Synthesis of shape-controlled hollow silica nanostructures with a simple soft-templating method and their application as superhydrophobic antireflective coatings with ultralow refractive indices

A soft-templating method for synthesizing shape-controlled hollow silica nanoparticles (HSNs), including worm-like hollow silica nanotubes (HSNTs), hollow silica nanospheres (HSNSs) was developed by simply changing the contents of the template, Poly(acrylic acid) (PAA). The possible formation mechanism of HSNs was investigated. Multi-functional coatings were prepared using HSNs as follows: HSNs sols were dip-coated on K9 glass, followed by chemical vapor deposition with 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (POTS). Results showed that a water contact angle as high as 153° was achieved on the coating after hydrophobic modification. The refractive indices of corresponding films ranged from 1.10 to 1.12 after calcination at 300–450 °C. The highest transmittance of coated K9 glass was much higher than that of blank K9 glass. The multi-functional coatings have potential applications in opto- and microelectronic fields due to their high transmittance, ultralow refractive indices and superhydrophobicity.