Fullerene film electrode

Simple redox solutes, ferrocene, N, N, N, JV-tetramethyl-l,4-phenylenediam-ine, decamethylferrocene, bis(i-propylcyclopentadienyl) iron(ll), [Ru(phen)j] (0104)2, [Fe(bpy)3](0104)2, [Co(bpy)3](0104)2, and iodine have been studied at electrodes modified with polymeric fullerene films. FuUerene-modified electrodes were prepared by electropolymerization of Cjq initiated by traces of dioxygen or by simultaneous electroreduction of fullerene and Pd(ll) acetate trimer. For the former films, the electrochemical activity decreases upon potential cycling. The electrochemical activity of the film is stabihzed by the redox solute added to the electropolimerization stage due to the catalytic oxidation of the fullerene film by the oxidized form of the redox system. Similarly, positively charged species can also be incorporated into the structure of the film. The reversible behavior of redox solutes decreases with the increase in the thickness of the Pd/C q film. This film also incorporates ferricinium ion, N, N, N, N-tetramethyl-l,4-phenylenediamine cation, decamethylferricinium ion, and to a smaller degree [Co(bpy)3]"+ [53]. 

Electrochemical reductions of fuUerene films in the presence of Brnsted acids yield hydrogenated fullerenes H Cgg, where n depends on the acid, its concentration, and on the electrode potential. Hydrogenated fullerene films behave as semiconductors with increased photoefficiency [67]. 

The use of electrodes modified with immobilized redox-active molecules provides a simple methodology by which to study the ultrathin film electrochemistry of water-insoluble redox-active molecules, encouraging the application of such techniques to biomimetic membranes in aqueous media. It is of interest to use monolayer and LB films of enzymes, proteins, and antibodies as biosensors or biomolecular switches because of their high sensitivity for their substrates and antigens, respectively. The formation of thin fullerene films including fullerene-lipid hybrid and fullerene-lipid composite bilayer membranes is of interest both from a fundamental and practical application point of view. Multiwalled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) are novel nanomaterials that have remarkable electronic, mechanical, and thermal properties, and specific functions. Soluble carbon nanotubes in aqueous and organic systems are of interest since their study allows the... 

Electrochemistry of LB films of fullerenes has been widely studied and remains the subject of much research effort from both theoretical and experimental approaches. Bard etal. have studied basic electrochemistry of Ceo fullerene LB films on an electrode in acetonitrile solutions [23]. The study indicated that reduction of the fullerene films could form insoluble films with incorporated electrolyte cations or lead to dissolution. The study on Cgo LB films has become a focus of considerable interest however, it is difficult to fabricate high-quality LB films of pure Cgo due to its intrinsic hydropho-bicity. Kajiyama et al. applied a multistep creep method as an LB technique for constructing a fairly homogeneous Ceo monolayer, which is regularly packed in a hexagonal array [44]. Kunitake etal. developed the electrochemical replacement method to form epitaxial adlayers of fullerenes on Au(lll) surfaces [45]. The wet process method consists of the transfer of Langmuir films of fullerene onto iodine-modified Au(lll) surfaces at an air-water interface followed by the electrochemical removal and replacement of iodine adlayers with fullerene adlayers in solution. The fullerene adlayers prepared by this method showed excellent quality and uniformity. A visuahzing... 

Carbon nanocoils, as well as carbon nanotubes, constitute a new class of carbon nanomaterials with properties that differ significantly from other forms of carbon. The structure of a nanocoil is similar to that of MWCNTs, except helical shape. The catalysts supported on carbon nanocoils exhibited better electrocatalytic performance compared with the catalyst supported on Vulcan XC-72 carbon. In particular, the Pt-Ru alloy catalyst supported on the CNC, which has both good crystallinity and a large surface area, showed a superior electrocatalytic performance, compared with other CNC catalysts [43]. A fuller-ene (Cso) film electrode was also suggested as a catalyst support for methanol oxidation after electrodeposition of Pt on these fullerene nanoclusters [44]. 

EQCM [172] significantly contributed to the elucidation of mechanisms of electrochemical reactions of fullerene films. The principle of the method is simple and based on frequency measurement of a piezoelectric quartz crystal. The frequency is sensitive to mass and viscosity changes on a thin metal film (electrode) deposited on the quartz crystal. Most commonly any contribution from shear forces is neglected and the observed fi-equency changes are regarded as being... 

Thin films of fullerenes, which were deposited on an electrode surface via, for example, drop coating, were largely heterogeneous, due to the entrapping of solvent molecules into their domains. Consequently, their electrochemical behaviour displayed different degrees of reversibility and stability depending on the time of electrolysis and the... 

Fulleride anions are often more soluble, especially in more polar solvents, than the parent fullerenes. For example, in bulk electrolysis experiments with tetra-n-butylammonium perchlorate (TBACIO4) as supporting electrolyte, carried out in acetonitrile where Cjq is completely insoluble, fairly concentrated, dark red-brown solutions of 50 can be obtained [81]. Upon reoxidation, a quantitative deposition of a neutral Cjq film on the surface of a gold/quartz crystal working electrode takes place. This Cjq film can be stepwise reductively doped with TBA, leading to (Cjo )... 

The fullerene-containing films have been deposited on the electrodes in electrolysis of the TFE solution. The operating voltage of the cell is 5-80 V for the TFE solution with one of the additives from KOH, NaBr, KBr etc. and equals 200-1600 V for the solution without additives. The films form on the cathode and the anode simultaneously. The 25-100 pm thick films are largely deposited on the anode and the 1-10 pm thick films are deposited on the cathode. The thickness of the films depends on the experiment duration. However the thick films can be produced on the cathode and the thin films can be produced on the anode if the composition of the working solution is varied or the volume proportions of components of the working solution is selected in a certain way. The deposited films are distinct not only in thickness, but also in structure, composition and other... 

It has been demonstrated that electrochemical deposition of fullerene-containing films from the TFE solutions on the nickel electrodes is possible in principle. It has been found that the thickness, structure, density and chemical composition of the films depend heavily on the type of hydrocarbon solvents for fullerenes, the chemical composition of a base electrolyte and conditions for electrolysis. 

In conclusion, the above surface film formation processes are expected to occur with all types of the carbons mentioned (including doped diamonds and fullerenes) in nonaqueous solvents containing metal ion salts. Hence, when carbon electrodes are utilized for electroanalysis or electrosynthesis in such solutions at low potentials, they should be considered as modified electrodes covered with surface films that are, at least partially, electronic insulators (but may be ion conductors). 

Whenever a new material is discovered, the focus quickly shifts from fundamental research to the more applied aspects. Fullerenes and carbon nanotubes are no different in that respect. In the case of fullerenes thousands of new materials are synthesized, but a market-suitable product is not yet available. Perhaps the carbon nanotubes are closer to applications. Graphite fibers have proven to be very useful and nanotubes are at the very least, an extreme in the spectrum of the graphite fiber size scale. They retain many of the favorable properties of graphite and add to them new properties related to their nanoscopic size, as pointed out above. Directions that appear to have some promise involve different properties. Nanotube lamps and displays are already looming on the horizon. Also, nanotube films may be used as electrodes in solid state heterostructures [182]. 

Fig. 33 Tapping mode AFM images of P3HT PCBM films without (a, b) and with aluminum top electrode (c, d) at different PCBM concentrations. Large crystalline PCBM dendrites are observed for the larger fullerene concentration. (Reprinted with permission from [175], 2004, Institnte of Physics Publishing)...

SECM experiments in the field of thin films on electrode surfaces have attracted considerable attraction, since very high lateral resolution in the mid-nanometer scale can be achieved in combination with STM like conically shaped tips. The materials dealt with include self-assembled monolayers (SAM), fullerene derivatives, and inorganic salts. 

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