One-step laser induced conversion of a gelatin-coated polyimide film into graphene: Tunable morphology, surface wettability and microsupercapacitor applications

Latest advances have witnessed the laser induction process on polyimide (PI) films for the formation of porous graphene. Herein, a fully converted graphene film was prepared by Nd:YAG laser scribing a gelatin coated PI film. It was found that the gelatin played the role of "shield" well in absorbing intense laser impact and benefit for the surface morphology modulation. Laser treatment lower than a critical fluence point of similar to 4.00 J mm(-2) contributed to a crater-like surface morphology due to the dispersed nature of Nd:YAG laser beam. By tuning laser fluence above the threshold, carbonized surface turned into continuous morphology. A fluid dynamics process accompany with outgassing occurred during the carbonization, and the surface morphology gradually varied from stretched droplets to porous strips and finally to amorphous porous structures. The morphology evolution in combination with surface chemistry are responsible for the significant wettability transition from superhydrophobic to superhydrophilic, and a Janus superhydrophobic/superhydrophilic surface wettability was achieved under a laser fluence of similar to 8.00 J mm(-2). Eventually, microsupercapacitors (MSCs) were fabricated to show the great potential of our prepared graphene in flexible electronics.