Ultrasensitive NO2 sensors based on Au/SnS2/SnO2 nanoflower-like heterojunctions at low temperature

The nanoflower-like Au/SnS2/SnO2 heterojunctions were synthesized following a combination process. In sequence, the SnS2/SnO2 nanoflowers were obtained by the thermal oxidation of the flower-like SnS2 that was firstly synthesized by a solvothermal method. Then, the nanoflower-like Au/SnS2/SnO2 heterojunctions were achieved by in-situ decoration of SnS2/SnO2 nanoflowers with gold nanoparticles. The as-synthesized Au/SnS2/SnO2 heterojunctions based chemiresistive-type sensor has exhibited a response of 22.3–8 ppm NO2 at 80 °C, which is much higher than that of the pristine SnS2 sensor (8.1). The response and recovery rate of the sensor is also increased by 1 ∼ 2 times. The theoretical calculation using the density function theory (DFT) based on the first principle was implemented to study the sensing mechanisms. The enhanced sensing performance could be mainly attributed to the formation of Au/SnS2/SnO2 heterojunctions.