Bioactive trans-resveratrol as dispersant of graphene in water. Molecular interactions

Currently, the preparation of high-quality graphene (G) dispersions is crucial due to the increasing demand for this nanomaterial in a wide range of industries. However, given the strong 7C-7C stacking tendency between G sheets, dispersant agents such as surfactants or polymers are required to attain stable and homogenous disper-sions in liquid media. In the present work, the effectiveness of resveratrol (RV), a fluorescent bioactive compound with antioxidant activity, as a dispersing agent for G in aqueous solutions was assessed. The interaction between G and RV was investigated via absorbance, fluorescence and Raman measurements. Dispersions were prepared via bath sonication, followed by probe ultrasonication and centrifugation, though the two last stages have little effect on the dispersion quality. The addition of G causes a quenching on RV fluorescence, and its magnitude raises with increasing G concentration, being the effect stronger up to 10 mg L-1. The change in the centrifugation speed and time have hardly influence on the RV fluorescence in the presence of G. The RV content remaining in the bulk solution after G dispersion, measured via UV-Vis absorption, decreases linearly with increasing G concentration. RV can effectively disperse all the G present in the sample up to 10 mg L-1; at higher concen-trations, the dispersing ability slightly decreases, and the G content is distributed between the bulk solution and the centrifuged residue. Besides, the fluorescence of RV dispersed in G is much higher in methanol than in an aqueous medium. TEM analysis confirms the good exfoliation of G upon ultrasonication in RV solutions and indicates that the layer thickness depends on the G/RV ratio. The results of this study could open new per-spectives for using natural products like resveratrol as biocompatible and efficient dispersing agents of G to be used in numerous applications, especially in biomedicine.