Anti-counterfeiting Labels Research Articles

Facile Synthesis of B/P Co-Doping Multicolor Emissive Carbon Dots Derived from Phenylenediamine Isomers and Their Application in Anticounterfeiting.

Carbon dots (CDs) possess a considerable number of beneficial features for latent applications in biotargeted drugs, electronic transistors, and encrypted information. The synthesis of fluorescent carbon dots has become a trend in contemporary research, especially in the field of controllable multicolor fluorescent carbon dots. In this study, an elementary one-step hydrothermal method was employed to synthesize the multicolor fluorescent carbon dots by co-doping unique phenylenediamine isomers (o-PD, m-PD, and p-PD) with B and P elements, which under 365 nm UV light exhibited signs of lavender-color, grass-color, and tangerine-color fluorescence, respectively. Further investigations reveal the distinctness in the polymerization, surface-specific functional groups, and graphite N content of the multicolor CDs, which may be the chief factor regarding the different optical behaviors of the multicolor CDs. This new work offers a route for the exploration of multicolor CDs using B/P co-doping and suggests great potential in the field of optical materials, important information encryption, and commercial anticounterfeiting labels.

Mechanically Tunable Circularly Polarized Luminescence of Liquid Crystal-Templated Chiral Perovskite Quantum Dots.

Endowing perovskite quantum dots (PQDs) with circularly polarized luminescence (CPL) offers great promise for innovative chiroptical applications, but the existing strategies are inefficient in acquiring stimuli-responsive flexible chiral perovskite films with large, tunable dissymmetry factor (glum) and long-term stability. Here, we report a strategy for the design and synthesis of luminescent cholesteric liquid crystal elastomer (Lumin-CLCE) films with mechanically tunable CPL, which is enabled by liquid crystal-templated chiral self-assembly and in situ covalent cross-linking of judiciously designed photopolymerizable CsPbX3 (X=Cl, Br, I) PQD nanomonomers into the elastic polymer networks. The resulting Lumin-CLCE films showcase circularly polarized structural color in natural light and noticeable CPL with a maximum glum value of up to 1.5 under UV light. The manipulation of CPL intensity and rotation direction is achieved by controlling the self-assembled helicoidal nanostructure and the handedness of soft helices. A significant breakthrough lies in the achievement of a reversible, mechanically tunable perovskite-based CPL switch activated by biaxial stretching, which enables flexible, dynamic anti-counterfeiting labels capable of decrypting preset information in specific polarization states. This work can provide new insights for the development of advanced chiral perovskite materials and their emerging applications in information encryption, flexible 3D displays, and beyond.

Flexible structural color label with tetra-mode iridescence in full three-dimensional space for sophisticated anti-counterfeiting

The attractive visual appearance provided by disordered surfaces has been proven, which demonstrates great anticounterfeiting potential. However, the real application is challenging due to complex processing and Si substrates. We fabricated flexible structural color anti-counterfeiting labels by printing ZnS spheres onto aluminized flexible films to form a disordered surface, resulting in specular-diffuse dual modes appearances. Especially, based on the directionality of Mie scattering, the diffuse mode displayed three-dimensional (3D) angle-dependent structural colors under ambient light and exhibited angle-sensitive dynamic structural colors in 3D space under the light source. The angle dependence of the specular mode and the 3D iridescent of the diffuse mode form a tetra-mode iridescence, which brings sophisticated anti-counterfeiting. The comprehensive color information is directly determined by the optical properties of ZnS and Al, which pose challenges for replication using alternative methods. Further, labels with multi-color dragon patterns were fabricated using ZnS spheres with different diameters, which greatly improves information security. More importantly, based on the tetra-mode, a verification method compatible with personal terminals has been developed, which can quickly identify authenticity.

Residual-dye-derived carbon dots from wastewater for anti-counterfeiting and information encryption

With the development of resource recycling awareness, the number of research on the synthesis and utilization of carbon dots (CDs) from natural wastes continues to grow. Meanwhile, the little-studied synthesis of CDs originating from industrial waste has also become more relevant. In this work, reactive yellow 95 (Y95) molecules in exhausted dyeing wastewater were used as carbon source. By a simple one-step hydrothermal method, the CDs with stimuli-responsive fluorescent chromotropic properties were obtained. With the addition of hydrochloric acid to the CDs solution, the emission of the CDs was red-shifted from 470 nm to 514 nm, and the fluorescence changed from blue to green. The phenomenon was attributed to the synergistic effect of more CO defects on the surface of CDs and the protonation of the carbonyl groups after adding acid. Based on acid-induced fluorescent chromotropic performance, we designed anti-counterfeiting labels for textiles and a double-switching information encryption anti-counterfeiting ink. This work synthesized responsive fluorescent CDs using waste dyes and showed great potential in the field of resource recycling.

Confinement reaction synthesis of CsPbBr3 quantum dots within long afterglow mesoporous materials as lighting equipment

Long afterglow materials are fluorescent materials with unique optical properties and excellent light-converting materials. However, long afterglow materials have the problem of emitting relatively single colors that are difficult to change, thus limiting their further application. Here, we propose a composite method of fully inorganic cesium lead perovskite quantum dots (QDs) with long afterglow materials, which uses the confinement reaction of CsPbBr3 in the pores of mesoporous CaAl2O4:Eu2+, Nd3+ (M-CAO) during high-temperature melting to form M-CAO-CsPbBr3. M-CAO-CsPbBr3 has better thermal and photostability than the common composite materials. Meanwhile, CsPbBr3 QDs can generate green afterglow emissions by absorbing the afterglow energy of M-CAO. In addition, the polydimethylsiloxane (PDMS) film formed by mixing the composite material phosphor M-CAO-CsPbBr3 with PDMS by heating and curing showed bright green fluorescence under 365 nm UV illumination, and it could still exhibit a weak green afterglow under dark conditions after stopping the irradiation. This article is an essential reference for long afterglow materials and anti-counterfeit labels.

Viscoelasticity-Controlled Relaxation in Wrinkling Surface for Multistage Time-Resolved Optical Information Encryption.

As counterfeit techniques continue to evolve, ensuring the security of conventional "static" encryption methods becomes increasingly challenging. Here, the viscoelasticity-controlled relaxation is introduced for the first time in a bilayer wrinkling system by regulating the density of hydrogen bond networks in polymer to construct a "dynamic" encryption material. The wrinkling surface can manipulate light during the dynamic relaxation process, exhibiting three stages with frosted glass, structural color, and mirror reflection. By regulating the viscoelasticity of skin layer through UV irradiation, the wavelength and the relaxation rate of the wrinkles can be controlled. As a result, dynamic wrinkling anti-counterfeiting patterns and time-resolved multistage information encryption are achieved. Crucially, the encryption material is developed as an anti-counterfeiting label for packing boxes in daily applications, allowing the encrypted information to be activated manually and identified by naked eyes, surpassing the existing time-resolved encryption materials in utilization potential. Besides, the dynamic hydrogen bond networks are extended to various dynamic interaction networks, demonstrating the versatility of the dynamic encryption strategy. This work not only provides an additional dimension for dynamic information encryption in daily practical use, but also offers theoretical guidance for the development of advanced optical anti-counterfeiting and smart display materials in the future.

Stable and ultralong room-temperature phosphorescent copolymers with excellent adhesion, resistance, and toughness.

Developing stable room-temperature phosphorescence (RTP) emission without being affected by moisture and mechanical force remains a great challenge for purely organic systems, due to their triplet states sensitive to the infinitesimal motion of phosphors and the oxygen quencher. We report a kind of highly robust phosphorescent systems, by doping a rigid phosphor into a copolymer (polyvinyl butyral resin) matrix with a balance of mutually exclusive features, including a rigidly hydrophilic hydrogen bond network and elastically hydrophobic constituent. Impressively, these RTP polymeric films have superior adhesive ability on various surfaces and showed reversible photoactivated RTP with lifetimes up to 5.82 seconds, which can be used as in situ modulated anticounterfeit labels. They can maintain a bright afterglow for over 25.0 seconds under various practical conditions, such as storage in refrigerators, soaking in natural water for a month, or even being subjected to strong collisions and impacts. These findings provide deep insights for developing stable ultralong RTP materials with desirable comprehensive performance.

Metal-organic framework photonic crystals with bidisperse particles-based brilliant structural colors and high optical transparency for elaborate anti-counterfeiting

Photonic crystals (PCs) have attracted great interest and wide applications in displays, printing, anti-counterfeiting, etc. However, two main challenges significantly hinder their applications: 1) the tradeoff between high optical transparency across the whole visible range and brilliant colors requiring a large refractive index contrast (Δn), and 2) the way of regulating structural colors by altering tens of different sizes. To address these issues, a new type of metal–organic framework (MOF)-based transparent photonic crystal (TPC) has been fabricated through self-assembling MOF particles into three-dimensional ordered structures which were then infiltrated by polydimethylsiloxane (PDMS). Compared to conventional PCs, these TPCs exhibit 1) both brilliant forward iridescent structural colors and high transmittance (>75 %) across the whole visible spectra range, and 2) conveniently adjustable colors based on bidisperse particles. The unique color-generating mechanism of the light diffraction by each plane lattice and the small Δn between MOF particles and PDMS are the keys to TPCs’ characteristics. Moreover, the prepared invisible anti-counterfeit labels can reversibly hide-reveal patterns with elaborate and exchangeable color contrast in a non-destructive way, showing potential applications in anti-counterfeiting, information encryption, and optical devices.

Fabrication of silver nanostructure array patterns (SNAPs) on silicon wafer for highly sensitive and reliable SERS substrates

Metal nanostructure arrays with large amounts of nano-gaps are important for surface enhanced Raman scattering applications, though the fabrications of such nanostructures are difficult due to the complex and multiple synthetic steps. In this research, we report silver nanostructure array patterns (SNAPs) on silicon wafer, which is fabricated with semiconductor manufacturing technology, Cu2O electrochemistry deposition, and Ag In-situ oxidation–reduction growth. Benefiting from the dense and uniform distribution of Ag nanowires, the fabricated SNAPs demonstrate a very strong and uniform surface-enhanced Raman scattering (SERS) effect. The efficiency of SNAPs was investigated by using rhodamine 6G (R6G) dye as an analyte molecule. The results show that the minimum detectable concentration of R6G can reach as low as 10−11 M, and the Raman signals in the random region show good signal homogeneity with a low relative standard deviation (RSD) of 4.77 %. These results indicate that the SNAPs perform a great sensitivity and uniformity as a SERS substrate. Furthermore, we used the SNAPs substrate to detect antibiotic sulfadiazine. The main peaks in sulfadiazine Raman and vibration modes assignments were obtained and the quantitative analysis model was established by principal component analysis (PCA). The detection and application results of sulfadiazine indicate that the SNAPs substrate can be applied for trace detection of antibiotics. In addition, we have cited the application of the SNAPs substrate in anti-counterfeiting labels. These practical applications demonstrate that the fabricated SNAPs can potentially provide a way to develop low-cost SERS platforms for environmental detections, biomedicine analysis, and commodities anti-counterfeiting.

Acetic acid-driven synthesis of environmentally stable MAPb0.5Sn0.5Br3 nano-assembly for anti-counterfeiting

In mixed Sn-Pb perovskites, the synergistic properties of tin (Sn) and lead (Pb) are leveraged, effectively combining the merits of Pb-based perovskites while simultaneously reducing Pb-associated toxicity. However, the propensity for Sn to undergo facile oxidation from Sn2+ to Sn4+ poses a significant challenge to the stability of these mixed perovskites, limiting their advancement. This study proposes an innovative acetic acid (HAc)-driven synthesis approach to obtain a stable chain-like MAPb0.5Sn0.5Br3 nano-assembly. Leveraging the acidic properties of HAc serves a dual purpose. Primarily, it curtails the oxidation of Sn2+ to Sn4+. Secondly, it orchestrates nanocrystals (NCs) into a more uniform and ordered chain-like assembly, a consequence of hydrogen bonding and coordination interactions facilitated by the HAc. Additionally, HAc demonstrates its capability to passivate MAPb0.5Sn0.5Br3 surface through coordination bonding with unsaturated sites (i.e., Sn2+ or Pb2+), thus effectively compensating for bromide vacancies. Introducing HAc during the synthesis process yields perovskite NCs with enhanced thermal resilience, optical and water stability. Drawing upon the different stimulus responses of synthesized perovskite NCs when exposed to external environment, the optical anti-counterfeiting labels are prepared. The findings provide a potent strategy for augmenting the stability of perovskite NCs, suggesting their potential applicability in anti-counterfeiting endeavors.

Multicolor-emitting Er3+ and Er3+/Yb3+ doped Zn2GeO4 phosphors combining static and dynamic identifications for advanced anti-counterfeiting application

Anti-counterfeiting labels based on luminescence materials are a newly emerging technique for protecting legal goods and intellectual property. In the anti-counterfeiting field to prevent forgery and cloning, luminescence materials with properties different from the commercialized and traditional ones are in urgent need. In this work, multicolor-emitting Er3+ single-doped and Er3+/Yb3+ co-doped Zn2GeO4 phosphors combining static and dynamic identifications were developed in order to achieve advanced anti-counterfeiting application. The variation of trap content with increasing the doping content of rare earth ions was analyzed through X − ray photoelectron spectroscopy, thermoluminescence analysis. It was found that there are two types of traps with different depth in Zn2GeO4 phosphors. The depths of the traps were experimentally confirmed to be 0.68 and 0.79 eV, respectively. The transient photocurrent response measurement confirmed the existence of charge carriers, and the mechanism for long persistent luminescence was deduced. The multicolor upconversion mechanisms under 980 and 1550 nm excitation were also discovered. Based on the multicolor steady and transient emission features, an anti-counterfeiting pattern was designed using the phosphors. Static and dynamic identification was demonstrated and presented in detail. Finally, it is indicated that the studied phosphors are excellent candidates for potential applications in luminescence anti-counterfeiting labels.

Magical fluorescent powder and ink for instantaneous imaging of latent fingerprints (level 1–3) and anti-counterfeiting labels

In the fingerprint research area, development of ‘old’ fingerprints (FPs) or FPs taken on porous, smooth surfaces, preservation of developed FPs and visualization of sweat pores are unsolved issues. In this report, we have synthesized and explored 4,5-bis(diethylene glycol) functionalized 1,8-naphthalimide (Naph-DG) dye for addressing these issues. The Naph-DG possesses high quantum yield (φ = 4.22) in solid-state suitable for the development of latent, old, stained FPs using powder dusting method on porous, non-porous and coloured surfaces up to levels 1–3. Depending upon the hydrophobicity of the surface, Naph-DG Chameleon emits blue, blue-greenish and greenish fluorescence on the ridges of the FPs. The practical applicability of Naph-DG was demonstrated using case studies. The FPs developed with Naph-DG can be lifted with scotch tape for preservation. The Naph-DG was also used (i) as a fluorescent ink for the development of anti-counterfeiting labels and (ii) for molecular recognition of Fe3+ as low as 42 nM in CH3CN.

A fluorescence–phosphorescence dual-emissive Cu3(pyrazolate)3 complex with highly tunable emission colours for anticounterfeiting and temperature sensing

An anti-counterfeit label and a luminescence thermometer are fabricated by the Cu3pyrazolate3 complex, showing luminescence switching between blue fluorescence and orange or red phosphorescence through modulating excitation energies or temperatures.

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

Information storage and security is one of the perennial hot issues in society, while the further advancements of related chemical anti-counterfeiting systems remain a formidable challenge. As emerging anti-counterfeiting materials, stimulus-responsive polymers (SRPs) have attracted extensive attention due to their unique stimulus-responsiveness and charming discoloration performance. At the same time, single-channel decryption technology with low-security levels has been unable to effectively prevent information from being stolen or mimicked. As a result, it would be of great significance to develop SRPs with multi-mode and multi-level anti-counterfeiting characteristics. This study summarizes the latest achievements in advance anti-counterfeiting strategies based on SRPs, including multi-mode anti-counterfeiting (static information) and multi-level anti-counterfeiting (dynamic information). In addition, the promising applications of such materials in anti-counterfeiting labels, identification platforms, intelligent displays, and others are briefly reviewed. Finally, the challenges and opportunities in this emerging field are discussed. This review serves as a useful resource for manipulating SRP-based anti-counterfeiting materials and creating cutting-edge information security and encryption systems.

Molten salt synthesized Tb3+, Pr3+ or Dy3+ single doped CaTa4O11 with persistent luminescence.

A series of Tb3+, Pr3+ and Dy3+ monodoped CaTa4O11(CTO) persistent luminescence (PersL) phosphors have been successfully synthesized using the molten salt method with KCl flux. The PersL color is green and orange for Tb3+ and Pr3+ or Dy3+ doped samples, respectively. The trap depth of Tb3+, Pr3+ and Dy3+ monodoped CTO is 0.33, 0.31 and 0.30 eV, respectively. The PersL time of 3 mol% Tb3+, 1 mol% Pr3+ and 1 mol% Dy3+ monodoped samples is 52.20, 35.00 and 59.46 s, respectively. Tb3+, Pr3+ and Dy3+ monodoped CTO phosphors can be used in luminescence displays and anti-counterfeit labels under commercial 254 nm UV light.

Anti-counterfeiting labels of photonic crystals with versatile structural colors.

Labels with structural color based on photonic crystals (PCs) have drawn significant attention due to their unique color emission, offering promising solutions for anti-counterfeiting applications. However, to meet the demands of future high-security applications, conventional structural color labels require further improvement. This study introduces a novel approach to fabricate highly encrypted anti-counterfeiting labels by combining close-packed and non-close-packed monolayers of nanoparticles (NPs) onto adhesive surfaces. The photonic crystals, arranged in specific geometric shapes, exhibit overt-covert characteristics. The hidden label is only revealed under specific external triggers, such as attaching or removing a transparent cover film. The principle of color modulation of the photonic crystal is elucidated, highlighting the role of packing density and refractive index matching. Additionally, the scalability and cost-effectiveness of the fabrication process in this study are expected to facilitate future commercialization. Various anti-counterfeiting applications, including water-responsive labels and multi-layer authentication, are demonstrated also, which enables higher security levels and versatility of this study.

Comprehension of the photoinduced charge transfer assisted energy transfer in Gd3+-based host sensitized tellurate phosphors for thermal sensing and anticounterfeiting labels.

A series of novel Eu3+-activated Ba2Gd2/3TeO6 (BGT) phosphors were successfully synthesised via a high temperature solid state reaction method. The crystal structure analysis showed that Eu3+-doped Ba2Gd2/3TeO6 double perovskite phosphors possess monoclinic symmetry with space group P21/n. The as-prepared phosphors can be efficiently excited by far-ultraviolet light to generate reddish orange luminescence of around 593 nm corresponding to the 5D0 → 7F1 transitions of Eu3+ ions. Gd3+ acts as a sensitizer for luminescence enhancement. The highest luminescence intensity corresponded to x = 0.11 Eu3+ concentration, and the critical distance was calculated to be 9.61 Å, indicating that multipolar interaction is behind the concentration quenching mechanism. Besides, the optimum concentration Eu3+-activated Ba2Gd2/3TeO6 phosphor exhibited color co-ordinates of (0.63, 0.36), a high color purity of 94.21% and a quantum efficiency of 18%. JO intensity parameters reveal the slight distortion of the crystal field around the activator ion. Notably, the maximum relative sensitivities of the BGT:0.11Eu3+ phosphor were found to be 0.19% K-1 within the temperature range of 300-500 K and 2.07% K-1 within 80-300 K, and it can potentially be used as a promising thermometer in high and low temperature regions, respectively. The luminescent labels based on fluorescent ink and PL chalk demonstrate the potential application of synthesized phosphors in anti-counterfeiting and security labeling.

A multidimensional anti-counterfeiting dynamic flexible label based on light/thermal responsive CLC microspheres

Compared to static anti-counterfeiting, polymorphic dynamic anti-counterfeiting typically incorporates additional parameters specifically to increase the complexity of decryption.

Robust lanthanide MOFs as multifunctional luminescent sensors for intelligent visualization monitoring of MEAA and texture code anti-counterfeiting applications

Ln-MOFs were designed for anti-counterfeiting labels by using texture codes. Moreover, three visual probes based on 1-Eu for MEAA detection are fluorescent films, RGB intelligent detection sensor platforms, and portable logic detectors.

基于纳米银SERS防伪图案防伪标签研究

基于纳米银SERS防伪图案防伪标签研究