Encapsulation of silver nanocomposites and effects of stabilizers

Silver nanocomposites (AgCPs) have been synthesized by chemical reduction from silver nitrate and sodium borohydride in presence of two stabilizers. Starch and poly (vinyl) alcohol, PVA with its rich source of polyhydroxy groups has been exploited for the capping of AgCPs. The ageing of NaBH4 aqueous solution, molar ratios of the reactants, nature of the stabilizers, mixing order of NaBH4 as well as capping agents have great influence on the morphology of AgCPs. We used the iodometric titration to conform the encapsulation of AgCPs inside the helical structure of starch. The reversible nature of encapsulation has been studied by UV-vis spectroscopic technique. Well-dispersed with an approximate size of 10 nm and aggregated with an approximate size of 24-52 nm AgCPs were observed in the absence and presence of stabilizers (starch and PVA), respectively. TEM images indicates that the reaction mixture containing different order of reactants and stabilizers (PVA + NaBH4 + Ag+, PVA + Ag+ + NaBH4, starch + NaBH4 + Ag+ and starch + Ag+ + NaBH4) have different morphology. Added electrolytes (NaCl, NaBr and NaI) do not detached the Ag+ ions from the surface of AgNCs.