Fast and selective detection of Cu²⁺ by a novel chromone-based colorimetric chemosensor

A novel colorimetric chemosensor, DCMB (2,4-dichloro-N′-((4-oxo-4H-chromen-3-yl) methylene) benzohydrazide), was designed to detect Cu²⁺. DCMB exhibited a rapid and highly selective colorimetric response to Cu²⁺, changing from colorless to yellowish green with negligible interference from other metal ions. The limit of detection of DCMB for Cu²⁺ was 1.19 μM, and the chemosensor remained effective for Cu²⁺ detection across pH 4–10. These features showed the potential of DCMB as a convenient indicator for Cu²⁺ monitoring. In environmental water samples such as tap, drinking, stream, and seawater, DCMB reliably recognized Cu²⁺ with good recovery. Additionally, DCMB-coated test strips enabled on-site detection of Cu²⁺, and a DCMB-based smartphone application offered a portable and practical quantification of Cu²⁺. The detection mechanism of DCMB for Cu²⁺ was proposed to be a 1:1 binding reaction by Job plot, ESI-MS, ¹H NMR titration, and DFT calculations.