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In the present work the fungus Helminthosporium tetramera used for the extracellular biosynthesis of
gold nanoparticles. The cell filtrate of H. tetramera reacted with AuCl¯ 4 ions, resulting formation of gold
nanoparticles within 12 hours. The gold nanoparticles were characterized by Visual analysis, UV-Vis
absorption spectroscopy and Transmission electron microscopy (TEM). The extracellular gold
nanoparticles exhibited maximum absorbance at 550 nm in UV-Vis spectroscopy. UV-spectral reading
clearly showed that as the incubation period increased the spectral absorbance also increased and stable
after 72 hr. This stability of gold nanoparticles also constant after two month. TEM showed polydisperse
spherical and occasionally triangular nanoparticles in the size range from 8-50 nm. Biological approach
using the fungi is a novel way towards the safe, cost effective and ecofriendly method for the synthesis of
gold nanoparticles is gaining importance in the field of nanotechnology.
Keywords: Helminthosporium tetramera, gold nanoparticles, UV-Vis absorption spectroscopy,
Transmission electron microscopy (TEM)