Sensitive, selective and low detection limit of NO2 gas sensor based on Cu/ZnO/rGO nanocomposites

ZnO and copper-doped ZnO nanocomposites with 1, 3, 5 and 7 wt% copper were synthesized using a simple co-precipitation method. Further, GO was synthesized by modified Hummer’s method and the formation of Cu/ZnO/rGO composites was carried out by using chemical route. The structural properties of the synthesized nanocomposites were investigated using X-ray diffraction spectroscopy that revealed a hexagonal wurtzite structure of ZnO which remained intact even after incorporation of Cu2+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{2+}$$\end{document} ions into ZnO lattice. Optical studies revealed increased defect density and oxygen vacancies in the ZnO structure that can be utilized effectively for NO2 sensing application. Moreover, 5 wt% Cu/ZnO (ZC5) exhibited a nanorod-like morphology. Furthermore, ZC5 showed excellent sensing response (SR = 5) towards NO2 with lower detection limit (LOD) of 1 ppm which further improved due to rGO incorporation (ZCR2) (SR = 6.79) at 200 °C. The synthesized nanocomposites also exhibited very good stability ≈\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\approx$$\end{document} 90 and 75%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} for ZC5 and ZCR2 nanocomposites, respectively, over 30 days. Thus, ZC5 and ZCR2 can potentially be utilized as effective NO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document} gas sensors.