Exploring ICT-FRET in Aliphatic Electroactive Fluorescent Polymers and Fluorometric/Electrochemical/Impedimetric Sensing of Picric Acid in Aqueous and Organic Media

In this work, condensation polymer (CP) containing −NH₂, −CONH–, and pyrrolidinone functionalities is synthesized by Aza-Michael addition of itaconic acid/ethylene-diamine, intramolecular cyclization, and condensation polymerization. Subsequently, light-emitting aliphatic polymers (LEAPs) are synthesized using 2-acrylamido-2-methylpropane-1-sulfonic acid, N,N-dimethylacrylamide, and in situ generated tertiary amidic 2-(N-(3-(dimethylamino)-3-oxopropyl)acrylamido)-2-methylpropane-1-sulfonic acid monomers. In LEAP3, the optimum incorporation of −CONH–/–CON< and −SO₃H heteroatomic subfluorophores (HASFs) is understood employing nuclear magnetic resonance and Fourier transform infrared spectroscopies. Thereafter, dual-state emissive aliphatic conducting polymers (DEACPs) having enhanced supramolecular interactions are synthesized, encapsulating CP in LEAP3. Among DEACPs, the optimal inclusions of HASFs/CP in the DEACP4 result in dual-state emission and significant conductivity, as indicated by density functional theory (DFT) calculations, spectroscopic analyses, fluorescence enhancements, and conductivities. In DEACP4, spectral overlap of CP (acceptor) absorption with LEAP3 (donor) emission and Lippert-Mataga/Mac-Rae/Weller’s/Rettig’s polarity plots indicate Förster resonance energy transfer and intramolecular charge transfer phenomena, respectively, as examined by the excitation-dependent emissions (EDEs)/time-correlated single photon count measurements, quantum yields, and DFT calculations. In DEACP4, solid-state fluorescence is indicated through the absorption spectrum, EDEs, and fluorescence microscopic images. The selective optoelectronic responses of DEACP4 toward picric acid (PA) are indicated through multimethod sensing in aqueous and organic media. In fluorometric, electrochemical, and impedimetric sensing of PA, limits of detection are measured to be 4.9701/3.7936, 3.5253/60.0403, and 49.4312/33.9121 nM in H₂O/DMSO, respectively. The impedance and current–voltage measurements reveal the conductive properties of DEACP4 (6.83 × 10^–5/4.21 × 10^–4 S cm^–1) and PA-DEACP4 (9.53 × 10^–5/5.12 × 10^–4 S cm^–1) in the solid-state/solution.