Crack-alleviated gold-assisted silica-titania three-layered fiber optic pH sensor

Gold-assisted silica-anatase (Au/AS) nanocomposite was synthesized by a sol-gel route at a low temperature (90 degrees C). Owing to sensing assessment, the mixture of indicators (bromophenol blue, phenol red, and creosol red) is encapsulated in Au/AS nanocomposite and deposited in three layers on optical fiber. TGA analysis confirmed the D-Au/AS nanocomposite thermal stability at higher temperatures <= 500 degrees C. SEM and EDX mapping confirmed the self-assembly of icosahedron structures at the nanometer scale. AFM revealed a porous triangular texture of three layers with RMS around 6 nm. The sensitivity of the three layers was estimated at around 17.7 counts/pH. The three layers of coated fiber revealed reversibility, stability, and fast response at 0.56 s in pH 12. The dynamic pH range of three-layer coated fiber was optimized at pH 1-12 and suggested that it has fast responsive sensing potential for applied fields.