Introduction to Graphene Materials

Introduction

• Graphene is a single-atom thick layer of graphite.
• It is the basic building block of other carbon structures, including graphite, charcoal, carbon nanotubes, and fullerenes.
• It is the strongest and thinnest material known.

Structure

• Graphene is a 2D crystal of carbon atoms arranged in a honeycomb lattice.
• Each carbon atom is sp² hybridized and bonded to its three nearest neighbors.

Dimensionality

• 0D materials include nanospheres, clusters, quantum dots, fullerenes, and gold.
• 1D materials include nanotubes, wires, rods, metal nanorods, carbon nanotubes, and metallic nanotubes.
• 2D materials include thin films, plates, layered structures, carbon coated nanoplates, and graphene sheets.
• 3D materials include bulk nanomaterials, polycrystals, liposomes, and polycrystalline materials.

History

• The first patent for graphene production was filed in 2002.
• In 2004, Andre Geim and Kostya Novoselov extracted single-atom-thick graphene sheets from graphite.
• Geim and Novoselov received the 2010 Nobel Prize in Physics for their groundbreaking research.

Mechanical Properties

• Graphene's strength was measured using Atomic Force Microscopy.
• Graphene is harder than diamond and 300 times harder than steel.
• Its tensile strength exceeds 1 TPa.
• It is stretchable up to 20% of its original length.

Chemical Properties

• Graphene is the most chemically reactive form of carbon.
• Each carbon atom is exposed for chemical reactions from both sides due to its 2D structure.
• Carbon atoms at the edges of graphene sheets are particularly reactive.
• Graphene burns at a low temperature (350°C).
• It has the highest ratio of edge carbons compared to similar materials like carbon nanotubes.
• Graphene is commonly modified with oxygen and nitrogen-containing functional groups.

Electronic Properties

• Graphene is a zero-overlap semimetal, with both holes and electrons as charge carriers.
• It has very high electrical conductivity, even exceeding copper.
• Electrons travel through graphene with almost no mass, reaching speeds of almost one hundredth the speed of light.
• High charge carrier mobility values of 10,000 cm²/Vs, and even up to 200,000 cm²/Vs, have been reported.

Thermal Properties

• Graphene is a perfect thermal conductor.
• Its thermal conductivity is higher than other carbon structures like carbon nanotubes, graphite, and diamond (> 5000 W/m/K) at room temperature.
• Graphite, the 3D version of graphene, has a thermal conductivity about 5 times lower (1000 W/m/K).
• Graphene's thermal conductance is isotropic, meaning it is the same in all directions.
• Its high electron mobility and thermal conductivity could lead to faster and more efficient heat dissipation in chips.

Optical Properties

• Graphene, despite its single-atom thickness, is visible to the naked eye.
• Due to its unique electronic properties, it absorbs 2.3% of the light passing through it.

Applications

• Graphene has potential in a wide range of applications, including electronics, bioengineering, filtration, lightweight/strong composite materials, photovoltaics and energy storage.

Biomedical

• Graphene could be used for high-speed DNA analysis.

Integrated Circuits

• Graphene's high carrier mobility and low noise make it suitable for use in field-effect transistors.
• Processors with 100 GHz transistors on 2-inch graphene sheets are being explored.
• Graphene-based integrated circuits have reached frequencies up to 10 GHz.
• Transistors printed on flexible plastic operate at 25 GHz.
• Terahertz-speed transistors are a possibility.

Optical Electronics

• Graphene's high electrical conductivity and optical transparency make it a candidate for transparent conducting electrodes.
• Its mechanical strength and flexibility offer advantages over brittle indium-tin oxide.
• Promising for optoelectronic applications: touchscreens, LCD displays, organic photovoltaic cells, and OLEDs.

Filters

• Desalination: Graphene oxide filters could outperform other desalination techniques due to precise control of pore size.
• Ethanol distillation: Graphene oxide membranes allow water vapor to pass through but are impermeable to other liquids and gases. This could revolutionize biofuel production and the alcoholic beverage industry.

Solar Cells

• Graphene is promising in dye-sensitized solar cells for photoelectrochemical energy conversion.
• Transparent, conductive, and ultrathin graphene films are fabricated from exfoliated graphite oxide.
• These films show high conductivity (550 S/cm) and transparency (> 70%) over 1000-3000 nm.

Energy Storage Devices

• Graphene's high surface area to mass ratio makes it suitable for conductive plates in supercapacitors.
• It could lead to supercapacitors with greater energy storage density.

Anti-Bacterial

• Graphene oxide is highly effective at killing bacteria like E. coli.
• It has potential in hygiene products and packaging for food preservation.

Other Applications

• Graphene nanoribbons
• IR detectors
• Single-molecule gas detection
• Piezoelectric materials
• Energy Harvesting
• Composite Materials
• Liquid Cells for Electron Microscopy
• Thermal management materials
• Optical Modulators
• Chemical sensors

Conclusion

• Graphene is a remarkable material with the potential to revolutionize various fields.
• Its diverse applications span from electronics and energy storage to biomedical devices.