title: Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures.
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.
authors.affiliation: The Biodesign Institute and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States.
authors.forename: Anirban
authors.initials: A
authors.lastname: Samanta
authors.forename: Zhengtao
authors.initials: Z
authors.lastname: Deng
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
mesh_terms: D019187:Cadmium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005978:Glutathione / Q000737:chemistry*; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013440:Sulfides / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties; D013691:Tellurium / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D017967:Zinc Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C034939:cadmium sulfide; D014867:Water; D005978:Glutathione; C031238:zinc sulfide; D013691:Tellurium; C028337:cadmium telluride