Papers by Author: Rui Xing Li

Abstract: White nanoparticles of calcia-doped ceria were prepared from the precipitate by reacting CeCl3-CaCl2 mixed solution with NaOH solution at pH 12 and the oxidation with hydrogen peroxide solution at 40oC, followed by the calcination at 700oC for 1 h. The sample before calcination contained significant amount of OH- in the lattice and was yellow, but the powders calcined above 700oC were white, indicating that cationic defect formed by replacing O2- with OH- played as the color center. Calcia-doped ceria particles were coated with amorphous silica by means of seeded polymerization technique using hydrolysis of tetraethylorthosilicate (TEOS) or acid hydrolysis of sodium silicate. The silica coating by seeded polymerization with TEOS was much more efficient for the reduction of catalytic activity of ceria for the oxidation of organic materials than that by acid hydrolysis of sodium silicate. It is confirmed that ceria particles caused far less damage to the DNA plasmids upon UV illumination than either the titania or the zinc oxide reference pigments.

Abstract: Novel superstructures of zinc oxide thin film with nano-rods and nano-screws were prepared via soft solution route without any polymer additives. The thin film of ZnO could be produced directly on the substrates. The yield of nano-rod and/or nano-screw was almost 100%. Small amount of nano-disk superstructure was also obtained. The superstructures of the film changed depending on the kind of treatment organic solvent such as methanol, butanol, i-propanol, hexane, etc. Monodispersed or symbiotic/multipod ZnO nanorods with hexagonal cross section or screw microstructure were successfully prepared.

Abstract: Because of the low refractive indices, plate-like cerium phosphates (CePs) are expected to be used as one of active ingredients in personal suncare cosmetics. Plate-like Ce2(PO4)2HPO4･H2O particles were synthesized via solvothermal reactions of Ce(NH4)2(NO3)6 or Ce(SO4)2･4H2O in phosphoric acid with or without nitric acid and sulfuric acid solutions. The variation of morphology of Ce2(PO4)2HPO4･H2O particles significantly depended on the variety of cerium salt, isothermal temperature and time, although all reaction products consisted of plate-like particles. This plate-like compound showed excellent UV light absorption and transparency in the visible light region. Consequently, it is suggested that the plate-like Ce2(PO4)2HPO4･H2O particles might be used as suncare products to give an ideal optical effect of both UV-shielding ability and transparency in the visible light region, as well as a good feeling on the skin.