Preparation of antireflective coatings with moisture resistance and a widely tunable refractive index by combining the sol-gel method with evaporation concentration

Optical coatings with tunable refractive indices (RIs) are of significant interest in the field of optics. However, it is still a challenge to fabricate such coatings conveniently and economically. Here, through a sol-gel method combined with a novel process, evaporation concentration, antireflective (AR) coatings with easily tunable RI, robust resistance to moisture and high transparency were prepared based on hollow silica nanoparticles (HSNs). A mechanism of particle growth and film formation was proposed to explain the morphologies of HSNs and coatings as well as the optical and hydrophobic properties of the coatings. By adjusting the concentration degree and MTES content, the RI and the water contact angle (WCA) of the obtained coatings were increased to 1.28 and 102.1°, respectively. Over a broad range of wavelengths, from 400 to 1100 nm, the maximum average transmittance of the coated glasses reached 97.52%, more than a 6% increase compared with that of uncoated low-iron glass. The methodology used to prepare such coatings with relatively outstanding AR properties and hydrophobic effects does not require any expensive equipment or time-consuming process, making it well suited for industrial production.