Propagative Exfoliation of High Quality Graphene

Abstract

High quality graphene materials that readily disperse in water or organic solvents are needed to achieve some of the most ambitious applications. However, current synthetic approaches are typically limited by irreversible structural damages, little solubility, or low scalability. Here, we describe a fundamental study of graphene chemistry and covalent functionalization patterns on sp² carbon lattices, from which a facile, scalable synthesis of high quality graphene sheets was developed. Graphite materials were efficiently exfoliated by reductive, propagative alkylation. The exfoliated, propagatively alkylated graphene sheets (PAGenes) not only exhibited high solubility in common solvents such as chloroform, water, and <i>N</i>-methyl-pyrrolidone, but also showed electrical conductivity as high as 4.1 × 10³ S/m, which is 5 orders of magnitude greater than those of graphene oxides. Bright blue photoluminescence, unattainable in graphene, was also observed. We attribute the rise of blue photoluminescence in PAGenes to small on-graphene sp² domains created by the propagative covalent chemistry, which may expand from graphene edges or existing defect sites leaving sp²-hybridized patches interlaced with sp³-hybridized regions. The intact sp² domains enable effective electrical percolation among different graphene layers affording the observed high electrical conductivity in PAGene films