Fabrication of ultra-high sensitive and selective CH₄ room temperature gas sensing of TiO₂ nanorods: Detailed study on the annealing temperature

Applications of ultra-highly sensitive and selective methane (CH₄) room temperature gas sensors are important for various operations especially in underground mining environment. Therefore, this study is set out to investigate the effect of annealing temperature on the sensitivity and selectivity of TiO₂-based sensors for detection of CH₄ gas at room temperature. TiO₂ nanoparticles synthesized using hydrothermal methods were annealed at various temperatures. Surface morphology analyses revealed that the nanoparticles transformed to nanorods after annealing at 700 °C. The results showed that the sensing properties are annealing temperature dependent. The 1.0 M TiO₂ nanostructures annealed at higher temperatures (700 °C) revealed improved sensing response to CH₄ gas at room temperature due to higher surface area of 180.51 m² g⁻¹ and point defects related to Ti³⁺ observed from electron paramagnetic resonance (EPR) and photoluminescence (PL) analyses. In addition, the 1.0 M TiO₂ sensing material annealed at 700 °C also revealed an excellent sensitivity and selectivity to CH₄ gas at room temperature compared to other gases (H₂, NH₃, and NO₂), indicating that the TiO₂ nanoparticles are possible candidates for motoring CH₄ at low concentration of ppm level.