Highly transparent superhydrophobic organic–inorganic nanocoating from the aggregation of silica nanoparticles

Transparent superhydrophobic nanocoating, possessing a sub-100 nm roughness, a high water contact angle (>160°) and a low sliding angle (<5°), has been prepared by a simple sol–gel dip-coating method. The desired hierarchical sub-100 nm roughness, which renders the nanocoating transparency, was created by using 3-aminopropyltriethoxylsilane (APTEOS) as aggregated agent. Cetyltrimethoxylsilane (CTMS) was adopted as modifying agent subsequently to give the nanocoating superhydrophobicity. The influence of experiment parameters on the transparency and superhydrophobicity of as-prepared nanocoating were investigated herein to get the optimum preparing conditions. The obtained nanocoating before and after modification were characterized and confirmed by various technologies including Fourier transform infrared (FT-IR) spectroscopy, 29Si CP (cross-polarization) MAS NMR, X-ray photoelectron spectroscopy (XPS), thermal analysis, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The as-prepared transparent superhydrophobic nanocoating exhibits a good moisture resistance, and it could switch from superhydrophobic (>160°) to superhydrophilic (0°) after heat-treating at a temperature higher than 500 °C.