单核/双壳结构CdSe/CdS/ZnS纳米晶的合成与发光性质

以巯基乙酸为稳定剂,在水溶液中合成了单核/双壳结构的CdSe/CdS/ZnS纳米晶。在内核CdSe和外壳ZnS之间的内壳CdS作为晶格匹配调节层,能够很好的改善核/壳界面处的性能,而且,最外层ZnS能够最大程度地使激子受限。用TEM和XPS对纳米晶进行了表征,并且用光致发光光谱和吸收光谱对不同核壳结构的纳米晶的发光性能进行了比较,结果表明单核/双壳结构的纳米晶具有更加优异的发光特性。

Synthesis and Luminescent Properties of Core/Shell/Shell Structural CdSe/CdS/ZnS Nanocrystals

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.