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

Abstract

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. ¹H-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 μmol L⁻¹ (R² = 0.997) and 0.064 μmol L⁻¹, respectively, with satisfactory selectivity over other anions. The method was also used for PPi detection in serum samples.