|Absar Ahmad1, Priyabrata Mukherjee2, Deendayal Mandal2, Satyajyoti Senapati2, Mohammad I. Khan1, Murali Sastry3, and Rajiv Kumar2
1Biochemical Sciences, 2Catalysis, and 3Materials Chemistry Divisions, National Chemical Laboratory, Pune-411 008, Maharashtra, India
Development of green chemistry protocols for the synthesis of inorganic nanoparticles is a problem of topical interest in nanotechnology. In this paper, we report on the development of a new biological method for the synthesis of gold nanoparticles using fungi. Exposure of the fungal biomass to aqueous AuCl4- ions results in either the intracellular or extra-cellular reduction of the metal ions depending on whether the fungus used is Verticillium or Fusarium oxysporum respectively. The gold nanoparticles exhibit tolerable monodispersity (size in the range 5-20 nm) and in the case of particles synthesized extra-cellularly, excellent long term stability as well. The reduction of the metal ions is believed to occur through an enzymatic process thus opening up the exciting possibility of extending the fungal-based method to the synthesis of nanoparticles over a range of chemical compositions in a rational manner. The metal ions were not toxic to the fungal cells and they continued to multiply after biosynthesis of the gold nanoparticles.