Characterising the self-assembly of ternary mixed ligand shell structures on Au nanoparticles and quantum dots using small-angle neutron scattering

Metallic and semiconductor nanoparticles and quantum dots have various coating and detection applications and can be functionalised into highly tunable ligand-shell nanoparticles. Ligand shells allow tuning the dispersion, self-assembly and surface active properties of the nanoparticles. However, understanding of the self-assembly process behind ligand shell structure remains limited. SANS combined with with physically informed Monte Carlo simulation offers improved understanding of the self-assembly process and equilibrium structures of ligand shells. Neutron scattering enables studying these multi-phase systems by contrast matching. It is understood that ligand-ligand interactions play a critical role in structure formation, so it is interesting to study ligands of different compositions and sizes. For this study, alkanethiol acids, alkanethiols, and thiolated polyethylene glycols are used to functionalise gold nanoparticles with up to three different components. A mixture of alkanethiol acids and alkanethiols is used to prepare amphiphilic nanoparticles, additionally functionalised with PEGs as a third component. The obtained SANS data is fitted via physically informed Monte Carlo methods to reproduce the physical structures of the ternary ligand shells. Comparisons between sample variations are used to estimate the effect of physical parameters such as adsorption rates, phase separation rates and ligand alignment rates dependent on ligand-ligand interactions.