Rare Earth Luminescent Materials Research Articles

Experimental Optimization, Design Synthesis, and Up-Conversion Luminescence Properties of Y4GeO8: Er3+/Yb3+ Red Phosphors

The Er3+/Yb3+ co-doped Y4GeO8 crystal powders were successfully synthesized us-ing a high-temperature solid-phase method. The crystal structure of the obtained phosphors was confirmed to be pure Y4GeO8 through X-ray diffraction (XRD) analysis. A regression equation correlating Er3+/Yb3+ doping concentrations with luminescent intensity was estab-lished based on the optimized theoretical model derived from experimental design. The op-timal concentrations of Er3+ and Yb3+ under 980 nm laser excitation were determined as 7.41% and 21.34%, respectively, while under 1550 nm laser excitation, the concentrations were 2.66% and 17.42%, respectively. The fluorescence emission spectra of the up-conver-sion samples were measured, revealing intense green and red emissions with peaks at 542, 546, and 654 nm under 980 nm excitation, and peaks at 546, 557, and 663 nm under 1550 nm excitation. These peaks correspond to transitions from 2H11/2 to 4I15/2, 4S3/2 to 4I15/2, and 4F9/2 to 4I15/2 energy levels. The relationship between up-conversion luminescence and laser op-erating current for the optimal samples under 980 nm and 1550 nm was investigated, uncov-ering that up-conversion luminescence occurs through both two-photon and three-photon processes. A detailed analysis and discussion of the up-conversion luminescence mecha-nisms were conducted. Furthermore, the relationship between up-conversion fluorescence and temperature for the optimal samples was studied, revealing excellent temperature-sens-ing characteristics under 980 nm and 1550 nm laser excitations. The calculated illumination region coordinates for the optimal samples under 980 nm and 1550 nm wavelength excitations were (0.5558, 0.4362) and (0.5256, 0.4687), respectively. The research highlights the potential of rare-earth ion-doped up-conversion luminescent materials for diverse anti-coun-terfeiting applications. In particular, the Y4GeO8: Yb3+/Er3+ phosphors, incorporating a dual-excitation mechanism, enhance the security of anticounterfeiting strategies in multifaceted scenarios. The study underscores the promising developments in this field.

Erbium-based hydrothermal YOF with stark sublevels for in vivo NIR II luminescence nanothermometer

Rare earth luminescent materials have attracted extensive attention in the biomedical field as noncontact temperature monitoring devices with microscopic resolution due to their properties in the visible and near-infrared regions. At the application level, it is required to have a certain temperature monitoring capability in the near-infrared region II window to enhance the tissue penetration depth. Here, two kinds of YOFs: Er[Formula: see text], Yb[Formula: see text] were prepared by co-precipitation and hydrothermal method, and the luminescence was enhanced by ion doping. An Er[Formula: see text]-based ratiometric nanothermometer of 4F[Formula: see text]I[Formula: see text] (672[Formula: see text]nm, upconversion luminescence) to 4I[Formula: see text]I[Formula: see text] (1580[Formula: see text]nm/1566[Formula: see text]nm, NIR II downshifting luminescence) were designed with the Stark energy level. When doped with 2% Zn[Formula: see text], the relative temperature sensitivity of YOF prepared by co-precipitation method was improved from 0.30% [Formula: see text] (30∘C) to 0.59% [Formula: see text] (30∘C), expanding its use as a temperature monitoring device possibility. The temperature sensitivity of YOF prepared by hydrothermal method was 1.01% [Formula: see text] (30∘C). Finally, the NIR II luminescence of the prepared nanothermometer was used as a control for temperature monitoring of heating sites in mice. The results showed that it can distinguish heating site from control site and no significant cytotoxicity or damage to the tissues was revealed, indicating its broad prospects in the biomedical field and other temperature monitoring scenarios in the future.

Novel CeF3:Tm3+, Er3+ nanoparticles: NIR up-down conversion luminescence properties based on energy transfer of Tm3+ and Ce3+

A novel CeF3:Tm3+, Er3+ NIR up-down conversion luminescent nanoparticles with highly efficient visible and near-infrared second window (NIR-II) emission were synthesized by direct precipitation and hydrothermal methods. The two different emission modes of visible-NIR II light of Er3+were realized through the energy transfer of Tm3+ and Ce3+at the excitation wavelength of 808 nm. Which successfully combined the narrow emission peaks of visible light and the deep tissue penetration advantage of NIR-II. First, the effects of preparation conditions on the structure, morphology, stability and luminescence properties of CeF3:Tm3+, Er3+ nanoparticles were analyzed by XRD, SEM, TEM and PL. The results showed that the crystallinity, morphology and luminescence intensity of CeF3:Tm3+,Er3+ nanoparticles produced by hydrothermal method (reaction time of 10 h) were optimal compared with that of direct precipitation method. CeF3: Tm3+,Er3+ nanoparticles has better thermal stability, and fluorescence lifetime of 5D0→7F2 (525 nm), 4I15/2→4I11/2 (1066 nm) and 4I15/2→4I13/2 (1386 nm) for Er3+ are 15.51 ns, 48.78 us and 57.06 us, separately. At the same time, the surface of CeF3:Tm3+, Er3+ nanoparticles was modified by PEG and Lys. And then the effects of the surface modification on the hydration size, zeta potential and up-down conversion luminescent properties (visible and NIR-II light emission) were investigated. The results show that the modification of PEG effectively slows down the agglomeration of CeF3:Tm3+, Er3+ nanoparticles and improves their stability and dispersion under the same conditions. More importantly, the modification of PEG effectively increases the up-conversion luminescence intensity of CeF3:Tm3+, Er3+ nanoparticles under 808 nm excitation. Moreover, the CeF3:Tm3+, Er3+-PEG nanoparticles with 20–40 nm showed stronger NIR up-down conversion emission intensity in aqueous solutions (pH = 5,6,7) and better thermal stability. Furthermore, the CeF3:Tm3+, Er3+-PEG nanoparticles has low cytotoxicity and good biocompatibility. This study provides a theoretical basis for the development of high-performance rare-earth NIR up-down conversion luminescence materials.

Photooxidation triggered ultralong afterglow in carbon nanodots

It remains a challenge to obtain biocompatible afterglow materials with long emission wavelengths, durable lifetimes, and good water solubility. Herein we develop a photooxidation strategy to construct near-infrared afterglow carbon nanodots with an extra-long lifetime of up to 5.9 h, comparable to that of the well-known rare-earth or organic long-persistent luminescent materials. Intriguingly, size-dependent afterglow lifetime evolution from 3.4 to 5.9 h has been observed from the carbon nanodots systems in aqueous solution. With structural/ultrafast dynamics analysis and density functional theory simulations, we reveal that the persistent luminescence in carbon nanodots is activated by a photooxidation-induced dioxetane intermediate, which can slowly release and convert energy into luminous emission via the steric hindrance effect of nanoparticles. With the persistent near-infrared luminescence, tissue penetration depth of 20 mm can be achieved. Thanks to the high signal-to-background ratio, biological safety and cancer-specific targeting ability of carbon nanodots, ultralong-afterglow guided surgery has been successfully performed on mice model to remove tumor tissues accurately, demonstrating potential clinical applications. These results may facilitate the development of long-lasting luminescent materials for precision tumor resection.

Optical transition tuning of Er3+ in continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors

Nowadays, the application scenarios of rare earth doped luminescent materials tend to be refined and complicated. The optical properties of rare earth doped materials are difficult to precisely control via the traditional design and synthesis methods, namely, changing doping concentration or preparative conditions. The aim of this study is to tune the optical transition properties of Er3+ in tungsto-molybdate NaY(MoxW1-xO4)2 (x = 0, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 0.99 and 1.0) phosphors by changing the host matrix. The Er3+ doped continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors were prepared via a solid state reaction technique at optimized calcination temperatures. The refractive indexes of the obtained solid solution samples were confirmed according to different models and compared. Subsequently, the optical transition intensity parameters, radiative transition rates and intrinsic radiative lifetimes of Er3+ in these solid solution phosphors were calculated in the framework of Judd-Ofelt theory. It was confirmed that the optical transition properties of Er3+ can be greatly tuned by the solid solution composition, and the tuning effects for different transitions are different. To validate the reliability of the Judd-Ofelt calculations, the temperature-dependent emission spectra of two green emissions of Er3+ for different solid solution samples were studied. It was found that the radiative transition rate ratios between two green emissions derived from theoretical calculations and experimental measurements are in reasonable agreement, thus proving that the optical transition calculations are reliable and the optical transition properties of Er3+ in the tungsto-molybdates can be tuned in a large range. This work reminds us of a new route for developing novel luminescence materials based on practical demands.

Design, synthesis, and thermal stability of rare earth luminescent materials

As a new generation of luminescent materials, aluminate rare earth materials have the characteristics of long luminescent time, adjustable wavelength and high brightness. Aluminate rare earth luminescent materials were prepared by high temperature solid-state method, and the luminescent properties of the luminescent materials were studied. Firstly, the author synthesized magnesium aluminate, calcium aluminates, and zinc aluminate matrix by combustion method. Then aluminate rare earth luminescent materials were prepared by high temperature solid phase method through raw material distribution, raw material mixing, drying, calcination, and post-treatment. Finally, a fluorescence spectrophotometer was used to measure the excitation and emission spectra of the prepared sample material. The research results indicate that the excitation wavelength does not affect the relationship between the emission wavelength and light intensity, the emission spectra of MgAl2O4:Tb3+ and CaAl2O4:Tb3+ exhibit narrowband transition emission states; When the mass fraction of rare earth factor Eu3+ in the activator is 6% and the temperature is 1300?C, the emission peak intensity of the luminescent material reaches its maximum value, and the luminescence intensity is the best.

Giant enhancement of anti-quenching upconversion luminescence in Sc2W3O12:Er3+/Yb3+ phosphors for temperature sensing

Although negative thermal expansion (NTE) materials provide a new strategy to overcome the thermal-quenching phenomenon in rare earth doped luminescent materials, the overall weak upconversion luminescence still restrict their application...

Polyarylether-based COFs coordinated by Tb3+ for the fluorescent detection of anthrax-biomarker dipicolinic acid.

In this study, a rare-earth hybrid luminescent material (lanthanide@COF) was constructed for the detection of a biomarker for anthrax (dipicolinic acid, DPA). JCU-505-COOH was prepared by the hydrolysis of the cyano group in JCU-505 via a post-synthetic modification strategy, then the carboxyl groups in JCU-505-COOH coordinated with Tb3+ ions, similar to pincer vising nut. The prepared Tb3+@JCU-505-COOH exhibited a turn-on response toward DPA, which allowed the lanthanide@COF to serve as a fluorescence sensor with excellent selectivity and high sensitivity (binding constant Ka = 3.66 × 103). The fluorescent probe showed satisfactory performance for the determination of DPA in saliva and urine with a detection limit of 0.6 μM. Moreover, we established a facile point-of-care testing (POCT) using the Tb3+@JCU-505-COOH-based fluorescent test paper together with a smartphone for the initial diagnosis of anthrax. As expected, Tb3+@JCU-505-COOH showed great potential for the rapid screening of anthrax due to low cost, simple operation, and wide applicability.

Enhancement mechanism of red up-conversion emission in single NaYbF<sub>4</sub>:2%Er<sup>3+</sup>@NaYbF<sub>4 </sub>micron core-shell structure

The construction of core-shell structure can effectively reduce the quenching effect on the surface of material and regulate ion-ion interaction, which has become one of the effective ways to enhance and regulate the spectral characteristics of rare-earth upconversion luminescent materials. In this paper, a variety of NaYbF<sub>4</sub>: 2%Er<sup>3+</sup> micron core-shell structures are constructed with the help of epitaxial growth technology, effectively improving the red up-conversion emission of Er<sup>3+</sup> ions. The prepared microcrystals with core-shell structures are of hexagonal phase microdisks, and their sizes are relatively uniform. In order to better obtain the material spectral data, a confocal microscopic spectroscopy is used to study spectral properties. Under 980 nm near-infrared laser excitation, the red emission intensity of single NaYbF<sub>4</sub>:2%Er<sup>3+</sup>@NaYbF<sub>4</sub>@NaYF<sub>4</sub> core-shell-shell microdisk is 4.6 times higher than that of NaYbF<sub>4</sub>:2%Er<sup>3+</sup> micron disk, and the red-to-green ratio increases from 6.3 to 8.1. Meanwhile, Ho<sup>3+</sup> ions are introduced into the NaYbF<sub>4</sub>:2%Er<sup>3+</sup>@NaYbF<sub>4</sub>: 2%Ho<sup>3+</sup> @NaYF<sub>4</sub> core-shell-shell microdisk, and the red emission intensity is nearly 6.7 times higher than that of single NaYbF<sub>4</sub>: 2%Er<sup>3+</sup> microdisk, and the red-to-green ratio increases from 6.3 to 9.4 through the interaction between ions. The microcrystal spectral characteristics and luminescence kinetics of different core-shell structures are studied, showing that the red emission enhancement of Er<sup>3+</sup> ions is mainly derived from the construction of different core-shell structures, which can effectively enhance the cross-relaxation between Er<sup>3+</sup> ions, the energy back transfer between Yb<sup>3+</sup> and Er<sup>3+</sup> ions, and the energy transfer from Ho<sup>3+</sup> ions to Er<sup>3+</sup> ions. The micron core-shell structures with efficient red emission in this study has great application prospects in the fields of luminescence, anti-counterfeiting and optoelectronic devices.

Excitation-Controlled Host-Guest Multicolor Luminescence in Lanthanide-Doped Calcium Zirconate for Information Encryption.

Efficient control over lanthanide luminescence by regulating excitations offers a real-time and reversible luminescence-managing strategy, which is of great importance and highly desirable for various applications, including multicolor display and information encryption. Herein, we studied the crystal structure, luminescence properties, and mechanisms of undoped and Tb3+/Eu3+-doped CaZrO3 in detail. The intrinsic purple-blue luminescence from host CaZrO3 and the introduced green/red luminescence from guest dopants Tb3+/Eu3+ were found to have different excitation mechanisms and, therefore, different excitation wavelength ranges. This enables the regulation of luminescent color through controlling the excitation wavelengths of Tb3+/Eu3+-doped CaZrO3. Furthermore, preliminary applications for information encryption with these materials were demonstrated using portable UV lamps of 254 and 302 nm. This study not only promotes the development of multicolor luminescence regulation in fixed-composition materials, but also advances the practical applications of lanthanide luminescent materials in visually readable, high-level anti-counterfeiting and information encryption.

Crystal structure and thermally enhanced photoluminescence in Eu(III) coordination polymers self-assembled from p-nitrobenzoic acid

Luminescent thermal quenching is a very troublesome thing for the practical application of luminescent materials, but also is a very common phenomenon. In theory, artificially reducing the number of quenching group around the luminescent lanthanide ion can effectively enhance the luminescence of lanthanide luminescent materials. In this paper, {[Eu2(NBA)6(H2O)4]∙H2O}n [Eu-NBA, NBA = p-nitrobenzoic acid] coordination polymers containing abundant coordination and interstitial water molecules were synthesized via hydrothermal methods. The chemical composition, crystal structures, and thermal stability of Eu-NBA coordination polymers were systemically investigated by Frontier-transfer infrared (FTIR) spectra, single-crystal X-ray diffraction and thermogravimetric analysis. X-ray diffraction analysis results revealed that Eu-NBA coordination polymers were crystallized into one-dimensional (1D) chain structures, where the adjacent Eu3+ ions were linked together by bidentate and/or tetradentate bridging carboxylate groups of the NBA ligands. The temperature-dependent photoluminescence spectra revealed that the shape and intensity of the luminescence spectra strongly depended on the coordination environment around Eu3+, and significant luminescent thermal enhancement was observed. These experimental results provided useful theoretical support for further understanding of the luminescence enhancement mechanism of lanthanide coordination polymers.

LaVO4: Eu3+ nano-islands onto silica for achieving fluorescence enhancement and their detection of Fe3+ ions and anti-counterfeiting applications

Rare earth (RE) composite fluorescent materials are favored by researchers in the field of anti-counterfeiting and ion sensing due to their fascinating optical properties. Ultra-small RE fluorescent nanoparticles are anchored on inorganic carriers by a simple preparation method to improve luminous intensity and hydrophilicity, which has not been explored yet. Herein, LaVO4: Eu3+ nano-islands anchored on silica with high fluorescence intensity and easy formation of stable colloidal solution is designed. Through a simple and mild hydrothermal approach, ultra-small LaVO4: Eu3+ nano-islands are highly dispersed on the surface of hierarchical hollow silica sphere (HHSS) to expose more luminescent centers. Remarkably, the stable HHSS@LaVO4: Eu3+ colloidal solution displayed highly sensitive and selective sensor for Fe3+ ions. The “island-sea synergy” structure formed by the LaVO4: Eu3+ nano-islands and the surrounding silica surface makes HHSS@LaVO4: Eu3+ to be an outstanding sensor for the effective detection of iron ions in water. In addition, HHSS@LaVO4: Eu3+ phosphor exhibit unique properties for anti-counterfeiting and encryption applications. These findings provide a promising strategy for the carrierisation of RE luminescent materials to improve optical properties and enable broader applications.

Synthesis of silicate clay minerals-based novel Mt/YF3:Eu3+ nanocomposites for regulated luminescent intensity-quantum yield-fluorescence lifetime

Rare earth luminescent materials have broad application prospects in the fields of white light LED lighting, flat panel display, biological imaging and so on. Here, we developed a novel silicate clay minerals-based montmorillonite nanosheet(Mt)/YF3:Eu3+ nanocomposites with strong luminescence performance. Mt carrier plays a three role: (1) reducing the size and improving dispersion of YF3: Eu3+ nanoparticles by surface effect; (2) narrowing down the band gap and increasing Urbach tail energy by interface effect; (3) reducing the shielding of the hole-electron Coulomb interactions while improving the exciton binding energy of YF3:Eu3+, thus improving the radiative recombination by dielectric effect. Therefore, orthogonal phase YF3: Eu3+ nanoparticles (diameter 20∼140 nm) binding to the surface of Mt via chemical bond interactions. The combination of Mt and YF3:Eu3+ not only enhanced luminescent intensity (about 2 times) but also improved the quantum yield (0.14% to 0.4%) and fluorescence lifetime (0.338 ns to 0.405 ns) of YF3:Eu3+ nanoparticles at 595 nm. In addition, the combination of Mt and YF3:Eu3+ give luminescent properties to Mt thereby improving the utilization rate of Mt and YF3: Eu3+ nanoparticles. It was found that the research supplies an insight on the development of new type luminescent materials, and hopefully it could promote them application in many fields.

Luminescent properties of lanthanide complexes and applications in security anti-counterfeiting and information encryption based on pH response

The development of advanced anti-counterfeiting strategies and materials based on rare earth luminescent materials has shown great applications in preventing serious counterfeiting forgery techniques. In this work, a series of lanthanide organic complexes [Ln3(PDC)3Bipy(H2O)3]·2H2O(Ln = Eu, Tb, EuxTb1-x, H2PDC: pyridine-3,5-dicarboxylicacid, H2Bipy: 2,2-bipyridine), were synthesized via hydrothermal method. The results of Fourier transform infrared spectra(FTIR), thermos-gravimetric analysis(TGA) and powder X-ray diffraction(XRD), illustrate that the complexes share similar structures. The complexes exhibit strong emission even with the presence of water molecules coordinated in the structure. By adjusting the Eu/Tb molar ratio of the complexes, tunable emission color from green, yellow to red was achieved. Furthermore, both the luminescence color and the intensity exhibit obvious changes when the pH of the solution (glycerol: H2O = 1:1 V/V) is varied from neutral to acid or to basicity. In addition, Eu3+ and Tb3+metal ions in the binuclear complexes respond differently to pH alteration, therefore the emission color and intensity of the binuclear complexes are tuned with pH. Based on the special pH response of the complexes, we demonstrated the potential utility of the samplesfor security anti-counterfeiting and information multiple encryption.

Novel broad spectral response perovskite solar cells: A review of the current status and advanced strategies for breaking the theoretical limit efficiency

• This review described in detail for the first time how to enhance the overall performance of the devices by broadening the absorption spectrum of perovskite solar cells. • We discussed the working principles, characteristics and latest developments of narrow-band gap PSCs and PSCs doped with rare earth up-conversion luminescent materials, and put forward the corresponding strategy. • We analyzed the working principles of tandem PSCs and integrated perovskite/organic solar cells, reviewed their latest developments in detail, and proposed forward-looking opinions. Perovskite solar cells (PSCs) have revolutionized photovoltaic research. The power conversion efficiency (PCE) of PSCs has now reached 25.7%, which is comparable to current state-of-the-art silicon-based cells. However, PSCs can only utilize light of 300–850 nm, resulting in wasted near-infrared (NIR) light, which occupies 45%–50% of entire solar spectrum, which is one of the main reasons limiting the development of efficiency. Related strategies to broaden NIR spectroscopy to break the theoretical limit efficiency of PSCs have recently attracted extensive attention. This review firstly outlines theoretical basis for improving the NIR spectroscopy, then systematically summarizes some key strategies and research progress to improve NIR spectroscopy of PSCs. We firstly provided a comprehensive overview of historical research experiments on narrow-gap perovskite absorber layers, rare earth up-conversion, tandem devices, and integrated perovskite/organic solar cells and given constructive suggestions for exceeding limit efficiency of PSCs. Finally, based on the development status of PSCs with NIR utilization, the current issues, solutions and future development directions of important aspects to improve NIR utilization of PSCs are systematically discussed. This review lays the foundation for the efficiency of PSCs beyond the Shockley-Queisser limit, and provides a certain development prospect.

Can Potted Plants Catch Mosquitoes? Applying Rare-Earth Luminescent Materials and Plant Energy to the Development of Innovative Mosquito-Trapping Potted Plants

Due to the global warming crisis, the spread of various infectious diseases is worsening, with mosquito-borne contagious diseases posing a significant threat. While many residential and public spaces contain plants, often for greening the environment and improving mental and physical well-being, the carbon dioxide released by these plants produces ideal habitats for mosquitoes. Considering the quality of life of urban residents and the development of health-related products simultaneously is an important topic. This study used diverse complementary techniques, such as energy-storing rare-earth luminescent materials, sustainable power generation using plant energy, blue light-emitting diodes, and environmentally friendly fermentation formula, to develop planting products with potential mosquito control functionality. The prototype design for this mosquito-trapping potted plant has been patented. The aim of this paper is to discuss the design principles adopted to improve the defects of existing mosquito-trapping designs, the green energy materials and techniques employed, the architecture configuration of the product prototype, and the test results. By integrating green materials and technology, the prototype can be self-powered without being plugged in to yield conspicuous energy savings. The results showed that the developed multi-function products, combined with the concept of energy sustainability, can improve global public health as well as individuals' physical and mental health.

Research on the progress of Ce3+,Tb3+ co-activated phosphate luminescent materials prepared by hydrothermal method

Due to the special optical properties of rare earth elements, rare earth luminescent materials have been widely used in lighting, medical radiological images, detection and recording of radiation field and other fields. Through the research and analysis of phosphate LaPO4:(Ce3+,Tb3+), Ca9Y (PO4):(Ce3+,Tb3+), GdPO4:(Ce3+,Tb3+) composite materials by the hydrothermal preparation of cerium-terbium co-activated, the hydrothermal preparation process (additives, reaction system pH, hydrothermal time, hydrothermal temperature, etc.), luminescent properties and application status were clarified. XRD and SEM were used to analyze the effect of hydrothermal preparation process on the phase composition and morphology of samples, and the energy transfer efficiency was determined. PL spectroscopic analysis shows that the 4f→5d and 5D4→7Fj (j=6,5,4,3) transitions in Ce3+-Tb3+ UV region have been demonstrated in a variety of matrix materials, enabling efficient energy transfer in co-doped ion combinations., and the concentration of doping ions will significantly affect the luminescence properties.

A pillar[5]arene noncovalent assembly boosts a full-color lanthanide supramolecular light switch.

A photo-responsive full-color lanthanide supramolecular switch was constructed from a synthetic 2,6-pyridine dicarboxylic acid (DPA)-modified pillar[5]arene (H) complexing with lanthanide ion (Ln3+ = Tb3+ and Eu3+) and dicationic diarylethene derivative (G1) through a noncovalent supramolecular assembly. Benefiting from the strong complexation between DPA and Ln3+ with a 3 : 1 stoichiometric ratio, the supramolecular complex H/Ln3+ presented an emerging lanthanide emission in the aqueous and organic phase. Subsequently, a network supramolecular polymer was formed by H/Ln3+ further encapsulating dicationic G1via the hydrophobic cavity of pillar[5]arene, which greatly contributed to the increased emission intensity and lifetime, and also resulted in the formation of a lanthanide supramolecular light switch. Moreover, full-color luminescence, especially white light emission, was achieved in aqueous (CIE: 0.31, 0.32) and dichloromethane (CIE: 0.31, 0.33) solutions by the adjustment of different ratios of Tb3+ and Eu3+. Notably, the photo-reversible luminescence properties of the assembly were tuned via alternant UV/vis light irradiation due to the conformation-dependent photochromic energy transfer between the lanthanide and the open/closed-ring of diarylethene. Ultimately, the prepared lanthanide supramolecular switch was successfully applied to anti-counterfeiting through the use of intelligent multicolored writing inks, and presents new opportunities for the design of advanced stimuli-responsive on-demand color tuning with lanthanide luminescent materials.

Analysis of influencing factors and changing laws on fluorescence lifetime of Er3+, Yb3+ Co-doped Gd2O2S phosphor

Although rare earth up-conversion luminescent materials have become a research topic for many researchers because of its excellent luminescent properties, the variation of its fluorescence lifetime is still a problem worth discussing. The Er3+, Yb3+ co-doped Gd2O2S phosphor prepared by the high temperature solid state method was used to study the change law of fluorescence lifetime. The effects of different calcining temperature (1000 °C–1175 °C), calcining time (3.0 h–5.5 h), concentration of Er3+ (0.1 mol% – 30 mol%) and the doping ratio of Er3+:Yb3+ (1:1–1:7) on the properties and fluorescence lifetime of the synthesized Er3+, Yb3+ co-doped Gd2O2S phosphor were investigated, and the orthogonal experiments were used to optimize the factors. The structure and morphology evolution of the Gd2O2S: Er3+, Yb3+ phosphor was systematically studied by X-ray powder diffraction (XRD). The fluorescence properties of Gd2O2S: Er3+, Yb3+ phosphor were studied from the aspects of emission spectrum and fluorescence lifetime. This work would provide a new perspective for applying fluorescence lifetime analysis of energy transfer in up-conversion luminescence materials.

Tailoring luminescent patterns with rare-earth photonic materials for anti-counterfeiting applications: A lightkey

Anti-counterfeiting strategies are competitively developed against fast-growing counterfeit markets as a cornerstone for the next generation of luminescent security inks, so it will be more difficult to mimic by ever increasing sophisticated counterfeiters. In particular, rare-earth doped up-conversion luminescent materials present important advantages such as invisibility in ambient light, excitation by low cost NIR irradiation, lack in background noise and negligible auto-fluorescence from the surface. Here we present colour tuneable up-conversion emissions in two families of rare-earth doped photonic materials (sol-gel derived nano-glass-ceramics and glasses prepared by melt quenching technique) for tailoring the overall emitted luminescence, as a sort of “lightkey”. In particular, intensity ratios among UV and VIS up-conversion emission bands can be tuned by modifying doping concentration level and excitation power density, as an additional security feature itself, giving rise to a multi-digit security code based on light-responsive encrypted patterns.