Low-temperature growth of a nitrogen-doped titania nanoflower film and its ability to assist photodegradation of rhodamine B in water

Successful application of titania photocatalysts for air and water remediation demands highly active titania thin films fabricated through a simple reaction that is easily scaled-up. In this study, titania thin films with a dual structure, that is, flower-like rutile aggregates sitting on top of an anatase layer, were fabricated simply by oxidizing metallic Ti plates with hydrogen peroxide solution containing trace amounts of hexamethylenetetramine and concentrated nitric acid at 353 K for 72 h. Low-temperature growth of the top flower-like rutile, with constructing blocks of tiny rutile nanorods, occurred only after 60 h of reaction when the solution contained almost no hydrogen peroxide or Ti(IV) ions. Tiny rutile nanorods were supposed to form through a dissolution precipitation mechanism and then orient and attach to form single-crystal nanorods with larger sizes, which self-organize to develop the flower-like rutile aggregates. After a subsequent thermal treatment to further improve the crystallinity, the titania film was utilized to assist photodegradation of Rhodamine B in water under ultraviolet light irradiation. Significant increased photocatalytic activity of the titania nanoflower film was achieved after natural aging of the titania thin film for certain durations. The present film possessed enhanced photocatalytic activity compared with the titania nanorod film we previously reported and the commercial Degussa P-25 titania coating as well.