Synthesis and Characterization of CdSe Nanocrystals Capped by CdS

CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2 mercaptoethanol as the stabilizer. The CdS capping with a higher band gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band edge photoluminescence. X ray powder diffraction, transmission electron microscopy and X ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.