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

Photoacoustic technique was employed to study the plating of Nickel. And on the other hand, Scanning Tunneling Microscopy (STM) cleared the difference of the surface in the presence and in the absence of the brightener. Also Scanning Electron Microscopy (SEM) was used for supporting the data of STM.

Investigation of Nickel Plating by Photoacoustic Spectroscopy (PAS) and Scanning Tunneling Microscopy (STM)

Zno thin film-based new electroless metal deposition

Electrochemical Reduction of CO_2 in Mircopores

The surfaces of the Ti-based bulk metallic glasses (Ti50Ni20Cu25Sn5) were modified by a hydrothermal method using sodium hydroxide (NaOH) solution, and the surface wettability was investigated. No reflections were observed in the XRD patterns of the NaOH-treated samples even though there was a clear change of the color, indicating formation of amorphous oxide phases. The Raman spectra showed peaks attributed to sodium titanate compounds (Na–O–Ti) and titanium oxide. Some of the samples were observed to have a very rough surface microstructure such as a “house-of-cards” or leaf-like structure. The water contact angle of the treated samples decreased with increasing treatment temperature and time. These results indicate that the wettability of the sample surface was able to be controlled from hydrophobic to hydrophilic by changing the conditions of the hydrothermal treatment.

Control of wetting on Ti-based bulk metallic glass surfaces by a hydrothermal method

Two novel photoresponsive systems utilizing photochemical and electrochemical techniques are presented. First, we have studied the photoelectrochemical behavior of several amphiphilic azobenzene derivatives (ABD) in assembled monolayer films and reported a unique route-specific hybrid phenomenon. The phenomenon is based on the following two observations: 1) cis-ABD in the monolayer film is reduced to hydrazobenzene (-NH-NH-) (HBD) at substantially more anodic potential than the trans isomer; 2) HBD is reoxidized only to trans-ABD and not to cis-ABD. These three states are linked together and thus can form a new memory system. For information storage, two means are possible. One is to limit the illumination area of the trans to cis isomerization with a focused laser beam; however, the storage density is limited by the optical diffraction limit of the laser spot (~108 bits/cm2). The other way is localized the electrochemical reduction area using a microelectrode controlled by scanning probe techniques. With this means, much higher density is expected (~1012 bits/cm2). In the second photoresponsive system, we have succeeded in obtaining visible light sensitive photochromism using MoO3. Pretreated MoO3 vacuum evaporated thin films, which were slightly blued by cathodic polarization in a nonaqueous electrolyte (electrochromism), showed strong color enhancement when irradiation in air by visible light. These films could be easily erased by anodic polarization in a nonaqueous electrolyte, with the coloration-decoloration process being reversible. This is in contrast to thin films which are blued in advanced by the band-gap irradiation in air, where a response to visible light irradiation does not occur. The MoO3 film is believed to change to an intermediate metastable state during the electrolytic pretreatment which is then converted by visible light into stable molybdenum bronze.

Akira Fujishima

Papers

Investigation of Nickel Plating by Photoacoustic Spectroscopy (PAS) and Scanning Tunneling Microscopy (STM)

Zno thin film-based new electroless metal deposition

Electrochemical Reduction of CO_2 in Mircopores

Control of wetting on Ti-based bulk metallic glass surfaces by a hydrothermal method

Novel Photoresponse Functions with Photochemical and Electrochemical Systems