Figure 4: Characterization of redox changes within TTF–PPEs.

Ultraviolet–vis absorption spectra changes (in anhydrous THF, 298 K) on successively adding oxidant Fe(ClO4)3·6H2O in solutions of (a) PPE and (b) TTF–PPE. The initial state TTF–PPE (black) and final dication state TTF2+–PPE (red) are indicated in bold. (b) Inset, the change of ESR spectrum with the addition of oxidant and blue curve refers to the radical state TTF·+–PPE. (c) and (d) C 1s XPS spectra for self-assembled films of PPE and TTF–PPE before and after oxidant treatment, respectively. A clear change in C 1s spectra for TTF–PPE films can be observed, which is absent for that of PPE.