A Sensitive Ammonia Sensor Using Long Period Fiber Grating Coated With Graphene Oxide/Cellulose Acetate

A novel functionalized long period fiber grating (LPFG) sensor based on graphene oxide (GO)/cellulose acetate (CA) composites was developed for ammonia sensing. The adsorption of ammonia molecules by GO/CA composite materials changes the coupling efficiency of long period grating, further leads to the resonance wavelength shift. The surface morphology and structure of GO/CA composites material were characterized using the Scanning Electron Microscope, Raman spectroscopy, X-ray diffractometer, thermal analyzer and Fourier transformation Infrared Spectrometer. The effect of humidity on the sensor probe efficiency was also investigated. The composite mechanism between GO and CA and the mechanism of ammonia adsorption by composite membrane were studied using the density functional theory (DFT). The DFT calculation shows that there is no chemical bond forming between CA and GO, but there is a tendency to form hydrogen bond. The ammonia optic fiber sensor exhibits excellent performance in response time (32 s), recovery time (68 s) and exhibits excellent sensitivity (98.32 pm/ppm).