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A pyrene based turn-on fluorescent polymeric probe was developed for the tunable detection of nerve agent mimics. Glycidyl methacrylate (GMA) and dimethyl­acrylamide (DMA) were copolymerized by reversible addition–fragmentation chain transfer (RAFT) polymerization to yield poly-(glycidyl methacrylate-co-dimethyl­acrylamide) [p­(GMA-co-DMA)]­(P1). The subsequent reaction of the secondary amine of 2-(2-((pyren-1-ylmethyl)-amino)-ethoxy)-ethanol with the epoxide unit of P1 yielded P2, which can detect diethyl cyanophosphate (DCNP), a nerve agent mimic, very efficiently by the turn-on fluorescence technique, induced by DCNP promoted intramolecular N-alkylation in both the solution and vapor phase. The lowest detection limit of P2 to DCNP was obtained as 0.1 mM, which is close to the toxicity limit of Tabun. Moreover, the detection of DCNP was successfully controlled by altering the purging of CO2/N2 gases or tuning the pH of the solution. P2 showed an efficient ON/OFF reversible fluorescence response toward CO2 and N2 gases, further helping tunable ON/OFF sensing of DCNP. The CO2-tunable detection of DCNP was further correlated to the pH-dependent control of detection sensitivity. At low pH, no change in the fluorescence enhancement was observed upon exposure to DCNP, whereas the fluorescence intensity of the probe remarkably increased at high pH. Thus, these CO2/pH controllable detection properties can offer new insights into the design of new stimuli-responsive polymeric probes with fluorescence turn-on detection of nerve agent mimics.

Thin-film probes have been developed for the reversible detection and separation of picric acid (PA) with extreme sensitivity in aqueous media. The free radical copolymerization of dimethylacrylamide (DMA), benzophenone acrylamide (BPAM), and glycidyl methacrylate (GMA) with a feed ratio of 95:1:4 yielded [p(DMA-co-BPAM-co-GMA)] (P1). P1 was transformed to the final polymeric probe, P2, by a subsequent ring-opening reaction between N-(pyren-1-yl-methyl)propan-1-amine (Py-PA) with the epoxide unit of P1. P2 exhibited rapid and selective sensing properties toward PA in aqueous media via turn-off fluorescence emission. The detection sensitivity was tuned precisely by varying the pH of the solution. After the immobilization of P2 on a quartz slide by spin-coating, followed by exposure to UV light, the resulting film exhibited an attogram-level detection limit toward PA. The photoinduced electron transfer together with an energy-transfer process between PA and the pyrene units of P2 were maximized by the strong π−π stacking of pyrene units of P2, which, in turn, induced rapid exciton energy diffusion. Furthermore, the separation of PA from the mixture of the various nitroaromatic compounds by the P2 film was achieved. Whereas the detection process of PA was reversible and repeatable over multiple cycles, the P2 film could be recycled.

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Thin polymeric films were developed for the vapor-phase sequential colorimetric detection of a nerve agent mimic and ammonia with high sensitivity. N-(4-Benzoylphenyl)acrylamide (BPAm), N,N-dimethylacrylamide (DMA), and (E)-2-(methyl(4-(pyridine-4yldiazenyl)phenyl)amino)ethyl acrylate (MPDEA, M1) were copolymerized via free radical polymerization (FRP) to yield p(BPAm-co-DMA-co-MPDEA), hereafter referred to as P1. P1 exhibits selective sensing properties toward diethyl chlorophosphate (DCP), a nerve agent mimic, in pure aqueous media. Upon the addition of DCP, the pyridine groups of P1 were quaternized with DCP, accompanied by a color change from yellow to pink due to the enhancement of the intramolecular charge transfer (ICT) effect. In situ generated quaternized P1, hereafter referred to as P2, after DCP sensing was used to selectively detect ammonia via dequaternization in an aqueous medium. Ammonia detection was indicated by a color change in the solution from pink back to yellow. A surface-immobilized P1 film was prepared and employed for the vapor-phase detection of DCP, demonstrating that an amount of as low as 2 ppm was detectable. Ammonia vapor was also successfully detected by the P2 film via the ammoniatriggered removal of the quaternized phosphates. Alternating exposure of the film to DCP and ammonia resulted in the corresponding color changes, thereby demonstrating the reversibility of the system. The reusability of the polymeric film for detecting DCP and ammonia in the vapor phase was confirmed by performing four sequential colorimetric detection cycles.