Facile Fabrication of Hierarchically Structured Silica Coatings from Hierarchically Mesoporous Silica Nanoparticles and Their Excellent Superhydrophilicity and Superhydrophobicity

Silica coatings with hierarchical structures were prepared on glass substrates via layer-by-layer assembly using hierarchically mesoporous silica nanoparticles as building block. These coatings demonstrated excellent superhydrophilic properties. After hydrophobic modification, the obtained coatings exhibited hydrophobic properties in the measurements of water contact angles by employing contact-mode and drip-mode, respectively. Water droplet of large volume (15 mu L) had a smaller sliding angle than that of small volume (3 mu L) when using the contact mode due to the role of gravity despite the existence of large adhesive force between water droplet and the coating surface, while very small sliding angles were noted when using the drop-mode because of the existence of kinetic energy. The transmittance of fabricated coatings was enhanced and reduced respectively, in the long and short wavelength range as compared with blank slide glass.