Metal oxide photoanodes for water splitting.

Solar hydrogen production through photocatalytically assisted water splitting has attracted a great deal of attention since its first discovery almost 30 years ago. The publication of investigations into the use of TiO2 photoanodes has continued apace since and a critical review of current trends is reported herein. Recent advances in the understanding of the behaviour of nanoparticulate TiO2 films is summarized along with a balanced report into the utility and nature of titania films doped with non-metallic elements and ordered, nanostructured films such as those consisting of nanotubes. Both of these are areas that have generated a not insignificant degree of activity. One goal of doping TiO2 has been to extend the photoresponse of the material to visible light. A similar goal has seen a resurgence in interest in Fe2O3 photoanodes. Herein, the influence of dopants on the photocurrent density observed at Fe2O3 photoanodes and, in this regard, the role of silicon has attracted much attention, and a little debate. Finally, we look beyond the binary oxides. Photoanodes made from new materials such as mixed metal oxides, perovskite structured semiconductors, metal (oxy)nitrides or composite electrodes offer the potential to either tailor the optical band gap or tune the conduction or valence band energetics. Recent work in this area is detailed here.

Crystallographically oriented mesoporous WO3 films: synthesis, characterization, and applications.

Mesoporous semiconducting films consisting of preferentially orientated monoclinic-phase nanocrystals of tungsten trioxide have been prepared using a novel version of the sol-gel method. Transformations undergone by a colloidal solution of tungstic acid, stabilized by an organic additive such as poly(ethylene glycol) (PEG) 300, as a function of the annealing temperature have been followed by means of a confocal Raman microscope. The shape and size of WO3 nanoparticles, the porosity, and the properties of the films depend critically on preparation parameters, such as the tungstic acid/PEG ratio, the PEG chain length, and the annealing conditions. Well-crystallized WO3 films combine excellent photoresponse to the blue region of the solar spectrum, up to 500 nm, with good transparency at wavelengths larger than 550 nm. Particular applications of these nanocrystalline WO3 films include photoelectrochemical and electrochromic devices.

[Use of principles of iontophoresis and electrophoresis for controlled release of medical substances]. / Utilisation du principe de l'iontophorèse ou de l'électrophorèse pour le contrôle de la libération de substances médicamenteuses.

The present review describes work done over the past twenty years on the controlled release of drugs using iontophoresis or electrophoresis techniques. Following a description of therapeutic applications, in vivo and in vitro studies have been discussed with emphasis on the potentials of such techniques to control drug release. Different mathematical models have been reviewed and an attempt has been made to combine them to explain the various configurations of systems currently used.