The synthesis of different metal oxide nanoparticles was carried out by the co-precipitation method . For the synthesis of ZnO and Fe2O3, ZnCl2•2H2O (1.36 g, 10.0 mmol, 1.0 eq) and FeCl3•6H2O (2.70 g, 9.98 mmol, 1.0 eq) were dissolved in 100 mL distilled water, respectively, and stirred at 80 °C for 30 min. The mixture was filtered, and ammonia solution (33%) was added dropwise until a pH of 10 was set. The nanoparticles precipitated as their respective hydroxides.