Micro-nano hierarchical superhydrophobic electrospray-synthesized silica layers

Abstract

This paper reports the preparation of superhydrophobic SiO2 layers with a micro-nano hierarchical surface structure. SiO2 layers, which were rough on the microscale, were prepared using an electrospraying method combined with a sol–gel chemical route. To create a nanoscale structure, the surface of the SiO2 layers was coated with Au nanoparticles using an ultraviolet-enhanced chemical reduction process, resulting in a micro-nano hierarchical surface structure. A subsequent fluorination treatment with a solution containing trichloro(1H,1H,2H,2H-perfluorooctyl)silane resulted in fluorination of the micro-nano hierarchical SiO2 layers. The resulting SiO2 layers showed outstanding repellency toward a range of liquid droplets, for example, a water-repellency of 170°. The surface fraction and work of adhesion of the fluorinated, micro-nano hierarchical SiO2 layers were estimated using the Cassie–Baxter and Young–Dupre equations, respectively. The long-term durability and ultraviolet resistance of the superhydrophobic SiO2 layers prepared in this study highlight their potential in a range of practical applications.