Mesoporous nanocomposite coatings for photonic devices: sol–gel approach

Thermally stable, optically active inorganic nanocomposites, i.e., aluminum–silicate (AS) and silica–titania (ST), are synthesized via acid-catalyzed low-temperature sol–gel method in order to get stable, crack-free coating material for photonic devices. The samples are characterized by atomic force microscope, field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett––Teller (BET) surface area, Barrett–Joyner–Halenda (BJH) pore size distribution surface analysis and UV–Vis spectroscopy. Microscopic results show good incorporation of ST and AS particles as composites with grain size within range of 12–17 and 62–109 nm, respectively. EDX analysis substantiated the stoichiometric formation of homogeneous nanocomposites. XRD of the films reveals primary polycrystalline anatase titania phase and mullite phase of ST and AS nanocomposites. FTIR confirms the heterogeneous bond linkage between titania, silica and alumina species. Furthermore, the fabricated samples have mesoporous nature with high surface area, large pore volume and diameter. The tunable refractive index of 1.33–1.35 with high transparency is obtained for synthesized nanocomposites. The experimental findings show that these physically modified and thermally stable alumina- and titania-doped silica-based composite coatings are promising for photonic devices modification.