Multi-stimuli-responsive di-9-phenylcarbazole-based luminogens with multicoloured changes: Acidichromism, metal ions detection, and applications

A new D-A-D structured organic fluorescent dye (BPCT-PA) based on two 9-phenylcarbazole groups as the electron donor, and pyrimidine-2-amine as the electron receptor has been designed and synthesized. BPCT-PA exhibits remarkable reversible acidichromism behavior, in which initial yellow solution and green emission immediately change into carmine solution and red emission upon stimulation with acid, which will convert back into initial states as it is exposed to base. In addition, BPCT-PA was highly selective toward trivalent ions (Al3+, Cr3+, and Fe3+) with significant absorption and fluorescence changes, thus realizing the visual detection of Al3+, Cr3+, and Fe3+. The interesting multi-stimuli-responsive and multicoloured display behavior of BPCT-PA make its potential as security ink and anti-counterfeiting material with high contrast and easy accessibility. Finally, we demonstrated that BPCT-PA could be applied in cell imaging as fluorochrome with good biocompatibility.