A versatile approach to the fabrication of TiO₂ nanostructures with reverse morphology and mesoporous Ag/TiO₂ thin films via cooperative PS-b-PEO self-assembly and a sol-gel process

Hybrid titanium dioxide (TiO₂) nanostructures with engineered morphologies were produced by a simple synthetic approach based on cooperative sol-gel chemistry and self-assembly of amphiphilic poly(styrene-block-ethylene oxide) (PS-b-PEO) block copolymer (BCP) via spin-coating common solutions of BCP and inorganic precursors. TiO₂ nanostructures with two extreme reverse morphologies, i.e., TiO₂ dot-in-PS matrix and PS dot-in-TiO₂ matrix, were obtained by increasing the volumetric ratio of the TiO₂ sol-gel precursor from 10 to 50 vol%. Incorporation of silver nitrate into the TiO₂ matrix afforded a hybrid Ag/TiO ₂ thin film with hexagonally packed arrays of PS nanodots. Upon removal of the PS-b-PEO template from the initial hybrid films by UV treatment, inorganic nanostructures having the same lateral morphologies as the initial films were derived. Among the structures investigated, the Ag/TiO₂ mesoporous film exhibited the best photocatalytic performance. The surface/internal morphology and the mechanism of structural evolution were investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and grazing-incidence small-angle X-ray scattering (GISAXS).