A method is disclosed for fabrication of NiO nanoparticles and NiO chip-like nanoflakes by solvothermal technique. Mixed organic alcohols were used as solvent to make a homogenous solution from a nickel containing salt (or complex) for production of NiO nanoparticles and chip-like nanoflakes. The solution was heated in a sealed flask sitting inside a warm furnace. The precipitate was filtered, rinsed, dried and calcined to produce nanoparticles or nanoflakes. The size of the particles was controllable by heating time and temperature. Similar procedures were used for production of both nanostructures except hydrogen peroxide addition to the initial solution for NiO chip-like nanoflakes fabrication.