Novel Fluorescence Sensing of D-A Type Imidazole Derivatives to Fe3+ and its Application on Rewritable Paper

D-A type fluorescent probe usually shows a fluorescence quenching response to Fe3+, and relatively few probes can exhibit the fluorescence color change response. Herein, two high-luminescence D-A type imidazole derivatives TPABM and TPAFM were synthesized and used as a Fe3+ fluorescent probe with an obvious fluorescence color change response and great sensing performance. The addition of Fe3+ not only quenched the original emission of TPABM and TPAFM, but also produced a new emission peak in the red-shifted direction, which caused their fluorescence color to change from deep-blue to green. This phenomenon could be attributed to the coordination between the molecular imidazole ring and Fe3+ in a 1:1 ratio, which efficiently decreased the LUMO energy level of the probe molecules and formed a new CT emission with a lower energy gap. Finally, the probe molecules not only showed the potential to detect Fe3+ in real water samples, but also could be applied to the preparation of rewritable paper in a very simple way. Using filter paper soaked with probe molecules as writing paper, Fe3+ aqueous solution as ink and NaF aqueous solution as an eraser, the cycle of fluorescence writing and erasing was realized under UV-irradiation.