Magnetic and electrochemical properties of nickel oxide nanoparticles obtained by the reverse-micellar route

Abstract

Homogeneous nanoparticles of nickel oxide (NiO) of 25 nm size with narrow size distribution have been synthesized by the reverse-micellar route using CTAB (cetyltrimethyl ammonium bromide) as the surfactant. FTIR studies show a broad absorption around 405-415 cm⁻¹ and a weak absorption around 82 cm⁻¹ corresponding to a surface-active mode, which is indicative of the nanocrystalline nature of the oxide. Magnetization studies show nearly temperature independent paramagnetism with high magnetic moment compared to bulk NiO. Cyclic voltammetric (CV) studies show well-resolved anodic peak (Ni⁺²→Ni⁺³+e⁻;) at 0.45 V at a scan rate of 1 mV/s, which shifts to 0.47 V at the scan rate of 100 mV/s. The cathodic peak (Ni⁺³+e⁻→Ni⁺²) is also observed at 0.34 V, which remains at the same position irrespective of the sweep rate. The quasireversible nature of the voltammograms suggests the usefulness of these materials for ultracapacitor applications.