Hierarchical amorphous nanofibers for transparent inherently super-hydrophilic coatings

Ultra-high specific surface area, hierarchical TiO₂ nanofibers were synthesized by electrospinning and directly self-assembled into highly porous films for application as transparent super-hydrophilic coatings. The evolution of the coating key structural properties such as fiber morphology and composition was mapped from the as-prepared sol-gel up to a calcination temperature of 500 °C. Main fiber restructuring processes such as formation of amorphous Ti-O bonds, crystallization, polymer decomposition and the organic removal were correlated to the resulting optical and wetting performance. Conditions for low-temperature synthesis of hierarchical coatings made of amorphous, mesoporous TiO₂ nanofibers with very high specific surface area were determined. The wetting properties of these amorphous and crystalline TiO₂ nanofiber films were investigated with respect to the achievement of inherently super-hydrophilic surfaces not requiring UV-activation. The surface stability of these amorphous TiO₂ nanofibers was assessed against current state-of-the-art crystalline super-hydrophilic TiO₂ preserving excellent anti-fogging performance upon an extended period of time (72 h) in darkness.