The MoS2/ZnO p-n heterostructure arrays for ultrasensitive ppb-level self-supporting NO2 gas sensors under UV irradiation

Abstract

Light irradiation has emerged as a promising strategy to promote low operating temperatures of metal oxides semiconductors gas sensors. Traditional sensors have high operating temperatures, low electron-hole separation, and low gas response. Therefore, MoS₂/ZnO heterostructure arrays were synthesized based on ITO conductive glass by hydrothermal and calcination methods as self-supporting sensors. Self-supporting sensors overcome limitations of traditional sensor fabrication. The successful preparation of self-supporting sensors is confirmed by a series of tests. The response of the gas sensor is determined as R_g/R_a or R_a/R_g (R_a and R_g indicate the resistance of the sensor in air and test gases). Regarding the gas-sensing performance, MoS₂/ZnO-20 self-supporting sensor under UV irradiation exhibits ultrahigh response of 1088.43 to 10 ppm NO₂ at 80 °C, which is 47 times higher than pure ZnO (23.21). Furthermore, operating temperature under UV irradiation is reduced by up to 60 °C. Additionally, MoS₂/ZnO-20 self-supporting sensor demonstrates rapid response/recovery time (100/3 s), high selectivity, and ultralow theoretical detection limit (10.37 ppb). The p-n charge separation mechanism is employed to elucidate sensing mechanism of MoS₂/ZnO self-supporting sensor for NO₂ under UV irradiation. The efficient photogenerated carrier separation efficiency, large surface area, and the presence of multiple heterostructures are responsible for the high gas-sensing performance of MoS₂/ZnO self-supporting sensor. Therefore, this study offers insights into the fabrication of ultrasensitive self-supporting sensors for low-temperature detection of NO₂ under light irradiation.

Keywords: MoS(2); P-n heterostructure; Self-supporting sensors; UV irradiation; ZnO.