Single-step fabrication of superhydrophobic urchin-like copper oxide nanopowders: Effect of structure-directing agents

Abstract

The use of superhydrophobic metal oxide nanoparticles has been considered for the construction of self-cleaning, anti-corrosion, anti-icing, anti-fogging, and oil/water separation surfaces, but the low chemical and thermal stabilities of applied organic modifiers restrict their wide applications. In this study, the superhydrophobic copper oxide nanoparticles with the hierarchical urchin, flower and spherical-like architectures were fabricated via a simple and facile single-step hydrothermal method without any post chemical modification. Taguchi experimental design was used to evaluate and optimize the synthesis parameters such as structure-directing agent concentration and its type, synthesis temperature, and the molar ratio of the complexing agent to the initial copper (II) ions. The wettability characteristics of synthesized samples were assessed based on the chemical composition of powders and their morphological structures. The scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses were used to characterize the resultant samples. The wettability properties of samples were determined by measuring the water contact angle (WCA) and contact angle hysteresis (CAH). The results confirmed that the synthesized sample under the optimum condition had an excellent superhydrophobic property with a WCA of 158.4⁰±2⁰ and CAH of 1.5⁰. The surface wettability evaluations also revealed that the morphology and surface free energy of the powders could be controlled simultaneously by alterations of type and concentration of the structure-directing agent, in order to enhance the anti-wetteing characteristics.