Stable ZnO/ionic liquid hybrid materials： novel dual-responsive superhydrophobic layers to light and anions

• Published in: Science China. Chemistry 2014-07, Vol.57 (7), p.1002-1009
• Main Authors: Li, HongLiang, Xin, BingWei, Feng, Lei, Hao, JingCheng
• Format: Article
• Language: English
• Subjects: Anion exchanging; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Contact angle; Covalent bonds; Hydrophobic surfaces; Hydrophobicity; Ionic liquids; Microscopy; Nanoparticles; Photoelectrons; Self-assembled monolayers; Self-assembly; Ultraviolet radiation; Wettability; X ray photoelectron spectroscopy; X射线光电子能谱; Zinc oxide; 扫描电子显微镜; 混合材料; 离子液体; 稳定性; 纳米ZnO; 自组装单分子膜; 阴离子交换
• ISSN: 1674-7291; 1869-1870
• DOI: 10.1007/s11426-014-5090-2

Novel dual-responsive superhydrophobic hybrid materials, ZnO/SAMs （self-assembled monolayers） of ionic liquids （ILs） with different counter-anions （I^-, BF4^-, PF6^- and Tf2N^-）, were synthesized and characterized. ZnO nanoparticles were first deposited on glass surfaces to produce roughness. Next, SAMs of fluorinated-alkyl-3-（3-triethoxysilylpropyl）-4,5-dihydro-imidazoliumiodide （abb. [C8Ftespim]I） were grafted onto these surfaces via -Si-O- covalent bonds using self-assembly technique. The I- ion could be subsequently exchanged with BF4, PF6-or Tf2N- through a simple aqueous anion-exchange reaction. The ZnO/ILs hybrid layers were characterized by atomic-force microscopy （AFM）, scanning-electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. Their wettability was estimated through the measurements of static and dynamic contact angles （CAs）. Compared to corresponding films of ZnO/[CsFtespim]I with CAs 140.7° ±2.0°, films of ZnO/[CsFtespim]PF6 and ZnO/[CsFtespim]Tf2N showed CAs with 154.0° ± 2.0° and 152.0° ± 2.0°, respectively that remained for a long time. This result suggests that anion-exchange can afford superhydrophobic materials. In addition, the wettability of ZnO/[CsFtespim]X hybrid layers can be reversibly switched by altering ultraviolet （UV） irradiation and dark storage, which shows a photo-induced reversible switch of wettability. The synergistic action of ZnO nanoparticles and SAMs of ILs produced light-anion dual-responsive superhydrophobic materials with ideal stability.