Abstract
Owing to fiber-optic pH sensing, phenolphthalein immobilized SiO2 nanoparticles (P-SNPs) and phenolphthalein immobilized SiO2–TiO2 nanoparticles (P-STNPs) are synthesized by low-temperature sol-gel route. The P-SNPs revealed hierarchical structure, surface roughness (Ra) 7 nm, surface area ∼442 m2/g, n (refractive index) 1.37 at 550 nm which is significant for pH sensing. The P-STNPs exhibited granular structure, low Ra 3 nm, surface area ∼219 m2/g, n around 1.52 at 550 nm. Both matrices are thermally stable around 250 °C. The P-SNPs and P-STNPs sensitivity is calculated ∼22 counts/pH and 19 counts/pH with the determination coefficient (R2) ∼ 0.99. The pka value of P-SNPs is measured ∼9.5 and time response 0.11s within pH 12 without leaching which is higher than P-STNPs (9.1) and 3.9 s with leaching. Experimental findings suggested P-SNPs have the potential for practical usage in intense basic media.
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•Phenolphthalein immobilized SiO2-TiO2 nanoparticles (P-STNPs) are synthesized by sol-gel route.•The P-SNPs revealed hierarchical structure, surface roughness 7 nm, surface area ~ 442 m2/g, and refractive index 1.37.•The P-SNPs and P-STNPs sensitivity is calculated ~ 22 counts/pH and 19 counts/pH with R2 ∼ 0.99.•The pka value of P-SNPs is measured ~ 9.5 and time response 0.11s within pH 12 without leaching.•Experimental findings suggested P-SNPs have the potential for practical usage in intense basic environment.