A Terbium Ion-Based Dual-Ligand Fluorescent Probe for Highly Selective and Sensitive Detection of Cu²⁺ Ions

In this study, a fluorescent probe (GMP-Tb-SSA) utilizing lanthanide coordination polymer nanoparticles, GMP-Tb, as a sensing platform, and 5-sulfosalicylic acid (SSA) as a cofactor ligand was proposed for the detection of copper ions (Cu²⁺). GMP-Tb was synthesized by the self-assembly of guanine monophosphate (GMP) and terbium ion (Tb³⁺), and SSA was introduced as a sensitizer into the GMP-Tb network. Cu²⁺ could efficiently inhibit the electron transfer from the ligand GMP to the central ion, Tb³⁺, leading to a significant quench of fluorescence of Tb³⁺. The method is highly selective with a linear range of 0 to 21 µM and a detection limit of 300 nM. It is not interfered by metal ions, amino acids, and other species, and can be successfully applied to the detection of Cu²⁺ in real water samples.