Olefin-linked conjugated fluorescent oligomer: Design, synthesis, photophysical studies and detection of nitroaromatic compounds (NACs) in aqueous media

Abstract

The development of novel fluorescent polymers has attracted significant attention owing to their potential applications in energy and environmental sciences. This study reports novel oligomer (TRZBT) synthesis via Wittig-Horner reaction using bithiophene aldehyde and triazine triethyl phosphite. The resulting oligomer possesses large porous morphology, which was confirmed using SEM analysis. Further, the chemical structure of TRZBT was confirmed by FT-IR, NMR, and GPC studies. The triazine acceptor (A) unit linked with bithiophene donor (D) unit through olefin π-conjugation resulted in a Donor-π-Acceptor (D-π-A) type oligomer. Detailed studies of the solvent-dependent photophysical properties of TRZBT were performed. Due to the alternate d-A structure of oligomer, enhanced intramolecular charge transfer (ICT) properties between D and A moiety was observed. Further, TRZBT in THF and THF: H2O (10:90) system effectively detected nitro-explosives in aqueous media, which exhibited high sensitivity, selectivity, and quick response via fluorescence quenching. TRZBT showed a higher quenching constant (Ksv) value of 4.91 × 105 M−1 towards picric acid as compared with other nitroaromatics. Significantly, the detection limit of 1.58 nM in a 100 % aqueous medium confirms that the synthesized material can detect even trace levels of the analyte.