Poly-tryptophan/carbazole based FRET-system for sensitive detection of nitroaromatic explosives.

Abstract

Sensitive detection of nitroaromatic explosives, a hot topic of worldwide concern, is greatly asked for, due to the adverse effect on ecosystems and human health originating from the excessive use and inadequate management. Here, we report the development of a Förster Resonance Energy Transfer (FRET) based sensor system for highly sensitive detection of nitro-aromatic compounds (NACs). The sensor system is composed of a copolymer poly[(N,N-dimethylacrylamide)-co-(Boc-Trp-EMA)] (RP) bearing tryptophan derivative in the side chain as donor and carbazole (CZ) as an acceptor. Primarily, the fluorescence of RP copolymer is quenched by non-radiative energy transfer to CZ which only happens once the two molecules are within Förster critical distance. The efficiency and rate of energy transfer process were calculated for this deliberated FRET system. This FRET pair exhibited a specific fluorescence response to NACs such as 2,4,6-trinitrophenol (TNP), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) with 6.4, 5.9 and 1.4 μM limit of detections (LODs), respectively. Interestingly, the order of sensitivities of the FRET pair to NACs was very high. The sensing process occurs through a static and dynamic quenching pathway, confirmed by Stern−Volmer analysis of steady-state and time-resolved fluorescence as well as UV–Vis Spectroscopy.