ZnS掺Mn磷光量子点对金属离子传感机理的探讨

Phosphorescent ZnS doped Mn quantum dots for sensing metal ions and responding mechanism

合成了以3-巯基丙酸或L-半胱氨酸修饰的水溶性ZnS掺Mn磷光量子点,磷光发射峰在590nm,产生于Mn2+的4T1-6A1跃迁。磷光信号稳定,不易受溶解氧的影响。检测了七种常见金属离子对磷光性质的影响,结果表明:对于3-巯基丙酸修饰的ZnS:Mn量子点,Cu2+,Mn2+,Fe3+,Co2+,Pb2+和Hg2+离子能有效猝灭其磷光,而Cd2+离子能增强量子点磷光;对于L-半胱氨酸修饰的ZnS:Mn量子点,Cu2+,Mn2+,Fe3+,Co2+,Pb2+,Hg2+以及Cd2+离子都能有效猝灭其磷光;猝灭方程呈现线性和指数两种形式。通过测量磷光寿命,推断猝灭机理主要为动态猝灭。这些结果为设计具有选择性的基于磷光量子点的离子传感器以及研究响应机理提供了实验和理论的参考。

Water-soluble Mn2＋ doped ZnS phosphorescent quantum dots （QDs） were prepared using 3- mercapto- propionic acid and L-cysteine as stabilizer. Phosphorescent emission peak was at 59Onto which originated from 4T1- 6A1 transition of Mn2＋ ions on Zn2＋ sites, and were excited by the energy transferred from the excited electron-hole pairs in the ZnS host. Two kinds of QDs were used to detect metal ions. For 3-MPA capped quantum dots, the presence of Cu2＋, Mn2＋, Fe3＋, Co2＋, Pb2＋, Hg2＋ resulted in quenching of phosphorescence while the presence of Cd2＋ resulted in enhancing of phosphorescence. For L-cysteine capped quantum dots, the presence of Cu2＋, Mn2＋, Fe3~, Co2＋, Pb2＋ ,Hg2＋ and Cd2＋ resulted in quenching of phosphorescence. By measuring the phosphorescence lifetime, we judged the quenching mechanism was mainly dynamic. The conclusions can provide references for both theory and experiment to design selective ion sensors based on phosphorescent quantum dots.