title: Design and synthesis of highly luminescent near-infrared-emitting water-soluble CdTe/CdSe/ZnS core/shell/shell quantum dots.
abstract: Applications of water-dispersible near-infrared (NIR)-emitting quantum dots (QDs) have been hampered by their instability and low photoluminescence (PL) efficiencies. In this paper, water-soluble highly luminescent NIR-emitting QDs were developed through constructing CdTe/CdSe/ZnS core/shell/shell nanostructure. The CdTe/CdSe type-II structure yields the QDs with NIR emission. By varying the size of CdTe cores and the thickness of the CdSe shell, the emission wavelength of the obtained nanostructure can span from 540 to 825 nm. In addition, the passivation of the ZnS shell with a substantially wide bandgap confines the excitons within the CdTe/CdSe interface and isolates them from the solution environment and consequently improves the stability of the nanostructure, especially in aqueous media. An effective shell-coating route was developed for the preparation of CdTe/CdSe core/shell nanostructures by selecting capping reagents with a strong coordinating capacity and adopting a low temperature for shell deposition. An additional ZnS shell was deposited around the outer layer of CdTe/CdSe QDs to form the core/shell/shell nanostructure through the decomposition of single molecular precursor zinc diethyldithiocarbamate in the crude CdTe/CdSe reaction solution. The water solubilization of the initially oil-soluble CdTe/CdSe/ZnS QDs was achieved through ligand replacement by 3-mercaptopropionic acid. The as-prepared water-soluble CdTe/CdSe/ZnS QDs possess PL quantum yields as high as 84% in aqueous media, which is one of the best results for the luminescent semiconductor nanocrystals.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, Department of Chemistry, and School of Bioengineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Wenjin
authors.initials: W
authors.lastname: Zhang
authors.forename: Guanjiao
authors.initials: G
authors.lastname: Chen
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Bang-Ce
authors.initials: BC
authors.lastname: Ye
authors.forename: Xinhua
authors.initials: X
authors.lastname: Zhong
mesh_terms: D019187:Cadmium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D049449:Luminescence; D045663:Quantum Dots; D018036:Selenium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012995:Solubility; D019265:Spectroscopy, Near-Infrared; D013440:Sulfides / Q000138:chemical synthesis / Q000737:chemistry*; D013691:Tellurium / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D017967:Zinc Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; D014867:Water; C058667:cadmium selenide; C031238:zinc sulfide; D013691:Tellurium; C028337:cadmium telluride