Ratiometric nanothermometer based on an emissive Ln3+-organic framework

Electronic Structure of a Neodymium(III) Tris(oxidiacetate) Complex from Luminescence Data and Ab Initio Calculations

Neodymium(III) is a near-infrared emissive and magnetic ion, which has found use in various high-technology applications. Yet, accurate predictions of the luminescent and magnetic properties of neodymium(III) based on the coordination environment remain to be done. Guidelines exist, but to build structure-property relationships for this element, more data are needed. Herein, we present a high-symmetry starting point. The tris(oxidiacetate) complex of neodymium(III) was prepared and crystallized, and access to the experimentally determined structure allowed us to quantify the symmetry of the compound and to perform calculations directly on the same structure that is investigated experimentally. The luminescent properties were determined and the electronic structure was computed using state-of-the-art ab initio methods. All electronic transitions in the range from 490 to 1400 nm were mapped experimentally. Using a Boltzmann population analysis, the combination of the excitation and emission spectra revealed the crystal field splitting of the 18 lowest-energy Kramers levels that experimentally could be unambiguously resolved. This assignment was supported by ab initio calculations, and the crystal field splitting was well reproduced. The electronic structure reported for the tris(oxidiacetate) complex was used to deduce the coordination structure in aqueous solution. Finally, the results are compared to empirical trends in the literature for the electronic structure of neodymium(III).

Investigation of the Sensing Properties of Lanthanoid Metal-Organic Frameworks (Ln-MOFs) with Terephthalic Acid

The solvothermal synthesis of LnCl3.nH2O with terephthalic acid (benzene-1,4-dicarboxylic acid, H2BDC) produced metal-organic frameworks (LnBDC), [Ln2(BDC)3(H2O)4]∞, where Ln = Sm, Eu, Tb, and Dy. The materials obtained were characterized by a number of physico-chemical techniques. The influence of the ionic radius of the lanthanides on the microstructural characteristics of the Ln-MOFs was evaluated by performing Rietveld refinement. The MOFs obtained were tested as fluorescent sensors for numerous cations and anions in water. The highly luminescent EuBDC and TbBDC demonstrated multi-responsive luminescence sensing functions to detect Ag(I), Fe(III), Cr(III), and Cr(VI), which are essential for their environmental applications. By applying the non-linear Stern-Volmer equation, the fluorescent quenching mechanism was determined. The stability of the obtained materials in water in a wide pH range (acidity pH = 4 and alkalinity pH = 9 solutions) was confirmed.

Recent Advances of Bimetallic-Metal Organic Frameworks: Preparation, Properties, and Fluorescence-Based Biochemical Sensing Applications

Bimetallic-metal organic frameworks (BiM-MOFs) or bimetallic organic frameworks represent an innovative and promising class of porous materials, distinguished from traditional monometallic MOFs by their incorporation of two metal ions alongside organic linkers. BiM-MOFs, with their unique crystal structure, physicochemical properties, and composition, demonstrate distinct advantages in the realm of biochemical sensing applications, displaying improvements in optical properties, stability, selectivity, and sensitivity. This comprehensive review explores into recent advancements in leveraging BiM-MOFs for fluorescence-based biochemical sensing, providing insights into their design, synthesis, and practical applications in both chemical and biological sensing. Emphasizing fluorescence emission as a transduction mechanism, the review aims to guide researchers in maximizing the potential of BiM-MOFs across a broader spectrum of investigations. Furthermore, it explores prospective research directions and addresses challenges, offering valuable perspectives on the evolving landscape of fluorescence-based probes rooted in BiM-MOFs.

Terpyridyl-Imidazole Based Ligand Coordinated to Ln(Hexafluoroacetyl acetonate)3 Core: Synthesis, Structural Characterization, Luminescence Properties, and Thermosensing Behaviors in Solution and PMMA Film

A new array of ternary lanthanide complexes of the form [Ln(hfa)3(tpy-HImzphen)] have been synthesized and thoroughly characterized wherein Ln = LaIII (1), EuIII (2), SmIII (3), and TbIII (4); hfa = hexafluoroacetylacetonate; and tpy-HImzphen = 2-(4-[2,2':6',2″]terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. Incorporation of tpy-HImzphen onto the Ln-hfa moiety induced a bathochromic shift of the absorption window of the complexes into the visible region. Extensive investigations of the luminescence characteristics have been conducted both at RT and at 77 K to understand the deactivation pathways of the complexes. Both steady-state and time-resolved emission spectral behaviors indicate four distinctive behaviors upon incorporation of tpy-HImzphen onto the lanthanide core, viz., a huge red-shift of the ligand-centered peak for LaIII; almost complete energy transfer for EuIII; very little energy transfer for SmIII, while reverse energy transfer in the case of TbIII. In addition, the EuIII-complex exhibits its excellence in luminescence thermometry in the solution state as well as in poly(methyl methacrylate) (PMMA) thin films. The thermosensitive luminescence response in solution was further utilized to mimic set-reset flip-flop logic operation. A plausible energy transfer scheme has been devised to explain dissimilar luminescence behaviors in the complexes. The role of LMCT was also considered for the observed thermosensing property of the Eu(III) complex.

Hydro-Photo-Thermo-Responsive Multicolor Luminescence Switching of a Ternary MOF Hybrid for Advanced Information Anticounterfeiting

Developing smart materials capable of solid-state multicolor photoluminescence (PL) switching in response to multistimuli is highly desirable for advanced anticounterfeiting. Here, a ternary MOF hybrid showing hydro-photo-thermo-responsive multicolor PL switching in the solid state is presented. This hybrid is constructed by co-immobilizing Eu3+ and methyl viologen (MV) cations within an anionic MOF via the cation-exchange approach. The confined guest cations are well arranged in the framework channels, facilitating the synergistic realization of stimuli-responsive multiple PL color-switching through intermolecular coupling. The hybrid undergoes a rapid and reversible PL color-switching from red to blue upon water simulation, which is achieved by activating the blue emission of the framework linker while simultaneously quenching the Eu3+ emission. Furthermore, the hybrid displays photo-thermo-responsive PL switching from red to dark. UV-light irradiation or heating triggers the chromic conversion of MV to its colored radical form, which exhibits perfect spectral overlap with Eu3+, thus activating Förster resonance energy transfer (FRET) from Eu3+ to MV radicals and quenching the Eu3+ emission. Inspired by these results, PL morse patterns are designed and fabricated using a novel triple-level encryption strategy, showcasing the exciting potential of this hybrid in advanced anticounterfeiting applications.

Large enhancement of red upconversion luminescence in beta Ba2Sc0.67Yb0.3Er0.03AlO5 phosphor via Mn2+ ions doping for thermometry

Here, this study reports single-band red upconversion emission in β-Ba2ScAlO5: Yb3+/Er3+ phosphor by doping Mn2+. The optimum concentration of Mn2+ ions in β-Ba2ScAlO5: Yb3+/Er3+ phosphor was 0.20. The intensity of red and green emissions is increased by 27.4 and 19.3 times, respectively. Compared with the samples without Mn2+ ions, the red-green integral strength ratio of β-Ba2ScAlO5: Yb3+/Er3+/Mn2+ sample was significantly increased by 28.4 times, reaching 110.9. The UCL mechanism was explored by analyzing the down-conversion luminescence spectra, absorption spectra, UCL spectra, and upconversion fluorescence lifetime decay curves of Yb3+/Er3+/Mn2+ co-doped β-Ba2ScAlO5. The enhancement of upconversion red light is achieved through energy transfer between defect bands and Er3+ ions, as well as energy transfer between Mn2+ ions and Er3+ ions. In addition, the Mn2+ doped β-Ba2ScAlO5: Yb3+/Er3+ red UCL phosphors have great potential for ambient temperature sensing in the 298-523 K temperature range. The maximum sensitivity of β-Ba2ScAlO5: Yb3+/Er3+/Mn2+ phosphor as a temperature sensor at 523 K is 0.0247 K-1.

Insights into NdIII to YbIII Energy Transfer and Its Implications in Luminescence Thermometry

This work challenges the conventional approach of using NdIII 4F3/2 lifetime changes for evaluating the experimental NdIII → YbIII energy transfer rate and efficiency. Using near-infrared (NIR) emitting Nd:Yb mixed-metal coordination polymers (CPs), synthesized via solvent-free thermal grinding, we demonstrate that the NdIII [2H11/2 → 4I15/2] → YbIII [2F7/2 → 2F5/2] pathway, previously overlooked, dominates energy transfer due to superior energy resonance and J-level selection rule compatibility. This finding upends the conventional focus on the NdIII [4F3/2 → 4I11/2] → YbIII [2F7/2 → 2F5/2] transition pathway. We characterized Nd0.890Yb0.110(BTC)(H2O)6 as a promising cryogenic NIR thermometry system and employed our novel energy transfer understanding to perform simulations, yielding theoretical thermometric parameters and sensitivities for diverse Nd:Yb ratios. Strikingly, experimental thermometric data closely matched the theoretical predictions, validating our revised model. This novel perspective on NdIII → YbIII energy transfer holds general applicability for the NdIII/YbIII pair, unveiling an important spectroscopic feature with broad implications for energy transfer-driven materials design.

Orthogonal Postsynthetic Copolymerization of Hydrogen-Bonded Organic Frameworks into a PolyHOF Membrane

Hydrogen-bonded organic frameworks (HOFs) have shown promise in various fields; however, the construction of HOF/polymer hybrid membranes that can maintain both structural and functional integrity remains challenging. In this study, we here fabricated a new HOF (HOF-50) with reserved polymerizable allyl group via charge-assisted H-bonds between the carboxylate anion and amidinium, and subsequently copolymerized the HOF with monomers to construct a covalently bonded HOF/polymer hybrid (polyHOF) membrane. The resulting polyHOF membrane not only exhibits customizable mechanical properties and extreme stability, but also shows an exceptional ratiometric luminescent temperature-sensing function with very high sensitivity and visibility even when the lanthanide content is two orders of magnitude lower than that of the reported mixed-lanthanide metal-organic frameworks (MOFs) and lanthanide-doped covalent organic frameworks (COFs). This orthogonal postsynthesis copolymerization strategy may provide a general approach for preparing covalently connected HOF/polymer hybrid membranes for diverse applications.

Intensity and lifetime ratiometric luminescent thermometer based on a Tb(III) coordination polymer

A three-dimensional terbium(III) coordination polymer of formula [Tb(bttb)0.5(2,5-pzdc)0.5]n (1) [H4bttb = 1,2,4,5-tetrakis(4'-carboxyphenyl)benzene and H2-2,5-pzdc = 2,5-pyrazinedicarboxylic acid] was obtained under hydrothermal conditions. The bttb4- tetraanion in 1 adopts the bridging and chelating-bridging pseudo-oxo coordination modes while the 2,5-pzdc2- dianion exhibits a rather unusual bis-bidentate bridging pseudo-oxo coordination mode, both ligands being responsible for the stiffness of the resulting 3D structure. Solid-state photoluminescent measurements illustrate that 1 exhibits remarkable green luminescence emission, the most intense band occurring in the region of 550 nm (5D4 → 7F5) with lifetimes at the millisecond scale. Thermometric performances of 1 reveal a maximum relative sensitivity (Sm) of 0.76% K-1 at 295 K (δT = 0.05 K), constituting a TbIII ratiometric solid luminescent thermometer over the physiological temperature range. Variable-temperature static (dc) magnetic susceptibility measurements for 1 in the temperature range 2.0-300 K show the expected behavior for the depopulation of the splitted mJ levels of the 7F7 ground state of the magnetically anisotropic terbium(III) ion plus a weak antiferromagnetic interaction through the carboxylate bridges. No significant out-of-phase magnetic susceptibility signals were observed for 1 in the temperature range 2.0-10.0 K, either in the absence or presence of a static dc magnetic field.

A terpyridyl-imidazole based europium tris-(β-diketonate) complex as an efficient molecular luminescent thermometer and single component white light emitter via synergy in energy transfer between ligands and Eu3

The thermosensing and thermochromic behavior of one of our recently reported terpyridyl-imidazole based ternary europium tris-(β-diketonate) complexes of the composition [Eu(tta)3(tpy-HImzphen)] (tta = 2-thenoyltrifluoroacetone and tpy-HImzphen = 2-(4-[2,2':6',2''] terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole) has been thoroughly investigated in this work. The said Eu(III) complex exhibits magnificent thermosensing as well as thermochromic properties and can be recommended as an excellent temperature sensor in a wide temperature domain of 273-343 K in terms of both emission intensity ratio (Sm = 5.78% K-1 at Tm = 343 K, δT = 0.012 K) and lifetime values (Sm = 3.36% K-1 at Tm = 333 K, δT = 0.009 K) or even in terms of its emitting color (red at 268 K, violet at 303 K, and blue at 343 K). Additionally, it displays remarkable solvent-induced luminescence behavior by displaying various emitting colors instead of its sole characteristic red emission upon varying the nature of the solvent. Finally, amalgamating these two features, we are able to attain white light emission (Commission Internationale de l'Eclairage coordinates: x = 0.34, y = 0.38) at 283 K from a single component. A plausible energy transfer mechanism has also been proposed in light of the existence of the ligand-to-metal charge transfer (LMCT) state as the quencher.

Composition Control in Molecular Cluster-Aggregates: A Toolbox for Optical Output Tunability via Energy Transfer Pathways

Composition control is a powerful tool for obtaining high-performance lanthanide (Ln) luminescent materials with adjustable optical outputs. This strategy is well-established for hierarchically structured nanoparticles, but it is rarely applied to molecular compounds due to the limited number of metal centers within a single unit. In this work, we present a series of molecular cluster-aggregates (MCAs) with an icosanuclear core {Ln2Eu2Tb16} (Ln = Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, and Yb) in which we explore composition control, akin to nanoparticles, to modulate the optical output. More specifically, we target to understand how the presence of a third LnIII doping ion would impact the well-known TbIII → EuIII energy transfer and the ratiometric optical thermometry performance based on the TbIII/EuIII pair. Photophysical properties at room and at varying temperatures were investigated. Based on experimental data and well-established intrinsic features, such as spin-orbit coupling strength and LnIII 4f energy levels' structure, we discuss the possible luminescent processes present in each MCA and provide insight into qualitative trends that can be rationally correlated throughout the series.

Hybrid multifunctionalized mesostructured stellate silica nanoparticles loaded with β-diketonate Tb3+/Eu3+ complexes as efficient ratiometric emissive thermometers working in water

Despite the great effort made in recent years on lanthanide-based ratiometric luminescent nanothermometers able to provide temperature measurements in water, their design remains challenging. We report on the synthesis and properties of efficient ratiometric nanothermometers that are based on mesoporous stellate nanoparticles (MSN) of ca. 90 nm functionalized with an acetylacetonate (acac) derivative inside the pores and loaded with β-diketonate-Tb3+/Eu3+ complexes able to work in water, in PBS or in cells. Encapsulating a [(Tb/Eu)9(acac)16(μ3-OH)8(μ4-O)(μ4-OH)] complex (Tb/Eu ratio = 19/1 and 9/1) led to hybrid multifunctionalized nanoparticles exhibiting a Tb3+ and Eu3+ characteristic temperature-dependent luminescence with a high rate Tb3+-to-Eu3+ energy transfer. According to theoretical calculations, the modifications of photoluminescence properties and the increase in the pairwise Tb3+-to-Eu3+ energy transfer rate by about 10 times can be rationalized as a change of the coordination number of the Ln3+ sites of the complex from 7 to 8 accompanied by a symmetry evolution from Cs to C4v and a slight shortening of intramolecular Ln3+-Ln3+ distances upon the effect of encapsulation. These nanothermometers operate in the 20-70 °C range with excellent photothermal stability, cyclability and repeatability (>95%), displaying a maximum relative thermal sensitivity of 1.4% °C-1 (at 42.7 °C) in water. Furthermore, they can operate in cells with a thermal sensitivity of 8.6% °C-1 (at 40 °C), keeping in mind that adjusting the calibration for each system is necessary to ensure accurate measurements.

Spotlight on Luminescence Thermometry: Basics, Challenges, and Cutting-Edge Applications

Luminescence (nano)thermometry is a remote sensing technique that relies on the temperature dependency of the luminescence features (e.g., bandshape, peak energy or intensity, and excited state lifetimes and risetimes) of a phosphor to measure temperature. This technique provides precise thermal readouts with superior spatial resolution in short acquisition times. Although luminescence thermometry is just starting to become a more mature subject, it exhibits enormous potential in several areas, e.g., optoelectronics, photonics, micro- and nanofluidics, and nanomedicine. This work reviews the latest trends in the field, including the establishment of a comprehensive theoretical background and standardized practices. The reliability, repeatability, and reproducibility of the technique are also discussed, along with the use of multiparametric analysis and artificial-intelligence algorithms to enhance thermal readouts. In addition, examples are provided to underscore the challenges that luminescence thermometry faces, alongside the need for a continuous search and design of new materials, experimental techniques, and analysis procedures to improve the competitiveness, accessibility, and popularity of the technology.

Synthesis and real-time monitoring of the morphological evolution of luminescent Eu(TCPP) MOFs

Real-time acquisition of the morphological information of nanomaterials is crucial to achieving morphological controllable synthesis, albeit being challenging. A novel device was designed, which integrated dielectric barrier discharge (DBD) plasma synthesis and simultaneous in situ spectral monitoring of the formation of metal-organic frameworks (MOFs). Important dynamic luminescence behaviors such as coordination induced emission (CIE), antenna effect (AE), and red-blue shift were continuously captured to reveal the spectral emission mechanism and energy transfer progress and verify the correlation with the morphological evolution of the MOFs. The prediction and control of morphology were successfully achieved with Eu(TCPP) as a model MOF. The proposed method will shed new light on exploring the spectral emission mechanism, energy conversion and in situ morphology monitoring of other luminescent materials.

A Novel Dye-Modified Metal-Organic Framework as a Bifunctional Fluorescent Probe for Visual Sensing for Styrene and Temperature

A novel fluorescent probe (C460@Tb-MOFs) was designed and synthesized by encapsulating the fluorescent dye 7-diethylamino-4-methyl coumarin (C460) into a terbium-based metal-organic framework using a simple ultrasonic impregnation method. It is impressive that this dye-modified metal-organic framework can specifically detect styrene and temperature upon luminescence quenching. The sensing platform of this material exhibits great selectivity, fast response, and good cyclability toward styrene detection. It is worth mentioning that the sensing process undergoes a distinct color change from blue to colorless, providing conditions for the accurate visual detection of styrene liquid and gas. The significant fluorescence quenching mechanism of styrene toward C460@Tb-MOFs is explored in detail. Moreover, the dye-modified metal-organic framework can also achieve temperature sensing from 298 to 498 K with high relative sensitivity at 498 K. The preparation of functionalized MOF composites with fluorescent dyes provides an effective strategy for the construction of sensors for multifunctional applications.

Lanthanide molecular cluster-aggregates as the next generation of optical materials

In this perspective, we provide an overview of the recent achievements in luminescent lanthanide-based molecular cluster-aggregates (MCAs) and illustrate why MCAs can be seen as the next generation of highly efficient optical materials. MCAs are high nuclearity compounds composed of rigid multinuclear metal cores encapsulated by organic ligands. The combination of high nuclearity and molecular structure makes MCAs an ideal class of compounds that can unify the properties of traditional nanoparticles and small molecules. By bridging the gap between both domains, MCAs intrinsically retain unique features with tremendous impacts on their optical properties. Although homometallic luminescent MCAs have been extensively studied since the late 1990s, it was only recently that heterometallic luminescent MCAs were pioneered as tunable luminescent materials. These heterometallic systems have shown tremendous impacts in areas such as anti-counterfeiting materials, luminescent thermometry, and molecular upconversion, thus representing a new generation of lanthanide-based optical materials.

Visual ratiometric optical thermometer with high sensitivity and excellent signal discriminability based on LiScSiO4:Ce3+, Tb3+ thermochromic phosphor

Developing optical thermometer phosphors with high sensitivity, high signal discriminability and strong fluorescence intensity is ongoing. A dual-emitting thermochromic phosphor, LiScSiO₄:Ce³⁺, Tb³⁺, was successfully synthesized via solid-state reaction method. The crystal structure, electronic structure, luminescent performance and thermal luminescence behaviors as well as the luminescence mechanism of LiScSiO₄:Ce³⁺, Tb³⁺ were systematically investigated. Due to the energy transfer and different thermoluminescence behaviors between Ce³⁺ and Tb³⁺, high relative sensitivity (2.2 % K^-1@473 K), excellent signal discriminability (5747 cm^-1), outstanding temperature resolution (0.067 K) and good repeatability, as well as efficient emission at high temperatures were achieved based on the fluorescence intensity ratio of Ce³⁺ and Tb³⁺, indicating its potential in ratiometric optical thermometer. Moreover, the excellent visualizing thermochromic enable LiScSiO₄:Ce³⁺, Tb³⁺ to be used as safety sign in variable temperature environment to monitor temperature distribution.

Engineering of metal-organic frameworks (MOFs) for thermometry

Metal-organic frameworks (MOFs ) are excellent candidates for use in chemistry, material sciences and engineering thanks to their interesting qualitative features and potential applications. Quite interestingly, the luminescence of MOFs can be engineered by regulation of the ligand design, metal ion selection and encapsulation of guest molecules within the MOF cavity. Temperature is a very crucial physical parameter and the market share of temperature sensors is rapidly expanding with technology and medicinal advancement. Among the wide variety of available temperature sensors, recently MOFs have emerged as potential temperature sensors with the capacity to precisely measure the temperature. Lanthanide-based thermometry has advantages because of its ratiometric response ability, high quantum yield and photostability, and therefore lanthanide-based MOFs were initially focused on to construct MOF thermometers. As science and technology have gradually changed, it has been observed that with the inclusion of dye, quantum dots, etc. within the MOF cavity, it is possible to develop MOF-based thermometry. This review consolidates the recent advances of MOF-based ratiometric thermometers and their mechanism of energy transfer for determining the temperature (thermal sensitivity and temperature uncertainty). In addition, some fundamental points are also discussed, such as concepts for guiding the design of MOF ratiometric thermometers, thermometric performance and tuning the properties of MOF thermometers.

A Multimodal Ratiometric Luminescent Thermometer Based on a Single-Dysprosium Metal-Organic Framework

The design of high-performance luminescent MOF thermometers with multi-operation modes has been long sought but remains a formidable challenge. In this work, for the first time, we present a multimodal luminescent ratiometric thermometer based on the single-lanthanide metal-organic framework (MOF) DyTPTC-2Me (H₄TPTC-2Me = 2',5'-dimethyl-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid). It not only has the characteristic luminescence of Dy³⁺ in which the atomic transitions from the ⁴I_15/2 and ⁴F_9/2 states (thermally coupled energy levels, TCELs) are included but also emits ligand fluorescence due to the efficient energy back-transfer of Dy³⁺ to the ligand, thus allowing accurate non-invasive determination of temperature by different modes. In particular, the TCEL-based emissions of the Dy³⁺ ions give ideal signals for measuring the temperature in the 303-423 K range. The emissions of the ligand and Dy³⁺ (⁴F_9/2 → ⁶H_13/2) are used for temperature sensing in the range of 423 to 503 K. Both two modes feature promising thermometric performance, including high relative sensitivity, high temperature resolution, and excellent repeatability. Their combination is thus beneficial to achieve more accurate temperature detection over a broad temperature range, which can broaden the application scope of the ratiometric luminescent thermometers.

Boosting the sensitivity with time-gated luminescence thermometry using a nanosized molecular cluster aggregate

Luminescence thermometry with trivalent lanthanide ions is a promising avenue for contactless temperature probing. The area has been growing exponentially for the last two decades, and its viability has been successfully demonstrated in various research domains. However, moving from laboratory equipment to real-life applications remains a challenging task. One of the reasons is the possibility of a background luminescence from the probing device or probed environment. To tackle this issue, we elegantly incorporate a rarely explored thermometric approach called time-gated luminescence thermometry (TGLT). Furthermore, we demonstrate an enhanced relative sensitivity through this innovative approach and a path to move toward practical application.

Lanthanide-Based Coordination Polymers Molecular Alloys Stability: A Thermochemical Approach

In this study, we investigate the thermodynamics of lanthanide-based coordination polymer molecular alloys. We demonstrate that if lanthanide ions have many chemical similarities, the solubility of homo-lanthanide-based coordination polymers can vary significantly from one lanthanide ion to another. Indeed, we experimentally determine the solubility constants of a series of isostructural homo-lanthanide coordination polymers, with general chemical formula [Ln₂(bdc)₃(H₂O)₄]_∞ with Ln = La-Er plus Y and where bdc^2- symbolizes 1,4-benzene-di-carboxylate. Then, we extend the study to two series of isostructural molecular alloys with general chemical formula [Ln_2xLn'_2 -2x(bdc)₃(H₂O)₄]_∞ with 0 ≤ x ≤ 1 based either on heavy ([Eu_2xTb_2 - 2x(bdc)₃(H₂O)₄]_∞) or light ( [Nd_2xSm_2-2x(bdc)₃(H₂O)₄]_∞) lanthanide ions. We found that whatever the solubility difference of the homo-nuclear compounds is, the configurational entropy is the main driving force of the stabilization of molecular alloys.

A rapid self-healing glassy polymer/metal-organic-framework hybrid membrane at room temperature

The development of repairable MOF-polymer hybrid materials will greatly extend their service life by repairing fractured parts on the spot; however, it is difficult for robust glassy polymers to self-heal below the glass transition temperature (T_g) as the polymer network is frozen. We herein report glassy polyMOF-RHP hybrid membranes by integrating lanthanide polyMOF (polyLnMOF) with randomly hyperbranched polymers (RHP) bearing a high density of hydrogen bonds. Since crystalline lanthanide MOFs act as multiconnected cross-linking agents and cross-link the interpenetrating polymer network, the obtained polyLnMOF-polymer membrane shows enhanced mechanical strength with a storage modulus of 3.09 GPa and a T_g up to 49 °C. Meanwhile, the high intersegment migration ability of the polyLnMOF-polymer network facilitates the exchange of hydrogen-bonded pairs even in the glassy state, leading to an instantaneous room-temperature self-healing ability. The polyLnMOF-polymer membranes inherit the ratiometric temperature-sensing behavior of pristine lanthanide MOFs, resulting in more processable temperature-sensing membranes. This work provides an appealing strategy for the design of mechanically robust, yet self-healing, MOF-polymer functional materials.

Self-optimized single-nanowire photoluminescence thermometry

Nanomaterials-based photoluminescence thermometry (PLT) is a new contact-free photonic approach for temperature sensing, important for applications ranging from quantum technology to biomedical imaging and diagnostics. Even though numerous new materials have been explored, great challenges and deficiencies remain that hamper many applications. In contrast to most of the existing approaches that use large ensembles of rare-earth-doped nanomaterials with large volumes and unavoidable inhomogeneity, we demonstrate the ultimate size reduction and simplicity of PLT by using only a single erbium-chloride-silicate (ECS) nanowire. Importantly, we propose and demonstrate a novel strategy that contains a self-optimization or "smart" procedure to automatically identify the best PL intensity ratio for temperature sensing. The automated procedure is used to self-optimize key sensing metrics, such as sensitivity, precision, or resolution to achieve an all-around superior PLT including several record-setting metrics including the first sensitivity exceeding 100% K^-1 (~138% K^-1), the highest resolution of 0.01 K, and the largest range of sensible temperatures 4-500 K operating completely within 1500-1800 nm (an important biological window). The high-quality ECS nanowire enables the use of well-resolved Stark-sublevels to construct a series of PL intensity ratios for optimization in infrared, allowing the completely Boltzmann-based sensing at cryogenic temperature for the first time. Our single-nanowire PLT and the proposed optimization strategy overcome many existing challenges and could fundamentally impact PL nano-thermometry and related applications such as single-cell thermometry.

Determination of the critical micelle concentration of surfactants using fluorescence strategies

The increasing importance of surfactants in various fields has led to growing interest in the comprehensive characterization of surfactants. The critical micelle concentration (CMC), the most fundamental property of surfactants, is a parameter that must be measured. In particular, with the continuous expansion of the molecular structure of surfactants, numerous novel amphiphilic molecules have been developed that are capable of forming ordered aggregates in various solvent systems. Fluorescence spectroscopy, based on the differences in fluorescence intensity and wavelength of the fluorescent probe in the solvent phase and micellar phase, can sensitively detect the CMC of surfactants. This review aims to summarize the various fluorescence methods used to determine the CMC, including aggregation-induced emission (AIE), excimer formation, intramolecular charge transfer (ICT), and other miscellaneous strategies. The difficulties and limitations in the CMC determination process are also described. Further suggestions are provided to guide the existing fluorescence probes and the corresponding fluorescence methods to detect critical aggregation concentrations of amphiphilic molecules.

Lanthanide-Based Langmuir–Blodgett Multilayers: Multi-Emissive, Temperature-Dependent Thin Films

Multi-emissive compounds have attracted significant attention from the research community owing to the wide array of potential application areas. However, to move towards application, such systems should be readily immobilized by solution-based methods to form soft materials such as gels and films. Herein we report the use of Langmuir–Blodgett (LB) deposition to easily immobilize luminescent lanthanide-based amphiphilic solids into multi-emissive ultrathin LB films, by multilayering different luminescent amphiphiles. Utilizing this technique, we have reliably fabricated dual- and triple-emissive films where the overall emission from the film is tuned. Furthermore, we have demonstrated that these multi-emissive films are temperature-dependent, with emission profiles significantly altering from 294 to 340 K, resulting in colour changes and potential application as ultrathin, contactless ratiometric thermometer coatings.

Europium(III)-Doped Gadolinium(III) Complex for High-Sensitivity Temperature Sensing in the Physiological Range

A new Eu³⁺-doped Gd³⁺ complex of formula [Eu_0.0135Gd_0.9865(pta)₃me-phen] was synthesized and structurally characterized (Hpta = benzoyltrifluoroacetone, me-phen = 5-methyl-1,10-phenanthroline). The photoluminescence study revealed that when the compound was excited at RT, under a 457 nm continuous laser, the material exhibited high luminescence due to the antenna effect of the ligands, as well as a good balance between the phosphorescence from the spin-forbidden triplet (from the organic ligands), and the characteristic lanthanide f-f transitions. The ratio between the previous emissions drastically changed when the sample was heated up to 62 °C inside a tubular furnace. This ratio was investigated using the luminescence intensity ratio method, to analyze the capabilities of the sample as a temperature sensor. The relative sensitivity reached a maximum of 11.4 °C^-1 %, maintaining a detection limit below 0.15 °C for the whole temperature range.

Unique Fluorescence Turn-On and Turn-Off-On Responses to Acids by a Carbazole-Based Metal-Organic Framework and Theoretical Studies

Distinct from predominately known fluorescence quenching (turn-off) detection, turn-on response to hazardous substances by luminescent metal-organic frameworks (LMOFs) could greatly avoid signal loss and susceptibility to environmental stimulus. However, such detection rarely occurs and lacks theoretical elucidations. Here, we present the first example of unique turn-on and unprecedented turn-off-on responses to a variety of acids by a stable 12-connected hexanuclear Y(III)-cluster-based LMOF material─JLU-MOF111, featuring the nondefault pcu topology. Benefiting from the "pocket" structures formed by the carbazole-containing ligands, JLU-MOF111 can sense multiple inorganic and organic acids via different degrees of fluorescence turn-on behaviors. Particularly, turn-on sensing of HNO₃, HCl, HBr, and TFA is hypersensitive with LODs as low as the ppb level. Theoretical calculations confirm weak interactions in acid-ligand complexes, which lead to constrained rotations of benzene moieties of the ligands when the complexes decay from excited states. These account for the turn-on response through reduced nonradiative energy consumption that competes with emissive decay. The turn-off-on response to 4-NBA and 3,5-DNBA involves an excited-state electron transfer process that dominates the turn-off stage and prohibited nonradiative decay that competes with the intrinsic emission of the ligand and dominates the turn-on stage. This work has a guiding significance for the full-scale understanding of turn-on and turn-off-on sensing performance in LMOF materials and beyond.

Fluorescent Eu3+/Tb3+ Metal-Organic Frameworks for Ratiometric Temperature Sensing Regulated by Ligand Energy

This work presents three series of Eu/Tb metal-organic frameworks (MOFs) containing benzophenone-4,4'-dicarboxylic acid (H₂BPNDC), 4,4'-dicarboxydiphenyl ether (H₂OBA), and terephthalic acid (H₂BDC) as the ligands. Eu/Tb MOFs have the same structural features in that their 3D frameworks are simplified as 2,3,10-connected {4².6}₂{4⁶.6¹⁸.8¹⁹.10²}{4}₂ topological networks. The solid-state fluorescence spectra of three Eu/Tb MOF series are attributed to the combined emissions of ⁵D₀ → ⁷F_J (J = 1-4) transitions in Eu³⁺ and ⁵D₄ → ⁷F_J (J = 6-5) transitions in Tb³⁺. The n_Eu:n_Tb of Eu/Tb MOFs is optimized as 1:69 based on the relationships between I_Tb(545)/I_Eu(614) and n_Eu:n_Tb; that is, Eu_0.0143Tb_0.9857-L (L = BPNDC^2-, OBA^2-, and BDC^2-) were selected to carry out the following temperature (T)-sensing tests. The fluorescence mechanism of Eu_0.0143Tb_0.9857-L can be explained by a ligand-to-metal charge transfer combined with an intermetallic Tb³⁺ → Eu³⁺ energy transfer. The T-dependent fluorescence indicates linear relationships with sensitivities of 1.85% K^-1 for Eu_0.0143Tb_0.9857-BPNDC, 6.49% K^-1 for Eu_0.0143Tb_0.9857-OBA, and 0.28% K^-1 for Eu_0.0143Tb_0.9857-BDC. The influence of T on the lowest excited triplet energy levels (T1 values) of the ligands reveals that the ligand energy regulation impacts their fluorescence properties, including the sensitivity, fluorescence quenching rate, quantum yield, and fluorescence lifetime. This shows that Eu_0.0143Tb_0.9857-BPNDC is sufficiently sensitive to T, making it applicable in noncontact T measurements.

Temperature-Sensitive Chameleon Luminescent Films Based on PMMA Doped with Europium(III) and Terbium(III) Anisometric Complexes

The spin-coating technique was used to produce composite films consisting of PMMA polymer doped with anisometric complexes of Eu(III) and Tb(III). It was found that an increase in the content of Tb3+ complexes intensifies emission of both ions due to the intermolecular energy transfer from the Tb(III) complex to the Eu(III) complex, which results in the increase in the relative luminescence quantum yield of Eu(III) ion by 36%. The temperature sensitivity of the film luminescence intensity and lifetime in the range of 296–363 K was investigated. The maximum relative sensitivity of the films reaches 5.44% × K−1 and exceeds that of all known lanthanide-containing thermal sensors designed for measuring physiological temperatures. In combination with changing luminescence color, such a sensitivity makes these films promising colorimetric thermal sensors for in situ temperature measurements.

Biomineralized Nano-Assemblies of Poly(Ethylene Glycol) Derivative with Lanthanide Ions as Ratiometric Fluorescence Sensors for Detection of Water and Fe3+ Ions

An effective strategy was developed to fabricate novel lanthanide ions–pyromellitic acid–methoxy poly(ethylene glycol) (Ln-PMA-MPEG) nano-assemblies. The amphiphilic partially esterified derivative (PMA-MPEG) of pyromellitic acid with methoxy poly(ethylene glycol) was designed and synthesized via the coupling reaction. Ln-PMA-MPEG nano-assemblies were rapidly fabricated using PMA-MPEG as a polymer ligand with Eu³⁺ ions or mixed Eu³⁺/Tb³⁺ ions through biomimetic mineralization in neutral aqueous systems. The size of the as-prepared materials could be designed in the range 80–200 nm with a uniform distribution. The materials were readily dispersed in various solvents and displayed visible color variations and different photoluminescent properties for solvent recognition. The mixed Eu/Tb-PMA-MPEG nanomaterials were investigated as ratiometric sensors for the detection of trace water in DMF and Fe³⁺ ions in aqueous solutions. The sensor materials can quantitatively detect trace water in DMF from 0% to 10% (v/v). The resultant materials also display a strong correlation between the double luminescence intensity ratios (I_Tb/I_Eu) and Fe³⁺ concentration, with a good linear detection concentration in the range of 0–0.24 mM and a limit of detection of 0.46 μM, and other metal ions did not interfere with the sensing mechanism for Fe³⁺ ions. The novel nano-assemblies have potential applications as ratiometric fluorescent nanosensors in the chemical industry as well as in biomedical fields.

A Highly Stable Yttrium Organic Framework as a Host for Optical Thermometry and D2 O Detection

The yttrium organic framework (Y0.89 Tb0.10 Eu0.01 )6 (BDC)7 (OH)4 (H2 O)4 (BDC=benzene-1,4-dicarboxylate) is hydrothermally stable up to at least 513 K and thermally stable in air in excess of 673 K. The relative intensities of luminescence of Tb3+ and Eu3+ are governed by Tb3+ -to-Eu3+ phonon-assisted energy transfer and Tb3+ -to-ligand back transfer and are responsible for the differing temperature-dependent luminescence of the two ions. This provides a ratiometric luminescent thermometer in the 288-573 K temperature range, not previously seen for MOF materials, with a high sensitivity, 1.69±0.04 % K-1 at 523 K. In aqueous conditions, loosely bound H2 O can be replaced by D2 O in the same material, which modifies decay lifetimes to yield a quantitative luminescent D2 O sensor with a useful sensitivity for practical application.

Photoluminescence properties of Er3+ and Er3+/Yb3+ doped tellurite glass and glass-ceramics containing Bi2Te4O11 crystals

Glass and glass-ceramics containing nanocrystals of Bi₂Te₄O₁₁ cubic phase co-doped with Er³⁺ and Yb³⁺ were prepared by heat treatment of the precursor tellurite glass and investigated for optical applications. Lanthanide doped tellurite glass and glass-ceramics have been extensively investigated because of their optical and photoluminescence performance for technological photonic applications. Er³⁺ and Er³⁺/Yb³⁺ doped TeO₂-GeO₂-K₂O-Bi₂O₃ tellurite glass compositions were prepared by the conventional melt-quenching method. Photoluminescence results showed the important role played by Yb³⁺ ions when co-doping with Er³⁺ ions in comparison with the Er³⁺ single-doped glass. Due to their larger absorption cross-section, Yb³⁺ species significantly absorbs 980 nm photons and effectively transfers them to Er³⁺ ions via a set of mechanisms including ground-state absorption (GSA), excited-state absorption (ESA), and energy transfer upconversion (ETU). Er³⁺/Yb³⁺ co-doped sample was chosen for the synthesis of transparent glass-ceramics by controlled heat treatment above T_g for 5 to 120 min. X-ray diffraction patterns, high-resolution transmission electron microscopy (TEM) images, and selected area electron diffraction (SAED) from Er³⁺/Yb³⁺ co-doped glass-ceramic samples were used to verify the nanocrystal precipitation, crystalline phase, and chemical nature. The structural change resulting from the crystallization of Bi₂Te₄O₁₁ nanocrystals was evaluated by the Raman shift of the bands between 300-500 cm^-1, which are assigned to the formation of Bi-O-Te linkages and the reduction of [TeO₃] depolymerized units. The effects of HT time on the glass-ceramic's optical and upconversion photoluminescence properties were studied in the visible range under excitation at 980 nm in terms of the energy transfer mechanisms from Yb³⁺ to Er³⁺. Results indicate that Er³⁺/Yb³⁺ co-doped tellurite glass and glass-ceramics are potential candidates for photonic applications in lighting, energy conversion, and luminescent solar cell concentrators.

Energy Transfer in Metal-Organic Frameworks for Fluorescence Sensing

The development of materials with outstanding performance for sensitive and selective detection of multiple analytes is essential for the development of human health and society. Luminescent metal-organic frameworks (LMOFs) have controllable surface and pore sizes and excellent optical properties. Therefore, a variety of LMOF-based sensors with diverse detection functions can be easily designed and applied. Furthermore, the introduction of energy transfer (ET) into LMOFs (ET-LMOFs) could provide a richer design concept and a much more sensitive and accurate sensing performance. In this review, we focus on the recent five years of advances in ET-LMOF-based sensing materials, with an emphasis on photochemical and photophysical mechanisms. We discuss in detail possible energy transfer processes within a MOF structure or between MOFs and guest materials. Finally, the possible sensing applications of the ET-LMOF-based sensors are highlighted.

Luminescent Dimeric Oxalate-Bridged Eu3+/Tb3+-Implanted Arsenotungstates: Tunable Emission, Energy Transfer, and Detection of Ba2+ Ion in Aqueous Solution

Two cases of lanthanide (Ln)-implanted arsenotungstates, K₁₇Na₂H₅[{(As₂W₁₉O₆₇(H₂O))Ln(H₂O)₂}₂(C₂O₄)]·87H₂O (Ln = Eu (1), Ln = Tb (2)) and their codoped derivatives Eu_xTb_1-x-POM (x = 0.01 (3), x = 0.04 (4), x = 0.1 (5), x = 0.2 (6)) were prepared and further characterized by powder X-ray diffraction, infrared spectra, and thermogravimetric analyses. An X-ray structural analysis of 1 and 2 indicates that they both present a dimeric oxalate-bridged Ln³⁺-implanted lanthanide arsenotungstate polyanion structure. Under the O → W LMCT excitation at 265 nm of arsenotungstate polyanions, the emissions of Ln³⁺ ions in 1 and 2 are sensitized and the lifetimes are prolonged. Codoped compounds 3-6 demonstrate a color-tunable emission from green to red by adjusting the Eu³⁺/Tb³⁺ ratio. Emission spectra and time-resolved emission spectroscopic studies were performed for 3 to further authenticate the energy transfer processes from excited arsenotungstates to the Eu³⁺ and Tb³⁺ metal ions and also between the Eu³⁺ and Tb³⁺ centers. More interestingly, 1 is an effective fluorescent probe for the recognition and detection of Ba²⁺ ions in aqueous solution. The optical properties of the Ln-implanted arsenotungstate compounds not only expressly reveal distinctive energy transfer processes in those compounds but also broaden the application of POM-based materials in the fluorescence sensing field.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

Synthesis and characterizations of YZ-BDC:Eu3+,Tb3+ nanothermometers for luminescence-based temperature sensing

In the present work, nanothermometers based on amorphous zirconium metal–organic frameworks co-doped with rare-earth ions (YZ-BDC:Eu³⁺,Tb³⁺ nanothermometers) with sizes of about 10–30 nm were successfully synthesized via a microwave-assisted hydrothermal method at 120 °C for 15 min. The determined BET surfaces area, total pore volume and average pore diameter were ∼530 m² g⁻¹, 0.45 cm³ g⁻¹ and 3.4 nm, respectively. Based on Fourier transform infrared spectroscopy (FTIR) and simultaneous thermal analysis (STA) results, the formation process of carboxylic acid salts and the molecular formula of the samples have been proposed. The thermometric properties of Zr-BDC:Eu³⁺,Tb³⁺ nanothermometers and their Y³⁺ ion co-doped counterparts (YZ-BDC:Eu³⁺,Tb³⁺) measured in the 133–573 K temperature range were compared. Moreover, the temperature-dependent CIE(x, y) chromaticity coordinates and emission color of the samples were also determined. As the temperature increased from 133 to 573 K, the emission color of Zr-BDC:Eu³⁺,Tb³⁺ nanothermometers without the presence of Y³⁺ ions changed from orange to red, while for YZ-BDC:Eu³⁺,Tb³⁺ nanothermometers, the emission color changed from yellow to orange, due to the strong effect of the presence of Y³⁺ ions on the luminescence intensity of Eu³⁺ and Tb³⁺ ions. The maximum relative sensitivity (S_Rmax) in both materials was close to 0.5%/K, however, the temperature range of their occurrence was significantly shifted toward higher temperatures due to doping with Y³⁺ ions. The obtained results showed that doping with Y³⁺ ions not only enables the modulation of the useful temperature range with high relative sensitivity, but also provides improved thermal stability.

In the present work, nanothermometers based on amorphous zirconium metal–organic frameworks co-doped with rare-earth ions (YZ-BDC:Eu³⁺,Tb³⁺) with sizes of about 10–30 nm were successfully synthesized via a microwave-assisted hydrothermal method at 120 °C for 15 min.

Recent advances on bimetallic metal-organic frameworks (BMOFs): Syntheses, applications and challenges

Bimetallic metal-organic frameworks (MOFs) possess two different metal ions as nodes in their molecular frameworks. They are prepared by either using one-pot syntheses wherein different metals are mixed with suitable...

Dual-emission 3D supramolecular framework hydrogel beads: highly selective detection of antibiotics and mechanism research

Ratiometric fluorescent probes based on coordination polymers (CPs) have been widely applied in optical applications. Therefore, it is very important to develop a dual-emitting gel material based on coordination polymers for specific recognition of molecules. Cu-atda (H2atda = 3,3'-(4-amino-1,2,4-triazol-3,5-diyl) dibenzoic acid) is synthesized with a porous structure and a large number of amino sites exposed on the surface, which can be regarded as a carrier for fluorescent molecules and well disperse in the SA hydrogel network. A dual-emission Eu3+ functionalized CP hydrogel bead (9A/Cu-atda@Eu3+/SA, 9A = 9-anthraldehyde and SA = sodium alginate) is successfully prepared, which presents ratiometric fluorescence detection of flumequine with a low detection limit (48 nM) and high selectivity. Furthermore, it also displays an excellent fluorescence quenching effect on nitrofuran antibiotics, exhibiting a dual functional performance. In addition, the fluorescence response mechanisms of flumequine and nitrofuran antibiotics are discussed in depth. As a portable material, visualization 9A/Cu-atda@Eu3+/SA beads provide an extensive and convenient application prospect for real-time monitoring of antibiotics in the water environment.

1D-Zigzag Eu3+/Tb3+ Coordination Chains as Luminescent Ratiometric Thermometers Endowed with Multicolor Emission

Two homometallic Coordination Polymers (CPs) with composition [Ln(hfac)₃bipy]_n (Ln³⁺ = Eu³⁺, 1, and Tb³⁺, 2; hfac = hexafluoroacetylacetonato, bipy = 4,4′-bipyridine) were used to develop a family of ratiometric luminescent thermometers containing Eu³⁺ and Tb³⁺ as red and green emitters, respectively. The thermometric properties of pure CPs and of their mixtures having an Eu³⁺/Tb³⁺ molar ratio of 1:1, 1:3, 1:5, and 1:10 (samples: Eu1Tb1, Eu1Tb3, Eu1Tb5, and Eu1Tb10) were studied in the 83–383 K temperature range. Irrespective of the chemical composition, we observed similar thermometric responses characterized by broad applicative temperature ranges (from 100 to 165 K wide), and high relative thermal sensitivity values (S_r), up to 2.40% K⁻¹, in the physiological temperature range (298–318 K). All samples showed emissions endowed with peculiar and continuous color variation from green (83 K) to red (383 K) that can be exploited to develop a colorimetric temperature indicator. At fixed temperature, the color of the emitted light can be tuned by varying composition and excitation wavelength.

Inside-Out/Outside-In Tunability in Nanosized Lanthanide-Based Molecular Cluster-Aggregates: Modulating the Luminescence Thermometry Performance via Composition Control

Modulating the optical property of a material via structural modification is a powerful tool for obtaining the desired optical output. If a material can be tuned inside (core) and outside (outer shell), then the degree of control is greater toward application. Herein, we present a lanthanide-based nanosized molecular cluster aggregate (MCA) that allows fine-tuning of the inner core via composition control akin to nanoparticles. At the same time, the tunable outer shell enables light-harvesting properties similar to molecular systems. As such {Eu₄Tb₁₆}, {Eu₃Gd₅Tb₁₂}, {Eu₂Gd₁₀Tb₈}, and {Eu₁Gd₁₅Tb₄} compositions were synthesized, and their photophysical properties were investigated in solution and in the solid state. Controlling the composition and spacing of the emitter ions with the optically silent Gd^III ions results in a decrease in the Tb^III → Eu^III energy-transfer process efficiency. Consequently, ratiometric luminescence thermometry performance is fine-tuned to reach a maximum relative sensitivity of 4.17% °C^-1 at 36 °C for the {Eu₄Tb₁₆} MCA. This study demonstrates that the optical properties are intrinsic to individual MCA species rather than a collective intermolecular effect. The color change observed close to room temperature for {Eu₂Gd₁₀Tb₈} suggests potential applications such as multistage anticounterfeiting technology.

A luminescent Zn-MOF exhibiting high water stability: selective detection of Cr(VI) ion and treatment activity on sepsis

A fresh metal-organic framework (MOF) based on the Zn ions as the metal ions has been prepared via the solvothermal method, and its chemical formula is [Zn(byia)(DMF)]·1.5DMF·7H₂O (1, byia =  5-(benzimidazol-2-yl) isophthalic acid). It is worth noting that the compound 1 has excellent water stability (which can be maintained in the water for at least a month). Most fascinating, in water, the compound 1 exhibits the strong blue luminescence, which can only be selectively quenched via the contaminant of the Cr₂O₇^2– ion. The selective luminescence quenching with low limits of detection and high values of K_sv proved its better sensing property, which can be compared with the contemporary materials. To development new strategy for the sepsis treatment, the biological activity and mechanism of the compound was explored. Firstly, the ELIA detection was performed in this experiment to assess the inhibition of compound against inflammatory factor storm during sepsis. Then, the inflammatory response in the immune cells was assessed by real time RT-PCR.