The adsorption of tetracycline, ciprofloxacin on reduced graphene oxide surfaces: Role of intermolecular interaction

In this study, the adsorptions of tetracycline (TC) and ciprofloxacin (CIP) molecules on different surfaces of reduced graphene oxide (rGO) are investigated by using quantum chemical calculations. Our results reveal stable configurations for both the molecules, rGO surfaces, and their complexes, highlighting the favorable arrangements of TC and CP on the rGO surfaces, which facilitates intermolecular interactions at functional group sites such as -O-, -OH, >CO, and -COOH. While the physical adsorption is observed for TC and CIP molecules on the rGO surface, the introduction of Ca2+ cation promotes chemical adsorption of these molecules on rGO. It is noticeable that the adsorption of TC and CIP on Ca2+-supported rGO is stronger of five times than on rGO surfaces. Importantly, our findings demonstrate that the adsorption affinity of TC is higher than that of CIP on both the pristine rGO and Ca2+-supported surfaces. The existence and role of surface interactions are further elucidated through AIM and NBO analyses, revealing an essential role of O/N/CH center dot center dot center dot O hydrogen bonds in stabilizing configurations of TC and CIP on the rGO surface models. Notably, the presence of Ca center dot center dot center dot O attractive electrostatic interaction enhances the stability of the adsorption configuration on the Ca2+-supported rGO surface. These insights emphasize the potential usage of rGO-based materials in the adsorption of antibiotic molecules for various environmental related applications.