Byssal threads inspired ionic cross-linked narce-like graphene oxide paper with superior mechanical strength

Artificial nacre-like graphene oxide paper has sparked great excitement in the scientific community for its unique properties. The preparation of a bioinspired high-strength nanocomposite paper via a simple vacuum-assisted assembly technique from graphene oxide (GO), tannic acid (TA) and Fe3+ ions is reported in this article. The fabricated papers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and dynamic mechanical analysis (DMA). We show that Fe3+ ions only induce limited improvement in the mechanical properties of the graphene oxide paper, while the efficient cross-linking of neighboring sheets by Fe3+–TA complex network can significantly improve the fracture strength and Young's modulus of graphene oxide paper by 150% and 521%, respectively, with an optimal content of 5.7 wt% Fe3+. With general surface binding affinity, TA molecules can be adsorbed to GO sheets and provide binding sites for Fe3+. The Fe3+–TA coordinated compound serves as the "mortar" to stick the GO "bricks" together. The mechanical properties of our paper can be simply varied by controlling the cross-linking condition. The obtained nacre-like ultrastrong GO papers could find potential in energy and sustainability applications.