Rapid detection of mercury (II) ions and water content by a new rhodamine B-based fluorescent chemosensor

A rhodamine B-based sensor ( RS ) was designed and synthesized by a combination of the spirolacton rhodamine B (fluorophore) and multidentate chelates (ionophore) with high affinity towards Hg 2+ . In the presence of Hg 2+ , the resulting red-orange fluorescence (under UV light) and naked eye red color of RS are supposed to be used for quantitative and qualitative measurement of Hg 2+ . Further fluorescent titration and analysis demonstrate that RS can selectively detect Hg 2+ within 1 s with a low limit of detection (LOD) of 16 nM in acetonitrile media, meanwhile, the association constant (K a ) was calculated to be 0.32 × 10 5  M −1 . More importantly, the resultant complex ( RSHg ) of RS and Hg 2+ has also been successfully applied to detect limited water content in acetonitrile solution.