Fullerenes look like soccerballs. Typically they form cages of sixty or more carbon atoms.
The picture at the left is that of C60, the most readily occurring fullerene.
Before 1985 only six pure crystalline forms of the element carbon were known, namely two kinds of graphite, two kinds of diamond, chaoit and carbon(VI). However in 1985, Robert F. Curl, Harold W. Kroto and Richard E. Smalley discovered a new form of carbon, now commonly referred to as buckyballs. Their discovery showed that 60 or 70 carbon atoms could cluster together to form a cage-like molecule. The molecular structure resembled the pattern of a soccer ball or the geodesic designs of Buckminster Fullerenes. Thus the name buckyballs or fullerenes. Since then the discovery has led to new research in polymers, endohedral metallofullerenes, semiconductors, and other various areas.
Our research group is primarily concerned with producing, extracting, and purifying endohedral metallofullerenes. These unique molecules could indeed be the next replacement for silicon in IC's and other computer chips. By doping the carbon with metals or metal oxides, one can actually create small quantities of buckyballs that encapsulate 1-4 metal atoms.
Although there are a variety of different methods of producing buckyballs our group uses the arc-vaporization method, a process that converts graphite rods to significant quantities of fullerenes. In order to produce the metallofullerenes, first each graphite rod is rod and repacked with a graphite and metal oxide mixture then annealed at 1100 degrees Celsius for 6 hours. Next the rods are placed in a special apparatus (shown below) that utilizes an arc-welder to flow approximately 105 amperes through the rod. Once an arc is struck at the tip of the rod, the graphite immediately begins to vaporize.
Of course as the graphite at the tip is continuously burned away, the arc gap becomes larger.As a result, the rods have to be continuously moved in or out to maintain a constant gap voltage, a task that proved to be tedious and time consuming until Jim Coulter recently implemented an automated servo circuit that detects the voltage gap and moves the rod accordingly. (E-mail Jim and tell him how much you love him for building the world's second automated fullerene generator.) As the graphite vaporizes, the majority of the carbon simply forms soot. However given an inert atmosphere of Helium gas at low pressures of 100-300 Torr (Atmospheric Pessure = 760 Torr), some of the carbon condenses on the sides of the liquid-cooled chamber and in the vacuum filter.
After burning a few graphite rods, one is only left with a large quantity of black carbon soot enriched with fullerenes and metallofullerenes. In order to extract the fullerenes, our group the fragrant ambrosia known as carbon disulfide. The toxic solvent dissolves the fullerenes present in the soot and allows us to fillter out the reaining carbon using a small Whatman extraction thimble as the filter. After the carbon disulfide is evaporated, we are left with a shiny sandy black substance containing a pure variety of fullerenes and metallofullerenes. The substance is then placed in Paul's automated chromatagraphy system (shown below).
This system does an initial seperation that seperates fullerenes into a total of six different weight classes. These six mixtures are then further purified
on other liquid chromatagraphy systems (left). Much of our research in fullerenes involves efforts to purify each metallofullerene through automation as well as our constant search on ways to isolate isomers of each
particular fullerene with the help of computers and new developments in chromatagraphy.
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