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Reactive High Power Impulse Magnetron Sputtering operated in multi-pulse mode (m-HiPIMS) of a pure Ti target in Ar/N 2 /O 2 gas mixture (mass flow rates of 50, 2 and 0.16 sccm, respectively) has been used for the deposition of titanium oxynitride (TiO x N y) thin films with variable content of nitrogen (from 0.6 at.% to 24.2 at.%). Increase of the nitrogen content in the deposited TiO x N y thin films determined a decrease of the optical bandgap energy and a corresponding increase of visible light adsorption. The photocatalytic activity for water molecule splitting of the films deposited on metallic substrate, which were used as the photo-anode in an electrochemical cell, has been investigated by measurements of photoelectrochemical current intensity versus biasing voltage during on/off cycles of visible light irradiation (sun light simulated by a xenon lamp). The as-deposited films have a short range order corresponding to rutile and anatase structures and showed very weak photocatalytic activity and chemical instability in the electrolyte of the photoelectrochemical cell. However, a post-deposition annealing treatment of the film with low content of nitrogen (0.6 at.%) improved considerably the visible-light photocatalytic activity, the film crystalline order and chemical stability.

Partial wetting on the nanoscale may result in the formation of sessile liquid nanodroplets on flat substrates. In this case, the molecular forces generate a strong interaction between nanodroplet interfaces. This interaction is expressed in the mean-field approximation by the disjoining pressure and determines an important deviation from the spherical cap shape of the nanodroplets. This deviation is observed on the atomic force microscopy images of sessile nanodroplets of oleic acid on glass. The disjoining pressure was manipulated by hydroxylation of the glass surface. This surface modification generated a strong negative disjoining pressure due to structural forces arising from the orientation of oleic acid molecules with their polar heads toward the substrate. As a result, the shape of oleic acid nanodroplets showed large deviations from the spherical cap shape, with the liquid-vapor interface tilting angle with respect to the plane substrate having a maximum (herein considered to be the contact angle) a certain distance from the substrate, followed by its decrease to zero at the droplet edge. The integration of the augmented Young-Laplace equation, where the dependence of the negative structural disjoining pressure on the interface separation distance was assumed to be an exponential decay, yielded height profiles of droplets in good agreement with the experiment.

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The postdischarge kinetics of reactive species produced by a surface dielectric barrier discharge (SDBD) ignited in closed-volume air for decomposition of organic molecules in aqueous solutions was investigated. A SDBD with surface of 6 cm 2 was operated in a closed volume (0.5 L) of air at atmospheric pressure. The voltage across the plasma gap, the charge transferred through the plasma, and the dissipated power were computed from the charge-voltage diagram to values of 3900V, 0.2 C, and 6W, respectively. The reactive species produced by the SDBD in a closed volume of air were active for decomposition of methylene blue molecules in small volumes of aqueous solution for a relatively long period of time af-position of organic molecules was approximately 11 minutes. However, SDBD operation in closed-volume air shortened the lifetime of polyimide dielectric of the discharge microelectrode system due to the increased humidity and reactivity of the active species generated by plasma. Measurement of relative humidity revealed that the discharge enhanced water evaporation. Atomic force microscopy investigations of dielectric surface in the discharge region roughness as the result of SDBD operation.