Fabrication of AgCu/TiO₂ nanoparticle-based sensors for selective detection of xylene vapor

The design and fabrication of innovative nanostructured materials that could display improved sensitivity, selectivity, and rapid response/recovery characteristics still present significant scientific challenges. Herein we report the timely selective detection of xylene vapour in benzene, toluene, ethylbenzene (BTE) and acetone vapours at low operating temperatures using an n-type AgCu/TiO₂ nanoparticle-based sensor. Switching from p-type to n-type conductivity was observed at higher AgCu loadings. The findings showed that sensor switching was not temperature- or gas-dependent. Among the AgCu loaded on TiO₂ nanoparticles, n-type 0.5% AgCu loaded on TiO₂ displayed a remarkable response (R_g/R_a ≈ 33.2) toward xylene vapour at 150 °C. The sensor exhibited superior selectivity, prompt response/recovery swiftness and good repeatability and stability towards xylene vapour in dry air and 40% relative humidity. This response was superior compared to the individual loading of 0.5 mol% Cu or Ag on a TiO₂ based sensor, validating that the contribution of both Ag and Cu had a substantial effect on the spill-over effect mechanism. Additionally, a high loading of 1.0 mol% AgCu resulted in a poor sensing performance. The superior xylene gas sensing characteristics were attributed to the catalytic activity and point defects induced by the loading of AgCu in TiO₂. The underlying mechanism for the improved sensing characteristics can be predominantly ascribed to the strong synergistic catalytic influence of the loading of n-type AgCu/TiO₂ nanoparticles, which reduced the activation energy and accelerated the reaction of xylene molecules and vigorous oxygen species. These findings could disclose a new potential in the fabrication of reliable sensors for portable devices for indoor/outdoor air quality monitoring.