Highly entangled TiO2 nanowires were directly synthesized by hydrothermal growth on Ti substrates at 180 degrees C utilizing various organic solvents to oxidize Ti. The growth mechanism, microstructure and phase transition of TiO2 nanowire membranes were investigated in detail. TiO2 nanowires, with diameters of 10-20 nm and lengths up to 100 mu m. show a phase transition from Type-B to anatase by annealing at 700 degrees C. Robust, free standing TiO2 nanowire membranes with millimeter level thickness can be cleaved from Ti substrates or directly prepared from thin Ti foils. These porous TiO2 membranes, while effective for mechanical microfiltration, can also photocatalytically degrade pharmaceuticals such as trimethoprim under UV irradiation. (C) 2011 Elsevier B.V. All rights reserved.