Molten salt synthesis of Na2Ti3O7 and Na2Ti6O13 one-dimensional nanostructures and their photocatalytic and humidity sensing properties

The molten salt synthesis of sodium titanate one-dimensional nanostructures at relatively low temperature (ca. 825 °C) was re-examined in detail to elucidate the roles of various experimental parameters. Two kinds of sodium titanate nanowires, i.e., Na2Ti3O7 and Na2Ti6O13, with almost the same diameters were obtained in the presence of excess sodium oxalate, which also played an important role in enhancing nanowires yield. High calcining temperature favours the formation of Na2Ti6O13-predominant product at high sodium content. The introducing of nonionic surfactant NP-9 not only improves the uniformity of nanowires, but also favours the formation of Na2Ti6O13 phase. The obtained Na2Ti3O7 and Na2Ti6O13 nanowires have good crystallinity and both grow along the [010] crystallographic directions. The synthesized Na2Ti6O13 nanowires exhibited good photocatalytic activity towards the degradation of methyl orange under ultraviolet light irradiation. A humidity sensor based on Na2Ti3O7 nanowires was fabricated and showed good sensing performance at room temperature.