Fullerenes and Graphene: Super Molecules of Nanotechnology

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Buckminsterfullerene

This is Buckminsterfullerene: an all-carbon molecule. Here, we show connectivity without individual carbon atoms. The molecule launched the Nanotechnology Revolution in the mid-1990s. Image built by John Jaksich using Chem Draw 14

Buckminsterfullerene, Graphene, and Silicon – all molecules that are launching a new era of technology. How did it all happen?

Chemical discoveries happen every day in laboratories throughout the world. Discovering the methods by which we can manipulate these critical molecules, and to effectively use them in nanotechnology makes history.

Buckminsterfullerene, for example, first regarded as a possible anomaly, eluded characterization for more than a decade. The breakthrough, launching the nanotechnology revolution, occurred when eventual Nobel laureates, Drs. Kroto, Curl, and Smalley realized Buckminsterfullerene was not an anomaly but a new form of carbon.

What are Fullerenes?

Similar to diamonds, fullerenes contain a ‘carbon-only’ molecular structure (or crystalline structure). Other molecules containing carbon atoms, such as proteins and sugars, are connected to not just other carbon atoms but to hydrogens, oxygens, sulfurs, and nitrogens.

The connectivity to different atoms confers a specialness or a way for the molecules to ‘react.’

Molecules that we associate with daily living, such as table sugar, or proteins, have a different type of chemical reactivity (or chemical bonding).

Table sugar, is in part, comprised of glucose – which has oxygens and hydrogens bonded to the carbon atoms. Proteins are comprised of individual amino acids.

Glucose and Phenylalanine

Glucose (left) and Phenylalanine (right). The molecular scaffolding and connectivity in glucose and phenylalanine assure a far greater reactivity dependent upon the presence of oxygens (the O symbol) and nitrogen (the N symbol). You encounter these molecules every day. Image built by John Jaksich using Chem Draw 14

 Discovery of Carbon Nanotubes

The first report of carbon nanotubes came in the journal Nature in 1991. Since that pivotal discovery, nanotubes revealed numerous properties (if properly scaled) that could revolutionize the electronics and information technology industries.

The first carbon nanotubes synthesized were multi-walled – resembling an onion. However, the multi-walled carbon nanotubes reacted badly with chemical reagents, despite showing much potential, with the least reactive nanotube corresponding to the ‘thickest nanotube.’

When single-walled carbon nanotubes were shown to possess an enhancement of properties, the realization of a possible electronics revolution spurred further research.

Because of enhanced reactivity, single-walled carbon nanotubes have been the subject of much research in the past two decades.

single walled carbon nanotube

Cutout of single walled carbon nanotube (carbon atoms omitted for clarity). Built by John Jaksich using Chem Draw 14.

Rebirth of Nanotechnology: Graphene

Graphene’s discovery in 2004 allowed chemists and materials scientists to think differently on the nature of modern electronics. Graphene is an excellent conductor of electricity and heat.

Could Silicon Wafer Chemistry be Extrapolated Onto Graphene (Carbon) Chemistry?

Carbon by its ‘innate nature’ will form four bonds—that is a rule that is seldom broken.

Silicon, directly underneath carbon on the periodic table, has a similar ‘reactive chemistry.’ (We call the concept that atoms in the Periodic Table behave similarly, ‘Periodicity.’) Silicon can form four bonds, similar to carbon, so silicon and carbon may at times be interchanged.

Rules of periodicity (as we know them) govern all chemical elements. The periodic table (as discovered by Mendeleyev) is based upon the fact that certain chemical elements behave similarly because of the periodicity.

On a deeper level, the differences between silicon and carbon occur because the silicon atom is a natural semiconductor of electricity-it requires a ‘dopant’ or an additive to be a conductor similar to graphene.

While graphene needs a ‘dopant’ to be a semiconductor, the ironic twist of the two elements may be explained in the following terms.

Carbon is element number six on the Periodic Table and silicon is element number 14; their chemistry is not as similar as the Periodic Table would have us believe because of the periodicity.

Silicon possesses all of the electrons that the carbon has – plus eight other electrons. To be a conductor of electricity there need to be free electrons, while to be a semi-conductor the electrons are not free to move.

Those eight electrons confer stability to silicon that carbon does not possess. (The Periodic Table possesses a rule of eight stabilities as well.)

Illustration of graphene structure

This is an illustration of graphene structure. (Individual carbons omitted for clarity.) The sheets of graphene are the most reactive of the three new forms of carbon in nanotechnology. Image built by John Jaksich using Chem Draw 14.

Graphene: Super Molecule

Because of graphene’s conductive state, it has garnered research dollars and publications as well. One important area where graphene molecules may be employed is in lithium ion batteries. Lithium ion batteries are augmented through employing a ‘graphene ink or fluid.’ The fluid balances (or slows) the battery’s natural degradation cycle.

One other area where graphene is employed to augment lithium ion batteries is through the development of Lithium/Sulfur batteries.

This area of development has been researched for the last decade. The breakthrough promises to deliver batteries that are three times more powerful and long lasting than conventional lithium batteries.

By using nitrogen-doped-graphene as a conductive media, the problem associated with sulfur degrading the battery’s life is alleviated. We await further results.

The Productive Road of Nanotechnology

The decades since the discovery of fullerene have been fruitful ones. The similarities between fullerenes, nanotubes, and graphene lie in their chemical scaffolding (or molecular structures).

The carbon-only molecules vaguely resemble chicken wire or honeycomb, and the scaffolding determined how the new forms of carbon would react with their environment.

The road to graphene, however, is one of excitement and anticipation. Perhaps it is best noted that we can determine our chemical destiny if given the right choices.

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