Ratiometric Fluorescent Ion Detection in Water with High Sensitivity via Aggregation-Mediated Fluorescence Resonance Energy Transfer Using a Conjugated Polyelectrolyte as an Optical Platform

Authors

  • Van Sang Le,

    1. Department of Nanofusion Technology, Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea
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  • Boram Kim,

    1. Department of Nanofusion Technology, Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea
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  • Wonho Lee,

    1. Department of Nanofusion Technology, Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea
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  • Ji-Eun Jeong,

    1. Department of Nanofusion Technology, Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea
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  • Renqiang Yang,

    1. Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong Province 266101, P. R. China
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  • Han Young Woo

    Corresponding author
    1. Department of Nanofusion Technology, Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea
    • Department of Nanofusion Technology, Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea.
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Abstract

A cationic conjugated polyelectrolyte was designed and synthesized based on poly(fluorene-co-phenylene) containing 5 mol% benzothiadiazole (BT) as a low energy trap and 15-crown-5 as a recognizing group for potassium ions. A potassium ion can form a sandwich-type 2:1 Lewis acid-based complex with 15-crown-5, to cause the intermolecular aggregation of polymers. This facilitates inter-chain fluorescence resonance energy transfer (FRET) to a low-energy BT segment, resulting in fluorescent signal amplification, even at dilute analyte concentrations. Highly sensitive and selective detection of K+ ions was demonstrated in water. The linear response of ratiometric fluorescent signal as a function of [K+] allows K+ quantification in a range of nanomolar concentrations with a detection limit of ≈0.7 × 10−9 M.

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