Charge Carrier Dynamics and pH Effect on Optical Properties of Anionic and Cationic Porphyrin–Graphene Oxide Composites

Abstract

Composites of graphene oxide (GO) functionalized with Sn(V) tetrakis (4-pyridyl)porphyrin (SnTPyP2+) and meso-tetrakis(4-phenylsulfonic acid)porphyrin (H4TPPS 4 2− ) were prepared at different pH values.Successful synthesis of water-soluble stable suspension of GO–SnTPyP2+ and GO–H4TPPS 4 2− was confirmed using various spectroscopic techniques, including scanning electronic microscopy (SEM), Raman spectroscopy, and ultraviolet–visible (UV–Vis) absorption. Variation of the pH was found to strongly influence the optical properties of the GO–SnTPyP2+ and GO–H4TPPS 4 2− composites, as demonstrated by the UV–Vis absorption results. Steady-state photoluminescence (PL) and time-resolved PL (TRPL) results for both composites showed PL quenching and decrease in the exciton mean lifetime, suggesting strong excited-state interactions between the different components. Moreover, charge carrier dynamics study revealed that insertion of GO into both porphyrin derivatives led to faster mean lifetime for excitons with a slight advantage in the case of the cationic porphyrin–GO composite, making it a better choice for charge separation applications thanks to the higher efficiency of charge/energy transfer interactions.