A review on plant mediated synthesis of silver nanoparticles as a greener approach

Abstract

Metal nanoparticles are used in all phases of science, including medical fields. They still seduce scientists to explore new dimensions for their respective value, which is usually attributed to their corresponding small sizes. Among the other metallic nanoparticles, silver nanoparticles (AgNPs) aroused a keen interest. The chemical methods used to synthesize AgNPs involve reducing and stabilizing agents, which subsequently become risks to the environment. For these reasons, the green synthesis of AgNPs is a significant area of interest. Among the variety of biological molecules used to synthesize AgNPs, the biological molecules obtained in the form of plant extracts are superior to others because of the ease of handling and the reduction of costs. Many plant parts have been used to synthesize AgNPs such as whole plants, leaves, seeds, bark etc. The synthesis of AgNPs by plant extracts is due to the presence of a large amount of organic chemicals such as carbohydrates, fats, proteins, enzymes and coenzymes, phenolic flavonoids, terpenoids, alkaloids, gum, etc., capable of donating an electron to reduce Ag+ ions to Ag0. The active ingredient responsible for the reduction of Ag+ ions varies depending on the extract used. The size and size distribution of AgNPs synthesized with plant extracts depend on plant extract concentration, silver nitrate concentration, pH of the medium, incubation time and temperature. These factors can be modified to refine the properties of AgNPs. Almost all of these conditions have an optimal value to obtain smaller size AgNPs with a narrow size distribution.