Immobilization of a series of Dawson type heteropolyanions

Attempts to immobilize a series of Dawson type heteropolyanions (HPAs) by a nodization and the use of polymeric, polyvinylpyridine (PVP), and conductin g pyrrole and N-methylpyrrole, films has been undertaken. A stable film of the Dawson Parent, [P2W18O62](6-) HPA was obtained on an anodized carbon el ectrode, the film exhibited thin layer behavior and was stable up to a pH v alue of 2.00. The same HPA was successfully immobilized in a protonated PVP film with the resultant modified electrode being stable between pH values of 1.00 and 8.00, with the redox activity of the immobilized HPA exhibiting the same pH dependence as shown by the solution phase species, It was show n that a stable polypyrrole film doped with the Dawson parent HPA was obtai ned when the cycling of the film was restricted to the first two tungsten-o xo based redox processes in buffer solutions more alkaline than 2.00, The C u-II Dawson HPA was successfully immobilized in a polypyrrole matrix exhibi ting good stability and clear redox activity for the Cu-II HPA. Poly(N-meth ylpyrrole) was found to be the most suitable conducting polymer film for th e immobilization of the Fell Dawson HPA. The film was found to be extremely stable to electrochemical cycling in a buffer solution of pH 4.50. The red ox activity of the immobilized HPA was clearly observed and well behaved. I n addition to this the electrocatalytic properties of the Fe-III HPA toward s the reduction of nitrite, as observed in solution, was preserved in the i mmobilized state.