The 2010 Nobel Prize in Physics was awarded "for groundbreaking experiments regarding the two-dimensional material graphene."
​
Graphene is an infinite monolayer of hexagonal sp2 bonded carbon network, which has zero band gap due to the delocalized electrons and has a semi-metallic behavior.
Graphene is a zero-band gap semiconductor (i.e., neither metal nor semiconductor), and its electrons behave as “massless” quasiparticles.
What is Graphene?
Graphene is a two-dimensional (2-D) crystalline allotrope of common carbon.
Graphene is a single layer of sp2 hybridized carbon atoms positioned 1.42 Angstroms apart in a hexagonal lattice.
Graphene's close relatives (i.e., other carbon allotropes): diamonds, buckyballs (C60), and carbon nanotubes.
Properties of Graphene
​
Considered “the wonder material of the 21st century”, graphene has exceptionally unique properties.
​
-
Graphene is only one-atom thick (or 0.335 nm) which makes it the thinnest material is known to exist. Graphene is one million times thinner than the diameter of a human hair.
-
Graphene is the strongest material known to exist. It is harder than diamond and 100-300 times stronger than steel.
-
Graphene has the breaking (intrinsic tensile) strength of 42 N/m, and a Young's modulus of 1 TPa.
-
Graphene is the lightest material known to exist with the density of 0.77 mg/m2.
-
Graphene is a superior conductor of electricity with high charge carrier mobility. The electrical resistivity of graphene is about 10−6 Ω⋅cm. The electron mobility in graphene at room temperature can exceed 15,000 cm2/(V·s).
-
Graphene conducts heat better than any other know material. The thermal conductivity for suspended single layer graphene is 1500–2500 W⋅m−1⋅K−1.
-
Graphene is flexible and pliable because it is only one atom thick. When a graphene sheet is stretched, it can extend up to 20% of its original length.
Optoelectronics of Graphene
Graphene is a highly efficient light-to-electricity converter.
-
Graphene can absorb a rather large 2.3% of white light which is also an exceptional property, especially considering that it is only 1 atom thick. This is due to the fact that the electrons in graphene are acting like massless charge carriers with very high mobility.
-
Due to a zero band gap and strong electron-electron interactions in graphene, photogenerated electrons are poorly coupled to the graphene surface and preferentially distribute their energy to multiple secondary electrons rather than produce lattice heating.
-
The crucial difference between graphene and conventional semiconductor materials is that in graphene light produces “hot” ballistic electrons that transfer their energy through a very efficient carrier–carrier scattering process, leading to multiple hot-carrier generation over a wide range of light frequencies.
Engineering Applications
​
-
Electronics: field-effect transistors, sensors, supercapacitors.
-
Photonics / Optoelectronics: transparent touch screens, light panels, and photovoltaic cells, light sources (mode-locked lasers and organic LEDs).
-
Composite: clothes, anti-corrosion coatings.
-
Aerospace: graphene-based structural components of an aircraft that will reduce its weight, improving in fuel efficiency and range; graphene-coated surfaces for measurements of the strain rate and for the prevention of electrical damage from lightning.
Biomedical Applications
Graphene is highly inert and chemically stable, which results in excellent biocompatibility. Graphene excitation can be used for useful applications.
​
-
Sensors
-
Electroactive scaffolds for tissue engineering
-
Drug Delivery
-
Biosensors
-
DNA sequencing
-
Medical implants