2.1. Preparation of the Ag NPs/CS-Starch bio-composite
At the outset the CS/starch mixed hydrogel was prepared by sonicating a
mixture of chitosan (98% NH2) and starch (0.5 g each)
in 100 mL of 1% (v/v) acetic acid followed by stirring overnight at
room temperature. Prior to addition of Ag precursor, it was then made
alkaline to pH 9 by adding dilute NaOH. An aqueous solution of
AgNO3 (30 mg in 10 mL) was added very slowly and
drop-wise to the hydrogel under ambient conditions and stirred for 2 h
maintaining a temperature of 100 ºC. Soon, the solution color changed
from colorless to grey, an indication of Ag NP formation. The
as-synthesized Ag NPs/CS-Starch bio-composite was retrieved by
centrifugation and washed well with DI-water followed by drying at 40
ºC.