Benzothiazole-Quinoline-Based Fluorescent Probe for Fe³⁺ and its Applications in Environmental and Biological Samples

Due to the its high abundance, iron ion contamination and toxicity is one of the most challenging issue for living beings. Although, iron is extremenly important for several body functions, excess amount of iron in the body can also be fatal. In last century, rapid industrialization, iron extraction and mismanagement of industrial waste disposal leads to iron contamination in water bodies. Therefore, versatile iron sensors needs to be develop which can be employed for detection in biological as well as real water samples. 8-hydroxyquinoline is well-known for its strong affinity towards transition metals including Fe³⁺. In this regard, we have synthesised benzothiazole-quinoline derived 1,2,3- triazole (4HBTHQTz), in which 4-(benzo[d]thiazol-2-yl)phenolic (4-HBT) group acts as a fluorophore. 4HBTHQTz showed high fluorescence and induced a selective decrease in fluorescence with Fe³⁺ at 380 nm (λ_ex. = 320 nm). The detection limit of 4HBTHQTz with Fe³⁺ is calculated as 0.64 μM, which is lower than the WHO recommended limit in drinking water. 4HBTHQTz works over the 5-8 pH range and has shown promising results for quantitative detection of Fe³⁺ in water samples collected from tap, river and seawater. 4HBTHQTz can also detect the Fe³⁺ in biological samples which is confirmed by fluorescence cell imaging using L929 mouse fibroblast cells. Overall, 4HBTHQTz showed advantages such as high selectivity, quick detection, and good limit of detection (LOD) for Fe³⁺.