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 degrees to 143 degrees 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 degrees to 138 degrees by precursor concentration. After surface modification by fluoroalkylsilane, these ordered pore arrays demonstrate superhydrophobicity with water CAs from 152 degrees to 165 degrees, depending on the precursor concentration. Especially for the ordered porous film fabricated by high precursor concentration (1.0 M), the large water CA (165 degrees) and small sliding angle (less than 5 degrees) 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.