Fig. 4: Schematic illustration of WPU–GOLM coatings.

a Diagram of preparation for WPU–GOLM coating with flat-oriented GO through the roll-coating method. b and c FTIR of GO, WPU, and WPU–GO materials. d The cross-section of the prepared WPU, WPU–GOLM, and WPU–GORM coatings (from top to bottom).