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 μM with detection limit of 0.13 μM. Additionally, this method displayed high sensitivity, selectivity and could be applied to the detection of Ag+ ions in water samples.