Long-range Ordered Graphitic Structure in Silk Fibers Delaminated using Dopamine and Thermal Treatment for Super-Flexible Electronic Textiles

Abstract Exfoliation has been used to obtain 2D materials with attractive properties, like graphene. The layered structure of silk and its structural transition to a pseudo-graphitic structure by heat treatment has attracted scientific interest because of its potential applications. Here we report that intercalating the silk layers with polydopamine (PDA) followed by thermal treatment delaminates the silk fibers. Cylindrical silk fibers with a diameter of 10 μm changed to graphitic ribbon-like structures with widths of approximately 65 nm. This structural transition was systematically investigated using thermally treated PDA-embedded silks at temperatures from 800 to 1450 °C. The graphitic structures start to be observed at 1000 °C, a much lower heat treatment temperature than previous studies using pure silk. Long-range ordered graphitic structures with a lattice distance of 3.4 Å formed most clearly at 1300 °C. ab-initio molecular dynamics calculations confirmed the microscopic origin of the experimental results. This method allows the fabrication of super-flexible, comparable to pure silk, and high-electrically conductive (277.3 S·cm-1) e-textiles. These thermally treated PDA-embedded silks were also functionalized with Fe2O3 and Bi2Te3 powders using the attachment ability of PDA. This work provides evidence that PDA plays a role in delaminating silk fibers and opens the potential for various applications.