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

Abstract

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.