graphene
/ GRAF-een /
Graphene is a single sheet of carbon just one atom thick, arranged in a honeycomb of hexagons. Peel one layer off graphite — ordinary pencil lead — and you have it. Two physicists first isolated it in 2004 using nothing more exotic than sticky tape, work that won the 2010 Nobel Prize in Physics.
Its properties come from the bonding: each carbon is covalently bonded to three neighbors in the plane, making it extraordinarily strong in-plane (E around 1 TPa, strength around 130 GPa), while electrons move through it almost unimpeded (very high mobility). It is also transparent and conducts both heat and electricity superbly. Graphene is the fundamental building block of the other carbon forms — graphite is stacked graphene, and a carbon nanotube is graphene rolled into a cylinder.
This matters for flexible electronics, sensors, composites, and coatings. The honest caveats: graphene has no band gap, so unlike silicon it cannot be simply switched off — a real obstacle for logic transistors — and the pristine single crystals behind headline results are worlds apart from the cheap 'graphene' flakes and powders sold commercially.
Every time you write with a pencil you smear off stacks of graphene: graphite is just graphene sheets stacked and weakly held together. In 2004 two physicists peeled single layers off graphite with ordinary sticky tape and measured a material in which electrons race almost unimpeded and a sheet is stronger, per unit weight, than steel — the work that won the 2010 Nobel Prize.
One layer of pencil lead is graphene; isolating and measuring it rewrote what a two-dimensional material can do.
Graphene has no band gap, so it cannot switch off like silicon — a fundamental hurdle for logic transistors — and cheap commercial 'graphene' powder is far from the pristine single crystals in headline results.