Supramolecular Structures Formed in Water by Graphene Oxide and Nonionic PEGylated Porphyrin: Interaction Mechanisms and Fluorescence Quenching Effects

Supramolecular nanostructures are obtained in aqueous solutions by noncovalent binding between graphene oxide (GO) sheets and uncharged porphyrin derivatives. The formation of the complexes is proved by studying the ground- and excited-state properties with the use of absorption, steady-state, and time-resolved fluorescence measurements. Despite the lack of charged groups in porphyrin, the complexes are stable and their binding is effective and occurs via two distinct interaction mechanisms. The results indicate that a fast deactivation process of emission is triggered, which is mainly static (and likely due to electron donor/acceptor action), even if small contribution of collisional (dynamic) quenching is present and depends on the GO sites that remained available after the complex formation. The obtained supramolecular structure also displays interesting prospects as the “turn-on” fluorescence sensor of cationic pollutants.