High refractive index and good mechanical property UV-cured hybrid films containing zirconia nanoparticles

UV-curable zirconia (ZrO₂) nanoparticle coatings, prepared by dispersing highly-crystalline zirconia nanoparticles (4 nm) in tetrahydrofuran with the aid of 3-glycidoxypropyltrimethoxysilane (GPTMS) and following addition of a cationic photoinitiator, were cast on silicon wafers (or glass substrates) by dip-coating or spin-coating and photopolymerized to get transparent ZrO₂ nanoparticle films. Ellipsometrical characterization indicates that the refractive index of the film changes from 1.63 to 1.77 at wavelength of 632 nm when the molar ratio of GPTMS-to-ZrO₂ decreases from 0.30 to 0.15. Nano-indentation tests show that the films exhibit robust mechanical performance though they are not heat-treated.