PEG-directed microwave-assisted hydrothermal synthesis of spherical α-Ni(OH)2 and NiO architectures

Spherical α-Ni(OH)2 architectures were synthesized by the microwave-assisted hydrothermal technique using PEG-6000 as the surfactant. NiO architectures with similar morphology were obtained by a simple thermal decomposition process of the precursor α-Ni(OH)2 at 400 °C for 2 h and were confirmed by the X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) revealed that the synthesized spherical α-Ni(OH)2 and NiO architectures were composed of stacked lamellar sheets and transmission electron microscopy (TEM) showed that the α-Ni(OH)2 and NiO architectures were polycrystalline. The effect of the PEG-6000 concentration on particle size was investigated and it was found that the average particle size of α-Ni(OH)2 architectures decreased from 4.689 μm at CPEG=2 mmol L−1 to 3.907 μm at CPEG=4 mmol L−1, and the corresponding average particle size of NiO decreased from 2.818 μm to 2.492 μm. The optical absorption band gap of NiO architectures was determined to be about 2.7–3.0 eV by UV–vis spectroscopy.