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

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.

Conjugated Poly(fluorene-quinoxaline) for Fluorescence Imaging and Chemical Detection of Nerve Agents with Its Paper-Based Strip

“…When the polymer concentration is further increased to 1.0 × 10 −4 M, or in the film state, the emission spectra of PQ only exhibit green emission at 521 nm, originating from the quinoxaline units, in which interchain aggregation is induced with increasing local concentration of the fluorene units around the quinoxaline moiety, resulting in enhanced interchain energy transfer to quinoxaline. 54 The fluorescence changes of PQ upon concentration changes can be easily seen with the naked eye under illumination with a UV lamp (Figure 2).…”

Principal factors that determine the extension of detection range in molecular beacon aptamer/conjugated polyelectrolyte bioassays

“…A range of cationic and anionic CPEs have been synthesized for specic applications including bioimaging, bioelectronics, uorescent probes and signaling mediation. [12][13][14][15][16][17] Structural diversity allows the optical and electronic properties of CPEs to be adjustable and consequently takes advantage of their light harvesting properties. 18,19 Molecular beacons (MB) are loop-stem hairpin-type signaling probes labeled with a uorophore and a quencher at the two different termini of the stem.…”

Modulation of Charge Density of Cationic Conjugated Polyelectrolytes for Improving the FRET‐Induced Sensory Signal with Enhanced On/Off Ratio

“…Swager and Liu and Bazan emphasized the antenna effect of CPEs, where the charge carriers or excitons generated in many optical units in a polymeric backbone of CPEs move and can be collected to a low energy site (acceptor) through a π‐conjugated backbone, giving rise to amplified fluorescent signal of the acceptor. A variety of CPEs‐based optical assays have demonstrated the selective and sensitive detection for a wide range of biological materials, such as DNA, RNA, peptide, ATP, thrombin, etc …”