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 Hg2+. In the presence of Hg2+, the resulting red-orange fluorescence (under UV light) and naked eye red color of IDS are supposed to be used for quantitative and qualitative measurement of Hg2+. Further fluorescent titration and analysis demonstrate that RS can selectively detect Hg2+ 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 x 10(5) M-1. More importantly, the resultant complex (RSHg) of RS and Hg2+ has also been successfully applied to detect limited water content in acetonitrile solution. (C) 2020 Published by Elsevier B.V.