“…To date, a wide variety of ZnO nanoparticle preparation methods have been put forward, from physicochemical synthesis to green biogenic synthesis. Initially, physicochemical synthesis was the common preparation means, which mainly includes the methods of precipitation [16][17][18][19][20][21], electrochemical deposition [22][23][24], hydrothermal synthesis [25][26][27][28][29][30][31][32], sol-gel process [33,34], solid state reaction [35,36], chemical vapor synthesis [37], gel combustion [38], microemulsion [39], solvothermal synthesis [40][41][42], spray pyrolysis [43], sputtering [44][45][46], sonication [47,48], microwave [49], thermal evaporation [50][51][52] and so on. Each of these methods has its own advantages.…”