Sodide and Organic Halides Effect Covalent Functionalization of Single-Layer and Bilayer Graphene

The covalent functionalization of single and bilayer graphene on SiO₂ (300 nm)/Si was effected through sequential treatment with the alkalide reductant [K(15-crown-5)₂]Na and electrophilic aryl or alkyl halides, of which the iodides proved to be the most reactive. The condensation reactions proceeded at room temperature and afforded the corresponding aryl- or alkyl-appended graphenes. For each sample, Raman and X-ray photoelectron spectroscopies were used to evaluate the degrees and uniformities of functionalization. Statistical analyses of the Raman data revealed that the introduction of the organic moieties was accompanied by sp³-rehybridization of the basal plane atoms. When bilayers consisting of ¹³C and ¹²C layers were treated, both the top and bottom sheets were decorated with organic groups. The reaction was followed using Raman spectroscopy, and the mechanism was studied by theoretical calculations. Indicative of its structure and reactivity, 4-pyridyl-decorated single-layer graphene was readily benzylated and appears to be an ideal platform to develop functional materials.