Wanggang Zhang

Photocatalytic activity of Ag nanoparticle-dispersed N-TiO2 nanofilms prepared by magnetron sputtering

Using magnetron sputtering, pure TiO2 nanofilms and Ag/TiO2 bilayer nanofilms doped with nitrogen were deposited on glass substrates. Heat treatment of the Ag/N-TiO2 nanofilms at 400 °C led to the formation of Ag nanoparticles, which were dispersed inside the TiO2 films as well as on the free surface of the TiO2 films. The photocatalytic activity of the Ag/N-TiO2 nanofilms with dispersed Ag nanoparticles was examined by UV-vis diffuse reflectance spectroscopy. The rate constants for the photodegradation of methylene blue (MB) in aqueous solutions of MB by N-TiO2-based nanofilms are about one order larger than those for self-degradation or for pure TiO2 nanofilms. The rate constants for the photodegradation of aqueous solutions of MB by the Ag/N-TiO2 nanofilms are larger than those for the N-TiO2 nanofilms. The Ag nanoparticles improve the photocatalytic activity of TiO2 films, possibly through the surface plasmon absorption effect of Ag nanoparticles, which activates photo-generated charge carriers through the transfer of plasmonic energy.

Fast diffusion of silver in TiO2 nanotube arrays

Summary Using magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10−18 m2/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag.

Effects of annealing temperature on the properties of copper films prepared by magnetron sputtering

Copper oxide thin films were prepared by a direct-current magnetron sputtering method followed by a thermal annealing treatment at 100–500 °C. The obtained films were characterized by X-ray diffraction, UV-vis absorption spectroscopy, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. With the increase of the annealing temperature, it was found that the films transformed sequentially from amorphous to single-phase Cu (100 °C), mixed-phase of Cu and Cu2O (150 °C), single-phase Cu2O (200 °C), then to mixed-phase of Cu2O and CuO (300 °C), and finally to single-phase CuO (400–500 °C). Further analyses indicated that the Cu/Cu2O thin films and the Cu2O thin films presented no further oxidation even on the surface in air atmosphere. Additionally, the visible-light photocatalytic behavior of the copper oxide thin films on the degradation of methylene blue (MB) was also investigated, indicating that the films with pure Cu2O phase or Cu/Cu2O mixed phases have excellent photocatalytic efficiencies.

High photocatalytic activity of Cu2O/TiO2/Pt composite films prepared by magnetron sputtering

Cu2O/TiO2/Pt three-layer films were deposited on glass substrates using magnetron sputtering method. The surface morphology and the optical properties of the composite film were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–Vis) and photoluminescence spectroscopy (PL). The photocatalytic activity of the samples was evaluated by the photocatalytic degradation of methyl orange (MO) aqueous solution under visible light irradiation. The results indicate that the Cu2O/TiO2/Pt composite films are made up of three layers which are Pt layer, anatase-TiO2 layer and Cu2O layer from bottom to top. The surface of the films is even and composed of regular-shaped spherical particles. The photocatalytic activity of the Cu2O/TiO2/Pt three-layer film is much higher than that of the Cu2O/TiO2 double-layer film. Such enhancement is ascribed to the presence of Pt layer, which further inhibits the photogenerated electron–hole recombination, prolongs the lifetime of the photogenerated carriers, increases the quantum efficiency and hence improves the photocatalytic activity of the film effectively.

Synthesis of Cu,N-Doped TiO2 Nanotube and Study on Photoelectric Properties

Cu,N-TiO2 nanotube (Cu,N-TNT) is prepared through a novel magnetron sputtering and anodic oxidation method. Then the morphology, structure and physicochemical property of Cu,N-TNT was analyzed by XRD, SEM, TEM, EDX and UV-vis-DR. The results indicate that the evenly doped copper is beneficial to the transformation of the TNT from anatase to rutile and play a key role in the morphology of the Cu,N-TNT. The doped Cu and N in the TNT influence the growth orientation of the TiO2 crystals, which result in the lattice distortion and wider the interplanar spacing 60s-Cu,N-TNT has less band gap and stronger absorption intensity in visible region than other Cu,N-TNT samples, which make the combination rate of photogenerated electron and photogenerated hole decrease greatly, thus beneficial to its physicochemical property.