Buckyballs, Fullerenes, and Carbon Nanotubes

In 1985, the story of carbon allotropes took a dramatic turn with the discovery of C60, which resulted in a new type of carbon structure, called the fullerenes (Kroto et al., 1985). This discovery earned the 1996 Nobel Prize in chemistry for Harold Kroto, Robert Curl, and 

There now are known to be a whole family of caged carbon structures having various numbers of carbon atoms, including C30, C50, C7o, C72, C76, Cg4, and the huge C540. The name fullerene has replaced the unwieldy, Buckminsterfullerene used to describe this general spheroid structure of carbon, although they still are referred to as Buckyballs . 

Of all the fullerene forms, the nearly spherical properties of C o have attracted the greatest attention, especially in the field of bioconjugation. In addition to its physical properties, C o fullerenes have unique photo-optical and electro-chemical properties, which make them useful as carriers for biomedical research applications. For instance, upon exposure to light C o will generate singlet oxygen, which can be used in vivo to cleave biological molecules, particularly DNA and RNA. Studies indicate that irradiation of Cgo in solution can be used to destroy virus contamination (Kasermann and Kempf, 1997). Solutions of Buckminsterfullerene are a deep purple color, whereas other sizes of fullerenes display a variety of other colors. 

Fullerene Cgo also functions efficiently as an antioxidant, actually being better than other lipid-soluble antioxidants at scavenging reactive oxygen species (ROS) (Wang et al., 1999). Water-soluble derivatives of C o, such as a poly-hydroxyl form, are able to function in the same respect in aqueous environments. 

Pure fullerenes are insoluble in aqueous environments and only sparingly soluble in many organic solvents. The greatest solubility is found in 1,2,4-trichlorobenzene (20 mg/ml), carbon disulfide (12 mg/ml), toluene (3.2 mg/ml), and benzene (1.8 mg/ml) (Wikipedia.org). Solubility calculations have been performed on (T, in 75 different organic solvents (Sivaraman et al., 2001). 

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Ceo was trivially named buckminsterfullerene" after R. Buckminster Fuller, the engineer, architect, and philosopher who used similar shapes to construct geodesic domes. Due to their spherical shape, Cgo molecules are sometimes colloquially called buckyballs. Compounds derived from Cgo and related carbon clusters that enclose space (such as C70, which is egg shaped, Cyg, Cg4, and others) are called fullerenes. Even carbon nanotubes are now known some carbon nanotubes are even being used as storage containers to deliver anticancer drugs into cells for chemotherapy applications. 

The following sections discuss many of the major particle types and provide bioconjugation options for the coupling of ligands to the surface of functionalized particles. Some additional nanoparticle constructs, including gold particles, dendrimers, carbon nanotubes, Buckyballs and fullerenes, and quantum dots are discussed more fully elsewhere (see Chapter 7 Chapter 9, Section 10 Chapter 15 and Chapter 24). 

Novel means of storing hydrogen are the subject of intensive research because of the problems with the methods described earlier. In particular, there has been considerable experimentation with hydrogen storage in fullerenes ( buckyballs or carbon nanotubes ), which are microscopic structures fashioned out of carbon. Recent research indicates that there is potential for buckyball storage through a combination of chemical and physical containment but at very high temperature and pressure.20 These novel... 

Eight allotropes of carbon (a) Diamond, (b) Graphite, (c) Lonsdaleite, (d) Ceo (Buckminster-fullerene or buckyball), (e) C54o, (f) C70, (g) Amorphous carbon, and (h) single-walled carbon nanotube or buckytube (The picture adopted from Wikipedia - http //en.wikipedia.org/wiki/ Allotropes of carbon)... 

Some nanoparticles are intentionally engineered and produced with very specific properties in mind such as shape, size, surface properties and chemistiy. These properties are reflected in aerosols, colloids, or powders. Often, the behavior of nanomaterials may depend more on surface area than particle composition itself. Relative-surface area is one of the principal factors that enhance its reactivity, strength and electrical properties. Some examples of these engineered nanomaterials are carbon buckyballs or fullerenes carbon nanotubes metal or metal oxide nanoparticles (e.g., gold, titanium dioxide) quantum dots, etc. 

Figure 19 Computer-generated images of carbon nanostructures showing (A) a spherical C60 fullerene Buckyball structure, (B) a conical form, (C) a SWNT and (D) a cylindrical multiwalled CNT MWNT. Abbreviations SWNT, single-walled nanotube MWNT, multiwalled nanotube. Source From Ref. 102.

A, Crystals of buckminsterfullerene (Ceo) are shown leading to a ball-and-stick model. The parent of the fullerenes, the buckyball, is a soccer ball-shaped molecule of 60 carbon atoms. B, Nanotubes are single or, as shown in this colorized transmission electron micrograph, concentric graphite-like tubes with fullerene ends. 

Fullernes form a group of carbon allotropes. There are spherical fullerenes nicknamed buckyballs and cylindrical fullerenes known as buckytubes or nanotubes. Fullerenes have yet to display all of their capabilities to scientists. One of the most promising areas of fullerene research involves the creation of nanotubes. Nanotubes are sheets of carbon that are rolled up into cylinders. These cylinders are strong—due to the hexagonal structure of the carbon atoms—and have unique conducting properties. Fullerene nano-technology on the horizon includes the development of faster computer chips, smaller electronic components, and more advanced space-exploration vehicles. 

Two other forms of carbon have been discovered more recently. In the form called Buckminsterfullerene, or buckyball (named after R. Buckminster Fuller, who popularized the geodesic dome), 60 carbon atoms are arranged as rings of 5 and 6 atoms to give a spherical cage-Uke structure. When a fullerene structure is stretched out, it produces a cylinder with a diameter of only a few nanometers, called a nanotube. Practical uses for buckybaUs and nanotubes have not yet been developed, but it is hopeful that they can be used in lightweight structural materials, heat conductors, computer parts, and medicine. 

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