Photopatternable and refractive-index-tunable sol-gel-derived silica-titania nanohybrid materials

Silica-titania nanohybrid materials were synthesized using functionalized organosilanes and organically chelated titanium alkoxide in a simple sol-gel process. The synthesized silica-titania nanohybrid materials exhibited good solution processability and homogeneous dispersion without any phase separation regardless of the ratio of the mixture of the two components. The silica-titania nanohybrid materials exhibited good photoinitiator solubility and effective photocurability with a high degree of degree under ultraviolet (UV) exposure. Because of their high photocurability and solution processability, the silica-titania nanohybrid materials were readily converted into silica-titania nanohybrid films and were used for direct photopatterning without requiring the developing process used in the photomask method. In particular, the refractive indices of the silica-titania nanohybrid materials could be decreased by decreasing the content of chelated titanium alkoxide in the materials. Moreover, the silica-titania nanohybrid films exhibited high transmittance in the visible wavelength range, and their surface roughnesses were very smooth, exhibiting values <1 nm. On the basis of these observations, the fabricated silica-titania nanohybrid materials can be used in solution-processable materials for producing optical and electro-optical elements.