Nanoarchitectonics of nest-like MnO2/TiO2 thin film for triethylamine sensing

Nanostructured composite oxides are widely used for detecting toxic volatile organic compounds; yet the contributions of the composition and nanostructure modulation need further clarifications. Herein, we develop directly a nest-like MnO2/TiO2 on alumina tubes for effective triethylamine sensing. The sensing body consisted of a pencil-drawing graphite layer on alumina tube, an intermediate layer of MnO2 nanosheets decorated with TiO2 nanoparticles, and a top layer of quasi-aligned TiO2 nanowires. The response of the MnO2/TiO2 sensors towards 100 ppm triethylamine at 200 °C is 6.8, which is superior to that of both components alone. It reveals that compositing MnO2 with TiO2 leads to a higher Mn4+/Mn3+ ratio and in turn more adsorbed oxygen on the surface, which contributes to the gas sensing performance. Heterojunctions between TiO2/MnO2 and homojunctions between TiO2 nanoparticles and TiO2 nanowires are also believed to provide additional resistance modulations to enhance the response. Nanostructure modulations further contribute to the response, as evidenced by the fact that the optimized response of decorating MnO2 nanosheets with TiO2 nanoparticles is 4.7, being lower than 6.8 for the nest-like MnO2/TiO2 sensor.