Superhydrophobic and oleophilic micro-nano hierarchical Pd-decorated SiO₂ layers

This paper reports a novel fluorinated micro-nano hierarchical Pd-decorated SiO₂ structure (hereafter called Pd/SiO₂), which was formed by the deposition of Pd nanoparticles (NPs) on SiO₂ microspheres. The SiO₂ layers with microscale roughness were fabricated by electrospraying a solution prepared using the sol-gel process. Subsequently, the Pd NPs were deposited using an ultraviolet reduction process. The resulting surfaces exhibited a micro-nano hierarchical morphology. After fluorination, the micro-nano hierarchical surface exhibited outstanding water repellency with a water contact angle (WCA) of 170° and a sliding angle <5°, indicating excellent superhydrophobic properties. The layers exhibited good long-term durability and excellent ultraviolet resistance. Interestingly, the surface was oleophilic (CA of oil ~10°). These results show the potential of employing superhydrophobic fluorinated Pd/SiO₂ layers in smart devices, such as self-cleanable surfaces and intelligent water/oil separation systems.