General Studies (Paper - 3) : Model Question & Answers

Question: What is graphene? Discuss its properties and mention at least three of its applications.

Answer: Graphene is a single layer of carbon packed in a hexagonal (honeycomb) lattice, with a Carbon-Carbon distance of 0.142 nm.

Properties of Graphene

Density of graphene: The unit hexagonal cell of graphene contains two carbon atoms and has an area of 0.052 nm2. We can thus calculate its density as being 0.77 mg/m2. A hypothetical hammock measuring 1m2 made from graphene would thus weigh 0.77 mg.

Optical transparency of graphene: Graphene is almost transparent, it absorbs only 2.3% of the light intensity, independent of the wavelength in the optical domain. Thus graphene is more than 100 times stronger than the strongest steel.

Electrical conductivity of graphene: This is somewhat higher than the conductivity of copper which is 0.60x106 Ω-1cm-1.

Thermal Conductivity: Thus graphene conducts heat 10 times better than copper.

Applications

Graphene has a number of properties which makes it interesting for several different applications. It is an ultimately thin, mechanically very strong, transparent and flexible conductor. Its conductivity can be modified over a large range either by chemical doping or by an electric field. The mobility of graphene is very high30 which makes the material very interesting for electronic high frequency applications. Recently it has become possible to fabricate large sheets of graphene. Using near-industrial methods, sheets with a width of 70 cm have been produced. Since graphene is a transparent conductor it can be used in applications such as touch screens, light panels and solar cells, where it can replace the rather fragile and expensive Indium-Tin-Oxide (ITO). Flexible electronics and gas sensors are other potential applications.