On the Way to Graphane-Pronounced Fluorescence of Polyhydrogenated Graphene

摘要

Although graphene and its unprecedented physical properties were discovered some time ago, first concepts on the chemical functionalization of the unreactive perfect graphene basal planes have been developed only recently. Increasing the solubility of graphene and combining its properties with those of other compound classes is of major interest. Another objective is the exploration of its intrinsic chemical reactivity and the synthesis of functional derivatives. In this regard, graphane, a fully hydrogenated graphene scaffold, represents a fundamental synthetic target. Theoretical studies on graphane were published in 2007 by Sofo et al. They demonstrated that the two energetically most favorable types of graphane consist of fused cyclohexane rings with either boat or chair configurations (Figure 1). The more stable chair configuration avoids CH staggering completely. Graphane is predicted to be an insulator with a band gap of 3.5 eV for the chair and 3.7 eV for the boat configuration. In computational studies on plausible hydrogenation mechanisms it was suggested that the deformation induced by the hydrogen addition to the sp~2-hybridized lattice atoms leads to increased reactivity in close proximity to these new C_(sp~3)H centers, hence favoring an "island-type" hydrogenation. In contrast to fullerenes and carbon nanotubes, addition reactions to graphene can take place at both sides of the carbon network. This can lead to strain-free configurations, which also explains the unexpected high reactivity of graphene we observed recently in arylation and alkylation reactions.