Crystal growth of titania by photocatalytic reaction

•Anatase-type titania crystals grew by a photocatalytic reaction.•Titanium hydroxide particles were deposited from a TiCl4 solution with NO3−.•The titanium hydroxide was dehydrated and transformed into titania at 353 K.•About 20 nm-sized titania crystals were formed on the original titania film.•The titania exhibited a photocatalytic activity similar to the original titania.

Substrate plates coated with anatase-type titania thin films were immersed in a solution of titanium (IV) chloride and lithium nitrate at 353 K during UV irradiation. About 20 nm-sized anatase-type titania crystals were formed on the original titania film consisting of almost the same sized particles. Nitrate ions in the solution were reduced to nitrite ions, and water was transformed into hydroxide ions by a photocatalytic reaction on the original titania film. The pH value increased on the titania surface, which caused the titanium hydroxide formation. The titanium hydroxide was then dehydrated and transformed into titania. The titania particles formed on the substrate exhibited a photocatalytic activity similar to the original titania.

Graphical abstractDownload high-res image (119KB)Download full-size image