Metal Cation-Responsive and Excitation-Dependent Nontraditional Multicolor Fluorescent Hydrogels for Multidimensional Information Encryption

Abstract

Fluorescent polymeric hydrogels especially multicolor fluorescent polymeric hydrogels (MFPHs) have important applications in information storage, encryption, and encoding. MFPHs are generally prepared by incorporating multiple traditional fluorescent materials into hydrogels. In recent years, nontraditional luminescent polymers without any traditional π-conjugated chromophores have received increasing attention. Here, we report a novel type of nontraditional MFPHs prepared by in situ polymerization of acrylamide (AAm) in the presence of poly(itaconic acid) (PITAc). The hydrogen-bonded mechanically strong PAAm/PITAc hydrogels show strong intrinsic fluorescence, and the fluorescence emission is excitation-dependent and metal cationresponsive. More impressively, the hydrogels treated with metal cations also possess excitation-dependent fluorescence. We developed a multi-ion inkjet printing (MIIP) technique to print texts or designed patterns onto the hydrogel surface using different metal cation solutions as inks, and then variable texts or patterns appear under the irradiation of UV, violet, and blue lights. Patterns can be further changed by selective printing, erasing, or reprinting on some regions. Therefore, multidimensional information encryption is achieved. This work provides a new strategy for preparing MFPHs for wide applications.

Information Storage Based on Stimuli‐Responsive Fluorescent 3D Code Materials

“…This multi-regulation capability endows the luminescent materials with versatility, especially showing bright prospects in information storage and anti-counterfeiting. [51,[135][136][137][138][139] Hence, integrating multiple stimuli responsiveness into one 3D code system can be a key direction for the development of variable 3D code systems. Multiple responsiveness means that the pattern of 3D codes can be transformed via diverse methods.…”

“…a-e) Reproduced with permission. [135] Copyright 2021, American Chemical Society. The code pattern under natural light and the pattern transformations upon different stimuli under UV light, corresponding to information masking and unmasking.…”

“…Wang and his co‐workers constructed a new kind of non‐traditional MFPHs through the situ polymerization of acrylamide (AAm) with the existence of poly(itaconic acid) (PITAc). [ 135 ] This non‐traditional MFPH exhibited interesting properties, including excitation‐dependent fluorescence (EDF) emission and metal‐cation responsive emission. The EDF means the fluorescent materials can show the fluorescence emission with different colors and intensities upon the excitation with different wavelengths.…”

“…The photos of the code pattern b) untreated or treated with c) Mn 2+ printing, d) EDTA erasing, and e) Zn 2+ printing under different light. a-e) Reproduced with permission [135]. Copyright 2021, American Chemical Society.…”

Multi-level encryption of information in morphing hydrogels with patterned fluorescence

“…Such tunable fluorescence is utilized to create patterned information that is concealed in daylight. 46–48…”