%0 Journal Article
%T Noncovalent Functionalization of Graphene in Suspension
%A Wenzhi Yang
%A Sultan Akhtar
%A Klaus Leifer
%A Helena Grennberg
%J ISRN Organic Chemistry
%D 2013
%R 10.1155/2013/656185
%X Suspensions of graphene, prepared from graphite foil by sonochemical exfoliation, have been treated with new nonpolar pyrenebutyric amides. The assemblies, in suspension and after deposition on solid supports, were characterized by NMR, absorption, and fluorescence spectroscopy and by transmission electron microscopy, where the well-defined shape and size of an appended [60]fulleropyrrolidine unit facilitates TEM detection of the nonstationary molecules. The accumulated evidence, also including direct comparisons of carbon nanotubes treated with pyrene amides under the same conditions, proves the successful noncovalent functionalization of graphene suspended in non-polar solvent with non-polar pyrene derivatives. 1. Introduction Graphene, the two-dimensional parent structural unit of three-dimensional graphite and one-dimensional carbon nanotubes [1, 2], has been treated theoretically since decades, with suggestions of numerous applications that would benefit from the predicted unusual electron transport properties of a defect-free extended delocalized aromatic carbon system [3]. When the material was shown to exist, a new expansive area opened, involving also experimentalists since reproducible production of high-quality graphene and controlled modification thereof are keys to any of the suggested applications [4]. The strategies include molecular synthesis [5] but the main ones are still micromechanical exfoliation from HOPG, [1¨C3] epitaxial growth on SiC surfaces [6], chemical vapour deposition on metals [7, 8], and chemical exfoliation, either via graphitic and graphene oxides [9, 10] or in direct sonochemical processes not involving any oxidative, acidic or reductive reagents [11, 12]. The latter gives, in a controllable and scalable fashion, dispersions/suspensions of graphene flakes well suited for further chemical manipulation, where protocols developed for carbon nanotube functionalizations have been obvious starting points [13¨C15]. Since covalent functionalization of the largely planar unsaturated carbon system introduces sp3 sites and by this permanent change of the electronic properties, such routes would be interesting mainly for permanent doping purposes [16, 17]. In contrast, non covalent routes would inflict only minor and temporary changes to the graphene -system and, as has been demonstrated for carbon nanotubes [18, 19], render possible the introduction of almost any functional unit in a potentially reversible fashion. Such strategies have been reported for graphene oxide [20, 21], for solid films of reduced graphene oxide [22] as
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2013/656185/