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1 1999

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Elektrochemiczne właściwości stałych warstw z udziałem fulerenów

Winkler Krzysztof, Płońska Marta E.

Wiadomości Chemiczne

1999

[Z] 53, 11-12

823--870

This paper reviews the results of the investigation of electrochemical properties of fullerenes and their derivatives in solid state. These systems can be divided into three groups: (i) crystalline thin films, (ii) non-crystalline Langmuir-Blodgett (LB) films and self-assembled monolayers (SAM), (iii) fullerene-based polymers. The electrochemical behaviour of crystalline films of fullerenes is very different from that of dissolved species. The method of the film preparation strongly influences the redox properties and morphology of the film. Fullerene films are composed of small crystallites. The layers grown upon vapour deposition and electrocrystallisation are more uniform than the solution (solvent)-cast films. The redox behaviour of crystalline fullerene films in polar solvents is mainly affected by the size of supporting electrolyte cations. For small cations of alkali and alkaline-earth metals a rapid deterioration in the electrochemical properties of fullerene films is observed during repeated potential cycling. This behaviour of the layer is attributed to the formation of an electrochemically inactive cation intercalated compound or dissolution of the fullerene salt. The manipulation of the time window of experiment and the solvent nature can favour one of the above processes over the other.(...) The voltammetric behaviour of LB films and SAMs containing fullerenes and their derivatives are less influenced by the medium. A much smaller structural reorganization upon electrochemical reactions is observed. Redox properties of the fullerene moieties in these structures are similar to these observed in solution. Tightly packed C(60) containing self-assembled layers exhibit resistive behaviour due to the resistance to ion incorporation. (... ) The polymeric network can also be formed through a copolymerization that utilises the formation of covalent bonds, between transition metal complexes and fullerenes. These films are insoluble in common organic solvents and adhere strongly to the electrode surface. They display very stable redox behaviour due to the presence of fullerene moieties in their structures. A significant decrease in resistivity in the potential region in which it is reduced is also observed. The rlrctrochemical switching between the doped (conducting) and undoped (non-conducting) states involves both electron and ion transport within the film. The overall control of charge percolation through electroactive material is governed by the transport of ions. Laser ablation of some of these electrochemically formed layers results in the formaton of C(59-2n)M (M=Pt and Ir) clusters.