Preparation of hollow titania nanoparticles of single-nanometer size using a PAMAM dendrimer template.

Hollow titania nanoparticles of single-nanometer size have been prepared from titanium oxysulfate (TiOSO₄) using poly(amidoamine) (PAMAM) dendrimer molecules (Generations 5 with amino terminal groups) as a template. At low pH (pH 1), hydrolysis of the titania precursor was attenuated and the sol-gel reaction preferentially proceeded at the dendrimer surface. Calcination at 450°C yielded crystalline titania nanoparticles of 5.5 nm diameter with a ~2 nm cavity. These hollow titania nanoparticles showed a larger band-gap energy than solid particles of corresponding size.