Dispersing graphite in water to obtain true (single-layer) graphene in bulk quantity in a liquid has been an unreachablegoal for materials scientists in the past decade. Similarly, a diagnostic tool to identify solubilized graphene in situ has beenlong awaited. Here we show that homogeneous stable dispersions of single-layer graphene (SLG) in water can be obtainedby mixing graphenide (negatively charged graphene) solutions in tetrahydrofuran with degassed water and evaporatingthe organic solvent. In situ Raman spectroscopy of these aqueous dispersions shows all the expected characteristics ofSLG. Transmission electron and atomic force microscopies on deposits confirm the single-layer character. The resultingadditive-free stable water dispersions contain 400 m2 l–1 of developed graphene surface. Films prepared from thesedispersions exhibit a conductivity of up to 32 kS m–1.

A very active branch of materials research based on allotropic carbon nanostructures has recentlyflourished, mainly due to their large potential of applications. Among the most outstanding structures aregraphene and carbon nanotubes which both possess interesting properties at the nanoscale, such as:electronic, mechanical, optical etc... When combined with various nanoparticles (NPs), their potential iseven larger. Exploiting these properties, which are mostly anisotropic, requires to transfer them to themacroscopic world through the preparation of ordered nanostructured composites materials. During theirprocessing, liquid crystal phases present an opportunity to arrange them into macroscopic assemblies ofNPs and nanocarbons with long-range ordering [1]. Nevertheless, achieving high orientational orderparameter and large monodomains remains a challenge. In this work we present some of our approaches toachieve large and well-ordered domains oflyotropic liquid crystals. For example the orderparameter of carbon-nanotubes based materialscan be finely tuned by controlling the length andentanglement of the nanotubes [2] and processesbased on shear are sufficient to easily achieve amacroscopic ordering. For graphene, it is knownthat graphene oxide (GO) flakes easily disperse inwater and spontaneously form liquid crystals athigh concentrations. However, most of their electronic functionalities are lost during the oxidationtreatments. Reduced graphene oxide (RGO) is of greater interest but chemical reduction of GO in watergenerally results in the aggregation of the flakes. We recently showed how to obtain water-based RGOliquid crystals stabilized by surfactant molecules [3]. Structural and thermodynamic characterizationsprovide indirect but statistical information on the dimensions of the graphene flakes. Combined with NPs,these graphene based liquid crystals are also useful to design novel coatings and functional materials.[1] Yuan J. et al. Nat. Commun. 6:8700 doi: 10.1038/ncomms9700 (2015).[2] Zakri, C. et al. Phil. Trans. R. Soc. A., 371, 20120499, pp 1-15 (2013)[3] Zamora-Ledezma, C. et al. J. Phys. Chem. Lett., 3 (17), pp 2425–2430 (2012)

We review the optical spectroscopy signatures of carbon nanotubes and graphene dispersed in aqueous suspensions.

Processing single-walled carbon nanotubes (SWNT) into thin films or composite nanomaterials, are key issues to take advantage of their mechanical, electrical and optical properties. In this talk, we will review our recent results on the preparation, structure and optical properties of SWNT-based inks, nanocomposites and thin films.