Optically functionalized hierarchical hematite assembled silica-titania nanocomposites for hydrocarbon detection: Fiber optic chemical sensor

Abstract Mesoporous hematite nanoparticles (HNPs) encapsulated SiO2–TiO2 nanocomposites (STNC) are synthesized and heat-treated at low-temperature 50 °C for 1h (STNC/1h) and 2h (STNC/2h) by sol-gel process for hydrocarbons chemical sensing. Microscopic analysis revealed the thermally stable hierarchical structure of HNPs, which changed into aggregated porous spherical morphology after encapsulation in STNC and heat treatment. The low surface area of HNPs ~55 m2/g which is increased up to 289 m2/g for H-STNC/2h, is advantageous to enhance sensing device activity. Magnetic properties exhibited the superparamagnetic behavior of H-STNC/2h. The H-STNC/2h coated fiber optic chemical sensor revealed a linear response towards the higher carbon chains, sensitivity is calculated as 5.3 counts per unit variations in the carbon chain at 515 nm with R2 ~ 0.98. The proposed magnetic sensing device has good reversibility, stability, and validity without any leaching traces.