Synthesis and sensing behavior of a new multichannel sensor based on thiazolyl ferrocene-rhodamine for Hg2+ detection

Abstract This work presented a multichannel sensor named RB-FC for Hg2+ detection, which was simply prepared by reaction of rhodamine B hydrazide with 2-amino-4-ferrocenylthiazole. Its structure was confirmed by FT-IR, NMR, MS and X-ray diffraction. The addition of Hg2+ destroyed the spirolactam ring, resulting in enhanced absorbance recorded by UV–visible and fluorescence spectroscopy, in addition to color change from colorless to pink observed by the naked eye. Moreover, the molecular configuration change of RB-FC caused by coordination effect of Hg2+ to the sensor influenced the the electron density in ferrocene group, therefore the electrochemical characteristic of Hg(II)-RB-FC was different from RB-FC. Importantly, the off–on mechanism, namely the opening of the rhodamine spirolactam induced by coordination of Hg2+ to O and S atoms of RB-FC with a 1:1 stoichiometric ratio, was proposed to account for fluorescence changes. The sensor of RB-FC in aqueous medium showed a low detection limit and a rapid response to Hg2+. The developed sensor can conveniently detect mercury ions with multichannel for colorimetry, fluorescence and electrochemistry.