Ruedas-Rama Maria Jose, Hall Elizabeth A H
Institute of Biotechnology, University of Cambridge, Cambridge, UK.
Analyst. 2008 Nov;133(11):1556-66. doi: 10.1039/b801507d. Epub 2008 Aug 1.
In this work, the first chloride ion sensor based on QD-lucigenin nanoparticles is reported. The mechanism uses the ability of semiconductor QDs to engage in short range exchange processes, leading to fluorescence changes. An acridinium dication (lucigenin) which is an electron acceptor, was self-assembled on the surface of negative charged QDs (capped with mercaptopropionic acid). Mutual quenching of the lucigenin and QD were observed. From a sphere of action, Perrin-type model, exchange was estimated to occur over a range of the order of 2 nm. The possibility of spin-orbit coupling (SOC) or electron transfer between the QD and the lucigenin dication (Luc(2+)) is discussed. The radical cation Luc(+) was not identified, but electron transfer from the QD conduction band to the Luc(2+), then electron transfer back, from the Luc(+) to the QD valence band, could lead to mutual quenching, without build up of Luc(+*) . SOC between the QD and lucigenin, with or without charge transfer being involved, can also account for the results obtained. Lucigenin is also a chloride-sensitive indicator dye, with a sensing mechanism based on SOC. In the QD-MPA-lucigenin conjugate luminescence is restored by adding chloride ion. Thus, the presence of chloride is transduced into an enhancement of the luminescence of QDs. Using this operating principle, a chloride ion sensor based on CdSe-ZnS core-shell QD nanoparticles, showed a very good linearity in the range 1-250 mM, with a detection limit 0.29 mM and a RSD of 2.5% (n = 10). In a study of interferences, the chloride sensitive QDs showed good selectivity to most of the other anions tested. The versatility of the system was also demonstrated in terms of fluorescent emission wavelength, which could be selected across a wide range through choice of QDs. Examples are shown for lambda(max) = 500, 540 and 620 nm. The results from samples mimicking physiological conditions suggested very good applicability in the determination of chloride ion in physiological samples.
在这项工作中，报道了首个基于量子点-光泽精纳米颗粒的氯离子传感器。其机制利用了半导体量子点参与短程交换过程的能力，从而导致荧光变化。一种作为电子受体的吖啶鎓二价阳离子（光泽精）自组装在带负电荷的量子点（用巯基丙酸包覆）表面。观察到了光泽精和量子点之间的相互猝灭。从作用范围、佩林型模型估计，交换发生在约2纳米的范围内。讨论了量子点与光泽精二价阳离子（Luc(2+)）之间自旋-轨道耦合（SOC）或电子转移的可能性。未鉴定出自由基阳离子Luc(+)，但从量子点导带向Luc(2+)的电子转移，然后从Luc(+)向量子点价带的电子回传，可能导致相互猝灭，而不会积累Luc(+*)。量子点与光泽精之间的SOC，无论是否涉及电荷转移，也可以解释所获得的结果。光泽精也是一种对氯离子敏感的指示染料，其传感机制基于SOC。在量子点-巯基丙酸-光泽精共轭物中，加入氯离子可恢复发光。因此，氯离子的存在被转化为量子点发光的增强。利用这一工作原理，基于CdSe-ZnS核壳量子点纳米颗粒的氯离子传感器在1-250 mM范围内表现出非常好的线性，检测限为0.29 mM，相对标准偏差为2.5%（n = 10）。在干扰研究中，对氯离子敏感的量子点对大多数测试的其他阴离子表现出良好的选择性。该系统的多功能性还体现在荧光发射波长方面，通过选择量子点可以在很宽的范围内进行选择。给出了λ(max)=500、540和620 nm的示例。模拟生理条件的样品结果表明，该传感器在生理样品中氯离子测定方面具有很好的适用性。
