A sensitive and selective mercury(II) sensor based on amplified fluorescence quenching in a conjugated polyelectrolyte/spiro-cyclic rhodamine system.

A novel fluorescence-based sensor for mercury(II) ion is described consisting of a water-soluble, anionic-conjugated polyelectrolyte (CPE) and spiro-cyclic rhodamine derivative (1). A solution containing the CPE (0.1 × 10(-6) M repeat unit concentration) and 1 (1 × 10(-6) M concentration) in aqueous solution exhibits a sensitive and selective turn-off fluorescence response to Hg(II). The Stern-Volmer quenching constant for quenching of the fluorescence of the system by Hg(II) is ≈1.5 × 10(7) M(-1) , and Hg(II) can be sensed with a detection limit <10 × 10(-9) M. A mechanism for the sensor response is proposed and it consists of efficient and selective complex formation between 1 and Hg(II), along with a very high association between the 1-Hg(II) complex and the anionic CPE.