Synthesis of hybrid graphene–porphyrin micro/nanofiber structures by ionic self-assembly

Abstract

Cationic mesa-tetra(4-pyridyl) porphine (TPyP)-graphene oxide (GO) hybrid structures have been synthesized by ionic self-assembly. The different aggregated structures shape were obtained through electrostatic and π–π stacking interactions, as indicated by redshift of porphyrin Soret band throughout the pH range of 1.5–9.1, fluorescence quenching, Raman spectra and Energy dispersive X-ray spectroscopy. A strong fluorescence quenching of the cationic porphyrin in the presence of graphene indicated that efficient electron or energy transfer occurred from the excited state of the cationic porphyrin to graphene. The investigation revealed a three-dimensional fiber structures formation under the acid conditions and leaf-like structures of the TPyP/GO assemblies under the alkaline conditions of the solution. The fibers morphology and cross-section was determined quantitatively by Scanning force microscopy; this revealed a diameter of the fibers up to hundreds of nanometers and the lengh up to hundreds of micrometers. The electrical properties of the fibers were investigated by spreading resistance and current–voltage characteristics measurements using Atomic Force Microscopy (AFM) with conductive cantilevers. The current–voltage characteristics fit to the Poole–Frenkel emission mechanism in the case of TPyP/GO sheets and Schottky emission dominate in the nanofibers case. This new graphene material shows a potential for energy, sensing and photonic applications.