Growth and optical property of PbS/ZnS nanocrystals

PbS quantum dots (QDs) were synthesized via colloidal hot-injection route, and then new PbS/ZnS nanoparticles (NCs) were prepared by two different routes. PbS/ZnS-A NCs were fabricated using the epitaxial growth method, and PbS/ZnS-B NCs were prepared by the cation substitution method. The structure and morphology of these NCs were characterized by XRD, TEM and vis-NIR absorption. The morphology can be controlled by different growth mechanisms. Epitaxial growth can result in the formation of nano-heterojunction of PbS-ZnS. Doping growth almost does not change the surface morphology of the PbS/ZnS NCs, but changes the relative growth rate of various crystal facets. For two kinds of PbS/ZnS NCs, the ground state exciton binding energy becomes stronger due to introducing of Zn, and there is an obvious blue shift in optical band gap with respect to the pure PbS QDs.