An anionic layered europium(iii) coordination polymer for solvent-dependent selective luminescence sensing of Fe3+ and Cu2+ ions and latent fingerprint detection

Abstract

An anionic layered coordination polymer [Eu(BTEC)_0.5(HCOO)(H₂O)₂] (1) has been successfully synthesized via a solvothermal method (H₄BTEC = 1,2,4,5-benzenetetracarboxylic acid, HCOOH = formic acid). Compound 1 possesses two-dimensional layers, which further generate a three-dimensional supramolecular network by hydrogen bonds existing between carboxylic oxygen, formate anion and H₂O molecules of two adjacent layers. Interestingly, 1 shows high luminescence quenching efficiency upon addition of Fe³⁺ ions when it was dispersed in water even in the presence of interfering ions such as Na⁺, Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Zn²⁺ and Al³⁺. When dispersed in DMSO solution, 1 displays excellent sensitivity and selectivity towards both Cu²⁺ and Fe³⁺ ions. Possible quenching mechanisms for detection of Fe³⁺ and Cu²⁺ ions were carefully investigated and proposed based on a dynamic quenching process, static quenching process and fluorescence inner filter effect. Moreover, the as-prepared particles can be used for visualizing latent fingerprints on various substrates. These results indicate that a Eu(III)-based coordination polymer has great potential in detection and security application.