Aqueous synthesis of Ag+ doped CdS quantum dots and its application in H2O2 sensing

Abstract

A novel detection system based on the fluorescence quenching of CdS–Ag₂S quantum dots (QDs) was designed for the direct measurement of hydrogen peroxide (H₂O₂). Experimental results showed that an excellent response to the concentrations of H₂O₂ was found within the range from 1.0 × 10⁻⁶ to 1.0 × 10⁻² M with a detection limit of 3.0 × 10⁻⁷ M. The CdS–Ag₂S QDs have been synthesized at room temperature in an aqueous solution using thioglycollic acid as stabilizing agents, which were spectra-tunable and water-soluble. Different influencing factors including pH, variable ratio of [Cd²⁺]/[S²⁻], dopant concentration, precursor concentration, and aging time of CdS–Ag₂S QDs were studied. It was found that the emission colors of the prepared CdS–Ag₂S QDs could be readily tuned from green to red by varying pH. Furthermore, the CdS–Ag₂S QDs were characterized by fluorescence and time-resolved emission spectroscopy, TEM, EDX, XRD, XPS, ESR. The long decay times, large surface area, and good chemical stability of the CdS–Ag₂S QDs have made this material suitable as a fluorescence probe.