Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures

Langmuir. 2012 May 29;28(21):8205-15. doi: 10.1021/la300515a. Epub 2012 May 14.

Abstract

Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cadmium Compounds / chemical synthesis
  • Cadmium Compounds / chemistry*
  • Glutathione / chemistry*
  • Molecular Structure
  • Nanoparticles / chemistry*
  • Particle Size
  • Sulfides / chemical synthesis
  • Sulfides / chemistry*
  • Surface Properties
  • Tellurium / chemistry*
  • Water / chemistry
  • Zinc Compounds / chemical synthesis
  • Zinc Compounds / chemistry*

Substances

  • Cadmium Compounds
  • Sulfides
  • Zinc Compounds
  • cadmium sulfide
  • Water
  • Glutathione
  • zinc sulfide
  • Tellurium
  • cadmium telluride