The structural model of graphene oxide
Apurva Sinha1, Shweta Agrawal2, Pranay Ranjan1, T. Rajagopala Rao2 and Ajay D. Thakur1
1Department of Physics, Indian Institute of Technology, Patna
2Department of Chemistry, Indian Institute of Technology, Patna
Graphene oxide (GO), a very potent precursor for the mass level production of graphene has owned a huge respect for its various vital applications in physics, medicine, chemistry etc. Graphene which is a two dimensional sheet of carbon atoms arranged in a hexagonal pattern has a sp2 hybridization. Oxygen functional groups (OFGs) like hydroxyl (-OH), carboxyl (-COOH), carbonyl (-CO), epoxides (C-O-C) bonded covalently to the carbon atoms of the parent graphene changes its hybridization from sp2 to sp3 and is called GO. The Density Functional Theory (DFT) help us determine the structure of GO. The computational results obtained benchmarked our experimental results. If the density and the nature of OFGs can be known completely, it becomes easy to tailor various vital properties of GO like its hydrophilicity, surface enhance Raman scattering (SERS), fluorescence quenching ability1 and more. Many models have been proposed beginning by Thiele et. al., Scholz et. al.2, followed by Mermoux et. al.3, Lerf et. al.4, Dreyer et. al.5, Froning et. al.6. We have used the Time dependent DFT based Raman spectra to characterize the structural model of a monolayer GO using Gaussian-16, M06-2x functional and 631-G∗ as basis set. We studied the effect on the Raman peaks shifts with the attachment of individual OFGs and multiple OFGs with their varying densities. By studying the different models of the oxidized GOs, we end up at the required model whose Raman peaks exactly matched with our experimentally reported values7.
References:
1. Chung, C.; Kim, Y.K.; Shin, D.; Ryoo, S.R.; Hong, B.H.; Min, D.H.; Biomedical Applications of Graphene and Graphene Oxide, Accounts Of Chemical Research, Vol. 46, 2013, 2211-2224.
2. Dimiev, A.M. and Eigler, S.; Graphene Oxide: Fundamentals and Applications, ISBN: 978-1-119-06940-9, 2016.
3. Mermoux, M.; Chabre, Y.; Rousseau, A.; FTIR and 13C NMR study of graphite oxide, Carbon, 29 (3), 1991, 469-474.
4. Lerf, A.; He, H.; Forster, M.; Klinowski, J., Structure of graphite oxide revisited. J. Phys. Chem.B, 102 (23), 1998, 4477-4482.
5. Dreyer, D.R.; Park, S.; Bielawski, C.W.; Ruoff, R.S., The chemistry of graphene oxide. Chem.Soc. Rev., 39 (1), 2010, 228-240.
6. Froning, J.P.; Lazar, P.; Pykal, M. Li. Q.; Dong, M.; Zboril, R.; Otyepka, M.; Direct mapping of chemical oxidation of individual graphene sheets through dynamic force measurements at the nanoscale, Nanoscale 9(1), 2017, 119-127.
7. Ranjan, P.; Agrawal, S.; Sinha, A.; Rao, T. R.; Balakrishnan, J.; Thakur, A. D.; A Low-Cost Non-explosive Synthesis of Graphene Oxide for Scalable Applications, Scientific Reports, 8, 2018, 12007.