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Yb <sup>3+</sup> /Ln <sup>3+</sup> /Mn <sup>4+</sup> (Ln = Er, Ho, and Tm) doped Na <sub/>3</sub> ZrF <sub/>7</sub> phosphors: oil–water interface cation exchange synthesis, dual-modal luminescence and anti-counterfeiting
摘要： Efficient dual-modal luminescence is highly desired for applications in high security anti-counterfeiting. In the present work, Yb3+/Ln3+/Mn4+ (Ln = Er, Ho, and Tm) tri-doped Na3ZrF7 phosphors were fabricated via oil–water interface cation exchange using Yb3+/Ln3+:Na3ZrF7 as the exchanging hosts. The as-prepared products exhibited typical Mn4+ red down-shifting luminescence under UV light excitation and Er3+ red, Ho3+ yellow and Tm3+ near-infrared multi-color upconversion emissions under 980 nm laser excitation. The Mn4+ dopants in the Na3ZrF7 host experienced strong crystal-field strength Dq of 3.63 and showed superior thermal stability with up to 90% of the initial emission intensity retained at 448 K. Steady-state and time-resolved emission spectra verified that there was no detrimental energy transfer interaction between Mn4+ and Ln3+, enabling bright and eye-visible bi-functional emissions for the present products. As a consequence, the as-prepared phosphors were demonstrated to be applicable in anti-counterfeiting by a proof of concept experiment of fluorescent labeling for specially designed patterns.
关键词： phosphors,upconversion,anti-counterfeiting,cation exchange,dual-modal luminescence
更新于2025-11-20 15:33:11
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Mini submersible pump assisted sonochemical reactors: Large-scale synthesis of zinc oxide nanoparticles and nanoleaves for antibacterial and anti-counterfeiting applications
摘要： Low cost, environmentally friendly and industrial-scale approaches for the synthesis of anti-counterfeiting and antibacterial materials are a challenging task. The current research reports novel and inexpensive approaches for the synthesis of zinc oxide nanostructures (ZnO-NSs) using Mini Submersible Pump (MSP) assisted sonochemical reactors. Zinc oxide nanoleaves (ZnO-NLs) were synthesized using MSP assisted sonochemical mixing reactor at gram-scale (4 g). Zinc oxide nanoparticles (ZnO-NPs) were synthesized using MSP assisted sonochemical flow loop reactor at gram-scale (11.5 g). Synthesized ZnO-NSs were characterized by UV-visible spectroscopy, fluorescence spectroscopy, XRD, FTIR, TGA, BET, FEG-SEM, and FEG-TEM. Bare ZnO-NPs and ZnO-NPs coated cotton fabric showed high antibacterial activity against diseases causing Gram-positive bacteria Staphylococcus aureus. Based on the UV fluorescence property of the ZnO-NLs, invisible security ink was developed for anti-counterfeiting applications. The invisible security ink was tested as a rubber stamp and fountain pen inks which were found to be stable on the various kinds of microporous papers. As compared to our previously reported method, disperser assisted sonochemical approach for ZnO-NLs synthesis; the current approach reduces the cost of equipment used from ~1700 to 4 USD. Both reactors are designed simply (less complicated), based on an environmentally friendly approach, highly scalable, increases the effectiveness of the sonochemical technique and suitable for industrial applications.
关键词： antibacterial,anti-counterfeiting,sonochemical reactors,Mini submersible pump,zinc oxide nanoparticles and nanoleaves
更新于2025-09-23 15:22:29
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Holographic colour prints for enhanced optical security by combined phase and amplitude control
摘要： Conventional optical security devices provide authentication by manipulating a specific property of light to produce a distinctive optical signature. For instance, microscopic colour prints modulate the amplitude, whereas holograms typically modulate the phase of light. However, their relatively simple structure and behaviour is easily imitated. We designed a pixel that overlays a structural colour element onto a phase plate to control both the phase and amplitude of light, and arrayed these pixels into monolithic prints that exhibit complex behaviour. Our fabricated prints appear as colour images under white light, while projecting up to three different holograms under red, green, or blue laser illumination. These holographic colour prints are readily verified but challenging to emulate, and can provide enhanced security in anti-counterfeiting applications. As the prints encode information only in the surface relief of a single polymeric material, nanoscale 3D printing of customised masters may enable their mass-manufacture by nanoimprint lithography.
关键词： holography,colour prints,anti-counterfeiting,optical security,phase and amplitude control
更新于2025-09-23 15:22:29
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Fractional-Order Spatial Steganography and Blind Steganalysis for Printed Matter: Anti-Counterfeiting for Product External Packing in Internet-of-Things
摘要： This paper advocates a novel conceptual formulation of the fractional-order spatial steganography and blind steganalysis for printed matter, which can be efficiently employed in the anti-counterfeiting for product external packing in Internet-of-Things (IoT). Traditional digital steganography is not printable. Within the limits of our knowledge, until now, there are not a well-established steganography and a corresponding steganalysis for printed matter in IoT, which should receive desired attention. Fractional calculus has potentially received prominence in applications in the domain of image processing mainly because of its strengths like long-term memory, nonlocality, and weak singularity. Therefore, in an attempt to overcome the aforementioned technical limitation of traditional digital steganography, this work has studied here, as an interesting theoretical problem, would it be possible to apply the capability of preserving the edges and textural details of fractional calculus to the achievement of the steganography and steganalysis for printed matter in IoT. Motivated by this inspiration, in this paper, this work introduces a novel conceptual formulation of a Fractional-order Spatial Steganography (FSS) and a Fractional-order Blind Steganalysis (FBS) for printed matter. At first, according to the opponent process theory of colour vision, to better achieve the imperceptibility of the hidden secret information, this work uses both the self-similar complex textures in a neighborhood and the opponent channel of blue versus yellow to implement FSS for printed matter. Secondly, without requiring a priori knowledge regarding the characteristics of the original carrier image, hidden secret image, and steganography, a FBS, a fractional-order multimodal function optimization algorithm, is proposed. Finally, the efficient capability of hiding secret information of FSS and that of detecting secret information of FBS are analyzed in detail experimentally, respectively. These two important advantages lead to the superiority of the proposed approach for defending against statistics attack, rotation and distortion attack, cropping attack, scaling attack, noise attack, and colour copy attack. The main contribution of this paper is the first preliminary attempt of a feasible achievement of a spatial steganography and a blind steganalysis for printed matter.
关键词： Printed Matter,Anti-counterfeiting,Fractional-order spatial steganography,Fractional calculus,Fractional-order blind steganalysis
更新于2025-09-23 15:22:29
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Controlled synthesis and panchromatic printing of highly luminescent NaYF4:Ln3+ upconversion hollow microtubes for information encryption on various packaging substrates
摘要： Lanthanide-ion doped β-NaYF4 crystals with bright and tunable upconversion luminescence are urgently demanded in anti-counterfeiting printing. Herein, novel highly luminescent hexagonal NaYF4:Ln3+ upconversion hollow microtubes (UCHMs) were controlled synthesized by a one-pot hydrothermal method employing poly(ethylene imine) (PEI) as ligand. The surface of the synthesized UCHMs was decorated by water-soluble polymer of PEI, rendering the hydrophilic nature of UCHMs. Besides, the synthesized UCHMs exhibited bright upconversion luminescence under the irradiation of a 980 nm laser due to the unique structure and morphology. Time-dependent morphology evolution showed that the formation of UCHMs experience a morphology change from nanoparticles to hexahedron to microprisms, and ultimately to microtubes via a dissolution-reconstruction formation mechanism. Furthermore, the resulting UCHMs were used as pigments for preparation of luminescent inks and their application in anti-counterfeiting printing was explored. To realize panchromatic printing, we prepared three-primary-color (RGB) UCHMs by rational tailoring the doping pairs and molar ratio of the lanthanide ions in UCHMs. Based on the superposition principle of the red-green-blue as three primary colors, a wide array of luminescent inks with panchromatic luminescent colors were prepared. The successful creation of securely light-responsive smart encryption patterns on various packaging substrates such as art paper, aluminum sheet, polyethylene terephthalate (PET) film and cardboard by screen printing was demonstrated. Our strategy provides a new route for controlled synthesis of hydrophilic UCHMs and the as-prepared UCHMs have great potential in application of packaging anti-counterfeiting.
关键词： Rare earth ion-doped NaYF4,Anti-counterfeiting,Hollow microtube,Screen printing,Hydrothermal
更新于2025-09-23 15:19:57
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Antia??Counterfeiting Microstructures Induced by Ultrashort Laser Pulses
摘要： Ultrashort pulsed laser enables selective ablation of metal films on glass substrates, ripple formation on metal surface, and defect generation inside functional glass, etc. Correspondingly, direct writing of computer-generated holograms (CGHs), ripple rendered structure color, and defect featured photostimulated luminescence can be realized. Due to the feature of small size or invisibility, these induced microstructures can be used for anti-counterfeiting.
关键词： ultrashort laser pulses,computer-generated holograms,defects,anti-counterfeiting microstructures,ripples
更新于2025-09-23 15:19:57
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Blue, green, and red full-color ultralong afterglow in nitrogen-doped carbon dots
摘要： Carbon dots (CDs) with tunable emission colors and multiple emission modes are highly desirable in advanced optical anti-counterfeiting. Some pioneering efforts to trigger additional long-lived emission modes, nevertheless, did not perfectly solve the issue of printability and color-tunability in practical applications. Herein, we developed an encapsulating-dissolving-recrystallization route for the synthesis of CD-based anti-counterfeiting inks, and accordingly realized blue, green, and red full-color afterglow emissions from these CD-based inks when printed on paper. The printed inks simultaneously possessed triple emission modes including fluorescence (FL), delayed fluorescence (DF), and room-temperature phosphorescence (RTP), among which the long-lived emissions (DF and RTP) could be selectively activated by using different excitation wavelengths. We believe that the proposed synthetic route in this work may promote the development of multicolor-encoded and multiple-mode-integrated optical anti-counterfeiting systems, and will expand the application of CD-based materials to the fields of sensing, photodynamic therapy and bio-imaging.
关键词： afterglow,anti-counterfeiting,carbon dots,full-color,multiple emission modes
更新于2025-09-19 17:15:36
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Ultrafast preparation of Europium(III) and Terbium(III) activated LaSr2F7 nanoparticles for white LEDs and anti-counterfeiting mark
摘要： Tunable color-emitting LaSr2F7 nanoparticle-based phosphor materials with single- or co-doped trivalent rare-earth ions (Eu3t/Tb3t) were synthesized via an ultrafast chemical precipitation technique. When Eu3t and Tb3t ions were doped into the LaSr2F7 nanoparticles, the photoluminescence behaviors were investigated and showed characteristic red and green emissions in their respective regions. Under 393 nm excitation, the LaSr2F7:xEu3t nanoparticles revealed the dominant red emission band (5D0 / 7F1) of Eu3t ions while the optimum doping concentration was obtained at 0.4 mol, indicating a quantum yield (QY) of 24.5%. Likewise, the LaSr2F7:yTb3t nanoparticles showed the f-f transition of Tb3t ions and an intense green-emission peak at 543 nm (5D4 / 7F5) was observed under 352 nm of excitation wavelength and the predominant doping concentration was 0.5 mol and the QY was estimated to be about 33.4%. By increasing the Eu3t ion concentration in the optimized LaSr2F7:Tb3t phosphors, the color emissions were turned from yellow to red under 365 nm excitation and the existed energy transfer ef?ciency in between the Tb3t and Eu3t ions was analyzed. Furthermore, the red-, green- and warm white-emitting devices were also fabricated by utilizing the optimal single- and co-doped samples for covering NUV chips. Ultimately, the LaSr2F7:Eu3t and LaSr2F7:Tb3t nanoparticles were further applied to a high-security ink for stabile anti-counterfeiting mark.
关键词： White LEDs,Ultrafast synthesis,Anti-counterfeiting mark,Energy transfer
更新于2025-09-19 17:13:59
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Plasmonic nanopapers: flexible, stable and sensitive multiplex PUF tags for unclonable anti-counterfeiting applications
摘要： Highly flexible and stable plasmonic nanopaper comprised of silver nanocubes and cellulose nanofibres was fabricated through a self-assembly-assisted vacuum filtration method. It shows significant enhancement of the fluorescence emission with an enhancement factor of 3.6 and Raman scattering with an enhancement factor of ~104, excellent mechanical properties with tensile strength of 62.9 MPa and Young’s modulus of 690.9 ± 40 MPa, and a random distribution of Raman intensity across the whole nanopaper. The plasmonic nanopapers were encoded with multiplexed optical signals including surface plasmon resonance, fluorescence and SERS for anti-counterfeiting applications, thus increasing security levels. The surface plasmon resonance and fluorescence information are used as the first layer of security and can be easily verified by the naked eye, while the unclonable SERS mapping is used as the second layer of security and can be readily authenticated by Raman spectroscopy using a computer vision technique.
关键词： cellulose nanofibres,fluorescence enhancement,silver nanocubes,anti-counterfeiting,SERS,plasmonic nanopaper
更新于2025-09-19 17:13:59
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Micropatterning and defect engineering of colloidal photonic crystals <i>via</i> laser direct writing
摘要： Micropatterning and defect engineering of colloidal photonic crystals (CPCs) play a significant role in the functionality of photonic crystals as they are crucial for optical chip integration, microcavity lasing, chemical sensing, etc. However, obstacles have arisen in recent years especially due to the lack of a general, cost-effective and versatile strategy to make these functional structures in one step. Traditional micro-/nanofabrication techniques may work for one structure but fail for another and the fabrication process is mostly complicated, which potentially incurs reproducibility issues. Here, point defects, waveguides and micropatterns with variable feature sizes (4B500 nm) can be easily created in polystyrene (PS)/SiO2 CPC films via laser direct writing, which is based on selective photodegradation of PS beads. By applying different laser powers or irradiation times, different coloured micropatterns and images with high resolution can be generated, which has great implications for image displays and anti-counterfeiting.
关键词： photodegradation,Micropatterning,colloidal photonic crystals,anti-counterfeiting,defect engineering,laser direct writing,image displays
更新于2025-09-16 10:30:52