Viscoelastic changes in Os-containing poly(allylamine) based redox hydrogels for amperometric enzyme electrodes: An EQCM study

Volume or mass and viscoelastic changes in Os(byp)(2)ClPyCH2NH2-poly(allyla mine) hydrogel (Os-PAA) cross-linked with glucose oxidase (GOx), have been measured by studying the electroacoustic impedance at 10 MHz. Film thicknes s and shear modulus have been obtained from imaginary and real components o f the EQCM acoustic impedance in transient (cyclic voltammetry and chronoam perometry) as well as steady state oxidation and reduction of the hydrogel. Swelling of the film during Os-II oxidation resulted in mass uptake and de crease of shear modulus. These quantities depend only on the degree of poly mer oxidation and not on film history or kinetics. Gravimetry beyond the Sa uerbrey mass limit could be realized by use of Martin's viscoelastic model to treat the quartz crystal impedance.