The SiO 2 –TiO 2 superhydrophilic coatings with photocatalytic activity via heat curing over a low temperature of 100 ℃ were fabricated without a high-temperature calcination process. The effects of the composite ratio of SiO 2 and TiO 2 on the stability of the sols, different treatment processes on the crystalline morphology of TiO 2 , and different solid contents of the sols on the coating properties were investigated. The surface morphology, optical properties and mechanical properties of the coatings were characterised by a water contact angle (WCA) analyser, UV spectroscopy, scanning electron microscopy (SEM) and multiple functional tests. The experimental results demonstrated that the SiO 2 –TiO 2 coating featuring both the intrinsic hydrophilicity of SiO 2 and photophilicity of TiO 2 had the WCA up to 3.5° and exhibited good photocatalytic, self-cleaning, anti-fogging, and mechanical properties.
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.
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