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Keywords:

  • aggregation;
  • chemosensor;
  • crown ether;
  • fluorescence;
  • potassium

Abstract

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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.