Highly sensitive fluorescent determination of sulfide using BSA-capped CdS quantum dots

Abstract

This work presented a novel nanosensor for the rapid detection of sulfide, which was based on the fluorescence “turn off–on” of bovine serum albumin-capped CdS quantum dots (BSA-CdS QDs). Cd²⁺ could react with S²⁻ to generate fluorescent CdS QDs in the presence of BSA. When Pb(II) was added to the BSA-CdS QD solution, the fluorescence of CdS QDs would “turn off” due to the coordination of Pb(II) and BSA presented on the CdS QD surface. The quenched fluorescence of CdS QDs could be “turned on” upon the addition of sulfide by forming a stable PbS compound. Quantitative analysis was performed by monitoring the fluorescence intensity variation of CdS QDs. Under the optimum conditions, a good linear range for sulfide detection from 0.16–4.8 μmol L⁻¹ was realized. With the detection limit down to 5.0 × 10⁻⁸ mol L⁻¹, the nanosensor exhibited good selectivity for sulfide in the presence of other anions.