Highly Efficient Room Temperature NO₂ Sensor Using Two-Phase TiO_x Heterogeneous Nanoparticles

In this study, we successfully synthesized two-phase titanium oxide (TiO_x) heterogeneous nanoparticles (NPs) using an advanced sol–gel method, a significant stride in developing efficient, room temperature (RT) NO₂ gas sensors. The prepared two-phase TiO_x heterogeneous NPs exhibited exceptional sensitivity to low concentrations of NO₂ gas at RT. The heightened gas response was attributed to a significant presence of oxygen vacancies, creating intermediate states within the two-phase heterostructures and thus narrowing the band gap. This facilitated electron transport from the valence band (VB) to the conduction band (CB), resulting in increased current at RT. The XPS analysis confirmed a substantial amount of chemisorbed oxygen O_2(ads)^– within the two-phase heterostructures, providing more chemisorption sites for nitrogen dioxide gas. This increase in chemisorption sites significantly improved the gas response. Furthermore, the introduction of zinc into the TiO_x NPs reduced their band gap, enhancing the background resistance signal-to-noise ratio and increasing the response while maintaining remarkable stability. In summary, our work introduces a promising RT NO₂ sensor based on two-phase TiO_x heterogeneous NPs, holding great potential for applications in environmental monitoring and gas sensing technology. In future work, we aim to delve deeper into the capabilities of the sensor, exploring broader applications and refining its design for enhanced practicality in environmental monitoring.