Facile fabrication of light-activated multi-level output system based on thienyl-diphenylethene: Toward intelligent multimodal security protection

Organic photochromic compounds represent a crucial class of smart-responsive materials, widely utilized in the fields comprising information storage and anti-counterfeiting. However, their practical applications are often hindered by intrinsic limitations, including lack of multifunctionality and poor stability. These shortcomings impede the realization of versatile performances, restrict compatibility with various anti-counterfeiting strategies, and consequently narrow their application prospects. Therefore, aiming at effectively keeping information security, it is imperative to develop novel materials capable of adapting to a broad range of encryption techniques. Herein this study, a thiophene-stilbene-based optical switching system was successfully developed in the solid state, based on three newly synthesized photochromic molecules: 3,3'-(2,2-diphenylethene-1,1-diyl)bis(benzo[b]thiophene) (2PBS), 3,3'-(2-phenylethene-1,1-diyl)bis(benzo[b]thiophene) (HPBS), and (Z)-1,2-bis(benzo[b]thiophen-3-yl)-1,2-diphenylethene (2PSF), whose reversible and high-contrast photochromic properties were found along with bright fluorescence emission. Upon exposure to ultraviolet (UV) light, the system suffered a rapid photochromic process from white to vivid red or violet, while quickly reverting to the original color under visible light, whereas this ideal material may effectively address practical application barriers required for time-dependent color changes and high sensitivity. In order to enhance its versatility, such a system is seamlessly integrated with various encryption mechanisms, e.g. temperature- and time-based strategies, based on the combination of an aryl vinyl backbone with photoactive thiophene moiety, in addition of integrating logic gates and computational base conversions, while embedding key decryption parameters into complex program logic to promote data protection. Surprisingly, this approach enables to simply achieve near-unlimited information storage by increasing the sample size, suggested by theoretical analysis.