Hydrophobic antireflective coatings with ultralow refractive index synthesized by deposition of methylated hollow silica nanoparticles

A new type of antireflective (AR) coating materials with easily tailorable refractive index were successfully prepared by the sol-gel method based on the deposition of colloidal hollow silica nanoparticles (HSNs). HSNs were synthesized using tetraethylorthosilicate (TEOS) as the precursor, and then modified by methyltriethoxysilane (MTES). It is found that the refractive index (n) can be precisely tuned between 1.15 and 1.09 by changing the MTES content, in a range that is not accessible to dense inorganic materials. AR properties of the coatings on K9 glasses were demonstrated. Furthermore, AR coatings are intrinsically hydrophobic with the water contact angle (WCA) up to 122.5 degrees. (C) 2016 Elsevier B.V. All rights reserved.