Fullerenes LB films

Tens of conductive LB films have been developed so far, including metallic and superconductive LB films. These LB films are classified into the categories anion radical salt, charge-transfer complex, cation radical salt, conducting polymer, and transition metal complex in this section. The LB films, with metallic temperature dependences of conductivity, and the fullerene LB films, which exhibit a superconducting transition, are discussed separately. 

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... 

Relatively homogeneous fullerene LB films can be formed by mixing with arachidic acid [333]. This mixed film was used to construct a heterostructure with a PHT-arachidic acid layer, although no (bi)polaron formation was observed [341]. Donor-acceptor complexes of Cso with tetra(hexadecylthio)-TTF and BEDT-TTF were subjected to LB work. In both cases, multilayer film was formed at the air-water interface. Conductivity values of 4 and 20 S/cm for the tetra-(hexadecylthio)-TTF/C6o and the BEDT-TTF/Ceo system, respectively, were obtained after iodine doping of LB films [342]. 

The friction and wear properties of fullerene LB fihns have been investigated. The coefficient of kinetic friction was measured using a steel ball-on-glass disk method, with the LB films deposited onto the glass disk [326,327]. The friction coefficient dropped from 0.8... 

Potassium-doped LB film prepared from 50 layers of fullerene (C60) and deposited on a polyethylene terephtphalate substrate Microwave absorption or low-field signal Superconductivity was observed at or below 8.1 K 121... 

The association of porphyrin and fullerene electron acceptors in LB films can also proceed via a stepwise, noncovalent formation of the assembly, as demonstrated by Shinkai and Ikeda (Figure 13.88). The host-guest interaction of Ceo with homooxa-calix[3]arene is the noncovalent interaction that assists film formation The fullerene absorption in the host-guest complex is used to determine a surface concentration of 1.4 x 10 ° molcrn" in the Ceo layer, which is then further covered with the polymer-sustained porphyrins 165 or 166. Porphyrin surface concentrations are then controlled by UV-visible absorption and are found to be 7.6 X 10 and 5.5 x 10 for 165 and 166, respectively. Photocurrent measurements performed under irradiation at 420 nm, with a 1.36 mW cm for a coating of 165, and at 430 nm, with a 1.53mWcm for a coating of 166, in... 

Figure 13.88. Self-assembled porphyrin-fullerene dyad in LB films.

In this chapter, the electrochemistry of Langmuir-Blodgett (LB) films of functionalized molecules including molecular wire compounds, phthalocyanines, artificial lipids, proteins and fullerene derivatives, and carbon nanotubes (CNTs) is described. 

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... 

The LB film prepared in the dark shows temperature dependent UV-vis absorption spectra. At lower temperatures, there is an electronic interaction between the fullerene moieties in the LB film. Upon heating over 47 C, which is the subphase transition temperature of the cast films of the fullerene lipid [28, 36], the electronic interaction of the fullerene moieties is loosened. The electronic interaction between the fullerene moieties can be controlled by the phase change of the film. The fundamental property of the self-assembled bilayer membrane film is maintained in the LB film prepared in the dark, indicating that the molecular orientations of the... 

We have reviewed a recent progress on the electrochemistry of LB films and related films of functionalized molecules including molecular wire compounds, phthalocyanines, artificial lipids, proteins and fullerene derivatives, and carbon nanotubes. Ultrathin films with ordered structures on substrates should be promising nanomaterials for future nanoelectronic and molecular-information transducers with controllable and fine structures at the molecular level. The construction of such artificial nanomolecular devices is a great challenge in the near future. 

Langmuir and LB films such as fullerenes can be attached into the branching shell of the dendritic structure and, thus, efficiently incorporated in thin ordered films. 

Langmuir-Blodgett (LB) technique has been also used for the preparation of Pc-based OFET, as it allows the fine control of both the structure and the thickness of the film at the molecular level [226,227], OFET devices based on amphiphilic tris(phthalocyaninato) rare earth, triple-decker complexes have been prepared by LB technique, showing good OFET performances [228], More recently, ambipolar transport has also been realized in OFET devices through a combination of holeconducting CuPc and n-conducting Cgo fullerene, in which the asymmetry of the... 

In a clever attempt to form Langmuir monolayers of pure Cgo> Metzger and collaborators prepared an amphiphilic derivative by a thermally reversible Diels-Alder reaction (Scheme 7) [99], The temporary introduction of the car-boxyhc acid functionality guarantees an efficient anchoring of the fullerene spheroid to the water layer. The monolayers could be successfully transferred onto sohd substrates to form LB monolayers and multilayers. Upon heating, the Diels-Alder adduct decomposes, giving back Cgo. Thus, the final film consists of mixed layers of pure Cgo and Cgo/adduct. 

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