title: Simple route to monodispersed silica-titania core-shell photocatalysts.
abstract: A monodispersed silica-titania core-shell photocatalyst was synthesized via a sol-gel route without the need of pH adjustment, cationic polyelectrolytes, or surfactants in a process where silica spheres were impregnated with hydrolyzed titanium tetrabutoxide, incubated at room temperature, and then condensed using an ethanol/water (1:1) solvent. Four coating cycles in a 10% v/v titania sol produced homogeneous titania shells. The quality of catalysts was assessed quantitatively using Rietveld analysis of powder X-ray diffraction patterns combined with X-ray fluorescence spectrometry. During calcination, the anatase-to-rutile transformation was delayed to 1000 degrees C, which is approximately 300 degrees C higher than usually observed. The thermal stability and surface area of titania were enhanced through the slow crystal growth of anatase. The photocatalytic activity of the core-shell photocatalysts calcined at 400-600 degrees C was found to be proportional to the thickness of titania but did not directly correlate with the surface area.
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798. shlim@ntu.edu.sg
authors.forename: Suo Hon
authors.initials: SH
authors.lastname: Lim
authors.forename: Nopphawan
authors.initials: N
authors.lastname: Phonthammachai
authors.forename: Stevin S
authors.initials: SS
authors.lastname: Pramana
authors.forename: T J
authors.initials: TJ
authors.lastname: White