Self-organization of nanoparticles in a TiO2 thin film on a glass substrate

Nanocrystalline titanium dioxide colloids have been synthesized using a sol-gel technique followed by growth under hydrothermal conditions in an alkaline environment at temperatures between 190 and 270 °C. Thin films have been made from aqueous suspension of these colloids. Grazing-incidence wide-angle X-ray diffraction (GIWAXD) analysis showed the films to be primarily the anatase crystal phase. This is in agreement with previous scanning electron microscopy (SEM) results, which had revealed a predominantly rod-like particle morphology after growth at lower temperatures. The formation of principally truncated tetragonal or tetrahedral bipyramidal nanocrystallites followed growth at higher temperatures. The rod-like particles self-organize into regular cubic arrays with the long axis of the rods aligned perpendicular to the film surface. This self-organization is dependent upon the base used in colloidal synthesis.