Shell-thickness dependent optical properties of CdSe/CdS core/shell nanocrystals coated with thiol ligands

Using CdSe/CdS core/shell nanocrystals with 1–10 monolayers of CdS shell as the model system, we studied effects of thiol ligands on optical properties of the nanocrystals. The core/shell nanocrystals with original ligands possessed near unity photoluminescence (PL) quantum yield and single-exponential PL decay dynamics. The effects of thiol ligands on optical properties were found to depend on the shell thickness, environment (with/without oxygen), and excitation power (single- or multi-exciton). Systematic and quantitative results reported in this work should provide necessary information for fundamental understanding and technical applications of quantum dots (QDs) coated with thiol ligands.