Preparation of a ZnS Shell on CdSe Quantum Dots Using a Single-Molecular ZnS Precursor

A simple synthetic route to the preparation of a thin ZnS shell on CdSe quantum dot cores from the air-stable, single-molecular precursor zinc diethyldithiocarbamate, Zn(S(2)CNEt(2))(2), in the three-component solvent system octadec-1-ene/oleylamine/tri-n-octylphosphine (ODE/OLA/TOP) is presented. The one-pot synthesis proceeds through heating of the solution of CdSe cores and the amount of crystalline Zn(S(2)CNEt(2))(2) corresponding to a shell thickness of two monolayers of ZnS to 110-120 degrees C for 1-2 h. The role of the surfactants OLA and TOP and the significance of the temperature and the amount of Zn(S(2)CNEt(2))(2) have been investigated with optical absorption and luminescence spectroscopy. We show that the presence of both OLA and TOP is crucial for the low-temperature growth and that the amount of precursor corresponding to two monolayers of ZnS results in the highest quality of core/shell CdSe/ZnS quantum dots.