Development of photocatalyst based on graphene oxide

Abstract

In recent years, graphene oxide (GO) has emerged to be a promising material for photocatalytic applications. Typically, its low photocatalytic activity can be improved by modification with visible light-absorbing molecules. In this work, we aim to develop an efficient photocatalyst based on GO by noncovalent fabrication with a hydrophobic photosensitizer, 2,7,12,17-tetrapropylporphycene (H₂Pc). First, GO was prepared by the modified Hummers’ method. H₂Pc was also successfully synthesized in 7 steps with an overall yield of 3%. Then, the H₂Pc-functionalized GO composite (GO/H₂Pc) was prepared by a simple self-assembly process. The resulting composite was found to be stable in aqueous solution for at least 7 days. Furthermore, interaction between GO and H₂Pc was investigated by UV-vis and fluorescence spectroscopy. Absorption bands of H₂Pc in GO/H2Pc were considerably broadened and red-shifted as compared to those of free H₂Pc. The spectral changes are likely resulted from the dye aggregation on the GO solid substrate through π-π stacking and hydrophobic interaction. Fluorescence quenching of H₂Pc by GO was also observed, presumably via photoinduced electron transfer (PET) process. This data suggests that H₂Pc is competent to transfer photoexcited electrons to the conduction bands of GO, which in turn could provide an efficient photocatalytic activity for the system. In addition, synthesis of GO/dye composites and spectroscopic studies were carried out with porphyrin derivatives for comparison purposes.