Polyvinyl alcohol/AlFFIVE-1-Ni-coated long-period fiber grating sensor for accurate online detection of SO2 concentration
This paper proposes a polyvinyl alcohol/AlFFIVE-1-Ni (PVA/KAUST-8)-coated long-period fiber grating (LPFG) SO 2 concentration sensor to accurately monitor SO 2 concentrations online. To enhance the adhesion strength between the fiber and a SO 2 -sensitive film, the etched LPFG surface was silanized using 3-aminopropyltriethoxysilane, and then coated with a PVA/KAUST-8 SO 2 -sensitive sol using the doctor blading method. A fluorosilane hydrophobic coating was deposited on the SO 2 -sensitive membrane surface and integrated with a LPFG temperature sensor, thereby effectively eliminating measurement interference caused by ambient temperature and humidity fluctuations during SO 2 concentration detection. The morphology and composition of the SO 2 -sensitive films were characterized using optical microscopy, field-emission scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. Furthermore, the working principle of the sensors for the detection of SO 2 was established. Under optimized parameters (LPFG diameter: 60 μm; PVA doping in PVA/KAUST-8: 12 wt%; SO 2 -sensitive film: 45 μm; fluorosilane composite layers: 12) within a humidity range of 0–60 % RH and a temperature range of 25–45 °C, the sensor demonstrated a good selective SO 2 detection with 2.79 pm/ppm sensitivity, 1.07 ppm detection limit, 390 s response time, and 8.89 % maximum relative error.
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