Covalent Crosslinking of Graphene Quantum Dots by McMurry Deoxygenation Coupling

Graphene quantum dots were covalently crosslinked forming ensembles of a few hundred nanometers in size by McMurry deoxygenation coupling reactions of peripheral carbonyl functional moieties catalyzed by TiCl₄ and Zn powders in refluxing THF, as evidenced by TEM, AFM, FTIR, Raman and XPS measurements. Photoluminescence measurements showed that after chemical coupling, the excitation and emission peaks blue-shifted somewhat and the emission intensity increased markedly, likely due to the removal of oxygenated species where quinone-like species are known to be effective electron acceptors and emission quenchers.