Application of the Surface Resistance technique to detect the different interactions of ClO4-, SO4 2- and C6H5SO3- anions and Cu(II) cation with a gold surface partially blocked with poly(o-aminophenol).

R. TUCCERI

The Journal of the Argentine Chemical Society

Asociación Química Argentina

Lugar: Buenos Aires; Año: 2006 vol. 94 p. 55 - 70

0365-0375

 In this work is demonstrated that the Surface Resistance (SR) technique can be applied to detect the different interactions of anions, such as, perchlorate, sulphate and benzenesulphonate and also a cation as Cu(II), with a gold film surface, even when the metal film surface is partially blocked with an electroactive polymer film. Poly(o-aminophenol) (POAP) was employed as electroactive polymer to cover the surface of the thin gold film electrode. Also, resistometric changes are even detected after that the polymer covers completely the metal surface. Dependence of the resistance change on the external electrolyte composition for polymer thickness lower than 0.25 mC cm–2 was attributed to a competition, at the gold film surface, between the redox process of the polymer and adsorption of different species contained in the electrolyte. This reflects a discontinuous character of polymer thickness lower than 0.25 mC cm–2 at the metal|polymer interface. For polymer thickness higher than 0.8 mC cm–2, the resistometric response becomes independent of both the external electrolyte composition and polymer thickness. Thus, polymer thickness higher than 0.8 mC cm–2 seem to be enough compact at the metal|polymer interface to prevent the interaction of the species contained in the supporting electrolyte with the gold film surface. However, the resistometric change, even observed, was attributed to the redox conversion of the polymer. In this connection, the redox conversion of POAP from amine to imine groups leads to an increase of the gold film resistance. This increase was explained as a transition from specular to diffuse scattering of conduction electrons of gold at the gold|POAP interface due to a less compact distribution of oxidised sites (imine) as compared with that of the reduced ones (amine).