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Density Gradient Ultracentrifugation of Graphene. Alexander Green and Mark Hersam National Science Foundation-Nanoelectronics Research Initiative Grant DMR-0520513.
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Density Gradient Ultracentrifugation of Graphene Alexander Green and Mark Hersam National Science Foundation-Nanoelectronics Research Initiative Grant DMR-0520513 The NSF-NRI supplement to IRG 4 of the Northwestern University MRSEC is developing unique combinations of materials, prototype devices, and experimental tools to study excitons in carbon-based nanomaterials. The program aims to explore, understand, and optimize the electrial generation of excitons, their stability, transport, and exciton-exciton interactions in monodisperse carbon nanotubes and graphene. One major thrust requires the isolation of monodisperse graphene flakes. This is accomplished in solution using density gradient ultracentrifugation. Stable graphene dispersions are produced using the bile salt sodium cholate, which promotes graphite exfoliation and results in graphene-surfactant complexes having buoyant densities that vary with graphene thickness. Graphene dispersions produced using density differentiation offer superior performance in transparent conductors to those produced using conventional sedimentation-based centrifugation techniques. Nano Letters, 9, 4931 (2009).