A selective colorimetric fluorescent chemosensor for Hg²⁺ in aqueous medium and in the solid state

A simple colorimetric and turn-on fluorescence receptor RN (Rhodamine-based derivative) was prepared and its cation-sensing properties were investigated. Receptor RN displayed a selective sensing of Hg²⁺ and showed an obvious colorimetric changing in aqueous solution (from colorless to pink color) and in the solid state (from red to pink color), respectively. The association constant of RN-Hg²⁺ complex was calculated to be 8.25×10⁹ M⁻¹, and the detection limit for Hg²⁺ was found to be 27 ppb.