Thiol ligands bound to the metallic core of nanoparticles determine their interactions with the environment and self-assembly. However, very little is known about how ligands organize around a core and influence self-assembly. Recent studies suggest that equilibrium between bound and free thiols alters the ligand coverage of the core, and the fractional coverage of the bound thiols on the surface of the Au core, referred to as core-ligand coverage, is adequately described by Langmuir adsorption kinetics of the free thiols in the bulk solution. Here, X-ray scattering and MD simulations investigate water-supported monolayers of gold-core nanoparticles as a function of the core-ligand coverage that is varied in experiments by adjusting the concentration of total thiols (sum of free and bound thiols). Simulations demonstrate that the presence of free thiols produces a nearly symmetrical coating of ligands bound on the core. X-ray measurements show that above a critical value of 95% core-ligand coverage the nanoparticle core rises above the water surface, the edge-to-edge distance between neighboring nanoparticles increases, and the nanoparticle coverage of the surface decreases. Note that, above this critical value of the core-ligand coverage, the elasticity of the water-supported monolayer of the gold-core nanoparticles also vanished and the film became viscoelastic. These results demonstrate the important role of free thiols: they regulate the organization of bound thiols on the core and the interactions of nanoparticles with their surroundings.<br/>In this talk, I will also provide a brief overview of the user science program in X-ray scattering from liquid interfaces at NSF’s ChemMatCARS (Sector 15 of the Advanced Photon Source at Argonne National Laboratory in the U.S.A.).

Revealing fundamental details surrounding nanoparticle self-assembly

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.