Synthesis of Highly Ordered TiO2 Nanorods on a Titanium Substrate Using an Optimized Hydrothermal Method

In this study, highly stable and well-oriented one-dimensional (1D) TiO2 nanorods were grown over a conductive titanium (Ti) substrate by optimizing various physical and chemical parameters involved in the hydrothermal method. Previous works have reported extensively on the synthesis of 1D TiO2 nanorods on fluorine-doped tin oxide-coated glass substrates using the hydrothermal method. However, glass substrates suffer from poor integration, compatibility, and stability issues when implemented in device applications. To overcome the challenges with glass substrates, in the current study, we propose an optimized hydrothermal route to synthesize highly ordered 1D TiO2 nanorods on a metal (Ti) substrate. The structural and morphological parameters of the nanostructures, including crystal phase, length, diameter, and density of nanorods, were studied with the help of field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction spectroscopy, and photoluminescence spectroscopy. The morphology of the nanostructures was varied by changing the chemical composition of the mother solution and physical parameters of time and temperature of the reactions involved during hydrothermal synthesis. It was shown that by optimizing the reaction parameters, multi-crystalline three-dimensional TiO2 nanoflowers could be transformed to single-crystalline 1D TiO2 nanorods. One-dimensional TiO2 nanorods on the Ti substrate were then implemented in a metal-insulator-metal (MIM) type of device (Au/TiO2 nanorods/Ti) and used for ethanol sensing. At 100 degrees C, the sensor showed the maximum response magnitude of 61% towards 300 ppm of ethanol.