Self-aligned growth of hexagonal TiO2 nanosphere arrays on α-MoO3 (010) surface

At present there are two basic types of self-assembly of inorganic nanomaterials: surfactant-assisted organization and patterned-substrate deposition. In this paper, we report a novel assembled scheme for fabrication of hexagonal superlattice arrays of anatase TiO2 nanospheres on the (010) crystal plane of alpha-MoO3 without the assistance of organic surfactants or substrate prefabrication. The growth and self-assembly of TiO2 nanospheres take place simultaneously under hydrothermal conditions at 150-200 degreesC according to a continuous self-aligned process in which the localized enrichment of hydrolysis product HF (TiF4 is the precursor for TiO2) is believed to play a crucial role in initiating the self-alignment. This growth-cum-assembly mechanism has also been validated with our various growth experiments and materials characterization. Key synthetic parameters have been identified and future explorations have been suggested for this ordered scheme.