“…As the reduction in size increases the surface area, thus, enhancing the photocatalytic activity of ZnO. A number of physical and chemical approaches are available to synthesize ZnO nanoparticles (ZnO NPs), for example, hydrothermal method [10], solvothermal method [11,12], microemulsion method [13], microwave method [14], thermal decomposition [15], precipitation [16], sol-gel [17], laser ablation [18] and sonochemical method [19]. Although these physical/chemical methods are effective to synthesize of ZnO NPs with different sizes and morphologies, but these methods are complex, and utilize hazardous organic solvents, toxic reagents, nonbiodegradable stabilizing agents and expensive instruments along with the tedious process control.…”