Layered SnSe2 microflakes and SnSe2/SnO2 heterojunctions for low-temperature chemiresistive-type gas sensing

Layered SnSe2 flakes and the SnSe2/SnO2 heterojunctions based chemiresistive-type sensors demonstrate good gas sensing properties at low temperatures. The pure SnSe2 based chemiresistive-type sensor indicated a good response and recovery to both NO2 and NH3 while also show a moderate response to hydrogen, CO, C3H6 and several typical volatile organic vapors such as methanol, ethanol, acetone and formaldehyde at near room temperature indicating a poor selectivity. However, compared to pristine SnSe2, SnSe2/SnO2 heterojunctions based chemiresistive-type sensor prepared by the thermal oxidation method shows much improved sensitivity and superior selectivity toward NO2 at 120 °C. Such impressive enhancements in the sensing performance can be attributed to the formation of SnSe2/SnO2 heterojunctions. The density functional theory (DFT) calculations revealed that there has lower adsorption energy and greater Bader charge value between the adsorbed NO2 and SnSe2/SnO2 heterojunction materials.