Characterization of TiO2 nanoparticles in langmuir-blodgett films

In this work we have synthesized TiO2 nanoparticles, using either a sol–gel base catalysed process in the interior of CTAB reversed micelles (TiO2 CTAB sol), or the neutralization of a TiO2/H2SO4 solution in the interior of AOT reversed micelles. From the absorption and emission data of the TiO2 nanoparticles it is possible to conclude that in the sol–gel route there remains alkoxide groups in the structure, originating transitions lower than the energy gap of TiO2 semiconductor. These transitions disappear in the neutralization procedure, where the alkoxide groups are absent in the structure. We have assigned the observed indirect and direct optical transitions according to the anatase band structure. TiO2 Langmuir-Blodgett (LB) films were prepared either by direct deposition of titanium isopropoxide or by deposition of the TiO2 CTAB sol. These films showed photoluminescence, which was attributed to band-gap emission and to surface recombination of defect states

Efficient charge storage in photoexcited TiO2 nanorod-noble metal nanoparticle composite systems RID C-5360-2009

Following 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

Hydrophobically 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

Tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine thin films: deposition, characterization and application

Thin films of pure tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine (TIPCuPc), a novel functionalized phthalocyanine, and its hybrid junctions with colloidal rod-like TiO2 nanocrystals (NCs) were deposited in order to elucidate their properties and application in piezoelectric chemical sensors. The strong tendency of the phthalocyanine to assembly was confirmed at the air/water interface by advanced Brewster Angle Microscopy (BAM) and UV-vis reflection spectroscopy techniques. In particular, H-type aggregates, in situ and at the air/water interface, self-associate in aligned 3D bulky domains. The characteristics of the molecule and of the assemblies were studied in the solid state by means of UV-vis spectroscopy, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and Atomic Force Microscopy (AFM). These studies prompted investigation of the operating conditions to process the bare TIPCuPc and related TiO2 NC-based hybrid junctions as sensing active layers for phenol pollutants integrated in a Quartz Crystal Microbalance (QCM). Interestingly, the preferentially oriented phthalocyanine LB-film undergoes chemical interactions with the NC film, which enhances the sensitivity of the QCM sensor

Low-dimensional chainlike assemblies of TiO2 nanorod-stabilized Au nanoparticles RID C-5360-2009

A 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

ZnO 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

Photocatalytic degradation of methyl red by TiO(2): Comparison of the efficiency of immobilized nanoparticles versus conventional suspended catalyst RID C-5449-2009 RID C-5360-2009

The photocatalytic efficiency of supported TiO(2) nanoparticles (mean size 6 nm), immobilized onto the inner walls of a cylindrical glass photoreactor was compared versus the performance of conventional TiO(2) Degussa P25 catalyst. For this purpose the degradation of methyl red dye was used as evaluation test. The obtained results showed that the TiO(2) Degussa P25 catalyst is more efficient than the supported nanoparticles. The poorer performance of the nanosized catalyst can be ascribed to the fact that the immobilization procedure turns out, in spite of the extremely high surface to volume ratio, in an overall reduction of active surface area available for target molecule adsorption, due to the low porosity of the supported catalyst layer. The kinetics of the investigated processes were monitored and a study on the reaction products and intermediates was carried out in order to evaluate possible difference in the reaction pathway in presence of immobilized nanoparticles versus suspended catalyst. The results demonstrate that the mechanisms of parent dye degradation in presence of supported TiO(2) nanoparticles, are the same as those occurring in presence of TiO(2) Degussa P25 catalyst. The present work describe the results obtained on the feasibility of scaling up the colloidal nanocrystal-based photocatalysis experiment: the comparison with a well standardized degradation method performed with a known material can allow a realistic evaluation of the advantages and the limits of the investigated nanoparticle towards the ultimate technology transfer. (c) 2006 Elsevier B.V. All rights reserved

UV-light-driven immobilization of surface-functionalized oxide nanocrystals onto silicon

TiO2 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