Optical spectroscopic studies of aqueous suspensions and composites of SWNT

We discuss the intrinsic optical spectroscopy (UV-vis-NIR absorption, Raman and photoluminescence)signatures of single layer graphene (SLG) and single wall carbon nanotubes (SWNT) dispersed indegassed water without additives, so called "eau de graphene" (EdN) [1-3] and ‘‘eau de nanotubes”(EdN) [4].The most characteristic signature of SLG in EdG is a narrow and symmetric 2D band with a widthdepending on processing conditions [2,3]. The position of the G and 2D bands indicate moderate biaxialcompressive strain and weak n doping. The intensity of the D band and the width of the G band arediscussed in terms of point-defect density and flake size. We show that point defects can be easily curedby preparing thin films from EdG and annealing at 800°C.The signatures of SWNT in EdN are found to be very close to those of SWNT dispersed in aqueoussuspensions stabilized with surfactants [4]. Absorption peaks appear to be even slightly better resolvedfor EdN, suggesting sharper excitonic resonances, which is also supported by the Raman data. Thesesignatures support that SWNT are dispersed as individuals in EdN, in a similar way SLG aredispersable in EdG [1-3].[1] G. Bepete et al, Nat. Chem. 2016, DOI 10.1038/NCHEM2669[2] G. Bepete et al, J. Phys. Chem. C 2016, 120 (49), 28204–28214.[3] G. Bepte et al, Phys. Stat. Solidi 2016, 10 (12), 895-899.[4] G. Bepete et al, to be publishe