posted on 2021-02-03, 21:08authored byPan Sun, Linsey M. Nowack, Wei Bu, Mrinal K. Bera, Sean Griesemer, Morgan Reik, Joshua Portner, Stuart A. Rice, Mark L. Schlossman, Binhua Lin
Thiol
ligands bound to the metallic core of nanoparticles determine
their interactions with the environment and self-assembly. Recent
studies suggest that equilibrium between bound and free thiols alters
the ligand coverage of the core. 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 on the core. X-ray
measurements show that above a critical value of 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. 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.