Superhydrophobic surfaces based on dandelion- like ZnO microspheres Qinmin Pan *, Yuexiang Cheng School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin , PR China Advisor ： S.C.Wang Student ： Shih-Kai Shu

Outline Introduction Experimental Procedures Results and Discussion Conclusion Future work

Introduction In the past decade, the fabrication of superhydrophobic surfaces with contact angle greater than 150 o had been attracted intensive interest because they had many potential applications in the fields such as self-cleaning, anti-corrosion, etc. It is well established that the wettability of solid materials is governed by both the chemical compositions and roughness of surfaces, and appropriate surface roughness is responsible for special wettability such as superhydrophobicity, superhydophilicity, and so on. As a result, a significant amount of effort was devoted to the construction of rough surfaces of binary structures at both microand nanometer scales. Some examples of these methods included solution-immersion, wet chemical process, electrodeposition, electroless galvanic deposition, and hierarchical self-assembly.

Despite many researches fabricated superhydrophobic surface on various substrates, few studies were focused on the surfaces of engineering metals, which largely limits wide application of superhydrophobic surfaces in industry. ZnO is a wide band gap semiconductor which has potential application in optical and electronic industries. ZnO films were prepared by chemical vapor deposition, epitaxial electrodeposition, thermal evaporation, cathodic electrolysis, and so on. Recently, ZnO nanorods arrays were used to create superhydrophobic surfaces via chemo- or electro-deposition. However, the superhydrophobic surfaces based on ZnO nanorods arrays generally displayed a large contact angle hysteresis when the ZnO nanorods were modified with moderate-length alkanoic acids.

In this paper, we describe a simple way to fabricate superhydrophobic surfaces with low contact angle hysteresis based on ZnO nanoneedles. To achieve this goal, a thin film of zinc is electroplated on a given substrate, then the zinc layer is converted to a film of ZnO nanoneedles by immersing in an aqueous solution of NH4OH, and finally the ZnO film is treated with n-dodecanoicacid to form a superhydrophobic surface. The process reported here can produce superhydrophobic surfaces at large scale and shows good reproducibility.

Experimental Procedures 電解液 65g/L 氯化鋅、 190g/L 氯化鉀、 30g/L 硼酸、增白劑 921A 32ml/L 和 921B 2ml/L 將銅基板做為電解液沉積的基板 ( 陰極 ) ，純金屬鋅基板作為陽級 電流密度為 10 mA/cm 2 在室溫下持續 140 秒 銅基板以去離子水清洗，並浸泡在含有 (NH 4 OH, 25%)1g 的 80 毫升 的去離子水中，並加熱至 80 o C 持續 4 小時，之後再以去離子水清洗。 浸泡在 20 mM 酒精溶液 和 n-dodecanoic acid 20 分鐘，調整表面自 由能，再以丙銅清洗乾淨。

Results and Discussion XRD pattern of the ZnO films formed on copper substrates. The XRD pattern indicates that all of the diffraction peaks are in good agreement with hexagonal phase of wurtzite-type ZnO (space group P63mc, JCPDS ).

SEM images of the ZnO films constructed on copper plates; (a) 500, (b) 1000, (c) 3000, (d) 5000.

FT-IR (a) and C1 s (b) spectra of the ZnO film modified with n-dodecanoic acid. There are two strong peaks located at 2877 and 2942 cm -1, indicating the presence of the long-chained aliphatic groups on the surface. The peaks at 1577 and 1473 cm1 suggest the existence of carboxylate ion. Furthermore, C1s spectrum of the ZnO surface clearly displays a strong peak at eV and a shoulder at eV, which are ascribed to the – CH 2 – and – COO groups, respectively.

Optical image of a water droplet on the surface of a ZnO film modified with ndodecanoic acid. The contact angles of the surfaces are about 150 o and the sliding angles are lower than 5 o, indicating the superhydrophobicity of the ZnO films.

Conclusion In summary, a simpleway to fabricate superhydrophobic surface with high contact angles and low sliding angle was proposed by combining the hydrothermal reaction and surface reaction. The procedure reported here is convenient, environmental-friendly compared to the conventional methods. Owing to the deposition of zinc films on various conducting or isolating substrates is a mature technology in industry, the present method can be easily extended to a wide range of substrates such as metals, glass and polymers.

Future work 製備溶膠 - 凝膠 3 層玻璃基板 接觸角量測 參數整理 PAPER REVIEW ： A Facile and Mild Synthesis of 1-D ZnO, CuO, and -Fe2O3 Nanostructures and Nanostructured Arrays

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