A Dual‐Functional “On‐Off‐On” Relay Fluorescent Probe for the Highly Sensitive Detection of Copper(II) and Phosphate Ions

A high‐efficiency dual‐functional on‐off‐on fluorescence probe: 2′–4′‐dihydroxydiphenyl‐8‐formyl‐7‐hydroxycoumarin hydrazine (L) based on photoelectron transfer mechanism (PET) was designed and synthesized, and its ion recognition characteristics were fully studied by spectroscopy. As expected, probe L shows highly sensitive to Cu2+ in EtOH‐HEPES (20 mM v/v, 80 : 20, pH =7.40) solution, and its detection limit up to 6.14 ×10−7 M. The stoichiometric ratio of L−Cu2+ complex was determined as 1 : 1 based on 1H NMR titration and ESI‐MS. Meanwhile, the resulted L−Cu2+ complex shows good selectivity for the phosphoric acid family anion (H2PO4−, HPO42− and PO43−), which denote probe L the dual‐function in rapid detection of Cu2+ and phosphate family's ions. A dual‐functional “On‐Off‐On” relay fluorescent probe for highly sensitive detect Cu2+ and phosphate ions was fabricated. The stoichiometric ratio of L−Cu2+ complex was determined as 1 : 1 based on 1H NMR titration and ESI‐MS. The detection limit for Cu2+ was up to 6.14 ×10−7 M. Meanwhile, the complex of L−Cu2+ show a high response to H2PO4−, HPO42− and PO43− which denote the probe L a better “on‐off‐on” properties.