Single-Source Precursor Route for Synthesis of High-Quality Green-emitting Quantum Dots and Their Hydrophilic Surface Modification

The high-quality green-emitting CdS 0 . 5 Se 0 .5 /8Zn 1 − x Cd x S/2ZnS QDs with “8” and “2” monolayers (ML) of corresponding shell were first synthesized by “thermal-cycling coupled single precursor” (TC-SP) approach. The component-gradient Zn 1− x Cd x S interlayer played a key role in the growth of thick shell by gradually buffering the large lattice mismatch (~9%) between the CdS 0 . 5 Se 0 .5 core and ZnS shell. Moreover, the Zn 1− x Cd x S gradient interlayer as well as ZnS outshell increased the potential barrier to prevent excitons from being trapped by surface defects. The photoluminescence quantum yields of the as-synthesized CdS 0 . 5 Se 0 .5 /8Zn 1 − x Cd x S/2ZnS core/shell QDs can reach to 70% in organic media and still maintain 60% after aqueous phase transfer. The green-emitting CdS 0 . 5 Se 0 .5 /8Zn 1 − x Cd x S/2ZnS core/shell QDs may be good candidates for applications of biomedical and photoelectric field.