Heterostructural CuO–ZnO Nanocomposites: A Highly Selective Chemical and Electrochemical NO2 Sensor

Abstract A simple one-step chemical method is employed for the successful synthesis of CuO(50%)–ZnO(50%) nanocomposites (NCs) and investigation of their gas sensing properties. The X-ray diffraction studies revealed that these CuO–ZnO NCs display a hexagonal wurtzite-type crystal structure. The average width of 50–100 nm and length of 200–600 nm of the NCs were confirmed by transmission electron microscopic images, and the 1:1 proportion of Cu and Zn composition was confirmed by energy-dispersive spectra, i.e., CuO(50%)–ZnO(50%) NC studies. The CuO(50%)–ZnO(50%) NCs exhibit superior gas sensing performance with outstanding selectivity toward NO2 gas at a working temperature of 200 °C. Moreover, these NCs were used for the indirect evaluation of NO2 via electrochemical detection of NO2– (as NO2 converts into NO2– once it reacts with moisture, resulting into acid rain, i.e., indirect evaluation of NO2). As compared with other known modified electrodes, CuO(50%)–ZnO(50%) NCs show an apparent oxidation of NO2– with a larger peak current for a wider linear range of nitrite concentration from 20 to 100 mM. We thus demonstrate that the as-synthesized CuO(50%)–ZnO(50%) NCs act as a promising low-cost NO2 sensor and further confirm their potential toward tunable gas sensors (electrochemical and solid state) (Scheme 1).