Papers by Author: Xi Wen Zhang

Abstract: Many efforts had been reported to modify the structure of electropun nanofibers in order to obtain superior functional properties of poly(vinyl-alcohol) (PVA). This paper discusses the influence of chitosan on the morphology of electropun PVA nanofibers and their related properties. Spider–net and fiber–bridging structured PVA nanofibers are successfully fabricated by blending with chitosan. Chitosan as natural cationic polysaccharide increases the excess charge of the host polymer PVA. Nanofibers are diverged into thinner nanofibers and a continuous web formed when electrical voltage applied. The presence of additional OH- groups from chitosan and larger surface area of the net structure for hydrogen bonding enhance the hydrophilicity and mechanical properties of the nanofiber mat as compare to pure PVA which are evaluated through water contact angle and tensile testing respectively.

Abstract: AZO/TiO2 double-layered semiconductor coupled films were prepared through sequentially depositing AZO and TiO2 films on glass substrates by radio frequency (RF) magnetron sputtering. PVP-pretreatment and post-annealing were performed on these double-layers to achieve an exposure of the AZO buried-layer in different baring conditions. The photocatalytic efficiencies of these buried-layer bared structures were measured through dye decomposition under ultraviolet irradiation. Silver mirror reactions were operated to explore a possible photocatalytic mechanism associated with these buried-layer bared conditions. The buried-layer bared AZO/TiO2 coupled films present 2 ~3 times of photocatalytic activity comparing to the normal AZO/TiO2 double-layered or single layered ones. It suggested that the self-built electrical field formed from coupling semiconductors reduces the recombination of electron-hole pairs, increases the yield of surface photogenerated charges, and enhances the photocatalysis.