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Séminaire George BEPETE - Mardi 23 octobre à 10h

par Christelle FLOUTIER -

Hydroxide ions stabilised single layer graphene in water and its application in fabrication of bulk Graphene/MoS2 heterostructure films and membranes
 
George BEPETE
 
Department of Chemistry and Centre for 2-Dimensional and layered Materials
The Pennsylvania State University, University Park

 
Abstract :

By taking advantage of its easily accessible electronic states, graphite may be electronically reduced to give negatively charged graphite intercalation compounds.[1] The negatively charged graphite intercalation compounds are spontaneously soluble and can be readily exfoliated down to single layer graphene in aprotic organic solvents due to the favourable entropic contribution of dissociating counter ions, yielding graphenide (negatively charged graphene) solutions.[2] The resulting graphenide solutions are prone to re-aggregation after air exposure and must be handled in a dry, oxygen-free environment. Here we show that homogeneous stable dispersions of single layer graphene in water with no surfactant (Eau de graphene) can be obtained by mixing graphenide solutions with previously degassed water and evaporating the organic solvent.[3,4] In situ Raman spectroscopy of these aqueous dispersions, transmission electron and atomic force microscopies on deposits confirm the single-layer character.[5] Following the same, individualized SWCNT can be stabilized in water without surfactant as Eau de nanotubes.[6] in water By mixing appropriate amounts of Eau de graphene and other dispersions of 2D materials like monolayer MoS2 in water, large area, thin and thick Graphene/MoS2 heterostructure films and membranes can be fabricated in a controllable way.

 
1. Clancy, A. J. et al. Charged Carbon Nanomaterials : Redox Chemistries of Fullerenes, Carbon Nanotubes, and Graphenes. Chem. Rev. 118, 7363–7408 (2018).
2. Pénicaud, A. & Drummond, C. Deconstructing graphite : Graphenide solutions. Acc. Chem. Res. 46, 129–137 (2013).
3. Bepete, G. et al. Surfactant-free single-layer graphene in water. Nat. Chem. 9, (2017).
4. Bepete, G. et al. ”Eau de graphene” from a KC8 graphite intercalation compound prepared by a simple mixing of graphite and molten potassium. Phys. Status Solidi - Rapid Res. Lett. 10, (2016).
5. Bepete, G., Pénicaud, A., Drummond, C. & Anglaret, E. Raman Signatures of Single Layer Graphene Dispersed in Degassed Water, “‘Eau de Graphene”’. J. Phys. Chem. C 120, 28204–28214 (2016).
6. Bepete, G. et al. Hydroxide Ions Stabilize Open Carbon Nanotubes in Degassed Water. ACS Nano, 12, 8606−8615 (2018).
 
Biography :

George Bepete completed his Ph.D. in Physical Chemistry at University of the Witwatersrand, Johannesburg in South Africa (2014). His thesis focused on the control of nitrogen and boron incorporation during CVD growth of nitrogen and boron doped carbon nanotubes and graphene materials. From there he joined the National Centre for Scientific Research, CNRS, in Bordeaux France, as a Postdoctoral Fellow, where he developed methods to produce surfactant-free dispersions of monolayer graphene and individualized SWNTs in water. In 2017 he received the French Carbon Society Young Researcher Award recognising significant contributions to carbon science for his work at CNRS on surfactant-free dispersions of single-layer graphene in water. Currently at Penn State, he is an Eberly Research Fellow, working on structure controllable synthesis of 3D assemblies made from unbundled SWNTs and monolayer graphene sheets including formation of bulk 2D-material layered heterostructures for application in energy storage and optoelectronics.

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