Anti-counterfeit Printing Research Articles

In Situ Fabrication of Lead-Free Double Perovskite/Polymer Composite Films for Optoelectronic Devices and Anticounterfeit Printing.

Lead-free double perovskites (DP) have the potential to become a rising star in the next generation of lighting markets by addressing the toxicity and instability issues associated with traditional lead-based perovskites. However, high concentrations of hydrochloric acid (HCl) were often employed as a solvent in the preparation of most DPs, accompanied by slow crystallization at high temperatures, which not only raised the risk and cost in the preparation process, but also had a potential threat to the environment. Here, an in situ fabrication strategy was proposed to realize the crystallization of DP in the polymer at low temperature with a mild dimethyl sulfoxide (DMSO) solvent, and subsequently obtained optically well-behaved Cs2Na0.8Ag0.2BiCl6/PMMA composite films (CFs) by doping with Ag+, generating bright orange luminescence with a photoluminescence quantum yield (PLQY) of up to 21.52%. Moreover, the growth dynamics of Cs2Na0.8Ag0.2BiCl6/PMMA CFs was further investigated by in situ optical transformation, which was extended to other DP-based polymer CFs. Finally, these CFs exhibited excellent performance in optoelectronic devices and anticounterfeit printing, the results of which provide a new pathway to advance the development of lead-free DP materials in the optical field.

Chiral Carbon Dots: Synthesis and Applications in Circularly Polarized Luminescence, Biosensing and Biology.

Chiral carbon dots (CDs) are a novel luminescent zero-dimensional carbon-based nanomaterial with chirality. They not only have the advantages of good biocompatibility, multi-color-emission, easy functionalization, but also exhibits highly symmetrical chiral optical characteristics, which broadens their applicability to enantioselectivity of some chiral amino acids like cysteine and lysine, asymmetric catalysis as well as biomedicine in gene expression and antibiosis. In addition, the exploration of the excited state chirality of CDs has developed its excellent circularly polarized luminescence (CPL) properties, opening up a new application scenario like recognition of chiral light sources and anti-counterfeit printing with information encryption. This review mainly focuses on the mature synthesis approaches of chiral CDs, including chiral ligand method and supramolecular self-assembly method, then we consider emerging applications of chiral CDs in CPL, biosensing and biological effect. Finally, we concluded with a perspective on the potential challenges and future opportunities of such fascinating chiral CDs.

Synthesis and Characterization of AIE Materials and Their Application for Anti-Counterfeit Printing

Synthesis and Characterization of AIE Materials and Their Application for Anti-Counterfeit Printing

Multifunctional Probes with High Utilization Rates: Self-Assembled Merocyanine Nanoparticles in Water as Acid-Base Indicators and Mitochondrion-Targeting Chemotherapeutic Agents.

Multifunctional probes with high utilization rates have great value in practical applications in various fields such as cancer diagnosis and therapy. Here we have synthesized two organic molecules based on merocyanine. They can self-assemble in water to form ∼1.5 nm nanoparticles. Both of them have good application potential in fluorescent anticounterfeit printing ink and pH detection. More importantly, they have excellent mitochondrial targeting ability, intracellular red light and near-infrared dual-channel imaging ability, strong antiphotobleaching ability, and in vivo and in vitro near-infrared imaging capabilities, showing superior chemotherapy capabilities and biocompatibility in the 4T1 tumor-bearing mouse model.

Green Synthesis of Tunable Fluorescent Carbon Quantum Dots from Lignin and Their Application in Anti-Counterfeit Printing.

Lignin converted to carbon quantum dots (CQDs) attracts tremendous attention for large-scale production of carbon nanomaterials and value-added disposal of biomass wastes (such as the black liquor from pulping industry and the residue from hydrolysis of biomass). The green synthesis of lignin-derived CQDs is reported via a facile two-step method with the adjustment of acid additives containing N or S. The resulting series of CQDs exhibit bright fluorescence in gradient colors from blue to yellowish green, among which the N, S co-doped CQDs with the addition of 2,4-diaminobenzene sulfonic acid show an optimal fluorescence quantum yield (QY) of 30.5%. The red-shift photoluminescence emission behaviors of these CQDs can be attributed to the increased graphitization degree and reduced optical energy band gaps (2.47 → 2.17 eV) with regard to the incorporation of various heteroatoms. The improved fluorescence QYs are consistent with the variation trend of the increased N/C content in the CQDs. The yellowish green-emissive CQDs with bright fluorescence, strong water solubility, and excellent chemical stability perform well in anti-counterfeiting printing. The promising and sustainable approach for the synthesis of tunable fluorescent CQDs exhibits the value-added utilization of lignin for the fluorescence ink production.

Smart screen-printed photochromic fabrics with fast color switching performance and high fatigue resistance for energy storage applications

Photochromic materials have great potential in various novel optoelectronic devices such as adaptive regulation, smart detection, information storage, and camouflage anti-counterfeiting displays. However, the problems of high sensitivity and not to be influenced by external factors are urgent to be solved. Here, we have successfully prepared smart photochromic fabrics for stimulus-responsive applications with high-sensitive spiropyran (SP) and a phase change material of butyl stearate as core materials and encapsulated by a highly translucent poly(methyl methacrylate) (PMMA) shell. And then, they are coated on the fabrics with water-based polyurethane (WPU) by a facile method of screen printing. The preparation of photochromic materials as the form of microcapusles aims at reducing external factors’ disturb and achieving a rapid response when in use. The phase change material of microcapusles acts as a thermal regulation effect on the whole system, providing energy storage and temperature regulation. The resultant reversible photochromic fabrics prepared by this method has the potential applications of tangible information storage (QR codes), anti-counterfeit printing and rewritable patterns due to their fast response and reusability under UV light.

Fabrication of carbon dots for sequential on-off-on determination of Fe3+ and S2- in solid-phase sensing and anti-counterfeit printing.

Glutathione and 2-aminopyridine are used as carbon sources to prepare carbon dots (CDs) by a one-step hydrothermal reaction. The results show that the average particle diameter of CDs is 8.64nm with uniform size distribution and the fluorescence quantum yield is 13.62%. We further demonstrate that novel CDs possess highly selective sensing of Fe3+ from 0.2 to 200μM with a low detection limit (0.194μM). Meanwhile, the fluorescence of CDs can be repeated many times by the addition of S2-. Moreover, the CDs are used for biological imaging of living cells with well cell penetrability and low toxicity. Furthermore, it is successfully applied for anti-counterfeiting and information encryption. More interestingly, it can be doped with hydrogel and filter paper to prepare solid-phase sensors exhibiting high sensitivity and fast response, demonstrating their tremendous potential for the simple, rapid, and low-cost monitoring of Fe3+ and S2-.

Harvesting Light To Produce Heat: Photothermal Nanoparticles for Technological Applications and Biomedical Devices.

The photothermal properties of nanoparticles (NPs), that is, their ability to convert absorbed light into heat, have been studied since the end of the last century, mainly on gold NPs. In the new millennium, these studies have developed into a burst of research dedicated to the photothermal ablation of tumors. However, beside this strictly medical theme, research has also flourished in the connected areas of photothermal antibacterial surface coatings, gels and polymers, of photothermal surfaces for cell stimulation, as well as in purely technological areas that do not involve medical biotechnology. These include the direct conversion of solar light into heat, a more efficient sun‐powered generation of steam and the use of inkjet‐printed patterns of photothermal NPs for anticounterfeit printing based on temperature reading, to cite but a few. After an analysis of the photothermal effect (PTE) and its mechanism, this minireview briefly considers the antitumor‐therapy theme and takes an in‐depth look at all the other technological and biomedical applications of the PTE, paying particular attention to photothermal materials whose NPs have joined those based on Au.

Tunable Photonic Microspheres of Comb-Like Supramolecules.

Photonic crystals (PCs) are ideal candidates for reflective color pigments with high color purity and brightness due to tunable optical stop band. Herein, the generation of PC microspheres through 3D confined supramolecular assembly of block copolymers (polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP) and small molecules (3-n-pentadecylphenol, PDP) in emulsion droplets is demonstrated. The intrinsic structural colors of the PC microspheres are effectively regulated by tuning hydrogen-bonding interaction between P2VP blocks and PDP, where reflected color can be readily tuned across the whole visible spectrum range. Also, the effects of both PDP and homopolymer (hPS) on periodic structure and optical properties of the microspheres are investigated. Moreover, the spectral results of finite element method (FEM) simulation agree well with the variation of structural colors by tuning the periodicity in PC microspheres. The supramolecular microspheres with tunable intrinsic structural color can be potentially useful in the various practical applications including display, anti-counterfeit printing and painting.

Facile synthesis and photoluminescence mechanism of green emitting xylose-derived carbon dots for anti-counterfeit printing

The realization of long-wavelength emissions and thoroughly understanding of photoluminescence (PL) mechanism are still huge challenges to be addressed for further development of carbohydrate-derived carbon dots (CDs). Herein, novel CDs with excellent green emission were synthesized from a precursor comprising of xylose and m-phenylenediamine in phosphoric acid solution via a simple microwave-assisted hydrothermal method. The PL efficiency was dependent on the combination of different acids and the precursor as well as the synthesis temperature, while the PL properties were mainly related to the acid base environment of precursor. Optical performance and structural characterization revealed that the oxygen-containing groups and protonated amino groups were mainly responsible for the blue and green emission properties, respectively. Moreover, a multi-center fluorescent mechanism on the different PL performances of xylose-derived CDs was proposed and verified by further investigating the pH-dependent PL behaviors. Based on the switching between green and blue emission in different pH regions, the xylose-derived CDs solution was demonstrated to be a promising fluorescent ink for anti-counterfeit printing. This research open a door for value-added utilization of xylose, as well as providing a facile and green strategy for large-scale preparation of CDs.

Excitation-tailored dual-color emission of manganese(II)-doped perovskite nanocrystals

Manganese(II)-doped perovskite nanocrystals with superior dual-color light emission properties are promising for optoelectronic applications. Here, we report that the emission color of these nanocrystals can be tailored by continuous-wave excitation because of the saturation of dopant emission at a record low light density (∼10 mW/cm2). By detuning the repetition rates of excitation laser sources, we show that the bottleneck of exciton-manganese(II) energy transfer caused by the imbalanced excitation and deexcitation of 4T1 states is the primary mechanism underlying the emission saturation properties. Such a dual-color luminescence tunable by weak excitation is promising for uses in potential applications such as luminescent solar concentrators, light intensity sensors, anti-counterfeit printing, and photo-switchable image markers.

Preparation of fluorescent waterborne polyurethane nanodispersion by high-gravity miniemulsion polymerization for multifunctional applications

Polymer encapsulated fluorescent nanoparticles have found many applications in bioimaging, fluorescent gels and inks. However, their translation into the practical products has been slow because it is still difficult to produce nanoparticles that are consistent “batch-to-batch” for scale-up. Herein, we develop a high-gravity miniemulsion polymerization route for fluorescent waterborne polyurethane (PU) by using rotating packed bed (RPB) reactor for process intensification. In optimized conditions, the PU nanoparticles obtained exhibited an average size of 137 nm with narrow size distribution. Dispersion stability of the PU nanodispersions was investigated and no significant sediments or aggregates were observed for up to one month. The 1,1,2,3,4,5-hexaphenylsilole dyes, a kind of typical aggregation-induced emission luminogens (AIEgens), could be in situ loaded in PU nanoparticles, forming fluorescent nanodispersions of AIEgens@PU in aqueous solution. The preliminary applications of AIEgens@PU nanodispersion for in vitro fluorescent labeling of cells, transparent fluorescent films and anti-counterfeit printing inks were demonstrated. This study demonstrated that the newly developed high-gravity miniemulsion polymerization method provides an effective route to waterborne PU nanodispersion for multifunctional applications.

Microwave-assisted synthesis of highly water-soluble LuVO4:Eu nanoparticles as anti-counterfeit fluorescent ink

Highly water-soluble LuVO4:Eu nanoparticles with an average diameter of 165 nm were synthesized by a simple and rapid microwave-assisted hydrothermal method with water as solvent and polyacrylic acid (PAA) as surfactant. The conditions for synthesizing high-quality LuVO4:Eu nanoparticles were screened out by adjusting pH, temperature and the concentration of Eu3+ ions. The solution of high-quality nanoparticles with relatively long fluorescence lifetime showed strong red emissions under ultraviolet excitation. Due to the high water-solubility and good fluorescence property, the aqueous solution of LuVO4:Eu nanoparticles was used as ink for anti-counterfeit printing, which meets various anti-counterfeit requirements.

Highly efficient and stable blue-emitting CsPbBr3@SiO2 nanospheres through low temperature synthesis for nanoprinting and WLED

Inorganic perovskite quantum dots (QDs) have attracted wide attention in display and solid-state lighting because of their easily tunable band-gaps and high photoluminescence quantum yields (PLQY) of green light emission. However, some drawbacks limit their practical applications, including the low PLQY of blue light emission and the instability in the moisture environment. In this work, efficient blue-light emitting CsPbBr3 perovskite QDs with PLQY of 72% were developed through a bandgap engineering approach. The achieved blue-light emitting PLQY is much higher than the values acquired in the inorganic perovskite QDs in the literature. And the emission color of the as-prepared QDs can be facially tuned by only adjusting the reaction temperature. Further, the mono-dispersed perovskite QDs@SiO2 composites were constructed benefiting from the low temperature synthesis. The optical performance of the QDs could be well persisted even in the moisture environment. Finally, the as-prepared QDs@SiO2 composite was fabricated as the QD ink on the anti-counterfeit printing technology, from which the obtained pattern would emit varied color under UV lamp. And the as-prepared composites was also applied for fabricating WLED, with Commission Internationale de l’Eclairage (CIE) color coordinates of (0.33, 0.38) and power efficiency of 32.5 lm W−1, demonstrating their promising potentials in solid-state lighting.

Adaptive Halftone Watermarking Algorithm Based on Particle Swarm Optimization

Digital watermarking has been widely used in copyright protection for digital images, but most of the watermarking algorithm can't resist print-and-scan process. Print-and-scan attack is a challenging problem for most of digital watermarks. A watermarking algorithm against print-and-scan attack based on PSO (Particle Swarm Optimization) is proposed in this paper. The watermark information is embedded in a halftone process for image screening with phase modulation method. The watermark is extracted by a template, which is optimized using the PSO algorithm. Both mean filtering and median filtering are used to remove noise from the recovered watermark image. The experimental results show the halftone watermarking algorithm optimized using PSO has better performance, it is robust under smearing attack and cropping attack, and has good resistance to print-and-scan process. It can be applied in the field of anti-counterfeit printing.

Researches on the Information Hiding Technology Used in Paper-Based Document Images

With the rapid development of the information technology and digital image copy devices, the information carrier shows off diversified trends. However paper media still play an important role in many areas serving as information carrier, and correspondingly the information security of paper documents faces great challenges. So how to solve the information security problems of paper media has become the hottest research topic. This paper proposes an information hiding method used in printed documents image based on the screen dots modulating shade composed of a large number of randomly arranged screen dots. These dots are classified into coding dots, anchor dots and perturbing dots respectively. Experimental results show that screen dots modulating shade using our method has larger information capacity and also has strong robustness against the attacks of print-scan processes. Moreover, this technology also can be widely used in many other areas, such as anti-counterfeit printing, anti-copy, document content tamper-proofing and document image retrieval etc.

Preliminary Study on the Green Anti-Counterfeiting Printing Materials

By using DiaionHP-20 and SephadexLH-20 to isolated and purify the pigment of Rhododendron simsii, a high concentration of fluorescent substances from plant organs was obtained, and then study on the anti-counterfeit marking test was carried out. The result reveals that though extracting the pigment in the petals by SephadexLH-20, 5 different fluorescence regions can be clearly seen, of which the yellow-green region was the most obvious one. Fluorescent pigment from plant organs is plant secondary organic metabolites which have non-toxic, non-radiation matters to human. Thus the deeper research of the fluorochrome from plant organ could not only be used in the antibacterial activity of fresh food preservation aiming at preventing the abuse of chemical preservation substance, but also develop a new type of anti-counterfeit printing materials---natural water-based fluorescent ink, and the result brings business opportunities to the new industry of “green anti-counterfeit printing”.

Study of Anti-Counterfeit Printing with Cylindrical Lens Sheet Basic on Screening Copy

Grating material can have security effects in print for its specific optical properties. In this paper, the technology of copyright protection used in Screening Copy is studied basic on the optical properties of cylindrical lens sheet and screening. Firstly, the relation of the parameter of cylindrical lens sheet and the parameters of half-tone image is studied. Achieving the arithmetic what used to set dot basic on the relation. Secondly, imitating the experiment in Photoshop cs2 and setting dot after transferring the image to halftone use the screening of it. Meanwhile, generate the layer which has the effect of cylindrical lens sheet and can get the imitate effect while rotate the layer. In the experiment, using the printer of Epson 7880 to print the image and examining the security through corresponding cylindrical lens sheet. The experiment proves the hidden information only can be seen though cylindrical lens sheet and it shows the anti-counterfeit way have well effect in screening copy. And the equipment and processes are not needed too much for this way, so the anti-counterfeit effect can be achieved in the condition of not adding cost.