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

Abstract

Eu³⁺-Doped CdS hexagonal nanocrystals (NCs), with an average size of ∼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 ⁵D₀ lifetime values are longer than those reported previously for sol–gel derived Eu³⁺-doped CdS NCs.