A Coordination Polymer for the Fluorescence Turn-On Sensing of Saccharin, 2-Thiazolidinethione-4-carboxylic Acid, and Periodate

A luminescent 1D coordination polymer (CP) [Zn₂L₂(H₂O)₄]·H₂O (1, H₂L = 1-(4-carboxyphenyl)-1H-pyrazole-3-carboxylic acid) was prepared by a solvothermal method. 1 shows excellent fluorescence properties and has an obvious fluorescence "turn-on" phenomenon for saccharin (SAC), 2-thiazolidinethione-4-carboxylic acid (TTCA), and periodate (IO₄^-). Between 0 and 60 μM concentration range of SAC, the fluorescence enhancement efficiency (K_EC) of 1 reaches 1.00 × 10⁵ M^-1 with the limit of detection (LOD) of 90 nM. 1 is the first CP-based sensing material for SAC detection. For TTCA detection, the K_EC is 2.73 × 10⁵ M^-1 at the 25-80 μM concentration range, and the LOD is 33 nM, the lowest LOD among the sensors that detect TTCA at present. For IO₄^- ion detection, when the IO₄^- ion concentration ranges from 0 to 10 μM, the K_EC is 2.34 × 10⁵ M^-1 and the LOD is as low as 39 nM. In order to better understand the sensing phenomenon, we also discuss in detail the sensing mechanisms for SAC, TTCA, and IO₄^- ions.