Ultrasensitive NO Gas Sensor Based on the Graphene Oxide-Coated Long-Period Fiber Grating

An ultrasensitive nitric oxide (NO) gas sensor based on the graphene oxide (GO)-coated long-period fiber grating (LPFG) was constructed successfully because of its excellent sensitivity to the surrounding refractive index (SRI) change. The surface morphology and structure of GO coated on LPFG were characterized by the scanning electron microscope (SEM), scanning probe microscope (SPM), and Raman spectroscopy, respectively. The adsorption principle of NO molecules by GO was calculated in detail by density functional theory (DFT) and further characterized by Fourier transform infrared spectrometry (FT-TR) and X-ray photoelectron spectroscopy (XPS). Our studies demonstrate that the adsorption principle of NO molecules by GO was the combined effect of physical adsorption and chemical adsorption because of the formation of C–N bonds between GO and NO and the oxidization of NO to NO₂. The NO sensor exhibits excellent sensing performance in the NO concentration range of 0 to 400 ppm.