Developing security inks, which can be permanently erased after reading
the information, is of great significance in enhancing the information
and data protection of ink anti-counterfeiting applications. Herein, a
novel TPE-derived AIE fluorescent molecule (TPE-PA) is synthesized,
which produces the strongest fluorescence in THF/water (5:95, v/v, the
same below) and EtOH/water (30:70) co-solvents. However, in co-solvents
of equal concentration, the fluorescence of TPE-PA pigment in EtOH/water
(30:70) was almost entirely quenched with UV light irradiation, whereas
in THF/water (5:95), despite the fluorescence showing a decreasing
trend, it was not entirely quenched. More intriguingly, TPE-PA pigment
self-assembles into fluorescent nanospheres of various particle sizes in
co-solvents, and while UV light irradiation quenches the fluorescence of
the nanospheres, the particle size of the microspheres marginally
reduces. EtOH/water (30:70) was selected as the co-solvent to explore
the potential application of the erasable fluorescent anti-counterfeit
ink in the field of information storage and encryption. Under ambient
and UV light, text written in this ink can be invisible and fluorescent,
respectively, but the fluorescence is gradually erased under constant UV
light irradiation. The latter can be attributed to the fluorescence
quenching caused by the photocyclization and subsequent photo-oxidation
of TPE derivatives. This kind of erasable invisible ink, which is
dominated by nanospheres, offers a wide range of applications, including
privacy protection, data encryption, and anti-counterfeiting.