Phase‐Transition‐Triggered Optical Switching for Multistage Information Encryption/Decryption

Abstract

such as light, [27] heat, [28] chemicals, [29] and electricity, [30] which have been demonstrated to be promising for information encryption/decryption. For that, a crucial point is to achieve optical switching for the color change on gel surface. [31,32] Kim et al. proposed a structure-color switching protocol on a micropatterned surface of DNA-hydrogel to realize encryption and decryption of information. [33] The structural color could be controlled by swelling and deswelling of passive micropillar structures. [34] Specific design of micro/nanostructures, variation of crosslinking density of network, [35] microphase separation, and hydrophobic association are capable of inducing color change on various gel surfaces; [36] however, it is hard to enable the optical switching.To address this disadvantage, introduction of fluorophores or quantum dots into the networks of polymeric gels is developed. [37][38][39] For example, Wu et al. reported a hydrogel containing 4′-(N-vinyl benzyl-4pyridinyl)-2,2′:6′,2″-terpyridine perchlorate in the network, where the shapeprogrammed changes triggered the switchable fluorescence under ultraviolet (UV) irradiation. [40] A photo-mechanically-modulated display system was designed on a hydrogel surface that enabled on-demand fluorescence patterning by photothermal effects. [41] (2-(4-vinylphenyl) ethene-1,1,2-triyl) tribenzene (TPE) is a well-known fluorescent molecule with aggregation-induced emission (AIE) properties, which is non-emissive in good solvents but highly emissive as it aggregates in poor solvents. This phenomenon is mainly attributed to the restriction of intramolecular motion effect. [42] The introduction of AIE molecules into semi-solid gel systems is an emerging field owing to the superiority of easy functionalization and comprehensible mechanism. Many stimulus-responsive gels based on AIEgens have been developed for information storage using optical switching. [43] However, there are few reports on a gel system that is capable of water swelling-induced opticalswitching for multistage information encryption/decryption. [44,45] Probably, this gel system is still limited by elaborate structural design and complex stimulus conditions. [46] Our previous work reported a swelling-induced switching of light reflection/penetration for information camouflage and encryption on a hydrogel surface, [47] which inspired us to further explore the innovative research on water swelling-induced optical switching for multistage information encryption/decryption. It remains challenging to enable the optical switching for safety-improved information encryption/decryption on a gel platform. Herein, a water swelling-induced optical-switching strategy is reported that can achieve multistage information encryption/decryption on an organohydrogel surface. Cationic moieties of methacrylamido propyl trimethyl ammonium chloride (MPTAC) and hydrophobic fluorophores of (2-(4-vinylphenyl) ethene-1,1,2triyl) tribenzene (TPE) are copolymerized into hydrophilic polyacrylamide network. The cationic m...

Stimulus-responsive polymer materials toward multi-mode and multi-level information anti-counterfeiting: recent advances and future challenges

“…A common strategy for achieving multi-mode anti-counterfeiting is to integrate fluorescent information under UV light and directly display information under visible light. Zhang's group 66 reported an organohydrogel containing cationic moieties called methacrylamido propyl trimethyl ammonium chloride (MPTAC) and hydrophobic fluorophores of (2-(4-vinylphenyl) ethene-1,1,2-triyl) tribenzene (TPE) in a polyacrylamide gel network (Fig. 3a).…”

A Short Review on Organohydrogels: Constructions and Applications

“…Generally, there are two main approaches to construct this type of organohydrogel, solvent replacement after preparing hydrogels [35] or directly polymerizing monomers in cosolvents. [36] For instance, Yu's team [37] developed a conductive MXene nanocomposite organohydrogel for strain sensors to address the long-term stability and durability problems of conventional conductive hydrogels. As shown in Figure 4, the conductive MXene nanosheet was first incorporated into the hydrogel network, which consists of polyvinylalcohol (PVA) and PAAM.…”

Multimode Dynamic Photoluminescence of Bi3+-Activated ZnGa2O4 for Optical Information Encryption

“…Information security is of great significance in the development of enterprises, social stability, military security, and even personal daily life. − Over the past few decades, a wide variety of technologies, including markering, holograms, magnetism, plasmonic labels, and luminescence, have been investigated for use in anticounterfeiting and information encryption. Among these technologies, luminescence has demonstrated great potential because of its timeliness, simplicity, multiencoding dimensions, and low cost. − So far, diverse luminescent materials featuring photoluminescence (PL), thermoluminescence (TL), upconversion luminescence (UCL), downconversion luminescence (DCL), persistent luminescence (PersL), mechanoluminescence (ML), and photostimulated luminescence (PSL) have been widely developed for high-level encryption. − However, most PL-based anticounterfeiting labels are easily falsified by certain alternatives due to their static luminescence color and intensity, single-emission mode, or simple design . Therefore, dynamic optical materials with multimode luminescence characteristics are highly desired for advanced anticounterfeiting and information encryption applications. − …”