The Effect of Preparation Method on the Morphology of TiO₂ nanowires

In this research, the synthesis of titanium dioxide (TiO2) nanowires from the same commercial anatase TiO2 as starting material has been carried out successfully using two different methods, namely hydrothermal and molten salt. The resulting TiO2 nanowires morphologies were evaluated using scanning electron microscopy (SEM). It was found that TiO2 nanowires prepared using hydrothermal method (TNWH) has smaller aspect ratios as compared to TiO2 prepared using molten salt (TNWMS). In a typical hydrothermal condition at 200 °C for 24 h, TiO2 nanowires were composed of nanowires with variable width from 70 to 450 nm and lengths from 1 to 3.2 μm resulted in aspect ratios of up to 46. Meanwhile in a typical molten salts condition at 825 °C for 8 h, the TiO2 nanowires were composed of nanowires with variable width from 160 nm to 1 μm and lengths from 1 to 15 μm, resulting in aspect ratios of up to 94. The SEM images depicted aggregates on TNWH while TNWMS has high quality single crystalline TiO2. Additionally, X-Ray Diffractogram (XRD) was also conducted to evaluate the crystal phase of TiO2 nanowires. The hydrothermal method resulted in mixture of TiO2 anatase and brookite phase while the molten salt resulted in TiO2 rutile phase due to high calcination temperatures. TNWMS has higher crystallinity compared to TNWH as confirmed from the XRD results. The Molten salt method appeared to be a promising method to produce high quality TiO2 nanowires for further application as catalyst based on the final characteristics of the nanowires.