Morphology-Dependent Correlation Between Photoluminescence and Photocatalytic Activity of Anatase-Titania Photocatalyst

Nanocrystalline particles and nanotubes of anatase-titania photocatalyst have been processed via sol-gel and hydrothermal methods, and subsequently surface-modified by depositing silver/silver oxide via ultraviolet-reduction technique. The samples have been characterized using different analytical techniques for determining their morphology, structure, specific surface-area, moisture-adsorption, photoabsorption, and photoluminescence. The photocatalytic activity, under the ultraviolet-radiation exposure, has been measured in an aqueous solution using the methylene blue as a model catalytic dye-agent and is compared with the photoluminescence intensity variations in air under different processing conditions for the two different morphologies of anatase-titania photocatalyst. It has been demonstrated that the conventional correlation between the photoluminescence and photocatalytic activity is highly morphology-dependent and is not obeyed by the nanotubes of anatase-titania. This has been primarily attributed to the change in the mechanism of photo-induced electron trapping in air and aqueous media, which controls the variation in the PL intensity and photocatalytic activity, as typically observed here for the pure and silver-deposited nanotubes of anatase-titania.