Robust ZnO/HNTs-based superhydrophobic cotton fabrics with UV shielding, self-cleaning, photocatalysis, and oil/water separation

In this work, robust superhydrophobic cotton fabrics with ultraviolet (UV) shielding, self-cleaning, photocatalysis, and oil/water separation were successfully prepared based on micro/nano hierarchical ZnO/HNTs (halloysite nanotubes) hybrid particles and silicone elastomer polydimethylsiloxane (PDMS). ZnO/HNTs hybrid particles were prepared by in-situ growth of ZnO nanoparticles on the surface of halloysite nanotubes (HNTs). ZnO/HNTs hybrid particles and PDMS were used to successively coat cotton fabrics by dip-coating approach. The coated cotton fabrics displayed excellent superhydrophobicity with a water contact angle (WCA) of 162.5 ± 1.0° owing to the roughness provided by micro/nano hierarchical ZnO/HNTs hybrid particles and low surface energy achieved by PDMS. After being exposed to the UV lamp for 5 h, about 90.8% of the methylene blue was degraded, indicating that the coated cotton fabrics had excellent photocatalytic activity. The as-prepared cotton fabrics also displayed outstanding self-cleaning and antifouling properties. In addition, due to both superhydrophobic and superoleophilic characteristics, the as-prepared cotton fabrics could be used to separate several oil/water mixtures and showed good recoverability. The superhydrophobic cotton fabrics also exhibited excellent UV shielding performance with a large ultraviolet protection factor (UPF) of 1643.28 due to strong ultraviolet-absorption, light scattering and frequent light reflection of ZnO nanoparticles from ZnO/HNTs composites coated on cotton fabrics. Importantly, the as-prepared cotton fabrics retained superhydrophobic performance after 2000 cycles rubbing, 90 h UV illumination, and immersing in acidic and alkali solutions with different pH values ranging from 1 to 14 for 1 h. These characteristics made multifunctional cotton fabrics a satisfactory candidate in various promising fields.