Potentiodynamic Optical Contrast

Abstract

Charged solid structures in the presence of an electrolyte form a electric double layer (EDL). The EDL determines the electrochemical activity and influences the electrical and optical polarizability of these structures. Building a microscope capable of detecting the influence of the EDL on the optical polarizability of particles would assist in research on the EDL and potentiodynamic reactions. I report on the capabilities and workings of our home-build total internal reflection microscope with enhanced stability and conductive flowcell samples. Results include the experimentally demonstration that with this custom total internal reflection microscope we can detect restructuring of the EDL at the nanoscale. The temporal and spatial characterization of the scattering signal demonstrate that the potentiodynamic optical contrast (PDOC) is proportional to the accumulated charge of polarizable ions at the interface and its time derivative represents the nanoscale ionic current.