(195b) Small-Angle Neutron Scattering On Hydrophobically Stabilized Metal Nanoparticles in Gas-Expanded Liquids

We have examined the structural properties of alkane thiol stabilizing ligands using Small Angle Neutron Scattering (SANS) as a function of CO2 composition in Gas-Expanded Liquids (GXLs). SANS was used to determine the solvation effects of nanoparticle ligands as well as the effective ligand length as a function of the solvent properties. Recent advances in metallic nanoparticle synthesis and processing have opened the door for new opportunities with novel applications. For many of these nanoparticle applications, monodispersity is critical because of their size-dependent functionality. CO2 has been shown to work as an anti-solvent for organic solvent dispersed metal nanoparticles providing a means to size-fractionate them into monodisperse populations. Here, the stabilizing ligands play a major role in the synthesis and application of metallic nanoparticles and allow for dispersion in various solvents. Manipulation of the nanoparticle surface chemistry through synthesis or ligand exchange affords significant opportunity for solution based ?green? processing and impacts their potential applications; the solvent ? ligand interactions are deterministic of the nanoparticle behavior in solution. Previous work demonstrates the use of an interaction energy model to predict the dispersibility of nanoparticles in gas-expanded liquids (GXLs) as a function of the solvent ? ligand interactions; however, questions remain regarding the stabilizing ligand structure.