Constructing stable Fe-coordinated tannate acid three-dimensional network for long-lasting superhydrophilicity of TiO2

Traditionally, nano-titanium dioxide (TiO 2 ) is widely regarded as an effective hydrophilic material due to its certain amount of hydroxyl groups. However, the limited hydroxyl groups and the poor network structure of the TiO 2 surface result in suboptimal hydrophilicity and stability. In this study, a stable and long-lasting superhydrophilic Fe-coordinated tannic acid (TA) network is constructed by introducing TA and Fe 3+ to form a hydroxyl-rich 3D network on the surface of TiO 2 . The hydrophilicity test results demonstrated that the Fe-TA/TiO 2 film exhibited exceptional superhydrophilic property with a water contact angle of 1.3°, significantly lower than that of the TA/TiO 2 film (18.2°) and the TiO 2 film (65°). Importantly, it maintained long-lasting superhydrophilicity (water contact angle < 10°) for more than 16 days. The superhydrophilicity and long-term stability of the Fe-TA/TiO 2 film can be attributed to the abundance of hydroxyl groups and the stable Fe-coordinated TA 3D networks. This study presents a promising methodology for optimizing the TiO 2 surface through metal-organic coordination for enhanced long-term superhydrophilicity.