ALTHOUGH the possibility of water photolysis has been investigated by many workers, a useful method has only now been developed. Because water is transparent to visible light it cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm (ref. 1).

Electrochemical Photolysis of Water at a Semiconductor Electrode

Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.

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Visible-Light Photocatalysis in Nitrogen-Doped Titanium Oxides

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

The surface science of titanium dioxide

We have developed the transparent photoactive TiO2 thin film coated on soda lime glass (SLG) by sol-gel process. Titanium dioxide thin films coated on SLG exhibit lower photocatalytic activity due to the thermal diffusion of Na ion from the SLG substrate. Thin SiO2 film precoating is very effective to prevent the thermal diffusion of Na ion. We have evaluated the photocatalytic decomposition of gaseous acetaldehyde and the photo-induced surface wettability of TiO2 films with and without SiO2 precoating layer. As expected, the TiO2 film on SiO2/SLG is more photoactive to decompose acetaldehyde than that on SLG. However, as for wettability conversion, there was little difference in the conversion rate between TiO2 film without SiO2, and TiO2 film with SiO2. Different dependence of Na ion diffusion on two kinds of photo-induced reaction on TiO2 is discussed based on the difference of the photo-induced reaction mechanism.

Photocatalytic Activity and Photo-Induced Wettability Conversion of TiO2 Thin Film Prepared by Sol-Gel Process on a Soda-Lime Glass

n型半導体であるTiO2(ルチル)を電極に用いて分極挙動を測定した。光照射しない時にはカソード分極下で水素発生が起こるが,アノード分極下ではほとんど電解電流が流れず顕著な電解整流作用を示した。TiO2電極表面に光照射すると,カソード電流は変化しないがアノード電流は著しく増加する。この電流はTiO2のバンドギァプ3.0eVに相当する415mμ以下の波長の光によってのみ生じ,また電流の大きさは光強度に比例する。立ち上り電位はpH4.7では-0.5V(vs.SCE)である。この電解酸化反応は従来n型半導体で報告されている電極自身の溶解反応ではなくて,水の電解による酸素の発生であることを確かめた。このことはいわゆる平衡電位より約1V以上も卑な電位で酸素発生がおこる“光増感電解酸化”であり,光のエネルギーを半導体が吸収したためである。またI-のI2への酸化も平衡電位より卑で起こることを確かめた。機構については半導体のバンドモデルから考察した。

Photosensitized Electrolytic Oxidation on Semiconducting n-Type TiO2 Electrode

Bactericidal effect of an energy storage TiO2–WO3 photocatalyst in dark

Transparent and Colored Magnetic Thin Films: (FeIIxCrII1-x)1.5[CrIII(CN)6]

Mesoporous photocatalytic titanium dioxide films with periodic structures were prepared by molding from two-dimensionally ordered arrays of monodisperse SiO2 particles. The morphology of the porous structures in these films was dependent upon the annealing temperature. The photocatalytic activity of the films was confirmed, as evidenced by the photodeposition of silver on the textured film surfaces. Attachment of the free-standing films to rigid supports allowed us to locate specific microscopic areas at will and to monitor the progress of the silver photodeposition in these areas using optical microscopy and scanning electron microscopy, with both secondary electron and backscattered electron detection. However, the repeated electron beam exposure in these selected areas was found to adversely affect the photoreducibility. Although the detailed film morphology did not affect the macroscopic photocatalytic activity, we found subtle differences in the silver nucleation process which depended upon the pore ...

Akira Fujishima

Papers

Photocatalytic Activity and Photo-Induced Wettability Conversion of TiO2 Thin Film Prepared by Sol-Gel Process on a Soda-Lime Glass

Photosensitized Electrolytic Oxidation on Semiconducting n-Type TiO2 Electrode

Bactericidal effect of an energy storage TiO2–WO3 photocatalyst in dark

Transparent and Colored Magnetic Thin Films: (FeIIxCrII1-x)1.5[CrIII(CN)6]

New Mesostructured Porous TiO2 Surface Prepared Using a Two-Dimensional Array-Based Template of Silica Particles