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  1. 1. Graphene The Thinnest material known so far to humanity Taranpreet singh (MS12044)
  2. 2. What is graphene? Graphene is the single atom layer of sp2 bonded carbon atoms tightly packed into 2dimensional (2D) honey comb lattice, graphene comes from the graphite one of the allotropic form of carbon. even 1mm of graphite consist of 300 million layer of graphene on top of each other. Graphene is a 2D building material for carbon materials of all other dimensionalities. It can be wrapped up into 0D buckyballs, rolled into 1D nanotubes or stacked into 3D graphite.
  3. 3. What is so interesting about graphene? Graphene is a miracle material of 21st century because of its unique properties and its application found in every field of research where graphene is offering new and exciting possibilities. And as with electronics, health sciences, medicine, energy, various fields of science the potential is mind-boggling. One can imagine with little effort a new generation of super-strong flak vests, military vehicles and spacecraft etc. all augmented by the addition of tiny sheets of incredibly light material. Graphene is strongest material of world it is stiffer than diamond, Thinnest material that can be imagine(thin as 100000 time thinner than human hair) and stretchable (up to 20% elastically)many other properties that make it the worlds miracle material .
  4. 4. Science before graphene came to picture More than 75 years ago Landau and peierls argued that 2D crystal were thermodynamically unstable and could not exist. The argument was latter than supported by mermin strongly supported by experimental observation that indeed, melting temperature of thin films rapidly decrease with decreasing thickness and thus the film become unstable and segregated into parts or decompose at the thickness of dozen atomic layers. For this reason atomic monolayer have so far been known only as an integral part of larger 3d structure. Usually grown epitaxially on top of monocrystal with matching crystal lattice. without 3d base, 2d materials presumed not to be exist until 2004 when it was falsified by experimental discovery of graphene. Referances • Peierls, R. E. Quelques proprietes typiques des corpses solides. Ann. I. H. Poincare 5, 177–222 (1935). • Landau, L. D. Zur Theorie der phasenumwandlungen II. Phys. Z. Sowjetunion 11, 26–35 • Mermin, N. D. Crystalline order in two dimensions. Phys. Rev. 176, 250–254 (1968).
  5. 5. Isolation of single atomic layer of graphene Back in year 2004 prof. Andre geim, prof. kostantin Novoselov at university of Manchester in uk, manage to isolate the single atomic layer of graphene from graphite using scotch-tape technique. This experiment of graphene has completely revelutionalized the graphene world for which they awarded with noble prize in 2010.
  6. 6. Synthesis of graphene
  7. 7. SYNTHESIS • TOP DOWN METHODS 1. Mechanical exfoliation of graphite using scotch-tape technique 2. Electrochemical exfoliation • BOTTOM UP 1. Chemical vapour deposition(CVD) 2. Epitaxial growth of graphene on Sic
  8. 8. Mechanical exfoliation
  10. 10. Chemical vapour deposition Graphene acquired from cvd process is high quality, on large scale with controllable number of layers, low defects. The CVD based graphene synthesis process typically involves a thin layer of a transition metal (usually a few hundred nanometers thick) deposited on a substrate e.g. SiO2. The substrate is then put into a furnace to be heated up to about 1000º C in a hydrocarbon gas (e.g. methane and hydrogen) environment. The transition metallic layer catalyzes the decomposition of hydrocarbon gas and the dissociated carbon atoms gradually absorbs into the metal layer or diffuses/remains on the metal surface depending on the metal. Experimentally, many different transition metal catalysts, (e.g. Ru, Ir, Pd, Ni, Cu) have been used to synthesize graphene and two distinct growth mechanisms have been proposed (Li, Cai et al. 2009). (I) Precipitated growth, in which decomposed C atoms dissolve into the catalyst first and then precipitate to the metal surface to form graphene during the subsequent cooling. This is because the solubility of carbon in the metal decreases with temperature and the concentration of carbon decrease exponentially from the surface into the bulk. The follow-up cooling process helps the carbon atoms to segregate to the metal surface to form graphene. (II). Diffusive mechanism, in which the decomposed C atoms remain or diffuse on the metal surface and then incorporate into graphene directly. Mechanism I corresponds to those metals that interact strongly with C atoms and has the binary phase of metal carbide (e.g., Ni) and growth mechanism II corresponds to those which have no metal carbide phase (e.g., Cu). For mechanism I, continuous precipitation of C from the interior of catalysts normally leads to the non-uniform, multilayer formation of graphene layer as carbon prefers to segregate at the nickel grain boundaries (Yu, Lian et al. 2008). This problem is alleviated in mechanism II (Li, Cai et al. 2009) and it is known to be the best for the synthesis of monolayer graphene.
  12. 12. Graphene superlatives • thinnest imaginable and strongest material ever measured • stiffest known material (stiffer than diamond) • most stretchable crystal (up to 20% elastically) • record thermal conductivity (outperforming diamond) • highest current density at room T (million times of those in copper) • highest intrinsic mobility (100 times more than in Si) • conducts electricity in the limit of no electrons • Good for flexible, wearable devices • It is transparent: One atom-thick layer sheet absorbs ~2.3% visible light (πα). • most impermeable (even He atoms cannot squeeze through)
  13. 13. Properties of graphene MORPHOLOGY The carbon-carbon bond length in graphene is 0.142 nm. Mechanical properties Worlds strongest material Ultimate tensile strength is 130GPa(0.4 Gpa steel),High surface to volume ratio, young modulus (0.5 Tpa)
  14. 14. Properties of graphene Impermeability Graphene is highly impermeable stopping other material to getting through. It is useful for detecting and trapping gases. Chemical properties Graphene is the only form of carbon (or solid material) in which every atom is available for chemical reaction from two sides (due to the 2D structure). Atoms at the edges of a graphene sheet have special chemical reactivity. Graphene has the highest ratio of edge atoms of any allotrope. Defects within a sheet increase its chemical reactivity. The onset temperature of reaction between the basal plane of single-layer graphene and oxygen gas is below 260 °C (530 K). Graphene burns at very low temperature (e.g., 350 °C (620 K)). Graphene is commonly modified with oxygen- and nitrogen-containing functional groups and analyzed by infrared spectroscopy and X-ray photoelectron spectroscopy.
  15. 15. Properties of graphene Optical properties It is transparent to light(97.7%)and electrons Electrical properties high electrical conductivity, high electron mobility, semi metal/zero gap semiconductor Thermal Properties best conductor of heat (better than even copper)
  17. 17. GRAPHENE APPLICATIONS OVERVIEW • Composites (Light weight, multifunctional and highly damage tolerant structures) • Paints and coatings (e.g. barrier, modification of optical/electrical properties of chemical derivatives of graphene). • Graphene Photonics (e.g. photomodulators, photodetectors, plasmonics, ultra-fast lasers, metamaterials). • Graphene electronics: specialist devices (e.g. high frequency transistors, spintronics) or in combination with other electronics technologies (e.g. printed electronics). • Flexible Electronics (e.g. as replacement for indium tin oxide in a range of applications such as touch screens, solar cells etc.) • Graphene sensors (e.g. chemical, strain sensors). • Energy storage (e.g. graphene-based batteries, super-capacitors).
  20. 20. GRAPHENE IN SUPERCAPACITOR • Cairo University graduate Maher El-Kady wired a small piece of graphene to an LED and found that graphene behaved as a super-capacitor, able to store a considerable amount of electricity. Their laser-scribed graphene is ideal as a super capacitor partially because of its enormous surface area, 1520 square meters per gram.
  21. 21. Lithium doping turn graphene into superconductor
  22. 22. GRAPHENE IN SOLAR CELLS Compare to traditional indium tin oxide solar cell, graphene based solar cell can be used because it is flexible, highly conducting, highly transparent and due to low cost because carbon is highly abundant, whereas traditional(ITO)solar cells are expansive because indium is very rare.
  23. 23. GRAPHENE IN OPTOELECTRONICS Graphene can be used as a material in optoelectronics on a large commercial scale specifically touch screen, liquid crystal display, organic light emitting diodes(oled), for a material to be used in optoelectronics it must transmit light ore than 90% and should have good conductivity and graphene have both of these properties not only that its also flexible.
  24. 24. GRAPHENE IN BODY ARMOR Layers of carbon one-atom thick can absorb blows that would punch through steel. Recent tests suggest that pure graphene performs twice as well as the fabric currently used in bulletproof vests, making it an ideal armor for soldiers and police.
  25. 25. GRAPHENE AEROGEL Chinese material scientist created the world lightest material, a graphene aerogel is about 7 time lighter than air(1.2mg/cm), its 1 cubic centimeter weighs about 0.16 milligram. Because of its elasticity and absorbent, it can absorb 850 time more than its weight, being good absorbent it can be used in environmental clean-up, where in the effected place this graphene aerogel can be spread and it can then absorb organic products like oil from water.(it doesn’t absorb water)*
  26. 26. GRAPHENE OXIDE USED FOR REMOVAL OF HIGH METALS FROM WATER Single layer graphene oxide with manganese ferrite magnetic nanoparticle shows best absorption properties for efficient removal of high metal Pb(II)/As(III)/As(V) from contaminated water. ACS Appl. Mater. Interfaces (2014), 6, 17426−17436
  27. 27. GRAPHENE SHEET AS WATER FILTER Researches of material science at MIT found that graphene sheet perforated with hole can be used in water filteration. Holes with diameter 1nm are big enough to let water molecule to pass through, small enough to stop any undesired chemical.
  28. 28. DNA SEQUENCING THROGH GRAPHENE SHEET Ultra-thin graphene provides an extremely precise test platform for DNA strand sequencing as the ionic current can recognize even a single Nucleotide of Dna. As molecules pass through the nanoporus holes, distinguishable ionic current is measured to interpret the sequence.