In recent years

nanocrystals(NCs)of semiconductor materials have been attracting considerable interest due to their size-tunable optical and electronic properties

and they have already been used as sensors

laser materials

thin film light-emitting devices(LEDs)

and biological labels.However

because of the high surface-to-volume ratio of nanoparticles

the surface properties have significant effects on their electronic and optical properties.It is for this reason that surface modification of these particles has been the subject of extensive investigation.In this report a simple one-pot synthetic route to prepare highly luminescent CdSe/ZnSe core-shell nanocrystals was presented.A ZnSe shell around a CdSe nanoparticles was formed by the reaction of selenium-richness on the surfaces of CdSe nanopaticles with Zn

2+

from the injected zinc stearate precursor.The core-shell structure was verified by X-ray diffraction(XRD)

X-ray photoelectron spectra(XPS)

transmission electron microscopy(TEM)

UV-vis absorption spectroscopy and photoluminescence(PL)spectro-scopy

respectively.The CdSe nanoparticles capped with wider band-gap ZnSe show successful passivation to remove surface defects.The X-ray diffraction patterns of the CdSe/ZnSe core-shell nanoparticles comparing with those of the bare CdSe cores shift to a higher angle.The X-ray photoelectron spectra analysis also clearly indicated the characteristic peaks such as Zn 2p

3/2

Zn 2p

1/2

and the Zn 2p signal detectable on the CdSe/ZnSe nanocrystals

indicating that Zn

2+

was strongly bound to the nanocrystal's surface.The transmission electron microscopy micrographs of the core-shell nanoparticles show well-defined spherical particles with larger diameters than those of the particles of the parent material.Consequently photoluminescence efficiencies improved observably.