Microwave synthesis, optical properties and surface area studies of NiO nanoparticles

• NiO nanoparticles have been prepared by microwave assisted method at different pH.
• Monophasic and highly crystalline NiO nanoparticles were established by using sophisticated techniques.
• Optical band gap increases on increasing the amount of NaOH.
• High surface areas in the range of 33.1–39.8 m2/g have been achieved.

We report here the synthesis of nickel oxide (NiO) nanoparticles by microwave-assisted method, using a common precipitating agent followed by calcination at 400 °C. The effect of the microwave and pH on the crystallite size, morphology, structure, energy band gap and surface area of NiO have been investigated by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV–vis) and BET surface area studies. It was observed that on increasing the volume of NaOH, the optical band gap energy (2.85–2.95 eV) and specific surface area (33.1–39.8 m2/g) increases, however the average particles size decreases (16.5–14 nm).