Time-dependent changes in the formation of titania-based films at the air-water interface

The growth of surfactant-assisted titanium dioxide-based films at the air-water interface previously reported (Henderson et al. Aust. J. Chem. 2003, 56, 933) has been monitored with a time resolution of minutes over the whole growth period by X-ray energy-dispersive reflectometry. Two new phenomena are described: (a) short-term shifts in the Bragg spacing of the layer structure and (b) the periodic disappearance of the diffraction from the film. We associate these with changes in the chemistry of the reacting mixture, with changes in the packing of the templated titanium species, and with macroscopic and (possibly) microscopic rippling of the solid film during growth.