Diffusional Transport to Nanoscopic Band Electrodes

摘要

Diffusion controlled reactions of electroactive molecules at 2 0-1000A wide platinum band electrodes are reported. The reduction of 5,6,11,12-Cp Ru(eta-C6H5)4napthacene 4+ and oxidation of Cp 2Fe (Cp = pentamethylcyclopentadienyl) occur at significantly lower rates at electrodes less than 200A wide than predicted by transport equations based on continuum fluid structure. The results are in qualitative agreement with a recently proposed size-effect theory that accounts for (i) finite dimensions of the reacting molecule and (ii) a decrease in molecular diffusivity near a charged electrode surface. Scanning tunneling microscopy of Pt films used in electrode fabrication indicates an average surface roughness of ca. 10-15A. Microelectrodes molecular transport; Interfacial fluid structure.(mjm)