Highly Sensitive and Selective Turn-on Fluorescent Probe for Hg2+ Based on Rhodamine 6G-Thiourea Conjugate.

An easily available novel fluorescent probe based on rhodamine 6G-thiourea conjugate (RGTU) has been synthesized. Upon mixed with Hg2+ in CH3CN-H2O (1:9, v/v), the dramatic enhancement of fluorescence intensity as well as the color change of the solution were observed. The presence of common coexisting alkali, alkaline earth, and transition metal ions showed small or no interference with the detection of Hg2+. The Job's plot and 1H NMR spectra indicated that Hg2+ induced spirolactam open to form 1:1 complex between RGTU and Hg2+.