Preparation and aggregate state regulation of co-assembly graphene oxide-porphyrin composite Langmuir films via surface-modified graphene oxide sheets

Constructing graphene oxide (GO)-based 2D nanomaterials via facile and appropriate methods have aroused much attention due to their potential applications in many fields. Herein, by Langmuir-Blodgett (LB) technique, we have successfully fabricated GO-based films composited with porphyrin molecules. By the reaction of diazotization and Fischer osazone, different surface states of GO sheets with sulfonate groups were obtained. The amphiphilic GO and surface modified GO sheets could spontaneously form composite films at the air/water interface with porphyrin molecules (TMPyP) by electrostatic interactions and p-p stacking. Since the sheets can perfectly float on the interface, the TMPyP molecules were adsorbed on the floating-layers and self-assembled into highly ordered J-aggregate structures. The morphological characterization results showed the composite films with smooth and dense surface. Due to the different surface state of the nanosheets, the aggregate states of porphyrin molecules were different which could be demonstrated in the UV-vis spectra. The results indicated that the induction of sulfonate groups and the types of oxygen-containing groups have played important roles for regulating the aggregate state of porphyrin molecules.