Anti-counterfeiting Labels Research Articles

Dual upconversion nanophotoswitch for security encoding

Light-harvesting lanthanide ions (Ln3+) doped NaYF4 inks could provide polychromatic patterns for opposing counterfeiting commodity infestation because of their distinctive upconversion photoluminescence (UPL) properties. Herein, three kinds of core-triple-shell Ln3+ ions doped NaYF4 upconversion nanocrystals (UCNCs) are synthesized through modified high-temperature coprecipitation, which demonstrate excellent UPL properties of independent emitting colors under 808 or 980 nm laser excitation. Additive mixing three kinds of 808 nm emitted red-green-blue (RGB) UCNCs colloid solution can precisely regulate the emissions of the suspension for achieving full-color display. The as-obtained RGB three-primary colors induced by 808 nm laser accomplish broader color gamut than traditional standard RGB (sRGB) model and printing cyan-magenta-yellow (CMY) model. In addition, various China zodiac patterns and complex multicolor images are printed by the as-formulated UCNCs inks through screen printing technology. The printed patterns present colorful and polychromatic sequential toning visualization patterns under 808 nm excitation, while present another succession of gradually changed versatile patterns under 980 nm excitation. As a proof of concept, transparent polyvinyl chloride (PVC) self-adhesive anti-counterfeiting label is attached to the bottle of wine package for practical application. The demonstration of multiple model patterns of Chinese zodiac and poetry images based on these core-triple-shell UCNCs can be selected as a conceivable substitute of traditional single model patterns, underlining the full-color anti-counterfeiting level.

Angular Photochromic LC Composite Film for an Anti-Counterfeiting Label.

In the harsh application environment, improving the mechanical properties of liquid crystal materials is a fundamental and important problem in the design of anti-counterfeit materials. In this paper, by a stepwise polymerization of first, photo-polymerization and subsequently thermal-polymerization, a coexistent polymer dispersed network was first constructed in cholesteric liquid crystal materials containing a photo-polymerizable system of urethane acrylate and a thermo-polymerizable system of isocyanate. Results revealed that the coexistent polymer dispersed network exhibited largely enhanced mechanical performance, and the networks obtained by different methods had different contributions to the enhancement of the peel strength and toughness of the composite films. Then an angular photochromic anti-fake label based on a coexistent polymer dispersed network with enhanced mechanical and apparent angular discoloration characteristics, suitable for practical applications, was successfully achieved.

Temperature-tunable lasing from dye-doped chiral microdroplets encapsulated in a thin polymeric film.

In the last decade, much interest has grown around the possibility to use liquid-crystal droplets as optical microcavities and lasers. In particular, 3D laser emission from dye-doped cholesteric liquid crystals confined inside microdroplets paves the way for many applications in the field of sensors or tunable photonics. Several techniques can be used to obtain small microresonators as, for example, dispersing a liquid crystal inside an immiscible isotropic fluid to create an emulsion. Recently, the possibility to obtain a thin free-standing film starting from an emulsion having a mixture of water and polyvinyl alcohol as isotropic matrix has been reported. After the water evaporation, a polymeric film in which the microdroplets are encapsulated has been obtained. Bragg-type laser emission has been recorded from the emulsion as well as from the thin film. Here, we report on the possibility to tune the laser emission as a function of temperature. Using a chiral dopant with temperature dependent solubility, the emitted laser wavelength can be tuned in a range of 40 nm by a temperature variation of 18 °C. The proposed device can have applications in the field of sensors and for the development of anti-counterfeiting labels.

Full Color Camouflage in a Printable Photonic Blue-Colored Polymer.

A blue reflective photonic polymer coating which can be patterned in full color, from blue to red, by printing with an aqueous calcium nitrate solution has been fabricated. Color change in the cholesteric liquid-crystalline polymer network over the entire visible spectrum is obtained by the use of nonreactive mesogen. The pattern in the coating is hidden in the blue color dry state and appears upon exposure to water or by exhaling breath onto it due to different degrees of swelling of the polymer network. The degree of swelling depends on the printed amount of calcium which acts as a cross-linker. The printed full color pattern can also be hidden simply by using a circular polarizer. The responsive full color camouflage polymers are interesting for various applications ranging from responsive house and automobile decors to anticounterfeit labels and data encryption.

Triple-shape memory effect in poly (ethylene terephthalate) (PET) film

PurposeThis paper aims to focus on achieving triple-shape memory effect (triple-SME) of a commercial poly (ethylene terephthalate) (PET) film with the thickness of 100 µm.Design/methodology/approachThe thermal characteristics and microstructure of PET film were characterized by differential scanning calorimetry, thermogravimetric analysis and wide-angle X-ray diffraction analysis. The dual-shape memory effect (dual-SME) of the PET film was then systematically investigated, and based on that, triple-SME in thin PET film was achieved.FindingsInvestigation of the dual-SME in PET film revealed the difference between recovery temperature and programming temperature reduced with increasing programming temperature. An obvious intermediate shape shifting between the original and final programmed shape was observed during shape recovery in triple-shape memory behaviors.Research limitations/implicationsCompared with dual-SME in polymer, relatively less work has been done on multi-SME in polymer, especially in thin polymer film. In this study, triple-SME in a PET film was investigated based on the results of dual-SME of the film. The main implication of the study is on how to achieve a watermark between the final programmed pattern and the original pattern, for the application of shape memory polymer in anti-counterfeiting label.Originality/valueDual- and triple-SMEs were achieved in a PET film that is only 100 µm in thickness, and the underlying mechanism for the difference between programming temperature and recovery temperature was discussed. For the novel application of triple-SME in anti-counterfeit label, the watermark during shape recovery in triple-SME can effectively prevent duplication.

Luminescent metal clusters/barium sulfate composites for white light-emitting devices and anti-counterfeiting labels.

The applications of luminescent metal nanoclusters (NCs) in device fabrication have been greatly limited by their tough solidifying process and poor stability. In this work, we report the facile preparation of metal NCs/barium sulfate (BaSO4) composites by incorporating luminescent metal NCs into BaSO4 matrix by subsequent addition of Ba2+ and SO42− ions into the aqueous dispersions of the metal NCs. The resulting NCs/BaSO4 composites maintained the luminescent colour of the metal NCs and possessed improved stability under external stimuli, such as heating, strong acid and organic solvents. The solid metal NCs/BaSO4 composites with blue, green and red emissions were suitable for the fabrication of white light-emitting devices (WLEDs) and multicolour anti-counterfeiting labels.

Emerging upconversion nanoparticles for industry and biomedical application

In recent years, the overwhelming majority of the upconversion nanoparticles (UCNPs) prominent applications have originated from their unique luminescent properties. Due to original properties of inorganic UCNPs they attract the interest in numerous fields. We discussed a number of UCNP assisted techniques, such as biomedical imaging, therapy agents, anti-counterfeit labels and 3D printing, showing highly versatile and translatable UCNP photoluminescent nanotechnology for the applications in industry and biomedicine.

Composites of CaAl2O4: Eu2+, Nd3+/Ca0.25Sr0.75S: Eu2+ in Polyacrylonitrile Fibers with Tri-Stimuli-Responsive Persistent Luminescence

In this study, ultraviolet(UV) light-excited CaAl2O4: Eu2+, Nd3+ and visible light-excited Ca0.25Sr0.75S: Eu2+ were incorporated in the polyacrylonitrile (PAN) fibers by wet-spinning. Scanning electron microscopy, X-ray diffraction, photoluminescence, and decay analysis were used to characterize the morphology, inner structure, photoluminescence and afterglow behavior of the composite fibers, respectively. The results indicated random distribution of the two inorganic phosphors into the PAN fiber. To investigate the stimuli-responsive properties of the composite fiber, experiments were performed under UV light, visible light and D65 lamp. The results revealed that, the obtained composite fibers featured a blue emission of CaAl2O4: Eu2+, Nd3+ at 450 nm and a red emission of Ca0.25Sr0.75S: Eu2+ at 620 nm. Furthermore, decay curves indicated the decrease of luminescence intensity of the composite fiber when the two phosphors were simultaneously excited, which are attributed to the different irradiation source. It is expected that this multicolor fiber could be used in high-level information anti-counterfeiting label in clothes and smart clothing.

Construction of Luminogen Exhibiting Multicolored Emission Switching through Combination of Twisted Conjugation Core and Donor-Acceptor Units.

Stimuli responsive luminescent materials, especially those exhibiting multicolor emission switching, have potential application in sensor, optical recording, security ink, and anti-counterfeit label. Through combination of twisted conjugation core and donor and acceptor units, a luminogen (2-(bis(4-(carbazol-9-yl)phenyl)methylene)malononitrile (1) was synthesized. Luminogen 1 can form three kinds of crystals emitting green (1GC, λem = 506 nm, ΦF = 19.8%), yellow-green (1YC, λem = 537 nm, ΦF = 17.8%), and orange (1OC, λem = 585 nm, ΦF = 30.0%) light upon 365 nm UV illumination. The emission of amorphous solid of 1 (1Am) overlaps with that of 1OC (λem = 585 nm), with quantum yield of 13.9%, which is seldom reported. Emission of 1 can be switched among green, yellow-green, and orange through morphology modulation upon exposure to thermal, solvent vapor, or mechanical stimuli. Finally, its potential application in optical recording was also investigated.

Highly phosphorescent hollow fibers inner-coated with tungstate nanocrystals

In order to develop luminescent microtubes from natural fibers, a facile biomimetic mineralization method was designed to introduce the CaWO4-based nanocrystals into kapok lumens. The structure, composition, and luminescence properties of resultant fibers were investigated with microscopes, x-ray diffraction, thermogravimetric analysis, and fluorescence spectrometry. The yield of tungstate crystals inside kapok was significantly promoted with a process at high temperature and pressure—the hydrothermal treatment. The tungstate crystals grown on the inner wall of kapok fibers showed the same crystal structure with those naked powders, but smaller in crystal size. The resultant fiber assemblies demonstrated reduced phosphorescence intensity in comparison to the naked tungstate powders. However, the fibers gave more stable luminescence than the naked powders in wet condition. This approach explored the possibility of decorating natural fibers with high load of nanocrystals, hinting potential applications in anti-counterfeit labels, security textiles, and even flexible and soft optical devices.

Using Anodic Aluminum Oxide Film and Nanoimprint to Produce Polymer Anti-counterfeit Labels

An anodic aluminum oxide (AAO) film fabrication process and photolithography were combined to produce a patterned array of nano-hemispheres. This barrier was then used as the substrate on which conductive metals were vapor-deposited to produce electrodes. Nano electroforming was then utilized to deposit nickel on the surface of the array of nano-hemispheres. The oxidized aluminum was etched with phosphoric acid to form a complementary array of nano-pits. Finally, the technique of nanoimprinting was used to transfer the unique structure of the barrier to a polymer. Scanning electron microscopy (SEM) was used to explore the effects of different voltages on the fabrication process and of phosphoric acid etching time on the shape of the barrier. An atomic force microscope (AFM) was used to verify that the nano-array structure of the aluminum oxide film had been completely replicated on the polymer. The regular arrangement of nano-hemispheres refract light and also cause interference, such an array is referred to as a photonic crystal. This type of special structure can be used in counterfeit protection and in many other optical applications.

Metal nanomaterials for optical anti-counterfeit labels

The global economic, security, and health challenges presented by counterfeit goods require new approaches toward anti-counterfeit labels.

Sub-micron silk fibroin film with high humidity sensibility through color changing

A Sub-micron silk fibroin film with high humidity sensibility through color changing is achieved by spin-coating fibroin aqueous solution, and it can be potentially applied for low-cost and fast humidity detection, as well as anti-counterfeit labels.

Preparation and RGB upconversion optic properties of transparent anti-counterfeiting films.

Advanced anti-counterfeiting labels have aroused an intensive interest in packaging industry to avoid the serious issue of counterfeit. However, the preparation and cost of the existing labels associated with the drawbacks, including the complex and high-cost equipment, limit the protection of the authenticity of goods. Herein, we developed a series of anti-counterfeiting labels based on multicolor upconversion micro-particles (UCMPs) inks via straightforward and low-cost solutions, including spin-coating, stamping and screen printing. The UCMPs were synthesized through a facile hydrothermal process and displayed tunable red (R), green (G) and blue (B) color by doping different lanthanide ions, which are Er3+/Tm3+, Yb3+/Er3+ and Yb3+/Tm3+ in NaYF4 hosts, respectively. The optimal UCMPs inks were deposited on a flexible polyethylene terephthalate (PET) substrate to obtain transparent anti-counterfeiting labels possessing higher transmittance, stronger upconversion fluorescence intensity and good photostability. Under ambient conditions, the patterns and films were transparent, but could exhibit multicolor light under 980 nm laser excitation. They can be used as anti-counterfeiting labels for die-cutting packages to further elevate the security of goods. The tunable and designable transparent anti-counterfeiting labels based on RGB UCMPs inks exhibit the merits of low-cost, easy-manufacture and versatility, underlying the practical application in the field of anti-counterfeiting.

A self-monitored fluorescence DNA anti-counterfeiting system based on silica coated SYBR Green I/DNA gelatin nanoparticles

Silica-coated SYBR Green I/DNA gelatin nanoparticles (SSDG NPs) with high stability and self-monitored of DNA activity were prepared for anti-counterfeiting label, which could be rapidly detected by UV irradiation and precisely detected by PCR and DNA sequencing.

Individual dual-emitting CdS multi-branched nanowire arrays under various pumping powers

High-quality Tin doped Cadmium Sulfide (CdS) comb-like nanostructures have been synthesized by a simple in situ seeding chemical vapor deposition process. The color-tunable dual emission of these comb-like nanostructures is demonstrated by changing the excitation power intensity. In fact, the color-tunable emission is in principal due to the variation of the dual emission intensity, which is proven by photoluminescence spectra and real color photoluminescence charge-coupled device images. Especially for different parts in the nano comb, the emission color can be varied even under the same pumping power. This is mainly due to the difference in local structure. By comparison, the color variation was not observed in pure CdS multi-branched nanostructures. The lifetime results demonstrate that the green emission originate from the recombination of free excitons. The origin of red emission is from the recombination of the dopant-induced intrinsic or extrinsic defect states. These findings provide potential applications of laser assisted anti-counterfeit label and micro-size monitors.

Tunable Design of Structural Colors Produced by Pseudo‐1D Photonic Crystals of Graphene Oxide

It is broadly observed that graphene oxide (GO) films appear transparent with a thickness of about several nanometers, whereas they appear dark brown or almost black with thickness of more than 1 μm. The basic color mechanism of GO film on a sub-micrometer scale, however, is not well understood. This study reports on GO pseudo-1D photonic crystals (p1D-PhCs) exhibiting tunable structural colors in the visible wavelength range owing to its 1D Bragg nanostructures. Striking structural colors of GO p1D-PhCs could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion during vacuum filtration. Moreover, the quantitative relationship between thickness and reflection wavelength of GO p1D-PhCs has been revealed, thereby providing a theoretical basis to rationally design structural colors of GO p1D-PhCs. The spectral response of GO p1D-PhCs to humidity is also obtained clearly showing the wavelength shift of GO p1D-PhCs at differently relative humidity values and thus encouraging the integration of structural color printing and the humidity-responsive property of GO p1D-PhCs to develop a visible and fast-responsive anti-counterfeiting label. The results pave the way for a variety of potential applications of GO in optics, structural color printing, sensing, and anti-counterfeiting.

Soft template synthesis of honeycomb-like ratiometric oxygen sensitive polystyrene nanospheres and their application in anti-counterfeit authentication and food packaging dynamic indication

A new methodology to obtain honeycomb-like oxygen-sensitive polystyrene nanospheres has been developed via a facile co-precipitation procedure. Commercially available triblock copolymer Pluronic F127 was utilized as a soft template to shape polystyrene into regular spherical nanostructures. The morphology of the prepared polystyrene nanospheres could be tuned through the modification of the initial concentration of F127 or polystyrene in the aqueous phase. The oxygen indicator, platinum(II)-tetrakis(pentafluorophenyl)porphyrin (maximal emission wavelength at 648nm), and the reference fluorophore, poly(9, 9-dioctylfluorene) (maximal emission wavelength at 440nm), were selected and doped into the polystyrene nanospheres for the ratiometric detection of oxygen. The honeycomb-like oxygen-sensitive polystyrene nanospheres exhibited satisfactory ratiometric luminescence responses to O2 with high quenching efficiency and full reversibility in oxygen sensing. More importantly, the as-prepared polystyrene nanospheres displayed distinct change from red to blue when they were exposed to air from a nitrogen atmosphere. These prepared polystyrene nanospheres can potentially be used as anti-counterfeit labels in the recognition of forged items, or acted as a dynamic signage for on shelf food packaging, since many foods are kept in a vacuum or in an inert gas, such as carbon dioxide or nitrogen.

Hidden Watermark of 3D Models by Just Noticeable Color Difference

A watermark is a subtle pattern on images or documents to prevent counterfeiting. For color 3D models, it is feasible for add watermarks on either texture images or vertex colors, as well. We propose a hidden watermark method by superimposing a just noticeable difference pattern on 3D color models. The color difference on the watermark is too small to be noticed and it will be enlarged under specific lighting conditions in the computer graphics environment. This idea is very similar to the anticounterfeit label on most banknotes. Thus, the watermark is almost invisible when rendering under formal white lights, but visible under violet lights.

Biocompatible upconversion ink for hidden anticounterfeit labeling

Ink for rapid the application of anticounterfeit labels by means of standard printing devices has been developed based on upconversion nanoparticles (nanophosphors). Printing ink is made of an aqueous dispersion of nanoparticles with a NaYF4:YbTm/NaYF4 core–shell structure at a concentration of 0.5 mg/mL. The surface of nanoparticles is modified with amphiphilic polymers. The biosafety of ink is demonstrated in primary cultures of human fibroblasts. The hidden labeling, which is invisible in ambient lighting, is performed by the method of inkjet printing on paper. A printed image is visualized by IR laser irradiation at a wavelength of 975 nm. It is demonstrated that additional modalities of protection can be obtained by encoding the spectra and intensities of the anti-Stokes luminescence lines when combining the dopant lanthanides in nanoparticles.