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.
Nianbing Zhong,Ming Chen,Yihao Luo,Zhengkun Wang,Xin Xin,Bruce E. Rittmann
We present a novel UV–visible-light photocatalytic optical hollow-fiber in which a hollow optical fiber (HOF) and TiO 2 -based composite are coupled for enhancement of photocatalytic activity toward degradation of 4-chlorophenol (4-CP). A HOF was coated with a TiO 2 -based composite composed of Er 3+ :YAlO 3 /SiO 2 /TiO 2 (EYST) and acting as the photocatalytic element. The EYST coating showed good light-inducing capacity at the fiber-coating interface and high photocatalytic activity driven by UV–visible light. The photocatalytic activity of the fabricated photocatalytic HOFs was investigated for degradation of 4-CP in aqueous solution in the wavelength spectrum of 360–780 nm. Examined were the effects of the EYST coating gradient and reactor operating conditions (pH and temperature) on the degradation of 4-CP. The EYST-coated HOF significantly enhanced the 4-CP degradation, dechlorination, and mineralization, compared to pure TiO 2 -coated HOF and EYST-coated solid optical fibers. Specifically, high photocatalytic activity was obtained when the EYST coating thicknesses at the HOF’s incident end and HOF’s hemispherical end were 10 and 160 μm, the pH was 6.0, and temperature was 55 °C.
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