Anti-counterfeiting Ink Research Articles

Tailored metal–organic tetrahedral nanocages with aggregation-induced emission for an anti-counterfeiting ink and stimulus-responsive luminescence

Tailored metal–organic tetrahedral nanocages with aggregation-induced emission for an anti-counterfeiting ink and stimulus-responsive luminescence.

Comprehensive Experimental Design of Organic Chemistry Based on Scientific Research Infiltration: Preparation of an Anti-Counterfeiting Ink

Comprehensive Experimental Design of Organic Chemistry Based on Scientific Research Infiltration: Preparation of an Anti-Counterfeiting Ink

Multicolor fluorescence switching material induced by force and acid

A novel D–A–D chromophore TBQM based on triphenylamine, acylhydrazone and dimethylamino was synthesized, and the emission properties of TBQM was studied in solutions as well as in aggregated state. TBQM showed obvious solvatochromism in different solutions. In addition, the reversible multicolor fluorescence switching properties under the stimulation of external forces and acid were also obtained. The fluorescence of TBQM changed from blue to bright blue, and finally to blue-green as the degree of grinding increased, which would recover after being fumigated by CH2Cl2. Meanwhile, TBQM could undergo twice protonation after fumigated by TFA. The fluorescence color changed from blue to bright blue, blue-green, and yellow-green until the fluorescence was quenched with the increasing of TFA fumigation time, which can be restored automatically or by TEA fumigation. Moreover, TBQM could be used as an advanced fluorescent anti-counterfeiting ink.

Room-temperature phosphorescence based on chitosan carbon dots for trace water detection in organic solvents and anti-counterfeiting application

Trace water is known to be an impurity in organic solvents, having an adverse effect on the chemical reaction or environmental safety. Developing a green, facile and non-toxic method for detecting trace water in various organic solvents is still a challenge. Distinct form conventional fluorescent probes, room-temperature phosphorescence (RTP) test paper (TP) has aroused wide concern owing to its characteristic optical performance, including long afterglow and non-background interference. Herein, we fabricated a new kind of RTP-TP on the basis of chitosan carbon dots (CDs). The anchoring effect of polyvinyl alcohol (PVA) promoted the restriction of vibration/rotation and hindered the non-irradiative quenching of CDs by forming intermolecular hydrogen bonds. However, water molecules could interrupt these hydrogen bonds and therefore the RTP phenomenon would be disappeared. Further, the RTP-TP was used to detect trace water in various organic solvents with high efficiency, excellent stability, and reliability. In addition, the CDs-PVA solution can be also used as anti-counterfeiting ink via various printing methods.

Excitation-dependent organic phosphors exhibiting different luminescence colors for information anti-counterfeiting

The development of organic phosphors with excitation-dependent luminescence color is tremendously challenging for organic room temperature phosphorescent (ORTP) systems. Herein, we designed and synthesized a series of novel ORTP materials based on pyranone. Under the excitation of 254 nm, the materials exhibited the rare phenomenon of emitting almost pure phosphorescence, whereas strong cyan photoluminescence and weak green phosphorescence were observed upon exposure to 360 nm excitation light. Experiment analysis and theoretical calculations demonstrate that the regulation of luminescent color is attributed to the different transition process of excitons from singlet excited states (S1 and S2) to triplet excited states (T1) under various excitation wavelengths. The materials still can maintain the crystalline state under various extreme conditions (ground, recrystallization, high pressure), thereby maintaining the ORTP properties. In addition, the ORTP properties of the materials are very stable to water/heat/light/air. Taking advantage of the multiple luminescence colors, excellent crystallinity and stability, these phosphors can be developed as an advanced anti-counterfeiting ink for printing and hand-painting on a wide range of media, showing an extremely ideal application prospect.

Applied to anti-counterfeiting and flexible composite utilizing photoluminescence properties of CdSe/ZnS nanocrystal quantum dots via hot-injection

Quantum dots with excellent luminescence properties are being studied in a wide range of fields, such as displays, sunlight, and bio-imaging; although quantum dots are the same material, unlike bulk materials, as their size decreases their optical and electrical properties change due to the quantum confinement effect. In this study, CdSe quantum dots were synthesized by a well-known hot-injection method and a ZnS shell layer was formed on the surface of the CdSe quantum dot core to enhance the properties, thereby synthesizing the CdSe/ZnS core/shell structure. At this time, the quantum yield increased more than twice, and the emission line width decreased. When anti-counterfeiting ink was made using quantum dots with enhanced luminescence characteristics and applied to a bank note, it was impossible to check with the naked eye, but letters and emblems could be confirmed under UV light. In addition, a composite made by mixing with a silicon-based polymer showed excellent flexibility; and, when applied on a blue LED chip, a single wavelength and bright light peculiar to quantum dots were realized.

Tetraphenylethylene based amphiphilic derivatives: The self-assembly, photo-responsiveness and their application for erasable fluorescent ink

Since the discovery of aggregation induced emission (AIE) phenomenon, various stimuli-responsive materials have been rapidly developed. However, the development of self-assembled amphiphilic light-responsive materials in aqueous solution needs to be solved urgently. In this work, three new amphiphilic tetraphenylethylene (TPE) derivatives (TPE-1, TPE-2 and TPE-3) with AIE properties and photochromism were synthesized and investigated. Owing to the different electron-donating abilities of the three groups attached to TPE units, the TPE-1, TPE-2 and TPE-3 displayed blue-green, yellow-green, and orange fluorescence emission in the aggregation state respectively. Furthermore, ordered nanoparticles formed via self-assembly in aqueous solution showed interesting photocyclization behaviors, which lead to fluorescence quenching under ultraviolet light irradiation (λ = 365 nm). Therefore, the compounds can be used as anti-counterfeiting ink in the information encryption due to their amphiphilicity and photo-responsiveness. This work contributes new members to the amphiphilic light-responsive materials family and demonstrates the potential for applications in the fields of optical information storage, information security protection, and erase/rewrite systems.

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

Synthesis and performance of ZnO quantum dots water-based fluorescent ink for anti-counterfeiting applications

In this study, the ZnO quantum dots (QDs) water-based fluorescent anti-counterfeiting ink was prepared with the polyvinylpyrrolidone (PVP) content of 0.15–0.17 g/mL, the ZnO QDs concentration of 4% and water as the solvent, which has good fluorescence, printability and resistance. According to the halftone technology, fluorescence quenching of the ZnO QDs by acid, and acid resistance of the organic fluorescent ink, a high-quality anti-counterfeiting method of fluorescent discoloration was proposed. The QDs ink has broad application prospects in the field of anti-counterfeiting green packaging.

Luminescent nanohybrid of ZnO quantum dot and cellulose nanocrystal as anti-counterfeiting ink

Luminescent quantum dot (QD) ink is currently a powerful tool for generating hidden information on paper substrates. Herein, we fabricated a nanohybrid ink of bacterial cellulose nanocrystal (BCNC) and UV-responsive ZnO QD via electrostatic self-assembly for improving solvent resistance and message encryption process. Under investigations on the printed areas, the nanohybrid can slightly infiltrate into the paper fibers and form a thin layer on the top of paper substrates, conferring an enhanced print permanence against wetting conditions while maintaining the daylight unobservability and its luminescent stability. The water resistance of the proposed nanohybrid ink enables developing a higher security level that the prints can be submerged in CuCl2 aqueous solutions to quench the luminescent message. The concealed message can eventually be revealed under UV light again after submerging in EDTA solution. Our ZnO QD/BCNC nanohybrid with eco-friendly nature therefore exhibits great potential as security marking ink for counterfeit protection with sustainable uses.

Orange-red emitting praseodymium doped yttrium-molybdate nanophosphors for multifunctional applications

Orange-red emitting praseodymium (Pr3+) activated yttrium molybdenum oxide (Y2MoO6) nanophosphors (NPs) were synthesized via low-temperature solution combustion method using Aloe vera gel as a surfactant and fuel. The synthesized NPs were subjected to structural, morphological, optical, and electrical studies. The powder X-ray diffraction (PXRD) study reveals that the Y2MoO6 composite consists of a monoclinic crystal phase. Peak shift to the left side was observed with increase in the doping concentration of Pr3+ ions into the crystal system, which is attributed to the strain. Foamy type morphology was revealed from scanning electron microscope studies, whereas the nanostructural features of the samples were confirmed by both transmission electron microscope and PXRD. From the diffused reflectance spectroscopy study, the optical band gap was estimated to be in the range of 3.36–3.48 eV. Fourier transforms infrared spectroscopy was used to identify the metal oxygen bonds along with the other types of bonds if any. The AC conductivity and dielectric properties were measured in the frequency range of 100 Hz–5 MHz. The photoluminescence (PL) studies revealed the characteristic of emission peaks of Pr3+ ions. The Commission International de l'Eclairage (CIE) coordinates were located in orange-red color. The average correlated color temperature analysis indicates that the Y2MoO6:Pr3+ NPs can be useful for use in warm light sources. The Y2MoO6: Pr3+ (5 mol%) NPs were used for the design of anti-counterfeiting ink in security applications. The tunable properties of the prepared Y2MoO6:Pr3+ NPs make them suitable for multifunctional applications.

NBN unit functionalized pyrene derivatives with different photophysical and anti-counterfeiting properties

Pyrene derivatives 1 and 2, containing a five or six-membered diazaborole moiety (NBN unit), have been designed and prepared by the reaction of the corresponding pyrene-boronic acids with diamines unit. Spectroscopic properties of dyes 1 and 2 in three solvents and solid-state were well investigated. Dye 1 had cyan emission with moderate quantum yield in THF. Almost no solvatochromism in absorption spectra are observed for dyes 1 and 2, whilst a remarkable solvatochromic emission is found for 1. Both dyes exhibited fluorescence with absolute quantum yields of 0.30 for 1, 0.09 for 2 in the solid-state. The relationships between structure and property, especially the electronic effect between the pyrene and five or six-membered NBN moiety, were systematically studied based on optical spectroscopy, X-ray analysis, and theoretical calculations. The solid-emissive dyes 1 and 2 could be applicable as anti-counterfeiting ink by the experiment of fluorescent labeling for writing pattern and banknote.

“On-off-on” fluorescence switch of graphene quantum dots: A cationic control strategy

Fluorescence switch based on graphene quantum dots (GQDs) is of great interest in the areas of environment, medicine and data security because of their promising applications. However, the known ternary “on-off-on” fluorescent switches of GQDs are very few due to the limited effective fluorescence recovery strategies. In this work, we proposed a new cationic control strategy and designed a novel “on-off-on” fluorescence switch, i.e., GQDs-Cu2+/Fe3+/Cr3+-Al3+/Ga3+/In3+, where the fluorescence of synthesized GQDs was quenched by Fe3+, Cu2+ and Cr3+, and subsequently was recovered by three kinds of Group IIIA ions Al3+, Ga3+ and In3+. The corresponding recovery degree can reach up to 0.81 compared with the pristine GQDs. The XPS results combining with quantum chemical calculations illustrated that the change of π-conjugated region caused by cations dominated the quenching and recovery of fluorescence. Furthermore, based on this “on-off-on” mechanism, a kind of anti-counterfeiting stealth ink for information encryption was also suggested. This work is the first report that Group IIIA ions Al3+, Ga3+ and In3+ can be used for fluorescence recovery, and the cationic control strategy proposed here provides a new and promising strategy for the development of “on-off-on” fluorescent switch in future studies.

Blue luminescent N,S-doped carbon dots encapsulated in red emissive Eu-MOF to form dually emissive composite for reversible anti-counterfeit ink.

Lanthanide metal-organic frameworks (Ln-MOFs) have demonstrated great potential in luminescence sensing and optical anti-counterfeiting. High-security anti-counterfeiting technology is of great importance and requires the development of universal luminescent materials with multiple modes of emission and adjustable photoluminescence. Herein, a 3D red light emission microporous europium(iii) metal-organic framework [Eu3(OH)(1,3-db)2(H2O)4]·3H2O (1) (1,3-db = 1,3-di(3',5'-dicarboxylpheny) benzene) was constructed from a zigzag [Eu3(COO)8] chain and π-electron-rich terphenyl-tetracarboxylate. Notably, the quenched fluorescence of 1 under hydrogen chloride vapor could be recovered upon fuming by a vapor of Et3N. Most strikingly, the strong blue light emission by nitrogen and sulfur co-doped carbon dots (N,S-CDs) could be encapsulated in 1 to generate a dual-emission composite, namely, N,S-CDs@Eu-MOF, which shows solvent-dependent photoluminescence: N,S-CD-related blue luminescence in water and Eu-MOF-related red emission in organic solvents. Taking advantage of the above unique reversible fluorescent behavior, Eu-MOF and N,S-CDs@Eu-MOF are prepared as fluorescent high-security inks to achieve data encryption and decryption on specific flower patterns.

Multifunctional lipophilic purines: a coping strategy for anti-counterfeiting, lipid droplet imaging and latent fingerprint development

A purine-based multifunctional material, with satisfactory lipophilicity and fluorescence properties, has potential to be applied in minutiae-level LFP development, waterproof anti-counterfeiting ink and LD imaging of living cells.

Isostructural Lanthanide Coordination Polymers with High Photoluminescent Quantum Yields by Effective Ligand Combination: Crystal Structures, Photophysical Characterizations, Biologically Relevant Molecular Sensing, and Anti-Counterfeiting Ink Application

Characteristically strong photoluminescence with high quantum yield and long emission lifetime plays vital roles for the sensing performance of functional lanthanide complexes. To enhance the energ...

Preparation of 1, 3, 6, 8-Pyrenesulfonic Acid Tetrasodium Salt Dye-Doped Silica Nanoparticles and Their Application in Water-Based Anti-Counterfeit Ink.

In order to improve the luminescent stability of water-based anti-counterfeit ink, a new fluorescent material is prepared by doping dye into silica nanoparticles. Water soluble anionic dye 1, 3, 6, 8-pyrenesulfonic acid sodium salt (PTSA) is selected as the dopant. In this work, PTSA is successfully trapped into silica nanoparticles (SiNPs) by the reverse microemulsion method using cationic polyelectrolyte poly (dimethyl diallyl ammonium chloride; PDADMAC) as a bridge. The UV absorption spectra, fluorescence emission spectra and fluorescent decay curves are used to describe the luminescent properties of the PTSA-doped silica nanoparticles (PTSA-SiNPs). In addition, the as-prepared PTSA-SiNPs and polyurethane waterborne emulsion are used to prepare water-based anti-counterfeit ink, and fluorescent patterns are successfully printed through screen-printing. The samples printed by the ink exhibit desirable fluorescence properties, heat stability, robust photostability, and a fluorescent anti-counterfeit effect, which makes the PTSA-SiNPs promising luminescent materials for anti-counterfeit applications.

Color-switchable hybrid dots/hydroxyethyl cellulose ink for anti-counterfeiting applications

Many anti-counterfeiting inks have been explored recently, most of them are commonly involved in weak fastness, high cost and long-term toxicity, impeding their real-life applications. Herein, an environment-friendly and inexpensive anti-counterfeiting ink with excellent fastness is reported. The untifake ink is developed by combining hybrid dots (silicon/carbon) with hydroxyethyl cellulose (HEC) binder. Interestingly, the HEC binder can effectively prevent from aggregation-induced quenching of hybrid dots. Subsequently, the customized patterns are successfully transferred onto different surfaces of various substrates including cotton fabric, cellulosic paper, glass, metal, silicon wafer and PET film, using the as-prepared ink by screen-printing technique, exhibiting that the hybrid dots/HEC ink possesses widespread practicability. Notably, fluorescent color of these patterns can be switchable by adjusting environmental pH-value, further imparting the as-prepared ink with excellent covert performance. This new fluorescent hybrid dots/HEC ink will be promising candidates for high-level anti-counterfeiting applications including food packaging, apparel and documents.

Photoluminescence of graphene quantum dots enhanced by microwave post-treatment

Graphene quantum dots (GQDs) have a great potential in sensors and bioimaging for their lower toxicity, perfect water solubility and bright luminescence. However, considerable efforts still need to devote to enhance the photoluminescence quantum yields (PLQYs) of GQDs. At first, high PLQYs are guaranteed by confined synthesizing GQDs/layered double hydroxides (LDHs) with well-defined structure. Followed by a convenient microwave post-treatment, PLQYs of GQDs are further improved from 21.0% to 34.6%. After microwave post-treatment, the integrity of π-conjugated system has been enhanced and non-radiative processes also have been reduced inside GQDs, which both confirmed to be responsible for the improvement of PL properties. This work may point out a new direction for enhancing the PLQYs of GQDs. Moreover, owing to the stability and well PL performance of GQDs/LDHs, it has a great potential application in the outdoor anti-counterfeiting inks.

Waterborne fluorescent dual anti-counterfeiting ink based on Yb/Er-carbon quantum dots grafted with dialdehyde nano-fibrillated cellulose

Nanofibrillated cellulose (NFC) is becoming popular in the field of anti-counterfeiting material due to its favorable biocompatibility, renewability, and easy modification properties, which give it great potentials as carrier of carbon quantum dots (CQDs). Herein, we report an effective method to fabricate Yb and Er doped CQDs grafted onto dialdehyde NFC (DANFC). Owning to special rheological properties of NFC, a waterborne fluorescent dual anti-counterfeiting ink was rationally designed and successfully prepared by adding NFC to waterborne ink to form a stable network structure and increase the thixotropy and yield stress. The resulting CQDs exhibited both photoluminescence (PL) and up-conversion luminescence (UCPL), emitting blue and green fluorescence at excitation wavelengths of 370 and 980 nm, respectively. The study provides a novel method to prepare the waterborne fluorescent dual anti-counterfeiting ink based on Yb and Er doped CQDs/DANFC composites, which provides a reference for its application in printing and packaging industry.