Design of Organic-Free Superhydrophobic TiO₂ with Ultraviolet Stability or Ultraviolet-Induced Switchable Wettability

Abstract

Superhydrophobic TiO 2 with great application potential is mainly obtained by surface modification with low surface energy organics, which is easily degraded under sunlight irradiation, which results in the loss of superhydrophobic properties. Herein, we developed a room-temperature pulsed chemical vapor deposition (pulsed CVD) method to develop amorphous TiO 2 -deposited TiO 2 nanoparticles. The ultraviolet stability/ultraviolet-induced reversible wettability switch had been simultaneously realized by different and controllable deposition cycles of amorphous TiO 2 . The superhydrophobic properties of the organic-free TiO 2 were determined by the micrometer− nanometer−sub-nanometer multiscale structure, the multiscale pore structure, and the large Young's contact angle resulting from carboxylic acid adsorption. Also, we found that the adsorption rate and adsorption stability of oxygen and water at the surface oxygen vacancies were the key to facilitate the reversible switching between superhydrophilic and superhydrophobic states, which was well demonstrated by experimental characterization and theoretical simulation. In addition, we also found that the resistance of dense amorphous TiO 2 films on the TiO 2 surface to the migration of photogenerated electrons and holes was the key to maintain the stable superhydrophobic properties of superhydrophobic TiO 2 under ultraviolet illumination. The powders were strongly ground and the coating surface was rubbed on the surface of the sandpaper, which still maintained superhydrophobic properties, providing favorable conditions for the application of superhydrophobic TiO 2 . This work modulates the ultraviolet stability and dark/ultraviolet-induced switchable superhydrophobicity/superhydrophilicity of coated TiO 2 by simply adjusting the number of deposition times in a pulsed CVD process for the first time, thus contributing to the development of organic-free superhydrophobic TiO 2 .

Synthesis and Applications of TiO2‐based Nanostructures as Photocatalytic Materials

“…The degradation rate constants of PMMA and PC decreased from 0.36 h À 1 to 0.018 h À 1 and from 0.23 h À 1 to 0.029 h À 1 , respectively, under single UV irradiation for 5 h. It indicates that the TiO 2 coatings prepared by this method can prevent the polymer degradation of PMMA and PC and improve their stability under UV irradiation. Yu et al [85] uses the CVD (pulsed CVD) method to coat amorphous TiO 2 nanoparticles or thin films on the surface of TiO 2 nano-particles at room temperature. It is found that the adsorption stability and the rate of oxygen and the water on surface oxygen vacancies are the keys of facilitating the reversible switching between superhydrophilic and superhydrophobic states, as shown in Figure 7.…”

“…83 Copyright 2022, Elsevier. [85] Reproduced with permission Ref. 85 Copyright 2022, American Chemical Society.…”

“…The degradation rate constants of PMMA and PC decreased from 0.36 h −1 to 0.018 h −1 and from 0.23 h −1 to 0.029 h −1 , respectively, under single UV irradiation for 5 h. It indicates that the TiO 2 coatings prepared by this method can prevent the polymer degradation of PMMA and PC and improve their stability under UV irradiation. Yu et al [85] . uses the CVD (pulsed CVD) method to coat amorphous TiO 2 nanoparticles or thin films on the surface of TiO 2 nanoparticles at room temperature.…”

“…Adsorption activation energy of H 2 O and O 2 on TiO 2 oxygen vacancies and optimized structures and adsorption energies of H 2 O and O 2 molecules adsorbed on TiO 2 oxygen vacancies [85]. Reproduced with permission Ref 85. Copyright 2022, American Chemical Society.…”

Recent Advances in Superhydrophobic Surfaces and Applications on Wood

“…The CVD method [ 36 ] is a modification method to achieve a modification effect by reacting certain substances in the solution with the modified material to form a new substance through a gas-phase reaction to build a roughness or a nano-scale thin film material on the surface of the wood material. The CVD method is a low-cost, simple, and effective method for the preparation of hierarchical micro- and nano-rough structures.…”