Effects of molecular structure on the grafting of diaminobenzene sulfonic acid onto graphene oxide

Abstract

Molecular grafting is an effective technique for introducing sulfo groups into materials such as graphene oxide (GO). Existing studies on the grafting molecules with sulfo groups onto GO have been empirical, and the analytical elucidation of this process remains insufficient. In this study, we experimentally and numerically investigated the adsorption and reduction reactions between GO and two types of diaminobenzene sulfonic acids (DBSAs), namely 2,4- and 2,5-DBSAs, that possess an equal number of functional groups but different coordination numbers. Composite films of GO and DBSA were prepared from a GO/DBSA solution using centrifugation and filtration. Initially, X-ray diffractometry was employed to confirm the intercalation of DBSAs between GO layers in GO/DBSA composite films. Subsequently, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were performed; the results indicated that the bonding in GO to the oxygen functional group was replaced by the bonding to the amino group of DBSA; moreover, 2,5-DBSA was more reactive towards GO than 2,4-DBSA. To further investigate the reactivity differences, density functional theory calculations were performed. The decrease in enthalpy after the reaction of 2,5-DBSA was found to be higher than that of 2,4-DBSA, suggesting higher reactivity for 2,5-DBSA.