1,720,993 research outputs found
Efficient charge storage in photoexcited TiO2 nanorod-noble metal nanoparticle composite systems RID C-5360-2009
No full textFollowing UV-illumination, TiO2 nanorod-stabilized noble metal (Ag, Au) nanoparticles dispersed in deaerated organic mixtures can sustain a higher degree of conduction band electron accumulation than that achievable with pristine titania
Synthesis of TiO2-Au composites by titania-nanorod-assisted generation of gold nanopartictes at aqueous/nonpolar interfaces RID C-5360-2009
No full textHydrophobically coated anatase TiO2 nanorods can assist the reduction of AuCl4- ions at aqueous/nonpolar solvent interfaces, which results in the generation of organic-soluble Au nanoparticles with tunable size in the absence of any metal ligands and/or phase-transfer agents. The titania- nanorod-driven modulation of interfacial energy and catalysis of gold nucleation provide straightforward access to nanocomposite solutions of TiO2-stabilized Au nanoparticles. Among colloidal approaches, this method represents a unique tool for the surfactantless, large-scale preparation of nanostructured semiconductor-metal hybrid systems with relevant technological potential in catalysis, photocatalysis, and charge-storage processes
Low-dimensional chainlike assemblies of TiO2 nanorod-stabilized Au nanoparticles RID C-5360-2009
No full textA simple and versatile light-based strategy to grow low-dimensional gold superstructures is presented; prolonged UV-irradiation of TiO2 nanorod-stabilized Au nanoparticles in organic media promotes the progressive formation of distinctive chainlike metal assemblies, namely segments of a few gold particles, 2D or quasi-1D large structures composed of interlacing lines of hundreds of metal units over areas of about 500 nm(2)
UV-induced photocatalytic degradation of azo dyes by organic-capped ZnO nanocrystals immobilized onto substrates RID C-5449-2009 RID C-5360-2009
No full textZnO nanocrystals (mean particle size: 6 nm) with different surface organic coating and commercial ZnO powder (mean particle size: 200 nm) have been immobilized onto transparent substrates and comparatively examined as photocatalysts for the UV-induced degradation of two azo dyes, Methyl Red and Methyl Orange, in water. The effects of the pH, of the catalyst surface status, and of the dye chemical structure on the course of the photocatalysis are discussed. Reasonable degradation pathways for both target molecules are proposed on the basis of the structural identification of several by-products. The results demonstrate that surfactant-capped ZnO nanocrystals exhibit more versatile performances than those of conventional ZnO-based photocatalysts, because the surface organic coating makes the oxide resistant to photocorrosion and to pH changes. Surface-protected ZnO nanocrystals can be regarded as a valuable alternative to standard TiO(2) photocatalysts. (c) 2005 Elsevier B.V. All rights reserved
Recombination Dynamics of Colloidal Nanocrystals in Functionalized-Poly- Methylmethacrylate Nanocomposites
No full textTwo colloidal methods, namely one pot and two steps approaches, have been exploited to synthesize light emitting CdSe/ZnS core-shell nanocrystals, differing in growth process of the inorganic ZnS shell and, therefore in the resulting surface chemistry of the two types of nanocrystals. The synthesized nanocrystals have been incorporated, by using an "ex situ" procedure, in different thermoplastic PMMA-based polymers, including PMMA co-polymer specifically functionalized by means of groups having high chemical affinity to nanocrystal surface, and the resulting nanocomposites have been processed in thin films. Spectroscopic steady state and time-resolved investigations, carried out both on nanocomposite solution and thin film samples, indicate as a change in the optical properties of the two steps nanocrystals is observed upon incorporation in polymers, especially in PMMA homopolymer, where significant aggregation of inorganic nanostructures occurs. On the contrary, the one pot CdSe/ZnS nanocrystals preserve in all investigated samples their long-lived radiative emission. Such nanocrystals result homogeneously dispersed in the polymers, providing high quality films and thus representing ideal candidates for future optical applications
Silver ions mediated photochemical synthesis of water soluble gold nanoparticles with control over size and morphology
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UV-light-driven immobilization of surface-functionalized oxide nanocrystals onto silicon
No full textTiO2 nanorods (NRs) and gamma-Fe2O3 nanocrystals (NCs) passivated with unsaturated long-chain carboxylic acids, namely 10-undecylenic acid (10UDA) and oleic acid (OLEA), are covalently anchored to Si(100) at room temperature by UV-light-driven reaction of hydrogenated silicon with the carbon-carbon double bond (-C=C-) moieties of the capping surfactants. The high reactivity of vinyl groups towards Si provides a general tool for attaching particles of both materials via Si-C bonds. Interestingly, TiO2 NRs were efficiently attached to silicon even when capped by OLEA. This latter finding has been explained by a photocatalytic mechanism involving the primary role of hydroxyl radicals that can be generated upon bandgap, TiO2 photoexcitation with UV light. The increased oxide coverage achievable on Si opens access to further surface manipulation, as demonstrated by the possibility of depositing an additional film of An nanoparticles onto TiO2 via TiO2-catalyzed visible-light-driven reduction of aqueous AuCl4- ions. Extensive morphological and chemical characterization of the obtained NC-functionalized Si substrates is provided to support the effectiveness of proposed photochemical approaches
Colloidal TiO2 nanocrystals/MEH-PPV nanocomposites: Photo(electro)chemical study
No full textAn extensive optical and photoelectrochemical study of blended systems composed of organic-capped TiO2 nanocrystals with either a spherical or rodlike morphology and a conjugated polymer, MEH-PPV, is presented. The absorption and emission properties of the heterojunctions have been characterized both in solution and in thin films. The blended structures deposited onto conductive substrates have been employed as active layers in photoelectrochemical systems. The investigation has been focused on the photoinduced charge transfer and recombination processes at the interface between the two components, as a function of the nanocrystal shape and surface coating, and of the film thickness. The presence of a large number of interfaces available for charge transfer is believed to play a fundamental role in enhancing the photoelectrochemical performances of the dispersed heterojunctions. The reported results suggest that such MEH-PPV/TiO2 heterojunctions may be exploited as potential active layers in future photovoltaic and photoelectrochemical devices
Nanocrystalline semiconductor/metal phthalocyanine hybrid-junctions: applications in photoelectrochemical and sensor devices
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