Development of a Biodegradable BODIPY‐<i>ε</i>‐Caprolactone System for Rapid Colorimetric Detection of Fluoride Ions in Environmental Samples

Fluoride ions (F^-) are well-known for their beneficial effects on oral health and their involvement in acting osteoporosis. But it is crucial to understand that consuming too much fluoride can of several adverse health effects. Dental fluorosis, urolithiasis, and even cancer can result from excessive fluoride exposure. This is why monitoring fluoride levels is so important. A 2,4-dinitrophenyl hydrazine derivative of a BODIPY-based aldehyde system (BDNP) is a sensitive, ratiometric, and selective naked-eye sensor that we have developed for the quick detection of fluoride ions in biological and environment samples showed a significant color change from pink-to-grey and a significant redshift in absorbance maxima when interacting with fluoride ions. The notable color shift demonstrates the effectiveness of both BDNP and Poly-BDNP in detecting fluoride ions. Interestingly, here we also showed that the ring-opening polymerization (ROP) technique-synthesized biodegradable and biocompatible ε-Caprolactone homopolymer of BDNP (Poly-BDNP) is a great system that can detect fluoride ions colorimetrically with a higher limit of detection (LOD) value than the monomer and rapid detection ability. Using the UV-visible spectroscopy study and the ¹H NMR spectroscopic titration technique, the interaction between BDNP and fluoride ions was examined. It was determined that the deprotonation of N-H protons triggers the intermolecular charge transfer (ICT) reaction, which results in the system's dramatic color change. The precision of both BDNP and Poly-BDNP in detecting F^- ions with LOD values of 7.73 µM and 87.9 nM, respectively, is determined by the ratiometric absorbance change of the sensor during the sensing process.