Vertical CuO nanowires array electrodes: Visible light sensitive photoelectrochemical biosensor of ethanol detection

Abstract

Photoelectrochemical (PEC) sensing using visible light has attracted great attention for high sensitivity with low undesired background noise. A CuO electrode with nanowires on Cu foil was synthesized by thermal oxidation and the devices was used to explore the PEC sensing for ethanol detection under visible light. The morphology, composition, optical, and PEC properties of CuO nanowires have been systematically investigated. The results showed that the CuO nanowires were present on the top surface of specimens with single phase and the thick interface layer were made of Cu2O between CuO nanowires and Cu foil substrate. The CuO nanowires on surface contained two types of nanowire (bend CuO Nws and vertical CuO Nws). With the temperature increasing, the Nws of first type decreased, and the Nws of second type started to increase. When the Cu foil were annealed at 700 °C, densely bundled CuO Nws array was vertically fabricated on the foil. The band gaps of CuO nanowires annealing at 400 °C, 500 °C, 600 °C, and 700 °C, were 1.715, 1.714, 1.698, 1.691 eV, indicating that CuO nanowires annealing at 700 °C can obtain the highest photoreponse. The photocurrent of the vertical CuO nanowires array annealing at 700 °C were calculated with 668 μA cm−2 about 2-fold, 6-fold and 10-fold higher than that to CuO nanowires annealing at 600 °C, 500 °C and 400 °C, respectively. Combing with the morphology of CuO nanowires annealing at different temperature, the vertivally-aligned nanowires array at 700°Cwas attractive than others. This vertical CuO nanowires device prepared at 700 °C is visible-light irradiation and shows the fast photoresponse, present a detection limit of 23.2 nM, which is much lower than those with the similar configurations reported previously. It is probable that the vertical CuO nanowires array may be applied as the proposed PEC sensor to determine ethanol in further.