A novel route to large-scale and robust free-standing TiO₂ nanotube membranes based on N₂ gas blowing combined with methanol wetting

We present a novel and straightforward approach to fabricate large-scale and robust free-standing TiO₂ nanotube (TNT) membranes. Simply by blowing N₂ gas onto as-anodized TNTs that are wetted with methanol, free-standing TNT membranes are produced. The approach also provides homogeneous and honeycomb-like Ti substrates after the detachment of TNT membranes. Through the second anodization of the honeycomb-like Ti substrates following the N ₂ blowing, TNT membranes comprising hexagonally close-packed and regularly ordered TNTs with clear open ends can be achieved. Characterization of the free-standing TNT membranes using Raman spectroscopy and a high-resolution transmission electron microscope reveals that anatase TiO₂ and crystalline graphitic carbon are embedded in the bottom surface of the free-standing TNT membranes.