A new benzothiazole azo dye colorimetric chemosensor for detecting Pb2+ ion

In this work, a new benzothiazole azo dye sensor (BTS) was synthesized, and its cation binding affinity was studied using the colorimetric method, UV-vis, and 1H NMR spectral data. The results revealed that the sensor BTS exhibits a remarkable tendency for Pb2+ ion to perform spontaneous visual color change from blue (BTS) to pink (BTS + Pb2+), without any color change in the aqueous solutions of other cations such as Hg2+, Cu2+, Al3+, Ni2+, Cd2+, Ag+, Ba2+, K+, Co2+, Mg2+, Na+, Ca2+, Fe2+, and Fe3+ ions. The observed selectivity could be due to the formation of the complex (BTS + Pb2+), which led to a blue shift from 586 nm (BTS) to 514 nm (BTS + Pb2+) in the UV spectrum. The job's plot provided the stoichiometry ratio of the complex (BTS + Pb2+) to be 1:1. The limit of detection (LOD) of BTS for Pb2+ ion sensing was obtained at 0.67 µM. Additionally, the binding constant for BTS toward Pb 2+ ion was studied using the Benesi-Hildebrand equation. As a result of the BTS test paper strips investigations, it was found that the synthesized sensor BTS could be used as a rapid colorimetric chemosensor for the detection of the Pb2+ ions in the distilled, tap, and sea waters.