International Journal of Basic and Applied Biology Print ISSN: 2349 – 5820; Online ISSN: 2349 – 5839; Volume. 2 No. 2, November 2014. pp. 55 – 59 © Krishi Sanskriti Publications http://www.krishisanskriti.org/ijbab.html Biological synthesis of silver nanoparticles by Neptunia oleraceae Sumita Singha 1 , Kundal Neog 2 , Partha Pratim Kalita 3 , Nayan Talukdar 4 , Manash Pratim Sarma 5 Department of Biochemistry Assam down Town University, Guwahati, Assam Abstract: Introduction: Green synthesis of nanoparticles is a novel way to synthesize nanoparticles by using biological sources. It is gaining attention due to its cost effectiveness, eco- friendly nature and large scale production possibilities. Again silver nanoparticles are of special interest to researcher due to its evocative physical and chemical properties. Aim: The study was designed to synthesize silver nanoparticles using the aqueous solution of Neptunia oleraceae fresh leaf extract and AgNO3. Materials and Methods: A fixed ratio of plant extract to metal ion was prepared and the colour change was observed that proved the formation of nanoparticles. The silver nanoparticles synthesized were confirmed by their change of colour to dark brown due to the phenomenon of surface plasmon resonance. The characterization was done by UV-VIS spectroscopy and X- RAY diffraction analysis. The size of the silver crystallites has been estimated using Debye Scherer formula. Stability of the nanoparticles under different conditions was studied and the phytochemicals responsible for the reduction of silver nanoparticles were also tested qualitatively. SEM was done to confirm the size and presence of the nanoparticles. Results: The size of the silver nanoparticles was found to be 8.35 nm, which confirms the formation of nanocrystalline silver. Again the shape of the nanoparticles was spherical and appeared in cluster. The biological synthesis of silver nanoparticles was possible by using the plant extract Neptunia oleraceae. Conclusion: The biological approach is the need of the hour in the field of nanotechnology and the advancement in India in this aspect is still in its infancy. Also, the antimicrobial activity of the silver nanoparticles synthesized by the current study needs to be carried out along with FTIR analysis to know the responsible phytochemicals. Keywords: biosynthesis, silvernanoparticles, Neptunia oleraceae, UV-VIS Spectrophotometer, XRAY Diffraction, SEM. 1. INTRODUCTION: Nanoparticles have been extensively used due to their immense application in diverse fields. Gold, carbon, iron, zinc, silver nanoparticles are of special interest as they have been found to show promising roles in different biological burning issues. In recent years, the concepts of nanotechnology are being applied in various fields’ like biotechnology, physics, chemistry, material sciences, engineering, medicine etc. Nanoparticles can be synthesized by various physical and chemical methods, but such methods encounters many problems like expensive reagent, hazardous reaction condition, tedious and sophisticated techniques to isolate nanoparticles etc. Moreover, these methods are also time consuming. Hence, cost effective, cheap, rapid and eco- friendly protocols to synthesize nanoparticles are the need of the hour. The impact of nanotechnology is growing all spheres of human life. The biological processes leading to the formation of nano scale inorganic material is strongly taken as an eco- friendly alternative to the other methods which suffers various drawbacks. Nano materials can be used as novel antimicrobial agents due to their unique properties which include attaching with the microbes and permeating their cells thereby destroying it completely. The biosynthesis of silver particles via green chemistry route and their effectiveness as antimicrobial agents has been immensely emphasized. Moreover, the biosynthetic method that uses plant extracts has attracted the scientists from different fields due to its simplicity, and environmentally-friendly nature as it does not involve the use of harsh, toxic and expensive chemicals. Biosynthesis would have greater commercial acceptance if the nanoparticles could be synthesized economically on a large scale in a faster rate. Presently, bacteria, fungi and algae are being used for the synthesis of nanoparticles but the green method which is using plant extract reduces the cost. Also it does not involve any special culture preparation and isolation techniques.