Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Scientific studies on photocatalysis started about two and a half decades ago. Titanium dioxide (TiO 2 ), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this review, current progress in the area of TiO 2 photocatalysis, mainly photocatalytic air purification, sterilization and cancer therapy are discussed together with some fundamental aspects. A novel photoinduced superhydrophilic phenomenon involving TiO 2 and its applications are presented.

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Titanium dioxide photocatalysis

Abstract Scientific studies on photocatalysis started about two and a half decades ago. Titanium dioxide (TiO 2 ), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this review, current progress in the area of TiO 2 photocatalysis, mainly photocatalytic air purification, sterilization and cancer therapy are discussed together with some fundamental aspects. A novel photoinduced superhydrophilic phenomenon involving TiO 2 and its applications are presented.

Titanium dioxide as photocatalysis

TiO2 photocatalysis and related surface phenomena

Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Understanding TiO2 photocatalysis: mechanisms and materials.

Plasmon-induced photoelectrochemistry in the visible region was studied at gold nanoparticle−nanoporous TiO2 composites (Au−TiO2) prepared by photocatalytic deposition of gold in a porous TiO2 film. Photoaction spectra for both the open-circuit potential and short-circuit current were in good agreement with the absorption spectrum of the gold nanoparticles in the TiO2 film. The gold nanoparticles are photoexcited due to plasmon resonance, and charge separation is accomplished by the transfer of photoexcited electrons from the gold particle to the TiO2 conduction band and the simultaneous transfer of compensative electrons from a donor in the solution to the gold particle. Besides its low-cost and facile preparation, a photovoltaic cell with the optimized electron mediator (Fe2+/3+) exhibits an optimum incident photon to current conversion efficiency (IPCE) of 26%. The Au−TiO2 can photocatalytically oxidize ethanol and methanol at the expense of oxygen reduction under visible light; it is potentially appli...

Mechanisms and Applications of Plasmon-Induced Charge Separation at TiO2 Films Loaded with Gold Nanoparticles

Photochromic materials, which change their colours reversibly in response to light, can be applied to smart windows, displays and memories1,2,3. Conventional photochromic materials respond in a monochromatic way, so that multicolour photochromism has required several different materials or filters combined appropriately. If multicolour photochromism could be achieved with a simple material, photochromic devices would be find a greater number of applications, including a rewritable colour copy paper or electronic paper4 and a high-density multi-wavelength optical memory. Here we report multicolour photochromism of TiO2 films loaded with silver nanoparticles by photocatalytic means. Its colour, initially brownish-grey, changes under monochromatic visible light to almost the same colour as that of the light; the apparently uniform Ag–TiO2 film can be almost any colour. Behaviour similar to persistent hole-burning effects5,6 is also observed. The colour reverts to brownish-grey under ultraviolet light, and these processes are repeatable.

Multicolour photochromism of TiO2 films loaded with silver nanoparticles.

THE development of low-cost, solid-state rechargeable batteries is of considerable technological importance. A key requirement of such batteries is that the density of energy stored electrochemically in the electrodes is high. In this context, the use of organic materials has attracted interest; they combine high theoretical energy storage capability with low weight and good mechanical strength. Here we report the development of a rechargeable lithium battery with a composite organic cathode based on a mixture of a dimercaptan and polyaniline. The redox behaviour of the dimercaptan, which is normally too slow for practical applications1,2, is accelerated when coupled to that of the polyaniline3–5 (which itself functions as an active cathode material). Intimate mixing of the two materials is achieved by casting them jointly from solution. The resulting electrode can be repeatedly charged to near its theoretical limit and discharged. The gravimetric energy density of our materials exceeds that of the oxide electrodes in commercially available lithium-ion batteries6, a feature that is likely to prove advantageous in applications where weight, rather than volume, is a critical factor.

Dimercaptan–polyaniline composite electrodes for lithium batteries with high energy density

Plasmon-induced photoelectrochemistry at metal nanoparticles supported on nanoporous TiO2

The photocatalytic degradation of bisphenol A (BPA), a representative endocrine disruptor, was carried out in TiO2 aqueous suspension. The main purposes were to confirm the total mineralization of BPA and to evaluate the estrogenic activity in the treated water during the photocatalytic reaction. An initial BPA concentration of 175 microM in water was totally degraded to carbon dioxide by TiO2-photocatalyzed reactions under UV irradiation of 10 mW cm-2 for 20 h. Four HPLC peaks indicating intermediate products appeared in chromatograms monitored at 275 nm, but the heights relative to that of the initial BPA were very low, at most 0.04 in the time period 5-10 h after the start of UV irradiation. All of the peaks finally disappeared after 20 h. For the treated water, the transcriptional estrogenic activity in response to human estrogen receptor in a yeast hybrid assay decreased drastically to less than 1% of the initial BPA's activity within 4 h. On the basis of these results, we conclude that TiO2 photocatalysis could be a useful technology for the purification of water containing BPA without generating any serious secondary pollution.

Tetsu Tatsuma

Papers

Mechanisms and Applications of Plasmon-Induced Charge Separation at TiO2 Films Loaded with Gold Nanoparticles

Multicolour photochromism of TiO2 films loaded with silver nanoparticles.

Dimercaptan–polyaniline composite electrodes for lithium batteries with high energy density

Plasmon-induced photoelectrochemistry at metal nanoparticles supported on nanoporous TiO2

Degradation of bisphenol A in water by TiO2 photocatalyst