RESEARCH PAPER Biosynthesis of silver nanoparticles using Ocimum sanctum (Tulsi) leaf extract and screening its antimicrobial activity Garima Singhal • Riju Bhavesh • Kunal Kasariya • Ashish Ranjan Sharma • Rajendra Pal Singh Received: 9 June 2010 / Accepted: 20 December 2010 / Published online: 7 January 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Development of green nanotechnology is generating interest of researchers toward ecofriendly biosynthesis of nanoparticles. In this study, biosyn- thesis of stable silver nanoparticles was done using Tulsi (Ocimum sanctum) leaf extract. These biosyn- thesized nanoparticles were characterized with the help of UV–vis spectrophotometer, Atomic Absorp- tion Spectroscopy (AAS), Dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Transmission electron microscopy (TEM). Stability of bioreduced silver nanoparticles was analyzed using UV–vis absorption spectra, and their antimicrobial activity was screened against both gram-negative and gram- positive microorganisms. It was observed that O. sanctum leaf extract can reduce silver ions into silver nanoparticles within 8 min of reaction time. Thus, this method can be used for rapid and ecofriendly biosynthesis of stable silver nanoparticles of size range 4–30 nm possessing antimicrobial activity suggesting their possible application in medical industry. Keywords Ocimum sanctum Á Silver nanoparticles Á XRD Á AAS Á DLS Á FTIR Á TEM Á Antimicrobial activity Á Nanomedicine Introduction Metal nanoparticles have a high specific surface area and a high fraction of surface atoms. Because of the unique physicochemical characteristics of nanoparti- cles, including catalytic activity, optical properties, electronic properties, antibacterial properties, and magnetic properties (Catauro et al. 2005; Crabtree et al. 2003; Krolikowska et al. 2003; Zhao and Stevens 1998), they are gaining the interest of scientist for their novel methods of synthesis. Silver is well known for possessing an inhibitory effect toward many bacterial strains and microorganisms commonly present in medical and industrial pro- cesses (Jiang et al. 2004). In medicines, silver and silver nanoparticles have a wide application including skin ointments and creams containing silver to prevent infection of burns and open wounds (Duran et al. 2005), medical devices and implants prepared with silver-impregnated polymers (Becker 1999; Silver 2003). In textile industry, silver-embedded fabrics are now used in sporting equipment (Klaus et al. 1999). Nanoparticles can be synthesized using various approaches including chemical, physical, and biolog- ical. Although chemical method of synthesis requires G. Singhal (&) Á R. Bhavesh Á K. Kasariya Á R. P. Singh Amity Institute of Nanotechnology, Amity University Uttar Pradesh, Noida, Uttar Pradesh, India e-mail: microbio.garima@gmail.com A. R. Sharma Infectious Disease Medical Research Center, College of Medicine, Hallym University, Chuncheon, Gangwan Do, South Korea 123 J Nanopart Res (2011) 13:2981–2988 DOI 10.1007/s11051-010-0193-y