Investigation of Extraction Yields of Exfoliated Graphene in Deionized Water from Organic Solvents

Organic solvent is suitable for the exfoliation of graphene. However, for the end application of exfoliated graphene it needs to extract and re-disperse to the required media. Extraction of exfoliated graphene from organic solvents to a polar solvent is a crucial challenge in graphene synthesis. The principal objective of this study is to examine the concentration yields of exfoliated graphene extraction and make a comparison of the estimated percentage concentrations of graphene in between organic solvents and deionized water (DW). Exfoliated graphene from the solvents N-Methyl-2-Pyrrolidone (NMP) and N, N-dimethylformamide (DMF) were taken. The extraction of exfoliated graphene was conducted by membrane filter using a vacuum filtration system. Concentration of exfoliated graphene solvents were estimated using Beer’s law by preparing separate standard graphs. It is seen that concentrations of exfoliated graphene in DW from both NMP and DMF solvents for all the centrifugation was reduced. These reductions were found to be varied from ~ 21 to 25.5%. Morphology analysis using TEM and FESEM images reveals that the few layers of graphene staked in the sonication assisted liquid phase exfoliated (LPE) graphene in both of NMP and DMF solvents. Very minor levels of aggregation occurred and very slight sedimentation appeared after centrifugation of 30 days.

Concentration; Extraction; Graphene; Re-dispersion; Solvents

A one atom thick graphene sheet of ultra-thin carbon film with two-dimensional planer’s geometry was first discovered by Novoselov et al. (2004). Various chemicals and natural resources (Supriadi et al., 2017) have been used as precursor materials for the fabrication of graphene. This carbon based material has a vast application in nanofluids (Ahlatli et al., 2016). Various types of graphene have been processed using various methods, such as chemical vapor growth (Hu et al., 2012), molecular building blocks by annealing of SiC substrates (Palma & Samorì, 2011), bottom-up growth through the wet ball-milling method (Leon et al., 2011), and burning Mg metal in solid CO₂ (dry ice) (Arifutzzaman et al., 2015). Due to their initial setup and very low final yielding limits, their wide implication of graphene fabrication (Ciesielski & Samorì, 2014), in this case green chemistry, could be a viable approach (Kusrini et al., 2015).

Commercially obtainable microcrystalline graphite flakes can be exfoliated into distinct graphene flakes by an interaction in a solvent (Kotov et al., 1996). To exfoliate the graphite flakes into separate layers, two different mechanical forces are required (Arao et al., 2016). One is normal force which changes the interlayer space, and the other is the lateral shared force which slides away from the sheets. Applying the shear force across the flake’s of graphite surfaces causes the exfoliation graphite into the separate graphene layers (Yang & Liu, 2014). This chemical or liquid exfoliation method possesses very modest and straight forward one-step processes to exfoliate graphene in the liquid solvents which is most widely used technique to produce graphene (O’Neill et al., 2011; Khan et al., 2012). The surface energy of the organic solvents NMP (40 m Jm^-2) or DMF (37 m Jm^-2) (Hernandez et al., 2008) perfectly matches the graphite (Zacharia et al., 2004) and fulfils the requirement for a successful exfoliation to graphene sheets (Compton et al., 2010). Sedimentation based centrifugation is used to separate the graphene (O’Neill et al., 2011). In this approach, a higher centrifugation rate (rpm) gives lower concentrations of the graphene (Khan et al., 2012).

An organic solvent is necessary for the exfoliation of graphite to get separate graphene sheets. However, for further application purposes, it may need to extract the graphene from the solvent produced and re-dispersed in to a required solvent. For example, organic solvents will be influenced highly on the thermal and electrical transport properties (Behabtu et al., 2010). Sometimes, it could have a high impact on the device performance. However, solvents with low boiling points, such as water, will be preferable because they are incompatible for exfoliation and very suitable for the end application, such as the preparation of the heat transfer of nanofluids (Ciesielski & Samorì, 2014).

Irin et al. (2015) analyzed the different techniques for removing solvents from graphene dispersion. They found that vacuum filtration was the most suitable way compared to the other techniques, such as dialysis and spray drying, to separate the graphene from the organic solvent dispersion, and re-disperse to other suitable media. After vacuum filtration, graphene flakes prevail with an ordered multi-layered film on the filter paper (Dikin et al., 2007). Due to the application of constant suction force by a vacuum pump to the graphene sheets at the interface of solid and liquid, sheets are placed parallel to the membrane filter (Yang et al., 2011). Repulsive force amongst the solvent and exfoliated graphene was sufficient in preventing the graphene sheets from the re-staking together before they touch the filters surface (Yang et al., 2011). For these reasons, most of the graphene sheets tend to prevail horizontally on the membrane filter surface during the suction by vacuum pump (Cheng & Li, 2013). Importantly, it was confirmed by Yang et al. (2011) that the chemically transformed graphene sheets never return to their graphite form farther in the created wet film on the membrane filter. Although, literature has found few reports on the analysis of graphene yields in different base liquids, and based on knowledge, there is no systematic investigation reporting on the analysis of extraction yields of exfoliated graphene from the exfoliating organic solvents into DW. Therefore, the objective of this research is to conduct a systematic investigation on the extracted exfoliate graphene concentration yields, and make a comparison among the percentage variation of concentration yields into two different organic solvents with DW.

Exfoliated graphene was effectively extracted from two different organic solvents, NMP and DMF, and re-dispersed into DW using a vacuum filtration process. From the investigation, it can be seen that concentrations of exfoliated graphene in DW from both solvents for all the centrifugation was found to be reduced. These reductions were found to be varied from ~21 to 25.5%. Morphology analysis using TEM and FESEM images reveals that, the few layers of graphene in the exfoliated graphene in both of solvents. Very minor levels of aggregation occurred and very slight sedimentation appeared after centrifugation of 30 days.

The authors acknowledge the lab facilities under the Manufacturing and materials Engineering Department in the International Islamic University Malaysia for conducting experiments reported in this work.

Arifutzzaman, A., Ismail, A.F., Yaacob, I.I., Alam, M.Z., Khan, A.A., 2019. Stability Investigation of Water Based Exfoliated Graphene Nanofluids. In: IOP Conference Series: Materials Science and Engineering, Volume 488(1), pp. 1–5

Ahlatli, S., Maré, T., Estellé, P., Doner, N., 2016. Thermal Performance of Carbon Nanotube Nanofluids in Solar Microchannel Collectors: An Experimental Study. International Journal of Technology, Volume 7(2), pp. 210–226

Arao, Y., Mizuno, Y., Araki, K., Kubouchi, M., 2016. Mass Production of High-aspect-ratio Few-layer-graphene by High-speed Laminar Flow. Carbon, Volume 102, pp. 330–338

Arifutzzaman, A., Yaacob, I.I., Hawlader, M.A., Maleque, M.A., 2015. Fabrication and Characterization of Graphene from Solid Carbon Dioxide. Advanced Materials Research, Volume 1115, pp. 418–421

Behabtu, N., Lomeda, J.R., Green, M.J., Higginbotham, A.L., Sinitskii, A., Kosynkin, D.V., Cohen, Y., 2010. Spontaneous High-concentration Dispersions and Liquid Crystals of Graphene. Nature Nanotechnology, Volume 5(6), pp. 406–411

Chen, H., Müller, M.B., Gilmore, K.J., Wallace, G.G., Li, D., 2008. Mechanically Strong, Electrically Conductive, and Biocompatible Graphene Paper. Advanced Materials, Volume 20(18), pp. 3557–3561

Cheng, C., Li, D., 2013. Solvated Graphenes: An Emerging Class of Functional Soft Materials. Advanced Materials, Volume 25(1), pp. 13–30

Ciesielski, A., Samorì, P., 2014. Graphene via Sonication Assisted Liquid-phase Exfoliation. Chemical Society Reviews, Volume 43(1), pp. 381–398

Compton, O.C., Nguyen, S.T., 2010. Graphene Oxide, Highly Reduced Graphene Oxide, and Graphene: Versatile Building Blocks for Carbon-based Materials. Nano Micro Small, Volume 6(6), pp. 711–723

Dikin, D.A., Stankovich, S., Zimney, E.J., Piner, R.D., Dommett, G.H., Evmenenko, G., Ruoff, R.S., 2007. Preparation and Characterization of Graphene Oxide Paper. Nature, Volume 448, pp. 457–460

Hernandez, Y., Nicolosi, V., Lotya, M., Blighe, F.M., Sun, Z., De, S., Boland, J.J., 2008. High-Yield Production of Graphene by Liquid-phase Exfoliation of Graphite. Nature Nanotechnology, Volume 3(9), pp. 563–568

Hu, B., Ago, H., Ito, Y., Kawahara, K., Tsuji, M., Magome, E., Mizuno, S., 2012. Epitaxial Growth of Large-area Single-layer Graphene Over Cu (1 1 1)/Sapphire by Atmospheric Pressure CVD. Carbon, Volume 50(1), pp. 57–65

Irin, F., Hansen, M.J., Bari, R., Parviz, D., Metzler, S.D., Bhattacharia, S.K., Green, M.J., 2015. Adsorption and Removal of Graphene Dispersants. Journal of Colloid and Interface Science, Volume 446, pp. 282–289

Khan, U., O’Neill, A., Porwal, H., May, P., Nawaz, K., Coleman, J.N., 2012. Size Selection of Dispersed, Exfoliated Graphene Flakes by Controlled Centrifugation. Carbon, Volume 50(2), pp. 470–475

Khan, U., O'Neill, A., Lotya, M., De, S., Coleman, J. N., 2010. High-concentration Solvent Exfoliation of Graphene. Nano Micro Small, Volume 6(7), pp. 864–871

Kotov, N.A., Dékány, I., Fendler, J.H., 1996. Ultrathin Graphite Oxide-Polyelectrolyte Composites Prepared by Self-assembly: Transition between Conductive and Non-conductive States. Advanced Materials, Volume 8(8), pp. 637–641

Kusrini, E., Harjanto, S., Yuwono, A.H., 2015. Applications of a Green Chemistry Design, a Clean Environment, and Bioenergy to Promote the Sustainability and Added Value of Products. International Journal of Technology, Volume 6(7), pp. 1065–1068

Leon, V., Quintana, M., Herrero, M.A., Fierro, J.L., de la Hoz, A., Prato, M., Vazquez, E., 2011. Few-layer Graphenes from Ball-milling of Graphite with Melamine. Chemical Communications, Volume 47(39), pp. 10936–10938

Liu, Y., Jin, W., Zhao, Y., Zhang, G., Zhang, W., 2017. Enhanced Catalytic Degradation of Methylene Blue by ?-Fe₂O₃/Graphene Oxide via Heterogeneous Photo-Fenton Reactions. Applied Catalysis B: Environmental, Volume 206, pp. 642–652

Lotya, M., King, P.J., Khan, U., De, S., Coleman, J.N., 2010. High-concentration, Surfactant-stabilized Graphene Dispersions. ACS Nano, Volume 4(6), pp. 3155–3162

Mehrali, M., Sadeghinezhad, E., Latibari, S.T., Kazi, S.N., Mehrali, M., Zubir, M.N.B.M., Metselaar, H.S.C., 2014. Investigation of Thermal Conductivity and Rheological Properties of Nanofluids Containing Graphene Nanoplatelets. Nanoscale Research Letters, Volume 9(15), pp. 1–12

Niyogi, S., Bekyarova, E., Itkis, M.E., McWilliams, J.L., Hamon, M.A., Haddon, R.C., 2006. Solution Properties of Graphite and Graphene. Journal of the American Chemical Society, Volume 128(24), pp. 7720–7721

Novoselov, K.S., Geim, A.K., Morozov, S.V., Jiang, D., Zhang, Y., Dubonos, S.V., Firsov, A.A., 2004. Electric Field Effect in Atomically Thin Carbon Films. Science, Volume 306(5696), pp. 666–669

O’Neill, A., Khan, U., Nirmalraj, P.N., Boland, J., Coleman, J.N., 2011. Graphene Dispersion and Exfoliation in Low Boiling Point Solvents. The Journal of Physical Chemistry C, Volume 115(13), pp. 5422–5428

Palma, C.A., Samorì, P., 2011. Blueprinting Macromolecular Electronics. Nature Chemistry, Volume 3(6), pp. 431–436

Supriadi, C.P., Kartini, E., Honggowiranto, W., Tri, K., 2017. Synthesis and Characterization of Carbon Material Obtained from Coconut Coir Dust by Hydrothermal and Pyrolytic Processes. International Journal of Technology, Volume 8(8), pp. 1470–1478

Vadukumpully, S., Paul, J., Valiyaveettil, S., 2019. Cationic Surfactant Mediated Exfoliation of Graphite into Graphene Flakes. Carbon, Volume 47(14), pp. 3288–3294

Yang, P., Liu, F., 2014. Understanding Graphene Production by Ionic Surfactant Exfoliation: A Molecular Dynamics Simulation Study. Journal of Applied Physics, Volume 116(1), pp. 1–11

Yang, X., Qiu, L., Cheng, C., Wu, Y., Ma, Z.F., Li, D., 2011. Ordered Gelation of Chemically Converted Graphene for Next-generation Electroconductive Hydrogel Films. Angewandte Chemie International Edition, Volume 50(32), pp. 7325–7328

Zacharia, R., Ulbricht, H., Hertel, T., 2004. Interlayer Cohesive Energy of Graphite from Thermal Desorption of Polyaromatic Hydrocarbons. Physical Review B, Volume 69(15), pp. 1–7