A Novel Pyrene-Based Fluorescent Probe for the Detection of Cu2+

A novel fluorescent probe (PYB) for selective and sensitive detection of Cu2+ ions was rationally designed and synthesized via a multi-step organic reaction using pyrene as the fluorophore and salicylaldehyde-diethylenetriamine Schiff base as the recognition moiety. The structural characterization of PYB was confirmed by 1H NMR, 13C NMR, and high-resolution mass spectrometry (HRMS). Photophysical properties investigation revealed that the probe exhibited strong fluorescence emission at 362 nm in DMF/HEPES-NaOH buffer solution (v:v = 1:1, pH 7.4), which underwent a significant fluorescence quenching response (quenching efficiency up to 77%) upon the addition of Cu2+, attributed to the formation of a 1:1 PYB-Cu2+ complex (binding constant K = 799.65 M−1). The probe showed excellent selectivity for Cu2+ over other common metal ions (Ba2+, Na+, Mg2+, Zn2+, Cd2+, Ca2+, Mn2+, Pb2+, Hg2+, Fe3+, Co2+), with a low detection limit of 8.35 × 10−7 M, which is well below the maximum allowable concentration of Cu2+ in drinking water specified by the World Health Organization (WHO). Furthermore, a portable fluorescent test strip based on PYB was successfully fabricated, enabling rapid and visual detection of Cu2+ under UV light. Fluorescence imaging experiments in living HepG2 cells demonstrated that PYB could penetrate cell membranes efficiently and realize the intracellular detection of exogenous Cu2+. These results collectively indicate that PYB holds great potential as a practical tool for Cu2+ detection in environmental monitoring, food safety, and biological systems.