A novel FRET-based fluorescent chemosensor of β-cyclodextrin derivative for TNT detection in aqueous solution

A new fluorescent sensor based on single water-soluble β-cyclodextrin (β-CD) molecule as the support carrier of donor and acceptor complex was designed, and used for TNT detection by fluorescence resonance energy transfer (FRET). In this sensing platform, per-6-amino-β-CD (per-6-NH2-β-CD) was used as the detection vehicle. The probe dye of fluorescein 5(6)-isothiocyanate (FITC) was covalently linked onto the per-6-NH2-β-CD rim with the grafting molar ratio of 1:1, the residual amino groups of per-6-NH2-β-CD can adsorb TNT molecules by forming Meisenheimer complex (TNT–amine complex) with TNT. The absorbtion spectrum of this complex has a spectral overlapping with the emission of FITC in aqueous solution, so it can strongly suppress the fluorescence emission of the adjacent FITC through FRET on β-CD vehicle. This FRET-based fluorescent sensing technique provides a facile, ultrasensitive and selective detection method for TNT molecule. The observed linear fluorescence intensity change could allow the quantitative detection TNT with the detection limit of 20 nM in water.