LAUSR

Abstract Sol-gel-based zinc doped silica-titania (ZST) nanocomposite matrix coated optical fiber has been prepared for pH sensing. Finding relies on evanescent wave absorption in a thin film deposited on the PCS fiber core. Four different dyes are encapsulated in silica-titania and zinc doped silica-titania nanocomposite and the formulation is optimized to suppress dye leaching and enhanced the dynamic pH range. Both matrices show porous, smooth, and crack-free films with low surface roughness (15 nm and 1 nm). The grain sizes are calculated ranged 66-166 nm and 43-105 nm for D-ST (dyes encapsulated silica-titania) and D-ZST (dyes encapsulated zinc doped silica-titania) nanocomposite matrix, respectively. Both matrices exhibited thermal stability at ≤ 500 °C. The D-ST and D-ZST showed pronounced pKa values 9.8 and 9.7, suggesting a broader response range. The D-ST and D-ZST matrix demonstrated sensitivity 28.43 counts/pH at 460 nm with R2 ∼ 0.96 and 13.90 counts/pH with R2 ∼ 0.98 at 441 nm, respectively. Fast time responsive signals are observed ∼ 1.69 s to 0.12 s from pH 1-12 for D-ST and 0.48 s to 0.14 s for D-ZST nanocomposite matrix confirmed fast response towards basic media. No traces of leaching are determined by multiple measurements in DI water.