Hydrogen-Plasma-Assisted Growth of Anatase TiO2 Nanoneedles on Ti Plates

Pure anatase TiO2 nanoneedles are prepared on substrates via a dry process that involves hydrogen plasma treatments followed by the oxidation of Ti plates at a low temperature of 500 degrees C. Scanning electron microscopy and high-resolution transmission electron microscopy images show that the nanoneedles have diameters and lengths in ranges of 20-50 nm and 100-200 nm, respectively, and are single-crystalline anatase structures that grow along the [116] direction. The TiO2 nanoneedles nucleate on microgrooves that result from the oxidation of microcracks induced by the hydrogen plasma. The diameters, lengths, and area densities of the TiO2 nanoneedles can be varied by adjusting the power of the hydrogen plasma. A stress-assisted vapor-solid mechanism for the formation of the nanoneedles is proposed. The room-temperature photoluminescence spectrum of the TiO2 nanoneedles exhibits a relatively strong ultraviolet emission centered at 375 nm and broad visible emission at around 640 nm. This study proposes a route for growing anatase-phase TiO2 one-dimensional nanostructues on substrates that have potential use in photocatalytic, photoelectrochemical, and sensing applications.