Mark A. Barteau

Polyoxometalates (H₃PMo₁₂O₄₀, H₃PW₁₂O₄₀, H₄PMo₁₁VO₄₀) supported on oxygen- and alkyl-functionalized graphene sheets were investigated. Discrete molecular species were directly observed by electron microscopy at loadings below 20 wt.%. The interaction between the polyoxometalates and the graphene surface was found to significantly impact their vibrational spectra and a linear correlation between the frequency of the M-O_c-M vibration and the dispersion was evidenced by FTIR. While bulk-like electronic properties were observed for small aggregates (2–5 nm), UV–vis spectroscopy and cyclic voltammetry revealed changes in the electronic structure of isolated molecular species as a result of their interaction with graphene. Because of the ability to disperse alkyl-functionalized graphene in a variety of polar and nonpolar solvents, the materials synthesized in this work provide an opportunity to disperse polyoxometalates in media in which they would not dissolve if unsupported.

Alkyl chains were grafted onto reduced graphene oxide sheets to allow their dispersion in toluene, a common and representative nonpolar solvent. The grafting occurred on a variety of oxygen-containing functionalities already present on reduced graphene oxide, such as hydroxyl and epoxide groups. The structure and the defect density of the sheets were not significantly altered during the synthesis. When dispersed in water–toluene mixtures, phase transfer from the aqueous to the organic phase was observed upon grafting. In addition, the dry powder obtained readily disperses in common organic solvents without the assistance of any sonication treatment.