Enhanced stability and emission intensity of aqueous CdTe/CdS core-shell quantum dots with widely tunable wavelength

摘要

The stability and photoluminescence (PL) emission intensity of quantum dots (QDs) are particularly interesting for various bioapplications. In this paper, monodisperse CdTe/CdS core-shell QDs were synthesized in aqueous phase. The size of CdTe core and the thickness of CdS shell played important roles in the properties of CdTe/CdS QDs. Transmission electron microscopy (TEM) images show that the average diameters of CdTe/CdS core-shell QDs increased to ~5 nm compared with that of CdTe core QDs (~3.6 nm). X-ray diffraction patterns show that the CdTe/CdS core-shell QDs possess cubic zinc blende structure. After the overgrowth of CdS shell on CdTe core, a widely tunable PL emission wavelength (485-720 nm) of the core-shell QDs can be obtained, which covers nearly the full visible spectrum. The PL intensity of the CdTe/CdS core-shell QDs shows two-fold increase compared with that of the CdTe core QDs. PL results show that the photostability of the samples is enhanced through the growth of CdS on the CdTe QDs.