Event Abstract

Fullerenes: Chemical structure and properties

  • 1 Aristotle University of Thessaloniki, Department of Pharmacology, Greece

Fullerenes are molecules composed entirely of carbon with spherical (buckyballs), ellipsoid, tubular (nanotubes) or a combination shape (nanobuds). They consist of hexagonal and pentagonal (sometimes also heptagonal) rings, with the latter necessary for the curvature of the molecule. Each carbon is sp2 hybridized and it is connected to other carbon atoms by one double bond and two single bonds. The smallest fullerene in which no two pentagons share an edge is C60, and as such it is the most common. The structure of C60 is that of a truncated icosahedron. Each vertex is replaced by a five-membered ring – a pentagon. This process also converts each of the twenty former triangular faces into six-membered rings – hexagons, with a carbon atom at the corners of each hexagon and a bond along each edge. Because the molecular strain tends to be concentrated in the five-membered rings that are responsible for closure, structures that avoid contiguous (edge-sharing) pentagons are particularly stable. It turns out that C60 and C70 are the smallest carbon clusters for which this can be achieved. They behave chemically and physically as electron-deficient alkenes rather than electron rich aromatic systems. They are soluble in organic solvents and they can easily accept electrons. Fullerenes modification by the addition of hydroxyl groups (fullerenols), can increase their solubility in water. Nanotubes are long, extremely thin, cylindrical carbon structures consisting of hexagonal graphite molecules attached at the edges. They are like rolled-up graphene sheets. Nanotubes may have a single cylinder or two or more concentric cylinders. Nanotubes have the following characteristics: wall thickness, number of concentric cylinders, cylinder radius, and cylinder length. Some nanotubes have a property called chirality, an expression of longitudinal twisting. Depending on their structure, nanotubes can have a metallic character or behave as semiconductors, and thus offer possibilities to create semiconductor–semiconductor and semiconductor–metal junctions, useful in devices. They are extremely strong materials and have good thermal conductivity. These structures may be assembled into microscopic mechanical systems called nanomachines. Because graphite can behave as a semiconductor, nanotubes might be used to build microscopic resistors, capacitors, inductors, diodes, or transistors. Concentric nanotubes might store electric charges because of capacitance among the layers, facilitating the construction of high-density memory chips. Fullerenes are chemically reactive and can be added to polymer structures to create new co-polymers with specific physical and mechanical properties. Their application as polymer transistors [Organic Field Effect Transistors (OFETS)] and photodetectors has also been increasing. Because their electrical resistance changes significantly when other molecules are attached to the carbon atoms, they can be used in developing sensors that can detect chemical vapors such as carbon monoxide or biological molecules. Another property of medical interest is that they can easily penetrate membranes and cell walls and serve as drug delivery systems. Fullerenes are powerful antioxidants, reacting readily and at a high rate with free radicals, which are often the cause of cell damage or death. They behave like "radical sponges," as they can sponge-up and neutralize 20 or more free radicals per fullerene molecule. The most interesting property for medical use is their antioxidant activity and their sensing/detecting ability, and the most interesting potential application of fullerenes in nanopharmacology is the development of targeted drug delivery systems.

Keywords: Fullerenes, buckyballs, Nanotubes, Targeted Drug Delivery, nanopharmacology

Conference: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010, Thessaloniki, Greece, 1 Oct - 5 Oct, 2010.

Presentation Type: Poster

Topic: Nanopharmacology / Nanomedicine

Citation: Tsachouridis S and Papaioannidou P (2010). Fullerenes: Chemical structure and properties. Front. Pharmacol. Conference Abstract: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010. doi: 10.3389/conf.fphar.2010.60.00206

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Received: 28 Oct 2010; Published Online: 04 Nov 2010.

* Correspondence: Dr. Paraskevi Papaioannidou, Aristotle University of Thessaloniki, Department of Pharmacology, Thessaloniki, Greece, ppap@auth.gr