Graphene PDF - Properties and Applications

# Graphene ## Introduction - Graphene can be described as a one-atom thick layer of graphite - It is the basic structural element of other allotropes, including graphite, charcoal, carbon nanotubes, and fullerenes - Graphene is the strongest, thinnest material known to exist. ## Structure - Grap...

# Graphene ## Introduction - Graphene can be described as a one-atom thick layer of graphite - It is the basic structural element of other allotropes, including graphite, charcoal, carbon nanotubes, and fullerenes - Graphene is the strongest, thinnest material known to exist. ## Structure - Graphene is a 2D crystal of carbon atoms, arranged in a honeycomb lattice - Each carbon atom is sp² hybridized and it is bound to its three neighbors ## Dimensionality | Dimension | Properties | Examples | |---|---|---| | 0D | Nanospheres, clusters | Quantum dots, Fullerenes, Gold | | 1D | Nanotubes, wires, rods | Metal nanorods, Carbon nanotubes, Metallic nanotubes | | 2D | Thin films, plates, layered structures | Carbon coated nanoplates, Graphene sheets | | 3D | Bulk NMs, polycrystals | Liposome, Polycrystalline | ## History - One of the very first patents pertaining to the production of graphene was filed in October, 2002 entitled, "Nano-scaled Graphene Plates" - Two years later, in 2004 Andre Geim and Kostya Novoselov at University of Manchester extracted single-atom-thick crystallites from bulk graphite - Geim and Novoselov received several awards for their pioneering research on graphene, notably the 2010 Nobel Prize in Physics. - The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov at the University of Manchester ## Mechanical Properties - To calculate the strength of graphene, scientists used a technique called Atomic Force Microscopy. - It was found that graphene is harder than diamond and about 300 times harder than steel. - The tensile strength of graphene exceeds 1 TPa. - It is stretchable up to 20% of its initial length. ## Chemical Properties - Graphene is chemically the most reactive form of carbon. - Only form of carbon (and generally all solid materials) in which each single atom is in exposure for a chemical reaction from two sides (due to the 2D structure). - Carbon atoms at the edge of graphene sheets have special chemical reactivity. - Graphene burns at very low temperature (e.g., 350 °C). - Graphene has the highest ratio of edgy carbons (in comparison with similar materials such as carbon nanotubes) - Graphene is commonly modified with oxygen- and nitrogen-containing functional groups. ## Electronic Properties - It is a zero-overlap semimetal (with both holes and electrons as charge carriers) with very high electrical conductivity. - Electrons are able to flow through graphene more easily than through even copper - The electrons travel through the graphene sheet as if they carry no mass, as fast as just one hundredth that of the speed of light. - High charge carrier mobility, for which values of 10,000 cm²/Vs, in some cases even 200,000 cm²/Vs were reported. ## Thermal Properties - Graphene is a perfect thermal conductor - Its thermal conductivity is much higher than all the other carbon structures as carbon nanotubes, graphite, and diamond (> 5000 W/m/K) at room temperature - Graphite, the 3 D version of graphene, shows a thermal conductivity about 5 times smaller (1000 W/m/K) - The ballistic thermal conductance of graphene is isotropic, i.e. same in all directions - The material's high electron mobility and high thermal conductivity could lead to chips that are not only faster but also better at dissipating heat. ## Optical Properties - Graphene, despite it is only 1 atom thick, is still visible to the naked eye. - Due to its unique electronic properties, it absorbs a high 2.3% of light that passes through it. ## Applications - While as of 2014, graphene is not used in commercial applications, many have been proposed and/or are under active development, in areas including electronics, biological engineering, filtration, lightweight/strong composite materials, photovoltaics, and energy storage. ### Biomedical - Graphene could soon be used to analyze DNA at a record-breaking pace. - That's the claim of a physicist in the US who has proposed a new way of reading the sequence of chemical bases in a DNA strand by sending the molecule through a tiny slit in a graphene sheet. ### Integrated Circuits - Graphene has a high carrier mobility, as well as low noise, allowing it to be used as the channel in a field-effect transistor. - Processors using 100 GHz transistors on 2-inch (51 mm) graphene sheets. - Graphene-based integrated circuit handled frequencies up to 10 GHz. - Transistors printed on flexible plastic that operate at 25 gigahertz - Terahertz-speed transistor ### Optical Electronics - Graphene's high electrical conductivity and high optical transparency make it a candidate for transparent conducting electrodes. - Graphene's mechanical strength and flexibility are advantageous compared to indium tin oxide, which is brittle. - So it would work very well in optoelectronic applications: touchscreens, liquid crystal displays, organic photovoltaic cells, and organic light-emitting diodes. ### Filters - **Desalination:** By very precise control over the size of the holes in the graphene sheet, graphene oxide filters could outperform other techniques of desalination by a significant margin. - **Ethanol distillation:** Graphene oxide membranes allow water vapor to pass through, but are impermeable to other liquids and gases. - Such membranes could revolutionize the economics of biofuel production and the alcoholic beverage industry. ### Solar cells ­- Graphene turned to be a promising material for photoelectrochemical energy conversion in dye sensitized solar cells. - The transparent, conductive, and ultrathin graphene films are fabricated from exfoliated graphite oxide, followed by thermal reduction. - The obtained films exhibit a high conductivity of 550 S/cm and a transparency of more than 70% over 1000-3000 nm. ### Energy Storage Devices - Due to the extremely high surface area to mass ratio of graphene, one potential application is in the conductive plates of Supercapacitors. - It is believed that graphene could be used to produce Supercapacitors with a greater energy storage density than is currently available. ### Anti-Bacterial - In 2010, the Chinese Academy of Sciences has found that sheets of graphene oxide are highly effective at killing bacteria such as Escherichia coli. - This means graphene could be useful in applications such as hygiene products or packaging that will help keep food fresh for longer periods of time. ### 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 wonder material that could revolutionize the world. It has the potential to be used in a wide range of applications, from electronics to energy storage to biomedical devices.