Extracellular synthesis of silver nanoparticles using culture supernatant of Aspergillus Niger

Abstract

A key aspect of nanotechnology concerns the development of reliable experimental protocols
for the synthesis of nanomaterials over a range of chemical compositions, sizes, and high
monodispersity. The impetus of synthesis has shifted from physical and chemical processes towards
‘green’ chemistry and bioprocesses .The use of microorganisms in the synthesis of nanoparticles is a
relatively recent, new, and exciting area of research with considerable potential for development .
Microorganisms like yeast, bacteria, and fungi play an important role in the remediation of toxic metals
by reducing them under stress conditions which forms the basis for the use of microorganisms in the
biosynthesis of nanoparticles
Material and methods:The biosynthesis of silver nanoparticles by A. niger isolated was carried
out in the present study. The fungal filtrate was treated with silver ions (AgNO3) in dark at 25 C, which
showed a change in colour from yellow to dark-brown.The colour change of the medium was monitored
by visual observation ,and the absorption spectrum of fungal filtrate was scanned in the range of 200–
800 nm by using UV-Visible spectrophotometer .The UVVisible spectra recorded after 24 hours of
incubation of the fungal filtrate and silver ions showed increase in absorption centered at 400
nm.Determination of size and morphology of the silver nanoparticle was determined from the bright
field images by TEM The protein content in the silver nanoparticles was also corroborated by the bright
field images of the silver nanoparticles and by ESI map for S atoms (from the protein).
conclusion:In this study, it has been demonstrated that Aspergillus niger is capable ofproducing
silver nanoparticales extracellularly and the silver nanoparticales arequite stable in solution.. SEM
suggests that aggregated particles due to the capping agent.