A selective fluorescent chemosensor for Cd²⁺ based on 8-hydroxylquinoline-benzothiazole conjugate and imaging...

A 8-hydroxylquinoline-benzothiazole conjugate (HQ-BT) was facilely synthesized by two steps with >60% total reaction yield. The HQ-BT showed a weak fluorescence that could be strongly enhanced by coordination with various metal ions such as Al³⁺, Cd²⁺, Zn²⁺ in methanol containing 1% water. Interestingly, the selectivity toward Cd²⁺ was achieved by increasing water fraction to 30% aqueous methanol solution. Thus, the HQ-BT was developed as a new and selective fluorescent chemosensor for Cd²⁺ in aqueous solution with a broad pH region 4-12. A good linear relationship between the fluorescence intensity and the Cd²⁺ concentration was found in the range of 0-5 μM with a detection limit of 0.1 μM (S/N = 3). It was also succesfully used for fluorescence imaging of Cd²⁺ in living cells.