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 |
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Pages (from-to) | 6396-6403 |
Number of pages | 8 |
Journal | Nano Letters |
Volume | 20 |
Issue number | 9 |
DOIs | |
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