Sensitive Hg (II) ion detection by fluorescent multilayer films fabricated with quantum dots

Stable, monodisperse CdTe quantum dots (QDs) capped with mercaptosuccinic acid were prepared facilely in aqueous medium, which were deposited on the quartz slides to form multilayer films by electrostatic interactions with poly(dimethyldiallyl ammonium chloride) (PDDA). The PDDA/QDs multilayer films are easily fabricated and show high photostability. The fluorescence of the multilayer films could be quenched effectively by Hg (II) ions without obvious shift in maximum photoluminescence emission wavelength, which can be used for the detection of Hg (II) ions. The electron transfer process between the capping ligands and Hg (II) ions should be mainly responsible for the remarkable quenching effect of Hg (II) ions. Under optimal conditions, the quenched fluorescence intensities of multilayer films are perfectly described by modified Stern–Volmer equation with the concentration of Hg (II) ions ranging from 0.01 μM to 1 μM.