Ethanol Gas Sensing Mechanism in ZnO Nanowires: An ab Initio Study

Solid-state nanostructured gas sensors based on oxide materials play an important role in environmental monitoring, chemical process control, and personal safety. Yet, the underlying operating mechanism is still not well comprehended, while a deeper understanding would possibly lead to the engineering of sensing elements with enhanced sensitivities. Here we present ab initio density functional theory calculations that provide a comprehensive description of the ethanol sensing mechanism for ZnO nanowires: our results reveal that the competitive adsorption at the nanostructure surfaces between the analyte and the oxygen molecules present in the atmosphere induces a switching in surface conductance between semiconducting and conducting behavior that is related to the ethanol concentration and can be detected electronically, thus disclosing the sensing mechanism.