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SiO2 Particles (sio2 + particle)

Distribution by Scientific Domains

Polymers and Materials Science	64%
Chemistry	35%

Distribution within Polymers and Materials Science

General & Introductory Materials Science	43%
Polymer Science & Technology General	32%

Selected Abstracts

Size-Tunable Highly Luminescent SiO2 Particles Impregnated with Number-Adjusted CdTe Nanocrystals

CHEMPHYSCHEM, Issue 4 2010
Ping Yang Dr.
Abstract Highly luminescent SiO2 particles impregnated with CdTe nanocrystals (NCs) are prepared by a sol,gel procedure. Partial ligand exchange from thioglycolic acid to 3-mercaptopropyltrimethoxysilane (MPS) on the NCs enables retention of the initial photoluminescence (PL) efficiency of the NCs in water, while the simultaneous addition of a poor solvent (ethanol) results in regulated assembly of the NCs through condensation of hydrolyzed MPS. The SiO2 particles thus prepared have, for example, a diameter of 16 nm and contain three NCs each. The PL efficiency of these particles is 40,%, while the initial efficiency is 46,% in a colloidal solution. The redshift and narrowed spectral width in PL observed after impregnation indicate that the concentration of NCs in these nearly reaches the ultimate value (on the order of 1021 particles per liter). The porosity of these particles is investigated by means of N2 adsorption,desorption isotherms. Due to the SiO2 shell, these particles have higher stability in phosphate-buffered saline buffer solution than the initial NCs. Their potential use for labeling in bio-applications is investigated by conjugating biotinylated immunoglobulin G to them by using streptavidin maleimide as linker. Successful conjugation is confirmed by electrophoresis in agarose gel. This preparation method is an important step towards fabricating intensely emitting biocompatible SiO2 particles impregnated with semiconductor NCs. [source]

Silica Supported Submicron SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ Spherical Particles with a Core,Shell Structure: Sol,Gel Synthesis and Characterization

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006
Cuikun Lin
Abstract X1 -Y2SiO5:Eu3+ and X1 -Y2SiO5:Ce3+ and/or Tb3+ phosphor layers have been coated on nonaggregated, monodisperse, submicron spherical SiO2 particles by a sol,gel process, followed by surface reaction at high temperature (1000 °C), to give core/shell structured SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), TEM, photoluminescence (PL), low voltage cathodoluminescence (CL), and time-resolved PL spectra and lifetimes are used to characterize these materials. The XRD results indicate that X1 -Y2SiO5 layers have been successfully coated on the surface of SiO2 particles, as further verified by the FESEM and TEM images. The PL and CL studies suggest that SiO2@Y2SiO5:Eu3+, SiO2@Y2SiO5:Tb3+ (or Ce3+/Tb3+), and SiO2@Y2SiO5:Ce3+ core/shell particles exhibit red (Eu3+, 613 nm: 5D0,7F2), green (Tb3+, 542 nm: 5D4,7F5), or blue (Ce3+, 450 nm: 5d-4f) luminescence, respectively. PL excitation, emission, and time-resolved spectra demonstrate that there is an energy transfer from Ce3+ to Tb3+ in the SiO2@Y2SiO5:Ce3+,Tb3+ core/shell particles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

STED Microscopy to Monitor Agglomeration of Silica Particles Inside A549 Cells,

ADVANCED ENGINEERING MATERIALS, Issue 5 2010
Sabrina Schübbe
The widespread use of engineered nanomaterials increases the exposure of the materials to humans. Therefore, it is necessary to know how these materials interact with cells. One approach is to trace particles by fluorescent labeling. The aim of the present work was to study the behavior of silica particles in A549 cells. For the first time, we applied stimulated emission depletion (STED) microscopy for this approach. Therefore, SiO2 particles conjugated with Atto647N were prepared by L -arginine-catalyzed hydrolysis of tetraethoxysilane. The Atto647N labeled SiO2 particles exhibit a mean size of 128,±,7,nm and a zeta-potential of ,11,mV in cell culture medium. STED microscopy enables subdiffraction resolution imaging of single Atto647N labeled SiO2 particles not only in pure solution but also in a cellular environment. To visualize Atto647N labeled SiO2 particles inside A549 cells, the membrane was labeled and image stacks, that give three-dimensional information, were taken after 5, 24, and 48 h exposure of particles to cells. During this incubation period, an increase in particle uptake was observed and STED micrographs allowed us to evaluate the agglomeration of Atto647N labeled SiO2 particles inside A549 cells. Our results show that STED microscopy is a powerful technique to study particles in a cellular environment. [source]

A Facile Synthesis and Characterization of Monodisperse Spherical Pigment Particles with a Core/Shell Structure,

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2007
C. Lin
Abstract In this paper, a facile sol,gel process for producing monodisperse, spherical, and nonaggregated pigment particles with a core/shell structure is reported. Spherical silica particles (245 and 385,nm in diameter) and Cr2O3, ,-Fe2O3, ZnCo2O4, CuFeCrO4, MgFe2O4, and CoAl2O4 pigments are selected as cores and shells, respectively. The obtained core/shell-structured pigment samples, denoted as SiO2@Cr2O3 (green), SiO2@,-Fe2O3 (red), SiO2@MgFe2O4 (brown), SiO2@ZnCo2O4 (dark green), SiO2@CoAl2O4 (blue), and SiO2@CuFeCrO4 (black), are well characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and UV-vis diffuse reflection, as well as by investigating the magnetic properties. The results of XRD and high-resolution TEM (HRTEM) demonstrate that the pigment shells crystallize well on the surface of SiO2 particles. The thickness of the pigment shell can be tuned by the number of coatings, to some extent. These pigment particles can be well dispersed in some solvents (such as glycol) to form relatively more stable suspensions than the commercial products. Apart from the color characteristics, some of pigments like SiO2@Cr2O3, SiO2@MgFe2O4, and SiO2@CuFeCrO4 also show magnetic properties with coercivities of 1098,Oe (5,K), 648,Oe (5,K), and 91,Oe (298,K), respectively. [source]

Transparent Nanocomposites of Radiopaque, Flame-Made Ta2O5/SiO2 Particles in an Acrylic Matrix,

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2005
H. Schulz
Abstract Mixed Ta2O5 -containing SiO2 particles, 6,14,nm in diameter, with closely controlled refractive index, transparency, and crystallinity are prepared via flame spray pyrolysis (FSP) at production rates of 6.7,100,g,h,1. The effect of precursor solution composition on product filler (particle) size, crystallinity, Ta dispersity, and transparency is studied using nitrogen adsorption, X-ray diffraction, optical microscopy, high-resolution transmission electron microscopy (HRTEM), and diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS). Emphasis is placed on the transparency of the composite that is made with Ta2O5/SiO2 filler and dimethylacrylate. Increasing Ta2O5 crystallinity and decreasing Ta dispersity on SiO2 decreases both filler and composite transparencies. Powders with identical specific surface area (SSA), refractive index (RI), and Ta2O5 content (24,wt.-%) show a wide range of composite transparencies, 33,78,%, depending on filler crystallinity and Ta dispersity. Amorphous fillers with a high Ta dispersity and an RI matching that of the polymer matrix lead to the highest composite transparency, 86,%. The composite containing 16.5,wt.-% filler that itself contains 35,wt.-% Ta2O5 has the optimal radiopacity for dental fillings. [source]

Self-Assembly and Micropatterning of Spherical-Particle Assemblies,

ADVANCED MATERIALS, Issue 7 2005
Y. Masuda
Spherical-particle assemblies (see Figure) are fabricated by micropatterning of methanol droplets containing SiO2. Hydrophilic regions of a patterned self-assembled monolayer (SAM) are covered with methanol solution containing SiO2 particles and immersed in decahydronaphthalene. The particles assemble to form micropatterns of spherical-particle assemblies on the hydrophilic regions of the SAM. [source]

Synthesis and properties of silica/polystyrene/polyaniline conductive composite particles

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005
Chia-Fen Lee
Abstract In this study, silica/polystyrene/polyaniline (SiO2/PS/PANI) conductive composite particles were synthesized by four sequential reactions. The nanosized SiO2 particles were synthesized from tetraethoxysilane (TEOS) by a sol,gel process with water as the solvent medium, followed by a surface modification with triethoxyvinylsilane; then the surface modified SiO2 particles were used as seeds to synthesize SiO2/PS composite particles with soapless seeded emulsion polymerization. Finally, the SiO2/PS particles were used as seeds to synthesize the SiO2/PS/PANI conductive composite particles. The sol,gel process of SiO2, the effect of surface modification, and several other factors that influenced polymerization of styrene in the soapless seeded emulsion polymerization will be discussed. Either potassium persulfate (KPS) or 2,2,-azobis(isobutyramidine) dihydrochloride (AIBA) was used as the initiator to synthesize the uniform SiO2/PS particles successfully, and the cross-section morphology of the SiO2/PS particles was found to be of a core,shell structure, with SiO2 as the core, and PS as the shell. The SiO2/PS particles were well dispersed in many organic solvents. In the following step to synthesize SiO2/PS/PANI conductive composite particles, sodium dodecyl sulfate (SDS) played an important role, specifically, to absorb aniline onto the surfaces of the SiO2/PS particles to carry out the polymerization of aniline over the entire surface of the particles. The conductivity of the SiO2/PS/PANI composite particles approached that of semiconductive materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 342,354, 2005 [source]

Structure Determination in Colloidal Crystal Photonic Bandgap Structures

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002
John Ballato
Structure/optical property relationships in photonic bandgap structures are evaluated by a novel combination of sample sectioning, microscopy, and image analysis. Disordered colloidal crystals of solution-derived, monosized SiO2 particles were sectioned by focused ion beam (FIB) milling and then imaged using field emission scanning electron microscopy (FE-SEM). Pair correlation and radial distribution functions of the particulate arrangement were generated directly from a binary color scale rendering of the FE-SEM images, therein defining the level of order or disorder in the structure. These experimentally obtained spatial correlation functions were used to compute the scattering spectral properties in an analogous, although inverse (i.e., solving the inverse scattering problem), method to that used in X-ray diffraction for structure determination. Using a first-order approximation to the scattering from a disordered structure, the bandwidth and midgap values for the colloidal crystal photonic bandgap materials were within 15% of those measured. This new methodology promises to provide a simple and direct approach for quantifying the structure/optical property relationships in ordered and disordered photonic crystals directly from standard microstructural imaging techniques. [source]

Indication of Local Phase Separation in Polyimide/Silica Hybrid Polymers,

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010
Antonino Bartolotta
Abstract PI/SiO2 hybrid polymers involving the in situ generation of SiO2 particles through the sol/gel route have emerged as promising materials in many fields of modern technology thanks to their unique structural characteristics. In this paper their structural and dynamic properties were investigated by FT-IR and DMTA as a function of SiO2 content. All data consistently highlight a loosening of polymeric structure due to the presence of SiO2 nanoparticles and suggest a silica-induced structural change most probably due to a sub-micrometer scale SiO2 phase separation. Our results demonstrate how the analysis of sub-glass ,-relaxation dynamics can be exploited to investigate sub-micro phase segregation in such materials. [source]

Preparation and characterization of novel hybrid thermoplastic poly(ether urethane)/poly(vinylidene fluoride) elastomers, and their application as solid polymer electrolytes

POLYMER INTERNATIONAL, Issue 5 2007
Ye Lin
Abstract A comb-like polyether, poly(3-2-[2-(2-methoxyethoxy)ethoxy]ethoxymethyl-3,-methyloxetane) (PMEOX), was reacted with hexamethylene diisocyanate and extended with butanediol in a one-pot procedure to give novel thermoplastic elastomeric poly(ether urethane)s (TPEUs). The corresponding hybrid solid polymer electrolytes were fabricated through doping a mixture of TPEU and poly(vinylidene fluoride) with three kinds of lithium salts, LiClO4, LiBF4 and lithium trifluoromethanesulfonimide (LiTFSI), and were characterized using differential scanning calorimetry, thermogravimetric analysis and Fourier transform infrared spectroscopy. The ionic conductivity of the resulting polymer electrolytes was then assessed by means of AC impedance measurements, which reached 2.1 × 10,4 S cm,1 at 30 °C and 1.7 × 10,3 S cm,1 at 80 °C when LiTFSI was added at a ratio of O:Li = 20. These values can be further increased to 3.5 × 10,4 S cm,1 at 30 °C and 2.2 × 10,3 S cm,1 at 80 °C by introducing nanosized SiO2 particles into the polymer electrolytes. Copyright © 2006 Society of Chemical Industry [source]

Surface properties of hydrosilylated polyolefins annealed in supercritical carbon dioxide

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2008
S.-H. Zhu
Abstract Two hydrosilylated polyolefin compounds are obtained by reacting polypropylene (PP) and polyethylene (PE) with di- and multi-functional hydride-terminated poly(dimethylsiloxane) (dH-PDMS and mH-PDMS), respectively. The PDMS-rich surface layers on these two samples show different Si concentrations but similar thicknesses. Samples of these materials are annealed in supercritical carbon dioxide (scCO2) at various temperatures and pressures for different periods of time. On the PP/dH-PDMS sample, an increase in the annealing temperature does not affect the Si concentration up to 120°C. However, the Si concentration is sharply reduced at T,=,150°C at which point the surface appears to be covered by SiO2 particles. Annealing the PP/dH-PDMS sample for short times leads to submicron scale SiO2 particle formation on the surface. The particles form aggregated clusters that spread all over the surface uniformly when the annealing time is extended. However, Si concentration on the PE/mH-PDMS sample surface is enhanced as the annealing temperature increases, reaching a maximum at an annealing temperature of 100°C. No particle formation is observed on the PE/mH-PDMS sample surface. The contact angle of both samples is found to increase with annealing temperature. Increasing the scCO2 pressure leads to a higher Si concentration on the surfaces of both samples. On the other hand, increasing the CO2 pressure leads to opposite trends in contact angle with the PP/dH-PDMS sample exhibiting an increasing contact angle and the PE/mH-PDMS sample exhibiting a decreasing one. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Nanoparticles by chemical synthesis, processing to materials and innovative applications,

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2001
Helmut Schmidt
Abstract Nanoparticles have been fabricated by using chemical synthesis routes under specific conditions. During a precipitation process from liquid phases, surface controlling agents (SCAs) have been added during or shortly after the formation of precipitates. These interfere with the nucleating and growing particle to avoid agglomeration and to control size. Nanoparticles from many systems have been fabricated. If the SCAs are bifunctional, the surfaces chemistry could be tailored and the zeta potential of these particles was tailored also. SiO2 particles have been used for gene targeting using this approach. In other investigations, FeOx nanoparticles have been surface modified by amino groupings together with a sonochemical route to obtain very stable coatings. These particles have been used for in vitro tumor cell penetration and hyperthermal treatment. Boehmite nanoparticles were used to serve as condensation catalysts to prepare very hard transparent coatings for polycarbonate and an overcoat with polymerizable nanoparticles was used to produce anti-reflective and ultrahard coatings. In systems with incorporated fluoro silanes, leading to low surface free energy coatings, nanoparticles were used to tailor the fluorine depth profile in self-aligning transparent easy-to-clean coatings by influencing the critical micelle concentration. The examples show the usefulness of the chemical nanoparticle approach for nanocomposite fabrication and the high potential of these materials for medical and industrial application. Copyright © 2001 John Wiley & Sons, Ltd. [source]