TEN FACTS ABOUT GRAPHENE: THE MATERIAL OF FUTURE

Recently there has been quite a buzz surrounding graphene which is being projected as the material of future with innumerable applications. The Nobel Prize in Physics 2010 was awarded jointly to Andre Geim and Konstantin Novoselov for their excellent work related to this material. 


Below are presented ten facts about graphene:

1. Graphene is the mother of all carbon allotropes, such as, C-60, carbon nanotubes, graphite, etc. It is essentially a single layer of sp² hybridized carbon atoms arranged in a honeycomb lattice (see Figure 1 below).

2.  A monolayer of graphene is around 0.5 nm thick.  

3. Graphene has excellent mechanical properties. It is stronger and stiffer than diamond and yet it has high flexibility.  

Figure 1: Two-dimensional structure of graphene with hexagonal arrangement of carbon atoms. The carbon atoms occupy the edges of the hexagons.

4.  Graphene can conduct light as well as electricity.Thus, it finds applications in touch screens, solar cell, lasers, photodetectors, etc.

5. Graphene has a perfect two dimensional crystal structure which is remarkable since thermodynamics suggests that 2D crystals are unstable. The 3D rippling (wrinkles) on its surface is believed to be the reason for stabilization of the 2D structure. Due to the 2D structure it has almost 100 % of its atoms on the surface. Thus, it has the highest surface area for its weight. 

6. Graphene’s electronic properties are extremely sensitive to adsorption of gas molecules on its surface. This is because it has all its atoms on the surface and adsorption of gas molecules cause measurable changes in its macroscopic properties (e.g. electrical resistance). The above make graphene extremely amenable in functioning as a gas sensor.  

   

7.  Graphene has excellent electrical properties and can conduct electricity even better than a metal, with the room temperature resistivity of the order of 1 micro Ohm-cm and extremely high mobility of charge carriers. Electrons in graphene travel ballistically over sub-micron distances. Therefore, graphene based transistors can operate at  higher frequencies as compared to silicon based ones.

8.  Graphene has been synthesized using one of the four primary methods; (i) micromechanical cleaving of graphite layers (ii) chemical cleaving of graphite layers (iii) chemical vapour deposition or its variant using suitable precursor gas and (iv) epitaxial growth.

9.   Raman spectroscopy is one of the easiest and most reliable methods of determining the presence of graphene and ascertaining its quality in terms of presence of defects, number of layers, etc.

10.Graphene is ambipolar i.e. its charge concentration can be continuously varied from n-type to p-type by application of gate voltage. 

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