In Situ Surface-enhanced Raman Scattering Spectroscopic Study of a Redox-active Deformable Hydrogel on a Roughened Au Electrode Surface

A highly deformable hydrogel, viologen pendant poly-L-lysine-based glutaraldehyde cross-linked hydrogel (PLLV-GA-gel), was characterized using surface-enhanced Raman scattering (SERS) signals under electrochemical control on a roughened Au electrode surface. We found that one-electron reduced forms remain near the electrode surface, preferentially as a dimer, even at the potentials at which all the viologens should be of a further reduced state. Implications of the SERS data were discussed in terms of heterogeneity and dimerization of one-electron reduced form viologens.