What color does graphene glow when heated? If you heat graphene hot enough, what color would it glow? Is the color within the visible range?
 A: Graphene is composed of a single atomic layer of graphite whose carbon atoms are very tightly bonded and organized into a hexagonal lattice.  The carbon to carbon bonds between the atoms in graphene are so tiny and so strong that they prevent destabilization due to thermal fluctuations.
Due to its ability to absorb large and varied amounts of light without heating up, graphene is very stable.  At 2,800 degrees K, graphene emits light which is slightly warmer than that emitted by an ordinary incandescent bulb.  Here is an account of the process which was used to get graphene to glow: http://www.kurzweilai.net/worlds-thinnest-light-source-made-from-graphene.
Another group of researchers appear to have obtained white light from graphene at 900 degrees K: http://www.nature.com/lsa/journal/v4/n1/full/lsa201510a.html.
And here's an account of an earlier study that tuned graphene to recognize long wavelength light as a source of optical bits: http://newscenter.lbl.gov/2011/09/04/graphene-thz/ (But this is for light reception, not emission).
