Graphene vs. Graphite

 

Graphene is a single isolated layer of graphite. It has a 2D arrangement and the carbon atoms are bonded in a hexagonal (honeycomb) structure in a continuous sheet. On the other hand, graphite is a naturally occurring mineral. Its structure is made up of numerous graphene sheets stacked over each other through pi bonds.

 

GRAPHENE: A WONDER MATERIAL

Graphene is a synthetic allotrope of carbon. It was first made in 2004 Professor Andre Geim and Professor Kostya Novoselov at Manchester University. They were awarded a noble prize in physics for this tremendous work. Graphene has unique properties such as high tensile strength, high conductivity, the vast surface area holding strength, and optical transparency making it a suitable material in advanced applications.

It is called a wonder material for some reasons:

• Graphene has the best conductivity shown any existing material. This is due to a pi layer of electrons all over its 2-D structure.
• It is carbon-based (non-metal), which makes it more usable than even metals.
• Its unique molecular compositions could make it the smallest and most useful filter i.e. for filtering seawater to get drinkable water. This could save millions of lives around the world.
• Graphene is one of the lightest weighed materials. It is in fact, 1000 times lighter than paper.
• The strength has obviously no questions i.e. it is 300 times stronger than steel and 40 times stronger than diamond.
• The flexibility of graphene is also tremendous.
• It is one of the most promising nanomaterials being the thinnest, strongest, and optically transparent than all other materials. It transmits more than 90% of the light it gets.
• Biomedical sensors can use this to detect disease causing agents such as viruses and bacteria, etc.
• It is also a perfect barrier, as not even helium gas can pass through it.
• Other than all other marvelous properties, it is also chemically inert, making it even more useful.

GRAPHITE

Graphite has layers of graphene interconnected through weak Van der Waal’s forces. The carbon atoms are present in hexagons and these hexagons are connected sidewise to form a honeycomb structure. The only difference between the structure of graphene and graphite is that graphene is 2-D while, graphite is a 3-D structure.

Each carbon atom forms 3 strong covalent bonds with neighboring 3 carbon atoms. The 4th bond is present in graphite, which is made across sheets. This bond is made p-orbitals so, a pi-bond creates a delocalized cloud of electrons. These layers are connected through weak forces so, it is slippery and the layers may slide over each other.

Some significant properties of graphite are explained below:

1. Thermodynamically stableStrong covalent bonds are present throughout the layers in the graphite. Also, delocalized pi bonds are present between the layers. This makes it highly stable. It sublimes at about 3600°C.

2. Soft and malleable

Graphite is easily scratchable and moldable. This is due to the presence of weak forces between the layers. When graphite is pressed or hammered, its layers slide over each other. Therefore, it is used in lubricants and pencils.

3. Good conductors

It is a good conductor of electricity when voltage is applied parallel to hexagonal layers. Its conductivity is in the order of ∼10⁴ S cm^-1. That is why it is vastly used in electrodes and conducting materials. However, it is not as good in conduction when current is to be passed between the layers i.e. perpendicular to the layers.

Creation or Isolation of Graphene

Scientists use a number of techniques to produce graphene. Mechanical exfoliation, also known as the adhesive tape technique, is one effective way of creating single layer and few layer graphene. However, various research institutions worldwide are trying to find the most efficient way of creating high-quality graphene cost effectively on a large scale.

Chemical vapour deposition (CVD) is the most suitable technique for producing monolayer or few layer graphene. This technique is capable of extracting carbon atoms from a carbon rich source reduction. However, a major drawback in this technique is the difficulty in locating a suitable substrate to grow graphene layers on as well as the complexity in removing the graphene layers from the substrate without altering or damaging the graphene’s atomic structure.