Colloidal silver nanoparticle solution was prepared using the
following previously described method. The bacterial culture,Salmonella typhirium was obtained from Microbiology Laboratory,
Tehran University, Tehran, Iran. Muller-Hinton broth
(MHB) was prepared, sterilized, and inoculated with a fresh
growth Salmonella typhirium. The cultured flasks were incubated
at 37 C for 24 h. After incubation, the cells were separated
from the culture broth by centrifugation (5000 rpm) for
15 min and washed two times with deionized water to obtain
some wet weight of cells (biomass).
The harvested cells were then resuspended in 50 mL of
deionized water for 24 h. The cells were then removed by a
0.22-mm Durapore membrane filter (PVDF), and the filtrate
obtained was extract of cell.
This solution prepared was a colorless liquid and was used
for the reduction of silver sulfate. The filtrate was added separately
to the reaction vessel containing silver sulfate at a concentration
of 0.0005 M. The reaction between this filtrate
and Ag+ ions was carried out in bright conditions for
30 min. The products were characterized by Uv–vis spectroscopy,
transmission electron microscopy (TEM), and dynamic
light scattering (DLS) (see Fig. 1).