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Inorganic Core (inorganic + core)
Selected AbstractsInterface Modifications of InAs Quantum-Dots Solids and their Effects on FET PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Michal Soreni-Harari Abstract InAs nanocrystals field-effect transistors with an ON/OFF ratio of 105 are reported. By tailoring the interface regions in the active layer step-by-step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 105. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal,nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub-gap states, and better electronic order (lower , parameter). Films with enhanced charge transport qualities retain their quantum-confined characteristics throughout the procedure, thus making them useful for optoelectronic applications. [source] Au@pNIPAM Thermosensitive Nanostructures: Control over Shell Cross-linking, Overall Dimensions, and Core GrowthADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Rafael Contreras-Cáceres Abstract Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N -isopropylacrylamide) (pNIPAM) shell are synthesized by grafting the gold nanoparticle surface with polystyrene, which allows the coating of an inorganic core with an organic shell. Through careful control of the experimental conditions, the pNIPAM shell cross-linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to a few hundred nanometers is tuned. The characterization of these core,shell systems is carried out by photon-correlation spectroscopy, transmission electron microscopy, and atomic force microscopy. Additionally, the porous pNIPAM shells are found to modulate the catalytic activity, which is demonstrated through the seeded growth of gold cores, either retaining the initial spherical shape or developing a branched morphology. The nanocomposites also present thermally modulated optical properties because of temperature-induced local changes of the refractive index surrounding the gold cores. [source] Formation of Inorganic/Organic Nanocomposites by Nitroxide-Mediated Polymerization in Bulk Using a Bimolecular SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 10 2004Julien Parvole Abstract Summary: A series of organic-inorganic nanoparticles were synthesized by nitroxide-mediated polymerization (NMP) of butyl acrylate initiated by a self-assembled monolayer of an azo initiator. The azo initiator was immobilized on silica particles in the presence of a stable nitroxide radical, SG1 (an acyclic , -phosphonylated nitroxide, N - tert -butyl- N -(1-diethylphosphono-2,2-dimethyl)propyl nitroxide). After preliminary qualitative characterization by X-ray spectroscopy (XPS) and Fourier-transform infrared (FTIR) measurements, the nanoparticles were studied by thermogravimetric analysis (TGA) to determine the polymer grafting density and to permit a comparison with corresponding values of the initiator monolayer. It was demonstrated that the grafting from polymerization exhibits a controlled character with a low polydispersity (,<,1.2) in a large range of molecular weights of the grafted chains (from 4,000 up to 145,000 g,·,mol,1) under the conditions when the stable radical SG1, acting as chain growth moderator tethered to the inorganic core, was used. [source] Grafting Polymer Brushes from Glass Fibers by Surface-Initiated ATRPMACROMOLECULAR REACTION ENGINEERING, Issue 3-4 2010Hongwen Zhang Abstract Grafting of PMMA and/or PS brushes from the surface of glass fibers by SI-ATRP has been investigated in order to achieve a controlled surface structure of the matrix. The surface composition and morphology of the modified glass fibers were analyzed by FTIR, XPS, TGA, and SEM. The results indicated that the surface composition and morphology were improved by grafting polymer after modification. The modified glass fibers were composed of an organic tube and an inorganic core. The organic content on the surface of modified glass fibers was high. GPC data of free polymer showed that the SI-ATRP from the surface of bromine-bound glass fibers proceeded in a controlled/"living" manner. [source] Reactions of Cl,/Cl2,, Radicals with the Nanoparticle Silica Surface and with Humic Acids: Model Reactions for the Aqueous Phase Chemistry of the AtmospherePHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Paula Caregnato ABSTRACT Reactions of chlorine radicals might play a role in aqueous aerosols where a core of inorganic components containing insulators such as SiO2 and dissolved HUmic-LIke Substances (HULIS) are present. Herein, we report conventional flash photolysis experiments performed to investigate the aqueous phase reactions of silica nanoparticles (NP) and humic acid (HA) with chlorine atoms, Cl,, and dichloride radical anions, Cl2,,. Silica NP and HA may be taken as rough models for the inorganic core and HULIS contained in atmospheric particles, respectively. Both Cl, and Cl2,, were observed to react with the deprotonated silanols on the NP surface with reaction rate constants, k ± ,, of (9 ± 6) × 107 M,1 s,1 and (7 ± 4) × 105 M,1 s,1, respectively. The reaction of Cl, with the surface deprotonated silanols leads to the formation of SiO, defects. HA are also observed to react with Cl, and Cl2,, radicals, with reaction rate constants at pH 4 of (3 ± 2) × 1010 M,1 s,1 and (1.2 ± 0.3) × 109 M,1 s,1, respectively. The high values observed for these constants were discussed in terms of the multifunctional heterogeneous mixture of organic molecules conforming HA. [source] Surface-initiated nitroxide-mediated polymerization: a tool for hybrid inorganic/organic nanocomposites ,in situ' synthesisPOLYMER INTERNATIONAL, Issue 10 2006Leïla Ghannam Abstract Hybrid silica particles comprised of an inorganic core and an organic polymer shell can be synthesized by surface-initiated nitroxide-mediated polymerization (SINMP) in the presence of a grafted alkoxyamine as initiator. The layer of initiator molecules attached or adsorbed to the particles surface is based on a nitroxide group. The synthesis and characterization of these alkoxyamine structures are briefly described. The grafted initiator particles are studied in order to determine the nature of the anchorage sites and the grafting density. With a stable radical or nitroxide as chain-growth moderator tethered to the inorganic core, it was demonstrated that the grafting from or to SINMP exhibits a control character with a very low polydispersity and good agreement between theoretical/experimental molecular weights. A comparative review of different alkoxyamines with a bimolecular system based on a grafted azoic initiator in the presence of an acyclic ,-phosphonylated nitroxide called SG1 is also described. Moreover, original methods for the synthesis of alkoxyamine grafted surface by in situ trapping of carbon radicals and some new developments for colored pigments will be reported. These topics could be one of the directions of the field in the next years. Copyright © 2006 Society of Chemical Industry [source] Study of ferrite ferrofluids by small-angle scattering of polarized neutronsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Massimo Bonini Nanoparticles consisting of a magnetic core (Fe3O4, CoFe2O4 and CuFe2O4) and a hydrophobic shell were prepared by chemical co-precipitation of the inorganic cores and by subsequently modifying the surface with dodecanoic acid. The nanoparticles were then dispersed in cyclohexane to form stable ferrofluids. These dispersions were investigated by small-angle scattering of polarized neutrons and the data were interpreted according to a `pearl-necklace' model, opportunely modified to account for the core,shell structure of the particles. Results of the fitting show that the particles consist of a magnetic core with a mean radius of 40,50,Å and an organic shell with a thickness of 7,8,Å. These nanoparticles assemble in fractal aggregates when a magnetic field is applied. [source] | ||||||||||