Colloidal Ⅳ-Ⅵ semiconductor nanocrystals (NCs) are of importance as potential applications ranging from electroluminescent devices to telecommunication.Notably,PbSenanocrstals provide high emission quantum yields in l~3 μ m spectra range.Size and shape tunable PbSenanocrystals were synthesized via typical non-coordinating solvent technique.[1]Shape and structurecharacterizations of samples were carried out by transmission electron microscope (TEM) and x-ray diffraction (XRD) analysis.A PbSe/CdSe core-shell nanostructure was realized by a cation exchange method for better chemical and optical stability.Blue shift of PbSe peak in photoluminescence spectra was observed as PbSenanocrystals was clad by CdSe shell.These stable nanocrystals can be applied in the fabrication of mid-infrared light-emitting-diodes (LED).