Electrochemical quartz crystal microbalance (EQCM) studies of films: Part 1. Ion and water transfers accompanying redox switching of Prussian Blue. Part 2. Adsorption of fibrinogen on gold modified electrodes with PPY

The Electrochemical Quartz Crystal Microbalance (EQCM) combined with cyclic voltammetry has been applied to kinetic studies and ion selectivity studies on Prussian Blue (PB) films. Two species transferred during redox switching of PB films. One, ion (mostly cation) and the other, solvent molecule (water) transferred under our experimental conditions. Chapter 2 and chapter 3 describe of PB redox switching in K₂SO₄ and in (NH ₄)₂SO₄ solutions, respectively. PB films had irreversible electrochemical behavior in both solutions. In K+ solutions, we observed an effect of anion on mass transfer, even though the primary K + was the transferring ion. Also, pH affected the nature of ion transfer. We found that (NH4)2SO4 concentration, voltage scan rates, scan direction, and charge level affected mass transfers. By utilizing information from pure K₂SO₄ and pure (NH ₄)₂SO₄ solutions, we were able to interpret the result of redox switching of PB films in 1:1 eqaui-molar mixture of K ₂SO₄ and (NH₄)₂SO₄ solutions. PB films were selective for transfer of NH₄+ over K+ at 4:1 ratio.; In the second part of this thesis, the adsorption of fibrinogen was investigated with the EQCM at a gold surface, and at polypyrrole (PPY). Fibrinogen is a key material in the cascade processes that produce thrombosis. Gold was chosen as a representative thrombogenic material and PPY was chosen as a model non-thrombogenic material. The adsorption process of fibrinogen on PPY and Au was potential dependent. Our studies revealed that adsorption of fibrinogen on PPY reached a constant time independent value; however, gold did not. On it, fibrinogen increased constantly with time.