Fluorescence turn-on detection of pyrophosphate based on aggregation-induced emission property of 5-chlorosalicylaldehyde azine

5-Chlorosalicylaldehyde azine (1) has been reported to exhibit a typical aggregation-induced emission (AIE) feature in our previous work. In this work, we further discovered that AIE fluorescence of 1 could be selectively quenched by Cu2+, hence 1 and Cu2+ complex was applied as a turn-on fluorescence probe for pyrophosphate (PPi) detection in aqueous solution. H-1-NMR data of the isolated products revealed that the addition of PPi underwent displacement of 1 in 1-Cu2+ complex, which led to the release of free 1 to aqueous solution, resulting in recovered AIE fluorescence. With fluorescence enhancement detection by the 1-Cu2+ complex, the linear range and detection limit for PPi were obtained as 0-15 mu mol L-1 (R-2 = 0.997) and 0.064 mmol L-1, respectively, with satisfactory selectivity over other anions. The method was also used for PPi detection in serum samples.