An AIE-active dual fluorescent switch with negative photochromism for information display and encryption

Abstract

A negative photochromic molecular switch with AIE and two-color fluorescence conversion properties was synthesized. This molecular switch was constructed by connecting two propyl sulfonic acid modified spiropyrans with one tetraphenylethene covalently, and the protonated ring-open form is its thermodynamically stable state. On one hand, thanks to the introduction of sulfonic acid modified spiropyrans, molecules exhibit the properties of the structural switch from the ring-open form to the ring-closed form under visible light irradiation. Therefore, the color change of the molecule under room light was achieved under the noninvasive stimulus of visible blue light. On the other hand, by the introduction of the fluorescent group tetraphenylethene, the reversible switch between two fluorescence states of the molecules can also be realized. The molecule incorporated PVP composite film exhibits an emission change from orange–red to blue upon visible light trigger, and the reversible emission switch can be realized through the heat treatment with good repeatability. Utilizing these properties, we further explored the application of the two-color emission molecular switch in the fields of fluorescence information display and encryption. The writing of fluorescent information can be achieved through blue light control. Moreover, in terms of information encryption, the information has a high security level and specific and sequential stimuli are needed to decrypt, and the real information will be locked by illegal decryption, which ensures the security of the information and shows good application prospects.