XPS/UPS studies of conducting polymers: Exchange doping of dye molecules into polymer matrix

The valence bands and the core levels of conducting polymers synthesized through electrochemical process with large organic cation molecules, such as dye molecules with π-electron systems, were investigated by XPS/UPS measurements. The present work clarified the identification of each electrochemical state of the synthesized materials. The present XPS/UPS study confirmed the exchange doping, where polycyclic molecules are injected into polymer matrix in the positive ionic form exchanging the original anion dopants, through electrochemical reduction in the case of polypyrrole-methylene blue system. Both the states of 2b₁ and 1a₂, corresponding to conductive and non-conductive states, were observed in the valence band spectrum of the electrochemically reduced state, which is different from the spectra of anion-doped conducting polymers.