Applicability of chemical derivatization - X-ray photoelectron spectroscopy (CD-XPS) to the characterization of complex matrices: case of electrosynthesized polypyrroles

Problems arising in the application of XPS coupled with derivatization reac tions (CD-XPS) to the characterization of complex matrices are stressed by considering the case of polypyrroles electrosynthesized from aqueous soluti on. In these materials oxygen- and nitrogen-carbon functionalities are cont emporaneously present, as well as acidic, basic, charged and reducible grou ps. The derivatizing agents titanium di-isopropoxide-bis(2,4-pentanedionate ) (TAA), trifluoroethanol (TFE) and pentafluorophenylhydrazine (PFPH) were used to label the C-OH, COOH and C=O groups, respectively, in the pristine (PPY) and in the overoxidized (PPYox) polymer. The case shows that, when re al samples are analysed, only the correlation among the information present in all the available spectra can supply the key to the interpretation of C D-XPS data, such as the actual stoichiometry and secondary effects. In part icular, it is showed that PFPH cannot be used as a reliable derivatizing ag ent for C=O groups in PPYox, due to the competition of a side reaction (alr eady reported for hydrazines) occurring on this particular substrate. This effect may be disregarded if a thorough control of the stoichiometry is not performed. (C) 1998 Elsevier Science B.V. All rights reserved.