Ethyl 2-cyano-3-(naphthalene-1-yl) acrylate (ECNA): a sensitive, selective fluorescence ‘turn-off’ chemodosimeteric probe for the detection of poisonous hydrazine hydrate and its vapour†

The broad spectrum of applications of so-called ‘devil's venom’ (hydrazine hydrate) has resulted in its entry into the soil and water, but it is a pollutant to the ecosystem and human health. Thus, capable monitoring techniques for hydrazine hydrate (Hz) are a hot research topic in environmental remediation. Small-molecular-probe-based fluorescence detection methods are usually established due to their simplicity and sensitivity. In the present manuscript, we demonstrate that ethyl-2-cyano-3-(naphthalene-1-yl)acrylate (ECNA) is an economical, easy-to-synthesize/commercially available chemodosimeteric probe for the effective detection of toxic Hz via absorption, emission spectroscopy and fluorescence photography methods. The detection mechanism has been confirmed by Fourier transform infra-red (FTIR), time-dependant density functional theory (TD-DFT), and mass spectroscopy (MS) studies. Paper strip, spray analysis and spot-test-based approaches have been employed to detect Hz. In addition, the vapour of aqueous Hz has been detected using ECNA-coated thin-layer chromatography (TLC) plates and paper strips. The ECNA powder exhibits a drastic colour change in response to Hz, and reveals a fluorescence ‘turn-off’ response. The bright fluorescence of ECNA is quenched ∼14 fold with a ∼20 nm blue shift in the presence of ∼1.6 μM of Hz. 1 : 1 ECNA : Hz binding with a K_b value of 3.35 μM⁻¹, a superior limit of detection (LOD) of 3.077 nM, and a favourable pH range were obtained. ECNA is a quick, real-time/on-site, easy-to-handle, selective, sensitive and cost-effective fluorescent probe for the proficient detection of Hz by the naked eye.