Monolayer faradaic impedance

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.

Patolsky, K, Zayats, M., Katz, E., and Willner, I. (1999) Precipitation of an insoluble product on enzyme monolayer electrodes for biosensor applications Characterization by faradaic impedance spectroscopy, cyclic voltammetry, and microgravimetric quartz crystal microbalance analyses. Anal. Chem. 71, 3171-3180... 

Fig. 2.18 An equivalent circuit representing an electrode/solution interface. The electrode surface is covered by a monolayer of a redox-active species. e ac potential across the faradaic unit of equivalent circuit, Ca double-layer capacitance, Rs -uncompensated solution resistance, Zf impedance representing solely the electron transfer reaction process of the monolayer, )> ac current due to the faradaic process, Z, total impedance of the whole system, ks. heterogeneous electron transfer rate constant of the monolayer of electroactive species, R charge transfer resistance, Q capacitance associated with the redox reaction of the adsorbed species.

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