Thermally stable and fast responsive mesoporous cresol red functionalized silica and titania nanomatrices: fiber optic ph sensors

Abstract

Owing to the fast responsive fiber optic pH sensing, silica nanomatrix (SNM) and titania nanomatrix (TNM) are synthesized by the sol–gel method at low temperatures. Cresol red (CR) is immobilized within SNM and TNM for sensing evaluation. Crack-free, crystallinity and porous surfaces with an average particle size of CR-SNM ~45 ± 0.4 nm and CR-TNM ~24 ± 0.4 nm are observed through microscopic analysis. The is observed in CR immobilized matrices. The CR-SNM shows lower roughness ~7 nm, a large surface area ~380 m2/g, thermal stability at ≤400 °C, and a refractive index 1.47. Whereas, CR-TNM revealed high roughness 48 nm, surface area 211 m2/g, and refractive index 1.76. The sensitivity of the CR-SNM coated fiber is estimated at around 52.8 counts/pH which is greater than CR-TNM coated fiber sensitivity 14.53 counts/pH. Moreover, CR-SNM shows response time 0.17 s at pH 12 which is faster than CR-TNM time response 0.48 s.