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The temperature dependence of L-type promoted Z-type ligand displacement on oleate-terminated semiconductor nanocrystals observed through NMR

Emile Drijvers (UGent) , Jonathan De Roo (UGent) , Jorick Maes (UGent) , Willem Walravens (UGent) , José Martins (UGent) and Zeger Hens (UGent)
Author
Organization
Project
  • IWT
Abstract
Ligand exchange is central in the processing semiconductor nanocrystals (NCs) and requires understanding of surface chemistry. In this respect, the Covalent Bond Classification provides an apt framework. This framework is most useful in order to describe recently developed ligand displacement schemes where association reactions are used to promote ligand desorption. For example, the displacement of Z-type metal carboxylates form CdSe or PbS NCs through complexation.1 Such reactions have raised extensive interest since they allow for a fine tuning of the ligand shell composition and could also occur during nanocrystal synthesis. Here, we analyse the thermodynamics of such association driven ligand displacement reactions, i.e. complex formation, by temperature dependent NMR. Most importantly, we find that these association reactions can render the overall ligand displacement reaction exothermic or endothermic, implying that the exchange equilibrium shifts to adsorption with increasing or decreasing temperature depending on the nature of the NC. By quantitative 1D 1H NMR, the thermodynamic equilibrium between adsorbed and displaced ligands can be mapped as a function of temperature. This provides us with key thermodynamic quantities such as the reaction enthalpy, which we compare for different materials and different association reactions. These results are most relevant for NC syntheses as they typically proceed at high temperature, where the adsorption of amine can prove negligible or substantial over the binding of metal carboxylates, but also to get NCs with ligand shells that have a finely tuned ligand density. References 1. N.C. Anderson, M.P. Hendricks, J.J. Choi, J.S. Owen J. Am. Chem. Soc. 2013, 135 (49), 18536–18548.
Keywords
NMR toolbox, surface chemistry, Quantum dots

Citation

Please use this url to cite or link to this publication:

MLA
Drijvers, Emile, et al. “The Temperature Dependence of L-Type Promoted Z-Type Ligand Displacement on Oleate-Terminated Semiconductor Nanocrystals Observed through NMR.” ChemCYS Book of Abstracts, Koninklijke Vlaamse Chemische Vereniging (KVCV). Jongerensectie, 2016.
APA
Drijvers, E., De Roo, J., Maes, J., Walravens, W., Martins, J., & Hens, Z. (2016). The temperature dependence of L-type promoted Z-type ligand displacement on oleate-terminated semiconductor nanocrystals observed through NMR. In ChemCYS book of abstracts. Blankenberge, Belgium: Koninklijke Vlaamse Chemische Vereniging (KVCV). Jongerensectie.
Chicago author-date
Drijvers, Emile, Jonathan De Roo, Jorick Maes, Willem Walravens, José Martins, and Zeger Hens. 2016. “The Temperature Dependence of L-Type Promoted Z-Type Ligand Displacement on Oleate-Terminated Semiconductor Nanocrystals Observed through NMR.” In ChemCYS Book of Abstracts. Koninklijke Vlaamse Chemische Vereniging (KVCV). Jongerensectie.
Chicago author-date (all authors)
Drijvers, Emile, Jonathan De Roo, Jorick Maes, Willem Walravens, José Martins, and Zeger Hens. 2016. “The Temperature Dependence of L-Type Promoted Z-Type Ligand Displacement on Oleate-Terminated Semiconductor Nanocrystals Observed through NMR.” In ChemCYS Book of Abstracts. Koninklijke Vlaamse Chemische Vereniging (KVCV). Jongerensectie.
Vancouver
1.
Drijvers E, De Roo J, Maes J, Walravens W, Martins J, Hens Z. The temperature dependence of L-type promoted Z-type ligand displacement on oleate-terminated semiconductor nanocrystals observed through NMR. In: ChemCYS book of abstracts. Koninklijke Vlaamse Chemische Vereniging (KVCV). Jongerensectie; 2016.
IEEE
[1]
E. Drijvers, J. De Roo, J. Maes, W. Walravens, J. Martins, and Z. Hens, “The temperature dependence of L-type promoted Z-type ligand displacement on oleate-terminated semiconductor nanocrystals observed through NMR,” in ChemCYS book of abstracts, Blankenberge, Belgium, 2016.
@inproceedings{7156610,
  abstract     = {Ligand exchange is central in the processing semiconductor nanocrystals (NCs) and requires understanding of surface chemistry. In this respect, the Covalent Bond Classification provides an apt framework. This framework is most useful in order to describe recently developed ligand displacement schemes where association reactions are used to promote ligand desorption. For example, the displacement of Z-type metal carboxylates form CdSe or PbS NCs through complexation.1 Such reactions have raised extensive interest since they allow for a fine tuning of the ligand shell composition and could also occur during nanocrystal synthesis.
Here, we analyse the thermodynamics of such association driven ligand displacement reactions, i.e. complex formation, by temperature dependent NMR. Most importantly, we find that these association reactions can render the overall ligand displacement reaction exothermic or endothermic, implying that the exchange equilibrium shifts to adsorption with increasing or decreasing temperature depending on the nature of the NC. By quantitative 1D 1H NMR, the thermodynamic equilibrium between adsorbed and displaced ligands can be mapped as a function of temperature. This provides us with key thermodynamic quantities such as the reaction enthalpy, which we compare for different materials and different association reactions. These results are most relevant for NC syntheses as they typically proceed at high temperature, where the adsorption of amine can prove negligible or substantial over the binding of metal carboxylates, but also to get NCs with ligand shells that have a finely tuned ligand density.
References
1. N.C. Anderson, M.P. Hendricks, J.J. Choi, J.S. Owen J. Am. Chem. Soc. 2013, 135 (49), 18536–18548.},
  author       = {Drijvers, Emile and De Roo, Jonathan and Maes, Jorick and Walravens, Willem and Martins, José and Hens, Zeger},
  booktitle    = {ChemCYS book of abstracts},
  keywords     = {NMR toolbox,surface chemistry,Quantum dots},
  language     = {eng},
  location     = {Blankenberge, Belgium},
  publisher    = {Koninklijke Vlaamse Chemische Vereniging (KVCV). Jongerensectie},
  title        = {The temperature dependence of L-type promoted Z-type ligand displacement on oleate-terminated semiconductor nanocrystals observed through NMR},
  year         = {2016},
}