Effect of TiO2 on electrical and magnetic properties of Ni0.35Cu0.12Zn0.35Fe2O4 synthesized by the microwave-hydrothermal method

The nanocomposites of xTiO(2)+(1-x)Ni0.53Cu0.12Zn0.35Fe2O4 (where 0 <= x >= 1) were prepared using microwave hydrothermal (M H) method at 165 degrees C/45 min. The as-synthesized powders were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The particle size of the powder varies from 18 to 35 nm. The as prepared powders were densified at 500 degrees C/30 min using microwave sintering method. The sintered composites were characterized by XRD and scanning electron microscopy (SEM). The bulk densities of the present composites were increasing with the addition of TiO2. The grain sizes of all the composite vary between 65 nm and 90 nm. The addition of TiO2 to ferrite increased the dielectric properties (epsilon' and epsilon `') also the resonant frequency of all the composites was found to be greater than 1 GHz. The imaginary part of permeability mu `' was found to increase with an increase of TiO2.

SnO2 nanowire anchored graphene nanosheet matrix for the superior performance of Li-ion thin film battery anode

All solid state batteries are essential candidate for miniaturizing the portable electronics devices. Thin film batteries are constructed by layer by layer deposition of electrode materials by physical vapour deposition method. We propose a promising novel method and unique architecture, in which highly porous graphene sheet embedded with SnO2 nanowire could be employed as the anode electrode in lithium ion thin film battery. The vertically standing graphene flakes were synthesized by microwave plasma CVD and SnO2 nanowires based on a vapour-liquid-solid (VLS) mechanism via thermal evaporation at low synthesis temperature (620 degrees C). The graphene sheet/SnO2 nanowire composite electrode demonstrated stable cycling behaviours and delivered a initial high specific discharge capacity of 1335 mAh g(-1) and 900 mAh g(-1) after the 50th cycle. Furthermore, the SnO2 nanowire electrode displayed superior rate capabilities with various current densities.

Visible light assisted photocatalytic degradation of organic dyes on TiO2-CNT nanocomposites

Carbon nanotubes (CNTs) uniformly decorated with nano-anatase TiO2 particles corresponding to different TiO2-CNT weight ratios (up to 90 % TiO2:10 % CNT) were prepared by employing sol-gel process. The nanocomposites were characterized by X-ray diffraction, IR, Raman, Scanning electron microscopy, Transmission electron microscopy, Photoluminescence, BET surface area and diffuse reflectance measurements. The composites show visible light assisted photocatalytic property, for example, the 90 % TiO2-10 % CNT composite completely degrades Indigo Carmine dye within 1 h of exposure to visible light. Similarly, Orange G and Congo Red dyes were decomposed within 2 h under visible light irradiation. The excellent visible light photocatalytic property of the composite is attributed to the synergetic effect of photoexcitation and photosensitization. This is due to the special nanoarchitecture wherein TiO2 nanoparticles are anchored to CNT surface that provides high specific interfacial area for photon absorption and electron trapping. Visible light assisted degradation profile of Indigo Carmine in the presence of TiO2-CNT nanocomposite and TEM image of the TiO2-CNT nanocomposite.

薄膜材料对TiO2基薄膜激光损伤阈值的影响

abstract {The optical property, structure, surface properties (roughness and defect density) and laser-induced damage threshold (LIDT) of TiO₂ films deposited by electronic beam (EB) evaporation of TiO₂ (rutile), TiO₂ (anatase) and TiO₂ + Ta₂O₅ composite materials are comparatively studied. All films show the polycrystalline anatase TiO₂ structure. The loose sintering state and phase transformation during evaporating TiO₂ anatase slice lead to the high surface defect density, roughness and extinction coefficient, and low LIDT of films. The TiO₂ + Ta₂O₅ composite films have the lowest extinction coefficient and the highest LIDT among all samples investigated. Guidance of selecting materials for high LIDT laser mirrors is given.}

Surface characteristics of SiO2-TiO2 strip fabricated by laser direct writing

SiO2-TiO2 sol-gel films are deposited on SiO2/Si by dip-coating technique. The SiO2-TiO2 strips are fabricated by laser direct writing using all ytterbium fiber laser and followed by chemical etching. Surface structures, morphologies and roughness of the films and strips are characterized. The experimental results demonstrate that the SiO2-TiO2 sol-gel film is loose in Structure and a shrinkage concave groove forms if the film is irradiated by laser beam. The surface roughness of both non-irradiated and laser irradiated areas increases with the chemical etching time. But the roughness of laser irradiated area increases more than that of non-irradiated area under the same etching time. After being etched for 28 s, the surface roughness value of the laser irradiated area increases from 0.3 nm to 3.1 nm.

The fabrication of TiO2-supported zeolite with core/shell heterostructure for ethanol dehydration to ethylene

The TiO2-supported zeolite with core/shell heterostructure was fabricated by coating aluminosilicate zeolite (ASZ) on the TiO2 inoculating seed via in situ hydrothermal synthesis. The catalysts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), nitrogen physisorption (BET), and Fourier transform infrared spectroscopy (FT-IR). The surface acidity of the catalysts was measured by pyridine-TPD method. The catalytic performance of the catalysts for ethanol dehydration to ethylene was also investigated. The results show that the TiO2-supported zeolite composite catalyst with core/shell heterostructure exhibits prominent conversion efficiency for ethanol dehydration to ethylene.

Preparation of TiO2, CeO2, and ZrO2 hierarchical structures in "one-pot" reactions

In this paper, a novel template of carbon foam is used in building hierarchical structures of TiO2, CeO2, and ZrO2. They had multiscale morphologies, from nanowalls, nanoparticles to layer nanostructures. Oil a hundred-micron scale, the product was a sponge-like material constructed by nanowalls. On a hundred-nanometer scale, the electron microscope images showed that the nanowalls were porous and assembled by polycrystalline nanoparticles. Meanwhile, on one nanometer scale, many nanoparticles exhibited layer nanostructures with about 1.1 run of thickness and spacing. In mechanism section, the process analysis and characterizations suggested that the hierarchical structures were the combined result of two templates in a "one-pot" reaction. The mesoporous nanowalls were derived from carbon foams, while the layer nanostructures were the replicas of graphite sheets. The method has potential utilizations in preparation of various adsorbent and catalyst.

Sol-gel-derived titanium oxide/copolymer composite based glucose biosensor

A new type of sol-gel-derived titanium oxide/copolymer composite material was developed and used for the construction of glucose biosensor. The composite material merged the best properties of the inorganic species, titanium oxide and the organic copolymer, poly(vinyl alcohol) grafting 4-vinylpyridine (PVA-g-PVP). The glucose oxidase entrapped in the composite matrix retained its bioactivity. Morphologies of the composite-modified electrode and the enzyme electrode were characterized with a scanning electron microscope. The dependence of the current responses on enzyme-loading and pH was studied. The response time of the biosensor was < 20 s and the linear range was up to 9 mM with a sensitivity of 405 nA/mM. The biosensor was stable for at least I month. In addition, the tetrathiafulvalene-mediated enzyme electrode was constructed for the decrease of detection potential and the effect of three common physiological sources that might interfere was also investigated.

Amperometric tyrosinase biosensor based on a sol-gel-derived titanium oxide-copolymer composite matrix for detection of phenolic compounds

A new type of tyrosinase biosensor was developed for the detection of phenolic compounds, based on the immobilization of tyrosinase in a sol-gel-derived composite matrix that is composed of titanium oxide sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. Tyrosinase entrapped in the composite matrix can retain its activity to a large extent owing to the good biocompatibility of the matrix. The parameters of the fabrication process and the variables of the experimental conditions for the enzyme electrode were optimized. The resulting sensor exhibited a fast response (20 s), high sensitivity (145.5 muA mmol(-1) 1) and good storage stability. A detection limit of 0.5 muM catechol was obtained at a signal-to-noise ratio of 3.

Reactivity of sub 1 nm supported clusters: (TiO2)(n) clusters supported on rutile TiO2 (110)

Metal oxide clusters of sub-nm dimensions dispersed on a metal oxide support are an important class of catalytic materials for a number of key chemical reactions, showing enhanced reactivity over the corresponding bulk oxide. In this paper we present the results of a density functional theory study of small sub-nm TiO2 clusters, Ti2O4, Ti3O6 and Ti4O8 supported on the rutile (110) surface. We find that all three clusters adsorb strongly with adsorption energies ranging from -3 eV to -4.5 eV. The more stable adsorption structures show a larger number of new Ti-O bonds formed between the cluster and the surface. These new bonds increase the coordination of cluster Ti and O as well as surface oxygen, so that each has more neighbours. The electronic structure shows that the top of the valence band is made up of cluster derived states, while the conduction band is made up of Ti 3d states from the surface, resulting in a reduction of the effective band gap and spatial separation of electrons and holes after photon absorption, which shows their potential utility in photocatalysis. To examine reactivity, we study the formation of oxygen vacancies in the cluster-support system. The most stable oxygen vacancy sites on the cluster show formation energies that are significantly lower than in bulk TiO2, demonstrating the usefulness of this composite system for redox catalysis.

An investigation into the effect of thickness of titanium dioxide and gold-silver nanoparticle titanium dioxide composite thin-films on photocatalytic activity and photo-induced oxygen production in a sacrificial system

Thin films of titanium dioxide and titanium dioxide with incorporated gold and silver nanoparticles were deposited onto glass microscope slides, steel and titanium foil coupons by two sol-gel dip-coating methods. The film's photocatalytic activity and ability to evolve oxygen in a sacrificial solution were assessed. It was found that photocatalytic activity increased with film thickness (from 50 to 500 nm thick samples) for the photocatalytic degradation of methylene blue in solution and resazurin redox dye in an intelligent ink dye deposited on the surface. Contrastingly, an optimum film thickness of similar to 200 nm for both composite and pure films of titanium dioxide was found for water oxidation, using persulfate (S2O82-) as a sacrificial electron acceptor. The nanoparticle composite films showed significantly higher activity in oxygen evolution studies compared with plain TiO2 films.

Nanocrystalline SnO2-based, UVB-activated, colourimetric oxygen indicator

Nanocrystalline SnO2, ncSnO(2), is used as a photosensitiser in a colourimetric O-2 indicator that comprises a sacrificial electron donor, glycerol, a redox dye, methylene blue (MB), and an encapsulating polymer, hydroxyethyl cellulose (HEC). Upon exposure to a burst of UVB light the indicator is activated (photo-bleached) as the MB is photoreduced by the ncSnO(2) particles. In the absence of oxygen, the film stays bleached, but recovers its original colour upon exposure to oxygen. Unlike its TiO2-based predecessor, the HEC/glycerol/MB/ncSnO(2) O-2 indicator is not activated by UVA light from white fluorescent lamps, but is by UVB light. This feature provides much greater control in the activation of the indicator. Other work shows the rate of activation depends upon I-0.75, where I is the UVB irradiance, indicating a partial dependence upon the electron-hole recombination process. The half-life of the recovery of the original colour of a UV-activated film, t(50), is directly proportional to the ambient level of oxygen. The advantages of using this indicator in modified atmosphere packaging as a possible quality assurance indicator are discussed briefly. (c) 2008 Elsevier B.V. All rights reserved.

Density functional theory study of mixed-phase TiO2: heterostructures and electronic properties

In this work, density functional theory calculations have been performed to study the geometric, electronic, and energetic properties of two-phase TiO2 composites built by joining two single-phase TiO2 slabs, aiming at verifying possible improvement of the photo-activities of the composites through phase separation of excitons. We find that such desired electronic properties can be determined by several factors. When both the HOMO and LUMO levels of one of the two single-phase TiO2 slabs are higher than the corresponding ones of the other, the composite may have native electronic structures with phase-separated HOMO-LUMO states, especially when the two slabs exhibit highly matched surface lattices. For those pairs of TiO2 slabs with the HOMO and LUMO levels of one phase being within the range of those of the other, though the energetically favored composite give HOMO-LUMO states within one phase, one may still be able to separate them and move the HOMO state to the interface region by destabilizing the interactions between the two slabs.