Delafossite AgAlO 2 modified long-period grating for highly-sensitive ammonia sensor

Owing to the unique merits of high sensitivity and large range detection, long-period grating (LPG) optical fiber sensor modified with functional coatings has attracted significant attention recently. As a refractive index sensor, the appropriate choice of the coating properties is critical for exploring the high-performance LPG sensor. In this study, p-type delafossite AgAlO2 (AAO) nanoparticles were proposed as a novel sensitive coating material for the cladding modification of LPG develop a high-sensitivity fiber-optic ammonia sensor. As the resistance/dielectric constant of AAO cladding layer is sensitive to concentration variation of ammonia vapor even at room temperature. Sensing performances of the LPG optical fiber sensor could be substantially enhanced with the presence of AAO cladding layer. A linear sensitivity of 2.07 pm/ppm to ammonia from 25 ppm to 400 ppm was achieved at room temperature. Moreover, the LPG sensor exhibits short response (38 s) and recovery time (50 s), and high selectivity to ammonia compared to several possible interfering vapors.