Tuning the structural, optical and electrical properties of NiO nanoparticles prepared by wet chemical route

Unsubstituted NiO and its derivatives with Cu⁺² and Zn⁺² were synthesized by co-precipitation method. Structural characterizations were done by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopic and scanning electron microscopic (SEM) techniques. XRD results confirmed the cubic phase of NiO and all its derivatives. The crystallite size for all compositions of NiO nanoparticles was found 10–20 nm. XRD data was also used to calculate other physical parameters like lattice constant, unit cell volume, micro-strain, dislocation density, X-rays density and porosity. It was found that the synthesized nanomaterials have single phase. XRD data was supported by FTIR results. Morphological studies confirmed the spherical nature of NiO particles with size <100 nm. Optical characterization was done by UV–Visible spectroscopic technique. The indirect band gap energy of NiO was ∼3.42 eV and band gap tuning was noticed in the case of transition metal cations substitution. Zn⁺² substituted NiO nano-crystallites exhibited lowest band gap energy (3.06 eV). The nanoparticles with lower band gap may have better photocatalytic and other related properties. DC electrical properties were recorded by two probe technique. An increase in electrical conductivity was noticed as a result of divalent transition metal cations substitution. Cu⁺² substituted NiO exhibited highest conductivity due to more conductive inherent nature of copper. Thus the Dc conductivity values for various compositions of NiO nanoparticles were observed in range 4.39 × 10^-10 to 4.50 × 10^-8 Scm^-1.