Solvent-induced changes in the graphene oxide absorption spectrum. The case of dimethylsulfoxide/water mixtures

Abstract

© 2019 Elsevier B.V. In the present contribution solvation pattern of graphene oxide (GO) in dimethylsulfoxide (DMSO)/H2O mixtures was investigated by means of UV–Vis absorption spectroscopy. It was shown that with increase of the DMSO content, xDMSO, the GO's n–π* transition band, appearing at 307 nm in water, blue-shifts by 34 nm in pure DMSO. Together with an observation of an isosbestic point at 320 nm this finding indicates the changes in the GO's first solvating layer. Analysis of the n–π* transition band transfer energy shows that at xDMSO ≲ 0.55 and xDMSO ≳ 0.55 the GO's groups containing C[dbnd]O fragments are preferentially solvated by H2O and DMSO molecules, respectively. In agreement with the latter, the Wallace-Katz analysis yields two absorbing species in the whole range of xDMSO and one species in water-rich and DMSO-rich regions. Quantum chemical calculations reveals formation of H-bonds between GO's carboxyl groups and both H2O and DMSO molecules. The binding energies of H2O and DMSO molecules with the GO's model basal surfaces point out at possible substitution of water molecules in the GO's first solvation layer by DMSO molecules.