Anti-counterfeiting Ink Research Articles

Enhanced Upconversion Photoluminescence of LiYF4: Yb3+/Ho3+ Crystals by Introducing Mg2+ Ions for Anti-Counterfeiting Recognition

By doping appropriate lanthanide ions, LiYF4 as a host luminescent material can simultaneously exhibit bright visible-light emission. A series of LiYF4:Yb3+/Ho3+ microparticles with different Mg2+ doping concentrations were synthesized and investigated. The crystal structure of the synthesized microparticles was tested by X-ray diffraction (XRD). Notably, a significant increase in the upconversion photoluminescence intensity of upconversion microparticles (UCMPs) was obtained by introducing Mg2+ ions under 980 nm laser excitation, and achieved a maximum level when the concentration of Mg2+ ions was 8 mol%. Additionally, the practicality of the resultant UCMPs used as the raw material of anti-counterfeiting ink was systematically investigated. These results prove that the Mg2+-doped LiYF4:Yb3+/Ho3+ are very promising as screen-printing materials for anti-counterfeiting recognition labels.

Strict Twice Iterative Optimization Strategy to Synthesize Ultrabright Fluorescent Carbon Dots for UV and pH Dual-Encryption Fluorescent Ink.

In this work, ultrabright fluorescent carbon dots (U-CDs) were synthesized by using a strict twice iterative optimization strategy. Their relative photoluminescence (PL) quantum yield is close to 100%, exceeding most of the reported fluorescent CDs and greatly boosting the practical applications of fluorescent CDs in many fields. Then serving as fluorescent anti-counterfeiting ink was taken as an example to briefly introduce the application of the U-CDs. The PL emission of the U-CDs is quenched at the range of pH < 4 or pH > 11 and restored at the range of pH = 5–10. This pH-sensitive PL feature allows the U-CDs to be used as fluorescent ink for pH and UV dual information encryption. The written or printed information is invisible under daylight but visible under UV light. After acid treatment or alkali treatment, the information is invisible even under a UV lamp but visible after neutralization treatment. This work provides a standardized scheme for optimizing the synthesis conditions of fluorescent CDs and paves the way for large-scale production of high-performance fluorescent CDs.

Construction of NaYF4: Yb, Ho/B, N-GQDs nanocomposites for double anti-counterfeiting fluorescence ink

Fluorescent nanomaterials with multiple anti-counterfeiting play a vital role in economic and social fields in our daily lives. In this work, a hybridized composite of boron and nitrogen co-doped graphene quantum dots (B, N-GQDs) and lanthanide-doped up-conversion NaYF4 was prepare for a double anti-counterfeiting application. The composite was obtained by one-pot hydrothermal method and it was commixed with glycerol in a ratio of 4 : 1 to prepare a fluorescence ink, which exhibited independent blue and green fluorescence emissions under ultraviolet light and near-infrared laser excitation. Therefore, it had a considerable application in confidential communications, logo designing and file encryptions.

Environmentally friendly gelatin-based ink with durability on low surface energy substrates for anti-counterfeiting printing

Recent research is keen to introduce biomass materials into inks to develop "green” printing, but little attention has been given to whether these inks can be truly widely used in printing industry. There are few bio-based inks suitable for low surface energy plastic such as polyethylene glycol terephthalate (PET), which is one of the most common printing substrates. Herein, waterborne polyurethane with polyfluoroalkyl side chain (F-WPU) was designed and synthesized to prepare fluorocarbon quantum dots (F-CDs). F-WPU and F-CDs were mixed together with gelatin to obtain environmentally friendly inks which were utilized to print on a low surface energy substrate. F-WPU (30 wt%) and F-CDs (0.5 wt%) significantly improve the mechanical properties of composites by forming an interpenetrating network system and hydrogen bonds , respectively. Abundant carbon-fluorine bonds effectively reduce the surface energy of gelatin, resulting in excellent hydrophobicity and strong adhesion to the PET surface. The thermal stability of the composite could significantly enhance to meet the promising needs for the further engineering applications. Besides, F-CDs could emit blue-green fluorescence based on conjugated structure and π→π* transition under a wider excitation wavelength. Therefore, the complex exhibited good transparency under sunlight and performed significant cyan fluorescence under an ultraviolet irradiation, in which can be efficiently developed and used in anti-counterfeiting labels and printing. Furthermore, the friction, soaking and kneading tests have been measured to seriously take the considerations for the stable dry and wet fastness for the PET films, which could industriously expand the ink applications. • A durable and environmentally friendly gelatin-based ink was prepared. • Fluorinated waterborne polyurethane and carbon quantum dots were obtained. • F-WPU and F-CDs enhanced the mechanical strength and hydrophobicity of gelatin. • F-CDs contributes fluorescence characteristics and anti-counterfeiting value. • Composite gelatin is a potential anti-counterfeiting ink for PET surface printing.

The pH sensitive fluorescence SiO2@TEuTTA/CS composite films and inks for anti-counterfeiting

Functional chitosan (CS) composite films have wide application prospects in many fields. Herein, the lanthanide inorganic-organic hybrid nanospheres with an average diameter of 252 nm (SiO2@TEuTTA) were synthesized by surface modification of silica nanospheres. And the SiO2@TEuTTA was used as luminescent materials and SiO2@TEuTTA/CS composite films were prepared by a simple solution casting method. Subsequently, the compositions and structure, fluorescence and mechanical properties of the SiO2@TEuTTA/CS composite films were characterized. The results show that the SiO2@TEuTTA/CS composite films not only have the smooth surface, high fluorescence property, good flexibility and transparency, but also can emit a bright red color under a 365 nm UV lamp. These provide an important basis for the application of the SiO2@TEuTTA/CS composite films on the anti-counterfeiting packing labels. Additionally, the SiO2@TEuTTA/CS solutions have been successfully used as anti-counterfeiting inks due to its transparency and pH sensitive properties. Compared with the traditional luminescent anti-counterfeiting inks, the pH sensitive SiO2@TEuTTA/CS inks can improve the level of information security, which indicates that the SiO2@TEuTTA/CS inks hold great promise for anti-counterfeiting fields.

Room-Temperature Synthesized Cd-Doped Cs3 Cu2 I5 : Stable and Excitation-Wavelength Dependent Dual-Color Emission for Advanced Anti-Counterfeiting.

With the development of intellectual properties, concern about advanced anti-counterfeiting is accumulating, which conventional single-modal luminescence can no longer satisfy. As one of rapidly developing 0D materials, copper-based perovskite shows great potential to realize multiple luminescent centers for complex emissions. In this work, Cd was doped into Cs3 Cu2 I5 and showed resultant emission at 560 nm which surprisingly showed a red-shifted excitation peak from that of intrinsic self-trapped emission, resulting in excitation-wavelength dependent emission. When the excitation wavelength increased from 290 nm to 330 nm, the emission of Cd-doped Cs3 Cu2 I5 changed from deep blue to cold white and finally yellow. Afterwards, Cd-doped Cs3 Cu2 I5 was mixed with polystyrene to prepare anti-counterfeiting ink for silk-screen printing. Meanwhile, Cd-doped Cs3 Cu2 I5 maintains outstanding stability after doping, no matter under ambient, continuous UV radiation or high-temperature environment. The intensity can be almost totally recovered after heating-and-cooling cycles. This study lays groundwork for future research into multiple luminescent center manipulation in 0D materials.

Upconverted persistent luminescent Zn3Ga2SnO8: Cr3+, Yb3+, Er3+ phosphor for composite anti-counterfeiting ink.

Herein, a novel colorless anti-counterfeiting luminous ink composite material, to the best of our knowledge, was prepared by incorporating upconverted persistent luminescent Zn3Ga2SnO8:1%Cr3+, 5%Yb3+, 0.5%Er3+ (ZGSO: Cr,Yb,Er) phosphors into a resin solution, followed by stirring. Owing to its small particle size and uniform distribution, ZGSO: Cr, Yb, Er exhibits long-lasting, persistent near-infrared emission at 696 nm following the stoppage of excitation by a 274 nm ultraviolet light and a 980 nm excitation. ZGSO: Cr, Yb, Er composites were prepared and exhibited characteristic peaks corresponding to upconversion and an afterglow curve following excitation at 980 nm. With various special luminescent modes, sharp emission peaks, and emission intensity varying over time, the emission light of composite ink is easy to detect and not easily confused. Furthermore, the prepared composite ink can be calligraphic, visualized, and observable, and has good light-emitting performance following UV excitation. Our work provides a meaningful way to fabricate multifunctional anti-counterfeiting luminous ink composites with an intense persistent luminescence for use in anti-counterfeiting signs, inspection imaging, and other complex industrial applications.

Construction of Multi-color fluorescent carbon dots by Aggregation-Induced emission

Aggregation-induced emission luminogens (AIEgens) have garnered significant attention because of their outstanding photophysical characteristics. AIEgens are used in fluorescence imaging, sensors, tumor treatment, and other related fields. However, the synthese of these AIEgens are relatively complicated and requires expensive raw materials. These drawbacks limit their applications and development to a certain extent. In this study, using cheap and convenient materials, we developed a new type of carbon dots (O-CDs) using a one-step solvothermal method, which has the potential to become a new AIEgen. O-CDs exhibit different fluorescence colors in different solvents, and they exist as monomers in ethylic acid and, ethanol alcohol, etc., exhibiting blue fluorescence. After adding water, the fluorescence of O-CDs gradually turns orange red, because the internal rotation of the disulfide bond molecules is restricted and the AIE effect occurs. Using the unique AIE performance of O-CDs, we fabricated an anti-counterfeiting luminous ink, that can be used for encryption in the reversible double switch mode.

White light emitting diode and anti-counterfeiting applications of microwave assisted synthesized green fluorescent carbon dots derived from waste curry leaves

We have prepared waste curry leaves extract derived carbon dots (CL-C dots) by microwave assisted method. The synthesized CL-C dots were well characterized by many techniques. Using HR-TEM images, the size of the synthesized CL-C dots were determined to be 3.55 nm. CL-C dots exhibits green fluorescence and obtained emission maximum at 425 nm upon the excitation at 340 nm. The green emissive CL-C dots quantum yield (QY) was determined to be 27.13%. The intensity ratio of ID/IG was, as calculated as 1.1 from the Raman spectrum. Moreover, CL-C dots were successfully applied for the preparation of the White Light Emitting Diode (WLED) device. The developed WLED has a colour coordinate value of (0.307, 0.354) and a colour correlated temperature of 6617 K. Finally, we have been used CL-C dots for anti-counterfeiting fluorescent ink application, it is a low-cost, simple-to-use substance that will eventually replace commercially available fluorescent inks. This research work offers a vision in the fields of materials science, WLED, energy, anti-counterfeiting and forensic science.

Smartphone-assisted paper-based multifunctional assay for on-site tandem detection of inorganic phosphate, neutral red and heparin

Today, easy availability and efficient detection assays in low-resource settings are mandatory. Therefore, a smartphone-assisted paper-based detection strategy using eosin Y (EY)-embed ZIF-8 nanocomposite for phosphate (Pi), neutral red (NR) and heparin (HP) on site testing was fabricated. After adding the targets in a specific order, the prepared strips produced brilliant color transitions (astonishing colors, ranging from pistachio to bright yellow for Pi, from bright yellow to jacinth for NR and from jacinth to light orange for HP). These variation on tonality can be evaluated by the smartphone-based readout device (Color Assist App) through the ratio change of B/(R + G + B), which exhibits superior performance of on-site detection in wastewater, including high sensitivity (LOD is 0.015, 0.031 and 0.014 mM for Pi, NR and HP, respectively), ultra-fast response time and excellent selectivity. This strips and smartphone dual-mode monitoring strategy may offer a convenient idea to identify Pi, NR and HP, with great prospects for environmental wastewater applications. Additionally, the probe was enabled for bioimaging of Pi, NR and HP in living cells. Finally, the related anti-counterfeiting fluorescent ink of probe was proposed on schedule.

One material, many possibilities via enrichment of luminescence in La2Zr2O7:Tb3+ nanophosphors for forensic stimuli aided applications

Engineering a single material with multidirectional applications is crucial for improving productivity, low cost, flexibility, least power consumption, etc. To achieve these requirements, novel design structures and high-performance materials are in urgent need. Lanthanide-doped nanophosphors have the greatest strengths and ability in order to tune their applications in various dimensions. However, applications of nanophosphor in latent fingerprints visualization, anti-counterfeiting, and luminescent gels/films are still in their infancy. This study demonstrated a simple strategy to enhance the luminescence of Tb3+ (1–11 mol %) doped La2Zr2O7 nanophosphors by conjugating various fluxes via a simple solution combustion route. The photoluminescence emission spectra reveal intense peaks at ~ 491, 546, 587, and 622 nm, which arises from 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions, respectively. The highest emission intensity was achieved in the NH4Cl flux assisted nanophosphor as compared to NaBr and NH4F assisted samples. The colorimetric images of fingerprints visualized using the optimized nanophosphor on forensic related surfaces exhibit level –III ridge details, including sweat pores, the width of the ridges, bifurcation angle, and the successive distance between sweat pores, etc. These results are decisive parameters that clearly support the statement “no two persons have ever been found to have the same fingerprints”. The anti-counterfeiting security ink was formulated using optimized nanophosphor and various patterns were designed by simple screen printing and dip pen technologies. The encoded information was decrypted only under ultraviolet 254 nm light. All the designed patterns are exhibit not just what it looks/feel like and how better it works. As a synergetic contribution of enhanced luminescence of the prepared nanophosphor, the green-emissive films were fabricated, which display excellent flexibility, uniformity, and transparency in the normal and ultraviolet 254 nm light illumination. The aforementioned results revealed that the prepared NH4Cl flux-assisted La2Zr2O7: Tb3+(7 mol %) NPs are considered to be the best candidate for multi-dimensional applications.

Graphene quantum dots via ion modification for improving photoluminescence stability in aqueous solution with heavy metal ions

Graphene quantum dots (GQDs) have shown growing potential in the applications of ion detection, anti-counterfeiting ink and light-emitting devices. However, the photoluminescence (PL) properties of GQDs will be lost when they interact with some heavy metal ions. Effective strategies to improve PL stability are still limited. In this work, we prepared a new kind of GQDs modified by scandium ions (Sc3+) to improve the PL of GQDs in aqueous solution containing heavy metal ions. The Sc3+ modified GQDs (Sc@GQDs) show a slight fluorescence enhancement compared with pristine GQDs. In addition, the PL of pristine GQDs could be quenched by Fe3+/Cu2+/Cr3+, while the PL of Sc@GQDs was kept stable with these heavy metal ions. Meanwhile, GQDs modified by Al3+ and Ga3+ exhibit similar results, which further verifies the universality of this method that GQDs modified by specific metal ions to maintain the PL of GQDs with heavy metal ions. As applications, Sc@GQDs may have great potential in the fields of fluorescent flexible device and fluorescent ink.

On–Off–On fluorescence sequential sensor for silver ions, thiamine and anti-counterfeiting application using mannitol derived carbon dots

We are reporting the synthesis of mannitol derived carbon dots (MCDs) and their application as silver ion and thiamine sensors. The synthesized MCDs were characterized by HR-TEM, FT-IR, UV–visible, fluorescence, XRD and Raman methods. The synthesized MCDs exhibit a blue emission at 444 nm and the quantum yield of the MCDs is 43.8%. The MCDs particle size was determined to be 3.09 nm with a mono-dispersed nature, using HR-TEM images. Next, we have used MCDs as a probe for the detection of silver ions and thiamine. Interestingly, the highly blue emitting MCDs fluorescence was quenched (ON–OFF) upon the addition of silver ions. On addition of thiamine into the same solution, the fluorescence was enhanced (OFF–ON) . Based on the emission intensity changes, we determined the concentrations of silver ions and thiamine. The limit of detection of silver ions and thiamine were calculated to be 0.5 nM and 0.57 nM (LOD = 3 S/m), individually. The MCDs show high selectively towards the detection silver ions and thiamine. To this end, we have applied this sensor method for the sensing of silver ions in water, silver antibiotic sulfadiazine cream and also thiamine in drugs and biological samples. Notably, we have developed a wax pencil, designed for on-site monitoring of silver ions and thiamine with a wax coated paper based kit. Further, we have successfully prepared an anti-counterfeiting fluorescent ink using mannitol derived carbon dots and a PEG solution. Our anti-counterfeiting fluorescent ink is a low cost material, easy to use and it can replace the commercially available fluorescent inks.

Eu3+-postdoped MOFs are used for fluorescence sensing of TNP, TC and pesticides and for anti-counterfeiting ink application

Two europium-postdoped metal organic frameworks (MOFs) Eu3+@1 and Eu3+@2 [1:{[Zn2(bta)(bpy)(H2O)2]·2H2O}n, 2:{[Ni(bta)(bpy)(H2O)2][Ni(bpy)·(H2O)4]·4H2O}n (H4bta = 1, 2, 3, 5-benzenetetracarboxylic acid, bpy = 4, 4′-dipyridine)] were prepared by hydrothermal synthesis and post-synthesis modification. MOFs 1–2 are all three-dimensional network structure connected by (bta)4- and bpy ligands. Eu3+@1 and Eu3+@2 in aqueous solution can achieve the quantitative detection of 2, 4, 6-trinitrobenzene (TNP), tetracycline (TC) and pesticides with high sensitivity and selectivity. In particular, when the volume of TNP increases to 50 μL, the luminescence quenching rate of Eu3+@2 can reach 99.7% and the LOD for TNP can reach 78 nM. Interestingly, Eu3+@1 has a good response to PTH (Pyrimethanil), while Eu3+@2 has a good selectivity to FLU (Fluazinam), and both can be used for rapid in-situ imaging detection of simulated pesticide residues on fresh vegetables. Under UV lamp, Eu3+@1 showed a significant fluorescence quenching effect on PTH in beans, while the fluorescence quenching effect of Eu3+@2 on FLU on cabbage was obvious. Surprisingly, two kinds of composite materials can be used as anti-counterfeiting ink functional material with strong anti-counterfeiting ability and long term stability.

Fluorescent self-healing waterborne polyurethane based on naphthalimide derivatives and its application in anti-counterfeiting

Waterborne polyurethane with high rigidity and self-healing properties plays an important role in polymer dyes and fluorescent anti-counterfeiting. In this paper, a naphthalimide derivative BHHNA-AM with high fluorescence and strong intermolecular hydrogen bonds was prepared and used as chain extender to synthesize a fluorescent waterborne polyurethane (PUAM). Intriguingly, the presence of highly rigid conjugate plane in molecules and strong non-covalent interaction between main chain and side chain amide group afforded PUAM film an autonomous self-healability at room temperature, the self-healing rate of scratched PUAM could be restored from 47.73% to 94.62% within 9 h, which could be widely used as thermoplastic adhesive. In addition, PUAM emulsion could be used as anti-counterfeiting ink printed on different substrates. After 14 days of UV irradiation and heat treatment, the color difference of printed products was less than 3.5, indicating excellent light resistance.

A cationic amphiphilic tetraphenylethylene derivative with hydrochromic sensitive property: Applications in anti-counterfeiting ink and rewritable paper

Since the discovery of aggregation induced emission (AIE) phenomenon, various stimuli-responsive materials have been rapidly developed, but there are still great challenges in the application of ink printing due to the bad water solubility. In this research, a new cationic amphiphilic TPE-functionalized pyridine salt (TPE-OTs) was designed, which shows good water solubility and hydrochromic properties. The optical properties of the compound have been studied, which is equipped with the typical AIEE characteristics and TICT effect. The compound can self-assemble to form aggregates with a particle size of about 30 nm in water. What is more, the compound is responsive to the environmental humidity, whose fluorescent color changes from green to yellow as the humidity gradually increased. Based on this characteristic, we applied it to the fluorescent anti-counterfeiting ink, realizing the protection and encryption of information.

Design and assembly of AIE-active fluorescent organic nanoparticles for anti-counterfeiting fluorescent hydrogels and inks.

Two kinds of AIE-active fluorescent organic nanoparticles were designed and constructed as anti-counterfeiting photoresponsive materials. One is fluorescent organic nanoparticles (TPELs) based on a self-assembly strategy, which were self-assembled from novel amphiphilic tetraphenylethylene (TPE) molecules decorated with a lactose moiety and different photoresponsive tags. The other is polymeric fluorescent organic nanoparticles (F-TPEs) derived from the nanoprecipitation strategy, which utilized pluronic copolymer F127 to encapsulate hydrophobic TPEs without lactosyl modifications. Upon UV light irradiation, these AIE-active materials exhibit different photooxidation behaviors in an aqueous solution to give cyan, orange and green fluorescence emissions, and they were successfully used as an anti-counterfeiting fluorescent hydrogel and ink.

Study of the Ph Effect on the Optical and Morphological Properties of S,N Self-Doped Carbon Dots Applied as Fluorescent Anti-Counterfeiting Ink and Ph Sensor

Study of the Ph Effect on the Optical and Morphological Properties of S,N Self-Doped Carbon Dots Applied as Fluorescent Anti-Counterfeiting Ink and Ph Sensor

Anti-counterfeiting SERS security labels derived from silver nanoparticles and aryl diazonium salts.

The development of anti-counterfeiting inks based on surface-enhanced Raman scattering (SERS) labels have attracted great interest in recent years for their use as security labels in anti-counterfeiting applications. Indeed, they are promising alternatives to luminescent inks, which suffer from several limitations including emission peak overlap, toxicity and photobleaching. Most of the reported SERS security labels developed so far rely on the use of thiolate self-assembled monolayers (SAMs) for the immobilization of Raman reporters on metallic nanoparticle surface. However, SAMs are prone to spontaneous desorption and degradation under laser irradiation, thereby compromising the ink long-term stability. To overcome this issue, we develop herein a new generation of SERS security labels based on silver nanoparticles (Ag NPs) functionalized by aryl diazonium salts, carrying various substituents (-NO2, -CN, -CCH) with distinguishable Raman fingerprints. The resulting SERS tags were fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption and SERS. Then, they were incorporated into ink formulations to be printed on polyethylene naphthalate (PEN) substrates, using handwriting or inkjet printing. Proof-of-concept Raman imaging experiments confirmed the remarkable potential of diazonium salt chemistry to design Ag NPs-based SERS security labels.

A colorimetric, NIR, ultrafast fluorescent probe for ferric iron detection based on the PET mechanism and its multiple applications

A novel colorimetric, NIR fluorescent probe for ultrafast detection of Fe3+ based on the PET mechanism has been developed. This probe can detect Fe3+ in actual water samples and image Fe3+ in living cells as well as be used for anti-counterfeiting ink.