Bright gradient-alloyed CdSeₓS₁₋ₓ quantum dots exhibiting cyan-blue emission

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DOIResolve DOI: https://doi.org/10.1021/acs.chemmater.5b04380
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Name affiliation
  1. National Research Council of Canada. Security and Disruptive Technologies
  2. National Research Council of Canada. Energy, Mining and Environment
  3. National Research Council of Canada
  4. National Research Council of Canada. Information and Communication Technologies
  5. National Research Council of Canada. Measurement Science and Standards
FormatText, Article
Journal titleChemistry of Materials
ISSN0897-4756
1520-5002
Volume28
Issue2
Pages618–625
Abstract
Highly emissive alloyed CdSeS quantum dots (QDs) with a gradient structure exhibiting photoluminescence (PL) peaking at 490 nm and an absolute quantum yield (QY) of 79% (in toluene with excitation wavelength of 430 nm) were designed and synthesized. The cyan-blue emitters were synthesized at 180 °C in 1-octadecene (ODE) with cadmium oleate (Cd(OA)2), tri-n-octylphosphine selenide (TOPSe), and tri-n-octylphosphine sulfide (TOPS) as the Cd, Se, and S precursors, respectively; importantly, a commercial secondary phosphine, diphenyl phosphine (DPP or HPPh2), was used as a beneficial additive. Also, our high Cd/(Se + S) feed molar ratio aids in shifting the equilibrium of the chalcogenide exchange, TOPE + HPPh2 ⇔ TOP + E═PPh2H, to the right. Density functional theory (DFT) calculations suggest that the formation of Se═PPh2H proceeds faster than that of S═PPh2H, which supports our high S/Se feed molar ratio used to synthesize the bright gradient-alloyed CdSeS QDs. Compositional and structural characterization was carried out using powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and solid-state nuclear magnetic resonance spectroscopy (NMR). Particularly, our solid-state 113Cd NMR analysis reveals that the highly emissive CdSeS QDs consist of a three-domain structure with a Se-rich inner core region, a Se/S equivalent middle region, and a S-rich outer region. The present study highlights the importance on the use of secondary phosphines together with high cation/anion feed molar ratios in the rational design and synthesis of high-quality metal chalcogenide QDs at relatively low temperature but with high yield and reproducibility.
Publication date
PublisherAmerican Chemical Society
LanguageEnglish
Peer reviewedYes
NPARC number21277214
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