Effect of Treatment time on Synthesis of silver Nanoparticles using Chitosan and its stability during Freezing

Chitosan, a bioactive polysaccharide extracted from shell fish waste can act as both reducing and stabilising agent for the synthesis of metal nanoparticles. In the present study, silver nanoparticles (AgNPs) were synthesised using chitosan with thermal treatment. Two treatment times studied were 15 and 30 min. The formation of chitosan silver nanocomposites resulted in change of visible colour from colourless to yellow in both samples. The characterisation was done using UVvisible spectroscopy. Both samples exhibited the surface plasmonic peak at ~420 nm. The absorbance and wavelength of peak maxima increased with increase in treatment time. The full width half wavelength of the samples reduced with increased treatment time. Hence the polydispersity of silver nanoparticles can be modified using the time of thermal treatment. The samples were studied for the changes under frozen conditions and both samples were found to be stable under storage at -18±2oC.