Aqueous Synthesis of Glutathione-Capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS Core/Shell/Shell Nanocrystal Heterostructures

• Published in: Langmuir Vol. 28; no. 21; pp. 8205 - 8215
• Main Authors: Samanta, Anirban, Deng, Zhengtao, Liu, Yan
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 29.05.2012
• Subjects: Cadmium Compounds - chemical synthesis; Cadmium Compounds - chemistry; Chemistry; Exact sciences and technology; General and physical 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; Encapsulation; Capping; Transition element compounds; Photoluminescence; Quantum yield; Wavelength; Thickness; Lifetime; Synthesis; Optical properties; Rate constant; Structure; Diameter; Nanocrystal
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la300515a

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.