Fullerenes basics

In investigating the metal coating of C70, we will also replace Ba by Ca in the data presented. The coaling of the fullerenes with the latter material is basically identical but exhibits additional interesting features that will be discussed below. Figure 3 shows two mass spectra, the upper one of C oCa, the lower of CvoCa, both obtained under similar conditions as the spec-... 

The standard method to synthesize MWCNTs is based on the electric-arc experiment proposed by Ebbesen and Ajayan [8]. Basically, the production system is similar to the one used by Kratschmer et al. [11] to produce macroscopic quantities of C o and the main difference between the two experiments is the inert gas pressure, that must be rather low (20-100 mbar) for an efficient fullerene production [11], but must be increased to 350-700 mbar to generate nanotubes efficiently [8],... 

A Friedel-Crafts-type reaction of phenols under basic conditions is also possible. Aqueous alkaline phenol-aldehyde condensation is the reaction for generating phenol-formaldehyde resin.34 The condensation of phenol with glyoxylic acid in alkaline solution by using aqueous glyoxylic acid generates 4-hydroxyphenylacetic acid. The use of tetraalkylammonium hydroxide instead of sodium hydroxide increases the para-selectivity of the condensation.35 Base-catalyzed formation of benzo[b]furano[60]- and -[70]fullerenes occurred via the reaction of C60CI6 with phenol in the presence of aqueous KOH and under nitrogen.36... 

In principle, there are four basic strategies to compensate for the repulsive effects between the hydrophobic fullerene surface and water (a) encapsulation in the internal hydrophobic moiety of water-soluble hosts like cyclodextrins (Andersson et al., 1992 Murthy and Geckeler, 2001), calixarenes (Kunsagi-Mate et al., 2004) or cyclotriveratrylenes (Rio and Nierengarten, 2002) (b) supramolecular or covalent incorporation of fullerenes or derivatives into water-soluble polymers (Giacalone and Martin, 2006) or biomolecules like proteins (Pellarini et al., 2001 Yang et al., 2007) (c) suspension with the aid of appropriate surfactants and (d) direct exohe-dral functionalization in order to introduce hydrophilic moieties. 

A comparable addition pattern with as many as five attached groups allowing further functionalization is represented in pentaaryl-fullerenes like 25-27 (Troshina et al., 2007 Zhong et al., 2006). Whereas the free acids are virtually insoluble in pure water, the use of basic water in the case of 25 (Zhong et al., 2006) and conversion of the polyacids 26 and 27 to the corresponding potassium salts leads to stable aqueous solutions with high fullerene concentrations. 

The most reasonable explanation for the observed differences in fullerene behavior as a part of complex C60/PVP in chemical and biological systems is the fact that the complex itself is stable in the pure water media. Dissolution in the saline causes the formation of fullerene precipitate, which, naturally reveals the photodynamic properties. But a basic difference between water-soluble C60 complexes with organic compounds (PVP, y-CD, etc.) from other forms used for biological investigations is the low degree of fullerene molecules association... 

The application of fullerene on the surfaces has an essential advantage in the studies with cell cultures as in this case we can obtain the maximum contact of cells with fullerene - cells adhere on the surface and colonize it as a confluent monolayer. That is the basic difference from the water-soluble complexes and micro-dispersed suspensions of fullerene C60. The pro-/antioxidant activities of fullerene were tested in chemical and biological systems. 

Covalent functionalization of fullerenes has also been used to obtain surface-modified fullerenes that are more compatible to polymer matrices in order to fabricate composites. In this context, four basic strategies were developed. The first one allows the fullerenes to react during the monomer polymerization, so that the fullerene can be attached to the polymer chain [111, 112]. Second, an already synthesized polymer is treated using specific conditions that allow the chemical reaction with fullerenes [113,114]. Third, the fullerenes are chemically bonded to a monomer which is polymerized or co-polymerized to obtain the modified monomer [115,116]. Fourth, a dendrimer can be synthesized around a fullerene which then acts as a nucleus [117,118]. 

Although there have been great advances in covalent functionalization of fullerenes to obtain surface-modified fullerene derivatives or fullerene polymers, the application of these compounds in composites still remains unexplored, basically because of the low availability of these compounds [132]. However, until now, modified fullerene derivatives have been used to prepare composites with different polymers, including acrylic [133,134] or vinyl polymers [135], polystyrene [136], polyethylene [137], and polyimide [138,139], amongst others. These composite materials have found applications especially in the field of optoelectronics [140] in which the most important applications of the fullerene-polymer composites have been in the field of photovoltaic and optical-limiting materials [141]. The methods to covalently functionalize fullerenes and their application for composites or hybrid materials are very well established and they have set the foundations that later were applied to the covalent functionalization of other carbon nanostructures including CNTs and graphene. 

A new class of conjugated hydrocarbons is that of the fullerenes [11], which represent an allotropic modification of graphite. Their electrochemistry has been studied in great detail during the last decade [126]. The basic entity within this series is the Ceo molecule (23). Because of its high electron affinity, it can be reduced up to its hexaanion (Fig. 4) [14,127]. Solid-state measurements indicate that the radical anion of Ceo reversibly dimerizes. NMR measurements confirm a u-bond formation between two radical anion moieties [128,129]. 

Application of the increasingly basic EGBs formed by the consecutive one-electron reductions of the fullerene, Cgo, is illustrated in Scheme 34 (potentials vs. Fc/Fc+) [94]. The reactions in Scheme 34 are catalytic since the addition products are less acidic than the carbon acids used, and the reactions can therefore be carried out using very small amounts of the PB. The reactions were carried out in a divided cell using MeCN/PhMe (2 3)-Bu4NBr. 

Fullerenes are another amorphous (no crystal stmcture) form of carbon that have the basic... 

Since there are 30 double bonds to react in fullerene Cgo, the [2-1-2] cycloaddition of Cgo molecules at these bonds results in the formation of so-called fullerene polymers [19]. Although it seemed important to clarify the structure and properties of the most basic unit of these polymers such as dimers and trimers, the method for preparation of these polymers such as high-pres-sure/high-temperature treatment or photoirradiation was not suitable to stop the [2-1-2] reaction at the stage of dimerization or trimerization. 

Cyclopropanation of Cjq with diethyl bromomalonate in toluene with NaH as auxiliary base proceeds smoothly at room temperature (Scheme 3.5). By-products are unreacted Cjq and higher adducts. The formahon of higher adducts is discussed in detail in Chapter 10. The monoadduct can be isolated easily from the reach on mixture by column chromatography. Saponificahon of such di(efhoxycarbonyl)-methylene adducts of Cgg is achieved by treatment with NaH in toluene at elevated temperatures and subsequent quenching with methanol (Scheme 3.6) [32], This method provides easy access to defined water-soluble fullerenes and can also be applied to higher adducts. These malonic acid derivatives of are very soluble in polar solvents, for example acetone, THF or basic water, but insoluble in aqueous acids. 

No other allotropic forms of carbon were known until ten years ago then arising from studies of interstellar carbonaceous molecules, a new form of carbon, namely fullerene or buckyballs , was discovered (Kroto et al 1985), for which the authors received the 1996 Nobel Prize for Chemistry. Its structure is basically a ball or spherically shaped cage consisting of pure carbon. The most stable... 

C6o fullerene surfaces were thermally functionalized with perfluoro-(3-oxo-penta-4-ene)sulfonyl fluoride and then converted into sulfonic acid derivatives by basic hydrolysis. The product mimiced the electroconductive properties of perfluorosulfonyl Nation 1100 resins. When the modified fullerence was blended with platinum nanoparticles imbedded in Nation 1100 the material was effective as electrodes in fuel cells. 

Weakly basic ligands such as alkenes and acetylenes only occasionally displace the fullerene [Eqs. (15)—(17)] ... 

Mass spectrometry is more than 100 years old and has yielded basic results and profound insights for the development of atomic physics. The rapid development of nuclear physics, in particular, would be unthinkable without the application of mass spectrometric methods. Mass spectrometry has contributed to conclusive evidence for the hypothesis of the atomic structure of matter. So far mass spectrometry has supplied specific results on the structure of the nucleus of atoms. Nobel prizes have been awarded to a number of scientists (Thomson, Wien, Aston, Paul, Fenn and Tanaka) associated with the birth and development of mass spectrometry, or in which mass spectrometry has aided an important discovery (e.g., for the discovery of fullerenes by Curl, Kroto and Smalley). 

The study [56] included calculations of PECs for nano-Ti02, nano-ZnO, nano-Ag, CNTs, and fullerenes for the USA, Europe, and Switzerland. In the first work [60], simulations were run to recalculate PECs for nano-Ti02, nano-Ag, and CNTs in Switzerland which were contrasted to the corresponding results of the initial and comparative modeling of Mueller and Nowack [8]. Basically, these simulations confirmed the nanomaterial flow modeling presented by Mueller and Nowack... 

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