DFT studies of fluorescence probe for selective detection of Zn2+ in the presence of Ca2+, Mg2+, Cu2+, and Hg2+ ions

Fluorescence sensors are an important analytical tool for monitoring biologically relevant analytes. For instance, an anthracene based sensor was designed and characterized for the detection of Zn2+ in our previous studies. However, the selective detection of such a sensor in the presence of other metal cations is a critically important factor for its practical application. In this work, we employed density functional theory calculations to study the selectivity of this anthracene sensor in the detection of Zn2+ in the presence of Ca2+, Mg2+, Cu2+, and Hg2+. DFT results indicate that the selectivity of the sensor on Zn2+ detection over the cations Ca2+, Mg2+, and Hg2+ due to the binding selectivity as Zn2+ binds favorably to the sensor while Ca2+, Mg2+, and Hg2+ are no binding. Although Cu2+ binds to the sensor stronger than Zn2+, the chelated sensor by Cu2+ reduces the UV-Vis absorption at the free sensor wavelength by 10 times and the fluorescence pathway is also enhanced by the chelation, thus resulting response selectivity of Zn2+ over Cu2+ . Therefore, the present DFT study shows that the sensor selectivity on Zn 2+ detection in the presence of Ca2+, Mg2+, Cu2+, and Hg2+ is due to a combination of binding selectivity and response selectivity.