On the Surface of Nanoparticles: Implications on Sensing, Separations, and Spectroscopy

This talk will focus on correlating the architecture, stability, and surface chemistry of solution-phase gold and silver nanoparticles to their stability inside a capillary in the presence of an electric field, impact in a capillary electrophoresis separation of potential Parkinson's disease biomarkers, and enhancement of surface enhanced Raman scattering (SERS) signatures from small molecules. First, nanoparticle concentration, core composition, and surface chemistry will be shown to play an important role in the capillary electrophoresis separation of both nanoparticles themselves and disease biomarkers. Interactions between nanoparticles and (1) other nanoparticles, (2) the capillary wall, and (3) target molecules will be shown to depend on the surface chemistry and charge on the nanoparticles as well as on nanoparticle concentration. Second, a novel method which entraps gold or gold-coated silver nanoparticles in thin silica membranes will be demonstrated. The silica membrane prevents electromagnetic coupling between the nanoparticle cores without blocking the active metal surface for enhanced SERS and refractive index sensing. Applications related to the direct and quantitative detection of small molecules will be discussed. Improvements in understanding what is on the surface chemistry of a nanoparticle and how that surface chemistry influences the activity of the nanoparticles will have ultimate implications on the detection of target biological and environmental toxins.