Transparent Hydrophobic Hybrid Silica Films by Green and Chemical Surfactants

Monodispersed and transparent hybrid silica wires were synthesized by the sol-gel method using the chemical surfactant trimethoxyoctylsilane (C₈TMOS or C₁₁H₂₆O₃Si) and, for the first time, by green surfactants (Nelumbo nucifera/lotus leaf extract). The purpose was to introduce a less toxic, cost-effective, and one-step easy approach to get superhydrophobic silica films. Each of the surfactants was used at two different concentrations to investigate hydrophobicity of the films. Assembly of silica wires was obtained by dip-coating and vacuum filtration methods on glass and cellulose acetate filter paper as substrates, respectively. The water contact angle (CA) up to 154° was measured for hybrid silica films on filter paper, which revealed their superhydrophobicity as compared to hydrophobic behavior of those films coated on a glass substrate with CA up to 135°. Chemical, optical, and structural properties of prepared films were characterized by Fourier transform infrared spectroscopy, UV-vis spectroscopy, scanning electron microscopy, thermogravimetry, and differential scanning calorimetry. The hybrid silica wires prepared displayed good transparency, low surface energy, and superhydrophobicity. These silica assemblies can create outstanding and multifunctional structures with superhydrophobic coatings for waterproof electronic devices, military uniforms, self-cleaning surfaces, etc.