This article describes a novel ion-pair recognition mode of a molecular probe (C-1) bearing chalcone moiety. C-1 can bind to metal nitrates selectively (metal = Zn2+, Ni2+, Co2+, Cd2+) with remarkable color change from yellow to purple. The mechanism was investigated via experimental and theoretical approaches. The results show that C-1 coordinate with metal ions by stoichiometric ratio 2:1, the nitrate anion binds with metal ion via electrostatic interaction, and binds with ligand via supramolecular interactions. Furthermore, the selected two-component sensor, C-1/Ni(NO3)(2), can detect water content in acetone, acetonitrile, ethanol and isopropanol with low detection limit by both colorimetric and fluorescence turn-on approach. The sensor has favorable linear relationships with water content within the range 0-10% in the above four solvents, and the detection limit in acetone, acetonitrile, ethanol and iso-propanol is 0.20%, 0.38%, 0.24% and 0.09%, respectively, showing great potential for water content monitoring. (C) 2018 Elsevier B.V. All rights reserved.