(703g) Self-Assembly of Nanotriangle Superlattices Facilitated by Repulsive Electrostatic Interactions for SERS Enhancement

Walker, D. A., Northwestern University
Browne, K. P., Northwestern University
Kowalczyk, B., Northwestern University
Grzybowski, B. A., Northwestern University

Assemblies of nanoscopic components into ordered suprastructures is a promising route to new types of nanomaterials with applications in optoelectronics and sensors, to name just a few. Specifically, non-spherically symmetric nanoparticles have garnered much attention in the field of surface enhanced Raman spectroscopy (SERS) due to their sharp edges where electro-magnetic fields are concentrated into ?hot-spots'. Here we present a technique to deposit close-packed mono- and multi-layers of metallic triangular nanoprisms onto solid-substrates. Surprisingly, this assembly is the result of repulsive electrostatic interactions which help mediate the strong van der Waals interactions that typically lead to indiscriminate ?sticking' of the particles. In this way, the electrostatic interactions act as a ?molecular lubricant' during assembly, allowing the nanotriangles to fine-tune their mutual orientations into large crystalline arrays. By ordering the nanotriangles, we produce regions where the ?hot-spots' are superimposed and can produce SERS enhancement effects an order of magnitude larger than disordered aggregates.