Selective Detection of Pyrophosphate Anions in Aqueous Medium Using Aggregation of Perylene Diimide as a Fluorescent Probe.

A water-soluble perylene diimide, aspartic acid-functionalized perylene diimide (APDI), has shown significant sequential "turn-off" and "turn-on" responses toward Cu2+ and inorganic pyrophosphate (PPi), respectively. APDI was found to show selectivity toward Cu2+ and inorganic PPi over adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate. The detection has been studied by absorption and emission spectroscopy techniques. Incorporation of Cu2+ into the solution of APDI results in a distinct quenching of the fluorescence intensity, while there was no spectral change in the presence of other metal ions. The formed APDI-Cu2+ ensemble can turn on its fluorescence signal when PPi is present. The detection of PPi could be traced by looking at the change in color of the solution under the naked eye. No interference was observed from other anions, making the APDI-Cu2+aggregate a highly selective biosensor for PPi.