Size-dependent reactivity of highly photoluminescent CdZnTeS alloyed quantum dots to mercury and lead ions

Water-soluble and highly photoluminescent (PL) quantum dots (QDs) are attractive for metal ion sensing. Their size-dependent properties including UV stability and reactivity are important aspects to deploy QDs as PL probes. Herein, CdZnTeS alloyed QDs with a bandgap ranging from 2.6 eV to 2.1 eV were synthesized by a one-pot procedure and their size dependent reactivities to Pb 2+ or Hg 2+ ions were examined. Optical study on mixtures of QDs and Pb 2+ or Hg 2+ revealed that only Hg 2+ can exchange Cd 2+ of mother QDs while both Pb 2+ and Hg 2+ could act as Z-type ligands enhancing the PL. The cation exchanging ability and the PL enhancement increase as QDs size decreases. The results demonstrated new understandings on the interaction between CdZnTeS alloyed QDs and heavy metal ions which could be useful to deploy QDs in metal ion sensing.