This post has nothing to do with dentistry, except perhaps for some vague ideas about new antibiotics. I have to post it though because this stuff is just so very cool...
When I was in college- sometime in the Late Mesozoic Era, I believe it was- the element carbon was known to exist in precisely two forms: diamonds and graphite. The one: beautiful, lustrous, valuable beyond compare. The other: highly useful in a pencilly way at times, but a sort of bland dull gray. Graphite Gray, in fact.
Yet we found in our chemistry classes that graphite was more stable over very long periods of time than carbon. Yep. Place a diamond and a lump of graphite in a perfectly sealed container and let a few billion years pass and when you open up your container you will find: two lumps of graphite. My friend Mark famously tried to convince his soon-to-be-fiancee Karen that a graphite engagement ring was a more valued expression of his love than some rusty old diamond could ever be.
It was a short conversation.
Here is what the diamond crystal lattice looks like:
The carbon-to-carbon bonds are so strong in this arrangement that diamonds are the hardest known mineral that occurs in nature. And as we know the crystal lattice is clear- almost, and it's that almost that makes each diamond unique and special.
Graphite is the most stable carbon structure. It is made up of many carbon ring (graphene) layers stacked together. Graphite is opaque gray, is soft and slippery, and conducts heat and electricity very well. Graphite looks like this:
Diamond and graphite were thought to be the only ways in which pure carbon atoms arranged themselves. Some years ago, however, scientists discovered buckyballs, the slang name for buckminsterfullerene. This substance was named for engineer Buckminster Fuller, because it resembles his geodesic domes. Buckyballs are 60-carbon spheres that look like little tiny soccer balls, although without any manufacturer or sponsor logos. Yet.
There is a whole family of molecules now called fullerenes, which are any molecule composed entirely of carbon. They come in spheres, ellipsoids, and tubes. Buckyballs and other fullerenes are being investigated for use in heat resistance, superconductivity, lubrication, and even in medicine as possible antibiotic components.
Another exciting form of carbon is the nanotube. These are made of a single layer of graphene which is rolled into a hollow tube:
The unique molecular structure of carbon nanotubes results in extraordinary large-scale properties, including high tensile strength, high electrical conductivity, high ductility, high heat conductivity, and relative chemical inactivity. Carbon nanotubes are among the strongest materials yet discovered in terms of tensile strength, the stiffest in terms of elastic modulus, and the hardest, beating out the diamond by about 20%. They also have some wild electrical properties. It may be possible to manufacture a practical carbon nanotube supercapacitor which would make every battery design on the planet obsolete overnight. No more heavy metals getting into the environment from our endless use of batteries! And imagine a laptop that could run for a week or two on a charge...
The fifth form of carbon is the most recently discovered. This is graphene:
Graphene takes the prize for weirdness in its properties. It is a one atom thick layer of hexagonal carbon rings. It is the strongest substance known to man, on a strength to weight basis. Potential uses of graphene range from super-strong structural members to antimicrobial medicines; it seems to be particularly good at killing E. coli. Graphene has the ideal properties to be an excellent component of integrated circuits. So we may see it someday in places as diverse as inside our computers and in our food packaging.
It is interesting to note that the 2010 Nobel Prize in Physics was won by Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene". This stuff may be thin, but it's pretty hot right now too.
Perhaps the weirdest thing of all about graphene is that, although it's only one atom thick, you can actually see it in transmitted light with your own eyes, because it absorbs 2.3% of white light:
The problem with that fact is, it completely dashes my plans to make super-strong graphene bar stools that are so clear that you can't see them at all- even when cold sober. Oh well...