Multilevel Static-Dynamic Anticounterfeiting Based on Stimuli-Responsive Luminescence in a Niobate Structure

Quadra-Mode Luminescent Phosphors for Force/Thermo-Encoded Information Storage and Anticounterfeiting Applications

Multimode luminescent materials possess diverse optical characteristics and play crucial roles in photocommunication and information security. Force-induced mechanoluminescence, as a distinctive excitation mode, exhibits impressive capabilities in the field of anticounterfeiting and information storage. Here, we integrate mechanoluminescence with the conventional luminescence modes (including up-conversion luminescence, down-conversion luminescence, and thermoluminescence (TL)) within LiNbO3 via well-tuned codoping of Er3+ and Pr3+. LiNbO3:Pr3+/Er3+ exhibits excitation-dependent photoluminescence (PL), enabling tunable emission colors ranging from green to red, while it shows green up-converted PL emissions owing to the electronic transitions of Er3+ ions. Both TL and mechanoluminescence emissions are achieved by employing intertrap levels, where mechanical or thermal stimulation releases carriers that transfer energy to Pr3+ ions, resulting in red emissions. Moreover, an underlying competitive interaction between TL and mechanoluminescence is revealed, which can be leveraged for force/thermo-encored information storage. This unique feature positions LiNbO3:Pr3+/Er3+ as novel recordable information storage labels to monitor the freshness of perishable goods such as food and medicine. In addition, quadra-mode luminescence material LiNbO3:Pr3+/Er3+ provides multidimensional codes via emission color and distribution, indicating its significant potential in advanced anticounterfeiting technology.

Unleashing the Potential of Defect Engineered Persistent Pr3+-Activated Phosphors for Multi-Dimensional Anti-Counterfeiting and X-Ray Imaging Applications

Persistent luminescence (PersL) in inorganic phosphors offers great potential for anti-counterfeiting and optical storage, with optimization of PersL, multicolor tuning, and defect engineering. This study presents a Ca3Ga2Ge3O12:Pr3+ (CGGO:Pr) phosphor with long-lasting PersL and multicolor emissions. Aliovalent codoping with Er3+ and Yb3+ ions optimizes deep/shallow trap redistribution, controlling trap depths from 0.98 to optimal 0.73 eV through the creation of new shallow electron traps (YbCa •, ErCa •) alongside existing VO levels. The smart Pr3+/Er3+/Yb3+:CGGO phosphor exhibits three-dimensional visible emissions under 275  and 380 nm excitation, as well as upconversion emissions under 980 nm laser irradiation. Hybrid density functional calculations, thermoluminescence, and positron annihilation lifetime spectroscopy revealed the nature and density of different traps controlling the PersL. Together, a single system featuring multicolor luminescence has been developed, exhibiting improved PersL and regulated trap depths (≈0.73 eV) suitable for robust and multimodal anti-counterfeiting of documents, pharmaceuticals, and industrial products. Furthermore, the composite PMMA-CGGO:Pr phosphor films have shown remarkable capability for X-ray imaging, achieving a resolution of 4 lp/mm, which exceeds that of commercial Gd2O2S:Tb screens. These findings highlight the potential of this work for advanced anti-counterfeiting and X-ray imaging applications, offering enhanced PersL with controlled trap depths.

PDDA-Assisted Synthesis of Magnetic Fluorescent Fe3O4@SiO2-CQD Composites

Magnetic fluorescent nanomaterials have broad application prospects as taggants in fields such as anticounterfeiting identification, suspicious object tracking, and potential fingerprint recognition in forensic medicine. It is a common method to synthesize magnetic fluorescent composite nanoparticles by preparing a shell on the surface of magnetic particles to load fluorescent materials. In this work, a magnetic fluorescence nanohybrid was synthesized by in situ encapsulation of carbon quantum dots (CQDs) during the preparation of a SiO2 shell on the surface of Fe3O4 nanoparticles. The traditional Stöber method was employed to synthesize the SiO2 shell. Meanwhile, CQDs were introduced into the hydrolysis process of tetraethyl orthosilicate. To address the issue of charge repulsion between the negatively charged hydrolysis intermediate of tetraethyl orthosilicate and the negatively charged CQDs, poly(diallyldimethylammonium chloride) with positive charge was introduced in the synthesis process. The repulsive charges in the reaction system were balanced by poly(diallyldimethylammonium chloride), allowing for the successful encapsulation of CQDs in the SiO2 shell. The structure, morphology, and magnetic and fluorescence properties of the prepared Fe3O4@SiO2-CQDs were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, a vibrating sample magnetometer, and a fluorescence spectrophotometer. The Fe3O4@SiO2-CQDs exhibited excellent magnetic and fluorescence properties, making them suitable for fluorescence labeling on various substrates and showing great potential in labeling, tracing, and fluorescence sensors.

Hydrogen-Bonded Organic Frameworks for Antibiotic Fluorescent Sensing Artificial Intelligence-Enhanced Anticounterfeiting

The paramount importance of anticounterfeiting measures in safeguarding consumers from counterfeit products lies in their ability to ensure product safety and reliability. Advanced luminescent anticounterfeiting materials, particularly those responsive to multiple stimuli, afford a dynamic and multilayered security assurance. This study presents the synthesis of a novel material, Eu/Tb@GC-3, via postsynthetic modification, which exhibits notable photoluminescent properties with emission at 544 and 614 nm. The material demonstrates high selectivity and sensitivity in detecting Nitrofural and Enrofloxacin, with limits of detection at 0.0122 and 0.0280 μM, respectively. Furthermore, multistimulus responsive luminescent fibers and inks were developed, facilitating intelligent anticounterfeiting labels. The integration of these labels with back-propagation neural networks (BPNNs) significantly enhances pattern recognition and authentication capabilities, providing an efficacious strategy to combat counterfeit products and ensure consumer safety.

Deep-trap ultraviolet persistent phosphor for advanced optical storage application in bright environments

Extensive research has been conducted on visible-light and longer-wavelength infrared-light storage phosphors, which are utilized as promising rewritable memory media for optical information storage applications in dark environments. However, storage phosphors emitting in the deep ultraviolet spectral region (200-300 nm) are relatively lacking. Here, we report an appealing deep-trap ultraviolet storage phosphor, ScBO3:Bi3+, which exhibits an ultra-narrowband light emission centered at 299 nm with a full width at half maximum (FWHM) of 0.21 eV and excellent X-ray energy storage capabilities. When persistently stimulated by longer-wavelength white/NIR light or heated at elevated temperatures, ScBO3:Bi3+ phosphor exhibits intense and long-lasting ultraviolet luminescence due to the interplay between defect levels and external stimulus, while the natural decay in the dark at room temperature is extremely weak after X-ray irradiation. The impact of the spectral distribution and illuminance of ambient light and ambient temperature on ultraviolet light emission has been studied by comprehensive experimental and theoretical investigations, which elucidate that both O vacancy and Sc interstitial serve as deep electron traps for enhanced and prolonged ultraviolet luminescence upon continuous optical or thermal stimulation. Based on the unique spectral features and trap distribution in ScBO3:Bi3+ phosphor, controllable optical information read-out is demonstrated via external light or heat manipulation, highlighting the great potential of ScBO3:Bi3+ phosphor for advanced optical storage application in bright environments.

Multilevel Anti-counterfeiting Barcode with Enhanced Information Encryption Based on Stimulus-Responsive Digital Polymers

In response to the escalating challenges of counterfeiting due to technological and socioeconomic advancements, a novel trilevel anti-counterfeiting Quick Response (QR) code system has been developed. This system integrates digital polymers with QR code and stimulus-responsive chromophores, i.e., rhodamine B (RB), rhodamine 6G (R6G), and spiropyran (SP), to provide a sophisticated security solution. This advanced barcode remains concealed until specific stimuli reveal it and can be scanned by a smartphone, enabling first and second level anti-counterfeiting. For the third level of security, the encrypted information within the digital polymers can only be deciphered using tandem mass spectrometry. This innovative approach not only enhances security features but also offers reversible visibility and a complex verification process. This trilevel system surpasses traditional single-level anti-counterfeiting methods and holds significant potential for future applications in protecting brand authenticity and managing data storage, contributing new concepts and techniques to the field of high-security anti-counterfeiting materials.

Encapsulating Fe3O4 Nanoparticles and Carbon Dots in a Metal-Organic Framework for Magnetic Fluorescent Taggants

Magnetic fluorescent composite nanomaterials have broad application prospects in the fields of biological imaging, anticounterfeiting identification, suspicious object tracking, and identification of latent fingerprints in forensic medicine. For an effective taggant, a clearly visible identifying mark is necessary to enable observers to capture labeling information quickly and accurately, even from a distance. The preparation method of magnetic fluorescent composite materials is complicated and usually needs different surface modification and assembly processes. The limited loading capacity of fluorescent materials also limits the fluorescence properties of the composite, so it is difficult to produce obvious fluorescence as a taggant to meet the requirements of visible labeling. In this study, a core-shell structure of a magnetic fluorescent composite was prepared by using the metal-organic framework ZIF-8 as the host of fluorescent materials and an encapsulation shell coated on the Fe3O4 nanoparticles. The porous ZIF-8 is beneficial for increasing the loading capacity of fluorescent materials to ensure the fluorescence performance of the composite materials. Further modification of the composite surface prevented the desorption of fluorescent materials from the pores of ZIF-8, enabling the samples to maintain good fluorescence properties even after multiple washing cycles. The preparation method is simple, rapid, and cost-effective, and the prepared magnetic fluorescent composite nanomaterial has high magnetic separation performance and fluorescence performance, making it a promising material for identification, marking, and tracking.

Nonstoichiometry-Induced Self-Activated Phosphors for Dynamic Anti-counterfeiting Applications

Optical signals with distinctive properties, such as contactless, fast response, and high identification, are harnessed to realize advanced anti-counterfeiting. However, the simultaneous attainment of multi-color, -temporal, and -modal luminescence performance remains a compelling and imperative pursuit. In our work, a temperature/photon-responded dynamic self-activated luminescence originating from nonstoichiometric Zn2GeO4 is developed with the modulation of intrinsic defects. The increased concentration of oxygen vacancies (VO••) contributes to an enhanced recombination of ZnGe″-VO••, ultimately improving the self-activated luminescence performance. Additionally, the photoluminescence (PL) color of the representative Zn2.2GeO4 sample changes from green to blue-white with the increased ultraviolet (UV) irradiation time. Concurrently, the emission color undergoes a variation from blue to green as the ambient temperature raises from 280 to 420 K. Remarkably, green long persistent luminescence (LPL) and photostimulated luminescence (PSL) behaviors are observed. Herein, this study elucidates a sophisticated anti-counterfeiting approach grounded in the dynamic luminescent attributes of nonstoichiometric Zn2GeO4, presenting a promising frontier for the evolution of anti-counterfeiting technologies.

Multimode-Responsive Luminescence of Er3+ Single-Activated CaF2 Phosphor for Advanced Information Encryption

The current optical anticounterfeit strategies that rely on multimode luminescence in response to the photon or thermal stimuli have significant importance in the field of anticounterfeiting and information encryption. However, the dependence on light and heat sources might limit their flexibility in practical applications. In this work, Er3+ single-doped CaF2 phosphors that show multistimuli-responsive luminescence have been successfully prepared. The as-obtained CaF2:Er3+ phosphor exhibits green photoluminescence (PL) and color-tunable up-conversation (UC) luminescence from red to green due to the cross-relaxation of Er3+ ions. Additionally, as-obtained CaF2:Er3+ phosphors also display green mechano-luminescence behavior, which is induced by the contact electrification between the CaF2 particles and PDMS polymers, enabling the phosphor to flexibly respond to mechanical stimuli. Moreover, feasible anticounterfeiting schemes with the capability of multistimuli-responsive and flexible decryption have been constructed, further expanding the application of optical materials in the field of advanced anticounterfeiting and information encryption.

Multimode Dynamic Photoluminescence of Bi3+-Activated ZnGa2O4 for Optical Information Encryption

Optical storage technology for information encryption is a popular means of safeguarding information. Herein, a Bi³⁺-activated ZnGa₂O₄ multimode dynamic photoluminescence (PL) material is developed. Upon being irradiated with an ultraviolet lamp at a fixed excitation wavelength of 254 nm, the ZnGa₂O₄: x% Bi³⁺ (x = 0.5-5.0) samples exhibit varying degrees of dynamic PL emission due to a distinct Bi³⁺ doping effect. The mechanism underlying the dynamic PL of ZnGa₂O₄: Bi³⁺ associated with Bi³⁺-activated trap concentration modulation is investigated using thermoluminescence spectra. Additionally, the ZnGa₂O₄: 5% Bi³⁺ sample shows a reversible thermally responsive dynamic PL with a color variation from blue to red upon heating from 283 to 393 K. Predesigned procedures based on single-wavelength-mediated photochromic and thermochromic dynamic PL emissions of ZnGa₂O₄: Bi³⁺ are designed for rewritable optical data storage and high-level information encryption. Also, an enhanced encryption scheme with a mask encoding technique applying a ZnGa₂O₄: Bi³⁺ hybridized polyvinylidene difluoride film is then proposed to increase the security level. Accordingly, this work provides a feasible way to rationally design dynamic PL material offering more creative designs for safeguarding information via encryption.

Admirable stability achieved by ns2 ions Co-doping for all-inorganic metal halides towards optical anti-counterfeiting

Optical materials play a momentous role in anti-counterfeiting field, such as authentication, currency and security. The development of tunable optical properties and optical responses to a range of external stimuli is quite imperative for the growing demand of optical anti-counterfeiting technology. Metal halide perovskites have attracted much attention of researchers due to their excellent optical properties. In addition, co-doping methods have been gradually applied to the research of metal halide perovskites, by which more abundant luminescence phenomena can be introduced into the host perovskite. Herein, the ns² ions of bismuth (Bi³⁺) and antimony (Sb³⁺) ions co-doped zero-dimensional Cs₂SnCl₆ metal halide with an excitation-wavelength-dependent emission phenomenon is synthesized as an efficient multimodal luminescent material, the luminescence of which is tunable and covers a wide region of color. What's more, a dynamic dual-emission phenomenon is captured when the excitation wavelength changes from 320 nm to 420 nm for Cs₂SnCl₆:Bi_0.08Sb_0.12 crystals. Moreover, the Bi³⁺ and Sb³⁺ doped metal halide material shows great enhancement in solvent resistance and thermal stability compared to the pristine Cs₂SnCl₆. The admirable stability and distinguishable photoluminescence (PL) phenomenon of this all-inorganic metal halide has great potential to be applied in optical anti-counterfeiting technology. Furthermore, the co-doping method can accelerate the discovery of new luminescence phenomena in original metal halide perovskites.

Dynamic anti-counterfeiting and information encryption of Sr3Y2Ge3O12: Tb3+, Er3+ phosphor via carriers filling and release processes

Complex and high-security-level anti-counterfeiting strategies with multiple luminescent modes are extremely critical for meeting the requirement of constantly developing information storage and information security. In this work, Tb³⁺ ions doped Sr₃Y₂Ge₃O₁₂ (SYGO) and Tb³⁺/Er³⁺ co-doped SYGO phosphors are successfully fabricated and are unitized for anti-counterfeiting and information encoding under distinct stimuli sources. The green photoluminescence (PL), long persistent luminescence (LPL), mechano-luminescence (ML), and photo-stimulated luminescence (PSL) behaviors are respectively observed under the stimuli of ultraviolet (UV), thermal disturbance, stress, and 980 nm diode laser. Based on the time-dependence of the filling and releasing rate of the carriers from the shallow traps, the dynamic information encryption strategy is proposed by simply changing the UV pre-irradiation time or shut-off time. Moreover, a tunable color from green to red is realized by prolonging the 980 nm laser irradiation time, which is attributed to the elaborate cooperation of the PSL and upconversion (UC) behaviors. The anti-counterfeiting method based on SYGO: Tb³⁺ and SYGO: Tb³⁺, Er³⁺ phosphors herein possess an extremely high-security level with attractive performance for designing advanced anti-counterfeiting technology.

Multimodal and Multicolor Anti-counterfeiting Realized in CaCd2Ga2Ge3O12 with a Single Activator of Mn2

The continuously growing significance of information security and authentication has put forward many new requirements and challenges for modern luminescent materials and anti-counterfeiting technologies. Recently, luminescent materials have attracted much attention in this field owing to their legibility, repeatability, multicolor, and multiple stimuli-responsive nature. In this work, the efficient multicolor and multimodal luminescence material CaCd₂Ga₂Ge₃O₁₂:Mn²⁺ was successfully designed and synthesized using the strategy of single-doped Mn²⁺ in a single matrix. Also, we combined the morphology, crystal structure, energy band calculation, luminescence properties, and trap analysis to study the optical data storage capacity of CaCd₂Ga₂Ge₃O₁₂:Mn²⁺. Interestingly, in the presence of the 254 nm UV lamp, the sample can exhibit a tunable emission color from bule to cyan to yellow by increasing the dopant concentration of Mn²⁺. Also, under the afterglow and thermoluminescence luminescence modes, it presented strong yellow emission centered at 558 nm. Based on the advantage of multiple tunable luminescence, samples were made into anti-counterfeiting ink and were used to print four optical devices through the screen printing technology. The results show that the material has excellent multicolor anti-counterfeiting properties under the three luminescence modes, which has contributed to the development of many kinds of luminescent anti-counterfeiting materials for security purposes.

A single-beam NIR laser-triggered full-color upconversion tuning of a Er/Tm:CsYb2F7@glass photothermal nanocomposite for optical security

The development of advanced luminescent materials is highly desirable for addressing the rising threat of forgery. However, it is challenging to achieve stable full-color upconversion (UC) tuning in the same matrix upon a single-beam light excitation so as to ensure that authentic items are irreproducible. Herein, hexagonal Er/Tm:CsYb₂F₇ nanocrystals (NCs) embedded inorganic glass via an in situ crystallization strategy is fabricated, which can emit blue, cyan, green, yellow, orange, red and near-infrared (NIR) UC emissions by simply modifying an incident 980 nm laser power. This UC tuning is attributed to the combination roles of the highly efficient laser-induced photothermal effect of the CsYb₂F₇ host and simultaneous emissions of Er and Tm activators. Importantly, the robust inorganic glass matrix endows Er/Tm:CsYb₂F₇ NCs with excellent water resistance and the ability to withstand high-power laser irradiation. Based on these unique characteristics, a proof-of-concept anti-counterfeiting experiment is designed. The results indicate that dynamic full-color UC luminescence patterns can be easily tuned by simply changing the power of the incident 980 nm laser. The present work not only confirms that the designed photothermal material can increase information security, but also provides a new idea for practical applications in the field of anti-counterfeiting.

Advanced Luminescence Anticounterfeiting Based on Dynamic Photoluminescence and Non-Pre-Irradiation Mechanoluminescence

Luminescence anticounterfeiting is one of the most significant technologies to protect information security. However, the luminescence of the present anticounterfeiting logo is static, which is easily counterfeited by substitutes, and it always requires an ultraviolet lamp in use, which is inconvenient in application. In this work, according to the present deficiencies of luminescence anticounterfeiting, an interesting phosphor CaZnGe₂O₆/Mn²⁺ with unique features of dynamic photoluminescence and non-pre-irradiation mechanoluminescence is developed for the first time. The photoluminescence color of the phosphor can dynamically change from green to red during irradiation, and the non-pre-irradiation mechanoluminescence of the phosphor-based elastomer can be easily stimulated by mechanics such as stretching, bending, or scratching with a finger. By combining the two features of the CaZnGe₂O₆/Mn²⁺ phosphor, an advanced dual-mode luminescence anticounterfeiting is designed, and a luminescence logo is fabricated for the anticounterfeiting test. The result demonstrates that this advanced luminescence anticounterfeiting based on the phosphor is not only safer but also more convenient in application.

High-level information encryption based on optical nanomaterials with multi-mode luminescence and dual-mode reading

High-level information encryption based on a visible up-conversion and invisible persistent luminescence material.

Time-dependent dynamic multicolor afterglow of simple LiGa5O8:Eu3+/Tb3+ particles for advanced anticounterfeiting and encryption

A series of LiGa5O8:Eu3+/Tb3+ phosphors exhibit time-dependent dynamic multicolor afterglow from blue to red or green over several seconds after ceasing the excitation.

Mechanoluminescence Rebrightening the Prospects of Stress Sensing: A Review

The emergence of new applications, such as in artificial intelligence, the internet of things, and biotechnology, has driven the evolution of stress sensing technology. For these emerging applications, stretchability, remoteness, stress distribution, a multimodal nature, and biocompatibility are important performance characteristics of stress sensors. Mechanoluminescence (ML)-based stress sensing has attracted widespread attention because of its characteristics of remoteness and having a distributed response to mechanical stimuli as well as its great potential for stretchability, biocompatibility, and self-powering. In the past few decades, great progress has been made in the discovery of ML materials, analysis of mechanisms, design of devices, and exploration of applications. One can find that with this progress, the focus of ML research has shifted from the phenomenon in the earliest stage to materials and recently toward devices. At the present stage, while showing great prospects for advanced stress sensing applications, ML-based sensing still faces major challenges in material optimization, device design, and system integration.

Effective Repeatable Mechanoluminescence in Heterostructured Li1- x Nax NbO3 : Pr3

Mechanoluminescence (ML) is a striking optical phenomenon that is achieved through mechanical to optical energy conversion. Here, a series of Li_{1 -x} Na_x NbO₃ : Pr³⁺ (x = 0, 0.2, 0.5, 0.8, 1.0) ML materials have been developed. In particular, due to the formation of heterostructure, the synthesized Li_0.5 Na_0.5 NbO₃ : Pr³⁺ effectively couples the trap structures and piezoelectric property to realize the highly repeatable ML performance without traditional preirradiation process. Furthermore, the ML performances measured under sunlight irradiation and preheating confirm that the ML properties of Li_0.5 Na_0.5 NbO₃ : Pr³⁺ can be ascribed to the dual modes of luminescence mechanism, including both trap-controllable and self-recoverable modes. In addition, DFT calculations further confirm that the doping of Na⁺ ions in LiNbO₃ leads to electronic modulations by the formation of the heterostructures, which optimizes the trap distributions and concentrations. These modulations improve the electron transfer efficiency to promote ML performances. This work has supplied significant references for future design and synthesis of efficient ML materials for broad applications.

Development of Diketopyrrolopyrrole-Based Smart Inks by Substituting Ionic Pendants and Engineering Molecular Packing Structures

A series of diketopyrrolopyrrole (DPP) luminogen amphiphiles were newly designed and synthesized by a single-step anionic exchange reaction for controlling the photoluminescence properties in both solution and solid states. Multicolor emission in response to thermal, mechanical, and chemical stimuli was successfully demonstrated by engineering well-defined supramolecular assemblies. Phase transformation from the metastable amorphous solid to the stable orthorhombic crystal of [DP-Im][Br] provided the reversibly patternable light emission. Self-organization into the smectic crystalline phase of [DP-Im][TFSI] allowed us to show the linearly polarized light emission. By simultaneously applying [DP-Im][Br] and [DP-Im][TFSI], we demonstrated the fabrication of smart sensors for packaging of food or vaccines that can detect thermal attacks.

Highly Stable Waterborne Luminescent Inks Based on MAPbBr3@PbBr(OH) Nanocrystals for LEDs and Anticounterfeit Applications

Waterborne polymers are advantageous in terms of cost, convenience, sustainability, and environmental friendliness. As lead halide perovskite (LHP) nanocrystals suffer from fast degradation in the presence of water, it is challenging to encapsulate LHP nanocrystals in waterborne polymers. In this work, luminescent MAPbBr₃@PbBr(OH) nanocrystals were synthesized via the aqueous grinding process in the presence of 2-methyl-imidazole (2-MIM) and oleylamime (OAm). 2-MIM triggers the formation of the PbBr(OH) matrix, and OAm acts as a size-control ligand to control the size of MAPbBr₃@PbBrOH particles in the nanoscale range. Highly stable waterborne luminescent inks were successfully prepared by blending MAPbBr₃@PbBr(OH) nanocrystals with waterborne polymers, including poly(vinylpyrrolidone), poly(vinyl acetate), and acrylate resins. Owning to the dual protection of the polymer matrix and PbBr(OH) to LHP quantum dots (QDs), the luminescent films exhibit excellent stability to the environment under thermal and light irradiation. The ink can be used as a phosphor to fabricate down-converting green and white light-emitting diodes (LEDs). Waterborne anticounterfeiting inks suitable for screen printing were prepared via formula tuning for the anticounterfeit purpose. The anticounterfeiting luminescent patterns can be screen printed on paper, cloth, and poly(ethylene terephthalate) (PET), with encryption and decryption of information being accurately and conveniently realized by switching UV irradiation.

Rapid Visual Authentication Based on DNA Strand Displacement

Novel ways to track and verify items of a high value or security is an ever-present need. Taggants made from deoxyribonucleic acid (DNA) have several advantageous properties, such as high information density and robust synthesis; however, existing methods require laboratory techniques to verify, limiting applications. Here, we leverage DNA nanotechnology to create DNA taggants that can be validated in the field in seconds to minutes with a simple equipment. The system is driven by toehold-mediated strand-displacement reactions where matching oligonucleotide sequences drive the generation of a fluorescent signal through the potential energy of base pairing. By pooling different "input" oligonucleotide sequences in a taggant and spatially separating "reporter" oligonucleotide sequences on a paper ticket, unique, sequence-driven patterns emerge for different taggant formulations. Algorithmically generated oligonucleotide sequences show no crosstalk and ink-embedded taggants maintain activity for at least 99 days at 60 °C (equivalent to nearly 2 years at room temperature). The resulting fluorescent signals can be analyzed by the eye or a smartphone when paired with a UV flashlight and filtered glasses.

Achieving Multimodal Emission in Zn4B6O13:Tb3+,Yb3+ for Information Encryption and Anti-counterfeiting

With the rapid development of technology, information security has always been considered a major challenge. In this work, the excellent combination of persistent luminescence, photoluminescence, up-conversion luminescence, and thermo-luminescence in a particular material Zn₄B₆O₁₃:Tb³⁺,Yb³⁺ synthesized via a solid-state reaction is reported, which can be used for the information encryption and anti-counterfeiting. Tb³⁺ ions were chosen as the emitting centers for multimodal emissions, and Yb³⁺ codoping can be used as electron traps and sensitizer to adjust trap distribution and efficient up-conversion luminescence in rare-earth-doped luminescent materials. Besides, the as-prepared luminescent materials exhibit high thermal stability and excellent water resistance. On the basis of these properties, the samples were used to print luminescent images through a screen printing process on the film and banknote. The luminescent image in a film is showing different patterns and on a banknote is showing green emissions under different stimulations. These multimodal emissions demonstrate that the as-prepared sample is suitable for advanced information encryption and anti-counterfeiting.

Luminescence in Manganese (II)-Doped SrZn2S2O Crystals From Multiple Energy Conversion

Under the excitation of ultraviolet, X-ray, and mechanical stress, intense orange luminescence (Mn2+, 4T1 → 6A1) can be generated in Mn2+-doped SrZn2S2O crystal in orthorhombic space group of Pmn21. Herein, the multiple energy conversion in SrZn2S2O:Mn2+, that is, photoluminescence (PL), X-ray-induced luminescence, and mechanoluminescence, is investigated. Insight in luminescence mechanisms is gained by evaluating the Mn2+ concentration effects. Under the excitation of metal-to-ligand charge-transfer transition, the most intense PL is obtained. X-ray-induced luminescence shows similar features with PL excited by band edge UV absorption due to the same valence band to conduction band transition nature. Benefiting much from trap levels introduced by Mn2+ impurities, the quenching behavior mechanoluminescence is more like the directly excited PL from Mn2+ d-d transitions. Interestingly, this concentration preference leads to varying degrees of spectral redshift in each mode luminescence. Further, SrZn2S2O:Mn2+ exhibits a good linear response to the excitation power, which makes it potential candidates for applications in X-ray radiation detection and mechanical stress sensing.

Multicolor luminescence and triple-mode emission of simple CaTiO3:Pr3+,Er3+ particles for advanced anti-counterfeiting

The multilevel anticounterfeiting QR code readily integrates the advantages of excitation wavelength-dependent PL emissions, a strong red afterglow and sensitive excitation power-dependent UCL emissions in one overall device.

Rare-earth-containing perovskite nanomaterials: design, synthesis, properties and applications

As star material, perovskites have been widely used in the fields of optics, photovoltaics, electronics, magnetics, catalysis, sensing, etc. However, some inherent shortcomings, such as low efficiency (power conversion efficiency, external quantum efficiency, etc.) and poor stability (against water, oxygen, ultraviolet light, etc.), limit their practical applications. Downsizing the materials into nanostructures and incorporating rare earth (RE) ions are effective means to improve their properties and broaden their applications. This review will systematically summarize the key points in the design, synthesis, property improvements and application expansion of RE-containing (including both RE-based and RE-doped) halide and oxide perovskite nanomaterials (PNMs). The critical factors of incorporating RE elements into different perovskite structures and the rational design of functional materials will be discussed in detail. The advantages and disadvantages of different synthesis methods for PNMs will be reviewed. This paper will also summarize some practical experiences in selecting suitable RE elements and designing multi-functional materials according to the mechanisms and principles of REs promoting the properties of perovskites. At the end of this review, we will provide an outlook on the opportunities and challenges of RE-containing PNMs in various fields.