Prominent Reducing Gas-Sensing Performances of n-SnO₂ Nanowires by Local Creation of p–n Heterojunctions by Functionalization with p-Cr₂O₃ Nanoparticles

A novel approach to improving the reducing gas-sensing properties of n-type nanowires (NWs), by locally creating p-n heterojunctions with p-type nanoparticles (NPs), is proposed. As a model system, this work investigates the sensing behaviors of n-SnO2 NWs functionalized with p-Cr2O3 NPs. Herein, n-SnO2 NWs demonstrate greatly improved reducing gas-sensing performance when functionalized with p-Cr2O3 NPs. Conversely, such functionalization deteriorates the oxidizing gas-sensing properties of n-SnO2 NWs. These phenomena are closely related to the local suppression of the conduction channel of n-type NWs, in the radial direction, beneath the p-n heterojunction by the flow of charge carriers. The approach used in this work can be used to fabricate sensitive reducing-gas sensors based on n-type NWs.