Synthesis and Photochemical Properties of White Calcia-Doped Ceria Nanoparticles via Soft Solution Processes
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.
T. Sato et al., "Synthesis and Photochemical Properties of White Calcia-Doped Ceria Nanoparticles via Soft Solution Processes", Advances in Science and Technology, Vol. 45, pp. 685-690, 2006