Correlation of membrane structure and transport activity using combined scanning electrochemical-atomic force microscopy

The iontophoretic transport of Fe(CN)64- across a synthetic track-etched polyethylene terephthalate membrane has been investigated using combined scanning electrochemical-atomic force microscopy (SECM-AFM). This approach allows local fluxes, measured by amperometrically detecting Fe(CN)64- emerging across the membrane, to be related to the corresponding membrane topography. By comparing AFM and electrochemical images, only a fraction of candidate pore sites - identified topographically - are found to be active to transport. The ability to characterise the dimensions of the active pores allows quantitative analysis of electrochemical data. In contrast, conventional SECM alone does not allow a structural interpretation of measured fluxes, and the spatial resolution is poorer, due to the need to employ greater tip to surface separations and often larger tips.