A sensitive paper-based sensor for fluoride detection in water using Tb3+ photoluminescence†

Fluoride is a vital trace mineral for healthy bones and teeth, but a higher intake can lead to nephrolithiasis, dental/skeletal fluorosis, etc. Many dry regions worldwide contain higher fluoride than the WHO permissible limit of 1.5 ppm, necessitating a simple fluoride detection protocol. We adopted a fluoride-triggered desilylation strategy, which releases a sensitizer and enhances Tb³⁺ luminescence in a TbCh gel matrix. Under the optimized assaying conditions, the pro-sensitizer exhibited a selective response with a detection limit of 27 ppb, well below the WHO permissible limit. We also immobilized the gels on paper discs to detect fluoride from real-life samples (e.g., toothpaste, groundwater), and the results were validated using the standard ISE method. The promising results suggest nonexpert users adapting the protocol in resource-limited areas to provide quality control analysis.