Superhydrophobic silica nanoparticles produced from rice husks, wettability at the macro- and nanoscale

The production of hydrophobic surfaces has gained significant industrial interest for various applications. Recent studies have demonstrated the use of different nanoparticles to synthesize superhydrophobic materials with excellent results. In this study, silica nanoparticles obtained from biomass (rice husks) were used as raw materials to make the surface hydrophobic using two methods: a wet impregnation process and dissolving the silica and condensation reaction to form the nanoparticle in the presence of stearic acid to functionalize the surface. The nanoparticles were characterized by AFM, FTIR, and dynamic light scattering to determine their size and composition. Hydrophobicity and wettability were measured macroscopically by contact angle in a flat surface and nanoscopically by atomic force microscopy. The macroscopic surface free Gibbs energy of the film was determined and compared with the adhesion energy of the individual nanoparticles determined by atomic force spectroscopy. Comparative analysis of macroscopic and nanoscopic measurements enhances our understanding of hydrophobic behavior at different size scales.