College of Materials Science & Engineering, South China University of Technology, Guangzhou 510640, PR China.
Analyst. 2012 Aug 21;137(16):3717-24. doi: 10.1039/c2an35434a. Epub 2012 Jun 26.
The quenching of quantum dots' emission by some analytes (Hg(2+), Pb(2+), etc.) has long been hindering the fabrication of QD-based 'turn-on' or ratiometric fluorescent sensors for these analytes. In this study, we demonstrate a facile solution for constructing a robust FRET-based ratiometric sensor for Hg(2+) detection in water with CdTe QDs as the donor. By using the reverse microemulsion approach, CdTe QDs were first embedded into nanosized silica particles, forming the QDs/silica cores, a positively charged ultrathin spacer layer was then deposited on each QDs/silica core, followed by the coating of a mercury ion probe on the particle surfaces. The resultant multilayered QDs/silica composite nanoparticles are dispersible in HEPES buffered water; and in the presence of mercury ions, the QDs inside the nanoparticles will not be quenched by mercury ions due to the existence of the positively charged spacer layer, but can transfer their excited energy to the acceptors (probe/Hg(2+) complex), thus achieving the FRET-based ratiometric sensing for mercury ions in totally aqueous media. With its detection limit of 260 nM, this QD-based sensor exhibits high selectivity toward mercury ion and can be used in a wide pH range. This strategy may be used to construct QDs-based ratiometric assays for other ions which quench the emission of QDs.
长期以来，一些分析物（Hg(2+)、Pb(2+)等）会猝灭量子点的发射，这一直阻碍着基于量子点的“开启”或比率荧光传感器的制造，用于这些分析物。在这项研究中，我们展示了一种简便的方法，用于构建基于 FRET 的比率荧光传感器，用于在水中检测 Hg(2+)，CdTe QDs 作为供体。通过使用反相微乳液法，首先将 CdTe QDs 嵌入纳米级硅颗粒中，形成 QDs/硅核，然后在每个 QDs/硅核上沉积一层正电荷的超薄间隔层，最后在颗粒表面涂覆汞离子探针。所得的多层 QDs/硅复合纳米颗粒可分散在 HEPES 缓冲水中；在存在汞离子的情况下，由于存在正电荷间隔层，纳米颗粒内的 QDs 不会被汞离子猝灭，但可以将它们的激发能量转移到受体（探针/Hg(2+)复合物），从而实现基于 FRET 的比率荧光传感用于完全水介质中的汞离子。该基于 QD 的传感器的检测限为 260 nM，对汞离子具有高选择性，可在较宽的 pH 范围内使用。该策略可用于构建用于猝灭 QD 发射的其他离子的基于 QD 的比率测定法。
