Highly Sensitive Detection of Nitro Compounds Using a Fluorescent Copolymer-Based FRET System

We report here that optically resonant donor copolymers are used to amplify the sensitivity of an electron-rich fluorescent copolymer toward electron-deficient nitroaromatic compounds (NACs). In a polymer–polymer system, we found that ultrafast Förster resonance energy transfer (FRET) enhances the sensitivity of the primeval fluorescent polymer sensor by 6-fold approximately toward the conventional NACs like 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and 2,4,6-trinitrophenol (TNP). The present article reports an optical sensor for sensitive detection of NACs by using a fluorescent probe based on FRET phenomena between P[DMA-co-(Boc-Trp-EMA)] (RP) bearing a tryptophan derivative as a donor and P[MMA-co-(Ala-HEMA)-co-(Dansyl-Ala-HEMA)] (DCP) bearing a dansyl derivative in the side chain as an acceptor. This elegant method thus paves the way to achieving a sensitivity <1 μM with a very high value of Stern–Volmer constant. Further, UV–vis absorbance spectroscopy, cyclic voltammetry, ultrafast transient absorption spectroscopy, time-resolved, and steady-state fluorescence spectroscopy were performed to establish the quenching mechanism comprehensively. We also carried out a contact mode analysis in solid-state phase through strip tests for visual detection of NACs in ambient conditions. This unique and quality performance of our sensing probe makes it convenient for naked-eye detection and therefore gives an escalation for stand-alone sensors for NACs, particularly reinforcement in the field of analytical and forensic sciences.