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/TiO2 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).