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Synthesis and characterization of CdTe/CdS and CdTe/CdSe core/shell type-II quantum dots in a noncoordinating solvent

A synthetic route to CdTe/CdS and CdTe/CdSe core/shell type-II quantum dots in noncoordinating solvents (1-octadecene) was obtained. The results showed redshift in the emission spectra of CdTe/CdS and CdTe/CdSe compared with the CdTe core nanocrystals. This phenomenon is believed to indicate the formation of core/shell nanostructures. Transmission electron microscopy and powder x-ray diffraction were also consistent with nanocrystals containing a core of nearly monodisperse CdTe with CdS or CdSe capping. The photoluminescence quantum yield was enhanced by epitaxial growth of CdS or CdSe shells. Stepwise increasing concentration of sulfur or selenium monomers into the CdTe core solution allowed the examination of monomer activities, which are very relevant for synthesizing core/shell quantum dots.