Monitoring and removal of trace heavy metal ions via fluorescence resonance energy transfer mechanism: In case of silver ions

The heavy metal ions pollution has attracted tremendous attention owing to their cumulative effect in organs. In this work, ZnS coated upconversion nanoparticles (denoted as UCNPs@ZnS) has been fabricated and firstly used as dual-functional fluorescence probe for simultaneously removal of heavy metals such as Ag+, Cu2+ or Hg2+ and detection of these ions residual in aqueous solution.. The upconversion fluorescence intensity of the UCNPs@ZnS suspension solution was quenched gradually with the addition of the Ag+, Cu2+ or Hg2+ aqueous solution, which is attributed to the formation of highly insoluble metal sulfides with narrower band-gap with enhanced fluorescence resonance energy transfer (FRET) efficiency. 3.98 mu mol Ag+ can be removed completely in presence of 1 mg UCNPs@ZnS core-shell nanoparticles. In addition, removal amount of Ag+ is proportional to the changes of the upconversion fluorescence intensity of the UCNPs@ZnS core-shell nanoparticles suspension solution. Therefore, this work could be extended to monitor and remove these heavy metal ions whose sulfides are less soluble than ZnS.