Photochemical & Photobiological Sciences PAPER Cite this: Photochem. Photobiol. Sci., 2019, 18, 2071 Received 21st February 2019, Accepted 20th June 2019 DOI: 10.1039/c9pp00088g rsc.li/pps Self-assembly of porphyrin on graphene oxide in aqueous medium: fabrication, characterization, and photocatalytic studies† Nagi El-Shafai, a,b Mohamed E. El-Khouly, * c,d Maged El-Kemary, b Mohamed S. Ramadan a and Mamdouh S. Masoud a We herein report the supramolecular self-assembly of a water soluble porphyrin, namely, 5,10,15,20-tetrakis (1-methyl-4-pyridinio)porphyrin-tetra( p-toluenesulfonate) (TMPyP), on the surface of graphene oxide (GO). The fabricated GO nanosheet and GO@TMPyP hybrid material composite have been characterized by using various spectroscopic and analytical techniques, e.g., scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spec- troscopy. The steady state absorption measurements of the GO@TMPyP self-assembly showed a signifi- cant red shift (∼20 nm) compared to those of the control TMPyP in water. The steady state fluorescence measurements showed a significant fluorescence quenching of the singlet excited state of TMPyP in the presence of GO. These findings suggest the electron transfer reaction from TMPyP to GO. The time resolved fluorescence measurements showed a considerable decrease in the lifetime of the singlet state of TMPyP in the presence of GO, from which the rate and efficiency of the electron transfers from TMPyP to GO were determined to be 1.93 × 10 9 s -1 and 91%, respectively. The transient absorption measure- ments showed a considerable quenching of the triplet excited state of TMPyP in the self-assembly. All these findings confirm the occurrence of efficient electronic interactions between TMPyP and GO in both the ground and excited states. In addition, the fabricated GO@TMPyP showed high photocatalytic activity for the degradation of methylene blue (MB) and methyl orange (MO) mixed dye pollutants in water under visible light irradiation. Introduction The use of supramolecular assemblies is an attractive and fruitful strategy to develop photofunctional materials and supramolecular electronics. 1,2 In recent years, supramolecular self-assembly structures have made considerable advances in the areas of solar energy conversion, catalysis, energy transfer, and electron transfer reactions. 3–6 Unlike the covalently linked systems, 7 the noncovalently assembled structures have advan- tages of the simplicity of construction and the fast interchange of components within the systems that avoid the lengthy synthetic routes that are sometimes required for covalent systems. 2–6,8 Among the photoactive species used in constructing self- assembly supramolecular complexes, porphyrin derivatives are widely used as photoactive building blocks for their unique structures. 3–6 In the case of porphyrin-based supramolecular complexes, porphyrins are noncovalently linked with other species using various binding modes, e.g., metal–ligand coordination, 9–11 hydrogen bonds, 12,13 anion binding, 14–20 electrostatic interactions and π–π stacking, 21 anion binding crown ether-ammonium cation binding, 22–25 etc. In the literature, several supramolecular systems of por- phyrin derivatives with carbon nanostructures (in particular fullerenes and carbon nanotubes) have been extensively exam- ined. Graphene – which is a single-layer planar sheet of sp 2 - bonded carbon atoms densely packed in a honeycomb crystal lattice – attracted much attention in recent years for its unique properties, e.g., hydrophobicity, high mechanical strength, chemical resistance, and large surface area. 26–35 Compared to the low solubility of graphene in aqueous medium, 36,37 gra- † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c9pp00088g a Department of Chemistry, Faculty of Science, Alexandria University, Egypt b Institute of Nanoscience and Nanotechnology, Kafrelsheikh University, Egypt c Department of Chemistry, Faculty of Science, Kafrelsheikh University, Egypt d Institute of Basic and Applied Sciences, Egypt-Japan Institute of Science and Technology, Alexandria, Egypt. E-mail: mohamed.elkhouly@ejust.edu.eg This journal is © The Royal Society of Chemistry and Owner Societies 2019 Photochem. Photobiol. Sci. , 2019, 18, 2071–2079 | 2071