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Multi-shelled upconversion nanostructures with enhanced photoluminescence intensity <i>via</i> successive epitaxial layer-by-layer formation (SELF) strategy for high-level anticounterfeiting
摘要： Owing to the ability to convert near-infrared (NIR) incident light into high-energy ultraviolet or visible light photons, lanthanide-doped upconversion nanoparticles (UCNPs) have attracted great attention in anticounterfeiting applications as appealing and unparalleled agents. To facilitate the efficient energy transfer and overcome the bottleneck of low upconverted photoluminescence, we report a one-pot successive epitaxial layer-by-layer formation (SELF) strategy based on ion layer adsorption and Oswald ripening to synthesize a series of high-quality monodispersed multi-shelled UCNPs with narrow size distribution (coefficient of variation less than 5 %). Up to 30 layers of uniform shell are successfully deposited by successive introduction of the shell precursor solutions, which results in fold change of 300 and 200 in upconverted emission intensities for Er3+ and Tm3+-doped multi-shelled UCNPs, respectively. Using as-prepared multi-shelled UCNPs via SELF approach in conjunction with fabricated downconversion nanoparticles (DCNPs), we develop a facile and cost-effective strategy based on dual-modal manipulation of luminescence in anticounterfeiting to provide extra high-level security protection. The genuine pattern with true information is easier to visualize with the naked eye under excitation of 980 nm near-infrared (NIR) laser, while the false information could be readily read out when exposed to ultraviolet (UV) light. Meanwhile, latent fingerprint recognition with low background interference and distinguishable details in ridge patterns is achieved taking advantage of the significantly improved brightness in multi-shelled UCNPs.
关键词： anticounterfeiting,Upconversion,enhanced photoluminescence,multi-shell,latent fingerprint
更新于2025-11-19 16:46:39
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Polymorphic Pure Organic Luminogens with Through Space Conjugation and Persistent Room Temperature Phosphorescence
摘要： Pure organic luminogens with persistent room temperature phosphorescence (p-RTP) have attracted increasing attention owing to their fundamental significance and potential applications in security inks, bioimaging, and photodynamic therapy. Previous p-RTP luminogens are normally with through bond conjugation. In this work, we report a pure organic luminogen, AN-MA, the Diels-Alder cycloaddition adduct of anthracene (AN) and maleic anhydride (MA), which possesses isolated phenyls and anhydride moiety. AN-MA exhibits aggregation-enhanced emission (AEE) characteristics, with efficiency of ~2% and up to 8.5% in solution and crystals, respectively. Two polymorphs of AN-MA are readily obtained, which can generate UV emission from individual phenyl rings together with bright blue emission owing to the effective through space conjugation. Moreover, p-RTP with lifetime of up to ~1.6 s is obtained in crystals. These results not only disclose a new system with both fluorescence and RTP dual emission, but also suggest an alternative through space conjugation strategy towards pure organic p-RTP luminogens with tunable emissions.
关键词： anticounterfeiting,pure organic luminogens,persistent room temperature phosphorescence,through space conjugation,polymorphism
更新于2025-09-23 15:23:52
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High Quantum Yield Single-Band Green Upconversion in La <sub/>2</sub> O <sub/>3</sub> :Yb <sup>3+</sup> , Ho <sup>3+</sup> Microcrystals for Anticounterfeiting and Plastic Recycling
摘要： Single-band green upconversion (UC) with high green purity and color stability is urgently required for plastic recycling and anticounterfeiting. However, it is very difficult to obtain single-band green emission for benchmark Yb3+/Er3+ activated UC materials (such as NaYF4:Yb3+,Er3+) due to the strong accompanying red UC. Herein, highly efficient and stable single-band green UC is reported in La2O3:Yb3+/Ho3+ (LYH) microcrystals with record high absolute UC quantum yield (UCQY) of 2.6% for single-band green UC. LYH yields pure green UC with large and stable intensity ratio, IGreen/IRed ≈ 18. LYH presents not only higher UCQY for a single-band green UC but also much more pure and stable green UC than the benchmark UC materials such as NaYF4:Yb3+,Er3+ and Gd2O2S:Yb3+,Er3+. These results suggest that the newly developed LYH can, in principle, be promising for anticounterfeiting and plastic recycling. Its proof-of-concept is demonstrated as a security label based on a transparent institute logo.
关键词： anticounterfeiting,high UC quantum yield,plastic recycling,upconversion materials,pure green UC
更新于2025-09-23 15:23:52
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Quaternary Supramolecular Nanoparticles as a Photoerasable Luminescent Ink and Photocontrolled Cella??Imaging Agent
摘要： Photoswitchable luminescent supramolecular assemblies based on cyclodextrins have attracted considerable attention owing to their potential applications as smart materials, but most of the assemblies reported to date emit green or blue light with low contrast and high interference. In this study, novel photoluminescent red-luminescent quaternary supramolecular nanoparticles (2) are constructed from a dithienylethene derivative (1), a β-cyclodextrin-functionalized ruthenium complex (Ru-HOP-CD), Pluronic F-127, and cetrimonium bromide. Compared with the binary assembly 1@Ru-HOP-CD, the quaternary nanoparticles exhibit high fluorescence resonance energy transfer efficiency, with Ru-HOP-CD acting as the donor and 1 as the acceptor. Owing to the reversible photoswitched interconversion of the two forms of the dithienylethene component, the fluorescence of the nanoparticles could be switched on/off by irradiation with UV or visible light, both in solution and in the solid state. As a result, the nanoparticles could be used as a photoerasable red-luminescent ink and as a photocontrolled cell-imaging agent. These functional nanoparticles can be expected to be useful in the fields of information security and biology.
关键词： anticounterfeiting,cell imaging,cyclodextrin,photoerasable luminescent ink,diarylethene
更新于2025-09-23 15:21:01
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Core/Shell Upconversion Nanocrystal Hybrids with Temperature-Dependent Emission Color Changes for Multilevel Anticounterfeiting Applications
摘要： This work presents a novel and highly secure anticounterfeiting strategy based on core/shell upconversion nanocrystal (UCNC) hybrids with temperature-responsive multicolor emissions. Opposite luminescent temperature-dependences are found for active-core@inert-shell (thermal quenching) and active-core@active-shell (thermally induced enhancement) UCNCs. Accordingly, their hybrids are designed to show obvious color changes with increasing temperature under 975 nm excitation. Various color-shifting pathways (from white to green, blue to green, etc.) are achieved by adjusting the core/shell NC combinations in the hybrids. Moreover, color changes of the printed patterns using the hybrid NC inks can be realized by the simple heating treatment, or by increasing the laser power and prolonging the irradiation time. The results indicate the great potential of these core/shell NC hybrids for anticounterfeiting applications with high-level security and convenient authentication methods.
关键词： upconversion,anticounterfeiting,nanocrystals,hybrids,luminescence
更新于2025-09-10 09:29:36
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Enhanced Red Emission in Er <sup>3+</sup> -Sensitized NaLuF <sub/>4</sub> Upconversion Crystals via Energy Trapping
摘要： Luminescence e?ciency of trivalent lanthanide-doped upconversion (UC) materials is signi?cantly limited by luminescence concentration quenching. In this work, red UC emission is dramatically enhanced in Er3+-sensitized NaLuF4 UC crystals through energy trapping under multiple excitation wavelengths. Cross-relaxation quenching and the energy migration to internal lattice defects are simultaneously suppressed by con?ning the excitation energy in the Er3+ activator after introducing the Tm3+ or Ho3+ energy trapping center. The enhanced red UC emission (Er3+: 660 nm) mainly comes from the e?ective excitation energy con?nement by Tm3+ and Ho3+ trapping centers through an easy energy transfer between Er3+ and Tm3+/Ho3+: 4I11/2 (Er3+) → 3H5 (Tm3+) → 4I13/2 (Er3+) and 4I11/2 (Er3+) → 5I6 (Ho3+) → 4I13/2 (Er3+). It is found that the con?ning e?ciency of excitation energy in Er3+-sensitized NaLuF4 crystals is higher than that in Yb3+/Er3+ cosensitized NaLuF4 crystals, and the luminescence e?ciency of Er3+-sensitized NaLuF4 crystals is much higher than that of Er3+-based host sensitization UC crystals (NaErF4). Moreover, Er3+-sensitized UC particles can be e?ciently excited by three di?erent wavelengths (808, 980, and 1532 nm), indicating huge advantages for applications in bioimaging, anticounterfeiting, and solar cells.
关键词： energy trapping,anticounterfeiting,NaLuF4,Er3+-sensitized,solar cells,bioimaging,upconversion,luminescence
更新于2025-09-09 09:28:46
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Highly-efficient, Chemically-stable, UV/blue Light Excitable Biluminescent Security Ink to Combat Counterfeiting
摘要： A strategy has been demonstrated to design a biluminescent security ink using Eu(TTA)3Phen (ETP) and fluorescein for protecting the currency and other essential documents viz. passport, bank cheque, certificates against counterfeiting. Biluminescent security ink exhibits strong red and green emission under 367 and 445 nm excitations, respectively. As it is quite challenging to prepare a material that possesses two prominent (green and red) and distinguishable colors upon excitation with two separate LEDs sources, emitting at different wavelengths, the biluminescent security ink would be hard to counterfeit as compared to the existing luminescent security ink that exhibits single color under UV light exposure. To check its feasibility for security application the patterns printed out using biluminescent security ink were kept under a hot and humid atmosphere for 150 days. Also, the ETP and fluorescein fluorophores were exposed to UV light for a prolonged time, which do not show any sign of deterioration in their luminescence intensities. Furthermore, to check their chemical stability printed patterns were also exposed to chemicals which have potential to wiped-out ink viz. detergent, ethanol, acetone, and sodium hypochlorite (bleach) solution and noticed that it is well stable against these chemicals. Because of the reasons mentioned above and easy availability of 367 and 445 nm LEDs at low cost, authors believe that the application of this biluminescent security ink can trigger to realize the full potential of this advanced security feature in detecting fake currency.
关键词： luminescence,lanthanide,security ink,anticounterfeiting,fluorescein
更新于2025-09-09 09:28:46