Scope and challenges for green synthesis of functional nanoparticles

Nanoscience and nanotechnology are the most promising area of material science which interlaces various disciplines of science. This specific arena re-opens the imbibed properties of an already known system, e.g. metal, composite, etc., in a different manner so that the electron charge density waves termed as plasmons are getting generated and thereby perturbing the intensity of incident and reflected light in proportionate to the mass. Synthesis of nanoparticles through biological routes involves microorganisms, bacteria, fungi, plant/leaves extract, etc. The process can be carried out either in extracellular and/or intracellular mode. However, in general, bio-nanoparticles’ synthesis using plant extract tend to occur intracellularly and is kinetically fast compared to that of microbial synthesis. The bio-sources effectively act as a natural laboratory that accelerates the synthesis of variable nanoparticles, like metal, metal oxide, bimetallic oxide, etc. Plant crude extract contains novel secondary metabolites which are responsible for nanoparticle formation. In addition, such groups function as capping agents and thereby retaining the dimension of nanoparticles as required for a specific application. However, understanding the basic study of reaction kinetics for a particular plant extract/microbe-metal pair or influence of a specific plant extract on variable metals salts has not been undertaken precisely. The significance of such a study on fundamental aspects enables the selection of appropriate plant extract and leads to the tailoring of the morphology of the resultant nanoparticle. The primary task, however, is to determine and analyse the role of the exact constituent required for reducing and capping action. The challenge lies in whether certain bio-compounds need to be eliminated as per the requisite of bio-synthesis. The chapter herein provides a comprehensive study on the plants and microbe-mediated synthesis of functional nanoparticles, the associated parameters and their application. Finally, the significance of green synthesis toward toxicogenomics and the involved challenges are discussed in terms of the mechanistic approach.