A benzimidazole-based ratiometric fluorescent sensor for Cr3+ and Fe3+ in aqueous solution

A novel ratiometric fluorescent sensor bearing two benzimidazole groups has been synthesized. The sensor showed a ratiometric fluorescence response with an enhancement of the ratios of emission intensities at 443 and 378 nm from 0.17 to 3.21 for Cr3+. The ratios of emission intensities at 443 and 380 nm were enhanced from 0.40 to 2.09 for Fe3+. Fe3+ revealed significant adsorption in the UV–vis region, which can be used to discriminate Cr3+ and Fe3+. Detection limits of the method for Cr3+ and Fe3+ were 25 μM and 2 μM, respectively. In addition, the sensor showed good selectivity to Cr3+ and Fe3+ over other metal ions.