**6. Biosynthesis of gold (Au) nanoparticles**

Water is the most accessible and cheapest solvent on earth. Since the advent of nanotechnology, water has been used as a solvent for the synthesis of various NPs [62]. Most research on the biosynthesis of NPs was done from angiosperms using plant extracts, mainly in gold NPs synthesis. Mechanisms of metal depletion and stabilization have also been explored by phytochemicals of plants. They can be helpful in forming NPs [63]. Plant extracts showed the green synthesized NPs to be effective in ions reduction. High variability suggests that this may be one of the reasons that produced large amounts of Au NPs using plant extract (**Table 1**) [64].
