Triethanolamine-capped CdSe quantum dots as fluorescent sensors for reciprocal recognition of mercury (II) and iodide in aqueous solution.

Water-soluble luminescent CdSe quantum dots surface-modified with triethanolamine (TEA-CdSe-QDs) were prepared with high stability. The fluorescence of the TEA-CdSe-QDs was greatly quenched only when Hg(2+) and I(-) coexisted in the solution, whereas addition of either Hg(2+) or I(-) individually has no noticeable effect on the fluorescence emission. Such a unique quenching effect could be used for reciprocal recognition of mercury (II) ions and/or iodide anions in aqueous solution with rather high selectivity and sensitivity. The detection limits of Hg(2+) or I(-) ion were 1.9 x 10(-7)mol L(-1) or 2.8 x 10(-7)mol L(-1), respectively. The adequate experiments showed that iodine (I) anions could bridge between TEA-CdSe-QDs and Hg(2+) to form a stable complex (QDs-I(-)-Hg(2+)) and the following effective electron transfer from the QDs to the Hg(2+) could be responsible for the fluorescence quenching of QDs.