Polymer/glutathione Au nanoclusters for detection of sulfides

A glutathione (GSH)-assisted approach in the presence of a polymer has been demonstrated for the preparation of stable and fluorescent gold nanoclusters (Au NCs). GSH acts as a reducing agent, while the polymer is used as a template to stabilize the as-formed Au NCs. The optimal pH value for the preparation of polymer-templated GSH-Au NCs is 11.0. With respect to the fluorescence intensity and stability, polydiallyldimethylammonium (PDDA) is more suitable than polystyrene sulfonate (PSS) for the preparation of Au NCs. When excited at 365 nm, the as-prepared PDDA/GSH-Au NCs prepared at pH 2.0 and 11.0 emit fluorescence at the wavelengths of 620 and 690 nm, respectively, which are assigned separately to GSH-Au and PDDA/GSH-Au NCs. Through the formation of Au₂S, hydrogen sulfide induces fluorescence quenching of the PDDA/GSH-Au NCs. The PDDA/GSH-Au NCs show sensitivity and selectivity for the quantitation of sulfide ions, with a linear detection range of 1–10 μM and a low detection limit (signal-to-noise ratio = 3) of 0.32 μM. The low-cost PDDA/GSH-Au NCs are stable against NaCl up to a concentration of 500 mM, and have been applied to the quantitation of sulfide ions in spring water samples with good accuracy and recovery.