High-resolution imaging of magnetic fields of banknote anti-counterfeiting strip using fiber diamond probe

Counterfeiting of modern banknotes poses a significant challenge,prompting the use of various preventive measures.One such measure is the magnetic anti-counterfeiting strip.However,due to its inherent weak magnetic properties,visualizing its magnetic distribution has been a longstanding challenge.In this work,we introduce an innovative method by using a fiber optic diamond probe,a highly sensitive quantum sensor designed specifically for detecting extremely weak magnetic fields.We employ this probe to achieve high-resolution imaging of the magnetic fields associated with the RMB 50denomination anti-counterfeiting strip.Additionally,we conduct computer simulations by using COMSOL Multiphysics software to deduce the potential geometric characteristics and material composition of the magnetic region within the anti-counterfeiting strip.The findings and method presented in this study hold broader significance,extending the RMB 50 denomination to various denominations of the Chinese currency and other items that employ magnetic anti-counterfeiting strips.These advances have the potential to significantly improve and promote security measures in order to prevent the banknotes from being counterfeited.

Luminescence regulation of Sb^(3+)in 0D hybrid metal halides by hydrogen bond network for optical anti-counterfeiting

The Sb^(3+) doping strategy has been proven to be an effective way to regulate the band gap and improve the photophysical properties of organic-inorganic hybrid metal halides(OIHMHs).However,the emission of Sb^(3+) ions in OIHMHs is primarily confined to the low energy region,resulting in yellow or red emissions.To date,there are few reports about green emission of Sb^(3+)-doped OIHMHs.Here,we present a novel approach for regulating the luminescence of Sb^(3+) ions in 0D C_(10)H_(2)_(2)N_(6)InCl_(7)·H_(2)O via hydrogen bond network,in which water molecules act as agents for hydrogen bonding.Sb^(3+)-doped C_(10)H_(2)2N_(6)InCl_(7)·H_(2)O shows a broadband green emission peaking at 540 nm and a high photoluminescence quantum yield(PLQY)of 80%.It is found that the intense green emission stems from the radiative recombination of the self-trapped excitons(STEs).Upon removal of water molecules with heat,C_(10)H_(2)_(2)N_(6)In_(1-x)Sb_(x)Cl_(7) generates yellow emis-sion,attributed to the breaking of the hydrogen bond network and large structural distortions of excited state.Once water molecules are adsorbed by C_(10)H_(2)_(2)N_(6)In_(1-x)Sb_(x)Cl_(7),it can subsequently emit green light.This water-induced reversible emission switching is successfully used for optical security and information encryption.Our findings expand the under-standing of how the local coordination structure influences the photophysical mechanism in Sb^(3+)-doped metal halides and provide a novel method to control the STEs emission.

Identification of a Printed Anti-Counterfeiting Code Based on Feature Guidance Double Pool Attention Networks

The authenticity identification of anti-counterfeiting codes based on mobile phone platforms is affected by lighting environment,photographing habits,camera resolution and other factors,resulting in poor collection quality of anti-counterfeiting codes and weak differentiation of anti-counterfeiting codes for high-quality counterfeits.Developing an anticounterfeiting code authentication algorithm based on mobile phones is of great commercial value.Although the existing algorithms developed based on special equipment can effectively identify forged anti-counterfeiting codes,the anti-counterfeiting code identification scheme based on mobile phones is still in its infancy.To address the small differences in texture features,low response speed and excessively large deep learning models used in mobile phone anti-counterfeiting and identification scenarios,we propose a feature-guided double pool attention network(FG-DPANet)to solve the reprinting forgery problem of printing anti-counterfeiting codes.To address the slight differences in texture features in high-quality reprinted anti-counterfeiting codes,we propose a feature guidance algorithm that creatively combines the texture features and the inherent noise feature of the scanner and printer introduced in the reprinting process to identify anti-counterfeiting code authenticity.The introduction of noise features effectively makes up for the small texture difference of high-quality anti-counterfeiting codes.The double pool attention network(DPANet)is a lightweight double pool attention residual network.Under the condition of ensuring detection accuracy,DPANet can simplify the network structure as much as possible,improve the network reasoning speed,and run better on mobile devices with low computing power.We conducted a series of experiments to evaluate the FG-DPANet proposed in this paper.Experimental results show that the proposed FG-DPANet can resist highquality and small-size anti-counterfeiting code reprint forgery.By comparing with the existing algorithm based on texture,it is shown that the proposed method has a higher authentication accuracy.Last but not least,the proposed scheme has been evaluated in the anti-counterfeiting code blurring scene,and the results show that our proposed method can well resist slight blurring of anti-counterfeiting images.

RFID Anti-Counterfeiting for Retailing Systems

Counterfeiting is one of the most serious problems in the consumer market. One promising approach for anti-counterfeiting is to attach a low-cost Radio-frequency Identification (RFID) tag to the product authentication. In this paper, we propose an RFID system for detecting counterfeiting products. This RFID system consists of the tag authentication protocol and the database correction protocol. We use the tag authentication protocol for authenticating tags without revealing their sensitive information. This protocol also allows the customer to freely inquire the tag. To prevent the widespread of the counterfeit products, we use the tag status information along with tag identity information. Meanwhile, the database correction protocol guarantees the correctness of the tag status. Our anti-counterfeiting system is the first work considering the seller who plays an important role in the consumer product supply chain. Finally, we show that anti-counterfeiting system is quite secure against counterfeiting and the tag authentication protocol is lightweight enough to be implemented in RFID-based applications.

Water-sensitive multicolor luminescence in lanthanide-organic framework for anti-counterfeiting

The developme nt of high-level an ti-co un terfeiti ng tech niq ues is of great sig nifica nee in econo mics and security issues.However,i ntricate read ing methods are required to obta in multi-level info rmati on stored in differe nt colors,which greatly limits the applicati on of an ti-co un terfeit ing tech no logy on sol ving real world problems.Here in,we realize multicolor information anti-counterfeiting under simply external stimulation by utilizing the functional groups and multiple emission centers of lanthanide metal organic framework(Ln-MOFs)to tune luminescence color.Water responsive multicolor luminescence represented by both the tunable color from red to blue within the visible region and high sensitive responsivity has bee n achieved,owing to the in creased nonr adiative decay pathways and enhan ced Eu3+-to-liga nd en ergy back tra nsfer.Remarkably,i nfo rmatio n hidde n in differe nt colors n eeds to be read with a specific water content,which can be used as an en crypti on key to en sure the security of the info rmati on for high-level an ti-co un terfeiti ng.

Versatile MXene Gels Assisted by Brief and Low‑Strength Centrifugation

Due to the mutual repulsion between their hydrophilic surface terminations and the high surface energy facilitating their ran-dom restacking,2D MXene nanosheets usually cannot self-assemble into 3D macroscopic gels with various applications in the absence of proper linking agents.In this work,a rapid spontaneous gelation of Ti3C2Tx MXene with a very low dispersion concentration of 0.5 mg mL^(-1) into multifunctional architectures under moderate centrifugation is illustrated.The as-prepared MXene gels exhibit reconfigurable internal structures and tunable rheological,tribological,electrochemical,infrared-emissive and photothermal-conversion properties based on the pH-induced changes in the surface chemistry of Ti_(3)C_(2)T_(x) nanosheets.By adopting a gel with optimized pH value,high lubrication,exceptional specific capacitances(~635 and~408 F g^(-1) at 5 and 100 mV s^(-1),respectively),long-term capacitance retention(~96.7%after 10,000 cycles)and high-precision screen-or extrusion-printing into different high-resolution anticounterfeiting patterns can be achieved,thus displaying extensive potential applications in the fields of semi-solid lubrication,control-lable devices,supercapacitors,information encryption and infrared camouflaging.

Monitoring of Sweat pH and Dual-Mode Anti-Counterfeiting from Metal-Organic Framework-Based Multifunctional Gel

Monitoring of sweat pH plays important roles in physiological health,nutritional balance,psychological stress,and sports performance.However,the combination of functional MOFs with phosphorescent material to acquire the real-time physiological information,as well as the application of dual mode anti-counterfeiting,has seldom been reported.Herein,we developed multifunctional gel films based on MOFs and phosphorescent dyes which responded to H+ions and the related mechanism was studied in detail.Upon exposure to H+,the composite gel film exhibited decreased fluorescent signal but enhanced room temperature phosphorescence(RTP),which could be utilized for sweat pH sensing through a dual-mode.Moreover,multifunctional gel films exhibited a potential application in information encryption and anti-counterfeiting by designing of stimulus responsive multiple patterns.This research provided a new avenue for portable and non-invasive sweat pH monitoring methods while also offering insights into stimulus-responsive multifunctional materials.

Field-Deployable Raman Anti-Counterfeit Screening of Tamiflu Capsules

In an effort to promote the availability of safe and effective drugs, the US Food and Drug Administration is developing spectroscopic methods to assess the quality of drugs in the field. Here we report a rapid screening classification method for Tamiflu (oseltamivir phosphate) capsules using a portable Raman spectrometer to perform screening on three solid oral dosage strengths of Tamiflu, 30 mg, 45 mg and 75 mg. Tamiflu is an antiviral drug that is stockpiled for use in the event of pandemic influenza outbreak. The qualitative classification methods reported were developed using the Raman spectra of intact capsules. The classification algorithms used were able to reliably distinguish the three dosage strengths of Tamiflu. These qualitative models are validated with additional Tamiflu samples from different batches and simulated counterfeits of Tamiflu. The probability that a test sample belongs to each dosage strength class is calculated, and strict class predictions are used to assign each sample to a particular class. The classification methods reported here enable development of user-independent, field-deployable methods for finished drug products and are able to correctly assign 92% of the validation samples using authentic Tamiflu and 100% of the simulated counterfeits.

Metal halide perovskite nanocrystals with enhanced photoluminescence and stability toward anti-counterfeiting highperformance flexible fibers

As a new type of light-collecting and luminescent material,all-inorganic cesium lead halide CsPbX_(3)(X=Cl,Br,I)perovskite nanocrystals(NCs)are expected to have a wide range of applications in the fields of photovoltaics,optoelectronics,and fluorescence anti-counterfeiting,etc.Therefore,improving the fluorescence performance and stability of CsPbX_(3)perovskite NCs to prompt their applications would promise both fundamental and practical significance for in-depth research in the field of halide perovskites.In this paper,we developed a modification strategy to introduce a halogen source,zinc bromide(ZnBr_(2))in hexane,to CsPbX_(3)perovskite that can be conducted under atmospheric conditions with reduced reaction cost and easier operation.The first work in this paper was to apply the modification strategy to CsPbI_(3)nanowires(NWs).Compared with the untreated NWs,the ZnBr_(2)/hexane modified CsPbI_(3)NWs exhibited better fluorescence properties.Subsequently,based on the study of perovskite NWs,we investigated perovskite nanocrystal-CsPbI_(3)nanorods(NRs)with different morphologies and sizes.It was found that the luminescence properties of nanorods(NRs)were superior.Later,we infiltrated the modified NRs into the aramid/polyphenylene sulfide(ACFs/PPS)composite paper yielded from our previous work to study its fluorescence performance for anti-counterfeiting.Their luminescence properties under ultraviolet light irradiation enable better performance in fluorescence anti-counterfeiting.The ZnBr_(2)/hexane modification strategy and the applications studied in this work will expand the scope of perovskite research,laying the foundation for the applications of fluorescent anti-counterfeiting,nano-photoelectric devices,and fluorescent composite materials.

Ultralong Organic Phosphorescence of Triazatruxene Derivatives for Dynamic Data Encryption and Anti-counterfeiting

Comprehensive Summary,Organic luminogens with persistent room temperature phosphorescence(RTP)have drawn tremendous attentions due to their promising potentials in optoelectronic devices,information storage,biological imaging,and anti-counterfeiting.In this work,six triazatruxene-based lumiogens with different peripheral substituents and configurations are synthesized and systematically studied.The results show that their fluorescence quantum yields in solid states range from 15.73%to 37.58%.Dispersing the luminogens as guest into the host(PPh_(3))could turn on the persistent RTP,where PPh_(3)acts as not only a rigid matrix to suppress the non-radiative transitions of the guest,but also provides energy transfer channels to the guest.The maximum phosphorescence efficiency and the longest lifetime could reach 29.35%and 0.99 s in co-crystal films of 6-TAT-CN/PPh_(3)and 5-TAT-H/PPh_(3),respectively.Moreover,these host-guest co-crystalline films exhibit great potentials in advanced dynamic data encryption and anti-counterfeiting.This work deepens the insight for low cost,halogen-free,and facile fabrication of all-organic persistent RTP materials.

Excitation-wavelength-dependent fluorescent organohydrogel for dynamic information anti-counterfeiting

Anti-counterfeiting labels with various fluorescent colors are of great importance in information encryption-decryption,but are still limited to static information display.Therefore,it is urgent to develop new materials and encryption-decryption logic for improving the security level of secret information.In this study,an organohydrogel made up of poly(N,N-dimethylacrylamide)(pDMA)hydrogel network and polyoctadecyl methacrylate(pSMA)organogel network that copolymerized with two fluorophores,6-acrylamidopicolinic acid moieties(6APA,fluorescent ligand)and spiropyran units(SPMA,photochromic monomer),was prepared by a two-step interpenetrating method.As UV light of 365nm and 254nm can both cleave C_(spiro)-O bonds of SPMA,and the green fluorescence of 6APA-Tb^(3+) can only be excited by 254nm light,the organohydrogel displays yellow and red under the irradiation of 254nm and 365 nm,respectively.In addition to wavelength selectivity,these two fluorophores are thermal-responsive,leading to the fluorescence variation of the organohydrogel during heating process.As a result,secret information loaded on the organohydrogel can be decrypted by the irradiation of UV light,and the authenticity of the information can be further identified by thermal stimulation.Our fluorescent organohydrogel can act as an effective anti-counterfeiting label to improve the information security and protect the information from being cracked.

Sustainable curcumin-based smart tough fluorescent hydrogels for anti-counterfeiting applications

There is currently great interest in developing an environment-friendly,low-cost,and scalable approach for producing stimuli-responsive fluorescent hydrogels(FHs)with excellent mechanical property,rewritable fluorescence,and dual anti-counterfeiting capabilities.Herein,by applying natural,environment-friendly,and sustainable curcumin as a responsive agent,tough pH-responsive FHs(pH-FHs)are fabricated via a facile preparation strategy.These materials have outstanding mechanical performances:ultimate stress of 180 kPa,an ultimate strain of~2500%,and good anti-fatigue performances against compression.These pH-FHs are able to sense ammonia and formaldehyde gas,resulting in both a color change and fluorescence for dual anti-counterfeiting functionality.This sensing information is stored individually by the pH-FHs and could be externally removed using formaldehyde gas to achieve a rewritable system.Our study provides valuable insights that are expected to facilitate the development of smart FHs for information encryption and anti-counterfeiting applications.

Lignin-derived dual-function red light carbon dots for hypochlorite detection and anti-counterfeiting

The efficient utilization of natural lignin,which is the main by-product of the cellulose industry,is crucial for enhancing its economic value,alleviating the environmental burden,and improving ecological security.By taking advantage of the large sp2 hybrid domain of lignin and introducing amino functional groups,new lignin-derived carbon dots(SPN-CDs)with red fluorescence were successfully synthesized.Compared with green and blue fluorescent materials,red SPN-CDs have desirable anti-interference properties of short-wave background and exhibit superior luminescence stability.The SPN-CDs obtained exhibited sensitive and distinctive visible color with fluorescence-dual responses toward hypochlorite.Considering this feature,a portable,low-cost,and sensitive fluorescence sensing paper with a low limit of detection of 0.249μmol∙L^(–1) was fabricated using the SPN-CDs for hypochlorite detection.Furthermore,a new type of visible-light and fluorescence dual-channel information encryption platform was constructed.Low-concentration hypochlorite can be employed as an accessible and efficient information encryption/decryption stimulus,as well as an information“eraser”,facilitating a safe and diversified transmission and convenient decryption of information.This work opens new avenues for high-value-added applications of lignin-based fluorescent materials.

Functionalization of cellulose carbon dots with different elements(N,B and S)for mercury ion detection and anti-counterfeit applications

Mercury ion(Hg^(2+)),as one of the most toxic heavy metal ions,accumulates easily in the environment,which can generate potential hazards to the ecosystem and human health.To effectively detect and remove Hg^(2+),we fabricated four types of carbon dots(CDs)using carboxymethyl nanocellulose as a carbon source doped with different elements using a hydrothermal method.All the CDs exhibited a strong fluorescence emission,excitation-dependent emission and possessed good water dispersibility.Moreover,the four fluorescent CDs were used for Hg^(2+)recognition in aqueous solution,where the CDs-N exhibited better sensitivity and selectivity for Hg^(2+)detection,with a low limit of detection of 8.29×10^(-6)mol/L.It was determined that the fluorescence quenching could be ascribed to a photoinduced charge-transfer processes between Hg^(2+)and the CDs.In addition,the CDs-N were used as a smart invisible ink for anticounterfeiting,information encryption and decryption.Furthermore,the CDs-N were immersed into a cellulose(CMC)-based hydrogel network to prepare fluorescent hydrogels capable of simultaneously detecting and adsorbing Hg^(2+).We anticipate that this research will open possibilities for a green method to synthesize fluorescent CDs for metal ion detection and fluorescent ink production.

Dual-mode emission of single-layered graphene quantum dots in confined nanospace： Anti-counterfeiting and sensor applications

Engineering of the luminescent properties for graphene quantum dots （GQDs） presents two enormous challenges： 1） The bandgap of GQDs is mainly determined by structural defects （size, shape, and the fraction of sp2 and sp3 domains）, which results in non-stoichiometric nature; 2） the preparation methods limit the achievement of an accurate chemical structure of GQDs, leading to many controversial explanations over the relationship between the structural defects and bandgaps. Here, single-layered GQDs with an exact structure are obtained by in-situ reaction of intercalated precursors in the confined nanospace of layered double hydroxides （LDHs）. Subsequently, the structure-property relationship is uncovered, demonstrating the enhanced fluorescence and activated room temperature phosphorescence of the as-pre- pared GQDs-LDHs, which originate from synergistic effects： 1） strong confine- ment provided by the nanospace of LDHs; 2） rich O-containing functional groups on the surface of GQDs resulting from LDH catalysis. Moreover, the colorless nature and dual-emission characteristics of GQDs-LDHs satisfy the preconditions as anti-counterfeiting markers for protecting valuable documents （bank notes, commercial invoices, etc.）. Particularly, owing to the low toxicity of GQDs and the edible property of LDHs, the GQDs-LDHs/gelatin capsules could be the new generation of potential green anti-counterfeiting material in the field of food and drugs.

"Chameleon-like" optical behavior of lanthanide-doped fluoride nanoplates for multilevel anti-counterfeiting applications

Lanthanide-based luminescent anti-counterfeiting materials are widely used in various kinds of products.However,the emission color of traditional lanthanide-based luminescent materials usually remains nearly unaltered upon different excitation lights,which may only work for single-level anti-counterfeiting.Herein,the NaYbF4∶2%Er@NaYF4 core/shell nanoplates (NPs) with "chameleon-like" optical behavior are developed.These NPs display single-band red or green downshifting (DS) emission upon excitation at 377 or 490 nm,respectively.Upon 980 nm excitation,the color of upconversion (UC) emission can be finely tuned from green to yellow,and to red with increasing the excitation power density from 0.1 to 4.0 W/cm^2.The proposed materials readily integrate the advantages of excitation wavelength-dependent DS single-band emissions and sensitive excitation power-dependent UC multicolor emissions in one and the same material,which has never been reported before.Particularly,the proposed NPs exhibit excellent performance as security labels on trademark tag and security ink on painting,thus revealing the great potential of these lanthanide-doped fluoride NPs in multilevel anti-counterfeiting applications.

Preparation and characterization of rare earth fluorescent anti-counterfeiting fiber via sol-gel method

A benzoic acid rare earth(Tb) complex was synthesized and characterized.The excitation and emission spectra of the complex were investigated,and then pure organic complex was incorporated with inorganic matrices(SiO2) through sol-gel method.The composition and structure of the hybrid complex was characterized through the IR spectra,TG,TEM and fluorescent spectrometer.Furthermore,the polypropylene(PP) fluorescent fiber with the organic-inorganic hybrid was prepared by melt spinning.The fluorescent and mechanical properties of the fiber were also tested.The results showed that after sol-gel coating the average particulate dimension of the hybrid rare earth complex was less than 100 nm and thermal stability was improved.Meanwhile,the fiber possessed excellent fluorescent and mechanical properties,which could be used as a candidate applied to excellent fluorescent anti-counterfeiting fiber.

Metal-organic framework film for fluorescence turn-on H2S gas sensing and anti-counterfeiting patterns

Hydrogen sulphide(H2 S)is a common air pollutant,which is produced in various industry processes.Therefore,it is of crucial importance to detect H2 S in real time.Many fluorescent sensors were reported aiming at detecting H2 S in solution;however,the fluorescence sensing of gaseous H2 S has not yet been reported.In this work,we utilized the post-functionalized fluorescent film,MIL-100(In)@Eu3+/Cu2+film,realizing fluorescence turn-on sensing of gaseous H2 S at room temperature for the first time with the limit of detection as low as 0.535 ppm,which is comparable to some reported fluorescent probes for S2-ions and semiconductor based gaseous H2 S sensors.The sensor was designed due to the strong affinity of H2 S with Cu2+.With the formation of CuS,the"antenna effect"between the ligand and Eu3+recovered,resulting in the fluorescence turn-on of Eu3+emission.Additionally,we proposed a new method to realize multi-colour anti-counterfeiting patterns with lanthanide ions ink,taking advantage of the extraordinary smooth surface and uncoordinated carboxylate groups within the MIL-100(In)film.

Multi-modal anti-counterfeiting and encryption enabled through silicon-based materials featuring pH-responsive fluorescence and room-temperature phosphorescence

Nano Research volume 13,pages1614–1619(2020)Cite this article 236 Accesses Metrics details Abstract Optical silicon(Si)-based materials are highly attractive due to their widespread applications ranging from electronics to biomedicine.It is worth noting that while extensive efforts have been devoted to developing fluorescent Si-based structures,there currently exist no examples of Si-based materials featuring phosphorescence emission,severely limiting Si-based wide-ranging optical applications.To address this critical issue,we herein introduce a kind of Si-based material,in which metal-organic frameworks(MOFs)are in-situ growing on the surface of Si nanoparticles(SiNPs)assisted by microwave irradiation.Of particular significance,the resultant materials,i.e.,MOFs-encapsulated SiNPs(MOFs@SiNPs)could exhibit pH-responsive fluorescence,whose maximum emission wavelength is red-shifted from 442 to 592 nm when the pH increases from 2 to 13.More importantly,distinct room-temperature phosphorescence(maximum emission wavelength:505 nm)could be observed in this system,with long lifetime of 215 ms.Taking advantages of above-mentioned unique optical properties,the MOFs@SiNPs are further employed as high-quality anti-counterfeiting inks for advanced encryption.In comparison to conventional fluorescence anti-counterfeiting techniques(static fluorescence outputs are generally used,thus being easily duplicated and leading to counterfeiting risk),pH-responsive fluorescence and room-temperature phosphorescence of the resultant MOFs@SiNPs-based ink could offer advanced multi-modal security,which is therefore capable of realizing higher-level information security against counterfeiting.

Multicolor luminescence of hexagonal NaYF_(4):Yb^(3+)/Ho^(3+)/Ce^(3+) microcrystals with tunable morphology under 940 nm excitation for temperature-responsive anti-counterfeiting

In this study,the hexagonal NaYF_(4):Yb^(3+)/Ho^(3+)/Ce^(3+) microcrystals were synthesized controllably,and upconversion luminescence excited at 940 nm and its application in temperature-responsive anti-counterfeiting are reported.It is clarified that the Ln^(3+)(Ln=Y+Yb+Ho+Ce)density ratio of bottom plane to side plane in the unit cell can be regulated by Ce^(3+) doping.It is also proved that the energy transfer of Yb^(3+) to Ho^(3+) is responsible for the activation of Ho^(3+)under 940 nm excitation,while the cross relaxation between Ho^(3+)and Ce^(3+)participates in the redistribution of electron population of^(5)S_(2)/^(5)F_(4)and^(5)F_(5)levels.Both theory and experiment confirm that the intensity ratio of red to green emission(I_(R)/I_(G))as a function of temperature as an independent variable has good linear characteristics in the temperature range of 300-500 K.Due to the good responsiveness of multicolor luminescence to temperature,the hexagonal NaYF_(4):Yb^(3+)/Ho^(3+)/Ce^(3+) with tunable morphology is a promising candidate for advanced temperature-responsive upconversion anti-counterfeiting.Our results provide a new pathway for the controllable synthesis of hexagonal NaYF_(4)microcrystals as well as the regulation of upconversion luminescence that is excited by wavelengths other than 980 nm and its application in anti-counterfeiting.