Abstract
| - This paper describes a new approach for quantificationof rates of molecular transport through patterned, orotherwise heterogeneous, porous films supported on conductive substrates. Scanning Electrochemical Microscopy(SECM) has been used to image molecular sieving ofredox active probes by thin, electropolymerized films ofFe(5-amino-1,10-phenanthroline)32+ on micropatternedand microdisk array electrodes. Films as thin as 12 nmcompletely block redox mediators with average moleculardiameters greater than 12 Å, whereas smaller diameterprobes (radii 5−8 Å) were observed to permeate selectively. SECM tip currents measured for three differentredox permeants/mediators are observed to decrease withincreasing polymer thickness, consistent with a transportmodel that includes partitioning into and diffusion withinthe polymer films. Permeabilities, PDf, within the poly-[Fe(5-NH2-phen)32+] films have been quantitatively determined from the SECM tip currents and are in excellentagreement with data previously obtained from rotating-disk electrochemistry. This new methodology provides aversatile approach for quantitative investigation of membrane transport and permeation selectivity with goodlateral spatial resolution.
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