A Tale of Tails: Thermodynamics of CdSe Nanocrystal Surface Ligand Exchange

Orian Elimelech; Omer Aviv; Meirav Oded; Uri Banin

doi:10.1021/acs.nanolett.0c01913

A Tale of Tails: Thermodynamics of CdSe Nanocrystal Surface Ligand Exchange

Orian Elimelech, Omer Aviv, Meirav Oded, Uri Banin^*

^*Corresponding author for this work

Institute of Chemistry

Research output: Contribution to journal › Article › peer-review

34 Scopus citations

Abstract

The surface ligands of semiconductor nanocrystals (NCs) are central for determining their properties and for their flexible implementation in diverse applications. Thus far, the thermodynamic characteristics of ligand exchange reactions were attained by indirect methods. Isothermal titration calorimetry is utilized to directly and independently measure both the equilibrium constant and the reaction enthalpy of a model ligand exchange reaction from oleate-capped CdSe NCs to a series of alkylthiols. Increased reaction exothermicity for longer chains, accompanied by a decrease in reaction entropy with an overall enthalpy-entropy compensation behavior is observed, explained by the length-dependent interchain interactions and the organization of the bound ligands on the NCs' surface. An increase in the spontaneity of the reaction with decreasing NC size is also revealed, due to their enhanced surface reactivity. This work provides a fundamental understanding of the physicochemical properties of the NC surface with implications for NC surface ligand design.

Original language	American English
Pages (from-to)	6396-6403
Number of pages	8
Journal	Nano Letters
Volume	20
Issue number	9
DOIs	https://doi.org/10.1021/acs.nanolett.0c01913
State	Published - 9 Sep 2020

Bibliographical note

Funding Information:
This research was supported by the Israel Science Foundation-National Science Foundation China (ISF-NSFC) joint research program (grant No. 2495/17). O.E. and O.A. acknowledge support from the Hebrew University Center for Nanoscience and Nanotechnology. U.B. thanks the Alfred & Erica Larisch memorial chair. We thank Dr. Roy Hoffman and Mr. Yair Ozery from the NMR lab in the Hebrew University of Jerusalem for their support in the NMR measurements and analysis. We thank Prof. Daniel Harries from the Hebrew University of Jerusalem for insightful discussions.

Publisher Copyright:
Copyright © 2020 American Chemical Society.

Keywords

CdSe nanocrystals
enthalpy-entropy compensation
isothermal titration calorimetry
ligand exchange
nanocrystal surface analysis

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10.1021/acs.nanolett.0c01913

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title = "A Tale of Tails: Thermodynamics of CdSe Nanocrystal Surface Ligand Exchange",

abstract = "The surface ligands of semiconductor nanocrystals (NCs) are central for determining their properties and for their flexible implementation in diverse applications. Thus far, the thermodynamic characteristics of ligand exchange reactions were attained by indirect methods. Isothermal titration calorimetry is utilized to directly and independently measure both the equilibrium constant and the reaction enthalpy of a model ligand exchange reaction from oleate-capped CdSe NCs to a series of alkylthiols. Increased reaction exothermicity for longer chains, accompanied by a decrease in reaction entropy with an overall enthalpy-entropy compensation behavior is observed, explained by the length-dependent interchain interactions and the organization of the bound ligands on the NCs' surface. An increase in the spontaneity of the reaction with decreasing NC size is also revealed, due to their enhanced surface reactivity. This work provides a fundamental understanding of the physicochemical properties of the NC surface with implications for NC surface ligand design.",

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author = "Orian Elimelech and Omer Aviv and Meirav Oded and Uri Banin",

note = "Funding Information: This research was supported by the Israel Science Foundation-National Science Foundation China (ISF-NSFC) joint research program (grant No. 2495/17). O.E. and O.A. acknowledge support from the Hebrew University Center for Nanoscience and Nanotechnology. U.B. thanks the Alfred & Erica Larisch memorial chair. We thank Dr. Roy Hoffman and Mr. Yair Ozery from the NMR lab in the Hebrew University of Jerusalem for their support in the NMR measurements and analysis. We thank Prof. Daniel Harries from the Hebrew University of Jerusalem for insightful discussions. Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

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N2 - The surface ligands of semiconductor nanocrystals (NCs) are central for determining their properties and for their flexible implementation in diverse applications. Thus far, the thermodynamic characteristics of ligand exchange reactions were attained by indirect methods. Isothermal titration calorimetry is utilized to directly and independently measure both the equilibrium constant and the reaction enthalpy of a model ligand exchange reaction from oleate-capped CdSe NCs to a series of alkylthiols. Increased reaction exothermicity for longer chains, accompanied by a decrease in reaction entropy with an overall enthalpy-entropy compensation behavior is observed, explained by the length-dependent interchain interactions and the organization of the bound ligands on the NCs' surface. An increase in the spontaneity of the reaction with decreasing NC size is also revealed, due to their enhanced surface reactivity. This work provides a fundamental understanding of the physicochemical properties of the NC surface with implications for NC surface ligand design.

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A Tale of Tails: Thermodynamics of CdSe Nanocrystal Surface Ligand Exchange

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