The effect of quenching of photoluminescence (PL) intensity of thiol-stabilized water-soluble ZnS-coated AgInS 2 nanocrystals (NCs) in the presence of Pb 2þ ions is investigated. The factors influencing the efficiency of quenching process such as NCs dilution, pH value, composition, and concentration of working buffer solution are studied. It is found that the increasing of NCs dilution as well as the acidity of buffer solution promotes PL quenching by Pb 2þ ions. In all media used, the decrease of PL intensity in the presence of Pb 2þ ions is accompanied by a red shift of the PL band. In 0.5 Â 10 -3 M citrate buffer solution, the red shift reached almost 5 nm. The degradation of the PL intensity is attributed to formation of some substances at the NC surface acting as the centers of nonradiative recombination. The red shift is ascribed to different quenching effect of Pb 2þ ions on the PL intensity of NCs of different sizes. The bimodal distribution of the NCs is proved by the PL study of NC fractions separated by ultracentrifugation. The obtained results could be useful for development of novel methods for detection of heavy metal ions.

The influence of ions of heavy metals Cu 2+ , Pb 2+ , Co 2+ , Ni 2+ , Cd 2+ , Ag + , and ions, which are common components of natural and drinking water (Na + , K + , Ca 2+ , Mg 2+) on the photoluminescence of nanocrystals AgInS 2 with ZnS shell (NCs AgInS 2 /ZnS) was investigated. Experimental data obtained confirm the assumption on the relationship between the level of quenching of NCs AgInS 2 / ZnS photoluminescence under exposure to the heavy metal ions and solubility constant of their sulfides. The concentration of ions Cu 2+ , which caused a statistically significant quenching of NCs AgInS 2 /ZnS photoluminescence, is below their maximum allowable concentration in natural waters. It opens up prospects of NCs AgInS 2 /ZnS for developing methods for environmental monitoring of the copper ions.