TiO₂ Nanorods and Pt Nanoparticles under a UV-LED for an NO₂ Gas Sensor at Room Temperature

Because the oxides of nitrogen (NO_x) cause detrimental effects on not only the environment but humans, developing a high-performance NO₂ gas sensor is a crucial issue for real-time monitoring. To this end, metal oxide semiconductors have been employed for sensor materials. Because in general, semiconductor-type gas sensors require a high working temperature, photoactivation has emerged as an alternative method for realizing the sensor working at room temperature. In this regard, titanium dioxide (TiO₂) is a promising material for its photocatalytic ability with ultraviolet (UV) photonic energy. However, TiO₂-based sensors inevitably encounter a problem of recombination of photogenerated electron-hole pairs, which occurs in a short time. To address this challenge, in this study, TiO₂ nanorods (NRs) and Pt nanoparticles (NPs) under a UV-LED were used as an NO₂ gas sensor to utilize the Schottky barrier formed at the TiO₂-Pt junction, thereby capturing the photoactivated electrons by Pt NPs. The separation between the electron-hole pairs might be further enhanced by plasmonic effects. In addition, it is reported that annealing TiO₂ NRs can achieve noteworthy improvements in sensing performance. Elucidation of the performance enhancement is suggested with the investigation of the X-ray diffraction patterns, which implies that the crystallinity was improved by the annealing process.