The change of the electron scattering at the gold film-poly-o-aminophenol film interface after deactivation and reactivation of the polymer film by treatment with ferric ions

TUCCERI, R.

Los Cocos, Córdoba, Agentina

Conferencia; 9th Latin American Conference on Physical Organic Chemistry; 2007

AAIFQ, Conicet, FCQ (UNC)

THE CHANGE OF THE ELECTRON SCATTERING  AT THE GOLD FILM-POLY(O-AMINOPHENOL) FILM INTERFACE AFTER DEACTIVATION AND REACTIVATION OF THE POLYMER FILM BY TREATMENT WITH FERRIC IONS Ricardo Tucceri INIFTA, Suc. 4, Casilla de Correo 16, 1900, La Plata, Argentina. Facultad de Ciencias Exactas, Universidad  Nacional de La Plata. Fax: 0054-221-425-4642, E-Mail: rtucce@inifta.unlp.edu.ar.  In the same way as in a previous work [1], in the present work, the Surface Resistance (SR) technique and the Rotating Gold Disk Electrode Voltammetry (RGDEV) were applied to study the de-activation and re-activation processes of poly(o-aminophenol) (POAP) films, by consecutive treatments with ferric cations and NH4OH, respectively. This study was made in order to establish if redox sites distributions of POAP, and consequently the electron transport rate, initially distorted by de-activation by treatment with ferric cations are able to completely relax after re-activation by contact with a NH4OH solution. In the same way as in [1], the experimental arrangement in the first series of experiments of this investigation (SR) is one in which a POAP film is supported on a thin gold film whose thickness (fm ~ 30 nm) is of the order of the mean free path of the conduction electrons of gold. By employing a thin gold film as a base electrode one can apply simultaneously both Cyclic Voltammetry (CV), to characterize quantitatively the redox species transformation on the gold film surface contacting the polymer film, and SR to investigate changes in the electronic properties at the gold|POAP interface during the redox conversion of the polymer. In the second series of experiments, RGDEV was applied. To this end, POAP films deposited on a rotating gold disk electrode also were subjected to the same processes of de-activation and then re-activation, in the presence of ferric ions and a NH4OH solution, respectively. On the assumption that the efficiency of the polymer to mediate in an electron-transfer reaction at the polymer½solution interface, such as, the reduction of p-benzoquinone (Q) [2], should be affected by changes of the redox sites distribution, the RGDEV allowed one to interpret the de-activation and re-activation in terms of the change of an electron diffusion coefficient (De). This study seems to be interesting because it can be considered as complementary of that presented in [1], where the permanent de-activation of POAP achieved after to apply high positive potentials, is studied. Also, with regard to practical applications of POAP, this work could be interesting because the first step of de-activation of POAP (treatment with ferric ions), leads to one of its most interesting applications, which is to act as ferric cation sensor. In this work is demonstrated that this ability is accompanied by a simultaneous decrease of its redox activity.  [1] R. Tucceri, J. Electroanal. Chem., 562 (2004) 173-186. [2] A. Bonfranceschi, A. Pérez Córdoba, S. Keunchkarian, S. Zapata, R. Tucceri, J. Electroanal. Chem., 477 (1999) 1.