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A review on Graphene Oxide
- 1. Presented by Satirtha Banik,Bs-Ms VIII CHEMISTRY
- 2. Contents:- Introduction Synthesis of Grapheneoxide Structure of Graphene oxide Reactivity • Reductions • Chemical functionalization References Acknowledgement
- 3. Introduction:- • Graphene oxide,formerly called graphitic oxide or graphitic acid, is a compound of carbon, oxygen, and hydrogen , obtained by treating graphite with strong oxidizers. • Structurally, GO can be visualized as a graphene sheet with its basal plane decorated by oxygen-containing groups. • Due to high affinity to water molecules by these groups, GO is hydrophilic and can be dissolved in water. • The solubility in water makes the deposition of the thin films of the GO straightforward.
- 4. Synthesis:- B. C.Brodie(1859) In 1859 when British chemist B. C. Brodie performed the reaction adding ‘‘potash of chlorate’’ (potassium chlorate; KClO3) to a slurry of graphite in fuming nitric acid (HNO3). Brodie determined that the resulting material was composed of carbon, hydrogen, and oxygen. GRAPHITE + Fuming HNO3 + KClO3 Graphene oxide
- 5. L. Staudenmaier improvedBrodie’s KClO3-fuming HNO3 preparation by adding the chlorate in multiple aliquots, with the addition of concentrated sulfuric acid, to increase the acidity of the mixture. Staudenmaier’s method(1898) GRAPHITE + Fuming HNO3 + Conc. H2SO4 + KClO3 Graphene oxide
- 6. Hofmann method(1937) Hofmannmethod involves reacting flake graphite with conc. HNO3, conc. H2SO4 in presence of potassium chlorate KClO3 to produce the desired oxidized product(GO). GRAPHITE + Conc. HNO3 + Conc. H2SO4 + KClO3 Graphene oxide
- 7. Hummers’ method(1958) Hummersand Offeman developed an alternate oxidation method by reacting graphite with a mixture of potassium permanganate (KMnO4) and concentrated sulfuric acid (H2SO4)6. The Hummers method uses a combination of potassium permanganate and sulfuric acid. GRAPHITE + Conc. H2SO4 + KMnO4 + NaNO3 Graphene oxide
- 8. Structural Features:- • 7Hofmannand Holst’s structure consisted of epoxy groups spread across the basal planes of graphite, with a net molecular formula of C2O. Hofmann and Holst’s structure Fig. 1 Hofmann and Holst’s structure(adapted from ref. 1).
- 9. • 8Ruess proposeda variation of this model which incorporated hydroxyl groups into the basal plane along with epoxide groups. Ruess’s model also altered the basal plane structure to an sp3 hybridized system, rather than the sp2 hybridized model of Hofmann and Holst. Ruess Structure Fig. 2 Reuss structure(adapted from ref. 1).
- 10. • 9In 1969,Scholz and Boehm suggested a model that completely removed the epoxide and ether groups, substituting regular quinoidal species in a corrugated backbone. Scholz-Boehm Structure Fig. 3 Scholz-Boehm structure(adapted from ref. 1).
- 11. • 10The mostwell-known model is the one by Lerf and Klinowski . Lerf and Klinowski propose that GO is built of aliphatic 6-membered rings containing hydroxyl groups, epoxide groups, and double bonds. In this model, the O functional groups lie both above and below the basal plane. Fig. 4 Variations of the Lerf-Klinowski model indicating ambiguity regarding the presence (left) or absence (right) of carboxylic acids on the periphery of the basal plane of the graphitic platelets of GO. (adapted from ref. 2). Lerf and Klinowski
- 12. Reactivity:- Reduction There areTHREE methods for reduction of Graphene oxide i.e. removal of oxygen functionalities:- • Chemical Reduction:- This is the traditional reduction process using chemical reducing reagents like hydrazine monohydrate11 , LiAlH4 etc. The most straightforward goal of any reduction protocol is to produce graphene-like materials by removing oxygen functional groups.
- 13. • Thermally-mediated reduction:-It is the process in which thermodynamically stable carbon dioxide species is achieved by directly heating GO in a furnace. 12 Exfoliation of the stacked structure occurs through the extrusion of carbon dioxide generated by heating GO to 1050 ⁰C. • Electrochemical reduction:- Another final method that shows promise for the reduction of graphene oxide relies on the electrochemical removal of the oxygen functionalities. Reduction began at 0.60 V and reached a maximum at 0.87 V. Elemental analysis of the resultant material revealed a C:O ratio of 23.9 : 1. Scheme Proposed reaction for the electrochemical reduction of graphene oxide in a sodium phosphate buffer (adapted from ref. 13).
- 14. Chemical Functionalization •At the carboxylic acid group of graphene oxide:- The coupling reactions often require activation of the acid group for example using thionyl chloride (SOCl2),14-17 Subsequent addition of nucleophilic species, such as amines or hydroxyls, produce covalently attached functional groups to graphene oxide platelets via the formation of amides or esters. Fig. 5 Functionalization of the carboxylic acid groups of graphene oxide showing the covalent attachment of fullerenes (adapted from ref.3 ).
- 15. • At theepoxy group of graphene oxide:- Graphene oxide contain chemically reactive epoxy groups on their basal planes. The epoxy groups can be easily modified through ring-opening reactions under various conditions. A likely mechanism for this reaction involves nucleophilic attack at the α-carbon by the amine. Fig. 6 Covalent functionalization of the epoxy groups of graphene oxide by an ionic liquid (R = 3-(3-methylimidazolium)propane) (adapted from ref.4 ).
- 16. • Functionalization ofreduced graphene oxide:- Reduced graphene oxides have been frequently modified by non-covalent physisorption of both polymers18-20 and small molecules21,22onto their basal planes via π-π stacking or van der Waals interactions. Fig. 7 Covalent functionalization of reduced graphene oxide platelets with diazonium salts (SDBS, sodium dodecylbenzenesulfonate) (adapted from ref.5 ).
- 17. References:- 1. T. Szabo,O. Berkesi, P. Forgo, K. Josepovits, Y. Sanakis, D. Petridis and I. Dekany, Chem. Mater., 2006, 18, 2740–2749. 28 A. Lerf, H. He, T. Riedl, M. Forster and J. Klinowski, Solid State Ionics, 1997, 101–103, 857–862. 2. A. Lerf, H. He, M. Forster and J. Klinowski, J. Phys. Chem. B, 1998, 102, 4477–4482. 3. Z.-B. Liu, Y.-F. Xu, X.-Y. Zhang, X.-L. Zhang, Y.-S. Chen and J.-G. Tian, J. Phys. Chem. B, 2009, 113, 9681–9686. 4. H. Yang, C. Shan, F. Li, D. Han, Q. Zhang and L. Niu, Chem. Commun., 2009, 3880–3882. 5. Q. Su, S. Pang, V. Alijani, C. Li, X. Feng and K. Mu¨ llen, Adv. Mater., 2009, 21, 3191–3195. 6. W. S. Hummers and R. E. Offeman, J. Am. Chem. Soc., 1958, 80, 1339. 7. U. Hofmann and R. Holst, Ber. Dtsch. Chem. Ges. B, 1939, 72, 754–771. 8. G. Ruess, Monatsh. Chem., 1946, 76, 381–417. 9. W. Scholz and H. P. Boehm, Z. Anorg. Allg. Chem., 1969, 369, 327–340.
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- 19. Acknowledgement:- I would likethank my mentor Dr. Mitali Saha madam for her constant support in making this Project by providing the best possible papers for me to study and make this project. I would also like to thank HOD, Dr. Tarun Kr. Mishra sir my for providing me all the support. I would like to thank all the faculty members of my department for their constant support since my joining in this institute. Finally I would like to thank all the staff, seniors & juniors for their best wishes.