A highly sensitive benzimidazole-based chemosensor for the colorimetric detection of Fe(II) and Fe(III) and the fluorometric detection of Zn(II) in aqueous media

A new dual chemosensor 1 for the colorimetric detection of Fe2+/(3+) and the fluorometric detection of Zn2+ has been developed and characterized. The sensor 1 has proven to be highly selective to Fe2+/(3+) with a color change from colorless to dark green in a near-perfect aqueous solution. 1 had low detection limits (1.21 mu M for Fe3+ and 1.18 mu M for Fe2+), which are lower than the World Health Organization guideline (5.36 mu M) for drinking water. Moreover, 1 showed a selective detecting ability for Zn2+ by 'OFF-ON' fluorescent response in aqueous solution. The detection limit (1.05 mu M) of 1 for Zn2+ was much lower than World Health Organization guideline (76 mu M) for drinking water. Interestingly, it could be recycled simply through treatment with an appropriate reagent such as EDTA (ethylenediaminetetraacetic acid). The sensing mechanism of 1 for Zn2+ was explained by the theoretical calculations. In particular, the sensor 1 could be used to quantify iron and zinc in water samples.