Electrochemistry and Langmuir trough studies of fullerene C60 and C70 films

Thin films of the fullerenes C{sub 60} and C{sub 70}, 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 C{sub 60} films indicates that neither the C{sub 60} film nor the completely reduced, C{sub 60}{sup -}, form is a good electronic conductor, while a partially reduced film displays enhanced conductivity. Langmuir trough studies of C{sub 60} and C{sub 70} 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. 42 refs., 18 figs., 1 tab.