Hydrophilic yet electrically conductive graphene films by local ambient controlled infrared laser irradiation

The graphene films that have been used widely in various applications possess a critical trade-off between the surface and bulk properties. The surface of graphene films should have a hydrophilic nature for imparting a chemical/physical compatibility at the heterogenous interfaces, but it indispensably gives rise to a generation of oxygen-involved defects in overall graphene films and, in turn, deteriorates the bulk properties of hydrophilic graphene films. In this study, we suggest a facile strategy for resolving such a critical issue by generating only the surficial defects that reside within the top surface of the graphene film rather than an overall bulk one. We achieved this by using mid-infrared laser irradiation, uniquely coupled with a sheath gas stream of either dry air or inert argon. Unlike conventional methods performed in open air or within a controlled gas chamber, the high-pressure gas stream-assisted laser irradiation technique enables the formation of hydrophilic graphene films without compromising electrical conductivity or causing unwanted volumetric defects. We demonstrate the practical feasibility of spatially mapping hydrophilic yet conductive graphene films through digital manufacturing. Additionally, we highlight the importance of this new type of graphene film by fabricating all-solid-state micro-supercapacitors, confirming a 3.9-fold improvement in performance compared to devices produced using traditional methods.