Acid–Base Chemistry of Porphyrin/Graphene Oxide Complex: Role of Electrostatic Interaction

The acid–base chemistry of cationic 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridinio)porphyrin (TMPyP) and graphene oxide (GO) complex was studied in aqueous solution using absorption and fluorescence spectroscopy. By varying the pH from 0 to 13, we controlled the electrostatic properties of TMPyP and/or GO. The neutrality on GO or negative charge on TMPyP induced the dissociation of the TMPyP/GO complex, indicating that the electrostatic attractive force is indispensable for both forming and preserving the complex. Furthermore, our results suggest that the molecular flattening of the TMPyP in the TMPyP/GO complex is mainly caused by the π–π interaction.