Anti-counterfeiting Applications Research Articles

Glass Disorder Modulated Luminescence in Zero-Dimensional Antimony-Chloride Coplanar Dimers for Optical Anti-counterfeiting.

Zero-dimensional metal halides have received wide attention due to their structural diversity, strong quantum confinement, and associated excellent photoluminescence properties. A reversible and tunable luminescence would be desirable for applications such as anti-counterfeiting, information encryption, and artificial intelligence. Yet, these materials are underexplored, with little known about their luminescence tuning mechanisms. Here we report a pyramidal coplanar dimer, (TBA)Sb2Cl7 (TBA = tetrabutylammonium), showing broadband emission wavelength tuning (585-650 nm) by simple thermal treatment. We attribute the broad color change to structural disorder induced by varying the heat treatment temperatures. Increasing the heating temperature transitions the material from long-range ordered crystalline phase to highly disordered glassy phase. The latter exhibits stronger electron-phonon coupling, enhancing the self-trapped exciton emission efficiency. The work provides a new material platform for manifold optical anti-counterfeiting applications and sheds light on the emission color tuning mechanisms for further design of stimuli-responsive materials.

Excitation power-dependent multicolor upconversion in NaLnF4:Er3+ under 1532 nm irradiation for anti-counterfeiting application

Upconversion (UC) materials are renowned for their ability to convert low-energy photons into high-energy ones. The manipulation of parameters allows for the observation of multicolored UC luminescence (UCL) within a single material system. While modulation of multicolored UCL commonly relies on excitation at approximately 980 nm, investigation into multicolored UC materials activated by a 1532 nm excitation source remains comparatively scarce. In this work, we introduce NaLnF4:Er3+ as a novel class of smart luminescent materials. When the power density of a 1532 nm laser increases from 0.5 to 20.0 W/cm2, the emission peak positions remain unchanged, but the red-to-green (R/G) ratio decreases significantly from 18.82 to 1.48, inducing a color shift from red to yellow and ultimately to green. In contrast, no color variation is observed when NaLnF4:Er3+ is excited with a 980 nm laser at different power densities. This power-dependent multicolored UCL of NaLnF4:Er3+ excited at 1532 nm can be attributed to the competitive processes of upward pumping and downward relaxation of electrons on the 4I9/2 level of Er3+. By utilizing the unique UC characteristics of NaLnF4:Er3+, its potential utility in anti-counterfeiting applications is demonstrated. Our research highlights the distinctive optical properties of NaLnF4:Er3+ and provides novel insights into the use of luminescent materials in optical anti-counterfeiting technologies.

Detection, detoxification, and anti-counterfeiting applications of pullulan-modified nitrogen-doped carbon dots

Nitrogen-doped carbon dots (N-CDs) modified with pullulan were prepared using a hydrothermal method for use in sensing, detoxification, and anti-counterfeiting applications. The excitation-independent N-CDs demonstrated selectivity for hydroquinone and 4-nitrophenol (4-NP) with detection limits of 58 and 13 nM. The N-CD-based detection method was extended to environmental samples such as bottled water, tap water, and river water, and acceptable relative standard deviations (RSDs) and good recoveries were found. In the presence of NaBH4, N-CDs converted the toxic MB to colorless leuco-methylene blue in 10.5 minutes, confirming that the catalytic ability of N-CDs can be evaluated using MB as a model pollutant. With an excellent quantum yield of 31%, the N-CDs had the potential as a fluorescent ink for anti-counterfeiting applications by helping to visualize fingerprints, drawings, and chemical structures under 365 nm UV light while being completely invisible in daylight and sunlight. The N-CDs have significant potential for industrial use as fluorescent inks, detoxification catalysts, and pollutant sensors.

Harnessing the duality of bases toward controlled color and fluorescence.

Bases can promote keto-enol tautomerism, a prevalent form of prototropic tautomerism, and facilitate the ring opening of anhydride ring structures. The intrinsic chemical distinctions between these processes provide an opportunity to modulate these seemingly parallel reactions. However, this potential remains largely unexplored. In this work, we report homophthalic anhydride, the first molecule exhibiting simultaneous halochromism, turn-on fluorescence (halofluorochromism), and subsequent self-destruction. Through comprehensive spectroscopic analysis and theoretical calculations, we unravel the mechanisms underlying these phenomena, revealing that the pivotal roles of the base's basicity and nucleophilicity specifically allow us to achieve controlled durations of color change and turn-on fluorescence. Capitalizing on these intriguing properties, we develop a highly dynamic CMY (cyan-magenta-yellow) palette ideal for entity encryption and anti-counterfeiting applications. Our work reshapes the understanding of the relationship between the basicity and nucleophilicity of bases, enriching the comprehension of keto-enol tautomerism and homophthalic anhydride chemistry, and unveils a spectrum of potential applications.

Tm3+ mediated multicolor luminescence of NaYbF4:Er,Tm@NaYF4 for advanced anti-counterfeiting.

Lanthanide doped multicolor luminescent materials have attracted extensive attention due to their advanced anti-counterfeiting properties. However, designing a simple, hard-to-copy and multicolor anti-counterfeiting strategy based on upconversion nanoparticles (UCNPs) remains a huge challenge. Herein, a strategy to modulate luminescence color by altering the mediating action of Tm3+ was proposed. As a proof of concept, the mediating action of Tm3+ was explored in NaYbF4:30%Er,1%Tm@NaYF4 by changing the doping ratio of Yb3+/Er3+/Tm3+, and red, yellow and blue luminescence was successfully obtained. Then, NaYbF4:x%Er,1%Tm@NaYF4 (x = 2, 10, 30, 50, 99), NaYbF4:x%Er@NaYF4 (x = 2, 10, 30, 50, 100) and NaYbF4:1%Tm@NaYF4:x%Er@NaYF4 (x = 2, 10, 30, 50, 100) were synthesized to further identify that the mediating action of Tm3+ was related to the doping ratio and distance between dopant ions. In addition, the luminescence color of NaYbF4:30%Er,1%Tm@NaYF4 changed from red to yellow with the increase of excitation power density. Based on the above, NaYbF4:Er,Tm@NaYF4 UCNPs show excellent performance in anti-counterfeiting of paintings, thus revealing their great potential in advanced anti-counterfeiting applications.

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

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

Tunable Multicolor-Emission in Eu3+ and Tb3+ Codoped Cs2NaInCl6:Sb3+ Double Perovskite Nanocrystals and its Dual-Model Anti-Counterfeiting and Temperature-Sensing Applications

Lead-free metal halide double perovskites with non-toxicity and stable self-trapped excitons (STEs) have received considerable attention in the field of photoelectric applications. However, it is difficult to achieve independent control of its photoluminescence performance to meet the requirements of multi-band emission. Herein, a doping strategy was employed to introduce lanthanide ions (Ln3+) into Cs2NaInCl6:Sb3+ nanocrystals (NCs), enabling the multicolor emission modulation ranging from blue to red and even white light. Benefiting from the efficient energy transfer from Sb-related self-trapped excitons to Ln3+ ions, green and red emissions originate from the 5D0→7FJ (J=1, 2, 3, 4) transition of Eu3+ ions and 5D4-7FJ (J = 6, 5, 4, 3) transition of Tb3+ ions, respectively. According to the tunable polychromatic photoluminescence characteristics of doped NCs, the dual-mode fluorescent anti-counterfeiting applications were exhibited. Furthermore, the distinct temperature sensitivities exhibited by blue (453 nm) and red (617 nm) emission in Cs2NaInCl6:Sb3+/Eu3+ NCs provide the opportunity for the optical thermometry, which demonstrates the maximum absolute and relative sensitivity are 0.0018 and 0.43% K−1, respectively. These results indicate that the synthesized codoped NCs have the potential applications in multifunctional fields, such as optical thermometer, fluorescence anti-counterfeiting, and multicolor-LEDs.

A new FRET-based fluorescent probe: Colorimetric and ratiometric detection of hypochlorite and anti-counterfeiting applications

Hypochlorite (ClO−), as the main component of widely used disinfectants in daily life, comes into closer contact with the human body, which can lead to a number of diseases. The high-performance method is increasingly needed to detect ClO− in our daily life. In this report, we successfully synthesized a FRET ratiometric fluorescent probe (NDAC) containing benzoxadiazole moieties and coumarin moieties bound via ethylenediamine. As expected, NDAC has excellent selectivity and anti-interference ability toward ClO−, and the ratio of fluorescence intensity (I471 nm/I533 nm) has a very good linear relationship with the concentration of ClO−, with a wide linear range (2.5 – 1750 μM) and low detection limit (0.887 μM). Furthermore, we have successfully applied it for the quantitative detection of ClO− in water samples in daily life. At the same time, there is a very clear change in the fluorescence color after the reaction of the NDAC with ClO−. The blue/green value (B/G) of this color change also shows a very good linear relationship to ClO− (5.0–1000 μM). Therefore, the NDAC has also been successfully used for test strip detection and quantitative detection of ClO− in actual samples through smartphone-based fluorescence image analysis, and this method can provide faster, more convenient and more accessible detection. In addition, NDAC sensors also have potential applications in the field of information anti-counterfeiting.

Ultra-long room temperature phosphorescent materials based on tetraphenylethylene derivatives for anti-counterfeiting and encryption applications

Stimuli-responsive room temperature phosphorescent materials have been the subject of considerable research activity in recent years. In this study, the tetraphenylethylene group was selected in combination with arylboronic acid (TIPE-BOH) and used to dope a rigid polyvinyl alcohol (PVA) matrix to generate a film material (TIPE-BOH-PVA) that exhibited an aggregation-induced emission (AIE) effect. The prepared film exhibits excellent room temperature phosphorescence (RTP) performance, with an enhanced emission wavelength and an afterglow time of up to 12 s. The triplet-to-singlet Förster resonance energy transfer (TS-FRET) has been utilized to modify the afterglow color by adding butyl rhodamine B (BRhB) and rhodamine 6G (R6G), employing a water phase without the use of organic solvents. The resultant material exhibits stimulus responsiveness; the RTP properties disappear when the material is exposed to water vapor, but are restored following thermal treatment. The material has potential applications in information encryption and erasure, double anti-counterfeiting ink, and fingerprint acquisition systems. This work offers a new strategy for the design of stimuli-responsive ultra-long RTP materials with far-ranging end applications.

Sustainable latent fingerprint enhancement with ink-free printing and shape memory behavior using Parthenium Hysterophorus-derived carbon dots

We developed a method to produce red fluorescent carbon dots from Parthenium hysterophorus leaves (PCDs) through hydrothermal carbonization. These PCDs exhibit consistent photoluminescence, emitting light regardless of excitation, with a 6.01 ns fluorescence lifetime and a 10.2% quantum yield. They possess a fine size of 4.4 nm, excellent hydrophilicity, and stability in a pH range of 4–11. Leveraging their optical properties, these PCDs function as precise nano-probes for detecting Fe3+ ions, demonstrating a linear correlation within 0 to 50 μM concentrations and a low detection limit of approximately 0.14 μM. Emitting light at about 620 nm, these PCDs remain visible even in daylight. When applied to fingerprints on various substrates and dried, they reveal distinct prints under 365 nm UV light, retaining stability for 24 h. This resilience is attributed to preventing fluorescence reduction, achieved through the coffee-ring effect and electrostatic interactions during drying. Employing deep learning with the YoLOv8 algorithm, fluorescence images of these latent fingerprints (LFPs) exceptionally resemble standard controls. These PCDs serve a dual role as fluorescent ink and nanocomposite films within a PVA matrix, demonstrating potential in anti-counterfeiting applications. This study presents a straightforward method for synthesizing PCDs with intense red luminescence, establishing them as a versatile platform for Fe3+ sensing, flexible fluorescent films, latent fingerprints, and anti-counterfeiting pursuits.

Hydrothermally synthesized fluorescent nitrogen-doped carbon dots for catalytic efficiency and anti-counterfeiting application

Here, Tylophora indica plant extract was utilized to create nitrogen-doped carbon dots by hydrothermal method. The synthesized NDCDs was employed to anti-counterfeiting and enhancing the catalytic activity of Malachite Green dye. The ultraviolet–visible spectroscopy and FT-IR measurements was used to analyze the optical properties and the development of NDCDs as well as the source of Tylophora indica. Using HR-TEM, XRD, and XPS, the structure and elemental contents of the produced NDCDs was investigated. The HRTEM images showed that the NDCDs had a d-spacing of 0.37 nm and an average particle size of 4.3 ± 1 nm. After being subjected to UV light at 365 nm, the produced NDCDs began to glow blue, with a quantum yield (QY) of 16.1 %. The ID and IG ratio values for NDCDs were found to be 0.86. With rate constant values calculated at 0.1830 min−1, respectively, the synthesized NDCDs were found to be a viable catalyst for the Malachite Green (MG) dye reduction process utilizing freshly prepared NaBH4. In addition, the NDCDs solution is used as fluorescent ink. The printed patterns retain their anti-counterfeiting properties even after being heated and stored in an environment for an extended period, indicating the NDCDs stability for prospective anti-counterfeiting applications.

Ultraviolet-B and Near-Infrared Dual-Band Luminescence in Bi3+/Bi2+ Codoped Persistent Phosphor for Optical Storage Application.

Discovering multifunctional luminescent materials to meet the demands of modern spectroscopy is of great significance. However, it is a standing challenge to enable multiple luminescence properties in a single material system via single metal ion doping. Here, we report the inherently Bi3+/Bi2+ codoped Ca3Ga2Ge3O12 persistent phosphor where Bi3+ is in situ reduced to Bi2+. This phosphor can act as an efficient multimodal luminescence material, which simultaneously exhibits long-lasting (>12 h) ultraviolet-B (UVB) and near-infrared (NIR) dual-band persistent luminescence after irradiation by 254 nm ultraviolet (UV) light. UVB and NIR afterglow are ascribed to the distinct Bi3+ and Bi2+ emitters, respectively, proven by comprehensive spectroscopic investigations including X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. Besides, this phosphor also exhibits exceptional photochromic features, accompanied by a rapid body color transformation from white to brown in response to 254 nm UV light within 60 s and excellent recovery capacity upon thermal or blue/white light stimulation. The combination of UVB persistent luminescence of Bi3+ and NIR afterglow of Bi2+ coupled with reversible white-to-brown photochromism phenomenon offers one type of promising multifunctional luminescence material, showing potential to be used for optical storage and anti-counterfeiting applications.

Anti-counterfeiting applications of antimony-doped zero-dimensional indium halide with temperature-responsive broad emission

While spatial-resolved luminescent anti-counterfeiting technology has reached maturity, achieving rapid responsiveness and exceptional fatigue resistance remains a challenge for high-security-level applications. Temperature-based multi-stimuli-responsive luminescent solid-state materials offer a promising solution to meet these requirements. In this study, we present a dual stimuli-responsive photoluminescence (PL) switching system that depends on both temperature and excitation wavelength, utilizing a Zero-Dimensional (0D) (PMA)4In0.98Sb0.02Cl7·H2O (PMA = benzylamine). Notably, (PMA)4In0.98Sb0.02Cl7·H2O exhibits orange broad-band emission at room temperature under both low-energy (365 nm) and high-energy (254 nm) irradiation. At 80 K, green light emission is observed under high-energy irradiation (254 nm), transforming into red emission when excited with low-energy wavelength (365 nm) at the same temperature. Moreover, the (PMA)4In0.98Sb0.02Cl7·H2O both in powder and film states demonstrate excellent stimuli-responsive performance, including short response times and superior cyclic reversibility. Therefore, this 0D (PMA)4In0.98Sb0.02Cl7·H2O can serve as a novel quarter-fold turn-on and tuning luminescent switch for encryption/decryption under the stimuli of temperature and excitation with rapid response and excellent fatigue resistance.

A multistimuli-responsive fluorescent polymer gel based on thioctic acid and hyperbranched polymer

Fluorescent gels with fast and reversible responses have attracted extensive attention, but it remains a huge challenge to synthesize high performance multistimuli-responsive fluorescent gel through a facile and versatile approach. In this work, a multistimuli-responsive fluorescent thioctic acid-crosslinked hyperbranched polymer gel (TLHP) was designed and fabricated by copolymerization of acrylic acid, amino-ended hyperbranched polymers (AHP), tetrakis(4-aminophenyl)ethene (TPE-4NH2) and thioctic acid (TA). The structures of the TLHP gel were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). AHP played an important role in the TLHP gel. The terminal amino groups of AHP and TPE-4NH2 in the network served as strong complexing centers with carboxylic groups of TA and acrylic acid by hydrogen bonding interactions, thus a unique toughening and self-healing strategy for the supramolecular network was established. Compared with poly(TA and acrylic acid) (TPAA), TLHP-0.4 % which incorporated 0.4 % TPE-4NH2 exhibited excellent mechanical properties, with tensile strength up to 438 kPa and stretchability up to 741 %, increased by 193.3 % and 45.3 %, respectively. In addition, TLHP-0.4 % was crosslinked through the dynamic covalent disulfide bonds and the noncovalent H-bonds between amino or carboxy groups, and exhibited fluorescence responsiveness to temperature, pH, and metal ions, greatly expanding the application of TLHP as rewritable printing ink and temperature-based erasing. The fluorescence of TLHP was also sensitive to Cu2+, and the intensity can be restored by EDTA solution to realize fluorescence “switching”. The multistimuli-responsive fluorescence of TLHP may have broad prospects in reversible patterning displays, multi-level anti-counterfeiting applications for information security, and various potential applications.

Photoluminescence investigation of novel red emitting NaLa(1-x)MgTeO6: XSm3+ phosphor with high color purity for n-UV based warm WLEDS and anti-counterfeiting applications

Recently, red phosphors are extensively developed to find applications in phosphor converted white LEDs (pc-WLEDs) and anti-counterfeiting. In this work, samarium doped sodium lanthanum magnesium tellurate (NaLaMgTeO6:Sm3+) red emitting phosphors have been synthesized for the first time via solid state reaction method. Rietveld refinement of XRD pattern reveals monoclinic crystal structure of NaLaMgTeO6. Under 404 nm (6H5/2 → 4F7/2) n-UV excitation, NLMT:Sm3+ phosphor shows red emission at 643 nm (45/2 → 69/2) with color purity 100 % and the obtained CCT value corresponds to warm light source. Temperature-dependent PL analysis of NLMT:Sm3+ exhibits good thermal stability. The anti-counterfeiting security ink was developed using optimized phosphor and the information was encrypted on different surfaces using the prepared security ink. The encrypted data was decoded only by n-UV light. The aforementioned results revealed that NLMT:Sm3+ is a highly effective phosphor as a red component for pc-WLEDs and luminescent dye for anti-counterfeiting applications.

Fluorescence-enhanced Cs2Ag0.3-xNaxZn0.35In1-yCl6:yM double perovskites for multimodal optical anti-counterfeiting

The excellent optical properties of lead-free halide double perovskites (LHDPs) Cs2AgInCl6 are of great importance in the field of anti-counterfeiting encryption. However, the fluorescence quantum yield of the existing Cs2AgInCl6-based materials is relatively low, and the fluorescence color is monochromatic, making it difficult to use in advanced multi-mode anti-counterfeiting applications. In this study, we synthesized Cs2Ag0.3-xNaxZn0.35In1-yCl6:yM (M = Cr/Bi) series LHDPs using an anti-solvent assisted co-precipitation method, improving the optical properties of Cs2AgInCl6-based materials by optimizing their composition. The fluorescence quantum yield of Zn–Na substituted Cr-doped Cs2Ag0.3-xNaxZn0.35In1-yCl6 LHDPs increased from 1.53 % to 82.57 % on the basis of Cs2AgInCl6. The Zn–Na substituted Bi-doped Cs2Ag0.3-xNaxZn0.35In1-yCl6 LHDPs exhibited dual-wavelength fluorescence emission at 407 and 650 nm, and the relative intensity between the two emission wavelengths changed via a change in the Bi doping amount, resulting in a change in the material's luminescence color. The as-synthesized LHDPs could be applied to multi-mode anti-counterfeiting, optical coding information storage, and art decoration applications.

Carbon dot-based afterglow composite with tunable room temperature phosphorescence and thermally activated delayed fluorescence and their anti-counterfeiting and encryption application

Carbon dots (CDs) based afterglow materials have attracted much attention owing to their low toxicity, environmental protection, stable luminescence, abundant raw materials, and low cost. However, CD-based afterglow materials with both room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) characteristics are rarely reported, which greatly limits their in-depth application in advanced anti-counterfeiting, intelligent sensing, and other fields. In this paper, Cu, N co-doped CDs (Cu, N-CDs) with dual emission centers were synthesized via a simple solvothermal method by heteroatom doping to enhance the spin–orbit coupling of CDs and regulate the luminescence properties of CDs. Then, boric acid (BA) was used as the matrix to synthesize Cu, N-CDs@BA composites by matrix-assisted method, and the electron transfer enhancement afterglow was realized by the inorganic electronic defects of the matrix. Cu, N-CDs@BA can realize the mutual conversion of TADF and RTP by changing the excitation wavelength or increasing the temperature. At the excitation of 285 nm, the room temperature afterglow of Cu, N-CDs@BA exhibit TADF, and the average afterglow lifetime is 94.21 ms. At the excitation of 365 nm, they exhibit RTP, and the average afterglow lifetime is 347.96 ms. Based on three different emission properties (fluorescence, RTP, and TADF), Cu, N-CDs@BA was applied in anti-counterfeiting and encryption, which shows good application potential.

Dynamic multicolor emissions of multimodal phosphors by Mn2+ trace doping in self-activated CaGa4O7

The manipulation of excitation modes and resultant emission colors in luminescent materials holds pivotal importance for encrypting information in anti-counterfeiting applications. Despite considerable achievements in multimodal and multicolor luminescent materials, existing options generally suffer from static monocolor emission under fixed external stimulation, rendering them vulnerability to replication. Achieving dynamic multimodal luminescence within a single material presents a promising yet challenging solution. Here, we report the development of a phosphor exhibiting dynamic multicolor photoluminescence (PL) and photo-thermo-mechanically responsive multimodal emissions through the incorporation of trace Mn2+ ions into a self-activated CaGa4O7 host. The resulting phosphor offers adjustable emission-color changing rates, controllable via re-excitation intervals and photoexcitation powers. Additionally, it demonstrates temperature-induced color reversal and anti-thermal-quenched emission, alongside reproducible elastic mechanoluminescence (ML) characterized by high mechanical durability. Theoretical calculations elucidate electron transfer pathways dominated by intrinsic interstitial defects and vacancies for dynamic multicolor emission. Mn2+ dopants serve a dual role in stabilizing nearby defects and introducing additional defect levels, enabling flexible multi-responsive luminescence. This developed phosphor facilitates evolutionary color/pattern displays in both temporal and spatial dimensions using readily available tools, offering significant promise for dynamic anticounterfeiting displays and multimode sensing applications.

Photo-Curable 3D Printing of Circularly Polarized Afterglow Metal-Organic Framework Monoliths.

Developing coordination complexes (such as metal-organic frameworks, MOFs) with circularly polarized luminescence (CPL) is currently attracting tremendous attention and remains a significant challenge in achieving MOF with circularly polarized afterglow. Herein, MOFs-based circularly polarized afterglow is first reported by combining the chiral induction approach and tuning the afterglow times by using the auxiliary ligands regulation strategy. The obtained chiral R/S-ZnIDC, R/S-ZnIDC(bpy), and R/S-ZnIDC(bpe)(IDC = 1H-Imidazole-4,5-dicarboxylate, bpy = 4,4'-Bipyridine, bpe = trans-1,2-Bis(4-pyridyl) ethylene) containing a similar structure unit display different afterglow times with 3, 1, and <0.1s respectively which attribute to that the longer auxiliary ligand hinders the energy transfer through the hydrogen bonding. The obtained chiral complexes reveal a strong chiral signal, obvious photoluminescence afterglow feature, and strong CPL performance (glum up to 3.7×10-2). Furthermore, the photo-curing 3D printing method is first proposed to prepare various chiral MOFs based monoliths from 2D patterns to 3D scaffolds for anti-counterfeiting and information encryption applications. This work not only develops chiral complexes monoliths by photo-curing 3D printing technique but opens a new strategy to achieve tunable CPL afterglow in optical applications.

One-step preparation and dual mode luminescence anti-counterfeiting application of LiYF4: Yb3+, Ho3+, Ce3+@ carbon quantum dot composite materials

In the field of fluorescent anti-counterfeiting, materials with single luminous mode are easy to be forged, which cannot meet the current anti-counterfeiting requirements. Currently reported bimodal light-emitting materials usually require multi-step and tedious synthesis steps. In this paper, LiYF4: Yb3+, Ho3+, Ce3+ upconversion micron particles (UCMPs)/carbon quantum dots (CDs) composite materials were prepared by one-step hydrothermal method, which greatly simplified the composite process of CDs and UCMPs. The upconversion wavelength (from green light to red light excited by 980 nm) can be achieved by changing the doping concentration of Ce3+ ions. Through the combination of CDs and UCMPs, an obvious dual mode luminescence phenomenon was achieved. Finally, screen printing was used to produce a clover pattern, which realized multi-color luminescence under 365 nm and 980 nm excitations respectively. The new fluorescence anti-counterfeiting composites, which uses simple and environmentally friendly one-step synthesis process, is expected to promote the development of fluorescence anti-counterfeiting field.