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 Fe3+ fluorescent probes with an obvious fluorescence color change and remarkable sensing performance. Upon the addition of Fe3+, the original emission of TPABM and TPAFM was quenched, while a new emission peak emerged in the red-shifted direction, resulting in the fluorescence color changing from deep blue to green. This phenomenon may be caused by the coordination between the molecular imidazole ring and Fe3+ with 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. Furthermore, the probe molecules exhibited the potential for detecting Fe3+ in actual water samples and could be appropriated for the preparation of rewritable paper using a simple method. By 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.