Synthesis, characterization and optical studies on lanthanide-doped CdS quantum dots: new insights on CdS → lanthanide energy transfer mechanisms

Eu3+-Doped CdS hexagonal nanocrystals (NCs), with an average size of similar to 4 nm, have been prepared through a simple methodology based on the direct precipitation of CdS NCs using 1-thioglycerol as a capping molecule. Steady-state and time-resolved photoluminescence studies (14-300 K) reveal an effective CdS NCs-to-Eu3+ energy transfer process involving surface localized states and mediated by a thermally activated exchange mechanism. Furthermore, the analysis of the optical data also points out the presence of two distinct Eu3+ local coordination sites with different relaxation kinetics and attributed to lattice-bound and surface-bound centres. The D-5(0) lifetime values are longer than those reported previously for sol-gel derived Eu3+-doped CdS NCs.