Ag/AgCl@TiO2 fibers B3LYP Cu and Pt nanoparticles FTIR HRTEM S-doping SCC-DFTB TiO2 TiO2 modification TiO2 nanotubes UV-visible XRD accumulated electrons adhesion anodization brookite bulk defects copper-modified titania excitons flame-spray pyrolysis flexible substrates formation mechanism graphene-TiO2 hardness heterojunction large-sized films lattice defects methanol photo-steam reforming microstreaming microwave irradiation