Fluorescence detection of iodide anion using a donor–acceptor (D–A) thiourea derivative

1-(4-acetyl-phenyl)-3-(4-N,N-dimethylaminophenyl)-thiourea is synthesized and characterized by NMR, IR, MS and elemental analysis. The probe exhibits the “turn-off” fluorescence response to iodide anion in THF/H2O (v/v = 9/1) pH = 7.4 Tris–HCl buffer solution, which is attributed to the intramolecular charge transfer (ICT). It is found that the probe has a detection limit of 0.336 μM. Such interesting results could be further supported by quantum chemical calculation, UV and 1H NMR titration. Moreover, the probe is applied to determine iodide in powdered milk and urine samples. This experiment shows a good agreement between added and detected concentration of the iodide in real samples.