Conductometric chemical sensor based on individual CuO nanowires

CuO nanowires with high crystalline quality are synthesized via a simple thermal oxidation method. Charge conduction on individual nanowires under a transverse electric field exhibits an intrinsic p-type semiconducting behavior. Variations in signal transducer in different chemical gas environments are measured on individual CuO nanowire field effect transistors. They demonstrate good performance to both NO₂ and ethanol gasses. In particular, the nanowire chemical sensor reveals a reverse response to ethanol vapor under temperature variation. Experimental results and first-principles calculations indicate that ethanol is oxidized in air at high temperature, resulting in the production of CO₂ and H₂O. The strong H₂O adsorption leads to the reversal behavior, due to the electron transfer from H₂O molecules to the CuO surface.