Near-infrared fluorogenic switches for the detection of Hg(ii) ions: applications in real samples and living cells

A unique turn-on NIR (near infrared) fluorescent sensor 9-(2-carboxyphenyl)-6-(diethylamino)-4-(4(vinyloxy) benzylidene)-1,2,3,4-tetrahydroxanthylium (NIRM) specific for Hg2+ detection was designed and synthesized. Upon interaction with Hg2+, the probe NIRM exhibited considerable emission enhancement along with a large Stokes shift (> 110 nm). The detection limit of NIRM for Hg2+ ions was 3.2 nM, which was lower than the maximum permissible limit of Hg2+ in drinking water recommended by the United States Environmental Protection Agency (USEPA). Consequently, the novel fluorescent sensor NIRM could be used for the recognition of Hg2+ in water samples as well as in living cells.