The Effect of Solvent Viscosity on Production of Few-layer Graphene from Liquid-phase Exfoliation of Graphite
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.13
The Effect of Solvent Viscosity on Production of Few-layer Graphene from Liquid-phase Exfoliation of Graphite Matthew A. Diasio1 and David L. Green1,2,3 1
Department of Materials Science and Engineering, University of Virginia, 395 McCormick Road, Charlottesville, VA 22904, U.S.A.
2
Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904, U.S.A.
3
Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA 22904, U.S.A.
Abstract:
Prior research into the liquid-phase exfoliation of graphite to produce few-layer graphene has focused primarily on the surface energy matching between graphite and solvent; however, the effect of other solvent properties, such as liquid viscosity, have not been systematically explored. In principle, a higher viscosity solvent should enable the production of graphene and other graphitic nanomaterials by liquid-phase exfoliation at lower shear rates than traditionally used organic solvents of low viscosity, such as N-methyl-2-pyrrolidone (NMP). Thus, at a given shear rate, more material should be exfoliated in the higher viscosity solvent. Hence, graphite suspensions in NMP, benzyl benzoate, and propylene glycol were exfoliated at various shear rates in a rheometer. Exfoliant concentrations were measured by ultravioletvisual (UV-vis) spectroscopy and quality characterization was performed by Raman spectroscopy and scanning electron microscopy (SEM). Graphite exfoliation in the more viscous propylene glycol solvent resulted in a higher exfoliant concentration than in the less viscous NMP and benzyl benzoate solvents across all shear rates. Benzyl benzoate lowered exfoliant levels, likely due to a poor surface energy match, resulting in particle attraction and aggregation. Characterization showed that at least some of our material is few-layer graphene.
INTRODUCTION:
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Graphene has caught the attention of scientists and engineers across fields because of its many impressive properties, especially its high mechanical strength and useful electronic properties[1], [2]. The inherent high surface area and specific volume of a two-dimensional material make graphene effective at the absorption of species for removal, or combined with the sensitivity of graphene’s electronic properties to adsorbed molecules, make it a promising sensor[3], [4]. Graphene can also be used as a selective filter or impermeable barrier for liquids and/or gases depending on how it is processed, with applications ranging from water desalination to food packaging[3], [5], [6]. There is also interest in modified graphene or graphene-based composites to break down pollutants[3], [7]. Graphene can be produced in many different ways, with both bottom-
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