Single molecule studies of diffusion at solid/liquid interfaces

COLL 115

Daniel K Schwartz, daniel.schwartz@colorado.edu and Andrei Honciuc, andrei.honciuc@colorado.edu. Department of Chemical and Biological Engineering, University of Colorado at Boulder, 424 UCB, Boulder, CO 80309-0424
We have tracked individual fatty-acid surfactant molecules adsorbed at the interface between fused silica and very dilute solution using total internal reflection fluorescence microscopy. A typical molecule moves randomly within a ~2 µm compartment for 1-10 seconds before escaping by jumping to another confined region and repeating the process, evidence of a complex energy landscape. The effective interfacial diffusion coefficient for the confined diffusion is ~0.05 μm2/s and essentially temperature-independent. The effective diffusion coefficient associated with the longer jumps between compartments increases systematically from 0.015 μm2/s to 0.05 μm2/s from 19 °C to 35 °C, consistent with an activation energy of ~40 kJ/mol for jumping.
 

The Physical Chemistry of Environmental Interfaces
2:00 PM-5:20 PM, Monday, April 7, 2008 Morial Convention Center -- Rm. 225, Oral

Division of Colloid & Surface Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008