Ⅱ-Ⅵ family semiconductor nanocrystals(such as CdSe

CdS

ZnS

ZnSe

and so on) have attracted most interests of scientists

recently.The synthesis methods have made great breakthrough in the improving the photo-stability and enhancing the luminescence efficiency during the past decades

of which the most successful way was the preparation of core/shell nanocrystals.However

most of the core/shell systems investigated were single core and single shell systems.The core/shell/shell structural CdSe/CdS/ZnS nanocrystals were synthesized in aqueous solution by using mercapto-acetate acid as stabilizer.The intermediate shell of CdS between the core of CdSe and the outer shell of ZnS could improve the core/shell interface quality as a lattice parameter adaptation layer

and the outer layer of ZnS could confine the exciton to a great extent.The core/shell/shell system combined the advantages of both core/shell systems of CdSe/CdS and CdSe/ZnS in theory.The nanocrystals were characterized by transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS).The TEM image showed that the nanocrystals exhibited sphericity

and the average size was less than 10 nm

and the aggregation occurred among the nanocrystals.The results of XPS confirmed the existence of cadmium

zinc

selenium and sulphur in the core/shell/shell structural samples

which demonstrated the formation of core/shell/shell structural CdSe/CdS/ZnS nanocrystals.The luminescence intensity of different core/shell structural nanocrystals was investigated by using the UV-Vis absorption and photoluminescence(PL) spectra

the results indicated that both of the intensity of absorption spectra and PL spectra of core/shell/shell structural CdSe/CdS/ZnS nanocrystals were the strongest of all

and the red shift was the most distinct of all

which attributed to the surface passivation on the core of CdSe and partial exciton leakage into the shell.By comparison

the results demonstrated that the core/shell/shell structural nanocrystals exhibited the best luminescent properties of all.