Engineering intrinsic defects in CuO NWs through laser irradiation: Oxygen vs copper vacancies

Defect engineering in CuO nanomaterials has been extensively investigated because this technology can greatly improve the performance of CuO components in a variety of applications. While many previous studies have focused on the role of oxygen vacancies, ( V O ), in CuO, little attention has been paid to that of copper vacancy centers, ( V Cu ), since the presence of these defects is often difficult to quantify. As a result, the specific roles played by these different vacancy centers on the measured properties of CuO have not been studied systematically. In this article, we show that the concentration of both V O and V Cu centers can be engineered in CuO NWs through nanosecond (ns) laser irradiation. The identification of these vacancies was achieved through X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Absorption spectra and diffuse reflectance spectra of laser-processed samples show that increasing the concentration of V O centers enhances the optical absorption of CuO in the visible region. Data obtained from Mott-Schottky and Nyquist plots, together with measured I-V characteristics, show that laser-induced V Cu centers can enhance the carrier concentration in CuO NWs. These data, in addition to O 1s XPS spectra on laser-processed and unprocessed samples as well as cyclic voltammetry, also indicate that laser irradiation can significantly enhance surface adsorption for applications in photo-electrochemistry and electrochemistry. To demonstrate the efficacy of this laser irradiation technique for potential electrochemistry applications, the role of laser-induced V Cu and V O defect centers in CuO NWs on the non-enzymatic sensing of glucose has also been investigated. We find that the introduction of V O centers in CuO NWs enhances the current response for glucose sensing while the presence of V Cu centers inhibits this response.