Neodymium Modified Chitosan/PMMA Integrated Thin-Core Fiber for Trace Fluoride Ion Detection

Using a segment of thin-core fiber (TCF), multimode fiber (MMF) and single-mode fiber (SMF), a fiber-optic sensor based on the SMF-MMF-TCF-MMF-SMF structure is fabricated and experimentally demonstrated. Based on the layer-by-layer self-assembly method, neodymium modified chitosan (Nd/CTS)/polymethyl methacrylate (PMMA) film is coated on the TCF surface, a Mach-Zehnder interferometer (MZI) sensor for fluoride-ion detection is obtained. With the increase of the fluoride-ion concentration, the monitoring trough shows redshift. Also, the high sensitivity of 14.145 nm/ppm, the rapid response time (about 60 s), the good logarithmic linear relationship (R
²
= 0.97175) at the concentration range of 0.002-0.04 ppm with high selectivity for fluoride ion are achieved. The sensor has the advantages of easy fabrication, good selectivity, low-temperature cross-sensitivity, and good stability, which is suitable for sensitive detection of trace fluoride ion.