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.

/pdf/visible-light-photocatalysis-in-nitrogen-doped-titanium-np6nklr9gh.pdf

Visible-Light Photocatalysis in Nitrogen-Doped Titanium Oxides

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

The surface science of titanium dioxide

The substitution of surface hydrogen on boron (B)-doped diamond electrodes during electrochemical hydrogen evolution was confirmed using TOF–ESD method. The results show that surface-H(D) was substituted by D(H) as a result of the reduction of D+(H+) in solution during the electrochemical hydrogen evolution at the B-doped diamond.

Direct Proof for Electrochemical Substitution of Surface Hydrogen of Boron-doped Diamond Electrode by TOF–ESD Method

Observation of the Trans-Cis Photoisomerization of Azobenzene Derivative in Langmuir-Blodgett Film by the Optical Second Harmonic Generation

The sections in this article are


Introduction
Photocatalytic Sterilization and Disinfection
Photocatalytic Antibacterial Tiles
Sterilizing Effect of TiO2
Destruction of Microbial Toxins
Photocatalytic Cancer Therapy


Photocatalytic Air Purification
Deodorization of Indoor Air
Treatment of Industrial Gaseous Effluents
Outdoor Air Purification (NOx Removal)


Photocatalytic Water Purification
Wastewater Purification
Drinking Water Purification
Remediation of Metal Contamination


Self-cleaning and Antifogging Surfaces
Self-cleaning Surfaces
Antifogging, Antibeading Surfaces


Conclusion
Acknowledgment

Applications of TiO2 Photocatalysis

Rotating ring-disk electrode (RRDE) technique, using a ZnO single crystal as the disk electrode, was applied to the study of spectral sensitization by rhodamine B (RhB) and supersensitization by hydroquinone (HQ) in acetonitrile. The primary product of spectral sensitization, i. e., RhB radical cation (RhB+·), was detected electrochemically at the Pt ring electrode. Upon addition of HQ to the electrolyte solution, the sensitized photocurrent was enhanced (supersensitization), and concomitantly the collection efficiency for RhB+· at the Pt ring electrode showed a decrease. Assuming that the supersensitization results from the reduction of RhB+· by HQ, the rate constant for this process was calculated to give 106 − 107 M−1 s−1. Taking into account the singlet lifetime of RhB* as well as the rate constant for the quenching of RhB* by HQ, the mechanism of spectral sensitization and supersensitization is discussed.



Unter Anwendung der rotierenden Ring-Scheiben-Elektroden (RRDE)-Technik, mit einem ZnO-Einkristall als Scheibenelektrode, wurden Untersuchungen der spektralen Sensibilisierung mit Rhodamin B (RhB) und ubersensibilisierung mit Hydrochinon (HQ) in Acetonitril durchgefuhrt. Das Primarprodukt der spektralen Sensibilisierung, das RhB-Kation-Radikal (RhB+·) wurde elektrochemisch an der Pt-Ring-Elektrode nachgewiesen. Nach Zusatz von HQ zur Elektrolytlosung wurde der sensibilisierte Photostrom erhoht (ubersensibilisierung), und zugleich verminderte sich die nachgewiesene Menge des RhB+· an der Pt-Ring-Elektrode. Unter der Annahme, das die ubersensibilisierung durch die Reduktion des RhB+· durch HQ verursacht wird, wurde die Geschwindigkeitskonstante fur diesen Prozes mit 106 − 107 M−1 s−1 berechnet. Unter Berucksichtigung sowohl der Singlet-Lebensdauer des RhB* wie auch der Geschwindigkeitskonstanten fur das Quenchen des RhB* durch HQ wird der Mechanismus der spektralen Sensibilisierung und Ubersensibilisierung diskutiert.

Study of Spectral Sensitization and Supersensitization by Means of the Rotating Ring‐Disk Electrode Technique

A method that uses a photochemical reaction to localize an electrochemical reaction has been described. The fatty acid derivatives of azobenzene organized in an ordered monolayer film were taken as the example. Owing to the significant difference in electrochemical reductivities of their geometric isomers, it was possible, by localizing the electrode reaction in a focussed laser beam, to create an electrochemical memory device. An electrostatic cis–trans isomerism phenomenon that was observed in the highly assembled monolayer film of the above azo compounds at the electrode/liquid interface, has been discussed. This novel reaction was attributed to the strong interaction between the highly oriented molecular dipoles and the electric field formed at the interface.

Akira Fujishima

Papers

Direct Proof for Electrochemical Substitution of Surface Hydrogen of Boron-doped Diamond Electrode by TOF–ESD Method

Observation of the Trans-Cis Photoisomerization of Azobenzene Derivative in Langmuir-Blodgett Film by the Optical Second Harmonic Generation

Applications of TiO2 Photocatalysis

Study of Spectral Sensitization and Supersensitization by Means of the Rotating Ring‐Disk Electrode Technique

Unique reactions of photoexcited organic molecules at the electrode/liquid interface