“…To explore the characteristics of both, n-and p-type semiconductor nanomaterials, MOS sensors have recently been made using p-n heterojunction nanostructures, which employ composites of p-and n-type semiconductors as functional materials to improve sensing characteristics. Thus, several p-n heterojunction nanostructure-based MOS sensors were fabricated and reported in the literature, for instance, SnO2/Co3O4, CuO/ZnO, NiO/ZnO, CuO/CuFe2O4, SnO2/CuO, WO3/CuO, and so on [22][23][24][25][26][27][28][29][30][38][39][40][41]. CuO/ZnO nanoparticles demonstrated good selectivity towards H2S gases among heterojunction nanomaterial-based MOS sensors due to the fact that the electron depletion layer on the surface of particles is enlarged by p-n heterojunctions, and the separation of electron-hole carriers increases the active sites of gas-solid reactions on the surface of the material [5][6][7][8]27].…”