Zhou Quanxiu, Li Zhaofa, Wang Qunfang, Peng Liang, Luo Shihe, Gu Feng Long
Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry, South China Normal University, Guangzhou 510006, People's Republic of China.
Analysis and Testing Centre, South China Normal University, Guangzhou 510006, People's Republic of China.
Anal Methods. 2021 May 27;13(20):2305-2312. doi: 10.1039/d1ay00432h.
In this work, poly(styrene-co-maleic anhydride)-capped CdSe/ZnS quantum dots (QDs) aminolyzed with ethanolamine are proposed as fluorescent probes for the detection of Cu2+ and Hg2+, and two different quenching mechanisms are discussed in detail. The coordination abilities of the surface polymer of CdSe/ZnS QDs and two metal ions are calculated by density functional theory (DFT). The photoinduced electron transfer from excited QDs to Cu2+ unoccupied orbitals is enhanced due to the coordination between Cu2+ and the surface polymer of QDs. The electron transfer consumes non-radiative energy and performs fluorescence quenching. For Hg2+, the formation of HgS and the slight aggregation of polymer-coated CdSe/ZnS QDs lead to fluorescence quenching. The probe is sensitive to both Cu2+ and Hg2+, and the response can be detected within 1 min without adjusting the pH. With the addition of a masking agent, Cu2+ and Hg2+ can be exclusively detected in coexistence with another ion. For Cu2+, a linear relation in the concentration ranging from 0.02 to 0.7 μM was found between the relative fluorescence intensity (F0/F) and the concentration of Cu2+; the limit of detection (S/N = 3) is 6.94 nM. For Hg2+, a linear relation ranging from 0.1 to 1.4 μM was found between ln(F0/F) and the concentration of Hg2+; the limit of detection is 20.58 nM.
在本工作中，提出了用乙醇胺氨解的聚（苯乙烯 - 马来酸酐）封端的CdSe/ZnS量子点（QDs）作为检测Cu2+和Hg2+的荧光探针，并详细讨论了两种不同的猝灭机制。通过密度泛函理论（DFT）计算了CdSe/ZnS量子点表面聚合物与两种金属离子的配位能力。由于Cu2+与量子点表面聚合物之间的配位作用，增强了从激发量子点到Cu2+未占据轨道的光致电子转移。电子转移消耗非辐射能量并导致荧光猝灭。对于Hg2+，HgS的形成以及聚合物包覆的CdSe/ZnS量子点的轻微聚集导致荧光猝灭。该探针对Cu2+和Hg2+均敏感，无需调节pH即可在1分钟内检测到响应。加入掩蔽剂后，可以在与另一种离子共存的情况下单独检测Cu2+和Hg2+。对于Cu2+，在相对荧光强度（F0/F）与Cu2+浓度之间发现浓度范围为0.02至0.7μM的线性关系；检测限（S/N = 3）为6.94 nM。对于Hg2+，在ln(F0/F)与Hg2+浓度之间发现范围为0.1至1.4μM的线性关系；检测限为20.58 nM。
