微反应器法制备ZnAl-LDH纳米片及LDH基疏水膜的组装

Preparation of Zn-Al layered double hydroxide nanosheets by microchannel reactor and fabrication of LDH-based hydrophobic films

层状双金属氢氧化物(LDH)纳米片可作为基本的结构单元或利用有机物修饰其表面使其功能化来构筑LDH基功能材料,但现有的制备方法存在使用有机溶剂、所得LDH纳米片表面吸附有机物、难以宏量制备等问题,限制了其实际应用。本文利用微反应器通过控制共沉淀过程中的p H值制备了Zn Al-LDH([Zn2+0.67Al3+0.33(OH)2]NO3·y H2O)纳米片,由于利用微反应器法制备LDH纳米片的过程中水是唯一的溶剂,所以得到的纳米片表面洁净且能够大量制备。通过XRD、TEM、AFM对所制备的LDH进行表征,结果表明,高p H值下得到的产物形貌不规整,并且存在Zn O小颗粒;当p H值降为7.9时,可得到粒径均匀且厚度为1.0-1.5 nm的Zn Al-LDH纳米片;将其与月桂酸钠简单混合后即可将月桂酸根修饰在其表面上,涂覆在玻璃基体得到高疏水性能的薄膜,其接触角高达149°,这为制备LDH基功能材料提供了一种简单的方法。

Layered double hydroxide(LDH)nanosheets can be used as basic building block or be modified with organic for the synthesisof LDH-based functional materials. But the current methods to prepare ultrathin LDH nanosheets have problems such as theutilization of toxic solvents,the adsorption of organic substances on the surface of LDH,or the difficulty in realizing macroscopicpreparation,which all limited the practical application of ultrathin LDH. In this paper,ZnAl-LDH nanosheets were prepared using amicrochannel reactor by controlling pH value during the co-precipitation process. The so-obtained nanosheets were naked(withoutorganic absorbed)because water was the only solution during the preparation,and nanosheets can be prepared in great amount. TheZnAl-LDH nanosheets were characterized by X-ray diffraction,transmission electron microscopy and atomic force microscopy. Theresults showed that products were not chemically pure but contained zinc oxide and the morphology was irregular in shape when pH value was high. When pH value was reduced to 7. 9,LDH nanosheets with the thickness of 1. 0-1. 5nm was obtained and the distributionof particle was quite narrow. The surface of ZnAl-LDH nanosheets was easily modified with sodium laurate through the simpleblend. The laurate-ZnAl-LDH film was composed of platelets lying perpendicular to the surface of the glass substrate and the watercontact angle was 149°,which provided a simple method to fabricate LDH-based functional materials.