Facile synthesis of chitosan-gold nanocomposite and its application for exclusively sensitive detection of Ag+ ions

This article reported a simple, green approach for preparing uniform gold nanoparticles (AuNPs) with chitosan as reducing and stabilizing agent in aqueous media. Furthermore, a simple, rapid, sensitive colorimetric method was developed for the detection of Ag+ ions using the as-prepared chitosan functionalized gold nanoparticles (CS-AuNPs) as a probe. The added Ag+ could first interact with the Au core to form a metallic bond, and then reduced by chitosan and deposited on the surface of AuNPs, leading to the formation of alloy Au-Ag core-shell NPs. The characteristic surface plasmon resonance (SPR) peak of CS-AuNPs at 520 nm was blue-shifted and the color of the solution changed from pink to orange with the Ag+ addition. Ag+ could be well determined ranging from 1.0 to 100 mu M with detection limit of 0.13 mu M. Additionally, this method displayed high sensitivity, selectivity and could be applied to the detection of Ag+ ions in water samples.