A new turn on coumarin-based fluorescence probe for Cr³⁺ detection in aqueous solution

Isatin-3-(7'-Methoxychromone-3'-methylidene) hydrazone (L) was synthesized based on chromone schiff base, and used to construct a novel sensor to detect Cr³⁺. Fluorescence detection experiments were carried out for a range of different concentrations of Cr³⁺ in aqueous solutions. A concentration calculation model was built on the basis of eliminating interference of excitation spectrum in the fluorescence spectra with mathematical method. Results showed that probe L displayed a 70-fold fluorescence enhancement upon the addition of Cr³⁺ due to the photo-induced electron transfer (PET) effect. On the other hand, metal ions except Cr³⁺ did not cause significant change in either the absorption or the fluorescence spectrum of L. In addition, L showed a good selectivity to Cr³⁺ over other metal cations, especially Al³⁺ and Cu²⁺. The probe L can detect Cr³⁺ highly and selectively by the direct chelation enhanced fluorescence with a detection limit of 3.14 × 10^-6 M. Furthermore, benefiting from their good water solubility and biocompatibility, cell imaging and real-time monitoring of Cr³⁺ in living HepG2 cells were successfully achieved.