Lookup NU author(s): Professor Andrew Houlton,
Dr Ben Horrocks
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The charge transport in films consisting of metal complexes bound to DNA monolayers on Si(111) substrates was probed using scanning electrochemical microscopy (SECM) in the steady-state feedback mode. Lateral charge transport on the substrate - the source of SECM feedback - was found to depend on the charge exchange rate between the surface and solution as well as the rate of diffusion of charged, surface-bound species. A semi-analytical description of the steady-state SECM experiment with lateral charge transport was developed and used to analyze steady-state approach curves in solutions of various metal complex mediators at Si(111)/DNA substrates. Several possible charge transfer mechanisms (e.g., physical surface diffusion, electron hopping between DNA-bound redox species and DNA-mediated long range electron transfer) were explored as possible explanations for high positive feedback observed in Ru(bipy) 32+ and Ru(NH3)63+ solutions. While Ru(bipy)33+ was found to inject charge into the silicon valence band across the organic monolayer, surprisingly fast charge diffusion in Ru(NH3)63+/dsDNA films (effective diffusion coefficient, 2.1 × 10-5 cm2 s-1) was attributed to physical diffusion of the ruthenium centers on the surface. Anionic metal complexes are excluded from the DNA film (FeCN 64-, IrCl63-) and show negative feedback in the SECM experiment. Co(bipy)33+ also shows negative feedback which is presumably due to a much lower electron transfer self-exchange rate compared to the Ru(NH3)63+/2+couple. © 2004 The Electrochemical Society, Inc.
Author(s): Mirkin MV, Lie LH, Houlton A, Horrocks BR
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: 205th Meeting of The Electrochemical Society
Year of Conference: 2004
Publisher: Electrochemical Society, Inc.