Ultrastructure features of camel cornea--collagen fibril and proteoglycans.

PubMed

Almubrad, Turki; Akhtar, Saeed

2012-01-01

  The uniform distribution of collagen fibrils and proteoglycans maintain the transparency of normal cornea. We describe the ultrastructural features of camel cornea including collagen fibrils and proteoglycans (PGs).   Camel corneas (of 6-, 8-, and 10-month-old animals) were fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer and processed for electron microscopy. The 'AnalySIS LS Professional' program was used to analyze the collagen fibril diameter.   The camel cornea consists of four layers: the epithelium (227 μm), stroma (388 μm), Descemet's membrane (DM), and endothelium. The epithelium constituted 36% of the camel cornea, whereas corneal stroma constituted 62% of the corneal thickness (629 μm). The PGs in the posterior stroma were significantly larger in number and size compared with the anterior and middle stroma. The collagen fibril diameter was 25 nm and interfibrillar spacing 40 nm. Fibrillar structures are present throughout the DM.   The structure of the camel cornea is very different from human and other animals. The unique structure of the cornea might be an adaptation to help the camel to survive in a hot and dry climate. The camel cornea may also be a good model to study the effect of hot and dry climates on the cornea. © 2011 American College of Veterinary Ophthalmologists.

Scalable synthesis of mesoporous titania microspheres via spray-drying method.

PubMed

Pal, Manas; Wan, Li; Zhu, Yongheng; Liu, Yupu; Liu, Yang; Gao, Wenjun; Li, Yuhui; Zheng, Gengfeng; Elzatahry, Ahmed A; Alghamdi, Abdulaziz; Deng, Yonghui; Zhao, Dongyuan

2016-10-01

Mesoporous TiO2 has several potential applications due to its unique electronic and optical properties, although its structures and morphologies are typically difficult to tune because of its uncontrollable and fast sol-gel reaction. In this study we have coupled the template-directed-sol-gel-chemistry with the low-cost, scalable, and environmentally benign aerosol (spray-drying) one-pot preparation technique for the fabrication of hierarchically mesoporous TiO2 microspheres and Fe3O4@mesoporous TiO2-x microspheres in a large scale. Parameters during the pre-hydrolysis and spray-drying treatment were varied to successfully control the bead diameter, morphology, monodispersity, surface area and pore size for improving their effectiveness for better application. Unlike to the previous aerosol synthetic approaches, where mainly quite a high temperature gradient with the strict control of spray-drying precursor concentration is implied, our strategy is lying on comparatively low drying temperature with an additional post-ultrasonication (further hydrolysis and condensation) route of the pre-calcined TiO2 samples. As-synthesized mesoporous microspheres have a size distribution from 500nm to 5μm, specific surface areas ranging from 150 to 162m(2)g(-1) and mean pore sizes of several nanometers (4-6nm). Further Fe3O4@mesoporous TiO2-x microspheres were observed to show remarkable selective phosphopeptide-enrichment activity which might have significant importance in disease diagnosis and other biomedical applications. Copyright © 2016. Published by Elsevier Inc.

Composite anode for lithium ion batteries

DOEpatents

de Guzman, Rhet C.; Ng, K.Y. Simon; Salley, Steven O.

2018-03-06

A composite anode for a lithium-ion battery is manufactured from silicon nanoparticles having diameters mostly under 10 nm; providing an oxide layer on the silicon nanoparticles; dispersing the silicon nanoparticles in a polar liquid; providing a graphene oxide suspension; mixing the polar liquid containing the dispersed silicone nanoparticles with the graphene oxide suspension to obtain a composite mixture; probe-sonicating the mixture for a predetermined time; filtering the composite mixture to obtain a solid composite; drying the composite; and reducing the composite to obtain graphene and silicon.

The impact of anthropogenic emissions on the otherwise pristine Amazonian rainforest: Insights on aerosol dynamics as observed during GoAmazon2014/5

NASA Astrophysics Data System (ADS)

Carbone, S.; Ferreira De Brito, J.; Cirino, G. G.; Rizzo, L. V.; Holanda, B. A.; Barbosa, H. M.; Ditas, F.; Pöhlker, C.; Chi, X.; Krüger, M. L.; Moran, D.; Saturno, J.; Andreae, M. O.; de Sá, S. S.; Liu, Y.; Martin, S. T.; Souza, R. A. F. D.; Wang, J.; Palm, B. B.; Jimenez, J. L.; Artaxo, P.

2015-12-01

The Amazon Basin during the wet season has one of the lowest aerosol concentrations worldwide, with air masses with negligible human impact covering thousands of kilometers of pristine forest. The natural environment is strongly modified near urbanized areas, in particular Manaus, a city of nearly two million people. This unique location provides the ideal laboratory to study isolated urban emissions as well the pristine environment by perturbing it in a relatively known fashion. The GoAmazon2014/5 experiment was designed with these questions in mind, combining remote sensing, in situ, and airborne measurements. This manuscript describes the measurements taken at the T0 site, upwind of Manaus, (the Amazonian Tall Tower Observatory, ATTO site), at the T2 site, near Manaus, frequently impacted by relatively fresh emissions from the city and at T3, 60 km downwind of Manaus. This work relates the aerosol dynamics of the mixture of anthropogenic emissions from Manaus and the biogenic air masses, and how it evolves from T2 to T3 under different atmospheric conditions. Focus is on the aerosol size distribution, supported by aerosol mass spectrometry and gas-phase composition, in particular at the T2 site. At T0, the aerosol number concentration has been observed to increase from an average of 380 cm-3 to 1750 cm-3 from the wet to the dry season. The mean geometric diameter increased as well, from 95 nm to 145 nm. Interestingly, at the T2 site no significant difference was observed in number concentration between wet and dry seasons (approximately 4300 cm-3) with an average diameter of 60 nm during the former and 97 nm in the latter. Such measurements provide a unique dataset to understand the aerosol life cycle and the impact of urban emissions in the heart of the Amazon Forest.

Production of nanofibrillated cellulose with superior water redispersibility from lime residues via a chemical-free process.

PubMed

Jongaroontaprangsee, Saranya; Chiewchan, Naphaporn; Devahastin, Sakamon

2018-08-01

Water removal during drying of nanofibrillated cellulose (NFC) generally results in the formation of hydrogen bonds between fibers, leading to irreversible fiber agglomeration and hence their poor water redispersibility. The feasibility of using lime residues after juice extraction to produce dried NFC possessing superior redispersibility was here investigated. After autoclaving at 110-130 °C for 2 h, high-shear homogenization at 3800 × g for 15 min and high-pressure homogenization at 40 MPa for 5 passes, NFC having the diameters of 5-28 nm and crystallinity index of 44-46% could be obtained. After hot air drying at 60 °C, dried NFC could be well dispersed in water, with viscoelastic property similar to that of the originally prepared NFC suspension. Pectin associated with cellulose nanofibrils helped prevent fiber aggregation during drying and hence facilitating nanofiber redispersion in water. This observed trend was opposite to that belonging to fiber undergone chemical treatments to remove non-cellulosic constituents. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electro-hydrodynamic generation of monodisperse nanoparticles in the sub-10 nm size range from strongly electrolytic salt solutions: governing parameters of scaling laws

NASA Astrophysics Data System (ADS)

Maißer, Anne; Attoui, Michel B.; Gañán-Calvo, Alfonso M.; Szymanski, Wladyslaw W.

2013-01-01

A charge reduced electro-hydrodynamic atomization (EHDA) device has been used to generate airborne salt clusters in the sub 10 nm size range. The focus of this study on that specific sub-micron range of electrospray droplets with relatively high electrical conductivities and permittivities aims to address the still existing controversy on the scaling laws of electrosprayed droplet diameters. In this study different concentrations of sodium chloride and potassium chloride—both show strong electrolytic behavior—have been electrosprayed from solutions in pure water, or from aqueous ammonium acetate buffer liquids of varying concentrations. The dry residue salt cluster diameter generated by the EHDA process have been measured using a differential mobility analyzer. The initial droplet diameter has been determined indirectly from the measured particle size following the steps of Chen et al. (J Aerosol Sci 26:963-977, 1995). Results have been compared to existing scaling laws valid for direct droplet measurements. They can be interpreted concisely on the basis of a realistic hypothesis on possible electrochemical effects taking place and affecting the droplet and thus nanoparticle formation in EHDA. The hypothesis developed in this work and the comparison with the experimental results are shown and discussed in the manuscript.

Adiabatic burst evaporation from bicontinuous nanoporous membranes

PubMed Central

Ichilmann, Sachar; Rücker, Kerstin; Haase, Markus; Enke, Dirk

2015-01-01

Evaporation of volatile liquids from nanoporous media with bicontinuous morphology and pore diameters of a few 10 nm is an ubiquitous process. For example, such drying processes occur during syntheses of nanoporous materials by sol–gel chemistry or by spinodal decomposition in the presence of solvents as well as during solution impregnation of nanoporous hosts with functional guests. It is commonly assumed that drying is endothermic and driven by non-equilibrium partial pressures of the evaporating species in the gas phase. We show that nearly half of the liquid evaporates in an adiabatic mode involving burst-like liquid-to-gas conversions. During single adiabatic burst evaporation events liquid volumes of up to 107 μm3 are converted to gas. The adiabatic liquid-to-gas conversions occur if air invasion fronts get unstable because of the built-up of high capillary pressures. Adiabatic evaporation bursts propagate avalanche-like through the nanopore systems until the air invasion fronts have reached new stable configurations. Adiabatic cavitation bursts thus compete with Haines jumps involving air invasion front relaxation by local liquid flow without enhanced mass transport out of the nanoporous medium and prevail if the mean pore diameter is in the range of a few 10 nm. The results reported here may help optimize membrane preparation via solvent-based approaches, solution-loading of nanopore systems with guest materials as well as routine use of nanoporous membranes with bicontinuous morphology and may contribute to better understanding of adsorption/desorption processes in nanoporous media. PMID:25926406

Spherical agglomerates of pure drug nanoparticles for improved pulmonary delivery in dry powder inhalers

NASA Astrophysics Data System (ADS)

Hu, Jun; Dong, Yuancai; Pastorin, Giorgia; Ng, Wai Kiong; Tan, Reginald B. H.

2013-04-01

The aim of this study was to produce micron-sized spherical agglomerates of pure drug nanoparticles to achieve improved aerosol performance in dry powder inhalers (DPIs). Sodium cromoglicate was chosen as the model drug. Pure drug nanoparticles were prepared through a bottom-up particle formation process, liquid antisolvent precipitation, and then rapidly agglomerated into porous spherical microparticles by immediate (on-line) spray drying. Nonporous spherical drug microparticles with similar geometric size distribution were prepared by conventional spray drying of the aqueous drug solution, which together with the mechanically micronized drug particles were used as the control samples. The three samples were characterized by field emission scanning electron microscopy, laser diffraction, Brunauer-Emmett-Teller analysis, density measurement, powder X-ray diffraction, and in vitro aerosol deposition measurement with a multistage liquid impinger. It was found that drug nanoparticles with a diameter of 100 nm were precipitated and agglomerated into highly porous spherical microparticles with a volume median diameter ( D 50 %) of 2.25 ± 0.08 μm and a specific surface area of 158.63 ± 3.27 m2/g. In vitro aerosol deposition studies showed the fine particle fraction of such spherical agglomerates of drug nanoparticles was increased by more than 50 % in comparison with the control samples, demonstrating significant improvements in aerosol performance. The results of this study indicated the potential of the combined particle engineering process of liquid antisolvent precipitation followed by immediate (on-line) spray drying in the development of novel DPI drug products with improved aerosol performance.

Design, physicochemical characterization, and optimization of organic solution advanced spray-dried inhalable dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine poly(ethylene glycol) (DPPE-PEG) microparticles and nanoparticles for targeted respiratory nanomedicine delivery as dry powder inhalation aerosols

PubMed Central

Meenach, Samantha A; Vogt, Frederick G; Anderson, Kimberly W; Hilt, J Zach; McGarry, Ronald C; Mansour, Heidi M

2013-01-01

Novel advanced spray-dried and co-spray-dried inhalable lung surfactant-mimic phospholipid and poly(ethylene glycol) (PEG)ylated lipopolymers as microparticulate/nanoparticulate dry powders of biodegradable biocompatible lipopolymers were rationally formulated via an organic solution advanced spray-drying process in closed mode using various phospholipid formulations and rationally chosen spray-drying pump rates. Ratios of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine PEG (DPPE-PEG) with varying PEG lengths were mixed in a dilute methanol solution. Scanning electron microscopy images showed the smooth, spherical particle morphology of the inhalable particles. The size of the particles was statistically analyzed using the scanning electron micrographs and SigmaScan® software and were determined to be 600 nm to 1.2 μm in diameter, which is optimal for deep-lung alveolar penetration. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) were performed to analyze solid-state transitions and long-range molecular order, respectively, and allowed for the confirmation of the presence of phospholipid bilayers in the solid state of the particles. The residual water content of the particles was very low, as quantified analytically via Karl Fischer titration. The composition of the particles was confirmed using attenuated total-reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and confocal Raman microscopy (CRM), and chemical imaging confirmed the chemical homogeneity of the particles. The dry powder aerosol dispersion properties were evaluated using the Next Generation Impactor™ (NGI™) coupled with the HandiHaler® dry powder inhaler device, where the mass median aerodynamic diameter from 2.6 to 4.3 μm with excellent aerosol dispersion performance, as exemplified by high values of emitted dose, fine particle fraction, and respirable fraction. Overall, it was determined that the pump rates defined in the spray-drying process had a significant effect on the solid-state particle properties and that a higher pump rate produced the most optimal system. Advanced dry powder inhalers of inhalable lipopolymers for targeted dry powder inhalation delivery were successfully achieved. PMID:23355776

Feasibility of haloperidol-anchored albumin nanoparticles loaded with doxorubicin as dry powder inhaler for pulmonary delivery.

PubMed

Varshosaz, Jaleh; Hassanzadeh, Farshid; Mardani, Amin; Rostami, Mahboubeh

2015-03-01

Haloperidol (Hal) is a ligand that can target sigma 2 receptors over-expressed in non-small cell lung cancer. Hal targeted nanoparticles of bovine serum albumin (BSA) were prepared for pulmonary delivery of doxorubicin (DOX). The conjugation was confirmed by Fourier transform infrared spectroscopy (FTIR) and (1)H nuclear magnetic resonance ((1)H NMR) spectroscopic methods. Nanoparticles were prepared by desolvation method from BSA-Hal and were loaded with DOX. They were characterized for their morphology, particle size, zeta potential, drug loading and release efficiency. The optimized nanoparticles were spray-dried using trehalose, l-leucin and mannitol as dry powder inhaler (DPI) in different inlet temperatures between 80 and 120°C. The obtained nanocomposites were characterized for their aerodynamic diameter, specific surface area (cm(2)/g) and fine particle fraction (FPF) by a Cascade Impactor device. The optimized nanoparticles showed particle size of 218 nm, zeta potential of -25.4 mV, drug entrapment efficiency of 89% and release efficiency of 56% until 2 h. After spray drying of these nanoparticles, the best results were obtained from mannitol with an inlet temperature of 80°C which produced a mean aerodynamic diameter of 4.58 μm, FPF of 66% and specific surface area of 6302.99 cm(2)/g. The obtained results suggest that the designed DPI could be a suitable inhaler for targeted delivery of DOX in pulmonary delivery.

Fabrication of self-aligned, nanoscale, complex oxide varactors

NASA Astrophysics Data System (ADS)

Fu, Richard X.; Toonen, Ryan C.; Hirsch, Samuel G.; Ivill, Mathew P.; Cole, Melanie W.; Strawhecker, Kenneth E.

2015-01-01

Applications in ferroelectric random access memory and superparaelectric devices require the fabrication of ferroelectric capacitors at the nanoscale that exhibit extremely small leakage currents. To systematically study the material-size dependence of ferroelectric varactor performance, arrays of parallel-plate structures have been fabricated with nanoscale dielectric diameters. Electron beam lithography and inductively coupled plasma dry etching have been used to fabricate arrays of ferroelectric varactors using top electrodes as a self-aligned etch mask. Parallel-plate test structures using RF-sputtered Ba0.6Sr0.4TiO3 thin-films were used to optimize the fabrication process. Varactors with diameters down to 20 nm were successfully fabricated. Current-voltage (I-V) characteristics were measured to evaluate the significance of etch-damage and fabrication quality by ensuring low leakage currents through the structures.

Purification of 1.9-nm-diameter semiconducting single-wall carbon nanotubes by temperature-controlled gel-column chromatography and its application to thin-film transistor devices

NASA Astrophysics Data System (ADS)

Thendie, Boanerges; Omachi, Haruka; Hirotani, Jun; Ohno, Yutaka; Miyata, Yasumitsu; Shinohara, Hisanori

2017-06-01

Large-diameter semiconductor single-wall carbon nanotubes (s-SWCNTs) have superior mobility and conductivity to small-diameter s-SWCNTs. However, the purification of s-SWCNTs with diameters larger than 1.6 nm by gel filtration has been difficult owing to the low selectivity of the conventional purification method in these large-diameter regions. We report a combination of temperature-controlled gel filtration and the gradient elution technique that we developed to enrich a high-purity s-SWCNT with a diameter as large as 1.9 nm. The thin-film transistor (TFT) device using the 1.9-nm-diameter SWCNT shows an average channel mobility of 23.7 cm2 V-1 s-1, which is much higher than those of conventional SWCNT-TFTs with smaller-diameters of 1.5 and 1.4 nm.

Design, characterization, and aerosol dispersion performance modeling of advanced spray-dried microparticulate/nanoparticulate mannitol powders for targeted pulmonary delivery as dry powder inhalers.

PubMed

Li, Xiaojian; Vogt, Frederick G; Hayes, Don; Mansour, Heidi M

2014-04-01

The purpose was to design and characterize inhalable microparticulate/nanoparticulate dry powders of mannitol with essential particle properties for targeted dry powder delivery for cystic fibrosis mucolytic treatment by dilute organic solution spray drying, and, in addition, to tailor and correlate aerosol dispersion performance delivered as dry powder inhalers based on spray-drying conditions and solid-state physicochemical properties. Organic solution advanced spray drying from dilute solution followed by comprehensive solid-state physicochemical characterization and in vitro dry powder aerosolization were used. The particle size distribution of the spray-dried (SD) powders was narrow, unimodal, and in the range of ∼500 nm to 2.0 μm. The particles possessed spherical particle morphology, relatively smooth surface morphology, low water content and vapor sorption (crystallization occurred at exposure above 65% relative humidity), and retention of crystallinity by polymorphic interconversion. The emitted dose, fine particle fraction (FPF), and respirable fraction (RF) were all relatively high. The mass median aerodynamic diameters were below 4 μm for all SD mannitol aerosols. The in vitro aerosol deposition stage patterns could be tailored based on spray-drying pump rate. Positive linear correlation was observed between both FPF and RF values with spray-drying pump rates. The interplay between various spray-drying conditions, particle physicochemical properties, and aerosol dispersion performance was observed and examined, which enabled tailoring and modeling of high aerosol deposition patterns.

Design, Characterization, and Aerosol Dispersion Performance Modeling of Advanced Spray-Dried Microparticulate/Nanoparticulate Mannitol Powders for Targeted Pulmonary Delivery as Dry Powder Inhalers

PubMed Central

Li, Xiaojian; Vogt, Frederick G.; Hayes, Don

2014-01-01

Abstract Background: The purpose was to design and characterize inhalable microparticulate/nanoparticulate dry powders of mannitol with essential particle properties for targeted dry powder delivery for cystic fibrosis mucolytic treatment by dilute organic solution spray drying, and, in addition, to tailor and correlate aerosol dispersion performance delivered as dry powder inhalers based on spray-drying conditions and solid-state physicochemical properties. Methods: Organic solution advanced spray drying from dilute solution followed by comprehensive solid-state physicochemical characterization and in vitro dry powder aerosolization were used. Results: The particle size distribution of the spray-dried (SD) powders was narrow, unimodal, and in the range of ∼500 nm to 2.0 μm. The particles possessed spherical particle morphology, relatively smooth surface morphology, low water content and vapor sorption (crystallization occurred at exposure above 65% relative humidity), and retention of crystallinity by polymorphic interconversion. The emitted dose, fine particle fraction (FPF), and respirable fraction (RF) were all relatively high. The mass median aerodynamic diameters were below 4 μm for all SD mannitol aerosols. Conclusion: The in vitro aerosol deposition stage patterns could be tailored based on spray-drying pump rate. Positive linear correlation was observed between both FPF and RF values with spray-drying pump rates. The interplay between various spray-drying conditions, particle physicochemical properties, and aerosol dispersion performance was observed and examined, which enabled tailoring and modeling of high aerosol deposition patterns. PMID:24502451

3-D loaded scaffolds obtained by supercritical CO2 assisted process

NASA Astrophysics Data System (ADS)

Cardea, S.; Reverchon, E.

2014-08-01

In this work, a supercritical CO2 (SC-CO2) drying process for the formation of 3-D PVDF-HFP loaded scaffolds was tested. Experiments at pressures ranging between 150 and 250 bar and at temperatures ranging between 35 and 55°C were performed. The PVDF-HFP- acetone-ethanol solution at 15% w/w polymer was selected as the base case. The drug (amoxicillin) concentration was varied from 20 to 30% w/w with respect to PVDF-HFP. SC- CO2 drying process was confirmed to be a valid alternative to generate loaded structures; indeed, scaffolds characterized by nanometric networks (with mean pore diameter of about 300 nm) with a homogeneous drug distribution were obtained. Drug controlled release experiments were also performed and a quasi-zero order release kinetic was observed.

Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

DOEpatents

Martino, Anthony; Yamanaka, Stacey A.; Kawola, Jeffrey S.; Showalter, Steven K.; Loy, Douglas A.

1998-01-01

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

PubMed

Cho, Seungho; Jang, Ji-Wook; Lee, Jae Sung; Lee, Kun-Hong

2010-10-01

We report a simple wet-chemical synthesis of ∼5 nm diameter ZnO nanorod arrays at room temperature (20 °C) and normal atmospheric pressure (1 atm) and their optical properties. They were single crystalline in nature, and grew in the [001] direction. These small diameter ZnO nanorod arrays can also be synthesized at 0 °C. Control experiments were also conducted. On the basis of the results, we propose a mechanism for the spontaneous growth of the small diameter ZnO structures. The optical properties of the 5 nm diameter ZnO nanorod arrays synthesized using this method were probed by UV-Visible diffuse reflectance spectroscopy. A clear blue-shift, relative to the absorption band from 50 nm diameter ZnO nanorod arrays, was attributed to the quantum confinement effects caused by the small nanocrystal size in the 5 nm diameter ZnO nanorods.

Development of dried serum spot sampling techniques for the assessment of trace elements in serum samples by LA-ICP-MS.

PubMed

Chantada-Vázquez, María Pilar; Moreda-Piñeiro, Jorge; Cantarero-Roldán, Alicia; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio

2018-08-15

A novel approach for serum analysis by dried matrix spot (DMS) technique is proposed. The methodology consists of sampling filter paper discs (2.7 mm in diameter) containing the large amount of serum retained after a single spotting. Several oxidizers (sodium chlorate, sodium azide, acetic acid, formic acid, 1-butyl-3-methylimidazoliumm chloride/bromide) were tested (oxidizers premixed with the sample before spotting, and papers previously soaked in concentrated additive/oxidizer solutions). Direct multi-element determination (Al, Be, Ca, Cu, Fe, K, Li, Mg, Mn, Mo, Na, P, Rb, Se, V, and Zn) in dried serum spots at very low levels was therefore assessed by laser ablation (LA) coupled with inductively coupled plasma - mass spectrometry (ICP-MS). Laser ablation was performed using a focused Nd: YAG laser beam in lineal scan mode (wavelength 213 nm, laser fluency 2.2 J cm -2 , repetition rate 20 Hz, laser spot diameter 90 µm, depth 0 µm, scanning speed 12 µm s -1 ). Matrix-matched calibration mode and 13 C as internal standard (for signal intensities normalization) was used throughout the work. Limits of quantification were found to be from 21 µg L -1 to 221 mg L -1 . Repeatability (seven ablations of the same dried serum spot) and reproducibility (two ablations of seven dried serum spot from the same material) offered RSDs below 12% for all analytes, which seems satisfactory for clinical purposes. The method was validated by analyzing several certified reference materials (Seronorm™ level I and II trace elements in serum), and it was applied to several DMS from serum samples from healthy adults. Copyright © 2018 Elsevier B.V. All rights reserved.

Aerosol Fluxes over Amazon Rain Forest Measured with the Eddy Covariance Method

NASA Astrophysics Data System (ADS)

Ahlm, L.; Nilsson, E. D.; Krejci, R.; Mårtensson, E. M.; Vogt, M.; Artaxo, P.

2008-12-01

We present measurements of vertical aerosol fluxes over the Amazon carried out on top of K34, a 50 meter high tower in the Cuieiras Reserve about 50 km north of Manaus in northern Brazil. The turbulent fluxes were measured with the eddy covariance method. The covariance of vertical wind speed from a sonic anemometer Gill Windmaster and total aerosol number concentration from a condensation particle counter (CPC) TSI 3010 provided the total number flux (diameter >0.01 μm). The covariance of vertical wind speed and size resolved number concentrations from an optical particle counter (OPC) Grimm 1.109 provided size resolved number fluxes in 15 bins from 0.25 μm to 2.5 μm diameter. Additionally fluxes of CO2 and H2O were derived from Li-7500 observations. The observational period, from early March to early August, includes both wet and dry season. OPC fluxes generally show net aerosol deposition both during wet and dry season with the largest downward fluxes during midday. CPC fluxes show different patterns in wet and dry season. During dry season, when number concentrations are higher, downward fluxes clearly dominate. In the wet season however, when number concentrations are lower, our data indicates that upward and downward fluxes are quite evenly distributed during course of a day. On average there is a peak in upward flux during late morning and another peak during the afternoon. Since the OPC fluxes in the same time show net deposition, there is an indication of net source of primary aerosol particles with diameters between 10 and 250 nm emitted from the rain forest. Future data analysis will hopefully shed light on origin and formation mechanism of these particles and thus provide a deeper insight in the rain forest - atmosphere interactions. The aerosol flux measurements were carried out as a part of the AMAZE project in collaboration with University of Sao Paulo, Brazil, and financial support was provided by Swedish International Development Cooperation Agency (SIDA).

Chitosan-Based Nano-Embedded Microparticles: Impact of Nanogel Composition on Physicochemical Properties

PubMed Central

Islam, Paromita; Water, Jorrit J.; Bohr, Adam; Rantanen, Jukka

2016-01-01

Chitosan-based nanogels have been widely applied as drug delivery vehicles. Spray-drying of said nanogels allows for the preparation of dry powder nano-embedded microparticles. In this work, chitosan-based nanogels composed of chitosan, alginate, and/or sodium tri-penta phosphate were investigated, particularly with respect to the impact of composition on the resulting physicochemical properties. Different compositions were obtained as nanogels with sizes ranging from 203 to 561 nm. The addition of alginate and exclusion of sodium tri-penta phosphate led to an increase in nanogel size. The nanogels were subsequently spray-dried to form nano-embedded microparticles with trehalose or mannitol as matrix excipient. The microparticles of different composition were mostly spherical with a smooth surface and a mass median aerodynamic diameter of 6–10 µm. Superior redispersibility was observed for microparticles containing amorphous trehalose. This study demonstrates the potential of nano-embedded microparticles for stabilization and delivery of nanogel-based delivery systems. PMID:28025505

Chitosan-Based Nano-Embedded Microparticles: Impact of Nanogel Composition on Physicochemical Properties.

PubMed

Islam, Paromita; Water, Jorrit J; Bohr, Adam; Rantanen, Jukka

2016-12-22

Chitosan-based nanogels have been widely applied as drug delivery vehicles. Spray-drying of said nanogels allows for the preparation of dry powder nano-embedded microparticles. In this work, chitosan-based nanogels composed of chitosan, alginate, and/or sodium tri-penta phosphate were investigated, particularly with respect to the impact of composition on the resulting physicochemical properties. Different compositions were obtained as nanogels with sizes ranging from 203 to 561 nm. The addition of alginate and exclusion of sodium tri-penta phosphate led to an increase in nanogel size. The nanogels were subsequently spray-dried to form nano-embedded microparticles with trehalose or mannitol as matrix excipient. The microparticles of different composition were mostly spherical with a smooth surface and a mass median aerodynamic diameter of 6-10 µm. Superior redispersibility was observed for microparticles containing amorphous trehalose. This study demonstrates the potential of nano-embedded microparticles for stabilization and delivery of nanogel-based delivery systems.

Effect of pretreatment on rehydration, colour and nanoindentation properties of potato cylinders dried using a mixed-mode solar dryer.

PubMed

Dhalsamant, Kshanaprava; Tripathy, Punyadarshini P; Shrivastava, Shanker L

2017-08-01

Desirable quality estimation is an important consumer driver for wider acceptability of mixed-mode solar drying of potatoes in food industries. The aim of this study is to characterise rehydration, colour, texture, nanoindentaion and microstructure of dried potato samples and to establish the influence of pre-drying treatment on the above qualities. The water absorption capacity and rehydration ability of solar dried potato were significantly influenced by pretreatment followed by rehydration temperature and sample diameter. The redness index (a*) of pretreated dried samples was lower with simultaneous higher value of yellowness index (b*), chroma (C*) and hue angle (h*). Also, the average nanohardness (H) of pretreated samples increased significantly by 22.64% compared to that of untreated samples. The average reduced modulus (E r ) and Young's modulus (E s ) of dried potato samples were 1.865 GPa and 1.403 GPa, respectively. Moreover, creep displacement of 43.27 nm was traced in the untreated potato samples during a 20 s dwell time under a constant load of 200 µN in the nanoindentation test. Micrographs revealed more uniform pore spaces in pretreated samples. Pretreated, thinner potato samples achieved better quality dried products in terms of rehydration, colour, texture and nanohardness indices with significantly improved microstructure and creep resistance properties. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Pulmonary delivery of antitubercular drugs using spray-dried lipid-polymer hybrid nanoparticles.

PubMed

Bhardwaj, Ankur; Mehta, Shuchi; Yadav, Shailendra; Singh, Sudheer K; Grobler, Anne; Goyal, Amit Kumar; Mehta, Abhinav

2016-09-01

The present study aimed to develop lipid-polymer hybrid nanoparticles (LPNs) for the combined pulmonary delivery of isoniazid (INH) and ciprofloxacin hydrochloride (CIP HCl). Drug-loaded LPNs were prepared by the double-emulsification solvent evaporation method using the three-factor three-level Box-Behnken design. The optimized formulation had a size of 111.81 ± 1.2 nm, PDI of 0.189 ± 1.4, and PDE of 63.64 ± 2.12% for INH-loaded LPN, and a size of 172.23 ± 2.31 nm, PDI of 0.169 ± 1.23, and PDE of 68.49 ± 2.54% for CIP HCl-loaded LPN. Drug release was found to be sustained and controlled at lower pH and followed the Peppas model. The in vitro uptake study in alveolar macrophage (AM) showed that uptake of the drugs was increased significantly if administered in the form of LPN. The stability study proved the applications of adding PLGA in LPN as the polymeric core, which leads to a much more stable product as compared to other novel drug delivery systems. Spray drying was done to produce an inhalable, dry, powdered form of drug-loaded LPN. The spray-dried (SD) powder was equally capable of producing nano-aggregates having morphology, density, flowability and reconstitutibility in the range ideal for inhaled drug delivery. The nano aggregates produced by spray drying manifested their aerosolization efficiency in terms of the higher emitted dose and fine particle fraction with lower mass median aerodynamic diameter. The in vivo study using pharmacokinetic and pharmacodynamic approaches revealed that maximum internalization efficiency was achieved by delivering LPN in SD powdered forms by pulmonary route.

Nanoscale Capillary Flows in Alumina: Testing the Limits of Classical Theory.

PubMed

Lei, Wenwen; McKenzie, David R

2016-07-21

Anodic aluminum oxide (AAO) membranes have well-formed cylindrical channels, as small as 10 nm in diameter, in a close packed hexagonal array. The channels in AAO membranes simulate very small leaks that may be present for example in an aluminum oxide device encapsulation. The 10 nm alumina channel is the smallest that has been studied to date for its moisture flow properties and provides a stringent test of classical capillary theory. We measure the rate at which moisture penetrates channels with diameters in the range of 10 to 120 nm with moist air present at 1 atm on one side and dry air at the same total pressure on the other. We extend classical theory for water leak rates at high humidities by allowing for variable meniscus curvature at the entrance and show that the extended theory explains why the flow increases greatly when capillary filling occurs and enables the contact angle to be determined. At low humidities our measurements for air-filled channels agree well with theory for the interdiffusive flow of water vapor in air. The flow rate of water-filled channels is one order of magnitude less than expected from classical capillary filling theory and is coincidentally equal to the helium flow rate, validating the use of helium leak testing for evaluating moisture flows in aluminum oxide leaks.

Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

DOEpatents

Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

1998-09-29

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

Green synthesis of silver nanoparticles from Moringa oleifera leaf extracts and its antimicrobial potential

NASA Astrophysics Data System (ADS)

Moodley, Jerushka S.; Babu Naidu Krishna, Suresh; Pillay, Karen; Sershen; Govender, Patrick

2018-03-01

In this study we report on the synthesis of silver nanoparticles (AgNPs) from the leaf extracts of Moringa oleifera using sunlight irradiation as primary source of energy, and its antimicrobial potential. Silver nanoparticle formation was confirmed by surface plasmon resonance at 450 nm and 440 nm, respectively for both fresh and freeze-dried leaf samples. Crystanality of AgNPs was confirmed by transmission electron microscopy, scanning electron microscopy with energy dispersive x-ray spectroscopy and Fourier transform infrared (FTIR) spectroscopy analysis. FTIR spectroscopic analysis suggested that flavones, terpenoids and polysaccharides predominate and are primarily responsible for the reduction and subsequent capping of AgNPs. X-ray diffraction analysis also demonstrated that the size range of AgNPs from both samples exhibited average diameters of 9 and 11 nm, respectively. Silver nanoparticles showed antimicrobial activity on both bacterial and fungal strains. The biosynthesised nanoparticle preparations from M. oleifera leaf extracts exhibit potential for application as broad-spectrum antimicrobial agents.

Nanoparticle Over Mirror plasmonic structures prepared with use of Au colloid produced by laser ablation in water

NASA Astrophysics Data System (ADS)

Sawczak, Mirosław; Zyskowski, Marcin; Karczewski, Jakub; Atanasov, Petar A.; Nedyalkov, Nikolay N.; Nikov, Rumen G.; Stankova, Nadya A.; Śliwiński, Gerard

2016-01-01

Recently, an intensive research is carried out on plasmonic structures due to their potential application in many areas such as sensing, light harvesting and energy conversion and storage. In particular, a growing interest is observed in the Nanoparticle Over Mirror (NOM) structures for which the lithography and surface chemical functionalization represent the most popular production routes1. However, the application of those techniques is limited by the low efficacy, process complexity and chemical contamination of nanoparticles (NP). In this work, we report the contamination-free and low cost fabrication method of NOMs based on wet coating and ultrasonic-assisted nanocolloid drying process. The glass plates covered with magnetron sputtered 100 nm thick Au film and subsequently with Al2O3 layers (6 - 36 nm) by means of pulsed laser deposition are used as substrates. Au NPs are produced in the form of colloidal suspension by means of laser ablation in water using the 1064 nm, 6 ns Nd:YAG laser. The NOM synthesis is finalized by imposing of the Au NP suspension onto the as prepared Au-Al2O3/glass substrates and dried. To avoid NP agglomeration, the wet coated substrates are sonicated using 20W, 20 kHz ultrasound generator. SEM inspection of the obtained NOM structures confirms the positive sonication effect, i.e. the presence of agglomerate-free, homogenous layers. These consist of NPs (36 nm average diameter) which are characterized by the resonance absorption band at 528 nm. For NOM structures the UV-vis spectra reveal increased infrared activity and peak shift in agreement with theoretical modeling2. The NOM structure characterization is completed by analysis of the SEM and profilometry measurement results.

Estimating air-drying times of small-diameter ponderosa pine and Douglas-fir logs

Treesearch

William T. Simpson; Xiping Wang

2004-01-01

One potential use for small-diameter ponderosa pine and Douglas-fir timber is in log form. Many potential uses of logs require some degree of drying. Even though these small diameters may be considered small in the forestry context, their size when compared to typical lumber thickness dimensions is large. These logs, however, may require uneconomically long kiln-drying...

A new scanning electron microscopy approach to image aerogels at the nanoscale

NASA Astrophysics Data System (ADS)

Solá, F.; Hurwitz, F.; Yang, J.

2011-04-01

A new scanning electron microscopy (SEM) technique to image poor electrically conductive aerogels is presented. The process can be performed by non-expert SEM users. We showed that negative charging effects on aerogels can be minimized significantly by inserting dry nitrogen gas close to the region of interest. The process involves the local recombination of accumulated negative charges with positive ions generated from ionization processes. This new technique made possible the acquisition of images of aerogels with pores down to approximately 3 nm in diameter using a positively biased Everhart-Thornley (ET) detector.

Effects of air temperature and velocity on the drying kinetics and product particle size of starch from arrowroot (Maranta arundinacae)

NASA Astrophysics Data System (ADS)

Caparanga, Alvin R.; Reyes, Rachael Anne L.; Rivas, Reiner L.; De Vera, Flordeliza C.; Retnasamy, Vithyacharan; Aris, Hasnizah

2017-11-01

This study utilized the 3k factorial design with k as the two varying factors namely, temperature and air velocity. The effects of temperature and air velocity on the drying rate curves and on the average particle diameter of the arrowroot starch were investigated. Extracted arrowroot starch samples were dried based on the designed parameters until constant weight was obtained. The resulting initial moisture content of the arrowroot starch was 49.4%. Higher temperatures correspond to higher drying rates and faster drying time while air velocity effects were approximately negligible or had little effect. Drying rate is a function of temperature and time. The constant rate period was not observed for the drying rate of arrowroot starch. The drying curves were fitted against five mathematical models: Lewis, Page, Henderson and Pabis, Logarithmic and Midili. The Midili Model was the best fit for the experimental data since it yielded the highest R2 and the lowest RSME values for all runs. Scanning electron microscopy (SEM) was used for qualitative analysis and for determination of average particle diameter of the starch granules. The starch granules average particle diameter had a range of 12.06 - 24.60 μm. The use of ANOVA proved that particle diameters for each run varied significantly with each other. And, the Taguchi Design proved that high temperatures yield lower average particle diameter, while high air velocities yield higher average particle diameter.

The Physics of Ultrabroadband Frequency Comb Generation and Optimized Combs for Measurements in Fundamental Physics

DTIC Science & Technology

2016-07-02

beams Superresolution machining Threshold effect of ablation means that structure diameter is less than the beam diameter fs pulses at 800 nm yield 200...Approved for public release: distribution unlimited. Applications of Bessel beams Superresolution machining Threshold effect of ablation means that... Superresolution machining Threshold effect of ablation means that structure diameter is less than the beam diameter fs pulses at 800 nm yield 200 nm

Encapsulated boron as an osteoinductive agent for bone scaffolds.

PubMed

Gümüşderelioğlu, Menemşe; Tunçay, Ekin Ö; Kaynak, Gökçe; Demirtaş, Tolga T; Aydın, Seda Tığlı; Hakkı, Sema S

2015-01-01

The aim of this study was to develop boron (B)-releasing polymeric scaffold to promote regeneration of bone tissue. Boric acid-doped chitosan nanoparticles with a diameter of approx. 175 nm were produced by tripolyphosphate (TPP)-initiated ionic gelation process. The nanoparticles strongly attached via electrostatic interactions into chitosan scaffolds produced by freeze-drying with approx. 100 μm pore diameter. According to the ICP-OES results, following first 5h initial burst release, fast release of B from scaffolds was observed for 24h incubation period in conditioned medium. Then, slow release of B was performed over 120 h. The results of the cell culture studies proved that the encapsulated boron within the scaffolds can be used as an osteoinductive agent by showing its positive effects on the proliferation and differentiation of MC3T3-E1 preosteoblastic cells. Copyright © 2015 Elsevier GmbH. All rights reserved.

[Seedling index of Salvia miltiorrhiza and its simulation model].

PubMed

Huang, Shu-Hua; Xu, Fu-Li; Wang, Wei-Ling; Du, Jun-Bo; Ru, Mei; Wang, Jing; Cao, Xian-Yan

2012-10-01

Through the correlation analysis on the quantitative traits and their ratios of Salvia miltiorrhiza seedlings and seedling quality, a series of representative indices reflecting the seedling quality of the plant species were determined, and the seedling index suitable to the S. miltiorrhiza seedlings was ascertained by correlation degree analysis. Meanwhile, based on the relationships between the seedling index and the air temperature, solar radiation and air humidity, a simulation model for the seedling index of S. miltiorrhiza was established. The experimental data of different test plots and planting dates were used to validate the model. The results showed that the root diameter, stem diameter, crown dry mass, root dry mass, and plant dry mass had significant positive relationships with the other traits, and could be used as the indicators of the seedling's health. The seedling index of S. miltiorrhiza could be calculated by (stem diameter/root diameter + root dry mass/crown dry mass) x plant dry mass. The stem diameter, root dry mass, crown dry mass and plant dry mass had higher correlations with the seedling index, and thus, the seedling index determined by these indicators could better reflect the seedling's quality. The coefficient of determination (R2) between the predicted and measured values based on 1:1 line was 0.95, and the root mean squared error (RMSE) was 0.15, indicating that the model established in this study could precisely reflect the quantitative relationships between the seedling index of S. miltiorrhiza and the environmental factors.

Dependence of light transmission through human skin on incident beam diameter at different wavelengths

NASA Astrophysics Data System (ADS)

Zhao, ZhongQuan; Fairchild, Paul W.

1998-05-01

For many skin treatments with light, it is important to have deep photon penetration into the skin. Because of absorption and scattering of photons by skin tissue, both the color and the diameter of the incident beam affect the penetration depth of photons. In this study, the dependence of light transmission through human skin tissues (ear lobs and between the fingers) has been measured in-vivo at six wavelengths (532 nm, 632 nm, 675 nm, 810 nm, 911 nm, and 1064 nm). The same measurement was also made on pig skin in-vitro for comparison. It was observed that (1) the photons at 1064 nm penetrate deeper than the other colors studied for a given incident beam diameter; and (2) the transmittance at a particular wavelength increases asymptotically with incident beam diameter. For some skin tissues, the transmittance flattens at about 8 mm for 532 nm photons and approaches saturation at about 12 mm for all other colors. The results on pig skin is similar.

Extraction of cellulose nanofibrils from dry softwood pulp using high shear homogenization.

PubMed

Zhao, Jiangqi; Zhang, Wei; Zhang, Xiaodan; Zhang, Xinxing; Lu, Canhui; Deng, Yulin

2013-09-12

The objective of this study was to extract cellulose nanofibrils (CNFs) from dry softwood pulp through a simple and environmentally friendly physical method of refining pretreatment coupled with high shear homogenization. An optical microscopy (OM) clearly showed the morphological development from the cellulose fibers to CNFs under repeated shear forces. The morphology, structure and properties of the obtained CNFs were comprehensively investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) spectra, X-ray diffraction (XRD) and thermogravimetric (TG) analysis. The results indicated that the CNFs had diameters mainly ranged from 16 to 28nm. Compared with the pulp fibers, the CNFs exhibited a slightly higher crystallinity and a lower thermal stability. Moreover, a novel nanopaper with high optical transparency was prepared from the obtained CNFs, and a possible mechanism for the high optical transparency was discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Nanofibrillated cellulose (CNF) from eucalyptus sawdust as a dry strength agent of unrefined eucalyptus handsheets.

PubMed

Vallejos, María Evangelina; Felissia, Fernando Esteban; Area, María Cristina; Ehman, Nanci Vanesa; Tarrés, Quim; Mutjé, Pere

2016-03-30

Nanofibrillated cellulose has been obtained from the cellulosic fraction of eucalyptus sawdust. The fractionation process involved the partial removal of hemicelluloses and lignin. CNF was obtained using TEMPO oxidation with NaOCl in basic medium followed by mechanical homogenization. The obtained CNF was subsequently used as a dry strength agent on unbleached unrefined eucalyptus pulp. The addition of 3, 6 and 9 wt.% of CNF increased lineally the tensile index of handsheets to about 55 N mg(-1) at 35°SR, compatible with papermachine runnability. The other mechanical properties also increased substantially, and porosity decreased moderately. The estimated specific surface and average diameter of these CNF were 60 m(2)g(-1), and of 41.0 nm, respectively. The addition of 9 wt.% of CNF produced an increase in mechanical strength, equivalent to that produced by PFI refining at 1600 revolutions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Presence of electrostatically adsorbed polysaccharides improves spray drying of liposomes.

PubMed

Karadag, Ayse; Özçelik, Beraat; Sramek, Martin; Gibis, Monika; Kohlus, Reinhard; Weiss, Jochen

2013-02-01

Spray drying of liposomes with conventional wall materials such as maltodextrins often yields nonfunctional powders, that is, liposomes break down during drying and rehydration. Electrostatically coating the surface of liposomes with a charged polymer prior to spray drying may help solve this problem. Anionic lecithin liposomes (approximately 400 nm) were coated with lower (approximately 500 kDa, LMW-C) or higher (approximately 900 kDa, HMW-C) molecular weight cationic chitosan using the layer-by-layer depositing method. Low (DE20, LMW-MD) or high molecular weight (DE2, HMW-MD) maltodextrin was added as wall material to facilitate spray drying. If surfaces of liposomes (1%) were completely covered with chitosan (0.4%), no bridging or depletion flocculation would occur, and mean particle diameters would be approximately 500 nm. If maltodextrins (20%) were added to uncoated liposomes, extensive liposomal breakdown would occur making the system unsuitable for spray drying. No such aggregation or breakdown was observed when maltodextrin was added to chitosan-coated liposomes. Size changed little or even decreased slightly depending on the molecular weight of maltodextrin added. Scanning electron microscopy images of powders containing chitosan-coated liposomes revealed that their morphologies depended on the type of maltodextrin added. Powders prepared with LMW-MD contained mostly spherical particles while HMW-MD powders contained particles with concavities and dents. Upon redispersion, coated liposomes yielded back dispersions with particle size distributions similar to the original ones, except for LMW-C coated samples that had been spray dried with HMW-MD which yielded aggregates (approximately 30 μm). Results show that coating of liposomes with an absorbing polymer allows them to be spray dried with conventional maltodextrin wall materials. Liposomes have attracted considerable attention in the food and agricultural, biomedical industries for the delivery of functional components. However, maintaining their stability in aqueous dispersion represents a challenge for their commercialization. Spray drying may promise a solution to that problem. However, prior to this study spray drying of liposomes often led to the loss of structural integrity. Results of this study suggest that spray drying might be used to produce commercially feasible liposomal powders if proper combinations of adsorbing and nonadsorbing polymers are used in the liquid precursor system. © 2013 Institute of Food Technologists®

Thickness and Elasticity of Gram-Negative Murein Sacculi Measured by Atomic Force Microscopy

PubMed Central

Yao, X.; Jericho, M.; Pink, D.; Beveridge, T.

1999-01-01

Atomic force microscopy was used to measure the thickness of air-dried, collapsed murein sacculi from Escherichia coli K-12 and Pseudomonas aeruginosa PAO1. Air-dried sacculi from E. coli had a thickness of 3.0 nm, whereas those from P. aeruginosa were 1.5 nm thick. When rehydrated, the sacculi of both bacteria swelled to double their anhydrous thickness. Computer simulation of a section of a model single-layer peptidoglycan network in an aqueous solution with a Debye shielding length of 0.3 nm gave a mass distribution full width at half height of 2.4 nm, in essential agreement with these results. When E. coli sacculi were suspended over a narrow groove that had been etched into a silicon surface and the tip of the atomic force microscope used to depress and stretch the peptidoglycan, an elastic modulus of 2.5 × 107 N/m2 was determined for hydrated sacculi; they were perfectly elastic, springing back to their original position when the tip was removed. Dried sacculi were more rigid with a modulus of 3 × 108 to 4 × 108 N/m2 and at times could be broken by the atomic force microscope tip. Sacculi aligned over the groove with their long axis at right angles to the channel axis were more deformable than those with their long axis parallel to the groove axis, as would be expected if the peptidoglycan strands in the sacculus were oriented at right angles to the long cell axis of this gram-negative rod. Polar caps were not found to be more rigid structures but collapsed to the same thickness as the cylindrical portions of the sacculi. The elasticity of intact E. coli sacculi is such that, if the peptidoglycan strands are aligned in unison, the interstrand spacing should increase by 12% with every 1 atm increase in (turgor) pressure. Assuming an unstressed hydrated interstrand spacing of 1.3 nm (R. E. Burge, A. G. Fowler, and D. A. Reaveley, J. Mol. Biol. 117:927–953, 1977) and an internal turgor pressure of 3 to 5 atm (or 304 to 507 kPa) (A. L. Koch, Adv. Microbial Physiol. 24:301–366, 1983), the natural interstrand spacing in cells would be 1.6 to 2.0 nm. Clearly, if large macromolecules of a diameter greater than these spacings are secreted through this layer, the local ordering of the peptidoglycan must somehow be disrupted. PMID:10559150

High-aluminum-affinity silica is a nanoparticle that seeds secondary aluminosilicate formation.

PubMed

Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J

2013-01-01

Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m(2) g(-1) and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates.

High-Aluminum-Affinity Silica Is a Nanoparticle That Seeds Secondary Aluminosilicate Formation

PubMed Central

Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J.

2013-01-01

Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m2 g-1 and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates. PMID:24349573

Ultrastructural networks in growth cones and neurites of cultured central nervous system neurons.

PubMed

Tsui, H C; Ris, H; Klein, W L

1983-09-01

We have examined growth cones and neurites of cultured central nervous system neurons by high-voltage electron microscopy. Embryonic chicken retina cells were cultured on polylysine-treated and Formvar-coated gold grids for 2-6 days, fixed, and critical point dried. Growth cones and neurites were examined as unembedded whole mounts. Three-dimensional images from stereo-pair electron micrographs of these regions showed a high degree of ultrastructural articulation, with distinct, non-tapering filaments (5-9 nm in diameter) joining both cytoskeletal and membranous components. In the central regions of growth cones, interconnected structures included microtubules, large membranous sacs (up to 400 nm), and irregular vesicles (25-75 nm). A denser filamentous network was prevalent at the edges of growth cones. This network, which frequently adjoined the surface membrane, linked vesicles of uniform size (35-40 nm). Such vesicles often were seen densely packed in growth cone protrusions that were about the size of small synaptic boutons. Prevalent structural interconnections within growth cones conceivably could play a logistic role in specific membrane assembly, intracellular transport, endocytosis, and secretion. Because such processes are not unique to growth cones, the extensive linkages we have observed may have implications for cytoplasmic structure in general.

Breakdown of Shape Memory Effect in Bent Cu-Al-Ni Nanopillars: When Twin Boundaries Become Stacking Faults.

PubMed

Liu, Lifeng; Ding, Xiangdong; Sun, Jun; Li, Suzhi; Salje, Ekhard K H

2016-01-13

Bent Cu-Al-Ni nanopillars (diameters 90-750 nm) show a shape memory effect, SME, for diameters D > 300 nm. The SME and the associated twinning are located in a small deformed section of the nanopillar. Thick nanopillars (D > 300 nm) transform to austenite under heating, including the deformed region. Thin nanopillars (D < 130 nm) do not twin but generate highly disordered sequences of stacking faults in the deformed region. No SME occurs and heating converts only the undeformed regions into austenite. The defect-rich, deformed region remains in the martensite phase even after prolonged heating in the stability field of austenite. A complex mixture of twins and stacking faults was found for diameters 130 nm < D < 300 nm. The size effect of the SME in Cu-Al-Ni nanopillars consists of an approximately linear reduction of the SME between 300 and 130 nm when the SME completely vanishes for smaller diameters.

Niobium oxide nanocolumns formed via anodic alumina with modulated pore diameters

NASA Astrophysics Data System (ADS)

Pligovka, A.; Zakhlebayeva, A.; Lazavenka, A.

2018-03-01

Niobium oxide nanocolumns with modulated diameters were formed for the first time. An Al/Nb bilayer specimen was prepared by successive sputter-deposition of 300 nm niobium layer and 1200 nm aluminum layer onto silicon wafer. Regular anodic alumina matrix with modulated pore diameters was formed by sequential anodization of initial specimen in tartaric acid at 180 V, and in oxalic acid at 37 V. Further potentiodynamic reanodization of the specimen up to 400 V causes the simultaneous growth of 440 nm continuous niobium oxide layer beneath the alumina film and two types of an array of oxide nanocolumns (thick – with 100 nm width and 630 nm high and thin – with 25 nm width and 170 nm high), which are the filling of the alumina pores. The morphology of the formed anodic niobium oxide nanocolumns with modulated diameters was determined by field emission scanning electron microscopy. The formed nanostructures can be used for perspective devices of nano- and optoelectronics such as photonic crystals.

Carbothermal transformation of a graphitic carbon nanofiber/silica aerogel composite to a SiC/silica nanocomposite.

PubMed

Lu, Weijie; Steigerwalt, Eve S; Moore, Joshua T; Sullivan, Lisa M; Collins, W Eugene; Lukehart, C M

2004-09-01

Carbon nanofiber/silica aerogel composites are prepared by sol-gel processing of surface-enhanced herringbone graphitic carbon nanofibers (GCNF) and Si(OMe)4, followed by supercritical CO2 drying. Heating the resulting GCNF/silica aerogel composites to 1650 degrees C under a partial pressure of Ar gas initiates carbothermal reaction between the silica aerogel matrix and the carbon nanofiber component to form SiC/silica nanocomposites. The SiC phase is present as nearly spherical nanoparticles, having an average diameter of ca. 8 nm. Formation of SiC is confirmed by powder XRD and by Raman spectroscopy.

Comparison of epidermal/dermal damage between the long-pulsed 1064 nm Nd:YAG and 755 nm alexandrite lasers under relatively high fluence conditions: quantitative and histological assessments.

PubMed

Lee, Ju Hwan; Park, So Ra; Jo, Jeong Ho; Park, Sung Yun; Seo, Young Kwon; Kim, Sung Min

2014-07-01

The purpose of this study was to compare degrees of epidermal/dermal tissue damage quantitatively and histologically after laser irradiation, to find ideal treatment conditions with relatively high fluence for skin rejuvenation. A number of recent studies have evaluated the clinical efficacy and safety of therapeutic lasers under relatively low fluence conditions. We transmitted the long-pulsed 1064 nm Nd:YAG and 755 nm Alexandrite lasers into pig skin according to different fluences and spot diameters, and estimated epidermal/dermal temperatures. Pig skin specimens were stained with hematoxylin and eosin for histological assessments. The fluence conditions comprised 26, 30, and 36 J/cm2, and the spot diameter conditions were 5, 8, and 10 mm. Pulse duration was 30 ms for all experiments. Both lasers produced reliable thermal damage on the dermis without any serious epidermal injuries, under relatively high fluence conditions. The 1064 nm laser provided more active fibrous formations than the 755 nm laser, while higher risks for tissue damages simultaneously occurred. The ideal treatment conditions for skin rejuvenation were 8 mm diameter with 30 J/cm2 and 10 mm diameter with 26 J/cm2 for the 1064 nm laser, and 8 mm diameter with 36 J/cm2 and 10 mm diameter with 26 J/cm2 for the 755 nm laser.

A hybrid chip based on aerodynamics and electrostatics for the size-dependent classification of ultrafine and nano particles.

PubMed

Kim, Yong-Ho; Park, Dongho; Hwang, Jungho; Kim, Yong-Jun

2009-09-21

Conventional virtual impactors experience a large pressure drop when they classify particles according to size, in particular ultrafine particles smaller than 100 nm in diameter. Therefore, most virtual impactors have been used to classify particles larger than 100 nm. Their cut-off diameters are also fixed by the geometry of their flow channels. In the proposed virtual impactor, particles smaller than 100 nm are accelerated by applying DC potentials to an integrated electrode pair. By the electrical acceleration, the large pressure drop could be significantly decreased and new cut-off diameters smaller than 100 nm could be successfully added. The geometric cut-off diameter (GCD) of the proposed virtual impactor was designed to be 1.0 microm. Performances including the GCD and wall loss were examined by classifying dioctyl sebacate of 100 to 600 nm in size and carbon particles of 0.6 to 10 microm in size. The GCD was measured to be 0.95 microm, and the wall loss was highest at 1.1 microm. To add new cut-off diameters, monodisperse NaCl particles ranging from 15 to 70 nm were classified using the proposed virtual impactor with applying a DC potential of 0.25 to 3.0 kV. In this range of the potential, the new cut-off diameters ranging from 15 to 35 nm was added.

Controlled growth of well-aligned carbon nanotubes with large diameters

NASA Astrophysics Data System (ADS)

Wang, Xianbao; Liu, Yunqi; Zhu, Daoben

2001-06-01

Well-aligned carbon nanotubes (CNTs) with large diameters (25-200 nm) were synthesized by pyrolysis of iron(II) phthalocyanine. The outer diameter up to 218.5 nm and the length of the well-aligned CNTs can be systematically controlled by varying the growth time. A tube-in-tube nano-structure with large and small diameters of 176 and 16.7 nm, respectively, was found. The grain sizes of the iron catalyst play an important role in controlling the CNT diameters. These results are of great importance to design new aligned CNT-based electron field emitters in the potential application of panel displays.

Stratification during evaporative assembly of multicomponent nanoparticle films

DOE PAGES

Liu, Xiao; Liu, Weiping; Carr, Amanda J.; ...

2018-01-03

Multicomponent coatings with layers comprising different functionalities are of interest for a variety of applications, including electronic devices, energy storage, and biomaterials. Rather than creating such a film using multiple deposition steps, we explore a single-step method to create such films by varying the particle Peclet numbers, Pe. Our hypothesis, based on recent theoretical descriptions of the stratification process, is that by varying particle size and evaporation rate such that Pe of large and small particles are above and below unity, we can create stratified films of polymeric and inorganic particles. In this paper, we present AFM on the surfacemore » composition of films comprising poly(styrene) nanoparticles (diameter 25–90 nm) and silica nanoparticles (diameter 8–14 nm). Previous studies on films containing both inorganic and polymeric particles correspond to large Pe values (e.g., 120–460), while we utilize Pe ~ 0.3–4, enabling us to test theories that have been developed for different regimes of Pe. We demonstrate evidence of stratification and effect of the Pe ratio, although our results agree only qualitatively with theory. Finally, our results also provide validation of recent theoretical descriptions of the film drying process that predict different regimes for large-on-top and small-on-top stratification.« less

Stratification during evaporative assembly of multicomponent nanoparticle films

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

Liu, Xiao; Liu, Weiping; Carr, Amanda J.

Multicomponent coatings with layers comprising different functionalities are of interest for a variety of applications, including electronic devices, energy storage, and biomaterials. Rather than creating such a film using multiple deposition steps, we explore a single-step method to create such films by varying the particle Peclet numbers, Pe. Our hypothesis, based on recent theoretical descriptions of the stratification process, is that by varying particle size and evaporation rate such that Pe of large and small particles are above and below unity, we can create stratified films of polymeric and inorganic particles. In this paper, we present AFM on the surfacemore » composition of films comprising poly(styrene) nanoparticles (diameter 25–90 nm) and silica nanoparticles (diameter 8–14 nm). Previous studies on films containing both inorganic and polymeric particles correspond to large Pe values (e.g., 120–460), while we utilize Pe ~ 0.3–4, enabling us to test theories that have been developed for different regimes of Pe. We demonstrate evidence of stratification and effect of the Pe ratio, although our results agree only qualitatively with theory. Finally, our results also provide validation of recent theoretical descriptions of the film drying process that predict different regimes for large-on-top and small-on-top stratification.« less

Effect of drying temperature on warp and downgrade of 2 by 4's from small-diameter ponderosa pine

Treesearch

William T. Simpson

2004-01-01

Kiln drying at high temperature may reduce warp in dimension lumber sawn from small-diameter trees. In this study, we examined the effect on warp of high drying temperatures in conjunction with top loading immediately after drying and after storage in typical conditions that result in further moisture loss. Eight-foot-long 2- by 4-in. (2 by 4) boards sawn from open-...

Method for interconverting drying and heating times between round and square cross sections of ponderosa pine

Treesearch

William T. Simpson

2005-01-01

To use small-diameter trees effectively as square timbers, we need to be able to estimate the amount of time it takes for these timbers to air-dry. Since experimental data on estimating air-drying time for small-diameter logs have been developed, this study looked at a way to relate that method to square timbers. Drying times were determined for a group of round cross-...

Comparison of Epidermal/Dermal Damage Between the Long-Pulsed 1064 nm Nd:YAG and 755 nm Alexandrite Lasers Under Relatively High Fluence Conditions: Quantitative and Histological Assessments

PubMed Central

Lee, Ju Hwan; Park, So Ra; Jo, Jeong Ho; Park, Sung Yun; Seo, Young Kwon

2014-01-01

Abstract Objective: The purpose of this study was to compare degrees of epidermal/dermal tissue damage quantitatively and histologically after laser irradiation, to find ideal treatment conditions with relatively high fluence for skin rejuvenation. Background data: A number of recent studies have evaluated the clinical efficacy and safety of therapeutic lasers under relatively low fluence conditions. Methods: We transmitted the long-pulsed 1064 nm Nd:YAG and 755 nm Alexandrite lasers into pig skin according to different fluences and spot diameters, and estimated epidermal/dermal temperatures. Pig skin specimens were stained with hematoxylin and eosin for histological assessments. The fluence conditions comprised 26, 30, and 36 J/cm2, and the spot diameter conditions were 5, 8, and 10 mm. Pulse duration was 30 ms for all experiments. Results: Both lasers produced reliable thermal damage on the dermis without any serious epidermal injuries, under relatively high fluence conditions. The 1064 nm laser provided more active fibrous formations than the 755 nm laser, while higher risks for tissue damages simultaneously occurred. Conclusions: The ideal treatment conditions for skin rejuvenation were 8 mm diameter with 30 J/cm2 and 10 mm diameter with 26 J/cm2 for the 1064 nm laser, and 8 mm diameter with 36 J/cm2 and 10 mm diameter with 26 J/cm2 for the 755 nm laser. PMID:24992273

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

Raghuwanshi, Vikram Singh; Garusinghe, Uthpala Manavi; Ilavsky, Jan

Controlling nanoparticles (NPs) aggregation in cellulose/NPs composites allows to optimise NPs driven properties and their applications. Polyelectrolytes are used to control NPs aggregation and their retention within the fibrous matrix. Here in this study, we aim at evaluating how a polyelectrolyte (Cationic Polyacrylamide; CPAM, molecular weight: 13 MDa, charge: 50%, Radius of gyration: 30–36 nm) adsorbs and re-conforms onto the surface of silica(SiO 2) NPs differing in diameter (8, 22 and 74 nm) and to investigate the respective NPs aggregation in cellulose matrices. SEM shows the local area distribution of NPs in composites. Ultra-SAXS (USAXS) allows to evaluate the averagemore » NPs size distribution and the inter-particle interactions at length scale ranging from 1 to 1000 nm. USAXS data analysis reveals that CPAM covers multiple NPs of the smaller diameter (8 nm), presumably with a single chain to form large size NPs aggregates. As the NPs diameter is increased to 22 nm, CPAM re-conforms over NP surface forming a large shell of thickness 5.5 nm. For the composites with NPs of diameter 74 nm, the CPAM chain re-conforms further onto NP surface and the surrounding shell thickness decreases to 2.2 nm. Lastly, structure factor analysis reveals higher structural ordering for NPs as increases their diameter, which is caused by different conformations adopted by CPAM onto NPs surface.« less

Effect of nanoparticles size and polyelectrolyte on nanoparticles aggregation in a cellulose fibrous matrix

DOE PAGES

Raghuwanshi, Vikram Singh; Garusinghe, Uthpala Manavi; Ilavsky, Jan; ...

2017-09-18

Controlling nanoparticles (NPs) aggregation in cellulose/NPs composites allows to optimise NPs driven properties and their applications. Polyelectrolytes are used to control NPs aggregation and their retention within the fibrous matrix. Here in this study, we aim at evaluating how a polyelectrolyte (Cationic Polyacrylamide; CPAM, molecular weight: 13 MDa, charge: 50%, Radius of gyration: 30–36 nm) adsorbs and re-conforms onto the surface of silica(SiO 2) NPs differing in diameter (8, 22 and 74 nm) and to investigate the respective NPs aggregation in cellulose matrices. SEM shows the local area distribution of NPs in composites. Ultra-SAXS (USAXS) allows to evaluate the averagemore » NPs size distribution and the inter-particle interactions at length scale ranging from 1 to 1000 nm. USAXS data analysis reveals that CPAM covers multiple NPs of the smaller diameter (8 nm), presumably with a single chain to form large size NPs aggregates. As the NPs diameter is increased to 22 nm, CPAM re-conforms over NP surface forming a large shell of thickness 5.5 nm. For the composites with NPs of diameter 74 nm, the CPAM chain re-conforms further onto NP surface and the surrounding shell thickness decreases to 2.2 nm. Lastly, structure factor analysis reveals higher structural ordering for NPs as increases their diameter, which is caused by different conformations adopted by CPAM onto NPs surface.« less

Synthesis of brushite particles in reverse microemulsions of the biosurfactant surfactin.

PubMed

Maity, Jyoti Prakash; Lin, Tz-Jiun; Cheng, Henry Pai-Heng; Chen, Chien-Yen; Reddy, A Satyanarayana; Atla, Shashi B; Chang, Young-Fo; Chen, Hau-Ren; Chen, Chien-Cheng

2011-01-01

In this study the "green chemistry" use of the biosurfactant surfactin for the synthesis of calcium phosphate using the reverse microemulsion technique was demonstrated. Calcium phosphates are bioactive materials that are a major constituent of human teeth and bone tissue. A reverse microemulsion technique with surfactin was used to produce nanocrystalline brushite particles. Structural diversity (analyzed by SEM and TEM) resulted from different water to surfactin ratios (W/S; 250, 500, 1000 and 40,000). The particle sizes were found to be in the 16-200 nm range. Morphological variety was observed in the as-synthesized microemulsions, which consisted of nanospheres (~16 nm in diameter) and needle-like (8-14 nm in diameter and 80-100 nm in length) noncalcinated particles. However, the calcinated products included nanospheres (50-200 nm in diameter), oval (~300 nm in diameter) and nanorod (200-400 nm in length) particles. FTIR and XRD analysis confirmed the formation of brushite nanoparticles in the as-synthesized products, while calcium pyrophosphate was produced after calcination. These results indicate that the reverse microemulsion technique using surfactin is a green process suitable for the synthesis of nanoparticles.

Diameter distribution in a Brazilian tropical dry forest domain: predictions for the stand and species.

PubMed

Lima, Robson B DE; Bufalino, Lina; Alves, Francisco T; Silva, José A A DA; Ferreira, Rinaldo L C

2017-01-01

Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.

Fabrication of 10nm diameter carbon nanopores

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

Radenovic, Aleksandra; Trepagnier, Eliane; Csencsits, Roseann

2008-09-25

The addition of carbon to samples, during imaging, presents a barrier to accurate TEM analysis, the controlled deposition of hydrocarbons by a focused electron beam can be a useful technique for local nanometer-scale sculpting of material. Here we use hydrocarbon deposition to form nanopores from larger focused ion beam (FIB) holes in silicon nitride membranes. Using this method, we close 100-200nm diameter holes to diameters of 10nm and below, with deposition rates of 0.6nm per minute. I-V characteristics of electrolytic flow through these nanopores agree quantitatively with a one dimensional model at all examined salt concentrations.

Control of optical bandgap energy and optical absorption coefficient by geometric parameters in sub-10 nm silicon-nanodisc array structure

NASA Astrophysics Data System (ADS)

Fairuz Budiman, Mohd; Hu, Weiguo; Igarashi, Makoto; Tsukamoto, Rikako; Isoda, Taiga; Itoh, Kohei M.; Yamashita, Ichiro; Murayama, Akihiro; Okada, Yoshitaka; Samukawa, Seiji

2012-02-01

A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO2 matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.

Conformation Effects on the Photoluminescence Behavior of Anchored MEH-PPV Pancakes and Brushes

NASA Astrophysics Data System (ADS)

Shih, Kuo Sheng; Chen, Po-Tsun; Yang, Arnold C.-M.

2012-02-01

Single molecular layer of poly[2-methoxy-5-(2'-ethylhexyl)oxy)-1,4- phenylenevinylene] (MEH-PPV) grafted on primed silicon wafer were synthesized, forming brushes (chain spacing 0.54 nm via graft-from) or pancakes (˜ 7nm to 34 nm via graft-to). For the tight-packed brushes, the PL emission peak, residing in the range from 434 nm to 550 nm depending on the chain length, was generally unchanged when transferring between the dry and solvent immersion states. However, for the pancakes, the emission peak blue-shifted dramatically (up to 100 nm) when dried in the air relative to that in the solvent. These shifts were fully reversible in the dry-wet cycles. The large blue shifts of the anchored pancakes were attributed to the mechanical stretching of entangled MEH-PPV segments in contact with substrate upon solvent loss. In contrast, the blue shifts disappeared and small red shifts emerged instead for extremely slowly drying (24 hrs drying time), revealing the stress-relaxation pathways in the equilibrium conditions. The drying-induced blue shift was also observed in the un-anchored drop-casting samples but the reversibility vanished. Finally, a large enhancement of PL intensity was accompanied with the blue shifts, manifesting the effect of the molecular constraints.

Controlling diameter distribution of catalyst nanoparticles in arc discharge.

PubMed

Li, Jian; Volotskova, Olga; Shashurin, Alexey; Keidar, Michael

2011-11-01

It is demonstrated that the diameter distribution of catalyst nanoparticles in arc discharge can be controlled by a magnetic field. The magnetic field affects the arc shape, shortens the diffusing time of the catalyst nanoparticles through the nucleation zone, and consequentially reduces the average diameters of nanoparticles. The average diameter is reduced from about 7.5 nm without magnetic field to about 5 nm is the case of a magnetic field. Decrease of the catalyst nanoparticle diameter with magnetic field correlates well with decrease in the single-wall carbon nanotube and their bundles diameters.

Fabrication of vertical nanowire resonators for aerosol exposure assessment

NASA Astrophysics Data System (ADS)

Merzsch, Stephan; Wasisto, Hutomo Suryo; Stranz, Andrej; Hinze, Peter; Weimann, Thomas; Peiner, Erwin; Waag, Andreas

2013-05-01

Vertical silicon nanowire (SiNW) resonators are designed and fabricated in order to assess exposure to aerosol nanoparticles (NPs). To realize SiNW arrays, nanolithography and inductively coupled plasma (ICP) deep reactive ion etching (DRIE) at cryogenic temperature are utilized in a top-down fabrication of SiNW arrays which have high aspect ratios (i.e., up to 34). For nanolithography process, a resist film thickness of 350 nm is applied in a vacuum contact mode to serve as a mask. A pattern including various diameters and distances for creating pillars is used (i.e., 400 nm up to 5 μm). In dry etching process, the etch rate is set high of 1.5 μm/min to avoid underetching. The etch profiles of Si wires can be controlled aiming to have either perpendicularly, negatively or positively profiled sidewalls by adjusting the etching parameters (e.g., temperature and oxygen content). Moreover, to further miniaturize the wire, multiple sacrificial thermal oxidations and subsequent oxide stripping are used yielding SiNW arrays of 650 nm in diameter and 40 μm in length. In the resonant frequency test, a piezoelectric shear actuator is integrated with the SiNWs inside a scanning electron microscope (SEM) chamber. The observation of the SiNW deflections are performed and viewed from the topside of the SiNWs to reduce the measurement redundancy. Having a high deflection of ~10 μm during its resonant frequency of 452 kHz and a low mass of 31 pg, the proposed SiNW is potential for assisting the development of a portable aerosol resonant sensor.

Manufacturing and advanced characterization of sub-25nm diameter CD-AFM probes with sub-10nm tip edges radius

NASA Astrophysics Data System (ADS)

Foucher, Johann; Filippov, Pavel; Penzkofer, Christian; Irmer, Bernd; Schmidt, Sebastian W.

2013-04-01

Atomic force microscopy (AFM) is increasingly used in the semiconductor industry as a versatile monitoring tool for highly critical lithography and etching process steps. Applications range from the inspection of the surface roughness of new materials, over accurate depth measurements to the determination of critical dimension structures. The aim to address the rapidly growing demands on measurement uncertainty and throughput more and more shifts the focus of attention to the AFM tip, which represents the crucial link between AFM tool and the sample to be monitored. Consequently, in order to reach the AFM tool's full potential, the performance of the AFM tip has to be considered as a determining parameter. Currently available AFM tips made from silicon are generally limited by their diameter, radius, and sharpness, considerably restricting the AFM measurement capabilities on sub-30nm spaces. In addition to that, there's lack of adequate characterization structures to accurately characterize sub-25nm tip diameters. Here, we present and discuss a recently introduced AFM tip design (T-shape like design) with precise tip diameters down to 15nm and tip radii down to 5nm fabricated from amorphous, high density diamond-like carbon (HDC/DLC) using electron beam induced processing (EBIP). In addition to that advanced design, we propose a new characterizer structure, which allows for accurate characterization and design control of sub-25nm tip diameters and sub-10nm tip edges radii. We demonstrate the potential advantages of combining a small tip shape design, i.e. tip diameter and tip edge radius, and an advanced tip characterizer for the semiconductor industry by the measurement of advanced lithography patterns.

Evaluation of Populus and Salix continuously irrigated with landfill leachate II. soils and early tree development.

PubMed

Zalesny, Ronald S; Bauer, Edmund O

2007-01-01

Soil contaminant levels and early tree growth data are helpful for assessing phytoremediation systems. Populus (DN17, DN182, DN34, NM2, and NM6) and Salix (94003, 94012, S287, S566, and SX61) genotypes were irrigated with landfill leachate or municipal water and tested for differences in (1) element concentrations (P, K, Ca, Mg, S, Zn, B, Mn, Fe, Cu, Al, and Na) of a topsoil layer and a layer of sand in tanks with a cover crop of trees or no trees and (2) height, diameter, volume, and dry mass of leaves, stems, and roots. Trees were irrigated with leachate or water during the final 12 wk of the 18-wk study. Differences in most soil element concentrations were negligible (P > 0.05) for irrigation treatments and cover main effects. Phosphorous, K, Mg, S, Zn, Mn, Fe, and Al concentrations were greater in topsoil than sand (P = 0.0011 for Mg; P < 0.0001 for others). There was broad variation between genera and among clones for all growth traits. The treatment x clone interaction governed height, volume, and root dry mass, with (94012, SX61), (NM2, S566, SX61), and (S287, S566) exhibiting the greatest levels, respectively,following leachate application. Given the broad amount of variability among and within these genera, there is great potential for the identification and selection of specific genotypes with a combination of elevated phytoremediation capabilities and tree yield. From a practical standpoint, these results may be used as a baseline for the development of future remediation systems.

High Performance Composite Dielectric Ink for Ultracapacitors

NASA Technical Reports Server (NTRS)

Rolin, Terry D. (Inventor); Hill, Curtis W. (Inventor)

2017-01-01

The present invention is a dielectric ink and means for printing using said ink. Approximately 10-20% of the ink is a custom organic vehicle made of a polar solvent and a binder. Approximately 30-70% of the ink is a dielectric powder having an average particle diameter of approximately 10-750 nm. Approximately 5-15% of the ink is a dielectric constant glass. Approximately 10-35% of the ink is an additional amount of solvent. The ink is deposited on a printing substrate to form at least one printed product, which is then dried and cured to remove the solvent and binder, respectively. The printed product then undergoes sintering in an inert gas atmosphere.

New Approach to Image Aerogels by Scanning Electron Microscopy

NASA Astrophysics Data System (ADS)

Solá, Francisco; Hurwitz, Frances; Yang, Jijing

2011-03-01

A new scanning electron microscopy (SEM) technique to image poor electrically conductive aerogels is presented. The process can be performed by non-expert SEM users. We showed that negative charging effects on aerogels can be minimized significantly by inserting dry nitrogen gas close to the region of interest. The process involves the local recombination of accumulated negative charges with positive ions generated from ionization processes. This new technique made possible the acquisition of images of aerogels with pores down to approximately 3nm in diameter using a positively biased Everhart-Thornley (E-T) detector. Well-founded concepts based on known models will also be presented with the aim to explain the results qualitatively.

Plasma-assisted reduction of silver ions impregnated into a natural zeolite framework

NASA Astrophysics Data System (ADS)

Osonio, Airah P.; Vasquez, Magdaleno R.

2018-02-01

A green, dry, and energy-efficient method for the fabrication of silver-zeolite (AgZ) composite via 13.56 MHz radio-frequency plasma reduction is demonstrated. Impregnation by soaking and ion-exchange deposition were performed to load the silver ions (Ag+) into the sodium-zeolite samples. Characterization was performed by optical emission spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller analyses. Results indicate the successful reduction of Ag+ to its metallic state on the surface of the zeolite with a mean diameter of 165 nm. This plasma-induced reduction technique opens possibilities in several areas including catalysis, adsorption, water treatment, and medicine.

Ethylene Gas Sensing Properties of Tin Oxide Nanowires Synthesized via CVD Method

NASA Astrophysics Data System (ADS)

Akhir, Maisara A. M.; Mohamed, Khairudin; Rezan, Sheikh A.; Arafat, M. M.; Haseeb, A. S. M. A.; Uda, M. N. A.; Nuradibah, M. A.

2018-03-01

This paper studies ethylene gas sensing performance of tin oxide (SnO2) nanowires (NWs) as sensing material synthesized using chemical vapor deposition (CVD) technique. The effect of NWs diameter on ethylene gas sensing characteristics were investigated. SnO2 NWs with diameter of ∼40 and ∼240 nm were deposited onto the alumina substrate with printed gold electrodes and tested for sensing characteristic toward ethylene gas. From the finding, the smallest diameter of NWs (42 nm) exhibit fast response and recovery time and higher sensitivity compared to largest diameter of NWs (∼240 nm). Both sensor show good reversibility features for ethylene gas sensor.

Shrinkage deformation of cement foam concrete

NASA Astrophysics Data System (ADS)

Kudyakov, A. I.; Steshenko, A. B.

2015-01-01

The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

Optimization of electrospun TSF nanofiber alignment and diameter to promote growth and migration of mesenchymal stem cells

NASA Astrophysics Data System (ADS)

Qu, Jing; Zhou, Dandan; Xu, Xiaojing; Zhang, Feng; He, Lihong; Ye, Rong; Zhu, Ziyu; Zuo, Baoqi; Zhang, Huanxiang

2012-11-01

Silk fibroin scaffolds are a naturally derived biocompatible matrix with the potential for reconstructive surgical applications. In this study, tussah silk fibroin (TSF) nanofiber with different diameters (400 nm, 800 nm and 1200 nm) and alignment (random and aligned) were prepared by electrospinning, then the growth and migration of mesenchymal stem cells (MSCs) on these materials were further evaluated. CD90 immunofluorescence staining showed that fiber alignment exhibited a strong influence on the morphology of MSCs, indicating that the alignment of the scaffolds could determine the distribution of cells. Moreover, smaller diameter and aligned TSF scaffolds are more favorable to the growth of MSCs as compared with 800 nm and 1200 nm random TSF scaffolds. In addition, the increased migration speed and efficiency of MSCs induced by three-D TSF were verified, highlighting the guiding roles of TSF to the migrated MSCs. More importantly, 400 nm aligned TSF scaffolds dramatically improved cell migratory speed and further induced the most efficient migration of MSCs as compared with larger diameter TSF scaffolds. In conclusion, the data demonstrate that smaller diameter and aligned electrospun TSF represent valuable scaffolds for supporting and promoting MSCs growth and migration, thus raising the possibility of manipulating TSF scaffolds to enhance homing and therapeutic potential of MSCs in cellular therapy.

Preparation and characterization of nanoparticles of carboxymethyl cellulose acetate butyrate containing acyclovir

NASA Astrophysics Data System (ADS)

Vedula, Venkata Bharadwaz; Chopra, Maulick; Joseph, Emil; Mazumder, Sonal

2016-02-01

Nanoparticles of carboxymethyl cellulose acetate butyrate complexed with the poorly soluble antiviral drug acyclovir (ACV) were produced by precipitation process and the formulation process and properties of nanoparticles were investigated. Two different particle synthesis methods were explored—a conventional precipitation method and a rapid precipitation in a multi-inlet vortex mixer. The particles were processed by rotavap followed by freeze-drying. Particle diameters as measured by dynamic light scattering were dependent on the synthesis method used. The conventional precipitation method did not show desired particle size distribution, whereas particles prepared by the mixer showed well-defined particle size ~125-450 nm before and after freeze-drying, respectively, with narrow polydispersity indices. Fourier transform infrared spectroscopy showed chemical stability and intactness of entrapped drug in the nanoparticles. Differential scanning calorimetry showed that the drug was in amorphous state in the polymer matrix. ACV drug loading was around 10 wt%. The release studies showed increase in solution concentration of drug from the nanoparticles compared to the as-received crystalline drug.

Enhancement of the wear resistance and microhardness of aluminum alloy by Nd:YaG laser treatment.

PubMed

Hussein, Haitham T; Kadhim, Abdulhadi; Al-Amiery, Ahmed A; Kadhum, Abdul Amir H; Mohamad, Abu Bakar

2014-01-01

Influence of laser treatment on mechanical properties, wear resistance, and Vickers hardness of aluminum alloy was studied. The specimens were treated by using Nd:YaG laser of energy 780 mj, wavelength 512 nm, and duration time 8 ns. The wear behavior of the specimens was studied for all specimens before and after treatment by Nd:YaG laser and the dry wear experiments were carried out by sing pinon-disc technique. The specimens were machined as a disk with diameter of 25 mm and circular groove in depth of 3 mm. All specimens were conducted by scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence analysis (EDS), optical microscopy, and Vickers hardness. The results showed that the dry wear rate was decreased after laser hardening and increased Vickers hardness values by ratio of 2.4:1. The results showed that the values of wear rate for samples having circular grooves are less than samples without grooves after laser treatment.

Fiber-Based 589 nm Laser for Sodium Guide Star

DTIC Science & Technology

2006-02-01

are combined in a 980/1060 nm WDM coupler and free-space launched through an isolator designed for 1060 nm into a 23 m long Yb doped fiber. This fiber...lenses. The final-stage amplifier comprised a 23 m long YDF with a core diameter of 8 lam and a D-shaped inner cladding of 400 jtm diameter. It was...resolution). (b) High resolution spectrum of the 1178 nm output beam at 534 m W output power, linewidth (FWHM) - 0. 6 nm (0.05 nm resolution). The

Ultrastructural networks in growth cones and neurites of cultured central nervous system neurons.

PubMed Central

Tsui, H C; Ris, H; Klein, W L

1983-01-01

We have examined growth cones and neurites of cultured central nervous system neurons by high-voltage electron microscopy. Embryonic chicken retina cells were cultured on polylysine-treated and Formvar-coated gold grids for 2-6 days, fixed, and critical point dried. Growth cones and neurites were examined as unembedded whole mounts. Three-dimensional images from stereo-pair electron micrographs of these regions showed a high degree of ultrastructural articulation, with distinct, non-tapering filaments (5-9 nm in diameter) joining both cytoskeletal and membranous components. In the central regions of growth cones, interconnected structures included microtubules, large membranous sacs (up to 400 nm), and irregular vesicles (25-75 nm). A denser filamentous network was prevalent at the edges of growth cones. This network, which frequently adjoined the surface membrane, linked vesicles of uniform size (35-40 nm). Such vesicles often were seen densely packed in growth cone protrusions that were about the size of small synaptic boutons. Prevalent structural interconnections within growth cones conceivably could play a logistic role in specific membrane assembly, intracellular transport, endocytosis, and secretion. Because such processes are not unique to growth cones, the extensive linkages we have observed may have implications for cytoplasmic structure in general. Images PMID:6577454

Films of brookite TiO2 nanorods/nanoparticles deposited by matrix-assisted pulsed laser evaporation as NO2 gas-sensing layers

NASA Astrophysics Data System (ADS)

Caricato, A. P.; Buonsanti, R.; Catalano, M.; Cesaria, M.; Cozzoli, P. D.; Luches, A.; Manera, M. G.; Martino, M.; Taurino, A.; Rella, R.

2011-09-01

Titanium dioxide (TiO2) nanorods in the brookite phase, with average dimensions of 3-4 nm × 20-50 nm, were synthesized by a wet-chemical aminolysis route and used as precursors for thin films that were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. A nanorod solution in toluene (0.016 wt% TiO2) was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser at a fluence of 350 mJ/cm2 and repetition rate of 10 Hz. Single-crystal Si wafers, silica slides, carbon-coated Cu grids and alumina interdigitated slabs were used as substrates to allow performing different characterizations. Films fabricated with 6000 laser pulses had an average thickness of ˜150 nm, and a complete coverage of the selected substrate as achieved. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of quite rough films incorporating individually distinguishable TiO2 nanorods and crystalline spherical nanoparticles with an average diameter of ˜13 nm. Spectrophotometric analysis showed high transparency through the UV-Vis spectral range. Promising resistive sensing responses to 1 ppm of NO2 mixed in dry air were obtained.

Synthesis of Brushite Particles in Reverse Microemulsions of the Biosurfactant Surfactin

PubMed Central

Maity, Jyoti Prakash; Lin, Tz-Jiun; Cheng, Henry Pai-Heng; Chen, Chien-Yen; Reddy, A. Satyanarayana; Atla, Shashi B.; Chang, Young-Fo; Chen, Hau-Ren; Chen, Chien-Cheng

2011-01-01

In this study the “green chemistry” use of the biosurfactant surfactin for the synthesis of calcium phosphate using the reverse microemulsion technique was demonstrated. Calcium phosphates are bioactive materials that are a major constituent of human teeth and bone tissue. A reverse microemulsion technique with surfactin was used to produce nanocrystalline brushite particles. Structural diversity (analyzed by SEM and TEM) resulted from different water to surfactin ratios (W/S; 250, 500, 1000 and 40,000). The particle sizes were found to be in the 16–200 nm range. Morphological variety was observed in the as-synthesized microemulsions, which consisted of nanospheres (~16 nm in diameter) and needle-like (8–14 nm in diameter and 80–100 nm in length) noncalcinated particles. However, the calcinated products included nanospheres (50–200 nm in diameter), oval (~300 nm in diameter) and nanorod (200–400 nm in length) particles. FTIR and XRD analysis confirmed the formation of brushite nanoparticles in the as-synthesized products, while calcium pyrophosphate was produced after calcination. These results indicate that the reverse microemulsion technique using surfactin is a green process suitable for the synthesis of nanoparticles. PMID:21747709

Rapid Fabrication of Silver Nanowires through Photoreduction of Silver Nitrate from an Anodic-Aluminum-Oxide Template

NASA Astrophysics Data System (ADS)

Lin, Yu-Hsuan; Chen, Kun-Tso; Ho, Jeng-Rong

2011-06-01

A method for rapidly fabricating dense and high-aspect-ratio silver nanowires, with wire diameter of 200 nm and wire length more than 30 µm, is reported. The fabrication process simply involves filling the silver nitrate solution into the pores of an anodic-aluminum-oxide (AAO) membrane through capillary attraction and irradiating the dried template AAO membrane using a pulsed ArF excimer laser. Through varying the thickness and pore diameter of the employed AAO membrane, the primary dimensions of the targeted silver nanowires can be plainly specified; and, by amending the initial concentration of the silver nitrate solution and adjusting the laser operation parameters, laser fluence and number of laser pulses, the surface morphology and size of the resulting nanowires can be finely regulated. The wire formation mechanism is considered through two stages: the period of precipitation of silver particles from the dried silver nitrate film through the laser-induced photoreduction; and, the phase of clustering, merging and fusing of the reduced particles to form nanowires in the template pores by the thermal energy owing to photothermal effect. This approach is straightforward and takes the advantage that all the fabrication processes can be executed in an ambient environment and at room temperature. In addition, by the excellence in local processing that the laser possesses, this method is suitable for precisely growing nanowires.

Diameter Control and Photoluminescence of ZnO Nanorods from Trialkylamines

DOE PAGES

Andelman, Tamar; Gong, Yinyan; Neumark, Gertrude; ...

2007-01-01

A novel solution method to control the diameter of ZnO nanorods is reported. Small diameter (2-3 nm) nanorods were synthesized from trihexylamine, and large diameter (50–80 nm) nanorods were synthesized by increasing the alkyl chain length to tridodecylamine. The defect (green) emission of the photoluminescence (PL) spectra of the nanorods varies with diameter, and can thus be controlled by the diameter control. The small ZnO nanorods have strong green emission, while the large diameter nanorods exhibit a remarkably suppressed green band. We show that this observation supports surface oxygen vacancies as the defect that gives rise to the green emission.

Capabilities of ICP-RIE cryogenic dry etching of silicon: review of exemplary microstructures

NASA Astrophysics Data System (ADS)

Sökmen, Ü.; Stranz, A.; Fündling, S.; Wehmann, H.-H.; Bandalo, V.; Bora, A.; Tornow, M.; Waag, A.; Peiner, E.

2009-10-01

Inductively coupled plasma (ICP) cryogenic dry etching was used to etch submicron pores, nano contact lines, submicron diameter pillars, thin and thick cantilevers, membrane structures and anisotropic deep structures with high aspect ratios in silicon for bio-nanoelectronics, optoelectronics and nano-micro electromechanical systems (NMEMS). The ICP cryogenic dry etching gives us the advantage of switching plasmas between etch rates of 13 nm min-1 and 4 µm min-1 for submicron pores and for membrane structures, respectively. A very thin photoresist mask can endure at -75 °C even during etching 70 µm deep for cantilevers and 300 µm deep for membrane structures. Coating the backsides of silicon membrane substrates with a thin photoresist film inhibited the lateral etching of cantilevers during their front release. Between -95 °C and -140 °C, we realized crystallographic-plane-dependent etching that creates facets only at the etch profile bottom. By varying the oxygen content and the process temperature, we achieved good control over the shape of the etched structures. The formation of black silicon during membrane etching down to 300 µm was delayed by reducing the oxygen content.

Heat generation of surface-modified magnetic γ-Fe2O3 nanoparticles in applied alternating magnetic field

NASA Astrophysics Data System (ADS)

Babič, Michal; Horák, Daniel; Molčan, Matúš; Timko, Milan

2017-08-01

In this report, we show preparation of colloidally stable poly(N,N-dimethylacrylamide-co-acrylic acid) (DMA)- and D-mannose (MAN)-coated maghemite nanoparticles and their ability to generate heat in an alternating magnetic field, which could make the particles applicable for hyperthermic therapy of cancer. The particles are obtained by coprecipitation reaction and characterized by transmission electron microscopy, dynamic light scattering, and AC calorimetric measurement of heat generated by the particles. While the dry particles were ca. 10 nm in diameter, their hydrodynamic size in water was within the range of 100 nm. Heating characteristics were measured in an LC circuit with a maximum field intensity of 6.8 kA · m-1 and frequency 190 kHz. The specific absorption rates of γ-Fe2O3, PDM@γ-Fe2O3, and MAN@γ-Fe2O3 nanoparticles were extrapolated to 10 kA · m-1, reaching about 15 W · g-1.

Synthesis of quantum dots via microreaction: structure optimization for microreactor system

NASA Astrophysics Data System (ADS)

Yang, Hongwei; Luan, Weiling; Cheng, Rui; Chu, Haijian; Tu, Shan-tung

2011-08-01

Microreactor systems existed as a powerful tool for the continuous synthesis of quantum dots. However, the lack of structure optimization for the discrete units led to empirical determination of the length scale, and the properties of the formed products varied in different cases. In this article, the optimizations for the micromixer volume and capillary diameter were presented based on the synthesis of CdSe nanocrystals (NCs). Spectra investigation revealed that the application of a small convective mixer of 36 μL led to 1/3 increase of CdSe concentration in the crude solution. The enhanced mixing of the precursors in this case was also demonstrated favorable to achieve CdSe NCs with narrow PL width. Fast heating and uniform reaction condition achieved in a narrow channel favored the preparation of high quality CdSe NCs under short residence time. However, the application of wide channel did not necessarily result in CdSe NCs with poor quality. Here, we demonstrated that high-quality CdSe NCs with narrow full width at half maximum (FWHM) as 32 nm and high quantum yield (QY) 34.7% could be prepared using an 844 μm inner diameter capillary. Based on the obtained results, the scaled-up synthesis of CdSe NCs was demonstrated, and a high quantity of 0.8 g dry CdSe NCs powder (3.5 nm, σ 8.2%) was obtained within 1 h.

Generation of the Submicron Soft X-Ray Beam Using a Fresnel Zone Plate

NASA Astrophysics Data System (ADS)

Nishikino, M.; Kawazome, H.; Tanaka, M.; Kishimoto, M.; Hasegawa, N.; Ochi, Y.; Kawachi, T.; Sukegawa, K.; Yamatani, H.; Nagashima, K.; Kato, Y.

We have developed a fully coherent x-ray laser at 13.9 nm and the application research has been started. The generation of submicron x-ray beam is important for the application of high intensity x-ray beam, such as the non-linear optics, the material science, and the biology. The submicron x-ray bee am is generated by the soft x-ray laser with using a Fresnel zone plate. The spot diameter is estimated about 680 nm (290 nm at FWHM) by the theoretical calculation. In this experiment, the diameter of the x-ray beam is measured by the knife-edge scan. The diameter and the intensity are estimated 730 nm (310 nm at FWHM) and 3x1011 W/cm2, respectively.

[Research on NEDC ultrafine particle emission characters of a port fuel injection gasoline car].

PubMed

Hu, Zhi-Yuan; Li, Jin; Tan, Pi-Qiang; Lou, Di-Ming

2012-12-01

A Santana gasoline car with multi-port fuel injection (PFI) system was used as the research prototype and an engine exhaust particle sizer (EEPS) was employed to investigate the exhaust ultrafine particle number and size distribution characters of the tested vehicle in new European driving cycle (NEDC). The tested results showed that the vehicle's nuclear particle number, accumulation particle number, as well as the total particle number emission increased when the car drove in accelerated passage, and the vehicle's particle number emission was high during the first 40 seconds after test started and when the speed was over 90 km x h(-1) in extra urban driving cycle (EUDC) in NEDC. The ultrafine particle distribution of the whole NEDC showed a single peak logarithmic distribution, with diameters of the peak particle number emission ranging from 10 nm to 30 nm, and the geometric mean diameter was 24 nm. The ultrafine particle distribution of the urban driving cycle named by the economic commission for Europe (ECE) e. g. ECE I, ECE II - IV, the extra urban driving cycle e. g. EUDC, and the idling, constant speed, acceleration, deceleration operation conditions of NEDC all showed a single peak logarithmic distribution, also with particle diameters of the peak particle number emission ranging from 10 nm to 30 nm, and the geometric mean diameters of different driving cycle and different driving mode were from 14 nm to 42 nm. Therefore, the ultrafine particle emissions of the tested PFI gasoline car were mainly consisted of nuclear mode particles with a diameter of less than 50 nm.

Research Update: Synthesis of sub-15-nm diameter silver nanowires through a water-based hydrothermal method: Fabrication of low-haze 2D conductive films

NASA Astrophysics Data System (ADS)

Jang, Hae-Won; Kim, Yong-Hoe; Lee, Ki-Wook; Kim, Yoon-Mi; Kim, Jin-Yeol

2017-08-01

We synthesized ultra-thin Ag nanowire (Ag NWs) with sub-15 nm diameters and aspect ratios of 1000 through a water-based high-pressure hydrothermal method in the presence of a tetrabutylammonium dichlorobromide organic salt and glucose reducing agent. In the crystal growth stage, the diameter of the NWs could be controlled by adjusting the pressure, and 15-nm diameter wires were obtained at a pressure of 190 psi. These 2D conductive Ag NW network films showed an excellent optical performance with low haze value of ≤1.0% and 94.5% transmittance at a low sheet resistance of 20 Ω/sq.

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 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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04465k

Diameter control of single-walled carbon nanotube forests from 1.3–3.0 nm by arc plasma deposition

PubMed Central

Chen, Guohai; Seki, Yasuaki; Kimura, Hiroe; Sakurai, Shunsuke; Yumura, Motoo; Hata, Kenji; Futaba, Don N.

2014-01-01

We present a method to both precisely and continuously control the average diameter of single-walled carbon nanotubes in a forest ranging from 1.3 to 3.0 nm with ~1 Å resolution. The diameter control of the forest was achieved through tuning of the catalyst state (size, density, and composition) using arc plasma deposition of nanoparticles. This 1.7 nm control range and 1 Å precision exceed the highest reports to date. PMID:24448201

Isolation of >1 nm Diameter Single-Wall Carbon Nanotube Species Using Aqueous Two-Phase Extraction.

PubMed

Fagan, Jeffrey A; Hároz, Erik H; Ihly, Rachelle; Gui, Hui; Blackburn, Jeffrey L; Simpson, Jeffrey R; Lam, Stephanie; Hight Walker, Angela R; Doorn, Stephen K; Zheng, Ming

2015-05-26

In this contribution we demonstrate the effective separation of single-wall carbon nanotube (SWCNT) species with diameters larger than 1 nm through multistage aqueous two-phase extraction (ATPE), including isolation at the near-monochiral species level up to at least the diameter range of SWCNTs synthesized by electric arc synthesis (1.3-1.6 nm). We also demonstrate that refined species are readily obtained from both the metallic and semiconducting subpopulations of SWCNTs and that this methodology is effective for multiple SWCNT raw materials. Using these data, we report an empirical function for the necessary surfactant concentrations in the ATPE method for separating different SWCNTs into either the lower or upper phase as a function of SWCNT diameter. This empirical correlation enables predictive separation design and identifies a subset of SWCNTs that behave unusually as compared to other species. These results not only dramatically increase the range of SWCNT diameters to which species selective separation can be achieved but also demonstrate that aqueous two-phase separations can be designed across experimentally accessible ranges of surfactant concentrations to controllably separate SWCNT populations of very small (∼0.62 nm) to very large diameters (>1.7 nm). Together, the results reported here indicate that total separation of all SWCNT species is likely feasible by the ATPE method, especially given future development of multistage automated extraction techniques.

New Particle Formation in the Tropical UTLS Near Costa Rica: Contrast January and February with June and August

NASA Astrophysics Data System (ADS)

Wilson, J. C.; Saad, M. S.; Axisa, D.

2017-12-01

Aerosol size distributions were measured in the 4 nm to 1000 nm diameter range from the NASA WB-57 aircraft based in Costa Rica from 2004 through 2007. The measurements were made with the Nuclei Mode Aerosol Size Spectrometer (NMASS) and the Focused Cavity Aerosol Spectrometer (FCAS). The NMASS consists of 5 condensation particle counters (CPCs) each operated with a different supersaturation of the working fluid (FC-43). Therefore each CPC has a different lower size cut off. The size cutoffs are near 4nm 8nm, 16 nm, 32nm and 50nm in diameter. The FCAS is an optical particle counter that detects and sizes particles in the 100 to 1000 nm diameter range. By considering counting statistics, it is possible to identify those time intervals during which the counts in the 4 nm channel exceeded the counts in the 8 nm channel. Thus it is possible to clearly identify when there are particles in the 4 to 8 nm diameter range present in the size distribution. These particles have a short lifetime due to coagulation and their presence is taken to be evidence of recent new particle formation (NPF). The measurements made in January-February are contrasted with measurements made in June and August and differences are seen in the frequency with which NPF occurred. We examine the roles of air mass origin as determined by back trajectories, pre-existing aerosol surface area, atmospheric motions and trace gas concentrations in contributing to this difference.

Interruption of Hydrogen Bonding Networks of Water in Carbon Nanotubes Due to Strong Hydration Shell Formation.

PubMed

Oya, Yoshifumi; Hata, Kenji; Ohba, Tomonori

2017-10-24

We present the structures of NaCl aqueous solution in carbon nanotubes with diameters of 1, 2, and 3 nm based on an analysis performed using X-ray diffraction and canonical ensemble Monte Carlo simulations. Anomalously longer nearest-neighbor distances were observed in the electrolyte for the 1-nm-diameter carbon nanotubes; in contrast, in the 2 and 3 nm carbon nanotubes, the nearest-neighbor distances were shorter than those in the bulk electrolyte. We also observed similar properties for water in carbon nanotubes, which was expected because the main component of the electrolyte was water. However, the nearest-neighbor distances of the electrolyte were longer than those of water in all of the carbon nanotubes; the difference was especially pronounced in the 2-nm-diameter carbon nanotubes. Thus, small numbers of ions affected the entire structure of the electrolyte in the nanopores of the carbon nanotubes. The formation of strong hydration shells between ions and water molecules considerably interrupted the hydrogen bonding between water molecules in the nanopores of the carbon nanotubes. The hydration shell had a diameter of approximately 1 nm, and hydration shells were thus adopted for the nanopores of the 2-nm-diameter carbon nanotubes, providing an explanation for the large difference in the nearest-neighbor distances between the electrolyte and water in these nanopores.

Characterization of Aerosols of Titanium Dioxide Nanoparticles Following Three Generation Methods Using an Optimized Aerosolization System Designed for Experimental Inhalation Studies

PubMed Central

Pujalté, Igor; Serventi, Alessandra; Noël, Alexandra; Dieme, Denis; Haddad, Sami; Bouchard, Michèle

2017-01-01

Nanoparticles (NPs) can be released in the air in work settings, but various factors influence the exposure of workers. Controlled inhalation experiments can thus be conducted in an attempt to reproduce real-life exposure conditions and assess inhalation toxicology. Methods exist to generate aerosols, but it remains difficult to obtain nano-sized and stable aerosols suitable for inhalation experiments. The goal of this work was to characterize aerosols of titanium dioxide (TiO2) NPs, generated using a novel inhalation system equipped with three types of generators—a wet collision jet nebulizer, a dry dust jet and an electrospray aerosolizer—with the aim of producing stable aerosols with a nano-diameter average (<100 nm) and monodispersed distribution for future rodent exposures and toxicological studies. Results showed the ability of the three generation systems to provide good and stable dispersions of NPs, applicable for acute (continuous up to 8 h) and repeated (21-day) exposures. In all cases, the generated aerosols were composed mainly of small aggregates/agglomerates (average diameter <100 nm) with the electrospray producing the finest (average diameter of 70–75 mm) and least concentrated aerosols (between 0.150 and 2.5 mg/m3). The dust jet was able to produce concentrations varying from 1.5 to 150 mg/m3, and hence, the most highly concentrated aerosols. The nebulizer collision jet aerosolizer was the most versatile generator, producing both low (0.5 mg/m3) and relatively high concentrations (30 mg/m3). The three optimized generators appeared suited for possible toxicological studies of inhaled NPs. PMID:29051446

Exposure assessment of nano-sized and respirable particles at different workplaces

NASA Astrophysics Data System (ADS)

Tsai, Chuen-Jinn; Huang, Cheng-Yu; Chen, Sheng-Chieh; Ho, Chi-En; Huang, Cheng-Hsiung; Chen, Chun-Wan; Chang, Cheng-Ping; Tsai, Su-Jung; Ellenbecker, Michael J.

2011-09-01

In this study, nanoparticle (NP, diameter < 100 nm) and respirable particles measurements were conducted at three different nanopowder workplaces, including the mixing area of a nano-SiO2-epoxy molding compound plant (primary diameter: 15 nm), bagging areas of a nano-carbon black (nano-CB) (primary diameter: 32 nm) and a nano-CaCO3 (primary diameter: 94 nm) manufacturing plant. Chemical analysis of respirable particle mass (RPM) and NPs was performed to quantify the content of manufactured nanoparticles in the collected samples. Nanopowder products obtained from the plants were used in the laboratory dustiness testing using a rotating drum tester to obtain particle mass and number distributions. The obtained laboratory data were then used to elucidate the field data. Both field and laboratory data showed that NP number and mass concentrations of manufactured materials were close to the background level. Number concentration was elevated only for particles with the electrical mobility diameter >100 nm during bagging or feeding processes, unless there were combustion-related incidental sources existed. Large fraction of nanomaterials was found in the RPM due to agglomeration of nanomaterials or attachment of nanomaterials to the larger particles. From this study, it is concluded that RPM concentration measurements are necessary for the exposure assessment of nanoparticles in workplaces.

White light supercontinuum generation in a Y-shaped microstructured tapered fiber pumped at 1064 nm.

PubMed

Cascante-Vindas, J; Díez, A; Cruz, J L; Andrés, M V

2010-07-05

We report the generation of supercontinuum in a Ge-doped Y-shape tapered fiber pumped at 1064 nm in the ns pump regime. The taper was designed to have long taper transitions and a taper waist with a core diameter of 0.9 mum. The large air-filling fraction and diameter of the air-hole microstructure reduces the confinement loss at long wavelengths so, enabling the extension of the spectrum to longer wavelengths. Along the taper transition the zero-dispersion wavelength decreases as the diameter of the taper becomes smaller. The spectral components generated along the taper transition pump the taper waist, enhancing the generation of short wavelengths. A flat spectrum spanning from 420 nm to 1850 nm is reported.

Gas sensing with gold-decorated vertically aligned carbon nanotubes

PubMed Central

Mudimela, Prasantha R; Scardamaglia, Mattia; González-León, Oriol; Reckinger, Nicolas; Snyders, Rony; Llobet, Eduard; Colomer, Jean-François

2014-01-01

Summary Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm) synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2) at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length. PMID:24991529

Gas sensing with gold-decorated vertically aligned carbon nanotubes.

PubMed

Mudimela, Prasantha R; Scardamaglia, Mattia; González-León, Oriol; Reckinger, Nicolas; Snyders, Rony; Llobet, Eduard; Bittencourt, Carla; Colomer, Jean-François

2014-01-01

Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm) synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2) at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length.

Selective-area growth of GaN nanocolumns on Si(111) substrates for application to nanocolumn emitters with systematic analysis of dislocation filtering effect of nanocolumns

NASA Astrophysics Data System (ADS)

Kishino, Katsumi; Ishizawa, Shunsuke

2015-06-01

The growth of highly uniform arrays of GaN nanocolumns with diameters from 122 to 430 nm on Si (111) substrates was demonstrated. The employment of GaN film templates with flat surfaces (root mean square surface roughness of 0.84 nm), which were obtained using an AlN/GaN superlattice (SL) buffer on Si, contributed to the high-quality selective-area growth of nanocolumns using a thin Ti mask of 5 nm thickness by rf-plasma-assisted molecular beam epitaxy. Although the GaN template included a large number of dislocations (dislocation density ˜1011 cm-2), the dislocation filtering effect of nanocolumns was enhanced with decreasing nanocolumn diameters (D). Systematic transmission electron microscopy (TEM) observation enabled us to explain the dependence of the dislocation propagation behavior in nanocolumns on the nanocolumn diameter for the first time. Plan-view TEM analysis was performed for nanocolumns with D = 120-324 nm by slicing the nanocolumns horizontally at a height of ˜300 nm above their bottoms and dislocation propagation through the nanocolumns was analyzed by the cross-sectional TEM observation of nanocolumns with D ˜ 200 nm. It was clarified that dislocations were effectively filtered in the bottom 300 nm region of the nanocolumns, the dislocation density of the nanocolumns decreased with decreasing D, and for narrow nanocolumns with D < 200 nm, dislocation-free crystals were obtained in the upper part of the nanocolumns. The dramatic improvement in the emission properties of GaN nanocolumns observed with decreasing diameter is discussed in relation to the decreased dislocation density. The laser action of InGaN/GaN-based nanocolumn arrays with a nanocolumn diameter of 170 nm and a period of 200 nm on Si under optical excitation was obtained with an emission wavelength of 407 nm. We also fabricated red-emitting InGaN-based nanocolumn light-emitting diodes on Si that operated at a wavelength of 652 nm, demonstrating vertical conduction through the AlN/GaN SL buffer to the Si substrate.

The Three-Dimensional Distribution of αA-Crystalline in Rat Lenses and Its Possible Relation to Transparency

PubMed Central

Zampighi, Guido A.; Zampighi, Lorenzo; Lanzavecchia, Salvatore

2011-01-01

Lens transparency depends on the accumulation of massive quantities (600–800 mg/ml) of twelve primary crystallines and two truncated crystallines in highly elongated “fiber” cells. Despite numerous studies, major unanswered questions are how this heterogeneous group of proteins becomes organized to bestow the lens with its unique optical properties and how it changes during cataract formation. Using novel methods based on conical tomography and labeling with antibody/gold conjugates, we have profiled the 3D-distribution of the αA-crystalline in rat lenses at ∼2 nm resolutions and three-dimensions. Analysis of tomograms calculated from lenses labeled with anti-αA-crystalline and gold particles (∼3 nm and ∼7 nm diameter) revealed geometric patterns shaped as lines, isosceles triangles and polyhedrons. A Gaussian distribution centered at ∼7.5 nm fitted the distances between the ∼3 nm diameter gold conjugates. A Gaussian distribution centered at ∼14 nm fitted the Euclidian distances between the smaller and the larger gold particles and another Gaussian at 21–24 nm the distances between the larger particles. Independent of their diameters, tethers of 14–17 nm in length connected files of gold particles to thin filaments or clusters to ∼15 nm diameter “beads.” We used the information gathered from tomograms of labeled lenses to determine the distribution of the αA-crystalline in unlabeled lenses. We found that αA-crystalline monomers spaced ∼7 nm or αA-crystalline dimers spaced ∼15 nm center-to-center apart decorated thin filaments of the lens cytoskeleton. It thus seems likely that lost or gain of long-range order determines the 3D-structure of the fiber cell and possible also cataract formation. PMID:21909355

Atomic layer deposition as pore diameter adjustment tool for nanoporous aluminum oxide injection molding masks.

PubMed

Miikkulainen, Ville; Rasilainen, Tiina; Puukilainen, Esa; Suvanto, Mika; Pakkanen, Tapani A

2008-05-06

The wetting properties of polypropylene (PP) surfaces were modified by adjusting the dimensions of the surface nanostructure. The nanostructures were generated by injection molding with nanoporous anodized aluminum oxide (AAO) as the mold insert. Atomic layer deposition (ALD) of molybdenum nitride film was used to control the pore diameters of the AAO inserts. The original 50-nm pore diameter of AAO was adjusted by depositing films of thickness 5, 10, and 15 nm on AAO. Bis(tert-butylimido)-bis(dimethylamido)molybdenum and ammonia were used as precursors in deposition. The resulting pore diameters in the nitride-coated AAO inserts were 40, 30, and 20 nm, respectively. Injection molding of PP was conducted with the coated inserts, as well as with the non-coated insert. Besides the pore diameter, the injection mold temperature was varied with temperatures of 50, 70, and 90 degrees C tested. Water contact angles of PP casts were measured and compared with theoretical contact angles calculated from Wenzel and Cassie-Baxter theories. The highest contact angle, 140 degrees , was observed for PP molded with the AAO mold insert with 30-nm pore diameter. The Cassie-Baxter theory showed better fit than the Wenzel theory to the experimental values. With the optimal AAO mask, the nanofeatures in the molded PP pieces were 100 nm high. In explanation of this finding, it is suggested that some sticking and stretching of the nanofeatures occurs during the molding. Increase in the mold temperature increased the contact angle.

Influence of the impact energy on the pattern of blood drip stains

NASA Astrophysics Data System (ADS)

Smith, F. R.; Nicloux, C.; Brutin, D.

2018-01-01

The maximum spreading diameter of complex fluid droplets has been extensively studied and explained by numerous physical models. This research focuses therefore on a different aspect, the bulging outer rim observed after evaporation on the final dried pattern of blood droplets. A correlation is found between the inner diameter, the maximum outer diameter, and the impact speed. This shows how the drying mechanism of a blood drip stain is influenced by the impact energy, which induces a larger spreading diameter and thus a different redistribution of red blood cells inside the droplet. An empirical relation is established between the final dried pattern of a passive bloodstain and its impact speed, yielding a possible forensic application. Indeed, being able to relate accurately the energy of the drop with its final pattern would give a clue to investigators, as currently no such simple and accurate tool exists.

Effect of distributor on performance of a continuous fluidized bed dryer

NASA Astrophysics Data System (ADS)

Yogendrasasidhar, D.; Srinivas, G.; Pydi Setty, Y.

2018-03-01

Proper gas distribution is very important in fluidized bed drying in industrial practice. Improper distribution of gas may lead to non-idealities like channeling, short circuiting and accumulation which gives rise to non-uniform quality of dried product. Gas distribution depends on the distributor plate used. Gas distribution mainly depends on orifice diameter, number of orifices and opening area of the distributor plate. Small orifice diameter leads to clogging, and a large orifice diameter gives uneven distribution of gas. The present work involves experimental studies using different distributor plates and simulation studies using ASPEN PLUS steady state simulator. The effect of various parameters such as orifice diameter, number of orifices and the opening area of the distributor plate on the performance of fluidized bed dryer have been studied through simulation and experimentation. Simulations were carried out (i) with increasing air inlet temperature to study the characteristics of solid temperature and moisture in outlet (ii) with increasing orifice diameter and (iii) with increase in number orifices to study the solid outlet temperature profiles. It can be observed from the simulation that, an increase in orifice diameter and number orifices increases solid outlet temperature upto certain condition and then after there is no effect with further increase. Experiments were carried out with increasing opening area (3.4 to 42%) in the form of increasing orifice diameter keeping the number of orifices constant and increasing number of orifices of the distributor plate keeping the orifice diameter constant. It can be seen that the drying rate and solid outlet temperature increase upto certain condition and then after with further increase in the orifice diameter and number of orifices, the change in the drying rate and solid outlet temperature observed is little. The optimum values of orifice diameter and number of orifices from experimentation are found to be 5 mm and 60 (22% opening area).

High-aspect-ratio and highly ordered 15-nm porous alumina templates.

PubMed

Martín, Jaime; Manzano, Cristina V; Caballero-Calero, Olga; Martín-González, Marisol

2013-01-01

Ordered anodic aluminum oxide (AAO) templates with pores <15 nm in diameter and an aspect ratio (length-to-diameter ratio) above 3 × 10(3) have been fabricated using a nonlithographic approach; specifically, by anodizing aluminum in an ethylene-glycol-containing sulfuric acid electrolyte. The pores are the smallest in diameter reported for a self-ordered AAO without pore aspect-ratio limitations and good ordering, which opens up the possibility of obtaining nanowire arrays in the quantum confinement regime that is of interest for efficient thermoelectric generators. The effect of the ethylene glycol addition on both the pore diameter and the ordering is evaluated and discussed. Moreover, 15-nm-diameter Bi(2)Te(3) and poly(3-hexyl thiophene) (P3HT) nanowires have been prepared using these AAO templates. As known, Bi(2)Te(3) is currently the most efficient thermoelectric bulk material for room-temperature operations and, according with theory, its Seebeck coefficient should be increased when it is confined to nanowires with diameters close to 10 nm. On the other hand, P3HT is one of the main candidates for integrating organic photovoltaic and thermoelectric devices, and its properties are also proposed to increase when it is confined to nanoscale structures, mainly due to molecular orientation effects.

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

Wang, Bochong; Kubota, Hitoshi, E-mail: hit-kubota@aist.go.jp; Yakushiji, Kay

The dependence on diameter of the emission power in MgO-based nano-pillar spin torque oscillators (STOs) was systematically investigated. A maximum emission power of over 2.5 μW was obtained around 300 nm in diameter, which is the largest reported to date among the out-of-plane precession STOs. By analyzing physical quantities, precession cone angle of the free-layer magnetization was evaluated. In the diameter range below 300 nm, the increase in power was mainly due to the increase of the injected current. The power decrease above 300 nm is possibly attributed to the decrease in the averaged precession cone angle, suggesting spatial phase difference of magnetization precession.more » This study provides the method for estimating the optimum STO diameter, which is of great importance in practical use.« less

Immersion and dry scanner extensions for sub-10nm production nodes

NASA Astrophysics Data System (ADS)

Weichselbaum, Stefan; Bornebroek, Frank; de Kort, Toine; Droste, Richard; de Graaf, Roelof F.; van Ballegoij, Rob; Botter, Herman; McLaren, Matthew G.; de Boeij, Wim P.

2015-03-01

Progressing towards the 10nm and 7nm imaging node, pattern-placement and layer-to-layer overlay requirements keep on scaling down and drives system improvements in immersion (ArFi) and dry (ArF/KrF) scanners. A series of module enhancements in the NXT platform have been introduced; among others, the scanner is equipped with exposure stages with better dynamics and thermal control. Grid accuracy improvements with respect to calibration, setup, stability, and layout dependency tighten MMO performance and enable mix and match scanner operation. The same platform improvements also benefit focus control. Improvements in detectability and reproducibility of low contrast alignment marks enhance the alignment solution window for 10nm logic processes and beyond. The system's architecture allows dynamic use of high-order scanner optimization based on advanced actuators of projection lens and scanning stages. This enables a holistic optimization approach for the scanner, the mask, and the patterning process. Productivity scanner design modifications esp. stage speeds and optimization in metrology schemes provide lower layer costs for customers using immersion lithography as well as conventional dry technology. Imaging, overlay, focus, and productivity data is presented, that demonstrates 10nm and 7nm node litho-capability for both (immersion & dry) platforms.

Fresnel Lens Characterization for Potential Use in an Unpiloted Atmospheric Vehicle DIAL Receiver System

NASA Technical Reports Server (NTRS)

Fastig, Shlomo; Deoung, Russell J.

1998-01-01

Acrylic plastic Fresnel lenses are very light and can have large diameters. Such lenses could be used in lidar telescope receivers if the focal spot is not too large or distorted. This research effort characterizes the focal spot diameter produced by a Fresnel lens with a diameter of 30.5 cm (12 in.). It was found that the focal spot diameter varied from 1.2 mm at 750 nm to 1.6 mm at 910 nm. The focal spot was irregular and not easily described by a Gaussian profile.

Cytotoxic and anti-angiogenic paclitaxel solubilized and permeation-enhanced by natural product nanoparticles

PubMed Central

Liu, Zhijun; Zhang, Fang; Koh, Gar Yee; Dong, Xin; Hollingsworth, Javoris; Zhang, Jian; Russo, Paul S.; Yang, Peiying; Stout, Rhett W.

2014-01-01

Paclitaxel (PTX) is one of the most potent intravenous chemotherapeutic agents to date, yet an oral formulation has been problematic due to its low solubility and permeability. Using the recently discovered solubilizing properties of rubusoside (RUB), we investigated this unique PTX-RUB formulation. Paclitaxel was solubilized by RUB in water to levels of 1.6 to 6.3 mg/mL at 10 to 40% weight/volume. These, nanomicellar, PTX-RUB complexes were dried to a powder which was subsequently reconstituted in physiologic solutions. After 2.5 hrs in gastric fluid 85 to 99% of PTX-RUB remained soluble, while 79 to 96% remained soluble in intestinal fluid. The solubilization of PTX was mechanized by the formation of water-soluble spherical nanomicelles between PTX and RUB with an average diameter of 6.6 nm. Compared with Taxol®, PTX-RUB nanoparticles were nearly four times more permeable in Caco-2 cell monocultures. In a side-by-side comparison with DMSO-solubilized PTX, PTX-RUB maintained the same level of cytotoxicity against three human cancer cell lines with IC50 values ranging from 4 nM to 20 nM. Additionally, tubular formation and migration of HUVECs were inhibited at levels as low as 5 nM. These chemical and biological properties demonstrated by the PTX-RUB nanoparticles may improve oral bioavailability and enable further pharmacokinetic, toxicologic, and efficacy investigations. PMID:25243454

Spontaneous and controlled-diameter synthesis of single-walled and few-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Inoue, Shuhei; Lojindarat, Supanat; Kawamoto, Takahiro; Matsumura, Yukihiko; Charinpanitkul, Tawatchai

2018-05-01

In this study, we explored the spontaneous and controlled-diameter growth of carbon nanotubes. We evaluated the effects of catalyst density, reduction time, and a number of catalyst coating on the substrate (for multi-walled carbon nanotubes) on the diameter of single-walled carbon nanotubes and the number of layers in few-walled carbon nanotubes. Increasing the catalyst density and reduction time increased the diameters of the carbon nanotubes, with the average diameter increasing from 1.05 nm to 1.86 nm for single-walled carbon nanotubes. Finally, we succeeded in synthesizing a significant double-walled carbon nanotube population of 24%.

Gold Nanoparticles of Diameter 13 nm Induce Apoptosis in Rabbit Articular Chondrocytes

NASA Astrophysics Data System (ADS)

Huang, Hao; Quan, Ying-yao; Wang, Xiao-ping; Chen, Tong-sheng

2016-05-01

Gold nanoparticles (AuNPs) have been widely used in biomedical science including antiarthritic agents, drug loading, and photothermal therapy. In this report, we studied the effects of AuNPs with diameters of 3, 13, and 45 nm, respectively, on rabbit articular chondrocytes. AuNPs were capped with citrate and their diameter and zeta potential were measured by dynamic light scattering (DLS). Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assay after the rabbit articular chondrocytes were pre-incubated with 3, 13, and 45 nm AuNPs, respectively, for 24 h. Flow cytometry (FCM) analysis with annexin V/propidium iodide (PI) double staining and fluorescence imaging with Hoechst 33258 staining were used to determine the fashion of AuNPs-induced chondrocyte death. Further, 13 nm AuNPs (2 nM) significantly induced chondrocyte death accompanying apoptotic characteristics including mitochondrial damage, externalization of phosphatidylserine and nuclear concentration. However, 3 nm AuNPs (2 nM) and 45 nm (0.02 nM) AuNPs did not induce cytotoxicity in chondrocytes. Although 13 nm AuNPs (2 nM) increased the intracellular reactive oxygen species (ROS) level, pretreatment with Nacetyl cysteine (NAC), a ROS scavenger, did not prevent the cytotoxicity induced by 13 nm AuNPs, indicating that 13 nm AuNPs (2 nM) induced ROS-independent apoptosis in chondrocytes. These results demonstrate the size-dependent cytotoxicity of AuNPs in chondrocytes, which must be seriously considered when using AuNPs for treatment of osteoarthritis (OA).

Hygroscopicity- and Size-Resolved Measurements of Submicron Aerosol on the East Coast of the United States

NASA Astrophysics Data System (ADS)

Phillips, B. N.; Royalty, T. M.; Dawson, K. W.; Reed, R.; Petters, M. D.; Meskhidze, N.

2018-02-01

Atmospheric measurements of aerosol size-resolved hygroscopicity at submicron sizes are carried out at the United States Army Corps of Engineers Field Research Facility in Duck, North Carolina. The scientific aim of the field deployment is to gain improved understanding of the springtime advection of aerosols from the East Coast of the United States over the Atlantic and help to constrain assessments of anthropogenic particle contributions to the marine boundary layer aerosol budget. Air mass back trajectories show that the aerosol sampled at the coast is largely of continental origin that either gets transported directly from the land or spends some time over the Atlantic Ocean. Aerosol size-resolved hygroscopicity measurements are consistent with air masses of both continental and marine background that are heavily influenced by the continental outflow. Aitken and accumulation mode mean diameters range from 49.1 ± 1.7 nm to 66.9 ± 0.8 nm and 142.8 ± 1.1 nm to 155.0 ± 2.8 nm, respectively. Hygroscopicity distributions for 96 nm, 188 nm, and 284 nm dry-sized particles show the mode hygroscopicity parameter range from 0.20 ± 0.01 to 0.54 ± 0.03, suggesting the presence of anthropogenic aerosols. We have used the method described by Royalty et al. (2017) to decompose the hygroscopicity distributions into three distinct classes based on the ambient aerosol hygroscopic properties relative to the hygroscopic properties of a reference compound. The method shows that continental outflow heavily influences aerosol chemical and physical properties at the East Coast, with hygroscopicities of submicron aerosols consistent with sulfate-containing species (62% to 83%), with small contributions from sodium- and carbon-containing particles (up to 9% and 37%, respectively).

A Year-round Observation of Size Distribution of Aerosol Particles at the Cape Ochiishi, Japan

NASA Astrophysics Data System (ADS)

Miura, K.; Mukai, H.; Hashimoto, S.; Uematsu, M.

2010-12-01

New particle formation by nucleation of gas-phase compounds emitted from marine biogenic sources is very important for climate change. To clarify the mechanism of the formation, size distributions of submicron aerosols have been measured at the Cape Ochiishi, facing the North Western Pacific Ocean where primary productivity is high. A test observation was done from 22nd May to 18th June 2008 and a year-round observation has been performed from 16th October 2009 to 7th September 2010. The size distribution from 10 nm to 487 nm in diameter was measured with a scanning mobility particle sizer (SMPS, TSI 3034). Sample air was dried to lower than 40%. Transport of sulfate, organic carbon (OC), and black carbon (BC) was estimated with Chemical weather FORecasting System (CFORS), developed by Prof. Uno, Kyushu University, Japan. Existence of inversion layer was estimated with temperature profile measured at surface, 10m, 30m, and 50m in altitude. The burst of the particles smaller than 20nm in diameter continuing longer than 3 hrs was observed ten times until 3rd November 2009. Two were observed in early summer and the other was in autumn. Banana shape was faintly observed five times. Transport of sulfate, OC, and BC was observed 3, 8, 9 times, respectively. Source of air mass was estimated with these elements, weather map, and wind direction. Five air masses were estimated to continental. Clearly nucleation related to marine sources was not observed. The size distribution of burst evens of maritime and continental air mass showed the shift of mode to larger diameter. Strong inversion of temperature was observed once. The value of size distribution did not show high. Minimum value of size distribution was observed in the strong rain on 27th October. Acknowledgments This study was partly supported by the Grant-in-Aids for Scientific Research on Priority Areas from the Ministry of Education, Culture, Sports, Science and Technology, Japan (18067005). The observation was performed at the monitoring station of the National Institute for Environmental Studies.

Nanohole and dot patterning processes on quartz substrate by R-θ electron beam lithography and nanoimprinting

NASA Astrophysics Data System (ADS)

Watanabe, Tsuyoshi; Taniguchi, Kazutake; Suzuki, Kouta; Iyama, Hiromasa; Kishimoto, Shuji; Sato, Takashi; Kobayashi, Hideo

2016-06-01

Fine hole and dot patterns with bit pitches (bp’s) of less than 40 nm were fabricated in the circular band area of a quartz substrate by R-θ electron beam lithography (EBL), reactive ion etching (RIE), and nanoimprinting. These patterning processes were studied to obtain minimum pitch sizes of hole and dot patterns without pattern collapse. The patterning on the circular band was aimed to apply these patterning processes to future high-density bit-patterned media (BPM) for hard disk drive (HDD) and permanent memory for the long life archiving of digital data. In hole patterning, a minimum-22-nm-bp and 8.2-nm-diameter pattern (1.3 Tbit/in.2) was obtained on a quartz substrate by optimizing the R-θ EBL and RIE processes. Dot patterns were replicated on another quartz substrate by nanoimprinting using a hole-patterned quartz substrate as a master mold followed by RIE. In dot patterning, a minimum-30-nm-bp and 18.5-nm-diameter pattern (0.7 Tbit/in.2) was obtained by introducing new descum conditions. It was observed that the minimum bp of successful patterning increased as the fabrication process proceeded, i.e., from 20 nm bp in the first EBL process to 30 nm bp in the last quartz dot patterning process. From the measured diameters of the patterns, it was revealed that pattern collapse was apt to occur when the value of average diameter plus 3 sigma of diameter was close to the bp. It was suggested that multiple fabrication processes caused the degradation of pattern quality; therefore, hole patterning is more suitable than dot patterning for future applications owing to the lower quality degradation by its simple fabrication process.

Polyhedral protein cages encase synaptic vesicles and participate in their attachment to the active zone.

PubMed

Zampighi, G A; Fisher, R S

1997-08-01

In an effort to elucidate the interactions between synaptic vesicles and the membrane of the active zone, we have investigated the structure of interneuronal asymmetric synapses in the neocortex of adult rats using thin-sectioning, freeze-fracture, and negative staining electron microscopy. We identified three subtypes of spherical synaptic vesicles. Type I were agranular vesicles of 47.5 +/- 3.8 nm (mean SD, n = 24) in diameter usually seen aggregated in clusters in the presynaptic bouton. Type II synaptic vesicles were composed of a approximately 45-nm-diameter lipid bilayer sphere encased in a cage 77 +/- 4.6 nm (mean SD, n = 42) in diameter. The cage was composed of open-faced pentamers 20-22 nm/side arranged as a regular polyhedron. Type II caged vesicles were found in clusters at the boutons, adhered to the active zone, and were also present in axons. Type III synaptic vesicles appeared as electron-dense spheres 60-75 nm in diameter abutted to the membrane of the active zone. Clathrin-coated vesicles and pits of 116.6 +/- 9 nm (mean SD, n = 14) in diameter were also present in both the pre- and postsynaptic sides. Freeze-fracture showed that some intrinsic membrane proteins in the active zone were arranged as pentamers exhibiting the same dimension of those forming cages (approximately 22 nm/side). From these data, we concluded that: (a) the presynaptic bouton contains a heterogeneous population of "caged" and "plain" synaptic vesicles and (b) type II synaptic vesicles bind to receptors in the active zone. Therefore, current models of transmitter release should take into account the substantial heterogeneity of the vesicle population and the binding of vesicular cages to the membrane of the active zone.

Biosynthesis of highly porous bacterial cellulose nanofibers

NASA Astrophysics Data System (ADS)

Hosseini, Hadi; Kokabi, Mehrdad; Mousavi, Seyyed Mohammad

2018-01-01

Bacterial cellulose nanofibers (BCNFs) as a sustainable and biodegradable polymer has drawn tremendous research attention in tissue engineering, bacterial sensors and drug delivery due to its extraordinary properties such as high purity, high crystallinity, high water absorption capacity and excellent mechanical strength in the wet state. This awesome properties, is attributed to BCNFs structure, therefore its characterization is important. In this work, the bacterial strain, Gluconacetobacter xylinus (PTCC 1734, obtained from Iranian Research Organization for Science and Technology (IROST)), was used to produce BCNFs hydrogel using bacterial fermentation under static condition at 29 °C for 10 days in the incubator. Then, the biosynthesized BCNFs wet gel, were dried at ambient temperature and pressure and characterized using Brunauer-Emmett-Teller (BET) and Field emission scanning electron microscopy (FE-SEM) analysis. FESEM image displayed highly interconnected and porous structure composed of web-like continuous, nanofibers with an average diameter of 48.5±2.1 nm. BET result analysis depicted BCNFs dried at ambient conditions had IV isotherm type, according to the IUPAC classification, indicating that BCNFs dried at ambient condition is essentially mesoporous. On the other hand, BET results depicted, mesoporous structure is around 85%. In addition, Specific surface area (SBET) obtained 81.45 m2/g. These results are in accordance with the FESEM observation.

Nanowire sensors and arrays for chemical/biomolecule detection

NASA Technical Reports Server (NTRS)

Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Ramanathan, K.; Bangar, M. A.; Chen, W.; Mulchandan, A.; Myung, N. V.

2005-01-01

We report electrochemical growth of single nanowire based sensors using e-beam patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable high density arrays. The electrodeposition technique results in nanowires with controlled dimensions, positions, alignments, and chemical compositions. Using this technique, we have fabricated single palladium nanowires with diameters ranging between 75 nm and 300 nm and conducting polymer nanowires (polypyrrole and polyaniline) with diameters between 100 nm and 200 nm. Using these single nanowires, we have successfully demonstrated gas sensing with Pd nanowires and pH sensing with polypirrole nanowires.

Low-temperature synthesis of single-walled carbon nanotubes with a narrow diameter distribution using size-classified catalyst nanoparticles

NASA Astrophysics Data System (ADS)

Kondo, Daiyu; Sato, Shintaro; Awano, Yuji

2006-05-01

Single-walled carbon nanotubes (SWNTs) with a narrow diameter distribution have been synthesized by hot-filament chemical vapor deposition using acetylene at 590 °C. Iron nanoparticles with diameters of 1.6, 2.0, 2.5, 5.0 and 10 nm (standard deviation: ≈10%) obtained with a differential mobility analyzer were used as a catalyst without any supporting materials on a substrate. SWNTs were obtained from 2.0 nm or smaller particles. The ratio of G band to D band in Raman spectra was as high as 35 without purification, indicating that high-quality SWNTs were synthesized. The SWNT diameters correlated with the particle diameters, demonstrating diameter-controlled SWNT growth.

Preparation, assessment, and comparison of α-chitin nano-fiber films with different surface charges.

PubMed

Zhang, Yan; Jiang, Jie; Liu, Liang; Zheng, Ke; Yu, Shiyuan; Fan, Yimin

2015-01-01

Chitin nano-fibers with positive and negative charges have been, respectively, produced from partially deacetylated and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidized α-chitin. The average diameters and lengths of the TEMPO-oxidized chitin nano-fibers (TOChN) were 14 ± 4.3 and 190 ± 140 nm, respectively, and the average diameters and lengths of the partially deacetylated chitin nano-fibers (DEChN) were 6 ± 1.7 and 320 ± 105 nm, respectively. A partially deacetylated chitin nano-fiber film (DEChN-F), a TEMPO-mediated and oxidized chitin nano-fiber film (TOChN-F), and a composite film (DE-TO-ChN-F) consisting of a combination of the two were prepared by drying the dispersions at 40 °C. The DEChN-F, TOChN-F, and DE-TO-ChN-F all have similar tensile strengths of approximately 90 MPa; however, the chitosan film (Chitosan-F) had a tensile strength of approximately 30 MPa. In addition, TOChN-F and DE-TO-ChN-F have a thermal weight loss at 210 °C, and DEChN-F has a thermal weight loss at 280 °C. DEChN-F was found to have antimicrobial activity with regards to Escherichia coli. Finally, the chitin nano-fiber films could be slightly degraded by cellulase, which provided a novel biological performance of the chitin nano-material.

Preparation, assessment, and comparison of α-chitin nano-fiber films with different surface charges

NASA Astrophysics Data System (ADS)

Zhang, Yan; Jiang, Jie; Liu, Liang; Zheng, Ke; Yu, Shiyuan; Fan, Yimin

2015-05-01

Chitin nano-fibers with positive and negative charges have been, respectively, produced from partially deacetylated and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidized α-chitin. The average diameters and lengths of the TEMPO-oxidized chitin nano-fibers (TOChN) were 14 ± 4.3 and 190 ± 140 nm, respectively, and the average diameters and lengths of the partially deacetylated chitin nano-fibers (DEChN) were 6 ± 1.7 and 320 ± 105 nm, respectively. A partially deacetylated chitin nano-fiber film (DEChN-F), a TEMPO-mediated and oxidized chitin nano-fiber film (TOChN-F), and a composite film (DE-TO-ChN-F) consisting of a combination of the two were prepared by drying the dispersions at 40 °C. The DEChN-F, TOChN-F, and DE-TO-ChN-F all have similar tensile strengths of approximately 90 MPa; however, the chitosan film (Chitosan-F) had a tensile strength of approximately 30 MPa. In addition, TOChN-F and DE-TO-ChN-F have a thermal weight loss at 210 °C, and DEChN-F has a thermal weight loss at 280 °C. DEChN-F was found to have antimicrobial activity with regards to Escherichia coli. Finally, the chitin nano-fiber films could be slightly degraded by cellulase, which provided a novel biological performance of the chitin nano-material.

Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds.

PubMed

Rowthu, Sriharitha; Böhlen, Karl; Bowen, Paul; Hoffmann, Patrik

2015-11-11

Ceramic surface microstructuring is a rapidly growing field with a variety of applications in tribology, wetting, biology, and so on. However, there are limitations to large-area microstructuring and fabrication of three-dimensional (3D) micro free forms. Here, we present a route to obtain intricate surface structures through in situ slip casting using polydimethylsiloxane (PDMS) negative molds which are replicated from excimer laser ablated polycarbonate (PC) master molds. PC sheets are ablated with a nanosecond KrF (λ = 248 nm) excimer laser mask projection system to obtain micron-scale 3D surface features over a large area of up to 3 m(2). Complex surface structures that include 3D free forms such as 3D topography of Switzerland, shallow structures such as diffractive optical elements (60 nm step) and conical micropillars have been obtained. The samples are defect-free produced with thicknesses of up to 10 mm and 120 mm diameter. The drying process of the slip cast alumina slurry takes place as a one-dimensional process, through surface evaporation and water permeation through the PDMS membrane. This allows homogeneous one-dimensional shrinkage during the drying process, independent of the sample's lateral dimensions. A linear mass diffusion model has been proposed to predict and explain the drying process of these ceramic colloidal suspensions. The calculated drying time is linearly proportional to the height of the slurry and the thickness of the negatively structured PDMS and is validated by the experimental results. An experimentally observed optimum Sylgard PDMS thickness range of ∼400 μm to 1 mm has achieved the best quality microstructured green compacts. Further, the model predicts that the drying time is independent of the microstructured areas and was validated using experimental observations carried out with microstructured areas of 300 mm(2), 1200 mm(2), and 120 cm(2). Therefore, in principle, the structures can be further replicated in areas up to 3 m(2) with the same drying time for the same slurry height. The surface-structured ceramics display interesting wetting properties, for example, eicosane-coated mesoporous microstructured alumina shows superhydrophobic behavior. Additionally, ceramic bulk samples could be further used as second-generation very hard and low-wear molds for further microfabrication.

In Situ Raman Analysis of CO₂-Assisted Drying of Fruit-Slices.

PubMed

Braeuer, Andreas Siegfried; Schuster, Julian Jonathan; Gebrekidan, Medhanie Tesfay; Bahr, Leo; Michelino, Filippo; Zambon, Alessandro; Spilimbergo, Sara

2017-05-15

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO₂) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO₂ into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve.

Passive bloodstains: from an impact energy to a final dried pattern

NASA Astrophysics Data System (ADS)

Smith, Fiona; Brutin, David

2016-11-01

Tracking down the origin of a blood droplet present on a crime scene has become of major importance in bloodstain pattern analysis. Passive bloodstains are not yet well understood. Accordingly the purpose of this research is to provide new tools to forensic investigators in the analysis of bloodstains arising from blood droplets dripping naturally. The study aims to understand the link between the final dried pattern of a passive bloodstain and its impact energy. Currently no such tool exists, and no correlation has yet been proven. This research was therefore focusing on a new parameter, the thicker outer rim observed on the dried final pattern. To do so, we created several passive bloodstains with different impact energies. A correlation was highlighted between the inner diameter, the maximum spreading diameter, the initial diameter of a blood droplet and its impact energy. This correlation shows how the drying mechanism of a blood droplet is influenced by its impact energy as it alters the red blood cells dispersion inside the droplet. The biological deposit and the final dried pattern are subsequently modified. ANR funded project: D-Blood Project.

Enhancement of the Wear Resistance and Microhardness of Aluminum Alloy by Nd:YaG Laser Treatment

PubMed Central

Hussein, Haitham T.; Kadhim, Abdulhadi; Al-Amiery, Ahmed A.; Kadhum, Abdul Amir H.; Mohamad, Abu Bakar

2014-01-01

Influence of laser treatment on mechanical properties, wear resistance, and Vickers hardness of aluminum alloy was studied. The specimens were treated by using Nd:YaG laser of energy 780 mj, wavelength 512 nm, and duration time 8 ns. The wear behavior of the specimens was studied for all specimens before and after treatment by Nd:YaG laser and the dry wear experiments were carried out by sing pinon-disc technique. The specimens were machined as a disk with diameter of 25 mm and circular groove in depth of 3 mm. All specimens were conducted by scanning electron microscopy (SEM), energy-dispersive X-ray florescence analysis (EDS), optical microscopy, and Vickers hardness. The results showed that the dry wear rate was decreased after laser hardening and increased Vickers hardness values by ratio of 2.4 : 1. The results showed that the values of wear rate for samples having circular grooves are less than samples without grooves after laser treatment. PMID:25136694

Starch nanoparticles resulting from combination of dry heating under mildly acidic conditions and homogenization.

PubMed

Kim, Jong Hun; Kim, Jiyeon; Park, Eun Young; Kim, Jong-Yea

2017-07-15

To modify starch granular structure, normal maize starch was subjected to dry heating with various amounts of 1.0M HCl (1.2, 1.4 or 1.6mL) and different treatment times (2, 4 or 8h). For all reaction conditions, at least 80% of the starch substance was recovered, and amylose and amylopectin B1 chains were preferentially cleaved. As acidic condition and/or treatment time increased, the treated granules were readily fragmented by homogenization. The treatment appeared to alter short-range crystalline structure (FT-IR), but long-range crystalline structure (XRD) remained intact. Homogenization for 60min fragmented the treated starch granules (subjected to reaction condition of 1.4mL/4h, 1.6mL/2h, and 1.6mL/4h) into nanoparticles consisting of individual platelet-like and spherical particles with diameters less than 100nm. However, the fragmentation caused obvious damage in the long-range crystalline structure of starch nanoparticles, while the short-range chain associations remained relatively intact. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gallium ion-assisted room temperature synthesis of small-diameter ZnO nanorods.

PubMed

Cho, Seungho; Kim, Semi; Lee, Kun-Hong

2011-09-15

We report a method for synthesizing small-diameter ZnO nanorods at room temperature (20 °C), under normal atmospheric pressure (1 atm), and using a relatively short reaction time (1 h) by adding gallium salts to the reaction solution. The ZnO nanorods were, on average, 92 nm in length and 9 nm in diameter and were single crystalline in nature. Quantitative analyses revealed that gallium atoms were not incorporated into the synthesized nanocrystals. On the basis of the experimental results, we propose a mechanism for the formation of small-diameter ZnO nanorods in the presence of gallium ions. The optical properties were probed by UV-Vis diffuse reflectance spectroscopy. The absorption band of the small-diameter ZnO nanorods was blue-shifted relative to the absorption band of the ~230 nm diameter ZnO nanorods (control samples). Control experiments demonstrated that the absence of metal ion-containing precipitants (except ZnO) at room temperature is essential, and that the ZnO nanorod diameter distributions were narrow for the stirred reaction solution and broad when prepared without stirring. Copyright © 2011 Elsevier Inc. All rights reserved.

Aerosol Inlet Characterization Experiment Report

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

Bullard, Robert L.; Kuang, Chongai; Uin, Janek

2017-05-01

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Aerosol Observation System inlet stack was characterized for particle penetration efficiency from 10 nm to 20 μm in diameter using duplicate scanning mobility particle sizers (10 nm-450 nm), ultra-high-sensitivity aerosol spectrometers (60 nm-μm), and aerodynamic particle sizers (0.5 μm-20 μm). Results show good model-measurement agreement and unit transmission efficiency of aerosols from 10 nm to 4 μm in diameter. Large uncertainties in the measured transmission efficiency exist above 4 μm due to low ambient aerosol signal in that size range.

Light-assisted drying (LAD) of small volume biologics: a comparison of two IR light sources

NASA Astrophysics Data System (ADS)

Young, Madison A.; Van Vorst, Matthew; Elliott, Gloria D.; Trammell, Susan R.

2016-03-01

Protein therapeutics have been developed to treat diseases ranging from arthritis and psoriasis to cancer. A challenge in the development of protein-based drugs is maintaining the protein in the folded state during processing and storage. We are developing a novel processing method, light-assisted drying (LAD), to dehydrate proteins suspended in a sugar (trehalose) solution for storage at supra-zero temperatures. Our technique selectively heats the water in small volume samples using near-IR light to speed dehydration which prevents sugar crystallization that can damage embedded proteins. In this study, we compare the end moisture content (EMC) as a function of processing time of samples dried with two different light sources, Nd:YAG (1064 nm) and Thulium fiber (1850 nm) lasers. EMC is the ratio of water to dry weight in a sample and the lower the EMC the higher the possible storage temperature. LAD with the 1064 and 1850 nm lasers yielded 78% and 65% lower EMC, respectively, than standard air-drying. After 40 minutes of LAD with 1064 and 1850 nm sources, EMCs of 0.27+/-.27 and 0.15+/-.05 gH2O/gDryWeight were reached, which are near the desired value of 0.10 gH2O/gDryWeight that enables storage in a glassy state without refrigeration. LAD is a promising new technique for the preparation of biologics for anhydrous preservation.

Optimized pulmonary gene transfection in mice by spray-freeze dried powder inhalation.

PubMed

Mohri, Kohta; Okuda, Tomoyuki; Mori, Asami; Danjo, Kazumi; Okamoto, Hirokazu

2010-06-01

Spray-freeze drying (SFD) is an attractive technique to prepare highly porous dry powders for inhalation. However, there have been few reports of its application to dry powder inhalers (DPIs). Therefore, in this study, we prepared dry plasmid DNA (pDNA) powders with different molecular ratios of chitosan to pDNA (N/P ratios) by SFD. All the pDNA powders were spherical and highly porous, with particles approximately 20-40microm in geometric diameter. The morphology changed little with the alteration of the N/P ratio. On electrophoresis, a band of linear pDNA was detected in the preparation without chitosan, suggesting the destabilization of pDNA through SFD. However, the addition of chitosan protected pDNA from destabilization. Moreover, the pDNA powders were evaluated for pulmonary gene transfection efficiency using an in vivo dual imaging technique for gene DPIs developed previously. Maximum gene expression was observed at 9-12h following pulmonary administration of the powders into mice. The powder with the N/P ratio of 10 had the highest gene transfection efficiency. A higher affinity of chitosan for pDNA and a smaller (approximately 100nm) pDNA/chitosan complex (N/Pf10) were found at pH 6.5 (in lung) than at pH 7.4 (in physiological conditions), suggesting that the effective compaction of pDNA by chitosan at the N/P ratio of 10 at pH 6.5 contributes to the gene transfection efficiency in the lung. These results suggest inhalable dry pDNA powders with chitosan prepared by SFD to be a suitable formulation for pulmonary gene therapy. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Equations for Estimating Biomass of Herbaceous and Woody Vegetation in Early-Successional Southern Appalachian Pine-Hardwood Forests

Treesearch

Katherine J. Elliott; Barton D. Clinton

1993-01-01

Allometric equations were developed to predict aboveground dry weight of herbaceous and woody species on prescribe-burned sites in the Southern Appalachians. Best-fit least-square regression models were developed using diamet,er, height, or both, as the independent variables and dry weight as the dependent variable. Coefficients of determination for the selected total...

The effects of nanostructures on the mechanical and tribological properties of TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Yoon, Yeoungchin; Park, Jeongwon

2018-04-01

TiO2 nanotubes were prepared by anodization on Ti substrates with a diameter variation of 30-100 nm, and the structure of the nanotubes were studied using x-ray diffraction and Raman spectroscopy, which confirmed the structure changes from the anatase phase to the rutile phase of TiO2 at a diameter below 50 nm. The tribological behaviors of TiO2 nanotubes were investigated with different diameters. The effectiveness of the rutile phase and the diameter size enhanced the frictional performance of TiO2 nanotubes.

Micromachined cascade virtual impactor with a flow rate distributor for wide range airborne particle classification

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

Kim, Yong-Ho; Maeng, Jwa-Young; Park, Dongho

2007-07-23

This letter reports a module for airborne particle classification, which consists of a micromachined three-stage virtual impactor for classifying airborne particles according to their size and a flow rate distributor for supplying the required flow rate to the virtual impactor. Dioctyl sebacate particles, 100-600 nm in diameter, and carbon particles, 0.6-10 {mu}m in diameter, were used for particle classification. The collection efficiency and cutoff diameter were examined. The measured cutoff diameters of the first, second, and third stages were 135 nm, 1.9 {mu}m, and 4.8 {mu}m, respectively.

The effects of nanostructures on the mechanical and tribological properties of TiO2 nanotubes.

PubMed

Yoon, Yeoungchin; Park, Jeongwon

2018-04-20

TiO 2 nanotubes were prepared by anodization on Ti substrates with a diameter variation of 30-100 nm, and the structure of the nanotubes were studied using x-ray diffraction and Raman spectroscopy, which confirmed the structure changes from the anatase phase to the rutile phase of TiO 2 at a diameter below 50 nm. The tribological behaviors of TiO 2 nanotubes were investigated with different diameters. The effectiveness of the rutile phase and the diameter size enhanced the frictional performance of TiO 2 nanotubes.

Strong focusing effect of 660 nm laser by microsized tapered glass tubes with different diameters

NASA Astrophysics Data System (ADS)

Lin, Chongnan; Luo, Xujia; Zhu, Xiaoyang; Zhu, Li; Wang, Hongcheng; Zhang, Ao; Xu, Runyu; Qu, Zheng; Chen, Ximeng; Zhang, Weiyi; Shao, Jianxiong

2017-09-01

A laser with a wavelength of 660 nm was focused by microsized tapered glass tubes with different diameters of the exit. By using the 3-μm optical fiber and micrometer displacement stages, we measured the light intensity distribution around the focal spot, the focal distance, and the transmission coefficient of the light transmitted through these tubes. The focusing effect for the glass tubes with smaller outlet diameters of the exit was found to be much stronger than those with larger diameters of the exit. Furthermore, the dependence of the size and distance and the maximum intensity of the focal spot on the tubes' diameter of exit are obtained.

Dielectrophoretic trapping of DNA-coated gold nanoparticles on silicon based vertical nanogap devices.

PubMed

Strobel, Sebastian; Sperling, Ralph A; Fenk, Bernhard; Parak, Wolfgang J; Tornow, Marc

2011-06-07

We report on the successful dielectrophoretic trapping and electrical characterization of DNA-coated gold nanoparticles on vertical nanogap devices (VNDs). The nanogap devices with an electrode distance of 13 nm were fabricated from Silicon-on-Insulator (SOI) material using a combination of anisotropic reactive ion etching (RIE), selective wet chemical etching and metal thin-film deposition. Au nanoparticles (diameter 40 nm) coated with a monolayer of dithiolated 8 base pairs double stranded DNA were dielectrophoretically trapped into the nanogap from electrolyte buffer solution at MHz frequencies as verified by scanning and transmission electron microscopy (SEM/TEM) analysis. First electrical transport measurements through the formed DNA-Au-DNA junctions partially revealed an approximately linear current-voltage characteristic with resistance in the range of 2-4 GΩ when measured in solution. Our findings point to the importance of strong covalent bonding to the electrodes in order to observe DNA conductance, both in solution and in the dry state. We propose our setup for novel applications in biosensing, addressing the direct interaction of biomolecular species with DNA in aqueous electrolyte media.

Nanoscale pillar arrays for separations

DOE PAGES

Kirchner, Teresa; Strickhouser, Rachel; Hatab, Nahla; ...

2015-04-01

The work presented herein evaluates silicon nano-pillar arrays for use in planar chromatography. Electron beam lithography and metal thermal dewetting protocols were used to create nano-thin layer chromatography platforms. With these fabrication methods we are able to reduce the size of the characteristic features in a separation medium below that used in ultra-thin layer chromatography; i.e. pillar heights are 1-2μm and pillar diameters are typically in the 200- 400nm range. In addition to the intrinsic nanoscale aspects of the systems, it is shown they can be further functionalized with nanoporous layers and traditional stationary phases for chromatography; hence exhibit broad-rangingmore » lab-on-a-chip and point-of-care potential. Because of an inherent high permeability and very small effective mass transfer distance between pillars, chromatographic efficiency can be very high but is enhanced herein by stacking during development and focusing while drying, yielding plate heights in the nm range separated band volumes. Practical separations of fluorescent dyes, fluorescently derivatized amines, and anti-tumor drugs are illustrated.« less

One pot synthesis of intriguing fluorescent carbon dots for sensing and live cell imaging.

PubMed

Jana, Jayasmita; Ganguly, Mainak; Das, Bodhisatwa; Dhara, Santanu; Negishi, Yuichi; Pal, Tarasankar

2016-04-01

We report a simple one-pot synthesis of highly fluorescent carbon dots (CDs) via modified hydrothermal (MHT) treatment of alkaline solution of dopamine and cysteine. These CDs (λex=320 nm, λem=390 nm, and quantum yield ∼ 5.1%) are of ∼ 2-3 nm in diameter. Further attempt of synthesizing CDs in some common water-miscible solvents ends up the fact that the MHT product from acetone medium is nonfluorescent. However, CDs, produced in aqueous medium, are so stable that they can be dried as a deliverable solid (WCD) without any alteration of fluorescing property if reversibly dispersed in water. Fluorescence of WCD is quenched selectively in acetone. Quenching occurs presumably due to the disruption of radiative recombination along with the hindrance in quantum confinement of the emissive energy traps to the particle surface. Successive quenching of fluorescence of WCD in different acetone concentration admixed in water paves the way to selective acetone sensing (LOD=8.75 × 10(-7) M). The synthesized CDs (in aqueous medium) are cytocompatible and are efficient fluorescent probe for cell imaging. Only living cells are recognized exclusively from fluorescence imaging leaving aside dead cells, while cells are treated with CDs. Copyright © 2015 Elsevier B.V. All rights reserved.

The characteristics and mechanisms of Au nanoparticles processed by functional centrifugal procedures

NASA Astrophysics Data System (ADS)

Shiau, Bo-Wen; Lin, Chien-Hung; Liao, Ying-Yen; Lee, Ya-Rong; Liu, Shih-Hao; Ding, Wei-Cheng; Lee, Jia-Ren

2018-05-01

In this work, the optical properties of Au nanoparticles processed by centrifugation techniques are studied. Most of the literature related to the control of nanoparticle size has focused on different preparation parameters; however, the wide size distribution is commonly an issue for follow-up investigations and further applications. Therefore, we developed a method in which specific-diameter particles can be effectively separated using different centrifugal procedures. The initial nanoparticle solution with a primary absorption peak at 534 nm is separated into discernible resonance wavelengths from 526 to 537 nm, with corresponding particle sizes from 30 to 55 nm. For the atomic force microscopy analysis of nanoparticle size, a dry cetyltrimethylammonium bromide (CTAB) film often covers the particles and interferes with the measurement; thus, CTAB has to be removed. However, if too much CTAB is removed, the surface of the Au nanoparticle becomes unstable, and the particles aggregate. Accordingly, we used UV spectroscopy to monitor the CTAB content; properly adjust the rotational speed and the number of centrifugation stages; and design a method that can effectively remove impurities, avoid clustering, and enable particle size measurement. The usually complicated procedures and high cost of preparation of specific-size Au nanoparticles are greatly simplified and reduced by the convenient extraction process proposed in this work, which would benefit related research and applications.

Plasma etching of superconducting Niobium tips for scanning tunneling microscopy

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

Roychowdhury, A.; Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742; Dana, R.

We have developed a reproducible technique for the fabrication of sharp superconducting Nb tips for scanning tunneling microscopy (STM) and scanning tunneling spectroscopy. Sections of Nb wire with 250 μm diameter are dry etched in an SF₆ plasma in a Reactive Ion Etcher. The gas pressure, etching time, and applied power are chosen to control the ratio of isotropic to anisotropic etch rates and produce the desired tip shape. The resulting tips are atomically sharp, with radii of less than 100 nm, mechanically stable, and superconducting. They generate good STM images and spectroscopy on single crystal samples of Au(111), Au(100),more » and Nb(100), as well as a doped topological insulator Bi₂Se₃ at temperatures ranging from 30 mK to 9 K.« less

Fabrication of large-area nano-scale patterned sapphire substrate with laser interference lithography

NASA Astrophysics Data System (ADS)

Xuan, Ming-dong; Dai, Long-gui; Jia, Hai-qiang; Chen, Hong

2014-01-01

Periodic triangle truncated pyramid arrays are successfully fabricated on the sapphire substrate by a low-cost and high-efficiency laser interference lithography (LIL) system. Through the combination of dry etching and wet etching techniques, the nano-scale patterned sapphire substrate (NPSS) with uniform size is prepared. The period of the patterns is 460 nm as designed to match the wavelength of blue light emitting diode (LED). By improving the stability of the LIL system and optimizing the process parameters, well-defined triangle truncated pyramid arrays can be achieved on the sapphire substrate with diameter of 50.8 mm. The deviation of the bottom width of the triangle truncated pyramid arrays is 6.8%, which is close to the industrial production level of 3%.

Probing plasmon resonances of individual aluminum nanoparticles

NASA Astrophysics Data System (ADS)

Wei, Zhongxia; Mao, Peng; Cao, Lu; Song, Fengqi

2018-01-01

The plasmon resonances of individual aluminum nanoparticles are investigated by electron energy-loss spectroscopy (EELS) in scanning transmission electron microscope (STEM). Surface plasmon mode and bulk plasmon mode of Al nanoparticles are clearly characterized in the EEL spectra. Discrete dipole approximation (DDA) calculations show that as the particle diameter increases from 20 nm to 100 nm, the plasmon resonance shifts to lower energy and higher mode of surface plasmon arises when the diameter reaches 60 nm and larger.

The Fate of Polyol-Made ZnO and CdS Nanoparticles in Seine River Water (Paris, France).

PubMed

da Rocha, Alice; Sivry, Yann; Gelabert, Alexandre; Beji, Zyed; Benedetti, Marc F; Menguy, Nicolas; Brayner, Roberta

2015-05-01

This study aims to characterize nanoparticles with different compositions and structures as well as seeing their evolutions over time in a natural environment such as Seine river water (Paris, France). Face centered cubic (fcc) and hexagonal (hcp) CdS as well as hexagonal (hcp) ZnO nanoparticles were synthesized by the Polyol method. CdS nanoparticles (i) cfc structure: are agglomerated, present 100 nm length with heterogeneous diameter and 10 m2 g(-1) specific surface area (S(g)) from Brunauer Emett and Teller (BET) measurements; (ii) hcp structure: 20 nm and S(g) = 67 m2 g(-1). ZnO hcp nanoparticles presents 50 nm length and 15 nm diameter and S(g) = 54 m2 g(-1). These results are in agreement with X-ray diffraction (XRD), and small angle X-ray scattering (SAXs). After 48 h interaction with Seine river water, cryo-TEM analysis showed that ZnO nanoparticles form spherical agglomerates with 300 nm diameter; CdS nanoparticles (fcc) are agglomerated presenting large diameters (> 500 nm); and CdS nanoparticles (hcp) are not agglomerated and present the same characteristics of the starting material. After 168h of contact with Seine river water, CdS (fcc) presents only 14% of dissolution, CdS (hcp) presents both 60% dissolution and 30% reprecipitation in a cadmium carbonate form and finally almost 90% of ZnO nanoparticles are dissolved.

Comparison of HeNe laser and sinusoidal non-uniform magnetic field seed pre-sowing treatment effect on Glycine max (Var 90-I) germination, growth and yield.

PubMed

Asghar, Tehseen; Iqbal, Munawar; Jamil, Yasir; Zia-Ul-Haq; Nisar, Jan; Shahid, Muhammad

2017-01-01

Recently, laser and magnetic field pre-sowing seed treatments attracted the attention of the scientific community in response to their positive effect on plant characteristics and the present study was exemplified for Glycine max Var 90-I. Seeds were exposed to laser (HeNe-wave length 632nm and density power of 1mW/cm 2 ) and magnetic field (sinusoidal non-uniform-50, 75 and 100mT for 3, 5min with exposure) and seed germination, seedling growth and yield attributes were compared. The germination (mean germination, germination percentage, emergence index, germination speed, relative germination coefficient, emergence coefficient of uniformity) growth (root dry weight, root length, shoot fresh weight and shoot dry weight, leaf dry & fresh weight, root fresh weight, leaf area, shoot length, plant total dry weight at different stages, stem diameter, number of leaves, vigor index I & II), biochemical (essential oil) and yield attributes (seed weight, count) were enhanced significantly in response to both laser and magnetic field treatments. However, magnetic field treatment furnished slightly higher response versus laser except relative water contents, whole plant weight and shoot length. Results revealed that both laser and magnetic field pre-sowing seed treatments affect the germination, seedling growth, and yield characteristics positively and could possibly be used to enhance Glycine max productivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis and characterization of bioresorbable calcium phosphosilicate nanocomposite particles for fluorescence imaging and biomedical applications

NASA Astrophysics Data System (ADS)

Morgan, Thomas T.

Organically doped calcium phosphosilicate nanoparticles (CPSNPs) were developed and characterized, driven by the need for non-toxic vectors for drug delivery and fluorescence biological imaging applications. In particular, advancement in drug delivery for the chemotherapeutic treatment of cancers is required to increase drug efficacy and improve patient quality of life. Additionally, brighter and more photostable fluorophores are needed to meet demands for improved sensitivity and experimental diversity, which may lead to improvements in early detection of solid tumors and advancement in understanding of biological processes. A literature survey on the state of the field for nanoparticle based biological fluorescence imaging and drug delivery is presented in Chapter 1. Chapter 2 focuses on the characterization techniques used in this work. The development and optical characterization of 20-40 nm diameter, citrate functionalized Cy3 amidite doped calcium phosphosilicate nanoparticles (Cy3 CPSNPs) for in vitro fluorescence imaging is outlined in Chapters 3 and 4, respectively. In particular, sodium citrate was used to functionalize the surface and provide electrosteric dispersion of these particles. CPSNPs stabilized with sodium citrate routinely exhibited highly negative zeta potentials greater than -25 mV in magnitude. Furthermore, the fluorescence quantum yield of the encapsulated fluorophore was improved by more than 4.5-fold when compared to the unencapsulated dye. The bioimaging and drug delivery capability of CPSNPs was explored. Cy3 CPSNPs dissolved quickly in the acidic environment experienced during endocytosis, releasing the encapsulated fluorophore. This is consistent with solution phase experiments that show the particles are dissolved at pH 5. CPSNPs loaded with fluorescein and a hydrophobic growth inhibitor, ceramide C6, proved the ability to simultaneously image and delivery of the hydrophobic drug to cells in vitro. Chapter 5 examined the colloidal stability of citrate and polyethylene glycol (PEG) functionalized CPSNPs in 70 volume % ethanol/30% water, both experimentally using TEM and theoretically using DLVO and polymeric steric dispersion theories. There are three basic mechanisms for colloidal stability for macroscopic suspensions (i.e., for particulate diameters down to ˜100nm), metastable electrostatic in which some finite degree of agglomeration continuously takes place because a finite energy barrier against agglomeration; and electrosteric and steric mechanisms in which infinitely high potential energy barriers toward agglomeration are present leading to thermodynamically stable suspensions. One of the fundamental issues addressed in this chapter was whether the mechanisms of electrosteric or steric dispersion, based on relatively large adsorbed polyelectrolytes for macroscopic size particulates, scales with particles in the range of ˜40 nm diameter such that a small, charged organic molecule such as citrate provides the thermodynamic colloidal stability of electrosteric mechanisms as suggested by preliminary theoretical calculations. The particle diameter-number distributions for as-prepared and after drying (at 25°C) and redispersion were used as metrics for thermodynamic colloidal stability. How efficiently particles redispersed after drying and reintroduction into the 70:30 ethanol:water solvent was used as the primary metric for whether the metastable electrostatic mechanism or thermodynamically stable electrosteric or steric approaches were responsible for the robust dispersion experimentally observed in the colloids. These experiments found that, even with the thin electrosteric layer provided by the adsorbed citrate, particles were electrosterically dispersed, and were unagglomerated when dried under argon and redispersed. Preliminary work outlining the synthesis and characterization of silver core, calcium phosphosilicate shell nanoparticles for surface plasmon coupled emission and metal enhanced fluorescence applications is discussed in Chapter 6. Thin (2-5 nm) calcium phosphosilicate shells were formed around agglomerated silver cores in the presence of 8-Methoxypyrene-1,3,6-trisulfonic acid trisodium salt (MPTS). Calcium phosphosilicate shells were consistently formed after 72 hours in the presence of 5x10-5 M CaCl2, 3x10 -5 M Na2HPO4, 3x10-6 M Na 2SiO3, and silver core nanoparticles prepared by citrate reduction in aqueous solution. However, the particles synthesized were agglomerated, resulting in a loss of the plasmon resonance peak, and the shells prepared were not thick enough to provide sufficient separation of the fluorophore from the surface to prevent quenching and allow plasmon resonance enhanced fluorescence. (Abstract shortened by UMI.)

Physicochemical interaction mechanism between nanoparticles and tetrasaccharides (stachyose) during freeze-drying.

PubMed

Kamiya, Seitaro; Nakashima, Kenichiro

2017-12-01

Nanoparticle suspensions are thermodynamically unstable and subject to aggregation. Freeze-drying on addition of saccharides is a useful method for preventing aggregation. In the present study, tetrasaccharides (stachyose) was employed as an additive. In addition, we hypothesize the interactive mechanism between stachyose and the nanoparticles during freeze-drying for the first time. The mean particle size of the rehydrated freeze-dried stachyose-containing nanoparticles (104.7 nm) was similar to the initial particle size before freeze-drying (76.8 nm), indicating that the particle size had been maintained. The mean particle size of the rehydrated normal-dried stachyose-containing nanoparticles was 222.2 nm. The powder X-ray diffraction of the freeze-dried stachyose-containing nanoparticles revealed a halo pattern. The powder X-ray diffraction of the normally dried stachyose-containing nanoparticles produced mainly a halo pattern and a partial peak. These results suggest an interaction between the nanoparticles and stachyose, and that this relationship depends on whether the mixture is freeze-dried or dried normally. In the case of normal drying, although most molecules cannot move rapidly thereby settling irregularly, some stachyose molecules can arrange regularly leading to some degree of crystallization and potentially some aggregation. In contrast, during freeze-drying, the moisture sublimed, while the stachyose molecules and nanoparticles were immobilized in the ice. After sublimation, stachyose remained in the space occupied by water and played the role of a buffer material, thus preventing aggregation.

Formation of small gold clusters in solution by laser excitation of interband transition

NASA Astrophysics Data System (ADS)

Mafuné, Fumitaka; Kondow, Tamotsu

2003-04-01

Gold nanoparticles with ˜10 nm in average diameter were prepared by laser ablation of a gold metal plate in an aqueous solution of sodium dodecyl sulfate (SDS) and were fragmented by excitation of an interband transition of gold nanoparticles under irradiation of an intense 355-nm pulsed laser. Fragmentation dynamics was investigated by comparing the fragmentation by excitation of a surface plasmon band of gold nanoparticles by a 532-nm laser. It is found that gold nanoparticles with 1.5-nm average diameter are produced together with small gold clusters by properly optimizing the surfactant concentration.

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

Kishino, Katsumi, E-mail: kishino@sophia.ac.jp; Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554; Ishizawa, Shunsuke

Bottom-up grown structurally graded InGaN-based nanocolumn photonic crystals, in which nanocolumns were arranged in triangular lattice and the nanocolumn diameter changed one-dimensionally from 93 to 213 nm with a fixed lattice constant of 250 nm, were fabricated. The spatial distribution of the diameter resulted in random-laser-like operation under optical excitation. A broad multi-wavelength lasing spectrum with more than 10 peaks was obtained with a full width at half maximum of 27 nm at 505 nm wavelength as well as lowering of the polarization degree, which is expected to be suitable for speckle contrast reduction in laser projection display applications.

Formation of hexagonal boron nitride nanoscrolls induced by inclusion and exclusion of self-assembling molecules in solution process

NASA Astrophysics Data System (ADS)

Hwang, Da Young; Suh, Dong Hack

2014-05-01

Unlike nanoscrolls of 2D graphene, those of 2D h-BN have not been demonstrated, except for only a few experimental reports. Nanoscrolls of h-BN with high yields and reproducibility are first synthesized by a simple solution process. Inner-tube diameters of BNSs including LCAs, N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide, a bile acid derivative and self-assembling material, can be controlled by adjusting the diameter of the LCA fiber which is grown by self-assembly. TEM and SEM images show that BNSs have a tube-like morphology and the inner-tube diameter of BNSs can be controlled in the range from 20 to 60 nm for a smaller diameter, up to 300 nm for a larger diameter by LCA fiber growth inside the BNSs. Finally, open cylindrical BNSs with hollow cores were obtained by dissolving LCAs inside BNSs.Unlike nanoscrolls of 2D graphene, those of 2D h-BN have not been demonstrated, except for only a few experimental reports. Nanoscrolls of h-BN with high yields and reproducibility are first synthesized by a simple solution process. Inner-tube diameters of BNSs including LCAs, N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide, a bile acid derivative and self-assembling material, can be controlled by adjusting the diameter of the LCA fiber which is grown by self-assembly. TEM and SEM images show that BNSs have a tube-like morphology and the inner-tube diameter of BNSs can be controlled in the range from 20 to 60 nm for a smaller diameter, up to 300 nm for a larger diameter by LCA fiber growth inside the BNSs. Finally, open cylindrical BNSs with hollow cores were obtained by dissolving LCAs inside BNSs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00897a

Electrospray ionization from nanopipette emitters with tip diameters of less than 100 nm.

PubMed

Yuill, Elizabeth M; Sa, Niya; Ray, Steven J; Hieftje, Gary M; Baker, Lane A

2013-09-17

Work presented here demonstrates application of nanopipettes pulled to orifice diameters of less than 100 nm as electrospray ionization emitters for mass spectrometry. Mass spectrometric analysis of a series of peptides and proteins electrosprayed from pulled-quartz capillary nanopipette emitters with internal diameters ranging from 37 to 70 nm is detailed. Overall, the use of nanopipette emitters causes a shift toward the production of ions of higher charge states and leads to a reduction in width of charge-state distribution as compared to typical nanospray conditions. Further, nanopipettes show improved S/N and the same signal precision as typical nanospray, despite the much smaller dimensions. As characterized by SEM images acquired before and after spray, nanopipettes are shown to be robust under conditions employed. Analytical calculations and numerical simulations are used to calculate the electric field at the emitter tip, which can be significant for the small diameter tips used.

Determination of detonation parameters for liquid High Explosives

NASA Astrophysics Data System (ADS)

Mochalova, Valentina; Utkin, Alexander

2011-06-01

The experimental investigation of detonation parameters and reaction zone structure in liquid HE (bis-(2-fluoro-2,2-dinitroethyl)formal (FEFO), tetranitromethane (TNM), nitromethane (NM)) was conducted. Detonation front in TNM and NM was stable while the instability of detonation in FEFO was observed. Von Neumann spike was recorded for these HE and its parameters were determined. The different methods for C-J point determination were used for each HE. For FEFO reaction time τ was found from experiments with different charge diameters (τ is approximately equal to 300 ns); for TNM - at fixed diameter and different lengths of charges (τ ~ 200 ns); for NM - at fixed diameter and length of charges, but detonation initiation was carried out by different explosive charges (τ ~ 50 ns). It was found that in TNM the detonation velocity depends on charge diameter. Maximum value of reaction rate in investigated liquid HE was observed after shock jump and induction time was not recorded.

Determination of detonation parameters for liquid high explosives

NASA Astrophysics Data System (ADS)

Mochalova, Valentina; Utkin, Alexander

2012-03-01

The experimental investigation of detonation parameters and reaction zone structure in liquid HE (bis-(2-fluoro-2,2-dinitroethyl)formal (FEFO), tetranitromethane (TNM), nitromethane (NM)) was conducted by means of laser interferometer VISAR. Detonation front in TNM and NM was stable while the instability of detonation in FEFO was observed. The parameters of Von Neumann spike were determined for these HE. The different methods for C-J point determination were used for each HE. For FEFO reaction time t was found from experiments with different charge diameters (τ is approximately equal to 300 ns); for TNM - at fixed diameter and different lengths of charges (τ ≈ 200 ns); for NM - at fixed diameter and length of charges, but detonation initiation was carried out by different explosive charges (τ ≈ 50 ns). It was found that in TNM the detonation velocity depends on charge diameter. Maximum value of reaction rate in investigated liquid HE was observed after shock jump.

Fabrication and electrical characterization of sub-micron diameter through-silicon via for heterogeneous three-dimensional integrated circuits

NASA Astrophysics Data System (ADS)

Abbaspour, R.; Brown, D. K.; Bakir, M. S.

2017-02-01

This paper presents the fabrication and electrical characterization of high aspect-ratio (AR) sub-micron diameter through silicon vias (TSVs) for densely interconnected three-dimensional (3D) stacked integrated circuits (ICs). The fabricated TSV technology features an AR of 16:1 with 680 nm diameter copper (Cu) core and 920 nm overall diameter. To address the challenges in scaling TSVs, scallop-free low roughness nano-Bosch silicon etching and direct Cu electroplating on a titanium-nitride (TiN) diffusion barrier layer have been developed as key enabling modules. The electrical resistance of the sub-micron TSVs is measured to be on average 1.2 Ω, and the Cu resistivity is extracted to be approximately 2.95 µΩ cm. Furthermore, the maximum achievable current-carrying capacity (CCC) of the scaled TSVs is characterized to be approximately 360 µA for the 680 nm Cu core.

Low-temperature synthesis and characterization of helical carbon fibers by one-step chemical vapour deposition

NASA Astrophysics Data System (ADS)

Jin, Yongzhong; Chen, Jian; Fu, Qingshan; Li, Binghong; Zhang, Huazhi; Gong, Yong

2015-01-01

Helical carbon fibers (HCNFs) were synthesized by one-step chemical vapour deposition using cupric tartrate as a catalyst at temperature below 500 °C. The bound rubber of natural rubber (NR)/HCNFs were also prepared in this study. The results of thermogravimetry-differential scanning calorimetry (TG/DSC) for cupric tartrate nanoparticles show that the transformation of C4H4CuO6 → Cu reaction occurs at ∼250-310 °C. The characterization of scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectrum for the synthesized products confirms that the synthesis of HCNFs is highly temperature-dependent. The straight fibers with the fiber diameter of 100-400 nm are obtained at 280 °C and HCNFs can be synthesized at higher temperature, with the coil diameter of 0.5-1 μm and fiber diameter of 100-200 nm at 380 °C, and the coil diameter of ∼100 nm and fiber diameter of ∼80 nm at 480 °C. The maximum of the bound-rubber content (37%) can be obtained with the addition of 100 wt.% HCNFs in NR, which indicates that the coiled configuration of HCNFs makes a noticeable contribution to the reinforcement of NR/CB system.

Superparamagnetic properties of carbon nanotubes filled with NiFe{sub 2}O{sub 4} nanoparticles

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

Stojak Repa, K.; Israel, D.; Phan, M. H., E-mail: phanm@usf.edu, E-mail: sharihar@usf.edu

2015-05-07

Multi walled carbon nanotubes (MWCNTs) were successfully synthesized using custom-made 80 nm pore-size alumina templates, and were uniformly filled with nickel ferrite (NFO) nanoparticles of 7.4 ± 1.7 nm diameter using a novel magnetically assisted capillary action method. X-ray diffraction confirmed the inverse spinel phase for the synthesized NFO. Transmission electron microscopy confirms spherical NFO nanoparticles with an average diameter of 7.4 nm inside MWCNTs. Magnetometry indicates that both NFO and NFO-filled MWCNTs present a blocking temperature around 52 K, with similar superparamagnetic-like behavior, and weak dipolar interactions, giving rise to a super-spin-glass-like behavior at low temperatures. These properties along with the uniformity of sub-100 nm structuresmore » and the possibility of tunable magnetic response in variable diameter carbon nanotubes make them ideal for advanced biomedical and microwave applications.« less

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part II: Experimental characterization

DOE PAGES

Wang, Jian; Pikridas, Michael; Pinterich, Tamara; ...

2017-06-08

A Fast Integrated Mobility Spectrometer (FIMS) with a wide dynamic size range has been developed for rapid aerosol size distribution measurements. The design and model evaluation of the FIMS are presented in the preceding paper (Paper I), and this paper focuses on the experimental characterization of the FIMS. Monodisperse aerosol with diameter ranging from 8 to 600 nm was generated using Differential Mobility Analyzer (DMA), and was measured by the FIMS in parallel with a Condensation Particle Counter (CPC). The mean particle diameter measured by the FIMS is in good agreement with the DMA centroid diameter. Comparison of the particlemore » concentrations measured by the FIMS and CPC indicates the FIMS detection efficiency is essentially 100% for particles with diameters of 8 nm or larger. For particles smaller than 20 nm or larger than 200 nm, FIMS transfer function and resolution can be well represented by the calculated ones based on simulated particle trajectories in the FIMS. For particles between 20 and 200 nm, the FIMS transfer function is boarder than the calculated, likely due to non-ideality of the electric field, including edge effects near the end of the electrode, which are not represented by the 2-D electric field used to simulate particle trajectories.« less

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part II: Experimental characterization

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

Wang, Jian; Pikridas, Michael; Pinterich, Tamara

A Fast Integrated Mobility Spectrometer (FIMS) with a wide dynamic size range has been developed for rapid aerosol size distribution measurements. The design and model evaluation of the FIMS are presented in the preceding paper (Paper I), and this paper focuses on the experimental characterization of the FIMS. Monodisperse aerosol with diameter ranging from 8 to 600 nm was generated using Differential Mobility Analyzer (DMA), and was measured by the FIMS in parallel with a Condensation Particle Counter (CPC). The mean particle diameter measured by the FIMS is in good agreement with the DMA centroid diameter. Comparison of the particlemore » concentrations measured by the FIMS and CPC indicates the FIMS detection efficiency is essentially 100% for particles with diameters of 8 nm or larger. For particles smaller than 20 nm or larger than 200 nm, FIMS transfer function and resolution can be well represented by the calculated ones based on simulated particle trajectories in the FIMS. For particles between 20 and 200 nm, the FIMS transfer function is boarder than the calculated, likely due to non-ideality of the electric field, including edge effects near the end of the electrode, which are not represented by the 2-D electric field used to simulate particle trajectories.« less

Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods

NASA Astrophysics Data System (ADS)

Tsai, Chuen-Jinn; Lin, Guan-Yu; Liu, Chun-Nan; He, Chi-En; Chen, Chun-Wan

2012-03-01

A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO2, primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30-50 nm), and nano-silicon dioxide (nano-SiO2, primary diameter: 10-30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1-2.1 μm and 166-261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3-6.0 μm and NMD: 156-462 nm), and the RD (MMAD: 5.2-11.2 μm and NMD: 198-479 nm). For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.

Ultrafast studies of gold, nickel, and palladium nanorods

NASA Astrophysics Data System (ADS)

Sando, Gerald M.; Berry, Alan D.; Owrutsky, Jeffrey C.

2007-08-01

Steady state and ultrafast transient absorption studies have been carried out for gold, nickel, and palladium high aspect ratio nanorods. For each metal, nanorods were fabricated by electrochemical deposition into ˜6μm thick polycarbonate templates. Two nominal pore diameters(10 and 30nm, resulting in nanorod diameters of about 40 and 60nm, respectively) were used, yielding nanorods with high aspect ratios (>25). Static spectra of nanorods of all three metals reveal both a longitudinal surface plasmon resonance (SPRL) band in the mid-infrared as well as a transverse band in the visible for the gold and larger diameter nickel and palladium nanorods. The appearance of SPRL bands in the infrared for high aspect ratio metal nanorods and the trends in their maxima for the different aspect ratios and metals are consistent with calculations based on the Gans theory. For the gold and nickel samples, time resolved studies were performed with a subpicosecond resolution using 400nm excitation and a wide range of probe wavelengths from the visible to the mid-IR as well as for infrared excitation (near 2000cm-1) probed at 800nm. The dynamics observed for nanorods of both metals and both diameters include transients due to electron-phonon coupling and impulsively excited coherent acoustic breathing mode oscillations, which are similar to those previously reported for spherical and smaller rod-shaped gold nanoparticles. The dynamics we observe are the same within the experimental uncertainty for 400nm and infrared (5μm) excitation probed at 800nm. The transient absorption using 400nm excitation and 800nm probe pulses of the palladium nanorods also reveal coherent acoustic oscillations. The results demonstrate that the dynamics for high aspect ratio metal nanorods are similar to those for smaller nanoparticles.

Facile Fabrication of Ordered Anodized Aluminum Oxide Membranes with Controlled Pore Size by Improved Hard Anodization.

PubMed

Fan, Jiangxia; Zhu, Xinxin; Wang, Kunzhou; Chen, Xiaoyuan; Wang, Xinqing; Yan, Minhao; Ren, Yong

2018-05-01

We have fabricated highly ordered anodized aluminum oxide (AAO) membranes with different diameter through improved hard anodization (HA) at high temperature. This process can generate thick AAO membranes (30 μm) in a short anodizing time with high growth rate 20-60 μm h-1 which is much faster than that in traditional mild two-step anodization. We enlarged the AAO pore diameter by adjusting the voltage rise rate at the same time, which has a great influence on current density and temperature. The AAO pore diameter varies from 60-110 nm to 160-190 nm. The pore diameter (Dp) of the AAO prepared by this improved process is much larger than that prepared by HA (40-60 nm) when H2C2O4 as electrolyte. It can expand potential use of the AAO membranes such as for the template-based synthesis of nanowires or nanotubes with modulated diameters and also for practical separation technology. We also has used the AAO with different diameters prepared by this improved HA to fabricate Co nanowires and γ-Fe2O3 superparamagnetic nanorods.

Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

PubMed

Helsper, Johannes P F G; Peters, Ruud J B; van Bemmel, Margaretha E M; Rivera, Zahira E Herrera; Wagner, Stephan; von der Kammer, Frank; Tromp, Peter C; Hofmann, Thilo; Weigel, Stefan

2016-09-01

Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based "diameters of gyration" (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

Nanofiber alignment of a small diameter elastic electrospun scaffold

NASA Astrophysics Data System (ADS)

Patel, Jignesh

Cardiovascular disease is the leading cause of death in western countries with coronary heart disease making up 50% of these deaths. As a treatment option, tissue engineered grafts have great potential. Elastic scaffolds that mimic arterial extracellular matrix (ECM) may hold the key to creating viable vascular grafts. Electrospinning is a widely used scaffold fabrication technique to engineer tubular scaffolds. In this study, we investigated how the collector rotation speed altered the nanofiber alignment which may improve mechanical characteristics making the scaffold more suitable for arterial grafts. The scaffold was fabricated from a blend of PCL/Elastin. 2D Fast Fourier Transform (FFT) image processing tool and MatLab were used to quantitatively analyze nanofiber orientation at different collector speeds (13500 to 15500 rpm). Both Image J and MatLab showed graphical peaks indicating predominant fiber orientation angles. A collector speed of 15000 rpm was found to produce the best nanofiber alignment with narrow peaks at 90 and 270 degrees, and a relative amplitude of 200. This indicates a narrow distribution of circumferentially aligned nanofibers. Collector speeds below and above 15000 rpm caused a decrease in fiber alignment with a broader orientation distribution. Uniformity of fiber diameter was also measured. Of 600 measures from the 15000 rpm scaffolds, the fiber diameter range from 500 nm to 899 nm was most prevalent. This diameter range was slightly larger than native ECM which ranges from 50 nm to 500 nm. The second most prevalent diameter range had an average of 404 nm which is within the diameter range of collagen. This study concluded that with proper electrospinning technique and collector speed, it is possible to fabricate highly aligned small diameter elastic scaffolds. Image J 2D FFT results confirmed MatLab findings for the analyses of circumferentially aligned nanofibers. In addition, MatLab analyses simplified the FFT orientation data providing an accurate, user friendly orientation measurement tool.

In Situ Raman Analysis of CO2—Assisted Drying of Fruit-Slices

PubMed Central

Braeuer, Andreas Siegfried; Schuster, Julian Jonathan; Gebrekidan, Medhanie Tesfay; Bahr, Leo; Michelino, Filippo; Zambon, Alessandro; Spilimbergo, Sara

2017-01-01

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO2) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO2 into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve. PMID:28505120

Effect of AOT Microemulsion Composition on the Hydrodynamic Diameter and Electrophoretic Mobility of Titanium Oxide Nanoparticles

NASA Astrophysics Data System (ADS)

Shaparenko, N. O.; Beketova, D. I.; Demidova, M. G.; Bulavchenko, A. I.

2018-05-01

The hydrodynamic diameter and electrophoretic mobility of titania nanoparticles in AOT microemulsions are studied depending on their water content (from 0 to 1.5 vol %), chloroform content in n-decane-chloroform mixture (from 0 to 30 vol %) and temperature (from 0 to 60°C). Considerable changes in diameter (from 20 to 400 nm) are detected upon adding water to the microemulsion. The electrophoretic mobility grows by 2-3 times upon adding chloroform, or as the temperature falls. The observed features allow us to halve the time of electrophoretic concentration for 140 nm TiO2 nanoparticles, and to concentrate 14 nm nanoparticles that do not exhibit electrophoretic mobility in the absence of chloroform.

Hierarchical structure and compressive deformation mechanisms of bighorn sheep (Ovis canadensis) horn.

PubMed

Huang, Wei; Zaheri, Alireza; Jung, Jae-Young; Espinosa, Horacio D; Mckittrick, Joanna

2017-12-01

Bighorn sheep (Ovis canadensis) rams hurl themselves at each other at speeds of ∼9 m/s (20 mph) to fight for dominance and mating rights. This necessitates impact resistance and energy absorption mechanisms, which stem from material-structure components in horns. In this study, the material hierarchical structure as well as correlations between the structure and mechanical properties are investigated. The major microstructural elements of horns are found as tubules and cell lamellae, which are oriented with (∼30⁰) angle with respect to each other. The cell lamellae contain keratin cells, in the shape of pancakes, possessing an average thickness of ∼2 µm and diameter of ∼20-30 µm. The morphology of keratin cells reveals the presence of keratin fibers and intermediate filaments with diameter of ∼200 nm and ∼12 nm, respectively, parallel to the cell surface. Quasi-static and high strain rate impact experiments, in different loading directions and hydration states, revealed a strong strain rate dependency for both dried and hydrated conditions. A strong anisotropy behavior was observed under impact for the dried state. The results show that the radial direction is the most preferable impact orientation because of its superior energy absorption. Detailed failure mechanisms under the aforementioned conditions are examined by bar impact recovery experiments. Shear banding, buckling of cell lamellae, and delamination in longitudinal and transverse direction were identified as the cause for strain softening under high strain rate impact. While collapse of tubules occurs in both quasi-static and impact tests, in radial and transverse directions, the former leads to more energy absorption and impact resistance. Bighorn sheep (Ovis canadensis) horns show remarkable impact resistance and energy absorption when undergoing high speed impact during the intraspecific fights. The present work illustrates the hierarchical structure of bighorn sheep horn at different length scales and investigates the energy dissipation mechanisms under different strain rates, loading orientations and hydration states. These results demonstrate how horn dissipates large amounts of energy, thus provide a new path to fabricate energy absorbent and crashworthiness engineering materials. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Free-Standing β-Ga2O3 Thin Diaphragms

NASA Astrophysics Data System (ADS)

Zheng, Xu-Qian; Lee, Jaesung; Rafique, Subrina; Han, Lu; Zorman, Christian A.; Zhao, Hongping; Feng, Philip X.-L.

2018-02-01

Free-standing, very thin, single-crystal β-gallium oxide (β-Ga2O3) diaphragms have been constructed and their dynamical mechanical properties characterized by noncontact, noninvasive optical measurements harnessing the multimode nanomechanical resonances of these suspended nanostructures. We synthesized single-crystal β-Ga2O3 using low-pressure chemical vapor deposition (LPCVD) on a 3C-SiC epilayer grown on Si substrate at temperature of 950°C for 1.5 h. The synthesized single-crystal nanoflakes had widths of ˜ 2 μm to 30 μm and thicknesses of ˜ 20 nm to 140 nm, from which we fabricated free-standing circular drumhead β-Ga2O3 diaphragms with thicknesses of ˜ 23 nm to 73 nm and diameters of ˜ 3.2 μm and ˜ 5.2 μm using a dry stamp-transfer technique. Based on measurements of multiple flexural-mode mechanical resonances using ultrasensitive laser interferometric detection and performing thermal annealing at 250°C for 1.5 h, we quantified the effects of annealing and adsorption of atmospheric gas molecules on the resonant characteristics of the diaphragms. Furthermore, we studied the effects of structural nonidealities on these free-standing β-Ga2O3 nanoscale diaphragms. We present extensive characterization of the mechanical and optical properties of free-standing β-Ga2O3 diaphragms, paving the way for realization of resonant transducers using such nanomechanical structures for use in applications including gas sensing and ultraviolet radiation detection.

Estimating air drying times of small-diameter ponderosa pine and Douglas-fir logs.

Treesearch

William T. Simpson; Xiping. Wang

2003-01-01

Because dense stands of softwood trees are causing forest health problems in the western United States, new ways to use this material need to be found. One option is to use this material as logs rather than sawing it into lumber. For many applications, logs require some degree of drying. Even though these logs may be considered small diameter, they are large compared...

A low-cost, high-yield fabrication method for producing optimized biomimetic dry adhesives

NASA Astrophysics Data System (ADS)

Sameoto, D.; Menon, C.

2009-11-01

We present a low-cost, large-scale method of fabricating biomimetic dry adhesives. This process is useful because it uses all photosensitive polymers with minimum fabrication costs or complexity to produce molds for silicone-based dry adhesives. A thick-film lift-off process is used to define molds using AZ 9260 photoresist, with a slow acting, deep UV sensitive material, PMGI, used as both an adhesion promoter for the AZ 9260 photoresist and as an undercutting material to produce mushroom-shaped fibers. The benefits to this process are ease of fabrication, wide range of potential layer thicknesses, no special surface treatment requirements to demold silicone adhesives and easy stripping of the full mold if process failure does occur. Sylgard® 184 silicone is used to cast full sheets of biomimetic dry adhesives off 4" diameter wafers, and different fiber geometries are tested for normal adhesion properties. Additionally, failure modes of the adhesive during fabrication are noted and strategies for avoiding these failures are discussed. We use this fabrication method to produce different fiber geometries with varying cap diameters and test them for normal adhesion strengths. The results indicate that the cap diameters relative to post diameters for mushroom-shaped fibers dominate the adhesion properties.

Mass spectrometric analysis and aerodynamic properties of various types of combustion-related aerosol particles

NASA Astrophysics Data System (ADS)

Schneider, J.; Weimer, S.; Drewnick, F.; Borrmann, S.; Helas, G.; Gwaze, P.; Schmid, O.; Andreae, M. O.; Kirchner, U.

2006-12-01

Various types of combustion-related particles in the size range between 100 and 850 nm were analyzed with an aerosol mass spectrometer and a differential mobility analyzer. The measurements were performed with particles originating from biomass burning, diesel engine exhaust, laboratory combustion of diesel fuel and gasoline, as well as from spark soot generation. Physical and morphological parameters like fractal dimension, effective density, bulk density and dynamic shape factor were derived or at least approximated from the measurements of electrical mobility diameter and vacuum aerodynamic diameter. The relative intensities of the mass peaks in the mass spectra obtained from particles generated by a commercial diesel passenger car, by diesel combustion in a laboratory burner, and by evaporating and re-condensing lubrication oil were found to be very similar. The mass spectra from biomass burning particles show signatures identified as organic compounds like levoglucosan but also others which are yet unidentified. The aerodynamic behavior yielded a fractal dimension (Df) of 2.09 +/- 0.06 for biomass burning particles from the combustion of dry beech sticks, but showed values around three, and hence more compact particle morphologies, for particles from combustion of more natural oak. Scanning electron microscope images confirmed the finding that the beech combustion particles were fractal-like aggregates, while the oak combustion particles displayed a much more compact shape. For particles from laboratory combusted diesel fuel, a Df value of 2.35 was found, for spark soot particles, Df [approximate] 2.10. The aerodynamic properties of fractal-like particles from dry beech wood combustion indicate an aerodynamic shape factor [chi] that increases with electrical mobility diameter, and a bulk density of 1.92 g cm-3. An upper limit of [chi] [approximate] 1.2 was inferred for the shape factor of the more compact particles from oak combustion.

Inverse opal photonic crystals with photonic band gaps in the visible and near-infrared

NASA Astrophysics Data System (ADS)

Jarvis, Brandon C.; Gilleland, Cody L.; Renfro, Tim; Gutierrez, Jose; Parikh, Kunjal; Glosser, R.; Landon, Preston B.

2005-08-01

Colloidal silica spheres with 200nm, 250nm, and 290nm diameters were self-assembled with single crystal crystallites 4-5mm wide and 10-15mm long. Larger spheres with diameters between 1000-2300nm were self-assembled with single crystal crystallites up to 1.5mm wide and 2mm long. The silica opals self-assembled vertically along the [100] direction of the face centered cubic lattice resulting in self-templated opals. Inverse opal photonic crystals with a partial band gap possessing a maximum in the near infrared at 3.8μm were constructed from opal templates composed of 2300nm diameter spheres with chalcogenide Ge33As12Se55 (AMTIR-1), a transparent glass in the near infrared with high refractive index. Inverse gold and gold/ polypropylene composite photonic crystals were fabricated from synthetic opal templates composed of 200-290nm silica spheres. The reflectance spectra and electrical conductance of the resulting structures is presented. Gold was infiltrated into opal templates as gold chloride and heat converted to metallic gold. Opals partially infiltrated with gold were co-infiltrated with polypropylene plastic for mechanical support prior to removal of the silica template with hydrofluoric acid.

ZnO and TiO2 particles: a study on nanosafety and photoprotection

NASA Astrophysics Data System (ADS)

Popov, Alexey; Zhao, Xin; Zvyagin, Andrei; Lademann, Jürgen; Roberts, Michael; Sanchez, Washington; Priezzhev, Alexander; Myllylä, Risto

2010-04-01

Nanoparticles of titanium dioxide (TiO2) and zinc oxide (ZnO) are used in sunscreens as protective compounds against UV radiation. We investigate these particles from the viewpoint of nanosafety (penetration into skin in vivo, production of free radicals when UV-irradiated) as well as UV protection. We show that: a) even after multiple applications, the particles remain within stratum corneum (uppermost skin layer); b) the optimal sizes are 62 nm and 45 nm, respectively for TiO2 and ZnO particles for 310-nm light and, correspondingly, 122 and 140 nm - for 400-nm radiation; c) in general, small particles (25 nm in diameter) are more photoactive than the larger ones (400 nm in diameter); however, on the background if porcine skin in vitro this difference is not seen and is substantially surpassed by skin contribution into production of free radicals.

Separation of methane-nitrogen mixtures using synthesis vertically aligned carbon nanotube membranes

NASA Astrophysics Data System (ADS)

Gilani, Neda; Daryan, Jafar Towfighi; Rashidi, Alimorad; Omidkhah, Mohammad Reza

2012-03-01

In this paper, capabilities of carbon nanotube (CNT) membranes fabricated in cylindrical pores of anodic aluminum oxide (AAO) substrate to separate the binary mixtures of CH4/N2 are studied experimentally. For this purpose, the permeability and selectivity of three CNT/AAO membranes with different growth time as 6 h, 12 h and 18 h are investigated. CNTs are grown vertically through holes of AAO with average pore diameter of 45 nm by chemical vapor deposition (CVD) of acetylene gas. CNT/AAO membranes with the same CNTs' outer diameters and different inner diameters are synthesized. The AAO are characterized by SEM analysis. In addition, SEM, TEM, BET N2 adsorption analysis and Raman spectroscopy are employed to characterize aligned CNTs. Study on permeability and selectivity of membranes for three binary mixtures of CH4/N2 showed that when the CNT inner diameters are 34 nm and 24 nm, viscous flow is the governing mechanism and insignificant selectivities of 1.2-1.24 are achieved. However, the membrane with CNT inner diameter and wall thickness of 8 nm and 16 nm respectively is considerably selective for CH4 over N2. It was also found that CH4 mole fraction in the feed and upstream feed pressure have major effect on permeability and selectivity. The membrane with 18 h synthesis time showed the selectivity is in the range of 1.8-3.85. The enhancement factor for N2 single gas diffusivity was also found to be about three times larger than that predicted by Knudsen diffusion model.

Controllable Fabrication of Non-Close-Packed Colloidal Nanoparticle Arrays by Ion Beam Etching

NASA Astrophysics Data System (ADS)

Yang, Jie; Zhang, Mingling; Lan, Xu; Weng, Xiaokang; Shu, Qijiang; Wang, Rongfei; Qiu, Feng; Wang, Chong; Yang, Yu

2018-06-01

Polystyrene (PS) nanoparticle films with non-close-packed arrays were prepared by using ion beam etching technology. The effects of etching time, beam current, and voltage on the size reduction of PS particles were well investigated. A slow etching rate, about 9.2 nm/min, is obtained for the nanospheres with the diameter of 100 nm. The rate does not maintain constant with increasing the etching time. This may result from the thermal energy accumulated gradually in a long-time bombardment of ion beam. The etching rate increases nonlinearly with the increase of beam current, while it increases firstly then reach its saturation with the increase of beam voltage. The diameter of PS nanoparticles can be controlled in the range from 34 to 88 nm. Based on the non-close-packed arrays of PS nanoparticles, the ordered silicon (Si) nanopillars with their average diameter of 54 nm are fabricated by employing metal-assisted chemical etching technique. Our results pave an effective way to fabricate the ordered nanostructures with the size less than 100 nm.

Improvement of optical damage in specialty fiber at 266 nm wavelength

NASA Astrophysics Data System (ADS)

Tobisch, T.; Ohlmeyer, H.; Zimmermann, H.; Prein, S.; Kirchhof, J.; Unger, S.; Belz, M.; Klein, K.-F.

2014-02-01

Improved multimode UV-fibers with core diameters ranging from 70 to 600 μm diameter have been manufactured based on novel preform modifications and fiber processing techniques. Only E'-centers at 214 nm and NBOHC at 260 nm are generated in these fibers. A new generation of inexpensive laser-systems have entered the market and generated a multitude of new and attractive applications in the bio-life science, chemical and material processing field. However, for example pulsed 355 nm Nd:YAG lasers generate significant UV-damages in commercially available fibers. For lower wavelengths, no results on suitable multi-mode or low-mode fibers with high UV resistance at 266 nm wavelength (pulsed 4th harmonic Nd:YAG laser) have been published. In this report, double-clad fibers with 70 μm or 100 μm core diameter and a large claddingto- core ratio will be recommended. Laser-induced UV-damages will be compared between these new fiber type and traditional UV fibers with similar core sizes. Finally, experimental results will be cross compared against broadband cw deuterium lamp damage standards.

Cyclosporine Amicellar delivery system for dry eyes.

PubMed

Kang, Han; Cha, Kwang-Ho; Cho, Wonkyung; Park, Junsung; Park, Hee Jun; Sun, Bo Kyung; Hyun, Sang-Min; Hwang, Sung-Joo

2016-01-01

The objectives of this study were to develop stable cyclosporine A (CsA) ophthalmic micelle solutions for dry-eye syndrome and evaluate their physicochemical properties and therapeutic efficacy. CsA-micelle solutions (MS-CsA) were created by a simple method with Cremophor EL, ethanol, and phosphate buffer. We investigated the particle size, pH, and osmolarity. In addition, long-term physical and chemical stability for MS-CsA was observed. To confirm the therapeutic efficacy, tear production in dry eye-induced rabbits was evaluated using the Schirmer tear test (STT). When compared to a commercial product, Restasis, MS-CsA demonstrated improvement in goblet-cell density and conjunctival epithelial morphology, as demonstrated in histological hematoxylin and eosin staining. MS-CsA had a smaller particle size (average diameter 14-18 nm) and a narrow size distribution. Physicochemical parameters, such as particle size, pH, osmolarity, and remaining CsA concentration were all within the expected range of 60 days. STT scores significantly improved in MS-CsA treated groups (P<0.05) in comparison to those of the Restasis-treated group. The number of goblet cells for rabbit conjunctivas after the administration of MS-CsA was 94.83±8.38, a significantly higher result than the 65.17±11.51 seen with Restasis. The conjunctival epithelial morphology of dry eye-induced rabbits thinned with loss of goblet cells. However, after 5 days of treatment with drug formulations, rabbit conjunctivas recovered epithelia and showed a relative increase in the number of goblet cells. The results of this study indicate the potential use of a novel MS for the ophthalmic delivery of CsA in treating dry eyes.

Cyclosporine Amicellar delivery system for dry eyes

PubMed Central

Kang, Han; Cha, Kwang-Ho; Cho, Wonkyung; Park, Junsung; Park, Hee Jun; Sun, Bo Kyung; Hyun, Sang-Min; Hwang, Sung-Joo

2016-01-01

Background The objectives of this study were to develop stable cyclosporine A (CsA) ophthalmic micelle solutions for dry-eye syndrome and evaluate their physicochemical properties and therapeutic efficacy. Materials and methods CsA-micelle solutions (MS-CsA) were created by a simple method with Cremophor EL, ethanol, and phosphate buffer. We investigated the particle size, pH, and osmolarity. In addition, long-term physical and chemical stability for MS-CsA was observed. To confirm the therapeutic efficacy, tear production in dry eye-induced rabbits was evaluated using the Schirmer tear test (STT). When compared to a commercial product, Restasis, MS-CsA demonstrated improvement in goblet-cell density and conjunctival epithelial morphology, as demonstrated in histological hematoxylin and eosin staining. Results MS-CsA had a smaller particle size (average diameter 14–18 nm) and a narrow size distribution. Physicochemical parameters, such as particle size, pH, osmolarity, and remaining CsA concentration were all within the expected range of 60 days. STT scores significantly improved in MS-CsA treated groups (P<0.05) in comparison to those of the Restasis-treated group. The number of goblet cells for rabbit conjunctivas after the administration of MS-CsA was 94.83±8.38, a significantly higher result than the 65.17±11.51 seen with Restasis. The conjunctival epithelial morphology of dry eye-induced rabbits thinned with loss of goblet cells. However, after 5 days of treatment with drug formulations, rabbit conjunctivas recovered epithelia and showed a relative increase in the number of goblet cells. Conclusion The results of this study indicate the potential use of a novel MS for the ophthalmic delivery of CsA in treating dry eyes. PMID:27382280

Formation of Size- and Position-Controlled Nanometer Size Pt Dots on GaAs and InP Substrates by Pulsed Electrochemical Deposition

NASA Astrophysics Data System (ADS)

Sato, Taketomo; Kaneshiro, Chinami; HiroshiOkada, HiroshiOkada; Hasegawa, Hideki

1999-04-01

Attempts were made to form regular arrays of size- andposition-controlled Pt-dots on GaAs and InP by combining an insitu electrochemical process with the electron beam (EB)lithography. This utilizes the precipitation of Pt nano-particles atthe initial stage of electrodeposition. First, electrochemicalconditions were optimized in the mode of self-assembled dot arrayformation on unpatterned substrates. Minimum in-plane dot diameters of22 nm and 26 nm on GaAs and InP, respectively, were obtained underthe optimal pulsed mode. Then, Pt dots were selectively formed onpatterned substrates with open circular windows formed by EBlithography, thereby realizing dot-position control. The Pt dot wasfound to have been deposited at the center of each open window, andthe in-plane diameter of the dot could be controlled by the number,width and period of the pulse-waveform applied to substrates. Aminimum diameter of 20 nm was realized in windows with a diameter of100 nm, using a single pulse. Current-voltage (I-V)measurements using an atomic force microscopy (AFM) system with aconductive probe indicated that each Pt dot/n-GaAs contact possessed ahigh Schottky barrier height of about 1 eV.

Achieving sub-50 nm controlled diameter of aperiodic Si nanowire arrays by ultrasonic catalyst removal for photonic applications

NASA Astrophysics Data System (ADS)

Chaliyawala, Harsh A.; Purohit, Zeel; Khanna, Sakshum; Ray, Abhijit; Pati, Ranjan K.; Mukhopadhyay, Indrajit

2018-05-01

We report an alternative approach to fabricate the vertically aligned aperiodic Si nanowire arrays by controlling the diameter of the Ag nanoparticles and tuneable ultrasonic removal. The process begins by sputtering the Ag thin film (t=5 nm) on the Si/SiO2 substrates. Followed by Ag thin film, annealed for various temperature (T=300°C, 400°C, 500°C and 600°C) to selectively achieve a high density, well-spaced and diameter controlled Ag nanoparticles (AgNPs) on the Si/SiO2 substrates. The sacrificial layer of AgNPs size indicates the controlled diameter of the Si nanowire arrays. Image J analysis for various annealed samples gives an indication of the high density, uniformity and equal distribution of closely packed AgNPs. Furthermore, the AgNPs covered with Au/Pd mesh (5 nm) as a template, was removed by ultrasonication in the etchant solution for several times in different intervals of preparation. The conventional and facile metal assisted electroless etching approach was finally employed to fabricate the vertically aperiodic sub-50 nm SiNWAs, can be applicable to various nanoscale opto-electronic applications.

Highly porous layers of silica nanospheres sintered by drying: scaling up of the elastic properties of the beads to the macroscopic mechanical properties.

PubMed

Lesaine, Arnaud; Bonamy, Daniel; Gauthier, Georges; Rountree, Cindy L; Lazarus, Véronique

2018-05-16

Layers obtained by drying a colloidal dispersion of silica spheres are found to be a good benchmark to test the elastic behaviour of porous media, in the challenging case of high porosities and nano-sized microstructures. Classically used for these systems, Kendall's approach explicitly considers the effect of surface adhesive forces onto the contact area between the particles. This approach provides the Young's modulus using a single adjustable parameter (the adhesion energy) but provides no further information on the tensorial nature and possible anisotropy of elasticity. On the other hand, homogenization approaches (e.g. rule of mixtures, and Eshelby, Mori-Tanaka and self-consistent schemes), based on continuum mechanics and asymptotic analysis, provide the stiffness tensor from the knowledge of the porosity and the elastic constants of the beads. Herein, the self-consistent scheme accurately predicts both bulk and shear moduli, with no adjustable parameter, provided the porosity is less than 35%, for layers composed of particles as small as 15 nm in diameter. Conversely, Kendall's approach is found to predict the Young's modulus over the full porosity range. Moreover, the adhesion energy in Kendall's model has to be adjusted to a value of the order of the fracture energy of the particle material. This suggests that sintering during drying leads to the formation of covalent siloxane bonds between the particles.

Angle-resolved reflection spectroscopy of high-quality PMMA opal crystal

NASA Astrophysics Data System (ADS)

Nemtsev, Ivan V.; Tambasov, Igor A.; Ivanenko, Alexander A.; Zyryanov, Victor Ya.

2018-02-01

PMMA opal crystal was prepared by a simple hybrid method, which includes sedimentation, meniscus formation and evaporation. We investigated three surfaces of this crystal by angle-resolved reflective light spectroscopy and SEM study. The angle-resolved reflective measurements were carried out in the 400-1100 nm range. We have determined the high-quality ordered surface of the crystal region. Narrow particle size distribution of the surface has been revealed. The average particle diameter obtained with SEM was nearly 361 nm. The most interesting result was that reflectivity of the surface turned out up to 98% at normal light incidence. Using a fit of dependences of the maximum reflectivity wavelength from an angle based on the Bragg-Snell law, the wavelength of maximum 0° reflectivity, the particle diameter and the fill factor have been determined. For the best surface maximum reflectivity wavelength of a 0° angle was estimated to be 869 nm. The particle diameter and fill factor were calculated as 372 nm and 0.8715, respectively. The diameter obtained by fitting is in excellent agreement with the particle diameter obtained with SEM. The reflectivity maximum is assumed to increase significantly when increasing the fill factor. We believe that using our simple approach to manufacture PMMA opal crystals will significantly increase the fabrication of high-quality photonic crystal templates and thin films.

A comparison of kiln-drying schedules and quality outcomes for 4/4-thickness black cherry lumber sawn from small-diameter logs

Treesearch

Matthew S. Scholl; Janice K. Wiedenbeck; Paul R. Blankenhorn; Charles D. Ray; Lee R. Stover; Brian W. Beakler

2008-01-01

With high stumpage prices, many sawmills are interested in the feasibility of processing smaller diameter hardwood logs. Most of these mills do not know the lumber yield, lumber grade, or cost of processing these logs. In this project we investigated the impact of alternative dry kiln schedules on the grade yields and defect occurrence in lumber sawn from small-...

Modeling particle nucleation and growth over northern California during the 2010 CARES campaign

NASA Astrophysics Data System (ADS)

Lupascu, A.; Easter, R.; Zaveri, R.; Shrivastava, M.; Pekour, M.; Tomlinson, J.; Yang, Q.; Matsui, H.; Hodzic, A.; Zhang, Q.; Fast, J. D.

2015-07-01

Accurate representation of the aerosol lifecycle requires adequate modeling of the particle number concentration and size distribution in addition to their mass, which is often the focus of aerosol modeling studies. This paper compares particle number concentrations and size distributions as predicted by three empirical nucleation parameterizations in the Weather Research and Forecast coupled with chemistry (WRF-Chem) regional model using 20 discrete size bins ranging from 1 nm to 10 μm. Two of the parameterizations are based on H2SO4 while one is based on both H2SO4 and organic vapors. Budget diagnostic terms for transport, dry deposition, emissions, condensational growth, nucleation, and coagulation of aerosol particles have been added to the model and are used to analyze the differences in how the new particle formation parameterizations influence the evolving aerosol size distribution. The simulations are evaluated using measurements collected at surface sites and from a research aircraft during the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted in the vicinity of Sacramento, California. While all three parameterizations captured the temporal variation of the size distribution during observed nucleation events as well as the spatial variability in aerosol number, all overestimated by up to a factor of 2.5 the total particle number concentration for particle diameters greater than 10 nm. Using the budget diagnostic terms, we demonstrate that the combined H2SO4 and low-volatility organic vapors parameterization leads to a different diurnal variability of new particle formation and growth to larger sizes compared to the parameterizations based on only H2SO4. At the CARES urban ground site, peak nucleation rates were predicted to occur around 12:00 Pacific (local) standard time (PST) for the H2SO4 parameterizations, whereas the highest rates were predicted at 08:00 and 16:00 PST when low-volatility organic gases are included in the parameterization. This can be explained by higher anthropogenic emissions of organic vapors at these times as well as lower boundary layer heights that reduce vertical mixing. The higher nucleation rates in the H2SO4-organic parameterization at these times were largely offset by losses due to coagulation. Despite the different budget terms for ultrafine particles, the 10-40 nm diameter particle number concentrations from all three parameterizations increased from 10:00 to 14:00 PST and then decreased later in the afternoon, consistent with changes in the observed size and number distribution. Differences among the three simulations for the 40-100 nm particle diameter range are mostly associated with the timing of the peak total tendencies that shift the morning increase and afternoon decrease in particle number concentration by up to two hours. We found that newly formed particles could explain up to 20-30 % of predicted cloud condensation nuclei at 0.5 % supersaturation, depending on location and the specific nucleation parameterization. A sensitivity simulation using 12 discrete size bins ranging from 1 nm to 10 μm diameter gave a reasonable estimate of particle number and size distribution compared to the 20 size bin simulation, while reducing the associated computational cost by ∼ 36 %.

Electrohydrodynamic (edh) drying of ginger slices (zingiber officinale)

NASA Astrophysics Data System (ADS)

Sumariyah; Khuriati, Ainie; Fachriyah, Enny

2018-05-01

Electrohydrodynamic (EHD) flow or ion wind of corona discharges has been generated utilizing pin-multi ring concentred electrodes. The pin was made of stainless steel with a tip diameter of 0.018 mm. The multi-ring constructed electrodes by a metal material connected to each other and each ring has a diameter of 24 mm, 16 mm and 8 mm in the same width and thickness is 4 mm and 1 mm. EHD was generated by using a DC high voltage of 5 kV. Pin as an active electrode of corona discharge and multi-ring concentric electrodes as a collector and passive electrodes. The ion wind or EHD flow is produced through changes in voltage and distance between electrodes. The ionic wind generated system outputs through multi-ring concentric electrodes which will further dry the sample. A circle ginger slices as a sample with a diameter of 26 mm with a thickness of 2 mm. The drying is done at the distance between the fixed electrodes of 4 mm and the varied voltages are 1.2 kV, 1.4 kV, and 1.6 kV. The sample drying time varied 30 minutes, 60 minutes, 90 minutes, 120 minutes and 150 minutes. The result of drying the sample at a fixed voltage is obtained moisture of ginger slices decreased with increased drying time.

Superconductivity of a Sn film controlled by an array of Co nanowires

NASA Astrophysics Data System (ADS)

Wei, Zhiyuan; Ye, Zuxin; Rathnayaka, Daya; Lyuksyutov, Igor; Wu, Wenhao; Naugle, Donald

2012-02-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized anodic aluminum oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

Superconductivity of a Sn film controlled by an array of Co nanowires

NASA Astrophysics Data System (ADS)

Wei, Z.; Ye, Z.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Wu, W.; Naugle, D. G.

2012-09-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

Synthesis and characterization of nanocrystalline mesoporous zirconia using supercritical drying.

PubMed

Tyagi, Beena; Sidhpuria, Kalpesh; Shaik, Basha; Jasra, Raksh Vir

2006-06-01

Synthesis of nano-crystalline zirconia aerogel was done by sol-gel technique and supercritical drying using n-propanol solvent at and above supercritical temperature (235-280 degrees C) and pressure (48-52 bar) of n-propanol. Zirconia xerogel samples have also been prepared by conventional thermal drying method to compare with the super critically dried samples. Crystalline phase, crystallite size, surface area, pore volume, and pore size distribution were determined for all the samples in detail to understand the effect of gel drying methods on these properties. Supercritical drying of zirconia gel was observed to give thermally stable, nano-crystalline, tetragonal zirconia aerogels having high specific surface area and porosity with narrow and uniform pore size distribution as compared to thermally dried zirconia. With supercritical drying, zirconia samples show the formation of only mesopores whereas in thermally dried samples, substantial amount of micropores are observed along with mesopores. The samples prepared using supercritical drying yield nano-crystalline zirconia with smaller crystallite size (4-6 nm) as compared to higher crystallite size (13-20 nm) observed with thermally dried zirconia.

Dry etching of copper phthalocyanine thin films: effects on morphology and surface stoichiometry.

PubMed

Van Dijken, Jaron G; Brett, Michael J

2012-08-24

We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure.

Synthesis, characterization and antistructure modeling of Ni nano ferrite

NASA Astrophysics Data System (ADS)

Kane, S. N.; Raghuvanshi, S.; Satalkar, M.; Reddy, V. R.; Deshpande, U. P.; Tatarchuk, T. R.; Mazaleyrat, F.

2018-05-01

We report the role played by cation distribution in determining magnetic properties by comparing dry gel, thermally annealed Ni ferrite prepared by sol-gel auto-combustion technique. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Mössbauer spectroscopy were used to characterize the samples. Both XRD and Mössbauer measurements validate the formation of spinel phase with grain diameter 39.13-45.53 nm. First time antistructural modeling for Ni ferrite is reported to get information on active surface centers. Decrease of Debye temperature θD in annealed sample shows enhancement of lattice vibrations. With thermal annealing experimental and Néel magnetic moment (nBe, nBN) increases, suggesting migration of Ni2+ from B to A site with concurrent migration of Fe3+ from A to B site (non-equilibrium cationic distribution), affecting magnetic properties.

Dynamic-mechanical and thermomechanical properties of cellulose nanofiber/polyester resin composites.

PubMed

Lavoratti, Alessandra; Scienza, Lisete Cristine; Zattera, Ademir José

2016-01-20

Composites of unsaturated polyester resin (UPR) and cellulose nanofibers (CNFs) obtained from dry cellulose waste of softwood (Pinus sp.) and hardwood (Eucalyptus sp.) were developed. The fiber properties and the influence of the CNFs in the dynamic-mechanical and thermomechanical properties of the composites were evaluated. CNFs with a diameter of 70-90 nm were obtained. Eucalyptus sp. has higher α-cellulose content than Pinus sp. fibers. The crystallinity of the cellulose pulps decreased after grinding. However, high values were still obtained. The chemical composition of the fibers was not significantly altered by the grinding process. Eucalyptus sp. CNF composites had water absorption close to the neat resin at 1 wt% filler. The dynamic-mechanical properties of Eucalyptus sp. CNFs were slightly increased and the thermal stability was improved. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fine tuning of nanopipettes using atomic layer deposition for single molecule sensing.

PubMed

Sze, Jasmine Y Y; Kumar, Shailabh; Ivanov, Aleksandar P; Oh, Sang-Hyun; Edel, Joshua B

2015-07-21

Nanopipettes are an attractive single-molecule tool for identification and characterisation of nucleic acids and proteins in solutions. They enable label-free analysis and reveal individual molecular properties, which are generally masked by ensemble averaging. Having control over the pore dimensions is vital to ensure that the dimensions of the molecules being probed match those of the pore for optimization of the signal to noise. Although nanopipettes are simple and easy to fabricate, challenges exist, especially when compared to more conventional solid-state analogues. For example, a sub-20 nm pore diameter can be difficult to fabricate and the batch-to-batch reproducibility is often poor. To improve on this limitation, atomic layer deposition (ALD) is used to deposit ultrathin layers of alumina (Al2O3) on the surface of the quartz nanopipettes enabling sub-nm tuning of the pore dimensions. Here, Al2O3 with a thickness of 8, 14 and 17 nm was deposited onto pipettes with a starting pore diameter of 75 ± 5 nm whilst a second batch had 5 and 8 nm Al2O3 deposited with a starting pore diameter of 25 ± 3 nm respectively. This highly conformal process coats both the inner and outer surfaces of pipettes and resulted in the fabrication of pore diameters as low as 7.5 nm. We show that Al2O3 modified pores do not interfere with the sensing ability of the nanopipettes and can be used for high signal-to-noise DNA detection. ALD provides a quick and efficient (batch processing) for fine-tuning nanopipettes for a broad range of applications including the detection of small biomolecules like RNA, aptamers and DNA-protein interactions at the single molecule level.

Diameter dependent thermoelectric properties of individual SnTe nanowires

DOE PAGES

Xu, E. Z.; Li, Z.; Martinez, J. A.; ...

2015-01-15

The lead-free compound tin telluride (SnTe) has recently been suggested to be a promising thermoelectric material. In this work, we report on the first thermoelectric study of individual single-crystalline SnTe nanowires with different diameters ranging from ~ 218 to ~ 913 nm. Measurements of thermopower S, electrical conductivity σ and thermal conductivity κ were carried out on the same nanowires over a temperature range of 25 - 300 K. While the electrical conductivity does not show a strong diameter dependence, the thermopower increases by a factor of two when the nanowire diameter is decreased from ~ 913 nm to ~more » 218 nm. The thermal conductivity of the measured NWs is lower than that of the bulk SnTe, which may arise from the enhanced phonon - surface boundary scattering and phonon-defect scattering. Lastly, temperature dependent figure of merit ZT was determined for individual nanowires and the achieved maximum value at room temperature is about three times higher than that in bulk samples of comparable carrier density.« less

Combination of small size and carboxyl functionalisation causes cytotoxicity of short carbon nanotubes

PubMed Central

Fröhlich, Eleonore; Meindl, Claudia; Höfler, Anita; Leitinger, Gerd; Roblegg, Eva

2012-01-01

The use of carbon nanotubes (CNTs) could improve medical diagnosis and treatment provided they show no adverse effects in the organism. In this study, short CNTs with different diameters with and without carboxyl surface functionalisation were assessed. After physicochemical characterisation, cytotoxicity in phagocytic and non-phagocytic cells was determined. The role of oxidative stress was evaluated according to the intracellular glutathione levels and protection by N-acetyl cysteine (NAC). In addition to this, the mode of cell death was also investigated. CNTs <8 nm acted more cytotoxic than CNTs ≥20 nm and carboxylated CNTs more than pristine CNTs. Protection by NAC was maximal for large diameter pristine CNTs and minimal for small diameter carboxylated CNTs. Thin (<8 nm) CNTs acted mainly by disruption of membrane integrity and CNTs with larger diameter induced mainly apoptotic changes. It is concluded that cytotoxicity of small carboxylated CNTs occurs by necrosis and cannot be prevented by antioxidants. PMID:22963691

Magnetic vortices in nanocaps induced by curvature

NASA Astrophysics Data System (ADS)

Abdelgawad, Ahmed M.; Nambiar, Nikhil; Bapna, Mukund; Chen, Hao; Majetich, Sara A.

2018-05-01

Magnetic nanoparticles with room temperature remanent magnetic vortices stabilized by their curvature are very intriguing due to their potential use in biomedicine. In the present study, we investigate room temperature magnetic chirality in 100 nm diameter permalloy spherical caps with 10 nm and 30 nm thicknesses. Micromagnetic OOMMF simulations predict the equilibrium spin structure for these caps to form a vortex state. We fabricate the permalloy caps by sputtering permalloy on both close-packed and sparse arrays of polystyrene nanoparticles. Magnetic force microscopy scans show a clear signature of a vortex state in close-packed caps of both 10 nm and 30 nm thicknesses. Alternating gradient magnetometry measurements of the caps are consistent with a remnant vortex state in 30 nm thick caps and a transition to an onion state followed by a vortex state in 10 nm thick caps. Out-of-plane measurements supported by micromagnetic simulations shows that an out-of-plane field can stabilize a vortex state down to a diameter of 15 nm.

Novel electrospun gas diffusion layers for polymer electrolyte membrane fuel cells: Part II. In operando synchrotron imaging for microscale liquid water transport characterization

NASA Astrophysics Data System (ADS)

Chevalier, S.; Ge, N.; Lee, J.; George, M. G.; Liu, H.; Shrestha, P.; Muirhead, D.; Lavielle, N.; Hatton, B. D.; Bazylak, A.

2017-06-01

This is the second paper in a two-part series in which we investigate the impact of the gas diffusion layer structure on the liquid water distribution in an operating polymer electrolyte membrane (PEM) fuel cell through the procedures of design, fabrication, and testing of novel hydrophobic electrospun gas diffusion layers (eGDLs). In this work, fibre diameters and alignment in eGDLs are precisely controlled, and concurrent synchrotron X-ray radiography and electrochemical impedance spectroscopy (EIS) are used to evaluate the influence of the controlled eGDL parameters on the liquid water distribution and on membrane liquid water content. For eGDLs with small fibre diameters (150-200 nm) and correspondingly smaller pore sizes, reduced liquid water accumulation under the flow field ribs is observed. However, more liquid water is pinned onto the eGDL - at the interface with flow field channels. Orienting fibre alignment perpendicular to the flow field channel direction leads to improved eGDL-catalyst layer contact and prevents rib-channel membrane deformation. On the other hand, eGDLs facilitate significant membrane dry-out, even under highly humidified operating conditions at high current densities.

Pyrolysis of Large Black Liquor Droplets

NASA Technical Reports Server (NTRS)

Bartkus, Tadas P.; Dietrich, Daniel L.; T'ien, James S.; Wessel, Richard A.

2007-01-01

This paper presents the results of experiments involving the pyrolysis of large black liquor droplets in the NASA KC-135 reduced gravity aircraft. The reduced gravity environment facilitated the study of droplets up to 9 mm in diameter extending the results of previous studies to droplet sizes that are similar to those encountered in recovery boilers. Single black liquor droplets were rapidly inserted into a 923 K oven. The primary independent variables were the initial droplet diameter (0.5 mm to 9 mm), the black liquor solids content (66.12% - 72.9% by mass), and the ambient oxygen mole fraction (0.0 - 0.21). Video records of the experiments provided size and shape of the droplets as a function of time. The results show that the particle diameter at the end of the drying stage (D(sub DRY)) increases linearly with the initial particle diameter (D(sub O)). The results further show that the ratio of the maximum swollen diameter (D(sub MAX)) to D(sub O) decreases with increasing D(sub O) for droplets with D(sub O) less than 4 mm. This ratio was independent of D(sub O) for droplets with D(sub O) greater than 4 mm. The particle is most spherical at the end of drying, and least spherical at maximum swollen size, regardless of initial sphericity and droplet size.

Pyrolysis of Large Black Liquor Droplets

NASA Technical Reports Server (NTRS)

Bartkus, Tadas P.; T'ien, James S.; Dietrich, Daniel L.; Wessel, Richard A.

2007-01-01

This paper presents the results of experiments involving the pyrolysis of large black liquor droplets in the NASA KC-135 reduced gravity aircraft. The reduced gravity environment facilitated the study of droplets up to 9 mm in diameter extending the results of previous studies to droplet sizes that are similar to those encountered in recovery boilers. Single black liquor droplets were rapidly inserted into a 923 K oven. The primary independent variables were the initial droplet diameter (0.5 mm to 9 mm), the black liquor solids content (66.12% - 72.9% by mass), and the ambient oxygen mole fraction (0.0 - 0.21). Video records of the experiments provided size and shape of the droplets as a function of time. The results show that the particle diameter at the end of the drying stage (D(sub DRY) ) increases linearly with the initial particle diameter (D(sub O)). The results further show that the ratio of the maximum swollen diameter (D(sub MAX)) to D(sub O) decreases with increasing D(sub O) for droplets with D(sub O) less than 4 mm. This ratio was independent of D(sub O) for droplets with D(sub O) greater than 4 mm. The particle is most spherical at the end of drying, and least spherical at maximum swollen size, regardless of initial sphericity and droplet size.

An AFM-based pit-measuring method for indirect measurements of cell-surface membrane vesicles

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

Zhang, Xiaojun; Department of Biotechnology, Nanchang University, Nanchang, Jiangxi 330031; Chen, Yuan

2014-03-28

Highlights: • Air drying induced the transformation of cell-surface membrane vesicles into pits. • An AFM-based pit-measuring method was developed to measure cell-surface vesicles. • Our method detected at least two populations of cell-surface membrane vesicles. - Abstract: Circulating membrane vesicles, which are shed from many cell types, have multiple functions and have been correlated with many diseases. Although circulating membrane vesicles have been extensively characterized, the status of cell-surface membrane vesicles prior to their release is less understood due to the lack of effective measurement methods. Recently, as a powerful, micro- or nano-scale imaging tool, atomic force microscopy (AFM)more » has been applied in measuring circulating membrane vesicles. However, it seems very difficult for AFM to directly image/identify and measure cell-bound membrane vesicles due to the similarity of surface morphology between membrane vesicles and cell surfaces. Therefore, until now no AFM studies on cell-surface membrane vesicles have been reported. In this study, we found that air drying can induce the transformation of most cell-surface membrane vesicles into pits that are more readily detectable by AFM. Based on this, we developed an AFM-based pit-measuring method and, for the first time, used AFM to indirectly measure cell-surface membrane vesicles on cultured endothelial cells. Using this approach, we observed and quantitatively measured at least two populations of cell-surface membrane vesicles, a nanoscale population (<500 nm in diameter peaking at ∼250 nm) and a microscale population (from 500 nm to ∼2 μm peaking at ∼0.8 μm), whereas confocal microscopy only detected the microscale population. The AFM-based pit-measuring method is potentially useful for studying cell-surface membrane vesicles and for investigating the mechanisms of membrane vesicle formation/release.« less

Economic fabrication of a novel hybrid planar Grating/Fresnel lens for miniature spectrometers.

PubMed

Zhou, Qian; Li, Xinghui; Geng, Menglin; Hu, Haifei; Ni, Kai; Zhong, Lunchao; Yan, Peng; Wang, Xiaohao

2018-03-05

We propose a new technique to fabricate a highly specialized optical element, a hybrid planar Grating/Fresnel lens (G-Fresnel), which is particularly useful to improve or enable more-affordable miniature/portable spectrometers. Both the Fresnel and the grating surface are fabricated simultaneously by sandwiching soft PDMS between a hard grating and a pre-replicated negative Fresnel surface. Several adhesion reduction techniques are also investigated that help improve both fabrication and cost efficiency (by reducing the solidification time) as well as the lifetime of the mold. Alignment errors are systematically analyzed, and their effects on the G-Fresnel lens evaluated. A compact fabrication platform was built, which is smaller than a volume of 160☓140☓106 mm 3 to fit into a conventional vacuum drying oven, for the fabrication of a G-Fresnel lens with a diameter of 25.4 mm, an equivalent focal length of 25 mm, and a blazed grating pattern with 600 lines/mm spacing. The solidification time was reduced to 2 hours thanks to the improved adhesion reduction technique that permits a PDMS drying-temperature as high as 65 °C. The fabricated G-Fresnel lens was evaluated with regard to both geometrical fabrication precision and optical performance. The measured results, using a step gauge and atomic force microscopy, confirm that this replication technique produces high-quality replicates of the master surface-profile. Furthermore, a prototype spectrometer that uses a G-Fresnel lens was built and evaluated. The spectrometer fits within a volume of about 100 mm☓50 mm☓30 mm, and it operates across a wide wavelength spectrum (450 nm to 650 nm). Both the calculation based on the optical software ZEMAX and the experimental measurements are consistent and confirm that the spectrometer with the G-Fresnel lens can provide a spectral resolution of better than 1.2nm.

Magneto-plasmonic Au-Coated Co nanoparticles synthesized via hot-injection method

NASA Astrophysics Data System (ADS)

Souza, João B., Jr.; Varanda, Laudemir C.

2018-02-01

A synthetic procedure is described for the obtaining of superparamagnetic Co nanoparticles (NPs) via hot-injection method in the presence of sodium borohydride. The Co NPs obtained have an average diameter of 5.3 nm and saturation magnetization of 115 emu g-1. A modified Langevin equation is fitted to the magnetization curves using a log-normal distribution for the particle diameter and an effective field to account for dipolar interactions. The calculated magnetic diameter of the Co NPs is 0.6 nm smaller than TEM-derived values, implying a magnetic dead layer of 0.3 nm. The magnetic core is coated with Au to prevent oxidation, resulting in water-stable magneto-plasmonic Co/Au core/shell NPs with saturation of 71.6 emu g-1. The coating adds a localized surface plasmon resonance property with absorbance in the so-called ‘therapeutic window’ (690-900 nm), suitable for biomedical applications. It is suggested that these multifunctional NPs are distinguished as a potential platform for applied and fundamental research.

[Characterization of microstructure of ibuprofen-hydroxypropyl-beta-cyclodextrin and ibuprofen-beta-cyclodextrin by atomic force microscope].

PubMed

Wang, Li-juan; Zhu, Zhao-jing; Che, Ke-ke; Ju, Feng-ge

2008-09-01

The microstructures of ibuprofen-hydroxypropyl-bets-cyclodextrin (IBU-HP-beta-CyD) and ibuprofen-beta-cyclodextrin (IBU-beta-CyD) were observed by atomic force microscope (AFM). The high resolving capability of AFM has the tungsten filament probe with the spring constant of 0.06 N x m(-1). Samples were observed in a small scale scanning area of 10.5 nm x 10.5 nm and 800 x 800 pixels. The original scanning images were gained by tapping mode at room temperature. Their three-dimensional reconstruction of microstructure was performed by G3DR software. The outer diameters of HP-beta-CyD and beta-CyD are 1.53 nm. The benzene diameter of IBU is 0.62 nm, fitting to the inner diameters of HP-beta-CyD and beta-CyD. The benzene and hydrophobic chain of IBU enter into the hole of cyclodextrin at 1:1 ratio. The results were evidenced by IR, X-ray diffraction and the phase solubility.

Broadband visible light source based on AllnGaN light emitting diodes

DOEpatents

Crawford, Mary H.; Nelson, Jeffrey S.

2003-12-16

A visible light source device is described based on a light emitting diode and a nanocluster-based film. The light emitting diode utilizes a semiconductor quantum well structure between n-type and p-type semiconductor materials on the top surface a substrate such as sapphire. The nanocluster-based film is deposited on the bottom surface of the substrate and can be derived from a solution of MoS.sub.2, MoSe.sub.2, WS.sub.2, and WSe.sub.2 particles of size greater than approximately 2 nm in diameter and less than approximately 15 nm in diameter, having an absorption wavelength greater than approximately 300 nm and less than approximately 650 nm.

Potential health effects of fume particles on the crew of spacecrafts

NASA Technical Reports Server (NTRS)

Ferin, Juraj; Oberdorster, Gunter

1992-01-01

The effect of the size of polymer (e.g., Teflon) particles in fumes inhaled by spacecraft personnel on the condition of the lung tissue and on the recovery of the exposed subjects was investigated in rats receiving a single intrapulmonary instillation, or repeated inhalation exposures to either TiO2 particles with primary particle diameter 20 nm, or TiO2 particles with primary particle diameter 250 nm. It was found that rats exposed to 20-nm-diam particles showed a dramatically higher toxicity and slower recovery compared to the group exposed to the 250-nm-diam particles, due to a larger extent of penetration of the interstitium of the lung by the finer particles.

Synthesis of neodymium hydroxide nanotubes and nanorods by soft chemical process.

PubMed

Shi, Weidong; Yu, Jiangbo; Wang, Haishui; Yang, Jianhui; Zhang, Hongjie

2006-08-01

A facile soft chemical approach using cetyltrimethylammonium bromide (CTAB) as template is successfully designed for synthesis of neodymium hydroxide nanotubes. These nanotubes have an average outer diameter around 20 nm, inner diameter around 2 nm, and length ranging from 100 to 120 nm, high BET surface area of 495.71 m(2) g(-1). We also find that neodymium hydroxide nanorods would be obtained when CTAB absented in reaction system. The Nd(OH)3 nanorods might act as precursors that are converted into Nd2O3 nanorods through dehydration at 550 degrees C. The nanorods could exhibit upconversion emission characteristic under excitation of 591 nm at room temperature.

Effect of atmospheric electricity on dry deposition of airborne particles from atmosphere

NASA Astrophysics Data System (ADS)

Tammet, H.; Kimmel, V.; Israelsson, S.

The electric mechanism of dry deposition is well known in the case of unattached radon daughter clusters that are unipolar charged and of high mobility. The problematic role of the electric forces in deposition of aerosol particles is theoretically examined by comparing the fluxes of particles carried by different deposition mechanisms in a model situation. The electric mechanism of deposition appears essential for particles of diameter 10-200 nm in conditions of low wind speed. The electric flux of fine particles can be dominant on the tips of leaves and needles even in a moderate atmospheric electric field of a few hundred V m -1 measured over the plane ground surface. The electric deposition is enhanced under thunderclouds and high voltage power lines. Strong wind suppresses the relative role of the electric deposition when compared with aerodynamic deposition. When compared with diffusion deposition the electric deposition appears less uniform: the precipitation particulate matter on the tips of leaves and especially on needles of top branches of conifer trees is much more intensive than on the ground surface and electrically shielded surfaces of plants. The knowledge of deposition geometry could improve our understanding of air pollution damage to plants.

Ultrastructure Features and Three-Dimensional Transmission Electron Tomography of Dhub Lizard (Uromastyx Aegyptia) Cornea and Its Adaptation to a Desert Environment.

PubMed

Akhtar, Saeed; Alkhalaf, Mousa; Khan, Adnan A; Almubrad, Turki M

2016-08-01

We report ultrastructural features and transmission electron tomography of the dhub lizard (Uromastyx aegyptia) cornea and its adaptation to hot and dry environments. Six corneas of dhub lizards were fixed in 2.5% glutaraldehyde and processed for electron microscopy and tomography. The ultrathin sections were observed with a JEOL 1400 transmission electron microscope. The cornea of the dhub lizard is very thin (~28-30 µm). The epithelium constitutes ~14% of the cornea, whereas the stroma constitutes 80% of the cornea. The middle stromal lamellae are significantly thicker than anterior and posterior stromal lamellae. Collagen fibril (CF) diameters in the anterior stroma are variable in size (25-75 nm). Proteoglycans (PGs) are very large in the middle and posterior stroma, whereas they are small in the anterior stroma. Three-dimensional electron tomography was carried out to understand the structure and arrangement of the PG and CFs. The presence of large PGs in the posterior and middle stroma might help the animal retain a large amount of water to protect it from dryness. The dhub corneal structure is equipped to adapt to the dry and hot desert environment.

Development and validation of a dried blood spot-HPLC assay for the determination of metronidazole in neonatal whole blood samples.

PubMed

Suyagh, Maysa Faisal; Iheagwaram, Godwill; Kole, Prashant Laxman; Millership, Jeff; Collier, Paul; Halliday, Henry; McElnay, James C

2010-05-01

A selective and sensitive high-performance liquid chromatography method with UV detection for the determination of metronidazole in dried blood spots (DBS) has been developed and validated. DBS samples [spiked or patient samples] were prepared by applying blood (30 microL) to Guthrie cards. Discs (6 mm diameter) were punched from the cards and extracted using water containing the internal standard, tinidazole. The extracted sample was chromatographed without further treatment using a reversed phase system involving a Symmetry(R) C18 (5 microm, 3.9 x 150 mm) preceded by a Symmetry(R) guard column of matching chemistry and a detection wavelength of 317 nm. The mobile phase comprised acetonitrile/0.01 M phosphate solution (KH(2)PO(4)), pH 4.7, 15:85, v/v, with a flow rate of 1 mL/min. The calibration was linear over the range 2.5-50 mg/mL. The limits of detection and quantification were 0.6 and 1.8 microg/mL, respectively. The method has been applied to the determination of 203 DBS samples from neonatal patients for a phamacokinetic/pharmacodynamic study.

Investigation of titanium dioxide nanoparticles toxicity and uptake by plants

NASA Astrophysics Data System (ADS)

Larue, C.; Khodja, H.; Herlin-Boime, N.; Brisset, F.; Flank, A. M.; Fayard, B.; Chaillou, S.; Carrière, M.

2011-07-01

Nanoparticles (NP) are introduced in a growing number of commercial products and their production may lead to their release in the environment. Plants may be a potential entry point for NP in the food chain. Up to now, results describing NP phytotoxical effects and plant accumulation are scarce and contradictory. To increase knowledge on titanium dioxide NP (TiO2-NPs) accumulation and impact on plants, we designed a study on three plant species, namely wheat (Triticum aestivum), oilseed rape (Brassica napus) and Arabidopsis thaliana. These plants were exposed in hydroponics to a panel of well-characterized TiO2-NPs, with diameters ranging from 12 to 140 nm, either anatase or rutile. Their accumulation in plant tissues is currently being assessed by complementary imaging techniques: scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-X-ray fluorescence (SR-μ-XRF) imaging and micro-particle induced X-ray emission (μ-PIXE) imaging. Moreover, the impact of TiO2-NP exposure on germination rate, root elongation, dry biomass and evapotranspiration is evaluated. Preliminary results are presented here, with data collected on wheat plants exposed to 12 nm and 25 nm anatase TiO2-NPs. These results show that TiO2-NPs are taken up by plants, and do not significantly alter their germination and root elongation. These results underline the necessity of deeper evaluation of nanoparticle ecotoxicity, and particularly on their interaction with plants.

Influence of HF acid catalyst concentration on properties of aerogel low-k thin films

NASA Astrophysics Data System (ADS)

Gaikwad, A. S.; Gupta, S. A.; Mahajan, A. M.

2016-08-01

The effect of hydrofluoric acid (HF) catalyst concentration in coating solution on chemical, physical and structural properties of silica aerogel thin films was investigated. The aerogel films were synthesized by using a sol-gel spin coating method followed by aging in ethanol and CO2 supercritical drying. The refractive index (RI) is observed to be reduced from 1.32 to 1.13 and porosity percentage increased from 30.21% to 71.64% in accordance with increasing HF concentration. Deposition of silica aerogel was confirmed from Fourier transform infrared spectroscopy measurement. The nanoporous nature of deposited films was confirmed from field effect scanning electron microscopy and observed pore diameter is in the range of 3.33 to 6.69 nm. The nanoporous nature of the film was also validated from atomic force microscopy and root mean square roughness was observed to be increased from 2.31 nm to 3.2 nm with increasing acid catalyst concentration in the coating solution. The calculated dielectric constant from CV measurement of fabricated metal-insulator-semiconductor structure for the silica aerogel formed at 0.8 ml HF concentration is observed to be 1.73. These deposited nanoporous silica aerogel low-k films with lower k value and smaller pore size have application as interlayer dielectric materials to minimize the disadvantages of porous materials.

Raman scattering and red fluorescence in the photochemical transformation of dry tryptophan particles

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

Lai, Chih Wei; Schwab, Mark; Hill, Steven C.

Tryptophan is a fluorescent amino acid common in proteins. Its absorption is largest for wavelengths λ ≲ 290 nm and its fluorescence emissions peak around 300–350 nm, depending upon the local environment. Here we report the observation of red fluorescence near 600 nm emerging from 488-nm continuous-wave (CW) laser photoexcitation of dry tryptophan (Trp) particles. With an excitation intensity below 0.5 kW/cm 2, dry Trp particles yield distinctive Raman scattering peaks in the presence of relatively weak and spectrally broad emissions with λ ~500–700 nm, allowing estimation of particle temperature at low excitation intensities. When the photoexcitation intensity is increasedmore » to 1 kW/cm 2 or more for a few minutes, fluorescence intensity dramatically increases by more than two orders of magnitude. The fluorescence continues to increase in intensity and gradually shift to the red when photoexcitation intensity and the duration of exposure are increased. The resulting products absorb at visible wavelengths and generate red fluorescence with λ ~ 650–800 nm with 633-nm CW laser excitation. In conclusion, we attribute the emergence of orange and red fluorescence in the Trp products to a photochemical transformation that is instigated by weak optical transitions to triplet states in Trp with 488-nm excitation and which may be expedited by a photothermal effect.« less

Raman scattering and red fluorescence in the photochemical transformation of dry tryptophan particles

DOE PAGES

Lai, Chih Wei; Schwab, Mark; Hill, Steven C.; ...

2016-05-19

Tryptophan is a fluorescent amino acid common in proteins. Its absorption is largest for wavelengths λ ≲ 290 nm and its fluorescence emissions peak around 300–350 nm, depending upon the local environment. Here we report the observation of red fluorescence near 600 nm emerging from 488-nm continuous-wave (CW) laser photoexcitation of dry tryptophan (Trp) particles. With an excitation intensity below 0.5 kW/cm 2, dry Trp particles yield distinctive Raman scattering peaks in the presence of relatively weak and spectrally broad emissions with λ ~500–700 nm, allowing estimation of particle temperature at low excitation intensities. When the photoexcitation intensity is increasedmore » to 1 kW/cm 2 or more for a few minutes, fluorescence intensity dramatically increases by more than two orders of magnitude. The fluorescence continues to increase in intensity and gradually shift to the red when photoexcitation intensity and the duration of exposure are increased. The resulting products absorb at visible wavelengths and generate red fluorescence with λ ~ 650–800 nm with 633-nm CW laser excitation. In conclusion, we attribute the emergence of orange and red fluorescence in the Trp products to a photochemical transformation that is instigated by weak optical transitions to triplet states in Trp with 488-nm excitation and which may be expedited by a photothermal effect.« less

Raman scattering and red fluorescence in the photochemical transformation of dry tryptophan particles.

PubMed

Lai, Chih Wei; Schwab, Mark; Hill, Steven C; Santarpia, Joshua; Pan, Yong-Le

2016-05-30

Tryptophan is a fluorescent amino acid common in proteins. Its absorption is largest for wavelengths λ ≲ 290 nm and its fluorescence emissions peak around 300-350 nm, depending upon the local environment. Here we report the observation of red fluorescence near 600 nm emerging from 488-nm continuous-wave (CW) laser photoexcitation of dry tryptophan (Trp) particles. With an excitation intensity below 0.5 kW/cm², dry Trp particles yield distinctive Raman scattering peaks in the presence of relatively weak and spectrally broad emissions with λ ∼500-700 nm, allowing estimation of particle temperature at low excitation intensities. When the photoexcitation intensity is increased to 1 kW/cm² or more for a few minutes, fluorescence intensity dramatically increases by more than two orders of magnitude. The fluorescence continues to increase in intensity and gradually shift to the red when photoexcitation intensity and the duration of exposure are increased. The resulting products absorb at visible wavelengths and generate red fluorescence with λ ∼ 650-800 nm with 633-nm CW laser excitation. We attribute the emergence of orange and red fluorescence in the Trp products to a photochemical transformation that is instigated by weak optical transitions to triplet states in Trp with 488-nm excitation and which may be expedited by a photothermal effect.

Diameter modulation of vertically aligned single-walled carbon nanotubes.

PubMed

Xiang, Rong; Einarsson, Erik; Murakami, Yoichi; Shiomi, Junichiro; Chiashi, Shohei; Tang, Zikang; Maruyama, Shigeo

2012-08-28

We demonstrate wide-range diameter modulation of vertically aligned single-walled carbon nanotubes (SWNTs) using a wet chemistry prepared catalyst. In order to ensure compatibility to electronic applications, the current minimum mean diameter of 2 nm for vertically aligned SWNTs is challenged. The mean diameter is decreased to about 1.4 nm by reducing Co catalyst concentrations to 1/100 or by increasing Mo catalyst concentrations by five times. We also propose a novel spectral analysis method that allows one to distinguish absorbance contributions from the upper, middle, and lower parts of a nanotube array. We use this method to quantitatively characterize the slight diameter change observed along the array height. On the basis of further investigation of the array and catalyst particles, we conclude that catalyst aggregation-rather than Ostwald ripening-dominates the growth of metal particles.

Synthesis of subnanometer-diameter vertically aligned single-walled carbon nanotubes with copper-anchored cobalt catalysts

NASA Astrophysics Data System (ADS)

Cui, Kehang; Kumamoto, Akihito; Xiang, Rong; An, Hua; Wang, Benjamin; Inoue, Taiki; Chiashi, Shohei; Ikuhara, Yuichi; Maruyama, Shigeo

2016-01-01

We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high-quality SWNTs are expected to pave the way to replace silicon for next-generation optoelectronic and photovoltaic devices.We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high-quality SWNTs are expected to pave the way to replace silicon for next-generation optoelectronic and photovoltaic devices. Electronic supplementary information (ESI) available: Comparison between the Co monometallic catalyst system and the Co/Mo bimetallic catalyst system, the effect of CVD temperature on the G/D ratio, the effect of ethanol partial pressure on the morphology, diameter and quality of SWNT films, and Raman spectra of the Si/SiO2 substrate. See DOI: 10.1039/c5nr06007a

Exposure Characteristics of Nanoparticles as Process By-products for the Semiconductor Manufacturing Industry.

PubMed

Choi, Kwang-Min; Kim, Jin-Ho; Park, Ju-Hyun; Kim, Kwan-Sick; Bae, Gwi-Nam

2015-01-01

This study aims to elucidate the exposure properties of nanoparticles (NPs; <100 nm in diameter) in semiconductor manufacturing processes. The measurements of airborne NPs were mainly performed around process equipment during fabrication processes and during maintenance. The number concentrations of NPs were measured using a water-based condensation particle counter having a size range of 10-3,000 nm. The chemical composition, size, and shape of NPs were determined by scanning electron microscopy and transmission electron microscopy techniques equipped with energy dispersive spectroscopy. The resulting concentrations of NPs ranged from 0.00-11.47 particles/cm(3). The concentration of NPs measured during maintenance showed a tendency to increase, albeit incrementally, compared to that measured during normal conditions (under typical process conditions without maintenance). However, the increment was small. When comparing the mean number concentration and standard deviation (n ± σ) of NPs, the chemical mechanical polishing (CMP) process was the highest (3.45 ± 3.65 particles/cm(3)), and the dry etch (ETCH) process was the lowest (0.11 ± 0.22 particles/cm(3)). The major NPs observed were silica (SiO2) and titania (TiO2) particles, which were mainly spherical agglomerates ranging in size from 25-280 nm. Sampling of semiconductor processes in CMP, chemical vapor deposition, and ETCH reveled NPs were <100 nm in those areas. On the other hand, particle size exceeded 100 nm in diffusion, metallization, ion implantation, and wet cleaning/etching process. The results show that the SiO2 and TiO2 are the major NPs present in semiconductor cleanroom environments.

A water-based fast integrated mobility spectrometer (WFIMS) with enhanced dynamic size range

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

Pinterich, Tamara; Spielman, Steven R.; Hering, Susanne

We developed a water-based fast integrated mobility spectrometer (WFIMS) with enhanced dynamic size range. The WFIMS builds on two established technologies: the fast integrated mobility spectrometer and laminar flow water-based condensation methodology. Inside WFIMS, particles of differing electrical mobility are separated in a drift tube and subsequently enlarged through water condensation. Particle size and concentration are measured via digital imaging at a frame rate of 10 Hz. When we measure particles of different mobilities simultaneously, the WFIMS resolves particle diameters ranging from 8 to 580 nm within 1 s or less. The performance of WFIMS was characterized with differential mobilitymore » analyzer (DMA) classified (NH 4) 2SO 2 particles with diameters ranging from 8 to 265 nm. The mean particle diameters measured by WFIMS were found to be in excellent agreement with DMA centroid diameters. Furthermore, detection efficiency of WFIMS was characterized using a condensation particle counter as a reference and is nearly 100% for particles with diameter greater than 8 nm. In general, measured and simulated WFIMS mobility resolutions are in good agreement. But, some deviations are observed at low particle mobilities, likely due to the non-idealities of the WFIMS electric field.« less

A water-based fast integrated mobility spectrometer (WFIMS) with enhanced dynamic size range

DOE PAGES

Pinterich, Tamara; Spielman, Steven R.; Hering, Susanne; ...

2017-06-08

We developed a water-based fast integrated mobility spectrometer (WFIMS) with enhanced dynamic size range. The WFIMS builds on two established technologies: the fast integrated mobility spectrometer and laminar flow water-based condensation methodology. Inside WFIMS, particles of differing electrical mobility are separated in a drift tube and subsequently enlarged through water condensation. Particle size and concentration are measured via digital imaging at a frame rate of 10 Hz. When we measure particles of different mobilities simultaneously, the WFIMS resolves particle diameters ranging from 8 to 580 nm within 1 s or less. The performance of WFIMS was characterized with differential mobilitymore » analyzer (DMA) classified (NH 4) 2SO 2 particles with diameters ranging from 8 to 265 nm. The mean particle diameters measured by WFIMS were found to be in excellent agreement with DMA centroid diameters. Furthermore, detection efficiency of WFIMS was characterized using a condensation particle counter as a reference and is nearly 100% for particles with diameter greater than 8 nm. In general, measured and simulated WFIMS mobility resolutions are in good agreement. But, some deviations are observed at low particle mobilities, likely due to the non-idealities of the WFIMS electric field.« less

Diameter-dependent optical constants of gold mesoparticles electrodeposited on aluminum films containing copper.

PubMed

Brevnov, Dmitri A; Bungay, Corey

2005-08-04

Electrodeposition of gold mesoparticles on anodized and chemically etched aluminum/copper films deposited on silicon wafers proceeds by instantaneous nucleation and with no diffusion limitations. Both of these phenomena favor the formation of relatively monodispersed gold particles. Under the reported electrodeposition conditions, the relative standard deviation of the particle diameter is 25%. The particle coverage is 7 x 10(8) particles cm(-2). The mean particle diameter varies as a function of electrodeposition time in the range of 40-80 nm. Optical constants of gold mesoparticles are resolved by spectroscopic ellipsometry. A two-layer optical model is constructed to determine both extinction coefficients and refractive indexes of gold mesoparticles as a function of the mean particle diameter. The absorption peak, associated with surface plasmons, is modeled with two Lorentz oscillators. Absorption peak maximums shift from 610 to 675 nm as the mean particle diameter increases from 42 to 74 nm. Electrodeposition of gold particles on technologically relevant substrates, such as aluminum/copper films, is expected to increase the utility of gold particles and facilitate their incorporation in nanostructured materials and a variety of electronic and optical devices.

Translocation of 40 nm diameter nanowires through the intestinal epithelium of Daphnia magna

PubMed Central

Mattsson, Karin; Adolfsson, Karl; Ekvall, Mikael T.; Borgström, Magnus T.; Linse, Sara; Hansson, Lars-Anders; Cedervall, Tommy; Prinz, Christelle N.

2016-01-01

Abstract Nanowires (NWs) have unique electrical and optical properties of value for many applications including lighting, sensing, and energy harnessing. Consumer products containing NWs increase the risk of NWs being released in the environment, especially into aquatic ecosystems through sewage systems. Daphnia magna is a common, cosmopolitan freshwater organism sensitive to toxicity tests and represents a likely entry point for nanoparticles into food webs of aquatic ecosystems. Here we have evaluated the effect of NW diameter on the gut penetrance of NWs in Daphnia magna. The animals were exposed to NWs of two diameters (40 and 80 nm) and similar length (3.6 and 3.8 μm, respectively) suspended in water. In order to locate the NWs in Daphnia, the NWs were designed to comprise one inherently fluorescent segment of gallium indium phosphide (GaInP) flanked by a gallium phosphide (GaP) segment. Daphnia mortality was assessed directly after 24 h of exposure and 7 days after exposure. Translocation of NWs across the intestinal epithelium was investigated using confocal fluorescence microscopy directly after 24 h of exposure and was observed in 89% of Daphnia exposed to 40 nm NWs and in 11% of Daphnia exposed to 80 nm NWs. A high degree of fragmentation was observed for NWs of both diameters after ingestion by the Daphnia, although 40 nm NWs were fragmented to a greater extent, which could possibly facilitate translocation across the intestinal epithelium. Our results show that the feeding behavior of animals may enhance the ability of NWs to penetrate biological barriers and that penetrance is governed by the NW diameter. PMID:27181920

Quantitative characterization of gold nanoparticles by field-flow fractionation coupled online with light scattering detection and inductively coupled plasma mass spectrometry.

PubMed

Schmidt, Bjørn; Loeschner, Katrin; Hadrup, Niels; Mortensen, Alicja; Sloth, Jens J; Koch, Christian Bender; Larsen, Erik H

2011-04-01

An analytical platform coupling asymmetric flow field-flow fractionation (AF(4)) with multiangle light scattering (MALS), dynamic light scattering (DLS), and inductively coupled plasma mass spectrometry (ICPMS) was established and used for separation and quantitative determination of size and mass concentration of nanoparticles (NPs) in aqueous suspension. Mixtures of three polystyrene (PS) NPs between 20 and 100 nm in diameter and mixtures of three gold (Au) NPs between 10 and 60 nm in diameter were separated by AF(4). The geometric diameters of the separated PS NPs and the hydrodynamic diameters of the Au and PS NPs were determined online by MALS and DLS, respectively. The three separated Au NPs were quantified by ICPMS and recovered at 50-95% of the injected masses, which ranged between approximately 8-80 ng of each nanoparticle size. Au NPs adhering to the membrane in the separation channel was found to be a major cause for incomplete recoveries. The lower limit of detection (LOD) ranged between 0.02 ng Au and 0.4 ng Au, with increasing LOD by increasing nanoparticle diameter. The analytical platform was applied to characterization of Au NPs in livers of rats, which were dosed with 10 nm, 60 nm, or a mixture of 10 and 60 nm nanoparticles by intravenous injection. The homogenized livers were solubilized in tetramethylammonium hydroxide (TMAH), and the recovery of Au NPs from the livers amounted to 86-123% of their total Au content. In spite of successful stabilization with bovine serum albumin even in alkaline medium, separation of the Au NPs by AF(4) was not possible due to association with undissolved remains of the alkali-treated liver tissues as demonstrated by electron microscopy images.

Hierarchically assembled Au microspheres and sea urchin-like architectures: formation mechanism and SERS study

NASA Astrophysics Data System (ADS)

Wang, Xiansong; Yang, Da-Peng; Huang, Peng; Li, Min; Li, Chao; Chen, Di; Cui, Daxiang

2012-11-01

The hierarchically assembled Au microspheres/sea urchin-like structures have been synthesized in aqueous solution at room temperature with and without proteins (bovine serum albumin, BSA) as mediators. The average diameter of an individual Au microsphere is 300-600 nm, which is composed of some compact nanoparticles with an average diameter of about 15 nm. Meanwhile, the sea urchin-like Au architecture exhibits an average diameter of 600-800 nm, which is made up of some nanopricks with an average length of 100-200 nm. These products are characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electronic microscopy (TEM). It is found that the BSA and ascorbic acid (AA) have great effects on the morphology of the resulting products. Two different growth mechanisms are proposed. The study on surface enhanced Raman scattering (SERS) activities is also carried out between Au microspheres and Au sea urchin-like architectures. It is found that Au urchin-like architectures possess much higher SERS activity than the Au microspheres. Our work may shed light on the design and synthesis of hierarchically self-assembled 3D micro/nano-architectures for SERS, catalysis and biosensors.The hierarchically assembled Au microspheres/sea urchin-like structures have been synthesized in aqueous solution at room temperature with and without proteins (bovine serum albumin, BSA) as mediators. The average diameter of an individual Au microsphere is 300-600 nm, which is composed of some compact nanoparticles with an average diameter of about 15 nm. Meanwhile, the sea urchin-like Au architecture exhibits an average diameter of 600-800 nm, which is made up of some nanopricks with an average length of 100-200 nm. These products are characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electronic microscopy (TEM). It is found that the BSA and ascorbic acid (AA) have great effects on the morphology of the resulting products. Two different growth mechanisms are proposed. The study on surface enhanced Raman scattering (SERS) activities is also carried out between Au microspheres and Au sea urchin-like architectures. It is found that Au urchin-like architectures possess much higher SERS activity than the Au microspheres. Our work may shed light on the design and synthesis of hierarchically self-assembled 3D micro/nano-architectures for SERS, catalysis and biosensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32405a

Optimizing heterosurface adsorbent synthesis for liquid chromatography

NASA Astrophysics Data System (ADS)

Bogoslovskii, S. Yu.; Serdan, A. A.

2016-03-01

The structural and geometric parameters of a silica matrix (SM) for the synthesis of heterosurface adsorbents (HAs) are optimized. Modification is performed by shielding the external surfaces of alkyl-modified silica (AS) using human serum albumin and its subsequent crosslinking. The structural and geometric characteristics of the SM, AS, and HA are measured via low-temperature nitrogen adsorption. It is found that the structural characteristics of AS pores with diameters D < 6 nm do not change during HA synthesis, while the volume of pores with diameters of 6 nm < D < 9 nm shrinks slightly due to the adsorption of albumin in the pore orifices. It is established that the volume of pores with diameters D > 9 nm reduces significantly due to adsorption of albumin. It is concluded that silica gel with a maximum pore size distribution close to 5 nm and a minimal proportion of pores with D > 9 nm is optimal for HA synthesis; this allows us to achieve the greatest similarity between the chromatographic retention parameters for HA and AS. The suitability of the synthesized adsorbents for analyzing drugs in biological fluids through direct sample injection is confirmed by chromatography. It was found that the percentage of the protein fraction detected at the outlet of the chromatographic column is 98%.

Ion wind generation and its application to drying of wild Ginger slices (Curcuma Xanthorhiza)

NASA Astrophysics Data System (ADS)

Sumariyah; Khuriati, Ainie; Fachriyah, Enny

2018-05-01

Temulawak or wild ginger is a herbal medicinal derived from lndonesia original. Wild ginger contains include an active compound as curcuminoid and antioxidant oleoresin components having a special quality to take care of health from various diseases. Drying is the important process to produce wild ginger (Curcuma xanthorrhiza) simplicia as raw material herbal medicine. In this study, has been dried of wild ginger using ion wind which yielded from corona discharge utilizing pin-multi ring concentred electrodes. Corona discharge was generated by using the fixed DC high voltage of 4,3 kV and drying was done at the distance between the fixed electrodes of 4 mm. Shaped of the five temulawak slices is a circle with a thickness of 2 mm and the diameter of 10 mm - 30 mm with 5 mm diameter interval. The sliced temulawak is placed just below the concentric multi-ring electrode and is 2 mm in distance. The wild ginger slices were dried with time varied 5-65 minutes with time interval 5 minutes. The researched result of drying of wild ginger slices obtained drying rate and shrinkage is inversely proportional to drying time.

Feasibility Study For Use Of Commercial Cask Vendor Dry Transfer Systems To Unload Used Fuel Assemblies In L-Area

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

Krementz, Dan; Rose, David; Dunsmuir, Mike

2014-02-06

The purpose of this study is to determine whether a commercial dry transfer system (DTS) could be used for loading or unloading used nuclear fuel (UNF) in L-Basin and to determine if a DTS pool adapter could be made for L-Basin Transfer Pit #2 that could accommodate a variety of DTS casks and fuel baskets or canisters up to 24” diameter.[1, 2] This study outlines the technical feasibility of accommodating different vendor dry transfer systems in the L-Basin Transfer Bay with a general work scope. It identifies equipment needing development, facility modifications, and describes the needed analyses and calculations. Aftermore » reviewing the L-Basin Transfer Bay area layout and information on the only DTS system currently in use for the Nuclear Assurance Corporation Legal Weight Truck cask (NAC LWT), the authors conclude that use of a dry transfer cask is feasible. AREVA was contacted and acknowledged that they currently do not have a design for a dry transfer cask for their new Transnuclear Long Cask (TN-LC) cask. Nonetheless, this study accounted for a potential future DTS from AREVA to handle fuel baskets up to 18” in diameter. Due to the layout of the Transfer Bay, it was determined that a DTS cask pool adapter designed specifically for spanning Pit #2 and placed just north of the 70 Ton Cask lid lifting superstructure would be needed. The proposed pool adapter could be used to transition a fuel basket up to 24” in diameter and ~11 feet long from a dry transfer cask to the basin. The 18” and 24” applications of the pool adapter are pending vendor development of dry transfer casks that accommodate these diameters. Once a fuel basket has been lowered into Pit #2 through a pool adapter, a basket cart could be used to move the basket out from under the pool adapter for access by the 5 Ton Crane. The cost to install a dry transfer cask handling system in L-Area capable of handling multiple vendor provided transport and dry transfer casks and baskets with different diameters and lengths would likely be on the same order of magnitude as the Basin Modifications project. The cost of a DTS capability is affected by the number of design variations of different vendor transport and dry transfer casks to be considered for design input. Some costs would be incurred for each vendor DTS to be handled. For example, separate analyses would be needed for each dry transfer cask type such as criticality, shielding, dropping a dry transfer cask and basket, handling and auxiliary equipment, procedures, operator training, readiness assessments, and operational readiness reviews. A DTS handling capability in L-Area could serve as a backup to the Shielded Transfer System (STS) for unloading long casks and could support potential future missions such as the Idaho National Laboratory (INL) Exchange or transferring UNF from wet to dry storage.« less

Novel Hollow Fiber Air Filters for the Removal of Ultrafine Particles in PM2.5 with Repetitive Usage Capability.

PubMed

Li, Manqing; Feng, Yingnan; Wang, Kaiyu; Yong, Wai Fen; Yu, Liya; Chung, Tai-Shung

2017-09-05

Severe air pollution has become a global concern, and there is a pressing need to develop effective and efficient air filters for removing airborne particulate matters (PMs). In this work, a highly permeable poly(ether sulfone) (PES) based hollow fiber membrane was developed via a one-step dry-jet wet spinning. For the first time, a hollow fiber membrane was used in removing the ultrafine particles (PMs with aerodynamic equivalent diameters of less than 100 nm) in PM 2.5 . The novel air filter was designed to possess the synergistic advantages of porous filters and fibrous filters with a sievelike outer surface and a fibrouslike porous substrate. A filtration efficiency of higher than 99.995% could be easily achieved when the self-support hollow fiber was challenged with less than 300 nm particulates. Without losses of the structural advantages, we have demonstrated that the permeation properties of the hollow fiber membrane can be facilely tailored via manipulation of the dope and bore fluid formulations. Various cleaning strategies were explored to regenerate the membrane performance after fouling. Both water rinse and backwash showed effectiveness to restore the membrane permeance for repetitive usage.

Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

NASA Astrophysics Data System (ADS)

Hussain, Tajamal; Shah, Asma Tufail; Shehzad, Khurram; Mujahid, Adnan; Farooqi, Zahoor Hussain; Raza, Muhammad Hamid; Ahmed, Mirza Nadeem; Nisa, Zaib Un

2015-12-01

Uniform porous anodized aluminum oxide (AAO) membrane has been synthesized by two-step anodization for fabricating tungsten trioxide (WO3) nanowires. Under assayed conditions, uniform porous structure of alumina (Al2O3) membrane with long range ordered hexagonal arrangements of nanopores was achieved. The self-assembled template possesses pores of internal diameter of 50 nm and interpore distance ( d int) of 80 nm with a thickness of about 80 µm, i.e., used for fabrication of nanostructures. WO3 nanowires have been fabricated by simple electroless deposition method inside Al2O3 nanopores. SEM images show tungsten trioxide nanowire with internal diameter of about 50 nm, similar to porous diameter of AAO template. XRD results showed that nanowires exist in cubic crystalline state with minor proportion of monoclinic phase.

Pentatwinned Cu Nanowires with Ultrathin Diameters below 20 nm and Their Use as Templates for the Synthesis of Au-Based Nanotubes

DOE PAGES

Luo, Ming; Zhou, Ming; Rosa da Silva, Robson; ...

2017-01-24

Here, we report a one-pot method for the facile synthesis of Cu nanowires in high purity, together with ultrathin diameters well below 20 nm. Selected area electron diffraction and high-resolution transmission electron microscopy studies confirm that the Cu nanowires are grown along the <110> direction to give pentatwinned, one-dimensional nanostructures, enclosed by five {100} facets on the side surface. A systematic study further indicates that it is critical to conduct the synthesis under an argon atmosphere in order to improve the purity and uniformity of the nanowires while keeping their diameters thinner than 20 nm. Finally, we demonstrate the usemore » of these nanowires as sacrificial templates for the synthesis of Au-based nanotubes through a galvanic replacement process.« less

Pentatwinned Cu Nanowires with Ultrathin Diameters below 20 nm and Their Use as Templates for the Synthesis of Au-Based Nanotubes

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

Luo, Ming; Zhou, Ming; Rosa da Silva, Robson

Here, we report a one-pot method for the facile synthesis of Cu nanowires in high purity, together with ultrathin diameters well below 20 nm. Selected area electron diffraction and high-resolution transmission electron microscopy studies confirm that the Cu nanowires are grown along the <110> direction to give pentatwinned, one-dimensional nanostructures, enclosed by five {100} facets on the side surface. A systematic study further indicates that it is critical to conduct the synthesis under an argon atmosphere in order to improve the purity and uniformity of the nanowires while keeping their diameters thinner than 20 nm. Finally, we demonstrate the usemore » of these nanowires as sacrificial templates for the synthesis of Au-based nanotubes through a galvanic replacement process.« less

Atomic force microscopy investigation of the giant mimivirus

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

Kuznetsov, Yuri G.; Xiao Chuan; Sun Siyang

2010-08-15

Mimivirus was investigated by atomic force microscopy in its native state following serial degradation by lysozyme and bromelain. The 750-nm diameter virus is coated with a forest of glycosylated protein fibers of lengths about 140 nm with diameters 1.4 nm. Fibers are capped with distinctive ellipsoidal protein heads of estimated Mr = 25 kDa. The surface fibers are attached to the particle through a layer of protein covering the capsid, which is in turn composed of the major capsid protein (MCP). The latter is organized as an open network of hexagonal rings with central depressions separated by 14 nm. Themore » virion exhibits an elaborate apparatus at a unique vertex, visible as a star shaped depression on native particles, but on defibered virions as five arms of 50 nm width and 250 nm length rising above the capsid by 20 nm. The apparatus is integrated into the capsid and not applied atop the icosahedral lattice. Prior to DNA release, the arms of the star disengage from the virion and it opens by folding back five adjacent triangular faces. A membrane sac containing the DNA emerges from the capsid in preparation for fusion with a membrane of the host cell. Also observed from disrupted virions were masses of distinctive fibers of diameter about 1 nm, and having a 7-nm periodicity. These are probably contained within the capsid along with the DNA bearing sac. The fibers were occasionally observed associated with toroidal protein clusters interpreted as processive enzymes modifying the fibers.« less

7 CFR 51.1015 - Serious damage.

Code of Federal Regulations, 2013 CFR

2013-01-01

... diameter; (c) Exanthema (ammoniation) which occurs as small spots over more than 25 percent of the fruit... circle one-half inch in diameter; (g) Sunburn which causes decided flattening of the fruit, marked drying...

7 CFR 51.1015 - Serious damage.

Code of Federal Regulations, 2014 CFR

2014-01-01

... diameter; (c) Exanthema (ammoniation) which occurs as small spots over more than 25 percent of the fruit... circle one-half inch in diameter; (g) Sunburn which causes decided flattening of the fruit, marked drying...

Investigation of H2S separation from H2S/CH4 mixtures using functionalized and non-functionalized vertically aligned carbon nanotube membranes

NASA Astrophysics Data System (ADS)

Gilani, Neda; Towfighi, Jafar; Rashidi, Alimorad; Mohammadi, Toraj; Omidkhah, Mohammad Reza; Sadeghian, Ahmad

2013-04-01

Separation of H2S from binary mixtures of H2S/CH4 using vertically aligned carbon nanotube membranes fabricated in anodic aluminum oxide (AAO) template was studied experimentally. Carbon nanotubes (CNTs) were grown in five AAO templates with different pore diameters using chemical vapor deposition, and CNT/AAO membranes with tubular carbon nanotube structure and open caps were selected for separation of H2S. For this, two tubular CNT/AAO membranes were fabricated with the CNT inner diameters of 23 and 8 nm. It was found that permeability and selectivity of the membrane with inner diameter of 23 nm for CNT were independent of upstream feed pressure and H2S feed concentration unlike that of CNT having an inner diameter of 8 nm. Selectivity of these membranes for separation of H2S was obtained in the ranges of 1.36-1.58 and 2.11-2.86, for CNTs with internal diameters of 23 and 8 nm, respectively. In order to enhance the separation of H2S from H2S/CH4 mixtures, dodecylamine was used to functionalize the CNT/AAO membrane with higher selectivity. The results showed that for amido-functionalized membrane, both upstream feed pressure and H2S partial pressure in the feed significantly increased H2S permeability, and selectivity for H2S being in the range of 3.0-5.57 respectively.

Stratum corneum drying drives vertical compression and lipid organization and improves barrier function in vitro.

PubMed

Iwai, Ichiro; Kunizawa, Naomi; Yagi, Eiichiro; Hirao, Tetsuji; Hatta, Ichiro

2013-03-27

The stratum corneum dehydrates after exogenous hydration due to skincare or bathing. In this study, sheets of stratum corneum were isolated from reconstructed human epidermis and the barrier function and structure of these sheets were assessed during drying with the aim of improving our understanding of skincare. Water diffusion through the sheets of stratum corneum decreased with drying, accompanied by decreased thickness and increased visible light transmission through the sheets. Electron paramagnetic resonance revealed that the order parameter values of stratum corneum lipids increased with drying. X-ray diffraction analysis revealed increases in the diffraction intensity of lamellar structures, with an 11-12 nm periodicity and spacing of 0.42 nm for lattice structures with drying. These results suggest that the drying process improves the barrier function of the stratum corneum by organizing the intercellular lipids in a vertically compressed arrangement.

High-Resolution, Large-Area, Nano Imprint Lithography

DTIC Science & Technology

2009-08-27

oxides as the seed layers can provide implication as the general synthetic route for the spontaneous growth of metal - silicide nanowires in large...nano-island array preparation , we have successfully fabricated patterned magnetic recording media as described in Fig. 2. About ~30 nm diameter Si...that we fabricated at UCSD with 5-50 nm diameter magnetic islands was used, since a large- area, hard disk size preparation was necessary, and since a

Fatigue resistance, electrochemical corrosion and biological response of Ti-15Mo with surface modified by amorphous TiO2 nanotubes layer.

PubMed

Campanelli, Leonardo C; Oliveira, Nilson T C; da Silva, Paulo Sergio C P; Bolfarini, Claudemiro; Palmieri, Annalisa; Cura, Francesca; Carinci, Francesco; Motheo, Artur J

2018-03-04

The objective of this work was a systemic evaluation of the anodizing treatment in a β-type Ti-15Mo alloy to grow a TiO 2 nanostructured layer for osseointegration improvement. The technical viability of the surface modification was assessed based on the resistance to mechanical fatigue, electrochemical corrosion, and biological response. By using an organic solution of NH 4 F in ethylene glycol, a well-organized array of 90 nm diameter nanotubes was obtained with a potential of 40 V for 6 h, while undefined nanotubes of 25 nm diameter were formed with a potential of 20 V for 1 h. Nevertheless, the production of the 90 nm diameter nanotubes was followed by micrometer pits that significantly reduced the fatigue performance. The undefined nanotubes of 25 nm diameter, besides the greater cell viability and improved osteoblastic cell differentiation in comparison to the as-polished surface, were not deleterious to the fatigue and corrosion properties. This result strengthens the necessity of an overall evaluation of the anodizing treatment, particularly the fatigue resistance, before suggesting it for the design of implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Experimental determination of surface heat transfer coefficient in a dry ice-ethanol cooling bath using a numerical approach.

PubMed

Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J

BACKGROUND: Dry ice-ethanol bath (-78 degree C) have been widely used in low temperature biological research to attain rapid cooling of samples below freezing temperature. The prediction of cooling rates of biological samples immersed in dry ice-ethanol bath is of practical interest in cryopreservation. The cooling rate can be obtained using mathematical models representing the heat conduction equation in transient state. Additionally, at the solid cryogenic-fluid interface, the knowledge of the surface heat transfer coefficient (h) is necessary for the convective boundary condition in order to correctly establish the mathematical problem. The study was to apply numerical modeling to obtain the surface heat transfer coefficient of a dry ice-ethanol bath. A numerical finite element solution of heat conduction equation was used to obtain surface heat transfer coefficients from measured temperatures at the center of polytetrafluoroethylene and polymethylmetacrylate cylinders immersed in a dry ice-ethanol cooling bath. The numerical model considered the temperature dependence of thermophysical properties of plastic materials used. A negative linear relationship is observed between cylinder diameter and heat transfer coefficient in the liquid bath, the calculated h values were 308, 135 and 62.5 W/(m 2 K) for PMMA 1.3, PTFE 2.59 and 3.14 cm in diameter, respectively. The calculated heat transfer coefficients were consistent among several replicates; h in dry ice-ethanol showed an inverse relationship with cylinder diameter.

Experimental Investigation of Minimum Quantity Lubrication in Meso-scale Milling with Varying Tool Diameter

NASA Astrophysics Data System (ADS)

Yusof, M. Q. M.; Harun, H. N. S. B.; Bahar, R.

2018-01-01

Minimum quantity lubrication (MQL) is a method that uses a very small amount of liquid to reduce friction between cutting tool and work piece during machining. The implementation of MQL machining has become a viable alternative to flood cooling machining and dry machining. The overall performance has been evaluated during meso-scale milling of mild steel using different diameter milling cutters. Experiments have been conducted under two different lubrication condition: dry and MQL with variable cutting parameters. The tool wear and its surface roughness, machined surfaces microstructure and surface roughness were observed for both conditions. It was found from the results that MQL produced better results compared to dry machining. The 0.5 mm tool has been selected as the most optimum tool diameter to be used with the lowest surface roughness as well as the least flank wear generation. For the workpiece, it was observed that the cutting temperature possesses crucial effect on the microstructure and the surface roughness of the machined surface and bigger diameter tool actually resulted in higher surface roughness. The poor conductivity of the cutting tool may be one of reasons behind.

Carbon dioxide gas purification and analytical measurement for leading edge 193nm lithography

NASA Astrophysics Data System (ADS)

Riddle Vogt, Sarah; Landoni, Cristian; Applegarth, Chuck; Browning, Matt; Succi, Marco; Pirola, Simona; Macchi, Giorgio

2015-03-01

The use of purified carbon dioxide (CO2) has become a reality for leading edge 193 nm immersion lithography scanners. Traditionally, both dry and immersion 193 nm lithographic processes have constantly purged the optics stack with ultrahigh purity compressed dry air (UHPCDA). CO2 has been utilized for a similar purpose as UHPCDA. Airborne molecular contamniation (AMC) purification technologies and analytical measurement methods have been extensively developed to support the Lithography Tool Manufacturers purity requirements. This paper covers the analytical tests and characterizations carried out to assess impurity removal from 3.0 N CO2 (beverage grade) for its final utilization in 193 nm and EUV scanners.

Optimization of the aerosolization properties of an inhalation dry powder based on selection of excipients.

PubMed

Minne, Antoine; Boireau, Hélène; Horta, Maria Joao; Vanbever, Rita

2008-11-01

The aim of this study was to investigate the influence of formulation excipients on physical characteristics of inhalation dry powders prepared by spray-drying. The excipients used were a series of amino acids (glycine, alanine, leucine, isoleucine), trehalose and dipalmitoylphosphatidylcholine (DPPC). The particle diameter and the powder density were assessed by laser diffraction and tap density measurements, respectively. The aerosol behaviour of the powders was studied in a Multi-Stage Liquid Impinger. The nature and the relative proportion of the excipients affected the aerosol performance of the powders, mainly by altering powder tap density and degree of particle aggregation. The alanine/trehalose/DPPC (30/10/60 w/w/w) formulation showed optimal aerodynamic behaviour with a mass median aerodynamic diameter of 4.7 microm, an emitted dose of 94% and a fine particle fraction of 54% at an airflow rate of 100 L/min using a Spinhaler inhaler device. The powder had a tap density of 0.10 g/cm(3). The particles were spherical with a granular surface and had a 4 microm volume median diameter. In conclusion, optimization of the aerosolization properties of inhalation dry powders could be achieved by appropriately selecting the composition of the particles.

Effect of Shock Precompression on the Critical Diameter of Liquid Explosives

NASA Astrophysics Data System (ADS)

Petel, Oren E.; Higgins, Andrew J.; Yoshinaka, Akio C.; Zhang, Fan

2006-07-01

The critical diameter of both ambient and shock-precompressed liquid nitromethane confined in PVC tubing are measured experimentally. The experiment was conducted for both amine sensitized and neat NM. In the precompression experiments, the explosive is compressed by a strong shock wave generated by a donor explosive and reflected from a high impedance anvil prior to being detonated by a secondary event. The pressures reached in the test sections prior to detonation propagation was approximately 7 and 8 GPa for amine sensitized and neat NM respectively. The results demonstrated a 30% - 65% decrease in the critical diameter for the shock-compressed explosives. This critical diameter decrease is observed despite a significant decrease in the predicted Von Neumann temperature of the detonation in the precompressed explosive. The results are discussed in the context of theoretical predictions based on thermal ignition theory and previous critical diameter measurements.

Formation of hexagonal boron nitride nanoscrolls induced by inclusion and exclusion of self-assembling molecules in solution process.

PubMed

Hwang, Da Young; Suh, Dong Hack

2014-06-07

Unlike nanoscrolls of 2D graphene, those of 2D h-BN have not been demonstrated, except for only a few experimental reports. Nanoscrolls of h-BN with high yields and reproducibility are first synthesized by a simple solution process. Inner-tube diameters of BNSs including LCAs, N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide, a bile acid derivative and self-assembling material, can be controlled by adjusting the diameter of the LCA fiber which is grown by self-assembly. TEM and SEM images show that BNSs have a tube-like morphology and the inner-tube diameter of BNSs can be controlled in the range from 20 to 60 nm for a smaller diameter, up to 300 nm for a larger diameter by LCA fiber growth inside the BNSs. Finally, open cylindrical BNSs with hollow cores were obtained by dissolving LCAs inside BNSs.

Drying firewood in a temporary solar kiln: a case study.

Treesearch

George R. Sampson; Anthony F. Gasbarro

1986-01-01

A pilot study was undertaken to determine drying rates for small diameter, unsplit paper birch firewood that was dried: (1) in a conventional top-covered pile; (2) in a simple, temporary solar kiln; and (3) in tree length. Drying rates were the same for firewood piles whether they were in the temporary solar kilns or only covered on top to keep rain or snow from...

Electrospun Poly(lactic acid-co-glycolic acid) Scaffolds for Skin Tissue Engineering

PubMed Central

Kumbar, Sangamesh G.; Nukavarapu, Syam Prasad; James, Roshan; Nair, Lakshmi S.; Laurencin, Cato T.

2008-01-01

Electrospun fiber matrices composed of scaffolds of varying fiber diameters were investigated for potential application of severe skin loss. Few systematic studies have been performed to examine the effect of varying fiber diameter electrospun fiber matrices for skin regeneration. The present study reports the fabrication of poly[lactic acid-co-glycolic acid] (PLAGA) matrices with fiber diameters of 150–225, 200–300, 250–467, 500–900, 600–1200, 2500–3000 and 3250–6000 nm via electrospinning. All fiber matrices found to have a tensile modulus from 39.23 ± 8.15 to 79.21 ± 13.71 MPa which falls in the range for normal human skin. Further, the porous fiber matrices have porosity between 38–60 % and average pore diameters between 10–14µm. We evaluated the efficacy of these biodegradable fiber matrices as skin substitutes by seeding them with human skin fibroblasts (hSF). Human skin fibroblasts acquired a well spread morphology and showed significant progressive growth on fiber matrices in the 350–1100 nm diameter range. Collagen type III gene expression was significantly up-regulated in hSF seeded on matrices with fiber diameters in the range of 350–1100 nm. Based on the need, the proposed fiber skin substitutes can be successfully fabricated and optimized for skin fibroblast attachment and growth. PMID:18639927

Study on effect of the surface variation of colloidal silica abrasive during chemical mechanical polishing of sapphire

NASA Astrophysics Data System (ADS)

Bun-Athuek, Natthaphon; Yoshimoto, Yutaka; Sakai, Koya; Khajornrungruang, Panart; Suzuki, Keisuke

2017-07-01

The surface and diameter size variations of colloidal silica particles during the chemical mechanical polishing (CMP) of sapphire substrates were investigated using different particle diameters of 20 and 55 nm. Dynamic light scattering (DLS) results show that the silica particles became larger after CMP under both conditions. The increase in particle size in the slurry was proportional to the material removal amount (MRA) as a function of the removed volume of sapphire substrates by CMP and affected the material removal rate (MRR). Transmission electron microscopy (TEM) images revealed an increase in the size of the fine particles and a change in their surface shape in the slurry. The colloidal silica was coated with the material removed from the substrate during CMP. In this case, the increase in the size of 55 nm diameter particles is larger than that of 20 nm diameter particles. X-ray fluorescence spectrometry (XRF) results indicate that the aluminum element from polished sapphire substrates adhered to the surfaces of silica particles. Therefore, MRR decreases with increasing of polishing time owing to the degradation of particles in the slurry.

Synthesis of subnanometer-diameter vertically aligned single-walled carbon nanotubes with copper-anchored cobalt catalysts.

PubMed

Cui, Kehang; Kumamoto, Akihito; Xiang, Rong; An, Hua; Wang, Benjamin; Inoue, Taiki; Chiashi, Shohei; Ikuhara, Yuichi; Maruyama, Shigeo

2016-01-21

We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high-quality SWNTs are expected to pave the way to replace silicon for next-generation optoelectronic and photovoltaic devices.

Analysis of Cervical Supernatant Samples Luminescence Using 355 nm Laser

NASA Astrophysics Data System (ADS)

Vaitkuviene, A.; Gegzna, V.; Kurtinaitiene, R.; Stanikunas, R.; Rimiene, J.; Vaitkus, J.

2010-05-01

The biomarker discovery for accurate detection and diagnosis of cervical carcinoma and its malignant precursors represents one of the current challenges in clinical medicine. Laser induced autofluorescence spectra in cervical smear content were fitted to predict the cervical epithelium diagnosis as a lab off "optical biopsy" method. Liquid PAP supernatant sediment dried on Quartz plate spectroscopy was performed by 355 nm Nd YAG microlaser STA-1 (Standa, Ltd). For comparison a liquid supernatant spectroscopy was formed by laboratory "Perkin Elmer LS 50B spetrometer at 290, 300, 310 nm excitations. Analysis of spectrum was performed by approximation using the multi-peaks program with Lorentz functions for the liquid samples and with Gaussian functions for the dry samples. Ratio of spectral components area to the area under whole experimental curve (SPP) was calculated. The spectral components were compared by averages of SPP using Mann-Whitney U-test in histology groups. Results. Differentiation of Normal and HSIL/CIN2+ cases in whole supernatant could be performed by stationary laboratory lamp spectroscopy at excitation 290 nm and emission >379 nm with accuracy AUC 0,69, Sens 0,72, Spec 0,65. Differentiation Normal versus HSIL/CIN2+ groups in dried enriched supernatant could be performed by 355 nm microlaser excitation at emission 405-424 nm with accuracy (AUC 0,96, Sens 0,91, Spec 1.00). Diagnostic algorithm could be created for all histology groups differentiation under 355 nm excitation. Microlaser induced "optical biopsy "looks promising method for cervical screening at the point of care.

Characteristics of nanolite crystallization in volcanic pyroclasts

NASA Astrophysics Data System (ADS)

Mujin, M.; Nakamura, M.; Miyake, A.

2017-12-01

Crystal nucleation and initial growth in silicate melt may control the number density and later stage growth of crystals, such as twinning and morphology, and are therefore fundamental but still poorly understood processes in magma crystallization. Petrographic and experimental studies on groundmass microlites shed light on their importance for understanding eruption dynamics, but most studies did not focus on nanometer scale crystals. Recently, we reported "nanolites (30 nm-1 µm in width)" and "ultrananolites (< 30 nm in diameter)", which are nanoscale crystals with extremely high number density, in the interstices of microlites in pyroclasts. In this presentation, we summarize their mineralogical and petrological characteristics in pyroclasts of the 2011 eruption of Shinmoedake (Kirishima volcano group)1. By covering a wide size-range of crystals (down to 1 nm in diameter) based on scanning electron microscopy with tungsten filament (W-SEM), field emission (FE)-SEM, and transmission electron microscopy (TEM), we found a clear size gap (hiatus) in the size distribution and presence of minimum crystal size. In a dense juvenile fragment, crystals were absent or their number densities were too low to measure the sizes of pyroxene with a diameter of < 20 nm and a width of 30-100 nm, plagioclase with a width of < 100 nm, and Fe-Ti oxide with a diameter of 2-10 nm and a width of 20-100 nm. In pumice clasts, crystals smaller than 100 nm were not found. These observations show that nucleation of nanoscale crystals almost paused (froze) in the late stage of crystallization, possibly due to a decrease in undercooling, increase in interfacial free energy, and decrease in diffusivity in a dehydrated melt, whereas crystal growth was mostly continuous. Ultrananolites were found in pyroxene and Fe-Ti oxide; notably, these were spherical, whereas nanolites and microlites were rectangular. The observed ultrananolite-sized particles might partly include "subcritical clusters", which are particles smaller than the critical nucleation size assumed in the transient nucleation models. References 1) Mujin and Nakamura, 2014, Geology, v.42, p.611-614, and Mujin et al, in revision, Am. Min.

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

Kyakuno, Haruka, E-mail: h-kyakuno@kanagawa-u.ac.jp; Institute of Physics, Faculty of Engineering, Kanagawa University, Yokohama 221-8686; Fukasawa, Mamoru

Single-wall carbon nanotubes (SWCNTs) are a good model system that provides atomically smooth nanocavities. It has been reported that water-SWCNTs exhibit hydrophobicity depending on the temperature T and the SWCNT diameter D. SWCNTs adsorb water molecules spontaneously in their cylindrical pores around room temperature, whereas they exhibit a hydrophilic-hydrophobic transition or wet-dry transition (WDT) at a critical temperature T{sub wd} ≈ 220-230 K and above a critical diameter D{sub c} ≈ 1.4-1.6 nm. However, details of the WDT phenomenon and its mechanism remain unknown. Here, we report a systematic experimental study involving X-ray diffraction, optical microscopy, and differential scanning calorimetry.more » It is found that water molecules inside thick SWCNTs (D > D{sub c}) evaporate and condense into ice Ih outside the SWCNTs at T{sub wd} upon cooling, and the ice Ih evaporates and condenses inside the SWCNTs upon heating. On the other hand, residual water trapped inside the SWCNTs below T{sub wd} freezes. Molecular dynamics simulations indicate that upon lowering T, the hydrophobicity of thick SWCNTs increases without any structural transition, while the water inside thin SWCNTs (D < D{sub c}) exhibits a structural transition, forming an ordered ice. This ice has a well-developed hydrogen bonding network adapting to the cylindrical pores of the SWCNTs. Thus, the unusual diameter dependence of the WDT is attributed to the adaptability of the structure of water to the pore dimension and shape.« less

S-Layer Architectures: Extending the Morphogenetic Potential of S-Layer Protein Self Assembly

DTIC Science & Technology

2012-07-11

virus  capsids  (typically  30  to  100nm  in   diameter)  or  hollow  (apo) ferritin  (12  nm  in  diameter)  S...R., Sleytr, U.B., Pum, D. J. Biol. Chem. 2011, 286, 27416-27424 30. Sára,  M.   Trends  Microbiol.  2001,  9,  47-­‐49.   31. Sára

Chirality correlation in double-wall carbon nanotubes as studied by electron diffraction

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

Hirahara, Kaori; Bandow, Shunji; Kociak, Mathieu

2006-05-15

Structural correlation between two adjacent graphitic layers in double-wall carbon nanotubes (DWNTs) was systematically examined by using electron diffraction. Chiral angles and tube diameters were carefully measured, and the chiral indices of individual DWNTs were accurately determined. As a result, it was found that the interlayer distances of DWNTs were widely distributed in the range between 0.34 and 0.38 nm. Chiralities of the inner and outer tubes tended to be distributed at higher chiral angles, approaching 30 deg., for the tubes with diameter D<{approx}3 nm. On the other hand, for the tubes with D>{approx}3 nm, the chiral angles were widelymore » distributed, covering the chiral map entirely. Therefore, we consider that tubes with small diameters have a tendency to form armchair type. Correlation of chiralities between the inner and outer tubes was found to be random.« less

Novel Iron-oxide Catalyzed CNT Formation on Semiconductor Silicon Nanowire

PubMed Central

Adam, Tijjani; U, Hashim

2014-01-01

An aqueous ferric nitrate nonahydrate (Fe(NO3)3.9H2O) and magnesium oxide (MgO) were mixed and deposited on silicon nanowires (SiNWs), the carbon nanotubes (CNTs) formed by the concentration of Fe3O4/MgO catalysts with the mole ratio set at 0.15:9.85 and 600°C had diameter between 15.23 to 90nm with high-density distribution of CNT while those with the mole ratio set at 0.45:9.55 and 730°C had diameter of 100 to 230nm. The UV/Vis/NIR and FT-IR spectroscopes clearly confirmed the presence of the silicon-CNTs hybrid structure. UV/Vis/NIR, FT-IR spectra and FESEM images confirmed the silicon-CNT structure exists with diameters ranging between 15-230nm. Thus, the study demonstrated cost effective method of silicon-CNT composite nanowire formation via Iron-oxide Catalyze synthesis. PMID:25237290

Fabrication and transport property of artificial structure of CNTs using SPM nano-manipulation

NASA Astrophysics Data System (ADS)

Maejima, K.; Kida, M.; Yaguchi, Y.; Sudo, K.; Kawamura, T.; Morimoto, T.; Aoki, N.; Ochiai, Y.

2007-04-01

We have established a novel manipulation technique using a glass-micro capillary under a high-resolution CCD microscope so far. Two isolated multi-wall carbon nanotubes (MWNTs) are settled to form a well-aligned cross structure. Recently, we have tried to develop a fine manipulation system using a scanning probe microscope with a silicon cantilever. Therefore, thinner high-quality MWNTs (˜10 nm in diameter) can be utilized in this system. At the junction, we have observed weak localization and Fano-like-effect, zero bias anomaly whose traces were visible even at room temperature with thick MWNTs (˜100 nm in diameter). On the other hand, with thinner high-quality MWNTs (˜10 nm in diameter), we have observed also anomalous I-V characteristic and Altshuler-Aronov-Spivak-like magneto-oscillations at low temperature in the nano-space transport.

Silicon crystallization in nanodot arrays organized by block copolymer lithography

NASA Astrophysics Data System (ADS)

Perego, Michele; Andreozzi, Andrea; Seguini, Gabriele; Schamm-Chardon, Sylvie; Castro, Celia; BenAssayag, Gerard

2014-12-01

Asymmetric polystyrene- b-polymethylmethacrylate (PS- b-PMMA) block copolymers are used to fabricate nanoporous PS templates with different pore diameter depending on the specific substrate neutralization protocol. The resulting polymeric templates are used as masks for the subsequent deposition of a thin ( h = 5 nm) amorphous Si layer by electron beam evaporation. After removal of the polymeric film and of the silicon excess, well-defined hexagonally packed amorphous Si nanodots are formed on the substrate. Their average diameter ( d < 20 nm), density (1.2 × 1011 cm-2), and lateral distribution closely mimic the original nanoporous template. Upon capping with SiO2 and high temperature annealing (1050 °C, N2), each amorphous Si nanodot rearranges in agglomerates of Si nanocrystals ( d < 4 nm). The average diameter and shape of these Si nanocrystals strongly depend on the size of the initial Si nanodot.

Fast detection of humidity with a subwavelength-diameter fiber taper coated with gelatin film.

PubMed

Zhang, Lei; Gu, Fuxing; Lou, Jingyi; Yin, Xuefeng; Tong, Limin

2008-08-18

A subwavelength-diameter tapered optical fiber coated with gelatin layer for fast relative humidity (RH) sensing is reported. The sensing element is composed of a 680-nm-diameter fiber taper coated with a 80-nm-thickness 8-mm-length gelatin layer, and is operated at a wavelength of 1550 nm. When exposed to moisture, the change in refractive index of the gelatin layer changes the mode field of the guided mode of the coated fiber, and converts a portion of power from guided mode to radiation mode, resulting in RH-dependent loss for optical sensing. The sensor is operated within a wide humidity range (9-94% RH) with high sensitivity and good reversibility. Measured response time is about 70 ms, which is one or two orders of magnitude faster than other types of RH sensors relying on conventional optical fibers or films.

Interactions and reversal-field memory in complex magnetic nanowire arrays

NASA Astrophysics Data System (ADS)

Rotaru, Aurelian; Lim, Jin-Hee; Lenormand, Denny; Diaconu, Andrei; Wiley, John. B.; Postolache, Petronel; Stancu, Alexandru; Spinu, Leonard

2011-10-01

Interactions and magnetization reversal of Ni nanowire arrays have been investigated by the first-order reversal curve (FORC) method. Several series of samples with controlled spatial distribution were considered including simple wires of different lengths and diameters (70 and 110 nm) and complex wires with a single modulated diameter along their length. Subtle features of magnetic interactions are revealed through a quantitative analysis of the local interaction field profile distributions obtained from the FORC method. In addition, the FORC analysis indicates that the nanowire systems with a mean diameter of 70 nm appear to be organized in symmetric clusters indicative of a reversal-field memory effect.

Correlation between size distribution and luminescence properties of spool-shaped InAs quantum dots

NASA Astrophysics Data System (ADS)

Xie, H.; Prioli, R.; Torelly, G.; Liu, H.; Fischer, A. M.; Jakomin, R.; Mourão, R.; Kawabata, R.; Pires, M. P.; Souza, P. L.; Ponce, F. A.

2017-05-01

InAs QDs embedded in an AlGaAs matrix have been produced by MOVPE with a partial capping and annealing technique to achieve controllable QD energy levels that could be useful for solar cell applications. The resulted spool-shaped QDs are around 5 nm in height and have a log-normal diameter distribution, which is observed by TEM to range from 5 to 15 nm. Two photoluminescence peaks associated with QD emission are attributed to the ground and the first excited states transitions. The luminescence peak width is correlated with the distribution of QD diameters through the diameter dependent QD energy levels.

Sol-Gel assembly of CdSe nanoparticles to form porous aerogel networks.

PubMed

Arachchige, Indika U; Brock, Stephanie L

2006-06-21

A detailed study of CdSe aerogels prepared by oxidative aggregation of primary nanoparticles (prepared at room temperature and high temperature conditions, >250 degrees C), followed by CO2 supercritical drying, is described. The resultant materials are mesoporous, with an interconnected network of colloidal nanoparticles, and exhibit BET surface areas up to 224 m2/g and BJH average pore diameters in the range of 16-32 nm. Powder X-ray diffraction studies indicate that these materials retain the crystal structure of the primary nanoparticles, with a slight increase in primary particle size upon gelation and aerogel formation. Optical band gap measurements and photoluminescence studies show that the as-prepared aerogels retain the quantum-confined optical properties of the nanoparticle building blocks despite being connected into a 3-D network. The specific optical characteristics of the aerogel can be further modified by surface ligand exchange at the wet-gel stage, without destroying the gel network.

Sun photometer and lidar measurements of the plume from the Hawaii Kilauea Volcano Pu'u O'o vent: Aerosol flux and SO2 lifetime

USGS Publications Warehouse

Porter, J.N.; Horton, K.A.; Mouginis-Mark, P. J.; Lienert, B.; Sharma, S.K.; Lau, E.; Sutton, A.J.; Elias, T.; Oppenheimer, C.

2002-01-01

Aerosol optical depths and lidar measurements were obtained under the plume of Hawaii Kilauea Volcano on August 17, 2001, ???9 km downwind from the erupting Pu'u O'o vent. Measured aerosol optical depths (at 500 nm) were between 0.2-0.4. Aerosol size distributions inverted from the spectral sun photometer measurements suggest the volcanic aerosol is present in the accumulation mode (0.1-0.5 micron diameter), which is consistent with past in situ optical counter measurements. The aerosol dry mass flux rate was calculated to be 53 Mg d-1. The estimated SO2 emission rate during the aerosol measurements was ???1450 Mg d-1. Assuming the sulfur emissions at Pu'u O'o vent are mainly SO2 (not aerosol), this corresponds to a SO2 half-life of 6.0 hours in the atmosphere.

Eugenol Nanoemulsion Stabilized with Zein and Sodium Caseinate by Self-Assembly.

PubMed

Wang, Lei; Zhang, Yue

2017-03-31

Eugenol-loaded nanoemulsion by zein and sodium caseinate (NaCas) was prepared without using specific equipment or organic solvents. The deprotonated eugenol in hot alkaline was added to NaCas/zein mixtures with different mass ratios at pH 11.5 and then neutralized to pH 7.0. The nanoemulsions showed a well-defined diameter (around 109-139 nm) and a negative surface potential (from -28.5 to -35.8 mV) with spherical morphology. The entrapment efficiency (EE) of 1% (v/v) eugenol reached 84.24% by 2% (m/v) NaCas/zein at a mass ratio of 1:1. This formulation also showed the narrowest size distribution and extraordinary stability during ambient storage (22 °C) up to 30 days and retained good redispersibility after spray- or freeze-drying. The current study showed a promising clean and low-cost strategy to deliver lipophilic compounds containing the hydroxyl group.

Gold Aerogels: Three-Dimensional Assembly of Nanoparticles and Their Use as Electrocatalytic Interfaces

PubMed Central

2016-01-01

Three-dimensional (3D) porous metal nanostructures have been a long sought-after class of materials due to their collective properties and widespread applications. In this study, we report on a facile and versatile strategy for the formation of Au hydrogel networks involving the dopamine-induced 3D assembly of Au nanoparticles. Following supercritical drying, the resulting Au aerogels exhibit high surface areas and porosity. They are all composed of porous nanowire networks reflecting in their diameters those of the original particles (5–6 nm) via electron microscopy. Furthermore, electrocatalytic tests were carried out in the oxidation of some small molecules with Au aerogels tailored by different functional groups. The beta-cyclodextrin-modified Au aerogel, with a host–guest effect, represents a unique class of porous metal materials of considerable interest and promising applications for electrocatalysis. PMID:26751502

Polymer nanoimprinting using an anodized aluminum mold for structural coloration

NASA Astrophysics Data System (ADS)

Kikuchi, Tatsuya; Nishinaga, Osamu; Natsui, Shungo; Suzuki, Ryosuke O.

2015-06-01

Polymer nanoimprinting of submicrometer-scale dimple arrays with structural coloration was demonstrated. Highly ordered aluminum dimple arrays measuring 530-670 nm in diameter were formed on an aluminum substrate via etidronic acid anodizing at 210-270 V and subsequent anodic oxide dissolution. The nanostructured aluminum surface led to bright structural coloration with a rainbow spectrum, and the reflected wavelength strongly depends on the angle of the specimen and the period of the dimple array. The reflection peak shifts gradually with the dimple diameter toward longer wavelength, reaching 800 nm in wavelength at 670 nm in diameter. The shape of the aluminum dimple arrays were successfully transferred to a mercapto-ester ultra-violet curable polymer via self-assembled monolayer coating and polymer replications using a nanoimprinting technique. The nanostructured polymer surfaces with positively and negatively shaped dimple arrays also exhibited structural coloration based on the periodic nanostructure, and reflected light mostly in the visible region, 400-800 nm. This nanostructuring with structural coloration can be easily realized by simple techniques such as anodizing, SAM coating, and nanoimprinting.

Multiple double cross-section transmission electron microscope sample preparation of specific sub-10 nm diameter Si nanowire devices.

PubMed

Gignac, Lynne M; Mittal, Surbhi; Bangsaruntip, Sarunya; Cohen, Guy M; Sleight, Jeffrey W

2011-12-01

The ability to prepare multiple cross-section transmission electron microscope (XTEM) samples from one XTEM sample of specific sub-10 nm features was demonstrated. Sub-10 nm diameter Si nanowire (NW) devices were initially cross-sectioned using a dual-beam focused ion beam system in a direction running parallel to the device channel. From this XTEM sample, both low- and high-resolution transmission electron microscope (TEM) images were obtained from six separate, specific site Si NW devices. The XTEM sample was then re-sectioned in four separate locations in a direction perpendicular to the device channel: 90° from the original XTEM sample direction. Three of the four XTEM samples were successfully sectioned in the gate region of the device. From these three samples, low- and high-resolution TEM images of the Si NW were taken and measurements of the NW diameters were obtained. This technique demonstrated the ability to obtain high-resolution TEM images in directions 90° from one another of multiple, specific sub-10 nm features that were spaced 1.1 μm apart.

Coherent-Interface-Assembled Ag2O-Anchored Nanofibrillated Cellulose Porous Aerogels for Radioactive Iodine Capture.

PubMed

Lu, Yun; Liu, Hongwei; Gao, Runan; Xiao, Shaoliang; Zhang, Ming; Yin, Yafang; Wang, Siqun; Li, Jian; Yang, Dongjiang

2016-10-26

Nanofibrillated cellulose (NFC) has received increasing attention in science and technology because of not only the availability of large amounts of cellulose in nature but also its unique structural and physical features. These high-aspect-ratio nanofibers have potential applications in water remediation and as a reinforcing scaffold in composites, coatings, and porous materials because of their fascinating properties. In this work, highly porous NFC aerogels were prepared based on tert-butanol freeze-drying of ultrasonically isolated bamboo NFC with 20-80 nm diameters. Then nonagglomerated 2-20-nm-diameter silver oxide (Ag 2 O) nanoparticles (NPs) were grown firmly onto the NFC scaffold with a high loading content of ∼500 wt % to fabricate Ag 2 O@NFC organic-inorganic composite aerogels (Ag 2 O@NFC). For the first time, the coherent interface and interaction mechanism between the cellulose I β nanofiber and Ag 2 O NPs are explored by high-resolution transmission electron microscopy and 3D electron tomography. Specifically, a strong hydrogen between Ag 2 O and NFC makes them grow together firmly along a coherent interface, where good lattice matching between specific crystal planes of Ag 2 O and NFC results in very small interfacial straining. The resulting Ag 2 O@NFC aerogels take full advantage of the properties of the 3D organic aerogel framework and inorganic NPs, such as large surface area, interconnected porous structures, and supreme mechanical properties. They open up a wide horizon for functional practical usage, for example, as a flexible superefficient adsorbent to capture I - ions from contaminated water and trap I 2 vapor for safe disposal, as presented in this work. The viable binding mode between many types of inorganic NPs and organic NFC established here highlights new ways to investigate cellulose-based functional nanocomposites.

Preparation of poly(BMA-co-MMA) particles by soap-free emulsion polymerization and its optical properties as photonic crystals.

PubMed

Lee, Ki-Chang; Choo, Hun-Seung

2014-11-01

Narrowly dispersed poly(BMA-co-MMA) and PBMA latices with particle diameters ranging within 216-435 nm were synthesized successfully by surfactant-free emulsion polymerization with KPS and AIBA. The average particle diameter and particle size distribution, average molecular weight and its distribution, glass transition temperature, reflectance spectra in visible wavelength, and refractive indices for the respective poly(BMA-co-MMA) latices and their photonic crystals were systematically investigated in terms of BMA/MMA ratio, BMA content, polymerization temperature, and DVB effect. The rate of polymerization increased with increasing MMA concentration in BMA/MMA ratio. The particle diameter increased with BMA concentration in BMA/MMA ratio. The molecular weight increased with BMA concentration in BMA/MMA ratio and monomer concentration. The drying of the latices offered self-assembled shiny colloidal crystal films showing the characteristic structural colors in visible wavelength. All the poly(BMA-co-MMA) latices prepared in the study were fallen within the range of photonic grade microspheres. The reflectance measurement on the colloidal photonic crystals having different particle diameters clearly exhibited narrow stopbands. The reflection maxima (λ(max)) measured in this study were well close to the λ(max) calculated, derived from the Bragg's equation. The refractive indices of poly(BMA-co-MMA) photonic crystals were found to be almost same as the theoretical values and increased proportionally from 1.50 to 1.57 with BMA content in BMA/MMA ratios. It was, thus, found that the optical reflectance properties of the poly(BMA-co-MMA) colloidal photonic crystals can be controlled easily by adjusting the reaction conditions and BMA/MMA ratio in soap-free emulsion copolymerization of BMA and MMA.

Vortex Mask: Making 80nm contacts with a twist!

NASA Astrophysics Data System (ADS)

Levenson, Marc D.; Dai, Grace; Ebihara, Takeaki

2002-12-01

An optical vortex has a phase that spirals like a corkscrew. Since any nonzero optical amplitude must have a well-defined phase, the axis of a vortex (where the phase is undefined) is always dark. Printed in negative resist, lowest order vortices would produce contact holes with 0.20.6 can be produced using a chromeless phase-edge mask composed of rectangles with phases of 0°, 90°, 180° and 270°. EMF and Kirchhoff-approximation simulations reveal that the image quality of the dark spots is excellent, and predict a process window with 15% exposure latitude and 400nm DOF for 80nm diameter spots on pitches >=250nm at σ=0.15. EMF simulations predict that the 0-270° phase step will not be excessively dark if the quartz wall is vertical. Chrome spots at the centers can control the diameters which otherwise are set by the parameters of the imaging system and exposure dose. Unwanted vortices can be erased from the image by exposing with a second, more conventional, trim mask. This method would be superior to the other ways of producing sub-wavelength vias, but successful implementation requires the development of appropriate negative-tone resist processes.

Gold Nanohole Array with Sub-1 nm Roughness by Annealing for Sensitivity Enhancement of Extraordinary Optical Transmission Biosensor

NASA Astrophysics Data System (ADS)

Zhang, Jian; Irannejad, Mehrdad; Yavuz, Mustafa; Cui, Bo

2015-05-01

Nanofabrication technology plays an important role in the performance of surface plasmonic devices such as extraordinary optical transmission (EOT) sensor. In this work, a double liftoff process was developed to fabricate a series of nanohole arrays of a hole diameter between 150 and 235 nm and a period of 500 nm in a 100-nm-thick gold film on a silica substrate. To improve the surface quality of the gold film, thermal annealing was conducted, by which an ultra-smooth gold film with root-mean-square (RMS) roughness of sub-1 nm was achieved, accompanied with a hole diameter shrinkage. The surface sensitivity of the nanohole arrays was measured using a monolayer of 16-mercaptohexadecanoic acid (16-MHA) molecule, and the surface sensitivity was increased by 2.5 to 3 times upon annealing the extraordinary optical transmission (EOT) sensor.

Replication of the nano-scale mold fabricated with focused ion beam

NASA Astrophysics Data System (ADS)

Gao, J. X.; Chan-Park, M. B.; Xie, D. Z.; Ngoi, Bryan K. A.

2004-12-01

Silicon mold fabricated with Focused Ion Beam lithography (FIB) was used to make silicone elastomer molds. The silicon mold is composed of lattice of holes which the diameter and depth are about 200 nm and 60 nm, respectively. The silicone elastomer material was then used to replicate slavery mold. Our study show the replication process with the elastomer mold had been performed successfully and the diameter of humps on the elastomer mold is near to that of holes on the master mold. But the height of humps in the elastomer mold is only 42 nm and it is different from the depth of holes in the master mold.

Sono-chemical synthesis of cellulose nanocrystals from wood sawdust using Acid hydrolysis.

PubMed

Shaheen, Th I; Emam, Hossam E

2018-02-01

Cellulose nanocrystal (CNC) is a unique material obtained from naturally occurring cellulose fibers. Owing to their mechanical, optical, chemical, and rheological properties, CNC gained significant interest. Herein, we investigate the potential of commercially non-recyclable wood waste, in particular, sawdust as a new resource for CNC. Isolation of CNC from sawdust was conducted as per acid hydrolysis which induced by ultrasonication technique. Thus, sawdust after being alkali delignified prior sodium chlorite bleaching, was subjected to sulfuric acid with concentration of 65% (w/w) at 60 ° C for 60min. After complete reaction, CNC were collected by centrifugation followed by dialyzing against water and finally dried via using lyophilization technique. The CNC yield attained values of 15% from purified sawdust. Acid hydrolysis mechanism exactly referred that, the amorphous regions along with thinner as well as shorter crystallites spreaded throughout the cellulose structure are digested by the acid leaving CNC suspension. The latter was freeze-dried to produce CNC powder. A thorough investigation pertaining to nanostructural characteristics of CNC was performed. These characteristics were monitored using TEM, SEM, AFM, XRD and FTIR spectra for following the changes in functionality. Based on the results obtained, the combination of sonication and chemical treatment was great effective in extraction of CNC with the average dimensions (diameter×length) of 35.2±7.4nm×238.7±81.2nm as confirmed from TEM. Whilst, the XRD study confirmed the crystal structure of CNC is obeyed cellulose type I with crystallinity index ∼90%. Cellulose nanocrystals are nominated as the best candidate within the range studied in the area of reinforcement by virtue of their salient textural features. Copyright © 2017 Elsevier B.V. All rights reserved.

Egg shell waste as heterogeneous nanocatalyst for biodiesel production: Optimized by response surface methodology.

PubMed

Pandit, Priti R; Fulekar, M H

2017-08-01

Worldwide consumption of hen eggs results in availability of large amount of discarded egg waste particularly egg shells. In the present study, the waste shells were utilized for the synthesis of highly active heterogeneous calcium oxide (CaO) nanocatalyst to transesterify dry biomass into methyl esters (biodiesel). The CaO nanocatalyst was synthesied by calcination-hydration-dehydration technique and fully characterized by infrared spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), brunauer-emmett-teller (BET) elemental and thermogravimetric analysis. TEM image showed that the nano catalyst had spherical shape with average particle size of 75 nm. BET analysis indicated that the catalyst specific surface area was 16.4 m 2  g -1 with average pore diameter of 5.07 nm. The effect of nano CaO catalyst was investigated by direct transesterification of dry biomass into biodiesel along with other reaction parameters such as catalyst ratio, reaction time and stirring rate. The impact of the transesterification reaction parameters and microalgal biodiesel yield were analyzed by response surface methodology based on a full factorial, central composite design. The significance of the predicted mode was verified and 86.41% microalgal biodiesel yield was reported at optimal parameter conditions 1.7% (w/w), catalyst ratio, 3.6 h reaction time and stirring rate of 140.6 rpm. The biodiesel conversion was determined by 1 H nuclear magnetic resonance spectroscopy (NMR). The fuel properties of prepared biodiesel were found to be highly comply with the biodiesel standard ASTMD6751 and EN14214. Copyright © 2017 Elsevier Ltd. All rights reserved.

Processing of surrogate nuclear fuel pellets for better dimensional control with dry bag isostatic pressing

DOE PAGES

Hoggan, Rita E.; Zuck, Larry D.; Cannon, W. Roger; ...

2016-05-26

A study of improved methods of processing fuel pellets was undertaken using ceria and zirconia/yttria/alumina as surrogates. Through proper granulation and vertical vibration (tapping) of the parts bag prior to dry bag isostatic pressing (DBIP), reproducibility of diameter profiles among multiple pellets of ceria was improved by almost an order of magnitude. Reproducibility of sintered pellets was sufficiently good to possibly avoid grinding. Deviation from the mean diameter along the length of multiple pellets, as well as, deviation from roundness, decreased after sintering. This is not generally observed with dry pressed pellets. Thus it is possible to machine to tolerancemore » before sintering if grinding is necessary.« less

Supercontinuum generation from 437 to 2850 nm in a tapered fluorotellurite microstructured fiber

NASA Astrophysics Data System (ADS)

Wang, F.; Jia, Z. X.; Yao, C. F.; Wang, S. B.; Hu, M. L.; Wu, C. F.; Ohishi, Y.; Qin, W. P.; Qin, G. S.

2016-12-01

We demonstrated supercontinuum (SC) generation in a tapered fluorotellurite microstructured fiber (MF) with a sub-micrometer core diameter. Fluorotellurite MFs based on TeO2-BaF2-Y2O3 glasses were fabricated by using a rod-in-tube method and a tapered fluorotellurite MF with a minimum core diameter of ~0.65 µm was prepared by employing a tapering system. A 1560 nm femtosecond fiber laser was used as the pumping source. With increasing the peak power of the launched pump laser to ~11 kW, SC light expanding from 437 to 2850 nm was generated in the tapered fluorotellurite MF. In addition, relatively strong blue-shifted dispersive wave at ~489 nm was also observed from the tapered fluorotellurite MF.

Mechanical characteriztion of single-stranded DNA and single-walled carbon nanotube hybrid structures

NASA Astrophysics Data System (ADS)

Rokadia, Husein Juzer

Hybrid nanostructures of single-stranded DNA (ssDNA) and single-walled carbon nanotubes are being proposed as the basis for the next generation of biosensors. For such biosensors, mechanical properties such as the Young's modulus of the hybrid structures play a critical role, which to the best of the author's knowledge is still unknown. Thus, the determination of the Young's modulus of the ssDNA/swCNT hybrid structures was the primary objective of this study. Hybrid structures of 30mer polyT ssDNA and HiPCORTM swCNTs were conjugated using a well known non-covalent interaction protocol. Atomic force microscopy (AFM) was used to scan and generate topographic images and perform nanoindentation tests on the hybrid structures. Molecular dynamics (MD) simulations using a commercial MD program, Materials StudioRTM were performed to study the nature of non-covalent interactions between the ssDNA and the swCNT on the pico-second timescale. AFM topography scans of the bare control HiPCORTM swCNTs indicated an average diameter of about 1.0 nm and length of 800 nm. Similarly, the control 30mer polyT ssDNA was found to resemble a half-hemispherical domed structure with an average height of 2.1 nm. Nanoindentation tests yielded the transverse Young's modulus of the control swCNTs to be 78.0 GPa. The control ssDNA were found to have a Young's modulus of 3.3 GPa and 4.0 MPa in dry and wet environments, respectively. Topographic scans of the ssDNA/swCNT hybrid structures showed the slender swCNTs fully or partially coated along their lengths by ssDNA. The height of the hybrid structures ranged from 2.5 nm to 7.5 nm. Nanoindentation tests on the ssDNA coated portions of the hybrid structures indicated that, their Young's modulus exponentially decreased with increasing coating thickness. Thinly coated sections were found to have a Young's modulus of 100.0 GPa and 7.0 MPa in dry and wet conditions respectively. The thick walled hybrid sections were found to have an average Young's modulus of 4.5 GPa and 1.0 GPa in the dry and wet environments, respectively. MD results indicated that the wrapping of the ssDNA had a significant impact on the hybrid structures. The longitudinal Young's modulus of a hybrid structure was found to be approximately 50.0 GPa, compared to a bare nanotube whose Young's modulus was approximately 800 GPa. Overall, the experimental and numerical results displayed consistent trends. The experimental results reported the swCNTs to have the highest transverse Young's modulus followed by the hybrids and the ssDNA. Similarly, the numerical simulations predicted the highest longitudinal Young's modulus for the swCNTs, followed by the hybrids and the DNA.

Decomposition and nutrient release from fresh and dried pine roots under two fertilizer regimes

Treesearch

Kim H. Ludovici; Lance W. Kress

2006-01-01

Root decomposition and nutrient release are typically estimated from dried root tissues; however, it is unlikely that roots dehydrate prior to decomposing. Soil fertility and root diameter may also affect the rate of decomposition. This study monitored mass loss and nutrient concentrations of dried and fresh roots of two size classes (

Dry Weight of Several Piedmont Hardwoods

Treesearch

Bobby G. Blackmon; Charles W. Ralston

1968-01-01

Forty-four sample hardwood trees felled on 24 plots were separated into three above-ground components- stem, branches, and leaves--and weighed for dry matter content. Tree, stand, and site variables were tested for significant relationships with dry weight of tree parts. Weight increase of stems was a logarithmic function ,of both stem diameter and height, whereas for...

House log drying rates in southeast Alaska for covered and uncovered softwood logs

Treesearch

David Nicholls; Allen Brackley

2009-01-01

Log moisture content has an important impact on many aspects of log home construction, including log processing, transportation costs, and dimensional stability in use. Air-drying times for house logs from freshly harvested trees can depend on numerous factors including initial moisture content, log diameter, bark condition, and environmental conditions during drying....

Transition of carbon nanostructures in heptane diffusion flames

NASA Astrophysics Data System (ADS)

Hu, Wei-Chieh; Hou, Shuhn-Shyurng; Lin, Ta-Hui

2017-02-01

The flame synthesis has high potential in industrial production of carbon nanostructure (CNS). Unfortunately, the complexity of combustion chemistry leads to less controlling of synthesized products. In order to improve the understanding of the relation between flames and CNSs synthesized within, experiments were conducted through heptane flames in a stagnation-point liquid-pool system. The operating parameters for the synthesis include oxygen supply, sampling position, and sampling time. Two kinds of nanostructures were observed, carbon nanotube (CNT) and carbon nano-onion (CNO). CNTs were synthesized in a weaker flame near extinction. CNOs were synthesized in a more sooty flame. The average diameter of CNTs formed at oxygen concentration of 15% was in the range of 20-30 nm. For oxygen concentration of 17%, the average diameter of CNTs ranged from 24 to 27 nm, while that of CNOs was around 28 nm. For oxygen concentration of 19%, the average diameter of CNOs produced at the sampling position 0.5 mm below the flame front was about 57 nm, while the average diameters of CNOs formed at the sampling positions 1-2.5 mm below the flame front were in the range of 20-25 nm. A transition from CNT to CNO was observed by variation of sampling position in a flame. We found that the morphology of CNS is directly affected by the presence of soot layer due to the carbonaceous environment and the growth mechanisms of CNT and CNO. The sampling time can alter the yield of CNSs depending on the temperature of sampling position, but the morphology of products is not affected.

Self-assembled nanotubes from single fluorescent amino acid

NASA Astrophysics Data System (ADS)

Babar, Dipak Gorakh; Sarkar, Sabyasachi

2017-04-01

Self-assembly of biomolecules has gained increasing attention as it generates various supramolecular structural assemblies having potential applications principally in biomedical sciences. Here, we show that amino acid like tryptophan or tyrosine readily aggregates as nanotubes via a simple self-assembly process. These were characterized by FTIR, scanning electron microscopy, and by fluorescence microscopy. Nanotubes prepared from tryptophan are having 200 nm inner diameter and those from tyrosine are having the same around 50 nm diameter.

Silicon Based Colloidal Quantum Dot and Nanotube Lasers

DTIC Science & Technology

2013-03-01

carrier density is theoretically and experimentally derived to be inversely proportional to the diameter; (b) demonstration of InGaN/ GaN light emitting...diodes and GaN single nanowire photonic crystal laser on silicon characterized by a lasing transition at λ=371.3 nm with a linewidth of 0.55 nm. The...derived to be inversely proportional to the diameter; (b) demonstration of InGaN/ GaN light emitting diodes and GaN single nanowire photonic crystal

Size resolved Internally Mixed Black Carbon and the Absorption Enhancement in the Indo-Gangetic Plain due to internally mixed BC

NASA Astrophysics Data System (ADS)

Tripathi, S. N.; Thamban, N.

2017-12-01

Indo-Gangetic Plain (IGP) is one of the most populated and polluted regions in northern India. Even though IGP is a well-known "absorbing aerosol hotspot", information of BC mixing state in IGP is mostly unknown. Our calculation on size resolved mixing state in IGP shown that the mixing state of BC changes with the core diameter of BC. The majority of BC particle were thickly coated ( 80%) at lower diameter (75-125 nm) and the externally mixed BC fraction was gradually increased at higher core diameter of BC (125-250 nm). The mean fraction of "thickly coated BC" particles (fTCBC) was found to be 61.6% for a BC core diameter of 70 to 450 nm, indicating that a large fraction of BC particles was internally mixed in IGP. The fTCBC increased after sunrise with a peak at about noontime, indicating that the formation of secondary organic aerosol under active photochemistry can enhance organic coating on a core of black carbon. A positive correlation between the fTCBC and the mass absorption cross-section at 781nm (MAC781) was also observed (r=0.58). Our results identify that the observed fTCBC in IGP could amplify the MAC781 approximately by a factor of 1.8, which may catalyze the positive radiative forcing.

Spin Polarization and Quantum Spins in Au Nanoparticles

PubMed Central

Li, Chi-Yen; Karna, Sunil K.; Wang, Chin-Wei; Li, Wen-Hsien

2013-01-01

The present study focuses on investigating the magnetic properties and the critical particle size for developing sizable spontaneous magnetic moment of bare Au nanoparticles. Seven sets of bare Au nanoparticle assemblies, with diameters from 3.5 to 17.5 nm, were fabricated with the gas condensation method. Line profiles of the X-ray diffraction peaks were used to determine the mean particle diameters and size distributions of the nanoparticle assemblies. The magnetization curves M(Ha) reveal Langevin field profiles. Magnetic hysteresis was clearly revealed in the low field regime even at 300 K. Contributions to the magnetization from different size particles in the nanoparticle assemblies were considered when analyzing the M(Ha) curves. The results show that the maximum particle moment will appear in 2.4 nm Au particles. A similar result of the maximum saturation magnetization appearing in 2.3 nm Au particles is also concluded through analysis of the dependency of the saturation magnetization MP on particle size. The MP(d) curve departs significantly from the 1/d dependence, but can be described by a log-normal function. Magnetization can be barely detected for Au particles larger than 27 nm. Magnetic field induced Zeeman magnetization from the quantum confined Kubo gap opening appears in Au nanoparticles smaller than 9.5 nm in diameter. PMID:23989607

Conductive atomic force microscopy measurements of nanopillar magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Evarts, E. R.; Hogg, C.; Bain, J. A.; Majetich, S. A.

2009-03-01

Magnetic tunnel junctions have been studied extensively for their magnetoresistance and potential uses in magnetic logic and data storage devices, but little is known about how their performance will scale with size. Here we examined the electronic behavior of 12 nm diameter magnetic tunnel junctions fabricated by a novel nanomasking process. Scanning electron microscopy images indicated feature diameter of 12 nm, and atomic force microscopy showed a height of 5 nm suggesting that unmasked regions have been milled on average to the oxide barrier layer, and areas should have the remnants of the free layer exposed with no remaining nanoparticle. Electrical contact was made to individual nanopillars using a doped-diamond-coated atomic force microscopy probe with a 40 nm radius of curvature at the tip. Off pillar we observed a resistance of 8.1 x 10^5 φ, while on pillar we found a resistance of 2.85 x 10^6 φ. Based on the RA product for this film, 120 φ-μm^2, a 12 nm diameter cylinder with perfect contact would have a resistance of 1.06 x 10^6 φ. The larger experimental value is consistent with a smaller contact area due to damaging the pillar during the ion milling process. The magnetoresistance characteristics of these magnetic tunnel junctions will be discussed.

Effect of sintering temperature of Ce3+-doped Lu3Al5O12 phosphors on light emission and properties of crystal structure for white-light-emitting diodes

NASA Astrophysics Data System (ADS)

Koizumi, Hiroshi; Watabe, Junya; Sugiyama, Shin; Hirabayashi, Hideaki; Homma, Tetsuya

2018-06-01

The effect of the sintering temperature of Ce3+-doped Lu3Al5O12 (Ce-LuAG) phosphors on the emission and properties of the crystal structure was studied. A cathodoluminescence peak at 317 nm, which was assigned to lattice defects, was exhibited in addition to emission peaks at 508 and 540 nm for the Ce-LuAG phosphors. The intensities of the 317 nm emission peak for the phosphors with mean particle diameters of 5.0 and 10.0 µm formed at a low sintering temperature of 1430 °C were higher than those for the phosphors with mean particle diameters of 18.0 and 20.5 µm formed at a high sintering temperature of 1550 °C. In contrast, the electroluminescence spectra for fabricated white-light-emitting diodes (LEDs) using the phosphors revealed that the intensity of the peak at 540 nm was strong for the mean particle diameters of 18.0 and 20.5 µm. The intensity of the 540 nm peak, which is attributed to the 4f→5d transition of the Ce3+ activator, showed a dependence on the sintering temperature. The relationship between the optical properties and the lattice defects is discussed.

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

Joseph Berkmans, A.; Jagannatham, M.; Priyanka, S.

Highlights: • Polymer wastes are converted into ultrafine and nano carbon tubes and spheres. • Simple process with a minimal processing time. • It is a catalyst free and solvent free approach. • This process forms branched ultrafine carbon tubules with nano channels. - Abstract: Upcycling polymer wastes into useful, and valuable carbon based materials, is a challenging process. We report a novel catalyst-free and solvent-free technique for the formation of nano channeled ultrafine carbon tubes (NCUFCTs) and multiwalled carbon nanotubes (MWCNTs) from polyethylene terephthalate (PET) wastes, using rotating cathode arc discharge technique. The soot obtain from the anode containsmore » ultrafine and nano-sized solid carbon spheres (SCS) with a mean diameter of 221 nm and 100 nm, respectively, formed at the lower temperature region of the anode where the temperature is approximately 1700 °C. The carbon spheres are converted into long “Y” type branched and non-branched NCUFCTs and MWCNTs at higher temperature regions where the temperature is approximately 2600 °C, with mean diameters of 364 nm and 95 nm, respectively. Soot deposited on the cathode is composed of MWCNTs with a mean diameter of 20 nm and other nanoparticles. The tubular structures present in the anode are longer, bent and often coiled with lesser graphitization compared to the nanotubes in the soot on the cathode.« less

Nano-liposomal dry powder inhaler of tacrolimus: preparation, characterization, and pulmonary pharmacokinetics.

PubMed

Chougule, Mahavir; Padhi, Bijay; Misra, Ambikanandan

2007-01-01

The studies were undertaken to evaluate feasibility of pulmonary delivery of liposomaly encapsulated tacrolimus dry powder inhaler for prolonged drug retention in lungs as rescue therapy to prevent refractory rejection of lungs after transplantation. Tacrolimus encapsulated liposomes were prepared by thin film evaporation technique and liposomal dispersion was passed through high pressure homogenizer. Tacrolimus nano-liposomes (NLs) were separated by centrifugation and characterized. NLs were dispersed in phosphate buffer saline (PBS) pH 7.4 containing different additives like lactose, sucrose, and trehalose, and L-leucine as antiadherent. The dispersion was spray dried and spray dried powders were characterized. In vitro and in vivo pulmonary deposition was performed using Andersen Cascade Impactor and intratracheal instillation in rats respectively. NLs were found to have average size of 140 nm, 96% +/- 1.5% drug entrapment, and zeta potential of 1.107 mV. Trehalose based formulation was found to have low density, good flowability, particle size of 9.46 +/- 0.8 microm, maximum fine particle fraction (FPF) of 71.1 +/- 2.5%, mean mass aerodynamic diameter (MMAD) 2.2 +/- 0.1 microm, and geometric standard deviation (GSD) 1.7 +/- 0.2. Developed formulations were found to have in vitro prolonged drug release up to 18 hours, following Higuchi's Controlled Release model. In vivo studies revealed maximal residence of tacrolimus within lungs of 24 hours, suggesting slow clearance from the lungs. The investigation provides a practical approach for direct delivery of tacrolimus encapsulated in NLs for controlled and prolonged retention at the site of action. It may play a promising role as rescue therapy in reducing the risk of acute rejection and chronic rejection.

Nano-liposomal dry powder inhaler of tacrolimus: Preparation, characterization, and pulmonary pharmacokinetics

PubMed Central

Chougule, Mahavir; Padhi, Bijay; Misra, Ambikanandan

2007-01-01

The studies were undertaken to evaluate feasibility of pulmonary delivery of liposomaly encapsulated tacrolimus dry powder inhaler for prolonged drug retention in lungs as rescue therapy to prevent refractory rejection of lungs after transplantation. Tacrolimus encapsulated liposomes were prepared by thin film evaporation technique and liposomal dispersion was passed through high pressure homogenizer. Tacrolimus nano-liposomes (NLs) were separated by centrifugation and characterized. NLs were dispersed in phosphate buffer saline (PBS) pH 7.4 containing different additives like lactose, sucrose, and trehalose, and L-leucine as antiadherent. The dispersion was spray dried and spray dried powders were characterized. In vitro and in vivo pulmonary deposition was performed using Andersen Cascade Impactor and intratracheal instillation in rats respectively. NLs were found to have average size of 140 nm, 96% ± 1.5% drug entrapment, and zeta potential of 1.107 mV. Trehalose based formulation was found to have low density, good flowability, particle size of 9.46 ± 0.8 μm, maximum fine particle fraction (FPF) of 71.1 ± 2.5%, mean mass aerodynamic diameter (MMAD) 2.2 ± 0.1 μm, and geometric standard deviation (GSD) 1.7 ± 0.2. Developed formulations were found to have in vitro prolonged drug release up to 18 hours, following Higuchi’s Controlled Release model. In vivo studies revealed maximal residence of tacrolimus within lungs of 24 hours, suggesting slow clearance from the lungs. The investigation provides a practical approach for direct delivery of tacrolimus encapsulated in NLs for controlled and prolonged retention at the site of action. It may play a promising role as rescue therapy in reducing the risk of acute rejection and chronic rejection. PMID:18203434

Measurements of cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals

NASA Astrophysics Data System (ADS)

Kumar, P.; Sokolik, I. N.; Nenes, A.

2011-04-01

This study reports laboratory measurements of particle size distributions, cloud condensation nuclei (CCN) activity, and droplet activation kinetics of wet generated aerosols from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. The dependence of critical supersaturation, sc, on particle dry diameter, Ddry, is used to characterize particle-water interactions and assess the ability of Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler theory (KT) to describe the CCN activity of the considered samples. Regional dust samples produce unimodal size distributions with particle sizes as small as 40 nm, CCN activation consistent with KT, and exhibit hygroscopicity similar to inorganic salts. Clays and minerals produce a bimodal size distribution; the CCN activity of the smaller mode is consistent with KT, while the larger mode is less hydrophilic, follows activation by FHH-AT, and displays almost identical CCN activity to dry generated dust. Ion Chromatography (IC) analysis performed on regional dust samples indicates a soluble fraction that cannot explain the CCN activity of dry or wet generated dust. A mass balance and hygroscopicity closure suggests that the small amount of ions (of low solubility compounds like calcite) present in the dry dust dissolve in the aqueous suspension during the wet generation process and give rise to the observed small hygroscopic mode. Overall these results identify an artifact that may question the atmospheric relevance of dust CCN activity studies using the wet generation method. Based on a threshold droplet growth analysis, wet generated mineral aerosols display similar activation kinetics compared to ammonium sulfate calibration aerosol. Finally, a unified CCN activity framework that accounts for concurrent effects of solute and adsorption is developed to describe the CCN activity of aged or hygroscopic dusts.

Causes and implications of dry season control of tropical wet forest tree growth at very high water levels: direct vs. indirect limitations

NASA Astrophysics Data System (ADS)

Dierick, D.; Oberbauer, S. F.; O'Brien, J. J.

2012-12-01

Despite the importance of tropical rain forests in the global carbon cycle, uncertainty remains on how these ecosystems will be affected by climate change. Previous studies in a Costa Rican lowland tropical rain forest (La Selva Biological Station, Sarapiqui, Costa Rica) revealed a significant, positive relationship between tree diameter increment and January to April dry season precipitation that extended up to high rainfall totals (Clark et al. 2010). Proposed mechanisms include a direct limitation of water availability or closely linked indirect controls such as altered micrometeorological conditions (direct vs. diffuse light, atmospheric humidity) and changes in plant phenology or C-allocation. Using an experimental approach we aim to test the hypothesis that water availability in the dry season directly controls tree diameter growth despite the high precipitation levels normally encountered (long term average for Jan-Apr is 890 mm). At three sites within the La Selva Biological Station a paired experimental and control plot were established. Each plot was 900 m2 in size and had at least 20 trees with diameter at breast height (dbh) over 10 cm. In the experimental plots we used irrigation to simulate a minimum daily precipitation equivalent to 10 mm.d-1 during the dry seasons of 2011 and 2012. This simulated precipitation amount matches the highest dry season total recorded for the years 1998 to 2009. The main response variables measured in experimental and control plots were monthly dendrometer-band diameter growth of trees above 10 cm dbh, sap flux density of a subset of trees and bi-weekly leaf litter production. Belowground variables included soil moisture, fine root production and soil respiration. Soil moisture data confirmed that experimental plots experienced consistently high water availability in the top 30 cm of the soil profile during the dry season, while control plots experienced repeated drying and rewetting of the soil. This difference in water availability was not reflected in observed tree diameter growth. Average monthly diameter increments over the course of the study were 0.31 ± 0.07 in treatment and 0.32 ± 0.09 mm.mo-1 in control plots with temporal trends being the same, suggesting that an immediate or lagged effect of additional precipitation on diameter growth is lacking. Patterns of leaf litter production also did not differ between treatment and control plots (average 7.3 ± 0.22 and 7.5 ± 1.75 Mg.ha-1.y-1 respectively) implying that leaf shedding was not reduced in treatment plots. Estimated fine root productivity in treatment and control plots was 3.2 ± 0.5 and 4.4 ± 1.7 Mg.ha-1.y-1 respectively. The absence of a clear response to irrigation treatment supports the view that other mechanisms such as shifting C-balances or leaf shedding in response to atmospheric humidity rather than a direct limitation of water availability control tree diameter increments in this Neo-tropical rainforest. Clark, D.B., Clark, D.A. & Oberbauer, S.F. 2010 Annual wood production in a tropical rain forest in NE Costa Rica linked to climatic variation but not to increasing CO2. Global Change Biology 16, 747-759.

Development of new resist materials for 193-nm dry and immersion lithography

NASA Astrophysics Data System (ADS)

Sasaki, Takashi; Shirota, Naoko; Takebe, Yoko; Yokokoji, Osamu

2006-03-01

We earlier developed new monocyclic fluoropolymers (FUGU) for F II resist materials. But, it is necessary for FUGU to improve of their characteristics, especially the dry-etching resistance, in order to apply for ArF lithography at fine design rules. We have tried to combine FUGUs with Adamntyl methacrylates based conventional ArF resist polymer. In this paper, we have investigated the role of cyclic fluorinated unit, FUGU, in 193 nm resist polymers by analyzing the dissolution behavior. We found that FGEAM showed high sensitivity and good dissolution contrast, compared with acrylate based conventional samples at low PEB temperature (100 °C). And this difference of sensitivity was clearly found when weak acidity PAGs were used. From the dissolution behaviors of FGEAM, FUGU unit can work to improve the resist sensitivity in acrylate based ArF resist polymers. And we also found that FGEAM showed long acid diffusion length on PEB process, compared with Conventional samples. These result show that FUGU unit has a unique characteristics of the sensitivity with 193nm exposure and the acid diffusion behavior. We also investigated a new series of fluorinated copolymers for 193-nm lithography, combination of FUGU monomer and acrylate units which are used in conventional ArF resist. Six ter-polymers of FUGU, combination of FUGU monomers and EAdMA, GBLMA and HAdMA were prepared. We found that FUGU ter-polymers had a good dry etching resistance keeping high transparency at 193nm. And FUGU ter-polymers showed high sensitivity toward 193nm exposure. FUGU ter-polymers also had a high hydrophobic properties compared conventional type ArF resist polymers. So we also expect FUGU ter-polymers to be useful for ArF dry and immersion lithography.

Leaf structural and photosynthetic characteristics, and biomass allocation to foliage in relation to foliar nitrogen content and tree size in three Betula species.

PubMed

Niinemets, Ulo; Portsmuth, Angelika; Truus, Laimi

2002-02-01

Young trees 0.03-1.7 m high of three coexisting Betula species were investigated in four sites of varying soil fertility, but all in full daylight, to separate nutrient and plant size controls on leaf dry mass per unit area (MA), light-saturated foliar photosynthetic electron transport rate (J) and the fraction of plant biomass in foliage (F(L)). Because the site effect was generally non-significant in the analyses of variance with foliar nitrogen content per unit dry mass (N(M)) as a covariate, N(M) was used as an explaining variable of leaf structural and physiological characteristics. Average leaf area (S) and dry mass per leaf scaled positively with N(M) and total tree height (H) in all species. Leaf dry mass per unit area also increased with increasing H, but decreased with increasing N(M), whereas the effects were species-specific. Increases in plant size led to a lower and increases in N(M) to a greater FL and total plant foliar area per unit plant biomass (LAR). Thus, the self-shading probably increased with increasing N(M) and decreased with increasing H. Nevertheless, the whole-plant average M(A), as well as M(A) values of topmost fully exposed leaves, correlated with N(M) and H in a similar manner, indicating that scaling of MA with N(M) and H did not necessarily result from the modified degree of within-plant shading. The rate of photosynthetic electron transport per unit dry mass (J(M)) scaled positively with N(M), but decreased with increasing H and M(A). Thus, increases in M(A) with tree height and decreasing nitrogen content not only resulted in a lower plant foliar area (LAR = F(L)/M(A)), but also led to lower physiological activity of unit foliar biomass. The leaf parameters (J(M), N(M) and M(A)) varied threefold, but the whole-plant characteristic FL varied 20-fold and LAR 30-fold, indicating that the biomass allocation was more plastically adjusted to different plant internal nitrogen contents and to tree height than the foliar variables. Our results demonstrate that: (1) tree height and N(M) may independently control foliar structure and physiology, and have an even greater impact on biomass allocation; and (2) the modified within-plant light availabilities alone do not explain the observed patterns. Although there were interspecific differences with respect to the statistical significance of the relationships, all species generally fit common regressions. However, these differences were consistent, and suggested that more competitive species with inherently larger growth rates also more plastically respond to N and H.

Leaf Structural and Photosynthetic Characteristics, and Biomass Allocation to Foliage in Relation to Foliar Nitrogen Content and Tree Size in Three Betula Species

PubMed Central

NIINEMETS, ÜLO; PORTSMUTH, ANGELIKA; TRUUS, LAIMI

2002-01-01

Young trees 0·03–1·7 m high of three coexisting Betula species were investigated in four sites of varying soil fertility, but all in full daylight, to separate nutrient and plant size controls on leaf dry mass per unit area (MA), light‐saturated foliar photosynthetic electron transport rate (J) and the fraction of plant biomass in foliage (FL). Because the site effect was generally non‐significant in the analyses of variance with foliar nitrogen content per unit dry mass (NM) as a covariate, NM was used as an explaining variable of leaf structural and physiological characteristics. Average leaf area (S) and dry mass per leaf scaled positively with NM and total tree height (H) in all species. Leaf dry mass per unit area also increased with increasing H, but decreased with increasing NM, whereas the effects were species‐specific. Increases in plant size led to a lower and increases in NM to a greater FL and total plant foliar area per unit plant biomass (LAR). Thus, the self‐shading probably increased with increasing NM and decreased with increasing H. Nevertheless, the whole‐plant average MA, as well as MA values of topmost fully exposed leaves, correlated with NM and H in a similar manner, indicating that scaling of MA with NM and H did not necessarily result from the modified degree of within‐plant shading. The rate of photosynthetic electron transport per unit dry mass (JM) scaled positively with NM, but decreased with increasing H and MA. Thus, increases in MA with tree height and decreasing nitrogen content not only resulted in a lower plant foliar area (LAR = FL/MA), but also led to lower physiological activity of unit foliar biomass. The leaf parameters (JM, NM and MA) varied threefold, but the whole‐plant characteristic FL varied 20‐fold and LAR 30‐fold, indicating that the biomass allocation was more plastically adjusted to different plant internal nitrogen contents and to tree height than the foliar variables. Our results demonstrate that: (1) tree height and NM may independently control foliar structure and physiology, and have an even greater impact on biomass allocation; and (2) the modified within‐plant light availabilities alone do not explain the observed patterns. Although there were interspecific differences with respect to the statistical significance of the relationships, all species generally fit common regressions. However, these differences were consistent, and suggested that more competitive species with inherently larger growth rates also more plastically respond to N and H. PMID:12099350

Low damage dry etch for III-nitride light emitters

NASA Astrophysics Data System (ADS)

Nedy, Joseph G.; Young, Nathan G.; Kelchner, Kathryn M.; Hu, Yanling; Farrell, Robert M.; Nakamura, Shuji; DenBaars, Steven P.; Weisbuch, Claude; Speck, James S.

2015-08-01

We have developed a dry etch process for the fabrication of lithographically defined features close to light emitting layers in the III-nitride material system. The dry etch was tested for its effect on the internal quantum efficiency of c-plane InGaN quantum wells using the photoluminescence of a test structure with two active regions. No change was observed in the internal quantum efficiency of the test active region when the etched surface was greater than 71 nm away. To demonstrate the application of the developed dry etch process, surface-etched air gaps were fabricated 275 nm away from the active region of an m-plane InGaN/GaN laser diode and served as the waveguide upper cladding. Electrically injected lasing was observed without the need for regrowth or recovery anneals. This dry etch opens up a new design tool that can be utilized in the next generation of GaN light emitters.

Crystal Initiation Structures in Developing Enamel: Possible Implications for Caries Dissolution of Enamel Crystals

PubMed Central

Robinson, Colin; Connell, Simon D.

2017-01-01

Investigations of developing enamel crystals using Atomic and Chemical Force Microscopy (AFM, CFM) have revealed a subunit structure. Subunits were seen in height images as collinear swellings about 30 nM in diameter on crystal surfaces. In friction mode they were visible as positive regions. These were similar in size (30–50 nM) to collinear spherical structures, presumably mineral matrix complexes, seen in developing enamel using a freeze fracturing/freeze etching procedure. More detailed AFM studies on mature enamel suggested that the 30–50 nM structures were composed of smaller units, ~10–15 nM in diameter. These were clustered in hexagonal or perhaps a spiral arrangement. It was suggested that these could be the imprints of initiation sites for mineral precipitation. The investigation aimed at examining original freeze etched images at high resolution to see if the smaller subunits observed using AFM in mature enamel were also present in developing enamel i.e., before loss of the organic matrix. The method used was freeze etching. Briefly samples of developing rat enamel were rapidly frozen, fractured under vacuum, and ice sublimed from the fractured surface. The fractured surface was shadowed with platinum or gold and the metal replica subjected to high resolution TEM. For AFM studies high-resolution tapping mode imaging of human mature enamel sections was performed in air under ambient conditions at a point midway between the cusp and the cervical margin. Both AFM and freeze etch studies showed structures 30–50 nM in diameter. AFM indicated that these may be clusters of somewhat smaller structures ~10–15 nM maybe hexagonally or spirally arranged. High resolution freeze etching images of very early enamel showed ~30–50 nM spherical structures in a disordered arrangement. No smaller units at 10–15 nM were clearly seen. However, when linear arrangements of 30–50 nM units were visible the picture was more complex but also smaller units including ~10–15 nM units could be observed. Conclusions: Structures ~10–15 nM in diameter were detected in developing enamel. While the appearance was complex, these were most evident when the 30–5 nM structures were in linear arrays. Formation of linear arrays of subunits may be associated with the development of mineral initiation sites and attendant processing of matrix proteins. PMID:28670283

Arrays of size and distance controlled platinum nanoparticles fabricated by a colloidal method

NASA Astrophysics Data System (ADS)

Manzke, Achim; Vogel, Nicolas; Weiss, Clemens K.; Ziener, Ulrich; Plettl, Alfred; Landfester, Katharina; Ziemann, Paul

2011-06-01

Based on emulsion polymerization in the presence of a Pt complex, polystyrene (PS) particles were prepared exhibiting a well defined average diameter with narrow size-distribution. Furthermore, the colloids contain a controlled concentration of the Pt precursor complex. Optimized coating of Si substrates with such colloids leads to extended areas of hexagonally ordered close-packed PS particles. Subsequent application of plasma etching and annealing steps allows complete removal of the PS carriers and in parallel nucleation and growth of Pt nanoparticles (NPs) which are located at the original center of the PS colloids. In this way, hexagonally arranged spherical Pt NPs are obtained with controlled size and interparticle distances demonstrating variability and precision with so far unknown parameter scalability. This control is demonstrated by the fabrication of Pt NP arrays at a fixed particle distance of 185 nm while systematically varying the diameters between 8 and 15 nm. Further progress could be achieved by seeded emulsion polymerization. Here, Pt loaded PS colloids of 130 nm were used as seeds for a subsequent additional emulsion polymerization, systematically enlarging the diameter of the PS particles. Applying the plasma and annealing steps as above, in this way hexagonally ordered arrays of 9 nm Pt NPs could be obtained at distances up to 260 nm. To demonstrate their stability, such Pt particles were used as etching masks during reactive ion etching thereby transferring their hexagonal pattern into the Si substrate resulting in corresponding arrays of nanopillars.Based on emulsion polymerization in the presence of a Pt complex, polystyrene (PS) particles were prepared exhibiting a well defined average diameter with narrow size-distribution. Furthermore, the colloids contain a controlled concentration of the Pt precursor complex. Optimized coating of Si substrates with such colloids leads to extended areas of hexagonally ordered close-packed PS particles. Subsequent application of plasma etching and annealing steps allows complete removal of the PS carriers and in parallel nucleation and growth of Pt nanoparticles (NPs) which are located at the original center of the PS colloids. In this way, hexagonally arranged spherical Pt NPs are obtained with controlled size and interparticle distances demonstrating variability and precision with so far unknown parameter scalability. This control is demonstrated by the fabrication of Pt NP arrays at a fixed particle distance of 185 nm while systematically varying the diameters between 8 and 15 nm. Further progress could be achieved by seeded emulsion polymerization. Here, Pt loaded PS colloids of 130 nm were used as seeds for a subsequent additional emulsion polymerization, systematically enlarging the diameter of the PS particles. Applying the plasma and annealing steps as above, in this way hexagonally ordered arrays of 9 nm Pt NPs could be obtained at distances up to 260 nm. To demonstrate their stability, such Pt particles were used as etching masks during reactive ion etching thereby transferring their hexagonal pattern into the Si substrate resulting in corresponding arrays of nanopillars. Electronic supplementary information (ESI) available: Detailed description of the experimental part (S1-S4) platinum concentration inside the polymer particles synthesized by a seeded polymerization from the same seed particles measured by ICP-OES (Fig. S1 and S5); SEM image of Pt complex containing PS particles after oxygen plasma treatment (Fig. S2 and S6); effect of hydrofluoric acid treatment on silicon oxide elevation under Pt NPs (Fig. S3 and S6); SEM images demonstrating the variability of Pt NP distance while keeping the diameter constant (Fig. S4 and S8); results of experimental determination of Pt content by ICP-OES (Tables S1 and S9); diameter of the particles at different fabrication states (Tables S2 and S10). See DOI: 10.1039/c1nr10169b

Ryanodine receptors regulate arterial diameter and wall [Ca2+] in cerebral arteries of rat via Ca2+-dependent K+ channels

PubMed Central

Knot, Harm J; Standen, Nicholas B; Nelson, Mark T

1998-01-01

The effects of inhibitors of ryanodine-sensitive calcium release (RyR) channels in the sarcoplasmic reticulum (SR) and Ca2+-dependent potassium (KCa) channels on the membrane potential, intracellular [Ca2+], and diameters of small pressurized (60 mmHg) cerebral arteries (100–200 μm) were studied using digital fluorescence video imaging of arterial diameter and wall [Ca2+], combined with microelectrode measurements of arterial membrane potential. Ryanodine (10 μm), an inhibitor of RyR channels, depolarized by 9 mV, increased intracellular [Ca2+] by 46 nm and constricted pressurized (to 60 mmHg) arteries with myogenic tone by 44 μm (∼22 %). Iberiotoxin (100 nm), a blocker of KCa channels, under the same conditions, depolarized the arteries by 10 mV, increased arterial wall calcium by 51 nm, and constricted by 37 μm (∼19 %). The effects of ryanodine and iberiotoxin were not additive and were blocked by inhibitors of voltage-dependent Ca2+ channels. Caffeine (10 mm), an activator of RyR channels, transiently increased arterial wall [Ca2+] by 136 ± 9 nm in control arteries and by 158 ± 12 nm in the presence of iberiotoxin. Caffeine was relatively ineffective in the presence of ryanodine, increasing [calcium] by 18 ± 5 nm. In the presence of blockers of voltage-dependent Ca2+ channels (nimodipine, diltiazem), ryanodine and inhibitors of the SR calcium ATPase (thapsigargin, cyclopiazonic acid) were without effect on arterial wall [Ca2+] and diameter. These results suggest that local Ca2+ release originating from RyR channels (Ca2+ sparks) in the SR of arterial smooth muscle regulates myogenic tone in cerebral arteries solely through activation of KCa channels, which regulate membrane potential through tonic hyperpolarization, thus limiting Ca2+ entry through L-type voltage-dependent Ca2+ channels. KCa channels therefore act as a negative feedback control element regulating arterial diameter through a reduction in global intracellular free [Ca2+]. PMID:9490841

Fabrication of curcumin-loaded bovine serum albumin (BSA)-dextran nanoparticles and the cellular antioxidant activity.

PubMed

Fan, Yuting; Yi, Jiang; Zhang, Yuzhu; Yokoyama, Wallace

2018-01-15

Bovine serum albumin (BSA)-dextran conjugate was prepared with glycation. Self-assembly nanoparticles were synthesized with a green, and facile approach. The effects of dry-heating time on the fabrication and characteristics of BSA-dextran conjugate nanoparticles were examined. Stable nanoparticles (<200nm) were formed after only 6h dry-heating because enough dextran was grafted onto the BSA to provide significant steric hindrance. Particle size decreased with the increase of dry-heating time and the lowest particle size (51.2nm) was obtained after 24h dry-heating. The nanoparticles were stable in a wide pH range (pH 2.0-7.0). The particle size of nanoparticles increased to 115nm after curcumin incorporation and was stable even after one-month storage. TEM results demonstrated that curcumin-loaded nanoparticles displayed a spherical structure and were homogeneously dispersed. Curcumin in BSA-dextran nanoparticle showed better stability, compared to free curcumin. In addition, BSA-dextran nanoparticles can improve the cellular antioxidant activity of curcumin in Caco-2 cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

Estimating aspen volume and weight for individual trees, diameter classes, or entire stands.

Treesearch

Bryce E. Schlaegel

1975-01-01

Presents allometric volume and weight equations for Minnesota quaking aspen. Volume, green weight, and dry weight estimates can be made for wood, bark, and limbs on the basis of individual trees, diameter classes, or entire stands.

Weight and volume equations and tables for six upland hardwoods in southern Illinois.

Treesearch

David J. Polak; Donald Raisanen; Richard C. Schlesinger; Les Stortz

1980-01-01

This paper presents tables of total tree green weight, green weight to a 5 cm and a 10 cm top diameter, dry weight to both 5 cm and 10 cm top diameter, and green volume to a 5 cm and 10 cm top diameter for six upland hardwood species. Both metric and English unit tables are included.

Nonhuman Primate Ocular Biometry

PubMed Central

Augusteyn, Robert C.; Maceo Heilman, Bianca; Ho, Arthur; Parel, Jean-Marie

2016-01-01

Purpose To examine ocular growth in nonhuman primates (NHPs) from measurements on ex vivo eyes. Methods We obtained NHP eyes from animals that had been killed as part of other studies or because of health-related issues. Digital calipers were used to measure the horizontal, vertical, and anteroposterior globe diameters as well as corneal horizontal and vertical diameters of excised globes from 98 hamadryas baboons, 551 cynomolgus monkeys, and 112 rhesus monkeys, at ages ranging from 23 to 360 months. Isolated lens sagittal thickness and equatorial diameter were measured by shadowphotogrammetry. Wet and fixed dry weights were obtained for lenses. Results Nonhuman primate globe growth continues throughout life, slowing toward an asymptotic maximum. The final globe size scales with negative allometry to adult body size. Corneal growth ceases at around 20 months. Lens diameter increases but thickness decreases with increasing age. Nonhuman primate lens wet and dry weight accumulation is monophasic, continuing throughout life toward asymptotic maxima. The dry/wet weight ratio reaches a maximum of 0.33. Conclusions Nonhuman primate ocular globe and lens growth differ in several respects from those in humans. Although age-related losses of lens power and accommodative amplitude are similar, lens growth and properties are different indicating care should be taken in extrapolating NHP observations to the study of human accommodation. PMID:26780314

Slow Light Semiconductor Laser

DTIC Science & Technology

2015-02-02

semi- conductor lasers, demonstrated here with a spectral linewidth of 18 kHz. Our approach circumvents historical limitations of laser design and it...Oxford 380). To turn the passive resonator into a high-Q hybrid laser, we smooth the waveguide sidewalls to improve Qsc by growing 15 nm of dry thermal ...oxide (oxidation times calculated using the Massoud model). We strip the oxide with HF (Transene Buffer HF- Improved), and regrow 20 nm of dry oxide

Hygroscopic behavior of water-soluble matter in marine aerosols over the East China Sea.

PubMed

Yan, Yu; Fu, Pingqing; Jing, Bo; Peng, Chao; Boreddy, S K R; Yang, Fan; Wei, Lianfang; Sun, Yele; Wang, Zifa; Ge, Maofa

2017-02-01

In this study, we investigated hygroscopic properties of water-soluble matter (WSM) in marine aerosols over the East China Sea, which were collected during a Natural Science Foundation of China (NSFC) sharing cruise in 2014. Hygroscopic growth factors (g) of WSM were measured by a hygroscopicity tandem differential mobility analyzer (H-TDMA) with an initial dry particle mobility diameter of 100nm. The observed g at 90% relative humidity (RH), g(90%) WSM , defined as the ratio of the particle diameter at 90% RH to that at RH<5% (initial dry diameter), ranged from 1.67 to 2.41 (mean±std: 1.99±0.23). The g values were lower than that of seawater (2.1) but comparable with those reported for marine aerosols (1.79-2.08). The H-TDMA retrieved hygroscopicity parameter of WSM, κ WSM , ranged from 0.46 to 1.56 (0.88±0.35). The observed g(90%) WSM during the daytime ranged from 1.67 to 2.40 (1.95±0.21) versus 1.71 to 2.41 (2.03±0.26) during the nighttime. κ WSM was 0.81±0.32 in the daytime and 0.95±0.40 in the nighttime. The day/night differences of g(90%) WSM and κ WSM indicated that nighttime marine aerosols were more hygroscopic than those in daytime, which was likely related to enhanced heterogeneous reaction of ammonium nitrate in nighttime and the higher Cl - /Na + molar ratios obtained (0.80) in nighttime than those (0.47) in daytime. Inorganic ions accounted for 72-99% of WSM with SO 4 2- being the dominant species, contributing to 47% of the total inorganic ion mass. The declined g(90%) comparing with sea water was likely due to the transport of anthropogenic aerosols, chemical aging of dust particles, the contribution of biomass burning products, and the aerosol hygroscopic growth inhibition of organics. Copyright © 2016 Elsevier B.V. All rights reserved.

Dry deposition fluxes and deposition velocities of trace metals in the Tokyo metropolitan area measured with a water surface sampler.

PubMed

Sakata, Masahiro; Marumoto, Kohji

2004-04-01

Dry deposition fluxes and deposition velocities (=deposition flux/atmospheric concentration) for trace metals including Hg, Cd, Cu, Mn, Pb, and Zn in the Tokyo metropolitan area were measured using an improved water surface sampler. Mercury is deposited on the water surface in both gaseous (reactive gaseous mercury, RGM) and particulate (particulate mercury, Hg(p)) forms. The results based on 1 yr observations found that dry deposition plays a significant if not dominant role in trace metal deposition in this urban area, contributing fluxes ranging from 0.46 (Cd) to 3.0 (Zn) times those of concurrent wet deposition fluxes. The deposition velocities were found to be dependent on the deposition of coarse particles larger than approximately 5 microm in diameter on the basis of model calculations. Our analysis suggests that the 84.13% diameter is a more appropriate index for each deposited metal than the 50% diameter in the assumed undersize log-normal distribution, because larger particles are responsible for the flux. The deposition velocities for trace metals other than mercury increased exponentially with an increase in their 84.13% diameters. Using this regression equation, the deposition velocities for Hg(p) were estimated from its 84.13% diameter. The deposition fluxes for Hg(p) calculated from the estimated velocities tended to be close to the mercury fluxes measured with the water surface sampler during the study periods except during summer.

A Dense Poly(ethylene glycol) Coating Improves Penetration of Large Polymeric Nanoparticles within Brain Tissue

PubMed Central

Nance, Elizabeth A.; Woodworth, Graeme F.; Sailor, Kurt A.; Shih, Ting-Yu; Xu, Qingguo; Swaminathan, Ganesh; Xiang, Dennis; Eberhart, Charles; Hanes, Justin

2013-01-01

Prevailing opinion suggests that only substances up to 64 nm in diameter can move at appreciable rates through the brain extracellular space (ECS). This size range is large enough to allow diffusion of signaling molecules, nutrients, and metabolic waste products, but too small to allow efficient penetration of most particulate drug delivery systems and viruses carrying therapeutic genes, thereby limiting effectiveness of many potential therapies. We analyzed the movements of nanoparticles of various diameters and surface coatings within fresh human and rat brain tissue ex vivo and mouse brain in vivo. Nanoparticles as large as 114-nm in diameter diffused within the human and rat brain, but only if they were densely coated with poly(ethylene glycol) (PEG). Using these minimally adhesive PEG-coated particles, we estimated that human brain tissue ECS has some pores larger than 200 nm, and that more than one-quarter of all pores are ≥100 nm. These findings were confirmed in vivo in mice, where 40- and 100-nm, but not 200-nm, nanoparticles, spread rapidly within brain tissue, only if densely coated with PEG. Similar results were observed in rat brain tissue with paclitaxel-loaded biodegradable nanoparticles of similar size (85 nm) and surface properties. The ability to achieve brain penetration with larger nanoparticles is expected to allow more uniform, longer-lasting, and effective delivery of drugs within the brain, and may find use in the treatment of brain tumors, stroke, neuroinflammation, and other brain diseases where the blood-brain barrier is compromised or where local delivery strategies are feasible. PMID:22932224

Bulk synthesis of nanoporous palladium and platinum powders

DOEpatents

Robinson, David B [Fremont, CA; Fares, Stephen J [Pleasanton, CA; Tran, Kim L [Livermore, CA; Langham, Mary E [Pleasanton, CA

2012-04-17

Disclosed is a method for providing nanoporous palladium and platinum powders. These materials were synthesized on milligram to gram scales by chemical reduction of tetrahalo-complexes with ascorbate in a concentrated aqueous surfactant at temperatures between -20.degree. C. and 30.degree. C. The prepared particles have diameters of approximately 50 nm, wherein each particle is perforated by pores having diameters of approximately 3 nm, as determined by electron tomography. These materials are of potential value for hydrogen and electrical charge storage applications.

Wavelength Independent Optical Microscopy and Lithography

DTIC Science & Technology

1987-10-31

methods have been used in the past to fabricate the submicron apertures needed in near-field microscopy (2-4). However, under this contract we developed an...screens. Durig, et al. (4) in Zurich produced apertures at the tip of a single crystal of quartz etched using HF to make a fine point and covered...stage pulling process was used . Scanning electron li __ NO iI |06 j JlliM ° wm ..... 3 micrographs of a 100nm diameter pipette and a 500nm diameter

Bulk synthesis of nanoporous palladium and platinum powders

DOEpatents

Robinson, David B; Fares, Stephen J; Tran, Kim L; Langham, Mary E

2014-04-15

Disclosed is a method for providing nanoporous palladium and platinum powders. These materials were synthesized on milligram to gram scales by chemical reduction of tetrahalo-complexes with ascorbate in a concentrated aqueous surfactant at temperatures between -20.degree. C. and 30.degree. C. The prepared particles have diameters of approximately 50 nm, wherein each particle is perforated by pores having diameters of approximately 3 nm, as determined by electron tomography. These materials are of potential value for hydrogen and electrical charge storage applications.

Growth of High-Quality Carbon Nanotudes on Free-Standing Diamond Substrates (Postprint)

DTIC Science & Technology

2010-03-01

thickness and consisting of 20 nm diameter tubes were observed to grow in a thermal CVD system using C2H2 as precursor, Transmission electron microscopy...multi walled CNTs forming a mat of 5 lm thickness and consisting of 20 nm diameter tubes were observed to grow in a thermal CVD system using C2H2...desired devices. For example, chip cooling with CNT microfin architectures have been recently proposed by Kordas et al. [5]. CNT films as thermal

High Sensitivity Refractometer Based on Reflective Smf-Small Diameter No Core Fiber Structure.

PubMed

Zhou, Guorui; Wu, Qiang; Kumar, Rahul; Ng, Wai Pang; Liu, Hao; Niu, Longfei; Lalam, Nageswara; Yuan, Xiaodong; Semenova, Yuliya; Farrell, Gerald; Yuan, Jinhui; Yu, Chongxiu; Zeng, Jie; Tian, Gui Yun; Fu, Yong Qing

2017-06-16

A high sensitivity refractive index sensor based on a single mode-small diameter no core fiber structure is proposed. In this structure, a small diameter no core fiber (SDNCF) used as a sensor probe, was fusion spliced to the end face of a traditional single mode fiber (SMF) and the end face of the SDNCF was coated with a thin film of gold to provide reflective light. The influence of SDNCF diameter and length on the refractive index sensitivity of the sensor has been investigated by both simulations and experiments, where results show that the diameter of SDNCF has significant influence. However, SDNCF length has limited influence on the sensitivity. Experimental results show that a sensitivity of 327 nm/RIU (refractive index unit) has been achieved for refractive indices ranging from 1.33 to 1.38, which agrees well with the simulated results with a sensitivity of 349.5 nm/RIU at refractive indices ranging from 1.33 to 1.38.

Electrical transport properties of small diameter single-walled carbon nanotubes aligned on ST-cut quartz substrates

PubMed Central

2014-01-01

A method is introduced to isolate and measure the electrical transport properties of individual single-walled carbon nanotubes (SWNTs) aligned on an ST-cut quartz, from room temperature down to 2 K. The diameter and chirality of the measured SWNTs are accurately defined from Raman spectroscopy and atomic force microscopy (AFM). A significant up-shift in the G-band of the resonance Raman spectra of the SWNTs is observed, which increases with increasing SWNTs diameter, and indicates a strong interaction with the quartz substrate. A semiconducting SWNT, with diameter 0.84 nm, shows Tomonaga-Luttinger liquid and Coulomb blockade behaviors at low temperatures. Another semiconducting SWNT, with a thinner diameter of 0.68 nm, exhibits a transition from the semiconducting state to an insulating state at low temperatures. These results elucidate some of the electrical properties of SWNTs in this unique configuration and help pave the way towards prospective device applications. PMID:25170326

Angular dependence of the magnetic properties of permalloy and nickel nanowires as a function of their diameters

NASA Astrophysics Data System (ADS)

Raviolo, Sofía; Tejo, Felipe; Bajales, Noelia; Escrig, Juan

2018-01-01

In this paper we have compared the angular dependence of the magnetic properties of permalloy (Ni80Fe20) and nickel nanowires by means of micromagnetic simulations. For each material we have chosen two diameters, 40 and 100 nm. Permalloy nanowires with smaller diameters (d = 40 nm) exhibit greater coercivity than nickel nanowires, regardless of the angle at which the external magnetic field is applied. In addition, both Py and Ni nanowires exhibit the same remanence values. However, the nanowires of larger diameters (d = 100 nm) exhibit a more complex behavior, noting that for small angles, nickel nanowires are those that now exhibit a greater coercivity in comparison to those of permalloy. The magnetization reversal modes vary as a function of the angle at which the external field is applied. When the field is applied parallel to the wire axis, it reverts through nucleation and propagation of domain walls, whereas when the field is applied perpendicular to the axis, it reverts by a pseudo-coherent rotation. These results may provide a guide to control the magnetic properties of nanowires for use in potential applications.

Time-dependent preparation of gelatin-stabilized silver nanoparticles by pulsed Nd:YAG laser

NASA Astrophysics Data System (ADS)

Darroudi, Majid; Ahmad, M. B.; Zamiri, Reza; Abdullah, A. H.; Ibrahim, N. A.; Sadrolhosseini, A. R.

2011-03-01

Colloidal silver nanoparticles (Ag-NPs) were successfully prepared using a nanosecond pulsed Nd:YAG laser, λ = 1064 nm, with laser fluence of approximately about 360 mJ/pulse, in an aqueous gelatin solution. In this work, gelatin was used as a stabilizer, and the size and optical absorption properties of samples were studied as a function of the laser ablation times. The results from the UV-vis spectroscopy demonstrated that the mean diameter of Ag-NPs decrease as the laser ablation time increases. The Ag-NPs have mean diameters ranging from approximately 10 nm to 16 nm. Compared with other preparation methods, this work is clean, rapid, and simple to use.

ZnO/(Hf,Zr)O2/ZnO-trilayered nanowire capacitor structure fabricated solely by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Fujisawa, Hironori; Kuwamoto, Kei; Nakashima, Seiji; Shimizu, Masaru

2016-02-01

HfO2-based thin films are one of the key dielectric and ferroelectric materials in Si-CMOS LSIs as well as in oxide electronic nanodevices. In this study, we demonstrated the fabrication of a ZnO/(Hf,Zr)O2/ZnO-trilayered nanowire (NW) capacitor structure solely by metalorganic chemical vapor deposition (MOCVD). 15-nm-thick dielectric (Hf,Zr)O2 and 40-nm-thick top ZnO electrode layers were uniformly grown by MOCVD on a ZnO NW template with average diameter, length, and aspect ratio of 110 nm, 10 µm, and ˜90, respectively. The diameter and aspect ratio of the resultant trilayerd NWs are 200-300 nm and above 30, respectively. The crystalline phase of HfO2 and stacked the structure are also discussed.

Formation of metal clusters in halloysite clay nanotubes

NASA Astrophysics Data System (ADS)

Vinokurov, Vladimir A.; Stavitskaya, Anna V.; Chudakov, Yaroslav A.; Ivanov, Evgenii V.; Shrestha, Lok Kumar; Ariga, Katsuhiko; Darrat, Yusuf A.; Lvov, Yuri M.

2017-12-01

We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length 1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3-5 nm metal particles on the tubes; (2) inside the tube's central lumen resulting in 10-12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube's wall allowing up to 9 wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions.

Formation of metal clusters in halloysite clay nanotubes.

PubMed

Vinokurov, Vladimir A; Stavitskaya, Anna V; Chudakov, Yaroslav A; Ivanov, Evgenii V; Shrestha, Lok Kumar; Ariga, Katsuhiko; Darrat, Yusuf A; Lvov, Yuri M

2017-01-01

We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c .50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3-5 nm metal particles on the tubes; (2) inside the tube's central lumen resulting in 10-12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube's wall allowing up to 9 wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions.

Influence of drying of chara cellulose on length/length distribution of microfibrils after acid hydrolysis.

PubMed

Horikawa, Yoshiki; Shimizu, Michiko; Saito, Tsuguyuki; Isogai, Akira; Imai, Tomoya; Sugiyama, Junji

2018-04-01

Chara is a genus of freshwater alga that is evolutionarily observed at the aquatic-terrestrial boundary, whose cellulose microfibrils are similar to those of terrestrial plants regarding the crystallinity and biosynthesis of cellulose. Oven-dried and never-dried celluloses samples were prepared from chara. Terrestrial plant cellulose samples were used as references. The lengths and length distributions of oven-dried and never-dried chara cellulose microfibrils after acid hydrolysis with or without pretreatment by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, which was used for efficient fibrillation of acid-hydrolyzed products, were observed by transmission electron microscopy. All terrestrial plant celluloses and oven-dried chara cellulose had short nanocrystal-like morphologies of 100-300 nm in length after acid hydrolysis. In contrast, the never-dried chara cellulose had much longer microfibrils of ∼970 nm in length after acid hydrolysis. These results indicated that disordered regions present periodically along the cellulose microfibrils, which cause the formation of cellulose nanocrystals after acid hydrolysis, are not present in inherent chara cellulose microfibrils in water, but are formed artificially under drying or dehydration conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Self-Cleaning Synthetic Adhesive Surfaces Mimicking Tokay Geckos.

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

Branson, Eric D.; Singh, Seema; Burckel, David Bruce

2006-11-01

A gecko's extraordinary ability to suspend itself from walls and ceilings of varied surface roughness has interested humans for hundreds of years. Many theories and possible explanations describing this phenomenon have been proposed including sticky secretions, microsuckers, and electrostatic forces; however, today it is widely accepted that van der Waals forces play the most important role in this type of dry adhesion. Inarguably, the vital feature that allows a gecko's suspension is the presence of billions 3 of tiny hairs on the pad of its foot called spatula. These features are small enough to reach within van der Waals distancesmore » of any surface (spatula radius %7E100 nm); thus, the combined effect of billions of van der Waals interactions is more than sufficient to hold a gecko's weight to surfaces such as smooth ceilings or wet glass. Two lithographic approaches were used to make hierarchal structures with dimensions similar to the gecko foot dimensions noted above. One approach combined photo-lithography with soft lithography (micro-molding). In this fabrication scheme the fiber feature size, defined by the alumina micromold was 0.2 um in diameter and 60 um in height. The second approach followed more conventional photolithography-based patterning. Patterned features with dimensions %7E0.3 mm in diameter by 0.5 mm tall were produced. We used interfacial force microscopy employing a parabolic diamond tip with a diameter of 200 nm to measure the surface adhesion of these structures. The measured adhesive forces ranged from 0.3 uN - 0.6 uN, yielding an average bonding stress between 50 N/cm2 to 100 N/cm2. By comparison the reported literature value for the average stress of a Tokay gecko foot is 10 N/cm2. Acknowledgements This work was funded by Sandia National Laboratory's Laboratory Directed Research & Development program (LDRD). All coating processes were conducted in the cleanroom facility located at the University of New Mexico's Center for High Technology Materials (CHTM). SEM images were performed at UNM's Center for Micro-Engineering on equipment funded by a NSF New Mexico EPSCoR grant. 4« less

Preparation and evaluation of tilmicosin-loaded hydrogenated castor oil nanoparticle suspensions of different particle sizes.

PubMed

Chen, Xiaojin; Wang, Ting; Lu, Mengmeng; Zhu, Luyan; Wang, Yan; Zhou, WenZhong

2014-01-01

Three tilmicosin-loaded hydrogenated castor oil nanoparticle (TMS-HCO-NP) suspensions of different particle sizes were prepared with different polyvinyl alcohol surfactant concentrations using a hot homogenization and ultrasonic technique. The in vitro release, in vitro antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability study were conducted to evaluate the characteristics of the suspensions. The in vitro tilmicosin release rate, antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability of the suspensions were evaluated. When prepared with polyvinyl alcohol concentrations of 0.2%, 1%, and 5%, the mean diameters of the nanoparticles in the three suspensions were 920±35 nm, 452±10 nm, and 151±4 nm, respectively. The three suspensions displayed biphasic release profiles similar to that of freeze-dried TMS-HCO-NP powders, with the exception of having a faster initial release. Moreover, suspensions of smaller-sized particles showed faster initial release, and lower minimum inhibitory concentrations and minimum bactericidal concentrations. Time-kill curves showed that within 12 hours, the suspension with the 151 nm particles had the most potent bactericidal activity, but later, the suspensions with larger-sized particles showed increased antibacterial activity. None of the three suspensions were cytotoxic at clinical dosage levels. At higher drug concentrations, all three suspensions showed similar concentration-dependent cytotoxicity. The suspension with the smallest-sized particle showed significantly more acute toxicity in mice, perhaps due to faster drug release. All three suspensions exhibited good stability at 4°C and at room temperature for at least 6 months. These results demonstrate that TMS-HCO-NP suspensions can be a promising formulation for tilmicosin, and that nanoparticle size can be an important consideration for formulation development.

Preparation and evaluation of tilmicosin-loaded hydrogenated castor oil nanoparticle suspensions of different particle sizes

PubMed Central

Chen, Xiaojin; Wang, Ting; Lu, Mengmeng; Zhu, Luyan; Wang, Yan; Zhou, WenZhong

2014-01-01

Three tilmicosin-loaded hydrogenated castor oil nanoparticle (TMS-HCO-NP) suspensions of different particle sizes were prepared with different polyvinyl alcohol surfactant concentrations using a hot homogenization and ultrasonic technique. The in vitro release, in vitro antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability study were conducted to evaluate the characteristics of the suspensions. The in vitro tilmicosin release rate, antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability of the suspensions were evaluated. When prepared with polyvinyl alcohol concentrations of 0.2%, 1%, and 5%, the mean diameters of the nanoparticles in the three suspensions were 920±35 nm, 452±10 nm, and 151±4 nm, respectively. The three suspensions displayed biphasic release profiles similar to that of freeze-dried TMS-HCO-NP powders, with the exception of having a faster initial release. Moreover, suspensions of smaller-sized particles showed faster initial release, and lower minimum inhibitory concentrations and minimum bactericidal concentrations. Time-kill curves showed that within 12 hours, the suspension with the 151 nm particles had the most potent bactericidal activity, but later, the suspensions with larger-sized particles showed increased antibacterial activity. None of the three suspensions were cytotoxic at clinical dosage levels. At higher drug concentrations, all three suspensions showed similar concentration-dependent cytotoxicity. The suspension with the smallest-sized particle showed significantly more acute toxicity in mice, perhaps due to faster drug release. All three suspensions exhibited good stability at 4°C and at room temperature for at least 6 months. These results demonstrate that TMS-HCO-NP suspensions can be a promising formulation for tilmicosin, and that nanoparticle size can be an important consideration for formulation development. PMID:24920902

NMR-NOE and MD simulation study on phospholipid membranes: dependence on membrane diameter and multiple time scale dynamics.

PubMed

Shintani, Megumi; Yoshida, Ken; Sakuraba, Shun; Nakahara, Masaru; Matubayasi, Nobuyuki

2011-07-28

Motional correlation times between the hydrophilic and hydrophobic terminal groups in lipid membranes are studied over a wide range of curvatures using the solution-state (1)H NMR-nuclear Overhauser effect (NOE) and molecular dynamics (MD) simulation. To enable (1)H NMR-NOE measurements for large vesicles, the transient NOE method is combined with the spin-echo method, and is successfully applied to a micelle of 1-palmitoyl-lysophosphatidylcholine (PaLPC) with diameter of 5 nm and to vesicles of dipalmitoylphosphatidylcholine (DPPC) with diameters ranging from 30 to 800 nm. It is found that the NOE intensity increases with the diameter up to ∼100 nm, and the model membrane is considered planar on the molecular level beyond ∼100 nm. While the NOE between the hydrophilic terminal and hydrophobic terminal methyl groups is absent for the micelle, its intensity is comparable to that for the neighboring group for vesicles with larger diameters. The origin of NOE signals between distant sites is analyzed by MD simulations of PaLPC micelles and DPPC planar bilayers. The slow relaxation is shown to yield an observable NOE signal even for the hydrophilic and hydrophobic terminal sites. Since the information on distance and dynamics cannot be separated in the experimental NOE alone, the correlation time in large vesicles is determined by combining the experimental NOE intensity and MD-based distance distribution. For large vesicles, the correlation time is found to vary by 2 orders of magnitude over the proton sites. This study shows that NOE provides dynamic information on large vesicles when combined with MD, which provides structural information. © 2011 American Chemical Society

Hierarchically assembled Au microspheres and sea urchin-like architectures: formation mechanism and SERS study.

PubMed

Wang, Xiansong; Yang, Da-Peng; Huang, Peng; Li, Min; Li, Chao; Chen, Di; Cui, Daxiang

2012-12-21

The hierarchically assembled Au microspheres/sea urchin-like structures have been synthesized in aqueous solution at room temperature with and without proteins (bovine serum albumin, BSA) as mediators. The average diameter of an individual Au microsphere is 300-600 nm, which is composed of some compact nanoparticles with an average diameter of about 15 nm. Meanwhile, the sea urchin-like Au architecture exhibits an average diameter of 600-800 nm, which is made up of some nanopricks with an average length of 100-200 nm. These products are characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electronic microscopy (TEM). It is found that the BSA and ascorbic acid (AA) have great effects on the morphology of the resulting products. Two different growth mechanisms are proposed. The study on surface enhanced Raman scattering (SERS) activities is also carried out between Au microspheres and Au sea urchin-like architectures. It is found that Au urchin-like architectures possess much higher SERS activity than the Au microspheres. Our work may shed light on the design and synthesis of hierarchically self-assembled 3D micro/nano-architectures for SERS, catalysis and biosensors.

Toward Reconciliation of STEM and SAXS Data from Ionomers by Investigating Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Benetatos, Nicholas; Smith, Brian; Heiney, Paul; Winey, Karen

2005-03-01

We have recently pioneered the use of scanning transmission electron microscopy (STEM) for direct, model independent imaging of the nano-scale morphology of ionomers. To date, the sizes of ionic aggregates determined in STEM experiments are inconsistent with SAXS data interpreted by the Yarusso-Cooper model. To address this discrepancy we have investigated a pair of model nanoparticles (11 and 55 atom Au clusters) with both STEM and SAXS. Using this model system we have improved our method of measuring nanometer scale objects and evaluated the importance of STEM probe size and specimen thickness. While the size of the STEM probe was inconsequential, specimen thicker than 50 nm showed significant depreciation of image quality, which limits our ability to accurately measure particle size. SAXS was performed on dilute suspensions of nanoparticles and fit using a monodisperse, hard-sphere form factor model. For Au11, STEM finds a diameter of 1.3 nm + .14 and SAXS finds a diameter of 1.4 nm. Similarly, both STEM and SAXS determine a diameter of 1.7 nm for Au55. Analysis of these model systems have allowed us to evaluate several factors of potential importance in reconciling STEM and SAXS data from ionomers.

Development of magnetic separation system of magnetoliposomes

NASA Astrophysics Data System (ADS)

Nakao, R.; Matuo, Y.; Mishima, F.; Taguchi, T.; Maenosono, S.; Nishijima, S.

2009-10-01

The magnetic separation technology using sub-microsized ferromagnetic particle is indispensable in many areas of medical biosciences. For example, ferromagnetic particles (200-500 nm) are widely used for cell sorting in stem cell research with the use of cell surface-specific antigens. Nanosized ferromagnetic particles (10-20 nm) have been suggested as more suitable in drug delivery studies given their efficiency of tissue penetration, however, the magnetic separation method for them has not been established. One of the major reasons is that magnetic force acting on the object particles decreases drastically as a particle diameter becomes small. In this study, magnetic force acting on the targets was enhanced by the combination of superconducting magnet and the filter consisting of ferromagnetic particle. By doing so, we confirmed that Fe 3O 4 of 20 nm in diameter was trapped in the magnetic filter under an external magnetic field of 0.5 T. Fe 3O 4 encapsulated with phospholipid liposomes of 200 nm in diameter was also shown to be trapped as external magnetic field of 1.5 T, but not of 0.5 T. We also showed the result of particle trajectory calculation which emulated well the experimental data.

Physicochemical properties of aerosol released in the case of a fire involving materials used in the nuclear industry.

PubMed

Ouf, F-X; Mocho, V-M; Pontreau, S; Wang, Z; Ferry, D; Yon, J

2015-01-01

For industrial concerns, and more especially for nuclear applications, the characterization of soot is essential for predicting the behaviour of containment barriers in fire conditions. This study deals with the characterization (emission factor, composition, size, morphology, microstructure) of particles produced during thermal degradation of materials found in nuclear facilities (electrical cables, polymers, oil and solvents). Small-scale experiments have been conducted for oxygen concentrations [O2] ranging from 15% to 21% in order to imitate the oxygen depletion encountered during a confined fire. Particles denote distinct shapes, from aggregates composed of monomers with diameters ranging from 31.2 nm to 52.8 nm, to compact nanoparticles with diameters ranging from 15 nm to 400 nm, and their composition strongly depends on fuel type. Despite the organic to total carbon ratio (OC/TC), their properties are poorly influenced by the decrease in [O2]. Finally, two empirical correlations are proposed for predicting the OC/TC ratio and the monomer diameter, respectively, as a function of the fuel's carbon to hydrogen ratio and the emission factor. Copyright © 2014 Elsevier B.V. All rights reserved.

Mechanical properties and mechanism of single crystal Cu pillar by in situ TEM compression and molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Lin, Kai-Peng; Fang, Te-Hua; Lin, Ying-Jhin

2018-02-01

In this study, we investigate the mechanical properties of single-crystal copper (Cu) nanopillars. Critical deformation variations of Cu-nanopillared structures are estimated using in situ transmission electron microscopy compression tests and molecular dynamics simulations. The Young’s moduli of Cu nanopillars with diameters of 2-6 nm were 90.20-124.47 GPa. The contact stiffnesses of the Cu nanopillars with diameters of 400 and 500 nm were 1.33 and 3.86 N m-1, respectively; the Poisson’s ratios for these nanopillars were 0.32 and 0.33. The yield strength of the nanopillars varied from 0.25 GPa at 500 nm to 0.42 GPa at 400 nm; the yield strength of single-crystal Cu nanopillars decreased with increasing diameter. The values of the indented hardness of the Cu block were 0.27 and 1.06 GPa, respectively. Through experimental work and molecular dynamics simulations, we demonstrate that Cu nanopillars exhibit internal stress transmission during compression. When compression reaches the maximum strain, it can be observed that Cu slips. Our results are useful for understanding the mechanical properties, contact, and local deformation of Cu nanopillars.

Fabrication of Meso-Porous Sintered Metal Thin Films by Selective Etching of Silica Based Sacrificial Template

PubMed Central

Dumée, Ludovic F.; She, Fenghua; Duke, Mikel; Gray, Stephen; Hodgson, Peter; Kong, Lingxue

2014-01-01

Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by shear mixing. The resulted powders were cold-sintered to form dense, hybrid thin films. The sacrificial silica template was then removed by selective etching in 12 wt% hydrofluoric acid solutions for 15 min to reveal a purely metallic meso-porous thin film material. The impact of the initial silica nano-particle diameter (7–20 nm) as well as the sintering pressure (5–20 ton·m−2) and etching conditions on the morphology and properties of the final nano-porous thin films were investigated by porometry, pyknometery, gas and liquid permeation and electron microscopy. Furthermore, the morphology of the pores and particle aggregation during shear mixing were assessed through cross-sectioning by focus ion beam milling. It is demonstrated that meso-pores ranging between 50 and 320 nm in average diameter and porosities up to 47% can be successfully formed for the range of materials tested. PMID:28344241

Emissions characterization of residential wood-fired hydronic heater technologies

NASA Astrophysics Data System (ADS)

Kinsey, John S.; Touati, Abderrahmane; Yelverton, Tiffany L. B.; Aurell, Johanna; Cho, Seung-Hyun; Linak, William P.; Gullett, Brian K.

2012-12-01

Residential wood-fired hydronic heaters (RWHHs) can negatively impact the local ambient air quality and thus are an environmental concern in wood burning areas of the U. S. Only a few studies have been conducted which characterize the emissions from RWHHs. To address the lack of emissions data, a study was conducted on four appliances of differing design using multiple fuel types to determine their thermal, boiler, and combustion efficiency as well as the emissions of carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC), nitrous oxide (N2O), methane (CH4), total particulate matter (PM) mass, and particle number as well as particle size distribution (PSD). Three of these appliances were fired with split-log cordwood with the fourth unit using hardwood pellets. The measured thermal efficiencies for the appliances tested varied from 22 to 44% and the combustion efficiencies from 81 to 98%. Depending on appliance and fuel type, the emission factors ranged from about 1300 to 1800 g kg-1 dry fuel for CO2, 8-190 g kg-1 dry fuel for CO, <1-54 g kg-1 dry fuel for THC and 6-120 mg kg-1 for N2O. For the particle phase pollutants, the PM mass emission factors ranged from 0.31 to 47 g kg-1 dry fuel and the PM number emission factors from 8.5 × 1010 to 2.4 × 1014 particles kg-1 dry fuel, also depending on the appliance and fuel tested. The PSD for all four appliances indicated a well established accumulation mode with evidence of a nucleation mode present for Appliances A and B. The average median aerodynamic particle diameters observed for the four appliances ranged from 84 to 187 nm while burning red oak or pellets. In general, the pellet-burning appliance had the highest overall operating efficiency and lowest emissions of the four units tested.

Flow Cytometry Pulse Width Data Enables Rapid and Sensitive Estimation of Biomass Dry Weight in the Microalgae Chlamydomonas reinhardtii and Chlorella vulgaris

PubMed Central

Chioccioli, Maurizio; Hankamer, Ben; Ross, Ian L.

2014-01-01

Dry weight biomass is an important parameter in algaculture. Direct measurement requires weighing milligram quantities of dried biomass, which is problematic for small volume systems containing few cells, such as laboratory studies and high throughput assays in microwell plates. In these cases indirect methods must be used, inducing measurement artefacts which vary in severity with the cell type and conditions employed. Here, we utilise flow cytometry pulse width data for the estimation of cell density and biomass, using Chlorella vulgaris and Chlamydomonas reinhardtii as model algae and compare it to optical density methods. Measurement of cell concentration by flow cytometry was shown to be more sensitive than optical density at 750 nm (OD750) for monitoring culture growth. However, neither cell concentration nor optical density correlates well to biomass when growth conditions vary. Compared to the growth of C. vulgaris in TAP (tris-acetate-phosphate) medium, cells grown in TAP + glucose displayed a slowed cell division rate and a 2-fold increased dry biomass accumulation compared to growth without glucose. This was accompanied by increased cellular volume. Laser scattering characteristics during flow cytometry were used to estimate cell diameters and it was shown that an empirical but nonlinear relationship could be shown between flow cytometric pulse width and dry weight biomass per cell. This relationship could be linearised by the use of hypertonic conditions (1 M NaCl) to dehydrate the cells, as shown by density gradient centrifugation. Flow cytometry for biomass estimation is easy to perform, sensitive and offers more comprehensive information than optical density measurements. In addition, periodic flow cytometry measurements can be used to calibrate OD750 measurements for both convenience and accuracy. This approach is particularly useful for small samples and where cellular characteristics, especially cell size, are expected to vary during growth. PMID:24832156

Self-Assembling Peptide Detergents Stabilize Isolated Photosystem Ion a Dry Surface for an Extended Time

PubMed Central

Kiley, Patrick; Zhao, Xiaojun; Vaughn, Michael; Baldo, Marc A; Bruce, Barry D

2005-01-01

We used a class of designed peptide detergents to stabilize photosystem I (PS-I) upon extended drying under N2 on a gold-coated-Ni-NTA glass surface. PS-I is a chlorophyll-containing membrane protein complex that is the primary reducer of ferredoxin and the electron acceptor of plastocyanin. We isolated the complex from the thylakoids of spinach chloroplasts using a chemical detergent. The chlorophyll molecules associated with the PS-I complex provide an intrinsic steady-state emission spectrum between 650 and 800 nm at −196.15 °C that reflects the organization of the pigment-protein interactions. In the absence of detergents, a large blue shift of the fluorescence maxima from approximately 735 nm to approximately 685 nm indicates a disruption in light-harvesting subunit organization, thus revealing chlorophyll−protein interactions. The commonly used membrane protein-stabilizing detergents, N-dodecyl-β-D-maltoside and N-octyl-β-D-glucoside, only partially stabilized the approximately 735-nm complex with approximately 685-nm spectroscopic shift. However, prior to drying, addition of the peptide detergent acetyl- AAAAAAK at increasing concentration significantly stabilized the PS-I complex. Moreover, in the presence of acetyl- AAAAAAK, the PS-I complex is stable in a dried form at room temperature for at least 3 wk. Another peptide detergent, acetyl-VVVVVVD, also stabilized the complex but to a lesser extent. These observations suggest that the peptide detergents may effectively stabilize membrane proteins in the solid-state. These designed peptide detergents may facilitate the study of diverse types of membrane proteins. PMID:15954800

Electronic transport behavior of diameter-graded Ag nanowires

NASA Astrophysics Data System (ADS)

Wang, Xue Wei; Yuan, Zhi Hao

2010-05-01

Ag nanowires with a graded diameter in anodic aluminum oxide (AAO) membranes were fabricated by the direct-current electrodeposition. The Ag nanowires have a graded-change in diameter from 8 to 32 nm, which is matched with the graded-change of the AAO pore diameter. Electronic transport measurements show that there is a transport behavior similar to that of a metal-semiconductor junction along the axial direction in the diameter-graded Ag nanowires. Such a novel homogeneous nanojunction will be of great fundamental and practical significance.

Dry etching of chrome for photomasks for 100-nm technology using chemically amplified resist

NASA Astrophysics Data System (ADS)

Mueller, Mark; Komarov, Serguie; Baik, Ki-Ho

2002-07-01

Photo mask etching for the 100nm technology node places new requirements on dry etching processes. As the minimum-size features on the mask, such as assist bars and optical proximity correction (OPC) patterns, shrink down to 100nm, it is necessary to produce etch CD biases of below 20nm in order to reproduce minimum resist features into chrome with good pattern fidelity. In addition, vertical profiles are necessary. In previous generations of photomask technology, footing and sidewall profile slope were tolerated, since this dry etch profile was an improvement from wet etching. However, as feature sizes shrink, it is extremely important to select etch processes which do not generate a foot, because this will affect etch linearity and also limit the smallest etched feature size. Chemically amplified resist (CAR) from TOK is patterned with a 50keV MEBES eXara e-beam writer, allowing for patterning of small features with vertical resist profiles. This resist is developed for raster scan 50 kV e-beam systems. It has high contrast, good coating characteristics, good dry etch selectivity, and high environmental stability. Chrome etch process development has been performed using Design of Experiments to optimize parameters such as sidewall profile, etch CD bias, etch CD linearity for varying sizes of line/space patterns, etch CD linearity for varying sizes of isolated lines and spaces, loading effects, and application to contact etching.

Spatially Controlled Fabrication of Brightly Fluorescent Nanodiamond-Array with Enhanced Far-Red Si-V Luminescence

PubMed Central

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia

2014-01-01

We demonstrate a novel approach to precise pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by scanning probe “Dip-Pen” nanolithography technique using electrostatically-driven transfer of nanodiamonds from “inked” cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond-dots in the far-red is achieved by incorporating Si-V defect centers in subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink, mechanism of ink transport, and effect of humidity, dwell time on nanodiamond patterning are investigated. The precision-patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm, 61 nm ± 3 nm, respectively and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm, 245 nm ± 23 nm, respectively using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of the next generation fluorescent based devices and applications. PMID:24394286

Cryo-transmission electron tomography of native casein micelles from bovine milk

PubMed Central

Trejo, R.; Dokland, T.; Jurat-Fuentes, J.; Harte, F.

2013-01-01

Caseins are the principal protein components in milk and an important ingredient in the food industry. In liquid milk, caseins are found as micelles of casein proteins and colloidal calcium nanoclusters. Casein micelles were isolated from raw skim milk by size exclusion chromatography and suspended in milk protein-free serum produced by ultrafiltration (molecular weight cut-off of 3 kDa) of raw skim milk. The micelles were imaged by cryo-electron microscopy and subjected to tomographic reconstruction methods to visualize the 3-dimensional and internal organization of native casein micelles. This provided new insights into the internal architecture of the casein micelle that had not been apparent from prior cryo-transmission electron microscopy studies. This analysis demonstrated the presence of water-filled cavities (~20 to 30 nm in diameter), channels (diameter greater than ~5 nm), and several hundred high-density nanoclusters (6 to 12 nm in diameter) within the interior of the micelles. No spherical protein submicellar structures were observed. PMID:22118067

Laser-treated electrospun fibers loaded with nano-hydroxyapatite for bone tissue engineering.

PubMed

Aragon, Javier; Navascues, Nuria; Mendoza, Gracia; Irusta, Silvia

2017-06-15

Core-shell polycaprolactone/polycaprolactone (PCL/PCL) and polycaprolactone/polyvinyl acetate (PCL/PVAc) electrospun fibers loaded with synthesized nanohydroxyapatite (HAn) were lased treated to create microporosity. The prepared materials were characterized by XRD, FTIR, TEM and SEM. Uniform and randomly oriented beadless fibrous structures were obtained in all cases. Fibers diameters were in the 150-300nm range. Needle-like HAn nanoparticles with mean diameters of 20nm and length of approximately 150nm were mostly encase inside the fibers. Laser treated materials present micropores with diameters in the range 70-120μm for PCL-HAn/PCL fibers and in the 50-90μm range for PCL-HAn/PVAC material. Only samples containing HAn presented bioactivity after incubation during 30days in simulated body fluid. All scaffolds presented high viability, very low mortality, and human osteoblast proliferation. Biocompatibility was increased by laser treatment due to the surface and porosity modification. Copyright © 2017 Elsevier B.V. All rights reserved.

Absorption spectra of localized surface plasmon resonance observed in an inline/picoliter spectrometer cell fabricated by a near ultraviolet femtosecond laser

NASA Astrophysics Data System (ADS)

Shiraishi, Masahiko; Nishiyama, Michiko; Watanabe, Kazuhiro; Kubodera, Shoichi

2018-03-01

Absorption spectra based on localized surface plasmon resonance (LSPR) were obtained with an inline/picoliter spectrometer cell. The spectrometer cell was fabricated into an optical glass fiber by focusing a near UV (NUV) femtosecond laser pulses at a wavelength of 400 nm with an energy of 30 μJ. The laser beam was focused from two directions opposite to each other to fabricate a through-hole spectrometer cell. A diameter of the cell was approximately 3 μm, and the length was approximately 62.5 μm, which was nearly equal to the core diameter of the optical fiber. Liquid solution of gold nanoparticles (GNPs) with a diameter of 5-10 nm was injected into the spectrometer cell with its volume of 0.4 pL. The absorption peak centered at 518 nm was observed. An increase of absorption associated with the increase of the number of nanoparticles was in agreement with the numerical calculation based on the Lambert-Beer law.

Simulation of Young’s moduli for hexagonal ZnO [0 0 0 1]-oriented nanowires: first principles and molecular mechanical calculations

NASA Astrophysics Data System (ADS)

Bandura, Andrei V.; Evarestov, Robert A.; Lukyanov, Sergey I.; Piskunov, Sergei; Zhukovskii, Yuri F.

2017-08-01

Morphologically reproducible wurtzite-structured zinc oxide nanowires (ZnO NWs) can be synthesized by different methods. Since ZnO NWs have been found to possess piezoelectricity, a comprehensive study of their mechanical properties, e.g. deformations caused by external compression or stretching, is one of the actual tasks of this paper. We have calculated wurtzite-structured [0 0 0 1]-oriented ZnO NWs whose diameters have been varied within 1-5 nm and 1-20 nm ranges when using either ab initio (hybrid DFT-LCAO) or force-field (molecular mechanical) methods, respectively (the minimum diameter d NW of experimentally synthesized NWs has been estimated on average to be ~20 nm). When using both chosen calculation approaches, the values of Young’s moduli determined for the mentioned ranges of NW diameters have been found to be qualitatively compatible (168-169 GPa for 5 nm NW thickness), whereas results of molecular mechanical simulations on Y NW for 20 nm-thick NWs (160-162 GPa) have been qualitatively comparable with those experimentally measured along the [0 0 0 1] direction of NW loading. In all the cases, a gradual increase of the NW diameter has resulted in an asymptotic decrease of Young’s modulus consequently approaching that (Y b) of wurtzite-structured ZnO bulk along its [0 0 0 1] axis. The novelty of this study is that we combine the computation methods of quantum chemistry and molecular mechanics, while the majority of previous studies with the same aim have focused on the application of different classical molecular dynamical methods.

Non-toxic dry-coated nanosilver for plasmonic biosensors

PubMed Central

Sotiriou, Georgios A.; Sannomiya, Takumi; Teleki, Alexandra; Krumeich, Frank; Vörös, Janos; Pratsinis, Sotiris E.

2013-01-01

The plasmonic properties of noble metals facilitate their use for in-vivo bio-applications such as targeted drug delivery and cancer cell therapy. Nanosilver is best suited for such applications as it has the lowest plasmonic losses among all such materials in the UV-visible spectrum. Its toxicity, however, can destroy surrounding healthy tissues and thus, hinders its safe use. Here, that toxicity against a model biological system (Escherichia coli) is “cured” or blocked by coating nanosilver hermetically with a about 2 nm thin SiO2 layer in one-step by a scalable flame aerosol method followed by swirl injection of a silica precursor vapor (hexamethyldisiloxane) without reducing the plasmonic performance of the enclosed or encapsulated silver nanoparticles (20 – 40 nm in diameter as determined by X-ray diffraction and microscopy). This creates the opportunity to safely use powerful nanosilver for intracellular bio-applications. The label-free biosensing and surface bio-functionalization of these ready-to-use, non-toxic (benign) Ag nanoparticles is presented by measuring the adsorption of bovine serum albumin (BSA) in a model sensing experiment. Furthermore, the silica coating around nanosilver prevents its agglomeration or flocculation (as determined by thermal annealing, optical absorption spectroscopy and microscopy) and thus, enhances its biosensitivity, including bioimaging as determined by dark field illumination. PMID:23730266

Characterization, Recovery Opportunities, and Valuation of Metals in Municipal Sludges from U.S. Wastewater Treatment Plants Nationwide.

PubMed

Westerhoff, Paul; Lee, Sungyun; Yang, Yu; Gordon, Gwyneth W; Hristovski, Kiril; Halden, Rolf U; Herckes, Pierre

2015-08-18

U.S. sewage sludges were analyzed for 58 regulated and nonregulated elements by ICP-MS and electron microscopy to explore opportunities for removal and recovery. Sludge/water distribution coefficients (KD, L/kg dry weight) spanned 5 orders of magnitude, indicating significant metal accumulation in biosolids. Rare-earth elements and minor metals (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) detected in sludges showed enrichment factors (EFs) near unity, suggesting dust or soils as likely dominant sources. In contrast, most platinum group elements (i.e., Ru, Rh, Pd, Pt) showed high EF and KD values, indicating anthropogenic sources. Numerous metallic and metal oxide colloids (<100-500 nm diameter) were detected; the morphology of abundant aggregates of primary particles measuring <100 nm provided clues to their origin. For a community of 1 million people, metals in biosolids were valued at up to US$13 million annually. A model incorporating a parameter (KD × EF × $Value) to capture the relative potential for economic value from biosolids revealed the identity of the 13 most lucrative elements (Ag, Cu, Au, P, Fe, Pd, Mn, Zn, Ir, Al, Cd, Ti, Ga, and Cr) with a combined value of US $280/ton of sludge.

Diameter-Sensitive Breakdown of Single-Walled Carbon Nanotubes upon KOH Activation.

PubMed

Ye, Jianglin; Wu, Shuilin; Ni, Kun; Tan, Ziqi; Xu, Jin; Tao, Zhuchen; Zhu, Yanwu

2017-07-19

While potassium hydroxide (KOH) activation has been used to create pores in carbon nanotubes (CNTs) for improved energy-storage performance, the KOH activation mechanism of CNTs has been rarely investigated. In this work, the reaction between single-walled CNTs (SWCNTs) and KOH is studied in situ by thermogravimetric analysis coupled to infrared (IR) spectroscopy and gas chromatography/mass spectrometry (MS). The IR and MS results clearly demonstrate the sequential evolution of CO, hydrocarbons, CO 2 , and H 2 O in the activation process. By using the radial breathing mode of Raman spectroscopy, a diameter-sensitive selectivity is observed in the reaction between SWCNTs and KOH, leading to a preferential distribution of SWCNTs with diameters larger than 1 nm after activation at 900 °C and a preferential removal of SWCNTs with diameters below 1 nm upon activation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of restricted geometry on the superconducting properties of low-melting metals (Review Article)

NASA Astrophysics Data System (ADS)

Kumzerov, Yu. A.; Naberezhnov, A. A.

2016-11-01

This is a review of results from studies of the effect of artificially restricted geometry (the size effect) on the superconducting properties of nanoparticles of low-melting metals (Hg, Pb, Sn, In). Restricted geometrical conditions are created by embedding molten metals under high pressure into nanoporous matrices of two types: channel structures based on chrysotile asbestos and porous alkali-borosilicate glasses. Chrysotile asbestos is a system of parallel nanotubes with channel diameters ranging from 2 to 20 nm and an aspect ratio (channel length to diameter) of up to 107. The glasses are a random dendritic three-dimensional system of interconnected channels with a technologically controllable mean diameter of 2-30 nm. Temperature dependences of the resistance and heat capacity in the region of the superconducting transition and the dependences of the critical temperature on the mean pore diameter are obtained. The critical magnetic fields are also determined.

Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy

PubMed Central

Chen, Y. T.; Karlsson, K. F.; Birch, J.; Holtz, P. O.

2016-01-01

Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated. PMID:26876009

Effects of nanopillar array diameter and spacing on cancer cell capture and cell behaviors

NASA Astrophysics Data System (ADS)

Wang, Shunqiang; Wan, Yuan; Liu, Yaling

2014-10-01

While substrates with nanopillars (NPs) have emerged as promising platforms for isolation of circulating tumor cells (CTCs), the influence of diameter and spacing of NPs on CTC capture is still unclear. In this paper, CTC-capture yield and cell behaviors have been investigated by using antibody functionalized NPs of various diameters (120-1100 nm) and spacings (35-800 nm). The results show a linear relationship between the cell capture yield and effective contact area of NP substrates where a NP array of small diameter and reasonable spacing is preferred; however, spacing that is too small or too large adversely impairs the capture efficiency and specificity, respectively. In addition, the formation of pseudopodia between captured cells and the substrate is found to be dependent not only on cell adhesion status but also on elution strength and shear direction. These findings provide essential guidance in designing NP substrates for more efficient capture of CTCs and manipulation of cytomorphology in future.While substrates with nanopillars (NPs) have emerged as promising platforms for isolation of circulating tumor cells (CTCs), the influence of diameter and spacing of NPs on CTC capture is still unclear. In this paper, CTC-capture yield and cell behaviors have been investigated by using antibody functionalized NPs of various diameters (120-1100 nm) and spacings (35-800 nm). The results show a linear relationship between the cell capture yield and effective contact area of NP substrates where a NP array of small diameter and reasonable spacing is preferred; however, spacing that is too small or too large adversely impairs the capture efficiency and specificity, respectively. In addition, the formation of pseudopodia between captured cells and the substrate is found to be dependent not only on cell adhesion status but also on elution strength and shear direction. These findings provide essential guidance in designing NP substrates for more efficient capture of CTCs and manipulation of cytomorphology in future. Electronic supplementary information (ESI) available: Additional details about calculation of maximal displacement of an individual NP; additional study of substrate wettability through Cassie's Law; additional details about selection of incubation time and shaking speeds. See DOI: 10.1039/c4nr02854f

Microstructure investigation on micropore formation in microporous silica materials prepared via a catalytic sol-gel process by small angle X-ray scattering.

PubMed

Shimizu, Wataru; Hokka, Junsuke; Sato, Takaaki; Usami, Hisanao; Murakami, Yasushi

2011-08-04

The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) < 2 nm and low fractal dimensions ∼2, which is identical to that of an ideal coil polymer, can selectively be synthesized, yielding the uniform micropores with diameters <2 nm in the solid materials. In contrast, the absence of HA or substitution of 1-propanol led to considerably different scattering behavior reflecting the particle-like aggregate formation in the precursor solution, which resulted in the formation of mesopores (diameter >2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications.

Synthesis of thick mesoporous gamma-alumina films, loading of Pt nanoparticles, and use of the composite film as a reusable catalyst.

PubMed

Dandapat, Anirban; Jana, Debrina; De, Goutam

2009-04-01

Nanocrystalline mesoporous gamma-Al2O3 film of high thickness has been developed and characterized. The films were prepared on ordinary glass substrates by a single dip-coating method using boehmite (AlOOH) sols derived from aluminum tri-sec-butoxide in presence of cetyltrimethylammonium bromide (CTAB) as structure-directing agent. The dried films were heat-treated at 500 degrees C in air to remove the organics and strengthen the network. The GIXRD of the heat-treated (500 degrees C) film shows a broad peak in the low-angle region supporting the formation of worm-hole-like disordered mesostructures. The high-angle GIXRD, FTIR, and TEM of the films confirm the formation of gamma-Al2O3. N2 adsorption-desorption analyses showed that the heat-treated (500 degrees C) film has a BET surface area of 171 m(2) g(-1) with a pore volume of 0.188 cm(3) g(-1) and mean pore diameter 4.3 nm. Pt nanoparticles (NPs) (approximately 2.7 mol % with respect to the equivalent AlO(1.5)) were generated inside the mesopores of the heat-treated films simply by soaking H2PtCl6 solutions into it, and followed by thermal decomposition at 500 degrees C. The surface area and pore volume of the Pt-incorporated film have been reduced to 101 m(2) g(-1) and 0.119 cm(3) g(-1) respectively, confirming the inclusion of Pt NPs inside the pores. FESEM and TEM studies revealed uniform distribution of Pt NPs (2-8.5 nm; average diameter 4.9 nm) in the films. Catalytic properties of the Pt-incorporated films were investigated in two model (one inorganic and other organic) systems: reduction of hexacyanoferrate(III) ions by thiosulfate to ferrocyanide, and p-nitrophenol to p-aminophenol. In both the cases, the catalyst showed excellent activities, and the reduction reactions followed smoothly, showing isosbestic points in the UV-visible spectra. The catalyst films can be separated easily after the reactions and reused several times.

Pore diameter effects on phase behavior of a gas condensate in graphitic one-and two-dimensional nanopores.

PubMed

Welch, William R W; Piri, Mohammad

2016-01-01

Molecular dynamics (MD) simulations were performed on a hydrocarbon mixture representing a typical gas condensate composed mostly of methane and other small molecules with small fractions of heavier hydrocarbons, representative of mixtures found in tight shale reservoirs. The fluid was examined both in bulk and confined to graphitic nano-scale slits and pores. Numerous widths and diameters of slits and pores respectively were examined under variable pressures at 300 K in order to find conditions in which the fluid at the center of the apertures would not be affected by capillary condensation due to the oil-wet walls. For the bulk fluid, retrograde phase behavior was verified by liquid volumes obtained from Voronoi tessellations. In cases of both one and two-dimensional confinement, for the smallest apertures, heavy molecules aggregated inside the pore space and compression of the gas outside the solid structure lead to decreases in density of the confined fluid. Normal density/pressure relationships were observed for slits having gaps of above 3 nm and pores having diameters above 6 nm. At 70 bar, the minimum gap width at which the fluid could pass through the center of slits without condensation effects was predicted to be 6 nm and the corresponding diameter in pores was predicted to be 8 nm. The models suggest that in nanoscale networks involving pores smaller than these limiting dimensions, capillary condensation should significantly impede transmission of natural gases with similar composition.

Optical and Nanoparticle Analysis of Normal and Cancer Cells by Light Transmission Spectroscopy

NASA Astrophysics Data System (ADS)

Deatsch, Alison; Sun, Nan; Johnson, Jeffery; Stack, Sharon; Szajko, John; Sander, Christopher; Rebuyon, Roland; Easton, Judah; Tanner, Carol; Ruggiero, Steven

2015-03-01

We have investigated the optical properties of human oral and ovarian cancer and normal cells. Specifically, we have measured the absolute optical extinction for intra-cellular material (lysates) in aqueous suspension. Measurements were conducted over a wavelength range of 250 to 1000 nm with 1 nm resolution using Light Transmission Spectroscopy (LTS). This provides both the absolute extinction of materials under study and, with Mie inversion, the absolute number of particles of a given diameter as a function of diameter in the range of 1 to 3000 nm. Our preliminary studies show significant differences in both the extinction and particle size distributions associated with cancer versus normal cells, which appear to be correlated with differences in the particle size distribution in the range of approximately 50 to 250 nm. Especially significant is a clearly higher density of particles at about 100 nm and smaller for normal cells. Department of Physics, Harper Cancer Research Institute, and the Office of Research at the University of Notre Dame.

Visualizing viral transport and host infection

NASA Astrophysics Data System (ADS)

Son, Kwangmin; Guasto, Jeffrey; Cubillos-Ruiz, Andres; Sullivan, Matthew; Stocker, Roman; MIT Team

2013-11-01

A virus is a non-motile infectious agent that can only replicate inside a living host. They consist of a <100 nm diameter capsid which houses their DNA, and a <20 nm diameter tail used to inject DNA to the host, which are classified into three different morphologies by the tail type: short tail (~ 10 nm, podovirus), rigid contractile tail (~ 100 nm, myovirus), or flexible noncontractile tail (~ 300 nm, siphovirus). Combining microfluidics with epifluorescent microscopy, we studied the simultaneous diffusive transport governing the initial encounter and ultimately the infection of a non-motile cyanobacteria host (~ 1 μm prochlorococcus) and their viral (phage) counterparts in real time. This methodology allows us to quantify the virus-host encounter/adsorption dynamics and subsequently the effectiveness of various tail morphologies for viral infection. Viral transport and the role of viral morphology in host-virus interactions are critical to our understanding of both ecosystem dynamics and human health, as well as to the evolution of virus morphology.

Physical vapor deposition of one-dimensional nanoparticle arrays on graphite: seeding the electrodeposition of gold nanowires.

PubMed

Cross, C E; Hemminger, J C; Penner, R M

2007-09-25

One-dimensional (1D) ensembles of 2-15 nm diameter gold nanoparticles were prepared using physical vapor deposition (PVD) on highly oriented pyrolytic graphite (HOPG) basal plane surfaces. These 1D Au nanoparticle ensembles (NPEs) were prepared by depositing gold (0.2-0.6 nm/s) at an equivalent thickness of 3-4 nm onto HOPG surfaces at 670-690 K. Under these conditions, vapor-deposited gold nucleated selectively at the linear step edge defects present on these HOPG surfaces with virtually no nucleation of gold particles on terraces. The number density of 2-15 nm diameter gold particles at step edges was 30-40 microm-1. These 1D NPEs were up to a millimeter in length and organized into parallel arrays on the HOPG surface, following the organization of step edges. Surprisingly, the deposition of more gold by PVD did not lead to the formation of continuous gold nanowires at step edges under the range of sample temperature or deposition flux we have investigated. Instead, these 1D Au NPEs were used as nucleation templates for the preparation by electrodeposition of gold nanowires. The electrodeposition of gold occurred selectively on PVD gold nanoparticles over the potential range from 700-640 mV vs SCE, and after optimization of the electrodeposition parameters continuous gold nanowires as small as 80-90 nm in diameter and several micrometers in length were obtained.

Analysis of silage composition by near-infrared reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Reeves, James B., III; Blosser, Timothy H.; Colenbrander, V. F.

1991-02-01

Two studies were performed to investigate the feasibility of using near infrared reflectance spectroscopy (NIRS) with undried silages. In the first study silages were analyzed for major components (e. g. dry matter crude protein and other forms of nitrogen fiber and in vitro digestible dry matter) and short chain fatty acids (SCFA). NIRS was found to operate satisfactorily except for some forms of nitrogen and SCFA. In study two various methods of grinding spectral regions and sample presentation were examined. Undried Wiley ground samples in a rectangular cell gave the best overall results for non-dry ice undried grinds with wavelengths between 1100 and 2498 nm. Silages scanned after drying however produced the best results. Intact samples did not perform as well as ground samples and wavelengths below 1100 nm were of little use. 2 .

Light assisted drying (LAD) for protein stabilization: optimization of laser processing parameters

NASA Astrophysics Data System (ADS)

Young, Madison A.; Antczak, Andrew T.; Elliott, Gloria D.; Trammell, Susan R.

2017-02-01

In this study, a novel light-based processing method to create an amorphous trehalose matrix for the stabilization of proteins is discussed. Near-IR radiation is used to remove water from samples, leaving behind an amorphous solid with embedded protein. This method has potential applications in the stabilization of protein-based therapeutics and diagnostics that are becoming widely used in the treatment and diagnosis of a variety of diseases. Freeze-drying or freezing are currently the standard for the preservation of proteins, but these methods are expensive and can be challenging in some environments due to a lack of available infrastructure. Light-assisted drying offers a relatively inexpensive method for drying samples. Proteins suspended in a trehalose solution are dehydrated using near-infrared laser light. The laser radiation speeds drying and as water is removed the sugar forms a protective matrix. The goal of this study is to determine processing parameters that result in fast processing times and low end moisture contents (EMC), while maintaining the functionality of embedded proteins. We compare the effect of changing processing wavelength, power and resulting sample temperature, and substrate material on the EMC for two NIR laser sources (1064 nm and 1850 nm). The 1850 nm laser resulted in the lowest EMC (0.1836+/-0.09 gH2O/gDryWeight) after 10 minutes of processing on borosilicate glass microfiber paper. This suggests a storage temperature of 3°C.

Postharvest monitoring of organic potato (cv. Anuschka) during hot-air drying using visible-NIR hyperspectral imaging.

PubMed

Moscetti, Roberto; Sturm, Barbara; Crichton, Stuart Oj; Amjad, Waseem; Massantini, Riccardo

2018-05-01

The potential of hyperspectral imaging (500-1010 nm) was evaluated for monitoring of the quality of potato slices (var. Anuschka) of 5, 7 and 9 mm thickness subjected to air drying at 50 °C. The study investigated three different feature selection methods for the prediction of dry basis moisture content and colour of potato slices using partial least squares regression (PLS). The feature selection strategies tested include interval PLS regression (iPLS), and differences and ratios between raw reflectance values for each possible pair of wavelengths (R[λ 1 ]-R[λ 2 ] and R[λ 1 ]:R[λ 2 ], respectively). Moreover, the combination of spectral and spatial domains was tested. Excellent results were obtained using the iPLS algorithm. However, features from both datasets of raw reflectance differences and ratios represent suitable alternatives for development of low-complex prediction models. Finally, the dry basis moisture content was high accurately predicted by combining spectral data (i.e. R[511 nm]-R[994 nm]) and spatial domain (i.e. relative area shrinkage of slice). Modelling the data acquired during drying through hyperspectral imaging can provide useful information concerning the chemical and physicochemical changes of the product. With all this information, the proposed approach lays the foundations for a more efficient smart dryer that can be designed and its process optimized for drying of potato slices. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Variation of nanopore diameter along porous anodic alumina channels by multi-step anodization.

PubMed

Lee, Kwang Hong; Lim, Xin Yuan; Wai, Kah Wing; Romanato, Filippo; Wong, Chee Cheong

2011-02-01

In order to form tapered nanocapillaries, we investigated a method to vary the nanopore diameter along the porous anodic alumina (PAA) channels using multi-step anodization. By anodizing the aluminum in either single acid (H3PO4) or multi-acid (H2SO4, oxalic acid and H3PO4) with increasing or decreasing voltage, the diameter of the nanopore along the PAA channel can be varied systematically corresponding to the applied voltages. The pore size along the channel can be enlarged or shrunken in the range of 20 nm to 200 nm. Structural engineering of the template along the film growth direction can be achieved by deliberately designing a suitable voltage and electrolyte together with anodization time.

Enlargement of halloysite clay nanotube lumen by selective etching of aluminum oxide.

PubMed

Abdullayev, Elshad; Joshi, Anupam; Wei, Wenbo; Zhao, Yafei; Lvov, Yuri

2012-08-28

Halloysite clay tubes have 50 nm diameter and chemically different inner and outer walls (inner surface of aluminum oxide and outer surface of silica). Due to this different chemistry, the selective etching of alumina from inside the tube was realized, while preserving their external diameter (lumen diameter changed from 15 to 25 nm). This increases 2-3 times the tube lumen capacity for loading and further sustained release of active chemical agents such as metals, corrosion inhibitors, and drugs. In particular, halloysite loading efficiency for the benzotriazole increased 4 times by selective etching of 60% alumina within the tubes' lumens. Specific surface area of the tubes increased over 6 times, from 40 to 250 m(2)/g, upon acid treatment.

Second harmonic generation quantitative measurements on collagen fibrils through correlation to electron microscopy

NASA Astrophysics Data System (ADS)

Bancelin, S.; Aimé, C.; Gusachenko, I.; Kowalczuk, L.; Latour, G.; Coradin, T.; Schanne-Klein, M.-C.

2015-03-01

Type I collagen is a major structural protein in mammals that shows highly structured macromolecular organizations specific to each tissue. This biopolymer is synthesized as triple helices, which self-assemble into fibrils (Ø =10-300 nm) and further form various 3D organization. In recent years, Second Harmonic Generation (SHG) microscopy has emerged as a powerful technique to probe in situ the fibrillar collagenous network within tissues. However, this optical technique cannot resolve most of the fibrils and is a coherent process, which has impeded quantitative measurements of the fibril diameter so far. In this study, we correlated SHG microscopy with Transmission Electron Microscopy to determine the sensitivity of SHG microscopy and to calibrate SHG signals as a function of the fibril diameter in reconstructed collagen gels. To that end, we synthetized isolated fibrils with various diameters and successfully imaged the very same fibrils with both techniques, down to 30 nm diameter. We observed that SHG signals scaled as the fourth power of the fibril diameter, as expected from analytical and numerical calculations. This calibration was then applied to diabetic rat cornea in which we successfully recovered the diameter of hyperglycemia-induced fibrils in the Descemet's membrane without having to resolve them. Finally we derived the first hyperpolarizability from a single collagen triple helix which validates the bottom-up approach used to calculate the non-linear response at the fibrillar scale and denotes a parallel alignment of triple helices within the fibrils. These results represent a major step towards quantitative SHG imaging of nm-sized collagen fibrils.

Airborne Measurements of Atmospheric Pressure made Using an IPDA Lidar Operating in the Oxygen A-Band

NASA Technical Reports Server (NTRS)

Riris, Haris; Abshire, James B.; Stephen, Mark; Rodriquez, Michael; Allan, Graham; Hasselbrack, William; Mao, Jianping

2012-01-01

We report airborne measurements of atmospheric pressure made using an integrated path differential absorption (IPDA) lidar that operates in the oxygen A-band near 765 nm. Remote measurements of atmospheric temperature and pressure are needed for NASA s Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission to measure atmospheric CO2. Accurate measurements of tropospheric CO2 on a global scale are very important in order to better understand its sources and sinks and to improve our predictions of climate change. The goal of ASCENDS is to determine the CO2 dry mixing ratio with lidar measurements from space at a level of 1 ppm. Analysis to date shows that with current weather models, measurements of both the CO2 column density and the column density of dry air are needed. Since O2 is a stable molecule that uniformly mixed in the atmosphere, measuring O2 absorption in the atmosphere can be used to infer the dry air density. We have developed an airborne (IPDA) lidar for Oxygen, with support from the NASA ESTO IIP program. Our lidar uses DFB-based seed laser diodes, a pulsed modulator, a fiber laser amplifier, and a non-linear crystal to generate wavelength tunable 765 nm laser pulses with a few uJ/pulse energy. The laser pulse rate is 10 KHz, and average transmitted laser power is 20 mW. Our lidar steps laser pulses across a selected line O2 doublet near 764.7 nm in the Oxygen A-band. The direct detection lidar receiver uses a 20 cm diameter telescope, a Si APD detector in Geiger mode, and a multi-channel scalar to detect and record the time resolved laser backscatter in 40 separate wavelength channels. Subsequent analysis is used to estimate the transmission line shape of the doublet for the laser pulses reflected from the ground. Ground based data analysis allows averaging from 1 to 60 seconds to increase SNR in the transmission line shape of the doublet. Our retrieval algorithm fits the expected O2 lineshapes against the measurements and determines the atmospheric pressure by minimizing the error between the observations and model. We first demonstrated our airborne lidar during flights during summer 2010. We made several improvements and made measurements during the Ascends flights during July 2011. More information about the technique, lidar instrument, airborne measurements, and pressure estimates will be described in the presentation.

[Epidemiologic study of tear film lipid layer thickness measurement in the population of Taishitun Community in Beijing].

PubMed

Liang, Q F; Du, X H; Su, Y D; Wang, N L; Wei, Z J; Labbé, Antoine

2017-07-11

Objective: To investigate the distribution of tear film lipid layer thickness (LLT) and the relationship between symptoms and signs of dry eye and tear film LLT in the population of Taishitun Community in Beijing. Methods: A cross-sectional study. From May 2016 to August 2016, three streets of Taishitun Community were randomly selected as survey districts and 540 persons were taken as investigation subjects. Every participant completed 6 items of dry eye examinations as follows: questionnaire (Ocular Surface Disease Index, OSDI), measurement of tear film LLT, tear film break-up time (TBUT), corneal and conjunctival staining, SchirmerⅠtest and the infrared meibomian photography. According to their age, all participants were divided into four groups: junior group (<18 years old), youth group (18 to 40 years old), middle-aged group (41 to 59 years old) and the elderly group (over 60 years old). With the OSDI criteria, no dry eye symptom group (score, <12 points), mild to moderate dry eye symptom group (score, 12 to 32) and severe dry eye symptom group (score, 33-100) were included. With the statistical methods of variance analysis and multivariate Logistic regression analysis, distribution of the variables of LLT and the relationship between dry eye symptoms and LLT were studied. Results: A total of 473 residents finally participated in this study, and the response ratio was 87.6%. The values of LLT were normally distributed. The average LLT was (59.87±18.50) nm [(60.16±19.15) nm in males and (59.67±18.57) nm in females], and the comparison of LLT with different genders was not statistically significant ( t= 0.198, P= 0.843). The tear film LLT of four different age groups had statistical significance ( F= 15.092, P< 0.05), and increased with age [(56.10±18.33) nm in the junior group, (54.60±16.29) nm in the youth group, (60.61±19.18) nm in the middle-aged group and (73.25±14.58) nm in the elderly group]. The LLT was inversely proportional to the severity of dry eye symptoms. With a thinner LLT, the symptoms of the subjects turned severe. In the elderly with different degrees of symptoms, the LLT was significantly different ( F= 0.019, P< 0.05), while in the youth and middle-aged groups with different degrees of symptoms, the LLT was not significantly different ( F= 0.096, P >0.05. F= 0.538, P >0.05). In the OSDI symptom questionnaire, only blurred vision and decreased visual acuity were related to the tear film LLT ( P< 0.05). There was no significant correlation between the TBUT, SchirmerⅠtest result, meibomian gland loss rate and the tear film LLT ( P> 0.05). Conclusions: In Taishitun Community of Beijing, the values of tear film LLT had a normal distribution. The LLT was positively correlated with age, but inversely correlated with the severity of the symptoms of dry eye. There was no significant correlation between the LLT and the TBUT, SchirmerⅠtest result and meibomian gland loss rate. (Chin J Ophthalmol, 2017, 53: 495-501) .

The fluorescence properties of aerosol larger than 0.8 μm in an urban and a PBA-dominated location

NASA Astrophysics Data System (ADS)

Gabey, A. M.; Stanley, W. R.; Gallagher, M. W.; Kaye, P. H.

2011-01-01

Dual-wavelength Ultraviolet light-induced fluorescence (UV-LIF) measurements were performed on ambient environmental aerosol in Manchester, UK (urban city centre, winter) and Borneo, Malaysia (remote, tropical), which are taken to represent environments with negligible and significant primary biological aerosol (PBA) influences, respectively. Single-particle fluorescence intensity and optical equivalent diameter were measured with a Wide Issue Bioaerosol Sensor, version 3 (WIBS3) in the diameter range 0.8 μm≤DP≤20 μm for 2-3 weeks and filters were analysed using energy dispersive X-ray (EDX) spectroscopy, which revealed mostly non-PBA dominated particle sizes larger than 1 μm in Manchester. The WIBS3 features three fluorescence channels: Fluorescence excited at 280 nm is recorded at 310-400 nm and 400-600 nm and fluorescence excited at 370 nm is detected at 400-600 nm. In Manchester the primary size mode of fluorescent and non-fluorescent material was at 1.2 μm. In Borneo non-fluorescent material peaked at 1.2 μm and fluorescent at 3-4 μm. The fluorescence intensity at 400-600 nm generally increased with DP at both sites, as did the 310-400 nm intensity in Borneo. In Manchester the 310-400 m fluorescence decreased at DP>4 μm, suggesting this channel offers additional discrimination between fluorescent particle types. Finally, the ratio of fluorescence intensity in two pairs of channels was investigated as a function of particle diameter and this varied significantly between the two environments, demonstrating that the fluorescent aerosol in each can in principle be distinguished using a combination of fluorescence and elastic scattering measurements.

Formation of metal clusters in halloysite clay nanotubes

DOE PAGES

Vinokurov, Vladimir A.; Stavitskaya, Anna V.; Chudakov, Yaroslav A.; ...

2017-02-16

We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3-5 nm metal particles on the tubes; (2) inside the tube’s central lumen resulting in 10-12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube’s wall allowing up to 9more » wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions.« less

Formation of metal clusters in halloysite clay nanotubes

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

Vinokurov, Vladimir A.; Stavitskaya, Anna V.; Chudakov, Yaroslav A.

We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3-5 nm metal particles on the tubes; (2) inside the tube’s central lumen resulting in 10-12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube’s wall allowing up to 9more » wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions.« less

Atomic scale characterization and surface chemistry of metal modified titanate nanotubes and nanowires

NASA Astrophysics Data System (ADS)

Kukovecz, Ákos; Kordás, Krisztián; Kiss, János; Kónya, Zoltán

2016-10-01

Titanates are salts of polytitanic acid that can be synthesized as nanostructures in a great variety concerning crystallinity, morphology, size, metal content and surface chemistry. Titanate nanotubes (open-ended hollow cylinders measuring up to 200 nm in length and 15 nm in outer diameter) and nanowires (solid, elongated rectangular blocks with length up to 1500 nm and 30-60 nm diameter) are the most widespread representatives of the titanate nanomaterial family. This review covers the properties and applications of these two materials from the surface science point of view. Dielectric, vibrational, electron and X-ray spectroscopic results are comprehensively discussed first, then surface modification methods including covalent functionalization, ion exchange and metal loading are covered. The versatile surface chemistry of one-dimensional titanates renders them excellent candidates for heterogeneous catalytic, photocatalytic, photovoltaic and energy storage applications, therefore, these fields are also reviewed.

Mechanical behavior enhancement of ZnO nanowire by embedding different nanowires

NASA Astrophysics Data System (ADS)

Vazinishayan, Ali; Yang, Shuming; Lambada, Dasaradha Rao; Wang, Yiming

2018-06-01

In this work, we employed commercial finite element modeling (FEM) software package ABAQUS to analyze mechanical properties of ZnO nanowire before and after embedding with different kinds of nanowires, having different materials and cross-section models such as Au (circular), Ag (pentagonal) and Si (rectangular) using three point bending technique. The length and diameter of the ZnO nanowire were measured to be 12,280 nm and 103.2 nm, respectively. In addition, Au, Ag and Si nanowires were considered to have the length of 12,280 nm and the diameter of 27 nm. It was found that after embedding Si nanowire with rectangular cross-section into the ZnO nanowire, the distribution of Von Misses stresses criterion, displacement and strain were decreased than the other nanowires embedded. The highest stiffness, the elastic deformation and the high strength against brittle failure have been made by Si nanowire comparison to the Au and Ag nanowires, respectively.

Structural and magnetic properties of self-assembled cobalt on porous silicon; experimental and micromagnetic investigations

NASA Astrophysics Data System (ADS)

Saidani, M.; Belkacem, W.; Bessais, L.; Mliki, N.

2017-08-01

In this paper, we report on self-assembled Co nanoparticles deposited in and on porous silicon (PS) matrix by using UHV evaporation. Four samples were prepared by varying the Co deposited thickness (t = 3, 5, 7 and 10 nm). All samples have been investigated by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Physical Properties Measurement System (PPMS). The increase of t has induced an increase of the nanoparticle diameter from 3 nm to about 150 nm. Referring to the magnetic characterizations, this increase has been followed by a single to multi-domain transition. Therefore, this has been evidenced by a switching from superparamagnetism to purely ferromagnetism accompanied by a change in the magnetic reversal dynamics. Thus, by performing micromagnetic calculation, we have shown that a transition from the uniform rotation to vortex state occurs at a critical diameter of about 55 nm.

Dielectrophoretic trapping of nanoparticles with an electrokinetic nanoprobe.

PubMed

Wood, Nicholas R; Wolsiefer, Amanda I; Cohn, Robert W; Williams, Stuart J

2013-07-01

A high aspect ratio 3D electrokinetic nanoprobe is used to trap polystyrene particles (200 nm), gold nanoshells (120 nm), and gold nanoparticles (mean diameter 35 nm) at low voltages (<1 V(rms)). The nanoprobe is fabricated using room temperature self-assembly methods, without the need for nanoresolution lithography. The nanoprobe (150-500 nm in diameter, 2-150 μm in length) is mounted on the end of a glass micropipette, enabling user-specified positioning. The nanoprobe is one electrode within a point-and-plate configuration, with an indium-tin oxide cover slip serving as the planar electrode. The 3D structure of the nanoprobe enhances dielectrophoretic capture; further, electro-hydrodynamic flow enhances trapping, increasing the effective trapping region. Numerical simulations show low heating (1 K), even in biological media of moderate conductivity (1 S/m). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of metal clusters in halloysite clay nanotubes

PubMed Central

Vinokurov, Vladimir A.; Stavitskaya, Anna V.; Chudakov, Yaroslav A.; Ivanov, Evgenii V.; Shrestha, Lok Kumar; Ariga, Katsuhiko; Darrat, Yusuf A.; Lvov, Yuri M.

2017-01-01

Abstract We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3–5 nm metal particles on the tubes; (2) inside the tube’s central lumen resulting in 10–12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube’s wall allowing up to 9 wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions. PMID:28458738

Determining the influential depth for surface reflectance of sediment by BRDF measurements.

PubMed

Zhang, H; Voss, K; Reid, R

2003-10-20

We measure the Bi-directional reflectance distribution function (BRDF) of ooid sand layers with three particle size distributions (0.5-1mm, 0.25-0.5mm and 0.125-0.25mm) and layer thicknesses on a reflecting mirror to determine the influential depth in the optical region at wavelengths of 658 nm (red), 570 nm (green) and 457 nm (blue). The hemispherical reflectance (albedo) was used as an indicator of BRDF changes between different layers. Measurements are carried out on both dry and water wetted grains. The results indicate that for both dry and wet and all size distributions, the influential depth is at most 2mm.

Influence of sewage sludge, as a substrate, in the plasticity of functional characteristics of plants.

PubMed

da Silva, Vicente Elício Porfiro Sales Gonçalves; Buarque, Patrícia Marques Carneiro; Ferreira, Wanessa Nepomuceno; Buarque, Hugo Leonardo de Brito; Silva, Maria Amanda Menezes

2018-04-24

This work aimed to evaluate the effect of sewage sludge application as fertilizer on the plasticity of functional characteristics of species commonly found in the Caatinga. The research was developed in the nursery of the Federal Institute of Education, Science and Technology of Ceará (IFCE), Quixadá campus, located in northeastern Brazil. Three treatments were applied: raw sludge, sanitized sludge, and no manipulation. In each treatment, five species were planted, each with five individuals, totaling 75 individuals, which were tagged, and 4 months after germination, they were destroyed to obtain dry matter content (TMSF) from leaf, stem (TMSC), fine root (TMSRF), and thick root (TMSRG); leaf area; height and diameter of the seedling; and length above and below the ground. The sanitized sludge was responsible for giving higher values for leaf area, height of the seedlings, and diameter and length of stem and root. However, the dry matter content of the fine roots was higher in the treatment without manipulation. At the community level, as TMSRG increased, TMSC also increased, the same occurred between TMSRG and TMSRF, TMSC and TMSRF, and stem length and leaf area. In the treatment without manipulation, there was a positive correlation between leaf area, height and plant diameter, and negative correlation between root length and plant diameter. Thus, it can be concluded that the use of sanitized sludge is a good tool to increase the availability of soil resources, conferring to individuals' greater dry matter content, greater leaf area, and higher height and diameter above the ground.

Effect of porosity variation on the electrochemical behavior of vertically aligned multi-walled carbon nanotubes.

PubMed

Raut, Akshay S; Parker, Charles B; Stoner, Brian R; Glass, Jeffrey T

2012-06-01

Electrochemical charge storage characteristics of vertically aligned multi-walled carbon nanotubes (MWCNTs) as a function of varying diameter and spacing are reported. It was observed that the specific capacitance of the MWCNTs increased as both diameter and inter-tube spacing decreased. The MWCNT films with 229 nm inter-MWCNT spacing exhibited specific capacitance of 228 F/g versus 70 F/g for 506 nm spacing, when tested in a non-aqueous electrolyte. Further, a trend in specific capacitance versus pore size is proposed. Coupled with previously reported trends observed in the sub-10 nm pore size regime, this is expected to offer better understanding of electrochemical behavior of porous carbon materials over a wide range of pore sizes.

Nanodiamonds do not provide unique evidence for a Younger Dryas impact

PubMed Central

Tian, H.; Schryvers, D.; Claeys, Ph.

2011-01-01

Microstructural, δ13C isotope and C/N ratio investigations were conducted on excavated material from the black Younger Dryas boundary in Lommel, Belgium, aiming for a characterisation of the carbon content and structures. Cubic diamond nanoparticles are found in large numbers. The larger ones with diameters around or above 10 nm often exhibit single or multiple twins. The smaller ones around 5 nm in diameter are mostly defect-free. Also larger flake-like particles, around 100 nm in lateral dimension, with a cubic diamond structure are observed as well as large carbon onion structures. The combination of these characteristics does not yield unique evidence for an exogenic impact related to the investigated layer. PMID:21173270

Magnetic properties of superparamagnetic nanoparticles loaded into silicon nanotubes.

PubMed

Granitzer, Petra; Rumpf, Klemens; Gonzalez, Roberto; Coffer, Jeffery; Reissner, Michael

2014-01-01

In this work, the magnetic properties of silicon nanotubes (SiNTs) filled with Fe3O4 nanoparticles (NPs) are investigated. SiNTs with different wall thicknesses of 10 and 70 nm and an inner diameter of approximately 50 nm are prepared and filled with superparamagnetic iron oxide nanoparticles of 4 and 10 nm in diameter. The infiltration process of the NPs into the tubes and dependence on the wall-thickness is described. Furthermore, data from magnetization measurements of the nanocomposite systems are analyzed in terms of iron oxide nanoparticle size dependence. Such biocompatible nanocomposites have potential merit in the field of magnetically guided drug delivery vehicles. 61.46.Fg; 62.23.Pq; 75.75.-c; 75.20.-g.

Synthesis of nanosized (<20 nm) polymer particles by radical polymerization in miniemulsion employing in situ surfactant formation.

PubMed

Guo, Yi; Zetterlund, Per B

2011-10-18

A novel method for synthesis of ultrafine polymeric nanoparticles of diameters less than 20 nm has been developed. The method is based on miniemulsion polymerization exploiting combination of the in situ surfactant generation approach (whereby the surfactant is formed at the oil-water interface by reaction between an organic acid and a base) and ultrasonication. Conventional radical polymerization and nitroxide-mediated radical polymerization of styrene have been conducted in miniemulsion using oleic acid/potassium hydroxide, demonstrating that particles with diameters less than 20 nm can be obtained by this approach at surfactant contents much lower than traditionally required in microemulsion polymerizations. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous droplet impingement dynamics and heat transfer on nano-structured surfaces

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

Shen, Jian; Graber, Christof; Liburdy, James

This study examines the hydrodynamics and temperature characteristics of distilled deionized water droplets impinging on smooth and nano-structured surfaces using high speed (HS) and infrared (IR) imaging at We = 23.6 and Re = 1593, both based on initial drop impingement parameters. Results for a smooth and nano-structured surface for a range of surface temperatures are compared. Droplet impact velocity, transient spreading diameter and dynamic contact angle are measured. The near surface average droplet fluid temperatures are evaluated for conditions of evaporative cooling and boiling. Also included are surface temperature results using a gold layered IR opaque surface on silicon.more » Four stages of the impingement process are identified: impact, boiling, near constant surface diameter evaporation, and final dry-out. For the boiling conditions there is initial nucleation followed by severe boiling, then near constant diameter evaporation resulting in shrinking of the droplet height. When a critical contact angle is reached during evaporation the droplet rapidly retracts to a smaller diameter reducing the contact area with the surface. This continues as a sequence of retractions until final dry out. The basic trends are the same for all surfaces, but the nano-structured surface has a lower dissipated energy during impact and enhances the heat transfer for evaporative cooling with a 20% shorter time to achieve final dry out. (author)« less

Characterisation of the porcine eyeball as an in-vitro model for dry eye.

PubMed

Menduni, Francesco; Davies, Leon N; Madrid-Costa, D; Fratini, Antonio; Wolffsohn, James S

2018-02-01

To characterise the anatomical parameters of the porcine eye for potentially using it as a laboratory model of dry eye. Anterior chamber depth and angle, corneal curvature, shortest and longest diameter, endothelial cell density, and pachymetry were measured in sixty freshly enucleated porcine eyeballs. Corneal steepest meridian was 7.85±0.32mm, corneal flattest meridian was 8.28±0.32mm, shortest corneal diameter was 12.69±0.58mm, longest corneal diameter was 14.88±0.66mm and central corneal ultrasonic pachymetry was 1009±1μm. Anterior chamber angle was 28.83±4.16°, anterior chamber depth was 1.77±0.27mm, and central corneal thickness measured using OCT was 1248±144μm. Corneal endothelial cell density was 3250±172 cells/mm 2 . Combining different clinical techniques produced a pool of reproducible data on the porcine eye anatomy, which can be used by researchers to assess the viability of using the porcine eye as an in-vitro/ex-vivo model for dry eye. Due to the similar morphology with the human eye, porcine eyeballs may represent a useful and cost effective model to individually study important key factors in the development of dry eye, such as environmental and mechanical stresses. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Short- and long-term stability of lyophilised melatonin-loaded lecithin/chitosan nanoparticles.

PubMed

Hafner, Anita; Dürrigl, Marjana; Pepić, Ivan; Filipović-Grčić, Jelena

2011-01-01

The aim of this study was to establish a freeze-drying process for melatonin-loaded lecithin/chitosan nanoparticles (NPs) to preserve their chemical and physical stability for a longer time period that what is possible in an aqueous suspension. Glucose and trehalose were investigated as potential excipients during freeze-drying of NP suspensions. Lecithin/chitosan NPs were characterised by mean diameter and zeta potential, ranging between 117.4 and 328.5 nm and 6.7 and 30.2 mV, respectively, depending on the lecithin type and chitosan content in the preparation. Melatonin loadings were up to 7.1%. For all lecithin/chitosan NPs, no notable differences in the mean particle size, size distribution, zeta potential or melatonin content were observed before or immediately after the lyophilisation process or after 7 months of storage at 4 °C. The residual moisture contents of lyophilisates with glucose and trehalose immediately after the lyophilisation process varied between 4.0-4.8% and 2.4-3.0%, respectively. All lecithin/chitosan NPs had a fully amorphous nature after the freeze-drying process, as indicated by modulated differential scanning calorimetry. NP lyophilisates with glucose had a low glass transition temperature (ca. 5 °C), confirming that lyophilisation with glucose as a cryoprotectant was not appropriate. All lyophilisates with trehalose had a glass transition temperature above the room temperature, allowing formation of the cake without a collapse of the structure, which was capable of preserving its characteristics and appearance following 7 months of storage at 4 °C.

Tuning the self-assembled 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol nanoarchitectures using the phase inversion method

NASA Astrophysics Data System (ADS)

Lai, Wei-Chi; Tseng, Shen-Jhen

2013-11-01

1,3:2,4-Di(3,4-dimethylbenzylidene) sorbitol (DMDBS) molecules can self-assemble into nanoscaled structures in organic solvents and polymer melts. The nanofibril structures were the mostly found. In this study, we used two phase inversion methods, i.e., dry and wet methods, to obtain different DMDBS nanoarchitectures. Poly(vinylidene fluoride) (PVDF) was chosen as polymer matrix, and the DMDBS structures were tuned by the process of PVDF membrane formation (crystallization and liquid-liquid demixing). When the membrane was prepared using the dry method, the DMDBS structure is controlled by the PVDF crystallization. Fewer DMDBS nanofibrils formed on the surfaces, and no nanofibrils were found in the cross-sections. On the other hand, when the membrane was prepared using the wet method, the liquid-liquid demixing (nonsolvent induced phase separation) occurred simultaneously as PVDF crystallized, and thus influenced the aggregation of DMDBS molecules. DMDBS is an amphiphilic molecule with two hydrophilic hydroxyl groups. The addition of nonsolvent (water) caused a large number of DMDBS molecules to aggregate outside the hydrophobic PVDF. In addition, a new structure "nanomat" was found. The mat was composed of DMDBS nanofibrils with diameters of 10-20 nm, similar to those observed in the dry method membranes. Fourier transform infra-red spectroscopy indicates that the DMDBS molecules self-assembled (aggregated) mainly through intermolecular hydrogen bonding in the presence of PVDF. The more intermolecular hydrogen bonding between DMDBS existed, the more excessive amounts of DMDBS molecules were, leading to the formation of nanomats.

Self-Assembly of Ordered Hybrid Materials with over 100 nm Domain Spacings and up to 15 nm Nanoparticles using Bottle Brush Block Copolymers

NASA Astrophysics Data System (ADS)

Song, Dongpo; Lin, Ying; Qian, Gang; Wang, Xinyu; Liu, Xiaohui; Li, Cheng; Watkins, James

2014-03-01

The preparation of well-ordered nanocomposites using block copolymers and nanoparticles (NPs) with precise control over their spatial organization at different length scales remains challenging, especially for NP cores up to 10 nm in diameter and for domain spacings greater than 100 nm. In this work, these challenges have been overcome using amphiphilic bottle brush block copolymers as templates for the self-assembly of ordered, periodic hybrid materials with domain spacings more than 130 nm using functionalized NPs with core diameters up to 15 nm. CdSe NPs of 10 nm or gold NPs of 15 nm bearing 11-mercaptoundecyl-hydroquinone or poly(4-vinylphenol) ligands were selectively incorporated within (polynorbornene-g-polystyrene)-b- (polynorbornene-g-polyethylene oxide) copolymers by taking advantage of hydrogen bonding between the ligand and PEO domain. Well-ordered composites with cylindrical and lamellar morphologies and NP loadings of up to 30 wt% in the target domains were achieved. This strategy provides a simple and robust means to create ordered hybrid materials of large domain spacings allowing for relatively large functional nanoparticles. This work was supported by the NSF Center for Hierarchical Manufacturing at the University of Massachusetts (CMMI-1025020).

78 FR 62597 - 36(b)(1) Arms Sales Notification

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-22

... Block II missiles, 1000 GBU-39/B Small Diameter Bomb (SDB) with BRU-61 carriage systems, 40 CATM-84H... missiles, 1000 GBU-39/B Small Diameter Bombs (SDB), 40 CATM-84H Captive Air Training Missiles (CATM), 20... Small Diameter Bomb (SDB) I weapon is a 250-lb class, all-up round (AUR) that provides greater than 50nm...

Biological treatment of chicken feather waste for improved biogas production.

PubMed

Forgács, Gergely; Alinezhad, Saeid; Mirabdollah, Amir; Feuk-Lagerstedt, Elisabeth; Horváth, Ilona Sárvári

2011-01-01

A two-stage system was developed which combines the biological degradation of keratin-rich waste with the production of biogas. Chicken feather waste was treated biologically with a recombinant Bacillus megaterium strain showing keratinase activity prior to biogas production. Chopped, autoclaved chicken feathers (4%, W/V) were completely degraded, resulting in a yellowish fermentation broth with a level of 0.51 mg/mL soluble proteins after 8 days of cultivation of the recombinant strain. During the subsequent anaerobic batch digestion experiments, methane production of 0.35 Nm3/kg dry feathers (i.e., 0.4 Nm3/kg volatile solids of feathers), corresponding to 80% of the theoretical value on proteins, was achieved from the feather hydrolyzates, independently of the pre-hydrolysis time period of 1, 2 or 8 days. Cultivation with a native keratinase producing strain, Bacillus licheniformis resulted in only 0.25 mg/mL soluble proteins in the feather hydrolyzate, which then was digested achieving a maximum accumulated methane production of 0.31 Nm3/kg dry feathers. Feather hydrolyzates treated with the wild type B. megaterium produced 0.21 Nm3 CH4/kg dry feathers as maximum yield.

Laser-induced retinal injury thresholds: variation with retinal irradiated area

NASA Astrophysics Data System (ADS)

Lund, David J.; Schulmeister, Karl; Seiser, Bernhard; Edthofer, Florian

2005-04-01

The retinal injury threshold for exposure to a laser source varies as a function of the irradiated area on the retina. Currently accepted guidelines for the safe use of lasers provide that the MPE will increase as the diameter of the irradiated area for retinal diameters between 25 mm and 1700 mm, based on the ED50 data available in the late 1970s. Recent studies by Zuclich and Lund produced data showing that the ED50 for ns-duration exposures at 532 nm and ms duration exposures at 590 nm varied as the square of the diameter of the irradiated area on the retina. This paper will discuss efforts to resolve the disagreement between the new data and the earlier data though an analysis of all accessible data relating the retinal injury threshold to the diameter of the incident beam on the retina and through simulations using computer models of laser-induced injury. The results show that the retinal radiant exposure required to produce retinal injury is a function of both exposure duration and retinal irradiance diameter and that the current guidelines for irradiance diameter dependence do not accurately reflect the variation of the threshold data.

Bulk nucleation and growth of inorganic nanowires and nanotubes

NASA Astrophysics Data System (ADS)

Sharma, Shashank

The nanometer scale materials such as nanowires and nanotubes will be of particular interest as building blocks for designing novel sensors, catalysts, electronic, optical, and optoelectronic devices. However, in order to realize these applications, bulk amounts of nanowires and nanotubes need to be synthesized with precise control over the nanostructure characteristics. In addition, the structure-property relationships for one-dimensional structures are expected to be different than their bulk when their diameters are less than a characteristic Bohr exciton radius. This fundamental curiosity also necessitates bulk synthesis of nanostructures. The current bulk nanowire synthesis methods utilize either nanometer scale porous molds or nanometer scale transition metal clusters to template one-dimensional growth. All these techniques have inherent limitations in terms of control over the nanowire diameter distribution, composition, the growth direction, and the ability to generate abrupt interfaces within individual nanowires. In this dissertation, a new concept for bulk nucleation and growth of one-dimensional nanostructures is proposed and demonstrated for a variety of inorganic material systems. In this technique, multiple nanowires nucleate and grow from pools of low-melting metal melts when exposed to an activated gas phase containing the necessary precursors. This concept, hereby termed Low Melting Metals and Activated Gas phase (LMAG) mediated method, is specifically demonstrated for the synthesis of, (a) silicon nanowires grown using molten gallium and silane precursors; (b) silicon compound nanowires using solution of molten gallium and appropriate gas phase precursors, and (c) metal-oxide nanostructures grown using direct reaction of the respective metal melts and oxygen precursors. Nanowires resulted from the same molten gallium pool at high densities (>1011/cm2) and with narrow diameter distribution. The silicon nanowires synthesized using the LMAG technique were single crystalline, defect free, and contained a non uniform, extremely thin oxide sheath (<1.5 nm). The nanowire diameter could be varied from 3 to 100 nm, with lengths up to hundreds of microns. Unique tubular and paintbrush-like morphologies were obtained in gallium oxide (Ga2O3) nanostructures. Small gallium droplets (<100 nm size) allowed Ga2O3 nanowire growth parallel to the substrate, followed by 2-dimensional nanoweb formation. These experiments using small gallium droplets resulted in the growth of crystalline Ga2O3 nanotubes with outer diameters as small as 5 nm and inner diameters as small as 2.5 nm.

Spectrometric Estimation of Total Nitrogen Concentration in Douglas-Fir Foliage

NASA Technical Reports Server (NTRS)

Johnson, Lee F.; Billow, Christine R.; Peterson, David L. (Technical Monitor)

1995-01-01

Spectral measurements of fresh and dehydrated Douglas-fir foliage, from trees cultivated under three fertilization treatments, were acquired with a laboratory spectrophotometer. The slope (first-derivative) of the fresh- and dry-leaf absorbance spectra at locations near known protein absorption features was strongly correlated with total nitrogen (TN) concentration of the foliage samples. Particularly strong correlation was observed between the first-derivative spectra in the 2150-2170 nm region and TN, reaching a local maximum in the fresh-leaf spectra of -0.84 at 2 160 nm. Stepwise regression was used to generate calibration equations relating first derivative spectra from fresh, dry/intact, and dry/ground samples to TN concentration. Standard errors of calibration were 1.52 mg g-1 (fresh), 1.33 (dry/intact), and 1.20 (dry/ground), with goodness-of-fit 0.94 and greater. Cross-validation was performed with the fresh-leaf dataset to examine the predictive capability of the regression method; standard errors of prediction ranged from 1.47 - 2.37 mg g(exp -1) across seven different validation sets, prediction goodness of fit ranged from .85-.94, and wavelength selection was fairly insensitive to the membership of the calibration set. All regressions in this study tended to select wavelengths in the 2100-2350 nm region, with the primary selection in the 2142-2172 nm region. The study provides positive evidence concerning the feasibility of assessing TN status of fresh-leaf samples by spectrometric means. We assert that the ability to extract biochemical information from fresh-leaf spectra is a necessary but insufficient condition regarding the use of remote sensing for canopy-level biochemical estimation.

Uncertainty propagation using the Monte Carlo method in the measurement of airborne particle size distribution with a scanning mobility particle sizer

NASA Astrophysics Data System (ADS)

Coquelin, L.; Le Brusquet, L.; Fischer, N.; Gensdarmes, F.; Motzkus, C.; Mace, T.; Fleury, G.

2018-05-01

A scanning mobility particle sizer (SMPS) is a high resolution nanoparticle sizing system that is widely used as the standard method to measure airborne particle size distributions (PSD) in the size range 1 nm–1 μm. This paper addresses the problem to assess the uncertainty associated with PSD when a differential mobility analyzer (DMA) operates under scanning mode. The sources of uncertainty are described and then modeled either through experiments or knowledge extracted from the literature. Special care is brought to model the physics and to account for competing theories. Indeed, it appears that the modeling errors resulting from approximations of the physics can largely affect the final estimate of this indirect measurement, especially for quantities that are not measured during day-to-day experiments. The Monte Carlo method is used to compute the uncertainty associated with PSD. The method is tested against real data sets that are monosize polystyrene latex spheres (PSL) with nominal diameters of 100 nm, 200 nm and 450 nm. The median diameters and associated standard uncertainty of the aerosol particles are estimated as 101.22 nm  ±  0.18 nm, 204.39 nm  ±  1.71 nm and 443.87 nm  ±  1.52 nm with the new approach. Other statistical parameters, such as the mean diameter, the mode and the geometric mean and associated standard uncertainty, are also computed. These results are then compared with the results obtained by SMPS embedded software.

Formulating food protein-stabilized indomethacin nanosuspensions into pellets by fluid-bed coating technology: physical characterization, redispersibility, and dissolution.

PubMed

He, Wei; Lu, Yi; Qi, Jianping; Chen, Lingyun; Yin, Lifang; Wu, Wei

2013-01-01

Drug nanosuspensions are very promising for enhancing the dissolution and bioavailability of drugs that are poorly soluble in water. However, the poor stability of nanosuspensions, reflected in particle growth, aggregation/agglomeration, and change in crystallinity state greatly limits their applications. Solidification of nanosuspensions is an ideal strategy for addressing this problem. Hence, the present work aimed to convert drug nanosuspensions into pellets using fluid-bed coating technology. Indomethacin nanosuspensions were prepared by the precipitation-ultrasonication method using food proteins (soybean protein isolate, whey protein isolate, β-lactoglobulin) as stabilizers. Dried nanosuspensions were prepared by coating the nanosuspensions onto pellets. The redispersibility, drug dissolution, solid-state forms, and morphology of the dried nanosuspensions were evaluated. The mean particle size for the nanosuspensions stabilized using soybean protein isolate, whey protein isolate, and β-lactoglobulin was 588 nm, 320 nm, and 243 nm, respectively. The nanosuspensions could be successfully layered onto pellets with high coating efficiency. Both the dried nanosuspensions and nanosuspensions in their original amorphous state and not influenced by the fluid-bed coating drying process could be redispersed in water, maintaining their original particle size and size distribution. Both the dried nanosuspensions and the original drug nanosuspensions showed similar dissolution profiles, which were both much faster than that of the raw crystals. Fluid-bed coating technology has potential for use in the solidification of drug nanosuspensions.

Tree Diameter Growth in the Dry Limestone Hills

Treesearch

C. B. Briscoe

1962-01-01

The dry limestone hill region of southwestern Puerto Rico, because of heavy, shallow soils and scant rainfall is not farmed, and is recognized as an area best suited for the growth of trees. With a mean temperature near 80°F and with rainfall averaging no more than 30 inches anually and much less during dry years, the site is adverse even for tree growth. Studies on...

MreB Orientation Correlates with Cell Diameter in Escherichia coli.

PubMed

Ouzounov, Nikolay; Nguyen, Jeffrey P; Bratton, Benjamin P; Jacobowitz, David; Gitai, Zemer; Shaevitz, Joshua W

2016-09-06

Bacteria have remarkably robust cell shape control mechanisms. For example, cell diameter only varies by a few percent across a given population. The bacterial actin homolog, MreB, is necessary for establishment and maintenance of rod shape although the detailed properties of MreB that are important for shape control remained unknown. In this study, we perturb MreB in two ways: by treating cells with the polymerization-inhibiting drug A22 and by creating point mutants in mreB. These perturbations modify the steady-state diameter of cells over a wide range, from 790 ± 30 nm to 1700 ± 20 nm. To determine which properties of MreB are important for diameter control, we correlated structural characteristics of fluorescently tagged MreB polymers with cell diameter by simultaneously analyzing three-dimensional images of MreB and cell shape. Our results indicate that the helical pitch angle of MreB inversely correlates with the cell diameter of Escherichia coli. Other correlations between MreB and cell diameter are not found to be significant. These results demonstrate that the physical properties of MreB filaments are important for shape control and support a model in which MreB organizes the cell wall growth machinery to produce a chiral cell wall structure and dictate cell diameter. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Phosphatidyl-hydroxytyrosol and phosphatidyl-tyrosol bilayer properties

USDA-ARS?s Scientific Manuscript database

Hydroxytyrosol and tyrosol phospholipids were enzymatically synthesized and investigated for their bilayer properties. Dynamic light scattering demonstrated that hand extrusion at 100 nm consistently resulted in liposomes of nearly 85 nm diameter for both phosphatidyl-hydroxytyrosol (DOPHT) and phos...

Patterning at the 10 nanometer length scale using a strongly segregating block copolymer thin film and vapor phase infiltration of inorganic precursors

NASA Astrophysics Data System (ADS)

Choi, Jonathan W.; Li, Zhaodong; Black, Charles T.; Sweat, Daniel P.; Wang, Xudong; Gopalan, Padma

2016-06-01

In this work, we demonstrate the use of self-assembled thin films of the cylinder-forming block copolymer poly(4-tert-butylstyrene-block-2-vinylpyridine) to pattern high density features at the 10 nm length scale. This material's large interaction parameter facilitates pattern formation in single-digit nanometer dimensions. This block copolymer's accessible order-disorder transition temperature allows thermal annealing to drive the assembly of ordered 2-vinylpyridine cylinders that can be selectively complexed with the organometallic precursor trimethylaluminum. This unique chemistry converts organic 2-vinylpyridine cylinders into alumina nanowires with diameters ranging from 8 to 11 nm, depending on the copolymer molecular weight. Graphoepitaxy of this block copolymer aligns and registers sub-12 nm diameter nanowires to larger-scale rectangular, curved, and circular features patterned by optical lithography. The alumina nanowires function as a robust hard mask to withstand the conditions required for patterning the underlying silicon by plasma etching. We conclude with a discussion of some of the challenges that arise with using block copolymers for patterning at sub-10 nm feature sizes.In this work, we demonstrate the use of self-assembled thin films of the cylinder-forming block copolymer poly(4-tert-butylstyrene-block-2-vinylpyridine) to pattern high density features at the 10 nm length scale. This material's large interaction parameter facilitates pattern formation in single-digit nanometer dimensions. This block copolymer's accessible order-disorder transition temperature allows thermal annealing to drive the assembly of ordered 2-vinylpyridine cylinders that can be selectively complexed with the organometallic precursor trimethylaluminum. This unique chemistry converts organic 2-vinylpyridine cylinders into alumina nanowires with diameters ranging from 8 to 11 nm, depending on the copolymer molecular weight. Graphoepitaxy of this block copolymer aligns and registers sub-12 nm diameter nanowires to larger-scale rectangular, curved, and circular features patterned by optical lithography. The alumina nanowires function as a robust hard mask to withstand the conditions required for patterning the underlying silicon by plasma etching. We conclude with a discussion of some of the challenges that arise with using block copolymers for patterning at sub-10 nm feature sizes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01409g

Nanoparticle diffusion in, and microrheology of, the bovine vitreous ex vivo

PubMed Central

Xu, Qingguo; Boylan, Nicholas J.; Suk, Jung Soo; Wang, Ying-Ying; Nance, Elizabeth; Yang, Jeh-Chang; McDonnell, Peter; Cone, Richard; Duh, Elia J.; Hanes, Justin

2013-01-01

Intravitreal injection of biodegradable nanoparticles (NP) holds promise for gene therapy and drug delivery to the back of the eye. In some cases, including gene therapy, NP need to diffuse rapidly from the site of injection in order to reach targeted cell types in the back of the eye, whereas in other cases it may be preferred for the particles to remain at the injection site and slowly release drugs that may then diffuse to the site of action. We studied the movements of polystyrene (PS) nanoparticles of various sizes and surface chemistries in fresh bovine vitreous. PS NP as large as 510 nm rapidly penetrated the vitreous gel when coated with polyethylene glycol (PEG), whereas the movements of NP 1190 nm in diameter or larger were highly restricted regardless of surface chemistry owing to steric obstruction. PS NP coated with primary amine groups (–NH2) possessed positively charged surfaces at the pH of bovine vitreous (pH = 7.2), and were immobilized within the vitreous gel. In comparison, PS NP coated with –COOH (possessing negatively charged surfaces) in the size range of 100–200 nm and at particle concentrations below 0.0025% (w/v) readily diffused through the vitreous meshwork; at higher concentrations (~0.1% w/v), these nanoparticles aggregated within vitreous. Based on the mobility of different sized PS-PEG NP, we estimated the average mesh size of fresh bovine vitreous to be ~550 ± 50 nm. The bovine vitreous behaved as an impermeable elastic barrier to objects sized 1190 nm and larger, but as a highly permeable viscoelastic liquid to non-adhesive objects smaller than 510 nm in diameter. Guided by these studies, we next sought to examine the transport of drug- and DNA-loaded nanoparticles in bovine vitreous. Biodegradable NP with diameter of 227 nm, composed of a poly(lactic-co-glycolic acid) (PLGA)-based core coated with poly(vinyl alcohol) rapidly penetrated vitreous. Rod-shaped, highly-compacted CK30PEG10k/DNA with PEG coating (neutral surface charge; diameter ~60 nm) diffused rapidly within vitreous. These findings will help guide the development of nanoparticle-based therapeutics for the treatment of vision-threatening ocular diseases. PMID:23369761

Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

NASA Technical Reports Server (NTRS)

Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

2009-01-01

Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

Sub-100-nm ordered silicon hole arrays by metal-assisted chemical etching

PubMed Central

2013-01-01

Sub-100-nm silicon nanohole arrays were fabricated by a combination of the site-selective electroless deposition of noble metals through anodic porous alumina and the subsequent metal-assisted chemical etching. Under optimum conditions, the formation of deep straight holes with an ordered periodicity (e.g., 100 nm interval, 40 nm diameter, and high aspect ratio of 50) was successfully achieved. By using the present method, the fabrication of silicon nanohole arrays with 60-nm periodicity was also achieved. PMID:24090268

Influence of shoulder diameter on Temperature and Z-parameter during friction stir welding of Al 6082 alloy

NASA Astrophysics Data System (ADS)

Kishore Mugada, Krishna; Adepu, Kumar

2018-03-01

In this research article, the effect of increasing shoulder diameter on temperature and Zener Holloman (Z)-parameter for friction stir butt welded AA6082-T6 was studied. The temperature at the Advancing side (AS) of weld was measured using the K-Type thermocouple at four different equidistant locations. The developed analytical model is utilized to predict the maximum temperature (Tpeak) during the welding. The strain, strain rate, Z- Parameter for all the shoulders at four distinct locations were evaluated. The temperature increases with increase in shoulder diameter and the maximum temperature was recorded for 24mm shoulder diameter. The computed log Z values are compared with the available process map and results shows that the values are in stable flow region and near to stir zone the values are in Dynamic recrystallization region (DRX). The axial load (Fz) and total tool torque (N-m) are found to be higher for shoulder diameter of 21 mm i.e., 6.3 kN and 56.5 N-m respectively.

1-mm catheterscope

NASA Astrophysics Data System (ADS)

Seibel, Eric J.

2008-02-01

Flexible endoscopes use one sensor element per display pixel. When diameter is reduced to the size of a catheter, there is a significant reduction in the number of pixels within the image. By placing a sub-millimeter microscanner at the tip of a catheter, image quality can be significantly improved. The microscanner consists of a 0.4 mm diameter piezoelectric tube with quadrant electrodes, surrounding a cantilevered singlemode optical fiber. At the distal end, the fiber microscanner is sealed with a 0.9 mm diameter lens assembly, creating a rigid length less than 10 mm at the tip of a highly flexible shaft. The cantilevered fiber is vibrated at the first mode of resonance for bending to generate a circular scan pattern. A spiral scan pattern is generated that constitutes an image frame by modulating the piezoelectric drive signals. By using a custom optical fiber at 80 microns cladding diameter, >10 KHz resonant scanning is achieved, resulting in a 30 Hz frame rate. Red (635 nm), green (532 nm), and blue (442 nm) laser light is scanned by coupling to the fiber scanner. The scanned illumination is detected in a non-confocal arrangement by having one or more optical fibers collecting the backscattered light at MHz pixel rates. Current 1-mm diameter catheterscopes generate 500-line images at maximum fields of view of 100 degrees and spatial resolutions of <20 microns with image zooming. Shaft length of four meters have been fabricated with flexibility of <10 mm bending radius to image previously inaccessible regions of the body.

Tailoring the morphology and luminescence of GaN/InGaN core-shell nanowires using bottom-up selective-area epitaxy

NASA Astrophysics Data System (ADS)

Nami, Mohsen; Eller, Rhett F.; Okur, Serdal; Rishinaramangalam, Ashwin K.; Liu, Sheng; Brener, Igal; Feezell, Daniel F.

2017-01-01

Controlled bottom-up selective-area epitaxy (SAE) is used to tailor the morphology and photoluminescence properties of GaN/InGaN core-shell nanowire arrays. The nanowires are grown on c-plane sapphire substrates using pulsed-mode metal organic chemical vapor deposition. By varying the dielectric mask configuration and growth conditions, we achieve GaN nanowire cores with diameters ranging from 80 to 700 nm that exhibit various degrees of polar, semipolar, and nonpolar faceting. A single InGaN quantum well (QW) and GaN barrier shell is also grown on the GaN nanowire cores and micro-photoluminescence is obtained and analyzed for a variety of nanowire dimensions, array pitch spacings, and aperture diameters. By increasing the nanowire pitch spacing on the same growth wafer, the emission wavelength redshifts from 440 to 520 nm, while increasing the aperture diameter results in a ˜35 nm blueshift. The thickness of one QW/barrier period as a function of pitch and aperture diameter is inferred using scanning electron microscopy, with larger pitches showing significantly thicker QWs. Significant increases in indium composition were predicted for larger pitches and smaller aperture diameters. The results are interpreted in terms of local growth conditions and adatom capture radius around the nanowires. This work provides significant insight into the effects of mask configuration and growth conditions on the nanowire properties and is applicable to the engineering of monolithic multi-color nanowire LEDs on a single chip.

An empirical model for transient crater growth in granular targets based on direct observations

NASA Astrophysics Data System (ADS)

Yamamoto, Satoru; Barnouin-Jha, Olivier S.; Toriumi, Takashi; Sugita, Seiji; Matsui, Takafumi

2009-09-01

The present paper describes observations of crater growth up to the time of transient crater formation and presents a new empirical model for transient crater growth as a function of time. Polycarbonate projectiles were impacted vertically into soda-lime glass sphere targets using a single-stage light-gas gun. Using a new technique with a laser sheet illuminating the target [Barnouin-Jha, O.S., Yamamoto, S., Toriumi, T., Sugita, S., Matsui, T., 2007. Non-intrusive measurements of the crater growth. Icarus, 188, 506-521], we measured the temporal change in diameter of crater cavities (diameter growth). The rate of increase in diameter at early times follows a power law relation, but the data at later times (before the end of transient crater formation) deviates from the power law relation. In addition, the power law exponent at early times and the degree of deviation from a power law at later times depend on the target. In order to interpret these features, we proposed to modify Maxwell's Z-model under the assumption that the strength of the excavation flow field decreases exponentially with time. We also derived a diameter growth model as: d(t)∝[1-exp(-βt)]γ, where d(t) is the apparent diameter of the crater cavity at time t after impact, and β and γ are constants. We demonstrated that the diameter growth model could represent well the experimental data for various targets with different target material properties, such as porosity or angle of repose. We also investigated the diameter growth for a dry sand target, which has been used to formulate previous scaling relations. The obtained results showed that the dry sand target has larger degree of deviation from a power law, indicating that the target material properties of the dry sand target have a significant effect on diameter growth, especially at later times. This may suggest that the previously reported scaling relations should be reexamined in order to account for the late-stage behavior with the effect of target material properties.

Spatially controlled fabrication of a bright fluorescent nanodiamond-array with enhanced far-red Si-V luminescence.

PubMed

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia; Catledge, Shane A

2014-01-31

We demonstrate a novel approach to precisely pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by a scanning probe 'dip-pen' nanolithography technique using electrostatically driven transfer of nanodiamonds from 'inked' cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond dots in the far-red is achieved by incorporating Si-V defect centers in a subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink and mechanism of ink transport, and the effect of humidity and dwell time on nanodiamond patterning are investigated. The precision patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm and 61 nm ± 3 nm, respectively, and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm and, 245 nm ± 23 nm, respectively, using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of next generation fluorescence-based devices and applications.

Irradiation effect of low-energy ion on polyurethane nanocoating containing metal oxide nanoparticles

NASA Astrophysics Data System (ADS)

Verma, Jaya; Nigam, Subhasha; Sinha, Surbhi; Sikarwar, B. S.; Bhattacharya, Arpita

2017-12-01

Irradiation effect of low-energy ion beam has been investigated on nanocoating developed with silica, titania and silica-titania core-shell nanoparticles embedded in an organic binder for nanopaint application. In this work, we have taken polyurethane as a model organic binder. Silica nanoparticles have been prepared through sol-gel synthesis with a particle size of 85 nm. Titania and core-shell nanoparticles have been prepared through both sol-gel and peptization process. Particle sizes obtained were 107 nm for titania and 240 nm for core-shell nanoparticles prepared through sol-gel process and 75 nm for TiO2 and 144 nm for core-shell nanoparticles prepared through peptization process. The coating formulations were developed with the above nanoparticles individually and nanoparticle concentration was varied from 1 to 6 wt% and the best performance in terms of hydrophobicity was obtained with 4 wt % of the nanoparticles in polyurethane coating formulation. All the coating formulations prepared were applied on a glass substrate and dried at 100°C. The dry film thickness obtained was around 100 µm in each case. These films dried on glass substrate were irradiated by nitrogen and argon ion beam with energy of 26 keV at fluences of 1014 to 1016 ions/cm2. The anti-algal property of the irradiated samples was improved and hydrophobicity was reduced.

Synthesis of iron oxide nanorods via chemical scavenging and phase transformations of intermediates at ambient conditions

NASA Astrophysics Data System (ADS)

Deshmukh, Ruchi; Mehra, Anurag; Thaokar, Rochish

2017-01-01

Chemically induced shape transformations of isotropic seeds, comprised of iron oxyhydroxides and iron oxide borate into nanorods, is reported. Transient growth studies show that the nanorods are formed via phase transformation and aggregation of various metastable species. Addition of tetra- methyl-ammonium hydroxide (TMAH) to the in situ synthesized seeds ensures a typical reaction pathway that favors formation of magnetite (Fe 3 O 4) via the steps of chemical etching, phase transformation of intermediates, and crystal consolidation. Whereas, with addition of sodium hydroxide (NaOH), either magnetite (Fe 3 O 4) or a mixture of ( γ-Fe 2 O 3 + α-FeOOH) is obtained. The shape with both the additives is always that of nanorods. When the seeds treated with TMAH were aged in an ultrasonication bath, rods with almost twice the length and diameter (length = 2800 nm, diameter = 345 nm) are obtained as compared to the sample aged without ultrasonication (length = 1535 nm, diameter = 172 nm). The morphology of nanostructures depending upon other experimental conditions such as, aging the sample at 60 ∘C, seeds synthesized under ultrasonication/ stirring or externally added are also examined and discussed in detail. All the samples show high coercivity and strong ferromagnetic behavior at room temperature and should be promising candidates as ferro-fluids for various applications.

Gold nanoparticle uptake in whole cells in liquid examined by environmental scanning electron microscopy.

PubMed

Peckys, Diana B; de Jonge, Niels

2014-02-01

The size of gold nanoparticles (AuNPs) can influence various aspects of their cellular uptake. Light microscopy is not capable of resolving most AuNPs, while electron microscopy (EM) is not practically capable of acquiring the necessary statistical data from many cells and the results may suffer from various artifacts. Here, we demonstrate the use of a fast EM method for obtaining high-resolution data from a much larger population of cells than is usually feasible with conventional EM. A549 (human lung carcinoma) cells were subjected to uptake protocols with 10, 15, or 30 nm diameter AuNPs with adsorbed serum proteins. After 20 min, 24 h, or 45 h, the cells were fixed and imaged in whole in a thin layer of liquid water with environmental scanning electron microscopy equipped with a scanning transmission electron microscopy detector. The fast preparation and imaging of 145 whole cells in liquid allowed collection of nanoscale data within an exceptionally small amount of time of ~80 h. Analysis of 1,041 AuNP-filled vesicles showed that the long-term AuNP storing lysosomes increased their average size by 80 nm when AuNPs with 30 nm diameter were uptaken, compared to lysosomes of cells incubated with AuNPs of 10 and 15 nm diameter.

Template-assisted fabrication of tin and antimony based nanowire arrays

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Kurowska, Elżbieta; Sulka, Grzegorz D.; Jaskuła, Marian

2012-10-01

Antimony nanowires with diameters ranging from 35 nm to 320 nm were successfully prepared by simple, galvanostatic electrodeposition inside the pores of anodic alumina membranes from a citrate based electrolyte. The use of the potassium antimonyl tartrate electrolyte for electrodeposition results in the formation of Sb/Sb2O3 nanowires. The structural features of the nanowire arrays were investigated by FE-SEM, and the nanowire composition was confirmed by EDS and XRD measurements. A distinct peak at about 27.5° in the XRD pattern recorded for nanowires formed in the tartrate electrolyte was attributed to the presence of co-deposited Sb2O3. Three types of dense arrays of Sn-SnSb nanowires with diameters ranging from 82 nm to 325 nm were also synthesized by DC galvanostatic electrodeposition into the anodic aluminum oxide (AAO) membranes for the first time. Only Sn and SnSb peaks appeared in the XRD pattern and both phases seem to have a relatively high degree of crystallinity. The influence of current density applied during electrodeposition on the composition of nanowires was investigated. It was found that the Sb content in fabricated nanowires decreases with increasing current density. The diameters of all synthesized nanowires roughly correspond to the dimensions of the nanochannels of AAO templates used for electrodeposition.

Number size distribution of fine and ultrafine fume particles from various welding processes.

PubMed

Brand, Peter; Lenz, Klaus; Reisgen, Uwe; Kraus, Thomas

2013-04-01

Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated.

Generation of polypeptide-templated gold nanoparticles using ionizing radiation.

PubMed

Walker, Candace Rae; Pushpavanam, Karthik; Nair, Divya Geetha; Potta, Thrimoorthy; Sutiyoso, Caesario; Kodibagkar, Vikram D; Sapareto, Stephen; Chang, John; Rege, Kaushal

2013-08-13

Ionizing radiation, including γ rays and X-rays, are high-energy electromagnetic radiation with diverse applications in nuclear energy, astrophysics, and medicine. In this work, we describe the use of ionizing radiation and cysteine-containing elastin-like polypeptides (C(n)ELPs, where n = 2 or 12 cysteines in the polypeptide sequence) for the generation of gold nanoparticles. In the presence of C(n)ELPs, ionizing radiation doses higher than 175 Gy resulted in the formation of maroon-colored gold nanoparticle dispersions, with maximal absorbance at 520 nm, from colorless metal salts. Visible color changes were not observed in any of the control systems, indicating that ionizing radiation, gold salt solution, and C(n)ELPs were all required for nanoparticle formation. The hydrodynamic diameters of nanoparticles, determined using dynamic light scattering, were in the range of 80-150 nm, while TEM imaging indicated the formation of gold cores 10-20 nm in diameter. Interestingly, C2ELPs formed 1-2 nm diameter gold nanoparticles in the absence of radiation. Our results describe a facile method of nanoparticle formation in which nanoparticle size can be tailored based on radiation dose and C(n)ELP type. Further improvements in these polypeptide-based systems can lead to colorimetric detection of ionizing radiation in a variety of applications.

Biodistribution of Encapsulated Indocyanine Green in Healthy Mice

PubMed Central

Yaseen, Mohammad A.; Yu, Jie; Jung, Bongsu; Wong, Michael S.; Anvari, Bahman

2009-01-01

Indocyanine Green (ICG) is a fluorescent probe used in various optically-mediated diagnostic and therapeutic applications. However, utility of ICG remains limited by its unstable optical properties and non-specific localization. We have encapsulated ICG within electrostatically-assembled mesocapsules (MCs) to explore its potential for targeted optical diagnosis and therapy. In this study, we investigate how the surface coating and size of the MCs influences ICG's biodistribution in vivo. ICG was administered intravenously to Swiss Webster mice as a free solution or encapsulated within either 100 nm diameter MCs coated with dextran; 500 nm diameter MCs coated with dextran; or 100 nm diameter MCs coated with 10 nm ferromagnetic iron oxide nanoparticles, themselves coated with polyethylene glycol. ICG was extracted from harvested blood and organs at various times and its amount quantified with fluorescence measurements. MCs containing ICG accumulated in organs of the reticuloendothelial system, namely the liver and spleen, as well as the lungs. The circulation kinetics of ICG remained unaffected by encapsulation; however, the deposition within organs other than the liver suggests a different biodistribution mechanism. Results suggest that the capsules' coating influences their biodistribution to a greater extent than their size. The MC encapsulation system allows for delivery of ICG to organs other than the liver, enabling the potential development of new optical imaging and therapeutic strategies. PMID:19799463

Beam spot diameter of the near-field scanning electron microscopy.

PubMed

Kyritsakis, A; Xanthakis, J P

2013-02-01

We have examined the beam spot diameter at the anode of the scanning electron microscopy (SEM) in the near-field mode as a function of the anode-tip distance d. The detector lateral resolution of this type of microscopy is approximately equal to this spot diameter. For our calculations we have simulated the apex region of the tip with an ellipsoid of revolution of radii R₁ and R₂ with R₁>R₂ as suggested by TEM images of the realistic tips. We have then solved the Laplace equation to obtain the electrostatic potential and to this we have added a spherical image potential. The calculated electrostatic field is highly asymmetric, being strong along the tip-axis and weakening quickly towards the sides. When a 3-dimensional WKB approximation is used to calculate the electron paths corresponding to such a potential, the latter are shown to bend significantly towards the vertical (tip-axis) direction producing a beam narrowing effect very similar to the beam narrowing effect we discovered for the traditional SEM case. When the values of R₁, R₂ are chosen from fittings to the TEM images of the tips used in the experiments, the beam spot diameter W at the anode (d=25 nm) varies from 12.5 nm to 9 nm depending on the fitted R₁, R₂. These values of W are considerably smaller than previously predicted by calculating solid angles of emission from spherical surfaces (41 nm) but also much closer to the detector lateral resolution (6-7 nm) obtained from differentiating the experimental current step. This trend continued at all other d examined. Furthermore the beam width W was found to decrease quickly with increasing sharpness S=R₁/R₂ of the tip and then saturate. W is also decreasing with decreasing R₁, R₂ with S kept constant. We deduce that the sharpness of the tip is important not only for creating high extraction fields but also for guaranteeing a very small beam spot diameter. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of Tube Diameter on The Design of Heat Exchanger in Solar Drying system

NASA Astrophysics Data System (ADS)

Husham Abdulmalek, Shaymaa; Khalaji Assadi, Morteza; Al-Kayiem, Hussain H.; Gitan, Ali Ahmed

2018-03-01

The drying of agriculture product consumes a huge fossil fuel rates that demand to find an alternative source of sustainable environmental friendly energy such as solar energy. This work presents the difference between using solar heat source and electrical heater in terms of design aspect. A circular-finned tube bank heat exchanger is considered against an electrical heater used as a heat generator to regenerate silica gel in solar assisted desiccant drying system. The impact of tube diameter on the heat transfer area was investigated for both the heat exchanger and the electrical heater. The fin performance was investigated by determining fin effectiveness and fin efficiency. A mathematical model was developed using MATLAB to describe the forced convection heat transfer between hot water supplied by evacuated solar collector with 70 °C and ambient air flow over heat exchanger finned tubes. The results revealed that the increasing of tube diameter augments the heat transfer area of both heat exchanger and electrical heater. The highest of fin efficiency was around 0.745 and the lowest was around 0.687 while the fin effectiveness was found to be around 0.998.

Atmospheric deposition of particles at a sensitive alpine lake: Size-segregated daily and annual fluxes from passive sampling techniques.

PubMed

Tai, Anna Y-C; Chen, L-W Antony; Wang, Xiaoliang; Chow, Judith C; Watson, John G

2017-02-01

Lake Tahoe, a North American alpine lake long appreciated for its clear water and geographic setting, has experienced a trend of declining water clarity due to increasing nutrient and particle inputs. Contributions from atmospheric deposition of particulate matter (PM) could be important, yet they are inadequately quantified. This study established a yearlong deposition monitoring network in the northern Lake Tahoe Basin. Dry deposition was quantified on surrogate surfaces while wet deposition was based on particles suspended in precipitation at 24-hour resolution. The particle size ranges by these passive techniques were 1-64μm and 0.5-20μm in diameter for dry and wet deposition, respectively. Dry deposition of submicrometer (0.5-1μm) particles was also estimated by extrapolation of a lognormal size distribution. Higher daily number deposition fluxes (NDF dry and NDF wet ) were found at a near-shore site, confirming substantial impacts of commercial and tourist activities. The two more isolated sites indicated a uniform regional background. On average, daily NDF dry is about one order of magnitude lower than daily NDF wet . Dry deposition velocities increased rapidly with particle size, as evidenced by collocated measurements of NDF dry and ambient particle number concentrations, though it seems less so for wet deposition due to different scavenging mechanisms. Despite fewer "wet" days than "dry" days during the monitoring period, wet processes dominated seasonal particle deposition, particularly in winter and spring when most precipitation occurred. Adopting sediment (insoluble, inorganic) particle fraction estimates from the literature, this study reports an annual particle flux of 2.9-5.2×10 10 #m -2 yr -1 for sediment particles with 1-20μm diameter and 6.1-11×10 10 #m -2 yr -1 for those with 0.5-20μm diameter. Implications of these findings to the current knowledge of atmospheric deposition in the Lake Tahoe Total Maximum Daily Load (TMDL) are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

NASA Astrophysics Data System (ADS)

Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Susi, T.; Jiang, H.; Nasibulin, A. G.; Kauppinen, E. I.

2015-07-01

We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3-4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ˜105 cm-3 prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

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

Nathanael, A. Joseph; Department of Nanomaterials Engineering, Chungnam National University, Daejeon, 305-764; Mangalaraj, D., E-mail: dmraj800@yahoo.com

In this study, undoped and yttrium (Y) doped nanocrystalline hydroxyapatite crystals were synthesized by the hydrothermal method at 180 Degree-Sign C for 24 h. Highly ordered and oriented hydroxyapatite (HAp) nanorods were prepared by yttrium doping and their nanostructure and physical properties were compared with those of undoped HAp rods. FESEM images showed that the doping with Y ions reduced the diameter (from 25 nm to 15 nm) and increased the length (from 95 nm to 115 nm) of the synthesized rods. The aspect ratio of the undoped and Y-doped nanorods were calculated to be 4.303 (SD = 0.0959) andmore » 7.61 (SD = 0.0355), respectively. Specific surface area (SSA) analysis showed that SSA also increased from 66.74 m{sup 2}/g to 68.57 m{sup 2}/g with the addition of yttrium. Y-doped HAp nanorod reinforced HMWPE composites displayed the better mechanical performance than those reinforced with pure HAp nanorods. The possible strengthening of nanorods and the increase of SSA due to the reduction in the size of nanorods in the presence of yttrium may have contributed to the strengthening of Y-doped HAp/HMWPE composites. - Graphical Abstract: Highly ordered and oriented yttrium doped hydroxyapatite (HAp) nanorods were prepared by hydrothermal method. For undoped HAp the average length of the nanorod is 95 nm with mean diameter of 24 nm and for a Y doped nanorod the average length is {approx} 115 nm and the mean diameter is 15 nm. Mechanical analysis was carried out by polymer/nanoparticle composite method. Highlights: Black-Right-Pointing-Pointer Yttrium doped hydroxyapatite nanorods were prepared by hydrothermal method. Black-Right-Pointing-Pointer The nanorods have highly uniform size distribution. Black-Right-Pointing-Pointer Yttrium substitution and nanostructure formation was confirmed by careful analysis. Black-Right-Pointing-Pointer Mechanical strength was analyzed by polymer nanoparticle reinforcement method.« less

Modeling particle nucleation and growth over northern California during the 2010 CARES campaign

NASA Astrophysics Data System (ADS)

Lupascu, A.; Easter, R.; Zaveri, R.; Shrivastava, M.; Pekour, M.; Tomlinson, J.; Yang, Q.; Matsui, H.; Hodzic, A.; Zhang, Q.; Fast, J. D.

2015-11-01

Accurate representation of the aerosol lifecycle requires adequate modeling of the particle number concentration and size distribution in addition to their mass, which is often the focus of aerosol modeling studies. This paper compares particle number concentrations and size distributions as predicted by three empirical nucleation parameterizations in the Weather Research and Forecast coupled with chemistry (WRF-Chem) regional model using 20 discrete size bins ranging from 1 nm to 10 μm. Two of the parameterizations are based on H2SO4, while one is based on both H2SO4 and organic vapors. Budget diagnostic terms for transport, dry deposition, emissions, condensational growth, nucleation, and coagulation of aerosol particles have been added to the model and are used to analyze the differences in how the new particle formation parameterizations influence the evolving aerosol size distribution. The simulations are evaluated using measurements collected at surface sites and from a research aircraft during the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted in the vicinity of Sacramento, California. While all three parameterizations captured the temporal variation of the size distribution during observed nucleation events as well as the spatial variability in aerosol number, all overestimated by up to a factor of 2.5 the total particle number concentration for particle diameters greater than 10 nm. Using the budget diagnostic terms, we demonstrate that the combined H2SO4 and low-volatility organic vapor parameterization leads to a different diurnal variability of new particle formation and growth to larger sizes compared to the parameterizations based on only H2SO4. At the CARES urban ground site, peak nucleation rates are predicted to occur around 12:00 Pacific (local) standard time (PST) for the H2SO4 parameterizations, whereas the highest rates were predicted at 08:00 and 16:00 PST when low-volatility organic gases are included in the parameterization. This can be explained by higher anthropogenic emissions of organic vapors at these times as well as lower boundary-layer heights that reduce vertical mixing. The higher nucleation rates in the H2SO4-organic parameterization at these times were largely offset by losses due to coagulation. Despite the different budget terms for ultrafine particles, the 10-40 nm diameter particle number concentrations from all three parameterizations increased from 10:00 to 14:00 PST and then decreased later in the afternoon, consistent with changes in the observed size and number distribution. We found that newly formed particles could explain up to 20-30 % of predicted cloud condensation nuclei at 0.5 % supersaturation, depending on location and the specific nucleation parameterization. A sensitivity simulation using 12 discrete size bins ranging from 1 nm to 10 μm diameter gave a reasonable estimate of particle number and size distribution compared to the 20 size bin simulation, while reducing the associated computational cost by ~ 36 %.

Synthesis and characterization of pHLIP® coated gold nanoparticles.

PubMed

Daniels, Jennifer L; Crawford, Troy M; Andreev, Oleg A; Reshetnyak, Yana K

2017-07-01

Novel approaches in synthesis of spherical and multispiked gold nanoparticles coated with polyethylene glycol (PEG) and pH Low Insertion Peptide (pHLIP ® ) were introduced. The presence of a tumor-targeting pHLIP ® peptide in the nanoparticle coating enhances the stability of particles in solution and promotes a pH-dependent cellular uptake. The spherical particles were prepared with sodium citrate as a gold reducing agent to form particles of 7.0±2.5 nm in mean metallic core diameter and ∼43 nm in mean hydrodynamic diameter. The particles that were injected into tumors in mice (21 µg of gold) were homogeneously distributed within a tumor mass with no staining of the muscle tissue adjacent to the tumor. Up to 30% of the injected gold dose remained within the tumor one hour post-injection. The multispiked gold nanoparticles with a mean metallic core diameter of 146.0±50.4 nm and a mean hydrodynamic size of ~161 nm were prepared using ascorbic acid as a reducing agent and disk-like bicelles as a template. Only the presence of a soft template, like bicelles, ensured the appearance of spiked nanoparticles with resonance in the near infrared region. The irradiation of spiked gold nanoparticles by an 805 nm laser led to the time- and concentration-dependent increase of temperature. Both pHLIP ® and PEG coated gold spherical and multispiked nanoparticles might find application in radiation and thermal therapies of tumors.

Passively Q-switched of EDFL employing multi-walled carbon nanotubes with diameter less than 8 nm as saturable absorber

NASA Astrophysics Data System (ADS)

Nur Fatin Zuikafly, Siti; Ahmad, Fauzan; Haniff Ibrahim, Mohd; Wadi Harun, Sulaiman

2017-11-01

The paper demonstrates passively Q-switched erbium-doped fiber laser implementing multiwalled carbon nanotubes (MWCNTs) based saturable absorber. The paper is the first to report the use of the MWCNTs with diameter less than 8 nm as typically, the diameter used is 10 to 20 nm. The MWCNTs is incorporated with water soluble host polymer, polyvinyl alcohol (PVA) to produce a MWCNTs polymer composite thin film which is then sandwiched between two fiber connectors. The fabricated SA is employed in the laser experimental setup in ring cavity. The Q-switching regime started at threshold pump power of 103 mW and increasable to 215 mW. The stable pulse train from 41.6 kHz to 76.92 kHz with maximum average output power and pulse energy of 0.17 mW and 3.39 nJ are produced. The shortest pulse width of 1.9 μs is obtained in the proposed experimental work, making it the lowest pulse width ever reported using MWCNTs-based saturable absorber.

Mechanisms of the self-organization of star-shaped polymers with a varied structure of branching center based on fullerene C{sub 60} in solutions

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

Lebedev, V. T., E-mail: vlebedev@pnpi.spb.ru; Toeroek, Gy.; Vinogradova, L. V.

The self-organization of star-shaped polymers in toluene has been studied by small-angle neutron scattering. Polystyrene stars with a mono-C{sub 60} branching center are ordered into globular clusters ({approx}1700 nm in diameter), whereas stars with a double (C{sub 60}-C{sub 60}) center are ordered into anisotropic structures (superchains), which are linked (depending on the concentration) into triads (chain clusters {approx}2500 nm in diameter). On the contrary, heteroarm polystyrene and poly-2-vinylpyridine stars with a C{sub 60} center are weakly associated into dimers. Moderately polar stars with arms composed of polystyrene and diblock copolymer (poly-2-vinylpyridine-poly-tret-butyl methacrylate) form short chains composed of four macromolecules, whilemore » stars of higher polarity based on polystyrene and poly-tret-butyl methacrylate form clusters containing {approx}12 macromolecules {approx}50 nm in diameter. Thus, by varying the structure of the center and the arm polarity, one can control the modes of star structuring.« less

Cryo-transmission electron tomography of native casein micelles from bovine milk.

PubMed

Trejo, R; Dokland, T; Jurat-Fuentes, J; Harte, F

2011-12-01

Caseins are the principal protein components in milk and an important ingredient in the food industry. In liquid milk, caseins are found as micelles of casein proteins and colloidal calcium nanoclusters. Casein micelles were isolated from raw skim milk by size exclusion chromatography and suspended in milk protein-free serum produced by ultrafiltration (molecular weight cut-off of 3 kDa) of raw skim milk. The micelles were imaged by cryo-electron microscopy and subjected to tomographic reconstruction methods to visualize the 3-dimensional and internal organization of native casein micelles. This provided new insights into the internal architecture of the casein micelle that had not been apparent from prior cryo-transmission electron microscopy studies. This analysis demonstrated the presence of water-filled cavities (∼20 to 30 nm in diameter), channels (diameter greater than ∼5 nm), and several hundred high-density nanoclusters (6 to 12 nm in diameter) within the interior of the micelles. No spherical protein submicellar structures were observed. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Comparison between Single-Walled CNT, Multi-Walled CNT, and Carbon Nanotube-Fiber Pyrograf III

NASA Astrophysics Data System (ADS)

Mousa, Marwan S.

2018-02-01

Single-Walled CNT (SWCNTs), Multi-walled Carbon Nanotubes (MWCNTs), and Carbon Nanotube-Fibers Pyrograf III PR-1 (CNTFs) were deposited by chemical vapor deposition under vacuum pressure value of (10-7mbar). Their structures were investigated by field emission microscopy. Carbon Nano-Fibers Pyrograf III PR-1 showed an average fiber diameter within the range of 100-200 nm and a length of (30-100) μm. Single-walled Carbon Nanotubes were produced by high-pressure Carbon Monoxide process with an average diameter ranging between (1-4) nm and a length of (1-3) μm. Thin Multiwall Carbon Nanotube of carbon purity (90%) showed an average diameter tube (9.5 nm) with a high-aspect-ratio (>150). The research work reported here includes the field electron emission current-voltage (I-V) characteristics and presented as Fowler-Nordheim (FN) plots and the spatial emission current distributions (electron emission images) obtained and analyzed in terms of electron source features. For the three types of emitters, a single spot pattern for the electron spatial; distributions were observed, with emission current fluctuations in some voltage region.

TOPICAL REVIEW: Synthesis and applications of magnetic nanoparticles for biorecognition and point of care medical diagnostics

NASA Astrophysics Data System (ADS)

Sandhu, Adarsh; Handa, Hiroshi; Abe, Masanori

2010-11-01

Functionalized magnetic nanoparticles are important components in biorecognition and medical diagnostics. Here, we present a review of our contribution to this interdisciplinary research field. We start by describing a simple one-step process for the synthesis of highly uniform ferrite nanoparticles (d = 20-200 nm) and their functionalization with amino acids via carboxyl groups. For real-world applications, we used admicellar polymerization to produce 200 nm diameter 'FG beads', consisting of several 40 nm diameter ferrite nanoparticles encapsulated in a co-polymer of styrene and glycidyl methacrylate for high throughput molecular screening. The highly dispersive FG beads were functionalized with an ethylene glycol diglycidyl ether spacer and used for affinity purification of methotrexate—an anti-cancer agent. We synthesized sub-100 nm diameter magnetic nanocapsules by exploiting the self-assembly of viral capsid protein pentamers, where single 8, 20, and 27 nm nanoparticles were encapsulated with VP1 pentamers for applications including MRI contrast agents. The FG beads are now commercially available for use in fully automated bio-screening systems. We also incorporated europium complexes inside a polymer matrix to produce 140 nm diameter fluorescent-ferrite beads (FF beads), which emit at 618 nm. These FF beads were used for immunofluorescent staining for diagnosis of cancer metastases to lymph nodes during cancer resection surgery by labeling tumor cell epidermal growth factor receptor (EGFRs), and for the detection of brain natriuretic peptide (BNP)—a hormone secreted in excess amounts by the heart when stressed—to a level of 2.0 pg ml - 1. We also describe our work on Hall biosensors made using InSb and GaAs/InGaAs/AlGaAs 2DEG heterostructures integrated with gold current strips to reduce measurement times. Our approach for the detection of sub-200 nm magnetic bead is also described: we exploit the magnetically induced capture of micrometer sized 'probe beads' by nanometer sized 'target beads', enabling the detection of small concentrations of beads as small as 8 nm in 'pumpless' microcapillary systems. Finally, we describe a 'label-less homogeneous' procedure referred to as 'magneto-optical transmission (MT) sensing', where the optical transmission of a solution containing rotating linear chains of magnetic nanobeads was used to detect biomolecules with pM-level sensitivity with a dynamic range of more than four orders of magnitude. Our research on the synthesis and applications of nanoparticles is particularly suitable for point of care diagnostics.

Synthesis and applications of magnetic nanoparticles for biorecognition and point of care medical diagnostics.

PubMed

Sandhu, Adarsh; Handa, Hiroshi; Abe, Masanori

2010-11-05

Functionalized magnetic nanoparticles are important components in biorecognition and medical diagnostics. Here, we present a review of our contribution to this interdisciplinary research field. We start by describing a simple one-step process for the synthesis of highly uniform ferrite nanoparticles (d = 20-200 nm) and their functionalization with amino acids via carboxyl groups. For real-world applications, we used admicellar polymerization to produce 200 nm diameter 'FG beads', consisting of several 40 nm diameter ferrite nanoparticles encapsulated in a co-polymer of styrene and glycidyl methacrylate for high throughput molecular screening. The highly dispersive FG beads were functionalized with an ethylene glycol diglycidyl ether spacer and used for affinity purification of methotrexate-an anti-cancer agent. We synthesized sub-100 nm diameter magnetic nanocapsules by exploiting the self-assembly of viral capsid protein pentamers, where single 8, 20, and 27 nm nanoparticles were encapsulated with VP1 pentamers for applications including MRI contrast agents. The FG beads are now commercially available for use in fully automated bio-screening systems. We also incorporated europium complexes inside a polymer matrix to produce 140 nm diameter fluorescent-ferrite beads (FF beads), which emit at 618 nm. These FF beads were used for immunofluorescent staining for diagnosis of cancer metastases to lymph nodes during cancer resection surgery by labeling tumor cell epidermal growth factor receptor (EGFRs), and for the detection of brain natriuretic peptide (BNP)-a hormone secreted in excess amounts by the heart when stressed-to a level of 2.0 pg ml(-1). We also describe our work on Hall biosensors made using InSb and GaAs/InGaAs/AlGaAs 2DEG heterostructures integrated with gold current strips to reduce measurement times. Our approach for the detection of sub-200 nm magnetic bead is also described: we exploit the magnetically induced capture of micrometer sized 'probe beads' by nanometer sized 'target beads', enabling the detection of small concentrations of beads as small as 8 nm in 'pumpless' microcapillary systems. Finally, we describe a 'label-less homogeneous' procedure referred to as 'magneto-optical transmission (MT) sensing', where the optical transmission of a solution containing rotating linear chains of magnetic nanobeads was used to detect biomolecules with pM-level sensitivity with a dynamic range of more than four orders of magnitude. Our research on the synthesis and applications of nanoparticles is particularly suitable for point of care diagnostics.

A convenient method to prepare emulsified polyacrylate nanoparticles from powders [corrected] for drug delivery applications.

PubMed

Garay-Jimenez, Julio C; Turos, Edward

2011-08-01

We describe a method to obtain purified, polyacrylate nanoparticles in a homogeneous powdered form that can be readily reconstituted in aqueous media for in vivo applications. Polyacrylate-based nanoparticles can be easily prepared by emulsion polymerization using a 7:3 mixture of butyl acrylate and styrene in water containing sodium dodecyl sulfate as a surfactant and potassium persulfate as a water-soluble radical initiator. The resulting emulsions contain nanoparticles measuring 40-50 nm in diameter with uniform morphology, and can be purified by centrifugation and dialysis to remove larger coagulants as well as residual surfactant and monomers associated with toxicity. These purified emulsions can be lyophilized in the presence of maltose (a non-toxic cryoprotectant) to provide a homogeneous dried powder, which can be reconstituted as an emulsion by addition of an aqueous diluent. Dynamic light scattering and microbiological experiments were carried out on the reconstituted nanoparticles. This procedure allows for ready preparation of nanoparticle emulsions for drug delivery applications. Copyright © 2011 Elsevier Ltd. All rights reserved.

DNA-Templated Pd Conductive Metallic Nanowires

NASA Astrophysics Data System (ADS)

Nguyen, K.; Monteverde, M.; Lyonnais, S.; Campidelli, S.; Bourgoin, J.-Ph.; Filoramo, A.

2008-10-01

Because of its unique recognition properties, its size and the sub-nanometric resolution, DNA is of particular interest for positioning and organizing nanomaterials. However, in DNA-directed nanoelectronic it can be envisioned to use DNA not only as a positioning scaffold, but also as a support for the conducting element. To ensure this function a metallization process is necessary and among the various DNA metallization methods the Pd based ones are of particular interest for carbon nanotube transistor connections. In this field, the major drawback of the existing methods is the fast kinetics of the process which lead to a stochastic growth. Here, we present a novel approach to DNA Pd metalization where the DNA molecule is previously deposited on a dry substrate in a typical nanodevice configuration. In our approach the progressive growth of nanowires is achieved by the slow and selective precipitation of PdO, followed by a subsequent reduction step. Thanks to this strategy we fabricated homogeneous, continuous and conductive Pd nanowires on the DNA scaffolds of very thin diameter (20-25 nm).

Porous starch/cellulose nanofibers composite prepared by salt leaching technique for tissue engineering.

PubMed

Nasri-Nasrabadi, Bijan; Mehrasa, Mohammad; Rafienia, Mohammad; Bonakdar, Shahin; Behzad, Tayebeh; Gavanji, Shahin

2014-08-08

Starch/cellulose nanofibers composites with proper porosity pore size, mechanical strength, and biodegradability for cartilage tissue engineering have been reported in this study. The porous thermoplastic starch-based composites were prepared by combining film casting, salt leaching, and freeze drying methods. The diameter of 70% nanofibers was in the range of 40-90 nm. All samples had interconnected porous morphology; however an increase in pore interconnectivity was observed when the sodium chloride ratio was increased in the salt leaching. Scaffolds with the total porogen content of 70 wt% exhibited adequate mechanical properties for cartilage tissue engineering applications. The water uptake ratio of nanocomposites was remarkably enhanced by adding 10% cellulose nanofibers. The scaffolds were partially destroyed due to low in vitro degradation rate after more than 20 weeks. Cultivation of isolated rabbit chondrocytes on the fabricated scaffold proved that the incorporation of nanofibers in starch structure improves cell attachment and proliferation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Characterization on White Etching Layer Formed During Ceramic Milling of Inconel 718

NASA Astrophysics Data System (ADS)

Kruk, A.; Wusatowska-Sarnek, A. M.; Ziętara, M.; Jemielniak, K.; Siemiątkowski, Z.; Czyrska-Filemonowicz, A.

2018-03-01

A comprehensive characterization of the near surface formed during the interrupted high-speed dry ceramic milling of IN718 was performed using light imaging, SEM/EDX, TEM and nano-hardness methods. It was found out that even an initial cut by a fresh tool creates a sub-surface alteration roughly 20 µm deep. The depth of altered sub-surface progressively changed to a roughly 40 µm when the tool reached an approximately half of its life, and almost 60 µm at the tool's end of the life. In the last two cases, the visible WEL (utilizing a light microscope) of the thickness roughly 6 and 15 µm was created, respectively. The outermost layer of the deformed subsurface was found to be for all three cases approximately 1.5 µm thick and composed of dynamically recrystallized γ phase grains with the average diameter of approximately 150 nm. This layer was free of δ phase and γ' or γ″ precipitates. It was followed by a plastically deformed zone.

A novel gellan-PVA nanofibrous scaffold for skin tissue regeneration: Fabrication and characterization.

PubMed

Vashisth, Priya; Nikhil, Kumar; Roy, Partha; Pruthi, Parul A; Singh, Rajesh P; Pruthi, Vikas

2016-01-20

In this investigation, we have introduced novel electrospun gellan based nanofibers as a hydrophilic scaffolding material for skin tissue regeneration. These nanofibers were fabricated using a blend mixture of gellan with polyvinyl alcohol (PVA). PVA reduced the repulsive force of resulting solution and lead to formation of uniform fibers with improved nanostructure. Field emission scanning electron microscopy (FESEM) confirmed the average diameter of nanofibers down to 50 nm. The infrared spectra (IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis evaluated the crosslinking, thermal stability and highly crystalline nature of gellan-PVA nanofibers, respectively. Furthermore, the cell culture studies using human dermal fibroblast (3T3L1) cells established that these gellan based nanofibrous scaffold could induce improved cell adhesion and enhanced cell growth than conventionally proposed gellan based hydrogels and dry films. Importantly, the nanofibrous scaffold are biodegradable and could be potentially used as a temporary substrate/or biomedical graft to induce skin tissue regeneration. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of sintering time on the performance of turmeric dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Basuki, Hidajat, R. Lullus Lambang G.; Suyitno, Kristiawan, Budi; Rachmanto, Rendy Adhi

2017-01-01

This study reports the effect of sintering time on the performance of the dye-sensitized solar cells with turmeric dyes as sensitizers. Sintering TiO2 semiconductors were conducted at a temperature of 450°C for 30, 50, 90, 120, 150, and 180 minutes. The natural dye was extracted from dried turmeric powders with ethanol solvent. The results show that size of grains and the opening area of TiO2 semiconductor depended on the sintering time. The improvement of the properties of TiO2 semiconductor allowed more turmeric dyes were adsorbed by the semiconductors and then improved the performance of solar cells. The sintering time of 150 minutes produced large grains with an average diameter of 68.87 nm, and a porosity area of 26.51% caused the performance of DSSCs was the highest among other sintering time. The Voc, Jsc, and efficiency of DSSCs with turmeric-based natural dyes 0.64 V, 0.47 mA/cm2, and 0.2%, respectively.

Dissolution and Characterization of Boron Nitride Nanotubes in Superacid.

PubMed

Kleinerman, Olga; Adnan, Mohammed; Marincel, Daniel M; Ma, Anson W K; Bengio, E Amram; Park, Cheol; Chu, Sang-Hyon; Pasquali, Matteo; Talmon, Yeshayahu

2017-12-19

Boron nitride nanotubes (BNNTs) are of interest for their unique combination of high tensile strength, high electrical resistivity, high neutron cross section, and low reactivity. The fastest route to employing these properties in composites and macroscopic articles is through solution processing. However, dispersing BNNTs without functionalization or use of a surfactant is challenging. We show here by cryogenic transmission electron microscopy that BNNTs spontaneously dissolve in chlorosulfonic acid as disentangled individual molecules. Electron energy loss spectroscopy of BNNTs dried from the solution confirms preservation of the sp 2 hybridization for boron and nitrogen, eliminating the possibility of BNNT functionalization or damage. The length and diameter of the BNNTs was statistically calculated to be ∼4.5 μm and ∼4 nm, respectively. Interestingly, bent or otherwise damaged BNNTs are filled by chlorosulfonic acid. Additionally, nanometer-sized synthesis byproducts, including boron nitride clusters, isolated single and multilayer hexagonal boron nitride, and boron particles, were identified. Dissolution in superacid provides a route for solution processing BNNTs without altering their chemical structure.

Nitride microlens arrays for blue and ultraviolet wavelength applications

NASA Astrophysics Data System (ADS)

Oder, T. N.; Shakya, J.; Lin, J. Y.; Jiang, H. X.

2003-05-01

Nitride microlens arrays with sizes as small as 10 μm in diameter have been fabricated on GaN and AlN epilayers using the method of photoresist reflow and inductively coupled plasma dry etching. The focal lengths of the microlenses varied from 7-30 μm as determined by theoretical fitting as well as by the near-field scanning optical microscopy measurement. Scanning electron and atomic force microscopies were used to obtain the surface profile of the microlenses which were found to match very well with hemispherical fitting and a surface roughness value around 1 nm was obtained. Nitride microlens arrays would be naturally chosen for green/blue to deep ultraviolet wavelength applications. In addition, nitride microlenses offer the possibility of integrating nitride-based microsize photonic devices as well as of coupling light into, out of, and between arrays of III-nitride emitters for other applications, such as spatially resolved fluorescence spectroscopy studies of biological and medical systems and optical links, thereby further expanding the applications of III nitrides.

Dextran Nanoparticle Synthesis and Properties

PubMed Central

Wasiak, Iga; Kulikowska, Aleksandra; Janczewska, Magdalena; Michalak, Magdalena; Cymerman, Iwona A.; Nagalski, Andrzej; Kallinger, Peter; Szymanski, Wladyslaw W.; Ciach, Tomasz

2016-01-01

Dextran is widely exploited in medical products and as a component of drug-delivering nanoparticles (NPs). Here, we tested whether dextran can serve as the main substrate of NPs and form a stable backbone. We tested dextrans with several molecular masses under several synthesis conditions to optimize NP stability. The analysis of the obtained nanoparticles showed that dextran NPs that were synthesized from 70 kDa dextran with a 5% degree of oxidation of the polysaccharide chain and 50% substitution with dodecylamine formed a NP backbone composed of modified dextran subunits, the mean diameter of which in an aqueous environment was around 100 nm. Dextran NPs could be stored in a dry state and reassembled in water. Moreover, we found that different chemical moieties (e.g., drugs such as doxorubicin) can be attached to the dextran NPs via a pH-dependent bond that allows release of the drug with lowering pH. We conclude that dextran NPs are a promising nano drug carrier. PMID:26752182

Dextran Nanoparticle Synthesis and Properties.

PubMed

Wasiak, Iga; Kulikowska, Aleksandra; Janczewska, Magdalena; Michalak, Magdalena; Cymerman, Iwona A; Nagalski, Andrzej; Kallinger, Peter; Szymanski, Wladyslaw W; Ciach, Tomasz

2016-01-01

Dextran is widely exploited in medical products and as a component of drug-delivering nanoparticles (NPs). Here, we tested whether dextran can serve as the main substrate of NPs and form a stable backbone. We tested dextrans with several molecular masses under several synthesis conditions to optimize NP stability. The analysis of the obtained nanoparticles showed that dextran NPs that were synthesized from 70 kDa dextran with a 5% degree of oxidation of the polysaccharide chain and 50% substitution with dodecylamine formed a NP backbone composed of modified dextran subunits, the mean diameter of which in an aqueous environment was around 100 nm. Dextran NPs could be stored in a dry state and reassembled in water. Moreover, we found that different chemical moieties (e.g., drugs such as doxorubicin) can be attached to the dextran NPs via a pH-dependent bond that allows release of the drug with lowering pH. We conclude that dextran NPs are a promising nano drug carrier.

Influence of particle size distribution on nanopowder cold compaction processes

NASA Astrophysics Data System (ADS)

Boltachev, G.; Volkov, N.; Lukyashin, K.; Markov, V.; Chingina, E.

2017-06-01

Nanopowder uniform and uniaxial cold compaction processes are simulated by 2D granular dynamics method. The interaction of particles in addition to wide-known contact laws involves the dispersion forces of attraction and possibility of interparticle solid bridges formation, which have a large importance for nanopowders. Different model systems are investigated: monosized systems with particle diameter of 10, 20 and 30 nm; bidisperse systems with different content of small (diameter is 10 nm) and large (30 nm) particles; polydisperse systems corresponding to the log-normal size distribution law with different width. Non-monotone dependence of compact density on powder content is revealed in bidisperse systems. The deviations of compact density in polydisperse systems from the density of corresponding monosized system are found to be minor, less than 1 per cent.

Mesoporous metal oxide microsphere electrode compositions and their methods of making

DOEpatents

Paranthaman, Mariappan Parans; Liu, Hansan; Brown, Gilbert M.; Sun, Xiao-Guang; Bi, Zhonghe

2016-12-06

Compositions and methods of making are provided for mesoporous metal oxide microspheres electrodes. The mesoporous metal oxide microsphere compositions comprise (a) microspheres with an average diameter between 200 nanometers (nm) and 10 micrometers (.mu.m); (b) mesopores on the surface and interior of the microspheres, wherein the mesopores have an average diameter between 1 nm and 50 nm and the microspheres have a surface area between 50 m.sup.2/g and 500 m.sup.2/g. The methods of making comprise forming composite powders. The methods may also comprise refluxing the composite powders in a basic solution to form an etched powder, washing the etched powder with an acid to form a hydrated metal oxide, and heat-treating the hydrated metal oxide to form mesoporous metal oxide microspheres.

Size-dependent capacitance of NiO nanoparticles synthesized with cathodic contact glow discharge electrolysis

NASA Astrophysics Data System (ADS)

Allagui, Anis; Alami, Abdul Hai; Baranova, Elena A.; Wüthrich, Rolf

2014-09-01

NiO nanoparticles of 70, 91 and 107 nm average diameter are synthesized by cathodic contact glow discharge electrolysis at 30, 36 and 42 VDC respectively, in 2 M H2SO4 + 0.5 M ethanol + 2.5 mg ml-1 of PVP, and are investigated for electrochemical energy storage. From the cyclic voltammetry and galvanostatic charge-discharge measurements in 1 M KOH, it was found that a maximum specific capacitance of 218 F g-1 is achieved with the 70 nm NiO nanoparticles at 2.7 A g-1. Larger nanoparticles of 91 and 107 nm diameter exhibit specific capacitances of 106 and 63 F g-1, respectively, suggesting a size-dependent capacitive performance enhanced with decreasing particles size.

Electron tomography study of isolated human centrioles.

PubMed

Ibrahim, Rana; Messaoudi, Cédric; Chichon, Francisco Javier; Celati, Claude; Marco, Sergio

2009-01-01

Centrioles are components of the centrosome, which is present in most eukaryotic cells (from protozoa to mammals). They organize the microtubule skeleton during interphase and the mitotic spindle during cell division. In ciliate cells, centrioles form basal bodies that are involved in cellular motility. Despite their important roles in biology, the detailed structure of centrioles remains obscure. This work contributes to a more complete model of centriole structure. The authors used electron tomography of isolated centrosomes from the human lymphoblast KE37 to explore the details of subdistal appendages and centriole lumen organization in mother centrioles. Their results reveal that each of the nine subdistal appendages is composed of two halves (20 nm diameter each) fused in a 40 nm tip that extends 100 nm from where it anchors to microtubules. The centriole lumen is filled at the distal domain by a 45 nm periodic stack of rings. Each ring has a 30 nm diameter, is 15 nm thick, and appears to be tilted at 53 degrees perpendicular to the centriole axis. The rings are anchored to microtubules by arms. Based on their results, the authors propose a model of the mother centriole distal structure. Copyright 2008 Wiley-Liss, Inc.

Preliminary Study of Water Repellent Properties of Red Pepper Seed Oil

NASA Astrophysics Data System (ADS)

Kurniawan, F.; Madurani, K. A.; Wahyulis, N. C.

2017-03-01

The water-repellent properties of red pepper seed oil (capsicol) have been studied. The oil was coated on the glass surface by spray technique. Water repellent properties were performed by measuring the contact angle of water droplets. The measurement was conducted by varying the drying time of the oil coating at room temperature. The optimum contact angle of the droplets on the glass with capsicol coating is 46.77°, which can be achieved in 30 min of drying time. It also obtained the smallest diameter of the droplets (0.47 cm). The longer drying time decrease the contact angles and increases the diameter. The results were compared with the bare glass and commercial water repellent. The contact angle of the droplets on the glass surface with capsicol coating is higher than bare glass, but lower than glass with commercial water repellent coating. It means that capsicol has the water-repellent properties.

Study of reversible magnetization in FeCoNi alloy nanowires with different diameters by first order reversal curve (FORC) diagrams

NASA Astrophysics Data System (ADS)

Samanifar, S.; Kashi, M. Almasi; Ramazani, A.

2018-05-01

Magnetic nanowires electrodeposited into solid templates are of high interest due to their tunable properties which are required for magnetic recording media and spintronic devices. Here, highly ordered arrays of FeCoNi NWs with varied diameters (between 60 and 150 nm) were fabricated into nanopores of hard-anodized aluminum oxide templates using pulsed ac electrodeposition technique. X-ray diffraction patterns indicated the formation of FeCoNi NWs with fcc FeNi and bcc FeCo alloy phases, being highly textured along the bcc [110] direction. Magnetic properties were studied by hysteresis loop measurements at room temperature and they showed reductions in coercivity and squareness values by increasing diameter. First-order reversal curve measurements revealed that, with increasing diameter from 60 to 150 nm, besides a transition from a single domain (SD) state to a pseudo SD state, an increase in the reversible magnetization component of the NWs from 11% to 24% occurred.

Cellulosic nanowhiskers. Theory and application of light scattering from polydisperse spheroids in the Rayleigh-Gans-Debye regime.

PubMed

Braun, Birgit; Dorgan, John R; Chandler, John P

2008-04-01

Mathematical treatment of light scattering within the Rayleigh-Gans-Debye limit for spheroids with polydispersity in both length and diameter is developed and experimentally tested using cellulosic nanowhiskers (CNW). Polydispersity indices are obtained by fitting the theoretical formfactor to experimental data. Good agreement is achieved using a polydispersity of 2.3 for the length, independent of the type of acid used. Diameter polydispersities are 2.1 and 3.0 for sulfuric and hydrochloric acids, respectively. These polydispersities allow the determination of average dimensions from the z-average mean-square radius (z) and the weight-average molecular weight (M w) easily obtained from Berry plots. For cotton linter hydrolyzed by hydrochloric acid, the average length and diameter are 244 and 22 nm. This compares to average length and diameter of 272 and 13 nm for sulfuric acid. This study establishes a new light-scattering methodology as a quick and robust tool for size characterization of polydisperse spheroidal nanoparticles.

Thermoluminescence of the Films, Nanocomposites, and Solutions of the Silicon Organic Polymer Poly(di- n-hexyl silane)

NASA Astrophysics Data System (ADS)

Ostapenko, N. I.; Kerita, O. A.; Ostapenko, Yu. V.

2018-03-01

A comparative study of low-temperature thermoluminescence (5-120 K) of silicon organic polymer poly(di-n-hexyl silane) films, nanocomposites (when the polymer is introduced into nanopores of silica MCM-41 and SBA-15 with diameter of pores 2.8 and 10 nm) as well as solutions of polymer in tetrahydrofuran with different concentrations from 10-3 to 10-5 mol/L was carried out. It was shown that it is possible to control the number of charge carrier traps, as well as their energy distribution by changing the diameter of silica nanopores. It is established that maxima and FWHMs of the thermoluminescence curves of nanocomposites significantly depend on the pore diameter of the nanoporous silica. This result agrees with the data obtained in the investigation of polymer solutions. In the nanocomposite with a minimum pore diameter (2.8 nm), the number and depth of the traps as well as dispersion of their energy are significantly reduced compared to their values in the polymer film.

Interaction of sunscreen TiO2 nanoparticles with skin and UV light: penetration, protection, phototoxicity

NASA Astrophysics Data System (ADS)

Popov, Alexey; Lademann, Jürgen; Priezzhev, Alexander; Myllylä, Risto

2009-07-01

Titanium dioxide (TiO2) nanoparticles are extensively used nowadays in sunscreens as protective compounds for human skin from UV radiation. In this paper, such particles are investigated from the viewpoint of penetration into living skin, UV protective properties (compared with silicon (Si) particles) and as sources of free radicals if UV-irradiated. We show that: a) even after multiple applications, the particles are located within the uppermost 3-μm-thick part of the skin; b) the optimal sizes are found to be 62 nm and 55 nm, respectively for TiO2 and Si particles for 310-nm light and, correspondingly, 122 and 70 nm - for 400-nm radiation; c) if applied onto glass, small particles of 25 nm in diameter produce an increased amount of free radicals compared to the larger ones of 400 nm in diameter and placebo itself; however, if applied onto porcine skin in vitro, there is no statistically distinct difference in the amount of radicals generated by the two kinds of particles on skin and by the skin itself. This proves that although particles as part of sunscreens produce free radicals, the effect is negligible in comparison to the production of radicals by skin in vitro.

RELATIONSHIP BETWEEN MEASURED WATER VAPOR GROWTH AND CHEMISTRY OF ATMOSPHERIC AEROSOL FOR GRAND CANYON, ARIZONA, IN WINTER 1990.

EPA Science Inventory

Size-resolved aerosol growth measurements (growth = moist particle diameter/dry particle diameter) and chemical composition monitoring were conducted during a 3 month period in the winter of 1990 at the South Rim of Grand Canyon National Park, AZ as part of the Navajo Generating ...

Aqueous chemical growth of alpha-Fe2O3-alpha-Cr203 nanocompositethin films

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

Vayssieres, Lionel; Guo, Jinghua; Nordgren, Joseph

2001-06-30

We are reporting here on the inexpensive fabrication and optical properties of an iron(III) oxide chromium(III) oxide nanocomposite thin film of corundum crystal structure. Its novel and unique-designed architecture consists of uniformed, well-defined and oriented nanorods of Hematite (alpha-Fe2O3) of 50 nm in diameter and 500nm in length and homogeneously distributed nonaggregated monodisperse spherical nanoparticles of Eskolaite (alpha-Cr2O3) of 250 nm in diameter. This alpha-Fe2O3 alpha-Cr2O3 nanocomposite thin film is obtained by growing, directly onto transparent polycrystalline conducting substrate, an oriented layer of hematite nanorods and growing subsequently, the eskolaite layer. The synthesis is carried out by a template-free, low-temperature,more » multilayer thin film coating process using aqueous solution of metal salts as precursors. Almost 100 percent of the light is absorbed by the composite film between 300 and 525 nm and 40 percent at 800 nm which yields great expectations as photoanode materials for photovoltaic cells and photocatalytic devices.« less

Effect of heating rate and plant species on the size and uniformity of silver nanoparticles synthesized using aromatic plant extracts

NASA Astrophysics Data System (ADS)

Hernández-Pinero, Jorge Luis; Terrón-Rebolledo, Manuel; Foroughbakhch, Rahim; Moreno-Limón, Sergio; Melendrez, M. F.; Solís-Pomar, Francisco; Pérez-Tijerina, Eduardo

2016-11-01

Mixing aqueous silver solutions with aqueous leaf aromatic plant extracts from basil, mint, marjoram and peppermint resulted in the synthesis of quasi-spherical silver nanoparticles in a range of size between 2 and 80 nm in diameter as analyzed by analytical high-resolution electron microscopy. The average size could be controlled by applying heat to the initial reaction system at different rates of heating, and by the specific botanical species employed for the reaction. Increasing the rate of heating resulted in a statistically significant decrease in the size of the nanoparticles produced, regardless of the species employed. This fact was more evident in the case of marjoram, which decreased the average diameter from 27 nm at a slow rate of heating to 8 nm at a high rate of heating. With regard to the species, minimum sizes of <10 nm were obtained with basil and peppermint, while marjoram and mint yielded an average size between 10 and 25 nm. The results indicate that aromatic plant extracts can be used to achieve the controlled synthesis of metal nanoparticles.

Effect of Morphology and Composition on the Hygroscopicity of Soot Aerosols

NASA Astrophysics Data System (ADS)

Williams, L.; Slowik, J.; Davidovits, P.; Jayne, J.; Kolb, C.; Worsnop, D.; Rudich, Y.

2003-12-01

Freshly generated soot aerosols are initially hydrophobic and unlikely to act as cloud condensation nuclei (CCN). However, during combustion many low vapor pressure gas products are formed that may then condense on existing soot aerosols. Additionally, soot particles may acquire coatings as they age, such as acids, salts, and oxygenated organics. An understanding of this aging process and its effect on soot hygroscopicity is necessary to address the potential of soot to act as a CCN. The transformation of soot from hydrophobic to hydrophilic is the focus of this work. An aim here is to determine the minimum coating required for hygroscopic growth. Soot particles produced by combustion of mixtures of fuel and air are size selected by a Differential Mobility Analyzer (DMA) and entrained in a laminar flow passing through a flow tube. The size selected soot particles are mixed with a controlled amount of the gas phase precursors to produce the coatings to be studied. Initial studies are focused on coatings of H2SO4, NH4NO3, and selected organics. The number of particles per unit volume of air is counted by a Condensation Particle Counter (CPC) and the particles are isokinetically sampled into an Aerosol Mass Spectrometer (AMS). Two distinct types of soot aerosols have been observed depending on the type of fuel and air mixture. With soot produced by the combustion of propane and air, the AMS shows a polydisperse particle size distribution with aerodynamic diameters ranging from 100 nm to 400 nm. The aerodynamic diameter is linearly related to the DMA-determined mobility diameter with the product density x shape factor = 1.2. The organic molecules in this soot are mostly PAH compounds. However, when kerosene is added to the propane flame, the soot particle morphology and composition is strikingly altered. While the DMA shows an essentially unchanged mobility diameter distribution, in the range 100 nm to 400, aerodynamic particle diameter is constant at about 100 nm, independent of the mobility diameter. This type of constancy of the aerodynamic diameter has been observed for soot particles in diesel engine exhaust and has been interpreted in terms of a size-dependent effective density. The soot chemical composition is also altered. In this soot the organics are mainly linear hydrocarbons. The differences between these two types of soot with respect to hygroscopicity and effective area are being investigated.

Circular single domains in hemispherical Permalloy nanoclusters

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

Araujo, Clodoaldo I. L de, E-mail: dearaujo@ufv.br; Fonseca, Jakson M.; Sinnecker, João P.

2014-11-14

We have studied ferromagnetic Permalloy clusters obtained by electrodeposition on n-type silicon. Magnetization measurements reveal hysteresis loops almost independent on temperature and very similar in shape to those obtained in nanodisks with diameter bigger than 150 nm. The spin configuration for the ground state, obtained by micromagnetic simulation, shows topological vortices with random chirality and polarization. This behavior in the small diameter clusters (∼80 nm) is attributed to the Dzyaloshinskii-Moriya interaction that arises in its hemispherical geometries. This magnetization behavior can be utilized to explain the magnetoresistance measured with magnetic field in plane and out of sample plane.

Structure of assemblies of metal nanowires in mesoporous alumina membranes studied by EXAFS, XANES, X-ray diffraction and SAXS.

PubMed

Benfield, Robert E; Grandjean, Didier; Dore, John C; Esfahanian, Hamid; Wu, Zhonghua; Kröll, Michael; Geerkens, Marcus; Schmid, Günter

2004-01-01

Mesoporous alumina membranes ("anodic aluminium oxide", or "AAO") are made by anodic oxidation of aluminium metal. These membranes contain hexagonal arrays of parallel non-intersecting cylindrical pores perpendicular to the membrane surface. By varying the anodisation voltage, the pore diameters are controllable within the range 5-250 nm. We have used AAO membranes as templates for the electrochemical deposition of metals within the pores to produce nanowires. These represent assemblies of one-dimensional quantum wires with prospective applications in electronic, optoelectronic and magnetic devices. Detailed characterisation of the structures of these nanowire assemblies on a variety of length scales is essential to understand their physical properties and evaluate their possible applications. We have used EXAFS, XANES, WAXS, high energy X-ray diffraction and SAXS to study their structure and bonding. In this paper we report the results of our studies of four different nanowire systems supported in AAO membranes. These are the ferromagnetic metals iron and cobalt, the superconducting metal tin, and the semiconductor gallium nitride. Iron nanowires in pores of diameter over the range 12 nm-72 nm are structurally very similar to bcc bulk iron. They have a strong preferred orientation within the alumina pores. Their XANES shows significant differences from that of bulk iron, showing that the electronic structure of the iron nanowires depends systematically on their diameter. Cobalt nanowires are composed of a mixture of hcp and fcc phases, but the ratio of the two phases does not depend in a simple way on the pore diameter or preparation conditions. In bulk cobalt, the fcc beta-phase is normally stable only at high temperatures. Strong preferred orientation of the c-axis in the pores was found. Tin nanowires in alumina membranes with pores diameters between 12 nm and 72 nm have a tetragonal beta-structure at ambient temperature and also at 80 K. Magnetic susceptibility measurements show that they are diamagnetic, and become superconducting at the same temperature as bulk tin (3.7 K). Gallium nitride nanowires have been prepared in alumina membranes with pore diameter 24 nm by a novel method. Gallium nitrate was deposited in the pores from aqueous solution and thermolysed at 1000 degrees C to form Ga2O3, which was reacted with ammonia at 1000 degrees C. The GaN nanowires have the wurtzite structure. Preparation at 1150 degrees C led to the incorporation of aluminium in the GaN. The mesoscopic ordering of the pores in the AAO membranes and their filling by metal nanowires has been studied by SAXS, which shows patterns of Bragg peaks arising from the pore arrays. Additionally, the cobalt nanowires have been the subject of an initial ASAXS study.

Scaffolds for bone regeneration made of hydroxyapatite microspheres in a collagen matrix.

PubMed

Cholas, Rahmatullah; Kunjalukkal Padmanabhan, Sanosh; Gervaso, Francesca; Udayan, Gayatri; Monaco, Graziana; Sannino, Alessandro; Licciulli, Antonio

2016-06-01

Biomimetic scaffolds with a structural and chemical composition similar to native bone tissue may be promising for bone tissue regeneration. In the present work hydroxyapatite mesoporous microspheres (mHA) were incorporated into collagen scaffolds containing an ordered interconnected macroporosity. The mHA were obtained by spray drying of a nano hydroxyapatite slurry prepared by the precipitation technique. X-ray diffraction (XRD) analysis revealed that the microspheres were composed only of hydroxyapatite (HA) phase, and energy-dispersive x-ray spectroscopy (EDS) analysis revealed the Ca/P ratio to be 1.69 which is near the value for pure HA. The obtained microspheres had an average diameter of 6 μm, a specific surface area of 40 m(2)/g as measured by Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis showed a mesoporous structure with an average pore diameter of 16 nm. Collagen/HA-microsphere (Col/mHA) composite scaffolds were prepared by freeze-drying followed by dehydrothermal crosslinking. SEM observations of Col/mHA scaffolds revealed HA microspheres embedded within a porous collagen matrix with a pore size ranging from a few microns up to 200 μm, which was also confirmed by histological staining of sections of paraffin embedded scaffolds. The compressive modulus of the composite scaffold at low and high strain values was 1.7 and 2.8 times, respectively, that of pure collagen scaffolds. Cell proliferation measured by the MTT assay showed more than a 3-fold increase in cell number within the scaffolds after 15 days of culture for both pure collagen scaffolds and Col/mHA composite scaffolds. Attractive properties of this composite scaffold include the potential to load the microspheres for drug delivery and the controllability of the pore structure at various length scales. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of drying environment on grain size of titanium dioxide nano-powder synthesized via sol-gel method

NASA Astrophysics Data System (ADS)

Zandi, Pegah; Hosseini, Elham; Rashchi, Fereshteh

2018-01-01

Titanium dioxide Nano powder has been synthesized from titanium isopropoxide (TTIP) in chloride media by sol-gel method. In this research, the effect of the drying environment, from air to oven drying at 100 °C, calcination time and temperature on nano TiO2 grain size was investigated. The synthesized powder was analyzed by x-ray diffraction and scanning electron microscope. Based on the results, the powder has been crystallized in anatase and rutile phases, due to different calcination temperatures. At temperatures above 600 °C, the Titanium dioxide nano powder has been crystallized as rutile. The crystalline structure of titanium dioxide nano powder changed because of the different calcination temperatures and time applied. The average particle size of the powder dried in air was larger than the powder dried in oven. The minimum particle size of the powder dried in air was 50 nm and in the oven was 9 nm, observed and calculated Williamson-Hall equation. All in all, with overall increasing of calcination time and temperature the grain size increased. Moreover, in the case of temperature, after a certain temperature, the grain size became constant and didn't change significantly.

Precision Optical Coatings for Large Space Telescope Mirrors

NASA Astrophysics Data System (ADS)

Sheikh, David

This proposal “Precision Optical Coatings for Large Space Telescope Mirrors” addresses the need to develop and advance the state-of-the-art in optical coating technology. NASA is considering large monolithic mirrors 1 to 8-meters in diameter for future telescopes such as HabEx and LUVOIR. Improved large area coating processes are needed to meet the future requirements of large astronomical mirrors. In this project, we will demonstrate a broadband reflective coating process for achieving high reflectivity from 90-nm to 2500-nm over a 2.3-meter diameter coating area. The coating process is scalable to larger mirrors, 6+ meters in diameter. We will use a battery-driven coating process to make an aluminum reflector, and a motion-controlled coating technology for depositing protective layers. We will advance the state-of-the-art for coating technology and manufacturing infrastructure, to meet the reflectance and wavefront requirements of both HabEx and LUVOIR. Specifically, we will combine the broadband reflective coating designs and processes developed at GSFC and JPL with large area manufacturing technologies developed at ZeCoat Corporation. Our primary objectives are to: Demonstrate an aluminum coating process to create uniform coatings over large areas with near-theoretical aluminum reflectance Demonstrate a motion-controlled coating process to apply very precise 2-nm to 5- nm thick protective/interference layers to large areas, Demonstrate a broadband coating system (90-nm to 2500-nm) over a 2.3-meter coating area and test it against the current coating specifications for LUVOIR/HabEx. We will perform simulated space-environment testing, and we expect to advance the TRL from 3 to >5 in 3-years.

The influence of shrinkage-cracking on the drying behaviour of White Portland cement using Single-Point Imaging (SPI).

PubMed

Beyea, S D; Balcom, B J; Bremner, T W; Prado, P J; Cross, A R; Armstrong, R L; Grattan-Bellew, P E

1998-11-01

The removal of water from pores in hardened cement paste smaller than 50 nm results in cracking of the cement matrix due to the tensile stresses induced by drying shrinkage. Cracks in the matrix fundamentally alter the permeability of the material, and therefore directly affect the drying behaviour. Using Single-Point Imaging (SPI), we obtain one-dimensional moisture profiles of hydrated White Portland cement cylinders as a function of drying time. The drying behaviour of White Portland cement, is distinctly different from the drying behaviour of related concrete materials containing aggregates.

Fast, reagentless and reliable screening of "white powders" during the bioterrorism hoaxes.

PubMed

Włodarski, Maksymilian; Kaliszewski, Miron; Trafny, Elżbieta Anna; Szpakowska, Małgorzata; Lewandowski, Rafał; Bombalska, Aneta; Kwaśny, Mirosław; Kopczyński, Krzysztof; Mularczyk-Oliwa, Monika

2015-03-01

The classification of dry powder samples is an important step in managing the consequences of terrorist incidents. Fluorescence decays of these samples (vegetative bacteria, bacterial endospores, fungi, albumins and several flours) were measured with stroboscopic technique using an EasyLife LS system PTI. Three pulsed nanosecond LED sources, generating 280, 340 and 460nm were employed for samples excitation. The usefulness of a new 460nm light source for fluorescence measurements of dry microbial cells has been demonstrated. The principal component analysis (PCA) and hierarchical cluster analysis (HCA) have been used for classification of dry biological samples. It showed that the single excitation wavelength was not sufficient for differentiation of biological samples of diverse origin. However, merging fluorescence decays from two or three excitation wavelengths allowed classification of these samples. An experimental setup allowing the practical implementation of this method for the real time fluorescence decay measurement was designed. It consisted of the LED emitting nanosecond pulses at 280nm and two fast photomultiplier tubes (PMTs) for signal detection in two fluorescence bands simultaneously. The positive results of the dry powder samples measurements confirmed that the fluorescence decay-based technique could be a useful tool for fast classification of the suspected "white powders" performed by the first responders. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Self-aggregation of water-dispersible nanocollagen helices.

PubMed

Van Duong, Hau; Chau, Trang The Lieu; Dang, Nhan Thi Thanh; Nguyen, Duc Van; Le, Son Lam; Ho, Thang Sy; Vu, Tuyen Phi; Tran, Thi Thi Van; Nguyen, Thanh-Dinh

2018-02-27

Inspired by nature, collagen is an outstanding polypeptide utilized to exploit its bioactivity and material design for healthcare technologies. In this study, we describe the self-aggregation of water-dispersible nanocollagen helices upon solidification to fabricate different forms of natural collagen materials. Chemically extracted native collagen fibrils are uniform anisotropic nanoparticles with an average diameter of about 50 nm and a high aspect ratio. The as-prepared collagen nanofibrils are soluble in sodium acetate-acetic acid buffer and are dispersible in water, thus generating collagen liquids that are used as distinct biopolymer precursors for materials development. Our interesting findings indicate that water-dispersible collagen-derived alcogels undergo critical point drying to self-arrange hierarchical nanofibrils into helix bundles in collagen sponge-like aerogels. Notably, using lyophilization to remove water in the biopolymer dispersion, a full regeneration of solidified fibers is achieved, producing collagen aerogels with lightweight characteristics similar to natural cottons. The self-aggregation of water-dispersible collagen occurs under freeze-drying conditions to turn individual nanofibrils into sheets with layered structures in the aerogel networks. The development of transparent, water resistant collagen bioplastic-like membranes was achieved by supramolecular self-assembly of water-dispersible collagen nanofibrils. Our efforts present a reliable concept in soft matter for creating promising collagen examples of liquids, hydrogels, aerogels, and membranes to increase utilization value of native collagen for biomedicine, pharmaceuticals, cosmetics, and nutrients.

Effects of ambient relative humidity and solvent properties on the electrospinning of pure hyaluronic acid nanofibers.

PubMed

Yao, Shenglian; Wang, Xiumei; Liu, Xi; Wang, Ronghan; Deng, Changsheng; Cuil, Fuzhai

2013-07-01

Nanofibers exist ubiquitously in natural extracellular matrix (ECM) of all kinds of human tissues forming hydrated interwoven network. Electrospinning nanotechnology has been proven to be a powerful technique to fabricate controllable nanofibers mimicking the natural ECM structures. Hyaluronic acid (HA), as a critical component of natural ECM, has been widely used in tissue engineering and regenerative medicine. In this study, pure HA nanofibers with average diameter of 33 +/- 5 nm, 59 +/- 12 nm, 79 +/- 12 nm and 113 +/- 19 nm were successfully prepared using different electrospinning parameters. The effect of the ambient relative humidity on HA electrospinnability was investigated for the first time in detail, which was proven to be one of the most important factors to control the morphology of HA nanofibers beside the solution properties. A critical value of humidity for a defined HA solution was observed, only below which HA nanofibers with similar diameters and morphologies could be successfully obtained. When the ambient relative humidity was higher than the critical value, the HA nanofibers started dissolving at the cross points and even fused together forming a spreading layer. Moreover, only a small amount of N, N-Dimethylformamide (DMF) was found to be required to promote the electrospinnability of HA solution by mixing with water as solvents. With the increase in the DMF content, the surface tension of the solution decreased significantly, which was thought to be benefit for the stable Taylor cone and fluid jet formation in electrospinning. At the same time, it should be noted that the conductivity of the solution also decreased with the increase of DMF content in the solution, which was believed to be responsible for the increasing diameters of HA nanofibers corresponding to higher DMF content. Controllable HA nanofibers with diameter below 100 nm have great promising for developing novel nanobiomaterials applied in tissue engineering and regenerative medicine.

SPECIATION OF GAS-PHASE AND FINE PARTICLE EMISSIONS FROM BURNING OF FOLIAR FUELS

EPA Science Inventory

Particle size distributions (10-1000 nm aerodynamic diameter), physical and chemical properties of fine particle matter (PM2.5) with aerodynamic diameter <2.5 micrometers, and gas-phase emissions from controlled open burning of assorted taxa were measured. Chemical speciation of ...

Production and Characterization of Nanosilica from Bagasse Through Biosynthesis Using Lactobacilus bulgaricus.

PubMed

Rahmawati, Nanda Yuli; Harisna, Azza Hanief; Khoirunnisa, Wulida; Yasvinawati, Niarisandi; Sumitro, Sutiman Bambang

2016-06-01

Bagasse has a potential as natural resource of nanosilica. Nanosilica biosynthetic production method is better than chemical or physical methods. The aim of this study is to determine the potential of Lactobacillus bulgaricus in nanosilica synthesis, the effect of the long incubation, and the effect of freeze drying to the nanosilica quality. The method consists of two steps. The first is performing biosynthesize using bagasse and Lactobacillus bulgaricus in dark place with temperature of 37 degress C for the period of 24 hours, 48 hours, and 72 hours. The second is analyzing particles and chemical of nanosilica characterization using Fourier Transformer Infrared Spectroscopy (FTIR), Particle Size Analyzer (PSA), X-ray Diffraction (XRD), some microscopes namely stereo, fluorescence, polarizing, Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX). The results show that nanosilica has spherical shaped, amorphous, and able to fluoresce when exposed by UV. The average size of particles are 104.6 nm in the 24 hours length incubated, 67.3 nm in the 48 hours length incubation, and 30.5 nm in the 72 hours length incubation. Samples using freeze drying have more complex and smaller structure than samples using air drying. The lengths of incubation influence the size and shape of nanosilica. Samples using freeze drying enable change the soil structure, and has beneficiary effect to improve soil fertility, as nanofertilizer. Whereas, the samples using air drying may use for glass or biofilm materials.

Formulating food protein-stabilized indomethacin nanosuspensions into pellets by fluid-bed coating technology: physical characterization, redispersibility, and dissolution

PubMed Central

He, Wei; Lu, Yi; Qi, Jianping; Chen, Lingyun; Yin, Lifang; Wu, Wei

2013-01-01

Background Drug nanosuspensions are very promising for enhancing the dissolution and bioavailability of drugs that are poorly soluble in water. However, the poor stability of nanosuspensions, reflected in particle growth, aggregation/agglomeration, and change in crystallinity state greatly limits their applications. Solidification of nanosuspensions is an ideal strategy for addressing this problem. Hence, the present work aimed to convert drug nanosuspensions into pellets using fluid-bed coating technology. Methods Indomethacin nanosuspensions were prepared by the precipitation-ultrasonication method using food proteins (soybean protein isolate, whey protein isolate, β-lactoglobulin) as stabilizers. Dried nanosuspensions were prepared by coating the nanosuspensions onto pellets. The redispersibility, drug dissolution, solid-state forms, and morphology of the dried nanosuspensions were evaluated. Results The mean particle size for the nanosuspensions stabilized using soybean protein isolate, whey protein isolate, and β-lactoglobulin was 588 nm, 320 nm, and 243 nm, respectively. The nanosuspensions could be successfully layered onto pellets with high coating efficiency. Both the dried nanosuspensions and nanosuspensions in their original amorphous state and not influenced by the fluid-bed coating drying process could be redispersed in water, maintaining their original particle size and size distribution. Both the dried nanosuspensions and the original drug nanosuspensions showed similar dissolution profiles, which were both much faster than that of the raw crystals. Conclusion Fluid-bed coating technology has potential for use in the solidification of drug nanosuspensions. PMID:23983465

Effect of Two-Step Metal Organic Chemical Vapor Deposition Growth on Quality, Diameter and Density of InAs Nanowires on Si (111) Substrate

NASA Astrophysics Data System (ADS)

Yu, Hung Wei; Anandan, Deepak; Hsu, Ching Yi; Hung, Yu Chih; Su, Chun Jung; Wu, Chien Ting; Kakkerla, Ramesh Kumar; Ha, Minh Thien Huu; Huynh, Sa Hoang; Tu, Yung Yi; Chang, Edward Yi

2018-02-01

High-density (˜ 80/um2) vertical InAs nanowires (NWs) with small diameters (˜ 28 nm) were grown on bare Si (111) substrates by means of two-step metal organic chemical vapor deposition. There are two critical factors in the growth process: (1) a critical nucleation temperature for a specific In molar fraction (approximately 1.69 × 10-5 atm) is the key factor to reduce the size of the nuclei and hence the diameter of the InAs NWs, and (2) a critical V/III ratio during the 2nd step growth will greatly increase the density of the InAs NWs (from 45 μm-2 to 80 μm-2) and at the same time keep the diameter small. The high-resolution transmission electron microscopy and selected area diffraction patterns of InAs NWs grown on Si exhibit a Wurtzite structure and no stacking faults. The observed longitudinal optic peaks in the Raman spectra were explained in terms of the small surface charge region width due to the small NW diameter and the increase of the free electron concentration, which was consistent with the TCAD program simulation of small diameter (< 40 nm) InAs NWs.

Surveying colloid sedimentation by coplanar waveguides

NASA Astrophysics Data System (ADS)

Duţu, C. A.; Vlad, A.; Roda-Neve, C.; Avram, I.; Sandu, G.; Raskin, J.-P.; Melinte, S.

2016-06-01

By using coplanar waveguides, direct access to the dielectric properties of aqueous solutions of polystyrene beads with different diameters from 330 nm to 10 μm is provided. The relative variation of the transmission parameter with respect to water is monitored, ranging from ˜ {3}% obtained for a 9.5% solution with 330 nm diameter beads to ˜22% for 10 μm diameter particles at the same concentration. To highlight its applicability in biosensing, the technique was further employed to survey the clustering between biotin and streptavidin-coated beads. The transmission parameter displays a ˜50% increase for mixtures containing nine volumes of biotin and one volume of streptavidin-modified beads (4.5 ng μl-1 of streptavidin) and reaches ˜400% higher values when equal volumes of biotin and streptavidin-coated beads (22.5 ng μl-1 of streptavidin) were mixed.

Resonant frequency analysis of Timoshenko nanowires with surface stress for different boundary conditions

NASA Astrophysics Data System (ADS)

He, Qilu; Lilley, Carmen M.

2012-10-01

The influence of both surface and shear effects on the resonant frequency of nanowires (NWs) was studied by incorporating the Young-Laplace equation with the Timoshenko beam theory. Face-centered-cubic metal NWs were studied. A dimensional analysis of the resonant frequencies for fixed-fixed gold (100) NWs were compared to molecular dynamic simulations. Silver NWs with diameters from 10 nm-500 nm were modeled as a cantilever, simply supported and fixed-fixed system for aspect ratios from 2.5-20 to identify the shear, surface, and size effects on the resonant frequencies. The shear effect was found to have a larger significance than surface effects when the aspect ratios were small (i.e., <5) regardless of size for the diameters modeled. Finally, as the aspect ratio grows, the surface effect becomes significant for the smaller diameter NWs.

Shape induced magnetic vortex state in hexagonal ordered cofe nanodot arrays using ultrathin alumina shadow mask

NASA Astrophysics Data System (ADS)

Sellarajan, B.; Saravanan, P.; Ghosh, S. K.; Nagaraja, H. S.; Barshilia, Harish C.; Chowdhury, P.

2018-04-01

The magnetization reversal process of hexagonal ordered CoFe nanodot arrays was investigated as a function of nanodot thickness (td) varying from 10 to 30 nm with fixed diameter. For this purpose, ordered CoFe nanodots with a diameter of 80 ± 4 nm were grown by sputtering using ultra-thin alumina mask. The vortex annihilation and the dynamic spin configuration in the ordered CoFe nanodots were analyzed by means of magnetic hysteresis loops in complement with the micromagnetic simulation studies. A highly pinched hysteresis loop observed at 20 nm thickness suggests the occurrence of vortex state in these nanodots. With increase in dot thickness from 10 to 30 nm, the estimated coercivity values tend to increase from 80 to 175 Oe, indicating irreversible change in the nucleation/annihilation field of vortex state. The measured magnetic properties were then corroborated with the change in the shape of the nanodots from disk to hemisphere through micromagnetic simulation.

Size dependent compressibility of nano-ceria: Minimum near 33 nm

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

Rodenbough, Philip P.; Chemistry Department, Columbia University, New York, New York 10027; Song, Junhua

2015-04-20

We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite sizemore » decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size.« less

GISAXS modelling of helium-induced nano-bubble formation in tungsten and comparison with TEM

NASA Astrophysics Data System (ADS)

Thompson, Matt; Sakamoto, Ryuichi; Bernard, Elodie; Kirby, Nigel; Kluth, Patrick; Riley, Daniel; Corr, Cormac

2016-05-01

Grazing-incidence small angle x-ray scattering (GISAXS) is a powerful non-destructive technique for the measurement of nano-bubble formation in tungsten under helium plasma exposure. Here, we present a comparative study between transmission electron microscopy (TEM) and GISAXS measurements of nano-bubble formation in tungsten exposed to helium plasma in the Large Helical Device (LHD) fusion experiment. Both techniques are in excellent agreement, suggesting that nano-bubbles range from spheroidal to ellipsoidal, displaying exponential diameter distributions with mean diameters μ=0.68 ± 0.04 nm and μ=0.6 ± 0.1 nm measured by TEM and GISAXS respectively. Depth distributions were also computed, with calculated exponential depth distributions with mean depths of 8.4 ± 0.5 nm and 9.1 ± 0.4 nm for TEM and GISAXS. In GISAXS modelling, spheroidal particles were fitted with an aspect ratio ε=0.7 ± 0.1. The GISAXS model used is described in detail.

Control of the Diameter and Chiral Angle Distributions during Production of Single-wall Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Nikolaev, Pavel; Holmes, William; Sosa, Edward; Boul, Peter; Arepalli, Sivaram; Yowell, Leonard

2008-01-01

Many applications of single wall carbon nanotubes (SWCNT), especially in microelectronics, will benefit from use of certain (n,m) nanotube types (metallic, small gap semiconductor, etc.). However, as produced SWCNT samples are polydispersed, with many (n,m) types present and typical approximate 1:2 metal/semiconductor ratio. It has been recognized that production of SWCNTs with narrow 'tube type populations' is beneficial for their use in applications, as well as for the subsequent sorting efforts. In the present work, SWCNTs were produced by a pulsed laser vaporization (PLV) technique. The nanotube type populations were studied with respect to the production temperature with two catalyst compositions: Co/Ni and Rh/Pd. The nanotube type populations were measured via photoluminescence, UV-Vis-NIR absorption and Raman spectroscopy. It was found that in the case of Co/Ni catalyst, decreased production temperature leads to smaller average diameter, exceptionally narrow diameter distribution, and strong preference toward (8,7) nanotubes. The other nanotubes present are distributed evenly in the 7-30 deg chiral angle range. In the case of Rh/Pd catalyst, a decrease in the temperature leads to a small decrease in the average diameter, with the chiral angle distribution skewed towards 30 o and a preference toward (7,6), (8,6) and (8,7) nanotubes. However, the diameter distribution remains rather broad. These results demonstrate that PLV production technique can provide at least partial control over the nanotube (n,m) populations. In addition, these results have implications for the understanding the nanotube nucleation mechanism in the laser oven.

Deep proton writing of high aspect ratio SU-8 micro-pillars on glass

NASA Astrophysics Data System (ADS)

Ebraert, Evert; Rwamucyo, Ben; Thienpont, Hugo; Van Erps, Jürgen

2016-12-01

Deep proton writing (DPW) is a fabrication technology developed for the rapid prototyping of polymer micro-structures. We use SU-8, a negative resist, spincoated in a layer up to 720 μm-thick in a single step on borosilicate glass, for irradiation with a collimated 12 MeV energy proton beam. Micro-pillars with a slightly conical profile are irradiated in the SU-8 layer. We determine the optimal proton fluence to be 1.02 × 104 μm-2, with which we are able to repeatably achieve micro-pillars with a top-diameter of 138 ± 1 μm and a bottom-diameter of 151 ± 3 μm. The smallest fabricated pillars have a top-diameter of 57 ± 5 μm. We achieved a root-mean-square sidewall surface roughness between 19 nm and 35 nm for the fabricated micro-pillars, measured over an area of 5 × 63.7 μm. We briefly discuss initial testing of two potential applications of the fabricated micro-pillars. Using ∼100 μm-diameter pillars as waveguides for gigascale integration optical interconnect applications, has shown a 4.7 dB improvement in optical multimode fiber-to-fiber coupling as compared to the case where an air-gap is present between the fibers at the telecom wavelength of 1550 nm. The ∼140 μm-diameter pillars were used for mold fabrication with silicone casting. The resulting mold can be used for hydrogel casting, to obtain hydrogel replicas mimicking human tissue for in vitro bio-chemical applications.

Construction of supramolecular helical nanofibers using renewable biomaterials: self-assembly of a cytidylic acid-appended bolaamphiphile in lemon juice.

PubMed

Iwaura, Rika; Ohnishi-Kameyama, Mayumi

2012-07-07

We performed the self-assembly of a 1,18-cytidylic acid-appended bolaamphiphile (C18C) in lemon juice, which contained citric acid, and succeeded in forming left-handed helical nanofibers with diameters, lengths, and pitches of ca. 6-7 nm, several hundred nm to 5 μm, and ca. 30-40 nm, respectively.

Cytotoxicity of aluminium oxide nanoparticles towards fresh water algal isolate at low exposure concentrations.

PubMed

Pakrashi, Sunandan; Dalai, Swayamprava; T C, Prathna; Trivedi, Shruti; Myneni, Radhika; Raichur, Ashok M; Chandrasekaran, N; Mukherjee, Amitava

2013-05-15

The growing commercial applications had brought aluminium oxide nanoparticles under toxicologists' purview. In the present study, the cytotoxicity of two different sized aluminium oxide nanoparticles (ANP(1), mean hydrodynamic diameter 82.6±22nm and ANP(2), mean hydrodynamic diameter 246.9±39nm) towards freshwater algal isolate Chlorella ellipsoids at low exposure levels (≤1μg/mL) using sterile lake water as the test medium was assessed. The dissolution of alumina nanoparticles and consequent contribution towards toxicity remained largely unexplored owing to its presumed insoluble nature. Herein, the leached Al(3+) ion mediated toxicity has been studied along with direct particulate toxicity to bring out the dynamics of toxicity through colloidal stability, biochemical, spectroscopic and microscopic analyses. The mean hydrodynamic diameter increased with time both for ANP(1) [82.6±22nm (0h) to 246.3±59nm (24h), to 1204±140nm (72h)] and ANP(2) [246.9±39nm (0h) to 368.28±48nm (24h), to 1225.96±186nm (72h)] signifying decreased relative abundance of submicron sized particles (<1000nm). The detailed cytotoxicity assays showed a significant reduction in the viability dependent on dose and exposure. A significant increase in ROS and LDH levels were noted for both ANPs at 1μg/mL concentration. The zeta potential and FT-IR analyses suggested surface chemical interaction between nanoparticles and algal cells. The substantial morphological changes and cell wall damage were confirmed through microscopic analyses (SEM, TEM, and CLSM). At 72h, significant Al(3+) ion release in the test medium [0.092μg/mL for ANP(1), and 0.19μg/mL for ANP(2)] was noted, and the resulting suspension containing leached ions caused significant cytotoxicity, revealing a substantial ionic contribution. This study indicates that both the nano-size and ionic dissolution play a significant role in the cytotoxicity of ANPs towards freshwater algae, and the exposure period largely determines the prevalent mode of nano-toxicity. Copyright © 2013 Elsevier B.V. All rights reserved.

High-voltage electric-field-induced growth of aligned ``cow-nipple-like'' submicro-nano carbon isomeric structure via chemical vapor deposition

NASA Astrophysics Data System (ADS)

Liao, Chengwei; Zhang, Yupeng; Pan, Chunxu

2012-12-01

In this study, a novel vertically aligned carbon material, named "cow-nipple-like" submicro-nano carbon isomeric structure, was synthesized by the thermal decomposition of C2H2 in a chemical-vapor deposition system with a high-voltage external electric field. The microstructures were characterized by using scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy, respectively. The results revealed that (1) the total height of the carbon isomeric structure was in a rang of 90-250 nm; (2) the carbon isomeric structure consisted of a submicro- or nano-sized hemisphere carbon ball with 30-120 nm in diameter at the bottom and a vertically grown carbon nanotube with 10-40 nm in diameter upon the carbon ball; (3) there was a sudden change in diameter at the junction of the carbon ball and carbon nanotube. In addition, the carbon isomeric structure showed an excellent controllability, that is, the density, height, and diameter could be controlled effectively by adjusting the precursor ferrocene concentration in the catalytic solution and C2H2 ventilation time. A possible growth model was proposed to describe the formation mechanism, and a theoretic calculation was carried out to discuss the effect of high-voltage electric field upon the growth of the carbon isomeric structure.

The effect of dimensionality of nanostructured carbon on the architecture of organic-inorganic hybrid materials.

PubMed

Misra, R D K; Depan, D; Shah, J

2013-08-21

The natural tendency of carbon nanotubes (CNTs) to agglomerate is an underlying reason that prevents the realization of their full potential. On the other hand, covalent functionalization of CNTs to control dispersion leads to disruption of π-conjugation in CNTs and the non-covalent functionalization leads to a weak CNT-polymer interface. To overcome these challenges, we describe the characteristics of fostering of direct nucleation of polymers on nanostructured carbon (CNTs of diameters (~2-200 nm), carbon nanofibers (~200-300 nm), and graphene), which culminates in interfacial adhesion, resulting from electrostatic and van der Waals interaction in the hybrid nanostructured carbon-polymer architecture. Furthermore, the structure is tunable through a change in undercooling. High density polyethylene and polypropylene were selected as two model polymers and two sets of experiments were carried out. The first set of experiments was carried out using CNTs of diameter ~2-5 nm to explore the effect of undercooling and polymer concentration. The second set of experiments was focused on studying the effect of dimensionality on geometrical confinements. The periodic crystallization of polyethylene on small diameter CNTs is demonstrated to be a consequence of the geometrical confinement effect, rather than epitaxy, such that petal-like disks nucleate on large diameter CNTs, carbon nanofibers, and graphene. The application of the process is illustrated in terms of fabricating a system for cellular uptake and bioimaging.

Optimization and characterization of high pressure homogenization produced chemically modified starch nanoparticles.

PubMed

Ding, Yongbo; Kan, Jianquan

2017-12-01

Chemically modified starch (RS4) nanoparticles were synthesized through homogenization and water-in-oil mini-emulsion cross-linking. Homogenization was optimized with regard to z-average diameter by using a three-factor-three-level Box-Behnken design. Homogenization pressure (X 1 ), oil/water ratio (X 2 ), and surfactant (X 3 ) were selected as independent variables, whereas z-average diameter was considered as a dependent variable. The following optimum preparation conditions were obtained to achieve the minimum average size of these nanoparticles: 50 MPa homogenization pressure, 10:1 oil/water ratio, and 2 g surfactant amount, when the predicted z-average diameter was 303.6 nm. The physicochemical properties of these nanoparticles were also determined. Dynamic light scattering experiments revealed that RS4 nanoparticles measuring a PdI of 0.380 and an average size of approximately 300 nm, which was very close to the predicted z-average diameter (303.6 nm). The absolute value of zeta potential of RS4 nanoparticles (39.7 mV) was higher than RS4 (32.4 mV), with strengthened swelling power. X-ray diffraction results revealed that homogenization induced a disruption in crystalline structure of RS4 nanoparticles led to amorphous or low-crystallinity. Results of stability analysis showed that RS4 nanosuspensions (particle size) had good stability at 30 °C over 24 h.

Growth control of carbon nanotubes using by anodic aluminum oxide nano templates.

PubMed

Park, Yong Seob; Choi, Won Seek; Yi, Junsin; Lee, Jaehyeong

2014-05-01

Anodic Aluminum Oxide (AAO) template prepared in acid electrolyte possess regular and highly anisotropic porous structure with pore diameter range from five to several hundred nanometers, and with a density of pores ranging from 10(9) to 10(11) cm(-2). AAO can be used as microfilters and templates for the growth of CNTs and metal or semiconductor nanowires. Varying anodizing conditions such as temperature, electrolyte, applied voltage, anodizing and widening time, one can control the diameter, the length, and the density of pores. In this work, we deposited Al thin film by radio frequency magnetron sputtering method to fabricate AAO nano template and synthesized multi-well carbon nanotubes on a glass substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). AAO nano-porous templates with various pore sizes and depths were introduced to control the dimension and density of CNT arrays. The AAO nano template was synthesize on glass by two-step anodization technique. The average diameter and interpore distance of AAO nano template are about 65 nm and 82 nm. The pore density and AAO nano template thickness are about 2.1 x 10(10) pores/cm2 and 1 microm, respectively. Aligned CNTs on the AAO nano template were synthesized by MPECVD at 650 degrees C with the Ni catalyst layer. The length and diameter of CNTs were grown 2 microm and 50 nm, respectively.

Tailoring magnetic properties in arrays of pulse-electrodeposited Co nanowires: The role of Cu additive

NASA Astrophysics Data System (ADS)

Esmaeili, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

2016-01-01

In this study, we aim to report the role of Cu additive in arrays of pulse-electrodeposited Co nanowires (NWs) with diameters from 30 to 75 nm, embedded in porous aluminum oxide templates. This features the role of Cu additive in composition and crystalline characteristics as well as in the magnetic properties of Co NWs. Increasing the duration of off-time between pulses during the electrodeposition of Co NWs made it possible to increase the amount of Cu content, so that Co-rich CoCu NWs were obtained. The parallel coercivity and squareness values increased up to 1500 Oe and 0.8 for 30 nm diameter Co94Cu6 NWs, starting from 500 Oe and 0.3 for pure Co NWs. On the other hand, although there was a substantial difference between the crystalline characteristics of 75 nm diameter pure Co and CoCu NWs, no considerable change in their magnetic properties was observed using hysteresis loop measurements. In this respect, the first-order reversal curve (FORC) analysis revealed strong inter-wire magnetostatic interactions for the CoCu NWs. Moreover, we studied the effect of thermal annealing, which resulted in an increase in the coercivity of CoCu NWs with different diameters up to 15%. As a result, the addition of small amount of Cu provides an alternative approach to tailoring the magnetic properties of Co NWs.

Development of an aerosol microphysical module: Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS)

NASA Astrophysics Data System (ADS)

Matsui, H.; Koike, M.; Kondo, Y.; Fast, J. D.; Takigawa, M.

2014-09-01

Number concentrations, size distributions, and mixing states of aerosols are essential parameters for accurate estimations of aerosol direct and indirect effects. In this study, we develop an aerosol module, designated the Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS), that can explicitly represent these parameters by considering new particle formation (NPF), black carbon (BC) aging, and secondary organic aerosol (SOA) processes. A two-dimensional bin representation is used for particles with dry diameters from 40 nm to 10 μm to resolve both aerosol sizes (12 bins) and BC mixing states (10 bins) for a total of 120 bins. The particles with diameters between 1 and 40 nm are resolved using additional eight size bins to calculate NPF. The ATRAS module is implemented in the WRF-Chem model and applied to examine the sensitivity of simulated mass, number, size distributions, and optical and radiative parameters of aerosols to NPF, BC aging, and SOA processes over East Asia during the spring of 2009. The BC absorption enhancement by coating materials is about 50% over East Asia during the spring, and the contribution of SOA processes to the absorption enhancement is estimated to be 10-20% over northern East Asia and 20-35% over southern East Asia. A clear north-south contrast is also found between the impacts of NPF and SOA processes on cloud condensation nuclei (CCN) concentrations: NPF increases CCN concentrations at higher supersaturations (smaller particles) over northern East Asia, whereas SOA increases CCN concentrations at lower supersaturations (larger particles) over southern East Asia. The application of ATRAS in East Asia also shows that the impact of each process on each optical and radiative parameter depends strongly on the process and the parameter in question. The module can be used in the future as a benchmark model to evaluate the accuracy of simpler aerosol models and examine interactions between NPF, BC aging, and SOA processes under different meteorological conditions and emissions.

Numerical analysis of single and multiple particles of Belchatow lignite dried in superheated steam

NASA Astrophysics Data System (ADS)

Zakrzewski, Marcin; Sciazko, Anna; Komatsu, Yosuke; Akiyama, Taro; Hashimoto, Akira; Kaneko, Shozo; Kimijima, Shinji; Szmyd, Janusz S.; Kobayashi, Yoshinori

2018-03-01

Low production costs have contributed to the important role of lignite in the energy mixes of numerous countries worldwide. High moisture content, though, diminishes the applicability of lignite in power generation. Superheated steam drying is a prospective method of raising the calorific value of this fuel. This study describes the numerical model of superheated steam drying of lignite from the Belchatow mine in Poland in two aspects: single and multi-particle. The experimental investigation preceded the numerical analysis and provided the necessary data for the preparation and verification of the model. Spheres of 2.5 to 30 mm in diameter were exposed to the drying medium at the temperature range of 110 to 170 °C. The drying kinetics were described in the form of moisture content, drying rate and temperature profile curves against time. Basic coal properties, such as density or specific heat, as well as the mechanisms of heat and mass transfer in the particular stages of the process laid the foundations for the model construction. The model illustrated the drying behavior of a single particle in the entire range of steam temperature as well as the sample diameter. Furthermore, the numerical analyses of coal batches containing particles of various sizes were conducted to reflect the operating conditions of the dryer. They were followed by deliberation on the calorific value improvement achieved by drying, in terms of coal ingredients, power plant efficiency and dryer input composition. The initial period of drying was found crucial for upgrading the quality of coal. The accuracy of the model is capable of further improvement regarding the process parameters.

Evaluation of 405 nm monochromatic light for inactivation of tulane virus on blueberry surfaces

USDA-ARS?s Scientific Manuscript database

The aim of this study was to evaluate the potential of 405 nm light as an intervention for virus contaminated blueberries. Tulane virus-contaminated-blueberries were treated with 4.2 mW/sq cm of 405 nm light for 5 to 30 min. To mitigate thermal heating due to the intense light, a dry ice-chilled ni...

Capacitively Coupled Plasma Discharge of Ionic Liquid Solutions to Synthesize Carbon Dots as Fluorescent Sensors.

PubMed

Ke, Ching-Bin; Lu, Te-Ling; Chen, Jian-Lian

2018-05-26

Oxygen and nitrogen capacitively coupled plasma (CCP) was used to irradiate mixtures of aliphatic acids in high boiling point solvents to synthesize fluorescent carbon dots (C-dots). With a high fluorescence intensity, the C-dots obtained from the O₂/CCP radiation of a 1-ethyl-3-methylimidazolium dicyanamide ionic liquid solution of citric acid were characterized with an average diameter of 8.6 nm (σ = 1.1 nm), nitrogen and oxygen bonding functionalities, excitation-independent emissions, and upconversion fluorescence. Through dialysis of the CCP-treated C-dots, two emissive surface states corresponding to their respective functionalities and emissions were identified. The fluorescence spectrum of the CCP-treated C-dots was different from that of the microwave irradiation and possessed higher intensity than that of hydrothermal pyrolysis. By evaluation of the fluorescence quenching effect on flavonoids and metal ions, the CCP-treated C-dots showed a high selectivity for quercetin and sensitivity to Hg 2+ . Based on the Perrin model, a calibration curve ( R ² = 0.9992) was established for quercetin ranging from 2.4 μM to 119 μM with an LOD (limit of detection) = 0.5 μM. The quercetin in the ethanol extract of the sun-dried peel of Citrus reticulata cv. Chachiensis was determined by a standard addition method to be 4.20 ± 0.15 mg/g with a matrix effect of 8.16%.

On the Role of low-energy electrons in the radiosensitization of DNA by gold nanoparticles

PubMed Central

Xiao, Fangxing; Zheng, Yi; Cloutier, Pierre; He, Yunhui; Hunting, Darel; Sanche, Léon

2013-01-01

Four different gold nanoparticle (GNP) preparations, including nude GNP and GNP coated either with thiolated undecane (S-C11H23), or with dithiolated diethylenetriaminepentaacetic (DTDTPA) or gadolinium (Gd) DTDTPA chelating agents were synthesized. The average diameters, for each type of nanoparticle are 5 nm, 10 and 13 nm, respectively. Dry films of plasmid DNA pGEM-3Zf(-), DNA with bound GNP and DNA with coated GNP were bombarded with 60 keV electrons. The yields of single and double strand breaks were measured as a function of exposure by electrophoresis. The binding of only one GNP without coating to DNA containing 3197 base pairs increases single and double strand breaks by a factor of 2.3 while for GNP coated with S-C11H23 this factor is reduced to 1.6. GNP coated with the DTDTPA and DTDTPA:Gd in same ratio with DNA, produce essentially no increment in damage. These results could be explained by the attenuation by the coatings of the intensity of low energy photoelectrons emitted from GNP. Thus, coatings of GNP may considerably attenuate short-range low energy electrons emitted from gold, leading to a considerable decrease of radiosensitization. According to our results, the highest radiosensitization should be obtained with GNP having the shortest possible ligand, directed to the DNA of cancer cells. PMID:22024607

Effect of BaTiO3 nano-particles on breakdown performance of propylene carbonate.

PubMed

Hou, Yanpan; Zhang, Zicheng; Zhang, Jiande; Liu, Zhuofeng; Song, Zuyin

2015-05-01

As an alternative to water, propylene carbonate (PC) has a good application prospect in the compact pulsed power sources for its breakdown strength higher than that of water, resistivity bigger than 10(9) Ω m, and low freezing temperature (-49 °C). In this paper, the investigation into dielectric breakdown of PC and PC-based nano-fluids (NFs) subjected to high amplitude electric field is presented with microsecond pulses applied to a 1 mm gap full of PC or NFs between spherical electrodes. One kind of NF is composed of PC mixed with 0.5-1.4 vol. % BaTiO3 (BT) nano-particles of mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol. % BT nano-particles of mean diameter ≈30 nm. The experimental results demonstrate the rise of permittivity and improvement of the breakdown strength of NFs compared with PC. Moreover, it is found that there exists an optimum fraction for these NFs corresponding to tremendous surface area in nano-composites with finite mesoscopic thickness. In concrete, the dielectric breakdown voltage of NFs is 33% higher than that of PC as the volume concentration of nano-particles with a 100 nm diameter is 0.9% and the breakdown voltage of NFs is 40% higher as the volume concentration of nano-particles with a 30 nm diameter is 0.6%. These phenomena are considered as the dielectric breakdown voltage of PC-based NFs is increased because the interfaces between nano-fillers and PC matrices provide myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.

Density Functional Theory Study of Oxygen Reduction Activity on Ultrathin Platinum Nanotubes

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

Matanovic, Ivana; Kent, Paul; Garzon, Fernando

2012-07-13

The structure, stability, and catalytic activity of a number of single- and double-wall platinum (n,m) nanotubes ranging in diameter from 0.3 to 2.0 nm were studied using plane-wave based density functional theory in the gas phase and water environment. The change in the catalytic activity toward the oxygen reduction reaction (ORR) with the size and chirality of the nanotube was studied by calculating equilibrium adsorption potentials for ORR intermediates and by constructing free energy diagrams in the ORR dissociative mechanism network. In addition, the stability of the platinum nanotubes is investigated in terms of electrochemical dissolution potentials and by determiningmore » the most stable state of the material as a function of pH and potential, as represented in Pourbaix diagrams. Our results show that the catalytic activity and the stability toward electrochemical dissolution depend greatly on the diameter and chirality of the nanotube. On the basis of the estimated overpotentials for ORR, we conclude that smaller, approximately 0.5 nm in diameter single-wall platinum nanotubes consistently show a huge, up to 400 mV larger overpotential than platinum, indicating very poor catalytic activity toward ORR. This is the result of substantial structural changes induced by the adsorption of any chemical species on these tubes. Single-wall n = m platinum nanotubes with a diameter larger than 1 nm have smaller ORR overpotentials than bulk platinum for up to 180 mV and thus show improved catalytic activity relative to bulk. We also predict that these nanotubes can endure the highest cell potentials but dissolution potentials are still for 110 mV lower than for the bulk, indicating a possible corrosion problem.« less

Wintertime hygroscopicity and volatility of ambient urban aerosol particles

NASA Astrophysics Data System (ADS)

Enroth, Joonas; Mikkilä, Jyri; Németh, Zoltán; Kulmala, Markku; Salma, Imre

2018-04-01

Hygroscopic and volatile properties of atmospheric aerosol particles with dry diameters of (20), 50, 75, 110 and 145 nm were determined in situ by using a volatility-hygroscopicity tandem differential mobility analyser (VH-TDMA) system with a relative humidity of 90 % and denuding temperature of 270 °C in central Budapest during 2 months in winter 2014-2015. The probability density function of the hygroscopic growth factor (HGF) showed a distinct bimodal distribution. One of the modes was characterised by an overall mean HGF of approximately 1.07 (this corresponds to a hygroscopicity parameter κ of 0.033) independently of the particle size and was assigned to nearly hydrophobic (NH) particles. Its mean particle number fraction was large, and it decreased monotonically from 69 to 41 % with particle diameter. The other mode showed a mean HGF increasing slightly from 1.31 to 1.38 (κ values from 0.186 to 0.196) with particle diameter, and it was attributed to less hygroscopic (LH) particles. The mode with more hygroscopic particles was not identified. The probability density function of the volatility GF (VGF) also exhibited a distinct bimodal distribution with an overall mean VGF of approximately 0.96 independently of the particle size, and with another mean VGF increasing from 0.49 to 0.55 with particle diameter. The two modes were associated with less volatile (LV) and volatile (V) particles. The mean particle number fraction for the LV mode decreased from 34 to 21 % with particle diameter. The bimodal distributions indicated that the urban atmospheric aerosol contained an external mixture of particles with a diverse chemical composition. Particles corresponding to the NH and LV modes were assigned mainly to freshly emitted combustion particles, more specifically to vehicle emissions consisting of large mass fractions of soot likely coated with or containing some water-insoluble organic compounds such as non-hygroscopic hydrocarbon-like organics. The hygroscopic particles were ordinarily volatile. They could be composed of moderately transformed aged combustion particles consisting of partly oxygenated organics, inorganic salts and soot. The larger particles contained internally mixed non-volatile chemical species as a refractory residual in 20-25 % of the aerosol material (by volume).

7 CFR 52.774 - Fill of container.

Code of Federal Regulations, 2013 CFR

2013-01-01

... the contents of the container upon a U.S. Standard No. 8 circular sieve of proper diameter containing... product evenly over the sieve. Without shifting the product, incline the sieve at an angle of 17° to 20... weight of the sieve and product less the weight of the dry sieve. A sieve eight inches in diameter is...

7 CFR 52.774 - Fill of container.

Code of Federal Regulations, 2014 CFR

2014-01-01

... the contents of the container upon a U.S. Standard No. 8 circular sieve of proper diameter containing... product evenly over the sieve. Without shifting the product, incline the sieve at an angle of 17° to 20... weight of the sieve and product less the weight of the dry sieve. A sieve eight inches in diameter is...

Thinning and burning in dry coniferous forests of the Western United States: effectiveness in altering diameter distributions

Treesearch

Andrew Youngblood

2010-01-01

Western United States land managers are conducting fuel reduction and forest restoration treatments in forests with altered structural conditions. As part of the National Fire and Fire Surrogate (FFS) study, thinning and burning treatments were evaluated for changing forest structure. Shifts between pretreatment and posttreatment diameter distributions at seven western...

Stellar integrated fluxes for 216 stars in the wavelength range 380 nm-900 NM

NASA Astrophysics Data System (ADS)

Petford, A. D.; Blackwell, D. E.; Booth, A. J.; Haddock, D. J.; Leggett, S. K.; Mountain, C. M.; Selby, M. J.; Arribas, S.

1988-09-01

The paper reports measurements of the integrated fluxes over the wavelength range 380 nm - 900 nm for 216 stars using a Reticon spectrometer in conjunction with the 1 m Kapteyn telescope of the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Methods are proposed for deriving visible integrated fluxes from 13-colour photometry, UBVRI and BV photometry. Such fluxes are useful for deriving stellar effective temperatures and angular diameters.

Graphene-doped polymer nanofibers for low-threshold nonlinear optical waveguiding

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

Meng, Chao; Yu, Shao-Liang; Wang, Hong -Qing

Graphene-doped polymer nanofibers are fabricated by taper drawing of solvated polyvinyl alcohol doped with liquid-phase exfoliated graphene flakes. Nanofibers drawn this way typically have diameters measured in hundreds of nanometers and lengths in tens of millimeters; they show excellent uniformity and surface smoothness for optical waveguiding. Owing to their tightly confined waveguiding behavior, light–matter interaction in these subwavelength-diameter nanofibers is significantly enhanced. Using approximately 1350-nm-wavelength femto-second pulses, we demonstrate saturable absorption behavior in these nanofibers with a saturation threshold down to 0.25 pJ pulse -1 (peak power ~1.3 W). Additionally, using 1064-nm-wavelength nanosecond pulses as switching light, we show all-opticalmore » modulation of a 1550-nm-wavelength signal light guided along a single nanofiber with a switching peak power of ~3.2 W.« less

The effect of processing on the properties of CuInS2 nanomaterials synthesized by simple hot injection route

NASA Astrophysics Data System (ADS)

Chen, Qin-Miao; Zhou, Fang-Fang; Yuan, Hong-Chun; Chen, Jin; Ni, Yi; Zhu, Xi-Fang; Dou, Xiao-Ming

2017-07-01

Chalcopyrite and wurtzite CuInS2 (CIS) nanomaterials were synthesized from Cu2+, In3+, thiourea with or without triethanolamine (TEA) by simple hot injection method at low temperature. The effect of synthesis duration on the various properties of the synthesized CIS nanomaterials was studied. It shows that for chalcopyrite CIS, the optimal synthesis duration is 60 min and the synthesized nanomaterial is in spherical shape with diameter of about 90 nm. However, for the wurtzite CIS, the optimal synthesis duration should reach 150 min and the synthesized nanomaterial looks like nanoplate with thicknesses of ˜10 nm and diameters near 100 nm. The photovoltaic characteristics of two types of nanomaterials are quite different. This study may contribute to the synthesis of CIS nanomaterials at low temperatures.

Graphene-doped polymer nanofibers for low-threshold nonlinear optical waveguiding

DOE PAGES

Meng, Chao; Yu, Shao-Liang; Wang, Hong -Qing; ...

2015-11-06

Graphene-doped polymer nanofibers are fabricated by taper drawing of solvated polyvinyl alcohol doped with liquid-phase exfoliated graphene flakes. Nanofibers drawn this way typically have diameters measured in hundreds of nanometers and lengths in tens of millimeters; they show excellent uniformity and surface smoothness for optical waveguiding. Owing to their tightly confined waveguiding behavior, light–matter interaction in these subwavelength-diameter nanofibers is significantly enhanced. Using approximately 1350-nm-wavelength femto-second pulses, we demonstrate saturable absorption behavior in these nanofibers with a saturation threshold down to 0.25 pJ pulse -1 (peak power ~1.3 W). Additionally, using 1064-nm-wavelength nanosecond pulses as switching light, we show all-opticalmore » modulation of a 1550-nm-wavelength signal light guided along a single nanofiber with a switching peak power of ~3.2 W.« less

In-situ Observation of Size and Irradiation Effects on Thermoelectric Properties of Bi-Sb-Te Nanowire in FIB Trimming

PubMed Central

Chien, Chia-Hua; Lee, Ping-Chung; Tsai, Wei-Han; Lin, Chien-Hung; Lee, Chih-Hao; Chen, Yang-Yuan

2016-01-01

In this report, the thermoelectric properties of a Bi0.8Sb1.2Te2.9 nanowire (NW) were in-situ studied as it was trimmed from 750 down to 490 and 285 nm in diameter by a focused ion beam. While electrical and thermal conductivities both indubitably decrease with the diameter reduction, the two physical properties clearly exhibit different diameter dependent behaviors. For 750 and 490 nm NWs, much lower thermal conductivities (0.72 and 0.69 W/m-K respectively) were observed as compared with the theoretical prediction of Callaway model. The consequence indicates that in addition to the size effect, extra phonon scattering of defects created by Ga ion irradiation was attributed to the reduction of thermal conductivities. As the NW was further trimmed down to 285 nm, both the electrical and thermal conductivities exhibited a dramatic reduction which was ascribed to the formation of amorphous structure due to Ga ion irradiation. The size dependence of Seebeck coefficient and figure of merit (ZT) show the maximum at 750 nm, then decrease linearly with size decrease. The study not only provides the thoroughly understanding of the size and defect effects on the thermoelectric properties but also proposes a possible method to manipulate the thermal conductivity of NWs via ion irradiation. PMID:27030206

Determination of Conjugation Efficiency of Antibodies and Proteins to the Superparamagnetic Iron Oxide Nanoparticles by Capillary Electrophoresis with Laser-Induced Fluorescence Detection

NASA Astrophysics Data System (ADS)

Wang, Fu-Hua; Yoshitake, Takashi; Kim, Do-Kyung; Muhammed, Mamoun; Bjelke, Börje; Kehr, Jan

2003-04-01

The method based on capillary electrophoresis with laser-induced fluorescence detection (CE/LIF) was developed for determination of magnetic iron oxide nanoparticles (hydrodynamic diameters of 100 nm) functionalized with molecules containing primary amino groups. The magnetic nanoparticles with carboxylic or aminopropyl-trimethoxysilane groups at their surface were conjugated to the model proteins (bovine serum albumin, BSA; streptavidin or goat anti-rabbit immunoglobulin G, IgG) using carbodiimide as a zero-length cross-linker. The nanoparticle-protein conjugates (hydrodynamic diameter 163-194 nm) were derivatized with naphthalene-2,3-dicarboxaldehyde reagent and separated by CE/LIF with a helium-cadmium laser (excitation at 442 nm, emission at 488 nm). The separations were carried out by using a fused-silica capillary (effective length 48 cm, inner diameter 75 um) and 100 mM sodium borate buffer (pH 9.2), the potential was 30 kV. The detection limit for BSA-conjugate was 1.3 pg/10 nl, i.e. about 20 amol. The present method provides an efficient and fast tool for sensitive determination of the efficacy of biomolecular functionalization of magnetic nanoparticles. The CE/LIF technique requires only negligible sample volumes for analysis, which is especially suitable for controlling the process of preparation of functionalized nanoparticles with unique properties aimed to be used for diagnostic or therapeutic purposes.

Influence of Thermal Modification and Morphology of TiO₂ Nanotubes on Their Electrochemical Properties for Biosensors Applications.

PubMed

Arkusz, Katarzyna; Paradowska, Ewa; Nycz, Marta; Krasicka-Cydzik, Elżzbieta

2018-05-01

The morphology of self-assembled TiO2 nanotubes layer plays a key role in electrical conductivity and biocompatibility properties in terms of cell proliferation, adhesion and mineralization. Many research studies have been reported in using a TiO2 nanotubes for different medical applications, there is a lack of unified correlation between TNT morphology and its electrochemical properties. The aim of this study was to examine the effects of diameter and annealing conditions on TiO2 nanotubes with identical height and their behaviour as biosensor platform. TiO2 nanotubes layer, 1000 nm thick with nanotubes of diameters in range: 25 ÷ 100 nm, was prepared by anodizing of the titanium foil in ethylene glycol solution. To change the crystal structure and improve the electrical conductivity of the semiconductive TiO2 nanotubes layer the thermal treatment by annealing in argon, nitrogen or air was used. Basing on the electrochemical tests, the XPS and scanning microscopy examinations, as well as the contact angle measurements and the amperometric detection of potassium ferricyanide, it was concluded that the 1000 nm thick TiO2 nanotubes layer with nanotubes of 50 nm diameter, annealed in argon, showed the best physicochemical properties, which helps investigate the adsorption immobilization mechanism. The possibility of using TNT as a biosensor platform was confirmed in hydrogen detection.

Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores.

PubMed

Pardon, Gaspard; Gatty, Hithesh K; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

2013-01-11

Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al(2)O(3)) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al(2)O(3) layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al(2)O(3) using ALD.

Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores

NASA Astrophysics Data System (ADS)

Pardon, Gaspard; Gatty, Hithesh K.; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

2013-01-01

Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al2O3) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al2O3 layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al2O3 using ALD.

Cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals

NASA Astrophysics Data System (ADS)

Kumar, P.; Sokolik, I. N.; Nenes, A.

2011-08-01

This study reports laboratory measurements of particle size distributions, cloud condensation nuclei (CCN) activity, and droplet activation kinetics of wet generated aerosols from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. The dependence of critical supersaturation, sc, on particle dry diameter, Ddry, is used to characterize particle-water interactions and assess the ability of Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler theory (KT) to describe the CCN activity of the considered samples. Wet generated regional dust samples produce unimodal size distributions with particle sizes as small as 40 nm, CCN activation consistent with KT, and exhibit hygroscopicity similar to inorganic salts. Wet generated clays and minerals produce a bimodal size distribution; the CCN activity of the smaller mode is consistent with KT, while the larger mode is less hydrophilic, follows activation by FHH-AT, and displays almost identical CCN activity to dry generated dust. Ion Chromatography (IC) analysis performed on regional dust samples indicates a soluble fraction that cannot explain the CCN activity of dry or wet generated dust. A mass balance and hygroscopicity closure suggests that the small amount of ions (from low solubility compounds like calcite) present in the dry dust dissolve in the aqueous suspension during the wet generation process and give rise to the observed small hygroscopic mode. Overall these results identify an artifact that may question the atmospheric relevance of dust CCN activity studies using the wet generation method. Based on the method of threshold droplet growth analysis, wet generated mineral aerosols display similar activation kinetics compared to ammonium sulfate calibration aerosol. Finally, a unified CCN activity framework that accounts for concurrent effects of solute and adsorption is developed to describe the CCN activity of aged or hygroscopic dusts.

Influence of smectite suspension structure on sheet orientation in dry sediments: XRD and AFM applications.

PubMed

Zbik, Marek S; Frost, Ray L

2010-06-15

The structure-building phenomena within clay aggregates are governed by forces acting between clay particles. Measurements of such forces are important to understand in order to manipulate the aggregate structure for applications such as dewatering of mineral processing tailings. A parallel particle orientation is required when conducting XRD investigation on the oriented samples and conduct force measurements acting between basal planes of clay mineral platelets using atomic force microscopy (AFM). To investigate how smectite clay platelets were oriented on silicon wafer substrate when dried from suspension range of methods like SEM, XRD and AFM were employed. From these investigations, we conclude that high clay concentrations and larger particle diameters (up to 5 microm) in suspension result in random orientation of platelets in the substrate. The best possible laminar orientation in the clay dry film, represented in the XRD 001/020 intensity ratio of 47 was obtained by drying thin layers from 0.02 wt.% clay suspensions of the natural pH. Conducted AFM investigations show that smectite studied in water based electrolytes show very long-range repulsive forces lower in strength than electrostatic forces from double-layer repulsion. It was suggested that these forces may have structural nature. Smectite surface layers rehydrate in water environment forms surface gel with spongy and cellular texture which cushion approaching AFM probe. This structural effect can be measured in distances larger than 1000 nm from substrate surface and when probe penetrate this gel layer, structural linkages are forming between substrate and clay covered probe. These linkages prevent subsequently smooth detachments of AFM probe on way back when retrieval. This effect of tearing new formed structure apart involves larger adhesion-like forces measured in retrieval. It is also suggested that these effect may be enhanced by the nano-clay particles interaction. 2010 Elsevier Inc. All rights reserved.

Aerosol optical properties relevant to regional remote sensing of CCN activity and links to their organic mass fraction: airborne observations over Central Mexico and the US West Coast during MILAGRO/INTEX-B

NASA Astrophysics Data System (ADS)

Shinozuka, Y.; Clarke, A. D.; Decarlo, P. F.; Jimenez, J. L.; Dunlea, E. J.; Roberts, G. C.; Tomlinson, J. M.; Collins, D. R.; Howell, S. G.; Kapustin, V. N.; McNaughton, C. S.; Zhou, J.

2009-09-01

Remote sensing of cloud condensation nuclei (CCN) would help evaluate the indirect effects of tropospheric aerosols on clouds and climate. To assess its feasibility, we examined relationships of submicron aerosol composition to CCN activity and optical properties observed during the MILAGRO/INTEX-B aircraft campaigns. An indicator of CCN activity, κ, was calculated from hygroscopicity measured under saturation. κ for dry 100 nm particles decreased with increasing organic fraction of non-refractory mass of submicron particles (OMF) as 0.34-0.20×OMF over Central Mexico and 0.47-0.43×OMF over the US West Coast. These fits represent the critical dry diameter, centered near 100 nm for 0.2% supersaturation but varied as κ(-1/3), within measurement uncertainty (~20%). The decreasing trends of CCN activity with the organic content, evident also in our direct CCN counts, were consistent with previous ground and laboratory observations of highly organic particles. The wider range of OMF, 0-0.8, for our research areas means that aerosol composition will be more critical for estimation of CCN concentration than at the fixed sites previously studied. Furthermore, the wavelength dependence of extinction was anti-correlated with OMF as -0.70×OMF+2.0 for Central Mexico's urban and industrial pollution air masses, for unclear reasons. The Angstrom exponent of absorption increased with OMF, more rapidly under higher single scattering albedo, as expected for the interplay between soot and colored weak absorbers (some organic species and dust). Because remote sensing products currently use the wavelength dependence of extinction albeit in the column integral form and may potentially include that of absorption, these regional spectral dependencies are expected to facilitate retrievals of aerosol bulk chemical composition and CCN activity over Central Mexico.

Aerosol optical properties relevant to regional remote sensing of CCN activity and links to their organic mass fraction: airborne observations over Central Mexico and the US West Coast during MILAGRO/INTEX-B

NASA Astrophysics Data System (ADS)

Shinozuka, Y.; Clarke, A. D.; Decarlo, P. F.; Jimenez, J. L.; Dunlea, E. J.; Roberts, G. C.; Tomlinson, J. M.; Collins, D. R.; Howell, S. G.; Kapustin, V. N.; McNaughton, C. S.; Zhou, J.

2009-05-01

Remote sensing of cloud condensation nuclei (CCN) would help evaluate the indirect effects of tropospheric aerosols on clouds and climate. To assess its feasibility, we examined relationships of submicron aerosol composition to CCN activity and optical properties observed during the MILAGRO/INTEX-B aircraft campaigns. An indicator of CCN activity, κ, was calculated from hygroscopicity measured under saturation. κ for dry 100-nm particles decreased with the organic fraction of non-refractory mass of submicron particles (OMF) as 10(-0.43-0.44*OMF) over Central Mexico and 10(-0.29-0.70*OMF) over the US West Coast. These fits represent the critical dry diameter, centered near 100 nm for 0.2% supersaturation but varied as κ(-1/3), within measurement uncertainty (~20%). The decreasing trends of CCN activity with the organic content, evident also in our direct CCN counts, were consistent with previous ground and laboratory observations of highly organic particles. The wider range of OMF, 0-0.8, for our research areas means that aerosol composition will be more critical for estimation of CCN concentration than at the fixed sites previously studied. Furthermore, the wavelength dependence of extinction was anti-correlated with OMF as -0.70*OMF+2.0 for Central Mexico's urban and industrial pollution air masses, for unclear reasons. The Angstrom exponent of absorption increased with OMF, more rapidly under higher single scattering albedo, as expected for the interplay between soot and colored weak absorbers (some organic species and dust). Because remote sensing products currently use the wavelength dependence of extinction albeit in the column integral form and may potentially include that of absorption, these regional spectral dependencies are expected to facilitate retrievals of aerosol bulk chemistry and CCN activity over Central Mexico.

Microencapsulation by spray drying of lemon essential oil: Evaluation of mixtures of mesquite gum-nopal mucilage as new wall materials.

PubMed

Cortés-Camargo, Stefani; Cruz-Olivares, Julian; Barragán-Huerta, Blanca E; Dublán-García, Octavio; Román-Guerrero, Angélica; Pérez-Alonso, César

2017-06-01

Mesquite gum (MG) and nopal mucilage (NM) mixtures were used for microencapsulation of lemon essential oil (LEO) by spray drying. Emulsions of MG, NM and MG-NM mixtures (25-75, 50-50, 75-25) were evaluated according to the droplet size (1.49-9.16 μm), viscosity and zeta potential (-16.07 to -20.13 mV), and microcapsules were characterised in particle size (11.9-44.4 μm), morphology, volatile oil retention (VOR) (45.9-74.4%), encapsulation efficiency (EE) (70.9-90.6%), oxidative stability and thermal analysis. The higher concentration of MG led to smaller droplet sizes and lower viscosity in the emulsions, and smaller particle sizes with the highest VOR in microcapsules. The higher concentration of NM induced to higher viscosity in the emulsions, and larger particle sizes with the highest values of EE and oxidative stability in microcapsules. This work shows evidence that MG-NM mixtures can have synergic effect in desirable characteristics such as retention and shelf life extension of LEO in microcapsules.

Influence of smectite hydration and swelling on atrazine sorption behavior.

PubMed

Chappell, Mark A; Laird, David A; Thompson, Michael L; Li, Hui; Teppen, Brian J; Aggarwal, Vaneet; Johnston, Cliff T; Boyd, Stephen A

2005-05-01

Smectites, clay minerals commonly found in soils and sediments, vary widely in their ability to adsorb organic chemicals. Recent research has demonstrated the importance of surface charge density and properties of exchangeable cations in controlling the affinity of smectites for organic molecules. In this study, we induced hysteresis in the crystalline swelling of smectites to test the hypothesis that the extent of crystalline swelling (or interlayer hydration status) has a large influence on the ability of smectites to adsorb atrazine from aqueous systems. Air-dried K-saturated Panther Creek (PC) smectite swelled less (d(001) = 1.38 nm) than never-dried K-PC (d(001) = 1.7 nm) when rehydrated in 20 mM KCl. Correspondingly, the air-dried-rehydrated K-PC had an order of magnitude greater affinity for atrazine relative to the never-dried K-PC. Both air-dried-rehydrated and never-dried Ca-PC expanded to approximately 2.0 nm in 10 mM CaCl2 and both samples had similar affinities for atrazine that were slightly lower than that of never-dried K-PC. The importance of interlayer hydration status in controlling sorption affinity was confirmed by molecular modeling, which revealed much greater interaction between interlayer water molecules and atrazine in a three-layer hydrate relative to a one-layer hydrate. The entropy change on moving atrazine from a fully hydrated state in the bulk solution to a partially hydrated state in the smectite interlayers is believed to be a major factor influencing sorption affinity. In an application test, choice of background solution (20 mM KCl versus 10 mM CaCl2) and air-drying treatments significantly affected atrazine sorption affinities for three-smectitic soils; however, the trends were not consistent with those observed for the reference smectite. Further, extending the initial rehydration time from 24 to 240 h (prior to adding atrazine) significantly decreased the soil's sorption affinity for atrazine. We conclude that interlayer hydration status has a large influence on the affinity of smectites for atrazine and that air-drying treatments have the potential to modify the sorption affinity of smectitic soils for organic molecules such as atrazine.