Anti-counterfeiting Applications Research Articles

Lateral flow assemblies and allied application of carbon quantum dots derived from cigarette tobacco in biosensing, anticounterfeiting and fluorescent films: Theoretical and experimental overview

The bio-sensing activity of fluorescence based nanoprobes is one of the most significant aspects to scrutinize the analytical pursuance in modern security and lateral flow assays. Herein, potent transmogrification of waste cigarette tobacco into fluorescent carbon quantum dots (CQDs) has been achieved by calcination approach. The waste transformation to CQDs holds diverse benefits, comprising high quantum yield, low toxicity and scale up synthesis. The developed CQDs were able to identify tetracycline with phenomenal selectivity and sensitivity through fluorescence based method. The sensing mechanism was fully explored using Density Functional Theory (DFT) and Molecular docking studies. Governing features comprising tetracycline concentration, interfering studies, and real water analysis on the identification of tetracycline were also investigated. Along with, the prepared CQDs act as colorimetric probe, facilitating the detection of tetracycline with the naked eye. The lateral flow device was constructed for the on-site detection of tetracycline in real water samples. To the best of our knowledge, the present work represents a novel approach to designing CQDs and demonstrates their significant potential for application in anticounterfeiting measures and lateral flow devices. This work holds significant prospective as the prepared CQDs was fully utilized to its maximum usage in developing films and fluorescent anti-counterfeiting applications. Concisely, current work opens up distinctive opportunities for rapid on-site, real-time and visualized surveillance of tetracycline using CQDs prepared with a quite simple green approach.

A triphenylamine derivative with multistimuli responsive behavior and high-contrast vapochromism of its Zn(II) complex

In this work, we designed and synthesized a novel multifunctional molecule, (E)-2-(4-(diphenylamino)styryl)-5-(4-pyridyl)-8-quinolinol (HL), which possessed D-π-A structure and exhibited optical responses to acid-base vapor and Zn(II) ions. Zn(II) complex of HL (W1) was obtained and characterized by SC-XRD. Spectral experiments demonstrated that complex W1 displayed aggregation-induced emission enhancement (AIEE) property, which was exact opposite to the aggregation-caused quenching effect of HL. The quantum yield of W1 (15%) was much higher than that of HL (2.1%) in the solid state. Both HL and complex W1 involved sp2 hybrid N atoms, whose protonation and deprotonation gave rise to reversible acidochromism with high contrast. The mechanism was clarified by XPS, 1H NMR, infrared spectroscopy, elemental analysis, PXRD and thermogravimetry results. Benefiting from excited state intramolecular proton transfer in HL together with AIEE of W1, HL could recognize Zn(II) sensitively in aqueous media. The detection limit of HL for Zn(II) reached as low as 5.02 × 10−8 M. An anti-counterfeiting application was realized using HL-loaded test strip, which exhibited fluorescence response, but no color change upon exposure to Zn(II) solution. In addition, HL and W1 solids were combined to develop a stimuli induced encryption/decryption strategy successfully based on their reversible acidochromic behaviors.

Polymer Network Film with Double Reflection Bands Prepared Using a Thermochromic Cholesteric Liquid Crystal Mixture.

Cholesteric liquid crystal polymer network (CLCN) films with a single reflection band have found applications for decoration and anticounterfeiting. The CLCN films with double reflection bands were more suitable for these applications. Herein, they were prepared by using thermochromic cholesteric liquid crystals (CLCs) through a two-step photopolymerization approach. At the first step, due to oxygen inhibition, the CLC monomers near the substrate surface were polymerized at a certain temperature. At the second step, those near the air were polymerized at another temperature. The wavelengths of these two reflection bands of the CLCN film were dominated by the two polymerization temperatures. Based on this approach, patterns with composite colors were prepared, which were suitably applied for decoration. Moreover, a double-layered CLCN film with a broad reflection band was prepared that could potentially be applied for displays.

Regulated polarization degree of upconversion luminescence and multiple anti-counterfeit applications

Regulated polarization degree of upconversion luminescence and multiple anti-counterfeit applications

A novel group of N,N-diaryl-1,2-benzenediamine room temperature phosphors based on structural engineering

Room temperature phosphorescence (RTP) has gained new momentum as a long-term topic along with the appearance of novel phosphors with versatile application potentials. Compared to traditional RTP materials, innovative pure organic phosphors have become promising alternatives due to their superiority in cost and processibility. However, the development of single-component organic phosphors with ultralong emission lifetimes and simple structures is still ongoing. Despite several kinds of organic phosphors being developed, the ones utilizing arylamine skeletons are barely reported. In this paper, we present a novel family of N,N-diaryl-1,2-benzenediamine phosphors with varying numbers of methyl substituents on terminal phenyl rings based on structural engineering. These molecules exhibited bright phosphorescence in the region of green to yellow light with a remarkably long lifetime up to 684 ms in crystalline states under ambient conditions. Comprehensive experimental and theoretical studies revealed that diverse intermolecular interactions and weak intramolecular hydrogen bonds co-contribute to the long-lived RTP emission. An encryption QR code was constructed, which displayed great potential in anti-counterfeiting applications. This work offered a novel structural motif for ultralong RTP material design and is constructive for material pool expansion.

One-pot Synthesis of High-performance Green-emitting Carbon Dots for Cd2+ Sensing and Anti-counterfeiting Applications.

This study presents a facile one-pot solvothermal synthesis of high-performance green fluorescent carbon dots (G-CDs) using o-phenylenediamine and ethylenediamine as precursors. The G-CDs show excellent optical, temporal, and chemical stability. Notably, they exhibit the highest quantum yield of 24.2% in ethanol and a strong green emission peaking at 546nm under 440-490nm excitation. In addition, G-CDs have outstanding salt resistance and multi-solvent compatibility. Due to its bright photoluminescence, G-CDs can be used as a secure ink for anti-counterfeiting. More remarkably, Cd2+ ions can efficiently quench the fluorescence of G-CDs with a detection limit of 0.152 µmol/L, enabling accurate quantification of Cd2+ in water systems. The simple synthesis of high-performance G-CDs expands their applicability in sensing and bioimaging.

Wavelength-multiplexed meta-image displays with Malus-assisted metasurface

A wavelength-multiplexed metasurface for four-channel display is proposed in this paper benefiting from the orientation degeneracy implied in Malus’s law. We construct the meta-atom by placing two nanorods with different sizes on a substrate, which can achieve amplitude manipulation at different wavelengths. The wavelength-multiplexed metasurface composed of these meta-atoms can display four independent binary grayscale images at different wavelengths in the reflection space. Numerical simulations validate the proposed wavelength-multiplexed metasurface with the ability to record and project four independent binary grayscale images at two wavelengths. With the advantages of high capacity, the proposed wavelength-multiplexed display metasurface will pave a way for multi-channel applications in nano-display, information storage, optical anticounterfeiting, and other relevant fields.

Lead-free Cs₂NaInCl₆:Bi³⁺/Mn2⁺ double perovskite nanocrystals to nanosheets with improved photoluminescence quantum yield for anti-counterfeit marks and LED applications

Lead-free double perovskites (DPs) in the form of two-dimensional (2D) nanosheets (NSs) have emerged as exceptional candidates compared to zero-dimensional (0D) nanocrystals (NCs). This preference is attributed to their intriguing fundamental properties and promising applications in optoelectronics. Notably, NSs offer superior performance due to their enhanced surface passivation capabilities, facilitating more efficient treatment of surface defects and thereby enhancing optoelectronic properties. However, the realization of Cs2NaInCl6 as lead-free DPs NSs is yet to be achieved. In this study, we successfully synthesized Cs2NaInCl6 co-doped with Bi3+/Mn2+ NSs. The two-step solution process synthesis enables us to achieve dimensionality control, progressing from 0D NCs to 2D NSs. Comprehensive optical spectroscopy analyses reveal that the NSs exhibit a suppressed non-radiative decay rate (Knr) of 5.03 × 10−3 ns−1 in contrast to NCs with a Knr of 3.21 × 10−2 ns−1. This observation is indicative of a well-passivated surface in NSs. In contrast, NSs with identical composition and surface morphology significantly enhance the photoluminescence quantum yields (PLQYs) up to 73%, which represents the highest PLQYs recorded in Cs2NaInCl6 DPs to the best of our knowledge. Beyond fundamental investigations, the study explores the practical applications of these NSs as anti-counterfeit marks created on a flexible substrate, demonstrating robust emission under UV light. Additionally, the fabrication and testing of a light-emitting diode (LED) showcase the versatility of these NSs in optoelectronic devices. This comprehensive exploration of the optical, morphological, and application aspects of Cs₂NaInCl₆ doped with Bi³⁺/Mn2⁺ NSs contributes valuable insights to the evolving landscape of lead-free perovskite materials, highlighting their potential for diverse technological applications.

Unconventional fluorescence behavior of ε-polylysine: Selective and sensitive detection of Cu2+ in real water samples, test paper strips, living cells, and anticounterfeiting applications

Herein, we report the clustering-triggered emission (CTE) behavior of ε-PL and its various applications. The CTE properties of ε-PL in solution were confirmed from the SEM analysis, DLS data, and the observation of the Tyndall effect. We explored these unique and unconventional photophysical characteristics of ε-PL for the selective detection of Cu2+ with a LOD of as low as 0.45 ppb (7.11 nM), which is much less than the safe limit set by the WHO for Cu2+ in drinking water (2 ppm). The quantum yield of ε-PL reduced from 0.24 to 0.008 upon Cu2+ addition, and the quenching was found to be dynamic in nature. Further, ε-PL was able to detect Cu2+ in real water samples (tap and lake water) as well as in living cells (MCF-7). For real-time applications, ε-PL-coated paper strips and silica gel were fabricated for rapid and convenient detection of Cu2+. The anti-counterfeiting application of ε-PL has also been demonstrated. These findings highlight an efficient method for the selective detection of Cu2+ by ε-PL, an unconventional fluorescent polymer without any chemical modifications, and its real-time applications in Cu2+ sensing and as an anti-counterfeit material. This potentiates its use in agriculture, waste management, medicine, and related fields.

Time-dependent dynamic photoluminescence of Eu3+-activated MgGa2O4 for advanced luminescence anticounterfeiting

In the modern society, luminescence anticounterfeiting plays a key part in information transmission. Nevertheless, most of the present luminescence anticounterfeiting logos are based on static photoluminescence (PL), which is easily counterfeited by substitutes. In this work, a time-dependent dynamic PL material, MgGa2O4:Eu3+, was successfully prepared. Under a portable 254 nm ultraviolet (UV) lamp irradiation, the PL color of the materials dynamically changes from red to pink to blue. After ceasing the UV irradiation, the blue persistent luminescence (PersL) with different afterglow time and bright was observed. The investigation reveals that the dynamic PL derives from the diverse time-dependent intensities of the MgGa2O4 trap-related emission and the Eu3+ 4f-4f transitions, and the Eu3+ dopant can introduce more traps into the host and consequently manipulate the dynamic PL and the PersL performances. The dynamic luminescent anticounterfeiting properties of the prepared material MgGa2O4:Eu3+ was investigated by a powder filling method, demonstrating the potential for applications in advanced anticounterfeiting.

Enhanced photoluminescence in (Ca, Zn)TiO3: Pr3+ afterglow phosphor for anti-counterfeiting application

Enhanced photoluminescence in (Ca, Zn)TiO3: Pr3+ afterglow phosphor for anti-counterfeiting application

Multisite Fine-Tuning in Hybrid Cadmium Halides Enables Wide Range Emissions for Anti-Counterfeiting.

Achieving tunable emissions spanning the spectrum, from blue to near-infrared (NIR) light, within a single component is a formidable challenge with significant implication, particularly in tailoring multicolor luminescence for anti-counterfeiting purposes. In this study, we demonstrate a broad spectrum of emissions, covering blue to red and extending into NIR light in [BPy]2CdX4 : xSb3+ (BPy=Butylpyridinium; X=Cl, Br; x=0 to 0.08) through precise multisite structural fine-tuning. Notably, the multicolor emissions from [BPy]2CdBr4 : Sb3+ manifest a distinctive pattern, transitioning from blue to yellow in tandem with the host [BPy]2CdBr4 and further extending from yellow to NIR with its homologous [BPy]2CdCl4 : Sb3+, resulting in the simultaneous presence of intersecting and independent emission colors. Detailed modulation of chemical composition enables partial luminescence switching, facilitating the creation of diverse patterns with multicolor luminescence by employing [BPy]2CdX4 : xSb3+ as phosphors. This study for the first time successfully implements several groups of tunable emission colors in a single matrix via multisite fine-tuning. Such an effective strategy not only develops the specific relationships between tunable emissions and adjustable compositions, but also introduces a cost-effective and straightforward approach to achieving unique, high-level, plentiful-color and multiple-information-storage labels for advanced anti-counterfeiting applications.

Development of reddish orange-emitting Y2Sn2O7:Eu3+phosphors for latent fingerprint detection and anti-counterfeit security ink

In forensic science, fingerprint detection and anti-counterfeiting technologies are crucial. Inorganic phosphors are potentially suitable materials for high-quality visualization and security. We synthesized novel Y2Sn2O7:Eu3+ (YSO:Eu3+) phosphors by a sol–gel method. They have a cubic structure and emit reddish orange emission from the Eu3+ ions electronic transition of 5D0→7F1. The optimal doping concentration of Eu3+ is 7 mol% and dipole-dipole interaction causes the quenching mechanism. The chromaticity coordinates of YSO:7Eu3+ phosphor are (0.6086, 0.3906). We used the optimized YSO:7Eu3+ phosphors for forensic applications, such as latent fingerprints and security ink. The latent fingerprints stained with YSO:7Eu3+ phosphors showed clear images and reliable level 1–3 characteristics. The security ink was visible on different surfaces. Our results indicate that the YSO:7Eu3+ phosphor can be used for visualizing latent fingerprints and anti-counterfeiting applications.

An investigation into multidimensional information encryption through structural color in electrically responsive subwavelength gratings

In the vanguard of safeguarding data integrity, optical encryption and anti-counterfeiting measures are indispensable. Structural color, with its inherent optical exclusivity, including tunable chromaticity and intricate high-resolution patterning, stands at the forefront of this domain. Despite its promise, the proliferation of structural color technologies in anti-counterfeiting applications is curtailed by the exorbitant production costs and the current limitations in information capacity and security. Addressing these constraints, our study delineates a novel encryption paradigm that interlaces color and digital data within a subwavelength grating matrix. This synergy is fortified by a tri-layered encryption schema, amalgamating electrical response signatures, inherent optical attributes, and the robust RSA algorithm, thereby elevating the information capacity exponentially to 10n and reinforcing multi-faceted security throughout transmission. Our approach heralds a new era in the realm of high density, secure information storage.

Multi-color luminescent material with Mn2+/Mn4+ non-stoichiometric ratio doped octahedra and its anti-counterfeiting applications

Mn ions in different valence states can emit light of different colors in an octahedral coordination environment, which is conducive to the development of a single matrix with multi-color luminescence and applications in the field of anti-counterfeiting. The dual mode multi-color luminescent material CaSb2O6: Mn has been successfully synthesized using a single Mn source in the atmosphere. The CaSb2O6 matrix itself can also absorb 285 nm UV light, emit blue light, and show a long afterglow phenomenon. Both Mn4+ and Mn2+ ions will appear in the [SbO6] octahedra, whether the Mn source adopts MnCO3 or MnO2. The Mn4+ ion exhibits red emission upon UV excitation at 347 nm. The Mn2+ ion can emit a bright green light at 285 nm excitation while exhibiting a long afterglow phenomenon. In this study, the Mn2+ doped octahedron showed unique green emission and broadens the range of its photoluminescence (PL) wavelength. The performance of the material's long afterglow properties on the digital codes demonstrates its potential for dynamic anti-counterfeiting.

A multifunctional Eu-MOF with multi-color and proton conduction switching and its anti-counterfeiting applications

Lanthanide metal-organic frameworks (Ln-MOFs) have exhibited remarkable capabilities in color change, luminescence, proton conduction through the strategic modification of metal nodes, organic ligands and channels or pores. By modifying the electron-deficient bipyridinium to contain carboxylic acid moieties and coordinating them with the luninescent Eu3+ ion, a unique and versatile Eu-MOF has been synthesized. Under UV light conditions, the complex shows an obvious color change from colorless to blue, which is due to the formation of viologen radicals after photoinduced electron transfer (PIET) process. As we all know, the changed color is caused by the alteration of absorption intensity, ultimately impacting its luminescence as well. Thus, the bright and strong red fluorescence of this complex is quenched upon continuous UV light irradiation, which may be attributed to intramolecular energy transfer from the excited state of the europium ion to the colored state of the CV ligand. Based on the control of multiple colors of the complex, the designed encryption model can realize multiple anti-counterfeiting of real numbers. In addition, the conductivity of this compound increases significantly after UV illumination, showing excellent photo-modulated proton conductivity. In short, our work has proposed a multifunctional bipyridinium-based Ln-MOF with photochromism, photo-switchable photoluminescence and proton conduction, which offers valuable insights for the creation of versatile switchable materials based on MOFs.

Development of a long-term fluorescent invisible marker using blue-emitting carbon dots

The development of novel anti-counterfeiting materials and technologies is vital in order to combat counterfeit activities, as existing technologies such as optical watermarking, micro-printing, laser holography, barcodes, RFID, and QR codes are widely known to counterfeiters and easily replicated. In particular, several challenges and issues, including high costs, low yields during synthesis, and the photo-bleaching effect associated with the use of luminescent materials in anti-counterfeiting applications are still need to be addressed. Carbon Dots (CDs) is a new emergent in carbon family with excellent luminescence properties. In this report, we describe a fast, cost-effective, and simple one-step heating method for synthesizing CDs. An invisible marker was produced by incorporating blue emitting CDs into the reservoir of a commercial sketch pen. The writings using the marker were not visible under normal light but emitted blue fluorescence under UV light (365 nm). The marker retained its fluorescence for up to six months without any decrease visible to the naked eye.

Charge carrier trapping management in Bi3+ and lanthanides doped Li(Sc,Lu)GeO4 for x-ray imaging, anti-counterfeiting, and force recording

Discovering energy storage materials with rationally controlled trapping and de-trapping of electrons and holes upon x-rays, UV-light, or mechanical force stimulation is challenging. Such materials enable promising applications in various fields, for instance in multimode anti-counterfeiting, x-ray imaging, and non-real-time force recording. In this work, photoluminescence spectroscopy, the refined chemical shift model, and thermoluminescence studies will be combined to establish the vacuum referred binding energy (VRBE) diagrams for the LiSc1−xLuxGeO4 family of compounds containing the energy level locations of Bi2+, Bi3+, and the lanthanides. The established VRBE diagrams are used to rationally develop Bi3+ and lanthanides doped LiSc1−xLuxGeO4 storage phosphors and to understand trapping and de-trapping processes of charge carriers with various physical excitation means. The thermoluminescence intensity of x-ray irradiated LiSc0.25Lu0.75GeO4:0.001Bi3+,0.001Eu3+ is about two times higher than that of the state-of-the-art x-ray storage phosphor BaFBr(I):Eu2+. Particularly, a force induced charge carrier storage phenomenon appears in Eu3+ co-doped LiSc1−xLuxGeO4. Proof-of-concept non-real-time force recording, anti-counterfeiting, and x-ray imaging applications will be demonstrated. This work not only deepens our understanding of the capturing and de-trapping processes of electrons and holes with various physical excitation sources, but can also trigger scientists to rationally discover new storage phosphors by exploiting the VRBEs of bismuth and lanthanide levels.

Photoswitching in a Liquid Crystalline Pt(II) Coordination Complex.

Photoswitching of photoluminescence has sparked tremendous research interests for super-resolution imaging, high-security-level anti-counterfeiting, and other high-tech applications. However, the excitation of photoluminescence is usually ready to trigger the photoswitching process, making the photoluminescence readout unreliable. Herein, we report a new photoswitch by the marriage of spiropyran with platinum(II) coordination complex. Viable photoluminescence can be achieved upon excitation by 480 nm visible light while the photoswitching can be easily triggered by 365 nm UV light. The feasible photoswitching may be benefited from the formed liquid crystalline (LC) phase of the designed photoswitch as a crystalline spiropyran is normally unable to implement photoswitching. Compared to the counterparts, this LC photoswitch can show distinct and reliable apparent colors and emission colors before and after photoswitching, which may promise the utility in high-security-level anti-counterfeiting and other advanced information technologies.

A Disposable Thermally Triggered Photonic Crystal Anti-Counterfeiting Tag with Irreversible Response and Multi-Step Color Changes.

Thermochromic photonic crystal (PC) is a promising material for anti-counterfeiting applications, but there are still challenges to further improve the anti-counterfeiting performance and the practicability in usage. Here, a disposable thermally triggered PC anti-counterfeiting tag with irreversible response and multi-step color changes is developed based on the thermochromic Silica/(Polyethylene glycol-Ethoxylated trimethylolpropane triacrylate) (SiO2 /(PEG-ETPTA)) double-layer film. The fast and irreversible thermal response come from the quick melting and infiltration of PEG-ETPTA into the PCs upon heating. The multi-step color change at different temperatures originated from the regioselective control of the UV curing degree of the PEG-ETPTA layer and the resulting thermochromic temperature of the double-layer film. Therefore, the invisible PC pattern on the tag can be revealed part by part upon heating and became invisible again after overheating, which offered diversified visual effects and enhanced anti-counterfeiting performances.