Mechanism of Formation of Faceted Titania Nanoparticles from Anodized Titania Nanotubes

Though researchers worldwide have attempted to fabricate faceted titania nanoparticles with a higher fraction of {001} facets, which have high surface energy, the approaches have focused on use of either a very aggressive heating schedule or highly corrosive chemicals like HF. The current article reports a simple method for the transformation of the titania nanotubes to faceted nanoparticles (size varying from 15–120 nm) at relatively low temperatures and heating rates, without the use of any other corrosive chemicals, utilizing only the electrolyte inside the titania nanotubes remnant from the anodization of the titanium substrate. The formation of faceted nanoparticles was found to be strongly dependent on fluorine concentration and on initial state of titania nanotubes (amorphous/crystalline) and annealing temperature. The formation of the unique “nanorod in nanoporous” structures has been reported for the first time. The current article deals with a detailed study of the formation of these unique nanostructures and proposes a mechanism for the same