Improved ppb-level NO2 conductometric sensor induced by trace Au on SnO2 nanosheet

As a main exhaust emission from vehicles, nitrogen dioxide is harmful to environment and human health. Gas sensors with high performance for nitrogen dioxide detection is essential. In this work, SnO2 nanosheet aggregates loaded with Au were used to fabricate a NO2 gas sensor. Pristine SnO2 was synthesized via a solvothermal method. Subsequently, the ultraviolet (UV) light-assisted reduction method was utilized to load Au nanoparticles and improve the sensing properties. The SnO2 modified with a trace of Au nanoparticles (0.5 wt%) shows high response to ppb-level NO2 (35–100 ppb) at a low temperature (90 °C). Besides excellent selectivity and long-term stability, the 0.5% Au/SnO2 based sensor can detect 2 ppb NO2 with the response value of 1.2. The enhanced sensing properties can be attributed to the interface interaction between Au and SnO2, causing the enhanced absorption capability for oxygen and NO2 molecules. Additionally, trace amount of loading Au can maintain small size of Au nanoparticles, making the active sites on SnO2 more effective. This work provides a convenient method for preparing a ppb-level NO2 gas sensor with high performance.