Dependence of the Band Gap of CdSe Quantum Dots on the Surface Coverage and Binding Mode of an Exciton-Delocalizing Ligand, Methylthiophenolate

Victor A. Amin, Kenneth O. Aruda, Bryan Lau, Andrew M. Rasmussen, Kedy Edme, Emily A Weiss

Research output: Contribution to journalArticle

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Abstract

Displacement of native octylphosphonate (OPA) ligands for methylthiophenolate (CH3-TP) on the surfaces of CdSe quantum dots (QDs) causes a moderate (up to 50 meV) decrease in the band gap (Eg) of the QD. Plots of the corresponding increase in apparent excitonic radius, ΔR, of the QDs versus the surface coverage of CH3-TP, measured by 1H NMR, for several sizes of QDs reveal that this ligand adsorbs in two distinct binding modes, (1) a tightly bound mode (Ka = 1.0 ± 0.3 × 104 M-1) capable of exciton delocalization, and (2) a more weakly bound mode (Ka = 8.3 ± 9.9 × 102 M-1) that has no discernible effect on exciton confinement. For tightly bound CH3-TP, the degree of delocalization induced in the QD is approximately linearly related to the fractional surface area occupied by the ligand for all sizes of QDs. Comparison of the dependence of ΔR on surface coverage of CH3-TP over a range of physical radii of the QDs, R = 1.1-2.4 nm, to analogous plots simulated using a 3D spherical potential well model yield a value for the confinement barrier presented to the excitonic hole by tightly bound CH3-TP of ∼1 eV.

Original languageEnglish
Pages (from-to)19423-19429
Number of pages7
JournalJournal of Physical Chemistry C
Volume119
Issue number33
DOIs
Publication statusPublished - Aug 20 2015

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Laser modes
Excitons
Semiconductor quantum dots
Energy gap
Ligands
quantum dots
excitons
ligands
plots
radii
LDS 751
Nuclear magnetic resonance
nuclear magnetic resonance
causes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Dependence of the Band Gap of CdSe Quantum Dots on the Surface Coverage and Binding Mode of an Exciton-Delocalizing Ligand, Methylthiophenolate. / Amin, Victor A.; Aruda, Kenneth O.; Lau, Bryan; Rasmussen, Andrew M.; Edme, Kedy; Weiss, Emily A.

In: Journal of Physical Chemistry C, Vol. 119, No. 33, 20.08.2015, p. 19423-19429.

Research output: Contribution to journalArticle

Amin, Victor A. ; Aruda, Kenneth O. ; Lau, Bryan ; Rasmussen, Andrew M. ; Edme, Kedy ; Weiss, Emily A. / Dependence of the Band Gap of CdSe Quantum Dots on the Surface Coverage and Binding Mode of an Exciton-Delocalizing Ligand, Methylthiophenolate. In: Journal of Physical Chemistry C. 2015 ; Vol. 119, No. 33. pp. 19423-19429.
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