Nanophase Segregation of Self-Assembled Monolayers on Gold Nanoparticles

Abstract

Nanophase segregation of a bi-component thiol self-assembled monolayer is predicted using atomistic molecular dynamics simulations and experimentally confirmed. The simulations suggest the formation of domains rich in acid-terminated chains, on one hand, and of domains rich in amide-functionalized ethylene glycol oligomers, on the other hand. In particular, within the amide-ethylene glycol oligomers region, a key role is played by the formation of inter-chain hydrogen bonds. The predicted phase segregation is experimentally confirmed by the synthesis of 35 and 15 nm gold nanoparticles functionalized with several binary mixtures of ligands. An extensive study by transmission electron microscopy and electron tomography using silica selective heterogeneous nucleation on acid-rich domains to provide electron contrast supports simulations and highlights patchy nanoparticles with a trend towards Janus nano-objects depending on the nature of the ligands and the particle size. These results validate our computational platform as an effective tool to predict nanophase separation in organic mixtures on a surface and drive further exploration of advanced nanoparticle functionalization.

Beyond the Compositional Threshold of Nanoparticle-Based Materials

“…In situ characterizations, like NAP-XPS and TEM 31 will be pertinent in this context, but again the example of gold particles draws future guidelines to understand hybrid interfaces, especially the organic layer composition and the ligands distribution, by Nuclear Magnetic Resonance 56 and electron tomography 57 coupled to Density Functional Theory calculations and molecular dynamic simulations. 56,57…”

Phase separation in mixed polymer brushes on nanoparticle surfaces enables the generation of anisotropic nanoarchitectures

“…A more elegant and scalable strategy to desymmetrize the scaffolds is to exploit specific interactions in ligand-modified nanoparticles in order to induce the formation of surface patterns. [28][29][30][31] The ability to control surface pattern formation on polymercoated nanoparticles recently received much focus in the polymer science community. 32,33 For example, constrained de-wetting of homopolymer ligands under bad solvent conditions had been demonstrated as a versatile paradigm in this regard.…”

Nanoparticle Assembling through Click Chemistry Directed by Mixed SAMs for Magnetic Applications

“…This result agrees with our earlier findings, stating that the Au−S binding energy is expected to be related to the sulfur hybridization. 30,32,54 Concerning the effect of the thiol adsorption on the Au(111) surface, a precursor state for the formation of an adatom can be seen (Figure 7). STM measurements and theoretical calculations showed that the S-CC assembly is more stable than S-CH 3 assembly.…”

“…5 This finding does not include entropic considerations to stabilization/formation, which are expected to be of similar magnitude for all SAMs because of the similar physicochemical properties of both thiol derivatives. 30,32,54 Furthermore, the binding energy (2.6 eV) was calculated to be constant throughout the mixture series. This result agrees with our earlier findings, stating that the Au−S binding energy is expected to be related to the sulfur hybridization.…”

“…11 Finally, we also investigated theoretically the structure of mixed SAMS at the periodic DFT level 31 and studied its dynamics, very recently. 32 Herein, we report on the structuring of nanoparticle assembly by adapting the click chemistry approach to mixed SAMs supported on gold thin films which were used to direct nanoparticle assemblies ( Figure 1). In contrast to our previous studies which were conducted on single components alkyneterminated SAMs, we took advantage of the ability of molecules to segregate in mixed SAMs in order to modulate the structure of nanoparticle assembly.…”