Synthesis, structural, magnetic and NO2 gas sensing property of CuO nanoparticles

Abstract Cupric oxide (CuO) nanoparticles are synthesized by the oxidation of Cu/Cu2O obtained by the chemical reduction of Cu2+ ions with ascorbic acid. XRD pattern confirmed the formation of CuO, and FE-SEM image shows the clusters consisting of 25–30 nm sized particles. The band gap energy (3.7 eV) from optical absorption spectra is blue shifted to that of bulk values. The Neel temperature, TN ≈ 230 K for paramagnetic to antiferromagnetic transition was clearly seen. The magnetic hysteresis loops at 5 K showed weak ferromagnetic behavior. Based on the dc electrical conductivity (300–500 K), the apparent activation energy was 0.36 eV. The NO2 gas sensing property of CuO was reasonably good in the temperature range of 200–300 °C, and the sensitivity increased with an increase in gas concentration but the effect of temperature is marginal.