Colorimetric and fluorescent probe for highly selective and sensitive recognition of Cu2+ and Fe3+ based on asymmetric squaraine dye

Abstract

An asymmetric squaraine, (Z)-2-((3-ethyl-1,1-dimethyl-1,3-dihydro-2H-benzo -[e]indol-2-ylidene)methyl)-4-((5-fluoro-3,3-dimethyl-3H-indol-1-ium-2-yl)methylene)-3-oxocyclobut-1-en-1-olate (FSQ) with high sensitivity and selectivity for detecting Cu2+ and Fe3+ has been synthesized. Compared with other tested metal cations (Hg2+, Ni2+, Mg2+, Pb2+, Al3+, Ag+, K+, Cr3+, Co2+, Ca2+,Ba2+,Na+, Zn2+, Cd2+), the colorimetric and fluorescence behaviors of the FSQ chemical sensors are significantly different in the presence of Cu2+and Fe3+. When Cu2+ was added, the color of FSQ solution turned from blue to purple, and the absorbance and fluorescence intensity decreased obviously. When Fe3+ was added, the color of FSQ solution turned from blue to yellow. The intensity of the maximum absorption peak at 657 nm decreased and the fluorescence intensity increased. Moreover, the binding mode of FSQ-Cu2+ and FSQ-Fe3+ was supporting by Job’s plot, FT-IR and 1H NMR. Therefore, the FSQ chemosensor maybe provide colorimetric and fluorescent methods for selective and sensitive detection of Cu2+ and Fe3+.