ABSTRACT
The quantitative scanning electrochemical microscopy (SECM) theory has been developed for various regimes of measurements and electrochemical mechanisms. Different operating modes of the SECM, e.g., feedback and generation/collection modes, steady-state and transient measurements, require significantly different theoretical descriptions. Feedback theory has been the basis for most quantitative SECM applications reported to date. The formulation of the steady-state SECM problem is significantly simpler. The SECM feedback current can be produced by ET across a molecular monolayer adsorbed on the substrate surface. The theory was developed for three possible pathways: mediated ET, direct electron tunneling through the monolayer, and ET through pinholes. The theory for a disk-shaped tip approaching a surface-bound spherical particle was developed for quantitatively analyzing the SECM current vs distance curves and evaluating the particle size.
