ELECTROCHEMISTRY AND LANGMUIR TROUGH STUDIES OF C-60 AND C-70 FILMS

Thin films of the fullerenes C60 and C70, formed by solution casting, were studied by cyclic voltammetry (CV) in MeCN solutions containing quaternary ammonium or alkali-metal salts as supporting electrolytes. The film shows four CV reduction waves and one oxidation wave. The CV behavior for the first reduction, coulometrically equivalent to a one-electron reduction, indicates a large structural reorganization of the film with intercalation of the supporting electrolyte cation and a small amount of dissolution. Upon oxidation of the reduced form, the structure rearranges to form the parent. Similar effects occur for the second reduction/reoxidation process. The size of the cations affects the nature of these CV waves. Scanning electrochemical microscopy (SECM) of the C60 films indicates that neither the C60 film nor the completely reduced, C60-, form is a good electronic conductor, while a partially reduced film displays enhanced conductivity. Langmuir trough studies of C60 and C70 show the preparation of highly incompressible monolayer and multilayer films at the air/water interface. Mixed films of the fullerenes with the surfactant arachidic acid can also be prepared.