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Utilizing self-exchange to address the binding of carboxylic acid ligands to CdSe quantum dots

Bernd Fritzinger (UGent) , Richard Capek (UGent) , Karel Lambert (UGent) , José Martins (UGent) and Zeger Hens (UGent)
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Abstract
We use solution NMR techniques to analyze the organic/inorganic interface of CdSe quantum dots (Q-CdSe) synthesized using oleic acid as a surfactant. It is shown that the resulting Q-CdSe are stabilized by tightly bound oleic acid species that only exchange upon addition of free oleic acid. The NMR analysis points toward a two-step exchange mechanism where free ligands are initially physisorbed within the ligand shell to end up as bound, chemisorbed ligands in a second step. Importantly, we find that every ligand is involved in this exchange process. By addition of oleic acid with a deuterated carboxyl headgroup, we demonstrate that the bound ligands are oleate ions and not oleic acid molecules. This explains why a dynamic adsorption/desorption equilibrium only occurs in the presence of excess free oleic acid, which donates the required proton. Comparing the number of oleate ligands to the excess cadmium per CdSe quantum dot, we find a ratio of 2:1. This completes the picture of Q-CdSe as organic/inorganic entities where the surface excess of Cd2+ is balanced by a double amount of oleate ligands, yielding overall neutral nanoparticles.
Keywords
COLLOIDAL NANOCRYSTALS, SURFACE STOICHIOMETRY, SEMICONDUCTOR NANOCRYSTALS, FIELD GRADIENT NMR, PBSE NANOCRYSTAL SOLIDS, ELECTRICAL-PROPERTIES, SOLAR-CELLS, NANOPARTICLES, SPECTROSCOPY, GROWTH

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Chicago
Fritzinger, Bernd, Richard Capek, Karel Lambert, José Martins, and Zeger Hens. 2010. “Utilizing Self-exchange to Address the Binding of Carboxylic Acid Ligands to CdSe Quantum Dots.” Journal of the American Chemical Society 132 (29): 10195–10201.
APA
Fritzinger, B., Capek, R., Lambert, K., Martins, J., & Hens, Z. (2010). Utilizing self-exchange to address the binding of carboxylic acid ligands to CdSe quantum dots. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 132(29), 10195–10201.
Vancouver
1.
Fritzinger B, Capek R, Lambert K, Martins J, Hens Z. Utilizing self-exchange to address the binding of carboxylic acid ligands to CdSe quantum dots. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. 2010;132(29):10195–201.
MLA
Fritzinger, Bernd, Richard Capek, Karel Lambert, et al. “Utilizing Self-exchange to Address the Binding of Carboxylic Acid Ligands to CdSe Quantum Dots.” JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132.29 (2010): 10195–10201. Print.
@article{1044641,
  abstract     = {We use solution NMR techniques to analyze the organic/inorganic interface of CdSe quantum dots (Q-CdSe) synthesized using oleic acid as a surfactant. It is shown that the resulting Q-CdSe are stabilized by tightly bound oleic acid species that only exchange upon addition of free oleic acid. The NMR analysis points toward a two-step exchange mechanism where free ligands are initially physisorbed within the ligand shell to end up as bound, chemisorbed ligands in a second step. Importantly, we find that every ligand is involved in this exchange process. By addition of oleic acid with a deuterated carboxyl headgroup, we demonstrate that the bound ligands are oleate ions and not oleic acid molecules. This explains why a dynamic adsorption/desorption equilibrium only occurs in the presence of excess free oleic acid, which donates the required proton. Comparing the number of oleate ligands to the excess cadmium per CdSe quantum dot, we find a ratio of 2:1. This completes the picture of Q-CdSe as organic/inorganic entities where the surface excess of Cd2+ is balanced by a double amount of oleate ligands, yielding overall neutral nanoparticles.},
  author       = {Fritzinger, Bernd and Capek, Richard and Lambert, Karel and Martins, Jos{\'e} and Hens, Zeger},
  issn         = {0002-7863},
  journal      = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
  keyword      = {COLLOIDAL NANOCRYSTALS,SURFACE STOICHIOMETRY,SEMICONDUCTOR NANOCRYSTALS,FIELD GRADIENT NMR,PBSE NANOCRYSTAL SOLIDS,ELECTRICAL-PROPERTIES,SOLAR-CELLS,NANOPARTICLES,SPECTROSCOPY,GROWTH},
  language     = {eng},
  number       = {29},
  pages        = {10195--10201},
  title        = {Utilizing self-exchange to address the binding of carboxylic acid ligands to CdSe quantum dots},
  url          = {http://dx.doi.org/10.1021/ja104351q},
  volume       = {132},
  year         = {2010},
}

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