Functionalization of graphene via 1,3-dipolar cycloaddition.

Few-layer graphenes (FLG) produced by dispersion and exfoliation of graphite in N-methylpyrrolidone were successfully functionalized using the 1,3-dipolar cycloaddition of azomethine ylides. The amino functional groups attached to graphene sheets were quantified by the Kaiser test. These amino groups selectively bind to gold nanorods, which were introduced as contrast markers for the identification of the graphene reactive sites. The interaction between gold nanorods and functionalized graphene was followed by UV-vis spectroscopy. The presence of the organic groups was confirmed by X-ray photoelectron spectroscopy and thermogravimetric analysis. The sheets were characterized by transmission electron microscopy, demonstrating the presence of gold nanorods distributed uniformly all over the graphene surface. This observation indicates that reaction has taken place not just at the edges but also at the internal C horizontal lineC bonds of graphene. Our results identify exfoliated graphene as a considerably more reactive structure than graphite and hence open the possibility to control the functionalization for use as a scaffold in the construction of organized composite nanomaterials.