Functionalized manganese-doped zinc sulfide core/shell quantum dots as selective fluorescent chemodosimeters for silver ion

Zinc sulfide quantum dots doped with Mn(II) ions and coated with a shell of zinc sulfide were prepared, and their surface was modified with iminodiacetic acid to form a QDs-conjugate (QDs-IDA). Such modification effectively improves the water-solubility and luminescence quantum yield of the quantum dots. The optical properties and structural features were characterized by photometry, H-1 NMR and fluorescence spectroscopy. The results displayed that QDs-IDA selectively respond to Ag (I) ion in phosphate buffer solution (pH 7.3) in quenching the fluorescence of QDs-IDA. A good linear relationship exists in the concentration range from 5.0 x 10(-7) mol center dot L-1 to 4.5 x 10(-6) mol center dot L-1 and the detection limit is 2.6 x 10(-7) mol center dot L-1. The sensing mechanism was assumed to result from complex formation between the iminodiacetic acid of QDs-IDA and silver (I) ion which promoted photo-induced electron transfer.