Au nanoparticle-modified ZnO/SnO₂ heterojunction nanocomposites for highly sensitive detection of NH₃

The development of resistive NH₃ gas sensor detection technology has important practical significance for environmental protection and human health monitoring. We prepared a novel gas-sensitive nanocomposite of ZnO/SnO₂ heterojunction modified by Au nanoparticles by simple synthesis methods including hydrothermal reduction, solvothermal, and wet impregnation. Then, we analyzed the crystallinity, morphology, and elemental composition of the prepared materials by different characterization means, which proved the successful preparation of Au-ZnO/SnO₂ materials. We tested the response performance of the prepared sensor to NH₃, and the Au-ZnO/SnO₂-2 (Zn/Sn = 0.3wt%) sensor has the best performance. Its response value to 100 ppm NH3 can be up to 11 at the optimal temperature 240 °C, which is about 8 times better performance than the unmodified SnO₂ sensor. In addition, it has fast response and recovery performance (1 min/13 min), good repeatability, long-term stability and selectivity. Finally, we analyzed the high sensing properties of Au-ZnO/SnO₂-2 materials, which can be attributed to the construction of heterojunction promoting electron transfer and the successful modification of Au nanoparticles increasing the adsorption site.