Synthesis and chemical modifications of in-situ grown anatase TiO ₂ microspheres with isotropically exposed {0 0 1} facets for superhydrophobic and self-cleaning properties

Excellent and robust hydrophobic materials generally benefit from specifically exposed surfaces i.e. always the low-energy surfaces, and well-defined micro/nano-structures that are achieved through advanced facilities and complicated process with a high cost. We hereof demonstrate that the superhydrophobicity and further self-cleaning properties are also attainable based on high-energy crystalline facets by an appropriate chemical modification. Specifically, anatase TiO ₂ microspheres were large-scale synthesized to exhibit isotropically exposed high-energy {0 0 1} facets through optimizing the HF/H ₂ O ₂ /H ₂ O ratio during hydrothermal processes. The formation of the microspheres was uncovered to be an in-situ "growth-cum-assembly" grown mechanism. Such high-energy {0 0 1} facets facilitate the strong coupling between the resultant TiO ₂ microspheres and the modifier (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) because the {0 0 1} facets offer abundant active sites for chemical bonding, showing great merits for superhydrophobicity (with water contact angle of 154 ± 2°, 6 μl droplets), and further stably surface self-cleaning i.e. easily removing surface contamination (e.g. Al ₂ O ₃ powders). This integrated strategy represents a milestone in design and fabrication of delicate composites with high-energy surfaces for specific functions and properties.