Modification Of Pristine Graphene Via Bergman Cyclization

Graphene, a two-dimensional material nanocarbon comprising layers of carbon atoms arranged in six-membered rings, is distinctly different from carbon nanotubes (CNTs) and fullerenes, and exhibits unique properties which have fascinated the scientific community. It has a large theoretical specific surface area, high Young’s modulus, intrinsic strength, high intrinsic mobility and thermal conductivity. Its optical transmittance and good electrical conductivity draw attention for many applications such as for transparent conductive electrodes, and many other potential applications. In the past years most research focused on the synthesis of graphene, preparation and applications of graphene nanocomposites, and functionalization of graphene oxide. However, few attentions were paid on the functionalization of pristine graphene. It was found that pristine graphene could only react with few mild reactants, such as the nitrene radicals produced by azidotrimethylsilane, azomethine ylides and aryne.In our research, Diradicals generated by enediyne’s Bergman cyclization (BC) were successfully grafted onto pristine graphene, which was prepared by direct exfoliation of natural graphite flakes in solvents. The presence of covalent linkages between graphene and BC products of enediyne compounds was confirmed by thermogravic analysis and atomic force micrography (AFM), and further supported by a control experiment. After modification oligomers were detected on graphene surface through AFM. It indicates that the diradicals can still initiate radical polymerization after grafted onto graphene. The modified graphene samples were also characterized by Raman and Fourier transform infrared spectroscopy. The modified graphene could be dispersed in organic solvents (such as tetrahydrofuran, 1-methyl-2-pyrrolidinone, N,N-dimethylformamide and o-dichlorobenzene), which were stable for weeks.