Quantified Binding Scale of Competing Ligands at the Surface of Gold Nanoparticles: The Role of Entropy and Intermolecular Forces

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 13; no. 20
• Main Authors: Goldmann, Claire, Ribot, François, Peiretti, Leonardo F., Quaino, Paola, Tielens, Frederik, Sanchez, Clément, Chanéac, Corinne, Portehault, David
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-05-2017; Wiley-VCH Verlag
• Subjects: Chemical Sciences; Composition; Coronas; Density functional theory; Exchanging; Gold; gold nanoparticles; Intermolecular forces; ligand exchange; Ligands; Magnetic properties; Modelling; multifunctional nanoparticles; Nanoparticles; Nanotechnology; NMR; Nuclear magnetic resonance; Self-assembled monolayers; Self-assembly; Thiols; ligand exchange; multifunctional nanoparticles; gold nanoparticles; nuclear magnetic resonance; density functional theory; Ligand exchange; Nuclear Magnetic Resonance; Gold nanoparticles; Multifunctional nanoparticles; Density Functional Theory
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201604028

A basic understanding of the driving forces for the formation of multiligand coronas or self‐assembled monolayers over metal nanoparticles is mandatory to control and predict the properties of ligand‐protected nanoparticles. Herein, 1H nuclear magnetic resonance experiments and advanced density functional theory (DFT) modeling are combined to highlight the key parameters defining the efficiency of ligand exchange on dispersed gold nanoparticles. The compositions of the surface and of the liquid reaction medium are quantitatively correlated for bifunctional gold nanoparticles protected by a range of competing thiols, including an alkylthiol, arylthiols of varying chain length, thiols functionalized by ethyleneglycol units, and amide groups. These partitions are used to build scales that quantify the ability of a ligand to exchange dodecanethiol. Such scales can be used to target a specific surface composition by choosing the right exchange conditions (ligand ratio, concentrations, and particle size). In the specific case of arylthiols, the exchange ability scale is exploited with the help of DFT modeling to unveil the roles of intermolecular forces and entropic effects in driving ligand exchange. It is finally suggested that similar considerations may apply to other ligands and to direct biligand synthesis.
Quantitative assessment by NMR of the surface composition of gold nanoparticles capped by competing thiol ligands unravels the relationship between the compositions of the ligand shell and the reaction medium. The combination with DFT calculations unveils the role of intermolecular forces and entropy on the stability of mixed ligand shells, toward further control of multifunctionality in hybrid nanoparticles.