X-ray photoelectron spectroscopy characterization of poly(2,3-diaminophenazine) films electrosynthesised on platinum

Films of poly(2,3-diaminophenazine) (PDAPh) were obtained on platinum substrates by electropolymerization (cyclic voltammetry, CV) of the monomer in acidic solutions. Limited investigations were performed by cyclic voltammetry and quartz crystal microbalance (QCM). CV showed that phenazine units are present along the polymer chains and exhibit their peculiar electrochemistry. QCM measurements confirmed the deposition of a film on the electrode surface during cyclic voltammetry on 2,3-diaminophenazine (DAPh) solutions. Film structures were thoroughly investigated by X-ray photoelectron spectroscopy (XPS) analysis both through curve fitting of C1s and N1s signals. XPS was also performed following chemical derivatization of samples for NH2, CO, COOH and OH groups with fluorinated markers. As a result, the presence of NH2 groups could be excluded, COOH and CO groups were found to be minor defects, whereas OH groups, more abundant, were assigned partly to oximic groups (–CN–OH). The possible presence of other structural defects involving nitrogen (N–N and N+–O−groups) was also suggested by XPS. Finally, theoretical calculations on electron spin densities of 2,3-diaminophenazine radicals seem to support a 1,2 coupling mechanism for 2,3-diaminophenazine electrochemical polymerization.