Cassie-model surface structure at nanoscale for unique air-layer mediated nanomaterial-protection

Surface structural modification is critical for regulating the physicochemical stability of nanomaterials. Cassie-model, which describes a phenomenon where an air layer exists between the superhydrophobic surface and liquid, has been widely applied in the design of surface structures to directly avoid the contact between the material and the liquid, thereby improving corrosion resistance. Although the construction of superhydrophobic interfaces to realize Cassie-model has achieved remarkable results, current researches mainly focus on macro-substrates. Whether this approach is viable for protecting particles at the nano-scale remains underexplored. Here, we report the fabrication of Fe 3 O 4 @rSiO 2 core@shell nanoparticles with a rough silica shell (rSiO 2 ) that exhibit exceptional acid resistance. We demonstrate that the nanoscale array structure on the surface of the rSiO 2 shell (height: 20 nm, diameter: 6 nm) can generate an air layer between the Fe 3 O 4 inner core and corrosive media. Due to the presence of the air protective layer induced by the Cassie-model surface structure, the Fe 3 O 4 nanoparticles retain their structure and function under highly acidic conditions (12 M HCl), and maintain their magnetothermal properties. Additionally, the unique surface roughness of the Fe 3 O 4 @rSiO 2 core@shell nanoparticles significantly enhances their bacterial adhesion capabilities, enabling drug-free structural-antibacterial performance even after exposure to strong acidic conditions. These findings open up new possibilities for the applications of nanomaterials in harsh environments.