(color online) Schematic of the doctor blading method used for coating film. (a) The top of the clean substrate is covered at two edges by parallel pieces of tape. (b) The prepared composite is dropped on the part of the substrate left uncovered. (c) Composite is pushed along by a glass slide to spread the wet film uniformly. (d) Wet film is dried at 100–150 °C for 0–60 min in the open air.