Selective fluorescent probe for Tl ions through metal-induced hydrolysis and its application for direct assay of artificial urine.

In this research, we report a simple fluorescent probe designed to detect thallium(iii) ions (Tl) in artificial urine samples. The Tl signaling probe (TP-1) was readily prepared from 2-acetyl-6-methoxynaphthalene and hydrazine. In a pH 4.8 acetate buffer solution containing 1% (v/v) ,-dimethylformamide as a solubilizer, probe TP-1 exhibited turn-on fluorescence signaling behavior in the presence of Tl. Other metal ions, anions, and major urine components such as uric acid, urea, and creatinine did not produce any noticeable fluorescence changes. The Tl signaling of TP-1 was attributed to the hydrolysis of the hydrazone moiety, yielding the parent fluorophore 2-acetyl-6-methoxynaphthalene. The detection limit of TP-1 for Tl sensing was 19 nM, and the signaling was completed within 2 min. Additionally, to further optimize the Tl signaling of the hydrazone derivatives, we compared the effect of structural variations between the closely related ketone-hydrazone (TP-1) and aldehyde-hydrazone (TP-2) derivatives. We confirmed that the ketone-hydrazone (TP-1) demonstrated rapid and stable Tl signaling behavior with satisfactory stability under the measurement conditions. Finally, as a practical application, a Tl assay in artificial urine samples was performed using a smartphone as a portable signaling measurement and data analysis device.