Tunable fluorescent pH sensor based on water-soluble perylene tetracarboxylic acid/Fe(3+).

A novel fluorescent pH sensor with tunable response range was designed based on highly fluorescent 3,4:9,10-perylene tetracarboxylic ammonium, which could coordinate the paramagnetic Fe(3+) ions to turn off its fluorescence and could also release Fe(3+) to turn on the fluorescence again at higher pH. The fluorescent pH sensor was tunable in the presence of different ligands in aqueous solution.