Nanofibrous films decorated with phosphorescent iridium(iii) complexes containing Ir–S–C–S structures for selective detection of Cu2+ ions in solution

Abstract

Copper ions (Cu²⁺) play an indispensable role in both the human body and eco-environment, so it is crucial to create simple, highly sensitive and selective sensors to recognize Cu²⁺ ions. In this work, three efficient iridium(III) complexes, [(L₁)₂Ir(Czdtc)] (Ir1, L₁ = 6-phenylnicotinaldehyde), [(L₂)₂Ir(Czdtc)] (Ir2, L₂ = 6-(4-(trifluoromethyl)phenyl)nicotinaldehyde) and [(L₃)₂Ir(Czdtc)] (Ir3, L₃ = 6-(4-methoxyphenyl)nicotinaldehyde) comprising a four-membered Ir–S–C–S ring backbone with 9H-carbazole-9-carbodithioate (Czdtc) as ancillary ligands, were synthesized within 10 minutes at room temperature, and developed as efficient chemical sensors to detect Cu²⁺ ions. Ir1–Ir3 exhibited broad emission bands peaking between 575 and 593 nm with PLQY in the range of 0.34–0.70 and lifetimes ranging from 1.3 to 1.8 μs. In acetonitrile solution, they showed a sensitive response to Cu²⁺ ions with a low detection limit on the order of 10⁻⁷ M with a stoichiometric ratio of 1 : 1, and distinct colorimetric changes (from orange-red to greenish-yellow) were observed by the naked eye. Nanofibrous films decorated with these complexes fabricated using the electrospinning technology could realize on-site detection of Cu²⁺ ions, based on an obvious contrasting luminescence color different from the background under a 365 nm UV lamp. Nanofibrous films decorated with the fast synthesized Ir1–Ir3 could be used as solid-phase sensing devices with low-cost, high efficiency and portability, providing a promising prospect for the detection of Cu²⁺ ions in the environment.