Figure 4.

Methods for AgNPs synthesis. (1) Physical: In this method, the bulk material, such as silver foil, is broken down utilizing high energy and material resources; however, the produced AgNPs lack uniform size and shape, the most used methods comprise evaporation-condensation and laser ablation; (2) Chemical: This process commonly involves the metal ionic sources being reduced by a reducing agent and stabilized by a capping agent to produce AgNPs of defined size and shape. However, these use toxic chemicals such as sodium borohydride; (3) Biological: These methods either use microbes or plant extracts to carry out bio-reduction of ionic solutions as well as use biological molecules to stabilize the final AgNPs to produce defined shape/size NPs, without the use of hazardous chemicals [18].