Fe2O3 nanotube coating micro-fiber interferometer for ammonia detection

Abstract This paper presents a convenient and effective method for the determination of ammonia concentration. The structure is manufactured of Fe2O3 coated tapered microfiber interferometer (MFI). The Fe2O3 nanotube coated on the MFI acts as sensing layer, which enhance the gas selectivity, adsorptivity for ammonia molecule and also enhances the evanescent field strength distribution of the sensor and changes the mode effective refractive index of guided mode in MFI. When the quantity of ammonia molecule adsorbed on the sensing layer changes, the transmission spectrum of the sensor will shift. By determining the wavelength shift of the dips of the transmission spectrum, the concentration of ammonia will be detected. The experimental results show that the tapered microfiber interferometer (MFI) sensor coated with Fe2O3 nanotube has better time response repeatability and high sensitivity in detecting ammonia gas at room temperature. The sensor has a sensitivity of 1.30 pm/ppm and can be used for the detection of harmful gas ammonia in the environment.