Today’s word is actually a related pair of words: graphene and silicene.
Before I dive in, a quick comment about the previous post (“gray vs. grey”). I sometimes receive ignorant notes regarding what I post here, but that one set a new (albeit manageably low) record. The basic theme of the response was “because” or, when more elaborate, “because that’s what I was taught.”
As I frequently tell students, it’s fine to have a negative opinion of something. I encourage it, and will sometimes have them read and respond to a piece of writing, and then afterwards tell them that I, myself, don’t actually like that piece. But when asked why you don’t like something, “because” is never an acceptable answer; you’ve got to follow through and explain yourself. So, in the unlikely event that anyone is wondering why they haven’t received a personal response to their comment, there you have it: it wasn’t worth your effort to make that comment, and it certainly isn’t worth mine to respond.
On to the matter at hand.
These two words, graphene and silicene, describe two materials that are new to science. That’s not to say they never existed before, only that humans didn’t know about them, or weren’t able to create them, until very recently.
Graphene is, to provide a definition:
[a] monolayer of carbon atoms having a hexagonal lattice structure and constituting a basic structural element of graphite, fullerenes, and carbon nanotubes.
In other, perhaps slightly simpler, language, graphene is an organized layer (that “hexagonal lattice structure”) of carbon atoms that’s only one atom thick. The image heading this entry depicts what a sheet of graphene might look like when rolled up into a tube…if you could actually see something that small, and if atoms actually looked like that on the nanoscale.
Because it’s so thin – only a single atom thick – and for practical purposes has no measurable thickness, it’s sometimes referred to as a “two-dimensional polymer.” It’s quite an amazing substance, with a range of properties that could eventually prove extremely useful for all sorts of technology (once the manufacturing cost drops low enough): it’s strong, it’s capable of tremendous electric and heat conduction, it’s elastic, it’s impermeable to gas at the atomic level, and it might even be antibacterial. If it weren’t so difficult to create, we might see it in numerous applications already.
Oh, wait: it’s not so difficult to create. In fact, it’s so simple in some ways that the team which received the Nobel Prize in 2010 for their extensive work with graphene, Geim and Novosolev, developed a way to create graphene simply by peeling sheets of it away from a graphite base using…Scotch tape. If you’ve got time and inclination, you can produce small amounts of graphene at your desk.
The physical description of graphene (single layers of carbon, in structured sheets) goes back to at least 1962; some scientists may have observed and noted small flakes of graphene in other experiments as early as the late 1940s. However, it was usually considered a byproduct, a residue, or some form of graphite, and was not much investigated. Credit for the modern “discovery” of graphene usually goes to Geim and Novosolev for their work beginning in 2004.
This special form of carbon seems to have existed with no specific label for some time, Eventually, possibly in an article in 1987, the term graphene was coined. It stuck: by 1992 it was being used in journal article titles. “Graphene” based on existing conventions for chemical naming, was recommended as the standard nomenclature for the substance within the scientific community by 1994.
Silicene is of even more recent coinage. It sounds like the name of a toy, perhaps a successor substance to silly putty, but it’s far more high-tech. Like graphene, silicene is a material that exists in two-dimensional single-atom sheets. Unlike graphene, silicene is composed of silicon atoms. The existence of silicene was proposed in 2007 (some speculation dates to the early 1990s), and the word was first used at that time. Ribbons of silicene were first created in 2010, with sheets first grown the following year. While materials scientists believe that silicene will share many properties with graphene and that – because it’s silicon – it will be more readily integrated into modern electronics, so far it has proven much more difficult to create. There’s no ‘Scotch tape method’ here (at least not yet).
Both of these words, graphene and silicene, are new enough that neither yet appears in most dictionaries. The definition quoted above for graphene is from the American Heritage Dictionary (AHD5) – all credit to AHD for being on top of this already. Oxford’s ODO (and the British and World English Dictionary) have definitions, but none has crossed over into the OED yet. No one, as far as I could uncover, yet has silicene in their dictionary.
We’ll definitely be encountering graphene a lot more in decades to come as it migrates into, and perhaps radically alters, the technology behind certain devices. Silicene has manufacturing problems, and a late start, but it might also find a place in the future vocabulary.