Determination of monolayer-protected gold nanoparticle ligand–shell morphology using NMR

Abstract

It is accepted that the ligand shell morphology of nanoparticles coated with a monolayer of molecules can be partly responsible for important properties such as cell membrane penetration and wetting. When binary mixtures of molecules coat a nanoparticle, they can arrange randomly or separate into domains, for example, forming Janus, patchy or striped particles. To date, there is no straightforward method for the determination of such structures. Here we show that a combination of one-dimensional and two-dimensional NMR can be used to determine the ligand shell structure of a series of particles covered with aliphatic and aromatic ligands of varying composition. This approach is a powerful way to determine the ligand shell structure of patchy particles; it has the limitation of needing a whole series of compositions and ligands' combinations with NMR peaks well separated and whose shifts due to the surrounding environment can be large enough. Binary mixtures of molecules on the surface of nanoparticles can arrange randomly or into different domains to form Janus, patchy or striped particles. Liuet al.show that NMR can be used to determine the ligand-shell morphology of particles coated with aliphatic and aromatic ligands.