Graphene and GO by bhargava
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The document discusses graphene, including its synthesis, properties, and applications, highlighting its remarkable mechanical and electrical attributes as a two-dimensional material. Graphene was isolated in 2004 by researchers Andre Geim and Kostya Novoselov, leading to significant interest in its potential uses in various fields like energy, electronics, and biomedical applications. It outlines three main synthesis methods: chemical vapor deposition, chemical or plasma exfoliation, and mechanical cleavage, along with its unique properties such as high strength, flexibility, and electrical conductivity.
Graphene and GO by bhargava
- 1. GRAPHENE: SYNTHESIS, PROPERTIES AND APPLICATIONS PRESENTED BY: M SAIBHARGAVA REDDY 17031D6609 Nano Technology
- 2. CONTENT Introduction Synthesis of Graphene Properties Applications A Decade of research References
- 3. Introduction : Forms of Carbon Carbon Diamond(high temp & pressure) SP3 hybridization:cubis Graphite(ambient conditions) SP2 hybridization:planar Nanostructures (specific growth conditons) SWNTs MWNTs Graphene SP2 &2D Fullerene CNT 2D&cylindrical
- 5. • A Tale OF A Nobel Prize • In the imagination of scientists one layer of carbon atoms in natural graphite, has been thought to have amaging properties. • For eg: the in plane mechanical strength should be even better than diamond and electrons are expected to move very fast in graphene due to reduced scattering effect. • However to produce this single layer of atoms on an insulator so that its electrical proparties can be measured is extremely difficult. • Andre Geim and Konstantin Novoselov, researchers of Manchester, were among those scientists who were looking hard for methods to isolate graphene. • They were driven by the idea to observe the electric field effect in metals, which meant they wanted to change the conductivity by applying an electric field to adjust the electron density.
- 6. • THE STORY OF GRAPHENE • Fascination with this material stems from its remarkable physical properties and the potential applications these properties offer for the future. Although scientists knew one atom thick, two-dimensional crystal graphene existed, no-one had worked out how to extract it from graphite. • That was until it was isolated in 2004 by two researchers at The University of Manchester, Prof Andre Geim and Prof Kostya Novoselov. This is the story of how that stunning scientific feat came about and why Andre and Kostya won the Nobel Prize in Physics for their pioneering work • What does graphene look like? • Graphene is made up of a hexagonal lattice of carbon atoms in a honeycomb like structure. • It is just one-atom thick but absorbs 2.3% of light so it can be seen with the naked eye. • It can potentially be used to create semi-transparent electronics.
- 7. WHAT CAN GRAPHENE DO? Graphene's properties Graphene: the world's first 2D material. Since graphene's isolation in 2004 it has captured the attention of scientists, researchers and industry worldwide. It is ultra-light yet immensely tough. It is 200 times stronger than steel, but it is incredibly flexible. It is the thinnest material possible as well as being transparent. It is a superb conductor and can act as a perfect barrier - not even helium can pass through it. Current applications At The University of Manchester, graphene research is focused on the following applications: Energy; Membranes; Composites and Coatings; Biomedical; Sensors; Electronics. This is only the start. These are only the first steps. The potential of graphene is limited only by imagination
- 8. SYNTHESIS OF GRAPHENE There are 3 main ways to synthesize graphene, they are: • Chemical Vapor Deposition • Chemical or Plasma Exfoliation from natural Graphite • Mechanical cleavage from natural Graphite
- 9. 1.chemical vapor deposition (CVD): • Graphene films can be produced by varying methods, which include mechanical and thermal exfoliation, chemical reduction and epitaxial growth; but the most common method used in production today is by chemical vapor deposition (CVD). • General : • Substrate exposed to one/more volatile precursors. • Precursors react and/or decompose on the substrate surface – Produce desired deposit. • Volatile by-product that are produced are removed by gas flow through the reaction chamber. • Experimental Conditions: • Substrate :Copper films (Varying thickness). • Precursor : Methane. • Desired deposit : Graphene.
- 10. • Graphene Growth on Cu : • It was shown to be self limited. • Times less than 10 min , Cu surface not fully covered. • Growth for 10 min, 60 min yielded similar structures. • Growth on Cu foils of varying thickness yielded similar graphene structure.
- 11. • Graphene Oxide • Graphene oxide (GO) is most commonly produced by the oxidation of graphite oxide. The oxidation process is beneficial, as it functionalizes the surface of the graphene layers with multiple species of oxygenated functional groups. The multiple functional groups provide an enhanced layer separation and improved hydrophilicity. The hydrophilicity allows the graphene oxide to undergo ultrasonic irradiation, which produces a single/a few graphene layers that are highly stable when dispersed in DI Water and other solvents.
- 12. 2.Chemical or Plasma Exfoliation from natural Graphite • Reduced Graphene Oxide (rGO) • There are many methods to reduce graphene oxide (GO) into reduced graphene oxide (rGO), but most fall into three main categories: chemical reduction, thermal reduction and electrochemical reduction. The other methods include hydrazine vapor treatment, annealing, laser and microwave reduction. The reduction process is vital to producing rGO, as it determines how consistent the rGO structure is with the GO precursor. Many commercial producers of Graphene Nanoplatelets are in fact providing a product similar to industrial scale rGO as their GNP product. However this method differs from the rGO most people refer to which is a higher quality research product used for nano enabled devices.
- 13. • Graphene Nanoplatelets • Graphene Nanoplatelets are typically synthesized by micromechanical cleavage of bulk graphite and can only produce graphene flakes in limited quantities which are mixed in with graphitic stacks. Large scale GNP production often uses mechanical cleavage followed by chemical reduction to produce the final GNP product. • Another method to make GNPs in bulk is by plasma exfoliation. A unique benefit of plasma exfoliation is the ability to synthesize and functionalize the GNPs to promote dispersion in the host matrix in a single, dry, processing step. The RF or Microwave Plasma Reactor has a vacuum applied to remove atmospheric contaminants as well as residual contaminants which are liberated during the plasma milling process. 3.Mechanical cleavage from natural Graphite:
- 15. • Mechanical Properties • The thinnest material ever (0.34 nm). • Breaking strength is 130 Gpa , more than 100 times greater than steel. • Stretchable up to 20% of its initial length. • Completely flexible. • Graphene’s Strength Enables High Performance Composites • Graphene is one of the strongest materials ever discovered with a tensile strength of 1.3 x 1011 Pa. In addition to having an unrivaled strength, it is also very lightweight (0.77 mgm-2). The mechanical strength of graphene is unmatched and as such can significantly enhance strength in many composite materials.
- 16. • Thermal Properties: • The repeating structure of graphene makes it an ideal material to conduct heat in plane. Interplane conductivity is problematic and typically other nanomaterials such as CNTs are added to boost interplane conductivity. The regular structure allows the movement of phonons through the material without impediment at any point along the surface. Graphene can exhibit two types of thermal conductivity- in-plane and inter-plane. The in-plane conductivity of a single-layered sheet is 3000-5000 W m-1 K-1, but the cross- plane conductivity can be as low as 6 W m-1 K-1, due to the weak inter-plane van der Waals forces. The specific heat capacity for graphene has never been directly measured, but the specific heat of the electronic gas in graphene has been estimated to be around 2.6 μ J g-1 K-1 at 5 K.
- 17. • Flexibility/Elasticity • The repeating sp2 hybridized backbone of graphene molecules allow for flexibility, as there is rotation around some of the bonds, whilst still providing enough rigidity and stability that the molecule can withstand changes in conformation and support other ions. This is a very desirable property as there are not many molecules that can be flexible and supportive at the same time. In terms of its elasticity, graphene has found to have a spring constant between 1-5 Nm-1, with a Young’s modulus of 0.5 TPa.
- 18. • Chemical and Biological properties: • Chemically rather stable. • Can be modified with oxygen and Nitrogen containing functional groups. • Used as a substrate to be interfaced with various biomolecules and cells. • Largely biocompatible.
- 19. • Electrical & Electronic Properties: • It is a semi metal(conductor). • High charge carrier mobility of 2.5*105 𝑐𝑚2/(Vs). • High Conductivity (35% higher than that of copper). • Flexible Graphene Transistors • Because graphene has a delocalized pi-electron system across the entirety of its surface, the movement of electrons is very fluid. The graphene system also exhibits no band gap, due to overlapped pi-electrons, allowing for an easy movement of electrons without the need to input energy into the system. The electronic mobility of graphene is very high and the electrons act like photons, with respect to their movement capabilities. The electrons are also able to move sub- micrometer distances without scattering. From tests done to date the electron mobility has found to be in excess of 15,000 cm2V-1s-1, with the potential of producing up to 200,000 cm2V-1s-1.
- 20. APPLICATINS • Sensors: • Many of graphenes properties are beneficial in sensor applications; as such, graphene could be used in sensors in various fields including bio-sensors, diagnostics, field effect transistors, DNA sensors and gas sensors • Batteries: • Graphene can be incorporated into both the anode or the cathode in various battery systems to increase the efficiency of the battery and improve the charge/discharge cycle rate. The excellent electrical conductivity, surface area and dispersibility of graphene enhances the beneficial properties present in many traditional inorganic-based electrodes
- 21. • Electron Emission Displays: • Graphene is an ideal material for use in electron emission displays as it exhibits a high aspect ratio and the dangling bonds at either end of the sheet allow for efficient electron tunneling. The linear disperisty that the graphene surface provides produces massless Dirac Fermions. When exposed to an electric field, the field emission liberated electrons avoid all back-scattering because their escape velocity is independent to their energy. Graphene can turn-on an electric field at 0.1 V µm-2, with a field enhancement factor of up to 3700. This can increase up to 4500 in screen printed graphene films. • Structural Composites: • Graphene is incorporated into various composites for applications where strength and weight are limiting factors, for example in the aerospace industry. Graphene is being incorporated into many materials to make the existing material stronger and more lightweight.
- 22. A DECADE OF RESEARCH
- 23. REFERENCES : • Huang X., Xiaoying Q., Boey F. and Zhang H., Graphene based composites, Chem Soc. Rev., 2012, 41, 666-686 • Zhou G., Yin L., Wang D. and Cheng H., A fibrous hybrid of graphene and sulfur nanocrystals for high performance lithium-sulfur batteries, ACS Nano, 2013, 7(6) • Cheng Q., Tang J., Zhang H., Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density, Phys. Chem. Chem. Phys., 2011, 13, 17615-17624 • www.cheaptubes.com • www.graphenea.com
- 24. THANK YOU …
- 25. 1 g Graphite Flakes 0.5 g NaNO3 Mix them with 50 ml of H2SO4 Stirred for 2hours temp @ (0 - 5C) Slowly add 3g of KMnO4 @ < 15C temp & Stir 2hours Add 46 ml of Water dropwise & stir 2 hours @100C to 35C Add 10ml of H2O2 & 150 ml of Water Color turns to yellow After purification with Ethanol & Water for several times After drying we get Graphene Oxide