A Reaction-Based Colorimetric Fluoride Probe: Rapid "Naked-Eye" Detection and Large Absorption Shift

Taking advantage of both the well-known azobenzene structure and the special fluoride-promoted cleavage reaction of the Si?O bond, a new ratiometric colorimetric probe (F-1) toward the fluoride anion was designed and synthesized by using intramolecular charge transfer (ICT) as a signal mechanism. Upon the addition of F- ions, the probe displayed apparent color changes from colorless to deep blue, with a dramatic shift of the maximum absorption wavelength (similar to 230 nm). With the aid of UV/Vis measurements, the detection limit could be as low as 15 mu M. The probe possessed much higher selectivity for fluoride over other common anions. Excitingly, by virtue of a dipstick approach, F-1 could serve as colorimetric probe for convenient measurements, without the requirement of any additional equipment.