Syntheses and photophysical properties of type-II CdSe/ZnTe/ZnS (core/shell/shell) quantum dots
Resource
Journal of Materials Chemistry 15: 3409-3414
Journal
Journal of Materials Chemistry
Journal Volume
15
Journal Issue
33
Pages
3409-3414
Date Issued
2005
Author(s)
Cheng, Chiu-Ting
Chen, Chun-Yen
Lai, Chih-Wei
Liu, Wei-Hsin
Pu, Shih-Chieh
Chou, Yi-Hsuan
Chiu, Hsin-Tien
Abstract
Syntheses of CdSe/ZnTe/ZnS (core/shell/shell) type-II quantum dots (QDs) are reported. Structural characterization was made via TEM, EDX, XPS and XRD. Photophysical properties were investigated via the interband emission (CdSe → ZnTe) and its associated quantum efficiency as well as relaxation dynamics. In comparison to the weak emission (Φf ∼ 4 × 10-3 in toluene) of CdSe/ZnTe (3.9/0.5 nm), capping ZnS (0.4 nm in thickness) enhances the CdSe → ZnTe interband emission by ∼ 30 fold (Φf ∼ 0.12), whereas the peak wavelength shifts only slightly to the red. By encapsulating dihydrolipoic acid (DHLA), water-soluble CdSe/ZnTe/ZnS QDs were also prepared, and they exhibited an interband emission at ∼ 930 nm with an emission yield of ∼ 0.1. Femtosecond pulse excitation (λex ∼ 1200 nm) measurement estimated a two-photon absorption cross section, σ, of ∼ 70 × 10 -50 cm4 s photon-1 for DHLA-capped CdSe/ZnTe/ZnS in water, supporting its suitability for the use as near-infrared (NIR) dyes in biomedical imaging. © The Royal Society of Chemistry 2005.
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