Biological synthesis of silver nanoparticles and their functional properties

A nanoparticle is defined as a small object between 1 and 100 nanometer in size and has a large surface to volume ratio. Silver nanoparticles (AgNPs) could be synthesized using various chemical and physical processes. However, these methods lead to hazardous by-products. In the recent past, AgNPs are produced by biological means. The size, shape and composition of AgNPs have significant effect on their biological applications. Aqueous solution of AgNP is not stable and rapidly undergoes agglomeration which is prevented by electrostatic or steric stabilization techniques with the help of capping or protective agents. The biologically synthesized nanoparticles are now favoured because it is a green alternative, mild, and does not need toxic chemicals and solvents. The scope of this review is to provide an overview of the various biological means researched for the synthesis of AgNPs, different techniques and chemicals used to develop stable solution, various techniques for their characterization, and their biological. The future research directions in this subject area are also dicussed.