Synthesis of a dual-response signal sensor and naked-eye recognition of hypochlorite in real water samples

Abstract

An innovative dual-modal colorimetric and fluorometric probe MDXM is synthesized based on the dihydro-1H-xanthene motif via Knoevenagel reaction. The incorporation of a malononitrile group into the dihydro-1H-xanthene motif via a double bond results in an extensive macroconjugated π-system, which endows MDXM with a pronounced molar absorptivity and effectively quenches the intramolecular charge transfer (ICT) effect. Upon exposure to hypochlorite, the C = C bond in MDXM undergoes cleavage, resulting in the formation of an aldehyde group. This process restores the ICT effect and manifests as a clear fluorescent ''turn-on'' signal at 530 nm, with a remarkably linear response across the ClO− concentration range of 0–60 μM. The probe achieves a notably low detection limit of 7.14 nM, reflecting its exceptional sensitivity. In the presence of 15 common metal ions and oxidizing agents, MDXM can specifically identify hypochlorite with excellent anti-interference ability. The response mechanism of MDXM to hypochlorite was confirmed through Nuclear Magnetic Resonance (NMR) spectroscopy and computational Density Functional Theory (DFT) calculations. The practical applicability of MDXM is underscored by its successful implementation in analyzing hypochlorite in 5 varied real water samples. This showcases MDXM's promise for environmental and analytical chemistry, providing a robust tool for hypochlorite detection in diverse settings.