Room-temperature phosphorescence by Mn-doped ZnS quantum dots hybrid with Fenton system for the selective detection of Fe2+

Abstract

The phosphorescent 3-mercaptopropionic acid (MPA) capped Mn-doped ZnS quantum dots (MPA–Mn:ZnS QDs)–Fenton hybrid system was developed for a highly sensitive detection of Fe²⁺ in environmental samples and biological fluids. The phosphorescence of the MPA–Mn:ZnS QDs can be effectively quenched by hydroxyl radicals produced from the Fenton reaction between Fe²⁺ and H₂O₂ at a low concentration level. However, the phosphorescence of the MPA–Mn:ZnS QDs cannot be quenched by either Fe²⁺ or H₂O₂ individually at the same concentration level. Thus, Fe²⁺ can be indirectly detected using the phosphorescence quenching caused by hydroxyl radicals based on the Fenton reaction. A possible mechanism for the quenching effect of Fe²⁺ was elucidated as electron transfer from the conduction band of the MPA–Mn:ZnS QDs to the unoccupied band of hydroxyl radicals. The phosphorescent hybrid system allowed a highly sensitive detection of Fe²⁺ in an aqueous solution with a wide linear range of 0.01–10 μM and a detection limit of 3 nM, and the precision for 11 replicate detections of 0.1 μM Fe²⁺ was 1.5% (relative standard deviation, RSD). The developed method was applied to determine Fe²⁺ in environmental samples and biological fluids with quantitative spike recoveries from 95% to 104%.