Considering the unique characteristics, versatile applicability and wide acceptance, we are motivated to develop graphitic materials. The three important graphitic materials of our interest are graphene, graphene oxide and reduced graphene oxide.
Graphene is an extraordinary two dimensional material composed of one atom thick monolayer of carbon atoms arranged in a honeycomb like structure. It is the thinnest and strongest crystalline material exhbiting high thermal and electrical conductivity.
Graphene is composed of only carbon atoms. Each carbon atom in graphene is sp2 hybridized and are tightly packed to form two-dimensional layer of hexagonal honeycomb like structures.
The simplest form of graphene is those containing only one layer of carbon atoms. It is known as monolayer graphene. If two carbon layers are stacked together, it is known as bilayer graphene. Similarly, chemical structures containing up to 10 layers of such packed carbon atoms come under the category 2D graphene.
There are different categories of graphitic materials. Graphene is considered as the building block of these graphitic materials. If the number of stacked carbon layers is greater than ten, it is considered to be 3D and no more called as graphene. This 3D materials containing more than ten graphene layers are known as graphite. Graphene wrapped up into zero dimensional structures are known as fullerenes. Graphene rolled up in to one dimensional structure are known as nanotubes. Oxidized product of graphene is known as graphene oxide. Reduced form of graphene oxide is known as reduced graphene oxide. Since the building block of all these materials is graphene, graphene is known as “mother of all graphitic materials”.
Graphene is known to possess several unique characteristics such as, good mechanical properties, transparency, high electrical conductivity, high thermal conductivity, large specific surface area etc.
Because of these unique characteristics, graphene and its derivatives are gaining significant attention of scientific research community. The statistical data retrieved from PubMed.gov shows that, there is an exponential hike in the number of graphene-based research from the year of 2010.
The oxidized form of graphene is known as graphene oxide. Unlike graphene, graphene oxide contains oxygen containing functional groups in its structure. Due to the presence of hydrophilic functional groups, graphene oxide can be easily dispersed in water and other organic solvents. Compared to graphene, graphene oxide is less electrically conducting. This is because of the presence of sp3 hybridized carbon atoms in graphene structure.
Similar to graphene, the frame work structure of graphene oxide also is honeycomb like. The difference is that, unlike graphene, graphene oxide contains carbon, oxygen and hydrogen atoms in its structure. The ratio between carbon and oxygen is known to be 2:1. Instead of sp2 hybridized carbon atom, graphene oxide contains sp3 hybrized carbon atoms also.
Due to the presence of large number of oxygen containing functional groups, graphene oxide is hydrophilic in nature. Hydrophilic nature of graphene oxide makes them dispersible in water and other organic solvents. The inherent characteristic high surface area and presence of large number of functional groups make graphene oxide as an effective adsorbent and reinforcement material.
The reduced form of graphene oxide is known as reduced graphene oxide. Since it is a reduced product, the number of oxygen containing functionalities will be less in reduced graphene oxide. The properties of reduced graphene oxide will be intermediate between graphene and graphene oxide.
Similar to graphene and graphene oxide, the frame work structure of reduced graphene oxide also is honeycomb like and devoted of having both sp2 and sp3 hybridized carbon atoms. It contains, carbon, hydrogen and oxygen atoms in its structure. However, the ratio between carbon and oxygen will be 246:1.
Due to the presence of oxygen containing functional groups, reduced graphene oxide is hydrophilic in nature. But it will be less hydrophilic than graphene oxide. Since it is hydrophilic, it can be dispersed in water or any other organic solvents. It also possesses good surface area and hence can be used for accommodating inorganic nanoparticles. It can also be used as an adsorbent and reinforcement materials. However, their efficiency as reinforcement material and adsorbent will be less compared to graphene oxide.
