Room-Temperature Phosphorescence Detection of Silver Ions Based on Glutathione Capped Mn-Doped ZnS Quantum Dots

A sensitive and selective room-temperature phosphorescence (RTP) assay of silver ions (Ag+) based on glutathione modified manganese-doped zinc sulfide quantum dots (GSH-MnZnS QDs) was developed. By using safe and low-cost materials, GSH-MnZnS QDs were easily synthesized in aqueous media, which emitted intense RTP even though the solution was not deoxygenated. However, the RTP of GSH-MnZnS QDs was strongly quenched by Ag+ due to the formation of Ag-GSH complex and the electron transfer from excited GSH-MnZnS QDs to Ag+. The observed results show that GSH-MnZnS QDs offer high sensitivity with a detection limit down to 36 nM and high selectivity over other metal ions in the presence of specific masking agents for Ag+ determination. The developed method was finally applied to the detection of Ag+ in water samples, and the spike-recoveries fell in the range of 95-106%.