673SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF ZINC OXIDE NANOPARTICLES SYNTHESIZED FROM Euphorbia hirta LThe study involved synthesis of Zinc Oxide nanoparticles using biological reducing agents. The aim was to compare the yield, nature and antimicrobial activity of nanoparticles synthesized using Euphorbia hirta L leaf extract. The phytochemical screening of plant leaf extract of E.hirta showed the presence of Alkaloids, Steroids, Flavanoids, Terpenoids, Tannins, glycosides and Reducing sugar which were found to be responsible for reduction and stabilization of zinc oxide nanoparticles. ZnO NP’s synthesized were characterized by FTIR and SEM. It was evident from SEM images that the size of the particles obtained by biological method is ranging from 100 -200nm. Antibacterial study was carried out on human bacterial and plant bacterial pathogens and their MIC values were determined. The antibacterial activity towards human bacterial and plant pathogen showed good sensitivity towards the green synthesized ZnO NP’s at all concentrations and maximum zone of inhibition occurred at the concentration of 30 μg/mL. Minimum Inhibitory concentrations of NPs against human pathogenic bacteria and plant bacterial pathogens, shows that all tested microorganisms were completely i nhibited at the concentration of 50 to 12.5 μg/ml of nano-ZnO. The antifungal activity of ZnO NPs against fungi shows that different concentration of ZnO nanoparticles caused significant inhibition in the spore germinationpoovizhijayarenu@gmail.comResearch6102015Zinc Oxide nanoparticles, biological method,FTIR,SEM,antibacterial study, antifungal activityPoovizhi J, Krishnaveni BAssistant Professor, Department of Biotechnology, Nandha Arts and Science College, Perundurai, Erode, India,Research Scholar, Department of Biotechnology, Maharaja Co-education Arts and Science College, Perundurai, Erode, India