Synthesis, characterization and antibacterial activity of hybrid chitosan-cerium oxide nanoparticles: As a bionanomaterials.

PubMed

Senthilkumar, R P; Bhuvaneshwari, V; Ranjithkumar, R; Sathiyavimal, S; Malayaman, V; Chandarshekar, B

2017-11-01

The hybrid chitosan cerium oxide nanoparticles were prepared for the first time by green chemistry approach using plant leaf extract. The intense peak observed around 292nm in the UV-vis spectrum indicate the formation of cerium oxide nanoparticles. The XRD pattern revealed that the hybrid chitosan-cerium oxide nanoparticles have a polycrystalline structure with cubic fluorite phase. The FTIR spectrum of prepared samples showed the formation of Ce-O bonds and chitosan main chains COC and CO. The FESEM image of hybrid chitosan cerium oxide nanoparticles revealed that the particles are spherical in shape with grains size varying from 23.12nm to 89.91nm. EDAX analysis confirmed the presence of Ce, O, C and N elements in the prepared sample. TEM images showed that the prepared hybrid chitosan-cerium oxide nanoparticles are predominantly uniform in size and most of the particles are spherical in shape with less agglomeration and the particles size varies from 3.61nm to 24.40nm. The prepared chitosan cerium oxide nanoparticles of 50μL concentration showed good antibacterial properties against test pathogens, which was confirmed by the FESEM analysis. The prepared small particle size facilitate that these hybrid ChiCO 2 NPs could effectively be used in biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrical four-point probing of spherical metallic thin films coated onto micron sized polymer particles

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

Pettersen, Sigurd R., E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang

Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental resultsmore » with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.« less

Investigating Aerosol Morphology Using Scattering Phase Functions Measured with a Laser Imaging Nephelometer

NASA Astrophysics Data System (ADS)

Manfred, K.; Adler, G. A.; Erdesz, F.; Franchin, A.; Lamb, K. D.; Schwarz, J. P.; Wagner, N.; Washenfelder, R. A.; Womack, C.; Murphy, D. M.

2017-12-01

Particle morphology has important implications for light scattering and radiative transfer, but can be difficult to measure. Biomass burning and other important aerosol sources can generate a mixture of both spherical and non-spherical particle morphologies, and it is necessary to represent these populations correctly in models. We describe a laser imaging nephelometer that measures the unpolarized scattering phase function of bulk aerosol at 375 and 405 nm using a wide-angle lens and CCD. We deployed this instrument to the Missoula Fire Sciences Laboratory to measure biomass burning aerosol morphology from controlled fires during the recent FIREX intensive laboratory study. Total integrated scattering signal agreed with that determined by a cavity ring-down photoacoustic spectrometer system and a traditional integrating nephelometer within instrument uncertainties. We compared measured scattering phase functions at 405 nm to theoretical models for spherical (Mie) and fractal (Rayleigh-Debye-Gans) particle morphologies based on the size distribution reported by an optical particle counter. We show that particle morphology can vary dramatically for different fuel types, and present results for two representative fires (pine tree vs arid shrub). We find that Mie theory is inadequate to describe the actual behavior of realistic aerosols from biomass burning in some situations. This study demonstrates the capabilities of the laser imaging nephelometer instrument to provide real-time, in situ information about dominant particle morphology that is vital for accurate radiative transfer calculations.

Multi-Wavelength Measurement of Soot Optical Properties: Influence of Non-Absorbing Coatings

NASA Astrophysics Data System (ADS)

Freedman, Andrew; Renbaum-Wollf, Lindsay; Forestieri, Sara; Lambe, Andrew; Cappa, Christopher; Davidovits, Paul; Onasch, Timothy

2015-04-01

Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. Important in quantifying the direct radiative impacts of soot in climate models, and specifically of black carbon (BC), is the assumed BC refractive index and shape-dependent interaction of light with BC particles. The latter assumption carries significant uncertainty because BC particles are fractal-like, being agglomerates of smaller (20-40 nm) spherules, yet many optical models such as Mie theory in particular, typically assume a spherical particle morphology. It remains unclear under what conditions this is an acceptable assumption. To investigate the ability of various optical models to reproduce observed BC optical properties, we obtained measurements of light absorption, scattering and extinction coefficients and thus single scattering albedo (SSA) of size-resolved soot particles. Measurements were made on denuded soot particles produced using both methane and ethylene as fuels. In addition, these soot particles were coated with dioctyl sebacate or sulfuric acid and the enhancement in the apparent mass absorption coefficient determined. Extinction and absorption were measured using a dual cavity ringdown photoacoustic spectrometer (CRD-PAS) at 405 nm and 532 nm. Scattering and extinction were measured using a CAPS PMssa single scattering albedo monitor (Aerodyne) at 630 nm. Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA, Cambustion), mobility size with a scanning mobility particle sizer (SMPS, TSI) and soot concentration with a CPC (Brechtel). The results will be interpreted in light of both Mie theory which assumes spherical and uniform particles and Rayleigh-Debye-Gans (RDG) theory, which assumes that the absorption properties of soot are dictated by the individual spherules. For denuded soot, effective refractive indices will be determined.

Metal-enhanced fluorescence of dye-doped silica nano particles.

PubMed

Gunawardana, Kalani B; Green, Nathaniel S; Bumm, Lloyd A; Halterman, Ronald L

2015-03-01

Recent advancements in metal-enhanced fluorescence (MEF) suggest that it can be a promising tool for detecting molecules at very low concentrations when a fluorophore is fixed near the surface of metal nanoparticles. We report a simple method for aggregating multiple gold nanoparticles (GNPs) on Rhodamine B (RhB)-doped silica nanoparticles (SiNPs) utilizing dithiocarbamate (DTC) chemistry to produce MEF in solution. Dye was covalently incorporated into the growing silica framework via co-condensation of a 3-aminopropyltriethoxysilane (APTES) coupled RhB precursor using the Stöber method. Electron microscopy imaging revealed that these mainly non-spherical particles were relatively large (80 nm on average) and not well defined. Spherical core-shell particles were prepared by physisorbing a layer of RhB around a small spherical silica particle (13 nm) before condensing an outer layer of silica onto the surface. The core-shell method produced nanospheres (~30 nm) that were well defined and monodispersed. Both dye-doped SiNPs were functionalized with pendant amines that readily reacted with carbon disulfide (CS2) under basic conditions to produce DTC ligands that have exhibited a high affinity for gold surfaces. GNPs were produced via citrate reduction method and the resulting 13 nm gold nanospheres were then recoated with an ether-terminated alkanethiol to provide stability in ethanol. Fluorescent enhancement was observed when excess GNPs were added to DTC coated dye-doped SiNPs to form nanoparticle aggregates. Optimization of this system gave a fluorescence brightness enhancement of over 200 fold. Samples that gave fluorescence enhancement were characterized through Transmission Emission Micrograph (TEM) to reveal a pattern of multiple aggregation of GNPs on the dye-doped SiNPs.

Iron Oxide Nanospheres and Nanocubes for Magnetic Hyperthermia Therapy: A Comparative Study

NASA Astrophysics Data System (ADS)

Nemati, Z.; Das, R.; Alonso, J.; Clements, E.; Phan, M. H.; Srikanth, H.

2017-06-01

Improving the heating capacity of magnetic nanoparticles (MNPs) for hyperthermia therapy is an important but challenging task. Through a comparative study of the inductive heating properties of spherical and cubic Fe3O4 MNPs with two distinct average volumes (˜7000 nm3 and 80,000 nm3), we demonstrate that, for small size (˜7000 nm3), the cubic MNPs heat better compared with the spherical MNPs. However, the opposite trend is observed for larger size (˜80,000 nm3). The improvement in heating efficiency in cubic small-sized MNPs (˜7000 nm3) can be attributed to enhanced anisotropy and the formation of chain-like aggregates, whereas the decrease of the heating efficiency in cubic large-sized MNPs (˜80,000 nm3) has been attributed to stronger aggregation of particles. Physical motion is shown to contribute more to the heating efficiency in case of spherical than cubic MNPs, when dispersed in water. These findings are of crucial importance in understanding the role of shape anisotropy and optimizing the heating response of magnetic nano-structures for advanced hyperthermia.

Analyses of scattering characteristics of chosen anthropogenic aerosols

NASA Astrophysics Data System (ADS)

Kaszczuk, Miroslawa; Mierczyk, Zygmunt; Muzal, Michal

2008-10-01

In the work, analyses of scattering profile of chosen anthropogenic aerosols for two wavelengths (λ1 = 1064 nm and λ2 = 532 nm) were made. As an example of anthropogenic aerosol three different pyrotechnic mixtures (DM11, M2, M16) were taken. Main parameters of smoke particles were firstly analyzed and well described, taking particle shape and size into special consideration. Shape of particles was analyzed on the basis of SEM pictures, and particle size was measured. Participation of particles in each fixed fraction characterized by range of sizes was analyzed and parameters of smoke particles of characteristic sizes and function describing aerosol size distribution (ASD) were determinated. Analyses of scattering profiles were carried out on the basis of both model of scattering on spherical and nonspherical particles. In the case of spherical particles Rayleigh-Mie model was used and for nonspherical particles analyses firstly model of spheroids was used, and then Rayleigh-Mie one. For each characteristic particle one calculated value of four parameters (effective scattering cross section σSCA, effective backscattering cross section σBSCA, scattering efficiency QSCA, backscattering efficiency QBSCA) and value of backscattering coefficient β for whole particles population. Obtained results were compared with the same parameters calculated for natural aerosol (cirrus cloud).

Structural analysis of Fe–Mn–O nanoparticles in glass ceramics by small angle scattering

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

Raghuwanshi, Vikram Singh, E-mail: vikram.raghuwanshi@helmholtz-berlin.de; Harizanova, Ruzha; Tatchev, Dragomir

2015-02-15

Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na{sub 2}O–62.9SiO{sub 2}–8.5MnO–15.0Fe{sub 2}O{sub 3−x} (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core–shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enrichedmore » in SiO{sub 2}. SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region. - Graphical abstract: Magnetic spherical core–shell nanoparticles in glass ceramics: SANSPOL and ASAXS investigations. - Highlights: • Formation and growth mechanisms of magnetic nanoparticles in silicate glass. • SANSPOL and ASAXS methods employed to evaluate quantitative information. • Analyses showed formation of nanoparticles with spherical core–shell structures. • Core of the particle is magnetic and surrounded by weak magnetic shell like region.« less

Functionally charged nanosize particles differentially activate BV2 microglia.

EPA Science Inventory

The effect of particle surface charge on the biological activation of immortalized mouse microglia (BV2) was examined. Nanosize (860-950 nm) spherical polystyrene microparticles (SPM) were coated with carboxyl (COOH-) or dimethyl amino (CH3)2-N- groups to give a net negative or p...

Aerosol Classification from High Spectral Resolution Lidar Measurements

NASA Astrophysics Data System (ADS)

Burton, S. P.; Hair, J. W.; Ferrare, R. A.; Hostetler, C. A.; Kahnert, M.; Vaughan, M. A.; Cook, A. L.; Harper, D. B.; Berkoff, T.; Seaman, S. T.; Collins, J. E., Jr.; Fenn, M. A.; Rogers, R. R.

2015-12-01

The NASA Langley airborne High Spectral Resolution Lidars, HSRL-1 and HSRL-2, have acquired large datasets of vertically resolved aerosol extinction, backscatter, and depolarization during >30 airborne field missions since 2006. The lidar measurements of aerosol intensive parameters like lidar ratio and color ratio embed information about intrinsic aerosol properties, and are combined to qualitatively classify HSRL aerosol measurements into aerosol types. Knowledge of aerosol type is important for assessing aerosol radiative forcing, and can provide useful information for source attribution studies. However, atmospheric aerosol is frequently not a single pure type, but instead is a mixture, which affects the optical and radiative properties of the aerosol. We show that aerosol intensive parameters measured by lidar can be understood using mixing rules for cases of external mixing. Beyond coarse classification and mixing between classes, variations in the lidar aerosol intensive parameters provide additional insight into aerosol processes and composition. This is illustrated by depolarization measurements at three wavelengths, 355 nm, 532 nm, and 1064 nm, made by HSRL-2. Particle depolarization ratio is an indicator of non-spherical particles. Three cases each have a significantly different spectral dependence of the depolarization ratio, related to the size of the depolarizing particles. For two dust cases, large non-spherical particles account for the depolarization of the lidar light. The spectral dependence reflects the size distribution of these particles and reveals differences in the transport histories of the two plumes. For a smoke case, the depolarization is inferred to be due to the presence of small coated soot aggregates. Interestingly, the depolarization at 355 nm is similar for this smoke case compared to the dust cases, having potential implications for the upcoming EarthCARE satellite, which will measure particle depolarization ratio only at 355 nm.

Self-organization of silver nanoparticles forming on chemical reduction to give monodisperse spheres

NASA Astrophysics Data System (ADS)

Yakutik, I. M.; Shevchenko, G. P.

2004-09-01

It was found possible to produce monodisperse spherical silver particles using K-Na-tartrate as the reductant for Ag + in the presence of gelatin. It was shown that the silver spheres form in the process of spontaneous self-organization of 10-15 nm-sized primary particles. The conditions making it possible to control the sizes of the monodisperse spheres in the range from 150 nm to 1.5 μm were specified.

Functionally Charged Polystyrene Particles Activate Immortalized Mouse Microglia (BV2): Cellular and Genomic Response

EPA Science Inventory

The effect of particle surface charge on the biological activation of immortalized mouse microglia (BV2) was examined. Same size (~850-950 nm) spherical polystyrene microparticles (SPM) with net negative (carboxyl, COOH-) or positive (dimethyl amino, CH₃)₂

Spherical silicon-shell photonic band gap structures fabricated by laser-assisted chemical vapor deposition

NASA Astrophysics Data System (ADS)

Wang, H.; Yang, Z. Y.; Lu, Y. F.

2007-02-01

Laser-assisted chemical vapor deposition was applied in fabricating three-dimensional (3D) spherical-shell photonic band gap (PBG) structures by depositing silicon shells covering silica particles, which had been self-assembled into 3D colloidal crystals. The colloidal crystals of self-assembled silica particles were formed on silicon substrates using the isothermal heating evaporation approach. A continuous wave Nd:YAG laser (1064nm wavelength) was used to deposit silicon shells by thermally decomposing disilane gas. Periodic silicon-shell/silica-particle PBG structures were obtained. By removing the silica particles enclosed in the silicon shells using hydrofluoric acid, hollow spherical silicon-shell arrays were produced. This technique is capable of fabricating structures with complete photonic band gaps, which is predicted by simulations with the plane wave method. The techniques developed in this study have the potential to flexibly engineer the positions of the PBGs by varying both the silica particle size and the silicon-shell thickness. Ellipsometry was used to investigate the specific photonic band gaps for both structures.

Sonochemical synthesis of silica particles and their size control

NASA Astrophysics Data System (ADS)

Kim, Hwa-Min; Lee, Chang-Hyun; Kim, Bonghwan

2016-09-01

Using an ultrasound-assisted sol-gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

Synthesis characterisation series of newly fabricated type II CdSe CdSe/CdTe nanocrystals and their optical properties

NASA Astrophysics Data System (ADS)

Ahmed, A. S.; Christopher, W.

2018-03-01

Nanocrystalline semiconductors exhibit different properties due to two basic factors. They possess high surface to volume ratio and the actual size of particle can determine the electronic and physical properties of the material. The small size results in an observable quantum confinement effect, defined by the increasing bandgap accompanied by the quantization of the energy levels to discrete values. In present work we have synthesized the series of cadmium selenide/cadmium telluride (CdSe/CdTe) core/shell and CdSe/CdTe/CdS core/shell/shell to investigate the biexciton energy through transient absorption measurements. These structures are type II nanocrystals are with a hole in the shell and the electron confined to the core. We specifically investigate the effect of nanoparticle shape on the electronic structure and ultrafast electronic dynamics in the band-edge exciton states of CdSe quantum dots, nanorods, and nanoplatelets. Particle size was chosen to enable straightforward comparisons of the effects of particle shape on the spectra and dynamics without retuning the laser source. In our results the Uv-vis showed only a mild redshift in the first excitonic an elongated tail with increasing shell thickness. High resolution Transmission Electron Microscopy (HRTEM) shows the slight agglomeration of the nanocrystals but still the size distribution was calculate able. Spherical small crystals ranging from 5.9 nm to 10 nm are observed. CdTe/CdSe structures were quasi spherical with a rough diameter 6 nm with some little agglomerated structure. . The spherical nanocrystals could be peanut shaped oriented along the c axis or the spherical only, which could explain the two peak emission. p-XRD results indicate the predominant wurtzite structure throughout.

nanoparticles but affecting morphology under broader view

NASA Astrophysics Data System (ADS)

Karkare, Manasi Manoj

2014-07-01

In this study, anatase titanium dioxide nanoparticles were successfully prepared by a sol-gel method using two different precursors, titanium isopropoxide and titanium butoxide. Hydrochloric acid or nitric acid was added to adjust the pH of the solution. The sols obtained were dried at 80 °C and calcined at 450 °C for 3 h. The nanostructures were characterised by scanning electron microscopy, FTIR and ultraviolet-visible spectroscopy. The phase transformations were investigated by an X-ray diffractometer. Highly crystalline anatase titania nanoparticles could be obtained through the controlled hydrolysis reaction rate. The sizes of synthesized particles were in the range 5-13 nm, i.e. 9 nm on an average and with a regular shape. The size of nanoparticles was not affected by the choice of precursor. The broad view of the samples prepared using titanium isopropoxide showed film-like structures, whereas the samples prepared using titanium butoxide showed spherical granules. A red shift of 0.13 eV was observed in the band gap in the case of non-spherical particles compared to spherical ones.

Poly(2-aminothiazole)-silica nanocomposite particles: Synthesis and morphology control

NASA Astrophysics Data System (ADS)

Zou, Hua; Wu, Di; Sun, Hao; Chen, Suwu; Wang, Xia

2018-04-01

Synthesis of conducting polymer-silica colloidal nanocomposites has been recognized as an effective method to overcome the poor processability of heterocyclic conducting polymers prepared by chemical oxidative method. However, the morphology control of such conducting polymer-silica nanocomposites was seldomly reported in the literature. Novel poly(2-aminothiazole)(PAT)-silica nanocomposite particles can be conveniently prepared by chemical oxidative polymerization of 2-aminothiazole using CuCl2 oxidant in the presence of ∼20 nm silica nanoparticles. The effects of varying the oxidant/monomer ratio and silica sol concentration on the morphology and size of the resulting PAT-silica nanocmposites have been studied. Optimization of the oxidant/monomer molar ratio and initial silica sol concentration allows relatively round spherical particles of 150-350 nm in diameter to be achieved. The nanocomposite particles have a well-defined raspberry-like morphology with a silica-rich surface, but a significant fraction of PAT component still exists on the surface and, which is beneficial for its applications. Furthermore, the surface compositions of the colloidal nanocomposites could be regulated to some extent. Based on the above results, a possible formation mechanism of the spherical nanocomposite particles is proposed.

Physico-chemical characterization of engineered metal oxide nanoparticles: the critical role of microscopy

NASA Astrophysics Data System (ADS)

La Fontaine, A.; Coleman, V. A.; Jämting, A. K.; Lawn, M.; Herrmann, J.; Miles, J. R.

2010-06-01

Three different methods for extracting zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles from commercially available sunscreen were investigated to determine the most appropriate route for producing a sample suitable for measuring the primary particle size. Direct dilution of the formulation, centrifugal methods and chemical washing were trialed in combination with ultrasonic processing and surfactant addition to generate samples that are suitable for particle size analysis. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to monitor the extraction and re-dispersion process. Washing with hexane, methanol and water to remove the formulation, in combination with pulsed high-powered ultrasonication and the addition of a charge-stabilizing surfactant was found to be the most efficient way of producing de-agglomerated samples. DLS measurements gave average hydrodynamic particle diameters of 87 nm for ZnO and 76 nm for TiO2, compared to equivalent spherical particle diameters of 21 +/- 12 nm for ZnO (81 particles) and 19 +/- 14 nm for TiO2 (81 particles) obtained from TEM analysis.

Phase Composition of Samarium Niobate and Tantalate Thin Films Prepared by Sol-Gel Method

NASA Astrophysics Data System (ADS)

Bruncková, H.; Medvecký, Ľ.; Múdra, E.; Kovalčiková, A.; Ďurišin, J.; Šebek, M.; Girman, V.

2017-12-01

Samarium niobate SmNbO4 (SNO) and tantalate SmTaO4 (STO) thin films ( 100 nm) were prepared by sol-gel/spin-coating process on alumina substrates with PZT interlayer and annealing at 1000°C. The precursors of films were synthesized using Nb or Ta tartrate complexes. The improvement of the crystallinity of monoclinic M'-SmTaO4 phase via heating was observed through the coexistence of small amounts of tetragonal T-SmTa7O19 phase in STO precursor at 1000°C. The XRD results of SNO and STO films confirmed monoclinic M-SmNbO4 and M'-SmTaO4 phases, respectively, with traces of orthorhombic O-SmNbO4 (in SNO). In STO film, the single monoclinic M'-SmTaO4 phase was revealed. The surface morphology and topography of thin films were investigated by SEM and AFM analysis. STO film was smoother with roughness 3.2 nm in comparison with SNO (6.3 nm). In the microstructure of SNO film, small spherical ( 50 nm) and larger cuboidal particles ( 100 nm) of the SmNbO4 phase were observed. In STO, compact clusters composed of fine spherical SmTaO4 particles ( 20-50 nm) were found. Effect of samarium can contribute to the formation different polymorphs of these films for the application to environmental electrolytic thin film devices.

Experimental Investigation of Nascent Soot Physical Properties and The Influence on Particle Morphology and Growth

NASA Astrophysics Data System (ADS)

Lieb, Sydnie Marie

Soot released to the atmosphere is a dangerous pollutant for human health and the environment. Understanding the physical properties and surface properties of these particles is important to properly explaining the growth of soot particles in flames as well as their interactions with other particles and gases in the environment. Particles below 15 nm in diameter, nascent soot particles, dominate the early growth stages of soot formation; previously these particles were characterized as hard graphitic spheres. New evidence derived from the current dissertation work, to a large extent, challenges this prior characterization. This dissertation study begins by revisiting the use of atomic force microscope (AFM) as a tool to investigate the structural properties of nascent soot. The impact of tip artifacts, which are known to complicate measurements of features below 10 nm in diameter, are carefully considered so as to provide a concise interpretation of the morphology of nascent soot as seen by AFM. The results of the AFM morphology collaborate with earlier photo- and thermal-fragmentation particle mass spectrometry and Fourier transform infrared spectroscopy that nascent soot is not a graphitized carbon material and that they are not spherical. Furthermore, phase mode imaging is introduced as a method to investigate the physical properties of nascent soot particles in a greater detail and finer resolution. The helium ion microscope (HIM) has been identified as a useful technique for the imaging of nascent soot. Using this imaging method nascent soot particles were imaged with a high resolution that had not been obtained by prior techniques. The increased contrast provides a closer look at the nascent soot particles and further suggested that these particles are not as structurally homogeneous as previously thought. Geometric shape analysis was performed to characterize the particles in terms of sphericity, circularity, and fractal dimension. The geometric analysis showed that the particles deviate from spherical and that they are not characterized by a defined structure. This observation supports the theory that nascent soot is not homogenous in structure or composition, and challenges the classical assumption that spherical growth and aggregation are separate, size dependent processes. In light of the new evidence that suggests nascent soot particles are structurally inhomogenous, careful consideration must be given to mobility measurements of particle mass and size. The interpretation of particle volume of irregularly shaped nascent soot particles is considered in this dissertation work. Additionally, uncertainties in the mass density of nascent soot are reviewed and the error in mass calculation is quantified.

Core-shell structured SiO2@YVO4:Dy3+/Sm3+ phosphor particles: sol-gel preparation and characterization.

PubMed

Wang, H; Yu, M; Lin, C K; Lin, J

2006-08-01

Spherical SiO(2) particles have been coated with YVO(4):Dy(3+)/Sm(3+) phosphor layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO(2)@YVO(4):Dy(3+)/Sm(3+) particles. X-ray diffraction (XRD), Fourier-transform IR spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting SiO(2)@YVO(4):Dy(3+)/Sm(3+) core-shell phosphors. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 300 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (20 nm for one deposition cycle). The core-shell particles show strong characteristic emission from Dy(3+) for SiO(2)@YVO(4):Dy(3+) and from Sm(3+) for SiO(2)@YVO(4):Sm(3+) due to an efficient energy transfer from YVO(4) host to them. The PL intensity of Dy(3+) and Sm(3+) increases with raising the annealing temperature and the number of coating cycles.

Size-Dependent Mechanism of Intracellular Localization and Cytotoxicity of Mono-Disperse Spherical Mesoporous Nano- and Micron-Bioactive Glass Particles

PubMed Central

Li, Yuli; Hu, Qing; Miao, Guohou; Zhang, Qing; Yuan, Bo; Zhu, Ye; Fu, Xiaoling; Chen, Xiaofeng; Mao, Chuanbin

2016-01-01

Mono-disperse spherical mesoporous nano- and micro- bioactive glass particles (NMBGs) can find potential use in bone tissue engineering. However, their size-dependent interaction with osteoblasts has never been studied. Herein, the proliferation, morphology, cytoskeleton organization and apoptosis of MC3T3-E1 osteoblasts are studied in response to the NMBGs with varying sizes (from 61 to 1085 nm) at different concentrations. Generally, smaller NMBGs at a lower dose show weaker cytotoxicity compared to the larger particles and higher doses, arising from a novel size-dependent mechanism of intracellular localization of NMBGs observed by electron and confocal microscopy. Specifically, NMBGs pass through perinuclear membrane of the cells to initiate endocytosis. Once internalized, the sizes of NMBGs are found to play a significant role in determining their intracellular localization. When the NMBGs are smaller than 174 nm, they are transported via the lysosomal pathway and phagocytized in lysosomes, resulting in little cytotoxicity at later time points. On the contrary, larger NMBGs (over 174 nm) escape from the lysosomes after endocytosis, and are localized inside the intra-cytoplasmic vacuoles or randomly in the cytoplasm of cells. Their lysosomal escape may damage the lysosomes, inducing cell apoptosis and thus the greater cytotoxicity. PMID:27305811

SURFACE CHEMICAL EFFECTS ON COLLOID STABILITY AND TRANSPORT THROUGH NATURAL POROUS MEDIA

EPA Science Inventory

Surface chemical effects on colloidal stability and transport through porous media were investigated using laboratory column techniques. Approximately 100 nm diameter, spherical, iron oxide particles were synthesized as the mobile colloidal phase. The column packing material was ...

Composition distributions in FePt(Au) nanoparticles

NASA Astrophysics Data System (ADS)

Srivastava, C.; Nikles, D. E.; Harrell, J. W.; Thompson, G. B.

2010-08-01

Ternary alloy FePt(Au) nanoparticles were prepared by the co-reduction of platinum(II) acetylacetonate and gold(III) acetate and the thermal decomposition of iron pentacarbonyl in hot phenyl ether in the presence of oleic acid and oleylamine ligands. This gave spherical particles with an average diameter of 4.4 nm with a range of diameters from approximately 1.6-9 nm. The as-synthesized particles had a solid solution, face-centered-cubic structure. Though the average composition of the particles was Fe44Pt45Au11, individual particle analysis by Scanning Transmission Electron Microscopy-X-ray Energy Dispersive Spectroscopy showed a broad distribution in composition. In general, smaller-sized particles tended to have a lower amount of Au as compared to larger-sized particles. As the Au content increased, the ratio of Fe/Pt widened.

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

Bakina, O. V., E-mail: ovbakina@ispms.tsc.ru; Glazkova, E. A., E-mail: eagl@ispms.tsc.ru; Svarovskaya, N. V., E-mail: nvsv@ispms.tsc.ru

In the current paper, the mixed SiO{sub 2}/Al{sub 2}O{sub 3} aerogel was synthesized by sol-gel method with subcritical drying and characterized. Tetraethoxysilane was used as a precursor of silicon sol. The flower-shaped alumina suspension was peptized to produce alumina sol. The aerogel texture, morphology, and structure were determined using scanning electron microscopy, X-ray diffraction, low-temperature nitrogen adsorption, and high-resolution spectroscopy. A special attention was paid to the pore structure of aerogel, and aerogel framework was formed by the spherical agglomerates containing spherical particles of silicon oxide and alumina nanopetals. The pore size distribution was bimodal with peaks of 5.5 nm andmore » 77 nm.« less

Focusing geometry-induced size tailoring of silver nanoparticles obtained by laser ablation in water

NASA Astrophysics Data System (ADS)

Stasic, Jelena; Joksic, Gordana; Zivkovic, Ljiljana; Mihailescu, Ion N.; Ghica, Corneliu; Kuncser, Andrei; Trtica, Milan

2014-10-01

Silver nanoparticles were obtained by picosecond laser ablation in water at 1064 nm, using focusing geometry to design the particles’ size. The position of the target surface with respect to the focal point strongly influences the NPs’ size: above and in the focus it is up to 20 nm and below focus ≤ 150 nm. Generated particles have a spherical shape. The solutions were further employed on human cells and the tests showed a deteriorating effect on DNA.

Synthesis of SiC nanoparticles by SHG 532 nm Nd:YAG laser ablation of silicon in ethanol

NASA Astrophysics Data System (ADS)

Khashan, Khawla S.; Ismail, Raid A.; Mahdi, Rana O.

2018-06-01

In this work, colloidal spherical nanoparticles NPs of silicon carbide SiC have been synthesized using second harmonic generation 532 nm Nd:YAG laser ablation of silicon target dipped in ethanol solution at various laser fluences (1.5-5) J/cm2. X-Ray diffraction XRD, scanning electron microscopy SEM, transmission electron microscope TEM, Fourier transformed infrared spectroscopy FT-IR, Raman spectroscopy, photoluminescence PL spectroscopy, and UV-Vis absorption were employed to examine the structural, chemical and optical properties of SiC NPs. XRD results showed that all synthesised SiC nanoparticles are crystalline in nature and have hexagonal structure with preferred orientation along (103) plane. Raman investigation showed three characteristic peaks 764,786 and 954 cm-1, which are indexing to transverse optic TO phonon mode and longitudinal optic LO phonon mode of 4H-SiC structure. The optical absorption data showed that the values of optical energy gap of SiC nanoparticles prepared at 1.5 J/cm2 was 3.6 eV and was 3.85 eV for SiC synthesised at 5 J/cm2. SEM investigations confirmed that the nanoparticles synthesised at 5 J/cm2 are agglomerated to form larger particles. TEM measurements showed that SiC particles prepared at 1.5 J/cm2 have spherical shape with average size of 25 nm, while the particles prepared at 5 J/cm2 have an average size of 55 nm.

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.

Synthesis of highly-monodisperse spherical titania particles with diameters in the submicron range.

PubMed

Tanaka, Shunsuke; Nogami, Daisuke; Tsuda, Natsuki; Miyake, Yoshikazu

2009-06-15

Monodisperse titania spheres with particle diameters in the range 380-960 nm were successfully synthesized by hydrolysis and condensation of titanium tetraisopropoxide. The preparation was performed using ammonia or dodecylamine (DDA) as a catalyst in methanol/acetonitrile co-solvent at room temperature. The samples were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and nitrogen sorption measurement. The use of DDA was effective for the synthesis of monodisperse titania spheres with low coefficient of variation. When the titania spherical particles with coefficient of variation less than 4% were obtained, the colloidal crystallization easily occurred simply by centrifugation. The monodispersity was maintained even after crystallization of the particles by high temperature annealing. The titania particles prepared using DDA had mesopores near the surface of the spheres, providing high pore accessibility to the sphere from the surface-air interface. The particle size uniformity and photocatalytic reactivity of the titania prepared using DDA were higher than those of the titania prepared using ammonia.

Self-assembled mesoporous Co and Ni-ferrite spherical clusters consisting of spinel nanocrystals prepared using a template-free approach.

PubMed

Yu, Byong Yong; Kwak, Seung-Yeop

2011-10-21

Based on a self-assembly strategy, spherical mesoporous cobalt and nickel ferrite nanocrystal clusters with a large surface area and narrow size distribution were successfully synthesized for the first time via a template-free solvothermal process in ethylene glycol and subsequent heat treatment. In this work, the mesopores in the ferrite clusters were derived mainly from interior voids between aggregated primary nanoparticles (with crystallite size of less than 7 nm) and disordered particle packing domains. The concentration of sodium acetate is shown herein to play a crucial role in the formation of mesoporous ferrite spherical clusters. These ferrite clusters were characterized in detail using wide-angle X-ray diffraction, thermogravimetric-differential thermal analysis, (57)Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, standard and high-resolution transmission electron microscopy, and other techniques. The results confirmed the formation of both pure-phase ferrite clusters with highly crystalline spinel structure, uniform size (about 160 nm) and spherical morphology, and worm-like mesopore structures. The BET specific surface areas and mean pore sizes of the mesoporous Co and Ni-ferrite clusters were as high as 160 m(2) g(-1) and 182 m(2) g(-1), and 7.91 nm and 6.87 nm, respectively. A model for the formation of the spherical clusters in our system is proposed on the basis of the results. The magnetic properties of both samples were investigated at 300 K, and it was found that these materials are superparamagnetic. This journal is © The Royal Society of Chemistry 2011

Synthesis of carbon-coated Na2MnPO4F hollow spheres as a potential cathode material for Na-ion batteries

NASA Astrophysics Data System (ADS)

Wu, Ling; Hu, Yong; Zhang, Xiaoping; Liu, Jiequn; Zhu, Xing; Zhong, Shengkui

2018-01-01

Hollow sphere structure Na2MnPO4F/C composite is synthesized through spray drying, following in-situ pyrolytic carbon coating process. XRD results indicate that the well crystallized composite can be successfully synthesized, and no other impurity phases are detected. SEM and TEM results reveal that the Na2MnPO4F/C samples show intact hollow spherical architecture, and the hollow spherical shells with an average thickness of 150 nm-250 nm are composed of nanosized primary particles. Furthermore, the amorphous carbon layer is uniformly coated on the surface of the hollow sphere, and the nanosized Na2MnPO4F particles are well embedded in the carbon networks. Consequently, the hollow sphere structure Na2MnPO4F/C shows enhanced electrochemical performance. Especially, it is the first time that the obvious potential platforms (∼3.6 V) are observed during the charge and discharge process at room temperature.

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

Apaydin, Ramazan Oguzhan; Ebin, Burcak; Gurmen, Sebahattin

Copper-Nickel (CuNi) nanostructured alloy particles were produced by Ultrasonic Spray Pyrolysis and Hydrogen Reduction Method (USP-HR) from high purity copper and nickel nitrate aqueous solutions. The effect of the precursor solution in the range of 0.1 and 0.5 mol/L on the morphology and crystallite size of CuNi nanoparticles were investigated under 2 h running time, 700 °C operating temperature and 0.5 L/min H{sub 2} flow rate. Particle size, morphology, composition and crystallite structure were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). Particle characterization studies show that nanostructured alloy particles have cubic crystal structuremore » and they are in submicron size range with spherical morphology. The crystallite sizes of the particles calculated with Scherrer formula are 40 and 34 nm and average particles sizes observed from the SEM images are 300 and 510 nm for each experiment respectively.« less

Triple-wavelength lidar observations of the linear depolarization ratio of dried marine particles

NASA Astrophysics Data System (ADS)

Haarig, Moritz; Ansmann, Albert; Baars, Holger; Engelmann, Ronny; Althausen, Dietrich; Bohlmann, Stephanie; Gasteiger, Josef; Farrell, David

2018-04-01

For aerosol typing with lidar, sea salt particles are usually assumed to be spherical with a consequently low depolarization ratio. Evidence of dried marine particles at the top of the humid marine aerosol layer with a depolarization ratio up to 0.1 has been found at predominately maritime locations on Barbados and in the Southern Atlantic. The depolarization ratio for these probably cubic sea salt particles has been measured at three wavelengths (355, 532 and 1064 nm) simultaneously for the first time and compared to model simulations.

[Color-tunable nano-material alpha-NaYF4 : Yb, Er, Tm prepared by microemulsion-hydrothermal method].

PubMed

Long, Dan-Dan; Zhang, Qing-Xia; Wang, Yu; Zhang, Fan; Wang, Yan-Fei; Zhou, Xin; Qi, Xiao-Hua; Zhang, Heng; Yan, Jing-Hui; Zou, Ming-Qiang

2013-08-01

NaYF4 : Yb3+, Er3+, Tm3+ nanoparticles were prepared by microemulsion-hydrothermal method. Crystal phase, morphology and structure of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The luminescence properties were studied by up-conversional fluorescence spectroscopy. The XRD patterns of as-prepared samples were in agreement with the PDF # 77-2042 of cubic NaYF4. SEM images of the particles showed that the samples were cotton-like spherical in shape and which were assembled by smaller nano-particles. The average size was 120 nm, while the shape was regular and the particle size was homogeneous. Under the excitation of 980 nm, the as-prepared particles could emit blue (438 and 486 nm), green (523 and 539 nm) and red (650 nm) light simultaneously. It can be seen from the color coordinates figure (CIE) that when doping concentration ratio of Tm3+ and E3+ increased from 0 to 2, the whole emitting light color of samples movedto green region. While the ratio was 1 : 1, pseudo white light was obtained. As the ratio changed from 2 to 7, the luminous color was moved to red region.

Core-shell monodisperse spherical mSiO2/Gd2O3:Eu3+@mSiO2 particles as potential multifunctional theranostic agents

NASA Astrophysics Data System (ADS)

Eurov, Daniil A.; Kurdyukov, Dmitry A.; Kirilenko, Demid A.; Kukushkina, Julia A.; Nashchekin, Alexei V.; Smirnov, Alexander N.; Golubev, Valery G.

2015-02-01

Core-shell nanoparticles with diameters in the range 100-500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5-100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m2 g-1) and pore volume (0.3 cm3 g-1), and are bright solid phosphor with superior stability in aqueous media. The core-shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent.

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

Hill, Steven C.; Williamson, Chatt C.; Doughty, David C.

This paper uses a mathematical model of fluorescent biological particles composed of bacteria and/or proteins (mostly as in Hill et al., 2013 [23]) to investigate the size-dependence of the total fluorescence emitted in all directions. The model applies to particles which have negligible reabsorption of fluorescence within the particle. The specific particles modeled here are composed of ovalbumin and of a generic Bacillus. The particles need not be spherical, and in some cases need not be homogeneous. However, the results calculated in this paper are for spherical homogeneous particles. Light absorbing and fluorescing molecules included in the model are aminomore » acids, nucleic acids, and several coenzymes. Here the excitation wavelength is 266 nm. The emission range, 300 to 370 nm, encompasses the fluorescence of tryptophan. The fluorescence cross section (C F) is calculated and compared with one set of published measured values. We investigate power law (Ad y) approximations to C F, where d is diameter, and A and y are parameters adjusted to fit the data, and examine how y varies with d and composition, including the fraction as water. The particle's fluorescence efficiency (Q F=C F/geometric-cross-section) can be written for homogeneous particles as Q absR F, where Q abs is the absorption efficiency, and R F, the fraction of the absorbed light emitted as fluorescence, is independent of size and shape. When Q F is plotted vs. m id or mi(m r-1)d, where m=m r+im i is the complex refractive index, the plots for different fractions of water in the particle tend to overlap.« less

Constraining Atmospheric Particle Size in Gale Crater Using REMS UV Measurements and Mastcam Observations at 440 and 880 nm

NASA Astrophysics Data System (ADS)

Mason, E. L.; Lemmon, M. T.; de la Torre-Juárez, M.; Vicente-Retortillo, A.; Martinez, G.

2015-12-01

Optical depth measured in Gale crater has been shown to vary seasonally, and this variation is potentially linked to a change in dust size visible from the surface. The Mast Camera (Mastcam) on the Mars Science Laboratory (MSL) has performed cross-sky brightness surveys similar to those obtained at the Phoenix Lander site. Since particle size can be constrained by observing airborne dust across multiple wavelengths and angles, surveys at 440 and 880 nm can be used to characterize atmospheric dust within and above the crater. In addition, Rover Environmental Monitoring Station (REMS) on MSL provides downward radiation flux from 250 nm (UVD) to 340 nm (UVA), which would further constrain aerosol properties. The dust, which is not spherical and likely contains irregular particles, can be modeled using randomly oriented triaxial ellipsoids with predetermined microphysical optical properties and fit to sky survey observations to retrieve an effective radius. This work provides a discussion on the constraints of particle size distribution using REMS measurements as well as shape of the particle in Gale crater in comparison to Mastcam at the specified wavelengths.

High-speed DNA-based rolling motors powered by RNase H

PubMed Central

Yehl, Kevin; Mugler, Andrew; Vivek, Skanda; Liu, Yang; Zhang, Yun; Fan, Mengzhen; Weeks, Eric R.

2016-01-01

DNA-based machines that walk by converting chemical energy into controlled motion could be of use in applications such as next generation sensors, drug delivery platforms, and biological computing. Despite their exquisite programmability, DNA-based walkers are, however, challenging to work with due to their low fidelity and slow rates (~1 nm/min). Here, we report DNA-based machines that roll rather than walk, and consequently have a maximum speed and processivity that is three-orders of magnitude greater than conventional DNA motors. The motors are made from DNA-coated spherical particles that hybridise to a surface modified with complementary RNA; motion is achieved through the addition of RNase H, which selectively hydrolyses hybridised RNA. Spherical motors move in a self-avoiding manner, whereas anisotropic particles, such as dimerised particles or rod-shaped particles travel linearly without a track or external force. Finally, we demonstrate detection of single nucleotide polymorphism by measuring particle displacement using a smartphone camera. PMID:26619152

Effect of silver on the shape of palladium nanoparticles

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

Gupta, Dikshita, E-mail: dgmonugupta@gmail.com; Barman, P. B.; Hazra, S. K.

We report a facile route to prepare palladium-silver nanoparticles at considerably low temperature. First the controlled synthesis of palladium nanoparticles was performed via reduction of sodium tetrachloropalladate (II) in ethylene glycol in the presence of PVP(polyvinylpyrrolidone) as capping agent. The reaction was carried out at three different temperatures-80°C, 100°C and 120°C for one hour. Short reaction time and low synthesis temperature adds advantage to this method over others. Formed palladium nanoparticles were nearly spherical with the average particle size of 7.5±0.5 nm, 9.5±0.5 nm and 10.5±0.5 nm at 80°C, 100°C and 120°C respectively. Secondly, the palladium-silver nanoparticles were prepared bymore » the simultaneous reduction of palladium and silver from their respective precursors in ethylene glycol at 100°C (optimized temperature). The shape and size distribution was studied by TEM (Transmission Electron Microscopy). The role of silver in transforming the shape of palladium nanoparticles from spherical to triangular has been discussed. Spherical symmetry of palladium nanoparticles is disturbed by the interaction of silver ions on the crystal facets of palladium nanoparticles. From UV-vis spectra, the absorption maxima of palladium nanoparticles at 205 nm and absorption maxima of palladium-silver nanoparticles at 272 nm revealed the partial evidence of their formation.« less

Nucleotide sequence and genome organization of a novel Panicovirus from Bermuda grass

USDA-ARS?s Scientific Manuscript database

Bermuda grass, (Cynodon dactylon) is widely used in tropical and subtropical areas for golf greens, athletic fields, and landscapes. Samples of Bermuda grass associated with decline symptoms were tested at the University of Minnesota plant virology lab. Spherical virus particles (28-30 nm) were obse...

Particle size-dependent organ distribution of gold nanoparticles after intravenous administration.

PubMed

De Jong, Wim H; Hagens, Werner I; Krystek, Petra; Burger, Marina C; Sips, Adriënne J A M; Geertsma, Robert E

2008-04-01

A kinetic study was performed to determine the influence of particle size on the in vivo tissue distribution of spherical-shaped gold nanoparticles in the rat. Gold nanoparticles were chosen as model substances as they are used in several medical applications. In addition, the detection of the presence of gold is feasible with no background levels in the body in the normal situation. Rats were intravenously injected in the tail vein with gold nanoparticles with a diameter of 10, 50, 100 and 250 nm, respectively. After 24 h, the rats were sacrificed and blood and various organs were collected for gold determination. The presence of gold was measured quantitatively with inductively coupled plasma mass spectrometry (ICP-MS). For all gold nanoparticle sizes the majority of the gold was demonstrated to be present in liver and spleen. A clear difference was observed between the distribution of the 10 nm particles and the larger particles. The 10 nm particles were present in various organ systems including blood, liver, spleen, kidney, testis, thymus, heart, lung and brain, whereas the larger particles were only detected in blood, liver and spleen. The results demonstrate that tissue distribution of gold nanoparticles is size-dependent with the smallest 10nm nanoparticles showing the most widespread organ distribution.

Atomic layer deposition of titanium oxide films on As-synthesized magnetic Ni particles: Magnetic and safety properties

NASA Astrophysics Data System (ADS)

Uudeküll, Peep; Kozlova, Jekaterina; Mändar, Hugo; Link, Joosep; Sihtmäe, Mariliis; Käosaar, Sandra; Blinova, Irina; Kasemets, Kaja; Kahru, Anne; Stern, Raivo; Tätte, Tanel; Kukli, Kaupo; Tamm, Aile

2017-05-01

Spherical nickel particles with size in the range of 100-400 nm were synthesized by non-aqueous liquid phase benzyl alcohol method. Being developed for magnetically guided biomedical applications, the particles were coated by conformal and antimicrobial thin titanium oxide films by atomic layer deposition. The particles retained their size and crystal structure after the deposition of oxide films. The sensitivity of the coated particles to external magnetic fields was increased compared to that of the uncoated powder. Preliminary toxicological investigations on microbial cells and small aquatic crustaceans revealed non-toxic nature of the synthesized particles.

Structural and optical properties of ZnO thin films prepared by RF sputtering at different thicknesses

NASA Astrophysics Data System (ADS)

Hammad, Ahmed H.; Abdel-wahab, M. Sh.; Vattamkandathil, Sajith; Ansari, Akhalakur Rahman

2018-07-01

Hexagonal nanocrystallites of ZnO in the form of thin films were prepared by radio frequency sputtering technique. X-ray diffraction analysis reveals two prominent diffraction planes (002) and (103) at diffraction angles around 34.3 and 62.8°, respectively. The crystallite size increases through (103) plane from 56.1 to 64.8 Å as film thickness changed from 31 nm up to 280 nm while crystallites growth through (002) increased from 124 to 136 Å as film thickness varies from 31 to 107 nm and dropped to 115.8 Å at thickness 280 nm. The particle shape changes from spherical to longitudinal form. The particle size is 25 nm for films of thickness below 107 nm and increases at higher thicknesses (134 and 280 nm) from 30 to 40 nm, respectively. Optical band gap is deduced to be direct with values varied from 3.22 to 3.28 eV and the refractive index are evaluated based on the optical band values according to Moss, Ravindra-Srivastava, and Dimitrov-Sakka models. All refractive index models gave values around 2.3.

UV-VIS depolarization from Arizona Test Dust particles at exact backscattering angle

NASA Astrophysics Data System (ADS)

Miffre, Alain; Mehri, Tahar; Francis, Mirvatte; Rairoux, Patrick

2016-01-01

In this paper, a controlled laboratory experiment is performed to accurately evaluate the depolarization from mineral dust particles in the exact backward scattering direction (ϴ=180.0±0.2°). The experiment is carried out at two wavelengths simultaneously (λ=355 nm, λ=532 nm), on a determined size and shape distribution of Arizona Test Dust (ATD) particles, used as a proxy for mineral dust particles. After validating the set-up on spherical water droplets, two determined ATD-particle size distributions, representative of mineral dust after long-range transport, are generated to accurately retrieve the UV-VIS depolarization from ATD-particles at exact backscattering angle, which is new. The measured depolarization reaches at most 37.5% at λ=355 nm (35.5% at λ=532 nm), and depends on the particle size distribution. Moreover, these laboratory findings agree with T-matrix numerical simulations, at least for a determined particle size distribution and at a determined wavelength, showing the ability of the spheroidal model to reproduce mineral dust particles in the exact backward scattering direction. However, the spectral dependence of the measured depolarization could not be reproduced with the spheroidal model, even for not evenly distributed aspect ratios. Hence, these laboratory findings can be used to evaluate the applicability of the spheroidal model in the backward scattering direction and moreover, to invert UV-VIS polarization lidar returns, which is useful for radiative transfer and climatology, in which mineral dust particles are strongly involved.

Tailoring shape and size of biogenic silver nanoparticles to enhance antimicrobial efficacy against MDR bacteria.

PubMed

Kumari, Madhuree; Pandey, Shipra; Giri, Ved Prakash; Bhattacharya, Arpita; Shukla, Richa; Mishra, Aradhana; Nautiyal, C S

2017-04-01

Spherical, rectangular, penta, and hexagonal silver nanoparticles of different dimensions were biosynthesized in an eco-friendly manner by biocontrol agent, Trichoderma viride by manipulating physical parameters, pH, temperature, and reaction time. The particles were characterized by UV-vis spectroscopy; Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and Fourier Transform Infra-red Spectroscopy (FTIR). Shape and size dependent antimicrobial activity of nanoparticles against human pathogens was observed. Maximum inhibition was found with spherical nanoparticles (2-5 nm) showing 40, 51, 43, 53.9 and 55.8% against Shigella sonnei, Escherichia coli, Serratia marcescens, Staphylococcus. aureus and Pseudomonas aeruginosa respectively, where as pentagonal and hexagonal nanoparticles (50-100 nm) demonstrated 32, 41, 31, 42.84 and 42.80% of inhibition as compared to control. Nanoparticles of different geometry and dimension established enhanced antagonistic activity against pathogens with all the tested antibiotics. Excellent antimicrobial efficacy was obtained with spherical nanoparticles of 2-5 nm with ampicillin and penicillin. Shape and size played major role in enhancing antimicrobial potential of silver nanoparticles, both singly and synergistically with antibiotics which can be exploited to combat the spread of multidrug resistant pathogens. Copyright © 2016. Published by Elsevier Ltd.

Impact of agglomeration state of nano- and submicron sized gold particles on pulmonary inflammation

PubMed Central

2010-01-01

Background Nanoparticle (NP) toxicity testing comes with many challenges. Characterization of the test substance is of crucial importance and in the case of NPs, agglomeration/aggregation state in physiological media needs to be considered. In this study, we have addressed the effect of agglomerated versus single particle suspensions of nano- and submicron sized gold on the inflammatory response in the lung. Rats were exposed to a single dose of 1.6 mg/kg body weight (bw) of spherical gold particles with geometric diameters of 50 nm or 250 nm diluted either by ultrapure water or by adding phosphate buffered saline (PBS). A single dose of 1.6 mg/kg bw DQ12 quartz was used as a positive control for pulmonary inflammation. Extensive characterization of the particle suspensions has been performed by determining the zetapotential, pH, gold concentration and particle size distribution. Primary particle size and particle purity has been verified using transmission electron microscopy (TEM) techniques. Pulmonary inflammation (total cell number, differential cell count and pro-inflammatory cytokines), cell damage (total protein and albumin) and cytotoxicity (alkaline phosphatase and lactate dehydrogenase) were determined in bronchoalveolar lavage fluid (BALF) and acute systemic effects in blood (total cell number, differential cell counts, fibrinogen and C-reactive protein) 3 and 24 hours post exposure. Uptake of gold particles in alveolar macrophages has been determined by TEM. Results Particles diluted in ultrapure water are well dispersed, while agglomerates are formed when diluting in PBS. The particle size of the 50 nm particles was confirmed, while the 250 nm particles appear to be 200 nm using tracking analysis and 210 nm using TEM. No major differences in pulmonary and systemic toxicity markers were observed after instillation of agglomerated versus single gold particles of different sizes. Both agglomerated as well as single nanoparticles were taken up by macrophages. Conclusion Primary particle size, gold concentration and particle purity are important features to check, since these characteristics may deviate from the manufacturer's description. Suspensions of well dispersed 50 nm and 250 nm particles as well as their agglomerates produced very mild pulmonary inflammation at the same mass based dose. We conclude that single 50 nm gold particles do not pose a greater acute hazard than their agglomerates or slightly larger gold particles when using pulmonary inflammation as a marker for toxicity. PMID:21126342

Size-dependent fluorescence of bioaerosols: Mathematical model using fluorescing and absorbing molecules in bacteria

DOE PAGES

Hill, Steven C.; Williamson, Chatt C.; Doughty, David C.; ...

2015-02-02

This paper uses a mathematical model of fluorescent biological particles composed of bacteria and/or proteins (mostly as in Hill et al., 2013 [23]) to investigate the size-dependence of the total fluorescence emitted in all directions. The model applies to particles which have negligible reabsorption of fluorescence within the particle. The specific particles modeled here are composed of ovalbumin and of a generic Bacillus. The particles need not be spherical, and in some cases need not be homogeneous. However, the results calculated in this paper are for spherical homogeneous particles. Light absorbing and fluorescing molecules included in the model are aminomore » acids, nucleic acids, and several coenzymes. Here the excitation wavelength is 266 nm. The emission range, 300 to 370 nm, encompasses the fluorescence of tryptophan. The fluorescence cross section (C F) is calculated and compared with one set of published measured values. We investigate power law (Ad y) approximations to C F, where d is diameter, and A and y are parameters adjusted to fit the data, and examine how y varies with d and composition, including the fraction as water. The particle's fluorescence efficiency (Q F=C F/geometric-cross-section) can be written for homogeneous particles as Q absR F, where Q abs is the absorption efficiency, and R F, the fraction of the absorbed light emitted as fluorescence, is independent of size and shape. When Q F is plotted vs. m id or mi(m r-1)d, where m=m r+im i is the complex refractive index, the plots for different fractions of water in the particle tend to overlap.« less

TOPO-capped silver selenide nanoparticles and their incorporation into polymer nanofibers using electrospinning technique

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

More, D.S.; Moloto, M.J., E-mail: makwenam@vut.ac.za; Moloto, N.

Highlights: • Ag{sub 2}Se nanoparticles produced spherical particles with sizes 12 nm (180 °C) and 27 nm (200 °C). • Higher temperature produced increased particle size (∼75 nm) and changed in shape. • Ag{sub 2}Se nanoparticles (0.2–0.6%) added into PVP (35–45%) to yield reduced fiber beading. • Polymer nanofibers electrospun at 11–20 kV produced fiber diameters of 425–461 nm. • Optical properties in the fibers were observed due to the Ag{sub 2}Se nanoparticles loaded. - Abstract: Electrospinning is the most common technique for fabricating polymer fibers as well as nanoparticles embedded polymer fibers. Silver selenide nanoparticles were synthesized using tri-n-octylphosphinemore » (TOP) as solvent and tri-n-octylphosphine oxide (TOPO) as capping environment. Silver selenide was prepared by reacting silver nitrate and selenium with tri-n-octylphosphine (TOP) to form TOP–Ag and TOP–Se solutions. Both absorption and emission spectra signify the formation of nanoparticles as well as the TEM which revealed spherical particles with an average particle size of 22 nm. The polymer, PVP used was prepared at concentrations ranging from (35 to 45 wt%) and the TOPO-capped silver selenide nanoparticles (0.2 and 0.6 wt%) were incorporated into them and electrospun by varying the voltage from 11 to 20 kV. The SEM images of the Ag{sub 2}Se/PVP composite fibers revealed the fibers of diameters with average values of 425 and 461 nm. The X-ray diffraction results show peaks which were identified due to α-Ag{sub 2}Se body centered cubic compound. The sharp peak observed for all the samples at 2θ = 44.5 suggest the presence of Ag in the face centered cubic which can be attributed to higher concentration of silver nitrate used with molar ratio of selenium to silver and the abundance of silver in the silver selenide crystal. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA) and ultraviolet–visible spectroscopy were used to characterize the structure of the PVP/Ag{sub 2}Se composite fibers.« less

Synthesis of spherical calcium phosphate particles for dental and orthopedic applications

PubMed Central

Bohner, Marc; Tadier, Solène; van Garderen, Noémie; de Gasparo, Alex; Döbelin, Nicola; Baroud, Gamal

2013-01-01

Calcium phosphate materials have been used increasingly in the past 40 years as bone graft substitutes in the dental and orthopedic fields. Accordingly, numerous fabrication methods have been proposed and used. However, the controlled production of spherical calcium phosphate particles remains a challenge. Since such particles are essential for the synthesis of pastes and cements delivered into the host bone by minimally-invasive approaches, the aim of the present document is to review their synthesis and applications. For that purpose, production methods were classified according to the used reagents (solutions, slurries, pastes, powders), dispersion media (gas, liquid, solid), dispersion tools (nozzle, propeller, sieve, mold), particle diameters of the end product (from 10 nm to 10 mm), and calcium phosphate phases. Low-temperature calcium phosphates such as monetite, brushite or octacalcium phosphate, as well as high-temperature calcium phosphates, such as hydroxyapatite, β-tricalcium phosphate or tetracalcium phosphate, were considered. More than a dozen production methods and over hundred scientific publications were discussed. PMID:23719177

Sol-gel preparation of hydrophobic silica antireflective coatings with low refractive index by base/acid two-step catalysis.

PubMed

Cai, Shuang; Zhang, Yulu; Zhang, Hongli; Yan, Hongwei; Lv, Haibing; Jiang, Bo

2014-07-23

Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A "core-shell" particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated.

Atomic force microscopy investigation of Mason-Pfizer monkey virus and human immunodeficiency virus type 1 reassembled particles

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

Kuznetsov, Yu. G.; Ulbrich, P.; Institute of Molecular Genetics, Czech Academy of Sciences, 166 10 Prague

2007-04-10

Particles of {delta}ProCANC, a fusion of capsid (Canada) and nucleocapsid (NC) protein of Mason-Pfizer monkey virus (M-PMV), which lacks the amino terminal proline, were reassembled in vitro and visualized by atomic force microscopy (AFM). The particles, of 83-84 nm diameter, exhibited ordered domains based on trigonal arrays of prominent rings with center to center distances of 8.7 nm. Imperfect closure of the lattice on the spherical surface was affected by formation of discontinuities. The lattice is consistent only with plane group p3 where one molecule is shared between contiguous rings. There are no pentameric clusters nor evidence that the particlesmore » are icosahedral. Tubular structures were also reassembled, in vitro, from two HIV fusion proteins, {delta}ProCANC and CANC. The tubes were uniform in diameter, 40 nm, but varied in length to a maximum of 600 nm. They exhibited left handed helical symmetry based on a p6 hexagonal net. The organization of HIV fusion proteins in the tubes is significantly different than for the protein units in the particles of M-PMV {delta}ProCANC.« less

Characterization and Potential Environmental Implications of Select Cu-Based Fungicides and Bactericides Employed in U.S. Markets

EPA Science Inventory

This exploratory study aimed to examine the extent and mineral speciation of nanosized Cu in two fungicide products (A and B) available in the U.S. markets. Electron microcopy results demonstrated the presence of spherical and polydisperse <100 nm Cu particles in product B. Oth...

Characterization and complete genome sequence of a previously uncharacterized panicovirus from Bermuda grass detected by high throughput sequencing

USDA-ARS?s Scientific Manuscript database

Bermuda grass samples were examined by transmission electron microscopy and 28-30 nm spherical virus particles were observed. Total RNA from these plants was subjected to high throughput sequencing (HTS). The nearly full genome sequence of a previously uncharacterized Panicovirus was identified from...

Effects of temperature and dissolved oxygen on Se(IV) removal and Se(0) precipitation by Shewanella sp. HN-41.

PubMed

Lee, Ji-Hoon; Han, Jaehong; Choi, Heechul; Hur, Hor-Gil

2007-08-01

Facultative anaerobic Shewanella sp. strain HN-41 was able to utilize selenite (Se(IV)) as a sole electron acceptor for respiration in anaerobic condition, resulting in reduction of Se(IV) and then precipitation of elemental Se nano-sized spherical particles, which were identified using energy-dispersive X-ray spectroscopy and X-ray absorption near-edge structure spectroscopy. When the effects on Se(IV) reduction to elemental Se were studied by varying incubation temperatures and dissolved oxygen contents, Se(IV) reduction occurred more actively with higher removal rate of Se(IV) in aqueous phase and well-shaped spherical Se(0) nanoparticles were formed from the incubations under N(2) (100%) or N(2):O(2) (80%:20%) at 30 degrees C with average diameter values of 181+/-40 nm and 164+/-24 nm, respectively, while relatively less amounts of irregular-shaped Se(0) nanoparticles were produced with negligible amount of Se(IV) reduction and removal under 100% of O(2). The Se particle size distributions based on scanning electron microscopy also showed a general tendency towards decreased Se particle size as oxygen content increased, whereas the particle size seemed uncorrelated to the change in the incubation temperature. These results also suggest that the size-controlled biological Se(0) nanospheres production may be achieved simply by changing the culture conditions.

Impact of and correction for instrument sensitivity drift on nanoparticle size measurements by single-particle ICP-MS

PubMed Central

El Hadri, Hind; Petersen, Elijah J.; Winchester, Michael R.

2016-01-01

The effect of ICP-MS instrument sensitivity drift on the accuracy of NP size measurements using single particle (sp)ICP-MS is investigated. Theoretical modeling and experimental measurements of the impact of instrument sensitivity drift are in agreement and indicate that drift can impact the measured size of spherical NPs by up to 25 %. Given this substantial bias in the measured size, a method was developed using an internal standard to correct for the impact of drift and was shown to accurately correct for a decrease in instrument sensitivity of up to 50 % for 30 nm and 60 nm gold nanoparticles. PMID:26894759

Synthesis and characterization of nano-sized zirconia powder synthesized by single emulsion-assisted direct precipitation.

PubMed

Chandra, Navin; Singh, Deepesh Kumar; Sharma, Meenakshi; Upadhyay, Ravi Kant; Amritphale, S S; Sanghi, S K

2010-02-15

For the first time, single reverse microemulsion-assisted direct precipitation route has been successfully used to synthesize tetragonal zirconia nanoparticles in narrow size range. The synthesized powder was characterized using FT-IR, XRD and HRTEM techniques. The zirconia nanoparticles obtained were spherical in shape and has narrow particle size distribution in the range of 13-31nm and crystallite size in the range of 13-23nm. Copyright 2009 Elsevier Inc. All rights reserved.

Target categorization of aerosol and clouds by continuous multiwavelength-polarization lidar measurements

NASA Astrophysics Data System (ADS)

Baars, Holger; Seifert, Patric; Engelmann, Ronny; Wandinger, Ulla

2017-09-01

Absolute calibrated signals at 532 and 1064 nm and the depolarization ratio from a multiwavelength lidar are used to categorize primary aerosol but also clouds in high temporal and spatial resolution. Automatically derived particle backscatter coefficient profiles in low temporal resolution (30 min) are applied to calibrate the lidar signals. From these calibrated lidar signals, new atmospheric parameters in temporally high resolution (quasi-particle-backscatter coefficients) are derived. By using thresholds obtained from multiyear, multisite EARLINET (European Aerosol Research Lidar Network) measurements, four aerosol classes (small; large, spherical; large, non-spherical; mixed, partly non-spherical) and several cloud classes (liquid, ice) are defined. Thus, particles are classified by their physical features (shape and size) instead of by source. The methodology is applied to 2 months of continuous observations (24 h a day, 7 days a week) with the multiwavelength-Raman-polarization lidar PollyXT during the High-Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE) in spring 2013. Cloudnet equipment was operated continuously directly next to the lidar and is used for comparison. By discussing three 24 h case studies, it is shown that the aerosol discrimination is very feasible and informative and gives a good complement to the Cloudnet target categorization. Performing the categorization for the 2-month data set of the entire HOPE campaign, almost 1 million pixel (5 min × 30 m) could be analysed with the newly developed tool. We find that the majority of the aerosol trapped in the planetary boundary layer (PBL) was composed of small particles as expected for a heavily populated and industrialized area. Large, spherical aerosol was observed mostly at the top of the PBL and close to the identified cloud bases, indicating the importance of hygroscopic growth of the particles at high relative humidity. Interestingly, it is found that on several days non-spherical particles were dispersed from the ground into the atmosphere.

Fabrication of Spherical AlSi10Mg Powders by Radio Frequency Plasma Spheroidization

NASA Astrophysics Data System (ADS)

Wang, Linzhi; Liu, Ying; Chang, Sen

2016-05-01

Spherical AlSi10Mg powders were prepared by radio frequency plasma spheroidization from commercial AlSi10Mg powders. The fabrication process parameters and powder characteristics were investigated. Field emission scanning electron microscope, X-ray diffraction, laser particle size analyzer, powder rheometer, and UV/visible/infrared spectrophotometer were used for analyses and measurements of micrographs, phases, granulometric parameters, flowability, and laser absorption properties of the powders, respectively. The results show that the obtained spherical powders exhibit good sphericity, smooth surfaces, favorable dispersity, and excellent fluidity under appropriate feeding rate and flow rate of carrier gas. Further, acicular microstructures of the spherical AlSi10Mg powders are composed of α-Al, Si, and a small amount of Mg2Si phase. In addition, laser absorption values of the spherical AlSi10Mg powders increase obviously compared with raw material, and different spectra have obvious absorption peaks at a wavelength of about 826 nm.

Structural and Magnetic Properties of Dilute Ca²⁺ Doped Iron Oxide Nanoparticles.

PubMed

Samar Layek; Rout, K; Mohapatra, M; Anand, S; Verma, H C

2016-01-01

Undoped and calcium substituted hematite (α-Fe₂O₃) nanoparticles are synthesized by surfactant-directed co-precipitation and post annealing method. The annealed nanoparticles were found to be in single phase in nature and crystallize in the rhombohedral structure with space group R3c as confirmed by Rietveld refinement of the X-ray diffraction (XRD) data. Average crystallite sizes are calculated to be 20 to 30 nm and 50 to 60 nm for the nanoparticles annealed at 400 and 600 °C respectively. Mössbauer spectra for all the nanoparticles could be fitted with a sextet corresponding to the single magnetic state of the iron atoms in its Fe³⁺ state in the hematite matrix. The FTIR and Raman spectra of all the samples correspond to specific modes of α-Fe₂O₃. UV-Vis spectra of annealed samples showed broad peaks in the range of 525-630 nm resulting from spin-forbidden ligand field transition together with the spin-flip transition among the 2t₂g states. The estimated band gap energies were in the range of 1.6 to 1.9 eV which are much lower than the reported values for nano hematite. From the room temperature magnetic hysteresis loop measurements, weak ferromagnetic behavior is observed in all undoped and Ca²⁺ doped hematite samples. Morin temperature (T(M)) is calculated to be 257 and 237 K for 1.45% doped samples with particle size 54 and 27 nm respectively. The sample with Ca content of 1.45 wt% when annealed at 400 °C showed that the particles were of different shapes which included both quasi spherical and rod shaped. On annealing the same sample at 600 °C, the nanorods collapsed to form bigger spherical and ellipsoidal particles.

Electrical and magnetic properties of spherical SmFeO{sub 3} synthesized by aspartic acid assisted combustion method

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

Yuvaraj, Subramanian; Layek, Samar; Vidyavathy, S. Manisha

2015-12-15

Highlights: • SmFeO{sub 3} is synthesized by simple combustion method using aspartic acid as the fuel. • The particles are spherical in shape with the size ranges between 150 and 300 nm. • Cole–Cole plot infers the bulk conduction mechanism. • Room temperature VSM analysis reveal the weak ferromagnetic behaviour of SmFeO{sub 3}. • Mössbauer analysis elucidates the +3 oxidation state of Fe atoms. - Abstract: Samarium orthoferrite (SmFeO{sub 3}) is synthesized by a simple combustion method using aspartic acid as fuel. Phase purity and functional groups are analyzed via X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analysis, whichmore » confirms the single phase formation of orthorhombic SmFeO{sub 3}. Approximately spherical particles with size range 150–300 nm is revealed by scanning electron microscope (SEM). The conductivity of the material is identified by the single semicircle obtained in the solid state impedance spectra at elevated temperatures. The calculated electrical conductivity increases with increasing temperature, inferring the semiconducting nature of SmFeO{sub 3}. A magnetic study at room temperature revealed weak ferromagnetic behaviour in SmFeO{sub 3} due to Dzyaloshinsky–Moriya antisymmetric exchange interaction mechanism. Mössbauer analysis confirmed the +3 oxidation state of iron and magnetic ordering of the sample at room temperature.« less

Miscibility Gap Closure, Interface Morphology, and Phase Microstructure of 3D Li xFePO 4 Nanoparticles from Surface Wetting and Coherency Strain

DOE PAGES

Welland, Michael J.; Karpeyev, Dmitry; O’Connor, Devin T.; ...

2015-09-10

We study the mesoscopic effects which suppress phase-segregation in Li xFePO 4 nanoparticles using a multiphysics phase-field model implement on a high performance cluster. We simulate 3D spherical particles of radii from 3nm to 40nm and examine the equilibrium microstructure and voltage profiles as a they depend on size and overall lithiation. The model includes anisotropic, concentration-dependent elastic moduli, misfit strain, and facet dependent surface wetting within a Cahn-Hilliard formulation. Here, we find that the miscibility gap vanishes for particles of radius ~ 5 nm, and the solubility limits change with overall particle lithiation. The corresponding voltage plateau, indicative ofmore » phase-segregation, changes in extent and also vanishes. Surface wetting is found to have a strong effect on stabilizing a variety of microstructures, exaggerating the shifting of solubility limits, and shortening the voltage plateau.« less

Characterization of Mixed Polypeptide Colloidal Particles by Light Scattering

NASA Astrophysics Data System (ADS)

Shuman, Hannah E.; Gaeckle, Grace K.; Gavin, John; Holland, Nolan B.; Streletzky, Kiril A.

2014-03-01

Temperature-dependent polymer surfactants have been developed by connecting three elastin-like polypeptide (ELP) chains to a charged protein domain (foldon), forming a three-armed star polymer. At low temperatures the polymer is soluble, while at higher temperatures it forms micelles. The behavior of mixtures of the three-armed star ELP (E20-Foldon) and H40-Linear ELP chains was analyzed under different salt and protein concentrations and various foldon to linear ELP ratio using Depolarized Dynamic Light Scattering. It was expected that under certain conditions the pure E20-Foldon would form spherical micelles, which upon adding the linear ELP would change in size and possibly shape. The pure E20-Foldon indeed formed largely spherical micelles with Rh of 10-20nm in solutions with 15-100mM salt and protein concentration between 10 μM and 100 μM. For the mixtures of 50 μM E20-Foldon and varying concentrations of H40-Linear in 25mM of salt, it was discovered that low and high H40-Linear concentration (4 μM and 50 μM) had only one transition. For the mixtures with of 10 and 25 μM of H40-Linear the two distinct transition temperatures were observed by spectrophotometry. The first transition corresponded to significantly elongated diffusive particles of apparent Rh of 30-50nm, while the second transition corresponded to slightly anisotropic diffusive particles with apparent Rh of about 20nm. At all H40-Linear concentrations studied, diffusive particles were seen above the second transition. Their radius and ability to depolarize light increased with the increase of H40-Linear concentration.

Shape control of the magnetic iron oxide nanoparticles under different chain length of reducing agents

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

Ngoi, Kuan Hoon; Chia, Chin-Hua, E-mail: chia@ukm.edu.my; Zakaria, Sarani

2015-09-25

We report on the effect of using reducing agents with different chain-length on the synthesis of iron oxide nanoparticles by thermal decomposition of iron (III) acetylacetonate in 1-octadecene. This modification allows us to control the shape of nanoparticles into spherical and cubic iron oxide nanoparticles. The highly monodisperse 14 nm spherical nanoparticles are obtained under 1,2-dodecanediol and average 14 nm edge-length cubic iron oxide nanoparticles are obtained under 1,2-tetradecanediol. The structural characterization such as transmission electron microscope (TEM) and X-ray diffraction (XRD) shows similar properties between two particles with different shapes. The vibrating sample magnetometer (VSM) shows no significant difference between sphericalmore » and cubic nanoparticles, which are 36 emu/g and 37 emu/g respectively and superparamagnetic in nature.« less

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

Formation of Polyelectrolyte Complex Colloid Particles between Chitosan and Pectin with Different Degree of Esterification

NASA Astrophysics Data System (ADS)

Wang, Hui; Sun, Hongyuan; He, Jieyu

2017-12-01

The effects of degree of esterification, pectin/chitosan ratio and pH on the formation of polyelectrolyte complex colloid particles between chitosan (CS) and pectin (PE) were investigated. Low methoxyl pectin (LPE) was achieved by de-esterifying high methoxyl pectin (HPE) with pectin methyl esterase. Turbidity titration and colorimetric method was used to determine the stability of complex colloid particles. The structure and morphology of complex particles were characterized by FTIR and TEM. When pectin solution was dropped into chitosan solution, complex colloidal dispersion was stable as PE/CS mass ratio was no more than 3:2. Colloidal particles of HPE-CS complex coagulated at larger ratio of PE/CS than LPE-CS. The maximum complex occurred at pH 6.1 for HPE-CS and pH 5.7 for LPE-CS, and decreasing pH leaded to the dissociation of complex particles. Electrostatic interactions between carboxyl groups on pectin and amino groups on chitosan were confirmed by FTIR. Colloidal particle sizes ranged from about 100 nm to 400 nm with spherical shape.

Monodisperse core-shell particles composed of magnetite and dye-functionalized mesoporous silica

NASA Astrophysics Data System (ADS)

Eurov, D. A.; Kurdyukov, D. A.; Medvedev, A. V.; Kirilenko, D. A.; Yakovlev, D. R.; Golubev, V. G.

2017-08-01

Hybrid particles with a core-shell structure have been obtained in the form of monodisperse spherical mesoporous silica particles filled with magnetite and covered with a mesoporous silica shell functionalized with a luminescent dye. The particles have a small root-mean-square size deviation (at most 10%), possess a specific surface area and specific pore volume of up to 250 m2/g and 0.15 cm3/g, respectively, and exhibit visible luminescence peaked at a wavelength of 530 nm. The particles can be used in diagnostics of cancerous diseases, serving simultaneously for therapeutic (magnetic hyperthermia and targeted drug delivery) and diagnostic (contrast agent for magnetic-resonance tomography and luminescent marker) purposes.

Polycation-Functionalized Nanoporous Silicon Particles for Gene Silencing on Breast Cancer Cells

PubMed Central

Zhang, Mingzhen; Xu, Rong; Xia, Xiaojun; Yang, Yong; Gu, Jianhua; Qin, Guoting; Liu, Xuewu; Ferrari, Mauro; Shen, Haifa

2013-01-01

Nanoporous silicon particles (pSi), with a pore size in the range of 20~60 nm, were modified with polyethyleimine (PEI) to yield pSi-PEI particles, which were subsequently complexed with siRNA. Thus, pSi-PEI/siRNA particles were fabricated, with the PEI/siRNA nanocomplexes mainly anchored inside the nanopore of the pSi particles. These hybrid particles were used as carriers to deliver siRNA to human breast cancer cells. Due to the gradual degradation of the pSi matrix under physiological conditions, the PEI/siRNA nanocomplexes were released from the pore interior in a sustained manner. Physicochemical characterization revealed that the released PEI/siRNA nanocomplexes exhibited well-defined spherical shape and narrow particle size distribution between 15 and 30 nm. Gene knockdown against the ataxia telangiectasia mutated (ATM) cancer gene showed dramatic gene silencing efficacy. Moreover, comprehensive biocompatibility studies were performed for the pSi-PEI/siRNA particles both in vitro and in vivo and demonstrated that the pSi-PEI particles exhibited significantly enhanced biocompatibility. As a consequence, PEI-modified porous silicon particles may have substantial potential as safe and effective siRNA delivery systems. PMID:24103653

Scaling analysis for the investigation of slip mechanisms in nanofluids

NASA Astrophysics Data System (ADS)

Savithiri, S.; Pattamatta, Arvind; Das, Sarit K.

2011-07-01

The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

Scaling analysis for the investigation of slip mechanisms in nanofluids

PubMed Central

2011-01-01

The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it. PMID:21791036

Modeling of the rough spherical nanoparticles manipulation on a substrate based on the AFM nanorobot

NASA Astrophysics Data System (ADS)

Zakeri, M.; Faraji, J.

2014-12-01

In this paper, dynamic behavior of the rough spherical micro/nanoparticles during pulling/pushing on the flat substrate has been investigated and analyzed. For this purpose, at first, two hexagonal roughness models (George and Cooper) were studied and then evaluations for adhesion force were determined for rough particle manipulation on flat substrate. These two models were then changed by using of the Rabinovich theory. Evaluations were determined for contact adhesion force between rough particle and flat substrate; depth of penetration evaluations were determined by the Johnson-Kendall-Roberts contact mechanic theory and the Schwartz method and according to Cooper and George roughness models. Then, the novel contact theory was used to determine a dynamic model for rough micro/nanoparticle manipulation on flat substrate. Finally, simulation of particle dynamic behavior was implemented during pushing of rough spherical gold particles with radii of 50, 150, 400, 600, and 1,000 nm. Results derived from simulations of particles with several rates of roughness on flat substrate indicated that compared to results for flat particles, inherent roughness on particles might reduce the rate of critical force needed for sliding and rolling given particles. Given a fixed radius for roughness value and increased roughness height, evaluations for sliding and rolling critical forces showed greater reduction. Alternately, the rate of critical force was shown to reduce relative to an increased roughness radius. With respect to both models, based on the George roughness model, the predicted rate of adhesion force was greater than that determined in the Cooper roughness model, and as a result, the predicted rate of critical force based on the George roughness model was closer to the critical force value of flat particle.

β-structure of the coat protein subunits in spherical particles generated by tobacco mosaic virus thermal denaturation.

PubMed

Dobrov, Evgeny N; Nikitin, Nikolai A; Trifonova, Ekaterina A; Parshina, Evgenia Yu; Makarov, Valentin V; Maksimov, George V; Karpova, Olga V; Atabekov, Joseph G

2014-01-01

Conversion of the rod-like tobacco mosaic virus (TMV) virions into "ball-like particles" by thermal denaturation at 90-98 °C had been described by R.G. Hart in 1956. We have reported recently that spherical particles (SPs) generated by thermal denaturation of TMV at 94-98 °C were highly stable, RNA-free, and water-insoluble. The SPs were uniform in shape but varied widely in size (53-800 nm), which depended on the virus concentration. Here, we describe some structural characteristics of SPs using circular dichroism, fluorescence spectroscopy, and Raman spectroscopy. It was found that the structure of SPs protein differs strongly from that of the native TMV and is characterized by coat protein subunits transition from mainly (about 50%) α-helical structure to a structure with low content of α-helices and a significant fraction of β-sheets. The SPs demonstrate strong reaction with thioflavin T suggesting the formation of amyloid-like structures.

Quercetin loaded biopolymeric colloidal particles prepared by simultaneous precipitation of quercetin with hydrophobic protein in aqueous medium.

PubMed

Patel, Ashok R; Heussen, Patricia C M; Hazekamp, Johan; Drost, Ellen; Velikov, Krassimir P

2012-07-15

Quercetin loaded biopolymeric colloidal particles were prepared by precipitating quercetin (water insoluble polyphenol) and zein (hydrophobic protein), simultaneously, by adding their hydro-alcoholic solution to aqueous solution in presence of sodium caseinate as an electrosteric stabiliser. The presence of protein resulted in altering the shape of quercetin precipitates from needle-like to spherical shape at higher zein proportions, as confirmed by transmission electron microscopy. The average particle size of zein:quercetin composite particles was below 200 nm (130-161 nm) with negative surface charge (-30 to -41 mV), as confirmed by dynamic light scattering and electrophoretic mobility data. Solid state characterisation (X-ray diffraction) and spectroscopic measurements (UV-Vis and IR spectroscopy) confirmed characteristic changes in quercetin due to the entrapment in the biopolymeric matrix of colloidal particles. Results from anti-oxidant study demonstrated the advantage of entrapping quercetin in the colloidal particles in terms of the chemical stability in the alkaline pH and against photodegradation under UV-light irradiation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Synthesis Structural and Optical Properties Of (Co, Al) co-doped ZnO Nano Particles

NASA Astrophysics Data System (ADS)

Swapna, P.; Venkatramana Reddy, S.

2018-02-01

We prepared (Co, Al) co-doped ZnO nanostructures using the method chemical co-precipitation successfully, at room temperature using PEG (Poly ethylene glycol) as stabilizing agent. Samples are prepared with different concentrations by keeping aluminium at 5 mol percent constant and varying the concentration of cobalt from 1 to 5 mol percent. After the preparation all the samples are carefully subjected to characterizations such as XRD, SEM with EDS, TEM, PL and UV-VIS-NIR. XRD pattern shows that all the samples possess hexagonal wurtzite crystal structure having no secondary phases pertaining to Al or cobalt, which shows successful dissolution of the dopents. TEM results shows the accurate size of particles and is confirmed the XRD data. SEM images of all the samples shows that particles are in nearly spherical shape, EDS spectrum reveals that incorporation of cobalt and aluminum in host lattice. PL spectrum shows that all the samples containing two prominent peaks centered at 420 nm and 446 nm. UV-VIS-NIR spectra has shown three absorptions peaks in the range of wavelength 550 nm to 700 nm, which are ascribed as typical d-d transitions of cobalt ions.

Synthetic approaches to construct viral capsid-like spherical nanomaterials.

PubMed

Matsuura, Kazunori

2018-06-06

This feature article describes recent progress in synthetic strategies to construct viral capsid-like spherical nanomaterials using the self-assembly of peptides and/or proteins. By mimicking the self-assembly of spherical viral capsids and clathrin, trigonal peptide conjugates bearing β-sheet-forming peptides, glutathiones, or coiled-coil-forming peptides were developed to construct viral capsid-like particles. β-Annulus peptides from tomato bushy stunt virus self-assembled into viral capsid-like nanocapsules with a size of 30-50 nm, which could encapsulate various guest molecules and be decorated with different molecules on their surface. Rationally designed fusion proteins bearing symmetric assembling units afforded precise viral capsid-like polyhedral assemblies. These synthetic approaches to construct artificial viruses could become useful guidelines to develop novel drug carriers, vaccine platforms, nanotemplates and nanoreactors.

Synthesis of silver nanoparticles stabilized with C-phycocyanin and for fluorimetric detection of copper ions

NASA Astrophysics Data System (ADS)

Wei, Nana; Hou, Yanhua; Lu, Zongbao; Yu, Huatong; Wang, Quanfu

2018-01-01

In this study, C-phycocyanin as protective agent, AgNO3 as raw material and NaBH4 as reducing agent synthesized C-phycocyanin-Ag nanoparticles (PC-AgNPs). The synthesis conditions of PC-AgNPs were determined by optimization. The maximum UV absorption peak of PC-AgNPs at 400 nm. The fluorescence excitation wavelength was 580 nm and the emission wavelength was 625 nm. PC-AgNPs was spherical in transmission electron microscope and the particles sizes were about 10-25 nm. In addition, fluorescence quenching was observed after adding copper ions to PC-AgNPs, which indicated that PC-AgNPs has potential applications in the detection of copper ions in diverse water environment.

Effect of Co doping, capping agent and optical-structural studies of ZnO:Co2+ nanoparticles

NASA Astrophysics Data System (ADS)

Taheri Otaqsara, S. M.

2011-08-01

Co2+ doped ZnO nanoparticles (NPs) using PEG as a capping agent were prepared by colloidal wet-chemical method. The structure, morphology and characteristics of as-prepared samples were investigated. X-ray diffraction patterns studies revealed wurtzite crystal phase. STM-TEM micrographs show a spherical shape and nearly well distribution with an average particle size of ~15-20 nm. UV-VIS spectra show the presence of exciton peak at 349 nm which can be effectively tuned versus cobalt doping and PEG concentration. PL studies were done under the excitation of 347 nm, which exhibited a UV (~386 nm) and visible (blue-orange) emission peak because of free-exciton recombination and oxygen vacancy.

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

PubMed Central

2013-01-01

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging. PMID:23962025

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

NASA Astrophysics Data System (ADS)

Atabaev, Timur Sh; Kim, Hyung-Kook; Hwang, Yoon-Hwae

2013-08-01

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging.

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

Tuhkala, M., E-mail: mtuhkala@ee.oulu.fi; Maček, M.; Siponkoski, T.

Highlights: • Elongated micrometre sized BaTiO{sub 3} particles had strong effect on permittivity. • Effect was significantly stronger compared to μm and nm sized spherical particles. • Properties could be tailored by varying the particle shapes of dielectric powders. • Could be utilized, e.g., in a production of electrical composites for RF applications. - Abstract: The effect of BaTiO{sub 3} particle shape on the properties of 0.98MgTiO{sub 3}–0.02BaTiO{sub 3} composite powders was characterized and analyzed using an indirectly coupled open-ended coaxial cavity resonator at gigahertz frequencies. Elongated micrometre sized BaTiO{sub 3} particles were found to have a significantly stronger effectmore » on permittivity when compared to composite powders having micro and nano sized spherical BaTiO{sub 3} particles. Inclusion permittivities and dielectric loss tangents of composite powders increased from that of pure MgTiO{sub 3} powder, 13.3 and 4.6 × 10{sup −3}, up to 15.7 and 1.7 × 10{sup −2} with needle shaped BaTiO{sub 3} particles, respectively. The presented results give valuable information for tailoring the properties of dielectrics which can be utilized in the vast field of electronic component manufacturing.« less

Observation of Dust Particle Gyromotion in a Magnetized Dusty Plasma

NASA Astrophysics Data System (ADS)

Compton, C. S.; Amatucci, W. E.; Gatling, G.; Tejero, E.

2008-11-01

In dusty plasma research, gyromotion of the dust has been difficult to observe experimentally. Previous experiments by Amatucci et al. have shown gyromotion of a single dust particle [1]. This early work was performed with alumina dust that had a size distribution and non-uniformly shaped particles. In the current experiment, evidence of spherical, monodispersed, dust particles exhibiting gyromotion has been observed. Silica particles 0.97 micrometers in diameter are suspended in a DC glow discharge argon plasma. The experiment is performed in the Naval Research Laboratory's DUsty PLasma EXperiment (DUPLEX Jr.). DUPLEX is a 61-cm tall by 46-cm diameter acrylic chamber allowing full 360 degree optical access for diagnostics. The neutral pressure for the experiment is 230 mTorr with a 275 V bias between the circular electrodes. The electrodes have a separation of 4 cm. A strong magnetic field is created by 2 pairs of neodymium iron boride magnets placed above and below the anode and cathode respectively. The resulting field is 1.4 kG. The dust particles are illuminated with a 25 mW, 672 nm laser. Images are captured using an intensified CCD camera and a consumer digital video cassette recorder. Recent evidence of gyromotion of spherical, monodispersed, dust particles will be presented. [1] Amatucci, W.E., et al., Phys. Plasmas, 11, 2097 (2004)

Phase stability in nanoscale material systems: extension from bulk phase diagrams

NASA Astrophysics Data System (ADS)

Bajaj, Saurabh; Haverty, Michael G.; Arróyave, Raymundo; Goddard Frsc, William A., III; Shankar, Sadasivan

2015-05-01

Phase diagrams of multi-component systems are critical for the development and engineering of material alloys for all technological applications. At nano dimensions, surfaces (and interfaces) play a significant role in changing equilibrium thermodynamics and phase stability. In this work, it is shown that these surfaces at small dimensions affect the relative equilibrium thermodynamics of the different phases. The CALPHAD approach for material surfaces (also termed ``nano-CALPHAD'') is employed to investigate these changes in three binary systems by calculating their phase diagrams at nano dimensions and comparing them with their bulk counterparts. The surface energy contribution, which is the dominant factor in causing these changes, is evaluated using the spherical particle approximation. It is first validated with the Au-Si system for which experimental data on phase stability of spherical nano-sized particles is available, and then extended to calculate phase diagrams of similarly sized particles of Ge-Si and Al-Cu. Additionally, the surface energies of the associated compounds are calculated using DFT, and integrated into the thermodynamic model of the respective binary systems. In this work we found changes in miscibilities, reaction compositions of about 5 at%, and solubility temperatures ranging from 100-200 K for particles of sizes 5 nm, indicating the importance of phase equilibrium analysis at nano dimensions.Phase diagrams of multi-component systems are critical for the development and engineering of material alloys for all technological applications. At nano dimensions, surfaces (and interfaces) play a significant role in changing equilibrium thermodynamics and phase stability. In this work, it is shown that these surfaces at small dimensions affect the relative equilibrium thermodynamics of the different phases. The CALPHAD approach for material surfaces (also termed ``nano-CALPHAD'') is employed to investigate these changes in three binary systems by calculating their phase diagrams at nano dimensions and comparing them with their bulk counterparts. The surface energy contribution, which is the dominant factor in causing these changes, is evaluated using the spherical particle approximation. It is first validated with the Au-Si system for which experimental data on phase stability of spherical nano-sized particles is available, and then extended to calculate phase diagrams of similarly sized particles of Ge-Si and Al-Cu. Additionally, the surface energies of the associated compounds are calculated using DFT, and integrated into the thermodynamic model of the respective binary systems. In this work we found changes in miscibilities, reaction compositions of about 5 at%, and solubility temperatures ranging from 100-200 K for particles of sizes 5 nm, indicating the importance of phase equilibrium analysis at nano dimensions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01535a

Fluorescence/depolarization lidar for mid-range stand-off detection of biological agents

NASA Astrophysics Data System (ADS)

Mierczyk, Z.; Kopczyński, K.; Zygmunt, M.; Wojtanowski, J.; Młynczak, J.; Gawlikowski, A.; Młodzianko, A.; Piotrowski, W.; Gietka, A.; Knysak, P.; Drozd, T.; Muzal, M.; Kaszczuk, M.; Ostrowski, R.; Jakubaszek, M.

2011-06-01

LIDAR system for real-time standoff detection of bio-agents is presented and preliminary experimental results are discussed. The detection approach is based on two independent physical phenomena: (1) laser induced fluorescence (LIF), (2) depolarization resulting from elastic scattering on non-spherical particles. The device includes three laser sources, two receiving telescopes, depolarization component and spectral signature analyzing spectrograph. It was designed to provide the stand-off detection capability at ranges from 200 m up to several kilometers. The system as a whole forms a mobile platform for vehicle or building installation. Additionally, it's combined with a scanning mechanics and advanced software, which enable to conduct the semi-automatic monitoring of a specified space sector. For fluorescence excitation, 3-rd (355 nm) and 4-th (266 nm) harmonics of Nd:YAG pulsed lasers are used. They emit short (~6 ns) pulses with the repetition rate of 20 Hz. Collecting optics for fluorescence echo detection and spectral content analysis includes 25 mm diameter f/4 Newton telescope, Czerny Turner spectrograph and 32-channel PMT. Depending on the grating applied, the spectral resolution from 20 nm up to 3 nm per channel can be achieved. The system is also equipped with an eye-safe (1.5 μm) Nd:YAG OPO laser for elastic backscattering/depolarization detection. The optical echo signal is collected by Cassegrain telescope with aperture diameter of 12.5 mm. Depolarization detection component based on polarizing beam-splitter serves as the stand-off particle-shape analyzer, which is very valuable in case of non-spherical bio-aerosols sensing.

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.

Characterisation of Fe-bearing particles and colloids in the Lena River basin, NE Russia

NASA Astrophysics Data System (ADS)

Hirst, Catherine; Andersson, Per S.; Shaw, Samuel; Burke, Ian T.; Kutscher, Liselott; Murphy, Melissa J.; Maximov, Trofim; Pokrovsky, Oleg S.; Mörth, Carl-Magnus; Porcelli, Don

2017-09-01

Rivers are significant contributors of Fe to the ocean. However, the characteristics of chemically reactive Fe remain poorly constrained, especially in large Arctic rivers, which drain landscapes highly susceptible to climate change and carbon cycle alteration. The aim of this study was a detailed characterisation (size, mineralogy, and speciation) of riverine Fe-bearing particles (>0.22 μm) and colloids (1 kDa-0.22 μm) and their association with organic carbon (OC), in the Lena River and tributaries, which drain a catchment almost entirely underlain by permafrost. Samples from the main channel and tributaries representing watersheds that span a wide range in topography and lithology were taken after the spring flood in June 2013 and summer baseflow in July 2012. Fe-bearing particles were identified, using Transmission Electron Microscopy, as large (200 nm-1 μm) aggregates of smaller (20-30 nm) spherical colloids of chemically-reactive ferrihydrite. In contrast, there were also large (500 nm-1 μm) aggregates of clay (illite) particles and smaller (100-200 nm) iron oxide particles (dominantly hematite) that contain poorly reactive Fe. TEM imaging and Scanning Transmission X-ray microscopy (STXM) indicated that the ferrihydrite is present as discrete particles within networks of amorphous particulate organic carbon (POC) and attached to the surface of primary produced organic matter and clay particles. Together, these larger particles act as the main carriers of nanoscale ferrihydrite in the Lena River basin. The chemically reactive ferrihydrite accounts for on average 70 ± 15% of the total suspended Fe in the Lena River and tributaries. These observations place important constraints on Fe and OC cycling in the Lena River catchment area and Fe-bearing particle transport to the Arctic Ocean.

Configuration of twins in glass-embedded silver nanoparticles of various origin

NASA Astrophysics Data System (ADS)

Hofmeister, H.; Dubiel, M.; Tan, G. L.; Schicke, K.-D.

2005-09-01

Structural characterization using high resolution electron microscopy and diffractogram analysis of silver nanoparticles embedded in glass by various routes of fabrication was aimed at revealing the characteristic features of twin faults occuring in such particles. Nearly spherical silver nanoparticles well below 10 nm size embedded in commercial soda-lime silicate float glass have been fabricated either by silver/sodium ion exchange or by Ag+ ion implantation. Twinned nanoparticles, besides single crystalline species, have frequently been observed for both fabrication routes, mainly at sizes above 5 nm, but also at smaller sizes, even around 1 nm. The variety of particle forms comprises single crystalline particles of nearly cuboctahedron shape, particles containing single twin faults, and multiply twinned particles containing parallel twin lamellae, or cyclic twinned segments arranged around axes of fivefold symmetry. Parallel twinning is distinctly favoured by ion implantation whereas cyclic twinning preferably occurs upon ion exchange processing. Regardless of single or repeated twinning, parallel or cyclic twin arrangement, one may classify simple twin faults of regular atomic configuration and compound twin faults whose irregular configuration consists of additional planar defects like associated stacking faults or secondary twin faults. Besides, a particular superstructure composed of parallel twin lamellae of only three atomic layers thickness is observed.

Evaluation of anti-cholinesterase, antibacterial and cytotoxic activities of green synthesized silver nanoparticles using from Millettia pinnata flower extract.

PubMed

Rajakumar, Govindasamy; Gomathi, Thandapani; Thiruvengadam, Muthu; Devi Rajeswari, V; Kalpana, V N; Chung, Ill-Min

2017-02-01

The aim of this study is to develop an easy and eco-friendly method for the synthesis of Ag-NPs using extracts from the medicinal plant, Millettia pinnata flower extract and investigate the effects of Ag-NPs on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), antibacterial and cytotoxicity activity. UV-Vis peak at 438 nm confirmed the Ag-NPs absorbance. The SEM analysis results confirmed the presence of spherical shaped Ag-NPs by a huge disparity in the particle size distribution with an average size of 49 ± 0.9 nm. TEM images revealed the formation of Ag-NPs with spherical shape and sizes in the range between 16 and 38 nm. The Ag-NPs showed an excellent inhibitory efficacy against AChE and BChE. The highest antibacterial activity was found against Escherichia coli (20.25 ± 0.91 mm). These nanoparticles showed the cytotoxic effects against brine shrimp (artemia saliana) nauplii with a LD 50 value of 33.92. Copyright © 2016 Elsevier Ltd. All rights reserved.

The margination propensity of spherical particles for vascular targeting in the microcirculation

PubMed Central

Gentile, Francesco; Curcio, Antonio; Indolfi, Ciro; Ferrari, Mauro; Decuzzi, Paolo

2008-01-01

The propensity of circulating particles to drift laterally towards the vessel walls (margination) in the microcirculation has been experimentally studied using a parallel plate flow chamber. Fluorescent polystyrene particles, with a relative density to water of just 50 g/cm3comparable with that of liposomal or polymeric nanoparticles used in drug delivery and bio-imaging, have been used with a diameter spanning over three order of magnitudes from 50 nm up to 10 μm. The number n∼s of particles marginating per unit surface have been measured through confocal fluorescent microscopy for a horizontal chamber, and the corresponding total volume V∼s of particles has been calculated. Scaling laws have been derived as a function of the particle diameter d. In horizontal capillaries, margination is mainly due to the gravitational force for particles with d > 200 nm and V∼s increases with d4; whereas for smaller particles V∼s increases with d3. In vertical capillaries, since the particles are heavier than the fluid they would tend to marginate towards the walls in downward flows and towards the center in upward flows, with V∼s increasing with d9/2. However, the margination in vertical capillaries is predicted to be much smaller than in horizontal capillaries. These results suggest that, for particles circulating in an external field of volume forces (gravitation or magnetic), the strategy of using larger particles designed to marginate and adhere firmly to the vascular walls under flow could be more effective than that of using particles sufficiently small (d < 200 nm) to hopefully cross a discontinuous endothelium. PMID:18702833

High-temperature LDV seed particle development

NASA Technical Reports Server (NTRS)

Frish, Michael B.; Pierce, Vicky G.

1989-01-01

The feasibility of developing a method for making monodisperse, unagglomerated spherical particles greater than 50 nm in diameter was demonstrated. Carbonaceous particles were made by pyrolyzing ethylene with a pulsed CO2 laser, thereby creating a non-equilibrium mixture of carbon, hydrogen, hydrocarbon vapors, and unpyrolyzed ethylene. Via a complex series of reactions, the carbon and hydrocarbon vapors quickly condensed into the spherical particles. By cooling and dispersing them in a supersonic expansion immediately after their creation, the hot newly-formed spheres were prevented from colliding and coalescing, thus preventing the problem of agglomeration which as plagued other investigators studying laser-simulated particle formation. The cold particles could be left suspended in the residual gases indefinitely without agglomerating. Their uniform sizes and unagglomerated nature were visualized by collecting the particles on filters that were subsequently examined using electron microscopy. It was found the mean particle size can be coarsely controlled by varying the initial ethylene pressure, and can be finely controlled by varying the fluence (energy/unit area) with which the laser irradiates the gas. The motivating application for this research was to manufacture particles that could be used as laser Doppler velocimetry (LDV) seeds in high-temperature high-speed flows. Though the particles made in this program will not evaporate until heated to about 3000 K, and thus could serve as LDV seeds in some applications, they are not ideal when the hot atmosphere is also oxidizing. In that situation, ceramic materials would be preferable. Research performed elsewhere has demonstrated that selected ceramic materials can be manufactured by laser pyrolysis of appropriate supply gases. It is anticipated that, when the same gases are used in conjunction with the rapid cooling technique, unagglomerated spherical ceramic particles can be made with little difficulty. Such particles would also be valuable to manufacturers of ceramic or abrasive products, and this technique may find its greatest commercial potential in those areas.

High-temperature LDV seed particle development

NASA Astrophysics Data System (ADS)

Frish, Michael B.; Pierce, Vicky G.

1989-05-01

The feasibility of developing a method for making monodisperse, unagglomerated spherical particles greater than 50 nm in diameter was demonstrated. Carbonaceous particles were made by pyrolyzing ethylene with a pulsed CO2 laser, thereby creating a non-equilibrium mixture of carbon, hydrogen, hydrocarbon vapors, and unpyrolyzed ethylene. Via a complex series of reactions, the carbon and hydrocarbon vapors quickly condensed into the spherical particles. By cooling and dispersing them in a supersonic expansion immediately after their creation, the hot newly-formed spheres were prevented from colliding and coalescing, thus preventing the problem of agglomeration which as plagued other investigators studying laser-simulated particle formation. The cold particles could be left suspended in the residual gases indefinitely without agglomerating. Their uniform sizes and unagglomerated nature were visualized by collecting the particles on filters that were subsequently examined using electron microscopy. It was found the mean particle size can be coarsely controlled by varying the initial ethylene pressure, and can be finely controlled by varying the fluence (energy/unit area) with which the laser irradiates the gas. The motivating application for this research was to manufacture particles that could be used as laser Doppler velocimetry (LDV) seeds in high-temperature high-speed flows. Though the particles made in this program will not evaporate until heated to about 3000 K, and thus could serve as LDV seeds in some applications, they are not ideal when the hot atmosphere is also oxidizing. In that situation, ceramic materials would be preferable. Research performed elsewhere has demonstrated that selected ceramic materials can be manufactured by laser pyrolysis of appropriate supply gases. It is anticipated that, when the same gases are used in conjunction with the rapid cooling technique, unagglomerated spherical ceramic particles can be made with little difficulty. Such particles would also be valuable to manufacturers of ceramic or abrasive products, and this technique may find its greatest commercial potential in those areas.

Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity

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

Kim, Sung A.; Jeong, Kyeong-Jun; Yethiraj, Arun

We report the discovery of an ionic small molecule surfactant that undergoes water-drive self- assembly into quasispherical micelles, which pack into the first lyotropic liquid crystalline Frank–Kasper σ phase. Small-angle X-ray scattering studies indicate that this unexpected, low-symmetry phase is characterized by a tetragonal unit cell, in which 30 sub-2 nm micelles of five discrete types are arranged into a tetrahedral close packing with exceptional translational order. Varying the relative amounts of surfactant and water in these lyotropic phases enables formation of a Frank–Kasper A15 sphere packing and a more common body-centered cubic structure. MD simulations reveal that the symmetrymore » breaking that drives the selection of the σ and A15 phases arises from a delicate interplay between the drive to maintain local spherical particle symmetry and the maximization of electrostatic cohesion between the soft micellar particles.« less

Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity

DOE PAGES

Kim, Sung A.; Jeong, Kyeong-Jun; Yethiraj, Arun; ...

2017-04-03

We report the discovery of an ionic small molecule surfactant that undergoes water-drive self- assembly into quasispherical micelles, which pack into the first lyotropic liquid crystalline Frank–Kasper σ phase. Small-angle X-ray scattering studies indicate that this unexpected, low-symmetry phase is characterized by a tetragonal unit cell, in which 30 sub-2 nm micelles of five discrete types are arranged into a tetrahedral close packing with exceptional translational order. Varying the relative amounts of surfactant and water in these lyotropic phases enables formation of a Frank–Kasper A15 sphere packing and a more common body-centered cubic structure. MD simulations reveal that the symmetrymore » breaking that drives the selection of the σ and A15 phases arises from a delicate interplay between the drive to maintain local spherical particle symmetry and the maximization of electrostatic cohesion between the soft micellar particles.« less

Aerosol Airmass Type Mapping Over the Urban Mexico City Region From Space-based Multi-angle Imaging

NASA Technical Reports Server (NTRS)

Patadia, F.; Kahn, R. A.; Limbacher, J. A.; Burton, S. P.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.

2013-01-01

Using Multi-angle Imaging SpectroRadiometer (MISR) and sub-orbital measurements from the 2006 INTEX-B/MILAGRO field campaign, in this study we explore MISR's ability to map different aerosol air mass types over the Mexico City metropolitan area. The aerosol air mass distinctions are based on shape, size and single scattering albedo retrievals from the MISR Research Aerosol Retrieval algorithm. In this region, the research algorithm identifies dust-dominated aerosol mixtures based on non-spherical particle shape, whereas spherical biomass burning and urban pollution particles are distinguished by particle size. Two distinct aerosol air mass types based on retrieved particle microphysical properties, and four spatially distributed aerosol air masses, are identified in the MISR data on 6 March 2006. The aerosol air mass type identification results are supported by coincident, airborne high-spectral-resolution lidar (HSRL) measurements. Aerosol optical depth (AOD) gradients are also consistent between the MISR and sub-orbital measurements, but particles having single-scattering albedo of approx. 0.7 at 558 nm must be included in the retrieval algorithm to produce good absolute AOD comparisons over pollution-dominated aerosol air masses. The MISR standard V22 AOD product, at 17.6 km resolution, captures the observed AOD gradients qualitatively, but retrievals at this coarse spatial scale and with limited spherical absorbing particle options underestimate AOD and do not retrieve particle properties adequately over this complex urban region. However, we demonstrate how AOD and aerosol type mapping can be accomplished with MISR data over complex urban regions, provided the retrieval is performed at sufficiently high spatial resolution, and with a rich enough set of aerosol components and mixtures.

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.

Optical absorption of carbon-gold core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Zhaolong; Quan, Xiaojun; Zhang, Zhuomin; Cheng, Ping

2018-01-01

In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.

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

NASA Astrophysics Data System (ADS)

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

2011-02-01

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

Synthesis of suitable SiO2 nano particles as the core in core-shell nanostructured materials.

PubMed

Ghahari, Mehdi; Aghababazadeh, Roya; Ebadzadeh, Touradj; Mirhabibi, Alireza; Brydson, Rik; Fabbri, Paola; Najafi, Farhod

2011-06-01

The effect of surfactant on the luminescent intensity of SiO2 @Y2O3:Eu3+ particles with a core shell structure is described. Core-shell particles are used in phosphor materials and employing spherical particles with a narrow size distribution is vital for the enhancement of luminescent properties. Three kinds of different surfactants were used to synthesis SiO2 nano particles via a sol gel process. The results demonstrated that comb polycarboxylic acid surfactant had a significant influence on the morphology and particle size distribution. Somehow, particles with 100 nm size and narrow size distribution were produced. These particles had relatively uniform packing, unlike particles produced with other surfactants or without surfactant which had irregular assembly. The photoluminescence intensity of SiO2 @Y2O3:Eu3+ particles that was synthesized by comb polycarboxylic acid surfactant was higher than those which were produced without surfactant.

The role of pore geometry in single nanoparticle detection

DOE PAGES

Davenport, Matthew; Healy, Ken; Pevarnik, Matthew; ...

2012-08-22

In this study, we observe single nanoparticle translocation events via resistive pulse sensing using silicon nitride pores described by a range of lengths and diameters. Pores are prepared by focused ion beam milling in 50 nm-, 100 nm-, and 500 nm-thick silicon nitride membranes with diameters fabricated to accommodate spherical silica nanoparticles with sizes chosen to mimic that of virus particles. In this manner, we are able to characterize the role of pore geometry in three key components of the detection scheme, namely, event magnitude, event duration, and event frequency. We find that the electric field created by the appliedmore » voltage and the pore’s geometry is a critical factor. We develop approximations to describe this field, which are verified with computer simulations, and interactions between particles and this field. In so doing, we formulate what we believe to be the first approximation for the magnitude of ionic current blockage that explicitly addresses the invariance of access resistance of solid-state pores during particle translocation. These approximations also provide a suitable foundation for estimating the zeta potential of the particles and/or pore surface when studied in conjunction with event durations. We also verify that translocation achieved by electro-osmostic transport is an effective means of slowing translocation velocities of highly charged particles without compromising particle capture rate as compared to more traditional approaches based on electrophoretic transport.« less

Investigation of scattering coefficients and anisotropy factors of human cancerous and normal prostate tissues using Mie theory

NASA Astrophysics Data System (ADS)

Pu, Yang; Chen, Jun; Wang, Wubao

2014-02-01

The scattering coefficient, μs, the anisotropy factor, g, the scattering phase function, p(θ), and the angular dependence of scattering intensity distributions of human cancerous and normal prostate tissues were systematically investigated as a function of wavelength, scattering angle and scattering particle size using Mie theory and experimental parameters. The Matlab-based codes using Mie theory for both spherical and cylindrical models were developed and applied for studying the light propagation and the key scattering properties of the prostate tissues. The optical and structural parameters of tissue such as the index of refraction of cytoplasm, size of nuclei, and the diameter of the nucleoli for cancerous and normal human prostate tissues obtained from the previous biological, biomedical and bio-optic studies were used for Mie theory simulation and calculation. The wavelength dependence of scattering coefficient and anisotropy factor were investigated in the wide spectral range from 300 nm to 1200 nm. The scattering particle size dependence of μs, g, and scattering angular distributions were studied for cancerous and normal prostate tissues. The results show that cancerous prostate tissue containing larger size scattering particles has more contribution to the forward scattering in comparison with the normal prostate tissue. In addition to the conventional simulation model that approximately considers the scattering particle as sphere, the cylinder model which is more suitable for fiber-like tissue frame components such as collagen and elastin was used for developing a computation code to study angular dependence of scattering in prostate tissues. To the best of our knowledge, this is the first study to deal with both spherical and cylindrical scattering particles in prostate tissues.

Aquatic Fern (Azolla Sp.) Assisted Synthesis of Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Jha, Anal K.; Prasad, K.

2016-02-01

Aquatic pteridophyte (Azolla sp.) was taken to assess its potential to synthesize the metal (Au) nanoparticles. The synthesized particles were characterized using X-ray, UV-visible, scanning and transmission electron microscopy analyses. Nanoparticles almost spherical in shape having the sizes of 5-17nm are found. UV-visible study revealed the surface plasmon resonance at 538nm. Responsible phytochemicals for the transformation were principally phenolics, tannins, anthraquinone glycosides and sugars present abundantly in the plant thereby bestowing it adaptive prodigality. Also, the use of Azolla sp. for the synthesis of gold nanoparticles offers the benefit of eco-friendliness.

Facile Large-scale synthesis of stable CuO nanoparticles

NASA Astrophysics Data System (ADS)

Nazari, P.; Abdollahi-Nejand, B.; Eskandari, M.; Kohnehpoushi, S.

2018-04-01

In this work, a novel approach in synthesizing the CuO nanoparticles was introduced. A sequential corrosion and detaching was proposed in the growth and dispersion of CuO nanoparticles in the optimum pH value of eight. The produced CuO nanoparticles showed six nm (±2 nm) in diameter and spherical feather with a high crystallinity and uniformity in size. In this method, a large-scale production of CuO nanoparticles (120 grams in an experimental batch) from Cu micro-particles was achieved which may met the market criteria for large-scale production of CuO nanoparticles.

Synthesis of Silver Nanoparticles Using Bombyxmori Silk Fibroin and Their Antibacterial Activity

NASA Astrophysics Data System (ADS)

Shivananda, C. S.; Lakshmeesha Rao, B.; Pasha, Azmath; Sangappa, Y.

2016-09-01

Present work describes the synthesis of colloidal silver nanoparticles using Bombyx mori silk fibroin under white light environment at room temperature. The bio reduction of silver ions showed the unique surface plasmon resonance (SPR) band at 420 nm which was confirmed by UV-visible spectroscopy. Transmission electron microscopy (TEM) showed the synthesized AgNPs are spherical in shape with the average particle size of 35-40 nm. X-ray diffraction (XRD) pattren evidenced the crystalline nature of the AgNPs with FCC structure. The biosynthesized AgNPs showed effective antibacterial activity against bacterial stains Bacillus subtilis, and Salmonella typhi.

Electron tomography and fractal aspects of MoS2 and MoS2/Co spheres.

PubMed

Ramos, Manuel; Galindo-Hernández, Félix; Arslan, Ilke; Sanders, Toby; Domínguez, José Manuel

2017-09-26

A study was made by a combination of 3D electron tomography reconstruction methods and N 2 adsorption for determining the fractal dimension for nanometric MoS 2 and MoS 2 /Co catalyst particles. DFT methods including Neimarke-Kiselev's method allowed to determine the particle porosity and fractal arrays at the atomic scale for the S-Mo-S(Co) 2D- layers that conform the spherically shaped catalyst particles. A structural and textural correlation was sought by further characterization performed by x-ray Rietveld refinement and Radial Distribution Function (RDF) methods, electron density maps, computational density functional theory methods and nitrogen adsorption methods altogether, for studying the structural and textural features of spherical MoS 2 and MoS 2 /Co particles. Neimark-Kiselev's equations afforded the evaluation of a pore volume variation from 10 to 110 cm 3 /g by cobalt insertion in the MoS 2 crystallographic lattice, which induces the formation of cavities and throats in between of less than 29 nm, with a curvature radius r k  < 14.4 nm; typical large needle-like arrays having 20 2D layers units correspond to a model consisting of smooth surfaces within these cavities. Decreasing D P , D B , D I and D M values occur when Co atoms are present in the MoS 2 laminates, which promote the formation of smoother edges and denser surfaces that have an influence on the catalytic properties of the S-Mo-S(Co) system.

Poly(Acrylic Acid-b-Styrene) Amphiphilic Multiblock Copolymers as Building Blocks for the Assembly of Discrete Nanoparticles

PubMed Central

Greene, Anna C.; Zhu, Jiahua; Pochan, Darrin J.; Jia, Xinqiao; Kiick, Kristi L.

2011-01-01

In order to expand the utility of current polymeric micellar systems, we have developed amphiphilic multiblock copolymers containing alternating blocks of poly(acrylic acid) and poly(styrene). Heterotelechelic poly(tert-butyl acrylate-b-styrene) diblock copolymers containing an α-alkyne and an ω-azide were synthesized by atom transfer radical polymerization (ATRP), allowing control over the molecular weight while maintaining narrow polydispersity indices. The multiblock copolymers were constructed by copper-catalyzed azide-alkyne cycloaddition of azide-alkyne end functional diblock copolymers which were then characterized by 1H NMR, FT-IR and SEC. The tert-butyl moieties of the poly(tert-butyl acrylate-b-styrene) multiblock copolymers were easily removed to form the poly(acrylic acid-b-styrene) multiblock copolymer ((PAA-PS)9), which contained up to 9 diblock repeats. The amphiphilic multiblock (PAA-PS)9 (Mn = 73.3 kg/mol) was self-assembled by dissolution into tetrahydrofuran and extensive dialysis against deionized water for 4 days. The critical micelle concentration (CMC) for (PAA-PS)9 was determined by fluorescence spectroscopy using pyrene as a fluorescent probe and was found to be very low at 2 × 10-4 mg/mL. The (PAA-PS)9 multiblock was also analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The hydrodynamic diameter of the particles was found to be 11 nm. Discrete spherical particles were observed by TEM with an average particle diameter of 14 nm. The poly(acrylic acid) periphery of the spherical particles should allow for future conjugation of biomolecules. PMID:21552373

Frequency dependent dielectric properties of Sr doped NiO nanostructures

NASA Astrophysics Data System (ADS)

Siddique, M. Naseem; Ahmed, Ateeq; Ali, T.; Tripathi, P.

2018-05-01

Ni1-xSrxO (x=0.0, 0.02) nanoparticles have been synthesized using sol-gel method calcined at temperature 600 °C. The XRD analysis result revealed that the calcined sample has a cubic structure with single phase structure. We have calculated crystallite size of samples using both Debye-Sherrer and William Hall (W-H) method which are found to be 19.69 nm, 22.39 nm and 28.50 nm, 33.27 nm, respectively. TEM image reveals the formation of spherical shaped particles. In addition, dielectric properties have been studied using LCR measurement and found that ɛ', ɛ″ and tan δ are decreases with increase in frequency whereas ac conductivity increases with increase in frequency. This behavior may be explained using Maxwell-Wagner and Koop theory.

Crystallization and preliminary X-ray analysis of a low density lipoprotein from human plasma.

PubMed

Prassl, R; Chapman, J M; Nigon, F; Sara, M; Eschenburg, S; Betzel, C; Saxena, A; Laggner, P

1996-11-15

Single crystals of human plasma low density lipoprotein (LDL), the major transport vehicle for cholesterol in blood, have been produced with a view to analysis of the three-dimensional structure by x-ray crystallography. Crystals with dimensions of approximately 200 x 100 x 50 microm have been reproducibly obtained from highly homogeneous LDL particle subspecies, isolated in the density ranges d = 1.0271-1. 0297 g/ml and d = 1.0297-1.0327 g/ml. Electron microscopic imaging of ultrathin-sectioned preparations of the crystals confirmed the existence of a regular, quasihexagonal arrangement of spherical particles of approximately 18 nm in diameter, thereby resembling the dimensions characteristic of LDL after dehydration and fixation. X-ray diffraction with synchrotron radiation under cryogenic conditions revealed the presence of well resolved diffraction spots, to a resolution of about 29 A. The diffraction patterns are indexed in terms of a triclinic lattice with unit cell dimensions of a = 16. 1 nm, b = 39.0 nm, c = 43.9 nm; alpha = 96.2 degrees, beta = 92.1 degrees, gamma = 102 degrees, and with space group P1.

Decomposition of Atmospheric Aerosol Phase Function by Particle Size and Morphology via Single Particle Scattering Measurements

NASA Astrophysics Data System (ADS)

Aptowicz, K. B.; Pan, Y.; Martin, S.; Fernandez, E.; Chang, R.; Pinnick, R. G.

2013-12-01

We report upon an experimental approach that provides insight into how particle size and shape affect the scattering phase function of atmospheric aerosol particles. Central to our approach is the design of an apparatus that measures the forward and backward scattering hemispheres (scattering patterns) of individual atmospheric aerosol particles in the coarse mode range. The size and shape of each particle is discerned from the corresponding scattering pattern. In particular, autocorrelation analysis is used to differentiate between spherical and non-spherical particles, the calculated asphericity factor is used to characterize the morphology of non-spherical particles, and the integrated irradiance is used for particle sizing. We found the fraction of spherical particles decays exponentially with particle size, decreasing from 11% for particles on the order of 1 micrometer to less than 1% for particles over 5 micrometer. The average phase functions of subpopulations of particles, grouped by size and morphology, are determined by averaging their corresponding scattering patterns. The phase functions of spherical and non-spherical atmospheric particles are shown to diverge with increasing size. In addition, the phase function of non-spherical particles is found to vary little as a function of the asphericity factor.

Seeds mediated synthesis of giant gold particles on the glass surface

NASA Astrophysics Data System (ADS)

Vasko, A. A.; Borodinova, T. I.; Marchenko, O. A.; Snegir, S. V.

2018-03-01

Herein, we present the protocols of synthesis of two types of gold particles which are in the great interest for the purpose of molecular electronics. The first type is the flat prisms with a triangular/hexagonal shape and a lateral size up to 80 µm. They were synthesized directly on a glass surface pretreated with (3-aminopropyl)-triethoxysilane molecules. The second type of particles was synthesized with using gold seeds with diameter of 18 nm. These seeds were deposited on a glass surface coated with APTES. The resulted three-dimensional structures with a form close to spherical increase in size up to 0.5-0.08 µm. Moreover, these particles grew up separately and did not merge during 48 h of synthesis.

A novel polyol method to synthesize colloidal silver nanoparticles by ultrasonic irradiation.

PubMed

Byeon, Jeong Hoon; Kim, Young-Woo

2012-01-01

A polyol synthesis of silver nanoparticles in the presence of ultrasonic irradiation was compared with other configurations (at ambient temperature, 120° C, and 120 °C with injected solutions) in the absence of ultrasonic irradiation in order to obtain systematic results for morphology and size distribution. For applying ultrasonic irradiation, rather fine and uniform spherical silver particles (21±3.7 nm) were obtained in a simple (at ambient temperature without mechanical stirring) and fast (within 4 min, 3.61×10(-3) mol min(-1)) manner than other cases (at ambient temperature (for 8 h, 0.03×10(-3) mol min(-1)): 86±16.8 nm, 120 °C (for 12 min, 1.16×10(-3) mol min(-1)): 64±14.9 nm, and 120 °C with injected solutions (during 12 min): 35±6.8 nm; all other cases contained anisotropic shaped particles). Even though the temperature of polyol reaction reached only at 80 °C (<120 °C) in the presence of ultrasonic irradiation, a uniform mixing (i.e. enhanced collision between silver particle and surrounding components) by ultrasonic irradiation might induce a better formation kinetics and morphological uniformity. Copyright © 2011 Elsevier B.V. All rights reserved.

Fluorescence labeling of colloidal core-shell particles with defined isoelectric points for in vitro studies.

PubMed

Daberkow, Timo; Meder, Fabian; Treccani, Laura; Schowalter, Marco; Rosenauer, Andreas; Rezwan, Kurosch

2012-02-01

In the light of in vitro nanotoxicological studies fluorescence labeling has become standard for particle localization within the cell environment. However, fluorescent labeling is also known to significantly alter the particle surface chemistry and therefore potentially affect the outcome of cell studies. Hence, fluorescent labeling is ideally carried out without changing, for example, the isoelectric point. A simple and straightforward method for obtaining fluorescently labeled spherical metal oxide particles with well-defined isoelectric points and a narrow size distribution is presented in this study. Spherical amorphous silica (SiO2, 161 nm diameter) particles were used as the substrate material and were coated with silica, alumina (Al2O3), titania (TiO2), or zirconia (ZrO2) using sol-gel chemistry. Fluorescent labeling was achieved by directly embedding rhodamine 6G dye in the coating matrix without affecting the isoelectric point of the metal oxide coatings. The coating quality was confirmed by high resolution transmission electron microscopy, energy filtered transmission electron microscopy and electrochemical characterization. The coatings were proven to be stable for at least 240 h under different pH conditions. The well-defined fluorescent particles can be directly used for biomedical investigations, e.g. elucidation of particle-cell interactions in vitro. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes

NASA Astrophysics Data System (ADS)

O'Brien, S. A.; Harvey, A.; Griffin, A.; Donnelly, T.; Mulcahy, D.; Coleman, J. N.; Donegan, J. F.; McCloskey, D.

2017-11-01

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter—the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

PubMed

O'Brien, S A; Harvey, A; Griffin, A; Donnelly, T; Mulcahy, D; Coleman, J N; Donegan, J F; McCloskey, D

2017-11-24

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Probing the magnetic behavior of single nanodots.

PubMed

Neumann, Alexander; Thönnissen, Carsten; Frauen, Axel; Hesse, Simon; Meyer, Andreas; Oepen, Hans Peter

2013-05-08

In this paper, a method is presented that has the sensitivity to measure magnetization behavior of single nanostructures. It is demonstrated that the technique gives the ability to separate different signals of single nanodots from a small ensemble of structures. Our method is based on the anomalous Hall-Effect and allows for resolving signals from spherical nanoparticles with diameter down to 3.5 nm. The method gives access to magnetic properties of particles in a wide thermal and dynamical range. The potential of the technique is demonstrated utilizing particles that are created from Co films sandwiched by Pt layers.

Synthesis of mesoscale, crumpled, reduced graphene oxide roses by water-in-oil emulsion approach

NASA Astrophysics Data System (ADS)

Sharma, Shruti; Pham, Viet H.; Boscoboinik, Jorge A.; Camino, Fernando; Dickerson, James H.; Tannenbaum, Rina

2018-05-01

Mesoscale crumpled graphene oxide roses (GO roses) were synthesized by using colloidal graphene oxide (GO) variants as precursors for a hybrid emulsification-rapid evaporation approach. This process produced rose-like, spherical, reduced mesostructures of colloidal GO sheets, with corrugated surfaces and particle sizes tunable in the range of ∼800 nm to 15 μm. Excellent reproducibility for particle size distribution is shown for each selected speed of homogenizer rotor among different sample batches. The morphology and chemical structure of these produced GO roses was investigated using electron microscopy and spectroscopy techniques. The proposed synthesis route provides control over particle size, morphology and chemical properties of the synthesized GO roses.

Preparation of Thermo-Responsive and Cross-Linked Fluorinated Nanoparticles via RAFT-Mediated Aqueous Polymerization in Nanoreactors.

PubMed

Ma, Jiachen; Zhang, Luqing; Geng, Bing; Azhar, Umair; Xu, Anhou; Zhang, Shuxiang

2017-01-25

In this work, a thermo-responsive and cross-linked fluoropolymer poly(2,2,2-Trifluoroethyl) methacrylate (PTFEMA) was successfully prepared by reversible addition-fragmentation chain transfer (RAFT) mediated aqueous polymerization with a thermo-responsive diblock poly(dimethylacrylamide- b - N -isopropylacrylamide) (PDMA- b -PNIPAM) that performed a dual function as both a nanoreactor and macro-RAFT agent. The cross-linked polymer particles proved to be in a spherical-like structure of about 50 nm in diameter and with a relatively narrow particle size distribution. ¹H-NMR and 19 F-NMR spectra showed that thermo-responsive diblock P(DMA- b -NIPAM) and cross-linked PTFEMA particles were successfully synthesized. Influence of the amount of ammonium persulfate (APS), the molar ratio of monomers to RAFT agent, influence of the amount of cross-linker on aqueous polymerization and thermo-responsive characterization of the particles are investigated. Monomer conversion increased from 44% to 94% with increasing the molar ratio of APS and P(DMA- b -NIPAM) from 1:9 to1:3. As the reaction proceeded, the particle size increased from 29 to 49 nm due to the consumption of TFEMA monomer. The size of cross-linked nanoparticles sharply decreased from 50.3 to 40.5 nm over the temperature range 14-44 °C, suggesting good temperature sensitivity for these nanoparticles.

Detection of virus-like particles in the liver of black and white ruffed lemurs with hepatitis.

PubMed

Worley, Michael B; Stalis, Ilse H

2002-04-01

Two young black and white ruffed lemurs (Varecia variegata variegata) died at the San Diego Zoo (San Diego, California, USA) with extensive liver lesions suggestive of acute viral infection. Immunoassays performed to detect hepatitis B virus (HBV) markers were negative. Polymerase chain reaction (PCR) primers overlapping the HBV core gene produced an amplicon of approximately 411 base pairs (bp) from serum DNA of a HBV-positive western lowland gorilla (Gorilla gorilla gorilla) but not from serum DNA of either lemur. Cesium chloride gradient fractions of liver homogenates from both lemurs contained a peak protein fraction with a density of 1.18 g/cm3. Electron microscopic analysis of fraction contents, concentrated by ultracentrifulgation, revealed numerous pleomorphic, spherical particles varying in diameter from 16-25 nm. In one of the lemurs, this peak fraction also contained a double-shelled virus-like particle 47-50 nm in diameter. The size, morphology, and density of these particles suggest they are members of the Hepadnaviridae, a group of hepatotropic DNA-genome viruses for which HBV is the prototype.

Synthesis of water dispersible boron core silica shell (B@SiO2) nanoparticles

NASA Astrophysics Data System (ADS)

Walton, Nathan I.; Gao, Zhe; Eygeris, Yulia; Ghandehari, Hamidreza; Zharov, Ilya

2018-04-01

Water dispersible boron nanoparticles have great potential as materials for boron neutron capture therapy of cancer and magnetic resonance imaging, if they are prepared on a large scale with uniform size and shape and hydrophilic modifiable surface. We report the first method to prepare spherical, monodisperse, water dispersible boron core silica shell nanoparticles (B@SiO2 NPs) suitable for aforementioned biomedical applications. In this method, 40 nm elemental boron nanoparticles, easily prepared by mechanical milling and carrying 10-undecenoic acid surface ligands, are hydrosilylated using triethoxysilane, followed by base-catalyzed hydrolysis of tetraethoxysilane, which forms a 10-nm silica shell around the boron core. This simple two-step process converts irregularly shaped hydrophobic boron particles into the spherically shaped uniform nanoparticles. The B@SiO2 NPs are dispersible in water and the silica shell surface can be modified with primary amines that allow for the attachment of a fluorophore and, potentially, of targeting moieties. [Figure not available: see fulltext.

Fluorescent nanodiamonds embedded in biocompatible translucent shells.

PubMed

Rehor, Ivan; Slegerova, Jitka; Kucka, Jan; Proks, Vladimir; Petrakova, Vladimira; Adam, Marie-Pierre; Treussart, François; Turner, Stuart; Bals, Sara; Sacha, Pavel; Ledvina, Miroslav; Wen, Amy M; Steinmetz, Nicole F; Cigler, Petr

2014-03-26

High pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fluorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fluorescent nanodiamonds (FNDs) in 10-20-nm thick translucent (i.e., not altering FND fluorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modification of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fluorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifically and they penetrate inside the cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorescent Nanodiamonds Embedded in Biocompatible Translucent Shells

PubMed Central

Rehor, Ivan; Slegerova, Jitka; Kucka, Jan; Proks, Vladimir; Petrakova, Vladimira; Adam, Marie-Pierre; Treussart, François; Turner, Stuart; Bals, Sara; Sacha, Pavel; Ledvina, Miroslav; Wen, Amy M.; Steinmetz, Nicole F.; Cigler, Petr

2016-01-01

High pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fluorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fluorescent nanodiamonds (FNDs) in 10–20-nm thick translucent (i.e., not altering FND fluorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modification of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fluorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifically and they penetrate inside the cells. PMID:24500945

Modeling light scattering by mineral dust particles using spheroids

NASA Astrophysics Data System (ADS)

Merikallio, Sini; Nousiainen, Timo

Suspended dust particles have a considerable influence on light scattering in both terrestrial and planetary atmospheres and can therefore have a large effect on the interpretation of remote sensing measurements. Assuming dust particles to be spherical is known to produce inaccurate results when modeling optical properties of real mineral dust particles. Yet this approximation is widely used for its simplicity. Here, we simulate light scattering by mineral dust particles using a distribution of model spheroids. This is done by comparing scattering matrices calculated from a dust optical database of Dubovik et al. [2006] with those measured in the laboratory by Volten et al. [2001]. Wavelengths of 441,6 nm and 632,8 nm and refractive indexes of Re = 1.55 -1.7 and Im = 0.001i -0.01i were adopted in this study. Overall, spheroids are found to fit the measurements significantly better than Mie spheres. Further, we confirm that the shape distribution parametrization developed in Nousiainen et al. (2006) significantly improves the accuracy of simulated single-scattering for small mineral dust particles. The spheroid scheme should therefore yield more reliable interpretations of remote sensing data from dusty planetary atmospheres. While the spheroidal scheme is superior to spheres in remote sensing applications, its performance is far from perfect especially for samples with large particles. Thus, additional advances are clearly possible. Further studies of the Martian atmosphere are currently under way. Dubovik et al. (2006) Application of spheroid models to account for aerosol particle nonspheric-ity in remote sensing of desert dust, JGR, Vol. 111, D11208 Volten et al. (2001) Scattering matrices of mineral aerosol particles at 441.6 nm and 632.8 nm, JGR, Vol. 106, No. D15, pp. 17375-17401 Nousiainen et al. (2006) Light scattering modeling of small feldspar aerosol particles using polyhedral prisms and spheroids, JQSRT 101, pp. 471-487

Spherical boron nitride particles and method for preparing them

DOEpatents

Phillips, Jonathan; Gleiman, Seth S.; Chen, Chun-Ku

2003-11-25

Spherical and polyhedral particles of boron nitride and method of preparing them. Spherical and polyhedral particles of boron nitride are produced from precursor particles of hexagonal phase boron nitride suspended in an aerosol gas. The aerosol is directed to a microwave plasma torch. The torch generates plasma at atmospheric pressure that includes nitrogen atoms. The presence of nitrogen atoms is critical in allowing boron nitride to melt at atmospheric pressure while avoiding or at least minimizing decomposition. The plasma includes a plasma hot zone, which is a portion of the plasma that has a temperature sufficiently high to melt hexagonal phase boron nitride. In the hot zone, the precursor particles melt to form molten particles that acquire spherical and polyhedral shapes. These molten particles exit the hot zone, cool, and solidify to form solid particles of boron nitride with spherical and polyhedral shapes. The molten particles can also collide and join to form larger molten particles that lead to larger spherical and polyhedral particles.

Transformation of Cerium Oxide Nanoparticles from a Diesel Fuel Additive during Combustion in a Diesel Engine.

PubMed

Dale, James G; Cox, Steven S; Vance, Marina E; Marr, Linsey C; Hochella, Michael F

2017-02-21

Nanoscale cerium oxide is used as a diesel fuel additive to reduce particulate matter emissions and increase fuel economy, but its fate in the environment has not been established. Cerium oxide released as a result of the combustion of diesel fuel containing the additive Envirox, which utilizes suspended nanoscale cerium oxide to reduce particulate matter emissions and increase fuel economy, was captured from the exhaust stream of a diesel engine and was characterized using a combination of bulk analytical techniques and high resolution transmission electron microscopy. The combustion process induced significant changes in the size and morphology of the particles; ∼15 nm aggregates consisting of 5-7 nm faceted crystals in the fuel additive became 50-300 nm, near-spherical, single crystals in the exhaust. Electron diffraction identified the original cerium oxide particles as cerium(IV) oxide (CeO 2 , standard FCC structure) with no detectable quantities of Ce(III), whereas in the exhaust the ceria particles had additional electron diffraction reflections indicative of a CeO 2 superstructure containing ordered oxygen vacancies. The surfactant coating present on the cerium oxide particles in the additive was lost during combustion, but in roughly 30% of the observed particles in the exhaust, a new surface coating formed, approximately 2-5 nm thick. The results of this study suggest that pristine, laboratory-produced, nanoscale cerium oxide is not a good substitute for the cerium oxide released from fuel-borne catalyst applications and that future toxicity experiments and modeling will require the use/consideration of more realistic materials.

Investigating biomass burning aerosol morphology using a laser imaging nephelometer

NASA Astrophysics Data System (ADS)

Manfred, Katherine M.; Washenfelder, Rebecca A.; Wagner, Nicholas L.; Adler, Gabriela; Erdesz, Frank; Womack, Caroline C.; Lamb, Kara D.; Schwarz, Joshua P.; Franchin, Alessandro; Selimovic, Vanessa; Yokelson, Robert J.; Murphy, Daniel M.

2018-02-01

Particle morphology is an important parameter affecting aerosol optical properties that are relevant to climate and air quality, yet it is poorly constrained due to sparse in situ measurements. Biomass burning is a large source of aerosol that generates particles with different morphologies. Quantifying the optical contributions of non-spherical aerosol populations is critical for accurate radiative transfer models, and for correctly interpreting remote sensing data. We deployed a laser imaging nephelometer at the Missoula Fire Sciences Laboratory to sample biomass burning aerosol from controlled fires during the FIREX intensive laboratory study. The laser imaging nephelometer measures the unpolarized scattering phase function of an aerosol ensemble using diode lasers at 375 and 405 nm. Scattered light from the bulk aerosol in the instrument is imaged onto a charge-coupled device (CCD) using a wide-angle field-of-view lens, which allows for measurements at 4-175° scattering angle with ˜ 0.5° angular resolution. Along with a suite of other instruments, the laser imaging nephelometer sampled fresh smoke emissions both directly and after removal of volatile components with a thermodenuder at 250 °C. The total integrated aerosol scattering signal agreed with both a cavity ring-down photoacoustic spectrometer system and a traditional integrating nephelometer within instrumental uncertainties. We compare the measured scattering phase functions at 405 nm to theoretical models for spherical (Mie) and fractal (Rayleigh-Debye-Gans) particle morphologies based on the size distribution reported by an optical particle counter. Results from representative fires demonstrate that particle morphology can vary dramatically for different fuel types. In some cases, the measured phase function cannot be described using Mie theory. This study demonstrates the capabilities of the laser imaging nephelometer instrument to provide realtime, in situ information about dominant particle morphology, which is vital for understanding remote sensing data and accurately describing the aerosol population in radiative transfer calculations.

Capacious and programmable multi-liposomal carriers

NASA Astrophysics Data System (ADS)

Yaroslavov, Alexander A.; Sybachin, Andrey V.; Zaborova, Olga V.; Migulin, Vasiliy A.; Samoshin, Vyacheslav V.; Ballauff, Matthias; Kesselman, Ellina; Schmidt, Judith; Talmon, Yeshayahu; Menger, Fredric M.

2015-01-01

Spherical polycationic brushes (SPBs) were synthesized by grafting polycationic chains onto 100 nm polystyrene particles. These particles were exposed to unilamellar egg-lecithin (EL) liposomes with a mean diameter of 40 nm that had been rendered anionic via the presence of 10 molar% of phosphatidylserine (PS1-). The liposomes also contained 30 mole% of a morpholinocyclohexanol-based lipid (MOCH) that undergoes a conformational flip when the pH is decreased from 7.0 to 5.0. Mixtures of SPBs and liposomes at pH 7 gave an electrostatically-driven complex possessing, on average, about 40 liposomes for each SPB particle. It was found that the bound liposomes rapidly release much of their contents when the pH is reduced from 7.0 to 5.0 owing mostly to a MOCH conformational change that creates defects in the bilayer membrane. The drop in pH does not, however, induce a separation of the liposomes from the SPBs. Around 50-60% of the liposome contents escape before, it is reasoned, lateral and transmembrane motion of the membrane components heals the defects and prevents further release. Remarkably, the liposomes complexed with SPB release their cargo much faster than the identical but non-complexed liposomes.Spherical polycationic brushes (SPBs) were synthesized by grafting polycationic chains onto 100 nm polystyrene particles. These particles were exposed to unilamellar egg-lecithin (EL) liposomes with a mean diameter of 40 nm that had been rendered anionic via the presence of 10 molar% of phosphatidylserine (PS1-). The liposomes also contained 30 mole% of a morpholinocyclohexanol-based lipid (MOCH) that undergoes a conformational flip when the pH is decreased from 7.0 to 5.0. Mixtures of SPBs and liposomes at pH 7 gave an electrostatically-driven complex possessing, on average, about 40 liposomes for each SPB particle. It was found that the bound liposomes rapidly release much of their contents when the pH is reduced from 7.0 to 5.0 owing mostly to a MOCH conformational change that creates defects in the bilayer membrane. The drop in pH does not, however, induce a separation of the liposomes from the SPBs. Around 50-60% of the liposome contents escape before, it is reasoned, lateral and transmembrane motion of the membrane components heals the defects and prevents further release. Remarkably, the liposomes complexed with SPB release their cargo much faster than the identical but non-complexed liposomes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06037g

Characterization of individual complex particles in urban atmospheric environment

NASA Astrophysics Data System (ADS)

Suzuki, K.; Takii, T.; Tomiyasu, B.; Nihei, Y.

2006-07-01

The origins of carrier particles of complex particles (iron-rich particles) collected from the urban atmospheric environment near to road traffic and a railroad were investigated from the detailed surface information using FE-SEM/EDS and TOF-SIMS analyses. From the FE-SEM/EDS analyses, the iron-rich particles were classified into two typical types (spherical type and non-spherical type). From the TOF-SIMS measurements, the characteristic secondary ions of spherical type of iron-rich particles were 23Na + and 39K +. The minor components of non-spherical type were Al, Ca and Ba. On the other hand, we carried out TOF-SIMS measurement to materials of rail origin and brake origin. From the comparison of these spectra pattern, it seemed that the spherical type of iron-rich particles was emitted from the rail origin. We concluded that the origin of non-spherical type of iron-rich particles were brake pad of vehicles.

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

Fedorovich, S V; Protsenko, I E

We report the results of numerical modelling of emission of a two-level atom near a metal nanoparticle under resonant interaction of light with plasmon modes of the particle. Calculations have been performed for different polarisations of light by a dipole approximation method and a complex multipole method. Depending on the distance between a particle and an atom, the contribution of the nonradiative process of electron tunnelling from a two-level atom into a particle, which is calculated using the quasi-classical approximation, has been taken into account and assessed. We have studied spherical gold and silver particles of different diameters (10 –more » 100 nm). The rates of electron tunnelling and of spontaneous decay of the excited atomic state are found. The results can be used to develop nanoscale plasmonic emitters, lasers and photodetectors. (nanooptics)« less

Effect of size and shape dependent anisotropy on superparamagnetic property of CoFe2O4 nanoparticles and nanoplatelets

NASA Astrophysics Data System (ADS)

Chandekar, Kamlesh V.; Kant, K. Mohan

2017-09-01

Superparamagnetic cobalt ferrite (CoFe2O4) spherical nanoparticles and rhomboidal nanoplatelets were synthesized by co-precipitation at 80 °C (S1) and hydrothermal route at 150 °C (S2). X-ray diffraction (XRD) pattern confirms formation of cubic inverse spinel structure of as prepared cobalt ferrite samples (S1 and S2) with average crystallite size of 13 nm and 18.7 nm for S1 and S2 respectively. Transmission electron microscopy (TEM) reveals spherical and rhomboidal shaped with average particle size 16.7 nm (S1) and 19.8 nm (S2). The zero field cooled magnetization MZFCvs. T exhibit a broad maxima at 400 K and 510 K for S1 and S2 respectively. The blocking temperature TB is obtained as 310 K and 341 K for S1 and S2 respectively, by fitting coercive field at different temperatures to T 1 / 2 law. The morphology of S1 and S2 corresponds to shape dependence of continuum approach. The effective demagnetization factors estimated as ΔN1 = 0 and ΔN2 = 0 . 749 for S1 and S2 samples respectively. The uniaxial anisotropy and shape anisotropy observed to be dominant in spherical shaped and rhomboidal shaped CoFe2O4 nanoparticles respectively. The uniaxial anisotropy constant of S1 sample is estimated as 56 (kJ/m3) at TB = 310 K whereas the effective anisotropy constant for S2 sample is 627 (kJ/m3) at TB = 341 K , in which shape anisotropy constant 605 (kJ/m3) dominates over contribution from uniaxial anisotropy constant 22 (kJ/m3) in S2 sample.

Pt-free carbon-based fuel cell catalyst prepared from spherical polyimide for enhanced oxygen diffusion

PubMed Central

Nabae, Yuta; Nagata, Shinsuke; Hayakawa, Teruaki; Niwa, Hideharu; Harada, Yoshihisa; Oshima, Masaharu; Isoda, Ayano; Matsunaga, Atsushi; Tanaka, Kazuhisa; Aoki, Tsutomu

2016-01-01

The development of a non-precious metal (NPM) fuel cell catalyst is extremely important to achieve globalization of polymer electrolyte fuel cells due to the cost and scarcity of platinum. Here, we report on a NPM cathode catalyst prepared by the pyrolysis of spherical polyimide nanoparticles that contain small amounts of Fe additive. 60 nm diameter Fe-containing polyimide nanoparticles were successfully synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with Fe(acac)3 (acac = acetylacetonate) as an additive. The particles were subsequently carbonized by multistep pyrolysis to obtain the NPM catalyst while retaining the small particle size. The catalyst has good performance and promising durability for fuel cell applications. The fuel cell performance under a 0.2 MPa air atmosphere at 80 °C of 1.0 A cm−2 at 0.46 V is especially remarkable and better than that previously reported. PMID:26987682

Antibacterial and catalytic activities of green synthesized silver nanoparticles.

PubMed

Bindhu, M R; Umadevi, M

2015-01-25

The aqueous beetroot extract was used as reducing agent for silver nanoparticles synthesis. The synthesized nanoparticles were characterized using UV-visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface plasmon resonance peak of synthesized nanoparticles was observed at 438 nm. As the concentration of beetroot extract increases, absorption spectra shows blue shift with decreasing particle size. The prepared silver nanoparticles were well dispersed, spherical in shape with the average particle size of 15 nm. The prepared silver nanoparticles are effective in inhibiting the growth of both gram positive and gram negative bacteria. The prepared silver nanoparticles reveal faster catalytic activity. This natural method for synthesis of silver nanoparticles offers a valuable contribution in the area of green synthesis and nanotechnology avoiding the presence of hazardous and toxic solvents and waste. Copyright © 2014 Elsevier B.V. All rights reserved.

Nanocrystalline Chalcopyrite Materials (CuInS2 and CuInSe2) via Low-Temperature Pyrolysis of Molecular Single-Source Precursors

NASA Technical Reports Server (NTRS)

Castro, Stephanie L.; Bailey, Sheila G.; Raffaelle, Ryne P.; Banger, Kulbinder K.; Hepp, Aloysius F.

2003-01-01

Nanometer sized particles of the chalcopyrite compounds CuInS2 and CuInSe2 were synthesized by thermal decomposition of molecular single-source precursors (PPh3)2CuIn(SEt)4 and (PPh3)2CuIn(SePh)4, respectively, in the non-coordinating solvent dioctyl phthalate at temperatures between 200 and 300 C. The nanoparticles range in size from 3 - 30 nm and are aggregated to form roughly spherical clusters of about 500 nm in diameter. X-ray diffraction of the nanoparticle powders shows greatly broadened lines indicative of very small particle sizes, which is confirmed by TEM. Peaks present in the XRD can be indexed to reference patterns for the respective chalcopyrite compounds. Optical spectroscopy and elemental analysis by energy dispersive spectroscopy support the identification of the nanoparticles as chalcopyrites.

Green synthesis of silver nanoparticles using Delphinium denudatum root extract exhibits antibacterial and mosquito larvicidal activities

NASA Astrophysics Data System (ADS)

Suresh, Gopal; Gunasekar, Poosali Hariharan; Kokila, Dhanasegaran; Prabhu, Durai; Dinesh, Devadoss; Ravichandran, Nagaiya; Ramesh, Balasubramanian; Koodalingam, Arunagirinathan; Vijaiyan Siva, Ganesan

2014-06-01

Green synthesis of silver nanoparticles (AgNPs) using aqueous root extract of Delphinium denudatum (Dd) by reduction of Ag+ ions from silver nitrate solution has been investigated. The synthesized DdAgNPs were characterized by using UV-Vis spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). The prepared DdAgNPs showed maximum absorbance at 416 nm and particles were polydispersed in nature, spherical in shape and the size of the particle obtained was ⩽85 nm. The DdAgNPs exhibited antibacterial activity against Staphylococcus aureus ATCC 6538, Bacillus cereus NCIM 2106, Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027. The DdAgNPs showed potent larvicidal activity against second instar larvae of dengue vector Aedes aegypti with a LC50 value of 9.6 ppm.

Synthesis and characterizations of spherical hollow composed of AgI nanoparticle using AgBr as the precursor

NASA Astrophysics Data System (ADS)

Yang, Ming; Zhou, Kui

2011-01-01

Hollow spheres of AgI with an average radius of 100-200 nm have been prepared by a simple reaction between AgBr suspension and KI in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of I- ions to AgBr surfaces and coagulation of the growing AgI in producing the spherical AgI particles. The products were characterized by X-ray powder diffraction, transmission electron microscopy, UV-vis absorption spectroscopy and X-ray photoelectron spectra techniques. The band gaps are estimated to be 2.95 eV according to the results of optical measurements of the hollow spheres of AgI.

Antifungal activity of gold nanoparticles prepared by solvothermal method

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

Ahmad, Tokeer, E-mail: tahmad3@jmi.ac.in; Wani, Irshad A.; Lone, Irfan H.

2013-01-15

Graphical abstract: Gold nanoparticles (7 and 15 nm) of very high surface area (329 and 269 m{sup 2}/g) have been successfully synthesized through solvothermal method by using tin chloride and sodium borohydride as reducing agents. As-prepared gold nanoparticles shows very excellent antifungal activity against Candida isolates and activity increases with decrease in the particle size. Display Omitted Highlights: ► Effect of reducing agents on the morphology of gold nanoparticles. ► Highly uniform and monodisperse gold nanoparticles (7 nm). ► Highest surface area of gold nanoparticles (329 m{sup 2/}g). ► Excellent antifungal activity of gold nanoparticles against Candida strains. -- Abstract:more » Gold nanoparticles have been successfully synthesized by solvothermal method using SnCl{sub 2} and NaBH{sub 4} as reducing agents. X-ray diffraction studies show highly crystalline and monophasic nature of the gold nanoparticles with face centred cubic structure. The transmission electron microscopic studies show the formation of nearly spherical gold nanoparticles of average size of 15 nm using SnCl{sub 2}, however, NaBH{sub 4} produced highly uniform, monodispersed and spherical gold nanoparticles of average grain size of 7 nm. A high surface area of 329 m{sup 2}/g for 7 nm and 269 m{sup 2}/g for 15 nm gold nanoparticles was observed. UV–vis studies assert the excitations over the visible region due to transverse and longitudinal surface plasmon modes. The gold nanoparticles exhibit excellent size dependant antifungal activity and greater biocidal action against Candida isolates for 7 nm sized gold nanoparticles restricting the transmembrane H{sup +} efflux of the Candida species than 15 nm sized gold nanoparticles.« less

Graphene Oxide-Promoted Reshaping and Coarsening of Gold Nanorods and Nanoparticles

PubMed Central

Pan, Hanqing; Low, Serena; Weerasuriya, Nisala; Shon, Young-Seok

2015-01-01

This paper describes thermally induced reshaping and coarsening behaviors of gold nanorods and nanoparticles immobilized on the surface of graphene oxide. Cetyltrimethylammonium bromide-stabilized gold nanorods with an aspect ratio of ~3.5 (54:15 nm) and glutathione-capped gold nanoparticles with an average core size of ~3 nm were synthesized and self-assembled onto the surface of graphene oxide. The hybrid materials were then heated at different temperatures ranging from 50 to 300 °C. The effects of heat treatments were monitored using UV–vis spectroscopy and transmission electron microscopy (TEM). These results were directly compared with those of heat-treated free-standing gold nanorods and nanoparticles without graphene oxide to understand the heat-induced morphological changes of the nanohybrids. The obtained results showed that the gold nanorods would undergo a complete reshaping to spherical particles at the temperature of 50 °C when they are assembled on graphene oxide. In comparison, the complete reshaping of free-standing gold nanorods to spherical particles would ultimately require a heating of the samples at 200 °C. In addition, the spherical gold nanoparticles immobilized on graphene oxide would undergo a rapid coarsening at the temperature of 100–150 °C, which was lower than the temperature (150–200 °C) required for visible coarsening of free-standing gold nanoparticles. The results indicated that graphene oxide facilitates the reshaping and coarsening of gold nanorods and nanoparticles, respectively, during the heat treatments. The stripping and spillover of stabilizing ligands promoted by graphene oxide are proposed to be the main mechanism for the enhancements in the heat-induced transformations of nanohybrids. PMID:25611371

Synthesis and structural characterization of transition metal doped MgO: Mg0.95Mn0.01TM0.04O (TM = Co, Ni, Cu)

NASA Astrophysics Data System (ADS)

Islam, Ishtihadah; Khandy, Shakeel Ahmad; Hafiz, Aurangzeb Khurram

2018-05-01

In the present work, preparation and characterization of transition metal doped MgO: Zn0.94Mn0.01TM0.05O (TM = Co, Ni and Cu) nano-particles have been reported. Transition metal doped samples of MgO were synthesized by Sol gel auto combustion method. Structural characterisation from XRD and SEM show the formation of single-phase primary particles, nearly of spherical shaped nano-crystallites. The crystallite size was found to be 78.2, 67.02, 78.11 and 64 nm for pure, Co, Cu and Ni doped MgMnO nano-particles, respectively. Hence, the average crystallite size increases monotonously from Co to Cu doping.

Preparation and characterization of copper oxide nanoparticles decorated carbon nanoparticles using laser ablation in liquid

NASA Astrophysics Data System (ADS)

Khashan, K. S.; Jabir, M. S.; Abdulameer, F. A.

2018-05-01

Carbon nanoparticles CNPs ecorated by copper oxide nano-sized particles would be successfully equipped using technique named pulsed laser ablation in liquid. The XRD pattern proved the presence of phases assigned to carbon and different phases of copper oxide. The chemical structure of the as-prepared nanoparticles samples was decided by Energy Dispersive Spectrum (EDS) measurement. EDS analysis results show the contents of Carbon, Oxygen and Copper in the final product. These nanoparticles were spherical shaped with a size distribution 10 to 80 nm or carbon nanoparticles and 5 to 50 nm for carbon decorated copper oxide nanoparticles, according to Transmission Electron Microscopy (TEM) images and particle-size distribution histogram. It was found that after doping with copper oxide, nanoparticles become smaller and more regular in shape. Optical absorption spectra of prepared nanoparticles were measured using UV–VIS spectroscopy. The absorption spectrum of carbon nanoparticles without doping indicates absorption peak at about 228 nm. After doping with copper oxide, absorption shows appearance of new absorption peak at about (254-264) nm, which is referred to the movement of the charge between 2p and 4s band of Cu2+ ions.

Cytotoxic potentials of biologically fabricated platinum nanoparticles from Streptomyces sp. on MCF-7 breast cancer cells.

PubMed

Baskaran, Balraj; Muthukumarasamy, Arulmozhi; Chidambaram, Siva; Sugumaran, Abimanyu; Ramachandran, Krithikadevi; Rasu Manimuthu, Thaneswari

2017-04-01

Biosynthesis of novel therapeutic nano-scale materials for biomedical and pharmaceutical applications has been enormously developed, since last decade. Herein, the authors report an ecological way of synthesising the platinum nanoparticles (PtNPs) using Streptomyces sp. for the first time . The produced PtNPs exhibited the face centred cubic system. The fourier transform infrared spectrum revealed the existence of amino acids in proteins which serves as an essential reductant for the formation of PtNPs. The spherical morphology of the PtNPs with an average size of 20-50 nm was observed from topographical images of atomic force microscopy and field emission scanning electron microscopy. The X-ray fluorescence spectrum confirms the presence of PtNPs with higher purity. The PtNPs size was further confirmed with transmission electron microscopy analysis and the particles were found to exist in the same size regime. Additionally, PtNPs showed the characteristic surface plasmon resonance peak at 262 nm. Dynamic light scattering studies report that 97.2% of particles were <100 nm, with an average particle diameter of about 45 nm. Furthermore, 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-tetrazolium assay based in vitro cytotoxicity analysis was conducted for the PtNPs, which showed the inhibitory concentration (IC 50 ) at 31.2 µg/ml against Michigan Cancer Foundation-7 breast cancer cells.

Cyclodextrin-assisted synthesis of tailored mesoporous silica nanoparticles

PubMed Central

2018-01-01

Mesoporous silica nanoparticles (MSNs) have sparked considerable interest in drug/gene delivery, catalysis, adsorption, separation, sensing, antireflection coatings and bioimaging because of their tunable structural properties. The shape, size and pore structure of MSNs are greatly influenced by the type of additives used, e.g., solvent and pore-templating agent. Here, we studied the influence of cyclodextrin (CD) molecules on the formation of MSNs. The nanoparticles over 100 nm in diameter were synthesized by surfactant-templated, hydrolysis–polycondensation reactions in the presence of pristine CD (β-CD) or hydroxypropyl-functionalized CDs (HP-γ-CD and HP-β-CD). Depending on the formulation conditions, differently shaped MSNs, such as bean-like, spherical, ellipsoid, aggregate and faceted were generated. The morphology and size of MSNs varied with the CD-type used. Generally, spherical particles were obtained with β-CD, while a faceted morphology was observed for the particles synthesized using HP-CDs. The particle size could be tuned by adjusting the amount of CD used; increasing the CD concentration led to larger particles. MSNs synthesized in the presence of β-CD displayed a smaller particle size than those produced with HP-functional CDs. FTIR, TGA and solid-state 13C NMR demonstrated the adsorption of CDs on the particle surfaces. The proposed concept allows for the synthesis of silica nanoparticles with control over particle shape and size by adjusting the concentration of additives in a simple, one-pot reaction system for a wide range of applications. PMID:29527443

Electrospraying technique for the fabrication of metronidazole contained PLGA particles and their release profile.

PubMed

Prabhakaran, Molamma P; Zamani, Maedeh; Felice, Betiana; Ramakrishna, Seeram

2015-11-01

Advanced engineering of materials for the development of drug delivery devices provides scope for novel and versatile strategies for treatment of various diseases. 'Electrospraying' was used to prepare PLGA microparticles and further encapsulate the drug, metronidazole (Met) within the particles to function as a drug delivery system. Two different solvents were utilized for the preparation of drug loaded PLGA particles, whereby the polymeric solution in dichloromethane (DCM) produced particles of bigger sizes than using trifluoroethanol (TFE). Scanning electron microscopy showed the spherical morphology of the particles, with sizes of 3946±407nm and 1774±167nm, respectively for PLGA-Met(DCM) and PLGA-Met(TFE). The FTIR spectroscopy proved the incorporation of metronidazole in the polymer, but without any specific drug-polymer interaction. The release of the drug from the particles was studied in phosphate buffered saline, where a sustained drug release was obtained for at least 41days. Cytotoxicity evaluation of the drug extract using mesenchymal stem cells (MSCs) showed not hindering the proliferation of MSCs, and the cell phenotype was retained after incubation in the drug containing media. Electrospraying is suggested as a cost-effective and single step process for the preparation of polymeric microparticles for prolonged and controlled release of drug. Copyright © 2015 Elsevier B.V. All rights reserved.

Chlorophyll Proteins of Photosystem I 1

PubMed Central

Mullet, John E.; Burke, John J.; Arntzen, Charles J.

1980-01-01

Data are presented which suggest the existence of a light-harvesting pigment-protein complex which is functionally and structurally associated with photosystem I (PSI) reaction centers. These observations are based on techniques which allow isolation of PSI using minimal concentrations of Triton X-100. Properties of density and self aggregation allowed purification of a “native” PSI complex. The isolated PSI particles appear as 106 Å spherical subunits when viewed by freeze fracture microscopy. When incorporated into phosphatidyl choline vesicles, the particles lose self-aggregation properties and disperse uniformly within the lipid membrane. The isolated PSI preparation contains 100 ± 10 chlorophylls/P700 (Chl a/b ratio greater than 18); this represents a recovery of 27% of the original chloroplast membrane Chl. These particles were enriched in Chl a forms absorbing at 701 to 710 nm. Chl fluorescence at room temperature exhibited a maximum at 690 nm with a pronounced shoulder at 710 nm. At 77 K, peak fluorescence emission was at 736 nm; in the presence of dithionite an additional fluorescence maximum at 695 nm was obtained at 77 K. This dual fluorescence emission peak for the PSI particles is evidence for at least two Chl populations within the PSI membrane subunit. The fluorescence emission observed at 695 nm was identified as arising from the core of PSI which contains 40 Chl/P700 (PSI-40). This core complex, derived from native PSI particles, was enriched in Chl a absorbing at 680 and 690 nm and fluorescing with maximal emission at 694 nm at 77 K. PSI particles consisting of the PSI core complex plus 20 to 25 Chl antennae (65 Chl/P700) could also be derived from native PSI complexes. These preparations were enriched in Chl a forms absorbing at 697 nm and exhibited a 77 K fluorescence emission maximum at 722 nm. A comparison of native PSI particles which contain 110 Chl/P700 (PSI-110) and PSI particles containing 65 Chl/P700 (PSI-65) provides evidence for the existence of a peripheral Chl-protein complex tightly associated in the native PSI complex. The native PSI subunits contain polypeptides of 22,500 to 24,500 daltons which are not found in the PSI-65 or PSI-40 subfractions. It is suggested that these polypeptides function to bind 40 to 45 Chl per structural complex, including the Chl which emits fluorescence at 736 nm. A model for the organization of Chl forms is presented in which the native PSI membrane subunit consists of a reaction center core complex plus two regions of associated light-harvesting antennae. The presence of energy “sinks” within the antennae is discussed. Images PMID:16661288

Size dependence of magneto-optical activity in silver nanoparticles with dimensions between 10 and 60 nm studied by MCD spectroscopy.

PubMed

Shiratsu, Taisuke; Yao, Hiroshi

2018-02-07

Size-dependent magneto-optical activity in Ag nanoparticles with dimensions from 10 to 60 nm is demonstrated with magnetic circular dichroism (MCD) spectroscopy. The Ag nanoparticles are prepared on the basis of a seeded-growth strategy using sodium citrate and/or tannic acid as reducing agents in aqueous solution. The obtained nanoparticles are roughly spherical, but those larger than ∼28 nm have a slight diversity of shapes with quasi-spherical polyhedrons. They exhibit a derivative-like MCD response in the localized surface plasmon resonance (LSPR) region, which originates from two circular modes of surface magnetoplasmons. With an increase in the nanoparticle diameter, the bisignated MCD signal is strongly distorted and weakened. Such a distortion for large-sized Ag nanoparticles can be phenomenologically simulated on the basis of both spectral inhomogeneity and MCD signal lobe asymmetry. Then the maximum value of MCD amplitude (MCD max ), which is obtained by normalization of the amplitude to the LSPR peak absorbance, first increases with increasing particle diameter and then decreases with a maximum for the 23 nm nanoparticle. Interestingly, the MCD max values are inversely correlated with the spectral bandwidth of LSPR extinction. This behaviour is discussed from a viewpoint of inhomogeneous effects of both spectral and size/shape distributions. We believe the present results will advance the design and application of optical devices based on magnetoplasmonics.

Synthesis and spectroscopic study of CdS nanoparticles using hydrothermal method

NASA Astrophysics Data System (ADS)

AL-Mamoori, Mohammed H. K.; Mahdi, Dunia K.; Al-Shrefi, Saif M.

2018-05-01

In this work, cadmium sulfide nanoparticles (powder) with diameter 50.8 nm was prepared using hydrothermal method. The structural and optical properties of CdS nanoparticles was studied by X-ray diffraction, FESEM, EDS, FTIR, UV-Diffuse Reflectance spectroscopy and Photoluminance spectrum. X-ray diffraction reveal the formation the purity of prepared phase of CdS particles with hexagonal wurtzite structure with particle size 31.8nm by using sheerer equation. The energy dispersion scattering (EDS) examination explains that the sample is composed of a large amount of Cd and S which are exactly CdS nanoparticles and there is a very small trace of (Zn) and (O) element observed because of there is a small pollutions in the measurement place of samples. FESEM shows the spherical shape of nanoparticles with around 50.8 nm diameter. The optical absorption spectral study identified the red shift of the sample in comparison to bulk ZnO in three dimensions. Photoluminance spectrum (PL) at room temperature showed that there are two luminescence peaks at 433.14 nm and 518.21nm. Samples demonstrate a sharp emission band at around 433.18 nm, which is attributed to the typical exciton luminescence. The broad band at 518.21nm which were attributed to the trapped luminescence. The green emission band at 518.21 nm was associated with the emission due to electronic transition from the conduction band to an accepter level due to interstitial sulphur ion.

Effect of particle size and dopant concentration on photophysical properties of Eu3+-doped rare earth oxysulphide phosphor coatings.

PubMed

Chakradhar, R P S; Basu, Bharathibai J; Lakshmi, R V

2011-02-01

Europium-doped rare-earth oxysulphides (red phosphors) are often used as reference luminophore in pyrene-based pressure sensor coatings for aerodynamic applications. Different red phosphor samples were characterized for their particle size, chemical composition, photoluminescent properties and temperature sensitivity. The red phosphor samples were characterized using energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and scanning electron microscopy (SEM) for morphology and particle size measurement. The particle size was in the range of 1.5-5.7 μm with morphology of hexagonal or spherical shape. It was found that phosphor with higher europium content exhibited higher luminescent emission intensity. The phosphor coatings were prepared by spraying a dispersion of the material in silicone resin. Smooth coatings were obtained by using phosphor samples with smaller particle size. Upon 334 nm excitation, the coatings showed characteristic luminescence 5D0→7FJ (J=0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 626 nm (5D0→7F2) of Eu3+ ions was stronger than the magnetic dipole transition located at 595 nm (5D0→7F1). Luminescence decay curves obeyed double exponential behaviour. The phosphor samples showed temperature sensitivity of -0.012 to -0.168%/°C in the temperature range of 25-50 °C. Copyright © 2010 Elsevier B.V. All rights reserved.

Soot superaggregates from flaming wildfires and their direct radiative forcing.

PubMed

Chakrabarty, Rajan K; Beres, Nicholas D; Moosmüller, Hans; China, Swarup; Mazzoleni, Claudio; Dubey, Manvendra K; Liu, Li; Mishchenko, Michael I

2014-07-01

Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimension Df ≈ 1.8 mobility diameter Dm ≤ 1 μm, and aerodynamic diameter Da ≤ 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic Df ≈ 2.6, Dm > 1 μm, and Da ≤ 300 nm that form via the cluster-dense aggregation mechanism. We present additional observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. At 550 nm wavelength, [corrected] we estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (D(f) ≈ 1.8) [corrected] aggregates, and ≈90% more warming than the volume-equivalent spherical soot particles simulated in climate models.

Noctilucent cloud particle size determination based on multi-wavelength all-sky analysis

NASA Astrophysics Data System (ADS)

Ugolnikov, Oleg S.; Galkin, Alexey A.; Pilgaev, Sergey V.; Roldugin, Alexey V.

2017-10-01

The article deals with the analysis of color distribution in noctilucent clouds (NLC) in the sky based on multi-wavelength (RGB) CCD-photometry provided with the all-sky camera in Lovozero in the north of Russia (68.0°N, 35.1°E) during the bright expanded NLC performance in the night of August 12, 2016. Small changes in the NLC color across the sky are interpreted as the atmospheric absorption and extinction effects combined with the difference in the Mie scattering functions of NLC particles for the three color channels of the camera. The method described in this paper is used to find the effective monodisperse radius of particles about 55 nm. The result of these simple and cost-effective measurements is in good agreement with previous estimations of comparable accuracy. Non-spherical particles, Gaussian and lognormal distribution of the particle size are also considered.

Continuous form-dependent focusing of non-spherical microparticles in a highly diluted suspension with the help of microfluidic spirals

NASA Astrophysics Data System (ADS)

Roth, Tanja; Sprenger, Lisa; Odenbach, Stefan; Häfeli, Urs O.

2018-04-01

Microfluidic spirals are able to focus non-spherical microparticles in diluted suspension due to the Dean effect. A secondary flow establishes in a curved channel, consisting of two counter-rotating vortices, which transport particles to an equilibrium position near the inner wall of the channel. The relevant size parameter, which is responsible for successful focusing, is the ratio between the particle diameter of a sphere and the hydraulic diameter, which is a characteristic of the microfluidic spiral. A non-spherical particle has not one but several different size parameters. This study investigated the minor and major axes, the equivalent spherical diameter, and the maximal rotational diameter as an equivalent to the spherical diameter. Using a polydimethylsiloxane (PDMS)-based microfluidic device with spirals, experiments were conducted with artificial peanut-shaped and ellipsoidal particles sized between 3 and 9 μm as well as with the bacteria Bacillus subtilis. Our investigations show that the equivalent spherical diameter, the major axis, and the maximal rotational diameter of a non-spherical particle can predict successful focusing. The minor axis is not suitable for this purpose. Non-spherical particles focused when the ratio of their equivalent spherical diameter to the hydraulic diameter of the channel was larger than 0.07. The particles also focused when the ratio between the maximal rotational diameter or the major axis and the hydraulic diameter was larger than 0.01. These results may help us to separate non-spherical biological particles, such as circulating tumor cells or pathogenic bacteria, from blood in future experimental studies.

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.

Ultrafine particle emissions from modern Gasoline and Diesel vehicles: An electron microscopic perspective.

PubMed

Liati, Anthi; Schreiber, Daniel; Arroyo Rojas Dasilva, Yadira; Dimopoulos Eggenschwiler, Panayotis

2018-08-01

Ultrafine (<100 nm) particles related to traffic are of high environmental and human health concern, as they are supposed to be more toxic than larger particles. In the present study transmission electron microscopy (TEM) is applied to obtain a concrete picture on the nature, morphology and chemical composition of non-volatile ultrafine particles in the exhaust of state-of-the-art, Euro 6b, Gasoline and Diesel vehicles. The particles were collected directly on TEM grids, at the tailpipe, downstream of the after-treatment system, during the entire duration of typical driving cycles on the chassis dynamometer. Based on TEM imaging coupled with Energy Dispersive X-ray (EDX) analysis, numerous ultrafine particles could be identified, imaged and analyzed chemically. Particles <10 nm were rarely detected. The ultrafine particles can be distinguished into the following types: soot, ash-bearing soot and ash. Ash consists of Ca, P, Mg, Zn, Fe, S, and minor Sn compounds. Most elements originate from lubricating oil additives; Sn and at least part of Fe are products of engine wear; minor W ± Si-bearing nearly spherical particles in Diesel exhaust derive from catalytic coating material. Ultrafine ash particles predominate over ultrafine soot or are nearly equal in amount, in contrast to emissions of larger sizes where soot is by far the prevalent particle type. This is probably due to the low ash amount per volume fraction in the total emissions, which does not favor formation of large ash agglomerates, opposite to soot, which is abundant and thus easily forms agglomerates of sizes larger than those of the ultrafine range. No significant differences of ultrafine particle characteristics were identified among the tested Gasoline and Diesel vehicles and driving cycles. The present TEM study gives information also on the imaging and chemical composition of the solid fraction of the unregulated sub-23 nm size category particles. Copyright © 2018 Elsevier Ltd. All rights reserved.

Optimization and design of pigments for heat-insulating coatings

NASA Astrophysics Data System (ADS)

Wang, Guang-Hai; Zhang, Yue

2010-12-01

This paper reports that heat insulating property of infrared reflective coatings is obtained through the use of pigments which diffuse near-infrared thermal radiation. Suitable structure and size distribution of pigments would attain maximum diffuse infrared radiation and reduce the pigment volume concentration required. The optimum structure and size range of pigments for reflective infrared coatings are studied by using Kubelka—Munk theory, Mie model and independent scattering approximation. Taking titania particle as the pigment embedded in an inorganic coating, the computational results show that core-shell particles present excellent scattering ability, more so than solid and hollow spherical particles. The optimum radius range of core-shell particles is around 0.3 ~ 1.6 μm. Furthermore, the influence of shell thickness on optical parameters of the coating is also obvious and the optimal thickness of shell is 100-300 nm.

Stabilization of miniemulsion droplets by cerium oxide nanoparticles: a step toward the elaboration of armored composite latexes.

PubMed

Zgheib, Nancy; Putaux, Jean-Luc; Thill, Antoine; D'Agosto, Franck; Lansalot, Muriel; Bourgeat-Lami, Elodie

2012-04-10

Stable methyl methacrylate (MMA) miniemulsions were successfully prepared using for the first time cerium oxide (CeO(2)) nanoparticles as solid stabilizers in the absence of any molecular surfactant. The interaction between MMA droplets and CeO(2) nanoparticles was induced by the use of methacrylic acid (MAA) as a comonomer. Both MAA and CeO(2) contents played a key role on the diameter and the stability of the droplets formed during the emulsification step. Cryo-transmission electron microscopy (TEM) images of the suspensions formed with 35 wt % of CeO(2) showed the presence of polydisperse 50-150 nm spherical droplets. More surprisingly, some nonspherical (likely discoidal) objects that could be the result of the sonication step were also observed. The subsequent polymerization of these Pickering miniemulsion droplets led to the formation of composite PMMA latex particles armored with CeO(2). In all cases, the conversion was limited to ca. 85%, concomitant with a loss of stability of the latex for CeO(2) contents lower than 35 wt %. This stability issues were likely related to the screening of the cationic charges present on CeO(2) nanoparticles upon polymerization. TEM images showed mostly spherical particles with a diameter ranging from 100 to 400 nm and homogeneously covered with CeO(2). Besides, for particles typically larger than 200 nm, a buckled morphology was observed supporting the presence of residual monomer at the end of the polymerization and consistent with the limited conversion. The versatility of these systems was further demonstrated using 35 wt % of CeO(2) and replacing MMA by n-butyl acrylate (BA) either alone or in combination with MMA. Stable monomer emulsions were always obtained, with the droplet size increasing with the hydrophobicity of the oil phase, pointing out the key influence of the wettability of the solid stabilizer. The polymerization of Pickering miniemulsion stabilized by CeO(2) nanoparticles proved to be an efficient strategy to form armored composite latex particles which may find applications in coating technology. © 2012 American Chemical Society

Method for making fine and ultrafine spherical particles of zirconium titanate and other mixed metal oxide systems

DOEpatents

Hu, Michael Z.

2006-05-23

Disclosed is a method for making amorphous spherical particles of zirconium titanate and crystalline spherical particles of zirconium titanate comprising the steps of mixing an aqueous solution of zirconium salt and an aqueous solution of titanium salt into a mixed solution having equal moles of zirconium and titanium and having a total salt concentration in the range from 0.01 M to about 0.5 M. A stearic dispersant and an organic solvent is added to the mixed salt solution, subjecting the zirconium salt and the titanium salt in the mixed solution to a coprecipitation reaction forming a solution containing amorphous spherical particles of zirconium titanate wherein the volume ratio of the organic solvent to aqueous part is in the range from 1 to 5. The solution of amorphous spherical particles is incubated in an oven at a temperature .ltoreq.100.degree. C. for a period of time .ltoreq.24 hours converting the amorphous particles to fine or ultrafine crystalline spherical particles of zirconium titanate.

Plasma in-liquid method for reduction of zinc oxide in zinc nanoparticle synthesis

NASA Astrophysics Data System (ADS)

Amaliyah, Novriany; Mukasa, Shinobu; Nomura, Shinfuku; Toyota, Hiromichi; Kitamae, Tomohide

2015-02-01

Metal air-batteries with high-energy density are expected to be increasingly applied in electric vehicles. This will require a method of recycling air batteries, and reduction of metal oxide by generating plasma in liquid has been proposed as a possible method. Microwave-induced plasma is generated in ethanol as a reducing agent in which zinc oxide is dispersed. Analysis by energy-dispersive x-ray spectrometry (EDS) and x-ray diffraction (XRD) reveals the reduction of zinc oxide. According to images by transmission electron microscopy (TEM), cubic and hexagonal metallic zinc particles are formed in sizes of 30 to 200 nm. Additionally, spherical fiber flocculates approximately 180 nm in diameter are present.

Cloud condensation nuclei activity and hygroscopicity of fresh and aged cooking organic aerosol

NASA Astrophysics Data System (ADS)

Li, Yanwei; Tasoglou, Antonios; Liangou, Aikaterini; Cain, Kerrigan P.; Jahn, Leif; Gu, Peishi; Kostenidou, Evangelia; Pandis, Spyros N.

2018-03-01

Cooking organic aerosol (COA) is potentially a significant fraction of organic particulate matter in urban areas. COA chemical aging experiments, using aerosol produced by grilling hamburgers, took place in a smog chamber in the presence of UV light or excess ozone. The water solubility distributions, cloud condensation nuclei (CCN) activity, and corresponding hygroscopicity of fresh and aged COA were measured. The average mobility equivalent activation diameter of the fresh particles at 0.4% supersaturation ranged from 87 to 126 nm and decreased for aged particles, ranging from 65 to 88 nm. Most of the fresh COA had water solubility less than 0.1 g L-1, even though the corresponding particles were quite CCN active. After aging, the COA fraction with water solubility greater than 0.1 g L-1 increased more than 2 times. Using the extended Köhler theory for multiple partially soluble components in order to predict the measured activation diameters, the COA solubility distribution alone could not explain the CCN activity. Surface tensions less than 30 dyn cm-1 were required to explain the measured activation diameters. In addition, COA particles appear to not be spherical, which can introduce uncertainties into the corresponding calculations.

Synthesis of FeCoB amorphous nanoparticles and application in ferrofluids

NASA Astrophysics Data System (ADS)

Zhao, Shuchun; Bian, Xiufang; Yang, Chuncheng; Yu, Mengchun; Wang, Tianqi

2018-03-01

Magnetic FeCoB amorphous nanoparticles were successfully synthesized by borohydride reduction in water/n-hexane (W/He) microemulsions. The as-prepared FeCoB alloys are amorphous and spherical nanoparticles with an average particle size about 10.7 nm, compared to FeCoB alloys with an average particle size about 304.2 nm which were synthesized by a conventional aqua-solution method. Furthermore, three kinds of FeCoB ferrofluids (FFs) were prepared by dispersing FeCoB particles into W/He microemulsion, water and silicone oil respectively. Results show that the W/He-based FeCoB FFs are superparamagnetic with saturation magnetization (Ms) reaching to 12.4 emu/g. Besides, compared to water-based and silicone oil-based FFs, W/He-based FeCoB FFs exhibit high stability, with magnetic weights decreasing slightly even under the magnetic field intensity of H = 210 mT. In the W/He-based FeCoB FFs, interfacial tensions of water phase and oil phase are supposed to prevent the agglomeration and sedimentation of FeCoB nanoparticles dispersed in different water droplets of the microemulsion, compared to the current stabilizing method of directly modifying the surface of particles.

Analysis of surgical smoke produced by various energy-based instruments and effect on laparoscopic visibility.

PubMed

Weld, Kyle J; Dryer, Stephen; Ames, Caroline D; Cho, Kuk; Hogan, Chris; Lee, Myonghwa; Biswas, Pratim; Landman, Jaime

2007-03-01

We analyzed the smoke plume produced by various energy-based laparoscopic instruments and determined its effect on laparoscopic visibility. The Bipolar Macroforceps, Harmonic Scalpel, Floating Ball, and Monopolar Shears were applied in vitro to porcine psoas muscle. An Aerodynamic Particle Sizer and Electrostatic Classifier provided a size distribution of the plume for particles >500 nm and <500 nm, and a geometric mean particle size was calculated. A Condensation Particle Counter provided the total particle-number concentration. Electron microscopy was used to characterize particle size and shape further. Visibility was calculated using the measured-size distribution data and the Rayleigh and Mie light-scattering theories. The real-time instruments were successful in measuring aerosolized particle size distributions in two size ranges. Electron microscopy revealed smaller, homogeneous, spherical particles and larger, irregular particles consistent with cellular components. The aerosol produced by the Bipolar Macroforceps obscured visibility the least (relative visibility 0.887) among the instruments tested. Particles from the Harmonic Scalpel resulted in a relative visibility of 0.801. Monopolar-based instruments produced plumes responsible for the poorest relative visibility (Floating Ball 0.252; Monopolar Shears 0.026). Surgical smoke is composed of two distinct particle populations caused by the nucleation of vapors as they cool (the small particles) and the entrainment of tissue secondary to mechanical aspects (the large particles). High concentrations of small particles are most responsible for the deterioration in laparoscopic vision. Bipolar and ultrasonic instruments generate a surgical plume that causes the least deterioration of visibility among the instruments tested.

Development of a DNA-liposome complex for gene delivery applications.

PubMed

Rasoulianboroujeni, M; Kupgan, G; Moghadam, F; Tahriri, M; Boughdachi, A; Khoshkenar, P; Ambrose, J J; Kiaie, N; Vashaee, D; Ramsey, J D; Tayebi, L

2017-06-01

The association structures formed by cationic liposomes and DNA (Deoxyribonucleic acid)-liposome have been effectively utilized as gene carriers in transfection assays. In this research study, cationic liposomes were prepared using a modified lipid film hydration method consisting of a lyophilization step for gene delivery applications. The obtained results demonstrated that the mean particle size had no significant change while the polydispersity (PDI) increased after lyophilization. The mean particle size slightly reduced after lyophilization (520±12nm to 464±25nm) while the PDI increased after lyophilization (0.094±0.017 to 0.220±0.004). In addition. The mean particle size of vesicles increases when DNA is incorporated to the liposomes (673±27nm). According to the Scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM) images, the spherical shape of liposomes confirmed their successful preservation and reconstitution from the powder. It was found that liposomal formulation has enhanced transfection considerably compared to the naked DNA as negative control. Finally, liposomal formulation in this research had a better function than Lipofectamine® 2000 as a commercialized product because the cellular activity (cellular protein) was higher in the prepared lipoplex than Lipofectamine® 2000. Copyright © 2017 Elsevier B.V. All rights reserved.

Biosynthesis of silver nanoparticles by using Ganoderma-mushroom extract

NASA Astrophysics Data System (ADS)

Ekar, S. U.; Khollam, Y. B.; Koinkar, P. M.; Mirji, S. A.; Mane, R. S.; Naushad, M.; Jadhav, S. S.

2015-03-01

Present study reports the biochemical synthesis of silver nanoparticles (Ag-NPs) from aqueous medium by using the extract of medicinal mushroom Ganoderma, as a reducing and stabilizing agents. The Ag-NPs are prepared at room temperature by the reduction of Ag+ to Ag in aqueous solution of AgNO3. The resultant particles are characterized by using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) measurement techniques. The formation of Ag-NPs is confirmed by recording the UV-visible absorption spectra for surface plasmon resonance (SPR) where peak around 427 nm. The prominent changes observed in FTIR spectra supported the reduction of Ag+ to Ag. The morphological features of Ag-NPs are evaluated from HRTEM. The spherical Ag-NPs are observed in transmission electron microscopy (TEM) studies. The particle size distribution is found to be nearly uniform with average particle size of 2 nm. The Ag-NPs aged for 15, 30, 60 and 120 days showed no profound effect on the position of SPR peak in UV-visible studies, indicating the protecting/capping ability of medicinal mushroom Ganoderma in the synthesis of Ag-NPs.

Ion Transport across Biological Membranes by Carborane-Capped Gold Nanoparticles

PubMed Central

2017-01-01

Carborane-capped gold nanoparticles (Au/carborane NPs, 2–3 nm) can act as artificial ion transporters across biological membranes. The particles themselves are large hydrophobic anions that have the ability to disperse in aqueous media and to partition over both sides of a phospholipid bilayer membrane. Their presence therefore causes a membrane potential that is determined by the relative concentrations of particles on each side of the membrane according to the Nernst equation. The particles tend to adsorb to both sides of the membrane and can flip across if changes in membrane potential require their repartitioning. Such changes can be made either with a potentiostat in an electrochemical cell or by competition with another partitioning ion, for example, potassium in the presence of its specific transporter valinomycin. Carborane-capped gold nanoparticles have a ligand shell full of voids, which stem from the packing of near spherical ligands on a near spherical metal core. These voids are normally filled with sodium or potassium ions, and the charge is overcompensated by excess electrons in the metal core. The anionic particles are therefore able to take up and release a certain payload of cations and to adjust their net charge accordingly. It is demonstrated by potential-dependent fluorescence spectroscopy that polarized phospholipid membranes of vesicles can be depolarized by ion transport mediated by the particles. It is also shown that the particles act as alkali-ion-specific transporters across free-standing membranes under potentiostatic control. Magnesium ions are not transported. PMID:29161496

Ion Transport across Biological Membranes by Carborane-Capped Gold Nanoparticles.

PubMed

Grzelczak, Marcin P; Danks, Stephen P; Klipp, Robert C; Belic, Domagoj; Zaulet, Adnana; Kunstmann-Olsen, Casper; Bradley, Dan F; Tsukuda, Tatsuya; Viñas, Clara; Teixidor, Francesc; Abramson, Jonathan J; Brust, Mathias

2017-12-26

Carborane-capped gold nanoparticles (Au/carborane NPs, 2-3 nm) can act as artificial ion transporters across biological membranes. The particles themselves are large hydrophobic anions that have the ability to disperse in aqueous media and to partition over both sides of a phospholipid bilayer membrane. Their presence therefore causes a membrane potential that is determined by the relative concentrations of particles on each side of the membrane according to the Nernst equation. The particles tend to adsorb to both sides of the membrane and can flip across if changes in membrane potential require their repartitioning. Such changes can be made either with a potentiostat in an electrochemical cell or by competition with another partitioning ion, for example, potassium in the presence of its specific transporter valinomycin. Carborane-capped gold nanoparticles have a ligand shell full of voids, which stem from the packing of near spherical ligands on a near spherical metal core. These voids are normally filled with sodium or potassium ions, and the charge is overcompensated by excess electrons in the metal core. The anionic particles are therefore able to take up and release a certain payload of cations and to adjust their net charge accordingly. It is demonstrated by potential-dependent fluorescence spectroscopy that polarized phospholipid membranes of vesicles can be depolarized by ion transport mediated by the particles. It is also shown that the particles act as alkali-ion-specific transporters across free-standing membranes under potentiostatic control. Magnesium ions are not transported.

Effective density and morphology of particles emitted from small-scale combustion of various wood fuels.

PubMed

Leskinen, Jani; Ihalainen, Mika; Torvela, Tiina; Kortelainen, Miika; Lamberg, Heikki; Tiitta, Petri; Jakobi, Gert; Grigonyte, Julija; Joutsensaari, Jorma; Sippula, Olli; Tissari, Jarkko; Virtanen, Annele; Zimmermann, Ralf; Jokiniemi, Jorma

2014-11-18

The effective density of fine particles emitted from small-scale wood combustion of various fuels were determined with a system consisting of an aerosol particle mass analyzer and a scanning mobility particle sizer (APM-SMPS). A novel sampling chamber was combined to the system to enable measurements of highly fluctuating combustion processes. In addition, mass-mobility exponents (relates mass and mobility size) were determined from the density data to describe the shape of the particles. Particle size, type of fuel, combustion phase, and combustion conditions were found to have an effect on the effective density and the particle shape. For example, steady combustion phase produced agglomerates with effective density of roughly 1 g cm(-3) for small particles, decreasing to 0.25 g cm(-3) for 400 nm particles. The effective density was higher for particles emitted from glowing embers phase (ca. 1-2 g cm(-3)), and a clear size dependency was not observed as the particles were nearly spherical in shape. This study shows that a single value cannot be used for the effective density of particles emitted from wood combustion.

The detached haze layer in Titan's mesosphere: The formation process

NASA Astrophysics Data System (ADS)

Lavvas, P.; Yelle, R. V.; Vuitton, V.

2008-09-01

Cassini observations made by the Imaging Science Subsystem (ISS) [1] and by the UltraViolet Imaging Spectrometer (UVIS) [2,3] have revealed the presence of a detached haze layer in Titan's mesosphere at an altitude of 520 km. Analysis of the observed optical properties presented in the accompanying talk [5], suggests that the average size of particles in the detached layer is of ~40 nm, with an imaginary index k < 0.3 at 187.5 nm and a number density of ˜30 particles cm-3, while calculations of the sedimentation velocity of the haze particles coupled with the derived number density imply a mass flux of 1.9-3.2 × 10-14 g cm-2 s-1. This is approximately equal to the mass flux required to explain the main haze layer and suggests that the main haze layer in Titan's stratosphere is formed primarily by sedimentation and coagulation of particles in the detached layer [5,6]. The HASI data clearly show that the haze is coincident with a temperature maximum. This rules out condensation as the source of the detached haze. We have also considered a more complicated scenario in which the detached layer is caused by an increase in the density of condensation nuclei near 520 km. This is motivated by the fact that silicate micrometeorites ablate near 500 km [7,8]. Recondensation of the refractory vapor creates `smoke' particles that could serve as condensation nuclei. Combination of Pioneer measurements along with theoretical estimations for the particles velocity distribution, suggest a mass flux of ~10-17 g cm-2 s-1 at Saturn's region [9], while measurements from the Cassini Dust Analyser (CDA) suggest a similar magnitude at Titan's location [10]. These fluxes are ~3 orders of magnitude smaller than the lower limit of the estimated mass flux out of the detached haze layer, so meteorite ablation can not be the direct cause of the aerosol layer. However, if the ablated meteoritic material reforms 1 nm particles, the implied number flux would be 2.4 × 103 particles cm-2 s-1, which is of the right order of magnitude to explain the detached layer. This hypothesis requires that additional material condense on the meteoritic smoke particles. Unfortunately, the main photochemical products on Titan (HCN, C2H2, C2H6, etc.) do not condense at the temperature and pressure in the detached layer. The saturation mixing ratio for species present in Titan's mesosphere are shown in Fig. 1. The vapour pressure of each species is calculated assuming the HASI vertical temperature profile [4]. The species that come closest to condensing are H2O and C6N2. There is some water vapor present from ablation of icy micrometeorites in Titan's atmosphere, but the mole fraction corresponding to saturation vapor pressure of water at 520 km is 1.6 × 10-2, many orders of magnitude larger than expected [11]. Similarly, the mole fraction of C6N2 at 520 km is expected to be much smaller than the saturation value of 5 × 10-6 [12]. Hence, the growth of particles through condensation cannot explain the detached haze layer. Advection processes in the atmosphere have been related to the formation of the Voyager detached haze layer [13]. In this picture, meridional winds transport the haze particles polewards, constraining them at a specific altitude region, before depositing them at the pole, while the upwelling part of the circulation transports large particles from the main haze layer upwards, enhancing in this way the opacity of the detached haze layer. Yet, the meridional winds are estimated to be υ~3 cm s-1 in the region of the stratospheric zonal jet near 0.1 mbar based on CIRS measurements [14]. Assuming this value to hold in the region of the detached haze layer implies a horizontal motion characteristic time of H~R/v = 108 s. A 40 nm particle has a settling velocity of υ S~1 cm s-1 at 500 km, and the characteristic time to fall 20 km is only 2 × 106 s implying that the particles fall out of the region before they are transported to the pole. Thus, the dynamical explanation for the Voyager detached haze fails by more than a factor of 50 for the detached layer at 520 km. The inefficiency of the above processes to provide enough mass flux to generate the detached layer along with the large mass flux retrieved by the observations [5,6] suggest that haze is formed in Titan's thermosphere by high-energy radical and ion chemistry. In this case the presence of the detached layer could be an optical illusion effect due to the increase of particles' size, along with the decrease of their settling velocity with decreasing altitude. In order to investigate this effect we used a microphysical model [15], which has been extended to describe both spherical and fractal particle growth [16]. We assume a gaussian production profile centered at 800 km and with a column mass production of 4.5 × 10-14 g cm-2 s-1. The particles grow as spheres or fractals depending on the fractal dimension, Df, (Df=2 for fractals and 3 for spheres). Using only spherical particle growth provides a good fit to the extinction observed by UVIS at 187.5 nm [3] above the detached haze layer, while the modeled extinction drops faster than the observed extinction at altitudes below the detached layer (Fig. 2). By setting the transition altitude of spherical to fractal growth at 510 km, the generated fractal particles provide an excellent fit to the observed extinction profile below the detached layer suggesting that the particles present there are indeed of fractal structure. At the same time, the transition from spheres to fractals aggregates, generates a well pronounced minimum in the total simulated extinction, which provides a very good fit to the observed detached haze layer extinction profile [3]. In addition, the calculated mass flux at 520 km is 3.1 × 10-14 g cm-2 s-1, which is within the limits defined by the optical analysis of the detached layer [5,6]. Finally, the calculated monomer size of the particles forming the fractal aggregates is 57 nm, is good agreement with the 50 nm size retrieved by the DISR measurements [17]. Our simulation of Titan's haze particle evolution suggests that the presence of the detached haze layer is due to the transition in the growth of particles from spherical to fractal structure. Further investigation of the processes defining the growth of the particles is required in order to understand why the transition takes place at this region and how the particles produced at higher altitudes are defining the vertical haze opacity in Titan's atmosphere.

Synthesis of silver nanoparticles by silver salt reduction and its characterization

NASA Astrophysics Data System (ADS)

Muzamil, Muhammad; Khalid, Naveed; Danish Aziz, M.; Aun Abbas, S.

2014-06-01

The wet chemical method route by metal salt reduction has been used to synthesize nanoparticles, using silver nitrate as an inorganic salt, aldehyde as a reducing agent and amino acid as a catalyst. During the reaction aldehyde oxidizes to carboxylic acid and encapsulates the silver nanoparticles to prevent agglomeration and provide barrier in the growth of particle. The existing work produces particles using lab grade chemical, here the presented work is by using industrial grade chemicals to make the process more cost & time effective. The nano silver powder has been studied for their formation, particle size, shape & compositional analysis using Scanning Electron Microscope (SEM) equipped with EDS. The particles size distributions were analyzed by Laser Particle Analyzer (LPA), structure & morphological analysis using x-ray diffraction (XRD) and Fourier-transform-infrared Spectroscopy (FTIR) confirmed the stabilization of particles by coating of carboxylic group. These studies infer that the particles are mostly spherical in shape and have an average size between 70 to 350 nm.

Light absorption and morphological properties of soot-containing aerosols observed at an East Asian outflow site, Noto Peninsula, Japan

NASA Astrophysics Data System (ADS)

Ueda, S.; Nakayama, T.; Taketani, F.; Adachi, K.; Matsuki, A.; Iwamoto, Y.; Sadanaga, Y.; Matsumi, Y.

2015-09-01

The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory-BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a heater maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the heater and was found to be 22-23 %. The largest enhancements (> 30 %) were observed under high absorption coefficient conditions when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption coefficient events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high density electron beam. The majority of the soot in all samples was found as mixed particles with spherical sulfate or as clusters of sulfate spherules. For samples showing high enhancement (> 30 %) of BC light absorption, TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be embedded into the sulfate. The SP2 measurements also suggested that the proportion of thickly-coated soot was greater. Thus, the observed enhancement of BC light absorption was found to differ according to the mixing states and morphology of soot-containing particles. The enhancement of BC light absorption in our in situ measurements and its relation with individual features of soot-containing particles will be useful to evaluate direct radiative forcing in the leeward areas of large emission sources of BC.

Fungus-mediated biological synthesis of gold nanoparticles: potential in detection of liver cancer

PubMed Central

Chauhan, Arun; Zubair, Swaleha; Tufail, Saba; Sherwani, Asif; Sajid, Mohammad; Raman, Suri C; Azam, Amir; Owais, Mohammad

2011-01-01

Background Nanomaterials are considered to be the pre-eminent component of the rapidly advancing field of nanotechnology. However, developments in the biologically inspired synthesis of nanoparticles are still in their infancy and consequently attracting the attention of material scientists throughout the world. Keeping in mind the fact that microorganism-assisted synthesis of nanoparticles is a safe and economically viable prospect, in the current study we report Candida albicans-mediated biological synthesis of gold nanoparticles. Methods and results Transmission electron microscopy, atomic force microscopy, and various spectrophotometric analyses were performed to characterize the gold nanoparticles. The morphology of the synthesized gold particles depended on the abundance of C. albicans cytosolic extract. Transmission electron microscopy, nanophox particle analysis, and atomic force microscopy revealed the size of spherical gold nanoparticles to be in the range of 20–40 nm and nonspherical gold particles were found to be 60–80 nm. We also evaluated the potential of biogenic gold nanoparticles to probe liver cancer cells by conjugating them with liver cancer cell surface-specific antibodies. The antibody-conjugated gold particles were found to bind specifically to the surface antigens of the cancer cells. Conclusion The antibody-conjugated gold particles synthesized in this study could successfully differentiate normal cell populations from cancerous cells. PMID:22072868

A comparison of field-dependent rheological properties between spherical and plate-like carbonyl iron particles-based magneto-rheological fluids

NASA Astrophysics Data System (ADS)

Tan Shilan, Salihah; Amri Mazlan, Saiful; Ido, Yasushi; Hajalilou, Abdollah; Jeyadevan, Balachandran; Choi, Seung-Bok; Azhani Yunus, Nurul

2016-09-01

This work proposes different sizes of the plate-like particles from conventional spherical carbonyl iron (CI) particles by adjusting milling time in the ball mill process. The ball mill process to make the plate-like particles is called a solid-state powder processing technique which involves repeated welding, fracturing and re-welding of powder particles in a high-energy ball mill. The effect of ball milling process on the magnetic behavior of CI particles is firstly investigated by vibrating sample magnetometer. It is found form this investigation that the plate-like particles have higher saturation magnetization (about 8%) than that of the spherical particles. Subsequently, for the investigation on the sedimentation behavior the cylindrical measurement technique is used. It is observed from this measurement that the plate-like particles show slower sedimentation rate compared to the spherical particles indicating higher stability of the MR fluid. The field-dependent rheological properties of MR fluids based on the plate-like particles are then investigated with respect to the milling time which is directly connected to the size of the plate-like particles. In addition, the field-dependent rheological properties such as the yield stress are evaluated and compared between the plate-like particles based MR fluids and the spherical particles based MR fluid. It is found that the yield shear stress of the plate-like particles based MR fluid is increased up to 270% compared to the spherical particles based MR fluid.

Electromagnetic properties of Fe-Co granular composite materials containing acicular nanoparticles

NASA Astrophysics Data System (ADS)

Kasagi, Teruhiro; Massango, Herieta; Tsutaoka, Takanori; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2018-03-01

Electromagnetic properties of acicular (needle-like) Fe76Co24 nanoparticle composite materials have been studied in microwave frequency range up to 20 GHz. The Fe76Co24 particles are commercially available acicular Fe76Co24 nanoparticles with an approximate length and diameter of 100 and 25 nm, respectively. The Fe76Co24 nanocomposites were prepared by embedding the Fe76Co24 nanoparticle in an appropriate resin. Since the metallic Fe76Co24 nanoparticles have an oxidized surface, even high particle content composites at 78 vol.%, which is in the percolated state, does not show metallic conduction; a low frequency plasmonic state with the negative permittivity spectrum was not observed. Meanwhile, the negative permeability spectrum caused by the magnetic resonance in Fe76Co24 alloy was obtained in the high particle content composites. From the measurement of the complex permeability spectra under the external dc magnetic field, it was clarified that the gyromagnetic spin rotation mainly contributes to the permeability spectrum of nanocomposites due to extremely small quantity of domain walls in the acicular nanoparticles. This result suggests that the negative permeability spectrum was caused by the gyromagnetic spin resonance. By the comparison of the complex permeability spectrum between the acicular Fe76Co24 nanocomposite and the spherical Fe50Co50 microcomposite, the gyromagnetic spin resonance frequency of the acicular nanocomposite tends to locate higher than that of the spherical microcomposite owing to the demagnetizing field effect. Therefore, it can be concluded that the negative permeability frequency band of the acicular nanocomposite is higher than that of the spherical microcomposite at the same particle content.

Phytosynthesis and Characterization of Silver Nanoparticles Using Callus of JATROPHA CURCAS: a Biotechnological Approach

NASA Astrophysics Data System (ADS)

Demissie, A. G.; Lele, S. S.

2013-06-01

The present study reports a rapid plant-based biosynthesis of silver nanoparticles using callus extract of Jatropha curcas L. The particle size and morphological analyses were carried out using Zetasizer, SEM, TEM. The physicochemical properties were monitored using UV-Vis spectroscopic, IR and DSC. The formation of silver nanoparticle was confirmed by using UV-Vis spectrophotometer and absorbance peaks at 421 nm. The silver nanoparticle was found to be a negatively charged with size ranging from 2 nm to 50 nm. The morphology of the nanoparticle is uniformly spherical and has a dispersion ratio of 0.14. The physicochemical study using DSC indicated significant thermal stability and crystalline nature of the nanoparticle. This intracellular biosynthesis of silver nanoparticles is simple, cheap and eco-friendly than other mechanical and chemical approaches.

Synthesis, Characterization and Comparative Luminescence Studies of Rare-Earth-Doped Gd2O3 Nanoparticles

NASA Astrophysics Data System (ADS)

Pyngrope, D.; Singh, L. R.; Prasad, A. I.; Bora, A.

2018-04-01

A facile direct precipitation method was used for the synthesis of luminescence nanomaterial. Gd2O3 doped with rare earth element Eu3+ is synthesized by polyol route. The synthesized nanoparticles show their characteristic red emission. The nanoparticles are characterized by x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence (PL) study. The synthesized nanoparticles are spherical particles with 30 nm size. The photoluminescence studies show the characteristic Eu3+ red emission. The PL study shows the intensity of the magnetic dipole transition ( 5 D0 \\to 7 F1 ) at 592 nm compared to that of the electronic dipole transition ( 5 D0 \\to 7 F2 ) at 615 nm. The nanomaterials can show significant application in various display devices and biomedical applications for tracking.

Sonochemical Synthesis of Silver Nanoparticles Using Starch: A Comparison

PubMed Central

Smita, Kumari; Cumbal, Luis; Debut, Alexis; Pathak, Ravinandan Nath

2014-01-01

A novel approach was applied to synthesize silver nanoparticles using starch under sonication. Colloidal silver nanoparticles solution exhibited an increase of absorption from 420 to 440 nm with increase starch quantity. Transmission electron microscopy followed by selected area electron diffraction pattern analysis indicated the formation of spherical, polydispersed, amorphous, silver nanoparticles of diameter ranging from 23 to 97 nm with mean particle size of 45.6 nm. Selected area electron diffraction (SAED) confirmed partial crystalline and amorphous nature of silver nanoparticles. Silver nanoparticles synthesized in this manner can be used for synthesis of 2-aryl substituted benzimidazoles which have numerous biomedical applications. The optimized reaction conditions include 10 ml of 1 mM AgNO3, 25 mg starch, 11 pH range, and sonication for 20 min at room temperature. PMID:24587771

Inertial migrations of cylindrical particles in rectangular microchannels: Variations of equilibrium positions and equivalent diameters

NASA Astrophysics Data System (ADS)

Su, Jinghong; Chen, Xiaodong; Hu, Guoqing

2018-03-01

Inertial migration has emerged as an efficient tool for manipulating both biological and engineered particles that commonly exist with non-spherical shapes in microfluidic devices. There have been numerous studies on the inertial migration of spherical particles, whereas the non-spherical particles are still largely unexplored. Here, we conduct three-dimensional direct numerical simulations to study the inertial migration of rigid cylindrical particles in rectangular microchannels with different width/height ratios under the channel Reynolds numbers (Re) varying from 50 to 400. Cylindrical particles with different length/diameter ratios and blockage ratios are also concerned. Distributions of surface force with the change of rotation angle show that surface stresses acting on the particle end near the wall are the major contributors to the particle rotation. We obtain lift forces experienced by cylindrical particles at different lateral positions on cross sections of two types of microchannels at various Re. It is found that there are always four stable equilibrium positions on the cross section of a square channel, while the stable positions are two or four in a rectangular channel, depending on Re. By comparing the equilibrium positions of cylindrical particles and spherical particles, we demonstrate that the equivalent diameter of cylindrical particles monotonously increases with Re. Our work indicates the influence of a non-spherical shape on the inertial migration and can be useful for the precise manipulation of non-spherical particles.

Magnetic properties of carbon-coated, ferromagnetic nanoparticles produced by a carbon-arc method

NASA Astrophysics Data System (ADS)

Brunsman, E. M.; Sutton, R.; Bortz, E.; Kirkpatrick, S.; Midelfort, K.; Williams, J.; Smith, P.; McHenry, M. E.; Majetich, S. A.; Artman, J. O.; De Graef, M.; Staley, S. W.

1994-05-01

The Krätschmer-Huffman carbon-arc method of preparing fullerenes has been used to generate carbon-coated transition metal (TM) and TM-carbide nanocrystallites. The magnetic nanocrystallites were extracted from the soot with a magnetic gradient field technique. For TM=Co the majority of nanocrystals exist as nominally spherical particles, 0.5-5 nm in radius. Hysteretic and temperature-dependent magnetic response, in randomly and magnetically aligned powder samples frozen in epoxy, correspond to fine particle magnetism associated with monodomain TM particles. The magnetization exhibits a unique functional dependence on H/T, and hysteresis below a blocking temperature TB. Below TB, the temperature dependence of the coercivity can be expressed as Hc=Hc0[1-(T/TB)1/2], where Hc0 is the 0 K coercivity.

Electrically-conductive proppant and methods for making and using same

DOEpatents

Cannan, Chad; Roper, Todd; Savoy, Steve; Mitchell, Daniel R.

2016-09-06

Electrically-conductive sintered, substantially round and spherical particles and methods for producing such electrically-conductive sintered, substantially round and spherical particles from an alumina-containing raw material. Methods for using such electrically-conductive sintered, substantially round and spherical particles in hydraulic fracturing operations.

Starch-assisted synthesis and optical properties of ZnS nanoparticles

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

Tian, Xiuying, E-mail: xiuyingt@yahoo.com; Wen, Jin; Wang, Shumei

Highlights: • ZnS spherical nanostructure was prepared via starch-assisted method. • The crystalline lattice structure, morphologies, chemical and optical properties of ZnS nanoparticles. • The forming mechanism of ZnS nanoparticles. • ZnS spherical nano-structure can show blue emission at 460–500 nm. - Abstract: ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis)more » spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130 nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2 μm. The band gap value of ZnS is 3.97 eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.« less

Method for preparing spherical thermoplastic particles of uniform size

DOEpatents

Day, J.R.

1975-11-17

Spherical particles of thermoplastic material of virtually uniform roundness and diameter are prepared by cutting monofilaments of a selected diameter into rod-like segments of a selected uniform length which are then heated in a viscous liquid to effect the formation of the spherical particles.

Void initiation from interfacial debonding of spherical silicon particles inside a silicon-copper nanocomposite: a molecular dynamics study

NASA Astrophysics Data System (ADS)

Cui, Yi; Chen, Zengtao

2017-02-01

Silicon particles with diameters from 1.9 nm to 30 nm are embedded in a face-centered-cubic copper matrix to form nanocomposite specimens for simulation. The interfacial debonding of silicon particles from the copper matrix and the subsequent growth of nucleated voids are studied via molecular dynamics (MD). The MD results are examined from several different perspectives. The overall mechanical performance is monitored by the average stress-strain response and the accumulated porosity. The ‘relatively farthest-traveled’ atoms are identified to characterize the onset of interfacial debonding. The relative displacement field is plotted to illustrate both subsequent interfacial debonding and the growth of a nucleated void facilitated by a dislocation network. Our results indicate that the initiation of interfacial debonding is due to the accumulated surface stress if the matrix is initially dislocation-free. However, pre-existing dislocations can make a considerable difference. In either case, the dislocation emission also contributes to the subsequent debonding process. As for the size effect, the debonding of relatively larger particles causes a drop in the stress-strain curve. The volume fraction of second-phase particles is found to be more influential than the size of the simulation box on the onset of interfacial debonding. The volume fraction of second-phase particles also affects the shape of the nucleated void and, therefore, influences the stress response of the composite.

PREPARATION OF SPHERICAL URANIUM DIOXIDE PARTICLES

DOEpatents

Levey, R.P. Jr.; Smith, A.E.

1963-04-30

This patent relates to the preparation of high-density, spherical UO/sub 2/ particles 80 to 150 microns in diameter. Sinterable UO/sub 2/ powder is wetted with 3 to 5 weight per cent water and tumbled for at least 48 hours. The resulting spherical particles are then sintered. The sintered particles are useful in dispersion-type fuel elements for nuclear reactors. (AEC)

Effect of Particle Morphology on the Reactivity of Explosively Dispersed Titanium Particles

NASA Astrophysics Data System (ADS)

Frost, David L.; Cairns, Malcolm; Goroshin, Samuel; Zhang, Fan

2009-12-01

The effect of particle morphology on the reaction of titanium (Ti) particles explosively dispersed during the detonation of either cylindrical or spherical charges has been investigated experimentally. The explosive charges consisted of packed beds of Ti particles saturated with nitromethane. The reaction behaviour of irregularly-shaped Ti particles in three size ranges is compared with tests with spherical Ti particles. The particle reaction is strongly dependent on particle morphology, e.g., 95 μm spherical Ti particles failed to ignite (in cylinders up to 49 mm in dia), whereas similarly sized irregular Ti particles readily ignited. For irregular particles, the uniformity of ignition on the particle cloud surface was almost independent of particle size, but depended on charge diameter. As the charge diameter was reduced, ignition in the conically expanding particle cloud occurred only at isolated spots or bands. For spherical charges, whereas large irregular Ti particles ignited promptly and uniformly throughout the particle cloud, the smallest particles dispersed nonuniformly and ignition occurred at isolated locations after a delay. Hence the charge geometry, as well as particle morphology, influences the reaction behaviour of the particles.

Isotropic Huygens dipoles and multipoles with colloidal particles

NASA Astrophysics Data System (ADS)

Dezert, Romain; Richetti, Philippe; Baron, Alexandre

2017-11-01

Huygens sources are elements that scatter light in the forward direction as used in the Huygens-Fresnel principle. They have remained fictitious until recently when experimental systems have been fabricated. In this Rapid Communication, we propose isotropic meta-atoms that act as Huygens sources. Using clusters of plasmonic or dielectric colloidal particles, Huygens dipoles that resonate at visible frequencies can be achieved with scattering cross sections as high as five times the geometric cross section of the particle surpassing anything achievable with a hypothetical simple spherical particle. Examples are given that predict extremely broadband scattering in the forward direction over a 1000 nm wavelength range at optical frequencies. These systems are important to the fields of nanoantennas, metamaterials, and wave physics in general as well as any application that requires local control over the radiation properties of a system as in solar cells or biosensing.

Superparamagnetism in carbon-coated Co particles produced by the Kratschmer carbon arc process

NASA Astrophysics Data System (ADS)

McHenry, M. E.; Majetich, S. A.; Artman, J. O.; Degraef, M.; Staley, S. W.

1994-04-01

A process based on the Kratschmer-Huffman carbon arc method of preparing fullerenes has been used to generate carbon-coated cobalt and cobalt carbide nanocrystallites. Magnetic nanocrystallites are extracted from the soot with a gradient field technique. For Co/C composites, structural characterization by x-ray diffraction and high-resolution transmission electron microscopy reveals the presence of a fcc Co phase, graphite, and a minority Co2C phase. The majority of Co nanocrystals exists as nominally spherical particles, 0.5-5 nm in radius. Hysteretic and temperature-dependent magnetic response, in randomly and magnetically aligned powder samples frozen in epoxy reveals fine-particle magnetism associated with monodomain Co particles. The magnetization exhibits a unique functional dependence on H/T, and hysteresis below a blocking temperature, TB~=160 K. Below TB, the temperature dependence of the coercivity is given by Hc=Hci[1-(T/TB)1/2], with Hci~=450 Oe.

Laser-assisted ignition and combustion characteristics of consolidated aluminum nanoparticles

NASA Astrophysics Data System (ADS)

Saceleanu, Florin; Wen, John Z.; Idir, Mahmoud; Chaumeix, Nabiha

2016-11-01

Aluminum (Al) nanoparticles have drawn much attention due to their high energy density and tunable ignition properties. In comparison with their micronscale counterpart, Al nanoparticles possess large specific surface area and low apparent activation energy of combustion, which reduce ignition delay significantly. In this paper, ignition and subsequently burning of consolidated Al nanoparticle pellets are performed via a continuous wave (CW) argon laser in a closed spherical chamber filled with oxygen. Pellets are fabricated using two types of nanoparticle sizes of 40-60 and 60-80 nm, respectively. A photodiode is used to measure the ignition delay, while a digital camera captures the location of the flame front. It is found that for the 40-60-nm nanoparticle pellets, ignition delay reduces with increasing the oxygen pressure or using the higher laser power. Analysis of the flame propagation rate suggests that oxygen diffusion is an important mechanism during burning of these porous nanoparticle pellets. The combustion characteristics of the Al pellets are compared to a simplified model of the diffusion-controlled oxidation mechanism. While experimental measurements of pellets of 40-60 nm Al particles agree with the computed diffusion-limiting mechanism, a shifted behavior is observed from the pellets of 60-80 nm Al particles, largely due to the inhomogeneity of their porous structures.

Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

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

Liu, Chunyang, E-mail: chunyangliu@126.com; Sui, Xin; Yang, Fang

2014-03-15

A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of themore » microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.« less

Three-dimensional calibration targets for optical coherence tomography

NASA Astrophysics Data System (ADS)

Gabriele Sandrian, Michelle; Tomlins, Pete; Woolliams, Peter; Rasakanthan, Janarthanan; Lee, Graham C.; Yang, Anna; Považay, Boris; Alex, Aneesh; Sugden, Kate; Drexler, Wolfgang

2012-03-01

The recent expansion of clinical applications for optical coherence tomography (OCT) is driving the development of approaches for consistent image acquisition. There is a simultaneous need for time-stable, easy-to-use imaging targets for calibration and standardization of OCT devices. We present calibration targets consisting of three-dimensional structures etched into nanoparticle-embedded resin. Spherical iron oxide nanoparticles with a predominant particle diameter of 400 nm were homogeneously dispersed in a two part polyurethane resin and allowed to harden overnight. These samples were then etched using a precision micromachining femtosecond laser with a center wavelength of 1026 nm, 100kHz repetition rate and 450 fs pulse duration. A series of lines in depth were etched, varying the percentage of inscription energy and speed of the translation stage moving the target with respect to the laser. Samples were imaged with a dual wavelength spectral-domain OCT system (λ=800nm, ▵λ~180nm, and λ=1325nm, ▵λ~100nm) and point-spread function of nanoparticles within the target was measured.

Bioinspired green synthesis of copper oxide nanoparticles from Syzygium alternifolium (Wt.) Walp: characterization and evaluation of its synergistic antimicrobial and anticancer activity

NASA Astrophysics Data System (ADS)

Yugandhar, Pulicherla; Vasavi, Thirumalanadhuni; Uma Maheswari Devi, Palempalli; Savithramma, Nataru

2017-10-01

In recent times, nanoparticles are attributed to green nanotechnology methods to know the synergistic biological activities. To accomplish this phenomenon, present study was aimed to synthesize copper oxide nanoparticles (CuO NPs) by using Syzygium alternifolium stem bark, characterized those NPs using expository tools and to elucidate high prioritized antimicrobial and anticancer activities. Synthesized particles exhibited a color change pattern upon synthesis and affirmed its respective broad peak at 285 nm which was analyzed through UV-vis spectroscopy. FT-IR study confirmed that phenols and primary amines were mainly involved in capping and stabilization of nanoparticles. DLS and Zeta potential studies revealed narrow size of particles with greater stability. XRD studies revealed the crystallographic nature of particles with 17.2 nm average size. Microscopic analysis by using TEM revealed that particle size range from 5-13 nm and most of them were spherical in shape, non-agglomerated and poly-dispersed in condition. Antimicrobial studies of particles showed highest inhibitory activity against E. coli and T. harzianum among bacterial and fungal strains, respectively. The scope of this study is extended by examining anticancer activity of CuO NPs. This study exhibited potential anticancer activity towards MDA-MB-231 human breast cancer lines. Overall, these examinations relate that the S. alternifolium is described as efficient well-being plant and probabilistically for the design and synthesis of nanoparticles for human health. This study paves a way to better understand antimicrobial and anticancer therapeutic drug potentials of nanoparticles to design and analysis of pharmaceuticals by in vivo and in vitro approaches.

Fate of nano- and microplastic in freshwater systems: A modeling study.

PubMed

Besseling, Ellen; Quik, Joris T K; Sun, Muzhi; Koelmans, Albert A

2017-01-01

Riverine transport to the marine environment is an important pathway for microplastic. However, information on fate and transport of nano- and microplastic in freshwater systems is lacking. Here we present scenario studies on the fate and transport of nano-to millimetre sized spherical particles like microbeads (100 nm-10 mm) with a state of the art spatiotemporally resolved hydrological model. The model accounts for advective transport, homo- and heteroaggregation, sedimentation-resuspension, polymer degradation, presence of biofilm and burial. Literature data were used to parameterize the model and additionally the attachment efficiency for heteroaggregation was determined experimentally. The attachment efficiency ranged from 0.004 to 0.2 for 70 nm and 1050 nm polystyrene particles aggregating with kaolin or bentonite clays in natural freshwater. Modeled effects of polymer density (1-1.5 kg/L) and biofilm formation were not large, due to the fact that variations in polymer density are largely overwhelmed by excess mass of suspended solids that form heteroaggregates with microplastic. Particle size had a dramatic effect on the modeled fate and retention of microplastic and on the positioning of the accumulation hot spots in the sediment along the river. Remarkably, retention was lowest (18-25%) for intermediate sized particles of about 5 μm, which implies that the smaller submicron particles as well as larger micro- and millimetre sized plastic are preferentially retained. Our results suggest that river hydrodynamics affect microplastic size distributions with profound implications for emissions to marine systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2010-05-01

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

Filler features and their effects on wear and degree of conversion of particulate dental resin composites.

PubMed

Turssi, C P; Ferracane, J L; Vogel, K

2005-08-01

Based on the incomplete understanding on how filler features influence the wear resistance and monomer conversion of resin composites, this study sought to evaluate whether materials containing different shapes and combinations of size of filler particles would perform similarly in terms of three-body abrasion and degree of conversion. Twelve experimental monomodal, bimodal or trimodal composites containing either spherical or irregular shaped fillers ranging from 100 to 1500 nm were examined. Wear testings were conducted in the OHSU wear machine (n = 6) and quantified after 10(5) cycles using a profilometer. Degree of conversion (DC) was measured by FTIR spectrometry at the surface of the composites (n = 6). Data sets were analyzed using one-way Anova and Tukey's test at a significance level of 0.05. Filler size and geometry was found to have a significant effect on wear resistance and DC of composites. At specific sizes and combinations, the presence of small filler particles, either spherical or irregular, may aid in enhancing the wear resistance of composites, without compromising the percentage of reacted carbon double bonds.

Shape Engineering of Biomass-Derived Nanoparticles from Hollow Spheres to Bowls via Solvent-Induced Buckling.

PubMed

Chen, Chunhong; Li, Xuefeng; Jiang, Deng; Wang, Zhe; Wang, Yong

2018-06-19

To realize the asymmetry for the hollow carbonaceous nanostructures remains to be a great challenge, especially when biomass is chosen as the carbon resource via hydrothermal carbonization (HTC). Herein, a simple and straightforward solvent induced buckling strategy is demonstrated for the synthesis of asymmetric spherical and bowllike carbonaceous nanomaterials. The formation of the bowllike morphology was attributed to the buckling of the spherical shells induced by the dissolution of the oligomers. The bowllike particles made by this solvent-driven approach demonstrated a well-controlled morphology and a uniform particle size of ~360 nm. The obtained nanospheres and nanobowls can be loaded with CoS2 nanoparticles to act as novel heterogeneous catalysts for the selective hydrogenation of aromatic nitro compounds. With the bowllike structure in hand, as expected, the CoS2/nanobowls catalyst showed good tolerance to a wide scope of reducible groups and afforded both high activity and selectivity in almost all the tested substrates (14). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-energy ball milling technique for ZnO nanoparticles as antibacterial material

PubMed Central

Salah, Numan; Habib, Sami S; Khan, Zishan H; Memic, Adnan; Azam, Ameer; Alarfaj, Esam; Zahed, Nabeel; Al-Hamedi, Salim

2011-01-01

Nanoparticles of zinc oxide (ZnO) are increasingly recognized for their utility in biological applications. In this study, the high-energy ball milling (HEBM) technique was used to produce nanoparticles of ZnO from its microcrystalline powder. Four samples were ball milled for 2, 10, 20, and 50 hours, respectively. The structural and optical modifications induced in the ‘as synthesized’ nanomaterials were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and photoluminescence emission spectra (PL). SEM and TEM results show a gradual decrease in particle size from around 600 to ∼30 nm, with increased milling time. The initial microstructures had random shapes, while the final shape became quite spherical. XRD analysis showed ZnO in a hexagonal structure, broadening in the diffracted peaks and going from larger to smaller particles along with a relaxation in the lattice constant c. The value of c was found to increase from 5.204 to 5.217 Å with a decrease in particle size (600 to ∼30 nm). PL result showed a new band at around 365 nm, whose intensity is found to increase as the particles size decreases. These remarkable structural and optical modifications induced in ZnO nanoparticles might prove useful for various applications. The increase in c value is an important factor for increasing the antibacterial effects of ZnO, suggesting that the HEBM technique is quite suitable for producing these nanoparticles for this purpose. PMID:21720499

Preparation and encapsulation of white/yellow dual colored suspensions for electrophoretic displays

NASA Astrophysics Data System (ADS)

Han, Jingjing; Li, Xiaoxu; Feng, Yaqing; Zhang, Bao

2014-11-01

C.I. Pigment Yellow 181 (PY181) composite particles encapsulated by polyethylene (PE) were prepared by dispersion polymerization method, and C.I. Pigment Yellow 110 (PY110) composite particles encapsulated by polystyrene (PS) with mini-emulsion polymerization method were achieved, respectively. The modified pigments were characterized by fourier transform infrared spectroscopy, scanning electron microscope and transmission electron microscope. Compared with the PE-coated PY 181 pigments, the PS-coated PY-110 particles had a narrow particle size distribution, regular spherical and average particle size of 450 nm. Suspension 1 and suspension 3 were prepared by the two composite particles dispersed in isopar M. A chromatic electrophoretic display cell consisting of yellow particles was successfully fabricated using dispersions of yellow ink particles in a mixed dielectric solvent with white particles as contrast. The response behavior and the contrast ratio to the electric voltage were also examined. The contrast ratio of pigments modified by polystyrene was 1.48, as well as the response time was 2 s, which were better than those of pigments modified by polyethylene.

Hydrogels in endovascular embolization. I. Spherical particles of poly(2-hydroxyethyl methacrylate) and their medico-biological properties.

PubMed

Horák, D; Svec, F; Kálal, J; Gumargalieva, K; Adamyan, A; Skuba, N; Titova, M; Trostenyuk, N

1986-05-01

Spherical macroporous particles based on poly(2-hydroxyethyl methacrylate) with defined porosity, swelling and morphology have been developed, and are suitable for endovascular occlusion of various organs. Unlike cylindrical particles, spherical particles are specifically suited for transcatheteral introduction. The method chosen for the preparation of such particles was suspension radical polymerization, where the monomers were dissolved in a mixture of higher-boiling alcohols, and the solution dispersed in water. Physicochemical and medico-biological properties of spherical particles were examined. The residual amounts of monomers and other low-molecular compounds were checked; haematological analyses showed that the value 10(-5) g/g of the polymer was not toxic and contributed to an irreversible aggregation of thrombocytes. The occlusion effect in the vascular lumen was stable. The histomorphological results fully demonstrated the perfect biocompatibility of artificial spherical emboli. The latter met the requirements of application to clinical practice.

Extracellular biosynthesis of silver nanoparticles: effects of shape-directing cetyltrimethylammonium bromide, pH, sunlight and additives.

PubMed

Hussain, Shokit; Akrema; Rahisuddin; Khan, Zaheer

2014-05-01

The work reported in this paper describes the preparation, morphology, stability and sensitivity of Ag-nanoparticles towards sunlight using Allium sativum, garlic extract for the first time. The synthesized silver particles show an intense surface plasmon resonance band in the visible region at 410 nm. The position of the wavelength maxima, blue and red shift, strongly depends on the sunlight and pH. TEM analysis revealed the presence of spherical, different size (from 5.0 to 30 nm) and garlic constituents bio-conjugated, stabilized and/or layered silver nanoparticles. The concentrations of garlic extract, cetyltrimethylammonium bromide, Ag(+) ions and reaction time play vital roles for nucleus formation and the growth processes. Sulfur-containing biomolecules of extract, especially cysteine, are responsible for the reduction of Ag(+) ions into metallic Ag(0). The agglomeration number of the silver nanoparticles (N Ag) and the average number of free electrons per particle (n fe) are calculated and discussed.

Preparation and characterization of polyol assisted ultrafine Cu-Ni-Mg-Ca mixed ferrite via co-precipitation method

NASA Astrophysics Data System (ADS)

Boobalan, T.; Pavithradevi, S.; Suriyanarayanan, N.; Manivel Raja, M.; Ranjith Kumar, E.

2017-04-01

Nanocrystalline spinel ferrite of composition Cu0.2Ni0.2Mg0.2Ca0.4Fe2O4 is synthesized by wet hydroxyl co-precipitation method in ethylene glycol as chelating agent and sodium hydroxide as precipitator at pH 8. Ethylene glycol is utilized as the medium which serves as the dissolvable and in addition a complexing specialist. The synthesized particles are annealed at various temperatures. Thermogravimetric investigation affirms that at 280 °C ethylene glycol is dissipated totally and stable phase arrangement happens over 680 °C. FTIR spectra of as synthesized and annealed at 1050 °C recorded between 400 cm-1 and 4000 cm-1. Structural characterizations of all the samples are carried out by X-ray diffraction (XRD) technique. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) affirm that the particles are spherical and cubic shape with the crystallite size of 12 nm to 32 nm. Magnetic measurements are performed utilizing vibrating sample magnetometer at room temperature.

Biosynthesis of Silver Nanoparticles Using Brown Marine Macroalga, Sargassum Muticum Aqueous Extract.

PubMed

Azizi, Susan; Namvar, Farideh; Mahdavi, Mahnaz; Ahmad, Mansor Bin; Mohamad, Rosfarizan

2013-12-18

Biological synthesis of nanoparticles is a relatively new emerging field of nanotechnology which has economic and eco-friendly benefits over chemical and physical processes of synthesis. In the present work, for the first time, the brown marine algae Sargassum muticum ( S. muticum ) aqueous extract was used as a reducing agent for the synthesis of nanostructure silver particles (Ag-NPs). Structural, morphological and optical properties of the synthesized nanoparticles have been characterized systematically by using FTIR, XRD, TEM and UV-Vis spectroscopy. The formation of Ag-NPs was confirmed through the presence of an intense absorption peak at 420 nm using a UV-visible spectrophotometer. A TEM image showed that the particles are spherical in shape with size ranging from 5 to 15 nm. The nanoparticles were crystalline in nature. This was confirmed by the XRD pattern. From the FTIR results, it can be seen that the reduction has mostly been carried out by sulphated polysaccharides present in S. muticum .

Biosynthesis of Silver Nanoparticles Using Brown Marine Macroalga, Sargassum Muticum Aqueous Extract

PubMed Central

Azizi, Susan; Namvar, Farideh; Mahdavi, Mahnaz; Ahmad, Mansor Bin; Mohamad, Rosfarizan

2013-01-01

Biological synthesis of nanoparticles is a relatively new emerging field of nanotechnology which has economic and eco-friendly benefits over chemical and physical processes of synthesis. In the present work, for the first time, the brown marine algae Sargassum muticum (S. muticum) aqueous extract was used as a reducing agent for the synthesis of nanostructure silver particles (Ag-NPs). Structural, morphological and optical properties of the synthesized nanoparticles have been characterized systematically by using FTIR, XRD, TEM and UV–Vis spectroscopy. The formation of Ag-NPs was confirmed through the presence of an intense absorption peak at 420 nm using a UV–visible spectrophotometer. A TEM image showed that the particles are spherical in shape with size ranging from 5 to 15 nm. The nanoparticles were crystalline in nature. This was confirmed by the XRD pattern. From the FTIR results, it can be seen that the reduction has mostly been carried out by sulphated polysaccharides present in S. muticum. PMID:28788431

Fluorescence of bioaerosols: mathematical model including primary fluorescing and absorbing molecules in bacteria.

PubMed

Hill, Steven C; Pan, Yong-Le; Williamson, Chatt; Santarpia, Joshua L; Hill, Hanna H

2013-09-23

This paper describes a mathematical model of fluorescent biological particles composed of bacteria, viruses, or proteins. The fluorescent and/or light absorbing molecules included in the model are amino acids (tryptophan, etc.); nucleic acids (DNA, RNA, etc.); coenzymes (nicotinamide adenine dinucleotides, flavins, and vitamins B₆ and K and variants of these); and dipicolinates. The concentrations, absorptivities, and fluorescence quantum yields are estimated from the literature, often with large uncertainties. The bioparticles in the model are spherical and homogeneous. Calculated fluorescence cross sections for particles excited at 266, 280, and 355 nm are compared with measured values from the literature for several bacteria, bacterial spores and albumins. The calculated 266- and 280-nm excited fluorescence is within a factor of 3.2 of the measurements for the vegetative cells and proteins, but overestimates the fluorescence of spores by a factor of 10 or more. This is the first reported modeling of the fluorescence of bioaerosols in which the primary fluorophores and absorbing molecules are included.

Co-Precipitation Synthesis of Gadolinium Aluminum Gallium Oxide (GAGG) via Different Precipitants

NASA Astrophysics Data System (ADS)

Sun, Yan; Yang, Shenghui; Zhang, Ye; Jiang, Jun; Jiang, Haochuan

2014-02-01

In order to obtain a uniform transparent ceramic scintillator, well-dispersed fine starting powders with high-purity, small grain size, spherical morphology and high sinter-ability are necessary. In this study, Ce3+ doped gadolinium aluminum gallium garnet Gd3Al3Ga2O12 (GAGG) powders were synthesized by the co-precipitation method. NH4OH, NH4HCO3 and the mixed solution of NH4OH and NH4HCO3 were used as precipitants, respectively. The precursor composition, phase formation process, microstructure, morphology, particle size distribution and luminescent properties of obtained GAGG powders were measured. The results show that powders prepared using the mixed precipitant exhibit the best microstructural morphology, good sinter-ability and highest luminescent intensity. Pure GAGG polycrystalline powders could be obtained at about 950°C for 1.5 h and the average size of the particles is about 50 nm. The photoluminescence spectrum shows a strong green-yellow emission near 540 nm.

Gnidia glauca flower extract mediated synthesis of gold nanoparticles and evaluation of its chemocatalytic potential

PubMed Central

2012-01-01

Background Novel approaches for synthesis of gold nanoparticles (AuNPs) are of utmost importance owing to its immense applications in diverse fields including catalysis, optics, medical diagnostics and therapeutics. We report on synthesis of AuNPs using Gnidia glauca flower extract (GGFE), its detailed characterization and evaluation of its chemocatalytic potential. Results Synthesis of AuNPs using GGFE was monitored by UV-Vis spectroscopy and was found to be rapid that completed within 20 min. The concentration of chloroauric acid and temperature was optimized to be 0.7 mM and 50°C respectively. Bioreduced nanoparticles varied in morphology from nanotriangles to nanohexagons majority being spherical. AuNPs were characterized employing transmission electron microscopy, high resolution transmission electron microscopy. Confirmation of elemental gold was carried out by elemental mapping in scanning transmission electron microscopic mode, energy dispersive spectroscopy and X-ray diffraction studies. Spherical particles of size ~10 nm were found in majority. However, particles of larger dimensions were in range between 50-150 nm. The bioreduced AuNPs exhibited remarkable catalytic properties in a reduction reaction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous phase. Conclusion The elaborate experimental evidences support that GGFE can provide an environmentally benign rapid route for synthesis of AuNPs that can be applied for various purposes. Biogenic AuNPs synthesized using GGFE exhibited excellent chemocatalytic potential. PMID:22548753

Crystallization of MgFe2O4 from a glass in the system K2O/B2O3/MgO/P2O5/Fe2O3

NASA Astrophysics Data System (ADS)

El Shabrawy, Samha; Bocker, Christian; Rüssel, Christian

2016-10-01

Spherical magnetic Mg-Fe-O nanoparticles were successfully prepared by the crystallization of glass in the system K2O/B2O3/MgO/P2O5/Fe2O3. The magnetic glass ceramics were prepared by melting the raw materials using the conventional melt quenching technique followed by a thermal treatment at temperatures in the range 560-700 °C for a time ranging from 2 to 8 h. The studies of the X-ray diffraction, electron microscopy and FTIR spectra confirmed the precipitation of finely dispersed spherical (Mg, Fe) based spinel nanoparticles with a minor quantity of hematite (α-Fe2O3) in the glass matrix. The average size of the magnetic nano crystals increases slightly with temperature and time from 9 to 15 nm as determined by the line broadening from the XRD patterns. XRD studies show that annealing the glass samples for long periods of time at temperature ≥604 °C results in an increase of the precipitated hematite concentration, dissolution of the spinel phase and the formation of magnesium di-borate phase (Mg2B2O5). For electron microscopy, the particles were extracted by two methods; (i) replica extraction technique and (ii) dissolution of the glass matrix by diluted acetic acid. An agglomeration of the nano crystals to larger particles (25-35 nm) was observed.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method.

PubMed

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M R; Kim, B Moon

2015-01-25

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method

NASA Astrophysics Data System (ADS)

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M. R.; Kim, B. Moon

2015-01-01

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology.

Effect of cutoff radius, long range interaction and temperature controller on thermodynamic properties of fluids: Methanol as an example

NASA Astrophysics Data System (ADS)

Obeidat, Abdalla; Jaradat, Adnan; Hamdan, Bushra; Abu-Ghazleh, Hind

2018-04-01

The best spherical cutoff radius, long range interaction and temperature controller were determined using surface tension, density, and diffusion coefficients of van Leeuwen and Smit methanol. A quite good range of cutoff radii from 0.75 to 1.45 nm has been studied on Coulomb cut-off and particle mesh Ewald (PME) long range interaction to determine the best cutoff radius and best long range interaction as well for four sets of temperature: 200, 230, 270 and 300 K. To determine the best temperature controller, the cutoff radius of 1.25 nm was fixed using PME long range interaction on calculating the above properties at low temperature range: 200-300 K.

One-Step Hydrothermal Approach to Synthesis Carbon Dots from D-Sorbitol for Detection of Iron(III) and Cell Imaging.

PubMed

Zhang, Junqiu; Yan, Juping; Wang, Yingte; Zhang, Yong

2018-07-01

A facile and economic approach to synthesis highly fluorescence carbon dots (CDs) via one-step hydrothermal treatment of D-sorbitol was presented. The as-synthesized CDs were characterized by good water solubility, well monodispersion, and excellent biocompatibility. Spherical CDs had a particle size about 5 nm and exhibited a quantum yield of 8.85% at excitation wavelength of 360 nm. In addition, the CDs can serve as fluorescent probe for sensitive and selective detection of Fe3+ ions with the detection limit of 1.16 μM. Moreover, the potential of the as-prepared carbon dots for biological application was confirmed by employing it for fluorescence imaging in MCF-7 cells.

Polycrystalline Si nanoparticles and their strong aging enhancement of blue photoluminescence

NASA Astrophysics Data System (ADS)

Yang, Shikuan; Cai, Weiping; Zeng, Haibo; Li, Zhigang

2008-07-01

Nearly spherical polycrystalline Si nanoparticles with 20 nm diameter were fabricated based on laser ablation of silicon wafer immersed in sodium dodecyl sulfate aqueous solution. Such Si nanoparticles consist of disordered areas and ultrafine grains of 3 nm in mean size and exhibit significant photoluminescence in blue region. Importantly, aging at ambient air leads to continuing enhancement of the emission (more than 130 times higher in 16 weeks) showing stable and strong blue emission. This aging enhancement is attributed to progressive passivation of nonradiative Pb centers corresponding to silicon dangling bonds on the particles' surface. This study could be helpful in pushing Si into optoelectronic field and Si-based full color display, biomedical tagging, and flash memories.

Insulin Particle Formation in Supersaturated Aqueous Solutions of Poly(Ethylene Glycol)

PubMed Central

Bromberg, Lev; Rashba-Step, Julia; Scott, Terrence

2005-01-01

Protein microspheres are of particular utility in the field of drug delivery. A novel, completely aqueous, process of microsphere fabrication has been devised based on controlled phase separation of protein from water-soluble polymers such as polyethylene glycols. The fabrication process results in the formation of spherical microparticles with narrow particle size distributions. Cooling of preheated human insulin-poly(ethylene glycol)-water solutions results in the facile formation of insulin particles. To map out the supersaturation conditions conducive to particle nucleation and growth, we determined the temperature- and concentration-dependent boundaries of an equilibrium liquid-solid phase separation. The kinetics of formation of microspheres were followed by dynamic and continuous-angle static light scattering techniques. The presence of PEG at a pH that was close to the protein's isoelectric point resulted in rapid nucleation and growth. The time elapsed from the moment of creation of a supersaturated solution and the detection of a solid phase in the system (the induction period, tind) ranged from tens to several hundreds of seconds. The dependence of tind on supersaturation could be described within the framework of classical nucleation theory, with the time needed for the formation of a critical nucleus (size <10 nm) being much longer than the time of the onset of particle growth. The growth was limited by cluster diffusion kinetics. The interfacial energies of the insulin particles were determined to be 3.2–3.4 and 2.2 mJ/m2 at equilibrium temperatures of 25 and 37°C, respectively. The insulin particles formed as a result of the process were monodisperse and uniformly spherical, in clear distinction to previously reported processes of microcrystalline insulin particle formation. PMID:16254391

Preparation of spherical particles by vibrating orifice technique

NASA Astrophysics Data System (ADS)

Shibata, Shuichi; Tomizawa, Atsushi; Yoshikawa, Hidemi; Yano, Tetsuji; Yamane, Masayuki

2000-05-01

Preparation of micrometer-sized spherical particles containing Rhodamine 6G (R6G) has been investigated for the spherical cavity micro-laser. Using phenyl triethoxy silane (PTES) as a starting material, R6G-doped monodisperse spherical particles were prepared by the vibrating orifice technique. Processing consists of two major processes: (1) Hydrolysis and polymerization of PTES and (2) Droplet formation from PTES oligomers by vibrating orifice technique. A cylindrical liquid jet passing through the orifice of 10 and 20 micrometers in diameter breaks up into equal- sized droplets by mechanical vibration. Alcohol solvent of these droplets was evaporated during flying with carrier gas and subsequently solidified in ammonium water trap. For making smooth surface and god shaped particles, control of molecular weight of PTES oligomer was essential. R6G-doped hybrid spherical particles of 4 to 10 micrometers size of cavity structure were successfully obtained. The spherical particles were pumped by a second harmonic pulse of Q- switched Nd:YAG laser and laser emission peaks were observed at wavelengths which correspond to the resonance modes.

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

Liu, Zhi-jie; Dai, Le-yang; Yang, De-zheng

Highlights: • A novel and high efficiency synthesizing AlN powders method combining mechanical ball milling and DBDP has been developed. • The particle size, the crystallite size, the lattice distortion, the morphology of Al{sub 2}O{sub 3} powders, and the AlN conversion rate are investigated and compared under the ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP. • The ball milled Al{sub 2}O{sub 3} powders with DBDP have small spherical structure morphology with very fine particles size and high specific surface area, which result in a higher chemical efficiency and a higher AlN conversion rate at lower thermalmore » temperature. - Abstract: In this paper, aluminum nitride (AlN) powers have been produced with a novel and high efficiency method by thermal annealing at 1100–1600 °C of alumina (Al{sub 2}O{sub 3}) powders which were previously ball milled for various time up to 40 h with and without the assistant of dielectric barrier discharge plasma (DBDP). The ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP and the corresponding synthesized AlN powers are characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscopy. From the characteristics of the ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP, it can be seen that the ball milled Al{sub 2}O{sub 3} powders with DBDP have small spherical structure morphology with very fine particles size and high specific surface area, which result in a higher chemical efficiency and a higher AlN conversion rate at lower thermal temperature. Meanwhile, the synthesized AlN powders can be known as hexagonal AlN with fine crystal morphology and irregular lump-like structure, and have uniform distribution with the average particle size of about between 500 nm and 1000 nm. This provides an important method for fabricating ultra fine powders and synthesizing nitrogen compounds.« less

Effect of alkali on the structure of cell envelopes of Chlamydia psittaci elementary bodies.

PubMed Central

Narita, T; Wyrick, P B; Manire, G P

1976-01-01

Suspensions of isolated cell envelopes of infectious elementary bodies (EB) of Chlamydia psittaci at alkaline pH showed a rapid, extensive decrease in absorbance, accompanied by the release of a cell envelope component in a sedimentable form. This phenomenon was observed both at 0 C and with envelopes which had been previously heated to 100 C. Monovalent and divalent cations effectively inhibited the turbidity loss, whereas ethylenediaminetetraacetate (EDTA) caused an accelerated decrease in turbidity. The turbidity loss observed after incubation of the envelopes at alkaline pH could be reversed to the level of the initial value by dialysis against distilled water containing Mg2+. Thin-section electron photomicrographs of purified EB exposed to alkaline buffer with EDTA revealed the loss of the internal contents of cells, but these cells still maintained their round shapes. The cell surface of treated EB appeared pitted in negatively stained preparations, whereas intact EB had a smooth surface. Electron microscopic studies on negatively stained preparations of the clear supernatant obtained after the treatment of the envelope with alkaline buffer containing EDTA demonstrated the presence of spherical particles, approximately 6 to 7 nm in diameter, and rodlike particles, which appeared to be made up of two or more spherical particles. Images PMID:1375

Production of zinc and manganese oxide particles by pyrolysis of alkaline and Zn-C battery waste.

PubMed

Ebin, Burçak; Petranikova, Martina; Steenari, Britt-Marie; Ekberg, Christian

2016-05-01

Production of zinc and manganese oxide particles from alkaline and zinc-carbon battery black mass was studied by a pyrolysis process at 850-950°C with various residence times under 1L/minN2(g) flow rate conditions without using any additive. The particular and chemical properties of the battery waste were characterized to investigate the possible reactions and effects on the properties of the reaction products. The thermodynamics of the pyrolysis process were studied using the HSC Chemistry 5.11 software. The carbothermic reduction reaction of battery black mass takes place and makes it possible to produce fine zinc particles by a rapid condensation, after the evaporation of zinc from a pyrolysis batch. The amount of zinc that can be separated from the black mass is increased by both pyrolysis temperature and residence time. Zinc recovery of 97% was achieved at 950°C and 1h residence time using the proposed alkaline battery recycling process. The pyrolysis residue is mainly MnO powder with a low amount of zinc, iron and potassium impurities and has an average particle size of 2.9μm. The obtained zinc particles have an average particle size of about 860nm and consist of hexagonal crystals around 110nm in size. The morphology of the zinc particles changes from a hexagonal shape to s spherical morphology by elevating the pyrolysis temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

Green synthesis of colloidal silver nanoparticles using natural rubber latex extracted from Hevea brasiliensis

NASA Astrophysics Data System (ADS)

Guidelli, Eder José; Ramos, Ana Paula; Zaniquelli, Maria Elisabete D.; Baffa, Oswaldo

2011-11-01

Colloidal silver nanoparticles were synthesized by an easy green method using thermal treatment of aqueous solutions of silver nitrate and natural rubber latex (NRL) extracted from Hevea brasiliensis. The UV-Vis spectra detected the characteristic surface plasmonic absorption band around 435 nm. Both NRL and AgNO 3 contents in the reaction medium have influence in the Ag nanoparticles formation. Lower AgNO 3 concentration led to decreased particle size. The silver nanoparticles presented diameters ranging from 2 nm to 100 nm and had spherical shape. The selected area electron diffraction (SAED) patterns indicated that the silver nanoparticles have face centered cubic (fcc) crystalline structure. FTIR spectra suggest that reduction of the silver ions are facilitated by their interaction with the amine groups from ammonia, which is used for conservation of the NRL, whereas the stability of the particles results from cis-isoprene binding onto the surface of nanoparticles. Therefore natural rubber latex extracted from H. brasiliensis can be employed in the preparation of stable aqueous dispersions of silver nanoparticles acting as a dispersing and/or capping agent. Moreover, this work provides a new method for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive.

Biogenic synthesis of silver nanoparticles by leaf extract of Cassia angustifolia

NASA Astrophysics Data System (ADS)

Amaladhas, T. Peter; Sivagami, S.; Akkini Devi, T.; Ananthi, N.; Priya Velammal, S.

2012-12-01

In this study Cassia angustifolia (senna) is used for the environmentally friendly synthesis of silver nanoparticles. Stable silver nanoparticles having symmetric surface plasmon resonance (SPR) band centred at 420 nm were obtained within 10 min at room temperature by treating aqueous solutions of silver nitrate with C. angustifolia leaf extract. The water soluble components from the leaves, probably the sennosides, served as both reducing and capping agents in the synthesis of silver nanoparticles. The nanoparticles were characterized using UV-Vis, Fourier transform infrared (FTIR) spectroscopic techniques and transmission electron microscopy (TEM). The nanoparticles were poly-dispersed, spherical in shape with particle size in the range 9-31 nm, the average size was found to be 21.6 nm at pH 11. The zeta potential was -36.4 mV and the particles were stable for 6 months. The crystalline phase of the nanoparticles was confirmed from the selected area diffraction pattern (SAED). The rate of formation and size of silver nanoparticles were pH dependent. Functional groups responsible for capping of silver nanoparticles were identified from the FTIR spectrum. The synthesized silver nanoparticles exhibited good antibacterial potential against Escherichia coli and Staphylococcus aureus.

3D-atom probe characterization of nano-precipitates in a PM processed tool steels

NASA Astrophysics Data System (ADS)

Niederkofler, M.; Leisch, M.

2004-07-01

The microstructure of a powder metallurgical processed high speed steel (nom. composition (wt.%): 1.6 C, 4.8 Cr, 2.0 Mo, 5.0 V, 105 W, 8.0 Co and balance Fe) has been examined using 3D-atom probe technique. By the depth profiling of the time to flight mass spectrometer and position sensitive recording, cylindrical volumes of 10-15 nm in diameter and up to 40 nm in depth have been probed and characterized. The depth profiling measurements of the samples show generally a very homogeneous structure which was expected by the powder metallurgical processing of the material. Different morphologies of the precipitates were recorded. Besides the needle shaped precipitates with an extend up to 20 nm and thickness of few atomic layers, platelets and spherical particles are observed as well. The species which can be assigned to the precipitates appear to some extend as MC molecules in the mass histogram, while the leading constituents in this MC are Mo, V and Cr. Beside distinct particles agglomerations like one-dimensional atomic chains of the alloy components are also observed in the 3D reconstructions of the tool steel matrix.

Synthesis, Optical and Structural Properties of Copper Sulfide Nanocrystals from Single Molecule Precursors

PubMed Central

Ajibade, Peter A.; Botha, Nandipha L.

2017-01-01

We report the synthesis and structural studies of copper sulfide nanocrystals from copper (II) dithiocarbamate single molecule precursors. The precursors were thermolysed in hexadecylamine (HDA) to prepare HDA-capped CuS nanocrystals. The optical properties of the nanocrystals studied using UV–visible and photoluminescence spectroscopy showed absorption band edges at 287 nm that are blue shifted, and the photoluminescence spectra show emission curves that are red-shifted with respect to the absorption band edges. These shifts are as a result of the small crystallite sizes of the nanoparticles leading to quantum size effects. The structural studies were carried out using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy. The XRD patterns indicates that the CuS nanocrystals are in hexagonal covellite crystalline phases with estimated particles sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes, with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microspheres on the surfaces, and EDS spectra confirmed the presence of CuS nanoparticles. PMID:28336865

Recycling of pneumatic scrap tyre into nano-crumb rubber by pulsed laser ablation in different pH media

NASA Astrophysics Data System (ADS)

Ezaan Khamsan, Nur; Bidin, Noriah; Islam, Shumaila; Daud, Suzairi; Krishnan, Ganesan; Bakar, Mohamad Aizat A.; Naqiuddin Razali, Muhamad; Khamis, Jamil

2018-05-01

Nano crumb rubber from scrap tyre is synthesized via 1064 nm pulsed Nd:YAG laser ablation in three different pH media i.e. DI-water (pH∼6.45), D-limonene (pH∼3.47) and NaOH solution (pH∼13.41). Field Emission Scanning Electron Microscope (FESEM) results show spherical morphology of crumb rubber with high degree of aggregation in DI-water and in D-limonene. However, dispersion of crumb rubbers is observed in NaOH solution. The smallest particles size is obtained in NaOH solution within the range of 10.9 nm – 74.3 nm. Energy-dispersive X-ray spectroscopy (EDX) and FTIR analysis confirmed the elements distribution and chemical bonding of rubber with DI-water, D-limonene and NaOH solution. The experimental findings shows that pulsed Nd:YAG laser ablation has potential for fabricating nano-crumb rubber in liquid media.

One-step formation of TiO2 hollow spheres via a facile microwave-assisted process for photocatalytic activity

NASA Astrophysics Data System (ADS)

Mohamad Alosfur, Firas K.; Ridha, Noor J.; Hafizuddin Haji Jumali, Mohammad; Radiman, S.

2018-04-01

Mesoporous TiO2 hollow spherical nanostructures with high surface areas were successfully prepared using a microwave method. The prepared hollow spheres had a size range between 200 and 500 nm. The spheres consisted of numerous smaller TiO2 nanoparticles with an average diameter of 8 nm. The particles had an essentially mesoporous structure, with a pore size in the range of 2-50 nm. The results confirmed that the synthesised of anatase TiO2 nanoparticles with specific surface area approximately 172.3 m2 g-1. The effect of ultraviolet and visible light irradiation and catalyst dosage on the TiO2 photocatalytic activity was studied by measuring the degradation rate of methylene blue. The maximum dye degradation performances with low catalyst loading (30 mg) were 99% and 63.4% using the same duration of ultraviolet and visible light irradiation, respectively (120 min).

Effect of Particle Morphology on the Reactivity of Explosively Dispersed Titanium Particles

NASA Astrophysics Data System (ADS)

Frost, David; Cairns, Malcolm; Goroshin, Samuel; Zhang, Fan

2009-06-01

The effect of particle morphology on the reaction of titanium (Ti) particles explosively dispersed during the detonation of either cylindrical or spherical charges has been investigated experimentally. The explosive charges consisted of packed beds of Ti particles saturated with nitromethane. The reaction behavior of irregularly-shaped Ti particles in three size ranges is compared with tests with spherical Ti particles. The particle reaction is strongly dependent on particle morphology, e.g., 95 μm spherical Ti particles failed to ignite (in cylinders up to 49 mm in dia), whereas similarly sized irregular Ti particles readily ignited. For irregular particles, the uniformity of ignition on the particle cloud surface was almost independent of particle size, but depended on charge diameter. As the charge diameter was reduced, ignition in the conically expanding particle cloud occurred only at isolated spots or bands. For spherical charges, although large irregular Ti particles ignited promptly and uniformly throughout the particle cloud, the smallest particles dispersed nonuniformly and ignition occurred at isolated locations. In general, particle ignition is a competition between particle heating (which is influenced by particle morphology, size, number density and the local thermodynamic history) and expansion cooling of the products.

Improved tunable range of the field-induced storage modulus by using flower-like particles as the active phase of magnetorheological elastomers.

PubMed

Tong, Yu; Dong, Xufeng; Qi, Min

2018-05-09

The field-induced storage modulus is an important parameter for the applications of magnetorheological (MR) elastomers. In this study, a model mechanism is established to analyze the potential benefits of using flower-like particles as the active phase compared with the benefits of using conventional spherical particles. To verify the model mechanism and to investigate the difference in dynamic viscoelasticity between MREs with spherical particles and flower-like particles, flower-like cobalt particles and spherical cobalt particles with similar particle sizes and magnetic properties are synthesized and used as the active phase to prepare MR elastomers. As the model predicts, MREs with flower-like cobalt particles present a higher crosslink density and enhanced interfacial bond strength, which leads to a higher storage modulus and higher loss modulus with respect to MREs with spherical cobalt particles. The tunable range of the field-induced storage modulus of MREs is also improved upon using the flower-like particles as the active phase.

Biosynthesis of spherical and highly stable gold nanoparticles using Ferulago Angulata aqueous extract: dual role of extract

NASA Astrophysics Data System (ADS)

Alizadeh, A.; Parsafar, S.; Khodaei, M. M.

2017-03-01

A biocompatible method for synthesizing of highly disperses gold nanoparticles using Ferulago Angulata leaf extract has been developed. It has been shown that leaf extract acts as reducing and coating agent. Various spectroscopic and electron microscopic techniques were employed for the structural characterization of the prepared nanoparticles. The biosynthesized particles were identified as elemental gold with spherical morphology, narrow size distribution (ranged 9.2-17.5 nm) with high stability. Also, the effect of initial ratio of precursors, temperature and time of reaction on the size and morphology of the nanoparticles was studied in more detail. It was observed that varying these parameters provides an accessible remote control on the size and morphology of nanoparticles. The uniqueness of this procedure lies in its cleanliness using no extra surfactant, reducing agent or any capping agent.

Electrochemical studies of mesoporous and copper-modified mesoporous TiO2 -anode material

NASA Astrophysics Data System (ADS)

Ajay Kumar, R.; Venkateswara Rao, A.; Rajesh, Ch.

2018-05-01

Herein, we developed a method to synthesize highly ordered mesoporous TiO2 (MT) and copper-modified M- TiO2 (CMT) with a high surface area by the hydrothermal method using Pluronic P-123 as a surfactant at 150 ° C. CMT with different copper concentrations (0.1, 0.2 and 0.3%) was synthesized. The structural characterization studies revealed that MT and CMT particles are in anatase phase. The average particle size was found to be 24± 0.8 nm for MT and that of CMT was 25± 0.6 , 27± 0.4 and 28± 0.3 nm, respectively. The presence of ordered spherical MT and CMT particles with uniform size distribution was confirmed by performing morphological studies using FE-SEM. Optical absorption studies indicate the presence of copper because of the red shift in the band gap and also a broad peak around 800nm when compared with MT. EIS studies point out an increase in conductivity from MT through 0.3% CMT by a decrease in the charge transfer resistance. Further, charge-discharge studies were carried on this material at room temperature for lithium-ion battery applications. CMT with 0.3% copper showed high initial discharge capacity and better cyclability. The results indicate that this material can act as a promising negative electrode.

Topological phase transformations and intrinsic size effects in ferroelectric nanoparticles

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

Mangeri, John; Espinal, Yomery; Jokisaari, Andrea M.

Here, composite materials comprised of ferroelectric nanoparticles in a dielectric matrix are being actively investigated for a variety of functional properties attractive for a wide range of novel electronic and energy harvesting devices. However, the dependence of these functionalities on shapes, sizes, orientation and mutual arrangement of ferroelectric particles is currently not fully understood. In this study, we utilize a time-dependent Ginzburg-Landau approach combined with coupled-physics finite-element-method based simulations to elucidate the behavior of polarization in isolated spherical PbTiO 3 or BaTiO 3 nanoparticles embedded in a dielectric medium, including air. The equilibrium polarization topology is strongly affected by particlemore » diameter, as well as the choice of inclusion and matrix materials, with monodomain, vortex-like and multidomain patterns emerging for various combinations of size and materials parameters. This leads to radically different polarization vs electric field responses, resulting in highly tunable size-dependent dielectric properties that should be possible to observe experimentally. Our calculations show that there is a critical particle size below which ferroelectricity vanishes. For the PbTiO 3 particle, this size is 2 and 3.4 nm, respectively, for high- and low-permittivity media. For the BaTiO 3 particle, it is ~3.6 nm regardless of the medium dielectric strength.« less

Topological phase transformations and intrinsic size effects in ferroelectric nanoparticles

DOE PAGES

Mangeri, John; Espinal, Yomery; Jokisaari, Andrea M.; ...

2017-01-06

Here, composite materials comprised of ferroelectric nanoparticles in a dielectric matrix are being actively investigated for a variety of functional properties attractive for a wide range of novel electronic and energy harvesting devices. However, the dependence of these functionalities on shapes, sizes, orientation and mutual arrangement of ferroelectric particles is currently not fully understood. In this study, we utilize a time-dependent Ginzburg-Landau approach combined with coupled-physics finite-element-method based simulations to elucidate the behavior of polarization in isolated spherical PbTiO 3 or BaTiO 3 nanoparticles embedded in a dielectric medium, including air. The equilibrium polarization topology is strongly affected by particlemore » diameter, as well as the choice of inclusion and matrix materials, with monodomain, vortex-like and multidomain patterns emerging for various combinations of size and materials parameters. This leads to radically different polarization vs electric field responses, resulting in highly tunable size-dependent dielectric properties that should be possible to observe experimentally. Our calculations show that there is a critical particle size below which ferroelectricity vanishes. For the PbTiO 3 particle, this size is 2 and 3.4 nm, respectively, for high- and low-permittivity media. For the BaTiO 3 particle, it is ~3.6 nm regardless of the medium dielectric strength.« less

Influence of Poly (Ethylene Glycol) and Oleylamine on the Formation of Nano to Micron Size Spherical SiO2 Particles

EPA Science Inventory

We report an eco-friendly synthesis of well–controlled, nano-to-micron-size, spherical SiO2 particles using non-hazardous solvent and a byproducts-producing system. It was found that the morphology and size of spherical SiO2 particles are controlled by adjusting the concentration...

Formulation and characterization of fisetin nanosuspension

NASA Astrophysics Data System (ADS)

Dzakwan, M.; Pramukantoro, G. E.; Mauludin, R.; Wikarsa, S.

2017-11-01

Fisetin (3,3,4,7-tetrahydroxyflavone) is a natural antioxidant that has shown to posses anticancer, antioxidant and anti-inflammatory properties. However, the poor solubility leads to poor bioavailability and limits its development. The aim of the study is to investigate the effect of fisetin nanosuspension using a precipitation-sonication method and additional stabilizers polysorbat 80, SLS, F68, PVP, PVA and HPMC on particle size average and the polydispersity index. The suspensions of microcrystalline FIS were prepared by a precipitation method with different proportion of stabilizers fixed. The nanosuspension produced was then characterized using Photon Correlation Spectroscopy (PCS) in term of particle size distribution, polydispersity index and morphology particle (SEM). Result showed fisetin nanosuspension were successfully prepared by anti-solvent precipitation with additional stabilizer SLS and PVA. The nanosuspension containing PVA showed smaller average particle size of 406 nm, a polydispersity index of 0.22±0.1 was obtained. The drug particles precipitated with the PVA as stabilizer were spherical in shape.

Synthesis characterization and luminescence studies of gamma irradiated nanocrystalline yttrium oxide

NASA Astrophysics Data System (ADS)

Shivaramu, N. J.; Lakshminarasappa, B. N.; Nagabhushana, K. R.; Singh, Fouran

2016-02-01

Nanocrystalline Y2O3 is synthesized by solution combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature. The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14-30 nm for samples synthesized using urea and 15-20 nm for samples synthesized using glycine respectively. Field emission scanning electron microscopy (FE-SEM) image of 1173 K annealed Y2O3 samples show well separated spherical shape particles and the average particle size is found to be in the range 28-35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y-O bond. Electron spin resonance (ESR) shows V- center, O2- and Y2 + defects. A broad photoluminescence (PL) emission with peak at 386 nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y2O3 nanopowder are studied at a heating rate of 5 K s- 1. The samples prepared by using urea show a prominent and well resolved peak at 383 K and a weak one at 570 K. It is also found that TL glow peak intensity (Im1) at 383 K increases with increase in γ-dose up to 6.0 kGy and then decreases with increase in dose. However, glycine used Y2O3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y2O3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detail.

Fabrication of self-assembled (-)-epigallocatechin gallate (EGCG) ovalbumin-dextran conjugate nanoparticles and their transport across monolayers of human intestinal epithelial Caco-2 cells.

PubMed

Li, Zheng; Gu, Liwei

2014-02-12

Nanoparticles have the potential to increase bioavailability of nutraceutical compounds such as (-)-epigallocatechin gallate (EGCG). Ovalbumin was conjugated with dextran using the Maillard reaction. The resultant ovalbumin-dextran (O-D) conjugates were self-assembled with EGCG to form EGCG O-D conjugate nanoparticles at pH 5.2 after heating at 80 °C for 60 min. Ovalbumin in EGCG O-D conjugate nanoparticles was further cross-linked by glutaraldehyde for 24 h at room temperature. EGCG O-D conjugate nanoparticles and cross-linked EGCG O-D conjugate nanoparticles in aqueous suspension had particle sizes of 285 and 339 nm, respectively, and showed a spherical morphology. The loading efficiencies of EGCG in these two nanoparticles were 23.4 and 30.0%, whereas the loading capacities were 19.6 and 20.9%, respectively. These nanoparticles showed positive zeta-potentials in a pH range from 2.5 to 4.0 but had negative charges at pH ≥5.0. EGCG O-D conjugate nanoparticles maintained a particle size of 183-349 nm in simulated gastric fluid (SGF) and 188-291 nm in simulated intestinal fluid (SIF) at 37 °C for 2 h, whereas cross-linked nanoparticles had particle sizes of 294-527 nm in SGF and 206-300 nm in SIF. Limited release of EGCG was observed in both nanoparticle systems in simulated gastric and intestinal fluids without and with digestive enzymes. EGCG O-D conjugate nanoparticles significantly enhanced the apparent permeability coefficient (Papp) of EGCG on Caco-2 monolayers compared with EGCG solution, suggesting that these nanoparticles may improve the absorption of EGCG.

Shear-induced aggregation or disaggregation in edible oils: Models, computer simulation, and USAXS measurements

NASA Astrophysics Data System (ADS)

Townsend, B.; Peyronel, F.; Callaghan-Patrachar, N.; Quinn, B.; Marangoni, A. G.; Pink, D. A.

2017-12-01

The effects of shear upon the aggregation of solid objects formed from solid triacylglycerols (TAGs) immersed in liquid TAG oils were modeled using Dissipative Particle Dynamics (DPD) and the predictions compared to experimental data using Ultra-Small Angle X-ray Scattering (USAXS). The solid components were represented by spheres interacting via attractive van der Waals forces and short range repulsive forces. A velocity was applied to the liquid particles nearest to the boundary, and Lees-Edwards boundary conditions were used to transmit this motion to non-boundary layers via dissipative interactions. The shear was created through the dissipative forces acting between liquid particles. Translational diffusion was simulated, and the Stokes-Einstein equation was used to relate DPD length and time scales to SI units for comparison with USAXS results. The SI values depended on how large the spherical particles were (250 nm vs. 25 nm). Aggregation was studied by (a) computing the Structure Function and (b) quantifying the number of pairs of solid spheres formed. Solid aggregation was found to be enhanced by low shear rates. As the shear rate was increased, a transition shear region was manifested in which aggregation was inhibited and shear banding was observed. Aggregation was inhibited, and eventually eliminated, by further increases in the shear rate. The magnitude of the transition region shear, γ˙ t, depended on the size of the solid particles, which was confirmed experimentally.

Rapid green synthesis of silver nanoparticles from Chrysanthemum indicum L and its antibacterial and cytotoxic effects: an in vitro study

PubMed Central

Arokiyaraj, Selvaraj; Arasu, Mariadhas Valan; Vincent, Savariar; Prakash, Nyayirukannaian Udaya; Choi, Seong Ho; Oh, Young-Kyoon; Choi, Ki Choon; Kim, Kyoung Hoon

2014-01-01

The present work reports a simple, cost-effective, and ecofriendly method for the synthesis of silver nanoparticles (AgNPs) using Chrysanthemum indicum and its antibacterial and cytotoxic effects. The formation of AgNPs was confirmed by color change, and it was further characterized by ultraviolet–visible spectroscopy (435 nm). The phytochemical screening of C. indicum revealed the presence of flavonoids, terpenoids, and glycosides, suggesting that these compounds act as reducing and stabilizing agents. The crystalline nature of the synthesized particles was confirmed by X-ray diffraction, as they exhibited face-centered cubic symmetry. The size and morphology of the particles were characterized by transmission electron microscopy, which showed spherical shapes and sizes that ranged between 37.71–71.99 nm. Energy-dispersive X-ray spectroscopy documented the presence of silver. The antimicrobial effect of the synthesized AgNPs revealed a significant effect against the bacteria Klebsiella pneumonia, Escherichia coli, and Pseudomonas aeruginosa. Additionally, cytotoxic assays showed no toxicity of AgNPs toward 3T3 mouse embryo fibroblast cells (25 μg/mL); hence, these particles were safe to use. PMID:24426782

Microencapsulation of puerarin nanoparticles by poly(l-lactide) in a supercritical CO(2) process.

PubMed

Chen, Ai-Zheng; Li, Yi; Chau, Foo-Tim; Lau, Tsui-Yan; Hu, Jun-Yan; Zhao, Zheng; Mok, Daniel Kam-Wah

2009-10-01

Puerarin nanoparticles were firstly prepared in the process of solution-enhanced dispersion by supercritical CO(2) (SEDS) and then successfully microencapsulated by poly(l-lactide) (PLLA) in a modified SEDS process. By adding an organic non-solvent, an initial puerarin solution with a higher degree of saturation and lower concentration was obtained and applied in the SEDS process. The resulting puerarin nanoparticles were then suspended in PLLA solution and microencapsulated by PLLA in a modified SEDS process, where an 'injector' was employed in the particle suspension delivery system. The puerarin nanoparticles exhibited a good spherical shape, a smooth surface and a narrow particle size distribution with a mean particle size of 188 nm. After microencapsulation the puerarin-PLLA microparticles had a mean size of 675 nm, a drug load of 23.6% and an encapsulation efficiency of 39.4%; after a burst release at the first stage, the drug was released in a sustained process. Compared with the parallel study of a co-precipitation process, this microencapsulation process is a much more promising technique to prepare a drug-polymer carrier for a drug delivery system, especially for protein drugs.

Dynamics of gold nanoparticles in synthetic and biopolymer solutions

NASA Astrophysics Data System (ADS)

Kohli, Indermeet

Soft matter systems of colloidal particles, polymers, amphiphiles and liquid crystals are ubiquitous in our everyday life. Food, plastics, soap and even human body is comprised of soft materials. Research conducted to understand the behavior of these soft matter systems at molecular level is essential for many interdisciplinary fields of study as well as important for many technological applications. We used gold nanoparticles (Au NPs) to investigate the length-scale dependent dynamics in semidilute poly(ethylene glycol) (PEG)-water, bovine serum albumin (BSA)-phosphate buffer, dextran and particulate solutions. In case of PEG-water solutions, fluctuation correlation spectroscopy was used to measure the diffusion coefficients (D) of the NPs as a function of their radius, Ro (2.5-10 nm), PEG volume fraction, φ (0-0.37) and molecular weight, Mw (5 kg/mol and 35 kg/mol). Our results indicate that the radius of gyration, Rg of the polymer chain is the crossover length scale for the NPs experiencing nanoviscosity or macroviscosity. In BSA-phosphate buffer solutions, we observed a monolayer formation at the NP surface with a thickness of 3.8 nm. The thickness of the adsorbed layer was independent of NP size. Best fit was obtained by the anticooperative binding model with the Hill coefficient of n = 0.63. Dissociation constant (KD) increased with particle size indicating stronger interaction of BSA with smaller sized NPs. We also contrasted the diffusion of gold nanoparticles (AuNPs) in crowded solutions of randomly branched polymer (dextran) and rigid, spherical particles (silica) to understand the roles played by the probe size and structure of the crowding agent in determining the probe diffusion. AuNPs of two different sizes (2.5 nm & 10 nm), dextran of molecular weight 70 kDa and silica particles of radius 10 nm were used. Our results indicated that the AuNP diffusion can be described using the bulk viscosity of the matrix and hydrodynamically dextran behaved similar to soft colloid. In all situations, we observed normal diffusion except for 2.5 nm sized AuNP particles in dextran solution at higher volume fraction. This was caused by transient trapping of particles within the random branches. The results showed the importance of macromolecular architecture in determining the transport properties in intracellular matrix and in cells with spiny dendrites.

Microwave Synthesis, Characterization, and Photoluminescence Properties of Nanocrystalline Zirconia

PubMed Central

Singh, A. K.; Nakate, Umesh T.

2014-01-01

We report synthesis of ZrO2 nanoparticles (NPs) using microwave assisted chemical method at 80°C temperature. Synthesized ZrO2 NPs were calcinated at 400°C under air atmosphere and characterized using FTIR, XRD, SEM, TEM, BET, and EDS for their formation, structure, morphology, size, and elemental composition. XRD results revealed the formation of mixed phase monoclinic and tetragonal ZrO2 phases having crystallite size of the order 8.8 nm from most intense XRD peak as obtained using Scherrer formula. Electron microscope analysis shows that the NPs were less than 10 nm and highly uniform in size having spherical morphology. BET surface area of ZrO2 NPs was found to be 65.85 m2/g with corresponding particle size of 16 nm. The band gap of synthesized NPs was found to be 2.49 eV and PL spectra of ZrO2 synthesized NPs showed strong peak at 414 nm, which corresponds to near band edge emission (UV emission) and a relatively weak peak at 475 and 562 nm. PMID:24578628

Synthesis and characterization of nanostructured titanium carbide for fuel cell applications

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

Singh, Paviter; Singh, Harwinder; Singh, Bikramjeet

2016-04-13

Titanium carbide (TiC) nanoparticles have been successfully synthesized by carbo-thermic reaction of titanium and acetone at 800 °C. This method is relatively low temperature synthesis route. It can be used for large scale production of TiC. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA) techniques. XRD analysis confirmed the formation of single phase TiC. XRD analysis confirmed that the particles are spherical in shape with an average particle size of 13 nm. DTA analysis shows that the phase is stable upto 900 °C and the material can be used formore » high temperature applications.« less

Synthesis of double-stranded RNA in a virus-enriched fraction from Agaricus bisporus

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

Sriskantha, A.; Wach, P.; Schlagnhaufer, B.

Partially purified virus preparations from sporophores of Agaricus bisporus affected with LaFrance disease had up to a 15-fold-higher RNA-dependent RNA polymerase activity than did comparable preparations from health sporophores. Enzyme activity was dependent upon the presence of Mg/sup 2 +/ and the four nucleoside triphosphates and was insensitive to actinomycin D, ..cap alpha..-amanitin, and rifampin. The /sup 3/H-labeled enzyme reaction products were double-stranded RNA (dsRNA) as indicated by CF-11 cellulose column chromatography and by their ionic-strength-dependent sensitivity to hydrolysis by RNase A. The principal dsRNA products had estimated molecular weights of 4.3 /times/ 10/sup 6/ and 1.4 /times/ 10/sup 6/.more » Cs/sub 2/SO/sub 4/ equilibrium centrifugation of the virus preparation resolved a single peak of RNA polymerase activity that banded with a 35-nm spherical virus particle containing dsRNAs with molecular weights of 4.3 /times/ 10/sup 6/ and 1.4 /times/ 10/sup 6/. The data suggest that the RNA-dependent RNA polymerase associated with the 35-nm spherical virus is a replicase which catalyzes the synthesis of the genomic dsRNAs.« less

High stable suspension of magnetite nanoparticles in ethanol by using sono-synthesized nanomagnetite in polyol medium

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

Bastami, Tahereh Rohani; Entezari, Mohammad H., E-mail: moh_entezari@yahoo.com

2013-09-01

Graphical abstract: - Highlights: • The sonochemical synthesis of magnetite nanoparticles was carried out in EG without any surfactant. • The nanoparticles with sizes ∼24 nm were composed of small building blocks with sizes ∼2 nm. • The hydrophilic magnetite nanoparticles were stable in ethanol even after 8 months. • Ultrasonic intensity showed a crucial role on the obtained high stable magnetite nanoparticles in ethanol. - Abstract: The sonochemical synthesis of magnetite nanoparticles was carried out at relatively low temperature (80 °C) in ethylene glycol (EG) as a polyol solvent. The particle size was determined by transmission electron microscopy (TEM).more » The magnetite nanoparticles with an average size of 24 nm were composed of small building blocks with an average size of 2–3 nm and the particles exhibited nearly spherical shape. The surface characterization was investigated by using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The stability of magnetite nanoparticles was studied in ethanol as a polar solvent. The nanoparticles showed an enhanced stability in ethanol which is due to the hydrophilic surface of the particles. The colloidal stability of magnetite nanoparticles in ethanol was monitored by UV–visible spectrophotometer. According to the results, the nanoparticles synthesized in 30 min of sonication with intensity of 35 W/cm{sup 2} (50%) led to a maximum stability in ethanol as a polar solvent with respect to the other applied intensities. The obtained magnetite nanoparticles were stable for more than12 months.« less

Microphysical Properties of Alaskan Volcanic Ash

NASA Astrophysics Data System (ADS)

Puthukkudy, A.; Espinosa, R.; Rocha Lima, A.; Remer, L.; Colarco, P. R.; Whelley, P.; Krotkov, N. A.; Young, K.; Dubovik, O.; Wallace, K.; Martins, J. V.

2017-12-01

Volcanic ash has the potential to cause a variety of severe problems for human health and the environment. Therefore, effective monitoring of the dispersion and fallout from volcanic ash clouds and characterization of the aerosol particle properties are essential. One way to acquire information from volcanic clouds is through satellite remote sensing: such images have greater coverage than ground-based observations and can present a "big picture" perspective. A challenge of remote sensing is that assumptions of certain properties of the target are often a pre-requisite for making accurate and quantitative retrievals. For example, detailed information about size distribution, sphericity, and optical properties of the constituent matter is needed or must be assumed. The same kind of information is also needed for atmospheric transport models to properly simulate the dispersion and fallout of volcanic ash. Presented here is a laboratory method to determine the microphysical and optical properties of volcanic ash samples collected from two Alaskan volcanoes with markedly different compositions. Our method uses a Polarized Imaging Nephelometer (PI-Neph) and a system that re-suspends the particles in an air flow. The PI-Neph measures angular light scattering and polarization of the re-suspended particles from 3o to 175o in scattering angle, with an angular resolution of 1o . Primary measurements include phase function and polarized phase function at three wavelengths (445nm, 532nm, and 661nm). Size distribution, sphericity, and complex refractive index are retrieved indirectly from the PI-Neph measurements using the GRASP (Generalized Retrieval of Aerosol and Surface Properties) inversion algorithm. We report the results of this method applied to samples from the Mt. Okmok (2008) and Mt. Katmai (1912) volcanic eruptions. To our knowledge, this is the first time direct measurements of phase matrix elements of ash from Mt. Okmok and Mt. Katmai have been reported. Retrieved microphysical properties show that Mt. Katmai ash is less absorbing than the Mt. Okmok ash in visible wavelengths. Phase function of these Alaskan volcanic ashes is smooth curve without any significant features. Phase function and polarized phase function measured do not exhibit strong spectral dependence in visible wavelengths.

Antioxidant properties of biohybrids based on liposomes and sage silver nanoparticles.

PubMed

Barbinta-Patrascu, Marcela Elisabeta; Bunghez, Ioana-Raluca; Iordache, Stefan Marian; Badea, Nicoleta; Fierascu, Radu-Claudiu; Ion, Rodica Mariana

2013-03-01

This paper is aimed to describe a simple and rapid eco-friendly bottom-up approach for the preparation of antioxidant silver bionanostructures using a leaf extract from sage (Salvia officinalis L.). The bioreduction property of sage in the synthesis of silver nanoparticles was investigated by UV-VIS and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy. During their preparation, the particle size analysis was performed by using Dynamic Light Scattering technique. Ultrasonic irradiation was used to obtain sage silver nanoparticles. The morphology (size and shape) of the herbal silver nanoparticles was evaluated by Scanning Electron Microscopy that revealed the formation of spherical phytonanoparticles with size less than 80 nm. In order to increase their stability and their biocompatibility, the sage silver nanoparticles were introduced in two types of liposomes: soybean lecithin- and Chla-DPPC-lipid vesicles which were prepared by thin film hydration method. X-Ray Fluorescence analysis confirmed the silver presence in liposomes/sage-AgNPs biohybrids. The stability of liposomes/herbal AgNPs bioconstructs was checked by zeta potential measurements. The most stable biohybrids: Chla-DPPC/sage-AgNPs with zeta potential value of -34.2 mV, were characterized by Atomic Force Microscopy revealing the spherical and quasi-spherical shaped profiles of these nanobiohybrids with size less than 96 nm. The antioxidant activity of the silver bionanostructures was evaluated using chemiluminescence assay. The developed eco-friendly silver phytonanostructures based on lipid membranes, nanosilver and sage extract, manifest strong antioxidant properties (between 86.5% and 98.6%).

Development, Characterization and Evaluation of Solid Lipid Nanoparticles as a potential Anticancer Drug Delivery System

NASA Astrophysics Data System (ADS)

Patel, Meghavi

Solid lipid nanoparticles (SLNs) consist of spherical solid lipid particles in the nanometer size range, which are dispersed in water or in an aqueous surfactant solution. SLN technology represents a promising new approach to deliver hydrophilic as well as lipophilic drugs. The commercialization of SLN technology remains limited despite numerous efforts from researchers. The purpose of this research was to advance SLN preparation methodology by investigating the feasibility of preparing glyceryl monostearate (GMS) nanoparticles by using three preparation methods namely microemulsion technique, magnetic stirring technique and temperature modulated solidification technique of which the latter two were developed in our laboratory. An anticancer drug 5-fluorouracil was incorporated in the SLNs prepared via the temperature modulated solidification process. Optimization of the magnetic stirring process was performed to evaluate how the physicochemical properties of the SLN was influenced by systematically varying process parameters including concentration of the lipid, concentration of the surfactant, type of surfactant, time of stirring and temperature of storage. The results demonstrated 1:2 GMS to tween 80 ratio, 150 ml dispersion medium and 45 min stirring at 4000 RPM speed provided an optimum formulation via the temperature modulated solidification process. SLN dispersions were lyophilized to stabilize the solid lipid nanoparticles and the lyophilizates exhibited good redispersibility. The SLNs were characterized by particle size analysis via dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), drug encapsulation efficiency and in vitro drug release studies. Particle size of SLN dispersion prepared via the three preparation techniques was approximately 66 nm and that of redispersed lyophilizates was below 500 nm. TEM images showed spherical to oval particles that were less dense in the core with a well-defined shell and the particle size was in agreement with the particle size analysis data obtained by DLS. DSC thermograms of the lyophilized SLNs indicate a reduction in the crystallinity order of GMS particles. The drug encapsulation efficiency was found to be approximately 30%. In vitro drug release studies from redispersed lyophilized SLNs showed that 17 % of the encapsulated drug was released within 2 h. The SLNs prepared in our lab demonstrated characteristics that can potentially be utilized in an anticancer drug delivery system. Future in vitro cell culture and in vivo animal model studies will delineate compatibility and utility of these formulations in biological systems.

A Facile pH Controlled Citrate-Based Reduction Method for Gold Nanoparticle Synthesis at Room Temperature.

PubMed

Tyagi, Himanshu; Kushwaha, Ajay; Kumar, Anshuman; Aslam, Mohammed

2016-12-01

The synthesis of gold nanoparticles using citrate reduction process has been revisited. A simplified room temperature approach to standard Turkevich synthesis is employed to obtain fairly monodisperse gold nanoparticles. The role of initial pH alongside the concentration ratio of reactants is explored for the size control of Au nanoparticles. The particle size distribution has been investigated using UV-vis spectroscopy and transmission electron microscope (TEM). At optimal pH of 5, gold nanoparticles obtained are highly monodisperse and spherical in shape and have narrower size distribution (sharp surface plasmon at 520 nm). For other pH conditions, particles are non-uniform and polydisperse, showing a red-shift in plasmon peak due to aggregation and large particle size distribution. The room temperature approach results in highly stable "colloidal" suspension of gold nanoparticles. The stability test through absorption spectroscopy indicates no sign of aggregation for a month. The rate of reduction of auric ionic species by citrate ions is determined via UV absorbance studies. The size of nanoparticles under various conditions is thus predicted using a theoretical model that incorporates nucleation, growth, and aggregation processes. The faster rate of reduction yields better size distribution for optimized pH and reactant concentrations. The model involves solving population balance equation for continuously evolving particle size distribution by discretization techniques. The particle sizes estimated from the simulations (13 to 25 nm) are close to the experimental ones (10 to 32 nm) and corroborate the similarity of reaction processes at 300 and 373 K (classical Turkevich reaction). Thus, substitution of experimentally measured rate of disappearance of auric ionic species into theoretical model enables us to capture the unusual experimental observations.

Magnetic and structural properties of nanoparticles of nickel oxide

NASA Astrophysics Data System (ADS)

Shim, Hyunja (Jenny)

In this dissertation, magnetic properties of NiO nanoparticles (NP) prepared by the sol-gel method in the size range D = 5 nm to 20 nm, with and without oleic acid (OA) coating, are reported. Transmission electron microscopy (TEM) studies show the morphology of the smaller particles to be primarily rod-like, changing over to nearly spherical shapes for D >10 nm. Average sizes D of NP determined by x-ray diffraction (XRD) are compared with the results from TEM. From the analysis of the XRD line intensities, the particle size dependence of the Debye-Waller factors for Ni and O atoms are derived. It is found that the Debye-Waller factors of nickel and oxygen atoms in smaller particles are larger than those in bulk NiO. For the coated and uncoated NiO nanorods of 5 nm diameter, variations of the magnetization M with temperature T (5 K to 370 K) and temperature variations of the EMR (electron magnetic resonance) spectra were measured to determine the respective blocking temperatures TB(m) and TB(EMR). The following differences are noted: (1) TB(m) is reduced from 230 K (uncoated) to 85 K(coated) for H = 25 Oe; (2) Decrease of TB(m) with H is weaker and the ratio TB(EMR)/T B(m) is smaller for the uncoated particles. These differences are due to stronger interparticle interaction present in the uncoated particles. Temperature variation (5 K-300 K) of the AC magnetic susceptibilities (chi' and chi") at various frequencies f (0.1-10,000 Hz) are reported for the coated and uncoated 5 nm diameter nanorods of NiO. Using the peak in chi' as the blocking temperature TB, it is observed that TB increases with increasing f. The data for the two samples fit the Vogel-Fulcher law: f = f0exp[-Ea/k(TB-T0)] with f 0 = 9.2 x 1011 Hz, Ea/k = 1085 K and T0 = 162 K (0 K) for the uncoated (coated) particles. This shows that T0 provides a good measure of the effects of interparticle interactions on magnetic relaxation and that these interactions are essentially eliminated with the OA coating. For all the particles, measurements of M versus T (5 K-370 K) in the zero-field cooled (ZFC) and field-cooled (FC) modes are used to determine the average blocking temperature TP. For the OA coated particles, TP increases with increase in size D as expected for superparamagnetic particles. However for the uncoated NP, TP decreases initially with increase in size for D < 10 nm; but for D > 10 nm, TP follows the same trend as for the coated NP. These differences are interpreted in terms of significant interparticle interaction. The data of M vs. the applied field H for T > TP are fit to the modified Langevin function: M = M0 L (muPH/kBT) + chiaH, to determine the magnetic moment muP per particle as a function of size D. The variation of muP with size D is interpreted in terms of the fraction of spins on the surface layer of the particles which contribute to mu P. It is observed that this fraction varies as 1/D reaching nearly 100 % for the 5 nm particles. From the temperature dependence of M0 and extrapolating to M0 → 0, the Neel temperatures TN for various sizes are determined. TN for NiO nanoparticles is found to decreases rapidly with decrease in size for D < 10 nm.

Luminescent properties of YVO4:Eu/SiO2 core-shell composite particles

NASA Astrophysics Data System (ADS)

Bao, Amurisana; Lai, Hua; Yang, Yuming; Liu, Zhilong; Tao, Chunyan; Yang, Hua

2010-02-01

We report an efficient process for preparing monodisperse SiO2@Y0.95Eu0.05VO4 core-shell phosphors using a simple citrate sol-gel method and without the use of surface-coupling silane agents or large stabilizers. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the resulting SiO2@Y0.95Eu0.05VO4 core-shell phosphors. The XRD results demonstrate that the Y0.95Eu0.05VO4 particles crystallization on the surface of SiO2 annealing at 800 °C is perfectly and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 500 nm and an average thickness of 50 nm), are not agglomerated, and have a smooth surface. The thickness of the YVO4:Eu3+ shells on the SiO2 cores could be easily tailored by changing the mass ratio of shell to core ( W = [YVO4]/[SiO2]) ( 50 nm for W = 30%). The Eu3+ shows a strong PL luminescence (dominated by 5D0 - 7F2 red emission at 618 nm) under the excitation of 320 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the values of W.

Effect of solvent type on the nanoparticle formation of atorvastatin calcium by the supercritical antisolvent process.

PubMed

Kim, Min-Soo; Song, Ha-Seung; Park, Hee Jun; Hwang, Sung-Joo

2012-01-01

The aims of this study were to identify how the solvent selection affects particle formation and to examine the effect of the initial drug solution concentration on mean particle size and particle size distribution in the supercritical antisolvent (SAS) process. Amorphous atorvastatin calcium was precipitated from seven different solvents using the SAS process. Particles with mean particle size ranging between 62.6 and 1493.7 nm were obtained by varying organic solvent type and solution concentration. By changing the solvent, we observed large variations in particle size and particle size distribution, accompanied by different particle morphologies. Particles obtained from acetone and tetrahydrofuran (THF) were compact and spherical fine particles, whereas those from N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO) were agglomerated, with rough surfaces and relatively larger particle sizes. Interestingly, the mean particle size of atorvastatin calcium increased with an increase in the boiling point of the organic solvent used. Thus, for atorvastatin particle formation via the SAS process, particle size was determined mainly by evaporation of the organic solvent into the antisolvent phase. In addition, the mean particle size was increased with increasing drug solution concentration. In this study, from the aspects of particle size and solvent toxicity, acetone was the better organic solvent for controlling nanoparticle formation of atorvastatin calcium.

Piper betle-mediated synthesis, characterization, antibacterial and rat splenocyte cytotoxic effects of copper oxide nanoparticles.

PubMed

Praburaman, Loganathan; Jang, Jum-Suk; Muthusamy, Govarthanan; Arumugam, Sengottaiyan; Manoharan, Koildhasan; Cho, Kwang-Min; Min, Cho; Kamala-Kannan, Seralathan; Byung-Taek, Oh

2016-09-01

The study reports a simple, inexpensive, and eco-friendly synthesis of copper oxide nanoparticles (CuONPs) using Piper betle leaf extract. Formation of CuONPs was confirmed by UV-visible spectroscopy at 280 nm. Transmission electron microscopy (TEM) images showed that the CuONPs were spherical, with an average size of 50-100 nm. The scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS) peak was observed approximately at 1 and 8 keV. The X-ray diffraction (XRD) studies indicated that the particles were crystalline in nature. CuONPs effectively inhibited the growth of phytopathogens Ralstonia solanacearum and Xanthomonas axonopodis. The cytotoxic effect of the synthesized CuONPs was analyzed using rat splenocytes. The cell viability was decreased to 94% at 300 μg/mL.

Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity

NASA Astrophysics Data System (ADS)

Bindhu, M. R.; Umadevi, M.

2013-01-01

Synthesis of silver nanoparticles using leaf extract of Hibiscus cannabinus has been investigated. The influences of different concentration of H. cannabinus leaf extract, different metal ion concentration and different reaction time on the above cases on the synthesis of nanoparticles were evaluated. The synthesized nanoparticles were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The prepared silver nanoparticles were monodispersed, spherical in shape with the average particle size of 9 nm and shows surface plasmon peak at 446 nm. The study also reveals that the ascorbic acid present in H. cannabinus leaf extract has been used as reducing agent. The prepared silver nanoparticle shows good antimicrobial activity against Escherichia coli, Proteus mirabilis and Shigella flexneri.

Green synthesis of stabilized spherical shaped gold nanoparticles using novel aqueous Elaeis guineensis (oil palm) leaves extract

NASA Astrophysics Data System (ADS)

Ahmad, Tausif; Bustam, Mohamad Azmi; Irfan, Muhammad; Moniruzzaman, Muhammad; Anwaar Asghar, Hafiz Muhammad; Bhattacharjee, Sekhar

2018-05-01

In the last decade, development of bioinspired protocols to synthesize gold nanoparticles (AuNPs) using plants and their extracts have been dealt by researchers due to their low cost, renewability and non-toxic features. A simple, cheap and ecofriendly method is reported to synthesize stabilized AuNPs of size 35-75 nm at room temperature using aqueous Elaeis guineensis (oil palm) leaves extract without addition of any external agent. Oil palm leaves mediated AuNPs were characterized using FTIR, UV-vis spectrophotometer, EDAX, XPS, FESEM, TEM, DLS and TGA. FTIR spectra results revealed contribution of phenolic, carboxylic, amines and amides in reduction of trivalent gold ions and stabilization of formed gold atoms. Reaction solution color change and UV-vis spectra confirmed reduction of gold ions to generate gold atoms. Reaction mechanism explained the role of phenolic compounds in reduction reaction using FTIR and UV-vis spectra results. EDAX and XPS results further validated the formation of metallic gold particles through bioreduction of gold ions. Crystal structure of metallic gold particles was confirmed through XRD peaks indexing to (111), (200), (220) and (311) planes. TEM and FESEM particles size measurements exhibited the formation of nanostructured AuNPs. Synthesis of well scattered and spherical shaped AuNPs was revealed through FESEM and TEM images. The excellent stability of AuNPs was shown through high negative zeta potential value (-14.7 ± 4.68 mV) and uniform dispersion in aqueous media. Our results disclosed the excellent potential of Elaeis guineensis (oil palm) leaves as reducing and stabilizing agents in green synthesis of well scattered spherical shaped AuNPs, which can be employed as strong candidates in medical drug delivery and industrial applications.

T-matrix Study of Scattering and Absorption of Light by Biomass Burning Aerosols

NASA Astrophysics Data System (ADS)

Poudel, Samin

The uncertainty in the measurements of aerosol optical properties has made it difficult to quantify the global impact of aerosols on Earth's climate and limits our ability to predict future climate changes. Morphology, size, volume, shape, fuel type, burning conditions, aging, and changes in chemical composition due to atmospheric processing of soot play a significant part in determining the optical properties of aerosols. The T-matrix method has been successfully used to reproduce experimental results of optical properties of spherical and non-spherical particles. In this work we applied the T-matrix method to extract the refractive index of biomass burning soot (burning pine tree) by reproducing experimentally determined single scattering albedo (SSA), scattering and extinction cross section values obtained by burning pine and collecting aerosols in two different ways: (1) from an outdoor burn drum to burn pine and collect soot in distilled water using an impinger and re-aerosolized the soot after several days to measure extinction and scattering cross sections using cavity ring down spectroscopy and nephelometry and (2) from a tube furnace in the lab to burn pine and the soot was introduced into an indoor smog chamber and soot particles sampled directly into the cavity ring down system and the nephelometer to measure extinction and scattering cross sections. Filter samples were also collected from both types of burning and electron microscopy images were used to obtain morphology and size information to conduct T-Matrix calculations. The experimentally measured optical properties from the impinger samples were reproduced using a refractive index of 1.345 + i0.096 for 300 and 400nm particles, while the results from the tube furnace samples were reproduced using 1.88 + i0.024 for 200 nm particles and 1.47 + i0.047 for 300 nm particles. This suggests that the impinger samples do not represent fresh soot since they are more absorbing and have lower SSA values compared to ours and other similar laboratory and field measurements for fresh soot. Morphology information from images of filter samples was used in the T-matrix calculation using refractive index of 1.88 + i0.024 to reproduce the SSA values for the fresh soot. It is shown that refractive indices used for fresh diesel soot or soot produced from propane 1.76 + i0.57 cannot be applied to biomass burning soot, as it provides a significantly lower SSA values in both cases.

Retrieval of Aerosol Optical Properties from Ground-Based Remote Sensing Measurements: Aerosol Asymmetry Factor and Single Scattering Albedo

NASA Astrophysics Data System (ADS)

Qie, L.; Li, Z.; Li, L.; Li, K.; Li, D.; Xu, H.

2018-04-01

The Devaux-Vermeulen-Li method (DVL method) is a simple approach to retrieve aerosol optical parameters from the Sun-sky radiance measurements. This study inherited the previous works of retrieving aerosol single scattering albedo (SSA) and scattering phase function, the DVL method was modified to derive aerosol asymmetric factor (g). To assess the algorithm performance at various atmospheric aerosol conditions, retrievals from AERONET observations were implemented, and the results are compared with AERONET official products. The comparison shows that both the DVL SSA and g were well correlated with those of AERONET. The RMSD and the absolute value of MBD deviations between the SSAs are 0.025 and 0.015 respectively, well below the AERONET declared SSA uncertainty of 0.03 for all wavelengths. For asymmetry factor g, the RMSD deviations are smaller than 0.02 and the absolute values of MBDs smaller than 0.01 at 675, 870 and 1020 nm bands. Then, considering several factors probably affecting retrieval quality (i.e. the aerosol optical depth (AOD), the solar zenith angle, and the sky residual error, sphericity proportion and Ångström exponent), the deviations for SSA and g of these two algorithms were calculated at varying value intervals. Both the SSA and g deviations were found decrease with the AOD and the solar zenith angle, and increase with sky residual error. However, the deviations do not show clear sensitivity to the sphericity proportion and Ångström exponent. This indicated that the DVL algorithm is available for both large, non-spherical particles and spherical particles. The DVL results are suitable for the evaluation of aerosol direct radiative effects of different aerosol types.

Effect of annealing on particle size, microstructure and gas sensing properties of Mn substituted CoFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, E. Ranjith; Kamzin, A. S.; Janani, K.

2016-11-01

Microstructure, morphological and gas sensor studies of Mn substituted cobalt ferrite nanoparticles synthesized by a simple evaporation method and auto- combustion method. The influence of heat treatment on phase and particle size of spinel ferrite nanoparticles were determined by X-ray diffraction and Mossbauer spectroscopy. The XRD study reveals that the lattice constant and crystallite size of the samples increases with the increase of annealing temperature. Last one was confirmed by Mossbauer data. The lowest size of particles of MnCoFe2O4 (~3 nm) is obtained by auto combustion method. The spherical shaped nanoparticles are recorded by TEM. Furthermore, conductance response of Mn-Co ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG) which showed a sensor response of ~0.19 at an optimum operating temperature of 250 °C.

Hierarchical nanoparticle assemblies formed by decorating breath figures.

PubMed

Böker, Alexander; Lin, Yao; Chiapperini, Kristen; Horowitz, Reina; Thompson, Mike; Carreon, Vincent; Xu, Ting; Abetz, Clarissa; Skaff, Habib; Dinsmore, A D; Emrick, Todd; Russell, Thomas P

2004-05-01

The combination of two self-assembly processes on different length scales leads to the formation of hierarchically structured nanoparticle arrays. Here, the formation of spherical cavities, or 'breath figures'-made by the condensation of micrometre-sized water droplets on the surface of a polymer solution-that self-assemble into a well-ordered hexagonal array, is combined with the self-assembly of CdSe nanoparticles at the polymer solution-water droplet interface. Complete evaporation of the solvent and water confines the particle assembly to an array of spherical cavities and allows for ex situ investigation. Fluorescence confocal, transmission electron and scanning electron microscope images show the preferential segregation of the CdSe nanoparticles to the polymer solution-water interface where they form a 5-7-nm-thick layer, thus functionalizing the walls of the holes. This process opens a new route to fabricating highly functionalized ordered microarrays of nanoparticles, potentially useful in sensory, separation membrane or catalytic applications.

Rapid Optimal SPH Particle Distributions in Spherical Geometries For Creating Astrophysical Initial Conditions

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

Raskin, Cody; Owen, J. Michael

Creating spherical initial conditions in smoothed particle hydrodynamics simulations that are spherically conformal is a difficult task. Here in this paper, we describe two algorithmic methods for evenly distributing points on surfaces that when paired can be used to build three-dimensional spherical objects with optimal equipartition of volume between particles, commensurate with an arbitrary radial density function. We demonstrate the efficacy of our method against stretched lattice arrangements on the metrics of hydrodynamic stability, spherical conformity, and the harmonic power distribution of gravitational settling oscillations. We further demonstrate how our method is highly optimized for simulating multi-material spheres, such asmore » planets with core–mantle boundaries.« less

Rapid Optimal SPH Particle Distributions in Spherical Geometries For Creating Astrophysical Initial Conditions

DOE PAGES

Raskin, Cody; Owen, J. Michael

2016-03-24

Creating spherical initial conditions in smoothed particle hydrodynamics simulations that are spherically conformal is a difficult task. Here in this paper, we describe two algorithmic methods for evenly distributing points on surfaces that when paired can be used to build three-dimensional spherical objects with optimal equipartition of volume between particles, commensurate with an arbitrary radial density function. We demonstrate the efficacy of our method against stretched lattice arrangements on the metrics of hydrodynamic stability, spherical conformity, and the harmonic power distribution of gravitational settling oscillations. We further demonstrate how our method is highly optimized for simulating multi-material spheres, such asmore » planets with core–mantle boundaries.« less

RAPID OPTIMAL SPH PARTICLE DISTRIBUTIONS IN SPHERICAL GEOMETRIES FOR CREATING ASTROPHYSICAL INITIAL CONDITIONS

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

Raskin, Cody; Owen, J. Michael

2016-04-01

Creating spherical initial conditions in smoothed particle hydrodynamics simulations that are spherically conformal is a difficult task. Here, we describe two algorithmic methods for evenly distributing points on surfaces that when paired can be used to build three-dimensional spherical objects with optimal equipartition of volume between particles, commensurate with an arbitrary radial density function. We demonstrate the efficacy of our method against stretched lattice arrangements on the metrics of hydrodynamic stability, spherical conformity, and the harmonic power distribution of gravitational settling oscillations. We further demonstrate how our method is highly optimized for simulating multi-material spheres, such as planets with core–mantlemore » boundaries.« less

Elongated dust particles growth in a spherical glow discharge in ethanol

NASA Astrophysics Data System (ADS)

Fedoseev, A. V.; Sukhinin, G. I.; Sakhapov, S. Z.; Zaikovskii, A. V.; Novopashin, S. A.

2018-01-01

The formation of elongated dust particles in a spherical dc glow discharge in ethanol was observed for the first time. Dust particles were formed in the process of coagulation of ethanol dissociation products in the plasma of gas discharge. During the process the particles were captured into clouds in the electric potential wells of strong striations of spherical discharge. The size and the shape of dust particles are easily detected by naked eye after the illumination of the laser sheet. The description of the experimental setup and conditions, the analysis of size, shape and composition of the particles, the explanation of spatial ordering and orientation of these particles are presented.

Spherical and cylindrical particle resonator as a cloak system

NASA Astrophysics Data System (ADS)

Minin, I. V.; Minin, O. V.; Eremeev, A. I.; Tseplyaev, I. S.

2018-05-01

The concept of dielectric spherical or cylindrical particle in resonant mode as a cloak system is offered. In fundamental modes (modes with the smallest volume correspond to |m| = l, and s = 1) the field is concentrated mostly in the equatorial plane and at the surface of the sphere. Thus under resonance modes, such perturbation due to cuboid particle inserted in the spherical or cylindrical particle has almost no effect on the field forming resonance regardless of the value of internal particle material (defect) as long as this material does not cover the region where resonance takes place.

Preparation of SiO2/(PMMA/Fe3O4) from monolayer linolenic acid modified Fe3O4 nanoparticles via miniemulsion polymerization.

PubMed

He, Lei; Li, Zhiyang; Fu, Jing; Deng, Yan; He, Nongyue; Wang, Zhifei; Wang, Hua; Shi, Zhiyang; Wang, Zunliang

2009-10-01

SiO2/(PMMA/Fe3O4) composite particles were prepared from linolenic acid (LA) instead of oleic acid (OA) modified Fe3O4 nanoparticles by miniemulsion polymerization. LA has three unsaturated double bonds with which it can polymerizate more easily than OA. And coating Fe3O4 with polymethyl methacrylate (PMMA) polymer beforehand can prevent magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of tetraethoxysilane (TEOS) by the steric hindrance. Finally, the resulting PMMA/Fe3O4 nanoparticles were coated with silica, forming SiO2/(PMMA/Fe3O4) core-shell structure particles. The sizes of nanoparticles with core-shell structure were in the range from 300 to 600 nm. The nanoparticles were spherical particles and had consistent size. The result of magnetic measurement showed that the composite particles had superparamagnetic property.

A hydroxyapatite coating covalently linked onto a silicone implant material.

PubMed

Furuzono, T; Sonoda, K; Tanaka, J

2001-07-01

A novel composite consisting of hydroxyapatite (HAp) microparticles covalently coupled onto a silicone sheet was developed. Initially, an acrylic acid (AAc) -grafted silicone sheet with a 16.7 microg/cm(2) surface graft density was prepared by corona-discharge treatment. The surface of sintered, spherical, carbonated HAp particles with an average diameter of 2.0 microm was subsequently modified with amino groups. The amino group surface density of the HAp particles was calculated to be approximately one amino molecule per 1.0 nm(2) of particle surface area. These samples were characterized with Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. After the formation of ammonium ionic bonds between both samples under aqueous conditions, they were reacted at 180 degrees C for 6 h in vacuo to form covalent bonds through a solid-phase condensation. The HAp particles were coupled to the AAc-grafted silicone surface by a covalent linkage. Further improvements in the adhesive and bioactive properties of the HAp-coated silicone material are expected.

Multiwalled carbon nanotube monoliths prepared by spark plasma sintering (SPS) and their mechanical properties.

PubMed

Uo, Motohiro; Hasegawa, Tomoka; Akasaka, Tsukasa; Tanaka, Isao; Munekane, Fuminori; Omori, Mamoru; Kimura, Hisamichi; Nakatomi, Reiko; Soga, Kohei; Kogo, Yasuo; Watari, Fumio

2009-01-01

Three types of multiwalled carbon nanotube (MWCNT) monoliths without any binders were obtained by spark plasma sintering (SPS) treatment at 2000 degrees C under 80 MPa sintering pressure. Three MWCNTs with different diameters: thin (slashed circle20-30 nm, CNT Co., Ltd., Korea), thick (slashed circle100 nm, Nano Carbon Technologies Co., Ltd., Japan) and spherical thin (slashed circle20-30 nm, granulated diameter = 1-3 microm, Shimizu Corporation, Japan) were employed for SPS. SEM observation confirmed that these materials maintained the nanosized tube microstructure of raw CNT powder after SPS treatment. The densest monolith was prepared with the spherical MWCNTs. The mechanical properties of this material were estimated by the dynamic hardness test. The elastic modulus of the monolith did not depend on the difference of MWCNTs, but the hardness of spherical MWCNTs was higher than that of thick MWCNTs. The high density and hardness of the spherical MWCNTs were caused by the high packing density during the SPS process because of its spherical granulation. Thus, the spherical MWCNTs were most useful for the MWCNT monolith preparation with the SPS process and its application as a bone substitute material and a bone tissue engineering scaffold material was suggested.

Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

PubMed Central

Rong, Guan; Liu, Guang; Zhou, Chuang-bing

2013-01-01

Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied. PMID:23997677

Effect of particle shape on mechanical behaviors of rocks: a numerical study using clumped particle model.

PubMed

Rong, Guan; Liu, Guang; Hou, Di; Zhou, Chuang-Bing

2013-01-01

Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied.

XMCD and XMCD-PEEM Studies on Magnetic-Field-Assisted Self-Assembled 1D Nanochains of Spherical Ferrite Particles

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

Zhang, Wen; Wong, Ping Kwan Johnny; Zhang, Dong

Quasi-1D nanochains of spherical magnetic ferrite particles with a homogeneous particle size of ≈200 nm and a micrometer-sized chain length are fabricated in this paper via a self-assembly method under an external magnetic field. This assisting magnetic field (H assist), applied during synthesis, significantly modifies the distribution of the Fe 2+O h, Fe 3+T d, and Fe 3+O h cations in the chains, as demonstrated by X-ray magnetic circular dichroism (XMCD) combined with theoretical analysis. This provides direct evidence of the nontrivial role of external synthetic conditions for defining the crystal chemistry of nanoscale ferrites and in turn their magneticmore » properties, providing an extra degree of freedom for intentional control over the performances of 1D magnetic nanodevices for various applications. Magnetic imaging, performed via XMCD in photoemission electron microscopy, further shows the possibility of creating and trapping a series of adjacent magnetic domain walls in a single chain, suggesting that there is great application potential for these nanochains in 1D magnetic nanodevices, as determined by field- or current-driven domain wall motions. Finally, practical control over the magnetic properties of the nanochains is also achieved by extrinsic dopants of cobalt and zinc, which are observed to occupy the ferrite ionic sites in a selective manner.« less

One stone, two birds: silica nanospheres significantly increase photocatalytic activity and colloidal stability of photocatalysts

NASA Astrophysics Data System (ADS)

Rasamani, Kowsalya D.; Foley, Jonathan J., IV; Sun, Yugang

2018-03-01

Silver-doped silver chloride [AgCl(Ag)] nanoparticles represent a unique class of visible-light-driven photocatalysts, in which the silver dopants introduce electron-abundant mid-gap energy levels to lower the bandgap of AgCl. However, free-standing AgCl(Ag) nanoparticles, particularly those with small sizes and large surface areas, exhibit low colloidal stability and low compositional stability upon exposure to light irradiation, leading to easy aggregation and conversion to metallic silver and thus a loss of photocatalytic activity. These problems could be eliminated by attaching the small AgCl(Ag) nanoparticles to the surfaces of spherical dielectric silica particles with submicrometer sizes. The high optical transparency in the visible spectral region (400-800 nm), colloidal stability, and chemical/electronic inertness displayed by the silica spheres make them ideal for supporting photocatalysts and significantly improving their stability. The spherical morphology of the dielectric silica particles can support light scattering resonances to generate significantly enhanced electric fields near the silica particle surfaces, on which the optical absorption cross-section of the AgCl(Ag) nanoparticles is dramatically increased to promote their photocatalytic activity. The hybrid silica/AgCl(Ag) structures exhibit superior photocatalytic activity and stability, suitable for supporting photocatalysis sustainably; for instance, their efficiency in the photocatalytic decomposition of methylene blue decreases by only ˜9% even after ten cycles of operation.

XMCD and XMCD-PEEM Studies on Magnetic-Field-Assisted Self-Assembled 1D Nanochains of Spherical Ferrite Particles

DOE PAGES

Zhang, Wen; Wong, Ping Kwan Johnny; Zhang, Dong; ...

2017-05-30

Quasi-1D nanochains of spherical magnetic ferrite particles with a homogeneous particle size of ≈200 nm and a micrometer-sized chain length are fabricated in this paper via a self-assembly method under an external magnetic field. This assisting magnetic field (H assist), applied during synthesis, significantly modifies the distribution of the Fe 2+O h, Fe 3+T d, and Fe 3+O h cations in the chains, as demonstrated by X-ray magnetic circular dichroism (XMCD) combined with theoretical analysis. This provides direct evidence of the nontrivial role of external synthetic conditions for defining the crystal chemistry of nanoscale ferrites and in turn their magneticmore » properties, providing an extra degree of freedom for intentional control over the performances of 1D magnetic nanodevices for various applications. Magnetic imaging, performed via XMCD in photoemission electron microscopy, further shows the possibility of creating and trapping a series of adjacent magnetic domain walls in a single chain, suggesting that there is great application potential for these nanochains in 1D magnetic nanodevices, as determined by field- or current-driven domain wall motions. Finally, practical control over the magnetic properties of the nanochains is also achieved by extrinsic dopants of cobalt and zinc, which are observed to occupy the ferrite ionic sites in a selective manner.« less

Pseudocapacitance of Co doped NiO nanoparticles and its room temperature ferromagnetic behavior

NASA Astrophysics Data System (ADS)

Bharathy, G.; Raji, P.

2018-02-01

Co doped NiO nanoparticles CoxNi1-xO (x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by the Sol-gel technique. The impact of Co doping concentration on structural, functional and magnetic properties of NiO nanoparticles was analyzed by X-ray diffraction (XRD), FESEM with EDAX, FTIR and VSM. The average crystallite size was measured to be 34 nm and 11 nm for NiO and Co doped NiO nanoparticles respectively. FESEM reveals that particles are spherical in shape with average size around 30 nm. The elemental composition was analyzed by EDAX. FTIR spectra reveal the existence of NiO peaks in the prepared samples, room temperature ferromagnetism was observed for pure and Co doped NiO nanoparticles by VSM. Pure NiO particles shows ferromagnetic behavior with low coercivity and it increases gradually when doping ratio increases. Higher saturation magnetization was obtained for the sample 0.1 M of Co doped NiO nanoparticle as 22.09 emu/gm. An attempt has been made to study the pseudocapacitance behavior of pure and Co doped NiO nano particles in various scan rates. Electrochemical studies show that 0.4 M Co doped sample gives better charge storage capacity with maximum specific capacitance of 379 Fg-1 at a scan rate of 20 mVs-1. It reveals that it is a promising electrode material for super capacitor applications.

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.

Physicochemical characterizations of nano-palm oil fuel ash

NASA Astrophysics Data System (ADS)

Rajak, Mohd Azrul Abdul; Majid, Zaiton Abdul; Ismail, Mohammad

2015-07-01

Palm Oil Fuel Ash (POFA) is known as a good supplementary cementing material due to its siliceous-rich content. The application of nanotechnology in the pozzolanic materials could invent new functions in the efficiency of physical and chemical properties of materials. Thus, the present study aims to generate nano-sized POFA and characterize the physicochemical properties of nano-palm oil fuel ash (nPOFA). The nPOFA was prepared by mechanically grinding micro POFA using a high intensity ball milling for 6 hours. The physicochemical properties of nPOFA were characterized via X-Ray Fluoresence (XRF), Scanning Emission microscopy- Energy Dispersive X-Ray (SEM-EDX), Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD). The particle size of nPOFA acquired from TEM analysis was in the range of 20 nm to 90 nm, while the average crystallite size calculated from XRD diffractogram was 61.5 nm. The resulting nPOFA has a BET surface area of 145.35 m2/g, which is more than 85% increment in surface area compared to micro-sized POFA. The morphology and elemental studies showed the presence of spherical as well as irregularly shaped and fine nPOFA particles contains with high silicon content. The presence of α-quartz as the major phase of the nPOFA was identified through XRD analysis. The study concludes that nPOFA has the potential as a supplementary cementing material due to the high silica content, high surface area and the unique behaviors of nano-structured particles.

Particle-based optical pressure sensors for 3D pressure mapping.

PubMed

Banerjee, Niladri; Xie, Yan; Chalaseni, Sandeep; Mastrangelo, Carlos H

2015-10-01

This paper presents particle-based optical pressure sensors for in-flow pressure sensing, especially for microfluidic environments. Three generations of pressure sensitive particles have been developed- flat planar particles, particles with integrated retroreflectors and spherical microballoon particles. The first two versions suffer from pressure measurement dependence on particles orientation in 3D space and angle of interrogation. The third generation of microspherical particles with spherical symmetry solves these problems making particle-based manometry in microfluidic environment a viable and efficient methodology. Static and dynamic pressure measurements have been performed in liquid medium for long periods of time in a pressure range of atmospheric to 40 psi. Spherical particles with radius of 12 μm and balloon-wall thickness of 0.5 μm are effective for more than 5 h in this pressure range with an error of less than 5%.

Green synthesis of silver nanoparticles using Coffea arabica seed extract and its antibacterial activity.

PubMed

Dhand, Vivek; Soumya, L; Bharadwaj, S; Chakra, Shilpa; Bhatt, Deepika; Sreedhar, B

2016-01-01

A novel green source was opted to synthesize silver nanoparticles using dried roasted Coffea arabica seed extract. Bio-reduction of silver was complete when the mixture (AgNO3+extract) changed its color from light to dark brown. UV-vis spectroscopy result showed maximum adsorption at 459 nm, which represents the characteristic surface plasmon resonance of nanosilver. X-ray crystal analysis showed that the silver nanoparticles are highly crystalline and exhibit a cubic, face centered lattice with characteristic (111), (200), (220) and (311) orientations. Particles exhibit spherical and ellipsoidal shaped structures as observed from TEM. Composition analysis obtained from SEM-EDXA confirmed the presence of elemental signature of silver. FTIR results recorded a downward shift of absorption bands between 800-1500 cm(-1) indicting the formation of silver nanoparticles. The mean particle size investigated using DLS was found to be in between 20-30 nm respectively. Anti-bacterial activity of silver nanoparticles on E. coli and S. aureus demonstrated diminished bacterial growth with the development of well-defined inhibition zones. Copyright © 2015 Elsevier B.V. All rights reserved.

Soot superaggregates from flaming wildfires and their direct radiative forcing

PubMed Central

Chakrabarty, Rajan K.; Beres, Nicholas D.; Moosmüller, Hans; China, Swarup; Mazzoleni, Claudio; Dubey, Manvendra K.; Liu, Li; Mishchenko, Michael I.

2014-01-01

Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimension Df ≈ 1.8 mobility diameter Dm ≤ 1 μm, and aerodynamic diameter Da ≤ 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic Df ≈ 2.6, Dm > 1 μm, and Da ≤ 300 nm that form via the cluster-dense aggregation mechanism. We present additional observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (Df ≈ 1.8) aggregates, and ≈90% more warming than the volume-equivalent spherical soot particles simulated in climate models. PMID:24981204

Green synthesis of colloidal silver nanoparticles using natural rubber latex extracted from Hevea brasiliensis.

PubMed

Guidelli, Eder José; Ramos, Ana Paula; Zaniquelli, Maria Elisabete D; Baffa, Oswaldo

2011-11-01

Colloidal silver nanoparticles were synthesized by an easy green method using thermal treatment of aqueous solutions of silver nitrate and natural rubber latex (NRL) extracted from Hevea brasiliensis. The UV-Vis spectra detected the characteristic surface plasmonic absorption band around 435 nm. Both NRL and AgNO(3) contents in the reaction medium have influence in the Ag nanoparticles formation. Lower AgNO(3) concentration led to decreased particle size. The silver nanoparticles presented diameters ranging from 2 nm to 100 nm and had spherical shape. The selected area electron diffraction (SAED) patterns indicated that the silver nanoparticles have face centered cubic (fcc) crystalline structure. FTIR spectra suggest that reduction of the silver ions are facilitated by their interaction with the amine groups from ammonia, which is used for conservation of the NRL, whereas the stability of the particles results from cis-isoprene binding onto the surface of nanoparticles. Therefore natural rubber latex extracted from H. brasiliensis can be employed in the preparation of stable aqueous dispersions of silver nanoparticles acting as a dispersing and/or capping agent. Moreover, this work provides a new method for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive. Copyright © 2011 Elsevier B.V. All rights reserved.

The Influence of Different Metal Ions on the Absorption Properties of Nano-Nickel Zinc Ferrite

PubMed Central

Ma, Zhijun; Mang, Changye; Weng, Xingyuan; Si, Liwei; Zhao, Haitao

2018-01-01

The hydrothermal method was used to dope different amounts of Co2+, Mn2+, and Cu2+ in nano-nickel zinc ferrite powder. X-ray diffraction (XRD), a scanning electron microscopy (TEM), and a vector network analyzer (VNA) were used to explore the influence of doping on particle size, morphology, and electromagnetic wave absorption performance. Pure nanometer cobalt nickel zinc ferrite phase was prepared using the hydrothermal method with an increasing Co2+ content. Results showed that the grain type structure changed from a spherical structure to an irregular quadrilateral structure with the average particle size increasing from 35 nm to 60 nm. The lattice constant increased from 0.8352 to 0.8404 nm with Co2+ doping. The increasing Co2+ can change the position of the absorption peak, increase the bandwidth of the absorber, and improve the performance of the materials in GHz low frequency. The doping ratio of Mn2+ can affect the size of the lattice constant, but nanocrystals are easy to reunite without improving the electromagnetic loss. However, the absorbance performance decreases. For the doping of Cu2+, there is an agglomeration phenomenon. When the doping quantity is 0.15, the absorbing wave performance becomes better. PMID:29641477

The Influence of Different Metal Ions on the Absorption Properties of Nano-Nickel Zinc Ferrite.

PubMed

Ma, Zhijun; Mang, Changye; Weng, Xingyuan; Zhang, Qi; Si, Liwei; Zhao, Haitao

2018-04-11

The hydrothermal method was used to dope different amounts of Co 2+ , Mn 2+ , and Cu 2+ in nano-nickel zinc ferrite powder. X-ray diffraction (XRD), a scanning electron microscopy (TEM), and a vector network analyzer (VNA) were used to explore the influence of doping on particle size, morphology, and electromagnetic wave absorption performance. Pure nanometer cobalt nickel zinc ferrite phase was prepared using the hydrothermal method with an increasing Co 2+ content. Results showed that the grain type structure changed from a spherical structure to an irregular quadrilateral structure with the average particle size increasing from 35 nm to 60 nm. The lattice constant increased from 0.8352 to 0.8404 nm with Co 2+ doping. The increasing Co 2+ can change the position of the absorption peak, increase the bandwidth of the absorber, and improve the performance of the materials in GHz low frequency. The doping ratio of Mn 2+ can affect the size of the lattice constant, but nanocrystals are easy to reunite without improving the electromagnetic loss. However, the absorbance performance decreases. For the doping of Cu 2+ , there is an agglomeration phenomenon. When the doping quantity is 0.15, the absorbing wave performance becomes better.

Green synthesis, characterization and catalytic activity of silver nanoparticles using Cassia auriculata flower extract separated fraction

NASA Astrophysics Data System (ADS)

Muthu, Karuppiah; Priya, Sethuraman

2017-05-01

Cassia auriculata L., the flower aqueous extract was fractionated by separating funnel using n-hexane (A1), chloroform (A2), ethyl acetate (A3) and triple distilled water (A4). The A4 fraction was concentrated and determined the presence of preliminary phytochemicals such as tannins, flavonoids, glycosides, carbohydrates and polyphenolic compounds. These phytochemical compounds acted as reducing as well as a stabilizing agent in the green synthesis of Ag NPs from aqueous silver ions. Initially, the colour change and UV-vis absorbance surface Plasmon resonance strong, wide band located at 435 nm has confirmed the synthesis of Ag NPs. The X-ray diffraction (XRD) pattern of Ag NPs shows a face-centered cubic crystal structure. The observed values were calculated by Debye-Scherrer equation to theoretical confirms the particle size of 18 nm. The surface morphology of Ag NPs was viewed by HRTEM, the particles are spherical and triangle shapes with sizes from 10 to 35 nm. Further, the Ag NPs was effective catalytic activity in the reduction of highly environmental polluted organic compounds of 4-nitrophenol and methyl orange. The green synthesis of Ag NPs seems to eco-friendly, cost-effective, conventional one spot synthesis and greater performance of catalytic degradation of environmentally polluted organic dyes.

Physicochemical characterisation of combustion particles from vehicle exhaust and residential wood smoke

PubMed Central

Kocbach, Anette; Li, Yanjun; Yttri, Karl E; Cassee, Flemming R; Schwarze, Per E; Namork, Ellen

2006-01-01

Background Exposure to ambient particulate matter has been associated with a number of adverse health effects. Particle characteristics such as size, surface area and chemistry seem to influence the negative effects of particles. In this study, combustion particles from vehicle exhaust and wood smoke, currently used in biological experiments, were analysed with respect to microstructure and chemistry. Methods Vehicle exhaust particles were collected in a road tunnel during two seasons, with and without use of studded tires, whereas wood smoke was collected from a stove with single-stage combustion. Additionally, a reference diesel sample (SRM 2975) was analysed. The samples were characterised using transmission electron microscopy techniques (TEM/HRTEM, EELS and SAED). Furthermore, the elemental and organic carbon fractions were quantified using thermal optical transmission analysis and the content of selected PAHs was determined by gas chromatography-mass spectrometry. Results Carbon aggregates, consisting of tens to thousands of spherical primary particles, were the only combustion particles identified in all samples using TEM. The tunnel samples also contained mineral particles originating from road abrasion. The geometric diameters of primary carbon particles from vehicle exhaust were found to be significantly smaller (24 ± 6 nm) than for wood smoke (31 ± 7 nm). Furthermore, HRTEM showed that primary particles from both sources exhibited a turbostratic microstructure, consisting of concentric carbon layers surrounding several nuclei in vehicle exhaust or a single nucleus in wood smoke. However, no differences were detected in the graphitic character of primary particles from the two sources using SAED and EELS. The total PAH content was higher for combustion particles from wood smoke as compared to vehicle exhaust, whereas no source difference was found for the ratio of organic to total carbon. Conclusion Combustion particles from vehicle exhaust and residential wood smoke differ in primary particle diameter, microstructure, and PAH content. Furthermore, the analysed samples seem suitable for assessing the influence of physicochemical characteristics of particles on biological responses. PMID:16390554

Simulation and scaling analysis of a spherical particle-laden blast wave

NASA Astrophysics Data System (ADS)

Ling, Y.; Balachandar, S.

2018-02-01

A spherical particle-laden blast wave, generated by a sudden release of a sphere of compressed gas-particle mixture, is investigated by numerical simulation. The present problem is a multiphase extension of the classic finite-source spherical blast-wave problem. The gas-particle flow can be fully determined by the initial radius of the spherical mixture and the properties of gas and particles. In many applications, the key dimensionless parameters, such as the initial pressure and density ratios between the compressed gas and the ambient air, can vary over a wide range. Parametric studies are thus performed to investigate the effects of these parameters on the characteristic time and spatial scales of the particle-laden blast wave, such as the maximum radius the contact discontinuity can reach and the time when the particle front crosses the contact discontinuity. A scaling analysis is conducted to establish a scaling relation between the characteristic scales and the controlling parameters. A length scale that incorporates the initial pressure ratio is proposed, which is able to approximately collapse the simulation results for the gas flow for a wide range of initial pressure ratios. This indicates that an approximate similarity solution for a spherical blast wave exists, which is independent of the initial pressure ratio. The approximate scaling is also valid for the particle front if the particles are small and closely follow the surrounding gas.

Simulation and scaling analysis of a spherical particle-laden blast wave

NASA Astrophysics Data System (ADS)

Ling, Y.; Balachandar, S.

2018-05-01

A spherical particle-laden blast wave, generated by a sudden release of a sphere of compressed gas-particle mixture, is investigated by numerical simulation. The present problem is a multiphase extension of the classic finite-source spherical blast-wave problem. The gas-particle flow can be fully determined by the initial radius of the spherical mixture and the properties of gas and particles. In many applications, the key dimensionless parameters, such as the initial pressure and density ratios between the compressed gas and the ambient air, can vary over a wide range. Parametric studies are thus performed to investigate the effects of these parameters on the characteristic time and spatial scales of the particle-laden blast wave, such as the maximum radius the contact discontinuity can reach and the time when the particle front crosses the contact discontinuity. A scaling analysis is conducted to establish a scaling relation between the characteristic scales and the controlling parameters. A length scale that incorporates the initial pressure ratio is proposed, which is able to approximately collapse the simulation results for the gas flow for a wide range of initial pressure ratios. This indicates that an approximate similarity solution for a spherical blast wave exists, which is independent of the initial pressure ratio. The approximate scaling is also valid for the particle front if the particles are small and closely follow the surrounding gas.

Sheet-like assemblies of spherical particles with point-symmetrical patches.

PubMed

Mani, Ethayaraja; Sanz, Eduardo; Roy, Soumyajit; Dijkstra, Marjolein; Groenewold, Jan; Kegel, Willem K

2012-04-14

We report a computational study on the spontaneous self-assembly of spherical particles into two-dimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far. We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin--a quasi-spherical protein.

Biosynthesis and characterization of Acalypha indica mediated copper oxide nanoparticles and evaluation of its antimicrobial and anticancer activity.

PubMed

Sivaraj, Rajeshwari; Rahman, Pattanathu K S M; Rajiv, P; Narendhran, S; Venckatesh, R

2014-08-14

Copper oxide nanoparticles were synthesized by biological method using aqueous extract of Acalypha indica leaf and characterized by UV-visible spectroscopy, XRD, FT-IR, SEM TEM and EDX analysis. The synthesised particles were highly stable, spherical and particle size was in the range of 26-30 nm. The antimicrobial activity of A.indica mediated copper oxide nanoparticles was tested against selected pathogens. Copper oxide nanoparticles showed efficient antibacterial and antifungal effect against Escherichia coli, Pseudomonas fluorescens and Candida albicans. The cytotoxicity activity of A.indica mediated copper nanoparticles was evaluated by MTT assay against MCF-7 breast cancer cell lines and confirmed that copper oxide nanoparticles have cytotoxicity activity. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of solid lipid nanoparticles as drug carriers for levothyroxine sodium with in vitro drug delivery kinetic characterization.

PubMed

Rostami, E; Kashanian, S; Azandaryani, A H

2014-05-01

The aim of this work was to produce and characterize solid lipid nanoparticles (SLN) containing levothyroxine sodium for oral administration, and to evaluate the kinetic release of these colloidal carriers. SLNs were prepared by microemulsion method. The particle size and zeta potential of levothyroxine sodium-loaded SLNs were determined to be around 153 nm,-43 mV (negatively charged), respectively by photon correlation spectroscopy. The levothyroxine entrapment efficiency was over 98%. Shape and surface morphology were determined by TEM and SEM. They revealed fairly spherical shape of nanoparticles.SLN formulation was stable over a period of 6 months. There were no significant changes in particle size, zeta potential and polydispersity index and entrapment efficiency, indicating that the developed SLNs were fairly stable.

Interaction of bilirubin with Ag and Au ions: green synthesis of bilirubin-stabilized nanoparticles

NASA Astrophysics Data System (ADS)

Shukla, Shashi P.; Roy, Mainak; Mukherjee, Poulomi; Tyagi, A. K.; Mukherjee, Tulsi; Adhikari, Soumyakanti

2012-07-01

We report a simple green chemistry to synthesize and stabilize monodispersed silver and gold nanoparticles sols by reducing aqueous solution of the respective metal salts in the presence of bilirubin (BR). No additional capping agent was used in the process of stabilization of the nanoparticles. As a completely new finding, we have observed that BR known to be toxic at higher concentration in one hand and conversely an antioxidant at physiological concentration reduces these metal ions to form the respective metal nanoparticles. Moreover, BR and its oxidized products also serve as capping agents to the nanoparticles. The particles were characterized by transmission electron microscopy. BR and its oxidized products capped nanoparticles are stable for months. The UV-Vis absorption spectra of the silver sol show the plasmon peak of symmetric spherical particles which was further reflected in the TEM images. The sizes of the silver particles were about 5 nm. These silver particles showed reasonably high antibacterial activity in Gram negative wild type E. coli. In the case of interaction of BR with gold ions, we could obtain cubic gold nanoparticles of average sizes 20-25 nm. Possible modes of anchorage of BR and/its oxidized products to silver nanoparticles were demonstrated by surface-enhanced resonance Raman spectroscopy (SERS) that in turn demonstrated the feasibility of using these nanoparticles as SERS substrates.

Hydrogels in endovascular embolization. II. Clinical use of spherical particles.

PubMed

Horák, D; Svec, F; Kálal, J; Adamyan, A A; Volynskii, Y D; Voronkova, O S; Kokov, L S; Gumargalieva, K Z

1986-11-01

In this study we report the results of clinical experiments, obtained with spherical particles made from poly(2-hydroxyethyl methacrylate) used in the embolization of arteriovenous anastomoses, in the suppression of pulmonary haemorrhage and haemoptysis and in the occlusion of some other arteries. So far we have used these particles in the treatment of 187 patients. It must be stressed that the advantage of spherical particles consists in the simplicity of their introduction into the blood vessel through a catheter, while in the blood vessel itself the particle swells in blood still more, when compared with the particle size in saline. This results in an immediate and permanent haemostatic effect. No revascularization occurs.

Mesospheric Ice particle sizes derived from two-color SME (1982-1986) and SNOE (1998- 2002) UV satellite measurements

NASA Astrophysics Data System (ADS)

Thomas, G. E.; Bailey, S. M.; Merkel, A. W.; Baumgarten, G.; Rusch, D. W.

2006-12-01

The UV spectrum of scattering from mesospheric ice particles (Polar Mesospheric Clouds) contains information on particle size, and on the microphysics of the cold summertime mesopause region. Nearly identical Ultraviolet Spectrometers were flown on both the Solar Mesosphere Explorer (SME) and Student Nitric Oxide Explorer (SNOE) satellites, both in sun-synchronous orbits reaching deep within the cold polar regions where PMC occur. The instruments measured two wavelengths simultaneously (265 and 296 nm for SME, 215 and 237 nm for SNOE), and detected PMC over a grand total of twenty PMC seasons, each covering five year periods (1982-1986 for SME) and (1998-2002 for SNOE). Using the well well-known wavelength dependence of Rayleigh scattering from thje cloud-free mesosphere we calibrate the two channels with respect to each other . The resulting accurate color ratios are then analyzed taking the brightness of the clouds into account, etc. Previous studies of the available spectral data (Rapp et al., 2006) suggested that non-spherical particles of large aspect ratios are required for consistency with the data then available. We test their results on a much more extensive data set for a large number of PMC seasons. Through the use of modern scattering theory, and predictions of the size distribution from microphysical models, such as the CARMA model, we report particle size and shape regimes which are consistent with the color ratios, obtained with different scattering geometries in both northern and southern hemispheres.

Collisions of droplets on spherical particles

NASA Astrophysics Data System (ADS)

Charalampous, Georgios; Hardalupas, Yannis

2017-10-01

Head-on collisions between droplets and spherical particles are examined for water droplets in the diameter range between 170 μm and 280 μm and spherical particles in the diameter range between 500 μm and 2000 μm. The droplet velocities range between 6 m/s and 11 m/s, while the spherical particles are fixed in space. The Weber and Ohnesorge numbers and ratio of droplet to particle diameter were between 92 < We < 1015, 0.0070 < Oh < 0.0089, and 0.09 < Ω < 0.55, respectively. The droplet-particle collisions are first quantified in terms of the outcome. In addition to the conventional deposition and splashing regimes, a regime is observed in the intermediate region, where the droplet forms a stable crown, which does not breakup but propagates along the particle surface and passes around the particle. This regime is prevalent when the droplets collide on small particles. The characteristics of the collision at the onset of rim instability are also described in terms of the location of the film on the particle surface and the orientation and length of the ejected crown. Proper orthogonal decomposition identified that the first 2 modes are enough to capture the overall morphology of the crown at the splashing threshold.

Effect of pH on the extra cellular synthesis of gold and silver nanoparticles by Saccharomyces cerevisae.

PubMed

Lim, Hyun-Ah; Mishra, Amrita; Yun, Soon-Il

2011-01-01

In the present study, the synthesis of gold and silver nanoparticles was investigated using the culture supernatant broth of the yeast Saccharomyces cerevisae. Gold nanoparticles were formed within 24 hours of gold ion coming in contact with the culture supernatant broth. In case of silver the reduction process took 48 hours. The synthesized nanoparticles were investigated by UV-Visible spectroscopy. Distinct surface plasmon peaks were observed at 540 nm and 415 nm for gold and silver nanoparticles respectively. Bio-TEM micrographs of the synthesized nanoparticles indicated that the particles were well dispersed and near spherical in shape. The size range of the gold and silver nanoparticles was around 20-100 nm and 5-20 nm respectively. XRD patterns showed the presence of three distinct peaks corresponding to gold and silver nanoparticles respectively. A pH range of 4 to 6 and 8 to 10 favored optimum synthesis of gold and silver nanoparticles respectively. The process of reduction being extra cellular could be used in future for downstream processing in an eco friendly manner.

Anti-fibrillogenic properties of phthalocyanines: effect of the out-of-plane ligands.

PubMed

Kovalska, V; Cherepanov, V; Losytskyy, M; Chernii, S; Senenko, A; Chernii, V; Tretyakova, I; Yarmoluk, S; Volkov, S

2014-12-15

The axially-coordinated phthalocyanines were previously reported as agents possessing strong anti-fibrillogenic properties. In the presented study we used the atomic force microscopy to investigate the intermediates and the products of insulin aggregation reaction formed in the presence of Zr and Hf phthalocyanine complexes that contain out-of-plane ligands of different size and nature. It is shown that while phthalocyanine-free insulin generated mostly amyloid fibrils with a diameter of 2-8nm and a length of up to 5μm, the presence of phthalocyanines with spatial bulky ligands (PcZrDbm2) leads to the redirection of the fibrillization reaction to the formation of the spherical oligomer aggregates with a diameter of 4-12nm. At the same time the phthalocyanine complex PcHfCl2 having the small-volume ligands induces the formation of large size insulin aggregates with a height of about 100nm that are supposed to be amorphous species. The study of the aggregation intermediates showed the certain similarity of the reaction passing for phthalocyanine-free insulin and insulin in the presence of PcZrDbm2. The large-size amorphous species were observed at the beginning of reaction, later they dissociated, leading to the formation and growth of the smaller size particles. The amyloid-sensitive cyanine dye 7519 demonstrates the strong fluorescent response both in the presence of fibrils and spherical oligomers, while it is non-sensitive to amorphous aggregates. Copyright © 2014 Elsevier Ltd. All rights reserved.

Uniwavelength lidar sensitivity to spherical aerosol microphysical properties for the interpretation of Lagrangian stratospheric observations

NASA Astrophysics Data System (ADS)

Jumelet, Julien; David, Christine; Bekki, Slimane; Keckhut, Philippe

2009-01-01

The determination of stratospheric particle microphysical properties from multiwavelength lidar, including Rayleigh and/or Raman detection, has been widely investigated. However, most lidar systems are uniwavelength operating at 532 nm. Although the information content of such lidar data is too limited to allow the retrieval of the full size distribution, the coupling of two or more uniwavelength lidar measurements probing the same moving air parcel may provide some meaningful size information. Within the ORACLE-O3 IPY project, the coordination of several ground-based lidars and the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) space-borne lidar is planned during measurement campaigns called MATCH-PSC (Polar Stratospheric Clouds). While probing the same moving air masses, the evolution of the measured backscatter coefficient (BC) should reflect the variation of particles microphysical properties. A sensitivity study of 532 nm lidar particle backscatter to variations of particles size distribution parameters is carried out. For simplicity, the particles are assumed to be spherical (liquid) particles and the size distribution is represented with a unimodal log-normal distribution. Each of the four microphysical parameters (i.e. log-normal size distribution parameters, refractive index) are analysed separately, while the three others are remained set to constant reference values. Overall, the BC behaviour is not affected by the initial values taken as references. The total concentration (N0) is the parameter to which BC is least sensitive, whereas it is most sensitive to the refractive index (m). A 2% variation of m induces a 15% variation of the lidar BC, while the uncertainty on the BC retrieval can also reach 15%. This result underlines the importance of having both an accurate lidar inversion method and a good knowledge of the temperature for size distribution retrieval techniques. The standard deviation ([sigma]) is the second parameter to which BC is most sensitive to. Yet, the impact of m and [sigma] on BC variations is limited by the realistic range of their variations. The mean radius (rm) of the size distribution is thus the key parameter for BC, as it can vary several-fold. BC is most sensitive to the presence of large particles. The sensitivity of BC to rm and [sigma] variations increases when the initial size distributions are characterized by low rm and large [sigma]. This makes lidar more suitable to detect particles growing on background aerosols than on volcanic aerosols.

The necessity of microscopy to characterize the optical properties of size-selected, nonspherical aerosol particles.

PubMed

Veghte, Daniel P; Freedman, Miriam A

2012-11-06

It is currently unknown whether mineral dust causes a net warming or cooling effect on the climate system. This uncertainty stems from the varied and evolving shape and composition of mineral dust, which leads to diverse interactions of dust with solar and terrestrial radiation. To investigate these interactions, we have used a cavity ring-down spectrometer to study the optical properties of size-selected calcium carbonate particles, a reactive component of mineral dust. The size selection of nonspherical particles like mineral dust can differ from spherical particles in the polydispersity of the population selected. To calculate the expected extinction cross sections, we use Mie scattering theory for monodisperse spherical particles and for spherical particles with the polydispersity observed in transmission electron microscopy images. Our results for calcium carbonate are compared to the well-studied system of ammonium sulfate. While ammonium sulfate extinction cross sections agree with Mie scattering theory for monodisperse spherical particles, the results for calcium carbonate deviate at large and small particle sizes. We find good agreement for both systems, however, between the calculations performed using the particle images and the cavity ring-down data, indicating that both ammonium sulfate and calcium carbonate can be treated as polydisperse spherical particles. Our results indicate that having an independent measure of polydispersity is essential for understanding the optical properties of nonspherical particles measured with cavity ring-down spectroscopy. Our combined spectroscopy and microscopy techniques demonstrate a novel method by which cavity ring-down spectroscopy can be extended for the study of more complex aerosol particles.

Equilibrium magnetic states in individual hemispherical permalloy caps

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

Streubel, Robert; Schmidt, Oliver G.; Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107 Chemnitz

2012-09-24

The magnetization distributions in individual soft magnetic permalloy caps on non-magnetic spherical particles with sizes ranging from 50 to 800 nm are investigated. We experimentally visualize the magnetic structures at the resolution limit of the x-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM). By analyzing the so-called tail contrast in XMCD-PEEM, the spatial resolution is significantly enhanced, which allowed us to explore magnetic vortices and their displacement on curved surfaces. Furthermore, cap nanostructures are modeled as extruded hemispheres to determine theoretically the phase diagram of equilibrium magnetic states. The calculated phase diagram agrees well with the experimental observations.

A kinetic model for heterogeneous condensation of vapor on an insoluble spherical particle.

PubMed

Luo, Xisheng; Fan, Yu; Qin, Fenghua; Gui, Huaqiao; Liu, Jianguo

2014-01-14

A kinetic model is developed to describe the heterogeneous condensation of vapor on an insoluble spherical particle. This new model considers two mechanisms of cluster growth: direct addition of water molecules from the vapor and surface diffusion of adsorbed water molecules on the particle. The effect of line tension is also included in the model. For the first time, the exact expression of evaporation coefficient is derived for heterogeneous condensation of vapor on an insoluble spherical particle by using the detailed balance. The obtained expression of evaporation coefficient is proved to be also correct in the homogeneous condensation and the heterogeneous condensation on a planar solid surface. The contributions of the two mechanisms to heterogeneous condensation including the effect of line tension are evaluated and analysed. It is found that the cluster growth via surface diffusion of adsorbed water molecules on the particle is more important than the direct addition from the vapor. As an example of our model applications, the growth rate of the cap shaped droplet on the insoluble spherical particle is derived. Our evaluation shows that the growth rate of droplet in heterogeneous condensation is larger than that in homogeneous condensation. These results indicate that an explicit kinetic model is benefit to the study of heterogeneous condensation on an insoluble spherical particle.

Optical properties of titanium-di-oxide (TiO2) prepared by hydrothermal method

NASA Astrophysics Data System (ADS)

Rahman, Kazi Hasibur; Biswas, Sayari; Kar, Asit Kumar

2018-05-01

Research on titanate and its derived TiO2 nanostructures with large specific surface area have received great attention due to their enhanced efficiency in photocatalysis, DSSC etc. Here, in this communication TiO2 powder has been prepared by hydrothermal method at 180 °C. In this work we have shown the changes in optical properties of the powder with two different sintering temperatures ‒ 500 °C and 800 °C. The as prepared powder was also studied. FESEM images show spherical particles for the as prepared samples which look more like agglomeration after sintering. Band gaps of the prepared samples were calculated from UV-Vis spectroscopy which lies in the range 2.85 eV ‒ 3.13 eV. The photoluminescence (PL) spectra of the prepared samples were recorded at room temperature in the range of 300‒700 nm. It shows two distinct peaks at 412 nm and 425 nm.

Investigation of organic solvents assisted nano magnesium oxide nanoparticles and their structural, morphological, optical and antimicrobial performance

NASA Astrophysics Data System (ADS)

Deepa, B.; Rajendran, V.

2018-01-01

Investigation on the structural, morphological, optical studies and antimicrobial performance of organic solvent assisted magnesium oxide (MgO) nanoparticles. Nanoparticles are in 16-18 nm of grain size prepared by sol-gel method. The XRD studies shows as synthesized products are in cubic phase with periclase structurer. The well disperesd spherical morphology were obtained in SEM and TEM. The organic solvent methanol had profound effects on the size of the nano particles. The optical absorption edge energy was present in UV region and the corresponding band gap energy values are 4.5 and 4.9 eV for water with ethanol and methanol mediated MgO sample respectively. The PL emission spectrum has a emission peak at 340 and 353 nm which is due to surface defects. The obtained MgO nanoparticles showed superior antimicrobial activities for the gram positive, gram negative and fungus strains using the ELISA reader at 450 nm.

Comparison study on biosynthesis of silver nanoparticles using fresh and hot air oven dried IMPERATA CYLINDRICA leaf

NASA Astrophysics Data System (ADS)

Najmi Bonnia, Noor; Fairuzi, Afiza Ahmad; Akhir, Rabiatuladawiyah Md.; Yahya, Sabrina M.; Rani, Mohd Azri Ab; Ratim, Suzana; Rahman, Norafifah A.; Akil, Hazizan Md

2018-01-01

The perennial rhizomatous grass; Imperata cylindrica (I. cylindrica) has been reported rich in various phytochemicals. In present study, silver nanoparticles were synthesized from aqueous leaf extract of I. cylindrica at two different leaf conditions; fresh leaves and hot-air oven dried leaves. Biosynthesized silver nanoparticles were characterized by UV-visible spectroscopy, field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Maximum absorption was recorded between 400 nm to 500 nm. FESEM analysis revealed that the silver nanoparticles predominantly form spherical shapes. The particles sizes were ranging from 22-37 nm. The elemental composition of the synthesized silver nanoparticles was confirmed by using energy dispersive X-ray spectroscopy (EDX) analysis. Fourier transform infrared spectroscopy (FTIR) confirmed the reducing and stabilizing actions came from biomolecules associated with I. cylindrica leaf extract. Thus in this investigation, an environmentally safe method to synthesized silver nanoparticles using local plant extract was successfully established.

Surface plasmon resonance enhanced light absorption and wavelength tuneable in gold-coated iron oxide spherical nanoparticle

NASA Astrophysics Data System (ADS)

Dasri, Thananchai; Chingsungnoen, Artit

2018-06-01

Surface plasmon in nano-sized particles, such as gold, silver, copper and their composites, has recently attracted a great deal of attention due to its possible uses in many applications, especially in life sciences. It is desirable for application devices with a tenability of surface plasmon wavelength and optical properties enhancement. This article presents enhanced optical light absorption and tunable wavelength in gold-coated magnetite (Fe3O4@Au core-shell) nanoparticles embedded in water using the theoretical method of discrete dipole approximation (DDA). The absorption spectra in the wavelengths from 350 to 900 nm were found to be the spectra obtained from Fe3O4@Au core-shell nanoparticles, and when compared with pure Fe3O4 nanoparticles, the surface plasmon resonance can be enhanced and tuned over the entire visible spectrum (viz. 350-800 nm) of the electromagnetic spectrum by varying the Au shell thickness (2-5 nm). Similarly, the Faraday rotation spectra can also be obtained.

ZrO2:Sm3+ nanophosphor: synthesis, Rietveld refinement, optical and thermoluminescent properties

NASA Astrophysics Data System (ADS)

Ponkumar, S.; Janaki, K.; Prakashbabu, D.; Ramalingam, H. B.; Munirathnam, K.; Sreekanth, T. V. M.; Dhoble, S. J.

2018-02-01

We have synthesized undoped and Sm3+ ions doped ZrO2 nanophosphors by solution combustion method. These nanophosphors crystallized in cubic structure. Rietveld refinement of the samples was performed to estimate lattice parameters. Spherical particles with the sizes of 10-25 nm were observed by transmission electron microscopy. Photoluminescence and thermoluminescence (TL) properties of samples were investigated. Under 400 nm excitation, the nanophosphors have intense red emission at 600 nm. The color coordinates (0.67, 0.33) were located in the red region of CIE diagram. TL properties of nanophosphors were studied by exposing the samples to γ-rays. 5 mol% Sm3+ doped ZrO2 nanophosphor has shown maximum TL intensity after γ-irradiation. To test suitability of the nanophosphors for practical application in dosimetry, the 5 mol% Sm3+ doped ZrO2 sample was irradiated by 14 MeV electron beam in various electron fluence ranging from 100 to 900 Gy and their TL response was recorded.

Synthesis of Nm-PHB (nanomelanin-polyhydroxy butyrate) nanocomposite film and its protective effect against biofilm-forming multi drug resistant Staphylococcus aureus.

PubMed

Kiran, George Seghal; Jackson, Stephen A; Priyadharsini, Sethu; Dobson, Alan D W; Selvin, Joseph

2017-08-22

Melanin is a dark brown ubiquitous photosynthetic pigment which have many varied and ever expanding applications in fabrication of radio-protective materials, food packaging, cosmetics and in medicine. In this study, melanin production in a Pseudomonas sp. which was isolated from the marine sponge Tetyrina citirna was optimized employing one-factor at a time experiments and characterized for chemical nature and stability. Following sonication nucleated nanomelanin (Nm) particles were formed and evaluated for antibacterial and antioxidant properties. Nanocomposite film was fabricated using combinations (% w/v) of polyhydroxy butyrate-nanomelanin (PHB:Nm) blended with 1% glycerol. The Nm was found to be spherical in shape with a diameter of 100-140 nm and showed strong antimicrobial activity against both Gram positive and Gram negative bacteria. The Nm-PHB nanocomposite film was homogeneous, smooth, without any cracks, and flexible. XRD and DSC data indicated that the film was crystalline in nature, and was thermostable up to 281.87 °C. This study represents the first report on the synthesis of Nm and fabrication of Nm-PHB nanocomposite film which show strong protective effect against multidrug resistant Staphyloccoccus aureus. Thus this Nm-PHB nanocomposite film may find utility as packaging material for food products by protecting the food products from oxidation and bacterial contamination.

Morphology controlled synthesis of nanoporous Co3O4 nanostructures and their charge storage characteristics in supercapacitors.

PubMed

Deori, Kalyanjyoti; Ujjain, Sanjeev Kumar; Sharma, Raj Kishore; Deka, Sasanka

2013-11-13

Cubic spinel Co3O4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co3O4 particles along [111] and [110] directions. UV-vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400-500 nm and 700-800 nm, respectively, related to the ligand to metal charge transfer events (O(2-) → Co(2+,3+)). Under the electrochemical study in two electrode assembly system (Co3O4/KOH/Co3O4) without adding any large area support or a conductive filler, the hexagonal platelet Co3O4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g(-1)), energy density 42.3 Wh kg(-1) and power density 1.56 kW kg(-1) at current density of 0.5 Ag(-1), that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co3O4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.

Characterization and evaluation of 5-fluorouracil-loaded solid lipid nanoparticles prepared via a temperature-modulated solidification technique.

PubMed

Patel, Meghavi N; Lakkadwala, Sushant; Majrad, Mohamed S; Injeti, Elisha R; Gollmer, Steven M; Shah, Zahoor A; Boddu, Sai Hanuman Sagar; Nesamony, Jerry

2014-12-01

The aim of this research was to advance solid lipid nanoparticle (SLN) preparation methodology by preparing glyceryl monostearate (GMS) nanoparticles using a temperature-modulated solidification process. The technique was reproducible and prepared nanoparticles without the need of organic solvents. An anticancer agent, 5-fluorouracil (5-FU), was incorporated in the SLNs. The SLNs were characterized by particle size analysis, zeta potential analysis, differential scanning calorimetry (DSC), infrared spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), drug encapsulation efficiency, in vitro drug release, and in vitro cell viability studies. Particle size of the SLN dispersion was below 100 nm, and that of redispersed lyophilizates was ~500 nm. DSC and infrared spectroscopy suggested that the degree of crystallinity did not decrease appreciably when compared to GMS. TEM and AFM images showed well-defined spherical to oval particles. The drug encapsulation efficiency was found to be approximately 46%. In vitro drug release studies showed that 80% of the encapsulated drug was released within 1 h. In vitro cell cultures were biocompatible with blank SLNs but demonstrated concentration-dependent changes in cell viability to 5-FU-loaded SLNs. The 5-FU-loaded SLNs can potentially be utilized in an anticancer drug delivery system.

The green synthesis of fine particles of gold using an aqueous extract of Monotheca buxifolia (Flac.)

NASA Astrophysics Data System (ADS)

Anwar, Natasha; Khan, Abbas; Shah, Mohib; Azam, Andaleeb; Zaman, Khair; Parven, Zahida

2016-12-01

This study deals with the synthesis and physicochemical investigation of gold nanoparticles using an aqueous extract of Monotheca buxifolia (Flac.). On the treatment of aqueous solution of tetrachloroauric acid with the plant extract, gold nanoparticles were rapidly fabricated. The synthesized particles were characterized by UV-Vis spectrophotometry (UV), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX) and Scanning electron microscopy (SEM). The formation of AuNPs was confirmed by noting the change in color through visual observations as well as via UV-Vis spectroscopy. UV‒Vis spectrum of the aqueous medium containing gold nanoparticles showed an absorption peak at around 540 nm. FTIR was used to identify the chemical composition of gold nanoparticles and Au-capped plant extract. The presence of elemental gold was also confirmed through EDX analysis. SEM analysis of the gold nanoparticles showed that they have a uniform spherical shape with an average size in the range of 70-78 nm. This green system showed to be better capping and stabilizing agent for the fine particles. Further, the antioxidant activity of Monotheca buxifolia (Flac.) extract and Au-capped with the plant extract was also evaluated using FeCl3/K3[Fe(CN)]6 in vitro assay.

Single-wall carbon nanohorns (SWNHs) inhibited proliferation of human glioma cells and promoted its apoptosis

NASA Astrophysics Data System (ADS)

Li, Yunjun; Zhang, Jinqian; Zhao, Ming; Shi, Zujin; Chen, Xin; He, Xihui; Han, Nanyin; Xu, Ruxiang

2013-08-01

Although single-wall carbon nanohorns (SWNHs) have been demonstrated to accumulate to cytotoxic levels within organs of various animal models and cell types, they have been exploited for cancer therapies. The role of SWNHs in human glioma cell lines was unclear. To address this question, the research about direct role of SWNHs on the growth, proliferation, and apoptosis of human glioma cell lines (U87, U251, and U373) had been performed. Our results indicate that particle size of SWNHs in water is between 342 and 712 nm, the films of SEM show that SWNHs on PS surface are individual particles. SWNHs significantly delayed mitotic entry of human glioma cell lines cells, and inhibited its proliferation in a time- and dose-dependent manner. SWNHs induced a significant increase in G1 phase and inhibition of S phase followed the gradually increasing concentrations. SWNHs in human glioma cell lines cells significantly induced apoptosis followed by their gradually increasing concentrations. The TEM images showed that individual spherical SWNHs particles smaller than 100 nm in diameters were localized inside lysosomes of human glioma cell lines. SWNHs inhibited mitotic entry, growth, and proliferation of human glioma cell lines, and promoted its apoptosis. SWNHs may be a novel opportunity or method for the research on treatment of human glioma.

Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity.

PubMed

Bindhu, M R; Umadevi, M

2013-01-15

Synthesis of silver nanoparticles using leaf extract of Hibiscus cannabinus has been investigated. The influences of different concentration of H. cannabinus leaf extract, different metal ion concentration and different reaction time on the above cases on the synthesis of nanoparticles were evaluated. The synthesized nanoparticles were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The prepared silver nanoparticles were monodispersed, spherical in shape with the average particle size of 9 nm and shows surface plasmon peak at 446 nm. The study also reveals that the ascorbic acid present in H. cannabinus leaf extract has been used as reducing agent. The prepared silver nanoparticle shows good antimicrobial activity against Escherichia coli, Proteus mirabilis and Shigella flexneri. Copyright © 2012 Elsevier B.V. All rights reserved.

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

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

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately andin situusing crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormal size distribution.more » The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. This work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Ultra-small (r<2 nm), stable (>1 year) copper oxide quantum dots with wide band gap

NASA Astrophysics Data System (ADS)

Talluri, Bhusankar; Prasad, Edamana; Thomas, Tiju

2018-01-01

Practical use of quantum dots (QDs) will rely on processes that enable (i) monodispersity, (ii) scalability, (iii) green approaches to manufacturing them. We demonstrate, a green, rapid, soft chemical, and industrial viable approach for obtaining quasi-spherical, ultra-small (size ∼2.4 ± 0.5 nm), stable (>1 yr), and monodispersed copper oxide QDs (r < 2 nm) based on digestive ripening (DR). These QDs show wide band gap (Eg∼5.3 eV), this substantial band gap increase is currently inexplicable using Brus' equation, and is likely due to surface chemistry of these strongly confined QDs. Capping with triethanolamine (TEA) results in reduction in the average particle diameter from 9 ± 4 nm to 2.4 ± 0.5 nm and an increase of zeta potential (ξ) from +12 ± 2 mV to +31 ± 2 mV. XPS and electron diffraction studies indicate that capped copper oxide QDs which have TEA chemisorbed on its surface are expected to partly stabilize Cu (I) resulting in mixed phase in these QDs. This result is likely to inform efforts that involve achieving monodisperse microstructures and nano-structures, of oxides with a tendency for multivalency.

Formation and characterization of high surface area thermally stabilized titania/silica composite materials via hydrolysis of titanium(IV) tetra-isopropoxide in sols of spherical silica particles.

PubMed

Khalil, Kamal M S; Elsamahy, Ahmed A; Elanany, Mohamed S

2002-05-15

A direct synthetic route leading to titania particles dispersed on nonporous spherical silica particles has been investigated; 5, 10, and 20% (w/w) titania/silica sols mixtures were achieved via hydrolyzation of titanium tetra-isopropxide solution in the mother liquor of a freshly prepared sol of spherical silica particles (Stöber particles). Titania/silica materials were produced by subsequent drying and calcination of the xerogels so obtained for 3 h at 400 and 600 degrees C. The materials were investigated by means of thermal analyses (TGA and DSC), FT-IR, N(2) gas adsorption-desorption, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM). In spite of the low surface area (13.1 m(2)/g) of the pure spherical silica particles calcined at 400 degrees C, high surface area and mesoporous texture titania/silica materials were obtained (e.g., S(BET) ca. 293 m(2)/g for the 10% titania/silica calcined at 400 degrees C). Moreover, the materials were shown to be amorphous toward XRD up to 600 degrees C, while reasonable surface areas were preserved. It has been concluded that dispersion of titania particles onto the surface of the nonporous spherical silica particles increase their roughness, therefore leading to composite materials of less firm packing and mesoporosity.

Enhanced photo-response of porous silicon photo-detectors by embeddingTitanium-dioxide nano-particles

NASA Astrophysics Data System (ADS)

Ali, Hiba M.; Makki, Sameer A.; Abd, Ahmed N.

2018-05-01

Porous silicon (n-PS) films can be prepared by photoelectochemical etching (PECE) Silicon chips n - types with 15 (mA / cm2), in 15 minutes etching time on the fabrication nano-sized pore arrangement. By using X-ray diffraction measurement and atomic power microscopy characteristics (AFM), PS was investigated. It was also evaluated the crystallites size from (XRD) for the PS nanoscale. The atomic force microscopy confirmed the nano-metric size chemical fictionalization through the electrochemical etching that was shown on the PS surface chemical composition. The atomic power microscopy checks showed the roughness of the silicon surface. It is also notified (TiO2) preparation nano-particles that were prepared by pulse laser eradication in ethanol (PLAL) technique through irradiation with a Nd:YAG laser pulses TiO2 target that is sunk in methanol using 400 mJ of laser energy. It has been studied the structural, optical and morphological of TiO2NPs. It has been detected that through XRD measurement, (TiO2) NPs have been Tetragonal crystal structure. While with AFM measurements, it has been realized that the synthesized TiO2 particles are spherical with an average particle size in the (82 nm) range. It has been determined that the energy band gap of TiO2 NPs from optical properties and set to be in (5eV) range.The transmittance and reflectance spectra have determined the TiO2 NPs optical constants. It was reported the effectiveness of TiO2 NPs expansion on the PS Photodetector properties which exposes the benefits in (Al/PS/Si/Al). The built-in tension values depend on the etching time current density and laser flounce. Al/TiO2/PS/Si/Al photo-detector heterojunction have two response peaks that are situated at 350 nm and (700 -800nm) with max sensitivity ≈ 0.7 A/W. The maximum given detectivity is 9.38at ≈ 780 nm wavelength.

Carbohydrate-directed synthesis of silver and gold nanoparticles: effect of the structure of carbohydrates and reducing agents on the size and morphology of the composites.

PubMed

Shervani, Zameer; Yamamoto, Yasushi

2011-04-01

A monosaccharide (β-D-glucose) and polysaccharide (soluble starch) were used as structure directing and subsequently stabilizing agents for the synthesis of spherical nanoparticles (NPs) and nanowires of silver and gold. Homogeneous monodispersed Ag(0) nanoparticles (Ag NPs) of 15 nm diameter were obtained when 10(-4)M AgNO(3) precursor salt was reduced in starch (1 wt%)-water gel by 1 wt% β-D-glucose. For a second preparation the effect of reducing agents on the synthesis of Au(0) metallic nanoparticles (Au NPs) of 2 × 10(-4)M concentration prepared in a β-D-glucose (0.03 M)-water dispersion was studied first in detail. Different equivalent amounts of NaBH(4) and a number of pH values were evaluated for the reduction of the Au salt HAuCl(4)·3H(2)O to obtain Au NPs. The type and the amount of reducing agent, as well as the pH of the solution was shown to affect the size and morphology of the NPs. NaBH(4) (4 equiv) produced the smallest (5.3 nm (σ 0.7)) metallic particles compared to larger particles (10.0 nm (σ 1.4)) when the salt was reduced by 1 equiv of NaBH(4). Addition of excess NaBH(4) caused the NPs to settle out as a precipitate forming a mesh or wire structure rather than monodispersed particles. Low pH (pH 6) resulted in incomplete reduction, while at pH 8 the salt was completely reduced. When the salt was reduced by NaOH at pH 8, the particles were larger (14.2 nm) and less homogeneous (σ 2.8) compared to those from NaBH(4) reduction. Copyright © 2011 Elsevier Ltd. All rights reserved.

Interactions of non-spherical particles in simple flows

NASA Astrophysics Data System (ADS)

Niazi, Mehdi; Brandt, Luca; Costa, Pedro; Breugem, Wim-Paul

2015-11-01

The behavior of particles in a flow affects the global transport and rheological properties of the mixture. In recent years much effort has been therefore devoted to the development of an efficient method for the direct numerical simulation (DNS) of the motion of spherical rigid particles immersed in an incompressible fluid. However, the literature on non-spherical particle suspensions is quite scarce despite the fact that these are more frequent. We develop a numerical algorithm to simulate finite-size spheroid particles in shear flows to gain new understanding of the flow of particle suspensions. In particular, we wish to understand the role of inertia and its effect on the flow behavior. For this purpose, DNS simulations with a direct-forcing immersed boundary method are used, with collision and lubrication models for particle-particle and particle-wall interactions. We will discuss pair interactions, relative motion and rotation, of two sedimenting spheroids and show that the interaction time increases significantly for non-spherical particles. More interestingly, we show that the particles are attracted to each other from larger lateral displacements. This has important implications for collision kernels. This work was supported by the European Research Council Grant No. ERC-2013-CoG-616186, TRITOS, and by the Swedish Research Council (VR).

Rapid green synthesis of spherical gold nanoparticles using Mangifera indica leaf

NASA Astrophysics Data System (ADS)

Philip, Daizy

2010-11-01

This paper reports the rapid biological synthesis of spherical gold nanoparticles at room temperature using fresh/dry leaf extract of Mangifera indica. This is a simple, cost-effective, stable for long time and reproducible aqueous synthesis method to obtain a self-assembly of nearly monodispersed Au nanoparticles of size ˜20 nm and 17 nm. The nanoparticles were obtained within 2 min of addition of the extract to the solution of HAuCl 4·3H 2O and the colloid is found to be stable for more than 5 months. Smaller and more uniformly distributed particles could be obtained with dried leaf extract. The nanoparticles obtained are characterized by UV-vis, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Crystalline nature of the nanoparticles in the fcc structure is confirmed by the peaks in the XRD pattern corresponding to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes, bright circular spots in the selected area electron diffraction (SAED) and clear lattice fringes in the high-resolution TEM image. The possible biomolecules responsible for efficient stabilization are suggested by studying the FTIR spectrum of the sample. This environmentally benign method provides much faster synthesis and colloidal stability comparable to those of chemical reduction.

Size Selective Green Synthesis of Silver and Gold Nanoparticles: Enhanced Antibacterial Efficacy of Resveratrol Capped Silver Sol.

PubMed

Shukla, Shashi P; Roy, Mainak; Mukherjee, Poulomi; Das, Laboni; Neogy, Suman; Srivastava, Dinesh; Adhikari, Soumyakanti

2016-03-01

In view of potential biomedical application of the noble metal nanoparticles, we report a size controlled yet simple and green synthesis of resveratrol stabilized silver and gold nanoparticles having low polydispersity of size. Here, resveratrol plays two simultaneous roles, reducing the metal ions and providing efficient capping of the small nanoparticles. This gives rise to specific size of silver and gold nanoparticles at specific ratios of metal to resveratrol. The particles have been characterized by XRD and transmission electron microscopy. The nanoparticle sols are stable for months. The UV Visible absorption spectra of the silver sol show the plasmon peak of spherical nanoparticles, presence of which is further reflected in the TEM images. Size of the silver particles obtained is in between 11 to 21 nm depending on the ratio of resveratrol to metal ion used. Resveratrol capped silver nanoparticles exhibit high antibacterial activity against Gram negative wild type E coli BW (25113). The minimum inhibitory concentration (MIC) of nano-silver against the bacterium has been estimated to be 6.48 μg/ml, which is significantly lower than that reported in some earlier as well as recent publications. Reaction of gold ions with resveratrol, on the other hand, produces gold nanoparticles of sizes varying from 7 to 29 nm at different ratios of resveratrol to the metal ions. Particles with higher size and aspect ratio are formed at lower concentration of the capping agent whereas particles with very small size and pseudo-spherical morphology are formed at higher capping concentration. Difference in the formation kinetics of silver and gold nanoparticles has been attributed to the different growth mechanisms in the two cases. Possible modes of anchorage of resveratrol to silver nanoparticles have been investigated using surface enhanced resonance Raman spectroscopy (SERS) which shows that the silver nanoparticles are capped by resveratrol molecule primarily through O-Ag linkages of the p-OH aromatic ring. This, in turn, demonstrates the feasibility of using these nanoparticles as SERS templates.

Experimental approach to the fundamental limit of the extinction coefficients of ultra-smooth and highly spherical gold nanoparticles.

PubMed

Kim, Dong-Kwan; Hwang, Yoon Jo; Yoon, Cheolho; Yoon, Hye-On; Chang, Ki Soo; Lee, Gaehang; Lee, Seungwoo; Yi, Gi-Ra

2015-08-28

The theoretical extinction coefficients of gold nanoparticles (AuNPs) have been mainly verified by the analytical solving of the Maxwell equation for an ideal sphere, which was firstly founded by Mie (generally referred to as Mie theory). However, in principle, it has not been directly feasible with experimental verification especially for relatively large AuNPs (i.e., >40 nm), as conventionally proposed synthetic methods have inevitably resulted in a polygonal shaped, non-ideal Au nanosphere. Here, mono-crystalline, ultra-smooth, and highly spherical AuNPs of 40-100 nm were prepared by the procedure reported in our recent work (ACS Nano, 2013, 7, 11064). The extinction coefficients of the ideally spherical AuNPs of 40-100 nm were empirically extracted using the Beer-Lambert law, and were then compared with the theoretical limits obtained by the analytical and numerical methods. The obtained extinction coefficients of the ideally spherical AuNPs herein agree much more closely with the theoretical limits, compared with those of the faceted or polygonal shaped AuNPs. In addition, in order to further elucidate the importance of being spherical, we systematically compared our ideally spherical AuNPs with the polygonal counterparts; effectively addressing the role of the surface morphology on the spectral responses in both theoretical and experimental manners.

Calibration of optical particle-size analyzer

DOEpatents

Pechin, William H.; Thacker, Louis H.; Turner, Lloyd J.

1979-01-01

This invention relates to a system for the calibration of an optical particle-size analyzer of the light-intercepting type for spherical particles, wherein a rotary wheel or disc is provided with radially-extending wires of differing diameters, each wire corresponding to a particular equivalent spherical particle diameter. These wires are passed at an appropriate frequency between the light source and the light detector of the analyzer. The reduction of light as received at the detector is a measure of the size of the wire, and the electronic signal may then be adjusted to provide the desired signal for corresponding spherical particles. This calibrator may be operated at any time without interrupting other processing.

Surface-enhanced Raman scattering (SERS) by molecules adsorbed at spherical particles: errata

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

Kerker, M.; Wang, D.S.; Chew, H.

1980-12-15

A model for Raman scattering by a molecule adsorbed at the surface of a spherical particle is articulated by treating the molecule as a classical electric dipole. This follows Moskovits's suggestion (J. Chem. Phys. 69, 4159 (1978)) and the experiments by Creighton et al. (J. Chem. Soc. Faraday Trans. II, 75, 790(1979)) that such a system may exhibit SERS simlar to that at roughened electrode surfaces. The molecule is stimulated by a primary field comprised of the incident and near-scattered fields. Emission consists of the dipole field plus a scattered field, each at the shifted frequency. Addition of feedback termsmore » between the dipole and the particle makes only a negligible contribution to the fields. For pyridine adsorbed at the surface of a silver sphere, the 1010 cm/sup -1/ band is enhanced by approx.10/sup 6/ if the radius is much less than the wavelengths and the excitation wavelength is approx.382 nm, a wavelength for which the relative refractive index of silver is close to m = ..sqrt..2i. Detailed results are given for the effect upon the angular distribution and the polarization of the Raman emission of particle size, distance from the surface, excitation wavelength, and location of the molecule upon the surface. These results simulate those observed at roughened silver electrodes and suggest that the mechanism of SERS at those electrodes may resemble the electromagnetic mechanism elucidated here. The authors predict that comparable effects should be observed for fluorescent scattering. 53 references, 9 figures.« less

Identifying Aerosol Type/Mixture from Aerosol Absorption Properties Using AERONET

NASA Technical Reports Server (NTRS)

Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Dickerson, R. R.; Thompson, A. M.; Slutsker, I.; Li, Z.; Tripathi, S. N.; Singh, R. P.;

Modification and investigation of silica particles as a foam stabilizer

NASA Astrophysics Data System (ADS)

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

2017-02-01

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

Surface chemical effects on colloid stability and transport through natural porous media

USGS Publications Warehouse

Puls, Robert W.; Paul, Cynthia J.; Clark, Donald A.

1993-01-01

Surface chemical effects on colloidal stability and transport through porous media were investigated using laboratory column techniques. Approximately 100 nm diameter, spherical, iron oxide particles were synthesized as the mobile colloidal phase. The column packing material was retrieved from a sand and gravel aquifer on Cape Cod, MA. Previous studies have indicated enhanced stability and transport of iron oxide particles due to specific adsorption of some inorganic anions on the iron oxide surface. This phenomenon was further evaluated with an anionic surfactant, sodium dodecyl sulfate. Surfactants constitute a significant mass of the contaminant loading at the Cape Cod site and their presence may contribute to colloidal transport as a significant transport mechanism at the site. Other studies at the site have previously demonstrated the occurrence of this transport mechanism for iron phosphate particles. Photon correlation spectroscopy, micro-electrophoretic mobility, and scanning electron microscopy were used to evaluate particle stability, mobility and size. Adsorption of negatively charged organic and inorganic species onto the surface of the iron oxide particles was shown to significantly enhance particle stability and transport through alterations of the electrokinetic properties of the particle surface. Particle breakthrough generally occurred simultaneously with tritiated water, a conservative tracer. The extent of particle breakthrough was primarily dependent upon colloidal stability and surface charge.

Surface area loss mechanisms of Pt3Co nanocatalysts in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Rasouli, S.; Ortiz Godoy, R. A.; Yang, Z.; Gummalla, M.; Ball, S. C.; Myers, D.; Ferreira, P. J.

2017-03-01

Pt3Co catalyst nanoparticles of 4.9 nm size present on the cathode side of a PEMFC membrane-electrode assembly (MEA) were analyzed by transmission electron microscopy after 10 K voltage cycles under different operating conditions. The operating conditions include baseline (0.4-0.95 V, 80° C, 100% Relative Humidity (RH)), high potential (0.4-1.05 V, 80° C, 100% RH), high temperature (0.4-0.95 V, 90° C, 100% RH), and low humidity (0.4-0.95 V, 80° C, 30% RH). Particle growth and particle loss to the membrane is more severe in the high potential sample than in the high temperature and baseline MEAs, while no significant particle growth and particle precipitation in the membrane can be observed in the low humidity sample. Particles with different morphologies were seen in the cathode including: 1-Spherical individual particles resulting from modified electro-chemical Ostwald ripening and 2-aggregated and coalesced particles resulting from either necking of two or more particles or preferential deposition of Pt between particles with consequent bridging. The difference in the composition of these morphologies results in composition variations through the cathode from cathode/diffusion media (DM) to the cathode/membrane interface.

The effect of steam sterilization on recombinant spider silk particles.

PubMed

Lucke, Matthias; Winter, Gerhard; Engert, Julia

2015-03-15

In this work, the recombinant spider silk protein eADF4(C16) was used to fabricate particles in the submicron range using a micromixing method. Furthermore, particles in the micrometer range were produced using an ultrasonic atomizer system. Both particle species were manufactured by an all-aqueous process. The submicroparticles were 332 nm in average diameter, whereas 6.70 μm was the median size of the microparticles. Both particle groups showed a spherical shape and exhibited high β-sheet content in secondary structure. Submicro- and microparticles were subsequently steam sterilized and investigated with respect to particle size, secondary structure and thermal stability. Sterilization temperature and time were increased to assess the thermal stability of eADF4(C16) particles. Actually, particles remained stable and their properties did not change even after autoclaving at 134°C. Both, the untreated and the autoclaved submicroparticles showed no overt cytotoxicity on human dermal fibroblasts after incubation for 72 h. The eADF4(C16) particles were already loaded with proteins and small molecules in previous studies. With that, we can provide a highly promising parenteral drug delivery system based on a defined polypeptide carrier, manufactured with an all-aqueous process and being fully sterilizable. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis characterization and luminescence studies of gamma irradiated nanocrystalline yttrium oxide.

PubMed

Shivaramu, N J; Lakshminarasappa, B N; Nagabhushana, K R; Singh, Fouran

2016-02-05

Nanocrystalline Y2O3 is synthesized by solution combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature. The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14-30 nm for samples synthesized using urea and 15-20 nm for samples synthesized using glycine respectively. Field emission scanning electron microscopy (FE-SEM) image of 1173 K annealed Y2O3 samples show well separated spherical shape particles and the average particle size is found to be in the range 28-35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y-O bond. Electron spin resonance (ESR) shows V(-) center, O2(-) and Y(2+) defects. A broad photoluminescence (PL) emission with peak at ~386nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y2O3 nanopowder are studied at a heating rate of 5 K s(-1). The samples prepared by using urea show a prominent and well resolved peak at ~383 K and a weak one at ~570 K. It is also found that TL glow peak intensity (I(m1)) at ~383 K increases with increase in γ-dose up to ~6.0 kGy and then decreases with increase in dose. However, glycine used Y2O3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y2O3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detail. Copyright © 2015. Published by Elsevier B.V.

Novel Discrete Element Method for 3D non-spherical granular particles.

NASA Astrophysics Data System (ADS)

Seelen, Luuk; Padding, Johan; Kuipers, Hans

2015-11-01

Granular materials are common in many industries and nature. The different properties from solid behavior to fluid like behavior are well known but less well understood. The main aim of our work is to develop a discrete element method (DEM) to simulate non-spherical granular particles. The non-spherical shape of particles is important, as it controls the behavior of the granular materials in many situations, such as static systems of packed particles. In such systems the packing fraction is determined by the particle shape. We developed a novel 3D discrete element method that simulates the particle-particle interactions for a wide variety of shapes. The model can simulate quadratic shapes such as spheres, ellipsoids, cylinders. More importantly, any convex polyhedron can be used as a granular particle shape. These polyhedrons are very well suited to represent non-rounded sand particles. The main difficulty of any non-spherical DEM is the determination of particle-particle overlap. Our model uses two iterative geometric algorithms to determine the overlap. The algorithms are robust and can also determine multiple contact points which can occur for these shapes. With this method we are able to study different applications such as the discharging of a hopper or silo. Another application the creation of a random close packing, to determine the solid volume fraction as a function of the particle shape.

Droplet characteristic measurement in Fourier interferometry imaging and behavior at the rainbow angle.

PubMed

Briard, Paul; Saengkaew, Sawitree; Wu, Xuecheng; Meunier-Guttin-Cluzel, Siegfried; Chen, Linghong; Cen, Kefa; Gréhan, Gérard

2013-01-01

This paper presents the possibility of measuring the three-dimensional (3D) relative locations and diameters of a set of spherical particles and discusses the behavior of the light recorded around the rainbow angle, an essential step toward refractive index measurements. When a set of particles is illuminated by a pulsed incident wave, the particles act as spherical light wave sources. When the pulse duration is short enough to fix the particle location (typically about 10 ns), interference fringes between these different spherical waves can be recorded. The Fourier transform of the fringes divides the complex fringe systems into a series of spots, with each spot characterizing the interference between a pair of particles. The analyses of these spots (in position and shape) potentially allow the measurement of particle characteristics (3D relative position, particle diameter, and particle refractive index value).

Field emission and explosive electron emission process in focused ion beam fabricated platinum and tungsten three-dimensional overhanging nanostructure

NASA Astrophysics Data System (ADS)

Singh, Abhishek Kumar

2018-06-01

Three-dimensional platinum and tungsten overhanging nanogap (∼70 nm) electrodes are fabricated on a glass substrate using focused ion beam milling and chemical vapour deposition processes. Current-voltage (I-V) characteristics of the devices measured at a pressure of ∼10-6 mbar shows space-charge emission followed by the Fowler-Nordheim (F-N) field emission. After the F-N emission, the system enters into an explosive emission process, at a higher voltage generating a huge current. We observe a sharp and abrupt rise in the emission current which marks the transition from the F-N emission to the explosive emission state. The explosive emission process is destructive in nature and yields micro-/nano-size spherical metal particles. The chemical compositions and the size-distribution of such particles are performed.

Improved resolution in extracellular vesicle populations using 405 instead of 488 nm side scatter

PubMed Central

McVey, Mark J.; Spring, Christopher M.; Kuebler, Wolfgang M.

2018-01-01

ABSTRACT Improvements in identification and assessment of extracellular vesicles (EVs) have fuelled a recent surge in EV publications investigating their roles as biomarkers and mediators of disease. Meaningful scientific comparisons are, however, hampered by difficulties in accurate, reproducible enumeration and characterization of EVs in biological fluids. High-sensitivity flow cytometry (FCM) is presently the most commonly applied strategy to assess EVs, yet its utility is limited by variant ability to resolve smaller EVs. Here, we propose the use of 405 nm (violet) wavelength lasers in place of 488 nm (blue) for side scatter (SSC) detection to obtain greater resolution of EVs using high-sensitivity FCM. To test this hypothesis, we modelled EV resolution by violet versus blue SSC in silico and compared resolution of reference beads and biological EVs from plasma and bronchoalveolar lavage (BAL) fluid using either violet or blue wavelength SSC EV detection. Mie scatter modelling predicted that violet as compared to blue SSC increases resolution of small (100–500 nm) spherical particles with refractive indices (1.34–1.46) similar to EVs by approximately twofold in terms of light intensity and by nearly 20% in SSC signal quantum efficiency. Resolution of reference beads was improved by violet instead of blue SSC with two- and fivefold decreases in coefficients of variation for particles of 300–500 nm and 180–240 nm size, respectively. Resolution was similarly improved for detection of EVs from plasma or BAL fluid. Violet SSC detection for high-sensitivity FCM allows for significantly greater resolution of EVs in plasma and BAL compared to conventional blue SSC and particularly improves resolution of smaller EVs. Notably, the proposed strategy is readily implementable and inexpensive for machines already equipped with 405 nm SSC or the ability to accommodate 405/10 nm bandpass filters in their violet detector arrays. PMID:29696076

Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Selective Laser Melting of Powder Produced by Granulation-Sintering-Deoxygenation Method

NASA Astrophysics Data System (ADS)

Sun, Pei; Fang, Z. Zak; Zhang, Ying; Xia, Yang

2017-12-01

Commercial spherical Ti powders for additive manufacturing applications are produced today by melt-atomization methods at relatively high costs. A meltless production method, called granulation-sintering-deoxygenation (GSD), was developed recently to produce spherical Ti alloy powder at a significantly reduced cost. In this new process, fine hydrogenated Ti particles are agglomerated to form spherical granules, which are then sintered to dense spherical particles. After sintering, the solid fully dense spherical Ti alloy particles are deoxygenated using novel low-temperature deoxygenation processes with either Mg or Ca. This technical communication presents results of 3D printing using GSD powder and the selective laser melting (SLM) technique. The results showed that tensile properties of parts fabricated from spherical GSD Ti-6Al-4V powder by SLM are comparable with typical mill-annealed Ti-6Al-4V. The characteristics of 3D printed Ti-6Al-4V from GSD powder are also compared with that of commercial materials.

Generation of a hollow dark spherical spot by 4pi focusing of a radially polarized Laguerre-Gaussian beam

NASA Astrophysics Data System (ADS)

Bokor, Nándor; Davidson, Nir

2006-01-01

The properties of the focal spot for 4pi focusing with radially polarized first-order Laguerre-Gaussian beams are calculated. It is shown that a focal spot that has an extremely sharp dark region at the center and an almost-perfect spherical symmetry can be achieved. When such a hollow dark spherical spot is used in 4pi fluorescence depletion microscopy, an axial FWHM spot size of ˜39 nm and a transverse FWHM spot size of ˜64 nm can be achieved simultaneously in a practical system.

Generation of a hollow dark spherical spot by 4pi focusing of a radially polarized Laguerre-Gaussian beam.

PubMed

Bokor, Nándor; Davidson, Nir

2006-01-15

The properties of the focal spot for 4pi focusing with radially polarized first-order Laguerre-Gaussian beams are calculated. It is shown that a focal spot that has an extremely sharp dark region at the center and an almost-perfect spherical symmetry can be achieved. When such a hollow dark spherical spot is used in 4pi fluorescence depletion microscopy, an axial FWHM spot size of approximately 39 nm and a transverse FWHM spot size of approximately 64 nm can be achieved simultaneously in a practical system.

Physicochemical characterizations of nano-palm oil fuel ash

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

Rajak, Mohd Azrul Abdul, E-mail: azrulrajak88@gmail.com; Preparatory Centre of Science and Technology, Universiti Malaysia Sabah, Jalan UMS, 88400, Kota Kinabalu, Sabah; Majid, Zaiton Abdul, E-mail: zaiton@kimia.fs.utm.my

2015-07-22

Palm Oil Fuel Ash (POFA) is known as a good supplementary cementing material due to its siliceous-rich content. The application of nanotechnology in the pozzolanic materials could invent new functions in the efficiency of physical and chemical properties of materials. Thus, the present study aims to generate nano-sized POFA and characterize the physicochemical properties of nano-palm oil fuel ash (nPOFA). The nPOFA was prepared by mechanically grinding micro POFA using a high intensity ball milling for 6 hours. The physicochemical properties of nPOFA were characterized via X-Ray Fluoresence (XRF), Scanning Emission microscopy- Energy Dispersive X-Ray (SEM-EDX), Transmission Electron Microscope (TEM)more » and X-Ray Diffraction (XRD). The particle size of nPOFA acquired from TEM analysis was in the range of 20 nm to 90 nm, while the average crystallite size calculated from XRD diffractogram was 61.5 nm. The resulting nPOFA has a BET surface area of 145.35 m{sup 2}/g, which is more than 85% increment in surface area compared to micro-sized POFA. The morphology and elemental studies showed the presence of spherical as well as irregularly shaped and fine nPOFA particles contains with high silicon content. The presence of α-quartz as the major phase of the nPOFA was identified through XRD analysis. The study concludes that nPOFA has the potential as a supplementary cementing material due to the high silica content, high surface area and the unique behaviors of nano-structured particles.« less

Structuring by field enhancement of glass, Ag, Au, and Co thin films using short pulse laser ablation

NASA Astrophysics Data System (ADS)

Ulmeanu, M.; Zamfirescu, M.; Rusen, L.; Luculescu, C.; Moldovan, A.; Stratan, A.; Dabu, R.

2009-12-01

Single pulse laser ablation of glass, Ag, Au, and Co thin films was experimentally investigated with a laser pulse width of 400 ps at a wavelength of 532 nm both in the far and near fields. In the far-field regime, the electromagnetic field results from a focused laser beam, while the near-field regime is realized by a combination of the focused laser beam incident on a spherical colloidal particle. For the near-field experiments we have used polystyrene colloidal particles of 700 nm diameter self-assembled or spin coated on top of the surfaces. Laser fluences applied are in the range of 0.01-10 J/cm2. The diameter and the morphologies of the ablated holes were investigated by optical microscopy, profilometry, scanning electron microscopy, and atomic force microscopy. The dependence of the shape of the holes reflects the fluence regime and the thermophysical properties, i.e., melting temperature and thermal diffusivity of the surfaces involved in the experiments. We give quantitative data about the fluence threshold, diameter, and depth ablation dependence for the far and near fields and discuss their values with respect to the enhancement factor of the intensity of the electromagnetic field due to the use of the colloidal particles. Theoretical estimations of the intensity enhancement were done using the finite-difference time-domain method by using the RSOFT software. The application of near fields allows structuring of the surfaces with structure dimension in the order of 100 nm and even below.

Mesoporous silica as the enzyme carrier for organophosphate detection and/or detoxification

NASA Astrophysics Data System (ADS)

Frančič, Nina; Nedeljko, Polonca; Lobnik, Aleksandra

2013-05-01

In the past decade, interest in mesoporous materials has developed dramatically since they can be useful in a number of applications, including adsorption and sensor technology. Mesoporous materials are a class of nanostrustures with well-defined mesoscale (2-50 nm) pores, surface areas up to 1000 m2/g and large pore volumes (~1.0 mL/g). In general, ordered mesoporous materials are formed from solution by co-assembly and cross-linking of network-forming inorganic species (typically oxides) in the presence of structure-directing agents (SDAs) [1]. The SDAs are typically surfactants or blockcopolymers that self-organize into mesoscale (2-50 nm) structures, according to the solution composition and processing conditions used [2]. Owing to their structural properties and regular morphology, mesoporous silicas (MPS) are promising materials for applications in the immobilization processes or as supports for bulky bio-molecules, such as enzymes. We report on the synthesis of mesoporous silica (MPS) particles and their potential use for immobilization of the enzyme hexahistidine tagged OPH (His6-OPH). Particle characterization points out a strong influence of the synthesis parameters (addition of ethyl acetate). BET results show a high specific surface area (300-450 m2/g) and an appropriate pore size distribution ranging from 10 to 40 nm. Immobilization of the enzyme His6-OPH, with the size of 72 kDa and isoelectric point (pI) of 8.5, was carried out in MPS particles of spherical morphology. Preliminary results indicate significant potential in use of encapsulated enzyme His6-OPH for the purpose of bio-sensing or in the detoxification processes of organophosphates.

The Particle Shape of WC Governing the Fracture Mechanism of Particle Reinforced Iron Matrix Composites.

PubMed

Li, Zulai; Wang, Pengfei; Shan, Quan; Jiang, Yehua; Wei, He; Tan, Jun

2018-06-11

In this work, tungsten carbide particles (WC p , spherical and irregular particles)-reinforced iron matrix composites were manufactured utilizing a liquid sintering technique. The mechanical properties and the fracture mechanism of WC p /iron matrix composites were investigated theoretically and experimentally. The crack schematic diagram and fracture simulation diagram of WC p /iron matrix composites were summarized, indicating that the micro-crack was initiated both from the interface for spherical and irregular WC p /iron matrix composites. However, irregular WC p had a tendency to form spherical WC p . The micro-cracks then expanded to a wide macro-crack at the interface, leading to a final failure of the composites. In comparison with the spherical WC p , the irregular WC p were prone to break due to the stress concentration resulting in being prone to generating brittle cracking. The study on the fracture mechanisms of WC p /iron matrix composites might provide a theoretical guidance for the design and engineering application of particle reinforced composites.

Morphology and structure of TixOy nanoparticles generated by femtosecond laser ablation in water

NASA Astrophysics Data System (ADS)

Donėlienė, Jolanta; Rudzikas, Matas; Rades, Steffi; Dörfel, Ilona; Peplinski, Burkhard; Sahre, Mario; Pellegrino, Francesco; Maurino, Valter; Ulbikas, Juras; Galdikas, Algirdas; Hodoroaba, Vasile-Dan

2018-04-01

In this work femto-second pulsed laser ablation in liquid (PLAL) procedure for the generation of titanium oxide nanoparticles (NP) is reported with the purpose of understanding morphology and structure of the newly generated NPs. Ablation duration was varied for optimization of NP generation processes between 10 and 90 min. Surface morphology of NPs as well as their size and shape (distribution) were analysed by various complementary electron microscopy techniques, i.e. SEM, TSEM and TEM. The crystalline structure of titanium oxide particles was investigated by XRD (two instruments operated in different geometries) and HR-TEM. Concentration of generated titanium oxide NPs in liquid was analysed by ICP-MS. A mix of crystalline (mainly anatase), partly crystalline and amorphous spherical titanium oxide NPs can be reported having a mean size between 10 and 20 nm, which is rather independent of the laser ablation (LA) duration. A second component consisting of irregularly shaped, but crystalline titanium oxide nanostructures is co-generated in the LA water, with more pronounced occurrence at longer LA times. The provenance of this component is assigned to those spherical particles generated in suspension and passing through the converging laser beam, being hence subject to secondary irradiation effects, e. g. fragmentation.

Chemiluminescent Diagnostics of Free-Radical Processes in an Abiotic System and in Liver Cells in the Presence of Nanoparticles Based on Rare-Earth Elements nReVO4:Eu3+ (Re = Gd, Y, La) and CeO2

NASA Astrophysics Data System (ADS)

Averchenko, E. A.; Kavok, N. S.; Klochkov, V. K.; Malyukin, Yu. V.

2014-11-01

We have used luminol-dependent chemiluminescence with Fenton's reagent to study the effect of nanoparticles based on rare-earth elements of different sizes and shapes on free-radical processes in abiotic and biotic cell-free systems, and also in isolated cells in vitro. We have estimated the effects of rare-earth orthovanadate nanoparticles of spherical (GdYVO4:Eu3+, 1-2 nm), spindle-shaped (GdVO4:Eu3+, 25 ×8 nm), and rod-shaped (LaVO4:Eu3+, 57 × (6-8) nm) nanoparticles and spherical CeO2 nanoparticles (sizes 1-2 nm and 8-10 nm). We have shown that in contrast to the abiotic system, in which all types of nanoparticles exhibit antiradical activity, in the presence of biological material, extra-small spherical (1-2 nm) nanoparticles of both types exhibit pro-oxidant activity, and also enhance pro-oxidant induced oxidative stress (for the pro-oxidants hydrogen peroxide and tert-butyl hydroperoxide). The effect of rare-earth orthovanadate spindle and rod shaped nanoparticles in this system was neutral; a moderate antioxidant effect was exhibited by 8-10 nm CeO2 nanoparticles.

Synthesis, characterization and magnetic properties of CoxCu1-x (x ∼ 0.01 - 0.3) granular alloys

NASA Astrophysics Data System (ADS)

Dhara, S.; Roy Chowdhury, R.; Lahiri, S.; Ray, P.; Bandyopadhyay, B.

2015-01-01

Nanostructured CoCu granular alloys have been prepared by borohydride reduction of CuCl2 and CoCl2 salt solutions using cetyltrimethylammonium bromide (CTAB) as a surfactant. Characterization by inductively coupled plasma optical emission spectroscopy (ICPOES), X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies yields spherical particles of CoxCu1-x (x ∼ 0.01 - 0.3) of average size 8-25 nm formed in a face-centered-cubic (fcc) lattice as in copper. Studies of zero-field-cooled/field-cooled (ZFC/FC) magnetization and thermoremanent magnetization (TRM) have been performed in the temperature range 4-300 K, and the results have been analyzed by independent particle model. At the lowest cobalt concentration (x ∼ 0.01), the alloy is superparamagnetic and there is no blocking of magnetization down to 4 K. For all other samples, the magnetization at low magnetic field is characterized by a blocking temperature distribution which is not influenced by the Co content in samples. Study of hysteresis loops shows that the magnetization at any temperature 4-300 K is a sum of ferromagnetic (FM), superparamagnetic (SPM) and paramagnetic (PM) contributions. The FM part increases and SPM part decreases with increase in Co content. However, the values of coercivity and magnetic anisotropy constant do not depend on Co content. The results suggest that CoxCu1-x alloys are formed in a spherical core-shell type structure with cobalt being concentrated near the core of particles.

Thermal diffusion behavior of hard-sphere suspensions.

PubMed

Ning, Hui; Buitenhuis, Johan; Dhont, Jan K G; Wiegand, Simone

2006-11-28

We studied the thermal diffusion behavior of octadecyl coated silica particles (R(h)=27 nm) in toluene between 15.0 and 50.0 degrees C in a volume fraction range of 1%-30% by means of thermal diffusion forced Rayleigh scattering. The colloidal particles behave like hard spheres at high temperatures and as sticky spheres at low temperatures. With increasing temperature, the obtained Soret coefficient S(T) of the silica particles changed sign from negative to positive, which implies that the colloidal particles move to the warm side at low temperatures, whereas they move to the cold side at high temperatures. Additionally, we observed also a sign change of the Soret coefficient from positive to negative with increasing volume fraction. This is the first colloidal system for which a sign change with temperature and volume fraction has been observed. The concentration dependence of the thermal diffusion coefficient of the colloidal spheres is related to the colloid-colloid interactions, and will be compared with an existing theoretical description for interacting spherical particles. To characterize the particle-particle interaction parameters, we performed static and dynamic light scattering experiments. The temperature dependence of the thermal diffusion coefficient is predominantly determined by single colloidal particle properties, which are related to colloid-solvent molecule interactions.

Optical extinction of highly porous aerosol following atmospheric freeze drying

NASA Astrophysics Data System (ADS)

Adler, Gabriela; Haspel, Carynelisa; Moise, Tamar; Rudich, Yinon

2014-06-01

Porous glassy particles are a potentially significant but unexplored component of atmospheric aerosol that can form by aerosol processing through the ice phase of high convective clouds. The optical properties of porous glassy aerosols formed from a freeze-dry cycle simulating freezing and sublimation of ice particles were measured using a cavity ring down aerosol spectrometer (CRD-AS) at 532 nm and 355 nm wavelength. The measured extinction efficiency was significantly reduced for porous organic and mixed organic-ammonium sulfate particles as compared to the extinction efficiency of the homogeneous aerosol of the same composition prior to the freeze-drying process. A number of theoretical approaches for modeling the optical extinction of porous aerosols were explored. These include effective medium approximations, extended effective medium approximations, multilayer concentric sphere models, Rayleigh-Debye-Gans theory, and the discrete dipole approximation. Though such approaches are commonly used to describe porous particles in astrophysical and atmospheric contexts, in the current study, these approaches predicted an even lower extinction than the measured one. Rather, the best representation of the measured extinction was obtained with an effective refractive index retrieved from a fit to Mie scattering theory assuming spherical particles with a fixed void content. The single-scattering albedo of the porous glassy aerosols was derived using this effective refractive index and was found to be lower than that of the corresponding homogeneous aerosol, indicating stronger relative absorption at the wavelengths measured. The reduced extinction and increased absorption may be of significance in assessing direct, indirect, and semidirect forcing in regions where porous aerosols are expected to be prevalent.

Fullerene-like organization of HIV gag-protein shell in virus-like particles produced by recombinant baculovirus.

PubMed

Nermut, M V; Hockley, D J; Jowett, J B; Jones, I M; Garreau, M; Thomas, D

1994-01-01

Virus-like particles produced by a recombinant baculovirus containing the HIV gag gene were examined by negative staining after delipidization. This technique demonstrated that the gag-protein shell consisted of radially arranged short rods which formed a network of ring-like structures. Similar structures were observed at the plasma membrane of infected cells which had been opened by wet-cleaving. Occasionally five or six subunits were observed forming a ring. These findings suggest that the gag-encoded precursor (pr55) is a rod-like molecule about 34 A in diameter and 85 A in length. A protein cylinder of such dimensions would have a molecular weight of 56K. The center-to-center distance of two neighboring rings formed by the rods was 66 +/- 8 A (N = 200) by direct measurements and 65 A as obtained from averaged images. This morphology and these dimensions indicate that the virus-like particles contain the gag precursor in the form of a near-spherical "fullerene-like" icosahedral shell. Our data indicate that the triangulation number of the rings equals 63. However, since one rod of pr55 is shared by two rings, the number of copies of the precursor will be 1890 as opposed to 2522 if the molecules were closely packed. The particle diameter of 102 nm deduced from the proposed model was close to the diameter obtained from thin sections of low-temperature-embedded specimens (103-108 nm).

Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

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

Ren, X. D., E-mail: renxd@mail.ujs.edu.cn; Liu, R.; Zheng, L. M.

2015-10-05

To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphousmore » carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.« less

Preparation of polycaprolactone nanoparticles via supercritical carbon dioxide extraction of emulsions.

PubMed

Ajiboye, Adejumoke Lara; Trivedi, Vivek; Mitchell, John C

2017-08-21

Polycaprolactone (PCL) nanoparticles were produced via supercritical fluid extraction of emulsions (SFEE) using supercritical carbon dioxide (scCO 2 ). The efficiency of the scCO 2 extraction was investigated and compared to that of solvent extraction at atmospheric pressure. The effects of process parameters including polymer concentration (0.6-10% w/w in acetone), surfactant concentration (0.07 and 0.14% w/w) and polymer-to-surfactant weight ratio (1:1-16:1 w/w) on the particle size and surface morphology were also investigated. Spherical PCL nanoparticles with mean particle sizes between 190 and 350 nm were obtained depending on the polymer concentration, which was the most important factor where increase in the particle size was directly related to total polymer content in the formulation. Nanoparticles produced were analysed using dynamic light scattering and scanning electron microscopy. The results indicated that SFEE can be applied for the preparation of PCL nanoparticles without agglomeration and in a comparatively short duration of only 1 h.

Synthesis and characterization of CdO nano particles by the sol-gel method

NASA Astrophysics Data System (ADS)

Vadgama, V. S.; Vyas, R. P.; Jogiya, B. V.; Joshi, M. J.

2017-05-01

Cadmium Oxide (CdO) is an inorganic compound and one of the main precursors to other cadmium compounds. It finds applications in cadmium plating, storage batteries, in transparent conducting film, etc. Here, an attempt is made to synthesize CdO nano particles by sol-gel technique. The gel was prepared using cadmium nitrate tetra hydrate (Cd(NO3)2.4H2O) and aqueous ammonium hydroxide (NH4OH) as a precursor. The synthesized powder is further characterized by techniques like Powder X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and Thermal gravimetric analysis (TGA). Powder XRD analysis suggested the nano-crystalline nature of the sample with the cubic crystal system. Nano scaled particles of spherical morphology with the size ranging from 50-100 nm are observed from TEM images. While, FT-IR study is used to confirm the presence of different functional groups. Thermo-gravimetric analysis suggests the highly thermally stable nature of the samples. The results are discussed.

Preparation of silver nano-particles immobilized onto chitin nano-crystals and their application to cellulose paper for imparting antimicrobial activity.

PubMed

Li, Zhihan; Zhang, Ming; Cheng, Dong; Yang, Rendang

2016-10-20

Immobilized silver nano-particles (Ag NPs) possess excellent antimicrobial properties due to their unique surface characteristics. In this paper, immobilized silver nano-particles were synthesized in the presence of chitin nano-crystals (CNC) based on the Tollens mechanism (reduction of silver ion by aldehydes in the chitosan oligosaccharides (COS)) under microwave-assisted conditions. The prepared Ag NPs-loaded CNC nano-composites were then applied onto the paper surface via coating for the preparation of antibacterial paper. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results confirmed that the Ag NPs were immobilized onto the CNC. The transmission electron microscope (TEM) and scanning electron microscopy (SEM) results further revealed that the spherical Ag NPs (5-12nm) were well dispersed on the surface of CNC. The coated paper made from the Ag NPs-loaded CNC nano-composites exhibited a high effectiveness of the antibacterial activity against E. coli or S. aureus. Copyright © 2016 Elsevier Ltd. All rights reserved.

In vitro assembly of a prohead-like structure of the Rhodobacter capsulatus gene transfer agent

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

Spano, Anthony J.; Chen, Frank S.; Goodman, Benjamin E.

2007-07-20

The gene transfer agent (GTA) is a phage-like particle capable of exchanging double-stranded DNA fragments between cells of the photosynthetic bacterium Rhodobacter capsulatus. Here we show that the major capsid protein of GTA, expressed in E. coli, can be assembled into prohead-like structures in the presence of calcium ions in vitro. Transmission electron microscopy (TEM) of uranyl acetate staining material and thin sections of glutaraldehyde-fixed material demonstrates that these associates have spherical structures with diameters in the range of 27-35 nm. The analysis of scanning TEM images revealed particles of mass {approx} 4.3 MDa, representing 101 {+-} 11 copies ofmore » the monomeric subunit. The establishment of this simple and rapid method to form prohead-like particles permits the GTA system to be used for genome manipulation within the photosynthetic bacterium, for specific targeted drug delivery, and for the construction of biologically based distributed autonomous sensors for environmental monitoring.« less

Methotrexate Nanoparticles Prepared with Codendrimer from Polyamidoamine (PAMAM) and Oligoethylene Glycols (OEG) Dendrons: Antitumor Efficacy in Vitro and in Vivo

NASA Astrophysics Data System (ADS)

Zhao, Yanna; Guo, Yifei; Li, Ran; Wang, Ting; Han, Meihua; Zhu, Chunyan; Wang, Xiangtao

2016-07-01

The novel methotrexate-loaded nanoparticles (MTX/PGD NPs) prepared with amphiphilic codendrimer PGD from polyamidoamine and oligothylene glycol dendrons were obtained via antisolvent precipitation method augmented by ultrasonication. Based on the excellent hydrophility of PGD, the drug-loaded nanoparticles could be investigated easily with the high drug-loading content (~85.2%, w/w). The MTX/PGD NPs possessed spherical morphology, nanoscaled particle size (approximately 182.4 nm), and narrow particle size distribution. Release of MTX from MTX/PGD NPs showed a sustained release manner and completed within 48 h. Hemolytic evaluation indicated MTX/PGD NPs presented good blood compatibility, and the cytotoxicity of nanoparticles against breast cancer cells in vitro, biodistribution in tumor tissue, and antitumor efficacy in vivo were enhanced significantly compared to MTX injection. According to the higher drug-loading content, enhanced antitumor efficacy, and appropriate particle size, MTX/PGD NPs as the drug delivery systems could have potential application for cancer chemotherapy in clinic.

Methotrexate Nanoparticles Prepared with Codendrimer from Polyamidoamine (PAMAM) and Oligoethylene Glycols (OEG) Dendrons: Antitumor Efficacy in Vitro and in Vivo

PubMed Central

Zhao, Yanna; Guo, Yifei; Li, Ran; Wang, Ting; Han, Meihua; Zhu, Chunyan; Wang, Xiangtao

2016-01-01

The novel methotrexate-loaded nanoparticles (MTX/PGD NPs) prepared with amphiphilic codendrimer PGD from polyamidoamine and oligothylene glycol dendrons were obtained via antisolvent precipitation method augmented by ultrasonication. Based on the excellent hydrophility of PGD, the drug-loaded nanoparticles could be investigated easily with the high drug-loading content (~85.2%, w/w). The MTX/PGD NPs possessed spherical morphology, nanoscaled particle size (approximately 182.4 nm), and narrow particle size distribution. Release of MTX from MTX/PGD NPs showed a sustained release manner and completed within 48 h. Hemolytic evaluation indicated MTX/PGD NPs presented good blood compatibility, and the cytotoxicity of nanoparticles against breast cancer cells in vitro, biodistribution in tumor tissue, and antitumor efficacy in vivo were enhanced significantly compared to MTX injection. According to the higher drug-loading content, enhanced antitumor efficacy, and appropriate particle size, MTX/PGD NPs as the drug delivery systems could have potential application for cancer chemotherapy in clinic. PMID:27388443

A modified Fermi-Walker derivative for inextensible flows of binormal spherical image

NASA Astrophysics Data System (ADS)

Suroğlu, Gülden Altay

2018-03-01

Fermi-Walker derivative and biharmonic particle play an important role in skillful applications. We obtain a new characterization on binormal spherical indicatrix by using the Fermi-Walker derivative and parallelism in space. We suggest that an inextensible flow is the necessary and sufficient condition for this particle. Finally, we give some characterizations for a non-rotating frame of this binormal spherical indicatrix.

Characterization of Particle Size Standard NIST 1019b with SynchrotronX-ray Microtomography and Digital Data Extraction

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

Friedrich, Jon M.; Rivers, Mark L.; Perlowitz, Michael A.

We show that synchrotron x-ray microtomography ({mu}CT) followed by digital data extraction can be used to examine the size distribution and particle morphologies of the polydisperse (750 to 2450 {micro}m diameter) particle size standard NIST 1019b. Our size distribution results are within errors of certified values with data collected at 19.5 {micro}m/voxel. One of the advantages of using {mu}CT to investigate the particles examined here is that the morphology of the glass beads can be directly examined. We use the shape metrics aspect ratio and sphericity to examine of individual standard beads morphologies as a function of spherical equivalent diameters.more » We find that the majority of standard beads possess near-spherical aspect ratios and sphericities, but deviations are present at the lower end of the size range. The majority (> 98%) of particles also possess an equant form when examined using a common measure of equidimensionality. Although the NIST 1019b standard consists of loose particles, we point out that an advantage of {mu}CT is that coherent materials comprised of particles can be examined without disaggregation.« less

Hydrothermal synthesis and magnetic properties of Mn doped ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Rashad, M. M.; Rayan, D. A.; El-Barawy, K.

2010-01-01

Nanocrystallite Mn doped Zn1-XS (X = 0 to 0.4) powders have been synthesized through a hydrothermal route. The effect of the hydrothermal temperature and Mn2+ ions substitution on the crystal structure, crystallite size, microstructure and magnetic properties were investigated using (XRD), (SEM) and (VSM). The results revealed that wurtzite zinc sulfide phase was formed using thiourea as a sulfur source at temperature 150- 200oC for 24 h. The crystallite size was (7.9-15.1 nm) was obtained at the same conditions. The doping of Mn2+ ions decreased the crystallite size of the formed ZnS wurtzite phase was in the range between 7.9 and 3.8 nm. SEM micrographs showed that the produced ZnS and Mn doped ZnS particles were appeared as spherical shape. The magnetic properties were improved by substitution of Mn2+ ions up to 0.2.

Green Synthesis of Silver Nanoparticles using Extract of Pinus merkusii Jungh & De Vriese Cone Flower

NASA Astrophysics Data System (ADS)

Azkiya, N. I.; Masruri, M.; Ulfa, S. M.

2018-01-01

The paper studies recent application of cone flower waste from Pinus merkusii Jungh & De Vriese for an environmentally unclear method for synthesis silver nanoparticle. Phytochemical characterization using iron trichloride solution showed the extract of Pinus merkusii cone flower contains of phenolic group of secondary metabolite. This group acts as both reducing and stabilizing agents. For the synthesis of silver nanoparticle, solution of silver nitrate is added to the extract at 60°C. The effect of extract concentration (5-20%) and time reaction (15-60 min) is investigated. The formation of silver nanoparticle is confirmed by the color change from yellowish to brown. Meanwhile, UV-Vis characterization of silver nanoparticle in extract 20% and 60 min reaction showed surface plasmon resonance (SPR) at 431 nm, and transmission electron microscope (TEM) revealed the particle size range in between 8 and 23 nm with a spherical in shape.

Sunlight-assisted synthesis of colloidal silver nanoparticles using chitosan as reducing agent

NASA Astrophysics Data System (ADS)

Susilowati, E.; Maryani; Ashadi

2018-04-01

The present study we explore an environmentally friendly colloidal silver nanoparticles preparation using chitosan as reducing agent and stabilizer. It develops a new strategy on preparation of silver nanoparticles through the gel phase using sodium hydroxide (NaOH) as accelerator reagent. Sunlight irradiation was employed to assisted reducing process of silver ions to silver nanoparticles. Localized surface plasmon resonance (LSPR) phenomenon of silver nanoparticles was investigated using UV-Vis spectrophotometer. The shape and size of silver particles were analyzed using TEM. The formation of silver nanoparticles was confirmed by the appearance of LSPR absorption peak at 396.0–412.0 nm. The absorption peak of LSPR were affected by NaOH amount, time of sulight irradiation and concentration of AgNO3. The produced silver nanoparticles were spherical with dominant size range of 5 to 8 nm as shown by TEM images. All colloidals were stable without any aggregation for 30 days after preparation.

Spectroscopic studies on some fluorescent mixed-ligand titanium(IV) complexes.

PubMed

Baranwal, Balram Prasad; Singh, Alok Kumar; Varma, Anand

2011-12-15

A novel route to synthesize some titanium(IV) complexes containing acetylacetone, straight chain carboxylic acid and hydroxycarboxylic acid ligands has been investigated. Complexes with the general formula [Ti(acac)Cl(2-n)(OOCR*)(n)(OOCC(15)H(31))] (where Hacac=acetylacetone, R*COOH=hydroxycarboxylic acids and n=1 or 2) have been isolated and characterized. Molecular weight determinations indicated mononuclear nature of the complexes. LMCT bands were observed in the electronic spectra. Infrared spectra suggested bidentate nature of the ligands. Fluorescent behaviour of the complexes was noticed on the basis of fluorescence spectra. Powder XRD indicated them to be semi-crystalline having the crystallite size in 136-185 nm range. Transmission electron microscopy (TEM) indicated spherical particles of ~ 200 nm diameter. On the basis of physico-chemical studies, it is suggested that titanium is having coordination number 7 or 8 in these complexes. Copyright © 2011 Elsevier B.V. All rights reserved.

Crystal structures and magnetic properties of magnetite (Fe{sub 3}O{sub 4})/Polyvinyl alcohol (PVA) ribbon

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

Ardiyanti, Harlina; Suharyadi, Edi, E-mail: esuharyadi@ugm.ac.id; Kato, Takeshi

2016-04-19

Ribbon of magnetite (Fe{sub 3}O{sub 4})/Polyvinyl Alcohol (PVA) nanoparticles have been successfully fabricated with various concentration of PVA synthesized by co-precipitation method. Particle size of nanoparticles Fe{sub 3}O{sub 4} sample and ribbon Fe{sub 3}O{sub 4}/PVA 25% sample is about 9.34 nm and 11.29 nm, respectively. The result of Vibrating Sample Magnetometer (VSM) showed that saturation magnetization value decreased from 76.99 emu/g to 15.01 emu/g and coercivity increased from 49.30 Oe to 158.35 Oe as increasing concentration of PVA. Atomic Force Microscopy (AFM) analysis showed that encapsulated PVA given decreasing agglomeration, controlled shape of nanoparticles Fe{sub 3}O{sub 4} more spherical and dispersed. Surfacemore » roughness decreased with increasing concentration of PVA.« less

Colorimetric As (V) detection based on S-layer functionalized gold nanoparticles.

PubMed

Lakatos, Mathias; Matys, Sabine; Raff, Johannes; Pompe, Wolfgang

2015-11-01

Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable. Copyright © 2015 Elsevier B.V. All rights reserved.

Ascorbic acid prevents cellular uptake and improves biocompatibility of chitosan nanoparticles.

PubMed

Elshoky, Hisham A; Salaheldin, Taher A; Ali, Maha A; Gaber, Mohamed H

2018-04-11

Chitosan nanoparticles have many applications, such as gene and drug delivery, due to their biocompatibility. Chitosan nanoparticles are currently produced by dissolution in acetic acid that affects the biocompatibility at acidic pH. Here, we synthesized and characterized chitosan (CS) and ascorbate chitosan (AsCS) nanoparticles and investigated their cytotoxic effects, internalization, and distribution in the human colon carcinoma cell line using confocal laser scanning microscopy (CLSM). The CS and AsCS nanoparticles were spherical with average particle sizes of 44±8.4nm and 87±13.6nm, respectively. CS nanoparticles were taken up by the cells and showed dose-dependent cytotoxicity. By contrast, AsCS nanoparticles were not internalized and showed no cytotoxicity. Therefore, AsCS nanoparticles are more biocompatible than CS nanoparticles and may be more suitable for extracellular drug delivery. Copyright © 2018 Elsevier B.V. All rights reserved.

Preparation and characterization of silver nanoparticles homogenous thin films

NASA Astrophysics Data System (ADS)

Hegazy, Maroof A.; Borham, E.

2018-06-01

The wet chemical method by metal salt reduction has been widely used to synthesize nanoparticles. Accordingly the silver nitrate used as silver precursor and sodium borohydrate as reduction agent. The silver nanoparticles were characterized by different characterization techniques including UV-VIS spectrometry, Transmission electron microscope (TEM), and Zeta potential technique. Thin films of the colloidal solution were fabricated using direct precipitation technique on ITO glass, silicon substrate and commercial glass substrate and characterized by imaging technique. The absorption peak of the silver nanoparticles colloidal solution was around 400 nm. The TEM images indicate that the silver nanoparticles had spherical shape and their sizes were from 10 to 17 nm. The particle size of the silver nanoparticles was confirmed by Zeta potential technique. The imaging technique indicated that the homogeneous distribution of the colloidal silver solution thin film on the silicon substrate was stronger than the ITO glass and inhomogeneous film was emerged on the commercial glass.

A moderate method for preparation DMSA coated Fe3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Song, L. N.; Gu, N.; Zhang, Y.

2017-01-01

A moderate way to prepare water soluble magnetic Fe3O4 nanoparticles has been developed. Firstly, oleic acid coated Fe3O4 is prepared by coprecipitation. Second, oleic acid were replaced by 2,3-dimercaptosuccinnic acid (DMSA) to prepare DMSA/Fe3O4 in the mixed solution of n-hexane and acetone. After dialysis and filtration the DMSA/Fe3O4 can be transferred into distilled water to form stable Fe3O4 nanoparticle solutions. The TEM images indicated that the particles had spherical shape and the nanoparticles were found to be 12 nm with a relatively narrow size distribution with the hydrodynamic size of 30 nm. And the result of VSM shows that DMSA/Fe3O4 nanoparticles have a saturation magnetization of 31 emu/g. The IR spectra indicated that the iron oxide was located by carboxyl matrix.

Formation of Polymeric Nanocubes by Self-Assembly and Crystallization of Dithiolane-Containing Triblock Copolymers

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

Margulis, Katherine; Zhang, Xiangyi; Joubert, Lydia -Marie

Template–free fabrication of non–spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self–assembly from aqueous solutions at room temperature. Nanocubes with edges of 40–200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self–assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solidmore » cubic particle formation. An approach for preserving the structures of these cubes in water by thiol– or photo–induced crosslinking was developed. In conclusion, the ability to solubilize a model hydrophobic drug, curcumin, was also explored.« less

Formation of Polymeric Nanocubes by Self-Assembly and Crystallization of Dithiolane-Containing Triblock Copolymers

DOE PAGES

Margulis, Katherine; Zhang, Xiangyi; Joubert, Lydia -Marie; ...

2017-10-27

Template–free fabrication of non–spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self–assembly from aqueous solutions at room temperature. Nanocubes with edges of 40–200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self–assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solidmore » cubic particle formation. An approach for preserving the structures of these cubes in water by thiol– or photo–induced crosslinking was developed. In conclusion, the ability to solubilize a model hydrophobic drug, curcumin, was also explored.« less

Method to produce large, uniform hollow spherical shells

DOEpatents

Hendricks, C.D.

1983-09-26

The invention is a method to produce large uniform hollow spherical shells by (1) forming uniform size drops of heat decomposable or vaporizable material, (2) evaporating the drops to form dried particles, (3) coating the dried particles with a layer of shell forming material and (4) heating the composite particles to melt the outer layer and to decompose or vaporize the inner particle to form an expanding inner gas bubble. The expanding gas bubble forms the molten outer layer into a shell of relatively large diameter. By cycling the temperature and pressure on the molten shell, nonuniformities in wall thickness can be reduced. The method of the invention is utilized to produce large uniform spherical shells, in the millimeter to centimeter diameter size range, from a variety of materials and of high quality, including sphericity, concentricity and surface smoothness, for use as laser fusion or other inertial confinement fusion targets as well as other applications.

Thermal stability, optical and Photoluminescence properties of spherical Ce x Zr1‑x O2 (x = 0.05) crystalline blue-emitting nanophosphors synthesized by microwave method

NASA Astrophysics Data System (ADS)

Manjunatha, S.; Dharmaprakash, M. S.

2018-03-01

Nanocrystalline ZrO2 based material is an impressive candidate for the various functional applications owing to their ease of preparation and high thermal stability. This paper reports the synthesis, structural and optical characterization of thermally stable monodispersed CexZr1‑xO2 (x = 0.05) nanoparticles. This method is based on the fact that, microwave irradiation allows the formation of size controlled and single phase cubic ZrO2 nanoparticles containing Ce+4 as a dopant. The XRD and Rietveld analysis revealed the formation of the crystalline cubic fluorite phase. The formation of nanoparticles was confirmed by FTIR. The morphology of the nanophosphors was characterised by FESEM and TEM. The optical band gap was calculated from the UV–visible absorption spectra and was found to vary from 3.93 to 4.25 eV with calcination temperature. It shows the decrease in the optical band gap from the pristine ZrO2. The particle size was measured by using HRTEM, and the average particle size was found to be 22 nm. Under the 268 nm Ultra Violet irradiation excitation a blue emission at 443 nm was observed at room temperature. The possible luminescence mechanism of CexZr1‑xO2 nanophosphor under UV excitation is discussed.

Structural transformation study of TiO2 nanoparticles annealing at different temperatures and the photodegradation process of eosin-Y

NASA Astrophysics Data System (ADS)

Pandi, P.; Gopinathan, C.

2018-04-01

Hydrothermal method was used to prepare TiO2 nanoparticles with annealing temperature at 500 °C-700 °C. The mixture of anatase-rutile phase was investigated by powerful tool of X-ray diffraction (XRD). The structural parameters of anatase and rutile mixture phaseTiO2 nanoparticles were calculated from the Rietveld refinement. The transformation rate of rutile was increased linearly with an annealing temperature of 500 °C-700 °C. The spherical morphology of the anatase and rutile mixed phase were obtained by scanning electron microscope and transmission electron microscope. The spherical particle of the anatase and rutile TiO2 shows with great aggregation with different size and within the range of few tens nm. The EDAX study revealed the presence of titanium and oxygen. The best photocatalytic activity was identified as the 87.04% of anatase and 12.96% of rutile mixer phase of TiO2. Various factors could be involved for a better photocatalytic activity.

Adsorption of Small Cationic Nanoparticles onto Large Anionic Particles from Aqueous Solution: A Model System for Understanding Pigment Dispersion and the Problem of Effective Particle Density.

PubMed

North, S M; Jones, E R; Smith, G N; Mykhaylyk, O O; Annable, T; Armes, S P

2017-02-07

The present study focuses on the use of copolymer nanoparticles as a dispersant for a model pigment (silica). Reversible addition-fragmentation chain transfer (RAFT) alcoholic dispersion polymerization was used to synthesize sterically stabilized diblock copolymer nanoparticles. The steric stabilizer block was poly(2-(dimethylamino)ethyl methacrylate) (PDMA) and the core-forming block was poly(benzyl methacrylate) (PBzMA). The mean degrees of polymerization for the PDMA and PBzMA blocks were 71 and 100, respectively. Transmission electron microscopy (TEM) studies confirmed a near-monodisperse spherical morphology, while dynamic light scattering (DLS) studies indicated an intensity-average diameter of 30 nm. Small-angle X-ray scattering (SAXS) reported a volume-average diameter of 29 ± 0.5 nm and a mean aggregation number of 154. Aqueous electrophoresis measurements confirmed that these PDMA 71 -PBzMA 100 nanoparticles acquired cationic character when transferred from ethanol to water as a result of protonation of the weakly basic PDMA chains. Electrostatic adsorption of these nanoparticles from aqueous solution onto 470 nm silica particles led to either flocculation at submonolayer coverage or steric stabilization at or above monolayer coverage, as judged by DLS. This technique indicated that saturation coverage was achieved on addition of approximately 465 copolymer nanoparticles per silica particle, which corresponds to a fractional surface coverage of around 0.42. These adsorption data were corroborated using thermogravimetry, UV spectroscopy and X-ray photoelectron spectroscopy. TEM studies indicated that the cationic nanoparticles remained intact on the silica surface after electrostatic adsorption, while aqueous electrophoresis confirmed that surface charge reversal occurred below pH 7. The relatively thick layer of adsorbed nanoparticles led to a significant reduction in the effective particle density of the silica particles from 1.99 g cm -3 to approximately 1.74 g cm -3 , as judged by disk centrifuge photosedimentometry (DCP). Combining the DCP and SAXS data suggests that essentially no deformation of the PBzMA cores occurs during nanoparticle adsorption onto the silica particles.

A potential nanobiotechnology platform based on infectious bursal disease subviral particles.

PubMed

Taghavian, Omid; Mandal, Manoj K; Steinmetz, Nicole F; Rasche, Stefan; Spiegel, Holger; Fischer, Rainer; Schillberg, Stefan

2012-03-07

We describe a novel nanobiotechnology platform based on subviral particles derived from infectious bursal disease virus (IBD-SVPs). The major virus coat protein VP2 assembles into spherical, 23 nm SVPs when expressed as a heterologous protein in the yeast Pichia pastoris . We recovered up to 38 mg of IBD-SVPs at > 95% purity from 1 L of recombinant yeast culture. The purified particles were able to tolerate organic solvents up to 20% concentration (ethanol or dimethylsulfoxide), they resisted temperatures up to 65 °C and remained stable over a wide pH range (2.5-9.0). We achieved bioconjugation to the amine groups of lysine residues and to the carboxyl groups of aspartic and glutamic acid residues, allowing the functionalization of IBD-SVPs with biotin. The accessibility of surface amine groups was measured using Alexa Fluor 488 N -hydroxysuccinimide (NHS) ester, an amine-selective fluorescent dye, revealing that approximately 60 dye molecules were attached to the surface of each particle. IBD-SVPs can therefore be exploited as a robust and versatile nanoscaffold to display diverse functional ligands.

The theory of nonstationary thermophoresis of a solid spherical particle

NASA Astrophysics Data System (ADS)

Kuzmin, M. K.; Yalamov, Yu. I.

2007-06-01

The theory of nonstationary thermophoresis of a solid spherical particle in a viscous gaseous medium is presented. The theory is constructed on the solutions of fluid-dynamics and thermal problems, each of which is split into stationary and strictly nonstationary parts. The solution of the stationary parts of the problems gives the final formula for determining the stationary component of the thermophoretic velocity of this particle. To determine the nonstationary component of the thermophoretic velocity of the particle, the corresponding formula in the space of Laplace transforms is derived. The limiting value theorems from operational calculus are used for obtaining the dependence of the nonstationary component of the thermophoretic velocity of the spherical particle on the strictly nonstationary temperature gradient for large and small values of time. The factors determining the thermophoretic velocity of the particle under investigation are determined.

Characterization of polylactic co-glycolic acid nanospheres modified with PVA and DDAB

NASA Astrophysics Data System (ADS)

Mulia, Kamarza; Satyapertiwi, Dwiantari; Devina, Ranee; Krisanti, Elsa

2017-02-01

The common treatment for diabetic retinopathy is corticosteroids intravitreal injection that sometimes lead to complications. Dexamethasone-loaded polylactic co-glycolic acid (PLGA) nanospheres, modified with dioctadecyldimethylammonium bromide (DDAB) as the cationic surfactant, is expected to prolong drug retention time. Zeta potential of the PLGA nanospheres prepared using non-ionic surfactant PVA and DDAB confirmed the cationic surfactant increase the surface charge of the PLGA nanospheres. The optimal formulation based on the particle size and high positive surface charge was the PLGA-DDAB nanospheres. SEM analysis showed spherical morphology of the nanospheres having diameter 626.9 ± 98.01 nm positive zeta potential of +22.5 mV.

Phytofabrication of bioinspired zinc oxide nanocrystals for biomedical application.

PubMed

Velmurugan, Palanivel; Park, Jung-Hee; Lee, Sang-Myeong; Jang, Jum-Suk; Yi, Young-Joo; Han, Sang-Sub; Lee, Sang-Hyun; Cho, Kwang-Min; Cho, Min; Oh, Byung-Taek

2016-09-01

In the present study, we investigated a novel green route for synthesis of zinc oxide nanoparticles (ZnO NPs) using the extract of young cones of Pinus densiflora as a reducing agent. Standard characterization studies were carried out to confirm the obtained product using UV-Vis spectra, SEM-EDS, FTIR, and XRD. TEM images showed that various shapes of ZnO NPs were synthesized, including hexagonal (wurtzite), triangular, spherical, and oval-shaped particles, with average sizes between 10 and 100 nm. The synthesized ZnO NPs blended with the young pine cone extract have very good activity against bacterial and fungal pathogens, similar to that of commercial ZnO NPs.

Kinetics and mechanism of dye adsorption on WO3 nanoparticles

NASA Astrophysics Data System (ADS)

Adhikari, Sangeeta; Mandal, Sandip; Sarkar, Debasish; Kim, Do-Heyoung; Madras, Giridhar

2017-10-01

Monoclinic WO3 nanoparticles were synthesized by a simple acid catalyzed co-precipitation reaction. Spherical particles with average size ∼55 nm were confirmed from electron microscopy followed by functional, structural and optical characterizations. The adsorption of methylene blue was examined by using WO3 nanoparticles and the capacity was higher than most of the reported studies. The effect of pH and material loading on adsorption was determined. The mechanism of adsorption was examined by XPS and a detailed explanation of surface phenomena was proposed. Regeneration study was carried and a high stability of heat treated WO3 towards adsorption of methylene blue was observed.

Characterization of Nanoencapsulated Centella asiatica and Zingiber officinale Extract Using Combination of Malto Dextrin and Gum Arabic as Matrix

NASA Astrophysics Data System (ADS)

Meliana, Y.; Harmami, S. B.; Restu, W. K.

2017-02-01

This research investigated nanoencapsulation of Centella asiatica and Zingiber officinale extract. The encapsulated extract was used as a complex matrix of multi-layered interfacial membranes between malto dextrin and gum Arabic. Characterization of nanoencapsulation using Transmission Electron Microscope (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and BET surface area (SA) showed the morphology, functional group and cumulative adsorption in the surface area of pores. The TEM image of the nanoencapsulated powders of Centella asiatica and Zingiber officinale extract showed a nearly spherical shape with the particle size of 664 nm from its average radius.

PLGA nano/microparticles loaded with cresyl violet as a tracer for drug delivery: Characterization and in-situ hyperspectral fluorescence and 2-photon localization.

PubMed

Lunardi, Claure N; Gomes, Anderson J; Palepu, Sandeep; Galwaduge, P Thilanka; Hillman, Elizabeth M C

2017-01-01

Here we present the production, characterization and in-vivo assessment of cresyl violet-loaded biodegradable PLGA nano/microparticles (CV-NP and CV-MP). We demonstrate that the beneficial spectral characteristics of cresyl violet make it suitable as a tracer for particle-based drug delivery using both hyperspectral wide field and two-photon excited fluorescence microscopy. Particles were prepared using a cosolvent method, after which the physicochemical properties such as morphology, particle size, drug entrapment efficiency, drug loading and in vitro drug release behavior were measured in addition to spectroscopic properties, such as absorption, fluorescence and infrared spectra. The particles were then tested in an in vivo mouse model to assess their biodistribution characteristics. The location and integrity of particles after injection was determined using both hyperspectral fluorescence and two-photon microscopy within intact organs in situ. Our results show that cresyl violet is efficiently entrapped into PLGA particles, and that the particles are spherical in shape, ranging from 300 to 5070nm in diameter. Particle biodistribution in the mouse was found to depend on particle size, as expected. Cresyl violet is shown to be an ideal tracer to assess the properties PLGA particle-based drug delivery in combination with our novel multi-scale optical imaging techniques for in-situ particle localization. Copyright © 2016 Elsevier B.V. All rights reserved.

ISDD: A computational model of particle sedimentation, diffusion and target cell dosimetry for in vitro toxicity studies

PubMed Central

2010-01-01

Background The difficulty of directly measuring cellular dose is a significant obstacle to application of target tissue dosimetry for nanoparticle and microparticle toxicity assessment, particularly for in vitro systems. As a consequence, the target tissue paradigm for dosimetry and hazard assessment of nanoparticles has largely been ignored in favor of using metrics of exposure (e.g. μg particle/mL culture medium, particle surface area/mL, particle number/mL). We have developed a computational model of solution particokinetics (sedimentation, diffusion) and dosimetry for non-interacting spherical particles and their agglomerates in monolayer cell culture systems. Particle transport to cells is calculated by simultaneous solution of Stokes Law (sedimentation) and the Stokes-Einstein equation (diffusion). Results The In vitro Sedimentation, Diffusion and Dosimetry model (ISDD) was tested against measured transport rates or cellular doses for multiple sizes of polystyrene spheres (20-1100 nm), 35 nm amorphous silica, and large agglomerates of 30 nm iron oxide particles. Overall, without adjusting any parameters, model predicted cellular doses were in close agreement with the experimental data, differing from as little as 5% to as much as three-fold, but in most cases approximately two-fold, within the limits of the accuracy of the measurement systems. Applying the model, we generalize the effects of particle size, particle density, agglomeration state and agglomerate characteristics on target cell dosimetry in vitro. Conclusions Our results confirm our hypothesis that for liquid-based in vitro systems, the dose-rates and target cell doses for all particles are not equal; they can vary significantly, in direct contrast to the assumption of dose-equivalency implicit in the use of mass-based media concentrations as metrics of exposure for dose-response assessment. The difference between equivalent nominal media concentration exposures on a μg/mL basis and target cell doses on a particle surface area or number basis can be as high as three to six orders of magnitude. As a consequence, in vitro hazard assessments utilizing mass-based exposure metrics have inherently high errors where particle number or surface areas target cells doses are believed to drive response. The gold standard for particle dosimetry for in vitro nanotoxicology studies should be direct experimental measurement of the cellular content of the studied particle. However, where such measurements are impractical, unfeasible, and before such measurements become common, particle dosimetry models such as ISDD provide a valuable, immediately useful alternative, and eventually, an adjunct to such measurements. PMID:21118529

Investigating the role of particle shape on colloid transport and retention in saturated porous media (Invited)

NASA Astrophysics Data System (ADS)

Li, Y.; Seymour, M.; Chen, G.; Su, C.

2013-12-01

Mechanistic understanding of the transport and retention of nanoparticles in porous media is essential both for environmental applications of nanotechnology and assessing the potential environmental impacts of engineered nanomaterials. Engineered and naturally occurring nanoparticles can be found in various shapes including rod-shape carbon nanotubes that have high aspect ratios. Although it is expected that nonspherical shape could play an important role on their transport and retention behaviors, current theoretical models for particle transport in porous media, however, are mostly based on spherical particle shape. In this work, the effect of particle shape on its transport and retention in porous media was evaluated by stretching carboxylate-modified fluorescent polystyrene spheres into rod shapes with aspect ratios of 2:1 and 4:1. Quartz crystal microbalance with dissipation experiments (QCM-D) were conducted to measure the deposition rates of spherical and rod-shaped nanoparticles to the collector (poly-L-lysine coated silica sensor) surface under favorable conditions. Under unfavorable conditions, the retention of nanoparticles in a microfluidic flow cell packed with glass beads was studied with the use of laser scanning cytometry (LSC). Under favorable conditions, the spherical particles displayed a significantly higher deposition rate compared with that of the rod-shaped particles. Theoretical analysis based on Smoluchowski-Levich approximation indicated that the rod-shaped particles largely counterbalance the attractive energies due to higher hydrodynamic forces and torques experienced during their transport and rotation. Under unfavorable conditions, significantly more attachment was observed for rod-shaped particles than spherical particles, and the attachment rate of the rod-shaped particles showed an increasing trend with the increase in injection volume. Rod-shaped particles were found to be less sensitive to the surface charge heterogeneity change than spherical particles. Increased attachment rate of rod-shaped particles was attributed to surface heterogeneity and possibly enhanced hydrophobicity during the stretching process.

Qualitative assessment of silver and gold nanoparticle synthesis in various plants: a photobiological approach

NASA Astrophysics Data System (ADS)

Rajasekharreddy, Pala; Usha Rani, Pathipati; Sreedhar, Bojja

2010-06-01

The development of rapid and ecofriendly processes for the synthesis of silver (Ag) and gold (Au) nanoparticles is of great importance in the field of nanotechnology. In this study, the extracellular production of Ag and Au nanoparticles was carried out from the leaves of the plants, Tridax procumbens L. (Coat buttons), Jatropa curcas L. (Barbados nut), Calotropis gigantea L. (Calotropis), Solanum melongena L. (Eggplant), Datura metel L. (Datura), Carica papaya L. (Papaya) and Citrus aurantium L. (Bitter orange) by the sunlight exposure method. Qualitative comparisons of the synthesized nanoparticles between the plants were measured. Among these T. procumbens, J. curcas and C. gigantea plants synthesized <20 nm sized and spherical-shaped Ag particles, whereas C. papaya, D. metel and S. melongena produced <20 nm sized monodispersed Au particles. The amount of nanoparticles synthesized and its qualitative characterization was done by UV-vis spectroscopy and transmission electron microscopy (TEM), respectively. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used for structural confirmation. Further analysis carried out by fourier transform infrared spectroscopy (FTIR), provided evidence for the presence of amino groups, which increased the stability of the synthesized nanoparticles.

Green Synthesis of Silver Nanoparticles Using an Aqueous Extract of Monotheca buxifolia (Flac.) Dcne

NASA Astrophysics Data System (ADS)

Anwar, Natasha; Khan, Abbas; Shah, Mohib; Anwar, Saad

2018-01-01

This study deals with the synthesis and physicochemical investigation of silver nanoparticles using an aqueous extract of Monotheca buxifolia (Flac.). On the treatment of aqueous solution of silver nitrate with the plant extract, silver nanoparticles were rapidly fabricated. The synthesized particles were characterized by using UV-visible spectrophotometry (UV), Fourier transform infrared spectroscopy (FTIR), Energy dispersive X-ray (EDX) and Scanning electron microscopy (SEM). The formation of AgNPs was confirmed by noting the change in colour through visual observations as well as via UV-Vis spectroscopy. UV-Vis spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 440 nm. FTIR was used to identify the chemical composition of silver nanoparticles and Ag-capped plant extract. The presence of elemental silver was also confirmed through EDX analysis. The SEM analysis of the silver nanoparticles showed that they have a uniform spherical shape with an average size in the range of 40-78 nm. This green system showed better capping and stabilizing agent for the fine particles. Further, in vitro the antioxidant activity of Monotheca buxifolia (Flac.) and Ag-capped with the plant was also evaluated using FeCl3/K3Fe (CN)6 essay.

Structural and Optical Properties of Ag Nanoparticles Synthesized by Thermal Treatment Method.

PubMed

Gharibshahi, Leila; Saion, Elias; Gharibshahi, Elham; Shaari, Abdul Halim; Matori, Khamirul Amin

2017-04-12

The modified thermal treatment method via alternate oxygen and nitrogen flow was successfully employed to synthesize very narrow and pure Ag nanoparticles. The structural and optical properties of the obtained metal nanoparticles at different calcination temperatures between 400 and 800 °C were studied using various techniques. The FTIR and EDX confirmed the formation of Ag nanoparticles without a trace of impurities. The XRD spectra revealed that the amorphous sample at 30 °C had transformed into the cubic crystalline nanostructures at the calcination temperature of 400 °C and higher. The TEM images showed the formation of spherical Ag nanoparticles in which the average particle size decreased with increasing calcination temperature from 7.88 nm at 400 °C to 3.29 nm at 800 °C. The optical properties were determined by UV-vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing calcination temperature from 2.75 eV at 400 °C to 3.04 eV at 800 °C. This was due to less attraction between conduction electrons and metal ions as the particle size decreases in corresponding to fewer numbers of atoms that made up the metal nanoparticles.

Structural and Optical Properties of Ag Nanoparticles Synthesized by Thermal Treatment Method

PubMed Central

Gharibshahi, Leila; Saion, Elias; Gharibshahi, Elham; Shaari, Abdul Halim; Matori, Khamirul Amin

2017-01-01

The modified thermal treatment method via alternate oxygen and nitrogen flow was successfully employed to synthesize very narrow and pure Ag nanoparticles. The structural and optical properties of the obtained metal nanoparticles at different calcination temperatures between 400 and 800 °C were studied using various techniques. The FTIR and EDX confirmed the formation of Ag nanoparticles without a trace of impurities. The XRD spectra revealed that the amorphous sample at 30 °C had transformed into the cubic crystalline nanostructures at the calcination temperature of 400 °C and higher. The TEM images showed the formation of spherical Ag nanoparticles in which the average particle size decreased with increasing calcination temperature from 7.88 nm at 400 °C to 3.29 nm at 800 °C. The optical properties were determined by UV-vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing calcination temperature from 2.75 eV at 400 °C to 3.04 eV at 800 °C. This was due to less attraction between conduction electrons and metal ions as the particle size decreases in corresponding to fewer numbers of atoms that made up the metal nanoparticles. PMID:28772762

About the possibility of magnetic and gravitational capture of the technogenic nanoparticles injected in the near-Earth space in high circular orbits

NASA Astrophysics Data System (ADS)

Kolesnikov, E. K.; Chernov, S. V.

2018-05-01

A detailed study of the conditions for the realization of the phenomena of magnetic and gravity capture (MGC) of nanoparticles (NP) injected into the near-Earth space in circular orbits with altitudes and inclinations characteristic for orbits of satellites of navigation systems (GLONASS, GPS, etc.) is carried out. Spherical aluminum oxide particles with radii from 4 to 100 nm were considered as injected particles. It was assumed that injection of NP is performed at various points of circular orbits with a height of 19130 km, an inclination angle to the equatorial plane equal to 64.8 degrees and a longitude of the ascending node of 0, 120 and 240 degrees. Calculations of the motion of nanoparticles in near-Earth space were performed for conditions of low level solar and geomagnetic activity. The results of numerical experiments show that for all the considered spatial orientations of the orbit of the parent body (PB) of the NP motion in the magnetic and gravitational capture mode with extremely long orbital existence times (more than two years) can be realized only for nanoparticles with radii in the narrow gap from 8.6 to 10.2 nm.

Nanoemulsion of ethanolic extracts of propolis and its antioxidant activity

NASA Astrophysics Data System (ADS)

Mauludin, R.; Primaviri, D. S.; Fidrianny, I.

2015-09-01

Propolis contains several antioxidant compounds which can be used in topical application to protect skin against free radical and prevent skin cancer and skin aging. Ethanolic extracts of propolis (EEP) provided the greatest antioxidant activity but has very small solubility in water thus was prepared in nanoemulsion (NE). EEP contains steroid/triterpenoid, flavonoid, and saponin. EEP had the value of DPPH scavenging activity 61.14% and IC50 0.41629 ppm. The best NE formulation consisted of 26.25% Kolliphor RH40; 8.75% glycerin; 5% rice bran oil; and 3% EEP. NE was transparent, had particle size of 23.72 nm and polydispersity index of 0.338. Based on TEM morphology, NE was almost spherical and has particle size below 50 nm. NE propolis revealed to be physically stable after stability test within 63 days at 25°C and passed 6 cycles of Freeze and Thaw test without separated. NE propolis reduced around 58% of free radical DPPH similar to antioxidant activity of the original extracts. Antioxidant activity of NE propolis is relatively stable after stored for 6 weeks. NE propolis was proven to be safe by primary irritation test with the value of primary irritation index (OECD) was 0.

Inhibitory effect of gold nanoparticles on the D-ribose glycation of bovine serum albumin.

PubMed

Liu, Weixi; Cohenford, Menashi A; Frost, Leslie; Seneviratne, Champika; Dain, Joel A

2014-01-01

Formation of advanced glycation end products (AGEs) by nonenzymatic glycation of proteins is a major contributory factor to the pathophysiology of diabetic conditions including senile dementia and atherosclerosis. This study describes the inhibitory effect of gold nanoparticles (GNPs) on the D-ribose glycation of bovine serum albumin (BSA). A combination of analytical methods including ultraviolet-visible spectrometry, high performance liquid chromatography, circular dichroism, and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry were used to determine the extent of BSA glycation in the presence of citrate reduced spherical GNPs of various sizes and concentrations. GNPs of particle diameters ranging from 2 nm to 20 nm inhibited BSA's AGE formation. The extent of inhibition correlated with the total surface area of the nanoparticles. GNPs of highest total surface area yielded the most inhibition whereas those with the lowest total surface area inhibited the formation of AGEs the least. Additionally, when GNPs' total surface areas were set the same, their antiglycation activities were similar. This inhibitory effect of GNPs on BSA's glycation by D-ribose suggests that colloidal particles may have a therapeutic application for the treatment of diabetes and conditions that promote hyperglycemia.

Inhibitory effect of gold nanoparticles on the D-ribose glycation of bovine serum albumin

PubMed Central

Liu, Weixi; Cohenford, Menashi A; Frost, Leslie; Seneviratne, Champika; Dain, Joel A

2014-01-01

Formation of advanced glycation end products (AGEs) by nonenzymatic glycation of proteins is a major contributory factor to the pathophysiology of diabetic conditions including senile dementia and atherosclerosis. This study describes the inhibitory effect of gold nanoparticles (GNPs) on the D-ribose glycation of bovine serum albumin (BSA). A combination of analytical methods including ultraviolet–visible spectrometry, high performance liquid chromatography, circular dichroism, and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry were used to determine the extent of BSA glycation in the presence of citrate reduced spherical GNPs of various sizes and concentrations. GNPs of particle diameters ranging from 2 nm to 20 nm inhibited BSA’s AGE formation. The extent of inhibition correlated with the total surface area of the nanoparticles. GNPs of highest total surface area yielded the most inhibition whereas those with the lowest total surface area inhibited the formation of AGEs the least. Additionally, when GNPs’ total surface areas were set the same, their antiglycation activities were similar. This inhibitory effect of GNPs on BSA’s glycation by D-ribose suggests that colloidal particles may have a therapeutic application for the treatment of diabetes and conditions that promote hyperglycemia. PMID:25473284

Shape effects on time-scale divergence at athermal jamming transition of frictionless non-spherical particles

NASA Astrophysics Data System (ADS)

Yuan, Ye; Jin, Weiwei; Liu, Lufeng; Li, Shuixiang

2017-10-01

The critical behaviors of a granular system at the jamming transition have been extensively studied from both mechanical and thermodynamic perspectives. In this work, we numerically investigate the jamming behaviors of a variety of frictionless non-spherical particles, including spherocylinder, ellipsoid, spherotetrahedron and spherocube. In particular, for a given particle shape, a series of random configurations at different fixed densities are generated and relaxed to minimize interparticle overlaps using the relaxation algorithm. We find that as the jamming point (i.e., point J) is approached, the number of iteration steps (defined as the "time-scale" for our systems) required to completely relax the interparticle overlaps exhibits a clear power-law divergence. The dependence of the detailed mathematical form of the power-law divergence on particle shapes is systematically investigated and elucidated, which suggests that the shape effects can be generally categorized as elongation and roundness. Importantly, we show the jamming transition density can be accurately determined from the analysis of time-scale divergence for different non-spherical shapes, and the obtained values agree very well with corresponding ones reported in literature. Moreover, we study the plastic behaviors of over-jammed packings of different particles under a compression-expansion procedure and find that the jamming of ellipsoid is much more robust than other non-spherical particles. This work offers an alternative approximate procedure besides conventional packing algorithms for studying athermal jamming transition in granular system of frictionless non-spherical particles.

Combustion synthesis and characterization of blue long lasting phosphor CaAl2O4: Eu2+, Dy3+ and its novel application in latent fingerprint and lip mark detection

NASA Astrophysics Data System (ADS)

Sharma, Vishal; Das, Amrita; Kumar, Vijay; Kumar, Vinay; Verma, Kartikey; Swart, H. C.

2018-04-01

This work investigates the structural, optical and photometric characterization of a Eu2+/Dy3+ doped calcium aluminates phosphor (CaAl2O4: Eu2+/Dy3+) for finger and lip print detections. Synthesis of CaAl2O4: Eu2+/Dy3+ (CAED) phosphors were carried out via a combustion synthesis method with urea as a fuel. Eu2+/Dy3+ doped CaAl2O4 phosphors have been studied with X-ray diffraction (XRD, Energy Dispersive X-Ray Spectroscopy Selected Area Diffraction (SAED) and High resolution Transmission Electron Microscope (HR-TEM). The XRD pattern shows that the synthesized Eu2+/Dy3+ doped CaAl2O4 phosphor have a single monoclinic structure and show that the addition of the dopant/co-dopants didn't change the crystal structure. The formation of monoclinic phase was confirmed by the selected area diffraction pattern. The TEM micrograph displays the morphology of the synthesized Eu2+/Dy3+ doped CaAl2O4 phosphors as spherical particles with an average particle size of 33 nm. The optical band gap was calculated using the diffuse reflectance for the synthesized nanophosphor powders. The photoluminescence emission spectra was recorded for the synthesized powder, with an excitation wavelength of 326 nm and the major bands was recorded at 447 nm corresponding to the blue color and two minor bands were recorded at 577 nm and 616 nm. To the best of our knowledge, this work is the first to show the use of CaAl2O4: Eu2+/Dy3+ nanophosphor in developing latent fingerprint and lip print effectively.

Controlling Particle Morphologies at Fluid Interfaces: Macro- and Micro- approaches

NASA Astrophysics Data System (ADS)

Beesabathuni, Shilpa Naidu

The controlled generation of varying shaped particles is important for many applications: consumer goods, biomedical diagnostics, food processing, adsorbents and pharmaceuticals which can benefit from the availability of geometrically complex and chemically inhomogeneous particles. This thesis presents two approaches to spherical and non-spherical particle synthesis using macro and microfluidics. In the first approach, a droplet microfluidic technique is explored to fabricate spherical conducting polymer, polyaniline, particles with precise control over morphology and functionality. Microfluidics has recently emerged as an important alternate to the synthesis of complex particles. The conducting polymer, polyaniline, is widely used and known for its stability, high conductivity, and favorable redox properties. In this approach, monodisperse micron-sized polyaniline spherical particles were synthesized using two-phase droplet microfluidics from Aniline and Ammonium persulfate oxidative polymerization in an oil-based continuous phase. The morphology of the polymerized particles is porous in nature which can be used for encapsulation as well as controlled release applications. Encapsulation of an enzyme, glucose oxidase, was also performed using the technique to synthesize microspheres for glucose sensing. The polymer microspheres were characterized using SEM, UV-Vis and EDX to understand the relationship between their microstructure and stability. In the second approach, molten drop impact in a cooling aqueous medium to generate non-spherical particles was explored. Viscoelastic wax based materials are widely used in many applications and their performance and application depends on the particle morphology and size. The deformation of millimeter size molten wax drops as they impacted an immiscible liquid interface was investigated. Spherical molten wax drops impinged on a cooling water bath, then deformed and as a result of solidification were arrested into various shapes such as ellipsoids, mushrooms, spherulites and discs. The final morphology of the wax particles is governed by the interfacial, inertial, viscous and thermal effects, which can be studied over a range of Weber, Capillary, Reynolds and Stefan numbers. A simplified Stefan problem for a spherical drop was solved. The time required to initiate a phase transition at the interface of the molten wax and water after impact was estimated and correlated with the drop deformation history and final wax particle shape to develop a capability to predict the shape. While the microfluidic synthesis approach offers precise control over morphology and functionality, large particle throughput is a limitation. The drop impact in a liquid medium emulsion approach is limited to crosslinking or heat sensitive materials but can be extended to large scale production for industrial applications. Both approaches are simple, robust and cost effective making them viable and attractive solutions for complex particle synthesis. The choice of the approach is dependent on considerations such as particle material, size, shape, throughput and end application.

A study of growth and thermal dewetting behavior of ultra-thin gold films using transmission electron microscopy

NASA Astrophysics Data System (ADS)

Sudheer, Mondal, Puspen; Rai, V. N.; Srivastava, A. K.

2017-07-01

The growth and solid-state dewetting behavior of Au thin films (0.7 to 8.4 nm) deposited on the formvar film (substrate) by sputtering technique have been studied using transmission electron microscopy. The size and number density of the Au nanoparticles (NPs) change with an increase in the film thickness (0.7 to 2.8 nm). Nearly spherical Au NPs are obtained for <3 nm thickness films whereas percolated nanostructures are observed for ≥3 nm thickness films as a consequence of the interfacial interaction of Au and formvar film. The covered area fraction (CAF) increases from ˜13 to 75 % with the change in film thickness from 0.7 to 8.4 nm. In-situ annealing of ≤3 nm film produces comparatively bigger size and better sphericity Au NPs along with their narrow distributions, whereas just percolated film produces broad distribution in size having spherical as well as elongated Au NPs. The films with thickness ≤3 nm show excellent thermal stability. The films having thickness >6 nm show capability to be used as an irreversible temperature sensor with a sensitivity of ˜0.1 CAF/°C. It is observed that annealing affects the crystallinity of the Au grains in the films. The electron diffraction measurement also shows annealing induced morphological evolution in the percolated Au thin films (≥3 nm) during solid-state dewetting and recrystallization of the grains.

Sub-diffraction-limit localization imaging of a plasmonic nanoparticle pair with wavelength-resolved dark-field microscopy.

PubMed

Wei, Lin; Ma, Yanhong; Zhu, Xupeng; Xu, Jianghong; Wang, Yaxin; Duan, Huigao; Xiao, Lehui

2017-06-29

In this work, with wavelength-resolved dark-field microscopy, the center-of-mass localization information from nanoparticle pairs (i.e., spherical (45 nm in diameter) and rod (45 × 70 nm) shaped gold nanoparticle pairs with different gap distances and orientations) was explored and compared with the results determined by scanning electron microscopy (SEM) measurements. When the gap distance was less than 20 nm, the scattering spectrum of the nanoparticle pair was seriously modulated by the plasmonic coupling effect. The measured coordinate information determined by the optical method (Gaussian fitting) was not consistent with the true results determined by SEM measurement. A good correlation between the optical and SEM measurements was achieved when the gap distance was further increased (e.g., 20, 40 and 60 nm). Under these conditions, well-defined scattering peaks assigned to the corresponding individual nanoparticles could be distinguished from the obtained scattering spectrum. These results would afford valuable information for the studies on single plasmonic nanoparticle imaging applications with the optical microscopy method such as super-localization imaging, high precision single particle tracking in a crowding environment and so on.

Spherical Harmonic Analysis of Particle Velocity Distribution Function: Comparison of Moments and Anisotropies using Cluster Data

NASA Technical Reports Server (NTRS)

Gurgiolo, Chris; Vinas, Adolfo F.

2009-01-01

This paper presents a spherical harmonic analysis of the plasma velocity distribution function using high-angular, energy, and time resolution Cluster data obtained from the PEACE spectrometer instrument to demonstrate how this analysis models the particle distribution function and its moments and anisotropies. The results show that spherical harmonic analysis produced a robust physical representation model of the velocity distribution function, resolving the main features of the measured distributions. From the spherical harmonic analysis, a minimum set of nine spectral coefficients was obtained from which the moment (up to the heat flux), anisotropy, and asymmetry calculations of the velocity distribution function were obtained. The spherical harmonic method provides a potentially effective "compression" technique that can be easily carried out onboard a spacecraft to determine the moments and anisotropies of the particle velocity distribution function for any species. These calculations were implemented using three different approaches, namely, the standard traditional integration, the spherical harmonic (SPH) spectral coefficients integration, and the singular value decomposition (SVD) on the spherical harmonic methods. A comparison among the various methods shows that both SPH and SVD approaches provide remarkable agreement with the standard moment integration method.

Influence of Poly(vinylpyrrolidone) concentration on properties of silver nanoparticles manufactured by modified thermal treatment method

PubMed Central

Saion, Elias; Gharibshahi, Elham; Shaari, Abdul Halim; Matori, Khamirul Amin

2017-01-01

Very narrow and pure silver nanoparticles were synthesized by modified thermal treatment method via oxygen and nitrogen flow in succession. The structural and optical properties of the calcined silver nanoparticles at 600°C with diverse Poly(vinylpyrrolidone) concentrations varied from 2% to 4% were studied by means of different techniques. Fourier transform infrared spectroscopy was used to monitor the production of pure Ag nanoparticles at a given Poly(vinylpyrrolidone) concentration. The X-ray powder diffraction spectra are evidence for the transformation of the amorphous sample at 30°C to the cubic crystalline nanostructures at the calcination temperatures for all Poly(vinylpyrrolidone) concentrations. The transmission electron microscopy images showed the creation of spherical silver nanoparticles with the average particle size decreased by increasing Poly(vinylpyrrolidone) concentrations from 4.61 nm at 2% to 2.49 nm at 4% Poly(vinylpyrrolidone). The optical properties were investigated by means of UV–vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing Poly(vinylpyrrolidone) concentrations from 2.83 eV at 2% Poly(vinylpyrrolidone) to 2.94 eV at 4% Poly(vinylpyrrolidone) due to decreasing particle size. This was due to less attraction between conduction electrons and metal ions for smaller particle size corresponding to fewer atoms that made up the metal nanoparticles. PMID:29045414

Computational analysis of non-spherical particle transport and deposition in shear flow with application to lung aerosol dynamics--a review.

PubMed

Kleinstreuer, Clement; Feng, Yu

2013-02-01

All naturally occurring and most man-made solid particles are nonspherical. Examples include air-pollutants in the nano- to micro-meter range as well as blood constituents, drug particles, and industrial fluid-particle streams. Focusing on the modeling and simulation of inhaled aerosols, theories for both spherical and nonspherical particles are reviewed to analyze the contrasting transport and deposition phenomena of spheres and equivalent spheres versus ellipsoids and fibers.

A Facile Method for Preparation of Polymer Particles Having a "Cylindrical" Shape.

PubMed

Li, Wei; Suzuki, Toyoko; Minami, Hideto

2018-06-16

A facile and novel approach to prepare monodisperse polystyrene (PS) particles having a "cylindrical" shape was discovered. The proposed synthetic method involved dispersion polymerization of the spherical PS particles stirred in a polyvinylpyrrolidone (PVP) aqueous solution for several hours using a magnetic stirrer at room temperature. In the presence of PVP, the spherical PS particles deformed into cylindrical shapes following stirring; however, the particles did not deform in the absence of PVP. The deformation rate of the particles was affected by the molecular weight of the dissolved PVP. This stirring method is not only highly efficient and provides high yield, but is also applicable to other materials such as polymethyl methacrylate. Moreover, the cylindrical particles were successfully applied as particulate surfactants in a Pickering emulsion system, which exhibited excellent stability as comparison with the system using spherical particles as a surfactant. In the latter case, the emulsion was left standing for more than 4 months. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE PAGES

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.; ...

2017-04-13

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormalmore » size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. As a result, this work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

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

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormalmore » size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. As a result, this work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

A mechanochemical approach to get stunningly uniform particles of magnesium-aluminum-layered double hydroxides

NASA Astrophysics Data System (ADS)

Zhang, Xiaoqing; Qi, Fenglin; Li, Shuping; Wei, Shaohua; Zhou, Jiahong

2012-10-01

A mechanochemical approach is developed in preparing a series of magnesium-aluminum-layered double hydroxides (Mg-Al-LDHs). This approach includes a mechanochemical process which involved manual grinding of solid salts in an agate mortar and afterwards peptization process. In order to verify the LDHs structure synthesized in the grinding process, X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) photos and thermogravimetry/differential scanning calorimetry (TG-DSC) property of the product without peptization were characterized and the results show that amorphous particles with low crystallinity and poor thermal stability are obtained, and the effect of peptization is to improve the properties, more accurately, regular particles with high crystallinity and good thermal stability can be gained after peptization. Furthermore, the fundamental experimental parameters including grinding time, the molar ratio of Mg to Al element (defined as R value) and the water content were systematically examined in order to control the size and morphologies of LDHs particles, regular hexagonal particles or the spherical nanostructures can be efficiently obtained and the particle sizes were controlled in the range of 52-130 nm by carefully adjusting these parameters. At last, stunningly uniform Mg-Al-LDHs particles can be synthesized under proper R values, suitable grinding time and high degree of supersaturation.

Diurnal Cycles of Aerosol Optical Properties at Pico Tres Padres, Mexico City: Evidences for Changes in Particle Morphology and Secondary Aerosol Formation

NASA Astrophysics Data System (ADS)

Mazzoleni, C.; Dubey, M.; Chakrabarty, R.; Moosmuller, H.; Onasch, T.; Zavala, M.; Herndon, S.; Kolb, C.

2007-12-01

Aerosol optical properties affect planetary radiative balance and depend on chemical composition, size distribution, and morphology. During the MILAGRO field campaign, we measured aerosol absorption and scattering in Mexico City using the Los Alamos aerosol photoacoustic (LAPA) instrument operating at 781 nm. The LAPA was mounted on-board the Aerodyne Research Inc. mobile laboratory, which hosted a variety of gaseous and aerosol instruments. During the campaign, the laboratory was moved to different sites, capturing spatial and temporal variability. Additionally, we collected ambient aerosols on Nuclepore filters for scanning electron microscopy (SEM) analysis. SEM images of selected filters were taken to study particle morphology. Between March 7th and 19th air was sampled at the top of Pico Tres Padres, a mountain on the north side of Mexico City. Aerosol absorption and scattering followed diurnal patterns related to boundary layer height and solar insulation. We report an analysis of aerosol absorption, scattering, and morphology for three days (9th, 11th and 12th of March 2006). The single scattering albedo (SSA, ratio of scattering to total extinction) showed a drop in the tens-of-minutes-to-hour time frame after the boundary layer grew above the sampling site. Later in the day the SSA rose steadily reaching a maximum in the afternoon. The SEM images showed a variety of aerosol shapes including fractal-like aggregates, spherical particles, and other shapes. The absorption correlated with the CO2 signal and qualitatively with the fraction of fractal-like particles to the total particle count. In the afternoon the SSA qualitatively correlated with a relative increase in spherical particles and total particle count. These observed changes in optical properties and morphology can be explained by the dominant contribution of freshly emitted particles in the morning and by secondary particle formation in the afternoon. SSA hourly averaged values ranged from ~0.63 in the morning to ~0.83 in the afternoon/night, indicating light absorbing aerosols, which have a large impact on radiative forcing.

Out-of-Equilibrium Dynamics of Colloidal Particles at Interfaces

NASA Astrophysics Data System (ADS)

Wang, Anna

It is widely assumed that when colloidal particles adsorb to a fluid-fluid interface, they reach equilibrium rapidly. Recently, however, Kaz et al. [Nature Materials, 11, 138-142 (2012)] found that a variety of functionalised latex microspheres breaching an aqueous phase-oil interface relax logarithmically with time toward equilibrium. The relaxation is so slow that the time projected for the particles to reach the equilibrium contact angle of 110° is months--far longer than typical experimental timescales. In this thesis, we seek to understand the out-of-equilibrium behaviour of particles near interfaces. Because contact line pinning is likely an extra source of dissipation at interfaces, we start with experiments to elucidate the origins of contact-line pinning and find that polymer hairs on aqueous dispersed polymer particles strongly pin the contact-line. For particles without polymer hairs, nanoscale surface roughness can also pin the contact-line, though with a lower energy. We then extend our digital holography capabilities to track non-spherical particles. We demonstrate that we can track the centre-of-mass of a colloidal spherocylinder to a precision of 35 nm in all three dimensions and its orientation to a precision of 1.5°. Furthermore, the measured translational and rotational diffusion coefficients for the spherocylinders agree with hydrodynamic predictions to within 0.3%. This new functionality enables us to track colloidal ellipsoids and spherocylinders as they breach interfaces. By comparing the adsorption trajectories of the non-spherical particles to what is predicted from energy minimisation, we learn that contact-line pinning affects not just the timescales of breaching, but also the pathway to equilibrium. In fact, a particle's path to equilibrium can have complications even before the particle breaches the interface. Some particles are attracted to the interface, but stay within a few nanometers without ever breaching. We refer to this binding-mode as 'non-capillary binding', and we investigate when this binding mode is present, what causes it, and how interparticle interactions depend on the binding mode. The last few chapters in this thesis are extensions of ideas developed in the first part. We track the run and tumble of E.coli to demonstrate the potential of digital holographic microscopy as an imaging tool for active particles. Taking all of the particle-interface literature into account, we also outline some simple design principles for making particle-stabilised Pickering emulsions.

Water-dispersible hydroxyapatite nanoparticles synthesized in aqueous solution containing grape seed extract

NASA Astrophysics Data System (ADS)

Zhou, Ruchao; Si, Shaoxiong; Zhang, Qiyi

2012-02-01

A novel and effective method for the preparation of water-dispersible nano-hydroxyapatite (nHAp) particles was reported. nHAp was prepared in the presence of grape seed polyphenol (GSP) solution with different concentrations. Chemical precipitation method was adopted to produce pure nHAp and modified nHAp (nHAp-GSP) at 60 °C for 2 h. The chemical nature of the products was detected by Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Moreover, the crystal structure and morphology of particles was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the spherical nHAp particles with a diameter of 20-50 nm could be synthesized at 60 °C. The zeta potential values of pure nHAp and nHAp-GSP are -0.36 mV and -26.1 mV respectively. According to the sedimentary time, the colloidal stability of nHAp-GSP in water could be improved dramatically with the increase of GSP content and the particles tended to exist as dispersive nanoparticles without aggregation. All the results indicated that GSP exhibited strong binding to nHAp and enhanced the colloidal stability of nHAp particles.

The sustained-release behavior and in vitro and in vivo transfection of pEGFP-loaded core-shell-structured chitosan-based composite particles

PubMed Central

Wang, Yun; Lin, Fu-xing; Zhao, Yu; Wang, Mo-zhen; Ge, Xue-wu; Gong, Zheng-xing; Bao, Dan-dan; Gu, Yu-fang

2014-01-01

Novel submicron core-shell-structured chitosan-based composite particles encapsulated with enhanced green fluorescent protein plasmids (pEGFP) were prepared by complex coacervation method. The core was pEGFP-loaded thiolated N-alkylated chitosan (TACS) and the shell was pH- and temperature-responsive hydroxybutyl chitosan (HBC). pEGFP-loaded TACS-HBC composite particles were spherical, and had a mean diameter of approximately 120 nm, as measured by transmission electron microscopy and particle size analyzer. pEGFP showed sustained release in vitro for >15 days. Furthermore, in vitro transfection in human embryonic kidney 293T and human cervix epithelial cells, and in vivo transfection in mice skeletal muscle of loaded pEGFP, were investigated. Results showed that the expression of loaded pEGFP, both in vitro and in vivo, was slow but could be sustained over a long period. pEGFP expression in mice skeletal muscle was sustained for >60 days. This work indicates that these submicron core-shell-structured chitosan-based composite particles could potentially be used as a gene vector for in vivo controlled gene transfection. PMID:25364253

The sustained-release behavior and in vitro and in vivo transfection of pEGFP-loaded core-shell-structured chitosan-based composite particles.

PubMed

Wang, Yun; Lin, Fu-xing; Zhao, Yu; Wang, Mo-zhen; Ge, Xue-wu; Gong, Zheng-xing; Bao, Dan-dan; Gu, Yu-fang

2014-01-01

Novel submicron core-shell-structured chitosan-based composite particles encapsulated with enhanced green fluorescent protein plasmids (pEGFP) were prepared by complex coacervation method. The core was pEGFP-loaded thiolated N-alkylated chitosan (TACS) and the shell was pH- and temperature-responsive hydroxybutyl chitosan (HBC). pEGFP-loaded TACS-HBC composite particles were spherical, and had a mean diameter of approximately 120 nm, as measured by transmission electron microscopy and particle size analyzer. pEGFP showed sustained release in vitro for >15 days. Furthermore, in vitro transfection in human embryonic kidney 293T and human cervix epithelial cells, and in vivo transfection in mice skeletal muscle of loaded pEGFP, were investigated. Results showed that the expression of loaded pEGFP, both in vitro and in vivo, was slow but could be sustained over a long period. pEGFP expression in mice skeletal muscle was sustained for >60 days. This work indicates that these submicron core-shell-structured chitosan-based composite particles could potentially be used as a gene vector for in vivo controlled gene transfection.

Powder XRD, TEM, FTIR and thermal studies of strontium tartrate nano particles

NASA Astrophysics Data System (ADS)

Lathiya, U. M.; Jethva, H. O.; Joshi, M. J.; Vyas, P. M.

2017-05-01

Strontium tartrate finds several applications, e.g., as non-linear optical and dielectric material, in tracer composition and ammunition unit, in treating structural integrity of bone. The growth of single crystals of strontium tartrate in silica gel has been widely reported. In the present study, strontium tartrate nano particles were synthesized by wet chemical method using strontium chloride, tartaric acid and sodium meta-silicate solutions in the presence of Triton X -100 surfactant. It was found that the presence of sodium meta-silicate facilitated the reaction for strontium tartrate product. The powder XRD study of strontium tartrate nano-particles suggested monoclinic crystal system and the average crystallite size was found to be 40 nm determined by applying Scherrer's formula. The TEM analysis indicated that the nano particles were spherical in nature. The FTIR spectrum confirmed the presence of various functional groups such as O-H,C-H, and C=O stretching mode. The thermal analysis was carried out by using TGA and DTA studies. The nano-particles were found to be stable up to 175°C and then decomposed through various stages. The results are compared with the bulk crystalline material available in the literature.

Anomalous change of Airy disk with changing size of spherical particles

NASA Astrophysics Data System (ADS)

Pan, Linchao; Zhang, Fugen; Meng, Rui; Xu, Jie; Zuo, Chenze; Ge, Baozhen

2016-02-01

Use of laser diffraction is considered as a method of reliable principle and mature technique in measurements of particle size distributions. It is generally accepted that for a certain relative refractive index, the size of the scattering pattern (also called Airy disk) of spherical particles monotonically decreases with increasing particle size. This fine structure forms the foundation of the laser diffraction method. Here we show that the Airy disk size of non-absorbing spherical particles becomes larger with increasing particle size in certain size ranges. To learn more about this anomalous change of Airy disk (ACAD), we present images of Airy disk and curves of Airy disk size versus particle size for spherical particles of different relative refractive indices by using Mie theory. These figures reveal that ACAD occurs periodically for non-absorbing particles and will disappear when the absorbing efficiency is higher than certain value. Then by using geometrical optics (GO) approximation, we derive the analytical formulae for the bounds of the size ranges where ACAD occurs. From the formulae, we obtain laws of ACAD as follows: (1) for non-absorbing particles, ACAD occurs periodically, and when the particle size tends to infinity, the period tends to a certain value. As the relative refractive index increases, (2) the particle size ranges where ACAD occurs shift to smaller values, (3) the period of ACAD becomes smaller, and (4) the width of the size ranges where ACAD occurs becomes narrower. In addition, we can predict from the formulae that ACAD also exists for particles whose relative refractive index is smaller than 1.

High explosive compound

DOEpatents

Crawford, Theodore C.

1976-01-01

1. A low detonation velocity explosive consisting essentially of a particulate mixture of ortho-boric acid and trinitrotoluene, said mixture containing from about 25 percent to about 65 percent by weight of ortho-boric acid, said ortho-boric acid comprised of from 60 percent to 90 percent of spherical particles having a mean particle size of about 275 microns and 10 percent to 40 percent of spherical particles having a particle size less than about 44 microns.

Emergence and Utility of Nonspherical Particles in Biomedicine

PubMed Central

Fish, Margaret B.; Thompson, Alex J.; Fromen, Catherine A.; Eniola-Adefeso, Omolola

2016-01-01

The importance of the size of targeted, spherical drug carriers has been previously explored and reviewed. Particle shape has emerged as an equally important parameter in determining the in vivo journey and efficiency of drug carrier systems. Researchers have invented techniques to better control the geometry of particles of many different materials, which have allowed for exploration of the role of particle geometry in the phases of drug delivery. The important biological processes include clearance by the immune system, trafficking to the target tissue, margination to the endothelial surface, interaction with the target cell, and controlled release of a payload. The review of current literature herein supports that particle shape can be altered to improve a system’s targeting efficiency. Non-spherical particles can harness the potential of targeted drug carriers by enhancing targeted site accumulation while simultaneously decreasing side effects and mitigating some limitations faced by spherical carriers. PMID:27182109

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

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

Wu, Aiping; Tian, Chungui, E-mail: tianchungui@yahoo.com.cn; Chang, Wei

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

Mulberry leaf extract mediated synthesis of gold nanoparticles and its anti-bacterial activity against human pathogens

NASA Astrophysics Data System (ADS)

Adavallan, K.; Krishnakumar, N.

2014-06-01

Gold nanoparticles (Au-NPs) were synthesized at room temperature using Morus alba (mulberry) leaf extract as reducing and stabilizing agent. The development of plant mediated synthesis of nanoparticles is gaining importance due to its simplicity, low cost, non-toxicity, eco-friendliness, long term stability and reproducible aqueous synthesis method to obtain a self-assembly of nearly monodispersed Au-NPs. The formation and morphology of biosynthesized nanoparticles are investigated with the help of UV-Vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) techniques. Au-NPs formation was screened by UV-Vis spectroscopy through color conversion due to surface plasmon resonance band at 538 nm for Au-NPs. DLS studies revealed that the average size of Au-NPs was 50 nm. TEM studies showed the particles to be nearly spherical with few irregular shapes and particle size ranges 15-53 nm. The AFM image clearly shows the surface morphology of the well-dispersed Au-NPs with less than 50 nm. The high crystallinity of nanoparticles is evident from bright circular spots in the selected area electron diffraction (SAED) pattern. X-ray diffraction pattern showed high purity and face-centered cubic structure of Au-NPs. The FT-IR results indicate the presence of different functional groups present in the biomolecule capping the nanoparticles. Further, biosynthesized Au-NPs show strong zone of inhibition against Vibrio cholera (gram-negative) and Staphylococcus aureus (gram-positive) whereas, chemically synthesized Au-NPs and mulberry leaf extract exhibit a fair zone of inhibition.

Adhesive interaction of elastically deformable spherical particles

NASA Astrophysics Data System (ADS)

D'yachenko, E. N.; Dueck, J. G.

2012-01-01

Two spherical particles that attract each other by van der Waals volume forces and can undergo deformation as a result of the attraction are considered. Small deformations of such particles can be described by the solution of the Hertz problem. The deformation of particles, in turn, alters the force of attraction between them. It has been established that the relationship between the adhesion and elasticity of the indicated particles is determined by the degree to which these particles deform and that the adhesion force acting between the particles depends on their elasticity, size, and the Hamaker constants.

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

NASA Astrophysics Data System (ADS)

Marsden, Nicholas; Flynn, Michael J.; Taylor, Jonathan W.; Allan, James D.; Coe, Hugh

2016-12-01

Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance. A custom detection laser system consisting of a high-powered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) single-particle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment - Dust (ICE-D) project. The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500-800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (Csca) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of Csca with respect to particle diameter result in a variation in R, resulting in large particle-size-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.

Optical and structure characterization of cinnamon nanoparticles synthesized by pulse laser ablation in liquid (PLAL)

NASA Astrophysics Data System (ADS)

Aqeel Salim, Ali; Bidin, Noriah; Bakhtiar, Hazri; Krishna Ghoshal, Sib; Azawi, Mohammed Al; Krishnan, Ganesan

2018-05-01

Organic nanoparticles development is under exploration due to its beneficial applications in nanobiomedical and research interests. PLAL technique of Q-switched 1064-Nd: YAG (10 ns pulse duration, repetition rate 1 Hz and laser energy 20-100 mJ) has inherent advantages and rapid growth of nanoparticles when compared to conventional methods because of the controlled fabricated nanoparticles, stability, and purity. Cinnamon sticks as a target are immersed in 5 ml ethanol medium and irradiated by a laser beam for the growth process. The morphology, optical characteristic, and bonding structure of cinnamon nanoparticles (CNPs) are determined and evaluated by transmission electron microscope (TEM), UV-Visible spectroscopy and Fourier transform infrared spectroscopy (FTIR). Spherical, homogenous and high crystallinity CNPs was revealed within the particle size range of 2 - 28 nm. The absorption band was found in the ultraviolent region around 259 nm and 319 nm. The present of FTIR spectra confirmed that the nanoparticles were covered by plant secondary metabolites. The experimental findings revealed that the synthesize CNPs in ethanol has a potential for nanomedicine applications.

COMPARISON OF NUMERICAL SCHEMES FOR SOLVING A SPHERICAL PARTICLE DIFFUSION EQUATION

EPA Science Inventory

A new robust iterative numerical scheme was developed for a nonlinear diffusive model that described sorption dynamics in spherical particle suspensions. he numerical scheme had been applied to finite difference and finite element models that showed rapid convergence and stabilit...

DLVO interaction energies between hollow spherical particles and collector surfaces

USDA-ARS?s Scientific Manuscript database

The surface element integration technique was used to systematically study Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies/forces between hollow spherical particles (HPs) and a planar surface or two intercepting half planes under different ionic strength conditions. The inner and outer ...

An Aspergillus aculateus strain was capable of producing agriculturally useful nanoparticles via bioremediation of iron ore tailings.

PubMed

Bedi, Ankita; Singh, Braj Raj; Deshmukh, Sunil K; Adholeya, Alok; Barrow, Colin J

2018-06-01

Mining waste such as iron ore tailing is environmentally hazardous, encouraging researchers to develop effective bioremediation technologies. Among the microbial isolates collected from iron ore tailings, Aspergillus aculeatus (strain T6) showed good leaching efficiency and produced iron-containing nanoparticles under ambient conditions. This strain can convert iron ore tailing waste into agriculturally useful nanoparticles. Fourier-transform Infrared Spectroscopy (FT-IR analysis) established the at the particles are protein coated, with energy dispersive X-ray Spectroscopy (EDX analysis) showing strong signals for iron. Transmission Electron Microscopy (TEM analysis) showed semi-quasi spherical particles having average size of 15 ± 5 nm. These biosynthesized nanoparticles when tested for their efficacy on seed emergence activity of mungbean (Vigna radiata) seeds, and enhanced plant growth at 10 and 20 ppm. Copyright © 2018 Elsevier Ltd. All rights reserved.

Experimental light scattering by small particles: system design and calibration

NASA Astrophysics Data System (ADS)

Maconi, Göran; Kassamakov, Ivan; Penttilä, Antti; Gritsevich, Maria; Hæggström, Edward; Muinonen, Karri

2017-06-01

We describe a setup for precise multi-angular measurements of light scattered by mm- to μm-sized samples. We present a calibration procedure that ensures accurate measurements. Calibration is done using a spherical sample (d = 5 mm, n = 1.517) fixed on a static holder. The ultimate goal of the project is to allow accurate multi-wavelength measurements (the full Mueller matrix) of single-particle samples which are levitated ultrasonically. The system comprises a tunable multimode Argon-krypton laser, with 12 wavelengths ranging from 465 to 676 nm, a linear polarizer, a reference photomultiplier tube (PMT) monitoring beam intensity, and several PMT:s mounted radially towards the sample at an adjustable radius. The current 150 mm radius allows measuring all azimuthal angles except for ±4° around the backward scattering direction. The measurement angle is controlled by a motor-driven rotational stage with an accuracy of 15'.

Nanosized amorphous calcium carbonate stabilized by poly(ethylene oxide)-b-poly(acrylic acid) block copolymers.

PubMed

Guillemet, Baptiste; Faatz, Michael; Gröhn, Franziska; Wegner, Gerhard; Gnanou, Yves

2006-02-14

Particles of amorphous calcium carbonate (ACC), formed in situ from calcium chloride by the slow release of carbon dioxide by alkaline hydrolysis of dimethyl carbonate in water, are stabilized against coalescence in the presence of very small amounts of double hydrophilic block copolymers (DHBCs) composed of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blocks. Under optimized conditions, spherical particles of ACC with diameters less than 100 nm and narrow size distribution are obtained at a concentration of only 3 ppm of PEO-b-PAA as additive. Equivalent triblock or star DHBCs are compared to diblock copolymers. The results are interpreted assuming an interaction of the PAA blocks with the surface of the liquid droplets of the concentrated CaCO3 phase, formed by phase separation from the initially homogeneous reaction mixture. The adsorption layer of the block copolymer protects the liquid precursor of ACC from coalescence and/or coagulation.

Development of a novel microemulsion for oral absorption enhancement of all-trans retinoic acid

PubMed Central

Subongkot, Thirapit; Ngawhirunpat, Tanasait

2017-01-01

This study was aimed to develop a novel microemulsion that contained oleth-5 as a surfactant to enhance the oral absorption of all-trans retinoic acid (ATRA). The prepared microemulsion was evaluated for its particle size, shape, zeta potential, in vitro release, in vitro intestinal absorption, intestinal membrane cytotoxicity and stability. The obtained microemulsion was spherical in shape with a particle size of <200 nm and a negative surface charge. The in vitro release of the ATRA-loaded microemulsion was best fit with the zero-order model. This microemulsion significantly improved the intestinal absorption of ATRA. Confocal laser scanning microscopy analysis using a fluorescent dye-loaded microemulsion also confirmed the intestinal absorption result. The intestinal membrane cytotoxicity of the ATRA-loaded microemulsion did not differ from an edible oil (fish oil). Stability testing showed that the ATRA-loaded microemulsion was more stable at 25°C than 40°C. PMID:28831254

Development of a novel microemulsion for oral absorption enhancement of all-trans retinoic acid.

PubMed

Subongkot, Thirapit; Ngawhirunpat, Tanasait

2017-01-01

This study was aimed to develop a novel microemulsion that contained oleth-5 as a surfactant to enhance the oral absorption of all-trans retinoic acid (ATRA). The prepared microemulsion was evaluated for its particle size, shape, zeta potential, in vitro release, in vitro intestinal absorption, intestinal membrane cytotoxicity and stability. The obtained microemulsion was spherical in shape with a particle size of <200 nm and a negative surface charge. The in vitro release of the ATRA-loaded microemulsion was best fit with the zero-order model. This microemulsion significantly improved the intestinal absorption of ATRA. Confocal laser scanning microscopy analysis using a fluorescent dye-loaded microemulsion also confirmed the intestinal absorption result. The intestinal membrane cytotoxicity of the ATRA-loaded microemulsion did not differ from an edible oil (fish oil). Stability testing showed that the ATRA-loaded microemulsion was more stable at 25°C than 40°C.

Improving the Performance of Gold-Nanoparticle-Doped Solid-State Dye Laser Using Thermal Conversion Effect

NASA Astrophysics Data System (ADS)

An, N. T. M.; Lien, N. T. H.; Hoang, N. D.; Hoa, D. Q.

2018-04-01

Energy transfer between spherical gold nanoparticles with size of more than 15 nm and molecules of organic dye 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4 H-pyran (DCM) has been studied. Such radiative energy transfer led to high local temperature, giving rise to a bleaching effect that resulted in rapid degradation of the laser medium. Gold nanoparticles were dispersed at concentrations from 5 × 109 particles/mL to 5 × 1010 particles/mL in DCM polymethylmethacrylate polymer using a radical polymerization process with 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. Using the fast thermoelectric cooling method, the laser medium stability was significantly improved. The output stability of a distributed feedback dye laser pumped by second-harmonic generation from a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was investigated. Moreover, bidirectional energy transfer between gold nanoparticles and dye molecules was observed.

Mechanistic approach to study conjugation of nanoparticles for biomedical applications.

PubMed

Uddin, Imran

2018-05-16

Interaction of nanoparticles with biological systems turns out to be vibrant for their efficient application in biomedical field. Here, we have shown antibiotic amakicin loaded nanoparticles are responsible for the dual role as reducing and stabilizing the silver nanoparticles without the use of any undesired chemicals. Synthesized nanoparticles are well-dispersed having quasi spherical morphology with an average particle size around 10-11 nm. Crystallinity of nanoparticles was measured using selected area electron diffraction (SAED) and powder XRD analysis which show that particles are perfectly crystalline with cubic phase of geometry. UV-Vis, FTIR and circular dichroism (CD) analysis explained the presence and interaction of antibiotic on the nanoparticle's surface. Amakicin functionalized Ag nanoparticles used in this study have shown enhanced antibacterial activity against E. coli. These studies will help in designing an in-depth understanding that how nanostructures can possibly interact with biological systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation

NASA Astrophysics Data System (ADS)

Ulvestad, A.; Welland, M. J.; Cha, W.; Liu, Y.; Kim, J. W.; Harder, R.; Maxey, E.; Clark, J. N.; Highland, M. J.; You, H.; Zapol, P.; Hruszkewycz, S. O.; Stephenson, G. B.

2017-05-01

Crystallographic imperfections significantly alter material properties and their response to external stimuli, including solute-induced phase transformations. Despite recent progress in imaging defects using electron and X-ray techniques, in situ three-dimensional imaging of defect dynamics remains challenging. Here, we use Bragg coherent diffractive imaging to image defects during the hydriding phase transformation of palladium nanocrystals. During constant-pressure experiments we observe that the phase transformation begins after dislocation nucleation close to the phase boundary in particles larger than 300 nm. The three-dimensional phase morphology suggests that the hydrogen-rich phase is more similar to a spherical cap on the hydrogen-poor phase than to the core-shell model commonly assumed. We substantiate this using three-dimensional phase field modelling, demonstrating how phase morphology affects the critical size for dislocation nucleation. Our results reveal how particle size and phase morphology affects transformations in the PdH system.

Biosynthesis of gold nanoparticles assisted by the intracellular protein extract of Pycnoporus sanguineus and its catalysis in degradation of 4-nitroaniline

NASA Astrophysics Data System (ADS)

Shi, Chaohong; Zhu, Nengwu; Cao, Yanlan; Wu, Pingxiao

2015-03-01

The development of green procedure for the synthesis of gold nanoparticles (AuNPs) has gained great interest in the field of nanotechnology. Biological synthetic routes are considered to be environmentally benign and cost-effective. In the present study, the feasibility of AuNPs' synthesis via intracellular protein extract (IPE) of Pycnoporus sanguineus was explored. The characteristics of generated particles of formation, crystalline nature, and morphology and dimension were analyzed by UV-vis spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. UV-vis spectra exhibited strong absorption peaks in 520 to 560 nm, indicating the formation of AuNPs. XRD analysis revealed that the formed AuNPs were purely crystalline in nature. TEM observation showed that AuNPs with various shapes including spherical, pseudo-spherical, triangular, truncated triangular, pentagonal, and hexagonal, ranging from several to several hundred nanometers, were synthesized under different conditions. The average size of AuNPs decreased from 61.47 to 29.30 nm as the IPE addition increased from 10 to 80 mL. When the initial gold ion concentration changed from 0.5 to 2.0 mM, the average size rose from 25.88 to 51.99 nm. As in the case of solution pH, the average size was 84.29 nm with solution pH of 2.0, which diminished to 6.07 nm with solution pH of 12.0. Fourier transform infrared (FTIR) analysis implied that the functional groups including hydroxyl, amine, and carboxyl were involved in the reduction of gold ions and stabilization of AuNPs. The catalysis results showed that 0.019 mg of AuNPs with average size of 6.07 nm could catalyze the complete degradation of 12.5 μmol of 4-nitroaniline within 6 min and the degradation rate increased drastically with the addition of AuNPs. All the results suggested that the IPE of P. sanguineus could be potentially applied for the eco-friendly synthesis of AuNPs.

Dechlorination of disinfection by-product monochloroacetic acid in drinking water by nanoscale palladized iron bimetallic particle.

PubMed

Chen, Chao; Wang, Xiangyu; Chang, Ying; Liu, Huiling

2008-01-01

Nanoscale palladized iron (Pd/Fe) bimetallic particles were prepared by reductive deposition method. The particles were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM), and Brunauer-Emmett-Teller-nitrogen (BET-N2) method. Data obtained from those methods indicated that nanoscale Pd/Fe bimetallic particles contained alpha-Fe0. Detected Pd to Fe ratio by weight (Pd/Fe ratio) was close to theoretical value. Spherical granules with diameter of 47 +/- 11.5 nm connected with one another to form chains and the chains composed nanoscale Pd/Fe bimetallic particles. Specific surface area of particles was 51 m2/g. The factors, such as species of reductants, Pd/Fe ratio, dose of nanoscale Pd/Fe bimetallic particles added into solutions, solution initial pH, and a variety of solvents were studied. Dechlorination effect of monochloroacetic acid by different reductants followed the trend: nanoscale Pd/Fe bimetallic particles of 0.182% Pd/Fe > nanoscale Fe > reductive Fe. When the Pd/Fe ratio was lower than 0.083%, increasing Pd/Fe ratio would increase dechlorination efficiency (DE) of MCAA. When the Pd/Fe ratio was higher than 0.083%, increasing Pd/Fe ratio caused a decrease in DE. Adding more nanoscale Pd/Fe bimetallic particles to solution would enhance DE. The DE of MCAA decreased as initial pH of solution increased.

Fabricating the spherical and flake silver powder used for the optoelectronic devices

NASA Astrophysics Data System (ADS)

Ju, Wei; Ma, Wangjing; Zhang, Fangzhi; Chen, Yixiang; Xie, Jinpeng

2018-01-01

The spherical and flake silver powder with different particle size for the optoelectronic devices was partly prepared by using chemical reduction and ball milling method, and charactered by scanning electron microscope (SEM), X-ray diffraction (XRD), laser particle size analyzer and thermo-gravimetric(TG) analyzer. The particle size of three series of spherical silver powder fabricated by chemical reduction is about 1.5μm, 1μm and 0.6μm, respectively; after being mechanical milling, the particle size of flake silver powder with high flaky rate is about 10μm, 6μm and 2μm respectively. Thermo gravimetric (TG) and XRD analyses showed that the silver powders have high purity and crystalline, and then the laser particle size and SEM analyses showed that the silver powders has good uniformity.

Fluidization of spherocylindrical particles

NASA Astrophysics Data System (ADS)

Mahajan, Vinay V.; Nijssen, Tim M. J.; Fitzgerald, Barry W.; Hofman, Jeroen; Kuipers, Hans; Padding, Johan T.

2017-06-01

Multiphase (gas-solid) flows are encountered in numerous industrial applications such as pharmaceutical, food, agricultural processing and energy generation. A coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach is a popular way to study such flows at a particle scale. However, most of these studies deal with spherical particles while in reality, the particles are rarely spherical. The particle shape can have significant effect on hydrodynamics in a fluidized bed. Moreover, most studies in literature use inaccurate drag laws because accurate laws are not readily available. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation with the flow, Reynolds number and packing fraction. In this work, the CFD-DEM approach is extended to model a laboratory scale fluidized bed of spherocylinder (rod-like) particles. These rod-like particles can be classified as Geldart D particles and have an aspect ratio of 4. Experiments are performed to study the particle flow behavior in a quasi-2D fluidized bed. Numerically obtained results for pressure drop and bed height are compared with experiments. The capability of CFD-DEM approach to efficiently describe the global bed dynamics for fluidized bed of rod-like particles is demonstrated.

Self assembly of anisotropic colloidal particles

NASA Astrophysics Data System (ADS)

Florea, Daniel; Wyss, Hans

2012-02-01

Colloidal particles have been successfully used as ''model atoms'', as their behavior can be more directly studied than that of atoms or molecules by direct imaging in a confocal microscope. Most studies have focussed on spherical particles with isotropic interactions. However, a range of interesting materials such as many supramolecular polymers or biopolymers exhibit highly directional interactions. To capture their behavior in colloidal model systems, particles with anisotropic interactions are clearly required. Here we use a colloidal system of nonspherical colloids, where highly directional interactions can be induced via depletion. By biaxially stretching spherical PMMA particles we create oblate spheroidal particles. We induce attractive interactions between these particles by adding a non-adsorbing polymer to the background liquid. The resulting depletion interaction is stronger along the minor axis of the oblate spheroids. We study the phase behavior of these materials as a function of the ellipsoid aspect ratio, the strength of the depletion interactions, and the particle concentration. The resulting morphologies are qualitatively different from those observed with spherical particles. This can be exploited for creating new materials with tailored structures.

The 4-parameter Compressible Packing Model (CPM) including a critical cavity size ratio

NASA Astrophysics Data System (ADS)

Roquier, Gerard

2017-06-01

The 4-parameter Compressible Packing Model (CPM) has been developed to predict the packing density of mixtures constituted by bidisperse spherical particles. The four parameters are: the wall effect and the loosening effect coefficients, the compaction index and a critical cavity size ratio. The two geometrical interactions have been studied theoretically on the basis of a spherical cell centered on a secondary class bead. For the loosening effect, a critical cavity size ratio, below which a fine particle can be inserted into a small cavity created by touching coarser particles, is introduced. This is the only parameter which requires adaptation to extend the model to other types of particles. The 4-parameter CPM demonstrates its efficiency on frictionless glass beads (300 values), spherical particles numerically simulated (20 values), round natural particles (125 values) and crushed particles (335 values) with correlation coefficients equal to respectively 99.0%, 98.7%, 97.8%, 96.4% and mean deviations equal to respectively 0.007, 0.006, 0.007, 0.010.

Direct Numerical Simulation of Oscillatory Flow Over a Wavy, Rough, and Permeable Bottom

NASA Astrophysics Data System (ADS)

Mazzuoli, Marco; Blondeaux, Paolo; Simeonov, Julian; Calantoni, Joseph

2018-03-01

The results of a direct numerical simulation of oscillatory flow over a wavy bottom composed of different layers of spherical particles are described. The amplitude of wavy bottom is much smaller in scale than typical bed forms such as sand ripples. The spherical particles are packed in such a way to reproduce a bottom profile observed during an experiment conducted in a laboratory flow tunnel with well-sorted coarse sand. The amplitude and period of the external forcing flow as well as the size of the particles are set equal to the experimental values and the computed velocity field is compared with the measured velocity profiles. The direct numerical simulation allows for the evaluation of quantities, which are difficult to measure in a laboratory experiment (e.g., vorticity, seepage flow velocity, and hydrodynamic force acting on sediment particles). In particular, attention is focused on the coherent vortex structures generated by the vorticity shed by both the spherical particles and the bottom waviness. Results show that the wavy bottom triggers transition to turbulence. Moreover, the forces acting on the spherical particles are computed to investigate the mechanisms through which they are possibly mobilized by the oscillatory flow. It was found that forces capable of mobilizing surface particles are strongly correlated with the particle position above the mean bed elevation and the passage of coherent vortices above them.

WE-H-BRA-08: A Monte Carlo Cell Nucleus Model for Assessing Cell Survival Probability Based On Particle Track Structure Analysis

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

Lee, B; Georgia Institute of Technology, Atlanta, GA; Wang, C

Purpose: To correlate the damage produced by particles of different types and qualities to cell survival on the basis of nanodosimetric analysis and advanced DNA structures in the cell nucleus. Methods: A Monte Carlo code was developed to simulate subnuclear DNA chromatin fibers (CFs) of 30nm utilizing a mean-free-path approach common to radiation transport. The cell nucleus was modeled as a spherical region containing 6000 chromatin-dense domains (CDs) of 400nm diameter, with additional CFs modeled in a sparser interchromatin region. The Geant4-DNA code was utilized to produce a particle track database representing various particles at different energies and dose quantities.more » These tracks were used to stochastically position the DNA structures based on their mean free path to interaction with CFs. Excitation and ionization events intersecting CFs were analyzed using the DBSCAN clustering algorithm for assessment of the likelihood of producing DSBs. Simulated DSBs were then assessed based on their proximity to one another for a probability of inducing cell death. Results: Variations in energy deposition to chromatin fibers match expectations based on differences in particle track structure. The quality of damage to CFs based on different particle types indicate more severe damage by high-LET radiation than low-LET radiation of identical particles. In addition, the model indicates more severe damage by protons than of alpha particles of same LET, which is consistent with differences in their track structure. Cell survival curves have been produced showing the L-Q behavior of sparsely ionizing radiation. Conclusion: Initial results indicate the feasibility of producing cell survival curves based on the Monte Carlo cell nucleus method. Accurate correlation between simulated DNA damage to cell survival on the basis of nanodosimetric analysis can provide insight into the biological responses to various radiation types. Current efforts are directed at producing cell survival curves for high-LET radiation.« less

Conventional and microwave combustion synthesis of optomagnetic CuFe2O4 nanoparticles for hyperthermia studies

NASA Astrophysics Data System (ADS)

Kombaiah, K.; Vijaya, J. Judith; Kennedy, L. John; Bououdina, M.; Al-Najar, Basma

2018-04-01

Nanosized copper ferrite (CuFe2O4) nanoparticles have been prepared by conventional (CCM) and microwave (MCM) combustion methods using Hibiscus rosa sinensis plant extract as a fuel. XRD and rietveld analysis confirmed the formation of single cubic phase and with crystallite size varying from 25 to 62 nm owing to grain growth after calcination. FT-IR analysis confirms the modes of the cubic CuFe2O4 phase, due to the stretching and bending vibrations. Spherical shaped particles are observed by scanning electron microscopy and the average particle size is found to be in the range of 50-200 nm. The chemical composition is confirmed by energy dispersive X-ray analysis. The optical band gap energy estimated using Kubelka-Munk function with the help of UV-Visible diffused reflectance spectroscopy, is found to be 2.34 and 2.22 eV for CCM and MCM respectively. Photoluminescence analysis indicates that both samples absorb light in the UV-visible region and exhibit emissions at 360, 376, and 412 nm. Magnetic measurements indicate a ferromagnetic behavior, where both magnetic properties very much influenced by the preparation method and calcination temperature: both saturation magnetization and coercivity are found higher when using CCM and MCM; from 29.40 to 34.09 emu/g while almost double from 224.4 to 432.2 Oe. The observed changes in physical properties are mainly associated with crystallinity, particle size, better chemical homogeneity, and cations distribution among tetrahedral/octahedral sites. The maximum specific absorption rate obtained was 14.63 W/g, which can be considered suitable and favorable for magnetic hyperthermia. This study highlighted the benefits of green synthesis of CuFe2O4 nanoparticles providing better magnetic properties for the platform of hyperthermia application.

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.

Atomizing apparatus for making polymer and metal powders and whiskers

DOEpatents

Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

2003-03-18

Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

Modelling sheet-flow sediment transport in wave-bottom boundary layers using discrete-element modelling.

PubMed

Calantoni, Joseph; Holland, K Todd; Drake, Thomas G

2004-09-15

Sediment transport in oscillatory boundary layers is a process that drives coastal geomorphological change. Most formulae for bed-load transport in nearshore regions subsume the smallest-scale physics of the phenomena by parametrizing interactions amongst particles. In contrast, we directly simulate granular physics in the wave-bottom boundary layer using a discrete-element model comprised of a three-dimensional particle phase coupled to a one-dimensional fluid phase via Newton's third law through forces of buoyancy, drag and added mass. The particulate sediment phase is modelled using discrete particles formed to approximate natural grains by overlapping two spheres. Both the size of each sphere and the degree of overlap can be varied for these composite particles to generate a range of non-spherical grains. Simulations of particles having a range of shapes showed that the critical angle--the angle at which a grain pile will fail when tilted slowly from rest--increases from approximately 26 degrees for spherical particles to nearly 39 degrees for highly non-spherical composite particles having a dumbbell shape. Simulations of oscillatory sheet flow were conducted using composite particles with an angle of repose of approximately 33 degrees and a Corey shape factor greater than about 0.8, similar to the properties of beach sand. The results from the sheet-flow simulations with composite particles agreed more closely with laboratory measurements than similar simulations conducted using spherical particles. The findings suggest that particle shape may be an important factor for determining bed-load flux, particularly for larger bed slopes.

Optimized spray drying process for preparation of one-step calcium-alginate gel microspheres

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

Popeski-Dimovski, Riste

Calcium-alginate micro particles have been used extensively in drug delivery systems. Therefore we establish a one-step method for preparation of internally gelated micro particles with spherical shape and narrow size distribution. We use four types of alginate with different G/M ratio and molar weight. The size of the particles is measured using light diffraction and scanning electron microscopy. Measurements showed that with this method, micro particles with size distribution around 4 micrometers can be prepared, and SEM imaging showed that those particles are spherical in shape.

Emerging Research and Clinical Development Trends of Liposome and Lipid Nanoparticle Drug Delivery Systems

PubMed Central

KRAFT, JOHN C.; FREELING, JENNIFER P.; WANG, ZIYAO; HO, RODNEY J. Y.

2014-01-01

Liposomes are spherical-enclosed membrane vesicles mainly constructed with lipids. Lipid nanoparticles are loaded with therapeutics and may not contain an enclosed bilayer. The majority of those clinically approved have diameters of 50–300 nm. The growing interest in nanomedicine has fueled lipid–drug and lipid–protein studies, which provide a foundation for developing lipid particles that improve drug potency and reduce off-target effects. Integrating advances in lipid membrane research has enabled therapeutic development. At present, about 600 clinical trials involve lipid particle drug delivery systems. Greater understanding of pharmacokinetics, biodistribution, and disposition of lipid–drug particles facilitated particle surface hydration technology (with polyethylene glycol) to reduce rapid clearance and provide sufficient blood circulation time for drug to reach target tissues and cells. Surface hydration enabled the liposome-encapsulated cancer drug doxorubicin (Doxil) to gain clinical approval in 1995. Fifteen lipidic therapeutics are now clinically approved. Although much research involves attaching lipid particles to ligands selective for occult cells and tissues, preparation procedures are often complex and pose scale-up challenges. With emerging knowledge in drug target and lipid–drug distribution in the body, a systems approach that integrates knowledge to design and scale lipid–drug particles may further advance translation of these systems to improve therapeutic safety and efficacy. PMID:24338748

Local characterization of hindered Brownian motion by using digital video microscopy and 3D particle tracking

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

Dettmer, Simon L.; Keyser, Ulrich F.; Pagliara, Stefano

In this article we present methods for measuring hindered Brownian motion in the confinement of complex 3D geometries using digital video microscopy. Here we discuss essential features of automated 3D particle tracking as well as diffusion data analysis. By introducing local mean squared displacement-vs-time curves, we are able to simultaneously measure the spatial dependence of diffusion coefficients, tracking accuracies and drift velocities. Such local measurements allow a more detailed and appropriate description of strongly heterogeneous systems as opposed to global measurements. Finite size effects of the tracking region on measuring mean squared displacements are also discussed. The use of thesemore » methods was crucial for the measurement of the diffusive behavior of spherical polystyrene particles (505 nm diameter) in a microfluidic chip. The particles explored an array of parallel channels with different cross sections as well as the bulk reservoirs. For this experiment we present the measurement of local tracking accuracies in all three axial directions as well as the diffusivity parallel to the channel axis while we observed no significant flow but purely Brownian motion. Finally, the presented algorithm is suitable also for tracking of fluorescently labeled particles and particles driven by an external force, e.g., electrokinetic or dielectrophoretic forces.« less

Microwave Polarized Signatures Generated within Cloud Systems: SSM/I Observations Interpreted with Radiative Transfer Simulations

NASA Technical Reports Server (NTRS)

Prigent, Catherine; Pardo, Juan R.; Mishchenko, Michael I.; Rossow, Willaim B.; Hansen, James E. (Technical Monitor)

2001-01-01

Special Sensor Microwave /Imager (SSM/I) observations in cloud systems are studied over the tropics. Over optically thick cloud systems, presence of polarized signatures at 37 and 85 GHz is evidenced and analyzed with the help of cloud top temperature and optical thickness extracted from visible and IR satellite observations. Scattering signatures at 85 GHz (TbV(85) less than or = 250 K) are associated with polarization differences greater than or = 6 K, approx. 50%, of the time over ocean and approx. 40% over land. In addition. over thick clouds the polarization difference at 37 GHz is rarely negligible. The polarization differences at 37 and 85 GHz do not stem from the surface but are generated in regions of relatively homogeneous clouds having high liquid water content. To interpret the observations, a radiative transfer model that includes the scattering by non-spherical particles is developed. based on the T-matrix approach and using the doubling and adding method. In addition to handling randomly and perfectly oriented particles, this model can also simulate the effect of partial orientation of the hydrometeors. Microwave brightness temperatures are simulated at SSM/I frequencies and are compared with the observations. Polarization differences of approx. 2 K can be simulated at 37 GHz over a rain layer, even using spherical drops. The polarization difference is larger for oriented non-spherical particles. The 85 GHz simulations are very sensitive to the ice phase of the cloud. Simulations with spherical particles or with randomly oriented non-spherical ice particles cannot replicate the observed polarization differences. However, with partially oriented non-spherical particles, the observed polarized signatures at 85 GHz are explained, and the sensitivity of the scattering characteristics to the particle size, asphericity, and orientation is analyzed. Implications on rain and ice retrievals are discussed.

Synthesis, characterization and application of Lagerstroemia speciosa embedded magnetic nanoparticle for Cr(VI) adsorption from aqueous solution.

PubMed

Srivastava, Shalini; Agrawal, Shashi Bhushan; Mondal, Monoj Kumar

2017-05-01

Lagerstroemia speciosa bark (LB) embedded magnetic nanoparticles were prepared by co-precipitation of Fe 2+ and Fe 3+ salt solution with ammonia and LB for Cr(VI) removal from aqueous solution. The native LB, magnetic nanoparticle (MNP), L. speciosa embedded magnetic nanoparticle (MNPLB) and Cr(VI) adsorbed MNPLB particles were characterized by SEM-EDX, TEM, BET-surface area, FT-IR, XRD and TGA methods. TEM analysis confirmed nearly spherical shape of MNP with an average diameter of 8.76nm and the surface modification did not result in the phase change of MNP as established by XRD analysis, while led to the formation of secondary particles of MNPLB with diameter of 18.54nm. Characterization results revealed covalent binding between the hydroxyl group of MNP and carboxyl group of LB particles and further confirmed its physico-chemical nature favorable for Cr(VI) adsorption. The Cr(VI) adsorption on to MNPLB particle as an adsorbent was tested under different contact time, initial Cr(VI) concentration, adsorbent dose, initial pH, temperature and agitation speed. The results of the equilibrium and kinetics of adsorption were well described by Langmuir isotherm and pseudo-second-order model, respectively. The thermodynamic parameters suggest spontaneous and endothermic nature of Cr(VI) adsorption onto MNPLB. The maximum adsorption capacity for MNPLB was calculated to be 434.78mg/g and these particles even after Cr(VI) adsorption were collected effortlessly from the aqueous solution by a magnet. The desorption of Cr(VI)-adsorbed MNPLB was found to be more than 93.72% with spent MNPLB depicting eleven successive adsorption-desorption cycles. Copyright © 2016. Published by Elsevier B.V.

Study on the RF inductively coupled plasma spheroidization of refractory W and W-Ta alloy powders

NASA Astrophysics Data System (ADS)

Chenfan, YU; Xin, ZHOU; Dianzheng, WANG; Neuyen VAN, LINH; Wei, LIU

2018-01-01

Spherical powders with good flowability and high stacking density are mandatory for powder bed additive manufacturing. Nevertheless, the preparation of spherical refractory tungsten and tungsten alloy powders is a formidable task. In this paper, spherical refractory metal powders processed by high-energy stir ball milling and RF inductively coupled plasma were investigated. By utilizing the technical route, pure spherical tungsten powders were prepared successfully, the flowability increased from 10.7 s/50 g to 5.5 s/50 g and apparent density increased from 6.916 g cm-3 to 11.041 g cm-3. Alloying element tantalum can reduce the tendency to micro-crack during tungsten laser melting and rapid solidification process. Spherical W-6Ta (%wt) powders were prepared in this way, homogeneous dispersion of tantalum in a tungsten matrix occurred but a small amount of flake-like shape particles appeared after high-energy stir ball milling. The flake-like shape particles can hardly be spheroidized in subsequent RF inductively coupled plasma process, might result from the unique suspended state of flaky particles under complex electric and magnetic fields as well as plasma-particle heat exchange was different under various turbulence models. As a result, the flake-like shape particles cannot pass through the high-temperature area of thermal plasma torch and cannot be spheroidized properly.

Sub-10 nm Silicon Nanopillar Fabrication Using Fast and Brushless Thermal Assembly of PS-b-PDMS Diblock Copolymer.

PubMed

Garnier, Jérôme; Arias-Zapata, Javier; Marconot, Olivier; Arnaud, Sandrine; Böhme, Sophie; Girardot, Cécile; Buttard, Denis; Zelsmann, Marc

2016-04-20

A new approach to obtaining spherical nanodomains using polystyrene-block-polydimethylsiloxane (PS-b-PDMS) is proposed. To reduce drastically the process time, we blended a copolymer with cylindrical morphology with a PS homopolymer. Adding PS homopolymer into a low-molar-mass cylindrical morphology PS-b-PDMS system drives it toward a spherical morphology. Besides, by controlling the as-spun state, spherical PDMS nanodomains could be kept and thermally arranged. This PS-homopolymer addition allows not only an efficient, purely thermal arrangement process of spheres but also the ability to work directly on nontreated silicon substrates. Indeed, as shown by STEM measurements, no PS brush surface treatment was necessary in our study to avoid a PDMS wetting layer at the interface with the Si substrate. Our approach was compared to a sphere-forming diblock copolymer, which needs a longer thermal annealing. Furthermore, GISAXS measurements provided complete information on PDMS sphere features. Excellent long-range order spherical microdomains were therefore produced on flat surfaces and inside graphoepitaxy trenches with a period of 21 nm, as were in-plane spheres with a diameter of 8 nm with a 15 min thermal annealing. Finally, direct plasma-etching transfer into the silicon substrate was demonstrated, and 20 nm high silicon nanopillars were obtained, which are very promising results for various nanopatterning applications.

Biological properties of purified recombinant HCV particles with an epitope-tagged envelope

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

Takahashi, Hitoshi; Akazawa, Daisuke; Toray Industries, Inc., Kanagawa

2010-05-14

To establish a simple system for purification of recombinant infectious hepatitis C virus (HCV) particles, we designed a chimeric J6/JFH-1 virus with a FLAG (FL)-epitope-tagged sequence at the N-terminal region of the E2 hypervariable region-1 (HVR1) gene (J6/JFH-1/1FL). We found that introduction of an adaptive mutation at the potential N-glycosylation site (E2N151K) leads to efficient production of the chimeric virus. This finding suggests the involvement of glycosylation at Asn within the envelope protein(s) in HCV morphogenesis. To further analyze the biological properties of the purified recombinant HCV particles, we developed a strategy for large-scale production and purification of recombinant J6/JFH-1/1FL/E2N151K.more » Infectious particles were purified from the culture medium of J6/JFH-1/1FL/E2N151K-infected Huh-7 cells using anti-FLAG affinity chromatography in combination with ultrafiltration. Electron microscopy of the purified particles using negative staining showed spherical particle structures with a diameter of 40-60 nm and spike-like projections. Purified HCV particle-immunization induced both an anti-E2 and an anti-FLAG antibody response in immunized mice. This strategy may contribute to future detailed analysis of HCV particle structure and to HCV vaccine development.« less

Design and synthesis of magnetic nanoparticles with gold shells for single particle optical tracking

NASA Astrophysics Data System (ADS)

Lim, Jitkang

The design, synthesis, and characterization of iron oxide core, gold shell nanoparticles are studied in this thesis. Firstly, nanoparticles with 18 +/- 1.7 nm diameter iron oxide cores with ˜5 nm thick gold shells were synthesized via a new seed-mediated electroless deposition method. The nanoparticles were superparamagnetic at room temperature and could be reversibly collected by a permanent magnet. These nanoparticles displayed a sharp localized surface plasmon resonance peak at 605 nm, as predicted by scattering theory, and their large scattering cross-section allowed them to be individually resolved in darkfield optical microscopy while undergoing Brownian motion in aqueous suspension. Later, commercially available 38 +/- 3.8 nm diameter spherical iron oxide nanoparticles (from Ocean Nanotech, Inc) were employed to make core-shell particles. These particles were decorated with cationic poly(diallyldimethylammonium chloride) (PDDA) which further promotes the attachment of small gold clusters. After gold seeding, the average hydrodynamic diameter of the core-shell particles is 172 +/- 65.9 nm. The magnetophoretic motion of these particles was guided by a piece of magnetized mu-metal. Individual particle trajectories were observed by darkfield optical microscopy. The typical magnetophoretic velocity achieved was within the range of 1--10 mum/sec. Random walk analysis performed on these particles while undergoing Brownian motion confirmed that individual particles were indeed being imaged. The particle size variation within the observed sample obtained through random walk analysis was within the size distribution obtained by dynamic light scattering. When the current to the solenoid used to magnetize the mu-metal was turned off, all the collected core-shell particles were readily redispersed by diffusion back into the surrounding environment. A Peclet number analysis was performed to probe the convective motion of nanospheres and nanorods under the influence of magnetophoresis and diffusion. Under most circumstances, magnetophoretic behavior dominates diffusion for nanorods, as the magnetic field lines tend to align the magnetic moment along the rod axis. The synthesis and dispersion of fluorophore-tagged nanorods are described. Fluorescence microscopy was employed to image the nanorod motion in a magnetic field gradient. The preliminary experimental data are consistent with the Peclet number analysis. Lastly, the colloidal stability of iron oxide core, gold shell nanoparticles in high ionic strength media was investigated. Such particles are sufficiently charged to be stable against flocculation without modification in low ionic strength media, but they require surface modification to be stably dispersed in elevated ionic strength media that are appropriate for biotechnological applications. Dynamic light scattering and ultraviolet-visible spectrophotometry were used to monitor the colloidal stability of core-shell particles in pH 7.4, 150 mM ionic strength phosphate buffered saline (PBS). While uncoated particles flocculated immediately upon being introduced into PBS, core-shell particles with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than five days in PBS. Adsorbed dextran allowed flocculation that was limited to the formation of small clusters, while poly(ethylene glycol) homopolymers ranging in molecular weight from 6,000 to 100,000 were ineffective steric stabilizers. The effectiveness of adsorbed Pluronic copolymers as steric stabilizers was interpreted in terms of the measured adsorbed layer thickness and extended DLVO theory predictions of the interparticle interactions.

Effects of Ni particle morphology on cell performance of Na/NiCl2 battery

NASA Astrophysics Data System (ADS)

Kim, Mangi; Ahn, Cheol-Woo; Hahn, Byung-Dong; Jung, Keeyoung; Park, Yoon-Cheol; Cho, Nam-ung; Lee, Heesoo; Choi, Joon-Hwan

2017-11-01

Electrochemical reaction of Ni particle, one of active cathode materials in the Na/NiCl2 battery, occurs on the particle surface. The NiCl2 layer formed on the Ni particle surface during charging can disconnect the electron conduction path through Ni particles because the NiCl2 layer has very low conductivity. The morphology and size of Ni particles, therefore, need to be controlled to obtain high charge capacity and excellent cyclic retention. Effects of the Ni particle size on the cell performance were investigated using spherical Ni particles with diameters of 0.5 μm, 6 μm, and 50 μm. The charge capacities of the cells with spherical Ni particles increased when the Ni particle size becomes smaller because of their higher surface area but their charge capacities were significantly decreased with increasing cyclic tests owing to the disconnection of electron conduction path. The inferior cyclic retention of charge capacity was improved using reticular Ni particles which maintained the reliable connection for the electron conduction in the Na/NiCl2 battery. The charge capacity of the cell with the reticular Ni particles was higher than the cell with the small-sized spherical Ni particles approximately by 26% at 30th cycle.

Porcine reproductive and respiratory syndrome virus: morphological, biochemical and serological characteristics of Quebec isolates associated with acute and chronic outbreaks of porcine reproductive and respiratory syndrome.

PubMed Central

Mardassi, H; Athanassious, R; Mounir, S; Dea, S

1994-01-01

Cytolytic and noncytolytic strains of the porcine reproductive and respiratory syndrome virus (PRRSV) were isolated in primary cultures of porcine alveolar macrophages (PAM) from lung homogenates of stillborn fetuses or blood samples of dyspneic piglets collected from Quebec pig farms having experienced acute or chronic outbreaks of PRRS. Serological identification of the virus was confirmed by indirect immunofluorescence and indirect protein A-gold immunoelectron microscopy using reference antiserum prepared from experimentally-infected specific pathogen free (SPF) piglets and monoclonal antibodies (MoAbs) directed against the p15 nucleocapsid (N) protein of the reference ATCC-VR2332 isolate. Intracytoplasmic enveloped viral particles that tended to accumulate into cytoplasmic vesicles were observed in the infected PAM; no budding was demonstrated at the level of the cytoplasmic membrane. The extracellular virions appeared as pleomorphic but mostly spherical enveloped particles, 50-72 nm in diameter (averaged diameter of 50 particles was 58.3 nm), with an isometric core about 25-30 nm. Buoyant density of the virus in CsCL density gradients was estimated to 1.18-1.20 g/mL. No hemagglutinating activity was demonstrated. Analysis of semipurified virions of isolate IAF-exp91 by radioimmunoprecipitation (RIPA) and Western immunoblotting experiments, using reference rabbit and porcine hyperimmune sera, revealed four major viral proteins, a predominant 15 kD N protein and three other proteins with predicted M(r_ of 19, 26 and 42 kD. Progeny viral particles produced in PRRSV-infected PAM in the presence of tunicamycin lacked the 42 kD protein, thus confirming its N-glycosylated nature. Immunoprecipitation experiments using the anti-ATCC-VR2332 MoAbs confirmed the close antigenic relationships between Quebec and American reference isolates of PRRSV. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. PMID:8143254

Molecular pathways in the transformation of model discoidal lipoprotein complexes induced by lecithin:cholesterol acyltransferase.

PubMed

Nichols, A V; Blanche, P J; Gong, E L; Shore, V G; Forte, T M

1985-05-17

Incubation (24 h, 37 degrees C) of discoidal complexes of phosphatidylcholine and apolipoprotein A-I (molar ratio 95 +/- 10 egg yolk phosphatidylcholine-apolipoprotein A-I; 10.5 X 4.0 nm, long X short dimension; designated, class 3 complexes) with the ultracentrifugal d greater than 1.21 g/ml fraction transformed the discoidal complexes to a small product with apparent mean hydrated and nonhydrated diameter of 7.8 and 6.6 nm, respectively. Formation of the small product was associated with marked reduction in phosphatidylcholine-apolipoprotein AI molar ratio of the complexes (on average from 95:1 to 45:1). Phospholipase A2 activity of lecithin:cholesterol acyltransferase participated in the depletion process, as evidenced by production of unesterified fatty acids. In the presence of the d greater than 1.21 g/ml fraction or partially purified lecithin:cholesterol acyltransferase and a source of unesterified cholesterol, the small product could be transformed to a core-containing (cholesteryl ester) round product with a hydrated and nonhydrated diameter of 8.6 and 7.5 nm, respectively. By means of cross-linking with dimethylsuberimidate, the protein moiety of the small product was shown to contain primarily two apolipoprotein A-I molecules per particle, while the large product contained three apolipoprotein A-I molecules per particle. The increase in number of apolipoprotein A-I molecules per particle during transformation of the small to the large product appeared to result from fusion of the small particles during core build-up and release of excess apolipoprotein A-I from the fusion product. The results obtained with the model complexes were consistent for the most part with recent observations (Chen, C., Applegate, K., King, W.C., Glomset, J.A., Norum, K.R. and Gjone, E. (1984) J. Lipid Res. 25, 269-282) on the transformation, by lecithin:cholesterol acyltransferase, of the small spherical high-density lipoproteins of patients with familial lecithin:cholesterol acyltransferase deficiency.

Characterization and complete genome sequence of a panicovirus from Bermuda grass by high-throughput sequencing.

PubMed

Tahir, Muhammad N; Lockhart, Ben; Grinstead, Samuel; Mollov, Dimitre

2017-04-01

Bermuda grass samples were examined by transmission electron microscopy and 28-30 nm spherical virus particles were observed. Total RNA from these plants was subjected to high-throughput sequencing (HTS). The nearly full genome sequence of a panicovirus was identified from one HTS scaffold. Sanger sequencing was used to confirm the HTS results and complete the genome sequence of 4404 nt. This virus was provisionally named Bermuda grass latent virus (BGLV). Its predicted open reading frames follow the typical arrangement of the genus Panicovirus. Based on sequence comparisons and phylogenetic analyses BGLV differs from other viruses and therefore taxonomically it is a new member of the genus Panicovirus, family Tombusviridae.

Facile and green synthesis of highly stable L-cysteine functionalized copper nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, Nikhil; Upadhyay, Lata Sheo Bachan

2016-11-01

A simple eco-friendly method for L-cysteine capped copper nanoparticles (CCNPs) synthesis in aqueous solution has been developed. Glucose and L-cysteine were used as reducing agent and capping/functionalizing agent, respectively. Different parameters such as capping agent concentration, pH, reaction temperature, and reducing agent concentration were optimized during the synthesis. The L-cysteine capped copper nanoparticle were characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Particle size and zeta potential analyser, and high resolution transmission electron microscopy. Spherical shaped cysteine functionalized/capped copper nanoparticles with an average size of 40 nm were found to be highly stable at room temperature (RT) for a period of 1 month

Carbon dots: emerging theranostic nanoarchitectures.

PubMed

Mishra, Vijay; Patil, Akshay; Thakur, Sourav; Kesharwani, Prashant

2018-06-01

Nanotechnology has gained significant interest from biomedical and analytical researchers in recent years. Carbon dots (C-dots), a new member of the carbon nanomaterial family, are spherical, nontoxic, biocompatible, and discrete particles less than 10nm in diameter. Research interest has focused on C-dots because of their ultra-compact nanosize, favorable biocompatibility, outstanding photoluminescence, superior electron transfer ability, and versatile surface engineering properties. C-dots show significant potential for use in cellular imaging, biosensing, targeted drug delivery, and other biomedical applications. Here we discuss C-dots, in terms of their physicochemical properties, fabrication techniques, toxicity issues, surface engineering and biomedical potential in drug delivery, targeting as well as bioimaging. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of interparticle interactions on size determination of zirconia and silica based systems – A comparison of SAXS, DLS, BET, XRD and TEM

PubMed Central

Pabisch, Silvia; Feichtenschlager, Bernhard; Kickelbick, Guido; Peterlik, Herwig

2012-01-01

The aim of this work is a systematic comparison of size characterisation methods for two completely different model systems of oxide nanoparticles, i.e. amorphous spherical silica and anisotropic facet-shaped crystalline zirconia. Size and/or size distribution were determined in a wide range from 5 to 70 nm using small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), nitrogen sorption (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM). A nearly perfect coincidence was observed only for SAXS and TEM for both types of particles. For zirconia nanoparticles considerable differences between different measurement methods were observed. PMID:22347721

Bio fabrication of silver nanoparticles as an effective wound healing agent in the wound care after anorectal surgery.

PubMed

Chai, Shi-Hong; Wang, Yating; Qiao, Yinghong; Wang, Pei; Li, Qiang; Xia, Chaofeng; Ju, Man

2018-01-01

Nowadays biological mediated syntheses of metal nanoparticles were utilized for various life caring applications. Our research group utilized Delonix elata leaf aqueous extract for the synthesis of silver nanoparticles. Further the synthesized silver nanoparticles were subjected for various characterization techniques which resulted in spherically agglomerated with biological components entrapped in it and also with average particle size of 36nm were studied and reported. Later the synthesized silver nanoparticles were subjected for wound healing property by size of measured lessions and body weight which results in better wound healing property were studied and discussed. Copyright © 2017. Published by Elsevier B.V.

Method for producing metallic microparticles

DOEpatents

Phillips, Jonathan; Perry, William L.; Kroenke, William J.

2004-06-29

Method for producing metallic particles. The method converts metallic nanoparticles into larger, spherical metallic particles. An aerosol of solid metallic nanoparticles and a non-oxidizing plasma having a portion sufficiently hot to melt the nanoparticles are generated. The aerosol is directed into the plasma where the metallic nanoparticles melt, collide, join, and spheroidize. The molten spherical metallic particles are directed away from the plasma and enter the afterglow where they cool and solidify.

Innate catalytic and free radical scavenging activities of silver nanoparticles synthesized using Dillenia indica bark extract.

PubMed

Mohanty, Alfa S; Jena, Bhabani S

2017-06-15

A green approach was envisaged for the rapid synthesis of stable silver nanoparticles in an aqueous medium using phenolic rich ethanolic bark extract from D. indica with marked free radical scavenging and reducing ability. Biosynthesis of silver nanoparticles (AgNPs) was confirmed and characterized by using UV-visible spectroscopy, particle size analyzer, X-ray diffractometry (XRD), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FT-IR). Bio-reduction of Ag+ was confirmed with the appearance of golden yellow coloration within 5-10min at 45°C with maximum absorbance at 421nm. XRD analysis of AgNPs indicated the crystalline nature of metallic Ag. As analyzed by TEM, AgNPs were found to be spherical in shape, well dispersed and size varied from 15 to 35nm and dynamic light scattering (DLS) studies showed the average particle size of 29nm with polydispersity index (PDI) of 0.280. Synthesized AgNPs were showing surface functionalization as revealed through FTIR studies. These AgNPs were observed to be highly stable at room temperature (28±2°C) for more than 3months, thereby indicating the ethanolic extract of D. indica was a reducing as well as a capping agent for stabilization of AgNPs. Moreover, these green synthesized AgNPs showed enhanced free radical scavenging and excellent catalytic activities when used in the reduction of 4-nitrophenol and methylene blue dye, at room temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

DNA Packaging Mutant: Repression of the Vaccinia Virus A32 Gene Results in Noninfectious, DNA-Deficient, Spherical, Enveloped Particles

PubMed Central

Cassetti, Maria Cristina; Merchlinsky, Michael; Wolffe, Elizabeth J.; Weisberg, Andrea S.; Moss, Bernard

1998-01-01

The vaccinia virus A32 open reading frame was predicted to encode a protein with a nucleoside triphosphate-binding motif and a mass of 34 kDa. To investigate the role of this protein, we constructed a mutant in which the original A32 gene was replaced by an inducible copy. The recombinant virus, vA32i, has a conditional lethal phenotype: infectious virus formation was dependent on isopropyl-β-d-thiogalactopyranoside (IPTG). Under nonpermissive conditions, the mutant synthesized early- and late-stage viral proteins, as well as viral DNA that was processed into unit-length genomes. Electron microscopy of cells infected in the absence of IPTG revealed normal-appearing crescents and immature virus particles but very few with nucleoids. Instead of brick-shaped mature particles with defined core structures, there were numerous electron-dense, spherical particles. Some of these spherical particles were wrapped with cisternal membranes, analogous to intracellular and extracellular enveloped virions. Mutant viral particles, purified by sucrose density gradient centrifugation, had low infectivity and transcriptional activity, and the majority were spherical and lacked DNA. Nevertheless, the particle preparation contained representative membrane proteins, cleaved and uncleaved core proteins, the viral RNA polymerase, the early transcription factor and several enzymes, suggesting that incorporation of these components is not strictly coupled to DNA packaging. PMID:9621036

Processes for making dense, spherical active materials for lithium-ion cells

DOEpatents

Kang, Sun-Ho [Naperville, IL; Amine, Khalil [Downers Grove, IL

2011-11-22

Processes are provided for making dense, spherical mixed-metal carbonate or phosphate precursors that are particularly well suited for the production of active materials for electrochemical devices such as lithium ion secondary batteries. Exemplified methods include precipitating dense, spherical particles of metal carbonates or metal phosphates from a combined aqueous solution using a precipitating agent such as ammonium hydrogen carbonate, sodium hydrogen carbonate, or a mixture that includes sodium hydrogen carbonate. Other exemplified methods include precipitating dense, spherical particles of metal phosphates using a precipitating agent such as ammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, or a mixture of any two or more thereof. Further provided are compositions of and methods of making dense, spherical metal oxides and metal phosphates using the dense, spherical metal precursors. Still further provided are electrodes and batteries using the same.

Dynamics of aspherical dust grains in a cometary atmosphere: I. axially symmetric grains in a spherically symmetric atmosphere

NASA Astrophysics Data System (ADS)

Ivanovski, S. L.; Zakharov, V. V.; Della Corte, V.; Crifo, J.-F.; Rotundi, A.; Fulle, M.

2017-01-01

In-situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. For the interpretations of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of the Stardust mission and analysis of samples of interplanetary dust have shown that these particles are highly aspherical, which should be taken into account in any credible model. The aim of the present work is to study the dynamics of ellipsoidal shape particles with various aspect ratios introduced in a spherically symmetric expanding gas flow and to reveal the possible differences in dynamics between spherical and aspherical particles. Their translational and rotational motion under influence of the gravity and of the aerodynamic force and torque is numerically integrated in a wide range of physical parameters values including those of comet 67P/Churyumov-Gerasimenko. The main distinctions of the dynamics of spherical and ellipsoidal particles are discussed. The aerodynamic characteristics of the ellipsoidal particles, and examples of their translational and rotational motion in the postulated gas flow are presented.

High-value utilization of egg shell to synthesize Silver and Gold-Silver core shell nanoparticles and their application for the degradation of hazardous dyes from aqueous phase-A green approach.

PubMed

Sinha, Tanur; Ahmaruzzaman, M

2015-09-01

The common household material, egg shell of Anas platyrhynchos is utilized for the synthesis of Silver and Gold-Silver core shell nanoparticles using greener, environment friendly and economic way. The egg shell extracts were acting as a stabilizing and reducing agents. This method avoids the use of external reducing and stabilizing agents, templates and solvents. The effects of various reaction parameters, such as reaction temperature, concentration in the formation of nanoparticles have also been investigated. The compositional abundance of gelatin may be envisaged for the effective reductive as well as stabilizing potency. The mechanisms for the formation of NPs have also been presented. The synthesized Ag NPs formed were predominantly spherical in nature with an average size of particles in the range of 6-26 nm. While, Au-Ag core shell nanoparticles formed were spherical and oval shaped, within a narrow size spectrum of 9-18 nm. Both the Ag NPs Au-and Ag core shell nanoparticles showed characteristic Bragg's reflection planes of fcc structure and surface plasmon resonance at 430 nm and 365 nm, respectively. The NPs were utilized for the removal of toxic and hazardous dyes, such as Rose Bengal, Methyl Violet 6 B and Methylene Blue from aqueous phase. Approximately 98.2%, 98.4% and 97% degradations of Rose Bengal, Methyl Violet 6 B, and Methylene Blue were observed with Ag NPs, while the percentage degradation of these dyes was 97.3%, 97.6% and 96% with Au-Ag NPs, respectively. Therefore, the present study has opened up an innovative way for synthesizing Ag NPs and Au-Ag bimetallic nanostructures of different morphologies and sizes involving the utilization of egg shell extract. The high efficiency of the NPs as photocatalysts has opened a promising application for the removal of hazardous dyes from the industrial effluents. Copyright © 2015 Elsevier Inc. All rights reserved.

Particles exposure while sitting at bus stops of hot and humid Singapore

NASA Astrophysics Data System (ADS)

Velasco, Erik; Tan, Sok Huang

2016-10-01

Transport microenvironments represent hotspots of personal exposure to airborne toxics, particularly of ultrafine particles. Thus, a large exposure may be experienced during daily commuting trips. Amongst these microenvironments, bus stops are critical because of the commuters' close proximity to fresh fumes rich in particles emitted by passing, idling and accelerating buses and motor vehicles, in general. Standing at a bus stop may represent a period of disproportionately high exposure and it is, therefore, essential to know the number, chemical composition and physical characteristics of such particles for a proper public health assessment and design of mobility strategies. On this account, a set of portable and battery operated sensors were used to evaluate a number of properties of the traffic particles to which thousands of citizens are daily exposed at bus stops of Singapore. In terms of fine particles, the exposure concentration was on average 1.5-3 times higher than the mean concentration at ambient level reported by the local authorities. On average 60% of those particles corresponded to black carbon. An important presence of particle-bound polycyclic aromatics was observed. The particle number concentration and active surface area were effective metrics to quantify ultrafine particles, as expected both showed strong correlations. The number of particles at bus stops was on average 3.5 times higher than at ambient level. The most alarming issue was probably the size of the particles. Assuming spherical particles, a median of 27 nm was estimated based on the active surface area and particle number data. Particles of this size form the nucleation mode, which is related to harmful health effects.

Dynamics and interactions of particles in a thermophoretic trap

NASA Astrophysics Data System (ADS)

Foster, Benjamin; Fung, Frankie; Fieweger, Connor; Usatyuk, Mykhaylo; Gaj, Anita; DeSalvo, B. J.; Chin, Cheng

2017-08-01

We investigate dynamics and interactions of particles levitated and trapped by the thermophoretic force in a vacuum cell. Our analysis is based on footage taken by orthogonal cameras that are able to capture the three dimensional trajectories of the particles. In contrast to spherical particles, which remain stationary at the center of the cell, here we report new qualitative features of the motion of particles with non-spherical geometry. Singly levitated particles exhibit steady spinning around their body axis and rotation around the symmetry axis of the cell. When two levitated particles approach each other, repulsive or attractive interactions between the particles are observed. Our levitation system offers a wonderful platform to study interaction between particles in a microgravity environment.

Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

PubMed

Hudait, Arpa; Molinero, Valeria

2014-06-04

Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by solution. We predict that micrometer-sized particles and nanoparticles have the same equilibrium internal structure. The variation of liquid-vapor surface tension with solute concentration is a key factor in determining whether a solution-embedded ice core or vapor-exposed ice cap is the equilibrium structure of the aerosols. In agreement with experiments, we predict that the structure of mixed-phase HNO3-water particles, representative of polar stratospheric clouds, consists of an ice core surrounded by freeze-concentrated solution. The results of this work are important to determine the phase state and internal structure of sea spray ultrafine aerosols and other mixed-phase particles under atmospherically relevant conditions.

Method of making polymer powders and whiskers as well as particulate products of the method and atomizing apparatus

DOEpatents

Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

2001-01-09

Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

Local lubrication model for spherical particles within incompressible Navier-Stokes flows.

PubMed

Lambert, B; Weynans, L; Bergmann, M

2018-03-01

The lubrication forces are short-range hydrodynamic interactions essential to describe suspension of the particles. Usually, they are underestimated in direct numerical simulations of particle-laden flows. In this paper, we propose a lubrication model for a coupled volume penalization method and discrete element method solver that estimates the unresolved hydrodynamic forces and torques in an incompressible Navier-Stokes flow. Corrections are made locally on the surface of the interacting particles without any assumption on the global particle shape. The numerical model has been validated against experimental data and performs as well as existing numerical models that are limited to spherical particles.

Curvature-induced capillary interaction of spherical particles at a liquid interface.

PubMed

Würger, Alois

2006-10-01

We consider a liquid interface with different principal curvatures +/-c and find that the mere presence of a spherical particle leads to a deformation field of quadrupolar symmetry; the corresponding "capillary quadrupole moment" is given by the ratio of the particle size and the curvature radius. The resulting pair interaction of nearby particles is anisotropic and favors the formation of aggregates of cubic symmetry. Since the single-particle trapping energy depends quadratically on curvature with a negative prefactor, a curvature gradient induces a lateral force that pushes the particles towards strongly curved regions of the interface. As an illustration we discuss the effects occurring on a catenoid.

Spherical composite particles of rice starch and microcrystalline cellulose: a new coprocessed excipient for direct compression.

PubMed

Limwong, Vasinee; Sutanthavibul, Narueporn; Kulvanich, Poj

2004-03-12

Composite particles of rice starch (RS) and microcrystalline cellulose were fabricated by spray-drying technique to be used as a directly compressible excipient. Two size fractions of microcrystalline cellulose, sieved (MCS) and jet milled (MCJ), having volumetric mean diameter (D50) of 13.61 and 40.51 microm, respectively, were used to form composite particles with RS in various mixing ratios. The composite particles produced were evaluated for their powder and compression properties. Although an increase in the microcrystalline cellulose proportion imparted greater compressibility of the composite particles, the shape of the particles was typically less spherical with rougher surface resulting in a decrease in the degree of flowability. Compressibility of composite particles made from different size fractions of microcrystalline cellulose was not different; however, using MCJ, which had a particle size range close to the size of RS (D50 = 13.57 microm), provided more spherical particles than using MCS. Spherical composite particles between RS and MCJ in the ratio of 7:3 (RS-MCJ-73) were then evaluated for powder properties and compressibility in comparison with some marketed directly compressible diluents. Compressibility of RS-MCJ-73 was greater than commercial spray-dried RS (Eratab), coprocessed lactose and microcrystalline cellulose (Cellactose), and agglomerated lactose (Tablettose), but, as expected, lower than microcrystalline cellulose (Vivapur 101). Flowability index of RS-MCJ-73 appeared to be slightly lower than Eratab but higher than Vivapur 101, Cellactose, and Tablettose. Tablets of RS-MCJ-73 exhibited low friability and good self-disintegrating property. It was concluded that these developed composite particles could be introduced as a new coprocessed direct compression excipient.

Non-spherical micro- and nanoparticles: fabrication, characterization and drug delivery applications.

PubMed

Mathaes, Roman; Winter, Gerhard; Besheer, Ahmed; Engert, Julia

2015-03-01

Micro- and nanoparticles in drug and vaccine delivery have opened up new possibilities in pharmaceutics. In the past, researchers focused mainly on particle size, surface chemistry and the use of various materials to control particle characteristics and functions. Lately, shape has been acknowledged as an important design parameter having an impact on the interaction with biological systems. In this review, we report on the latest developments in fabrication methods to tailor particle geometry, summarize analytical techniques for non-spherical particles and highlight the most important findings regarding their interaction with biological systems and their potential applications in drug delivery. The impact of shape on particle internalization into different cell types and particle biodistribution has been extensively studied in the past. Current research focuses on shape-dependent uptake mechanisms and applications for tumour therapy and vaccination. Different fabrication methods can be used to produce a variety of different particle types and shapes. Key challenges will be the transfer of new non-spherical particle fabrication methods from lab-scale to industrial large-scale production. Not all techniques may be scalable for the production of high quantities of particles. It will also be challenging to transfer the promising in vitro findings to suitable in vivo models.

Ion size effects on the electrokinetics of spherical particles in salt-free concentrated suspensions

NASA Astrophysics Data System (ADS)

Roa, Rafael; Carrique, Felix; Ruiz-Reina, Emilio

2012-02-01

In this work we study the influence of the counterion size on the electrophoretic mobility and on the dynamic mobility of a suspended spherical particle in a salt-free concentrated colloidal suspension. Salt-free suspensions contain charged particles and the added counterions that counterbalance their surface charge. A spherical cell model approach is used to take into account particle-particle electro-hydrodynamic interactions in concentrated suspensions. The finite size of the counterions is considered including an entropic contribution, related with the excluded volume of the ions, in the free energy of the suspension, giving rise to a modified counterion concentration profile. We are interested in studying the linear response of the system to an electric field, thus we solve the different electrokinetic equations by using a linear perturbation scheme. We find that the ionic size effect is quite important for moderate to high particles charges at a given particle volume fraction. In addition for such particle surface charges, both the electrophoretic mobility and the dynamic mobility suffer more important changes the larger the particle volume fraction for each ion size. The latter effects are more relevant the larger the ionic size.

Wear particles of single-crystal silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Sliding friction experiments, conducted in vacuum with silicon carbide /000/ surface in contact with iron based binary alloys are described. Multiangular and spherical wear particles of silicon carbide are observed as a result of multipass sliding. The multiangular particles are produced by primary and secondary cracking of cleavage planes /000/, /10(-1)0/, and /11(-2)0/ under the Hertzian stress field or local inelastic deformation zone. The spherical particles may be produced by two mechanisms: (1) a penny shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and (2) attrition of wear particles.

Determination of the coma dust back-scattering of 67P for phase angles from 1.2° to 75°

NASA Astrophysics Data System (ADS)

Fink, Uwe; Doose, Lyn

2018-07-01

A phase curve is derived for the dust coma of comet 67P/Churyumov-Gerasimenko (67P) from 1.2° to 74° using images from the OSIRIS camera system on board the Rosetta mission during the period 2014 July 25 to 2015 February 23 as the spacecraft approached the comet. We analyzed 123 images of the continuum filter at 612.6 nm and 60 images of the 375 nm UV continuum filter of the Wide Angle Camera. Our method of extracting a phase curve, close to the nucleus, taking into account illumination conditions, activity of the comet, strong radial radiance intensity decrease and varying phase angles across the image, is described in detail. Our derived backscattering phase curve is considerably steeper than earlier published data. The radiance of the scattering dust in the 612.6 nm filter increases by about a factor of 12 going from a phase angle of 75° to a phase angle of 2.0°. The phase curve for the 375 nm filter is similar but there is reasonable evidence that the I/F color ratio between the two filters changes from a roughly neutral color ratio of 1.2 to a more typical red color of ∼ 2.0 as the activity of the comet increases. No substantial change in the shape of the phase curve could be discerned between 2014 August and 2015 February 19-23 when the comet increased considerably in activity. The phase curve behavior on the illuminated side of the comet and the dark side is in general similar. A comparison of our phase curve with a recent phase curve for 67P by Bertini et al. for the phase angle range ∼15°-80°, where our two reductions overlap, shows good agreement (as does our color ratio between the 612.6 nm and the 375 nm filters) despite the fact that the two phase curve determinations observed the comet at different dust activity levels, at different distances from the nucleus and used completely different observing and data reduction methodologies. Trial scattering calculations demonstrate that the observed strong backscattering most likely arises from particles in the size range 1-20 μm. Our observed backscattering phase curve gives no constraints on the real index of refraction, the particle size distribution or the minimum and maximum particle size cut-offs. However, an upper limit to the imaginary index of refraction of ∼0.01 was required, making these particles quite transparent. Simple spherical scattering calculations including particle size distributions can fit the general characteristics of the phase curve but cannot produce a satisfactory detailed fit.

Preparation and characterization of a novel conformed bipolymer paclitaxel-nanoparticle using tea polysaccharides and zein.

PubMed

Li, Shuqin; Wang, Xiuming; Li, Weiwei; Yuan, Guoqi; Pan, Yuxiang; Chen, Haixia

2016-08-01

To improve the aqueous solubility of the anticancer agent paclitaxel (PTX), a newly conformed bipolymer paclitaxel-nanoparticle using tea polysaccharide (TPS) and zein was prepared and characterized. Tea polysaccharide was used as a biopolymer shell and zein was as the core and the optimal formula was subjected to the characteristic study by TEM, DSC, FTIR and in vitro release study. Results showed that the optimal particle was acquired with particle yield at 40.01%, drug loading at 0.12% and diameters around 165nm when the concentration of tea polysaccharide was set at 0.2%, and the amount of PTX:zein=1:10. The particle was a nanoparticle with spherical surface and the encapsulated PTX was in an amorphous form rather than cystalline form. PTX was interacted with zein and polysaccharide through O H and CO groups and it had a sustained release. The results suggested that the novel bipolymer might be a promising agent for PTX delivery and tea polysaccharide was demonstrated its function in drug delivery system. Copyright © 2016 Elsevier Ltd. All rights reserved.

Enzyme-directed assembly of nanoparticles in tumors monitored by in vivo whole animal imaging and ex vivo super-resolution fluorescence imaging.

PubMed

Chien, Miao-Ping; Carlini, Andrea S; Hu, Dehong; Barback, Christopher V; Rush, Anthony M; Hall, David J; Orr, Galya; Gianneschi, Nathan C

2013-12-18

Matrix metalloproteinase enzymes, overexpressed in HT-1080 human fibrocarcinoma tumors, were used to guide the accumulation and retention of an enzyme-responsive nanoparticle in a xenograft mouse model. The nanoparticles were prepared as micelles from amphiphilic block copolymers bearing a simple hydrophobic block and a hydrophilic peptide brush. The polymers were end-labeled with Alexa Fluor 647 dyes leading to the formation of labeled micelles upon dialysis of the polymers from DMSO/DMF to aqueous buffer. This dye-labeling strategy allowed the presence of the retained material to be visualized via whole animal imaging in vivo and in ex vivo organ analysis following intratumoral injection into HT-1080 xenograft tumors. We propose that the material is retained by virtue of an enzyme-induced accumulation process whereby particles change morphology from 20 nm spherical micelles to micrometer-scale aggregates, kinetically trapping them within the tumor. This hypothesis is tested here via an unprecedented super-resolution fluorescence analysis of ex vivo tissue slices confirming a particle size increase occurs concomitantly with extended retention of responsive particles compared to unresponsive controls.

Bio-mediated synthesis of TiO2 nanoparticles and its photocatalytic effect on aquatic biofilm.

PubMed

Dhandapani, Perumal; Maruthamuthu, Sundram; Rajagopal, Gopalakrishnan

2012-05-02

The nano-TiO(2) was synthesized biologically employing Bacillus subtilis (FJ460362). These nanoparticles were characterized by FTIR, TGA-DTA, UV-Visible spectroscopy, XRD and TEM. FTIR and TGA results confirm that the organic impurities were completely removed while calcinating the resultant products. Band gap value was estimated from the UV-Visible spectrum and anatase crystal phase was confirmed by XRD. TEM images reveal that these particles were agglomerated; mostly spherical in shape with an average particle size of 10-30nm. The synthesized nano-TiO(2) particles were coated on glass slides, biofilm were grown and subjected to irradiation of polychromatic light to understand photocatalytic activity in controlling the aquatic biofilm. The bacterial killing process was established by Epi-fluorescence microscopy. The results reveal that biogenic TiO(2) nanomaterial acts as good photocatalyst by the generation of H(2)O(2) in the vicinity of the TiO(2)-biofilm interfaces to suppress the growth of the aquatic biofilm. Copyright © 2012 Elsevier B.V. All rights reserved.

A propofol microemulsion with low free propofol in the aqueous phase: formulation, physicochemical characterization, stability and pharmacokinetics.

PubMed

Cai, WeiHui; Deng, WanDing; Yang, HuiHui; Chen, XiaoPing; Jin, Fang

2012-10-15

The purpose of this study was to develop a propofol microemulsion with a low concentration of free propofol in the aqueous phase. Propofol microemulsions were prepared based on single-factor experiments and orthogonal design. The optimal microemulsion was evaluated for pH, osmolarity, particle size, zeta potential, morphology, free propofol in the aqueous phase, stability, and pharmacokinetics in beagle dogs, and comparisons made with the commercial emulsion, Diprivan(®). The pH and osmolarity of the microemulsion were similar to those of Diprivan(®). The average particle size was 22.6±0.2 nm, and TEM imaging indicated that the microemulsion particles were spherical in appearance. The concentration of free propofol in the microemulsion was 21.3% lower than that of Diprivan(®). Storage stability tests suggested that the microemulsion was stable long-term under room temperature conditions. The pharmacokinetic profile for the microemulsion showed rapid distribution and elimination compared to Diprivan(®). We conclude that the prepared microemulsion may be clinically useful as a potential carrier for propofol delivery. Copyright © 2012 Elsevier B.V. All rights reserved.

Formulation and Evaluation of Solid Lipid Nanoparticles of Ramipril

PubMed Central

Ekambaram, P; Abdul, Hasan Sathali A

2011-01-01

Solid lipid nanoparticles are typically spherical with an average diameter between 1 and 1000 nm. It is an alternative carrier system to tradition colloidal carriers, such as, emulsions, liposomes, and polymeric micro and nanoparticles. Ramipril is an antihypertensive agent used in the treatment of hypertension. Its oral bioavailability is 28% and it is rapidly excreted through the renal route. This drug has many side effects such as, postural hypotension, hyperkalemia, and angioedema, when given as an immediate dosage form. To overcome the side effects and to increase the bioavailability of ramipril, solid lipid nanoparticles of ramipril are prepared by using lipids (glyceryl monostearate and glyceryl monooleate) with stabilizers (tween 80, poloxamer 188, and span 20). The prepared formulations have been evaluated for entrapment efficiency, drug content, in-vitro drug release, particle size analysis, scanning electron spectroscopy, Fourier transform-infrared studies, and stability. A formulation containing glyceryl monooleate, stabilized with span 20 as surfactant showed prolonged drug release, smaller particle size, and narrow particle size distribution, as compared to other formulations with different surfactants and lipids. PMID:21897661

Efficient acetone sensor based on Ni-doped ZnO nanostructures prepared by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Darunkar, Swapnil S.; Acharya, Smita A.

2018-05-01

Ni-doped ZnO thin film was prepared by home-built spray pyrolysis unit for the detection of acetone at 300°C. Scanning electron microscopic (SEM) images of as-developed thin film of undoped ZnO exhibits large quantity of spherical, non-agglomerated particles with uniform size while in Ni-doped ZnO, particles are quite non-uniform in nature. The particle size estimated by using image J are obtained to be around 20-200 nm. Ni-doping effect on band gaps are determined by UV-vis optical spectroscopy and band gap of Ni-doped ZnO is found to be 3.046 eV. Nickel doping exceptionally enhances the sensing response of ZnO as compared to undoped ZnO system. The major role of the Ni-doping is to create more active sites for chemisorbed oxygen on the surface of sensor and correspondingly, to improve the sensing response. The 6 at.% of Ni-doped ZnO exhibits the highest response (92%) for 100 ppm acetone at 300 °C.

Stabilized chitosan/Fe(0)-nanoparticle beads to remove heavy metals from polluted sediments.

PubMed

Liu, T; Sun, Y; Wang, Z L

2016-01-01

Sediment contamination by heavy metals has become a widespread problem that can affect the normal behaviors of rivers and lakes. After chitosan/Fe(0)-nanoparticles (CS-NZVI) beads were cross-linked with glutaraldehyde (GLA), their mechanical strength, stability and separation efficiency from the sediment were obviously improved. Moreover, the average aperture size of GLA-CS-NZVI beads was 20.6 μm and NZVI particles were nearly spherical in shape with a mean diameter of 40.2 nm. In addition, the pH showed an insignificant effect on the removal rates from the sediment. Due to the dissolution of metals species into aqueous solutions as an introduction of the salt, the removal rates of all heavy metals from the sediment were increased with an increase of the salinity. The competitive adsorption of heavy metals between the sediment particles and GLA-CS-NZVI beads became stronger as the sediment particles became smaller, leading to decreased removal rates. Therefore, the removal efficiency could be enhanced by optimizing experimental conditions and choosing appropriate materials for the target contaminants.

Preservation of anthocyanins in solid lipid nanoparticles: Optimization of a microemulsion dilution method using the Placket-Burman and Box-Behnken designs.

PubMed

Ravanfar, Raheleh; Tamaddon, Ali Mohammad; Niakousari, Mehrdad; Moein, Mahmoud Reza

2016-05-15

Anthocyanins are the main polyphenol components from red cabbage (Brassica oleracea L. Var. Capitata f. Rubra) extracts that have inherent antioxidant activities. Anthocyanins are effectively stable in acidic gastric digestion conditions, with nearly 100% phenol content recovery. However, the total phenol content recovery after simulated pancreatic digestion was approximately 25%. To protect anthocyanins against harsh environmental conditions (e.g., pH and temperature), solid lipid nanoparticles were prepared by the dilution of water in oil (w/o) microemulsions containing anthocyanins in aqueous media. The formulations were characterized for particle size and encapsulation efficiency. The formulation parameters (e.g., volume of the internal aqueous phase, homogenization time and the percentages of total lipid, total surfactant or stabilizer) were optimized using the Placket-Burman and Box-Behnken experimental designs. Entrapment efficiency (89.2 ± 0.3%) was calculated when the mean particle size was 455 ± 2 nm. A scanning electron microscopy study revealed the spherical morphology of the particles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Study of static and dynamic magnetic properties of Fe nanoparticles composited with activated carbon

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

Pal, Satyendra Prakash, E-mail: sppal85@gmail.com; Department of Physical Sciences, Indian Institute of Science Education and Research, Mohali, Knowledge city, Sector81, SAS Nagar, Manauli-140306, Punjab; Kaur, Guratinder

2016-05-23

Nanocomposite of Fe nanoparticles with activated carbon has been synthesized to alter the magnetic spin-spin interaction and hence study the dilution effect on the static and dynamic magnetic properties of the Fe nanoparticle system. Transmission electron microscopic (TEM) image shows the spherical Fe nanoparticles dispersed in carbon matrix with 13.8 nm particle size. Temperature dependent magnetization measurement does not show any blocking temperature at all, right up to the room temperature. Magnetic hysteresis curve, taken at 300 K, shows small value of the coercivity and this small hysteresis indicates the presence of an energy barrier and inherent magnetization dynamics. Langevinmore » function fitting of the hysteresis curve gives almost similar value of particle size as obtained from TEM analysis. Magnetic relaxation data, taken at a temperature of 100 K, were fitted with a combination of two exponentially decaying function. This diluted form of nanoparticle system, which has particles size in the superparamagnetic limit, behaves like a dilute ensemble of superspins with large value of the magnetic anisotropic barrier.« less

Effect of squalane on mebendazole-loaded Compritol® nanoparticles.

PubMed

Graves, Richard A; Ledet, Grace A; Nation, Cedric A; Pramar, Yashoda V; Bostanian, Levon A; Mandal, Tarun K

2015-01-01

The objective of this study is to develop nanostructured lipid formulations of Compritol for the delivery of mebendazole. The formulations were prepared with Compritol 888 ATO, squalane, and Pluronic F68. Nine batches with different amounts of modifier, squalane, and drug were prepared. The formulations were characterized by evaluating particle size, morphology, and zeta potential. The thermal properties of the formulations were analyzed by differential scanning calorimetry (DSC). The encapsulation efficiency of each formulation and the drug release rates from each formulation were quantified by UPLC. The particles were spherical and had median particle sizes between 300 and 600 nm (50th percentile). A linear relationship was observed between Compritol/squalane composition and the melting point of the mixture. The DSC scans of the formulations revealed some recrystallization of the drug from the formulations, and the amount of recrystallization correlated with the amount of squalane in the formulation. Approximately, 70% efficiency of encapsulation was observed in the formulations with 30% (w/w) squalane, and these formulations also had faster dissolution rates compared to the other formulations. Overall, the formulations with 30% squalane are the preferred formulation for future testing.

Hydrodynamic entrainment in micro-confined suspensions and its implications for two-point microrheology

NASA Astrophysics Data System (ADS)

Aponte-Rivera, Christian; Zia, Roseanna N.

2017-11-01

We study hydrodynamic entrainment in spherically confined colloidal suspensions of hydrodynamically interacting particles as a model system for intracellular and other micro-confined biophysical transport. Modeling of transport and rheology in such materials requires an accurate description of the microscopic forces driving particle motion and of particle interactions with nearby boundaries. We carry out dynamic simulations of concentrated, spherically confined colloids as a model system to study the effect of 3D confinement on entrainment and rheology. We show that entrainment between two tracer particles exhibits qualitatively different functional dependence on inter-particle separation as compared to an unbound suspension, and develop a scaling theory that collapses the concentrated mobility of spherically confined suspensions for all volume fractions and particle to cavity size ratios onto a master curve. For widely separated particles, the master curve can be predicted via a Green's function, which suggests a framework with which to conduct two-point microrheology measurements near confining boundaries. The implications of these results for experiments in micro-confined biophysical systems, such as the interior of eukaryotic cells, are discussed.

Optical equivalence of isotropic ensembles of ellipsoidal particles in the Rayleigh-Gans-Debye and anomalous diffraction approximations and its consequences

NASA Astrophysics Data System (ADS)

Paramonov, L. E.

2012-05-01

Light scattering by isotropic ensembles of ellipsoidal particles is considered in the Rayleigh-Gans-Debye approximation. It is proved that randomly oriented ellipsoidal particles are optically equivalent to polydisperse randomly oriented spheroidal particles and polydisperse spherical particles. Density functions of the shape and size distributions for equivalent ensembles of spheroidal and spherical particles are presented. In the anomalous diffraction approximation, equivalent ensembles of particles are shown to also have equal extinction, scattering, and absorption coefficients. Consequences of optical equivalence are considered. The results are illustrated by numerical calculations of the angular dependence of the scattering phase function using the T-matrix method and the Mie theory.

Cellular delivery of PEGylated PLGA nanoparticles.

PubMed

Pamujula, Sarala; Hazari, Sidhartha; Bolden, Gevoni; Graves, Richard A; Chinta, Dakshinamurthy Devanga; Dash, Srikanta; Kishore, Vimal; Mandal, Tarun K

2012-01-01

The objective of this study was to investigate the efficiency of uptake of PEGylated polylactide-co-gycolide (PLGA) nanoparticles by breast cancer cells. Nanoparticles of PLGA containing various amounts of polyethylene glycol (PEG, 5%-15%) were prepared using a double emulsion solvent evaporation method. The nanoparticles were loaded with coumarin-6 (C6) as a fluorescence marker. The particles were characterized for surface morphology, particle size, zeta potential, and for cellular uptake by 4T1 murine breast cancer cells. Irrespective of the amount of PEG, all formulations yielded smooth spherical particles. However, a comparison of the particle size of various formulations showed bimodal distribution of particles. Each formulation was later passed through a 1.2 µm filter to obtain target size particles (114-335 nm) with zeta potentials ranging from -2.8 mV to -26.2 mV. While PLGA-PEG di-block (15% PEG) formulation showed significantly higher 4T1 cellular uptake than all other formulations, there was no statistical difference in cellular uptake among PLGA, PLGA-PEG-PLGA tri-block (10% PEG), PLGA-PEG di-block (5% PEG) and PLGA-PEG di-block (10% PEG) nanoparticles. These preliminary findings indicated that the nanoparticle formulation prepared with 15% PEGylated PLGA showed maximum cellular uptake due to it having the smallest particle size and lowest zeta potential. © 2011 The Authors. JPP © 2011 Royal Pharmaceutical Society.

Photocatalytic equipment with nitrogen-doped titanium dioxide for air cleaning and disinfecting

NASA Astrophysics Data System (ADS)

Son Le, Thanh; Buu Ngo, Quoc; Dung Nguyen, Viet; Chau Nguyen, Hoai; Hien Dao, Trong; Tin Tran, Xuan; Kabachkov, E. N.; Balikhin, I. L.

2014-03-01

Nitrogen-doped TiO2 nanoparticle photocatalysts were synthesized by a sol-gel procedure using tetra-n-butyl orthotitanate as a titanium precursor and urea as a nitrogen source. Systematic studies for the preparation parameters and their impact on the material's structure were carried out by multiple techniques: thermogravimetric and differential scanning calorimetric analysis, x-ray diffraction, scanning electron microscope, transmission electron microscopy, energy dispersive x-ray spectroscopy and UV-Vis diffuse reflectance spectrophotometry showed that the nitrogen-doped TiO2 calcined at 500 °C for 3 h exhibited a spherical form with a particle size about 15-20 nm and crystal phase presented a mixture of 89.12% anatase. The obtained product was deposited on a porous quartz tube (D = 74 mm l = 418 mm) to manufacture an air photocatalytic cleaner as a prototype of the TIOKRAFT company's equipment. The created air cleaner was able to remove 60% of 10 ppm acetone within 390 min and degrade 98.5% of bacteria (total aerobic bacteria and fungi, 300 cfu m-3) within 120 min in a 10 m3 box. These photodegradation activities of N-TiO2 are higher than that of the commercial nano-TiO2 (Skyspring Inc., USA, particle size of 5-10 nm).

Nanodosimetry of Auger electrons: A case study from the decay of 125I and 0-18-eV electron stopping cross sections of cytosine

NASA Astrophysics Data System (ADS)

Michaud, M.; Bazin, M.; Sanche, L.

2013-03-01

Radiopharmaceuticals emitting Auger electrons are often injected into patients undergoing cancer treatment with targeted radionuclide therapy (TRT). In this type of radiotherapy, the radiation source is radial and most of the emitted primary particles are low-energy electrons (LEEs) having kinetic energies distributed mostly from zero to a few hundred electron volts with very short ranges in biological media. These LEEs generate a high density of energy deposits and clustered damage, thus offering a relative biological effectiveness comparable to that of alpha particles. In this paper, we present a simple model and corresponding measurements to assess the energy deposited near the site of the radiopharmaceuticals in TRT. As an example, a calculation is performed for the decay of a single 125I radionuclide surrounded by a 1-nm-radius spherical shell of cytosine molecules using the energy spectrum of LEEs emitted by 125I along with their stopping cross sections between 0 and 18 eV. The dose absorbed by the cytosine shell, which occupies a volume of 4 nm3, is extremely high. It amounts to 79 kGy per decay of which 3%, 39%, and 58% is attributed to vibrational excitations, electronic excitations, and ionization processes, respectively.

Influence of C or In buffer layer on photoluminescence behaviour of ultrathin ZnO film

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

Saravanan, K., E-mail: saravanan@igcar.gov.in; Jayalakshmi, G.; Krishnan, R.

We study the effect of the indium or carbon buffer layer on the photoluminescence (PL) property of ZnO ultrathin films deposited on a Si(100) substrate. The surface morphology of the films obtained using scanning tunnelling microscopy shows spherical shaped ZnO nanoparticles of size ∼8 nm in ZnO/C/Si and ∼22 nm in ZnO/Si samples, while the ZnO/In/Si sample shows elliptical shaped ZnO particles. Further, the ZnO/C/Si sample shows densely packed ZnO nanoparticles in comparison with other samples. Strong band edge emission has been observed in the presence of In or C buffer layer, whereas the ZnO/Si sample exhibits poor PL emission. The influencemore » of C and In buffer layers on the PL behaviour of ZnO films is studied in detail using temperature dependent PL measurements in the range of 4 K–300 K. The ZnO/C/Si sample exhibits a multi-fold enhancement in the PL emission intensity with well-resolved free and bound exciton emission lines. Our experimental results imply that the ZnO films deposited on the C buffer layer showed higher particle density and better exciton emission desired for optoelectronic applications.« less

Soot Superaggregates from Flaming Wildfires and Their Direct Radiative Forcing

NASA Technical Reports Server (NTRS)

Chakrabarty, Rajan K.; Beres, Nicholas D.; Moosmuller,Hans; China, Swarup; Mazzoleni, Claudio; Dubey, Manvendra K.; Liu, Li; Mishchenko, Michael I.

2014-01-01

Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimension D(sub f) approximately equals 1.8 mobility diameter D(sub m) (is) less than or equal to 1 micron, and aerodynamic diameter D(sub a) (is) less than or equal to 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic D(sub f) approximately equals 2.6,D(sub m) (is) greater than 1 micron, and D(sub a) is less than or equal to 300 nm that form via the cluster-dense aggregation mechanism.We present additional observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (D(sub f) approximately equals 1.8) aggregates, and approximately equals 90% more warming than the volume-equivalent spherical soot particles simulated in climate models.

Key-lock colloids in a nematic liquid crystal.

PubMed

Silvestre, Nuno M; Tasinkevych, M

2017-01-01

The Landau-de Gennes free energy is used to study theoretically the effective interaction of spherical "key" and anisotropic "lock" colloidal particles. We assume identical anchoring properties of the surfaces of the key and of the lock particles, and we consider planar degenerate and perpendicular anchoring conditions separately. The lock particle is modeled as a spherical particle with a spherical dimple. When such a particle is introduced into a nematic liquid crystal, it orients its dimple at an oblique angle θ_{eq} with respect to the far field director n_{∞}. This angle depends on the depth of the dimple. Minimization results show that the free energy of a pair of key and lock particles exhibits a global minimum for the configuration when the key particle is facing the dimple of the lock colloidal particle. The preferred orientation ϕ_{eq} of the key-lock composite doublet relative to n_{∞} is robust against thermal fluctuations. The preferred orientation θ_{eq}^{(2)} of the dimple particle in the doublet is different from the isolated situation. This is related to the "direct" interaction of defects accompanying the key particle with the edge of the dimple. We propose that this nematic-amplified key-lock interaction can play an important role in self-organization and clustering of mixtures of colloidal particles with dimple colloids present.

Biomimetic synthesis of silver nanoparticles by Citrus limon (lemon) aqueous extract and theoretical prediction of particle size.

PubMed

Prathna, T C; Chandrasekaran, N; Raichur, Ashok M; Mukherjee, Amitava

2011-01-01

In the present study, silver nanoparticles were rapidly synthesized at room temperature by treating silver ions with the Citrus limon (lemon) extract. The effect of various process parameters like the reductant concentration, mixing ratio of the reactants and the concentration of silver nitrate were studied in detail. In the standardized process, 10(-2)M silver nitrate solution was interacted for 4h with lemon juice (2% citric acid concentration and 0.5% ascorbic acid concentration) in the ratio of 1:4 (vol:vol). The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance as determined by UV-Visible spectra in the range of 400-500 nm. X-ray diffraction analysis revealed the distinctive facets (111, 200, 220, 222 and 311 planes) of silver nanoparticles. We found that citric acid was the principal reducing agent for the nanosynthesis process. FT-IR spectral studies demonstrated citric acid as the probable stabilizing agent. Silver nanoparticles below 50 nm with spherical and spheroidal shape were observed from transmission electron microscopy. The correlation between absorption maxima and particle sizes were derived for different UV-Visible absorption maxima (corresponding to different citric acid concentrations) employing "MiePlot v. 3.4". The theoretical particle size corresponding to 2% citric acid concentration was compared to those obtained by various experimental techniques like X-ray diffraction analysis, atomic force microscopy, and transmission electron microscopy. Copyright © 2010 Elsevier B.V. All rights reserved.

Multiscale Experimental and Numerical Approach to the Powder Particle Shape Effect on Al-Al2O3 Coating Build-Up

NASA Astrophysics Data System (ADS)

Leger, P. E.; Sennour, M.; Delloro, F.; Borit, F.; Debray, A.; Gaslain, F.; Jeandin, M.; Ducos, M.

2017-10-01

Aluminum (Al) powders with spherical and irregular particle shapes were mixed with two alumina (Al2O3) powders with either a spherical or an angular particle shape to achieve high-performance cold-sprayed coatings onto steel. Two effects of the aluminum particle shape were observed. First, coating microstructure observation showed impinging heterogeneity depending on particle shape. Second, particle jet differences depending on particle morphology were shown by velocity maps. From the latter, SEM and XRD, three effects of the alumina particle shape were also shown, i.e., higher in-flight velocity of angular particles, fragmentation of spherical hollow particles and embedding of alumina particles with aluminum. Numerical simulation of particle impacts was developed to study the densification of Al coating due to Al2O3 addition through elucidation of Al-Al2O3 interaction behavior at the scale of the coating. Al/Al and Al/Al2O3 interfaces were investigated using TEM to understand coating strengthening effects due to alumina addition at the scale of the particle. As a whole, Al and Al2O3 particle shape effects were claimed to explain coating mechanical properties, e.g., microhardness and coating-substrate bond strength. This study resulted in specifying criteria to help cold spray users in selecting powders for their applications, to meet economic and technical requirements.

Synthesis of multivalent sialyllactosamine-carrying glyco-nanoparticles with high affinity to the human influenza virus hemagglutinin.

PubMed

Ogata, Makoto; Umemura, Seiichiro; Sugiyama, Naohiro; Kuwano, Natsuki; Koizumi, Ami; Sawada, Tadakazu; Yanase, Michiyo; Takaha, Takeshi; Kadokawa, Jun-Ichi; Usui, Taichi

2016-11-20

A series of multivalent sialoglyco-conjugated nanoparticles were efficiently synthesized by using highly-branched α-glucuronic acid-linked cyclic dextrins (GlcA-HBCD) as a backbone. The sialoglycoside-moieties, with varying degrees of substitution, could be incorporated onto the preformed nanoparticles. These synthesized particles, which are highly soluble in aqueous solution, were shown to have a spherical nanostructure with a diameter of approximately 15nm. The interactions of the sialoglyco-nanoparticles (Neu5Acα2,6LacNAc-GlcA-HBCDs) with human influenza virus strain A/Beijing/262/95 (H1N1) were investigated using a hemagglutination inhibition assay. The sialoglyco-nanoparticle, in which the number of sialic acid substitution is 30, acted as a powerful inhibitor of virus binding activity. We show that both distance and multiplicity of effective ligand-virus formation play important roles in enhancing viral inhibition. Our results indicate that the GlcA-HBCD backbone can be used as a novel spherical nanocluster material for preparing a variety of glyco-nanoparticles to facilitate molecular recognition. Copyright © 2016 Elsevier Ltd. All rights reserved.

Green synthesis, characterisation and bioactivity of plant-mediated silver nanoparticles using Decalepis hamiltonii root extract.

PubMed

Rashmi, Venkatasubbaiah; Sanjay, Konasur R

2017-04-01

Consistent search of plants for green synthesis of silver nanoparticles (SNPs) is an important arena in Nanomedicine. This study focuses on synthesis of SNPs using bioreduction of silver nitrate (AgNO 3 ) by aqueous root extract of Decalepis hamiltonii . The biosynthesis of SNPs was monitored by UV-vis analysis at absorbance maxima 432 nm. The fluorescence emission spectra of SNPs illustrated the broad emission peak 450-483 nm at different excitation wavelengths. The surface characteristics were studied by scanning electron microscope and atomic force microscopy, showed spherical shape of SNPs and dynamic light scattering analysis confirmed the average particle size 32.5 nm and the presence of metallic silver was confirmed by energy dispersive X-ray. Face centred cubic structure with crystal size 33.3 nm was revealed by powder X-ray diffraction. Fourier transform infrared spectroscopy indicated the biomolecules involved in the reduction mainly polyols and phenols present in root extracts were found to be responsible for the synthesis of SNPs. The stability and charge on SNPs were revealed by zeta potential analysis. In addition, on therapeutic forum, the synthesised SNPs elicit antioxidant and antimicrobial activity against Bacillus cereus , Bacillus licheniformis , Escherichia coli , Pseudomonas aeruginosa and Staphylococcus aureus .

Space Radiation Detector with Spherical Geometry

NASA Technical Reports Server (NTRS)

Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)

2011-01-01

A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.

Space Radiation Detector with Spherical Geometry

NASA Technical Reports Server (NTRS)

Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)

2012-01-01

A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.

Studies by immune electron microscopy of hepatitis B surface antigen in PLC/PRF/5 cells.

PubMed

Shibayama, T; Watanabe, T; Kojima, H; Yoshikawa, A; Watanabe, S; Kamimura, T; Suzuki, S; Ichida, F

1984-01-01

Electron microscopic studies of the morphology of hepatitis B surface antigen (HBsAg) produced by PLC/PRF/5 cells in vitro were carried out. Aggregates of 20-nm spherical particles in 3-day culture supernatants were observed by immune electron microscopy (IEM). Aggregates of tubular structures were found with IEM in the extracts of the cells. Tubular structures 18 to 22 nm in diameter were seen by electron microscopy (EM) in the cisternae of the endoplasmic reticulum in 2-3% of the cells. The tubular structures in the cytoplasm and extracts of PLC/PRF/5 cells resembled those observed in the hepatocytes of human carriers of hepatitis B virus (HBV). Intracellular localization of HBsAg in PLC/PRF/5 cells by direct peroxidase-conjugated antibody staining was observed on the tubular structures and the cisternal wall, which contained these structures. Rotation technique analysis indicated that the tubular structures were composed of 11 or 12 subunits.

The Green synthesis of gold nanoparticles using an aqueous root extract of Morinda citrifolia L

NASA Astrophysics Data System (ADS)

Suman, T. Y.; Radhika Rajasree, S. R.; Ramkumar, R.; Rajthilak, C.; Perumal, P.

2014-01-01

In the present work, we describe the synthesis of gold nanoparticles using an aqueous root extract of Morinda citrifolia. UV-vis spectroscopy, XRD, FTIR, FE-SEM, EDX and TEM were performed to characterize the formation of gold nanoparticles. The synthesized gold nanoparticles were characterized by a peak at 540 nm in the UV-vis spectrum. The XRD peaks at 38°, 44°, 64° and 77° can be indexed to the (1 1 1), (2 0 0), (2 2 0) and (3 1 1) Bragg's reflections of cubic structure of metallic gold, respectively. The FTIR result showed that extract containing protein might be responsible for the formation of the nanoparticles and may play an important role in the stabilization of the formed nanoparticles. FESEM images revealed that the particles were triangle and mostly spherical in shape. TEM images clearly revealed the size of the nanoparticles were 12.17-38.26 nm in size.

The Green synthesis of gold nanoparticles using an aqueous root extract of Morinda citrifolia L.

PubMed

Suman, T Y; Rajasree, S R Radhika; Ramkumar, R; Rajthilak, C; Perumal, P

2014-01-24

In the present work, we describe the synthesis of gold nanoparticles using an aqueous root extract of Morinda citrifolia. UV-vis spectroscopy, XRD, FTIR, FE-SEM, EDX and TEM were performed to characterize the formation of gold nanoparticles. The synthesized gold nanoparticles were characterized by a peak at 540 nm in the UV-vis spectrum. The XRD peaks at 38°, 44°, 64° and 77° can be indexed to the (111), (200), (220) and (311) Bragg's reflections of cubic structure of metallic gold, respectively. The FTIR result showed that extract containing protein might be responsible for the formation of the nanoparticles and may play an important role in the stabilization of the formed nanoparticles. FESEM images revealed that the particles were triangle and mostly spherical in shape. TEM images clearly revealed the size of the nanoparticles were 12.17-38.26 nm in size. Copyright © 2013 Elsevier B.V. All rights reserved.