Interferometric optical fiber sensor with a polyoxometalate-doped xerogel for the selective detection of ammonia

This study presents the development and evaluation of an interferometric optical fiber sensor (I-OFS) based on a Single Mode Fiber-No Core Fiber-Single Mode Fiber (SMF-NCF-SMF) structure and functionalized with a silica xerogel doped with a titanium (IV)-containing polyoxomolibdate (GeMoTi). The behavior of the sensor was tested under saturated atmospheres of ammonia, water, and various volatile organic compounds (VOCs), including ethanol, acetone, and toluene. The response is characterized in terms of wavelength shifts, which are highlightable for ammonia due to its strong chemical interactions with the doped xerogel. The response and recovery times were evaluated for each analyte, pointing out ammonia as the compound with the fastest and most stable detection performance. These results reinforce the hypothesis of using GeMoTi-doped xerogels to enhance the selectivity of I-OFS for the detection of closely related amines.