A Lawsone-DAMN based cotorimetric chemosensor for rapid naked-eye detection of mercury(II)

We designed and synthesized a new calorimetric chemosensor L based on the combination of 3-hydroxy-1,4-dioxo-1,4-dihydronaphthalene-2-carbaldehyde 2 and diaminomaleonitrile 3 moieties. The recognition abilities of the probe with a range of metal ions were evaluated and their optical properties have been systematically investigated. Chemosensor L exhibited well defined naked-eye visible color changes from yellow to pink for Hg2+ detection in acetonitrile. Other ions, including Na+, Ca2+, CO2+, Ni2+, Cu2+, Mn2+, Sn2+, Hg2+, Fe3+, and Th4+, had a negligible influence on the probe behaviour. The limit of detection (LOD) was 1.1 x 10(-7) M using the UV-vis changes. For the selective recognition of Hg2+ ions, it forms a 1:1 stoichiometric complex involving naphthoquinone hydroxyl and diaminomaleonitrile nitrogen functionalities. The complex formation was proposed to be in a 1:1 ratio based on Job's plot, H-1 NMR titrations, ESI-mass spectrometry analysis and DFT calculations. Test strips based on L were fabricated, which could act as convenient and efficient Hg2+ test kits. The results consistently indicated that Lawsone-DAMN is an ideal sensor, which can be utilised to monitor Hg2+ in solution over a wide pH range.