Plant Extract as Reducing Agent in Synthesis of Metallic Nanoparticles: A Review

The aim of this paper is to discuss on the roles of plant extract in the synthesis of metallic nanoparticles. Recently, green technology through biosynthesis method has drawn great attention compared to the physical and chemical method. Biosynthesis was found to be more energy efficient and able to eliminate the use of hazardous chemicals. The biosynthesis using plant extract has several advantages since the use of microorganism required stringent control on cell culture. Furthermore, the reaction rate is much faster as compared to that of the microorganism methods. The important compounds in the plant extract are hydroxyl and carbonyl groups which act as reducing agent as well as stabilizing agent. Several studies have been carried out to optimize the extraction of these compounds such as plant drying technique, extraction temperature and type of extraction's solvent. The common method used to quantify the concentration of reducing agents in the extract is through Folin-Ciocalteu method. Utilization of plant extract not only capable of producing well dispersed monometallic nanoparticles, but also bimetallic nanoparticles. Previous studies revealed that concentration of plant extract has significant effect on particle size and shape as well as particle distribution.