Aqueous dispersions of gold nanoparticles are colloidally stable, usually, due to electrostatic repulsion from the charged headgroups of bound ions or ligands.  While the average surface charge of colloidal nanoparticles may be inferred from zeta potential measurements,  the dynamics of these ligands on the nanoparticle surface are difficult to study. Moreover, at the centimeter scale, the fundamental surface chemistry on nanoparticles can affect the mechanical properties of nanoparticle-polymer composites.  In keeping with the multiscale spirit of this symposium, studies will be described that range from the nanoparticle surface level all the way to the centimeter-scale composite level.  At the nanoparticle surface level, on-particle ligand dynamics can be quantified by NMR T2 measurements, should the scientist be fortunate enough to avoid nanoparticle aggregation within the NMR tube. In a study that used 1-25 nm gold cores, it was found that a particular quaternary ammonium ligand was the most floppy for sub-4 -nm particles, in spite of having a larger ligand density on these smaller size cores.  The results were rationalized with molecular dynamics simulations.  At macroscopic length scales, the dispersion of colloidal gold nanorods into hydrogels demonstrated an increased ability to stretch the gel, for a particular surface chemistry that recapitulated the chemistry of the gels themselves.

Ligand dynamics on colloidal gold surfaces: From NMR to stretchable composites

ACS Spring 2022

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