Bag et al. Int. J. Res. Chem. Environ. Vol.3 Issue 2 April 2013(128-135) 128 International Journal of Research in Chemistry and Environment Vol. 3 Issue 2 April 2013(128-135) ISSN 2248-9649 Research Paper Ocimum sanctum (Tulasi) Stem Extract Mediated Size Controlled Green Synthesis of Polyshaped Gold Nanoparticles and Its Application in Catalysis Paul Koushik and * Bag Braja Gopal Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721102, West Bengal, INDIA Available online at: www.ijrce.org (Received 22 nd December 2012, Accepted 03 rd February 2013) Abstract: The stem extract of Ocimum sanctum, a well known aromatic herb of great medicinal importance, has been used for the synthesis of gold nanoparticles at room temperature under very mild condition without any extra stabilizing or capping agents. The size of the nanoparticles could be controlled by varying the concentration of the stem extract. The gold nanoparticles were characterized by Surface Plasmon Resonance Spectroscopy, HRTEM, Energy dispersive X-ray spectroscopy and X-Ray diffraction studies. The catalytic activity of the synthesized gold nanoparticles has also been demonstrated. Introduction Gold nanoparticles (AuNPs) with high surface to volume ratio posses unique optoelectronic properties. Because of their biocompatibility, stability, and oxidation resistance, AuNPs have attracted great attention over other nanomaterials [1] . AuNPs exhibit different colors depending upon their size, shape, surrounding chemical environment and degree of aggregation and have found applications in biodiagnostics, [2-8] drug delivery, medicine, biotechnology, catalysis, [9] electronics, [10-14] etc. Various methods have been developed over the years for the synthesis of AuNPs. Among these synthetic methods, the solution phase reductive synthesis of AuNPs using plant extracts as the reducing agent in water has gained significance in recent years because of the following reasons: (i) plant based chemicals are renewable chemicals in contrast petroleum based chemicals that are depleting fast, [15] (ii) the aqueous medium is more eco-friendly, (iii) the reactions do not require heat or ultraviolet radiation treatment, (iv) the method requires no external stabilizing agent as the plant extract acts both as a