GRAPHENE – WONDER MATERIAL OF 21ST CENTURY

Graphene is the thinnest, strongest and among the most conductive materials known. It offers exceptionally high surface area, high electric conductivity, and mechanical robustness. Graphene remains substantially expensive than activated carbons. Nevertheless, its applications are increasing by the day, and costs are going downwards as technologies progress and production scales go upwards.

Technically, graphene is a form of carbon consisting of a single layer of atoms in honeycomb nanostructure. Several hundreds of graphene layers build up in nature, the result is graphite. The name ‘graphene’ was coined by Hanns-Peter Boehm in 1987, when he isolated single sheets from graphite. The term graphene is derived from ‘graphite’ and suffix ‘-ene’, indicating its double bond structure. Despite being transparent. It appears black since it absorbs all visible light wavelengths. Various experiments and early work were done between 1859 and1984. Major research on graphene and development started since 2004, when its superior properties drew attraction of science community.

Unique properties of Graphene

• Thinnest material known- just one atom thick.
• Extremely high tensile strength of 130 gigapascals – 200 time stronger than steel.
• Young’s modulus ~ 1000 Gpa: among stiffest and strongest materials known.
• Highly elastic- Can stretch 20%, and bend significantly without breaking.
• Surface density just ~ 0.77 mg/sq.m. Volume density ~ 2.2 gm/cc. similar to graphite.
• Highest single layer surface of 2,630 sq.m./gm (practical area up to 750 sq.m./gm. due to agglomeration or stacking of sheets under Van Der Waal forces).
• Thermal conductivity ~ 4800-5300 W/mK is better than copper or diamond.
• Conductivity extremely high, up to 100 MS/m, better than copper.
• Electron mobility far greater than copper or silicon.
• Exceptionally high transparency of 97.4% tr for white light.

With so many unique features, graphene is today viewed as a wonder material with exceptional capabilities for in a wide-ranging field for numerous applications. There are still more peculiar properties being investigated- graphene semiconductor, as electrical and thermal insulation are some of them, while graphene aerogels, twisted graphene and other forms are also under ongoing research.

Main Types of graphene

Graphene is available in several forms, each with its own peculiarities. Graphene can be classified by the number of carbon layers, chemical modification, physical shape, and method of production.

The main types are monolayer graphene, graphene oxide, reduced graphene oxide, laser scribed graphene (LSG), and crumpled graphene.

1) Monolayer or Pristine graphene

Monolayer graphene is a single, continuous sheet of carbon atoms arranged in a hexagonal—or honeycomb—lattice. It has excellent electron mobility, thermal conductivity, strength, flexibility, and optical transparency.  Monolayer graphene is commonly produced by chemical vapor deposition (CVD), mechanical exfoliation, or epitaxial growth on substrates.

2) Graphene oxide

Graphene oxide, or GO, is graphene that has been chemically modified with oxygen-containing groups, such as hydroxyl, epoxy, carbonyl, and carboxyl groups. These groups make GO more hydrophilic, allowing it to disperse relatively easily in water and other polar solvents.

GO is generally much less electrically conductive because its oxygen groups disrupt the continuous carbon network. However, its chemical reactivity and dispersibility are valuable for membranes, coatings, sensors, composites, and biomedical research. For energy storage, GO can contribute pseudocapacitance through surface chemical reactions. It can also act as a precursor for reduced graphene oxide.

3) Reduced graphene oxide

Reduced graphene oxide, or rGO, is produced by removing some of the oxygen groups from graphene oxide through chemical, thermal, electrochemical, or photochemical treatment. Reduction improves electrical conductivity.

Compared with GO, rGO normally has:

• Higher electrical conductivity.
• Lower oxygen content.
• Greater suitability for electrodes
• Better performance in batteries, supercapacitors, and conductive composites.

4) Laser Scribed Graphene (LSG)

In one process, a high-power laser beam converts   carbon-rich surfaces into graphene in a single step. photo thermal or photochemical effect. A porous architecture helps keep sheets separated and creates channels for electrolyte ions. It can also reduce electrode resistance and improve mechanical stability.

5) Crumpled graphene

Crumpled graphene is graphene that has been deliberately folded, wrinkled, or compressed into a three-dimensional, irregular structure. Crumpled graphene resists restacking and aggregation. Crumpling keeps more surface accessible and creates internal spaces for ions, molecules, or other particles.

Crumpled graphene is often combined with activated carbon, carbon nanotubes, metal oxides, or conducting polymers. Activated carbon contributes microporosity, while crumpled graphene provides conductive pathways and structural spacing. Metal oxides and conducting polymers can add pseudocapacitance, increasing energy storage but sometimes reducing long-term cycle stability.

For ultracapacitors, it is particularly promising as a conductive, high-surface-area framework and as a component of graphene–activated-carbon or graphene–pseudocapacitive composites. It is not necessarily a replacement for all electrode materials, but it can make graphene more practical by ensuring that a larger portion of its surface remains accessible during processing and operation.

In addition to these, few layer,, multilayer, quantum dots, nanoplatelets are other forms graphene available or under research phases.

Hybrid and composite materials

In practical electrodes, graphene is often combined with activated carbon rather than used alone. This composite is generally more practical than ideal monolayer graphene. Graphene structures—such as 3D foams, aerogels, or composites with activated carbon—can achieve specific capacitances on the order of 140–160 F/g with good energy storage and power delivery capability and cycling stability.

• Activated carbon/graphene hybrids: Graphene improves capacitance and reduce ESR while activated carbon provides a microporous network with high surface area. Graphene (e.g., 30 wt%) can give significantly higher capacitance and better retention at high current densities.
• Graphene–carbon nanotube (CNT) networks create 3D structures where CNTs act as spacers to prevent graphene restacking and provide mechanical reinforcement, while graphene offers large surface area and planar conduction paths.
• Graphene functions as a high‑power supercapacitor electrode paired with a higher‑capacitance pseudocapacitive electrode.

Applications of graphene

Applications of graphene are found in medicine, electronics, light processing, energy. Sensors, environmental and some other fields.

• Electronics and energy: Opto-electronic applications like touch- and flexible displays, and as clear conductors in phones and displays.  Graphene in microchips make them faster because electron move faster.
• Energy storage applications: Supercapacitors and batteries are using them extensively particularly in new generation devices. Lately, it also finds usein solar cells. Supercapacitors are being commonly used today extensively in vehicle energy storage and energy recovery systems.
• Materials and structures: Mixed with rubbers, plastics and concrete, graphene boosts their strrength without adding heavy weight. It is painted onto boats or metal structures to prevent rust and corrosion. It finds way into tennis rackets and bicycles to make them lighter and tougher.
• Health and environment: Graphene sheets with microscale holes block salt and toxins in water filters. Graphene detects miniscule amounts of DNA damage or disease markers in blood and saliva. It is also used to carry drugs for medical treatment directly to target cells inside the body. Several biomedical equipment and sensors use graphene for its unique properties. Graphene can be useful for water purification and desalination of water.

Graphene can be formed into other material forms like carbon nanotubes (CNT) or fullerene etc. for their own special applications.