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 Na ₂Ti₆O₁₃, 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 Na ₂Ti₆O₁₃ phase. The obtained Na ₂Ti₃O₇ and Na₂Ti₆O ₁₃ nanowires have good crystallinity and both grow along the [010] crystallographic directions. The synthesized Na₂Ti₆O ₁₃ 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.