A Turn‐On Fluorescent Chemical Sensor Based on Benzo[f]Chromen Structure for Cu ²⁺ ‐Sensitive Detection as Well as Applications

A simple Schiff base probe (E)-N'-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene) picolinohydrazide (CHH) was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H nuclear magnetic resonance spectra (¹H NMR), ¹³C nuclear magnetic resonance spectra (¹³C NMR), and high-resolution mass spectrometry (HR-MS). The probe CHH shows high sensitivity and selectivity for the recognition of Cu²⁺ in EtOH-H₂O (1:1, v/v), and exhibits an enhanced fluorescence phenomenon. The binding constant of CHH for Cu²⁺ is 2.74 × 10⁵ M⁻¹, and the binding stoichiometry of CHH and Cu²⁺ is 1:1. The fluorescence intensity of CHH (10 μM) is well linearized with the Cu²⁺ concentration at 0-10 μM, and it has a detection limit of 1.42 nM, which is lower than the detection limits of most similar probes. The reusability of the probe was evaluated by successively adding Cu²⁺ and disodium ethylenediaminetetraacetate (Na₂EDTA) to the CHH solution. The probe CHH was used to quantitatively detect Cu²⁺ in actual water samples from different water sources. The recovery rates were within an acceptable range, indicating that the probe CHH can be used for the quantitative detection of Cu²⁺ in actual water samples. Furthermore, the probe was applied for fingerprint detection, showing great potential in fingerprint detection and anti-counterfeiting.