Thin films of indium nitride, InN, were produced by reactive magnetron DC sputtering. By post treatment in dinitrogen, N-2, in the temperature range 350-500 degrees C a set of films gradually going from InN to indium oxide, In2O3 was obtained (due to dioxygen impurities in the annealing gas). Those films were characterized by X-ray diffraction, optical-, resistivity- and photoelectrochemical measurements for the aim of direct watersplitting in a photoelectrochemical cell.Surprisingly, the caused change in the film composition by annealing gave no significant change in the room temperature resistivity, but the free electron density and the optical properties were affected. In 0.1 M NaOH annealing improved the photoresponse of the thin films. A pronounced optimum was observed for films annealed at 425 degrees C. Even for those films the quantum efficiency was low; at most 2% of the photons at 350 nm were transformed into readable photoelectrons. The onset wavelength for photocurrent was located around 600 run (2.1 eV), which is far off from the onset of absorption 900 nni (1.4 eV). (c) 2005 Elsevier B.V. All rights reserved.

Langmuir and Langmuir-Blodgett (LB) films of a variety of polyoxometalates of different shapes, sizes, and charges were prepared by taking advantage of the adsorption properties of these polyanions on a positively charged monolayer of an organic surfactant spread on water. Three different aspects were investigated. 1) The electrochemical and electrochromic properties of LB films containing the easily reducible polyoxoanion [P2Mo18O62]6-. Absorbance changes of these LB films deposited onto an ITO substrate have been induced by repeated switching of the applied potential. These changes are due to the formation of the colored reduced forms of the polyanion. Coloration and bleaching of the LB film occur very quickly and are reversible. 2) The preparation of LB films based on magnetic polyoxometalates, such as the Keggin anions, [CoW12O40]6- and [SiMn(OH2)W11O39]6-, or containing magnetic clusters of increasing nuclearities such as [Co4(H2O)2(PW9O34)2]10- and [Co4(H2O)2(P2W15O62)2]16- based on a Co4O16 ferromagnetic cluster, and the polyoxometalates [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16- and [Ni9(OH)3-(H2O)6(HPO4)2(PW9O34)3]16- based on a nonanuclear M9O36 cluster. 3) The preparation of LB films of the giant heteropolyoxomolybdate, [Na3(NH4)12][Mo57Fe6(NO)6O174(OH)3-(H2O)24]76 H2O.

AbstractThe dinuclear copper(II) complexes {[Cu2(1,3‐tpbd)(H2O)(OAc)2](ClO4)2}0.23{[Cu2(1,3‐tpbd)(H2O)2(OAc)](ClO4)3}0.77·0.77H2O (1), [Cu2(1,3‐tpbd)(H2O)2(OAc)2](ClO4)2·2H2O (2), and the tetranuclear copper(II) complex [Cu4(1,3‐tpbd)2(H2O)2(SO4)4]·8H2O (3) {1,3‐tpbd = 1,3‐bis[bis(2‐pyridylmethyl)amino]benzene} were synthesised and structurally characterised by X‐ray diffraction. Variable‐temperature (2.0−290 K) magnetic susceptibility measurements on these complexes as well as on the dinuclear copper(II) complex [Cu2(1,3‐tpbd)(H2O)2(ClO4)3]ClO4 (4) (whose structure was published earlier) were performed. In contrast to 2 and 3, significant ferromagnetic coupling with J = +9.3 cm−1 was observed for 4 (the Hamiltonian being defined as Hˆ = −J Sˆ1·Sˆ2). Density functional theory (DFT) calculations were used successfully for the interpretation of the ferromagnetic coupling observed in 4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

This paper describes the photoelectrochemical response in aqueous electrolyte of nitrogen-doped titanium dioxide, TiO2-xNx. Thin film electrodes were prepared by reactive DC magnetron sputtering in an environment of Ar, O-2, and N-2. A typical film thickness was 0.85 mum. The crystal structure of the photoelectrochemically active films was mainly of rutile character, and scanning and transmission electron microscopy showed a highly porous parallel penniform nanostructure. It was conclusively shown that dioxygen could be generated from water by illumination of the TiO2-xNx electrodes at moderate anodic potentials. The current density under 1000 W m(-2) visible light from a sulfur lamp was 0.2 mA cm(-2) at 0.55 V vs Ag/AgCl. Current-voltage characteristics under illumination were strongly dependent on the scan direction. Scanning the electrode from cathodic toward anodic potentials gave an onset potential similar to that of normal rutile TiO2, whereas a reversed scan gave an onset of photocurrent (depending on the light source) anodically upshifted by up to 0.8 V from its normal position. Moreover, a cathodic current was observed during the latter scans. This current was induced by the illumination at anodic potentials. This nonfaradic current was ascribed to photoinduced electron trap states distributed in an approximately 1.3 V wide range negative of the conduction band (CB) edge. These states also were active as electron-hole recombination centers. The density of this new set of states was similar to2 x 10(20) cm(-3), i.e., similar to the density of nitrogen atoms. They can be activated by light, even at wavelengths beyond 700 nm, and work as long-lived electron traps; hence, they have properties that are different from those of the earlier found Till (3d) states, also located below the CB of TiO2. The new states occur as a consequence of the nitrogen doping, but is not necessarily an intrinsic property of pure TiO2-xNx. Recombination via the new states-in conjunction with slow hole transport in the nitrogen-created band above the valence band edge-was suggested to be the cause of the large anodic shift of the onset potential for cathodic scans and of the moderate water oxidation efficiency of the TiO2-xNx thin film electrodes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

This paper describes the photoelectrochemical response in aqueous electrolyte for nitrogen-doped titanium dioxide, TiO2−xNx. The electrodes were prepared by reactive DC magnetron sputtering in an environment of argon, oxygen and nitrogen. The crystal structure of the photoelectrochemically active films was mainly of rutile character and scanning and transmission electron microscopy revealed a highly porous parallel penniform microstructure. The nitrogen-doped TiO2 generated a monochromatic incident photon-to-current efficiency response in good agreement with the optical spectrum. The onset wavelength for photoresponse was located around 550nm. The visible light response for TiO2−xNx compared to TiO2 prepared without nitrogen was considerably improved at moderate bias. However, severe recombinations were observed in the nitrogen-doped material indicating that the doping sites could serve as recombination centres.

A positively charged monolayer spread at the gas-water interface was used to induce the crystallization of Prussian Blue derivatives. The interfacial crystal nucleation and growth lead to nanocubes oriented parallel to the interface. Such processes appear at much lower concentrations of the precursor ions than in bulk. These experiments open new opportunities for selecting the crystalline phases of various molecular materials.

The elaboration of new Langmuir-Blodgett (LB) films containing Prussian blue and a surfactant derivative of the ruthenium tris(bipyridine) complex using a semi-amphiphilic approach is described in this paper. The redox and photoelectrochemical properties of these hybrid lamellar materials have been studied in aqueous KCl solutions. Dependencies of the cyclic voltammetry response on the number of deposited layers and the scan rate demonstrate that the hybrid LB films can be considered as a quasireversible system with a finite diffusion space. A large cathodic photocurrent is recorded when the LB films are irradiated with polychromatic light at a negative applied potential, indicating that both PB and the derivative of ruthenium tris(bipyridine) complex play an important role in the light-energy conversion process. A linear dependence of the cathodic photocurrent response on the number of deposited layers has also been exhibited and should be correlated to the presence of structural defects in the multilayers.