Sonication Exfoliation of Defect-Free Graphene in Aqueous Silk Nanofiber Solutions

Green processes to exfoliate graphene would be advantageous but is challenged by issues such as stability and dispersibility. Here, stable silk fibroin nanofibers (SFNs) with high crystallinity (β-sheet content) and high net negative charge were endowed with hydrophobic features yet excellent water dispersibility. These nanofibers were used to exfoliate graphite into graphene in aqueous solutions. A high concentration (1.92 mg mL–1) and yield (approaching 20%) were achieved for the exfoliated graphene dispersions using low initial graphite concentrations via sonication treatment. This approach was superior to most protein-assisted exfoliation processes reported to date, and the graphene obtained in the process exhibited fewer defects, good conductivity, and cell compatibility. The graphene prepared by this new process provided an option for SF-graphene composite materials and devices where defect-free graphene with improved performance through the introduction of SFNs into the preparation strategies will bring a desired revolution in graphene materials.