Enhanced Optical Properties of Core/Shell/Shell CdTe/CdS/ZnO Quantum Dots Prepared in Aqueous Solution

New quantum dots (QDs) were fabricated with a core/shell/shell structure consisting of CdTe core/CdS shell/ZnO shell. Despite the high lattice mismatch between CdS and ZnO, a ZnO shell was successfully introduced by basic hydrolysis of Zn(OAc)(2) at the surface of core/shell CdTe/CdS QDs stabilized by 3-mercaptopropionic acid (MPA). The core/shell/shell CdTe/CdS/ZnO@MPA QDs exhibited a significant redshift of emission peaks (up to 50 nm for green-emitting CdTe/CdS QDs) when the shell grew. By changing the size of the core or the thickness of the ZnO shell, the emission colors of the obtained nanocrystals can be tuned between the green and red regions of the spectrum following an identical procedure. The influence of ZnO shell growth on photoluminescence (PL) quantum yields was found to be more pronounced for CdTe/CdS samples with green or yellow emission for which quantum yields increased up to three times. The epitaxial growth of the ZnO shell was confirmed by X-ray photoclectron spectroscopy and luminescence decay experiments. Because of the passivation 017 Surface defects, a PL lifetime of 33.6 ns was measured for core/shell/shell CdTe/CdS/ZnO QDs prepared with a Zn/Cd ratio of 0.8, while it was only 17.7 ns for core/shell CdTe/CdS QDs.