Fig. 2

Schematic representation of intracellular synthesis mechanisms of ZnO NPs. The intracellular mechanisms involve the transportation of metal ions into the cell wall by electrostatic attraction. The metal ions are reduced to a metal atom by the enzymes found in the cell wall and then initiate the nuclei growth to form NPs in periplasmic space and cytoplasm. The intracellular synthesis requires ultrasonication to obtain the purified NPs