Investigation on the growth mechanism and chemical structure of a very thin, insulating, film synthesized on Pt substrates by electropolymerization of OAP (o-aminophenol ) in water at neutral pH. Combined surface and electrochemical studies

1. Introduction Organic films electrodeposited on metallic surfaces can reveal interesting properties and be of great utility in many areas of research, for example, as basic components in electrocatalysis, biosensor and electrochromic devices, as protective agents against corrosion and more, depending on film characteristics which in turn depend on chemical composition and morphology, growth conditions and electrochemical environments. In the last decades attention was focused on organic films made of aromatic compounds such as phenols, anilines and more recently ortho-aminophenols, OAPs. Notably, OAP films show tunable properties depending on pH, evidencing remarkable electroactivities or a strong passivating behaviour if synthesized in acidic and in neutral/ basic media, respectively [1]. 2. Insulating POAP Here we report on the electrochemical and surface characterization of poly-ortho-aminophenol, POAP, an insulating film, few nanometres thick, grown on platinum from OAP solution (5 mM) at neutral pH (phosphate buffer, I=0.1M) by cyclic voltammetry, CV. In this work XPS has represented the main means for the qualitative and semi-quantitative investigation of POAP and used in ‘Medium Area’ acquisition modality for the following comparative experiments: Reproducibility and UHV stability tests, Angle-resolved XPS (In depth analysis for the estimation of film thickness, Study of the growth mechanisms (influence of the CV cycles numbers on film composition) 3. Hypotheses on the mechanism of polymerization The obtained results, compared for the different experimental conditions, have allowed to formulate hypotheses on the polymerization mechanism and repeat chemical structure of POAP. The influence of interface reactions on film composition and morphology could here be rationalized, thanks to a well-established XPS curve-fitting procedure [2] and combined AFM and CV analyses. In perspectives, the characteristics of this film as permselective membrane [3] are considered also in view of possible bio-applications. References [1] R.Tucceri, P.Arnal, A.Scian, ISRN Polymer Science (2012): A Review Article [2] J.E.Castle, A.M.Salvi, Journal Electron Spectroscopy and Related Phenomena, 114-116 (2001) [3] A. Guerrieri, R. Ciriello, D. Centonze, Biosensors and Bioelectronics, 24, 1550–1556 (2009)