A "turn-on" fluorescent chemosensor with excellent selectivity and satisfactory sensitivity on Hg(2+) detection in 100% water media has been established employing a carbohydrate based Ferrier carbocyclization reaction. The probe has also presented satisfactory results for the imaging of Hg(2+) ions in cells and organisms.

A ''turn-on'' fluorescence probe for Cu 2+ detection has been reported according to a Cu 2+ triggered spirolactam ring-opening reaction. The probe is a double-responsive fluorescent and colorimetric Cu 2+ -specific sensor in aqueous solution containing 20% of acetonitrile with high selectivity and excellent sensitivity (limit of detection is 12 mg L À1 ). Furthermore, the significant color changes visible to the naked eye at the concentration of 3 mM (ca. 0.20 mg L À1 ) are about ten times lower than the WHO (World Health Organization) recommended level (2.0 mg L À1) for Cu 2+ ions in drinking water.

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