Highly Sensitive Ratiometric Fluorescent Paper Sensors for the Detection of Fluoride Ions

Two sensitive and ratiometric fluorescent probes (probe I and probe II) were developed for the detection of fluoride ions. Probe I can detect fluoride ions quantitatively within a range of 0-6 mu M and a detection limit of 73 nM, while probe II has a range of 0-40 mu M and a detection limit of 138 nM. The test strips from probe I are quickly able to recognize F- (5 min) inside of the F- safety level in drinking water (1.0 mg/L, similar to 5 mu M) under 254 nm ultraviolet light, and the test strips from probe II quickly recognize F- (12 min) in dangerously high F- levels in water (4.0 mg/L, similar to 21 mu M) under 254 nm ultraviolet light. This combination of fluorescent paper sensors from probe I and probe II can be used as a simple and convenient tool to determine whether water is safe to drink or dangerous.