A highly sensitive and selective colorimetric/fluorescent probe for the detection of Ag plus based on a croconium dye

A novel colorimetric and fluorescent probe, 2,5-bis[3-ethyl-2-methylbenzothiazole]-croconine (BBC) has been synthesized and characterized. The BBC dye can effectively recognize Ag+ in the presence of potentially competitive metal ions (Co2+, Na+, Cd2+, K+, Mg2+, Zn2+, Ca2+, Ba2+, Ni2+, Cr3+, Al3+), which exhibited visible color change and fluorescence spectra behaviors. The Benesi-Hildebrand plot accurately showed the binding constant of BBC-Ag+. Correspondingly, the 1:1 stoichiometric structure of BBC and Ag+ was evaluated by using Job's plot. Moreover, the complex mechanism of BBC toward Ag+ were also investigated by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR). The results indicated that BBC could be used as a high effective colorimetric and fluorescent sensor to identify Ag+.