Permeation of electroactive organic probes through an electroinactive and passivating poly-ophenylenediamine (PPD) film electropolymerized on Pt and glassy carbon (GC) electrodes has been investigated by cyclic and rotating disk electrode (RDE) voltammetry. The access of solutes to the metal-polymer interface appears mainly governed by specific chemical interactions, influencing partition, and diffusion phenomena, rather than by exclusion effects based on molecular size or charge. Potential cycling of the film induces fine modifications in the chemical/physical structure of the polymer, as evidenced by electron spectroscopy for chemical analysis (ESCA) measurements and by an enhanced permeation of certain solutes. The membrane is, however, stable in the pH and potential range usually employed in its application, that is, as an enzyme-entrapping membrane in amperometric biosensors; because of membrane permselectivity, the electrochemical response of the most common electroactive interferents is deeply depressed.

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Articles you may be interested inLow contact resistivity of metals on nitrogen-doped cuprous oxide (Cu2O) thin-films J. Appl. Phys. 112, 084508 (2012); 10.1063/1.4758305Structure and corrosion behavior of platinum/ruthenium/nitrogen doped diamondlike carbon thin films An x-ray photoelectron spectroscopy ͑XPS͒ analysis was performed of polypyrroles ͑PPy͒ electrosynthesized on Pt in aqueous solution. Spectra were recorded both for the as-synthesized ͑pristine͒ polymer ͑specimen 1͒ and for the so-called ''overoxidized'' PPy ͑specimen 2͒. Electrosynthesis was accomplished potentiostatically at ϩ0.7 V vs SCE in KCl 10 mM containing pyrrole 0.4 M. Overoxidized PPy was obtained by keeping the pristine polymer at the electrosynthesis potential for 5 h, in phosphate buffer solution ͑pH 7͒. C, N, O ͑1s͒, and Cl 2p ͑pristine͒ spectra are included. Some minor elements, P ͑in the overoxidized polymer͒, Na ͑in some overoxidized samples͒, and Si ͑in other samples of both types of PPy, but not in those here reported͒, were also detected.

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X-ray photoelectron spectroscopy (XPS) is used in the present study to investigate the oxidation state and the structural role of titanium in two melanites with different Ti0 2 content (-3 % and-6 % wt) from M.Vulture (Italy). The Ti2p-XPS spectra can be satisfactorily fitted when Ti 3+ is lodged on octahedral and Ti 4+ distributed over octahedral and tetrahedral sites. The XPS direct estimates of Ti site populations match very weil with those indirectly obtained from Mössbauer spectroscopy (MS) through the Fe distribution. In addition, good agreement between the Fe 2+ JFe 3+ ratios estimated by both XPS and MS has been found using Fe 3 0 4 as a standard for interpreting Fe2p photoelectron spectra.

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