Monolayer-functionalized electrode

The reconstitution of apo-enzymes on relay-cofactor monolayer-functionalized electrodes was used to align redox enzymes and to establish electrical contact... 

Figure 5.42 Cyclic amperometric responses of a ft-CD functionalized monolayer on photoswitching of the bipyridinium-azobenzene diad currents are measured at a constant potential of —0.6 V. From M. Lahav, K. T. Ranjit, E. Katz and I. Willner, Photosimulated interactions of bipyridinium-azobenzene with a /3-aminocyclodextrin monolayer-functionalized electrode An optoelectronic assembly for the amperometric transduction of recorded optical signals, Isr.. Chem., 37, 185-195 (1997). Reproduced by permission of Laser Pages...

The association of the DNP-Ab to the antigen-monolayer-functionalized electrode leads to the electrical insulation of the electrode support and to the introduction of an electron barrier at the electrode surface. Thus, in the presence of an electrically wired enzyme (e.g., ferrocene-tethered glucose oxidase), the bioelectrocatalytic current is inhibited upon the formation of... 

Marx-Tibbon, S., Ben-Dov, I., and Willner, I. Electrochemical and quartz-crystal-microbalance transduction of light-controlled supramolecular interactions for monolayer-functionalized electrodes./. Am. Chem. Soc. 1996,118, 4717-4718. 

Katz E, Filanovsky B, WiUner I. A biofuel cell based on two immiscible solvents and glucose oxidase and microperoxidase-11 monolayer-functionalized electrodes. New J... 

Riskin M, Basnar B, Katz E, Willner I. Cyclic control of the surface properties of a monolayer-functionalized electrode by the electrochemical generation of Hg nanoclusters. Chem Eur J 2006 12 8549-8557. 

Underpotential deposition of heavy metals on H2 evolving electrodes is a well known problem [133], The existence of a direct correlation between H2 evolution activity and metal work function, makes UPD very likely on high work function electrodes like Pt or Ni. Cathode poisoning for H2 evolution is aggravated by UPD for two reasons. First, deposition potentials of UPD metals are shifted to more anodic values (by definition), and second, UPD favors a monolayer by monolayer growth causing a complete coverage of the cathode [100]. Thus H2 evolution may be poisoned by one monolayer of cadmium for example, the reversible bulk deposition potential of which is cathodic to the H2 evolution potential. 

As dehydrogenases (DH) are widely distributed enzymes, a number of studies have been carried out with these biocatalysts. For example, Willner el al. [20] have used a PQQ-monolayer functionalized gold electrode for the catalytic oxidation of NADH in the presence of Ca2+. In this scheme, the pyrrolo-quinoline quinine co-factor, PQQ, was covalently linked, as before for the GOx system [15, 20, 21], to the Au electrode,... 

Gauging catalysis by reference to an electrode where electrons are delivered (or eaten up) in an outer-sphere manner, redox catalysis is not expected to operate at a monolayer coated electrode (Figure 4.10), since, as discussed in Section 4.2.1, redox catalysis results from the three-dimensional dispersion of the catalyst. In contrast, there is no reason that chemical catalysis could not be operative at a monolayer coated electrode. For the same reasons, both redox catalysis and chemical catalysis are expected to function at multilayer electrode coatings (Figure 4.10). 

Figure 5.41 Optoelectronic functions of the cyclodextrin-monolayer-modified electrode and bipyridinium-azobenzene diad, as reported by Willner and co-workers [73]. Photoisomerization of the diad alters its ability to include in the cyclodextrin cavity and consequently write to the electrode...

Figure 3-5. (A) Assembly of reconstituted glucose oxidase on a PQQ-FAD monolayer linked to an Au-electrode. (H i Faradaic impedance spectra of the modified electrode at time intervals of reconstitution, (a) 0.1 h, (b) 0.25 h. (c) 0.5 h. (d) 1 h. (e) 2 h, (f) 4 h. Inset Interfacial electron transfer resistance of the modified electrode at time-intervals of reconstitution. (C) Cyclic voltammograms corresponding to the bioelectrocatalyzed oxidation of glucose, 80 mM, by the enzyme-functionalized electrode at time-intervals of reconstitution (a) 0 h, (b) 0.1 h, (c) 0.25 h, (d) 0.5 h, (e) 1 h, (f) 2 h, (g) 4 h. Inset Electrocatalytic currents transduced by the enzyme-modified electrode at time-intervals of reconstitution. Reproduced with permission from ref. 32. Copyright 2002 American Chemical Society.

Reconstitution of apo-glucose dehydrogenase on a PQQ-monolayer-functionalized Au-electrode led to an active configuration of the enzyme on the electrode support, but it lacked direct electrical contact with the electrode... 

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