Highly Selective Hybrid InSe-Graphene for NO₂ Gas Sensing with High Humidity Tolerance

p-type pristine InSe, pristine graphene, and the corresponding hybrid InSe-graphene gas sensor that is highly selective to NO₂ have been developed. These materials are produced at an environmentally friendly temperature of 35 °C by the Liquid Phase Exfoliation (LPE) technique. Then their deposition was performed on alumina transducers for achieving chemoresistive gas sensors. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and Raman spectroscopy were used to analyze the materials. The multilayered crystalline structure is revealed by HRTEM. Studies on gas-sensing properties showed that the response of the hybrid InSe-graphene sensor to 1 ppm of NO₂ is three times higher than the one of the pristine graphene sensor, whereas the pristine InSe sensor was not responsive. While under dry conditions, the response to NO₂ (1 ppb) was 3.41%, under humid conditions (RH 50%), the responsiveness was significantly increased to 6.16% and to 14.42% for sensors operated at 150 and 250 °C, respectively.