Facile Synthesis and Photoluminescence of Near-Infrared-Emitting Cdtexse1-X and Cdtexse1-X/Cdyzn1-Ys Quantum Dots

High-quality colloidal photoluminescent (PL) CdTexSe1-x quantum dots (QDs) with gradient distribution of components, consisting of Te-rich inner cores and Se-rich outer shells, were synthesized via a facile organic method using stearic acid as a capping agent. The transmission electron microscopy observation and X-ray diffraction analysis indicated that the CdTexSe1-x QDs revealed a "dot" shaped morphology and exhibited a zinc-blende structure which located between those of bulk CdTe and CdSe (with the lattice parameters between those of bulk CdTe and CdSe). The ternary CdTexSe1-x QDs were emitting in the red to near-infrared (NIR) range. In order to enhance the PL properties and reduce the sensitivity to oxidation of CdTe-based QDs, the CdTexSe1-x QDs were coated with CdyZn1-yS multishells by using different growth kinetics of CdS and ZnS. The coated QDs exhibited a controlled red shift of PL compared with the initial CdTexSe1-x cores and revealed much improved PL intensity. Because of thier tunable emission from red to NIR, these composite QDs open new possibilities in band gap engineering and in developing NIR fluorescent probes for biological imaging and detection.