FULLERENES Roberto Bartali

ABSTRACT Fullerenes are very interesting carbon molecule, they can be made artificially (in laboratories) and can be found in meteorites and in the interstellar medium. This is a description of fullerenes, their origin and their applications. FULLERENE DESCRIPTION

The discovery of fullerene is one of a long series of discoveries and technological development driven by astonomical research.

Figure 1 The need to discover why an absorption line at 210 nm were present in the interstellas médium and in nebulae, allowed the production of fullerenes.

Figure 2 Dr. Kroto, discoverer of fullerenes and a model of the molecula.

H. Kroto (figure 2) from Sussex University, R. Smalley and R.C. Smalley, in

1985 (Kroto et al 1985), discovered the presence of fullerene when they worked on experiments aimed to simulate in laboratory conditions under which carbon nucleate, as it does in red giant star atmosphere (Bleeke 2001); another important, and unknown,

feature was the absorption at 217.5 nm in the intestellar medium (figure 1), which can now be explained because of the presence of fullerenes

(Iglesias-Groth 2004). Carbon is one of the most abundant atoms in the universe, it forms a very large quantity (thousands) of

compounds, but there are only four types of pure carbon molecule (figure 3): graphite, fullerene, diamond and ceraphite also known as chaoite. All fours are present in nature and are found in meteorites, so they were formed before or during the formation of planets in our solar system. Fullerenes were first discovered in Allende carcbonaceous chondrite, which

contains also nanodiamonds, chaoite was found in Ries meteor crater; graphite is present also in chondrites. The differences between them are the number of atoms, the way they are bonded together and the crystallization form (they are the only 4 known carbon

Figure 3 Crystal structure of different carbon molecule.

allotropes). This fact is interesting because carbon can produce the hardest material know (diamond) and one of the softest (chaoite). Fullerene and diamond are three dimensional molecule, instead graphite is a set of superimposed planar molecule and chaoite are crystals bonded to the edges of graphite. A special case of a cylindrical fullerene is called nanotube.

A Graphite molecule is composed of a set of hexagons and it is planar, instead all others allotropes are formed by other geometric figures like pentagons and heptagons; all four carbon molecule can also be made in laboratory. A Fullerene can be dissolved in common solvents at room temperature.

Figure 5 Structure of a 540 carbon atoms arranged as a fullerene molecula.

Figure 4 Structure of a C60 carbon molecula.

There are a large quantity of fullerene molecule, the smallest one contains 20 atoms of carbon

(C20) arranged to form exclusively pentagons. Natural most common fullerene is C60 (figure 4), in which the atoms are arranged in hexagons and pentagons forming a sphere similar to a soccer ball; but it can be formed by several hundreds of atoms (figure 5). Technically speaking, the structure

of a fullerene is a truncated icosahedron.

Figure 6 A nested fullerene formed by a C540, a C240 and a C60.

An important and interesting feature of

fullerenes is that they can grow as nested units (figure 6). This is, a fullerene inside

another (up to 100 possible shells) with a separation between them of 3.4 angstrom which is the distance between sheets of graphite. This molecule are more stable and shows that atoms or other molecule can

be carried inside them, so, also due to their stability, they may travel intact during millions of years. This

kind of fullerenes are commonly known as buckyonion.

FULLERENES IN METEORITES AND INTER STELLAR MEDIUM (ISM) Noble gases encapsulated into fullerenes show isotopic ratios not corresponding to Earth atmosphere condition, so they were delivered by meteorites, evidences of this are in Allende, Tagish lake and Murchison meteorites (Pizzariello 2001)(figure 7), in the K/T boundary layer and in the P/T layer (even if in much less amount) (Becker et al 2001). During the AGB phase of the life of a star, they expell large quantities of Carbon, most of it in CO and C2H2 forms (Kimura 2006). It is though that carbon derivative compounds like PAH and fullerenes are derived from CO and C2H2 molecule due to their high stability. Titanium, Zirconium and Molibdenum carbides crystals are

found in the core of graphitic spherule, this imply that they formed before the carbon based case.

Figure 7 Abundance of fullerenes found in Tagish lake and Murchison chondrites meteorites, measured by Laser Desorption Mass Spectrometry (LDMS) technique.

FULLERENES IN GEOLOGY RECORDS High abundance of iridium and the pesence of fullerenes (Parthasarathy et al) in sediment layers associated to known large meteoritic impacts, suggest that fullerenes are not a byproduct of volcanism, but they are left by an extraterrestrial carrier (meteorites). The best evidence of this is that the concentration of iridium in layers associated with volcanism, above and below the K/T boundary in the Anjar volcano-sedimentary sequence, is much lower that that of the K/T layer. Iridium is generated during the impact phase. Fullerenes with trapped argon and helium showed to be extraterrestrial due to the isotope ratios measured, that resembles that’s of carbonaceous chondrites. These fullerenes are present not only in meteorites such the Allende and Murchison, but even in rocks, specially those corresponding to geologic time coincident to large mass extinction. This is the case of the Permian-Triassic (Becker et al 2001) extinction occurred 251 million years ago (figure 8) and the Cretaceous-Tertiary extinction about 65 million years ago. These extinction occurred during a very short period of time, consistent to a catastrophic phenomenon like a giant meteorite impact (an asteroid or a cometary nucleous about 9 km diameter). Poreda, following the hypothesis that noble gasses are carried inside fullerenes and then (Poreda 2001) delivered by carbonaceous chondrites, analized gasses in samples of Murchison, Allende and Tagish meteorites. The abundance of Xe, Ne, Ar and Kr are very similar with planetary gas ratios, so this is an important evidence that fullerenes can trap, transport, and retain other atoms without react with them.

Becker and Poreda share many papers on this argument, and an important consecuence of their studies is that (Becker et al 2005) fullerenes and noble gases are formed in carbon rich stars. Gasses are trapped into fullerenes and then accumulated in

the solar nebula prior to the solar system formation. This imply that the origin and the true nature of terrestrial planetary atmospheres is presolar.

Figure 8 Fullerenes found in the Sasayama sediments aged 251 million years old (Permian Triassic Boundary).

Heymann (Heymann et al 2002 and 2003) are on the opposite side, they say that fullerenes are produced on Earth by biologic activity because most of them are not recognized to be of extraterrestrial origin. They though that PAH are the precursor molecule for

fullerenes. PAH, in mildly reducing conditions in contact with sulfur (from bacterial activity, wheatering and

degradation of biologic matter) and heat, can be trimmerized asymmetrically around one of the trhee pentagons, forming bowl shaped intermediate molecule. OTHER APPLICATIONS OF FULLERENES In medicine, many applications are under study. The Fullerene molecule is large, stable and hydrophobic, so it can be used as a carrier for active substances. It is also an empty molecule, so it can easily carry substances inside. Another example, is as a direct attack to diseases (Bleeke 2001) one possible use is as an inhibitor of the enzyme of VIH. In semiconductor and computer industry (Benjamin 2005), fullerenes can be used to reduce size and increasing the commutation speed of transistors, fullerenes doped with other atoms, show superconducting properties at relatively high temperature. Due to their spherical form, they can be used also as lubricants. REFERENCES: Becker et al, IMPACT EVENT AT THE PERMIAN-TRIASSIC BOUNDARY: EVIDENCE FROM EXTRATERRESTRIAL NOBLE GASES IN FULLERENES, Science, 2001, 2001Sci...291.1530B. Becker et al, THE ROLE OF FULLERENES IN THE NATURE OF PLANETARY ATMOSPHERES, American Geophysical Union, 2005, 2005AGUFM.P51A0905B. Becker L., Poreda R., FULLERENE AND MASS EXTINCTIONS IN THE GEOLOGIC RECORD, 2001, Meteoritical Society Meeting.

Poreda R., Becker L., FULLERENE AND THE NATURE OF PLANETARY ATMOSPHERES, 2001, 64th Annual Meteoritical Society Meeting. Becker L., Poreda R., PLANETARY GASES AND FULLERENES AT THE PERMIAN-TRIASSIC BOUNDARY, 2001, Lunar and Planetary Science XXXII. Heymann D., ARE BIOGENIC PAHs PRECURSORS FOR FULLERENES ON EARTH?, 2002, Lunar and Planetary Science XXXIII. Heymann et al, BIOGENIC FULLERENES?, International Journal of Astrobiology, Vol. 2, 2003. Rietmeijen et al, REVISITING C60 FULLERENE IN CARBONACEOUS CHONDRITES AND INTERPLANETARY DUST PARTICLES: HRTEM AND RAMAN MICROSPECTROSCOPY, 2005, Lunar and Planetery Sciences. Benjamin et al, TOWARDS A FULLERENE-BASED QUANTUM COMPUTER, 2005, arXiv:quant-ph/0511198 v1 21, 2005. Dimitrijevic M. S., FULLERENES AND ASTRONOMY, 2005, Proc IV Serbian-Bulgarian Astronomical conference. Iglesias-Groth S., FULLERENES AND BUCKYONIONS IN THE INTERSTELLAR MEDIUM, 2004, ApJ 608:L37–L40, 2004. Matsuda J., Omori H., THE TRAPPING EFFICIENCY OF HELIUM IN FULLERENE AND ITS IMPLICATION TO THE PLANETARY SCIENCE, 2004, Workshop on Chondrites and Protoplanetary Disk. Kimura Y., Nuth A., NEW FORMATION ROUTE FOR CARBIDE-CORE, GRAPHITIC-CARBON MANTLE GRAINS BASED ON FULLERENES, 2006, Lunar and Planetary Science XXXVII. Parthasarathy et al., NATURAL FULLERENES FROM THE K/T BOUNDARY LAYER AT ANJAR, KUTCH, INDIA, Catastrophic Events Conference. Pizzariello S. et al, THE ORGANIC CONTENT OF THE TAGISH LAKE METEORITE, Science 293, 2236, 2001. Fullerene structure library, http://www.chem.sunysb.edu/msl/fullerene.html Bleeke J.R., Frey R., Fullerene science module, 2001, http://www.chemistry.wustl.edu/~edudev/Fullerene/fullerene.html Periodic table of elements, 2003, http://www.radiochemistry.org/periodictable/elements/6.html

Kroto, H. W., Heath, J. R., O’Brien, S. C., Curl, R. R., & Smalley, R. E. 1985, Nature, 318, 162. IMAGE CREDITS Figure 1 Absorption line. http://www.univie.ac.at/spectroscopy/fks/forschung/ergebnisse/fullerene.htmFigure 2 Dr. H. Kroto. http://newsimg.bbc.co.uk/media/images/40577000/jpg/_40577211_harry_kroto203.jpgFigure 3 Carbon molecule structures. http://www.mrsec.wisc.edu/Edetc/IPSE/educators/activities/carbon.htmlFigure 4 C60 molecula. http://people.umass.edu/jtchen/research/nanograndpa.htmFigure 5 C540 molecula. http://content.answers.com/main/content/wp/en/thumb/9/95/250px-Fullerene_c540.pngFigure 6 Nested fullerenes. http://www.3dchem.com/moremolecules.asp?ID=218&othername=Nested%20FullereneFigure 7 Fullerenes in meteorites (Pizzariello et. Al, Science 293, 2001). http://www.sciencemag.org.ezproxy.lib.swin.edu.au/cgi/reprint/293/5538/2236.pdfFigure 8 Fullerenes in geologic records. http://www.sciencemag.org.ezproxy.lib.swin.edu.au/cgi/reprint/291/5508/1530.pdf