Multi-heterostructure and surface free radicals induced enhanced ammonia gas sensing performance of polyaniline/tin phosphide/nitrogen-doped reduced graphene oxide at room temperature.

Exploration of novel sensing materials and sensing strategies to provide highly sensitive and selective ammonia (NH) gas detection is imperative for environmental pollution monitoring. Herein, a multi-heterostructure and surface free radical activation strategy is employed to enhance the NH sensing performance of tin phosphide (SnP) at room temperature (RT). Characterizations confirm the uniform dispersion of SnP on nitrogen-doped reduced graphene oxide (N-rGO) and the effective coating of polyaniline (PANI) film. The PANI/SnP/N-rGO sensors show a well sensing ability to NH gas with a high sensitivity (3.1 @ 40 ppm) at RT, good selectivity and a low detection limit of 36.8 ppb. The multi-heterostructure can enable precise modulation of electronic properties and energy barriers. Additionally, the sensing material shows enhanced responses with increasing relative humidity, exhibiting a response of 2.7 to 10 ppm NH at the relative humidity of 70 %. This improvement is attributed to the formation of hydroxyl radicals through the dissociation of surface adsorbed water molecules, which promotes the surface gas adsorption. This study offers an effective strategy for fabricating highly sensitive sensing materials and advances the research on new sensing mechanisms.