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.