Author Bio: Yik Zhang recommends that everyone keeps a journal to be filled with thoughts,
innovations, questions, and drawings of things in life. Also he begrudgingly does ChemE by
being unprepared for class.
Key Words: Nanotechnology, material science, fullerene, carbon, sphere, nobel, buckyball
Written on: October 17th 2013
Prepared for USC Illumin Article
The Curiously Awesome Buckminsterfullerene: A Spherical Introduction
Abstract:
Memorable in its shape and herculean in its
structural integrity and strength, Carbon-60 (C60), or more
affectionately called the buckminsterfullerene or
buckyball, is the third allotrope of carbon after graphite
and diamond (Fig. 1) [1]. While its extraordinary stability
was initially suspect to highly circumstantial evidence,
continual research eventually verified this coveted
property and set off major investigations toward its
Michael Strӧck/ Wikimedia Commons
Figure 1: Eight examples of carbon
allotropes.a is diamond, b is graphite,
and d is C60
scientific curiosity and technological applications. Aside from its mesmerizing spherical
symmetry, the buckyball has been identified as a potential candidate for use in cancer treatment
and has even been theorized to explain the origin of life.
Introduction and History:
While nanotechnology appears to be a relatively recent field, the first application of it can
be traced back to medieval Europe's beautifully stained church windows. Interestingly enough,
the discovery of the C60 molecule was a noted yet unintentional peculiarity within an experiment
involving the laser evaporation of graphite. Throughout the joint research experiment,
researchers Harold Kroto from University of Sussex, and Robert Curl, Richard Smalley, and
graduate student James Heath of Rice University noted a recurring peak associated with 720
atomic mass units that correlates to a group of sixty carbon atoms [2]. The intrigue of what
structural form could possibly encompass this large group of atoms eventually drove the group
towards the conclusion of soccer ball-like structure. The discovery in 1985 by the senior
researchers later won them the 1996 Noble Prize in Chemistry, drawing international attention to
the field of pure carbon molecules, now classified under the term fullerenes.
Complementing the uniqueness of its shape is
the origin of the name buckminsterfullerene where it
was named after its resemblance to the architecture
of geodesic domes (Fig. 2) and made famous by
American architect Richard Buckminster [2]. While
C60 is the most famous carbon cluster, later research
Erik16/Wikimedia Commons
Figure 2: Picture of Spaceship Earth at Epcot, Walt
Disney World, and an example of a geodesic sphere.
by Smalley and his colleagues showed that other
carbon clusters like C26 and C70 that exist. Normally,
such prestigious awards are not given to discoveries of single molecules, however the buckyball
discovery lead not only to new, useful derivatives, but invoked within the scientific community a
reinvigoration of interest regarding carbon's versatility and role in
future science exploration.
Properties:
C60 is composed of twenty hexagons and twelve pentagons
(Fig. 3), with a carbon atom at each polygon's vertex and a sp2
hybridized bond and 60 π bonds spread throughout the molecule
[2]. The mathematics behind the geodesic resemblance finds that
Wikimedia Commons
Figure 3: A depiction of a basic
buckyball structure. Shown are
20 hexagons and 12 pentagons.
this truncated icosahedral cage structure grants stability at high temperature and pressure [3] due
to its distribution of molecular strain [4]. It is at the pentagon locations that the molecule is most
susceptible to chemical attacks, a point which will later be revisited [5].
One property relating to size is its shared property with quantum dots, another nanomaterial.
Both materials act as the role of the acceptor and are photosensitive or reactive to the properties
of light in that it is capable of absorbing certain wavelengths of light from neighboring
molecules. Aqueous solutions of pure C60 are purple in color as it is the result of the individual
molecules absorbing wavelengths associated with green and emitting both red and blue
wavelengths [6].
When compressed to less than 70% of its initial volume, the solid form of the molecule
will exhibit physical properties akin to the hardness of a diamond though will quickly regain its
original volume when the pressure is released [5].
Lastly, there is a theoretical limit to the stable formation for these molecules. All evennumbered clusters ranging from C3 to C600 are hollow fullerenes though below C32, the structure
is unable to maintain its stability [5]. Various applications can benefit from these properties and
will be detailed in the following section.
Applications:
Going back to the process of photoinduced electron transfer, one such application
proposes that C60 and a semiconductor polymer known as MEH-PPV can be separately spun on
top of one another to create a heterojunction device [7]. This device enables a large
photoresponse due to the transfer of electrons from the donor, the polymer, to the acceptor, C60.
In general, both the mechanical and electrical engineering fields can appreciate this process as to
create new materials that have the electronic and optical properties of semiconductors while
maintaining the mechanical properties and advantages associated with polymers [7]. The most
useful aspect of buckyball is its various derivatives that involve changing the molecule's surface
chemistry and constituent groups. A modification by
insertion, replacement, or attachment of atoms or
constituent groups alters the properties of the molecule yet
will maintain the familiar spherical shape.
One application involves the buckyball as a
transport molecule. As the sixty carbon atoms are arranged
and spaced out in a manner that leaves the interior empty,
this vacuous area is capable of sheltering and isolating atoms
Wikimedia Commons
Figure 4: A general example of an
endohedral metallofullerene. The red
sphere is the metal atom.
or small molecules. These alterations, specifically for metal atoms, define a specific kind of
buckyball, the endohedral metallofullerene (Fig. 4). It was also discovered that irradiation with
intense laser light causes the carbon skeleton to shrink in size. The inwards collapse will
eventually cease when the skeleton fits just comfortably
around the metal atom. This forms a molecule that
protects its contents within a sturdy carbon frame and
becomes easier to interact with as opposed to attempts to
directly transport material like radioactive isotopes or
highly sensitive biomaterial used to treat cancer cells.
EERE/ Wikimedia Commons
Figure 5: Example of refueling a hydrogen vehicle.
Perhaps the most exciting one with regards to
energy storage is the buckyball's ability to have transition metal atoms be bound to its surface.
Hydrogen as it currently stands is viewed as a clean energy alternative to fossil fuels though
massive adoption in automotive technology has yet to occur due to hazards involving high
pressure hydrogen environments that could lead to hazardous combustions. However, through
the buckyball, suitable and efficient absorbents for high density, room temperature, ambient
pressure storage of hydrogen can be created [8].
Furthermore, the optical and photophysical applications have generated a noticeable
amount of research and attention. One researcher has demonstrated that films of
polyvinylcarbazole doped with fullerenes are an excellent photoconductor while another found
that fullerene films treated in plasma have contributed to greater nucleation and synthesis of
diamond films on silicon surfaces [1].
Future:
As with most immerging technologies, the future of the utility and ubiquity of the
buckyball is intrinsically tied to its cost and appeal to researchers and industry alike. Yet as
researcher Arthur F. Hedbard, the individual responsible for leading the discovery of
superconductivity on the buckyball field states, "There remain an uncountable number of
intercalation possibilities not only with respect to the pristine fullerene framework but also with
respect to modified fullerene frameworks consisting of fullerenes with encapsulated metals
atoms or replaced carbon atoms" [1].Theoretically, buckyballs can be related to any molecule
and there lies its greatest value. A greater adaptation of the buckyball’s transport capabilities
within society inspires what can only be described as virtually boundless progress in medicine,
science, and technology.
Works Cited:
[1] A.F. Hebard, "Buckminsterfullerene", Annu. Rev. Mater. Sci, vol. 23, pp. 159-191, 1993
[2] H.W. Kroto et al, "C60: Buckminsterfullerene", Chem. Rev., vol. 91, no. 6, pp. 1213-1235,
May, 1991.
[3] A. Karton et al, "Evaluation of the heats of formation of corannulene and C60 by means of
high-level theoretical procedures", J. of Phys. Chem. A, vol. 117, no. 8, pp. 1834, 2013.
[4] S. Tomita et al, "Stability of Buckminsterfullerene, C60", Chemical Physics Letters, vol. 383,
pp. 120-125, Nov, 2003.
[5] Randall Frost, "Buckminsterfullerene", in Gale Encyclopedia of Science, 4th ed., Ed K Lee
Lerner and Brenda Wilmoth Lerner Detroit, Gale Virtual Ref. Library, 2008, pp. 680-681.
[6] M.S. Dresselhaus et al, "Science of fullerenes and carbon nanotubes", Academic Press, pp.
437, 1996.
[7] N.S. Sarieiftei et al, "Photoinduced Electron Transfer from a Conducting Polymer to
Buckminsterfullerene", Science: New Series, vol. 258, no. 5087, pp. 1474-1476, Nov, 1992.
[8] Yufeng Zhao et al, "Hydrogen Storage in Novel Organometallic Buckyballs", Physical
Review Letters, vol. 94, no. 15, pp.155504(1-4), Apr, 2005.