Shell surface sulfidation mediated the plasmonic response of Au@Ag NPs for colorimetric sensing of sulfide ions and sulfur

Sulfur-bearing species have received a great deal of interest due to their potential risks and applications as well as their specific interaction with metal nanoparticles. This interaction influenced greatly the properties and functionality of nanoparticles, but is still poorly understood. In this paper, the sulfidation reaction between sulfur species (S, SH-, S2-) and Ag were investigated by using plasmonic Au@Ag as model. We report here that sulfide and bisulfides can cause the rapid transformation of Au@Ag2S with varying degree accompanying tunable surface plasmonic resonance and color production. The SPR evolution reflected the much slower reaction kinetic between S and Au@Ag than that of sulfide. The linear relationship was found between SPR maximum or absorption and the concentration of sulfide and sulfides, making it applicable to detect them by using spectroscopy or with naked eyes. This method exhibits high sensitivity and selectivity to bisulfide and sulfide against a variety of metal ions and anions. Since sulfur species and Ag NPs are wide used in biological and environmental system, these results may provide insights for finding new applications in combination of metal NPs and sulfur containing molecules.