanic displacement reaction silver nano-inukshuks were prepared directly on germanium surfaces. Morphology, 3-dimensional (3D) structure, chemical composition and optical properties of the silver nanostructurs were investigated using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and cathodoluminescence (CL) spectroscopy. Exact 3D morphology was reconstructed in the by tomography mode of TEM.

  5. Silica Nanowires: Growth, Integration, and Sensing Applications

    PubMed Central

    Kaushik, Ajeet; Kumar, Rajesh; Huey, Eric; Bhansali, Shekhar; Nair, Narayana; Nanir, Madhavan

    2014-01-01

    This review (with 129 refs.) gives an overview on how the integration of silica nanowires (NWs) into micro-scale devices has resulted, in recent years, in simple yet robust nano-instrumentation with improved performance in targeted application areas such as sensing. This has been achieved by the use of appropriate techniques such as di-electrophoresis and direct vapor-liquid-growth phenomena, to restrict the growth of NWs to site-specific locations. This also has eliminated the need for post-growth processing and enables nanostructures to be placed on pre-patterned substrates. Various kinds of NWs have been investigated to determine how their physical and chemical properties can be tuned for integration into sensing structures. NWs integrated onto interdigitated micro-electrodes have been applied to the determination of gases and biomarkers. The technique of directly growing NWs eliminates the need for their physical transfer and thus preserves their structure and performance, and further reduces the costs of fabrication. The biocompatibility of NWs also has been studied with respect to possible biological applications. This review addresses the challenges in growth and integration of NWs to understand related mechanism on biological contact or gas exposure and sensing performance for personalized health and environmental monitoring. PMID:25382871

  6. Direct nano-scale patterning of Ag films using hard X-ray induced oxidation.

    PubMed

    Kim, Jae Myung; Lee, Su Yong; Kang, Hyon Chol; Noh, Do Young

    2015-01-01

    The morphological change of silver nano-particles (AgNPs) exposed to an intense synchrotron X-ray beam was investigated for the purpose of direct nano-scale patterning of metal thin films. AgNPs irradiated by hard X-rays in oxygen ambient were oxidized and migrated out of the illuminated region. The observed X-ray induced oxidation was utilized to fabricate nano-scale metal line patterns using sectioned WSi2/Si multilayers as masks. Lines with a width as small as 21 nm were successfully fabricated on Ag films on silicon nitride. Au/Ag nano-lines were also fabricated using the proposed method.

  7. Preparation of a magnetofluorescent nano-thermometer and its targeted temperature sensing applications in living cells.

    PubMed

    Wang, Zhuyuan; Ma, Xueqin; Zong, Shenfei; Wang, Yuzhong; Chen, Hui; Cui, Yiping

    2015-01-01

    A magnetic fluorescent nano-thermometer is presented. To fabricate the nano-thermometer, magnetic nanoparticles (Fe3O4) were first encapsulated with a silica layer. Then a poly (N-isopropylacrylamide) (pNIPAM) copolymer shell with Rhodamine B isothiocyanate (RhBITC) embedded inside was further coated, which was denoted as the pNIPAM-co-RhBITC shell. Finally, gold nanoparticles were introduced onto the copolymer shell by in-situ growth method and the nano-thermometer (denoted as Fe3O4@SiO2@(pNIPAM-co-RhBITC)/Au) was obtained. The nano-thermometer shows dual responses to both magnetism and temperature. Specifically, the fluorescence intensity of the nano-thermometer decreases as the temperature increases, which makes the nano-thermometer suitable for intracellular temperature sensing. Using this nano-thermometer, temperature changes in live HeLa cells can be successfully detected. Moreover, due to the Fe3O4 component, magnetic field guided targeting can be realized, thus targeted temperature sensing can be achieved for living cells. Cellular temperature changes can be easily detected using the proposed nano-thermometer in the range of 26°C to 41°C with a sensitivity of -4.84%°C(-1).

  8. Preparation of high-performance polymer electrolyte nanocomposites through nanoscale silica particle dispersion

    NASA Astrophysics Data System (ADS)

    Lee, Chang Hyun; Park, Ho Bum; Park, Chi Hoon; Lee, So Young; Kim, Ju Young; McGrath, James E.; Lee, Young Moo

    Nano-level dispersion with a minimum amount of non-porous and surface-functionalized nanoparticles is a key to tune physically a common polymer material with poor durability to a powerful material with excellent stability even under harsh fuel cell conditions. Surfactants composed of hydrophobic cores and hydrophilic outer shells are used to assist a homogenous distribution of surface-treated (hydrophilic and hydrophobic) silica nanoparticles. In particular, their effect on nanoparticle dispersion is conspicuous in polymer electrolyte nanocomposites containing hydrophilic surface-treated silica. The hydrophilic silica acts as an additional proton conductor in the acid electrolyte medium, leading to improved proton conductivity without any negative side-effects on the mechanical and chemical durability of the membrane material. The well-distributed hydrophilic silica nanoparticles are beneficial in preventing methanol permeation via compact polymer packing and in strengthening the membrane stability under hot aqueous conditions. Finally, the efficacy of the nano-level dispersion is electrochemically verified in terms of high single-cell performance and further extended life time as a result of a synergistic effect of improved proton conductivity, reduced methanol permeability and excellent hydrolytic durability.

  9. Sonochemical procedures; the main synthetic method for synthesis of coinage metal ion supramolecular polymer nano structures.

    PubMed

    Shahangi Shirazi, Fatemeh; Akhbari, Kamran

    2016-07-01

    During the last two decades, supramolecular polymers have received great attention and the number of their synthesized compounds is still growing. Although people have long been interested in their crystalline network form it was only until 2005 that the first examples of nano- or microscale coordination polymers particles be demonstrated. This review tries to give an overview of all nano supramolecular compounds which were reported from coinage metal ions, their attributed synthetic procedures and to investigate the relation between the dimensions of coinage metal ions (Cu, Ag and Au) coordination and supramolecular polymers with their nano-structural morphologies and dimensions. Eleven compounds (from twenty compounds) with nano-structure morphology were prepared by sonochemical process and Ag(I) coordination and supramolecular polymer nano-structures can be easily prepared by sonochemical procedures. PMID:26964923

  10. Sonochemical procedures; the main synthetic method for synthesis of coinage metal ion supramolecular polymer nano structures.

    PubMed

    Shahangi Shirazi, Fatemeh; Akhbari, Kamran

    2016-07-01

    During the last two decades, supramolecular polymers have received great attention and the number of their synthesized compounds is still growing. Although people have long been interested in their crystalline network form it was only until 2005 that the first examples of nano- or microscale coordination polymers particles be demonstrated. This review tries to give an overview of all nano supramolecular compounds which were reported from coinage metal ions, their attributed synthetic procedures and to investigate the relation between the dimensions of coinage metal ions (Cu, Ag and Au) coordination and supramolecular polymers with their nano-structural morphologies and dimensions. Eleven compounds (from twenty compounds) with nano-structure morphology were prepared by sonochemical process and Ag(I) coordination and supramolecular polymer nano-structures can be easily prepared by sonochemical procedures.

  11. Viscoelasticity of Epoxy nano-composites

    NASA Astrophysics Data System (ADS)

    Ahuja, Suresh

    2013-03-01

    Nanocomposites have been modeled in a multiscale covering from molecular scale (e.g., molecular dynamics, Monte Carlo), microscale (e.g., Brownian dynamics, dissipative particle dynamics, lattice Boltzmann, time-dependent Ginzburg-Landau method, dynamic density functional theory method) to mesoscale and macroscale (e.g., micromechanics, equivalent-continuum and self-similar approaches, finite element method) The presence of layered silicates in nonaqueous polymers changes the viscoelastic behavior of the unfilled matrix from liquid-like to solid-like because of the formation of a three-dimensional percolating network of exfoliated or intercalated stacks. This gel-like behavior is a direct consequence of the highly anisotropic nature of the nanoclays which prevents their free rotation and the dissipation of stress. Particle to particle interactions is the dominant mechanism in fumed silica nanocomposites whereas particle to polymer interaction is the dominant one in colloidal silica nanocomposites at identical filler concentrations. These interactions are balanced in each nanocomposite systems by the silica surface treatments (chain grafting, silane modification) and the molecular weight of the matrix. Two different types of nanocomposite structures exist namely, intercalated nanocomposites where the polymer chains are sandwiched between silicate layers and exfoliated nanocomposites where the layers can be considered individually but remain more or less dispersed in the polymer matrix. Yield stress from Carreau-Yasuda model has been correlated to exfoliation. Also, equilibrium modulus and zero shear rate viscosity has been used to analyze percolation threshold and sol-gel transition. Nano clays organically functionalized were mixed with Epoxy in a high shear mixer.

  12. Mesoporous Silica Nanoparticles and Films for Cargo Delivery

    NASA Astrophysics Data System (ADS)

    Guardado Alvarez, Tania Maria

    Mesoporous silica materials are well known materials that can range from films to nanoparticles. Mesoporous silica nanoparticles (MSNs) and mesoporous silica films have been of increasing interest among the scientific community for its use in cargo delivery. Silica provides ease of functionalization, a robust support and biocompatibility. Several methods have been used in order to give the mesoporous silica nanomaterials different qualities that render them a useful material with different characteristics. Among these methods is surface modification by taking advantage of the OH groups on the surface. When a molecule attached to the surface can act as a molecular machine it transforms the nanomaterial to act as delivery system that can be activated upon command. The work covered in this thesis focuses on the development and synthesis of different mesoporous silica materials for the purpose of trapping and releasing cargo molecules. Chapter 2 focuses in the photoactivation of "snap-top" stoppers over the pore openings of mesoporous silica nanoparticles that releases intact cargo molecules from the pores. The on-command release can be stimulated by either one UV photon or two coherent near-IR photons. Two-photon activation is particularly desirable for use in biological systems because it enables good tissue penetration and precise spatial control. Chapter 3 focuses on the design and synthesis of a nano-container consisting of mesoporous silica nanoparticles with the pore openings covered by "snap-top" caps that are opened by near-IR light. A photo transducer molecule that is a reducing agent in an excited electronic state is covalently attached to the system. Near IR two-photon excitation causes intermolecular electron transfer that reduces a disulfide bond holding the cap in place, thus allowing the cargo molecules to escape. The operation of the "snap-top" release mechanism by both one- and two photon is described. This system presents a proof of concept of a near

  13. Modified silicas with different structure of grafted methylphenylsiloxane layer.

    PubMed

    Bolbukh, Yuliia; Terpiłowski, Konrad; Kozakevych, Roman; Sternik, Dariusz; Deryło-Marczewska, Anna; Tertykh, Valentin

    2016-12-01

    The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed. Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. Results suggest that the highest hydrophobicity (contact angle θ = 135°-140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces. PMID:27295258

  14. Modified silicas with different structure of grafted methylphenylsiloxane layer

    NASA Astrophysics Data System (ADS)

    Bolbukh, Yuliia; Terpiłowski, Konrad; Kozakevych, Roman; Sternik, Dariusz; Deryło-Marczewska, Anna; Tertykh, Valentin

    2016-06-01

    The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed. Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. Results suggest that the highest hydrophobicity (contact angle θ = 135°-140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces.

  15. The Dissociated Amorphous Silica Surface: Model Development and Evaluation.

    PubMed

    Hassanali, Ali A; Zhang, Hui; Knight, Chris; Shin, Yun Kyung; Singer, Sherwin J

    2010-11-01

    At pH 7, amorphous silica has a characteristic negative charge due to the deprotonation of silanol groups on the surface. Electrokinetic phenomena and transport of biomolecules in devices depend sensitively on the surface morphology, distribution of ions and solvent, and adsorption properties of solutes close to the surface in the electrical double layer region. Hence, simulation of these phenomena requires detailed atomistic models of the double layer region. In this Article, we extend our undissociated silica surface model [J. Phys. Chem. B 2007, 111, 11181-11193] to include dissociated Si-O(-) groups, which interact with both water and salt (Na(+) and Cl(-)). We have also conducted ab initio molecular dynamics (AIMD) simulations of a smaller system consisting of a hydrated silica slab. The radial distribution functions predicted by the empirical model are in qualitative agreement with those from the AIMD simulations. The hydrophobic and hydrophilic nature of silanol-poor and silanol-rich regions of the amorphous silica surface observed in our empirical model is reproduced in the AIMD simulations of the smaller slab. In the initial stages of our AIMD simulations, we observe various chemical processes that represent different hydroxylation mechanisms of the surface.

  16. Preparation, purification, and characterization of aminopropyl-functionalized silica sol.

    PubMed

    Pálmai, Marcell; Nagy, Lívia Naszályi; Mihály, Judith; Varga, Zoltán; Tárkányi, Gábor; Mizsei, Réka; Szigyártó, Imola Csilla; Kiss, Teréz; Kremmer, Tibor; Bóta, Attila

    2013-01-15

    A new, simple, and "green" method was developed for the surface modification of 20 nm diameter Stöber silica particles with 3-aminopropyl(diethoxy)methylsilane in ethanol. The bulk polycondensation of the reagent was inhibited and the stability of the sol preserved by adding a small amount of glacial acetic acid after appropriate reaction time. Centrifugation, ultrafiltration, and dialysis were compared in order to choose a convenient purification technique that allows the separation of unreacted silylating agent from the nanoparticles without destabilizing the sol. The exchange of the solvent to acidic water during the purification yielded a stable colloid, as well. Structural and morphological analysis of the obtained aminopropyl silica was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements, Fourier-transform infrared (FTIR), (13)C and (29)Si MAS nuclear magnetic resonance (NMR) spectroscopies, as well as small angle X-ray scattering (SAXS). Our investigations revealed that the silica nanoparticle surfaces were partially covered with aminopropyl groups, and multilayer adsorption followed by polycondensation of the silylating reagent was successfully avoided. The resulting stable aminopropyl silica sol (ethanolic or aqueous) is suitable for biomedical uses due to its purity. PMID:23068887

  17. Synthesis of Nano-Bowls with a Janus Template

    PubMed Central

    Emerson, Chris D.; Zhang, Chen; Anzenberg, Paula; Akkiraju, Siddhartha; Lal, Ratnesh

    2015-01-01

    Colloidal particles with two or more different surface properties (Janus particles) are of interest in catalysis, biological imaging, and drug delivery. Eccentric nanoparticles are a type of Janus particle consisting of a shell that envelops the majority of a core particle, leaving a portion of the core surface exposed. Previous work to synthesize eccentric nanoparticles from silica and polystyrene have only used microemulsion techniques. In contrast we report the solgel synthesis of eccentric Janus nanoparticles composed of a silica shell around a carboxylate-modified polystyrene core (Janus templates). In addition, we have synthesized nano-bowl-like structures after the removal of the polystyrene core by organic solvent. These Janus templates and nanobowls can be used as a versatile platform for site-specific functionalization or controlled theranostic delivery. PMID:25431230

  18. Synthesis of nano-bowls with a Janus template.

    PubMed

    Mo, Alexander H; Landon, Preston B; Emerson, Chris D; Zhang, Chen; Anzenberg, Paula; Akkiraju, Siddhartha; Lal, Ratnesh

    2015-01-14

    Colloidal particles with two or more different surface properties (Janus particles) are of interest in catalysis, biological imaging, and drug delivery. Eccentric nanoparticles are a type of Janus particle consisting of a shell that envelops the majority of a core particle, leaving a portion of the core surface exposed. Previous work to synthesize eccentric nanoparticles from silica and polystyrene have only used microemulsion techniques. In contrast we report the sol-gel synthesis of eccentric Janus nanoparticles composed of a silica shell around a carboxylate-modified polystyrene core (Janus templates). In addition, we have synthesized nano-bowl-like structures after the removal of the polystyrene core by organic solvent. These Janus templates and nanobowls can be used as a versatile platform for site-specific functionalization or controlled theranostic delivery. PMID:25431230

  19. Porous Silica-Supported Solid Lipid Particles for Enhanced Solubilization of Poorly Soluble Drugs.

    PubMed

    Yasmin, Rokhsana; Rao, Shasha; Bremmell, Kristen E; Prestidge, Clive A

    2016-07-01

    Low dissolution of drugs in the intestinal fluid can limit their effectiveness in oral therapies. Here, a novel porous silica-supported solid lipid system was developed to optimize the oral delivery of drugs with limited aqueous solubility. Using lovastatin (LOV) as the model poorly water-soluble drug, two porous silica-supported solid lipid systems (SSL-A and SSL-S) were fabricated from solid lipid (glyceryl monostearate, GMS) and nanoporous silica particles Aerosil 380 (silica-A) and Syloid 244FP (silica-S) via immersion/solvent evaporation. SSL particles demonstrated significantly higher rate and extent of lipolysis in comparison with the pure solid lipid, depending on the lipid loading levels and the morphology. The highest lipid digestion was observed when silica-S was loaded with 34% (w/w) solid lipid, and differential scanning calorimeter (DSC) analysis confirmed the encapsulation of up to 2% (w/w) non-crystalline LOV in this optimal SSL-S formulation. Drug dissolution under non-digesting intestinal conditions revealed a three- to sixfold increase in dissolution efficiencies when compared to the unformulated drug and a LOV-lipid suspension. Furthermore, the SSL-S provided superior drug solubilization under simulated intestinal digesting condition in comparison with the drug-lipid suspension and drug-loaded silica. Therefore, solid lipid and nanoporous silica provides a synergistic effect on optimizing the solubilization of poorly water-soluble compound and the solid lipid-based porous carrier system provides a promising delivery approach to overcome the oral delivery challenges of poorly water-soluble drugs.

  20. Porous Silica-Supported Solid Lipid Particles for Enhanced Solubilization of Poorly Soluble Drugs.

    PubMed

    Yasmin, Rokhsana; Rao, Shasha; Bremmell, Kristen E; Prestidge, Clive A

    2016-07-01

    Low dissolution of drugs in the intestinal fluid can limit their effectiveness in oral therapies. Here, a novel porous silica-supported solid lipid system was developed to optimize the oral delivery of drugs with limited aqueous solubility. Using lovastatin (LOV) as the model poorly water-soluble drug, two porous silica-supported solid lipid systems (SSL-A and SSL-S) were fabricated from solid lipid (glyceryl monostearate, GMS) and nanoporous silica particles Aerosil 380 (silica-A) and Syloid 244FP (silica-S) via immersion/solvent evaporation. SSL particles demonstrated significantly higher rate and extent of lipolysis in comparison with the pure solid lipid, depending on the lipid loading levels and the morphology. The highest lipid digestion was observed when silica-S was loaded with 34% (w/w) solid lipid, and differential scanning calorimeter (DSC) analysis confirmed the encapsulation of up to 2% (w/w) non-crystalline LOV in this optimal SSL-S formulation. Drug dissolution under non-digesting intestinal conditions revealed a three- to sixfold increase in dissolution efficiencies when compared to the unformulated drug and a LOV-lipid suspension. Furthermore, the SSL-S provided superior drug solubilization under simulated intestinal digesting condition in comparison with the drug-lipid suspension and drug-loaded silica. Therefore, solid lipid and nanoporous silica provides a synergistic effect on optimizing the solubilization of poorly water-soluble compound and the solid lipid-based porous carrier system provides a promising delivery approach to overcome the oral delivery challenges of poorly water-soluble drugs. PMID:27048207

  1. A hydrothermal peroxo method for preparation of highly crystalline silica-titania photocatalysts.

    PubMed

    Krivtsov, Igor; Ilkaeva, Marina; Avdin, Viacheslav; Khainakov, Sergei; Garcìa, Jose R; Ordòñez, Salvador; Dìaz, Eva; Faba, Laura

    2015-04-15

    A new completely inorganic method of preparation of silica-titania photocatalyst has been described. It has been established that the addition of silica promotes crystallinity of TiO2 anatase phase. Relative crystallinity and TiO2 crystal size in the silica-titania particles increase with the silica content until SiO2/TiO2 molar ratio of 0.9, but at higher molar ratios they start to decrease. The single-source precursor containing peroxo titanic (PTA) and silicic acids has been proved to be responsible for high crystallinity of TiO2 encapsulated into amorphous silica. It has been proposed that peroxo groups enhance rapid formation of crystalline titania seeds, while silica controls their growth. It has been concluded from the TEM that the most morphologically uniform anatase crystallites covered with SiO2 particles are prepared at SiO2/TiO2 molar ratio of 0.4. This sample, according to (29)Si NMR, also shows the high content of hydroxylated silica Q(3) and Q(2) groups, and it is the most photocatalytically active in UV-assisted decomposition of methylene blue among the tested materials. It has been determined that the increase in the amount of the condensed Q(4) silica in the mixed oxides leads to the decrease in photocatalytic performance of the material, despite its better crystallinity. High crystallinity, low degree of incorporation of Ti atoms in SiO2 in the mixed oxide and adsorption of methylene blue in the vicinity of photoactive sites on the hydroxylated silica have been considered as the main factors determining the high degradation degree of methylene blue in the presence of silica-titania.

  2. New plasma technique for the deposition of silica layers for integrated optics applications

    NASA Astrophysics Data System (ADS)

    Panciatichi, Cristina; Natascia De Leo, Maria C.

    2000-03-01

    An inductively coupled plasma torch has been used for the synthesis of high-purity, low OH concentration, fused silica layers, for integrated optics applications. This technique is very versatile and the same apparatus can be used to deposit silica layers doped with different elements but this work is particularly devoted to the germanium-doped silica layers. The torch, designed and built in-house, operates at atmospheric pressure and is posed by a 13.56 MHz, 5.4 kW, RF generator. The gaseous reactants are injected in the plasma tail flame by a silica nozzle. Planar silica targets are suitably moved over the torch exit in order to obtain the desired deposition. The samples made by means of this chemical vapor deposition process have been chemically and physically analyzed using various techniques: optical microscopy, scanning electron microscopy, atomic force microscopy, x-ray diffractometer, UV, visible and IR spectroscopy, to test their morphological, geometrical, chemical and optical characteristics. By this plasma- assisted technique it has been possible to achieve the deposition of pure and germanium doped silica layers with good optical and morphological characteristics. Preliminary direct UV photoinduction experiments are very promising: a high refractive index change has been measured.

  3. Synthesis of nano-bowls with a Janus template

    NASA Astrophysics Data System (ADS)

    Mo, Alexander H.; Landon, Preston B.; Emerson, Chris D.; Zhang, Chen; Anzenberg, Paula; Akkiraju, Siddhartha; Lal, Ratnesh

    2014-12-01

    Colloidal particles with two or more different surface properties (Janus particles) are of interest in catalysis, biological imaging, and drug delivery. Eccentric nanoparticles are a type of Janus particle consisting of a shell that envelops the majority of a core particle, leaving a portion of the core surface exposed. Previous work to synthesize eccentric nanoparticles from silica and polystyrene have only used microemulsion techniques. In contrast we report the sol-gel synthesis of eccentric Janus nanoparticles composed of a silica shell around a carboxylate-modified polystyrene core (Janus templates). In addition, we have synthesized nano-bowl-like structures after the removal of the polystyrene core by organic solvent. These Janus templates and nanobowls can be used as a versatile platform for site-specific functionalization or controlled theranostic delivery.Colloidal particles with two or more different surface properties (Janus particles) are of interest in catalysis, biological imaging, and drug delivery. Eccentric nanoparticles are a type of Janus particle consisting of a shell that envelops the majority of a core particle, leaving a portion of the core surface exposed. Previous work to synthesize eccentric nanoparticles from silica and polystyrene have only used microemulsion techniques. In contrast we report the sol-gel synthesis of eccentric Janus nanoparticles composed of a silica shell around a carboxylate-modified polystyrene core (Janus templates). In addition, we have synthesized nano-bowl-like structures after the removal of the polystyrene core by organic solvent. These Janus templates and nanobowls can be used as a versatile platform for site-specific functionalization or controlled theranostic delivery. Electronic supplementary information (ESI) available: Particle size distribution before and after centrifugation during the wash process, SEM and TEM images used in quantification of Janus template yield and population break down. See DOI: 10

  4. Precipitated silica as flow regulator.

    PubMed

    Müller, Anne-Kathrin; Ruppel, Joanna; Drexel, Claus-Peter; Zimmermann, Ingfried

    2008-08-01

    Flow regulators are added to solid pharmaceutical formulations to improve the flow properties of the powder mixtures. The primary particles of the flow regulators exist in the form of huge agglomerates which are broken down into smaller aggregates during the blending process. These smaller aggregates adsorb at the surface of the solid's grains and thus diminish attractive Van-der-Waals-forces by increasing the roughness of the host's surface. In most cases amorphous silica is used as flow additive but material properties like particle size or bond strength influence the desagglomeration tendency of the agglomerates and thus the flow regulating potency of each silica. For some silica types we will show that the differences in their flow regulating potency are due to the rate and extent by which they are able to cover the surface of the host particles. Binary powder mixtures consisting of a pharmaceutical excipient and an added flow regulator were blended in a Turbula mixer for a defined period of time. As pharmaceutical excipient corn starch was used. The flow regulators were represented by a selection of amorphous silicon dioxide types like a commercial fumed silica and various types of SIPERNAT precipitated silica provided by Evonik-Degussa GmbH, Hanau, Germany. Flowability parameters of the mixtures were characterized by means of a tensile strength tester. The reduction of tensile strength with the blending time can be correlated with an increase in fragmentation of the flow regulator. PMID:18595668

  5. The Toxicity of Precipitated Silica

    PubMed Central

    Byers, P. D.; Gage, J. C.

    1961-01-01

    The proportion of respirable particles in dust clouds generated from three samples of precipitated silica has been shown to range between one-quarter and one-third by weight. After a single intratracheal dose of the silicas to rats, chemical analysis shows a progressive disappearance of silica from the lungs, though it is still detectable after 12 months. Some silica appears in the liver and kidneys but in two of the three samples none remains after 12 months. The nature and duration of the lung lesions produced in rats after a single intratracheal injection are described. A mild degree of fibrosis was observed which showed a steady regression with time and was to some extent influenced by the nature of the silica injected. The lesions showed little resemblance to those arising from quartz and were more akin to those produced by non-fibrogenic dusts. Recommendations are made for the precautions to be taken during the industrial handling of these dusts. Images PMID:13875292

  6. Gold nanoparticles embedded in silica hollow nanospheres induced by compressed CO2 as an efficient catalyst for selective oxidation.

    PubMed

    Guo, Li; Zhang, Ran; Chen, Chen; Chen, Jizhong; Zhao, Xiuge; Chen, Angjun; Liu, Xuerui; Xiu, Yuhe; Hou, Zhenshan

    2015-03-01

    Metal nanoparticles embedded in hollow materials are important due to their wide applications in catalysis. In this work, we disclosed a nontraditional synthetic pathway to prepare silica hollow nanospheres by hydrothermal treatment in the presence of compressed CO2. Especially, the silica hollow nanospheres with an outer diameter of about 16 nm and an inner pore size of 7 nm were obtained using 1.0 MPa CO2. The formation mechanism of silica hollow nanospheres induced by CO2 was investigated by high-pressured UV/Vis spectroscopy. Moreover, gold nanoparticles (2.5 nm) embedded in the silica hollow nanospheres were prepared by a one-pot synthesis using HAuCl4 as a precursor. The current synthetic route of nano-catalysts was simple and facile, in which no etching agent was needed in the process of the hollow material preparation. Besides, this nano-catalyst showed an excellent catalytic performance in epoxidation of styrene with high conversion (82.2%) and selectivity (90.2%) toward styrene oxide, as well as in the selective oxidation of ethylbenzene with good conversion (26.6%) and selectivity (87.8%) toward acetophenone. Moreover, the Au nanoparticles (AuNPs) embedded in silica hollow nanospheres exhibited an excellent recyclability in both the oxidation reactions.

  7. Stabilizing Surfactant Templated Cylindrical Mesopores in Polymer and Carbon Films through Composite Formation with Silica Reinforcement

    SciTech Connect

    Song, Lingyan; Feng, Dan; Lee, Hae-Jeong; Wang, Chengqing; Wu, Quanyan; Zhao, Dongyuan; Vogt, Bryan D.

    2010-10-22

    A facile approach to maintain the periodic mesostructure of cylindrical pores in polymer-resin and carbon films after thermal template removal is explored through the reactive coassembly of resol (carbon precursor) and tetraethylorthosilicate (silica precursor) with triblock copolymer Pluronic F127. Without silica, a low porosity, disordered film is formed after pyrolysis despite the presence of an ordered mesostructure prior to template removal. However for silica concentration greater than 25 wt %, pyrolysis at 350 C yields a mesoporous silica-polymer film with well-defined pore mesostructure. These films remain well ordered upon carbonization at 800 C. In addition to the mesostructural stability, the addition of silica to the matrix impacts other morphological characteristics. For example, the average pore size and porosity of the films increase from 3.2 to 7.5 nm and 12 to 45%, respectively, as the concentration of silica in the wall matrix increases from 0 to 32 wt %. The improved thermal stability of the ordered mesostructure with the addition of silica to the matrix is attributed to the reinforcement of the mechanical properties leading to resistance to stress induced collapse of the mesostructure during template removal.

  8. Ordered mesoporous silica prepared by quiescent interfacial growth method - effects of reaction chemistry

    PubMed Central

    2013-01-01

    Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed. PMID:24237719

  9. Synthesis of superparamagnetic silica-coated magnetite nanoparticles for biomedical applications

    SciTech Connect

    Kaur, Navjot Chudasama, Bhupendra

    2015-05-15

    Multifunctional superparamagnetic iron oxide nanoparticles (SPIONs) coated with silica are widely researched for biomedical applications such as magnetic resonance imaging, tissue repair, cell separation, hyperthermia, drug delivery, etc. In this article synthesis of magnetite (Fe{sub 3}O{sub 4}) nanoparticles and their coating with SiO{sub 2} is reported. Fe{sub 3}O{sub 4} nanoparticles were synthesized by chemical co-precipitation and it was coated with silica by hydrolysis and condensation of tetraethylorthosilicate. XRD, FTIR, TEM and VSM techniques were used to characterize bare and coated nanoparticles. Results indicated that the average size of SPIONS was 8.4 nm. X-ray diffraction patterns of silica coated SPIONS were identical to that of SPIONS confirming the inner spinal structure of SPIONS. FTIR results confirmed the binding of silica with the magnetite and the formation of the silica shell around the magnetite core. Magnetic properties of SPIONS and silica coated SPIONS are determined by VSM. They are superparamagnetic. The major conclusion drawn from this study is that the synthesis route yields stable, non-aggregated magnetite-silica core-shell nanostructures with tailored morphology and excellent magnetic properties.

  10. Synthesis of superparamagnetic silica-coated magnetite nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Kaur, Navjot; Chudasama, Bhupendra

    2015-05-01

    Multifunctional superparamagnetic iron oxide nanoparticles (SPIONs) coated with silica are widely researched for biomedical applications such as magnetic resonance imaging, tissue repair, cell separation, hyperthermia, drug delivery, etc. In this article synthesis of magnetite (Fe3O4) nanoparticles and their coating with SiO2 is reported. Fe3O4 nanoparticles were synthesized by chemical co-precipitation and it was coated with silica by hydrolysis and condensation of tetraethylorthosilicate. XRD, FTIR, TEM and VSM techniques were used to characterize bare and coated nanoparticles. Results indicated that the average size of SPIONS was 8.4 nm. X-ray diffraction patterns of silica coated SPIONS were identical to that of SPIONS confirming the inner spinal structure of SPIONS. FTIR results confirmed the binding of silica with the magnetite and the formation of the silica shell around the magnetite core. Magnetic properties of SPIONS and silica coated SPIONS are determined by VSM. They are superparamagnetic. The major conclusion drawn from this study is that the synthesis route yields stable, non-aggregated magnetite-silica core-shell nanostructures with tailored morphology and excellent magnetic properties.

  11. Enhanced clearance of silica from mouse lung after instillation of a leukocyte chemotactic factor.

    PubMed

    Adamson, I Y; Prieditis, H; Bowden, D H

    1994-01-01

    It has been suggested that increased recruitment of phagocytes and subsequent clearance of particles may follow instillation of a leukocyte chemoattractant to lungs containing silica. The present study quantitated serially the silica content in alveolar spaces, in lung tissue and in hilar lymph nodes of mice that received 2 mg silica only, compared to a group that also received 100 micrograms intratracheal chemotactic factor N-formyl-L-methionyl-leucyl-phenylalanine (FMLP) at 2 and 3 weeks after silica. These mice showed a supplemental increase in alveolar macrophages and neutrophils, and an increase in silica was measured in lavaged cells and fluid soon after FMLP injection. At all times to 16 weeks, the silica content of lung tissue was significantly lower in mice that also received FMLP, and in this group, pulmonary fibrosis was much reduced, as shown morphologically and biochemically. In addition, there was reduced translocation of silica to lymph nodes in FMLP-treated mice. The results indicate that induction of a controlled inflammatory response in the alveoli at a time when particles are present in the pulmonary interstitium can accelerate clearance by increasing phagocyte traffic to the alveoli. The subsequent reduction in particle content of the lung is associated with a lower level of pulmonary fibrosis.

  12. Local liquid phase deposition of silicon dioxide on hexagonally close-packed silica beads.

    PubMed

    Yoon, Seo Young; Park, Yi-Seul; Lee, Jin Seok

    2015-01-13

    Liquid phase deposition (LPD) is a useful method for the production of oxide film with low reaction temperature and production cost. With the report that the LPD of oxide films is conformally processed with uniform thickness and composition, there has been significant attention given to investigating its kinetic controls and growth mechanism on the flat surface. In this work, we explored the LPD of silicon dioxide on the hexagonally close-packed silica beads array as a nanostructured surface. The deposition and etching reactions of SiO2 occurred locally and simultaneously on silica beads, and were distinguished from the amount of fumed silica added in LPD solution. From locally competitive reactions, we obtained the anisotropic morphology of close-packed silica beads, and proposed a mechanism for the local LPD of SiO2 driven by nanostructured surfaces. This work contributes highly to improve metal oxide-based engineering, and also provide greater insight into the topography-driven LPD.

  13. Thermal Insulation Composite Prepared from Carbon Foam and Silica Aerogel Under Ambient Pressure

    NASA Astrophysics Data System (ADS)

    Liu, Heguang; Li, Tiehu; Shi, Yachun; Zhao, Xing

    2015-10-01

    Carbon foam/silica aerogel composite as a promising thermal insulation material was prepared under ambient pressure successfully in the present work. Carbon foam was prepared by pretreatment, foaming, and carbonization process, while silica aerogel was synthesized by sol-gel method. The microstructure, morphology characteristics, compression strength, and thermal properties of composite were characterized by infrared spectroscopy, x-ray diffraction, scanning electron microscope, universal testing machine, and laser flash thermal detector, respectively. Results showed that silica aerogel was successfully synthesized in the surface foam cells of carbon foam due to the closed cell structure of carbon foam. Moreover, the compressive strength of the carbon foam was not affected by the silica aerogel in the cell structure of carbon foam, while its thermal insulation property at room temperature was improved.

  14. Stress development in particulate, nano-composite and polymeric coatings

    NASA Astrophysics Data System (ADS)

    Jindal, Karan

    2009-12-01

    The main goal of this research is to study the stress, structural and mechanical property development during the drying of particulate coatings, nano-composite coatings and VOC compliant refinish clearcoats. The results obtained during this research establish the mechanism for the stress development during drying in various coating systems. Coating stress was measured using a controlled environment stress apparatus based on cantilever deflection principle. The stress evolution in alumina coatings made of 0.4 mum size alumina particles was studied and the effect of a lateral drying was investigated. The stress does not develop until the later stages of drying. A peak stress was observed during drying and the peak stress originates due to the formation of pendular rings between the particles. Silica nanocomposite coatings were fabricated from suspension of nano sized silicon dioxide particles (20 nm) and polyvinyl alcohol (PVA) polymer. The stress in silica nano-composite goes through maximum as the amount of polymer in the coating increases. The highest final stress was found to be ˜ 110MPa at a PVA content of 60 wt%. Observations from SEM, nitrogen gas adsorption, camera imaging, and nano-indentation were also studied to correlate the coatings properties during drying to measured stress. A model VOC compliant two component (2K) acrylic-polyol refinish clearcoat was prepared to study the effects of a new additive on drying, curing, rheology and stress development at room temperature. Most of the drying of the low VOC coatings occurred before appreciable (20%) crosslinking. Tensile stress developed in the same timeframe as drying and then relaxed over a longer time scale. Model low VOC coatings prepared with the additive had higher peak stresses than those without the additive. In addition, rheological data showed that the additive resulted in greater viscosity buildup during drying.

  15. Thermo-mechanical properties of high aspect ratio silica nanofiber filled epoxy composites

    NASA Astrophysics Data System (ADS)

    Ren, Liyun

    The optimization of thermo-mechanical properties of polymer composites at low filler loadings is of great interest in both engineering and scientific fields. There have been several studies on high aspect ratio fillers as novel reinforcement phase for polymeric materials. However, facile synthesis method of high aspect ratio nanofillers is limited. In this study, a scalable synthesis method of high aspect ratio silica nanofibers is going to be presented. I will also demonstrate that the inclusion of high aspect ratio silica nanofibers in epoxy results in a significant improvement of epoxy thermo-mechanical properties at low filler loadings. With silica nanofiber concentration of 2.8% by volume, the Young's modulus, ultimate tensile strength and fracture toughness of epoxy increased ~23, ~28 and ~50%, respectively, compared to unfilled epoxy. At silica nanofiber volume concentration of 8.77%, the thermal expansion coefficient decreased by ˜40% and the thermal conductivity was improved by ˜95% at room temperature. In the current study, the influence of nano-sized silica filler aspect ratio on mechanical and thermal behavior of epoxy nanocomposites were studied by comparing silica nanofibers to spherical silica nanoparticles (with aspect ratio of one) at various filler loadings. The significant reinforcement of composite stiffness is attributed to the variation of the local stress state in epoxy due to the high aspect ratio of the silica nanofiber and the introduction of a tremendous amount of interfacial area between the nanofillers and the epoxy matrix. The fracture mechanisms of silica nanofiber filled epoxy were also investigated. The existence of high aspect ratio silica nanofiber promotes fracture energy dissipation by crack deflection, crack pinning as well as debonding with fiber pull-out leading to enhanced fracture toughness. High aspect ratio fillers also provide significant reduction of photon scattering due to formation of a continuous fiber network

  16. Silica-gold nanoparticles for atheroprotective management of plaques: results of the NANOM-FIM trial

    NASA Astrophysics Data System (ADS)

    Kharlamov, Alexander N.; Tyurnina, Anastasiya E.; Veselova, Vera S.; Kovtun, Olga P.; Shur, Vladimir Y.; Gabinsky, Jan L.

    2015-04-01

    Background: Atheroregression becomes an attractive target for cardiovascular treatment. Some clinical trials have demonstrated that intensive therapy with rosuvastatin or recombinant ApoA-I Milano can partially reduce the total atheroma volume (TAV) up to 6.38 mm3 or 14.1 mm3 respectively. Our previous bench studies of selected nanotechnologies documented TAV reduction up to an unprecedented 79.4 mm3. Methods: The completed observational three arms (n = 180) first-in-man trial (the NANOM FIM trial) assessed (NCT01270139) the safety and feasibility of two delivery techniques for nanoparticles (NP), and plasmonic photothermal therapy (PPTT). Patients were assigned to receive either (1) nano-intervention with delivery of silica-gold NP in a bioengineered on-artery patch (n = 60), or (2) nano-intervention with delivery of silica-gold iron-bearing NP with targeted micro-bubbles and stem cells using a magnetic navigation system (n = 60) versus (3) stent implantation (n = 60). The primary outcome was TAV at 12 months. Results: The mean TAV reduction at 12 months in the Nano group was 60.3 mm3 (SD 39.5; min 41.9 mm3, max 94.2 mm3; p < 0.05) up to mean 37.8% (95% CI: 31.1%, 51.7%; p < 0.05) plaque burden. The analysis of the event free survival of the ongoing clinical follow-up shows the significantly lower risk of cardiovascular death in the Nano group when compared with others (91.7% vs. 81.7% and 80% respectively; p < 0.05) with no cases of the target lesion-related complications. Conclusions: PPTT using silica-gold NP associated with significant regression of coronary atherosclerosis.Background: Atheroregression becomes an attractive target for cardiovascular treatment. Some clinical trials have demonstrated that intensive therapy with rosuvastatin or recombinant ApoA-I Milano can partially reduce the total atheroma volume (TAV) up to 6.38 mm3 or 14.1 mm3 respectively. Our previous bench studies of selected nanotechnologies documented TAV reduction up to an

  17. Polymer-Silica Nanocomposites: A Versatile Platform for Multifunctional Materials

    NASA Astrophysics Data System (ADS)

    Chiu, Chi-Kai

    Solution sol-gel synthesis is a versatile approach to create polymer-silica nanocomposite materials. The solution-to-solid transformation results in a solid consisting of interconnected nanoporous structure in 3D space, making it the ideal material for filtration, encapsulation, optics, electronics, drug release, and biomaterials, etc. Although the pore between nano and meso size may be tunable using different reaction conditions, the intrinsic properties such as limited diffusion within pore structure, complicated interfacial interactions at the pore surfaces, shrinkage and stress-induced cracking and brittleness have limited the applications of this material. To overcome these problems, diffusion, pore size, shrinkage and stress-induced defects need further investigation. Thus, the presented thesis will address these important questions such as whether these limitations can be utilized as the novel method to create new materials and lead to new applications. First, the behaviors of polymers such as poly(ethylene glycol) inside the silica pores are examined by studying the nucleation and growth of AgCl at the surface of the porous matrix. The pore structure and the pressure induced by the shrinkage affect have been found to induce the growth of AgCl nanocrystals. When the same process is carried out at 160 °C, silver metallization is possible. Due to the shrinkage-induced stresses, the polymer tends to move into open crack spaces and exterior surfaces, forming interconnected silver structure. This interconnected silver structure is very unique because its density is not related to the size scale of nanopore structures. These findings suggest that it is possible to utilize defect surface of silica material as the template to create interconnected silver structure. When the scale is small, polymer may no longer be needed if the diffusion length of Ag is more than the size of silica particles. To validate our assumption, monoliths of sol-gel sample containing AgNO3

  18. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  19. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  20. Physisorbed Water on Silica at Mars Temperatures

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Sriwatanapongse, W.; Quinn, R.; Klug, C.; Zent, A.

    2002-01-01

    The usefulness of nuclear magnetic resonance spectroscopy in probing water interactions on silica at Mars temperatures is discussed. Results indicate that two types of water occur with silica at Mars temperatures. Additional information is contained in the original extended abstract.