A highly thermal and pH-stable fluorescence sensor for rapid detection of Hg2+, Fe3+, and tetracycline in aqueous solutions

Abstract

Under solvothermal conditions, one new Cd^II coordination polymer [Cd(bbimc)(ata)]_n (1)] based on carbazole ligand 3,6-bis(1H-benzo[d]imidazol-1-yl)-9-methyl-9H-carbazole (bbimc) and 2-aminoterephthalic acid ligand (H₂ata) was synthesized. Single-crystal structural determination revealed that 1 takes a two-dimensional (2D) structure with an sql topology. In particular, 1 shows good thermal (413 °C) and excellent acid/base stability in aqueous solutions with pH values of 1–13. Furthermore, 1 could selectively detect Hg²⁺, Fe³⁺, and antibiotics (TC: tetracycline; CTC: chlortetracycline) in aqueous solutions with high selectivity and sensitivity through a turn-off effect, and the detection limits are 0.246 μM (Hg²⁺), 0.342 μM (Fe³⁺), 0.208 μM (TC), and 0.307 μM (CTC). Moreover, the detection mechanism analysis by experiment and theoretical calculation revealed that competitive absorption (CA) and photoinduced electron transfer (PET) are largely responsible for sensing Fe³⁺ and the two antibiotics (TC, CTC). However, the weak interaction between Hg²⁺ and –NH₂ of the framework structure contributes to partial luminescence quenching.