EQCM study of the redox processes of polyvinylferrocene film in L-glutamine solution

In this paper, we investigate the polyvinylferrocene (PVF) redox behavior in contact with a bathing solution containing L-glutamine (Gln) by electrochemical quartz crystal microbalance (EQCM). Our study shows that the interaction of PVF with Gin is dramatically different from PVF redox behavior in salt solutions, e.g., NaClO ₄. Rather than the doping of anion in anodic process and undoping of anion in cathodic process, Gin doping and undoping are observed in either anodic or cathodic process depending on the redox potential. This effect is rationalized by the strong preadsorption of Gin in the reduced PVF film and the local pH change that subsequently changes the Gin zwitterions charge states during the oxidation and reduction of PVF. OH ^- ions also act as counterions and play critical roles in the redox switching of PVF processes in Gin bathing solution.