Azobenzene-Containing Block Copolymer Templates for Robust Au@TiO2 Nanoporous Network Films toward Hot-Electron-Mediated Efficient Visible-Light Photocatalysis

Robust metallic doped semiconducting networks of precise organization, over large scales and small dimensionality, hold great application potential in the basis of photocatalytic materials. Herein, a facile method to fabricate robust Au@TiO2 hierarchical nanoporous network films is reported, which is templated by thermally stable poly(4-vinylpyridine)-block-poly{11-[4-(4-butylphenylazo)phenoxy]undecyl methacrylate} (P4VP-b-PMA(11C)Az) liquid crystalline (LC) block copolymers (BCPs). A P4VP100-b-PMA(11C)Az15 thin film can self-assemble to form ∼50 nm orderly packed PMA(11C)Az periodic spheres in the P4VP matrix via a solvent-annealing process. When these spherical P4VP100-b-PMA(11C)Az15 films with different thicknesses were exposed to the sol–gel titania precursors alcohol solutions with titanium(IV) isopropoxide (TIPT) and titanium tetrachloride (TiCl4; mass ratio, 3:1), titania was well-formed in the P4VP phase during the calcination process. After a further deposition–precipitation (DP) process, ∼10 nm Au nanoparticles were homogeneously doped in robust TiO2 nanoporous network films. The photocatalytic performance of the obtained robust Au@TiO2 films was studied in detail. It displays significantly enhanced visible light photocatalytic activity. The enhancement mechanism was ascribed to the injection of hot electrons of photoexcited Au nanoparticles to robust porous TiO2 films, which was confirmed by 420 nm Xe laser-induced fast photodegradation of rhodamine B.