Ultralow refractive index coatings consisting of mesoporous silica nanoparticles

Highly porous coatings having ultralow refractive index (n=1.07) and good transparency were obtained using mesoporous silica nanoparticles. Excellent antireflection performance was achieved with six antireflection layers including the mesoporous film as the top layer. The average reflectance in the entire visible wavelength region (380-780 nm) was 0.04-0.22% at incident angle of 0 degrees-40 degrees. This facile technique for ultralow reflection coatings is potentially applicable to various optical devices to remove many problems caused by reflection.