Facile fabrication and tuning of TiO2 nanoarchitectured morphology using magnetron sputtering and its applications to photocatalysis

This paper reports a comprehensive investigation into fabrication of TiO2 nanorods using standard reactive sputtering without applying any further treatment. This approach was considerably different from the typical solution-based process for making TiO2 nanorods. The key features of this research are that a growth model of TiO2 nanorods is proposed based on the random distribution of anatase TiO2 (1 0 1) on a fluorine-doped tin oxide substrate. In addition, three critical factors, the morphology, band gap tuning, and chemical environment, were examined simultaneously to enhance photocatalysis of TiO2 nanorods. We observed that the morphology can be modulated by varying the sputtering parameters and N2 doping. Scanning electron microscopy and transmission electron microscopy results indicated a unique large polycrystalline nanorod bundle that was composed of various small highly textured nanorods dominated by the low energy facets of anatase (1 0 1). X-ray photoelectron spectroscopy was performed to confirm that Route B (an Ar (20 mTorr)/N2 (10 mTorr) atmosphere followed by O2 postannealing) was an effective approach for doping N2 into TiO2 nanorods, in which some Ti3+ formed (Ti3+Ti4+−) to maintain charge neutrality in the N2-doped TiO2 (N-TiO2) system, because of the substitutional formation of N3− O2−−. The sample exhibited higher photocatalytic efficiency than did pristine TiO2 nanorods. Approximately 80% of methylene blue decomposed in 90 min at a pH of 10 under visible light illumination.