Dynamic Fluorescent Anti-Counterfeiting Labels Based on Conjugated Polymers Confined in Submicron Fibrous Membranes

Abstract

Developing a new anti-counterfeiting strategy is of great significance to combating the global counterfeiting problem. Here we report the construction of a dynamic fluorescence response system for anti-counterfeiting by combining the photochromism induced by the ring-opening of spiropyran (SP) to merocyanine (MC) with the fluorescence resonance energy transfer (FRET) between the conjugated polymer and MC. After elucidating the design principle, a new conjugated polymer, PPETE-SP, consisting of a poly­[p-(phenylene ethynylene)-alt-(thienylene-ethynylene)] (PPETE) backbone with pendant SP, was synthesized and characterized. With poly­(methyl methacrylate) (PMMA) as the matrix, the PPETE-SP/PMMA fibrous membrane was prepared via electrospinning. Under the irradiation of UV light, the fluorescent color of the membrane dynamically changed from green to light green, then light pink, and finally pink, and this process was reversible under visible light. The fluorescence emission switch was examined for 10 cycles and proved to have good repeatability, indicating that the membrane can be directly used as an anti-counterfeiting label for multiple verifications. The FRET efficiency was found to be about 61% based on the FRET study with confocal laser scanning microscopy. The covalent bonding between PPETE backbone and SP, the confinement of PPETE-SP chains in the fibrous membrane, as well as employing PMMA as the matrix were demonstrated to be crucial in realizing the photochromism and the FRET. Different anti-counterfeiting modes were proposed, providing rich selections for operation of verification. Such facile-to-operate and hard-to-imitate dynamic fluorescent responsive materials are very promising for use in practical anti-counterfeiting applications.

Dynamic Fluorescence Materials Based on Naphthalimide-Functionalized Silica Aerogels and Applications in Advanced Information Encryption

“…Among these, fluorescent anticounterfeiting materials are widely explored because of their remarkable visibility, multilayer protection, and user-friendliness, which provide powerful anticounterfeiting measures for commodities and documents. − However, most fluorescent anticounterfeiting materials are based on their static features or signals, which greatly limits the encryption of advanced information. , In view of this, materials that can be switched to multiple states under external stimuli as needed would be promising candidates. These fluorescent patterns show dynamic color change with time after being exposed to external stimuli and show a vivid display of encrypted information, so they have a higher security level because of the increase in anticounterfeiting dimension. − …”

Dual host–guest interaction-mediated photoswitchable fluorescent supramolecular polymers for anti-counterfeiting and encryption

“…Owing to the flexible design and easy preparation, many phtotoswitchable fluorescent polymeric nanoparticles and films have been developed for the construction of encryption or anti-counterfeiting system. 4,7,[14][15][16][17][18] However, nanoparticles with poor processability and films with low flexibility in the regulation of optical performance still hinder their applicability in anticounterfeiting and information encryption. [19][20][21] Therefore, the development of novel PFPs with excellent processability and the flexibility of optical performance regulation are desired for anticounterfeiting and encryption.…”

Carbon Dots@Allophane Core–Shell Nanoparticles with Long-Lifetime Room-Temperature Phosphorescence for Anti-Counterfeiting Applications

“…Advanced optical anti-counterfeiting technology plays a crucial role in safeguarding important information and high-value items. − Room-temperature phosphorescence (RTP) materials have extensive application prospects as novel optical anti-counterfeiting materials because of their long-lifetime emission and ability to eliminate background emission interference. − Currently, traditional RTP materials primarily include inorganic compounds containing rare-earth ions and organic compounds with molecular structures. − Unfortunately, these materials require complicated preparation and purification processes, exhibit poor stability, and are expensive, all of which severely restrict their potential applications. Carbon dots (CDs) have attracted the interest of researchers as a promising category of RTP materials because of their abundant precursor sources, straightforward synthesis, low toxicity, and excellent stability. − Nevertheless, fabricating CDs with a long phosphorescence lifetime and exceptional stability remains a challenge because of issues such as unstable triplet excitons, vibrational dissipation of molecules, and environment-induced quenching.…”