Laser patterning and induced reduction of graphene oxide functionalized silk fibroin

Abstract

This paper presents a one-step method for patterning and reducing graphene oxide functionalized in silk fibroin using femtosecond laser induced forward transfer (LIFT). Such approach renders fibroin, a natural biopolymer with excellent biocompatibility, chemical stability, and mechanical properties, improved electrical conductivity in a controlled and localized way. Composite films based on silk fibroin and graphene oxide/reduced graphene oxide were fabricated by spin coating at room temperature. The films composition was characterized by micro-Raman spectroscopy demonstrating the presence of graphene oxide in the silk fibroin matrix. The influence of pulse energy on the fs laser transfer process was investigated, yielding a threshold energy of 24.0 nJ. Additionally, the laser-induced reduction of graphene oxide attained by LIFT was determined by Raman spectroscopy and further confirmed by an increase in the electrical conductivity. The approach presented here proved to be an efficient route to simultaneously produce micrometric patterns of graphene oxide/silk fibroin composite (with line widths on the order of 1 mu m), and reduction of graphene oxide, opening new opportunities for the development of green composites for electronics devices, including for instance microfluidic sensors, capacitors and LEDs.