Glutathione-modified ultrasmall Ce3+and Tb3+-doped SrF2 nanocrystals for fluorescent determination of Hg(II) and Pb(II) ions

We report on the microwave-assisted synthesis of ultrasmall Ce3+ and Tb3+-doped SrF2 nanocrystals (NCs) capped with glutathione (GSH). The NCs have an average size of about 5 nm and show bright green fluorescence upon photoexcitation at 290 nm. Fluorescence is strongly quenched by Hg(II) and Pb(II). This finding was applied to design a method for the fairly selective determination of these ions. The detection limits (for the 3 sigma/slope criterion) are 20 mu M and 30 mu M for Hg(II) and Pb(II) ions, respectively. The intensity of the luminescence can be restored by the addition of ethylenediaminetetraacetic acid (EDTA), and this suggests that these NCs can be used as reusable fluorescent probes.