A selective fluorescent resonance energy transfer quenching and resonance light scattering enhancement dual-recognition probe for 2,4,6-trinitrotoluene

Fluorescein isothiocyanate (FITC) conjugated to polyethylenimine (PEI) (FITC&PEI) was synthesized and characterized. The nitrogen-containing organic groups played a key role in sensing nitroaromatic compounds that can bind 2,4,6-trinitrotoluene (TNT) to form TNT anions through an acid–base pairing interaction and FITC dye conjugation. The formation of TNT anions efficiently quenched the emission of FITC dye at 516   nm by fluorescent resonance energy transfer and induced the enhancement of a resonance light scattering (RLS) signal. A novel, dual-channel chemosensory FITC&PEI probe was thus constructed. Meanwhile, the FITC&PEI probe also exhibited highly selective fluorescence and RLS responses for TNT over other nitroaromatic compounds. Very good linearity was observed within the ranges of 3.0–150   nM TNT (detection limit down to 0.5   nM and RSD of 5.8%, n   =   7) for fluorescence and 1.0–150   nM TNT (detection limit down to 0.2   nM and RSD of 8.4%, n   =   7) for RLS. The proposed methods were well-suited for detecting and distinguishing trace amounts of TNT in aqueous solution.