Mesoporous nanostructures-based fiber optic pH sensors: Synthesis, structure-tailoring, physiochemical and sensing stimuli

Abstract Owing to opto-chemical sensing, three matrices i.e., SiO2, TiO2, and SiO2-TiO2 are synthesized and a mixture of four different organic dyes encapsulated in them through the sol-gel method. Thermally stable, large surface area 434 m2/gm, 197 m2/gm, 332 m2/g, and refractive index 1.49, 1.8, 1.5 at 632 nm are observed for d -SNPs (dyes encapsulated silica nanoparticles), d -TNPs (dyes encapsulated titania nanoparticles), and d -STNPs (dyes encapsulated silica-titania nanoparticles), respectively. When the evanescent field interacts with the fiber optic coating, absorption varied due to pH change and the output intensity is recorded as a sensor response in terms of transmission. The prepared sensors exhibited linear response, non-leachability, and stability towards high pH 12. The fast time response is estimated ∼ 0.35 s, 0.33 s, and 0.31 s in pH 12 for d -SNPs, d -TNPs, and d -STNPs, respectively. Therefore, these prepared optical fiber sensing devices have the potential for practical pH sensing applications.