Optical Fiber pH Sensors Based on PAni-coated Microstructured Optical Fibers
Résumé
In this paper, we report the analysis of a novel optical fiber pH sensor based in polyaniline coating applied on a trenched core-free (only-bridge) silica fiber. The results are compared to another pH sensor based on side-polished silica fiber. The pH sensitive polymer is synthetized over the fiber sample by means of oxidative polymerization, keeping records of the time where the reaction occurs to improve the sensitivity. The response to pH is enhanced in the case of the trenched core-free bridge fiber due to the higher interaction of the evanescent field with the polyaniline film, thus, the surrounding media. The sensitivity in the linear zone of operation is 1.1 mW/pH, and a total transmittance of 55 % in the pH range of 4.2 to 8.1. The repeatability of both sensors was checked, showing a high capability to perform studies in liquid samples due to its temperature independence, good sensitivity and long-term stability.
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