Fluorescent sensors developed at the University of Birmingham, England, may lead the way to the fluorescent imaging of fluoride in living systems. The sensors consist of boronic acid receptor units directly attached to aromatic fluorophores. Research fellows Neil Spencer and Tony D. James, and postgraduate student Christopher R. Cooper, have demonstrated that the fluorescence of these compounds decreases on the addition of fluoride ions at low concentrations [ Chem. Commun. , 1998 , 1365]. This is the first example of a simple and direct method of detecting fluoride by fluorescence, James tells C&EN. The sensors rely on Lewis acid-base interactions between the boronic acids and the fluoride anions. The anions bind with the boron atoms to form tetrahedral boronate anions that quench fluorescence by photoinduced electron transfer to the fluorophore. The sensors operate at about pH 5.5 and can detect fluoride concentrations as low as 5 mM. Fluoride concentrations are currently determined using electrodes ...