Electrochemical Quartz Crystal Impedance Study of Redox Hydrogel Mediators for Amperometric Enzyme Electrodes
Quartz crystal impedance around the resonant frequency at 10 MHz of a composite quartz crystal resonator has been studied simultaneously with cyclic voltammetry. A modified quartz crystal with a redox hydrogel (poly(allylamine)-ferrocene cross-linked with glucose oxidase) and immersed in liquid elec...
| Publicado: |
1997
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00032700_v69_n23_p4833_Etchenique http://hdl.handle.net/20.500.12110/paper_00032700_v69_n23_p4833_Etchenique |
| Aporte de: |
| Sumario: | Quartz crystal impedance around the resonant frequency at 10 MHz of a composite quartz crystal resonator has been studied simultaneously with cyclic voltammetry. A modified quartz crystal with a redox hydrogel (poly(allylamine)-ferrocene cross-linked with glucose oxidase) and immersed in liquid electrolyte was used. Impedance parameters (Rf and XLf) of the surface redox gel film were obtained by fitting the resonator transfer function |Vo/Vi| vs ω to a BVD equivalent circuit and analyzed with the multiple nonpiezoelectric layer model of Martin. Two limiting hydrogel layers of the same composition were studied while oxidizing and reducing the ferrocene/ferricenium moieties attached to the swollen polymer backbone: thin and thick redox hydrogel films. For the thin films, the Sauerbrey approximation was valid. The mass/thickness and film viscosity changes that resulted from the anion and water exchange were evaluated while redox switching the polymer on the assumption of negligible storage modulus G′ and a density of 1. For thick gel layers, on the other hand, the penetration depth of the acoustic wave was far less than the film thickness, and a liquid-like behavior was apparent. Film storage modulus and film loss modulus were simultaneously evaluated with the cyclic voltammetry. |
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