Effect of Cu2O Substrate on Photoinduced Hydrophilicity of TiO2 and ZnO Nanocoatings.

The effect of a Cu2O substrate on the photoinduced alteration of the hydrophilicity of TiO2 and ZnO surfaces was studied. It was demonstrated that the formation of heterostructures Cu2O/TiO2 and Cu2O/ZnO strongly changed the direction of the photoinduced alteration of surface hydrophilicity: while both TiO2 and ZnO demonstrate surface transition to superhydrophilic state under UV irradiation and no significant alteration of the surface hydrophilicity under visible light irradiation, the formation of Cu2O/TiO2 and Cu2O/ZnO heterostructures resulted in photoinduced decay of the surface hydrophilicity caused by both UV and visible light irradiation. All observed photoinduced changes of the surface hydrophilicity were compared and analyzed in terms of photoinduced alteration of the surface free energy and its polar and dispersive components. Alteration of the photoinduced hydrophilic behavior of TiO2 and ZnO surfaces caused by formation of the corresponding heterostructures with Cu2O are explained within the mechanism of electron transfer and increasing of the electron concentration on the TiO2 and ZnO surfaces.

Spectroscopic studies of ozone in cryosolutions: FT-IR spectra of 16O3 in liquid nitrogen, oxygen, argon and krypton.

We have measured and interpreted the IR spectra of ozone dissolved in liquid nitrogen, oxygen, argon, and krypton in the 650-4700cm-1 spectral region at 79-117K. Frequency shifts, band intensities and bandshapes of 22 spectral features of soluted ozone were analyzed. The bands of the А1 symmetry have a complex contour and possess an excess intensity with respect to the value of the purely vibrational transition moment. It was found that this effect is related to the manifestation of the Coriolis interaction. The bandshape distortion manifests itself as an additional intensity from the side of the В1 symmetry band being an intensity source in the case of the Coriolis interaction.

Light-Controlled ZrO2 Surface Hydrophilicity.

In recent years many works are aimed at finding a method of controllable switching between hydrophilicity and hydrophobicity of a surface. The hydrophilic surface state is generally determined by its energy. Change in the surface energy can be realized in several different ways. Here we report the ability to control the surface wettability of zirconium dioxide nano-coatings by changing the composition of actinic light. Such unique photoinduced hydrophilic behavior of ZrO2 surface is ascribed to the formation of different active surface states under photoexcitation in intrinsic and extrinsic ZrO2 absorption regions. The sequential effect of different actinic lights on the surface hydrophilicity of zirconia is found to be repeatable and reversibly switchable from a highly hydrophilic state to a more hydrophobic state. The observed light-controllable reversible and reproducible switching of hydrophilicity opens new possible ways for the application of ZrO2 based materials.

Photoinduced hydrophilic conversion of hydrated ZnO surfaces.

Here we focused on the study of the effect of the zinc oxide nano-coatings surface acidity on the surface hydrophilicity and photoinduced hydrophilic conversion. A three-step procedure was used to have the initial state of the ZnO surface free of organics and to control the conditions during the water wetting and the irradiation steps. The kinetics of photoinduced hydrophilic conversions for ZnO films were obtained and demonstrated a dependence on the initial hydrophilic state. No conversion into the superhydrophilic state was observed for ZnO nano-films independently of the surface acidity. Irradiation in the ultraviolet and visible spectral regions showed the existence of "slow" and "fast" processes in the photoinduced hydrophilic conversion of the ZnO surface. A multi-layered model of hydroxyl-hydrated coverage of the surface is proposed to explain the experimental results.

IR spectroscopic testing of surfaces in water ice and in icy mixtures with prussic acid or ammonia.

An experimental technique is developed for spectral studies of ice films deposited at 77 K onto the ZnSe inner windows of a cell, so that the spectra could be registered in the presence of gaseous adsorbate. Pure H2O or D2O ice as well as HCN/D2O and ND3/D2O mixed icy films with different dopant/water ratios (1:10, 1:5, and 1:1) were investigated. The surface area of ice deposited at 77 K H2O estimated from adsorption measurements was about 160 m2/g. Bands of dangling hydroxyl groups disappear on raising the temperature up to 130-160 K when the changes of bulk absorption provide evidence for a phase transition from amorphous to polycrystalline ice. Surface properties of icy films were characterized by low-temperature adsorption of CO and CHF3. Insertion of small doses of HCN or ammonia does not change the acid/base strength of dangling hydroxyl groups or coordinately unsaturated surface oxygen atoms, but it changes the proportion between the concentrations of these sites as compared with pure water ice. For high dopant concentrations, the dangling hydroxyls were not observed, and the dominant adsorption sites for CO are likely to be the unsaturated oxygen atoms, while serious structural changes occur in the bulk of ices.