Biomimetics with self-assembled monolayer of catalytically active tethered isoalloxazine on Au electrodes

ERNESTO J. CALVO; M. SILVINA ROTHACHER; CECILIA BONAZZOLA; IAN WHEELDON; ROBERTO C. SALVAREZZA; MARIA ELENA VELA; GUILLERMO BENITEZ

Coimbra, Portugal

Simposio; BIOELECTROCHEMISTRY 2005; 2005

International Society of Electrochemistry

A new biomimetic nanostructured electrocatalyst comprised of a self-assembled monolayer flavin covalently attached to Au by reaction of methylformylisoalloxazine with chemisorbed cysteamine is introduced. Examinations by Fourier transform infrared spectroscopy and scanning tunneling microscopy (STM) show that the flavin molecules are oriented perpendicular to the surface with a 2 nm separation between flavin molecules. As a result of the contrast observed in the STM profiles between areas only covered by unreacted cysteamine and those covered by flavin-cysteamine moieties, it can be seen that the flavin molecules rise 0.7 nm -cysteamine moieties, it can be seen that the flavin molecules rise 0.7 nm above the chemisorbed cysteamines. The SAM flavin electrocatalyst undergoes fast electron transfer with the underlying Au and shows activity toward the oxidation of enzymatically active â-NADH at pH 7 and very low potential (-0.2 V vs Ag/AgCl), a requirement for use in an enzymatic biofuel cell, and a 100-fold increase in activity with respect to the collisional reaction in solution. Modification of the local environment of the flavin molecules affect the electrocatalytic activity.