Weichang Hao

Photocatalytic properties of BiOX (X = Cl, Br, and I)

A novel series of photocatalysts, bismuth oxyhalide (BiOX, X = Cl, Br, and I), were synthesized by a hydrolysis method. The powder samples were characterized by the use of X-ray diffraction (XRD), scanning electron microscope, and UV-Vis spectrophotometer. The XRD pattern showed that all the BiOX were well crystallized in the tetragonal structure. The band gaps of the sheet-shaped compounds BiOX (X = Cl, Br, and I) were 3.44, 2.76, and 1.85 eV, respectively. BiOBr showed the highest photocatalytic activity in degrading rhodamine B (RhB) and evolving O2 for its proper valence band (VB). BiOI has no photocatalytic activity. BiOCl showed the highest activity in decomposing isopropanol because of electron-hole pair separation through trapping electrons by oxygen vacancies.

Preparation and characterization of a new long afterglow indigo phosphor Ca12Al14O33:Nd,Eu

A new phosphor Ca12Al14O33:Nd,Eu was synthesized by a traditional solid-state reaction method and the luminescent properties were investigated. The phosphors are well crystallized by calcination at 1200 °C. The excitation and the emission spectra show the characteristic broadband of the Eu2+ ion and the emission light is indigo. Doping Nd3+ ion in the phosphor results in indigo long afterglow phosphorescence (the time for the phosphorescence intensity to decrease to 10% of its initial value is about 50 s) when the excitation light is cut off. The emission intensity decreases with the increase of Nd3+ ion concentration. Whereas, the phosphorescence intensity and afterglow time improve when the concentration of Nd3+ ion increases.

Formation and capacitance properties of Ti-Al composite oxide film on aluminum

Abstract Al specimens were covered with TiO 2 film by sol-gel dip-coating and then anodized in ammonium adipate solution. The structure, composition and capacitance properties of the anodic oxide film were investigated by transmission electron microscopy (TEM), Auger electron spectroscopy (AES), X-ray diffractometry (XRD) and electrochemical impedance spectroscopy (EIS). It was found that an anodic oxide film with a dual-layer structure formed between TiO 2 coating and Al substrate. The film consisted of an inner Al 2 O 3 layer and an outer Ti-Al composite oxide layer. The thickness of layers varied with the number of times of sol-gel dip-coating. The capacitance of anodic oxide films formed on coated specimens was at most 80% higher than that without TiO 2 . In film formation mechanism, it was claimed that the formation of composite oxide film was mainly affected by the structure of micro-pores network in TiO 2 coating which had an influence on Al 3+ and O 2− ions transport during the anodizing.

Employment of a metal microgrid as a front electrode in a sandwich-structured photodetector

A highly UV-transparent metal microgrid was prepared and employed as the front electrode in a sandwich-structured ultraviolet (UV) photodetector using TiO(2) thin film as the semiconductor layer. The photo-generated charger carriers travel a shorter distance before reaching the electrodes in comparison with a photodetector using large-spaced interdigitated metal electrodes (where distance between fingers is several to tens of micrometers) on the surface of the semiconductor film. This photodetector responds to UV light irradiation, and the photocurrent intensity increases linearly with the irradiation intensity below 0.2 mW/cm(2).

Controllable synthesis of Zn0.95Co0.05O nanowires and nanotubes by electrophoretic deposition method

Zn0.95Co0.05O nanotubes, as well as nanowires, were controllably synthesized by electrophoretic deposition method using anodic aluminum oxide (AAO) as template, and the mechanism of electrophoretic deposition was discussed. Careful characterization indicates that the prepared nanotubes and nanowires are of poly-crystal wurtzite structure and composed with 8–15 nm nano-crystals. The doped Co2+ occupied the Zn2+ sites in the ZnO lattice. Magnetic investigation indicates that the obtained nanotubes and nanowires are of room-temperature ferromagnetic. The magnetism of the nanotubes is much higher than that of the nanowires for the surface-preferential Co distribution.