ZnS-CdS核壳纳米微晶的制备与光学特性

采用微乳液法制备了核壳结构ZnS/CdS纳米微晶.以XRD、TEM表征其结构、粒度和形貌,UV、PL表征其光学性能.制得的纳米微晶近似呈球形,粒径4～5nm.研究了不同CdS壳层厚度的ZnS/CdS纳米微晶的光学性能,PL谱表明壳层CdS的修饰可减少ZnS的表面缺陷,表面态发射和非辐射跃迁减少,带边直接复合发光的几率增大,发光效率大大提高;在壳层CdS达到一定厚度时,PL谱却表现为CdS的特征发射,同时发现核心ZnS对壳层CdS的发光具有增强作用,提出了ZnS/CdS发光机理的能带模型.

Preparation of Core-shell Structure ZnS-CdS Nanocrystals and Their Optical Properties

ZnS/CdS core-shell structure nanocrystals were synthesized in microemulsion. The size and the shape of nanocrystals were characterized by TEM.The structure and the optical properties were characterized by XRD,UV absorption spectra and PL,respectively.The diameter of nanocrystals is about 4-5nm.It was discussed the influence of shell thickness on the optical properties of ZnS/CdS nanocrystal.PL spectra indicate that CdS cover can reduce surface defects of ZnS greatly, then nonradiative transition and surface state emission decreased ,direct recombination rate of band-edge emission increased,the luminous efficiency improved greatly when it has appropriate shell thickness. The PL spectra of ZnS/CdS exhibit characteristic spectrum of CdS when the thickness of CdS shell reachs a special value. It is found that ZnS core can enhance luminescence of CdS shell in ZnS/CdS core-shell structure nanocrystal, and then present a energy band model of luminescence mechanism.