Superhydrophobicity of 2D ZnO ordered pore arrays formed by solution-dipping template method

Large-scale 2-dimensional ZnO ordered pore arrays (films) were fabricated by a solution-dipping colloidal monolayer method. The morphologies of the films are precursor-concentration-dependent. Higher concentration leads to rougher morphology. The wettability of such ordered porous films was studied. It was shown that the ordered pore structure of as-prepared samples can effectively enhance the hydrophobicity of ZnO and the water contact angle (CA) on the film surface increases from 125° to 143° with the rise of precursor concentration from 0.3 to 1.0 M, indicating concentration-controlled hydrophobicity. Meanwhile, a photoinduced reversal transition of wettability between hydrophobicity and hydrophilicity was observed on these films. The difference between hydrophobic and hydrophilic CAs can be tuned from 89° to 138° by precursor concentration. After surface modification by fluoroalkylsilane, these ordered pore arrays demonstrate superhydrophobicity with water CAs from 152° to 165°, depending on the precursor concentration. Especially for the ordered porous film fabricated by high precursor concentration (1.0 M), the large water CA (165°) and small sliding angle (less than 5°) were obtained. This work has demonstrated that if such ordered pore arrays are used for some micro- or nanodevices, they will be waterproof and even self-cleaning.