Graphene Properties and Applications

Graphene materials have ultrahigh surface area, high strength, and exceptional conductivity making them highly valuable for various applications. Its large surface area enhances energy storage, sensor sensitivity, and water purification efficiency. Graphene's incredible strength and lightweight nature are ideal for flexible electronics and mechanical reinforcement. Additionally, its excellent electrical and thermal conductivity support advanced electronic devices, energy storage systems, and efficient heat management.

Properties	Graphene
Dimensionality	2D
Thickness	~ 1 nm, one atom thick
Surface Area	Extremely high specific surface area - ~2600 m²/g
Appearance	Transparent and colorless
Strength	Strongest material known to exist: Tensile strength = 130 GPa Elastic Modulus = 1.1 TPa
Bonding	Each carbon participates in three σ bonds (C-C) and a π bond (hybridized sp² bonding) Bond lengths = 0.142 nm
Conductivity	Exceptionally electrically and thermally conductive: Thermal Conductivity = 5 x 10³ W/mK Electron Conductivity = 106 S/m Resistance = 31 Ω/sq Electron mobility = (2 x 10⁵ cm²/V.s) Zero-gap semiconductor/semimetal
Stability	Chemically reactive edges and surface which can be functionalised with other elements

Ultra-high Surface Area

The ultrahigh specific surface area (~2600 m²/g ) of graphene is a result of it being 2D and therefore majority exposed surface. This property is crucial for surface active applications such as:

Energy Storage

Graphene has a greater charge accumulation in supercapacitors resulting in high energy and power densities. This is as a result of its high surface area which leads to more efficient ion transport in lithium ion batteries.

Sensors

The surface of graphene is highly sensitive to changes in environment producing a measurable response to gases, biomolecules and chemicals. Graphene can be modified with receptors to enable selectivity.

Water Purification

Graphene effectively removes contaminants and pathogens at a molecular level.

Composite Materials

The high surface area ensures better interaction with the matrix material, enhancing the mechanical, thermal, and electrical properties of the composite.

Solar Cells

Graphene improves the efficiency of charge collection and transport, leading to more efficient photovoltaic devices.

Conductive Inks and Coatings

Graphene enhances the conductivity of inks and pastes used in printed electronics, flexible circuits, and transparent conductive films.

High Strength

Graphene is the strongest material known to exist. It is predicted to withstand 130 GPa of stress before breaking. This is referred to as its tensile strength value. 130 GPa is approximately 1.2 million times greater than atmospheric pressure. For comparison, diamond has a tensile strength of 2.8 GPa which can be as high as 80-90 GPa on the microscale.

Graphene’s elastic modulus (1.1 TPa) describes the ratio of applied stress to change in shape. This huge value means that graphene holds strong under immense stress. Being both incredibly strong and stiff as well as lightweight makes graphene suitable for a wide range of applications.

Flexible Electronics

Graphene is seen as a strong alternative for current electrodes substrates such as ITO which is brittle and chemically unstable. Graphene has been used in light-emitting diodes, solar cells and field-effect transistors. Graphene is also being used within wearable electronics such as sensors which can monitor human health.

Mechanical Reinforcement

Even very low loadings of graphene within a composite material such as polymers or concrete can provide significant reinforcement. Less than 1% (by weight) graphene additives sees significant improvements. This makes graphene composites attractive for replacing metals in applications such as construction, automotive and aerospace. Graphene-reinforced materials are being used to manufacture high-performance sports equipment, such as tennis rackets, bicycle frames, and helmets, offering improved strength and reduced weight. This includes grip on trainers which are 50% more hard wearing and last more than 1,000 miles.

Biomedicine

Graphene based nanocomposites have been used for tissue engineering and regenerative medicine. Graphene imparts high strength to the engineering of bone, nerve, heart and muscle. It can promote stem cells to grow and develop into specific types of cells.

Conductivity

Graphene is exceptionally electrically and thermally conductive. Graphene has an electron conductivity of 106 S/m and thermal conductivity of 5 x 10³ W/mK . Electrons can flow very easily (electron mobility is 2 x 10⁵ cm²/V.s ) with very little resistance (31 Ω/sq ). This makes graphene suitable for a range of electronic and thermal applications, including:

Electronics

The use of graphene materials in flexible electronics has already been mentioned. The combination of transparency, strength, flexibility, and high electrical conductivity makes it attractive to researchers across various fields. This includes a range of electronic applications, such as:

Field Effect Transistors

Graphene transistors can operate at higher speeds than traditional silicon transistors (electron mobility of ≤1400 cm2/V.s – 140 times slower than graphene). Graphene excellent stability, low-power operation and low-cost fabrication. This means graphene is suitable for future high-speed electronics.

Semiconductors

Graphene has been used as a semiconductor through recent developments in processing so that it has a band gap. This means electrons can hop from lower energy to higher energy states, allowing for a switching from “on” and “off”. It can either being conducting or not conducting which creates the binary (ones and zeros) system needed for computors.

Energy Storage

Systems where both the anode and cathode are made with graphene materials are promising alternative energy-storage devices. Reactions happen quickly at both graphene electrodes. This is because graphene is a porous (honeycomb-like) material with high electrical conductivity. This means graphene batteries have high power and energy density. Graphene batteries are comparable to conventional lithium ion batteries and are seen as a promising alternative due to their higher power density.

The advancement of electronic devices has brought with it the need for improving thermal management. Effective heat dissipation management in electronic devices is crucial for ongoing advancements.

Thermal Applications

Graphene can be incorporated into thermal interface materials (TIMs) to enhance heat transfer between components, leading to more efficient cooling in electronics. ). Graphene has been used in the cooling of photovoltaic solar panels in order to reduce deterioration caused by high temperatures.

The high thermal conductivity and compatibility with different materials means graphene can be applied to reduce the build-up of heat. This is particularly useful for high-power-batteries where temperature rises can negatively impact performance or lead to cell rupture and in the worst cases explosions. Graphene can be used to improve thermal conductivity within a battery without degrading heat storage ability.

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Graphene vs Graphite

Graphene is a single layer of carbon atoms arranged in a hexagonal pattern, like a sheet of paper. Graphite, on the other hand, is made up of many layers of graphene stacked on top of each other, like a stack of paper.

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