(408f) Structural Evaluation of Gold Nanoparticles with an Ionic Organic Corona: Single Component, High Nanoparticle Volume Fraction Fluids for Enhanced Optical Properties and Processability

Gold nanoparticles are of great interest due to their applications in surface enhanced Raman scattering (SERS), sensing and signaling, and multifunctional composites. Traditional synthetic techniques result in solutions with a low particle number density, aggregated dispersions at higher concentrations, and often intractable or waxy solids upon solvent removal. Maximizing the number density of nanoparticles to enable amorphous local order (glass or liquid) is advantageous for processing and specific pay offs for optical applications, where minimizing optical loss due to scaling is critical.

In contrast to polymeric or oligomeric surface functionalization, covalent passivation with organic based ionic liquids yields liquid-like behavior of the nanoparticle solid with organic fractions less than 20wt%. In the neat state, films appear gold in color and consist of self-assembled, hexagonally close packed arrays of gold nanoparticles. The optical characteristics (transmission and reflection) strongly depend on the particle size, diameter variation, and the molecular details (thickness, composition) of the corona. Perturbations of the film, such as by exposure to solvents, temperature or mechanical deformation disrupt the ordering, result in a change of the optical spectra. The results from small angle neutron scattering, transmission electron microscopy and x-ray diffraction will be summarized to yield structural details of the ionic organic corona and to establish relationships between the molecular details of the corona and the macroscopic optical, electrical and mechanical properties.