A polydiacetylene (PDA) impregnated poly(vinylidene fluoride) (PVDF) membrane for sensitive detection of fluoride ions.

Fluoride is present in groundwater and drinking water across the world and plays crucial roles in regulating oral health. Although a 0.7-1.2 ppm concentration of fluoride in water supplies is deemed optimal for enamel development and dental health, its higher concentration causes endemic fluorosis, acute gastric, urolithiasis, and kidney infection, making the detection of fluoride highly important. However, the standard methods of fluoride detection, such as potentiometric or ion-selective detection, require specific instruments and often pre-treatment before analysis and do not offer the scope for on-site detection. Herein, we report the development of a polydiacetylene (PDA) grafted poly(vinylidene fluoride) (PVDF) membrane for sensitive solid-phase detection of fluoride. The sensors were prepared by functionalizing PDA with the boronic acid functionality as the F - recognition unit and impregnating it on PVDF strips. Upon exposure to fluoride, the strips displayed a visible color change from blue to red. The solid-phase sensor showed selectivity against common anions and can detect F - ions as low as 0.11 ppm. The real sample analysis in water and toothpaste and validation by ion chromatography demonstrate its potential application as an efficient lab-on-membrane for fluoride ions.