Sensing enhancement ammonia gas sensor based on a hybrid film fiber

Abstract

A sensing enhancement sensor based on hybrid film fiber has been proposed to detect ammonia. The hybrid film coated on the MMF-SMF-MMF (Multimode Fiber–Single-mode Fiber–Multimode Fiber) structure is composed of single-walled carbon nanotubes with carboxylic acid groups (SWCNTs-COOH) self-assembled film and the silver film that was used to excite surface plasmon polariton (SPP) which contribute to enhancing the sensitive for refractive index (RI). The presence of free carboxylic acid functional groups and large surface area on the SWCNTs-COOH leads to high adsorption and selectivity toward amine compounds. The sensor works under a wavelength modulation scheme. And the resonance wavelength showed a red shift with an increase of the effective RI of the SWCNTs-COOH self-assembled film affected by ammonia concentration. The experimental results show that the sensor coated with hybrid film has high sensitivity and selectivity to ammonia gas. The proposed sensor is linearly responsive to ammonia concentration in the range 0 - 30 ppm, with a maximum sensitivity of 0.8 nm/ppm, the resolution 0.375 ppm, and the measured response 30 s, respectively. Finally, the sensor also has the advantages of simple structure and compact size, excellent stability, and low cost.