Three-Dimensional Integration of CuO-Si Hierarchical Nanowires for Electrochemical Detection of N₂H₄

Abstract

Nanowire-based heterostructures (HSs) are on the focal point, because of the exceptional accessibility of active sites to stimulate catalytic reactions and, consequently, the performance of devices fabricated from them. However, the integration of CuO and Si nanowires (NWs) into a three-dimensional (3-D) hierarchical (3-D CuO-Si HNW) HS presents a massive challenge, because of agglomeration, which leads to a loss of active sites. Herein, we present the first report of 3-D CuO-Si HNW synthesis, in which Si NWs were fabricated by metal-assisted chemical etching and CuO NWs were obtained by using an alkaline wet chemical process in only 25 s, followed by thermal annealing at 180 °C. Field-emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy, Raman analysis, and X-ray photoelectron spectroscopy revealed the formation of uniformly and well-integrated CuO and Si NWs. The precisely engineered 3-D CuO-Si HNW were utilized to fabricate electrochemical sensors for the detection of N2H4. Electrochemical study revealed high sensitivity (800 μA/(mM cm2)), a low limit of detection (0.9620 μM), and a limit of quantification of 3.2060 μM, because of the synergistic effect of CuO and Si NWs integrated into a single HS. Besides, the long-term stability, reproducibility, and excellent selectivity showed the potential of 3-D CuO-Si HNWs for commercial N2H4 sensing in the future.