Optic fiber with Er3+:YAlO3/SiO2/TiO2 coating and polymer membrane for selective detection of phenol in water

We present a high-selectivity photochemical fiber-optic sensor in which a plastic optical fiber (POF), TiO 2 -based composite, and polymer membrane are coupled for detection of phenol concentrations in water. A thinned POF is coated with TiO 2 -based composite, which is composed of Er 3+ :YAlO 3 /SiO 2 /TiO 2 (EYST) and acts as the sensing region. The EYST coating shows good light-inducing capacity at the core–coating interface and high photocatalytic activity in the visible light region. The polymer membrane is synthesized using PEBA2533 doped with β-cyclodextrin and shows high phenol selectivity and permeability; thus, phenol molecules can freely permeate the membrane and are then transferred, become attached to the surface of TiO 2 nanoparticles, and are photocatalytically degraded. Photocatalytic degradation of phenol improves the refractive index (RI) and absorbance of the solution because of the photocatalytic byproducts; consequently, the transmitted output light intensity of the sensor changes, and the phenol concentration is accurately detected by measuring the change in the light intensity. Experimental results indicate that the prepared device detects phenol in water with high selectivity and pH independence; in phenol detection, the novel sensor shows a sensitivity of −0.195 × 10 −3 (mg/L) −1 and a low limit of detection of 40 μg/L.