Highly selective manganese-doped zinc sulfide quantum dots based label free phosphorescent sensor for phosphopeptides in presence of zirconium (IV)

We report a room-temperature phosphorescence (RTP) sensor for phosphopeptides based on zirconium (IV)-modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs). This sensor incorporates the advantages of the well-known Zr4+-phosphopeptide affinity pair and the RTP properties of doped QDs. The RTP of Mn-doped ZnS QDs capped with MPA can be effectively quenched by Zr4+. The high affinity of phosphopeptides to Zr4+ enables the dissociation of the ion from the surface of MPA-capped ZnS QDs, thereby forming a stable complex with phosphopeptides in the solution, and recovering the RTP of the QDs. The Zr4+-induced RTP quenching and subsequent phosphopeptide-induced RTP recovery for MPA-capped ZnS QDs provide a solid basis for the present RTP sensor based on QDs for the detection of phosphopeptides. The detection limit for phosphopeptides is 0.9 ng mL−1, the relative standard deviations is 2.5%, and the recovery of urine and serum samples with phosphopeptides addition rangs from 96% to 105% at optimal conditions. The proposed method was successfully applied to biological fluids and obtained satisfactory results.