Template-assisted generation of three-dimensionally branched titania nanotubes on a substrate

Due to their high aspect ratio titania nanotubes have more surface area that enhances their ability towards harnessing light. Herein, we report on a template-assisted method to synthesize branched titania nanotubes anchored on a substrate. The branched structure consists of units of six or more tubes connected at their base; each tube has a dimension of approximately 6 mm long, 600 nm wide and 65 nm thick wall. Our approach takes advantage of hydrothermally processed branched ZnO nanorod (NR) arrays that act as sacrificial templates. After chemical dissolution of the ZnO film that inherently forms during ZnO-NR processing, the titania overlayer is coated atop of the template and annealed at 350 degrees C to produce the anatase nanostructure. Removal of the template under mild acidic conditions reveals the anatase tubes. The processes employed are well suited for large-scale application. The highly textured surface of the nanotubes also exhibits low reflectivity when compared to its thin film counterpart.