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Mn ions in different valence states can emit light of different colors in an octahedral coordination environment, which is conducive to the development of a single matrix with multi-color luminescence and applications in the field of anti-counterfeiting. The dual mode multi-color luminescent material CaSb 2 O 6 : Mn has been successfully synthesized using a single Mn source in the atmosphere. The CaSb 2 O 6 matrix itself can also absorb 285 nm UV light, emit blue light, and show a long afterglow phenomenon. Both Mn4+ and Mn2+ ions will appear in the [SbO 6 ] octahedra, whether the Mn source adopts MnCO 3 or MnO 2. The Mn4+ ion exhibits red emission upon UV excitation at 347 nm. The Mn2+ ion can emit a bright green light at 285 nm excitation while exhibiting a long afterglow phenomenon. In this study, the Mn2+ doped octahedron showed unique green emission and broadens the range of its photoluminescence (PL) wavelength. The performance of the material's long afterglow properties on the digital codes demonstrates its potential for dynamic anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are a unique class of multifunctional hybrid crystals that have been successfully utilized in diverse ranges of applications. However, since MOFs are prone to aqueous degradation, the development of stable luminescent MOF platforms in aqueous media is still a huge challenge. Here, a novel dual-ligand Eu3+/DUT-52-COOH composite is prepared based on the luminescent DUT-52 prototype structure via a dual-ligand strategy and a post-synthetic modification (PSM) method. The functionalized Eu3+/DUT-52-COOH material exhibits dual emission and good photothermal stability in aqueous media. Thus, Eu3+/DUT-52-COOH is developed as a ratiometric luminescent sensor to achieve highly selective and sensitive detection of Cu2+ and Cr2O72− in aqueous solutions and has a low detection limit of 3.43 μM and 25.7 nM, respectively. This work is one of the few cases of detecting Cu2+ and Cr2O72− in aqueous media based on a DUT-52, and the detection signals can be observed by the bare eye without using sophisticated analytical instruments. The possible sensing mechanism is discussed in detail. The results obtained in this project may provide broad prospects for developing smart sensing systems to accomplish highly efficient, easily operable and quantitative intelligent recognition of Cu2+ and Cr2O72−. [ABSTRACT FROM AUTHOR]

BaGdF5:Yb,Er/Tm materials with dual-mode luminescence were synthesized using oleic acid and a simple one-pot hydrothermal method. The as-obtained materials show different colors under different excitation light wavelengths, showing red, green and blue up-conversion luminescence under irradiation with a 980 nm laser, and blue down-conversion luminescence when excited at 324 nm. The blue down-conversion color might originate from the defects or electron centers produced by the oleic acid molecules adsorbed on the material's surface. BaGdF5:Yb,Er/Tm materials are used to prepare fluorescent ink, and a series of patterns obtained by screen printing can display different colors under different ambient light wavelengths. This work provides simple and promising fluorescent materials for anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

The development of graphene oxide/rare earth complexes luminescent materials is limited due to the strong quenching ability of graphene oxide. However, the hybrid materials with pyromellitic acid (PMA) as ligand not only have better performance, but also have stronger luminescence intensity. Herein we tested the effect of the carboxylic acid structure of PMA on the luminescence intensity of graphene oxide/rare earth complexes hybrid materials. Phthalic acid (PA), Isophthalic acid (i-PA) and Terephthalic acid (p-PA) are selected as test ligand, representing the o-position, meta-position and para-position effects of PMA. By comparing the luminescence intensity, we found that o-position effect is helpful for the ligand to sensitize rare earth ions, and meta-position and para-position effects are helpful for the graphene oxide sheets (GOSs) to improve the luminescence intensity of hybrid materials and inhibit the quenching effect of the GOSs. Furthermore, we speculate on the relationship between the distance of π–π stacking of GOSs and rare earth complexes and luminescence intensity of hybrid materials. This work provides an important reference for the design of graphene oxide/rare-earth aromatic carboxylic acid hybrid luminescent materials. [ABSTRACT FROM AUTHOR]

NaMnF3:Yb,Er and NaMnF3:Yb,Er@NaGdF4:xEu (x = 0, 0.3, 0.6, and 0.9) samples were synthesized by a simple hydrothermal method. The as-obtained NaMnF3:Yb,Er particles show a single red emission under the irradiation of infrared light (980 nm), due to the energy exchange transfer process between Mn2+ ions and Er3+ ions. Notably, further growth of NaGdF4:Eu on the basis of NaMnF3:Yb,Er enhanced the green up-conversion luminescence of Er3+ ions, which gradually shifted from red to green with the increase of the Gd3+ ion doping amount. In addition, NaMnF3:Yb,Er@NaGdF4:Eu exhibits red color under ultraviolet excitation (397 nm). These results provide a possible means for controlling the luminescence properties of the lanthanide doped up-conversion system. The luminescent film synthesized with NaMnF3:Yb,Er@NaGdF4:Eu can show different luminescent colors under different light irradiation (near infrared and ultraviolet), which indicates that they have potential applications in multi-mode anti-counterfeiting. [ABSTRACT FROM AUTHOR]

The development of advanced luminescent materials with simple synthesis and a high safety factor is still a great challenge for anti-counterfeiting applications. Herein, multi-mode emission NaYF4:Ln (Ln = Er/Tm, Yb/Er, Yb/Tm)/NaYF4:Ce,Mn composites were synthesized by employing a hydrothermal method. These materials show an excitation source-dependent color change, and could show red, green and blue up-conversion (UC) luminescence under the irradiation of a 980 nm laser and exhibit green and blue down-conversion (DC) luminescence at 254 nm and 365 nm, respectively. The energy transfer mechanism of the UC and DC luminescence of the samples was discussed in detail. Moreover, the composite materials were further fabricated into fluorescent anti-counterfeit inks, and various multi-mode fluorescent patterns were created by screen printing technology. This work provides a simple and promising material with outstanding fluorescence properties for security and anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Te4+-doped Cs2ZrCl6 vacancy-ordered perovskites with excitation wavelength-dependent tunable color have been synthesised by a simple precipitation method at room temperature, with two luminescent centres originating from the Te4+ and the STE (self-trapping exciton) of the Cs2ZrCl6 itself, respectively. They exhibit two different emission characteristics at 254 nm and 365 nm excitation wavelengths. At an excitation wavelength of 254 nm, the emission characteristics allow Te4+-doped Cs2ZrCl6 to exhibit tunable emission from blue to white to yellow under the control of Te4+ doping. And the excitation wavelength of 365 nm shows yellow emission. Te4+ doped Cs2ZrCl6 phosphors were used for optical anti-counterfeiting, and the anti-counterfeiting patterns were well distinguished under 254 nm and 365 nm UV lamps, demonstrating the potential of this excitation wavelength-dependent tunable color material for optical anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Highly transparent ultrathin films (UTFs) were fabricated via layer-by-layer assembly of 110-Phenanthroline monohydrate (Phen)–8-hydroxyquinoline (Hq)–Al3+(Phen–Hq–Al), polyvinyl alchol(PVA) and Mg–Al-layered double hydroxide (LDH)nanosheets. UV–visible absorption and fluorescence spectroscopy showed regular growth of UTFs increasing the numbers of assembly. The structure and morphology of Mg–Al-layered double hydroxide and UTFs were measured by Fourier transform infrared spectroscopy, XRD and SEM. We found that it can detect Fe3+ ion with relative selectivity and high sensitivity (Ksv = 2.214 × 104 M−1) which indicates that UTFs can be a potential fluorescent probe for selectively of the Fe3+ ion. [ABSTRACT FROM AUTHOR]

Searching for fast-responding, recycling, and portable materials for ammonia detection is highly desirable in industrial fields. Here, we report a robust luminescent hydrogel consisting of PVA and layered rare-earth hydroxide (LRH) material synthesized via an in situ method. The hydrogel exhibits a unique response time to different ammonia environments via a fluorescence quenching pattern, and the whole process can be recognized by the naked eye. Furthermore, a fluorescence self-recovery behavior enables the potential application of the hydrogel in ammonia detection. The mechanism of response was elucidated by analyzing fluorescence spectra and studying the changes of hydrogen bonds in the hydrogel. [ABSTRACT FROM AUTHOR]

The method to regulate the concentration of graphene oxide (GO) via changing polarity of solution was developed, then the Tb(acac)n(PMA)n/GO composites were synthesized by coordination bond. The tunable photoluminescence property is achieved under different concentration of GO dispersion. The mechanism of tunable luminescence also is elucidated in details. Simultaneously, the strong thermal stability of Tb(acac)n(PMA)n/GO complexes series is performed because of the function of PMA, which suggests potential application in optical fields such as photo-electric device. [ABSTRACT FROM AUTHOR]

The crystal phase and energy band adjustment of halide perovskites have become the focus of research. Sb3+ doped lead-free indium-based perovskites A 2 InX 5 ·H 2 O:Sb3+ (A=Cs+, Rb+; X = Cl-, Br-) are synthesized at room temperature. Through changing the crystal phase structure, an intelligent anti-counterfeiting material is used to monitor water vapor and high temperature. Moreover, the Rb 2 InBr 5 ·H 2 O:Sb3+ achieves broadband near-infrared (NIR) emission with a high photoluminescence quantum efficiency (PLQY) of 54.3%. The NIR light-emitting diode shows that the device can effectively achieve NIR imaging. Theoretical calculations further clarified that the regular changes in luminescence originate from energy band modulation. This work provides a broader sight for the synthesis, luminescence mechanism and application of indium-based perovskite. • Indium-based perovskite with controllable luminescence properties was synthesized at room temperature. • The reversible change of crystal phase is used for smart anti-counterfeiting. • High-efficiency quantum yield of Rb 2 InBr 5 ·H 2 O:Sb3+ is used in near-infrared light-emitting diodes. • Theoretical calculation combined with experiments prove that broadband emission originate from band gap adjustment. [ABSTRACT FROM AUTHOR]

In this work, organic-inorganic hybrid ultrathin transparent films (UTFs), produced by layer-by-layer (LBL) assembly of the europium inclusion complex of -cyclodextrin (-CD) and Mg-Al-layered double hydroxide (MgAl-NO3-LDHs) nanosheets, are reported. UV-visible (UV-Vis) absorption and fluorescence spectroscopy show orderly growth of the europium inclusion complex of -CD/layered double hydroxide (EICC/LDH) films with an increasing number of deposition cycles. X-ray diffraction and scanning electron microscopy measurements indicate that the films feature periodic layered structures with uniform surface morphology. Moreover, when EICC is assembled with inorganic rigid LDH nanosheets, the lifetimes are prolonged due to the isolation effect, and the UTFs are transparent with high brightness, which indicate that these films could serve as new optical materials. Transparent and high-brightness fluorescent ultrathin films (UTFs) were fabricated via layer-by-layer assembly deposition of europium inclusion of -cyclodextrin (EICC) and MgAl-NO3- layered dual hydroxide (LDH) nanosheets. EICC was assembled with inorganic rigid LDH nanosheets, which prolonged the lifetimes. The UTF showed a periodic long-range ordered and regular structure and tunable red emission intensity. These hybrid films have considerable potential for applications in the design of various LDH-based optical devices. [ABSTRACT FROM AUTHOR]

Excitation dependent luminescent materials, which have attracted significant scientific attention in the field of information security owing to information storage and luminescence properties. However, it remains a formidable challenge in developing excitation dependent luminescent materials with a simple synthesis method and predictably modulated luminescent outputs. Herein, a novel Ln3+/Fluorescent dyes@MOFs strategy is developed to generate excitation dependent continuous color-changing luminescent materials via a hydrothermal method and post-synthetic modification (PSM), based on metal-organic frameworks (MOFs) matrix doped with lanthanide cations and fluorescent dyes encapsulated into the lanthanide MOFs. The continuous proportional emission of mixed luminescence appeared within a single matrix in response to the different excitation wavelength and the proportional emission control (PEC) mechanism between the two luminescent centers is proposed. In addition, the photoluminescence platform demonstrates a distinct security method based on covert color that are controlled by distinct excitation wavelengths and excellent luminescence stability have also been verified in these new materials. • Ln3+/Hoc@UIO-66(DPA) achieve excitation wavelength-dependent continuous color-tunable luminescence in a single mixture. • Proportional emission control (PEC) mechanism is proposed. • Ln3+/Hoc@UIO-66(DPA) (Ln = Eu, Tb) materials have potential applications in the field of anticounterfeiting. • The materials are acid and alkali resistant, have high thermal stability, and can be multi-functional luminescent. [ABSTRACT FROM AUTHOR]

A novel precursor PMA–Si was synthesized by modifying 1,2,4,5-benzene-tetracarboxylic acid (PMA) with 3-aminopropyltriethoxysilane (APTES). Then the hybrids were prepared by PMA–Si coordinating to lanthanide ions (Eu 3+ and Tb 3+ ) in sol–gel process. In order to improve luminescent efficiency, 1,10-Phenanthroline (Phen) was introduced to the system as the second ligand. As-prepared compounds in sol condition were coated on quartz plates to form a layer of thin film, which was different from other similar hybrids. The properties of the hybrids were characterized by FT-IR, fluorescence spectra, TG and SEM. The results showed that the obtained materials enhanced thermal stability, mechanical resistances, waterproofness as well as machining properties. [ABSTRACT FROM AUTHOR]

In this paper, a graphene oxide/rare-earth complexes hybrid material without 1,10-Phenanthroline based on 4′-paraphenyl-carboxyl-2,2':6′,2″-terpyridine (Hcptpy) as ligand, graphene oxide sheets (GOSs) as inorganic matrix and europium ion as luminescence center has been synthesized via non-covalent approach between GOSs and Hcptpy. This obtained hybrid material exhibits stronger luminescence intensity, better thermal stability and longer decay lifetime than pure Eu3+ complexes. Moreover, a transparent and strongly luminescent thin film also is prepared by self-assembly at room temperature. This thin film shows great potential applications in the area of optics. • A GOSs/rare-earth complexes hybrid material was synthesized without Phen. • The obtained hybrid material exhibits better performance than pure Eu3+ complexes. • A polymer film was synthesized by self-assembly of Eu-Hcptpy/GOSs and PMMA. • The obtained film has excellent transmittance and luminescent properties. [ABSTRACT FROM AUTHOR]

Luminescent dye molecules have attracted enormous research interest, whereas, there are inherent drawbacks that limit their utilization across a broad variety of fields. Herein, a novel dual-luminescent carboxylic acid functionalization Eu3+/Hoc@UIO-66(H 3 BTC) (Hoc = 7-hydroxycoumarin) was prepared by introducing luminescent dye molecules (Hoc) into the UiO-66-type dual-ligand metal−organic frameworks (MOFs) utilize the encapsulation approach and postsynthetic modification (PSM). UIO-66(H 3 BTC) was constructed using 1,4-dicarboxybenzene (TPA) as the first ligand, which can restrict the aggregation-induced quenching of Hoc dyes and maintains the Hoc dyes stably included after preparation. 1,3,5-benzenetricar boxylic acid (H 3 BTC) was used as a second ligand to sensitize Eu3+ ions for the antenna effect emission and provide detection sites. Eu3+/Hoc@UIO-66(H 3 BTC) material possesses blue luminescence from Hoc molecules as well as red luminescence from Eu3+ when irradiated by UV lamp, which can be used for ratiometric luminescence detection of Cu2+/Fe3+ through reference to the intensity ratios of two emitting peaks. Eu3+/Hoc@MOFs(H 3 BTC) as a luminescence sensor, displays an ultrahigh sensitivity (Cu2+:4.58 μM, Fe3+:18 μM), strong ant-interference ability, and fast response for detecting analytes. This project demonstrates that the dual-ligand Zr-based MOFs and luminescence dyes offers a novel ratiometric luminescence detection platform for heavy metal ions visible identification. • MOFs includes free –COOH groups that can sensitize Eu3+ ions to realize luminescence and provide site-specific assays. • Eu3+/Hoc@UIO-66(H 3 BTC) overcome (ACQ) effects to encapsulate Hoc dye molecule luminescence. • The advantages of dye encapsulation for detection are proven, with dual emission improving sensitivity. • The ratiometric sensor possess a wide linear concentration range, low LOD and visible detection. [ABSTRACT FROM AUTHOR]

NaYF 4 :Yb, Er with nitrogen-doped graphene quantum dots (N-GQDs) mixture was synthesized by a simple one-pot hydrothermal method. The as-obtained mixture shows green color under the irradiation of infrared light (980 nm), and exhibits blue color by means of ultraviolet excitation (365 nm). The luminescence of NaYF 4 :Yb, Er and N-GQDs are not affected by each other. And the synthesized mixture directly incorporated into a polyvinyl alcohol (PVA) matrix can obtain a transparent luminescent film. The luminescent film also shows different luminescent colors under different light irradiation (980 nm or 365 nm). This result indicates that it has a potential application value in anti-counterfeiting packaging. • The NaYF 4 :Yb, Er with N-GQDs mixture was synthesized by a one-pot hydrothermal method. • The obtained material exhibits shows green color under 980 nm and blue color under 365 nm. • A polymer luminescent film was synthesized by self-assembly of the mixture and PVA. • The obtained film has a potential application value in anti-counterfeiting packaging. [ABSTRACT FROM AUTHOR]

A water-soluble Eu(III) hybrid composite based-on DPA and Phen as ligands, graphene oxide sheets (GOSs) as inorganic matrix, and Eu3+ as luminescence center has been synthesized, namely, Eu–DPA–Phen/GOSs. Compared with single Eu(III) complexes named Eu–DPA–Phen, Eu–DPA–Phen/GOSs not only retains the high luminescence intensity but also shows better solubility, higher stability, and longer fluorescence lifetime. It can be used as a fluorescent probe to detect Cu2+ ions in liquid medium and mixed with polyvinyl alcohol (PVA) to produce a self-supporting film with high luminescence intensity, good stability, mechanical properties. This film is also sensitive to Cu2+ ions and convenient to carry. Thus, it has a great potential in the field of flexible and foldable luminescent devices and fluorescence sensing. [ABSTRACT FROM AUTHOR]

• The NaYF 4 :Ln/NaYF 4 :Eu composite possesses up-conversion and down-shifting luminescence properties. • The composite possesses excellent compatibility and fluorescence purity. • They can be prepared into fluorescent patterns and provide a potentiality for anti-counterfeiting. Herein, a series of novel dual-mode NaYF 4 :Ln/NaYF 4 :Eu (Ln = Yb, Er, Tm) composites involving up-conversion and down-shifting luminescence have been prepared by a facile synthetic method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, up-conversion and down-shifting fluorescence spectrometer were used to characterize the materials. By doping different lanthanide ions and tailoring the molar ratio of the doped lanthanide ions, three kinds of composites were obtained which could exhibit three-primary-color (red-green-blue, abbreviating as RGB) up-conversion luminescence under the irradiation of 980 nm laser, and generate red down-shifting color under the excitation of 393 nm. The composites show excellent photoluminescence properties, which attribute to NaYF 4 served as a major matrix for both the up-conversion and down-shifting materials. Moreover, the work provides a promising material for anti-counterfeiting application. [ABSTRACT FROM AUTHOR]

The spectroscopic behavior of ionic Eu3+ or Tb3+ complexes of an aromatic carboxyl-functionalized organic salt as well as those of the hybrid materials derived from adsorption of the ionic complexes on Laponite clay are reported. X-ray diffraction (XRD) patterns suggest that the complexes are mainly adsorbed on the outer surfaces of the Laponite disks rather than intercalated within the interlayer spaces. Photophysical data showed that the energy-transfer efficiency from the ligand to Eu3+ ions in the hybrid material is increased remarkably with respect to the corresponding ionic complex. The hybrid material containing the Eu3+ complex shows bright red emission from the prominent 5D0→7F2 transition of Eu3+ ions, and that containing the Tb3+ complex exhibits bright green emission due to the dominant 5D4→7F5 transition of Tb3+ ions. [ABSTRACT FROM AUTHOR]