A colorimetric and fluorescence “turn-on” sensor for Fe(III) ion based on imidazole-functionalized polydiacetylene

Abstract

Stimulus-responsive colorimetric conjugated polymers have received significant attention in the field of chemosensors. Owing to a brilliant blue-to-red color transition and a fluorescence turn-on feature that occurs in response to physical and chemical stimuli, polydiacetylenes (PDAs) have been extensively used as sensor matrices. Herein, we describe a PDA based colorimetric and fluorescence turn on sensor for detection of Fe(III) ion. In the effort, we showed that an imidazole-containing PDA (PDA-Im) displays a blue-to-red color change along with turn on of red fluorescence upon exposure to Fe(III) ion. The PDA-Im sensor system has wide linear ranges, and a respective limits of detection (LOD) of 9 µM for Fe(III) ion. In addition, the new PDA based sensor can be utilized to detect Fe(III) ions in human serum. FT-IR spectroscopic study revealed both amide and imidazole moieties are involved in the metal binding event. The Fe(III) ion binding transfers mechanical energy to the polymer backbone and results in the twisting of the conjugated ene-yne structures, leading to the blue-shift of the absorption maximum.