Highly Sensitive Fluorescent Probe for Selective Detection of Hg²⁺

<div><p>A selective and sensitive chromogenic and fluorogenic dual signal responding fluoride-sensor (L), comprising the well-known rhodamine 6G fluorophore and 2,2′-bipyridine was prepared and spectroscopically characterized. After mercury ion was added to the CH₃CN solution of L, a color change from colorless to pink-red, which indicated that the sensor can serve as a sensitive “naked-eye” indicator for mercury ion. The high emission selectivity is due to the formation of L-Hg²⁺ 1:2 complex leads to spirocycle opening of L.</p>