Hydrothermal synthesis of potassium/sodium titanate nanofibres and their ultraviolet properties

Potassium/sodium titanate nanofibres have been successfully prepared using titanium dioxide (TiO2) microspheres as the starting material, KOH and NaOH solution as the solvent. Powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and UV-vis spectrophotometer are used to characterise various properties of the obtained nanofibres. The morphology and size of products have a close relationship with the quantity of KOH/NaOH. The nanofibres surfaces are smooth, which exhibit a wire-like morphology with a large aspect ratio. The diameter of these nanofibres falls in the range of 15-30 nm and the length ranges from several hundreds of nanometres to several micrometres. It is found that the morphologies of titanate nanofibres strongly depend on the hydrothermal conditions, in which alkali plays an important role during the whole process. The result shows that the reaction activity of NaOH with TiO2 is better than that of KOH, because the radius of K (1.33 angstrom) is significantly larger than that of Na (0.97 angstrom). The aspect ratio of the products becomes larger with the increase of the KOH concentration. When the size of the titanate nanowire samples decrease, the results show that UV-vis spectra are blue-shift. These nanofibres are wideband semiconductors with a bandgap from 3.15 to 3.38 eV. This work has provided an effective method to synthesise titanate nanofibres in alkali solution, which may also be applicable to the preparation of other nanomaterials.