Anti-counterfeiting Technology Research Articles

Green synthesis of N,S dual heteroatom-doped fluorescent carbon dots (N,S-CDs) and their applications in gentamicin sensing and dual-switch anti-counterfeiting encryption

Herein, we report a facile one-step solvothermal synthesis of nitrogen and sulfur co-doped fluorescent carbon dots (N,S-CDs) using benzoic acid as the carbon source and sulfonamide as the doping agent. The synthesized N,S-CDs exhibit stable photoluminescence with an impressive fluorescence quantum yield of 16.8 %. These N,S-CDs maintain their luminescent properties under various challenging conditions, including high salt concentrations, elevated temperatures, UV radiation exposure, acidic or alkaline environments, long-term storage, and different solvents. Notably, the photoluminescence of N,S-CDs is excitation-wavelength dependent, with emission wavelengths tunable from 470 nm to 585 nm. Furthermore, the N,S-CDs display distinct fluorescent hues in aqueous and ethanolic media, presenting a novel dual-switch anti-counterfeiting ink system. Leveraging the sensitivity of N,S-CDs to gentamicin, we have developed a facile and rapid detection method for this antibiotic, which has been successfully applied to the analysis of authentic milk samples. This research contributes a novel and efficient protocol for the fabrication of high-performance carbon dots, thereby expanding their potential applications in food analysis and anti-counterfeiting technologies.

Hybrid metal halide family with color-time-dual-resolved phosphorescence for multiplexed information security applications

Luminescent materials with engineered optical properties play an important role in anti-counterfeiting and information security technology. However, conventional luminescent coding is limited by fluorescence color or intensity, and high-level multi-dimensional luminescent encryption technology remains a critically challenging goal in different scenarios. To improve the encoding capacity, we present an optical multiplexing concept by synchronously manipulating the emission color and decay lifetimes of room-temperature phosphorescence materials at molecular level. Herein, we devise a family of zero-dimensional (0D) hybrid metal halides by combining organic phosphonium cations and metal halide tetrahedral anions as independent luminescent centers, which display blue phosphorescence and green persistent afterglow with the highest quantum yields of 39.9 % and 57.3 %, respectively. Significantly, the luminescence lifetime can be fine-tuned in the range of 0.0968–0.5046 μs and 33.46–125.61 ms as temporary time coding through precisely controlling the heavy atomic effect and inter-molecular interactions. As a consequence, synchronous blue phosphorescence and green afterglow are integrated into one 0D halide platform with adjustable emission lifetime acting as color- and time-resolved dual RTP materials, which realize the multiple applications in high-level anti-counterfeiting and information storage. The color-lifetime-dual-resolved encoding ability greatly broadens the scope of luminescent halide materials for optical multiplexing applications.

A novel thermally-stable red phosphor CaYGaO4:Eu3+ for WLEDs and anti-counterfeiting ink

In this paper, CaYGaO4:xEu3+ (CYGO:xEu3+)phosphors were synthesized for the first time using a high-temperature solid-state method. The samples were characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). Their energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to further investigate the microscopic composition of the samples. The forbidden bandwidths and densities of states of CYGO and CYGO:0.25Eu3+ were calculated by first principles methods. The emission and excitation spectra of the samples were tested by fluorescence spectroscopy, which showed that the samples can be excited by both UV and blue light. When the sample heated to 473 K, the luminescence intensity under 393 and 463 nm excitation stays at 83.99 % and 85.19 % of the room temperature, respectively, which demonstrates that CYGO:0.3Eu3+ possesses excellent thermal stability. The color coordinates (CIE), correlated color temperature (CCT) and color purity (CP) of the samples were also investigated. In order to explore its application in the field of white light-emitting diodes (WLEDs), CYGO:0.3Eu3+ was mixed with commercial blue and green phosphors in a certain ratio, and the chip was made into a WLED with 395 nm excitation, and the CIE of the lamps were (0.3338, 0.3521), with a correlated CCT of 5448 K, and a color rendering index (CRI) of Ra = 86.2. The thermal imaging performance of the small lamps was also evaluated for sustained usage, revealing minimal temperature fluctuations and excellent thermal stability. Consequently, CYGO:Eu3+ exhibits promising potential for applications in the field of WLEDs. Additionally, CYGO:0.3Eu3+ was selected as a representative sample for the creation of fluorescent ink and its subsequent application on various media. The outcomes indicate that this phosphor possesses promising potential for use in the field of anti-counterfeiting ink technology.

Ultralong room temperature phosphorescence and broad color-tunability persistent luminescence via new strategy

Pure organic materials with ultralong room-temperature phosphorescence (RTP) and persistent luminescence in broad color gamut exhibit tremendous potential and broad application prospects due to their unique optical properties. This article proposes a simple strategy, polyatomic synergistic effect, to endow persistent luminescent materials with ultralong lifetime and broad color-tunability through polyatomic synergistic effect and non-traditional phosphorescence resonance energy transfer (PRET). By leveraging the polyatomic synergistic effect to enhance the intersystem crossing (ISC) in bibenzimidazole (BBI) derivatives and suppress the non-radiative transition process, ultralong persistent room-temperature phosphorescence has been successfully achieved after incorporating BBI-Cl-M into poly(methyl methacrylate) (PMMA) to form a rigid matrix(BBI-Cl-M@PMMA). Specifically, the ester functionalized bibenzimidazole with modified chlorine on molecular skeleton (BBI-Cl-M) demonstrates a remarkable phosphorescent lifetime (τp) of up to 256.4 ms. In addition, the behaviors and mechanism of RTP via polyatomic synergistic effect have been further understood by theoretical calculation and single crystal analysis. Subsequently, utilizing BBI-Cl-M as the energy donor and Rhodamine B (RB) as the energy acceptor, persistent and multicolor organic afterglow covering from green to red has been realized successfully by simply regulating the doping composition and concentration of PRET systems. These RTP materials have also been applied in underwater afterglow emission and multilevel anti-counterfeiting technology successfully.

Sextuplet luminescence with dynamically variable color/brightness in chromium activated gallium-silicate solid solution in R3 space group

The development of dynamic multi-color luminescence is a tremendous challenge for anti-counterfeiting. Herein, we have successfully synthesized Cr3+ activated gallium-silicate base material systems as the effective luminescent materials responsive to multiple field stimulation, exhibiting sextuplet luminescence including photoluminescence, strong red persistent luminescence (PersL), photo/thermo stimulated luminescence (PSL/TSL), photo-stimulated PersL and up-conversion luminescence (UCL). The luminescence quenching temperature is also improved in Cr3+,Yb3+,Er3+ co-doping sample relatives to Cr3+ single-doping phosphor. Especially, when Er3+ and Yb3+ are co-doped into Cr3+ activated phosphor system, UV preirradiated phosphor not only demonstrates an additional UCL from Er3+ ions accompanied with red PSL from the Cr3+ under NIR laser irradiation, but also leads to a dynamic change in color/brightness under the extension of NIR laser irradiation time. The multimode luminescence mechanisms are also proposed. Based on excellent luminescence characteristics, multi-color and multi-mode anti-counterfeiting patterns have been designed, especially appearing of dynamic anti-counterfeiting on luminescent color/brightness, which provides new dimensions for anti-counterfeiting technologies.

Fast and Accurate Recognition of Perovskite Fluorescent Anti-counterfeiting Labels Based on Lightweight Convolutional Neural Networks.

Anti-counterfeiting technology has always been a key issue in the field of information security. Physical Unclonable Function (PUF) labels, which are random patterns produced by a stochastic process, emerge as an effective anti-counterfeiting strategy due to the inherent randomness of their physical patterns. In this study, we developed a high-throughput droplet array generation technique based on surface tension confinement to prepare perovskite crystal films with controllable shapes and sizes. We utilized the random distribution of perovskite nanocrystal particles to construct the PUF textures of the labels. Compared to other anti-counterfeiting labels, our labels not only possess fluorescent properties but also feature microscale dimensions (less than 5.3 × 10-2mm2), low cost (less than 3 × 10-4 USD), and high encoding capacity (1.7 × 101956), providing support for multilevel anti-counterfeiting protection. Additionally, we introduce an innovative PUF recognition method based on a Partial Convolutional Network (PaCoNet), effectively addressing the limitations of previous methods, in terms of recognition accuracy and speed. Experimental validation on a data set of perovskite nanocrystal films with up to 60 different macroscopic shapes and unique microscopic textures demonstrates that our method achieves a recognition accuracy of up to 99.65% and significantly reduces the recognition time per image to just 0.177 s, highlighting the potential application of these labels in the field of anti-counterfeiting.

Phonon-mediated infrared plasmonic metamaterial emitters towards high-capacity multifunctional encoding and display

This study introduces what we believe is a novel approach to manipulating light in the mid-infrared spectrum through phonon-mediated metal-insulator-metal (MIM) cavities. Leveraging the unique interactions between resonantly excited electric and magnetic dipoles and phonons within silicon dioxide spacers, we have developed a technology different from traditional methods that rely on geometric modifications of nanostructures, offering a more versatile and effective means of tailoring light-matter interactions at the nanoscale. Our experimental results showcase the ability of these MIM cavities to perform multifunctional information encoding, display, and concealment with high precision. Notably, we encoded 13 distinct gray levels, surpassing previous capabilities in the long-wave infrared spectrum using metamaterial emitters. Furthermore, the incorporation of rotating nanorod structures enabled the encoding of grayscale patterns through polarization states, enhancing the potential for high-capacity information storage. The study also demonstrates the capability of these structures for subwavelength-resolution printing and near-diffraction-limit information encoding in the long-wave infrared band. We have successfully employed an innovative ink coating method, transparent in the long-wave infrared but opaque in the visible spectrum, to conceal encoded information, thereby adding a layer of security. In summary, the phonon-mediated infrared plasmonic metamaterial emitters presented in this work pave the way for future research in high-capacity information storage, anti-counterfeiting, and security technologies.

A high security coding and anti-counterfeiting method based on the nonlinear magnetization response of superparamagnetic nanomaterials

Traditional coding methods based on graphics and digital or magnetic labels have gradually decreased their anti-counterfeiting because of market popularity. This paper presents a new magnetic anti-counterfeiting coding method. This method uses a high-performance coding material, which, along with small changes to the material itself and the particle size of the superparamagnetic nanomaterials, results in a large difference in the nonlinear magnetization response. This method, which adopts 12-site coding and establishes a screening model by measuring the voltage amplitude of 12-site variables, can code different kinds of products, establishing long-term stable coding and decoding means. Through the anti-counterfeiting experiment of wine, the experiment results show that the authenticity of the coded products can be verified using the self-developed magnetic encoding and decoding system. The new coding technology can verify the anti-counterfeiting of 9000 products, with a single detection accuracy of 97% and a detection time of less than one minute. Moreover, this coding method completely depends on the production batch of the superparamagnetic nanomaterials, which is difficult to imitate, and it provides a new coding anti-counterfeiting technology for related industries with a wide range of potential applications.

Light-responsive multimode luminescence in photochromism transparent wood for anti-counterfeiting application

With the rapid development of information technology, people’s security awareness of information protection is enhanced, and the requirements for anti-counterfeiting technology have become higher and higher on different occasions. Smart materials with light stimulus response have attracted extensive attention in the development of anti-counterfeiting materials, especially next-generation intelligent transparent wood. Inspired by the color-changing behavior of plants and animals in nature, a photochromic transparent wood (PTW) composite with light-stimulated response was prepared by compounding rare earth luminescent complexes with transparent wood (TW). PTW exhibits high transmittance (85.5 %). Moreover, PTW exhibits different optical states under different light conditions, namely, colorless under sunlight and bright red fluorescence under 365-nm UV light, and the process is reversible. Additionally, PTW patterned by laser etching offered greater flexibility and personalization in terms of stimulus-response, and its information security under different light stimuli is demonstrated. Meanwhile, the PTW prepared can be applied to different products and their packaging as an invisible anti-counterfeiting label, and the storage and protection of information is realized under visible light, and the decoding of information is implemented in UV light, so as to achieve the invisible anti-counterfeiting of information. More importantly, invisible information can be clearly identified even in black packaging. The design concepts and techniques of this study provide an inspiration to combine smart responsive materials with wood-based materials to develop intelligent responsive materials, and also provides support for the subsequent design and preparation of invisible anti-counterfeiting materials.

Development of Stable Water-Soluble Supratomic Silver Clusters Utilizing A Polyoxoniobate-Protected Strategy: Giant Core-Shell-Type Ag8@Nb162 Fluorescent Nanocluster.

Atomically precise low-nuclearity (n<10) silver nanoclusters (AgNCs) have garnered significant interest due to their size-dependent optical properties and diverse applications. However, their synthesis has remained challenging, primarily due to their inherent instability. The present study introduces a new feasible approach for clustering silver ions utilizing highly negative and redox-inert polyoxoniobates (PONbs) as all-inorganic ligands. This strategy not only enables the creation of novel Ag-PONb composite nanoclusters but also facilitates the synthesis of stable low-nuclearity AgNCs. Using this method, we have successfully synthesized a small octanuclear rhombic [Ag8]6+ AgNC stabilized by six highly negative [LiNb27O75]14- polyoxoanions. This marks the first PONb-protected superatomic AgNC, designated as {Ag8@(LiNb27O75)6} (Ag8@Nb162), with an aesthetically spherical core-shell structure. The crystalline Ag8@Nb162 is stable under ambient conditions, What's more, it is water-soluble and able to maintain its molecular cluster structure intact in water. Further, the stable small [Ag8]6+ AgNC has interesting temperature- and pH-dependent reversible fluorescence response, based on which a multiple optical encryption mode for anti-counterfeit technology was demonstrated. This work offers a promising avenue for the synthesis of fascinating and stable PONb-protected AgNCs and sheds light on the development of new-type optical functional materials.

Circularly Polarized Room Temperature Phosphorescence through Twisting-Induced Helical Structures from Polyvinyl Alcohol-Based Fibers Containing Hydrogen-Bonded Dyes.

Room temperature phosphorescence (RTP) materials have garnered significant attention owing to its distinctive optical characteristics and broad range of potential applications. However, the challenge remains in producing RTP materials with more simplicity, versatility, and practicality on a large scale, particularly in achieving chiral signals within a single system. Herein, we show that a straightforward and effective combination of wet spinning and twisting technique enables continuously fabricating RTP fibers with twisting-induced helical chirality. By leveraging the hydrogen bonding interactions between polyvinyl alcohol (PVA) and quinoline derivatives, along with the rigid microenvironment provided by PVA chains, typically, Q-NH2@PVA fiber demonstrates outstanding phosphorescent characteristics with RTP lifetime of 1.08 s and phosphorescence quantum yield of 24.6 %, and the improved tensile strength being 1.7 times than pure PVA fiber (172±5.82 vs 100±5.65 MPa). Impressively, the transformation from RTP to circularly polarized room temperature phosphorescence (CP-RTP) is readily achieved by imparting left- or right-hand helical structure through simply twisting, enabling large-scale production of chiral Q-NH2@PVA fiber with dissymmetry factor of 10-2. Besides, an array of displays and encryption patterns are crafted by weaving or seaming to exemplify the promising applications of these PVA-based fibers with outstanding adaptivity in cutting-edge anti-counterfeiting technology.

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.

Trap-controllable near-ultraviolet elastico-mechanoluminescence of Ce3+ doped phyllosilicate with melilite-type structure

Mechanoluminescence (ML) materials have attracted much attention because of their mechano-optical conversion characteristics, which have shown broad application prospects in stress sensing and anti-counterfeiting technology in the past few decades. However, elastico-ML has not been demonstrated at the near-ultraviolet (NUV) range. In this study, a novel NUV elastico-ML material (Ca, Sr)8Mg3Al2Si7O28:Ce3+ (CSMASOC) with a melilite-type structure is successfully developed. The ML properties of CSMASOC were optimized by adjusting the doping concentration of Ce3+ and cation substitution, and the ML mechanism was also explored by analyzing the ML test under different irradiation conditions and thermoluminescence spectra. The results confirmed that the ML in CSMASOC was derived from 5d-4f transition of Ce3+, and CSMASOC belongs to trap-controllable ML material. In addition, NUV ML material CSMASOC is combined with several commercial phosphors, and constructed multi-color ML in the visible light range. The developed NUV ML materials and the constructed multi-color ML system in this work are critical for expanding the types of ML materials and promoting the practical application of ML materials.

Multi-color and multi-mode luminescence tuning in persistent phosphors by trap engineering

Conventional persistent luminescent phosphors face a significant challenge in developing a single material for multi-color anti-counterfeiting. In this study, a wide range of Cr3+ activated gallium germanate-based persistent phosphors are successfully synthesized using high-temperature solid phase approach. By incorporating Cr3+ and Er3+ as dual emitting centers, and utilizing Yb3+ as a sensitizer and electron traps, the resulting phosphors exhibit an exceptional combination of photoluminescence, up-conversion luminescence, persistent luminescence, photo/thermo-stimulated luminescence, followed by photo-stimulated persistent luminescence in a single material system. Beyond its multi-mode emissions, the luminescence color output can be conveniently controlled by adjusting annealing time, Yb3+ ion doping concentration, excitation wavelength, or excitation power. A systematic study of trap distribution related to PersL has been conducted by regulating annealing temperature, time, doping concentration and type. The responding multi-mode luminescent mechanisms are also proposed. Particularly, these phosphors demonstrated outstanding performance as security labels in advanced anti-counterfeiting applications. This research holds the potential to inspire the design and development of more intricate luminescence anti-counterfeiting materials and technologies.

Programmable multimode optical encryption of advanced printable security inks by integrating structural color with Down/Up- conversion photoluminescence

Optical information encryption with high encoding capacities can significantly boost the security level of anti-counterfeiting in the scenario of guaranteeing the authenticity of a wide scope of common and luxury goods. In this work, a novel counterfeiting material with high-degree complexity is fabricated by microencapsulating cholesteric liquid crystals and triplet–triplet annihilation upconversion fluorophores to integrate structural coloration with fluorescence and upconversion photoluminescence. Moreover, the multimode security ink presents tailorable optical behaviors and programmable abilities on flexible substrates by various printing techniques, which offers distinct information encryption under different optical modes. The advanced strategy provides a practical versatile platform for high-secure-level multimode optical inks with largely enhanced encoding capacities, programmability, printability, and cost-effectiveness, which manifests enormous potentials for information encryption and anti-counterfeiting technology.

Fluorescent Materials Based on Spiropyran for Advanced Anti-Counterfeiting and Information Encryption.

In daily life, counterfeit and substandard products, particularly currency, medicine, food, and confidential documents, are capable of bringing about very serious consequences. The development of anti-counterfeiting and authentication technologies with multilevel securities is a powerful means to overcome this challenge. Among various anti-counterfeiting technologies, fluorescent anti-counterfeiting technology is well-known and commonly used to fight counterfeiters due to its wide material source, low cost, simple usage, good concealment, and simple response mechanism. Spiropyran is favored by scientists in the fields of anti-counterfeiting and information encryption due to its reversible photochromic property. Here, we summarize the current available spiropyran-based fluorescent materials from design to anti-counterfeiting applications. This review will be help scientists to design and develop fluorescent anti-counterfeiting materials with high security, high performance, quick response, and high anti-counterfeiting level.

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.

Hollow SiO2 photonic crystal - graphene quantum dots composite and its application in multi-level intelligent anti-counterfeiting through regulation synergistic effect of structural color and fluorescence

The research on composite materials with rainbow color (structural color) and ultraviolet excitation characteristics (fluorescence) is the development direction of the new generation of functional photonic engineering materials. Herein, composite materials composed of hollow SiO2 photonic crystals (PCs) with nanometer thickness and PEGDA gel containing graphene quantum dots (GQDs) were prepared to achieve fluorescence regulation effect and thus apply in multi-level intelligent anti-counterfeiting. Due to the SiO2 shell thickness of 20–41 nm, the Bragg diffraction law explained that the material underwent secondary refraction, resulting in a wide photonic band gap (PBG). On the other hand, due to the comparison of refractive index between air (n = 1) and composite material (n = 1.46), the transmittance of the composite materials were only 21 %–26 %, indicating strong refractive ability. Therefore, we constructed a PC structure with a wide photonic bandgap (PBG) to provide better wavelength selectivity and coverage range, which would significantly increase the effect of structural color on fluorescence. Based on the unique quantum dot size effect of GQDs, we also investigated the fluorescence enhancement effect with 157 nm FWHM located on PC materials. Therefore, artificial design and control of both fluorescence enhancement and fluorescence suppression had been achieved through multi-level regulation of structural color. We further utilized these properties to create multi-level anti-counterfeiting verification patterns, such as a 3 × 3 digital encoding matrix. The authenticity of the product information must be verified through stepwise identification under specified conditions. This intelligent anti-counterfeiting technology offers a novel approach to safeguard information security.

Force/Acid-Activated and Radical-Regulated photochromic luminescence in a binuclear Zero-Dimensional complex for multi-level anti-counterfeiting

Traditional static optical anti-counterfeiting technology can only output a single emission signal, which is easy to replicate and difficult to meet the needs in current high-tech fields. Multi-level stimuli-responsive luminescent materials with internal logical relationship can improve the degree of anti-counterfeiting and resist against the flood of counterfeiting. In this work, we propose to use force and acid dual stimuli to restrict the dissipation path of photogenerated free radicals, which further lead to the radical-actuated photochromic luminescence (PCL) performance. Based on this strategy, a zero-dimensional (0D) dinuclear zinc complex Zn2(9-AC)4(IM)2 (1) with blue luminescent properties (450 nm) was designed and synthesized. The interaction between 9-AC and IM (as 9-AC/IM exciplex) can be cut off by force-induced rearrangement of structural units in the spatial dimensions or acid-induced protonation of 9-AC, achieving the luminescent transformation from 9-AC/IM exciplex (447 nm) to 9-AC/9-AC excimer (480 nm) or 9-HAC (485 nm). At the same time, the PCL performance was activated and the emission intensity quenching rate increased from 4.77 % to 93.86 % or 44.93 % under UV light irradiation, respectively. The solid-state ultraviolet–visible absorption spectra, electron paramagnetic resonance spectra and theoretical calculation confirmed that the activation of PCL performance is due to the fact that the 9-AC• radicals are more difficult to dissipate upon force- or acid-induced stimuli. Combining mechanochromic luminescence (MCL) and PCL, a dynamic anti-counterfeiting quick response (QR) code with multi-level and fast-responsive logic sequence have been designed, which are promising for the application in time-resolved information encryption. This work provides an effective strategy to construct multi-level stimuli-responsive luminescence as novel anti-counterfeiting materials by changing the photogenerated free radical dissipation pathway to activate PCL properties.

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.