Particle interactions with surfaces in aqueous environments occur on the kT-energy scale. Investigating these interactions takes extremely sensitive, non-intrusive measurements. Total internal reflection microscopy (TIRM), which applies state-of-the-art evanescent wave scattering and video microscopy techniques, meets these requirements. Using TIRM we can track in real-time and space different engineered particles (silica and gold) at the silica-water interface. Our approach allows us to determine quantitatively the nature and relative importance of the different particle-surface forces (e.g. electrostatic, steric and van der Waals), and how these forces, diffusion coefficients, and stability respond to changes in solution conditions (i.e., pH and ionic strength). We have used TIRM to understand how silica gel layers present on silica particles and surfaces contribute to interaction potentials as a function of solution conditions. We have also used TIRM to measure the trajectories of gold rods interacting with silica surfaces as they diffuse through model two-dimensional porous media.

Using total internal reflection microscopy to quantitatively interrogate particle interactions at silica-water interfaces

245th National Meeting (2013)

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