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Spherical Nanoparticles (spherical + nanoparticle)
Selected AbstractsFacile and Reproducible Synthesis of Nanostructured Colloidal ZnO Nanoparticles from Zinc Acetylacetonate: Effect of Experimental Parameters and Mechanistic InvestigationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009Alessia Famengo Abstract A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Photoelectrochemical Study of Nanostructured ZnO Thin Films for Hydrogen Generation from Water SplittingADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Abraham Wolcott Abstract Photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting. The ZnO thin films are fabricated using three different deposition geometries: normal pulsed laser deposition, pulsed laser oblique-angle deposition, and electron-beam glancing-angle deposition. The nanostructured films are characterized by scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and photoelectrochemical techniques. Normal pulsed laser deposition produces dense thin films with ca. 200,nm grain sizes, while oblique-angle deposition produces nanoplatelets with a fishscale morphology and individual features measuring ca. 900 by 450,nm on average. In contrast, glancing-angle deposition generates a highly porous, interconnected network of spherical nanoparticles of 15,40,nm diameter. Mott-Schottky plots show the flat band potential of pulsed laser deposition, oblique-angle deposition, and glancing-angle deposition samples to be ,0.29, ,0.28 and +0.20,V, respectively. Generation of photocurrent is observed at anodic potentials and no limiting photocurrents were observed with applied potentials up to 1.3,V for all photoelectrochemical cells. The effective photon-to-hydrogen efficiency is found to be 0.1%, 0.2% and 0.6% for pulsed laser deposition, oblique-angle deposition and glancing-angle deposition samples, respectively. The photoelectrochemical properties of the three types of films are understood to be a function of porosity, crystal defect concentration, charge transport properties and space charge layer characteristics. [source] Two-Dye Core/Shell Zeolite Nanoparticles: A New Tool for Ratiometric pH MeasurementsADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Tristan Doussineau Abstract The preparation of core/shell nanoparticles that enable ratiometric pH measurement is described. The core of the nanoparticles consists of a zeolite- , matrix that exhibits a 3-hydroxyflavone reference dye within the porous network. Coating an amorphous silica shell containing a fluorosensor around the zeolite through the Stöber process provides pH sensitivity to the nanoparticles. Morphological characterization (dynamic light scattering, transmission electronic microscopy) demonstrates the control of the sensing silica shell around the zeolite cores, leading to highly monodisperse spherical nanoparticles, while structural characterization (wide-angle X-ray diffraction, nitrogen adsorption) shows the amorphous character of the shell. Spectral characterization via UV/Vis absorption and steady-state fluorescence shows good pH sensitivity of the resulting nanosensors with a pKa suitable for bioanalytical applications. [source] Syzygium cumini leaf and seed extract mediated biosynthesis of silver nanoparticles and their characterizationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2010Vineet Kumar Abstract BACKGROUND: Plant mediated synthesis of metallic nanoparticles has been studied and reported, however, to date, the biomolecules involved in the synthesis of metallic nanoparticles have not been characterized. This study was therefore undertaken to characterize the biomolecules of Syzygium cumini involved in the synthesis of silver nanoparticles. RESULTS: Synthesis kinetics and morphological characterization of silver nanoparticles (SNP) synthesized using leaf extract (LE) and seed extract (SE) as well as their polar (water) fractions from Syzygium cumini were compared. The polyphenols content and high performance liquid chromatography (HPLC) profile of different fractions revealed good correlation between size and synthesis rate of SNP. SE contains more polyphenols and biochemical constituents than LE and therefore, showed higher synthesis rate and bigger sized SNP. To analyse the nature of biomolecules involved in the synthesis of SNP, LE and SE were fractionated on a polarity basis by solvent,solvent partitioning. Only the water fractions of LE and SE showed potential for SNP synthesis. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis of SNP indicated that all fractions catalyze the synthesis of spherical nanoparticles. The average size of SNP synthesized by LE, leaf water fraction, SE and seed water fraction were 30, 29, 92, and 73 nm respectively. CONCLUSION: Results suggest that only highly polar soluble constituents are responsible for SNP synthesis. The size of SNP was found to be directly correlated with the amount of polyphenols as well as surfactants present in the reaction solution. Thus, the amount of polyphenols could be one of the crucial parameters determining the size and distribution of SNP. Copyright © 2010 Society of Chemical Industry [source] Tailored composite polymer,metal nanoparticles by miniemulsion polymerization and thiol-ene functionalizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2010Kim Y. van Berkel Abstract A simple and modular synthetic approach, based on miniemulsion polymerization, has been developed for the fabrication of composite polymer,metal nanoparticle materials. The procedure produces well-defined composite structures consisting of gold, silver, or MnFe2O4 nanoparticles (,10 nm in diameter) encapsulated within larger spherical nanoparticles of poly(divinylbenzene) (,100 nm in diameter). This methodology readily permits the incorporation of multiple metal domains into a single polymeric particle, while still preserving the useful optical and magnetic properties of the metal nanoparticles. The morphology of the composite particles is retained upon increasing the inorganic content and also upon redispersion in organic solvents. Finally, the ability to tailor the surface chemistry of the composite nanoparticles and incorporate steric stabilizing groups using simple thiol-ene chemistry is demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1594,1606, 2010 [source] Synthesis of Zirconia Nanoparticles in a Continuous-Flow Microwave ReactorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Federica Bondioli Monodispersed zirconia colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of tetra- n -propylzirconate by using a continuous microwave synthesis process. The flow rate was varied from 50 to 100 mL/min in order to establish the optimum conditions required to obtain unagglomerated zirconia nanopowders. The results were compared with those obtained in batch systems. In particular as the flow rate is decreased from 100 to 50 mL/min the particle became spherical with a mean particle size of about 100 nm. [source] Four photon laser spectroscopy of local heterogeneities in solids in 0 , 60 GHzLASER PHYSICS LETTERS, Issue 4 2007A. F. Bunkin Abstract The spectra of coherent four photon scattering in fused quartz and crown glass K8 have been measured in the range ±2 cm,1. It's shown that both samples contain the features of Brillouin scattering on longitudinal and transversal hypersound. In the samples the sharp resonances of OH molecules rotations are detected for the first time in the range 1.3,1.6 cm,1. In fused quartz the fine structure of spectrum in the range ±0.3 cm,1 is observed. The last features are attributed to the own modes 0.165 cm,1 and 0.26 cm,1 of spherical nanoparticles, which was studied in the synthetic opal earlier. The diameter of these SiO2 spheres was estimated as 880 ± 30 nm. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Microstructure Formation and Property of Chitosan-Poly(acrylic acid) Nanoparticles Prepared by Macromolecular ComplexMACROMOLECULAR BIOSCIENCE, Issue 10 2005Qi Chen Abstract Summary: We report here a study on the microstructure formation process of polymeric nanoparticles based on polyelectrolyte complexes. When polyanion poly(acrylic acid) (PAA) was dropped into polycation chitosan (CS) solution, CS-PAA nanoparticles with diverse microstructure would be formed under different experimental conditions. The microstructure of CS-PAA nanoparticles changed from solid spherical nanoparticles to core-shell separative ones and turned back to solid spherical ones with the variation of preparation conditions. The influence of molecular weight of CS and PAA, shell cross-linking, dropping temperature on the size, stability and morphology of CS-PAA nanoparticles were also studied. The nanoparticle size was affected by the molecular weight of CS and PAA, the ratio of amino group to carboxyl group (na/nc) and the incubation temperature as well. The shell-cross-linking provides a means to stabilize these nanoparticles. These nanoparticles can encapsulate plasmid DNA very well, which makes them have great potential in gene delivery. Microstructure of non-cross-linked CS-PAA nanoparticles, encapsulated plasmid DNA, at various na/nc. [source] Studies on Preparation and Fluorescent Properties of a Novel Photo-Sensitive Nanoparticle Composed of Europium Ion and Cinnamic Acid DerivativeMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2009Dongjian Shi Abstract A novel fluorescent and photo-sensitive nanoparticle was self-assembled from an europium-based random copolymer, europium coordinated poly(methylacrylic acid)- co -poly(cinnamyl acrylate) (PMCFA-Eu3+), which was synthesized from methylacrylic acid (MAA), and Eu3+ -cinnamyl acrylate derivative (CFA) by radical polymerization. DLS and TEM results indicated the formation of spherical nanoparticles with 120,nm in diameter. The PMCFA-Eu3+ complex showed stronger fluorescence than Eu3+, indicating the effective energy transferred from the ligand to Eu3+. Moreover, the photo-crosslinking of the cinnamate groups induced a decrease in the diameter and an increase in the fluorescent properties of the PMCFA-Eu3+ nanoparticles. This functional nanoparticle might be useful as a carrier and a fluorescence probe in biomedical and fluorescent fields. [source] | |||||||||||||