过渡金属离子顺磁猝灭稀土离子发光

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Herein we describe the design, synthesis and characterization of a phenhomazine ligand with six pendant acetate arms designed for the combined coordination of copper(II) and lanthanide(III) ions, with the perspective of the development of a "turn-off" copper sensor. The key step for the ligand preparation was the one-step endomethylene bridge fission of a diamino Tröger's base with a concomitant alkylation. Fluorescence and absorption spectroscopies as well as nuclear magnetic resonance (NMR) experiments were performed in order to analyze and understand the coordination properties of the ligand. Transition metal coordination was driven by the synergistic effect of the free nitrogen atoms of the diazocinic core and the two central acetate arms attached to those nitrogens, whereas lanthanide coordination is performed by external acetate arms, presumably forming a self-assembled 2:2 metallosupramolecular structure. The terbium complex shows the typical green emission with narrow bands and long luminescence lifetimes. The luminescence quenching produced by the presence of copper(II) ions was analyzed. This work sets therefore a starting point for the development of a phenhomazine-based "turn-off" copper(II) sensor.

Fluorescent lanthanide complexes have favorable features for fluorescence-based sensors compared to organic fluorophores and quantum dots. They exhibit very long fluorescence lifetimes, sharp emission bands, and stability with respect to photo-bleaching, without blinking. However, these complexes are usually hydrophobic, and many are excited by UV light, making them hazardous and incompatible with aqueous environments and biological samples. In this work, the strong fluorescent Eu3+-induced aggregates of polysaccharides (EIAP) was used to improve their aqueous solubility, and to tune the appropriate excitation wavelength in the visible range for avoiding toxicity of UV light in biological applications. The complexes exhibit bright fluorescence with an excitation maximum in the visible range, near 405 nm. EIAP 3 also exhibit rapid quenching response in the presence of transition metal ions. This enables the detection of Cu2+ and Fe3+ below 1 ppm. The reverse of quenching response of copper by the addition of a chelating agent makes it possible to recover the fluorescence property. Successfully, the EIAP exhibit cytocompatibility with mammalian cells. Thus, these new polysaccharide-based complexes have the potential for rapid, sensitive and selective metal ion sensors for the environmental systems.

Due to their notable antimicrobial activity and optical properties, Schiff base ligands, along with their lanthanide and transition metal complexes, have seen extensive use in various applications. However, despite their potential, a comprehensive investigation into lanthanide and transition metal complexes using the same Schiff base ligand has not been reported to date. In this study, coordination compounds of lanthanide and transition metal ions were synthesized from the Schiff base ligand salicylaldehyde‐dipropylenetriamine. These complexes were characterized by elemental analysis, 1H and 13C NMR, mass spectroscopy, Fourier‐transform infrared spectroscopy ultraviolet–visible spectroscopy (UV–Vis), fluorescence spectroscopy, molar conductivity measurements, and thermogravimetric studies. Furthermore, the molecular structure of the Co (II) complex was determined by means of X‐ray crystallography. Thermogravimetric studies illustrated endothermic and non‐spontaneous degradation pathways of the complexes. UV–Vis spectra showed a new absorption band attributed to the ligand‐to‐metal charge transfer peak supporting the complexation between the ligand and metals. The lanthanide complexes exhibited distinctive luminescence emissions in the Sm (III), Tb (III), and Eu (III) complexes. This observation suggests that the ligand possesses the capability to absorb and efficiently transfer energy to the metal center of these lanthanide ions, thereby resulting in their characteristic luminescent properties. Additionally, antimicrobial investigations revealed that transition metal complexes generally exhibited antimicrobial activity against both gram‐positive and gram‐negative bacterial strains compared to lanthanide metal complexes, in most cases. However, it is noteworthy that the Dy (III) complex displayed the lowest minimum inhibitory concentration and minimum biocidal concentration values of 16 μg/ml against Staphylococcus epidermidis, indicating its potential as a candidate for the treatment of this pathogenic bacterium. The main purpose of this article is to investigate the variations in the synthesis and characterization of lanthanide and transition metal complexes utilizing the same Schiff base ligand suitable for applications in the pharmaceutical industry and optical material sciences.

This study explores the utilization of metal-organic frameworks (MOFs), particularly those incorporating lanthanide-based elements for their fluorescence capabilities, to create an advanced barcode system. By exploiting the modular nature of MOFs, we have developed a material capable of dynamic information encoding and robust against counterfeiting efforts. We introduce a novel barcode prototype that exhibits visible color shifts and fluorescence modulation when exposed to a specific sequence of chemical and thermal stimuli. The barcode is composed of MOF-808, which is modified with transition metals like iron or cobalt, and europium cations. These components are embedded within polyvinylidene fluoride (PVDF) to form a composite. This embedding process ensures that the MOF particles remain reactive to specific trigger molecules, enabling a distinct read-out sequence. The decoding process, involving exposure to ammonia, heating at 120 °C, and treatment with HCl, triggers observable changes in fluorescence and color, depending on the transition metal used. Our investigations with Eu,Co-MOF-808, and Eu,Fe-MOF-808 composites have resulted in the creation of a barcode prototype that demonstrates the feasibility of using europium-modified and unmodified transition metal modified MOF-808@PVDF composites for enhanced security applications.

Lanthanide-transition metal complexes continue to be of interest, not only because of their synthetic challenge but also of their promising magnetic properties. Computational work examining the chemical bonding between lanthanides and transition metals in PyCp2Ln-TMCp(CO)2 (DyPyCp22- = [2,6-(CH2C5H3)2C5H3N]2-) reveals strong Ln-TM dative bonds. Gas-phase optimized geometries are in good agreement with experimental structures at the density functional theory (DFT) level with large-core pseudopotentials. From La to Lu, there is a small increase in the bond dissociation energy, as well as a decrease in Ln-Fe bond lengths. Energy decomposition analyses attribute this trend to an increase in the electrostatic contribution from the decreasing bond length and a modest increase in the orbital contribution. The natural bond orbital analysis clearly indicates that 3d6 "lone pairs" in the [FeCp(CO)2]- fragment act as a Lewis bases donating nearly 0.5 electron to Ln virtual orbitals of mainly d character. The interfragment bonding was also quantified by the quantum theory of atoms in molecules, which indicates that the Ln-Fe bond is more covalent than the Ca-Fe bond in the hypothetical CpCa-FeCp(CO)2 but less covalent than the Zn-Fe bond in the hypothetical CpZn-FeCp(CO)2. Further comparisons suggest that to the [PyCp2Ln]+ cation the [FeCp(CO)2]- anion appears much like a halide. Overall, these Ln-TM dative bonds appear to have strong electrostatic contributions as well as significant orbital mixing and dispersion contributions.

A new strategy for the easy polymerization of anionic [Ln(Qcy)4]− (HQcy-4-(cyclohexanecarbonyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one) into two-dimensional layers of [AgLn(Qcy)4]n (Ln = Sm, Eu, Gd, Tb and Dy) is proposed by binding the single molecular anions [Ln(Qcy)4]− to silver cations through the coordination of the pyridinic nitrogen atoms of the pyrazolonate rings. The luminescent properties of [AgLn(Qcy)4]n have been studied in detail, and it was shown that the previously described low photoluminescence quantum yield (PLQY) of [Eu(Qcy)4]− is due to Ligand-To-Metal Charge Transfer (LMCT) quenching, which is effectively suppressed in the heterometallic [AgEu(Qcy)4]n polymer. Sensibilization coefficients for H3O[Eu(Qcy)4], [AgEu(Qcy)4]n, and H3O[Sm(Qcy)4] complexes (n ≈ 1) were estimated via theoretical analysis (also by using Judd-Ofelt theory for Sm3+) and PLQY measurements.

Two basically isostructural lanthanide-based metal-organic frameworks (Ln-MOFs), {[Eu(dptz)(H2O)2]Cl·3H2O}n (JLNU-10-Eu, JLNU = Jilin Normal University) and {[Tb(dptz)(NO3)(H2O)]·7H2O}n (JLNU-10-Tb), have been successfully synthesized by employing 3-(3,5-dicarboxylphenyl)-5-(pyrid-2-yl)-1H-1,2,4-triazole (H2dptz) as a flexible carboxylic acid ligand through solvothermal reactions. Single-crystal structural studies on Ln-MOFs manifested that the compounds have a two-dimensional (2D) layered structure. Furthermore, fluorescence sensing experiments indicated that JLNU-10-Eu and JLNU-10-Tb had significant fluorescence quenching effects on Cr2O72-, Fe3+, and TNP. It should be noted that the KSV value of JLNU-10-Eu in sensing Fe3+ could reach 7.36 × 103, and the limit of detection (LOD) was 0.57. The luminescence quenching mechanism is discussed in detail through some relevant experiments. Additionally, a series of Ln-MOFs, JLNU-10-EuxTb1-x (x = 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1), have been obtained by simply regulating the molar ratio of Eu3+ and Tb3+. Particularly, JLNU-10-Eu0.8Tb0.2 can achieve white light emission at an excitation wavelength of 300 nm. The CIE coordinates are (0.316, 0.332), which are very approximate to ideal white light. JLNU-10-Eu0.2Tb0.8 as a luminescence thermometer exhibits good linearity over the temperature range of 303-373 K with a high sensitivity of 4.1% K-1 at 373 K. The construction of multifunctional Ln-MOFs displays prospective applications in fluorescent probes, white light-emitting diodes, and luminescence thermometers.

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Lanthanides have seen rapid growth in the pharmaceutical and biomedical field, thus necessitating the development of hybrid metal–organic materials capable of exerting defined biological activities. Ternary hybrid lanthanide compounds were synthesized through reaction systems of Ln(III) (Ln = La, Nd, Eu) involving the antioxidant flavonoid chrysin (Chr) and 1,10-phenanhtroline (phen) under solvothermal conditions, thus leading to pure crystalline materials. The so-derived compounds were characterized physicochemically in the solid state through analytical (elemental analysis), spectroscopic (FT-IR, UV-visible, luminescence, ESI-MS, circular dichroism, 151Eu Mössbauer), magnetic susceptibility, and X-ray crystallographic techniques. The analytical and spectroscopic data corroborate the 3D structure of the mononuclear complex assemblies and are in line with theoretical calculations (Bond Valence Sum and Hirshfeld analysis), with their luminescence suggesting quenching on the flavonoid-phen electronic signature. Magnetic susceptibility data suggest potential correlations, which could be envisioned, supporting future functional sensors. At the biological level, the title compounds were investigated for their (a) ability to interact with bovine serum albumin and (b) antibacterial efficacy against Gram(−) (E. coli) and Gram(+) (S. aureus) bacteria, collectively revealing distinctly configured biological profiles and suggesting analogous applications in cellular (patho)physiologies.

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New antimony phosphate glasses doped with samarium (III) oxide and co-doped with copper metallic nanoparticles (CuNPs) were obtained by the melt quenching technique. The samples were analyzed by X-ray diffraction analysis (XRD), electron paramagnetic resonance (EPR), ultraviolet-visible (UV–Vis) and photoluminescence (PL) spectroscopies. XRD data suggested that all the obtained samples showed an amorphous nature. EPR data suggested the existence of Cu2+ ions octahedrally surrounded by six oxygen atoms. The dipole–dipole interactions between Cu2+ ions were predominant. UV–Vis spectra revealed the presence of Sm3+ and Cu2+ ions in the samples. The values for nephelauxetic and bonding parameters were also calculated. The negative values obtained for bonding parameter indicate an ionic character of the bonds from the glass network. Photoluminescence spectra exhibited emissions from samarium ions and revealed the influence of dopant nature on of rare-earth ions emissions. The obtained results indicate that the studied materials are suitable for solid state lasers.

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Magnetic separations present a promising approach for the recovery of rare earth (RE) elements from mixtures, particularly when coupled with precipitation techniques that enhance process efficiency and selectivity. However, the magnetic properties of RE materials typically encountered in the separations industry are not well characterized. Here, we synthesized a series of RE materials, combining four REspraseodymium (Pr), neodymium (Nd), terbium (Tb), and dysprosium (Dy)with three precipitating agentshydroxide, oxalate, and dibutyl phosphate. All materials showed typical paramagnetic behavior consistent with the Curie–Weiss law. At low temperatures, we observed weak antiferromagnetic correlations, which were more pronounced for the lighter RE ions (Pr, Nd). Particle morphology and crystallography analyses showed that the dibutyl phosphates were well-ordered metal–organic frameworks, the oxalates were crystals with mixed hydration states, and the hydroxides were mostly amorphous. Regardless of the degree of crystallinity, the effective magnetic moments aligned well with theoretical estimates based on Hund’s rules and 4f electron configurations of the corresponding RE ions. For a given RE ion, the magnetophoretic response was thus determined by the size of the particles rather than specific metal–ligand coupling, with dibutyl phosphate promoting the formation of larger crystals that were the most strongly attracted to magnets.

Rational control of triplet‐state emissions in organic molecules is key to advancing organic phosphors for optoelectronic applications. However, achieving precise modulation of both afterglow intensity and lifetime remains challenging. Here, a tunable afterglow system based on 1,10‐phenanthroline (1,10‐phen), enabled by rare‐earth (RE3+) complexation and incorporation into SiO2 microparticles (MPs) under hydrothermal conditions, is presented. Doping 1,10‐phen into SiO2 MPs activates phosphorescence at 488 nm, with a quantum yield of 2.59% and a lifetime of 1.14 s. Upon coordination with various RE3+ ions (La3⁺, Y3⁺, Gd3⁺, Lu3⁺), both the quantum yield (3.00–9.02%) and afterglow lifetime (0.07–1.46 s) are finely tunable. Remarkably, Gd3⁺, through its paramagnetic effect, enhances intersystem crossing more efficiently than the heavy‐atom effect of Lu3⁺, resulting in a higher quantum yield but a shorter afterglow duration. In contrast, Y3⁺, which lacks a heavy‐atom effect, increases the rigidity of the 1,10‐phen framework, thereby improving the phosphorescence quantum yield to 3.11% and extending the afterglow lifetime to 1.46 s. These findings highlight a versatile and effective strategy for tuning the optical properties of organic molecules via RE3+ complexation within SiO2 matrices, offering promising potential for the development of advanced photonic crystal platforms in optoelectronic technologies.

This study explored the preparation of the rare earth complex phosphor Eu(PTA)1.5phen, which was used to modify zinc-rich protective coatings. The methods employed in this study included FTIR spectroscopy, SEM, EDS, EIS, fluorescence spectroscopy, XRD, and XPS to examine the impact of varying concentrations of Eu(PTA)1.5phen on Fe3⁺ sensing, fluorescence quenching, and the performance of the coating. The results showed that Eu(PTA)1.5phen exhibits excellent fluorescence properties, with a maximum emission intensity of 1.8 × 108 and a quantum yield of 89.26%. Fluorescence quenching by Fe3⁺ allows for the quantification of steel corrosion. Corrosion tests revealed that adding Eu(PTA)1.5phen enhanced the compactness of the zinc-rich coatings. The optimal performance was obtained when using 3 wt.% Eu(PTA)1.5phen, leading to a corrosion current density of 6.76 × 10⁻7 A/cm2. The XRD and XPS analyses indicated that introducing Eu3⁺ does not influence the corrosion products present in the coating. This research showed that zinc-rich coatings enhanced with rare earth fluorescence not only safeguarded the steel substrate but also allow for the real-time tracking of Fe3⁺ concentrations in both the coating and the substrate. This approach offers a method for timely and effective corrosion prevention and corrosion identification, providing new insights for the development of advanced protective coatings and practical applications.

Our study is focused on the structural and morphological characteristics, optical behaviour and photocatalytic properties of undoped and 5 at% Eu3+-, Gd3+- and Y3+-doped CeO2 nanoparticles prepared by a green hybrid sol-gel combustion method. Several techniques such as X-ray diffraction powder (XRD), Transmission Electron Microscopy (TEM), UV-Vis spectroscopy, Photoluminescence spectroscopy (PL) and Electron Paramagnetic Resonance (EPR) have been used to investigate the obtained samples. Moreover, the correlation between the characteristics and properties has been studied. The nanoparticles observed by TEM exhibit a pseudo-spherical shape, except for Y3+-doped CeO2, which presents an acicular shape. The average size of undoped and rare-earth-doped CeO2 nanoparticles is below 10 nm, in good agreement with the calculations performed based on XRD analyses. From UV-Vis analyses it has been deduced that with doping the band gap energy decreases, which shows that additional levels are introduced by doping into the CeO2 band gap. The EPR spectra evidence similar behaviour for all doped samples. The photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) under UV light irradiation. The photodegradation mechanism has been studied in depth based on the formation of electron-hole pairs, and to evidence the reactive oxygen species, ESR coupled with spin-trapping experiments was performed. In the case of Y-doped CeO2 nanoparticles, the generation of both •OOH and •O2− radicals involved in RhB photodegradation was highlighted.

Fluoride based lattice is attractive for reducing phonon‐induced quenching in rare‐earth (RE) based luminescent materials. However, due to the strong affinity between RE and oxygen, the synthesis of fluoride‐based complexes has to be protected under anhydrous conditions, and many known fluoride bridged RE clusters are unstable in air. Here, by using the “mixed‐ligand” strategy a family of fluoride bridged RE clusters is synthesized, namely RE16(μ4‐F)6(μ3‐F)12(tBuCOO)18[N(CH2CH2O)3]4 (RE = Eu, EuFC‐16; RE = Tb, TbFC‐16), which are highly stable in air and decomposed thermally only when heating above 435 °C. Moreover, both clusters exhibit high photoluminescence quantum yields (PLQYEuFC‐16 = 87.7%, PLQYTbFC‐16 = 99.0%). Upon warming, EuFC‐16 and TbFC‐16 display excellent structural, thermal, and chroma stability. Thus, EuFC‐16 and TbFC‐16 have the potential to be used in light‐emitting diode (LED) devices, offering many advantages over commercial phosphors. First, both clusters are soluble in UV‐curable resin at any mixing rate, and the emission colors can be tuned from magenta, turquoise, willow green, and ivory to pure white if mixing blue phosphor BAM:Eu2+. Second, the clusters are hydrophobic, and the LEDs work well after soaking in water, indicating a good quality for outdoor lighting.

Facilitating different chemistries between the rare earth (RE = La-Lu, Sc, Y) ions is of significant interest for their separations. While the bulk of attention has been on maximizing the small differences in their ground state chemistry, interest is beginning to shift toward the differences in their electronic excited states. In this work, we demonstrate modulation of the photostationary state of an azobenzene derivative, Na1, via chelation to a series of REIIIDO3A (DO3A = 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) complexes. The extent of photoisomerization of 1- follows the trend in REIII Lewis acidity with two exceptions: SmIII and ErIII. UV-vis spectroscopy, titration experiments, and computational analysis show that these exceptions are a result of energy transfer rather than differences in ground state chemistry. These results open a pathway to differentiate REs by new photochemical means.

Excessive use of gentamicin sulfate can cause severe nephrotoxicity and ototoxicity, abnormal levels of Fe3+ intake can also cause serious damage to body. Therefore, establishing a fast and accurate detection method for the above-mentioned substances is of great significance. However, traditional detection methods such as high-performance liquid chromatography still have certain problems such as high cost and complex operation. Fluorescent MOFs are favored by analysts due to their high specific surface area, high porosity, adjustable pore size, and good stability. In this paper, we have synthesized four rare earth MOFs based on the pyridinecarboxylic acid ligand (H2L), which are [Eu(L)1/2H2O]n, [Gd(L)1/2H2O]n, [Sm(L)1/2H2O]n, [Y(L)3/2H2O·DMF]n. The structures of four MOFs were confirmed by single crystal X-ray diffraction, which proved that MOF-1, MOF-2 and MOF-3 were isostructural, and all the four MOFs were three-dimensional structures. In the fluorescence test, gentamicin sulfate and Fe3+ can cause significant fluorescence quenching of MOF-1 and MOF-4 respectively, and show good selectivity and anti-interference performance, as well as low detection limit and wide detection range. This work may provide a possibility for the detection of gentamicin sulfate and iron ions in complex environments.

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The degree of aggregation of neutral, 9-coordinate rare earth coordination complexes has been shown to affect their ligand field, as revealed by diffusion-ordered NMR spectroscopy (DOSY-NMR) measurements on Y(III) complexes, paramagnetic NMR analyses of Yb and Tb analogues and emission spectral studies with the EuIII systems. In non-polar media a lipophilic tris-isopropyl complex, [Ln.L2 ] tends to aggregate in chloroform and dichloromethane giving rise to oligomers, whereas in acetic and trifluoroacetic acid the more polar parent complex, [Ln.L1 ], also aggregates, profoundly affecting the pseudocontact shift and the form of the Eu emission spectrum. Such behaviour has important implications in the design of responsive spectral probes.

LnCl3(THF)3 (Ln = Y, La ÷ Nd, Sm ÷ Lu) readily react with the tridentate 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3tach) ligand to form mono- or binuclear lanthanide trichloride complexes, depending on the stoichiometry of the reaction and the ionic radius of the metal: mononuclear pseudosandwich [LnCl3(Me3tach)2], (Ln = Y, La ÷ Ho) or binuclear complexes [Ln2Cl6(Me3tach)3], or [LnCl3(Me3tach)(THF)]2 (Ln = Sm, Tb). Detailed analysis of the NMR data of [LnCl3(Me3tach)2] complexes with paramagnetic lanthanide ions showed that their structures remained unchanged in the toluene solution. A series of isomorphous complexes [LnCl3(Me3tach)(Py)2] (Ln = La, Sm, Tb, Er, Lu; Py = pyridine) have been obtained by the recrystallization of either mononuclear or binuclear complexes from pyridine. Complexes of terbium and europium ions with the Me3tach ligand exhibit relatively high quantum yields of metal-centered luminescence (0.39 and 0.32, respectively).

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The interest in the generation of photoluminescence in lanthanide(III) single-molecule magnets (SMMs) is driven by valuable magneto-optical correlations as well as perspectives toward magnetic switching of emission and opto-magnetic devices linking SMMs with optical thermometry. In the pursuit of enhanced magnetic anisotropy and optical features, the key role is played by suitable ligands attached to the 4f metal ion. In this context, cyanido complexes of d-block metal ions, serving as expanded metalloligands, are promising. We report two novel discrete coordination systems serving as emissive SMMs, {[DyIII(H2O)3(tmpo)3]2[PtIVBr2(CN)4]3}·2H2O (1) and {[DyIII(H2O)(tmpo)4]2[PtIVBr2(CN)4]3}·2CH3CN (2) (tmpo = trimethylphosphine oxide), obtained by combining DyIII complexes with uncommon dibromotetracyanidoplatinate(IV) ions, [PtIVBr2(CN)4]2-. They are built of analogous Z-shaped cyanido-bridged {Dy2Pt3} molecules but differ in the coordination number of DyIII (C.N. = 8 in 1, C.N. = 7 in 2) and the number of coordinated tmpo ligands (three in 1, four in 2) which is related to the applied solvents. As a result, both compounds reveal DyIII-centred slow magnetic relaxation but only 1 shows SMM character at zero dc field, while 2 is a field-induced SMM. The relaxation dynamics in both systems is governed by the Raman relaxation mechanism. These effects were analysed using ac magnetic data and the results of the ab initio calculations with the support of magneto-optical correlations based on low-temperature high-resolution emission spectra. Our findings indicate that heteroligand halogeno-cyanido PtIV complexes are promising precursors for emissive SMMs with the further potential of sensitivity to external stimuli that may be related to the lability of the axially positioned halogeno ligands.

Conspectus The unique photon emission signatures of trivalent lanthanide cations (Ln3+, where Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) enables multicolor emission from semiconductor nanoparticles (NPs) either through doping multiple Ln3+ ions of distinct identities or in combination with other elements for the creation of next-generation light emitting diodes (LEDs), lasers, sensors, imaging probes, and other optoelectronic devices. Although advancements have been made in synthetic strategies to dope Ln3+ in semiconductor NPs, the dopant(s) selection criteria have hinged largely on trial-and-error. This combinatorial approach is often guided by treating NP–dopant(s) energy transfer dynamics through the lens of spectral overlap. Over the past decade, however, we have demonstrated that the spectral outcomes correlate better with the placement of Ln3+ energy levels with respect to the band edges of the semiconductor, and oxide, host. In this Account, we describe how the Ln3+ energy level alignments affect the dopant emission intensities and dictate interdopant energy transfer processes in semiconductor nanoparticle hosts. This Account begins with a concise primer on the emission characteristics of trivalent lanthanides, the challenges that are associated with realizing meaningful lanthanide luminescence, and how semiconductor nanoparticles can act as a host to sensitize lanthanide emission. We then describe a semiempirical approach that can be used to place the lanthanide ground and luminescent energy levels with respect to the band edges of the host semiconductor nanoparticle. The ability of this model to track and predict the lanthanide sensitization efficiency is illustrated for singly doped zinc sulfide (ZnS), titanium dioxide (TiO2), and cesium lead chloride (CsPbCl3) perovskite hosts. Next, we discuss how knowledge of energy level offsets can be used to select dopant(s) for tunable multicolor emission by identifying different charge trapping processes for semiconductors doped with single and multiple lanthanides and discussing their impact on sensitization outcomes. Following this discussion, the Account lists viable Ln3+ combinations in ZnS NPs based on the charge trapping model and shows the limitations of spectral overlap models in predicting viable Ln3+ dopant combinations. Feasible f-f and d-f codopant combinations based on charge trapping are presented for TiO2 and CsPbCl3 NPs. The intricacies of interdopant energy migration and spin considerations that dictate the dopant(s) sensitization efficiencies are made known. Finally, we use these considerations to predict NP–dopant(s) combinations that should exhibit concerted emissions from the blue to the near-infrared (NIR) region, thereby enabling the design of bespoke optoelectronic properties. The Account ends with some forward-looking thoughts, arguing for the need to develop better quantitative models in order to explore the Ln3+ sensitization mechanisms and presenting ideas for applications of doped semiconductor NPs in energy and health that would be aided by interdopant energy transfer dynamics.

We report an effective strategy toward tunable room-temperature multicolor to white-light emission realized by mixing three different lanthanide ions (Sm3+, Tb3+, and Ce3+) in three-dimensional (3D) coordination frameworks based on hexacyanidoruthenate(II) metalloligands. Mono-lanthanide compounds, K{LnIII(H2O)n[RuII(CN)6]}·mH2O (1, Ln = La, n = 3, m = 1.2; 2, Ln = Ce, n = 3, m = 1.3; 3, Ln = Sm, n = 2, m = 2.4; 4, Ln = Tb, n = 2, m = 2.4) are 3D cyanido-bridged networks based on the Ln–NC–Ru linkages, with cavities occupied by K+ ions and water molecules. They crystallize differently for larger (1, 2) and smaller (3, 4) lanthanides, in the hexagonal P63/m or the orthorhombic Cmcm space groups, respectively. All exhibit luminescence under the UV excitation, including weak blue emission in 1 due to the d-d 3T1g → 1A1g electronic transition of RuII, as well as much stronger blue emission in 2 related to the d-f 2D3/2 → 2F5/2,7/2 transitions of CeIII, red emission in 3 due to the f-f 4G5/2 → 6H5/2,7/2,9/2,11/2 transitions of SmIII, and green emission in 4 related to the f-f 5D4 → 7F6,5,4,3 transitions of TbIII. The lanthanide emissions, especially those of SmIII, take advantage of the RuII-to-LnIII energy transfer. The CeIII and TbIII emissions are also supported by the excitation of the d-f electronic states. Exploring emission features of the LnIII–RuII networks, two series of heterobi-lanthanide systems, K{SmxCe1–x(H2O)n[Ru(CN)6]}·mH2O (x = 0.47, 0.88, 0.88, 0.99, 0.998; 5–9) and K{TbxCe1–x(H2O)n[Ru(CN)6]}·mH2O (x = 0.56, 0.65, 0.93, 0.99, 0.997; 10–14) were prepared. They exhibit the composition- and excitation-dependent tuning of emission from blue to red and blue to green, respectively. Finally, the heterotri-lanthanide system of the K{Sm0.4Tb0.599Ce0.001(H2O)2[Ru(CN)6]}·2.5H2O (15) composition shows the rich emission spectrum consisting of the peaks related to CeIII, TbIII, and SmIII centers, which gives the emission color tuning from blue to orange and white-light emission of the CIE 1931 xy parameters of 0.325, 0.333.

The synthesis and magnetic properties of two pairs of isomeric, exchange-coupled complexes, [LnCl6(TiCp2)3] (Ln = Gd, Tb), are reported. In each isomeric pair, the central lanthanide ion adopts either a pseudo-octahedral (O-Ln) or trigonal prismatic geometry (TP-Ln) yielding complexes with C1 or C3h molecular symmetry, respectively. Ferromagnetic exchange coupling is observed in TP-Ln as indicated by the increases in χmT below 30 K. For TP-Gd, a fit to the susceptibility reveals ferromagnetic coupling between the Gd3+ ion and the Ti3+ ions (J = 2.90(1) cm−1). In contrast to O-Tb, which shows no single-molecule magnetic behavior, the TP-Tb complex presents slow magnetic relaxation with a 100s-blocking temperature of 2.3 K and remanent magnetization at zero field up to 3 K. The calculated electronic structures of both compounds imply that trigonal prismatic geometry of TP-Tb is critical to the observed magnetic behavior.

Doping lead-free halide perovskite nanocrystals with trivalent lanthanide ions has emerged as a promising strategy for engineering their optical properties in various photonic applications. Here, we report the design and synthesis of a series of lead-free double halide perovskite (Cs2Na(In/Y/Gd)Cl6) nanocrystals co-doped with a pair of different lanthanides (e.g., Tb3+, Dy3+, and Eu3+) as emission centers, and ns2 ions (Sb3+ or Bi3+) as sensitizers. The tunability of the delayed photoluminescence spectral density was achieved through the selective excitation of lanthanide dopants either via ligand-to-metal charge transfer (e.g., Eu3+) or via ns2 ion s-p transitions (e.g., Dy3+ or Tb3+). The intensities of the narrow lanthanide f-f emission bands can, therefore, be tuned by modulating the excitation wavelength and/or dopant ratio, allowing for the accurate engineering of the emission color coordinates and spectral density. We also demonstrated time-resolved tuning of the photoluminescence spectral density for the investigated nanocrystal host lattices co-doped with transition-metal (Mn2+) and lanthanide ions, owing to a large difference between the decay dynamics for Mn2+ d-d and lanthanide f-f transitions. The rational co-doping of double halide perovskite nanocrystals reported in this work provides a new strategy for generating pre-designed multilevel luminescent signatures for protection against counterfeiting.

New transition metal substituted milarite silicates of the general formula A2B2C[T(2)3T(1)12O30] were prepared by a conventional solid state technique and their structures determined by powder X-ray diffraction (PXRD) methods. Raman spectroscopic studies indicated expected Raman bands. The oxidation states of the transition elements were confirmed by XPS studies. The optical absorption bands were rationalized based on the ligand-centered emission and allowed d-d transitions. The white compounds exhibited good deep UV cut off values, suggesting their possible use as optical filters. The white compounds also showed good near-infrared (NIR) reflectivity comparable to that of the commercial TiO2. The rare earth substituted compounds, Na2Mg2.5Ca0.5-xLnxZn2Si12O30, exhibited intense red (Eu3+), green (Tb3+) and blue (Tm3+) emissions. An optimal composition having all the three lanthanide ion substitutions resulted in white light emissions in Na2Mg2.5Ca0.48Tm0.01Tb0.02Eu0.01Zn2Si12O30. The presence of Co2+ in the Na2Mg3Co2Si12O30 compound facilitated the study of the oxygen evolution reaction (OER) with good values that are comparable to those of RuO2. The white compounds have reasonably good dielectric constant values with low dielectric loss, which indicates their possible use in communication devices. The milarite based compounds exhibited considerable potential towards new colored compounds, white light emission and OER properties. The present study suggests that it is profitable to explore mineral structures towards new and known material properties.

Two novel lanthanide mercury materials, [Gd(IA)3(H3O)2Hg3Br6]n·2nCl (1) and [La(IA)3(H3O)2Hg3Br6]n·2nCl (2) (IA = isonicotinic anion), have been prepared under solvothermal conditions and characterized by single-crystal X-ray diffraction techniques. They are isomorphic and characterized by a three-dimensional (3-D) framework structure. The lanthanide ions are bound by eight oxygen atoms to exhibit a square antiprismatic geometry. The solid-state photoluminescence experiment discovers that compound 1 shows a strong emission in the red region. Compound 1 possesses CIE (Commission Internationale de I'Éclairage) chromaticity coordinates of 0.7347 and 0.2653. Its CCT (correlated color temperature) is 6514 K. Compound 2 displays yellow photoluminescence and it has CIE chromaticity coordinates of 0.4411 and 0.5151. The CCT of compound 2 is 3633 K. Solid-state UV/Vis diffuse reflectance spectra revealed that their semiconductor band gaps are 2.16 eV and 2.85 eV, respectively.

Two new lanthanide mercury halide compounds with isonicotinic acid as a ligand, namely, [Gd(HIA)2(IA)(H2O)2(HgCl2)]n(nHgCl4)·3nH2O (1) (HIA = isonicotinic acid) and {[Nd(HIA)3(DMF)(H2O)]n}[(Hg4Br11)n](2HgBr2)(nBr)·nH3O·0.5nH2O (2) (DMF = N,N'-Dimethylformamide), were synthesized by means of solvothermal reactions and characterized by single-crystal X-ray diffraction. Compound 1 is characterized by a two-dimensional (2-D) layer-like structure, while compound 2 features a one-dimensional (1-D) chain-like structure. The lanthanide ions in both compounds are eight coordination and show a square antiprism geometry. The mercury ions exhibit various coordination motifs. Compound 1 shows a ultraviolet upconversion photoluminescence emission, while compound 2 displays red photoluminescence. The photoluminescence emissions come from the characteristic emissions of the 4f electron intrashell transitions of the 6P7/2 → 8S7/2 of the Gd3+ ions in compound 1 and the 4F9/2 → 4I9/2, 4F7/2 + 4S3/2→ 4I9/2, 4F5/2 + 2H9/2→ 4I9/2, 4F3/2 → 4I9/2 of the Nd3+ ions in compound 2. Compound 2 has CIE (Commission Internationale de I'Éclairage) chromaticity coordinates (0.7142, 0.2857) and its CCT (correlated color temperature) is 138224 K. Solid-state UV/Vis diffuse reflectance spectra discovered that their semiconductor band gaps are 3.12 eV and 3.23 eV, respectively.

This study presents a halide exchange mediated cation exchange reaction to co-dope d- and f-block elements in CsPbX3 NPs at room temperature. Addition of MnCl2 and YbCl3 to CsPbBr3 NPs induces ion exchange reactions generating the corresponding CsPbBr3/MnCl2YbCl3 NPs. In addition to the perovskite emission, the NPs display sensitized Mn2+ and Yb3+ emissions in concert spanning the UV, visible, and NIR spectral region. Structural and spectroscopic characterizations indicate a substitutional displacement of Pb2+ by the Mn2+ and Yb3+. The identity of the host halide in modulating the ion exchange reactions was also tested. An effective perovskite host NP is presented that can be used to incorporate d-f or f-f dopant combinations to realize a gamut of dopant emission lines. A charge trapping based photophysical model is developed that focuses on rational energy alignments to predict dopant emissions semi-empirically and aids the design of optimal perovskite host-multi-dopant combinations.

Due to the lack of effective synthetic strategies, the preparation of chemically stable chiral Ag(I) cluster-based materials for assembly remains challenging. Here, we have developed an approach to synthesize three pairs of chiral Ln-Ag(I) cluster-based metal-organic frameworks (MOFs) named l-LnAg5-3D (Ln = Gd for 1-L, Eu for 2-L, and Tb for 3-L) and d-LnAg5-3D (Ln = Gd for 1-D, Eu for 2-D, and Tb for 3-D) by employing a chiral Ag(I) cluster ({Ag5S6}) as the node and Ln3+ ion as the inorganic linker. Structural analysis revealed that the chiral ligands induced chirality through the entire structure, resulting in a chiral helix arrangement of the C3-symmetric chiral {Ag5S6} nodes and Ln3+ ions. These compounds showed high solvent stability in various polar organic solvents. The solid-state circular dichroism (CD) spectra of compounds l-LnAg5-3D and d-LnAg5-3D exhibited obvious mirror symmetrical peaks. The emission spectra in the solid state revealed that compound 1-L only exhibited the emission peak of {Ag5S6}, while compounds 2-L and 3-L exhibited overlapping peaks of Ln3+ and {Ag5S6} at different excitation wavelengths. This demonstrates the tunable photoluminescence from {Ag5S6} to Ln3+ by introducing different Ln3+ ions and manipulating the excitation wavelengths. The study underscores the enhanced stability of Ag(I) cluster-based MOFs achieved through the incorporation of Ln3+ ions and establishes chiral Ln-Ag(I) cluster-based MOFs as promising candidates for advanced materials with tunable photoluminescence.

The judicious selection and combination of multicomponents provide great potential for the further exploration of new polyoxometalate (POM) materials. Here, a delicate control on tungstate, SbIII and BiIII sources, Eu3+ ions, and organic molecules led to the discovery of a novel multimetal cluster-embedded POM [H2N(CH3)2]9Na8H5{[Eu4(H2O)6Sb4Bi2W2O12](SbW9O33)2(SbW8O31)2}·78H2O (1). The polyoxoanion of 1 was constructed from four in situ-formed [SbW8O31]11- and [SbW9O33]9- building blocks connected by two hexa-metallic [Eu2(H2O)3Sb2BiWO6]9+ clusters, to be a rare member of Sb- and Bi-coexisting POM. The most impressive characteristic of 1 is the intricate [Eu2(H2O)3Sb2BiWO6]9+ cluster linker, which contains a SbIII-BiIII coinserted [Sb2BiWO6]3+ core grasping one [Eu1(H2O)2]3+ cation and one [Eu2(H2O)]3+ cation on both sides through Sb-O-Eu and Bi-O-Eu bonds. Functionalized by luminescence centers of Eu3+ ions, 1 can emit intense emission in water and be capable of detecting the biomarker of carcinoids, 5-hydroxyindoleacetic acid (5-HIAA) with a low limit of detection of 0.43 μM, high selectivity, and excellent anti-interference, as well as fast response (12 s). The high detectability of 1 for 5-HIAA is relevant to the underlying dynamic quenching and energy-transfer mechanism. In urine conditions, remarkable recognition of 1 for 5-HIAA and satisfactory recoveries were achieved, indicative of the possibility of 1 in detecting 5-HIAA in a real environment. This work reveals the special clustering effect of SbIII and BiIII atoms in the assembly of neoteric POM species and also promotes the application of POMs as potential diagnostic tool in the early detection of carcinoids.

Multifunctional materials, which exhibit diverse physical properties, are candidates for the new generation of smart devices that realize many tasks simultaneously. Particular attention is given to single-phase multifunctional materials that offer the new physical effects induced by the coupling between introduced properties. Complexes of lanthanide(3+) ions are an attractive source of multifunctionality since they combine luminescent functionalities related to their f-f or d-f electronic transitions with magnetic anisotropy that originates from spin-orbit coupling and crystal-field effects. The resulting luminescent single-molecule magnets (SMMs) link the area of functional luminophores, applicable in light-emitting diodes or sensing, with the field of molecular magnets, applicable for high-density data storage, and offer additional advantages, e.g., fruitful magneto-optical correlations and the switching of emission by a magnetic field. It was recently shown that luminescent lanthanide SMMs can provide multifunctionality that is richly expanded towards their sensitivity to solvent exchange, temperature, or light, as well as the generation of electrical properties, such as super-ionic conductivity and ferroelectricity, or non-centrosymmetricity- and chirality-related effects, e.g., second-harmonic generation and circularly polarized luminescence. Here, we discuss the pioneering reports on multifunctional materials that use luminescent lanthanide SMMs, with the emphasis of our contribution relying on the functionalization of 4f metal complexes through their insertion into heterometallic d-f coordination compounds.

We designed four ternary lanthanide tris-(β-diketonate) complexes of the form [Ln(tta)3(tpy-HImzphen)], where Ln = LaIII, EuIII, SmIII and TbIII; tta = (2-theonyltrifluoroacetonate) and tpy-HImzphen = 2-(4-[2,2':6',2'']terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. All the complexes have been thoroughly characterized by standard analytical tools and spectroscopic techniques including single crystal X-ray diffraction. In situ generation of the complexes was also monitored via absorption and emission spectroscopy upon incremental addition of the respective lanthanide precursor {Ln(tta)3(H2O)2} to the dichloromethane solution of the terpyridyl-imidazole ligand. The photophysical behaviors of all the complexes were thoroughly investigated via absorption and both steady-state and time-resolved emission spectroscopic techniques. The emission spectral measurements were carried out at both room temperature and 77 K to understand the deactivation dynamics of the excited states and elucidate the distinctive luminescence responses from the four lanthanide metal ions owing to the introduction of the terpyridyl-based ancillary ligand.

The trigonal lanthanide complexes LnL (H3L = tris(((3-formyl-5-methylsalicylidene)amino)ethyl)amine) contain three pendant aldehyde groups and are known to react with primary amines. Reacting LnL (Ln = Yb, Lu) with 1-octadecylamine yields the novel aliphatic lanthanide complexes LnL18 (H3L18 = tris(((3-(1-octadecylimine)-5-methylsalicylidene)amino)ethyl)amine) where the three aldehyde groups are transformed to 1-octadecylimine groups. Herein the syntheses, structural characterisation and magnetic properties of LnL18 are presented. The crystal structure of YbL18 shows that the reaction of YbL with 1-octadecylamine leads to only very subtle perturbations in the first coordination sphere of Yb(III), with the Yb(III) ion retaining its heptacoordination and similar bond lengths and angles to the ligand. The three octadecyl chains in each complex were found to direct crystal packing into lipophilic arrays of van der Waals interaction-driven hydrocarbon stacking. The static magnetic properties of YbL18 were compared to those of the non-derivatised complex YbL. The energy level splitting of the 2F7/2 ground multiplet was found, by emission spectroscopy, to be very similar between the derivatised and non-derivatised complexes. A.c. magnetic susceptibility measurements on YbL18 and YbL diluted at 4.8% and 4.2% into the diamagnetic hosts LuL18 and LuL, respectively, revealed that the spin-lattice relaxation of both complexes is governed by a low temperature direct process and a high temperature Raman process. In the high temperature regime, the derivatised complex was also found to have faster spin-lattice relaxation, which is likely due to the increased number of phonons in the octadecyl chains.

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The novel ligand H3PC3PA was synthesized from pyclen and methyl-6-(bromomethyl)picolinate with 82% overall yield, and its rare-earth complexes (La, Eu, Gd, Tb, Lu, Y) were isolated and characterized by HR-MS and analytical HPLC. Solution 1H and 13C NMR studies of the diamagnetic [Lu(PC3PA)] and [Y(PC3PA)] chelates evidenced non-coordination of the picolinate moiety at the N6 position to the metal. The 1H NMR spectrum of [Lu(PC3PA)] showed diastereotopic CH2 signals corresponding to a single, rigid isomer in solution, while [Y(PC3PA)] displayed sharp signals at higher temperatures, and diffusion-ordered NMR spectroscopy (DOSY) confirmed a single monomer species. [Eu(PC3PA)] and [Tb(PC3PA)] in water showed broad absorption bands at 269 nm due to the picolinate chromophore. [Eu(PC3PA)] displays red emission with a splitting of the 7FJ manifold characteristic of a low-symmetry coordination environment, while [Tb(PC3PA)] shows typical 5D4-7FJ transitions of Tb3+. Emission lifetimes confirmed monohydration of both complexes, in accordance with a non-coordinating picolinate pendant. The relaxivity of [Gd(PC3PA)], r1p = 3.97 mM-1 s-1 (20 MHz, 298 K), is comparable to that of commercial MRI contrast agents. The dissociation half-life of [Gd(PC3PA)] (22 min at pH 1, 25 °C) is short in comparison to that of analogous complexes, evidencing that the non-coordinating picolinate accelerates proton-assisted dissociation.

The molecular symmetry in rare earth (RE) coordination chemistry is critically important for controlling the electronic structure of the RE ion and the resulting magnetic and photophysical properties. Here, we report a family of complexes with unusual C3-point symmetry: [REIII(Br4catH)3(tpa)] (Br4catH- = tetrabromocatecholate, tpa = tris(2-pyridylmethyl)amine). The synthesis and solid-state characterisation of eleven analogues (RE = Y, Sm to Lu) were performed, enabling a systematic investigation of the effect of symmetry on various physical properties across the RE series. The crystal structures reveal a unique cooperative coordination motif, featuring a cyclic hydrogen-bonding network between the atypical monodentate monoprotonated Br4catH- ligands. Electrochemical analysis reveals a single oxidation process that suggests a concerted three-electron oxidation of all tetrabromocatecholate ligands to semiquinonate. Furthermore, single-molecule magnet (SMM) behaviour was investigated, revealing unexpected in-field slow magnetic relaxation for both Dy and Yb analogues, which can be rationalised by the effect of C3-symmetry. Finally, luminescence measurements were performed to probe the CF splitting of the Yb analogue and quantify the error in the overall CF splitting predicted by ab initio calculations. The governing effects of C3-symmetry are consistent observations in all RE3+ metals studied in this work, manifesting in the concerted three-electron oxidation, SMM behaviour, ground state composition, and luminescence properties.

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The reaction of fluoride anions with mononuclear rare-earth(III) complexes of the hexaazamacrocycle derived from 2,6-diformylpyridine and ethylenediamine affords trinuclear coordination compounds [Ln3L3(μ2-F)4(NO3)2](NO3)3. The X-ray crystal structures of these complexes show triplex cationic complexes where the three roughly parallel macrocyclic lanthanide(III) units are linked by bis-μ2-F bridges. The detailed analysis of the photophysical properties of the [Eu3L3(μ2-F)4(NO3)2](NO3)3·2H2O and [Tb3L3(μ2-F)4(NO3)2](NO3)3·3H2O complexes reveals different temperature dependence of luminescence intensity and luminescence decay time of the Eu(III) and Tb(III) derivatives. The spectra of mixed species of average composition [Eu1.5Tb1.5L3(μ2-F)4(NO3)2](NO3)3·3H2O are in accordance with the ratiometric luminescent thermometer behavior. Measurements of the direct-current (dc) magnetic susceptibility of the [Dy3L3(μ2-F)4(NO3)2](NO3)3·2H2O complex indicate possible ferromagnetic interactions between the Dy(III) ions. Alternating current (ac) susceptibility measurements of this complex indicate single-molecule magnet behavior in zero dc field with magnetic relaxation dominated by Orbach mechanism and an effective energy barrier Ueff = 12.3 cm–1 (17.7 K) with a pre-exponential relaxation time, τ0 of 7.3 × 10–6 s. A similar reaction of mononuclear macrocyclic complexes with a higher number of fluoride equivalents results in polymeric {[Ln3L3(μ2-F)5](NO3)4}n complexes. The X-ray crystal structure of the Nd(III) derivative of this type shows trinuclear units that are additionally linked by single fluoride bridges to form a linear coordination polymer.

CuLaO2 is a rare-earth and dopant-free inorganic compound able to emit green light upon blue excitation. Its absorption amounts to 90% but its internal quantum efficiency is poor (<17%). The origin of this deleterious radiationless behavior is addressed by investigating the spectroscopic properties of this compound under the action of temperature and hydrostatic pressure in the 15-400 K and 1 bar-40 kbar intervals, and by combining the spectroscopic data with earlier results of DFT calculations. A two-step radiationless process is demonstrated, involving radiative re-absorption and cross-over to excitonic states.

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With the developing need for luminous materials with better performance, lanthanide-doped nanocrystals have been widely studied for their unique luminescence properties such as their narrow bandwidth emission, excellent chemical stability, and photostability, adjustable emission color, high signal-to-background ratio, deeper tissue penetration with less photo-damage, and low toxicity, etc., which triggered enthusiasm for research on the broad applications of lanthanide-doped nanocrystals in bioimaging, anti-counterfeiting, biosensing, and cancer diagnosis and treatment. Considerable progress has been made in the past few decades, but low upconversion luminescence efficiency has been a hindrance in achieving further progress. It is necessary to summarize the recently relevant literature and find solutions to improve the efficiency. The latest experimental and theoretical studies related to the deliberate design of rare earth luminescent nanocrystals have, however, shown the development of metal ion-doped approaches to enhance the luminescent intensity. Host lattice manipulation can enhance the luminescence through increasing the asymmetry, which improves the probability of electric dipole transition; and the energy transfer modulation offers a reduced cross-relaxation pathway to improve the efficiency of the energy transfer. Based on the mechanisms of host lattice manipulation and energy transfer modulation, a wide range of enhancements at all wavelengths or even within a particular wavelength have been accomplished with an enhancement of up to a hundred times. In this mini review, we present the strategy of metal ion-doped lanthanide nanocrystals to cope with the issue of enhancing luminescence, overview the advantages and tricky challenges in boosting the luminescence, and provide a potential trend of future study in this field.

Herein, hexaazamacrocyclic ligand LN6 was employed to construct a series of photochromic rare-earth complexes, [Ln(LN6)(NO3)2](BPh4) [1-Ln, Ln = Dy, Tb, Eu, Gd, Y; LN6 = (3E,5E,10E,12E)-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane-3,5,10,12-tetraene]. The behavior of photogenerated radicals of hexaazamacrocyclic ligands was revealed for the first time. Upon 365 nm light irradiation, complexes 1-Ln exhibit photochromic behavior induced by photogenerated radicals according to EPR and UV-vis analyses. Static and dynamic magnetic studies of 1-Dy and irradiated product 1-Dy* indicate weak ferromagnetic interactions among DyIII ions and photogenerated LN6 radicals, as well as slow magnetization relaxation behavior under a 2 kOe applied field. Further fitting analyses show that the magnetization relaxation in 1-Dy* is markedly different from 1-Dy. Time-dependent fluorescence measurements reveal the characteristic luminescence quenching dynamics of lanthanide in the photochromic process. Especially for irradiated product 1-Eu*, the luminescence is almost completely quenched within 5 min with a quenching efficiency of 98.4%. The results reported here provide a prospect for the design of radical-induced photochromic lanthanide single-molecule magnets and will promote the further development of multiresponsive photomagnetic materials.

Inorganic phosphates doped with rare-earth and transition-metal ions are of great interest due to their tunable optical properties and potential in white-light-emitting applications. In this study, Ca₈MgLa(PO₄)₇ phosphors co-doped with Eu2+ and Mn2+ ions were synthesized via the solid-state reaction method and comprehensively characterized by structural and spectroscopic techniques. Phase-pure samples with different activator ratios were analyzed to elucidate the correlation between composition, local coordination environment, and photoluminescence behavior. Detailed temperature-dependent emission studies revealed pronounced spectral evolution associated with thermally activated redistribution of Eu2+ emission among crystallographically distinct sites, as well as with host lattice expansion. The observed changes are discussed in terms of energy transfer and electron-phonon coupling mechanisms responsible for broadband emission and thermal quenching. To evaluate the application potential, the compound was mixed with a relevant polymer to produce a composite, which was then characterized spectrally. Additionally, a simulation of its performance under industrial conditions was carried out. Results showed that after 2000 h of aging tests, the quantum efficiency of Ca8MgLa(PO4)7:1 %Eu2+:10 %Mn2+ remained stable, with a 10 % increase in luminescence intensity.

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Objectives. The work set out to summarize the results of the studies of aluminum oxynitrides (AlONs) doped with rare earth (REM) and transition metals (TM) and to highlight the main effects of REM and TM dopants on the formation, phase composition, and optical properties of the AlON.Results. The presented analysis of the literature data includes the results of our own studies of the AlON doped with REM and TM ions. The influence of REM and TM additives on the formation of AlON and its phase com position, as well as optical properties, was considered.Conclusions. It is clearly shown that the doping with REM and TM ions enhances the formation of pure AlON phase via high-temperature synthesis from oxide and nitride. The oxynitride matrix exhibits reducing properties with respect to both REM and TM. Doping with the REM ions leads to the emergence of luminescent properties in the visible range, while doping with TM ions affects the band gap in AlON as a semiconductor. The solubility limits of all metals in the AlON matrix do not exceed 1–2 at. % vs Al. Concentration quenching of luminescence is observed at REM contents from 0.1 to 0.5 at. %.

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A terbium-doped yttrium-based metal-organic framework, [Tb0.2Y0.8(FDA)(Ox)0.5(H2O)2]·H2O, 1 {where H2FDA = furan-2,5-dicarboxylic acid and Ox = oxalate}, was successfully synthesized using the hydrothermal technique as a phosphor material along with a large Stokes shift and low self-quenching of luminescence for the rapid visible detection of toxic anions in an aqueous medium. To confirm the structure and phase purity of compound 1, single crystals of the isomorphous pure yttrium-based compound [Y(FDA)(Ox)0.5(H2O)2]·H2O, 1a, were synthesized under similar experimental conditions. The single crystal X-ray data of compound 1a confirmed the three-dimensional metal-organic framework formed by the connectivity of the Y3+ ion with furan-2,5-dicarboxylate and the oxalate moiety. The phase purity of compounds 1 and 1a was confirmed by powder X-ray diffraction. Compound 1 was systematically characterized via TGA, SEM and EDX elemental mapping analysis. The aqueous dispersion of compound 1 showed highly intense visible green emission upon excitation at 265 nm. The emissions of compound 1 were utilized for the luminescence-based visible detection of toxic anions in the aqueous medium through luminescence quenching. The observed limit of detection (LOD) was 1.1 nM, 2.2 nM and 6.5 nM for chromate (CrO42-), permanganate (MnO4-) and phosphates (PO43-, H2PO4- and HPO42-), respectively, and the observed KSV values were superior to those of all other metal-organic frameworks previously reported. More importantly, the LODs are significantly lower than the level recommended for these anions towards human life.

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The principles of the design of responsive luminescent probes and sensors based on lanthanide emission are summarised, based on a mechanistic understanding of their mode of action. Competing kinetic pathways for deactivation of the excited states that occur are described, highlighting the need to consider each of the salient quenching processes. Such an analysis dictates the choice of both the ligand and its integral sensitising moiety for the particular application. The key aspects of quenching involving electron transfer and vibrational and electronic energy transfer are highlighted and exemplified. Responsive systems for pH, pM, pX and pO2 and selected biochemical analytes are distinguished, according to the nature of the optical signal observed. Signal changes include both simple and ratiometric intensity measurements, emission lifetime variations and the unique features associated with the observation of circularly polarised luminescence (CPL) for chiral systems. A classification of responsive lanthanide probes is introduced. Examples of the operation of probes for reactive oxygen species, citrate, bicarbonate, α1-AGP and pH are used to illustrate reversible and irreversible transformations of the ligand constitution, as well as the reversible changes to the metal primary and secondary coordination sphere that sensitively perturb the ligand field. Finally, systems that function by modulation of dynamic quenching of the ligand or metal excited states are described, including real time observation of endosomal acidification in living cells, rapid urate analysis in serum, accurate temperature assessment in confined compartments and high throughput screening of drug binding to G-protein coupled receptors.

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Proteins with hetero-bimetallic metal centers can catalyze important reactions and are challenging to design. Azurin is a mononuclear copper center that has been extensively studied for electron transfer. Here we inserted the lanthanide binding tag (LBT), which binds lanthanide with sub μM affinity, into the copper binding loop of azurin, while keeping the type 1 copper center unperturbed. The resulting protein, Az-LBT, which has two metal bonding centers, shows strong luminescence upon coordination with Tb3+ and luminescence quenching upon Cu2+ binding. The in vitro luminescence quenching has high metal specificity and a limit-of-detection of 0.65 μM for Cu2+. With the low background from lanthanide's long luminescence lifetime, bacterial cells expressing Az-LBT in the periplasm also shows sensitivity for metal sensing.

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The study of optical transitions in lanthanide(III) ions has evolved separately from molecular photophysics, but the framework still applies to these forbidden transitions. In this study, a detailed photophysical characterization of the [Tb(H2O)9]3+ aqua ion was performed. The luminescence quantum yield (Φlum), excited state lifetime (τobs), radiative (kr ≡ A) and nonradiative (knr) rate constants, and oscillator strength (f) were determined for Tb(CF3SO3)3 in H2O/D2O mixtures in order to map the radiative and nonradiative transition probabilities. It was shown that the intense luminescence observed from Tb3+ compared to other Ln3+ ions is not due to a higher transition probability of emission but rather due to a lack of quenching, quantified by quenching to O-H oscillators in the aqua ion of kq(OH) = 2090 s-1 for terbium and kq(OH) = 8840 s-1 for europium. In addition, the Horrocks method of determining inner-sphere solvent molecules has been revisited, and it was concluded that the Tb3+ is 9-coordinated in aqueous solution.

The upconversion of manganese (Mn2+) exhibits a green light output with a much longer lifetime than that of lanthanide ions, showing great potential in the frontier applications like information security and anti-counterfeiting. Mn2+ can be activated by energy migration upconversion. However, there exists serious quenching interactions between Mn2+ and the lanthanides at the core-shell interfacial area, which would markedly reduce the role of Tm3+ as a ladder to facilitate the up-transition and subsequently limit the upconversion of Mn2+. Here, we propose a mechanistic strategy to enhance the upconversion luminescence of Mn2+ by spatial control of energy migration among Gd sublattice through introducing an additional migratory NaGdF4 interlayer within the commonly used core-shell nanostructure. This design can not only isolate the interfacial quenching interactions between the sensitized core and luminescent shell, but also allow an efficient channel for energy transport, resulting in enhanced upconversion of Mn2+. Moreover, the relatively long lifetime of Mn2+ (around 32.861 ms) provides new possibilities to utilize the temporal characteristic for the frontier application of multi-level anti-counterfeiting through combining the time-gating technology.

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Designing luminescence lifetime sensor in the second near-infrared (NIR-II) window is a great challenge due to the difficult structural construction. Here, we report a tumor redox responsive and easy synthesized material, amorphous manganese oxide (MnO x ) with indirect bandgap of 1.02 eV as energy acceptor to build a luminescence resonance energy transfer (LRET) toolbox for universally regulating NIR-I to NIR-II luminescence lifetimes of lanthanide nanoparticles, in which energy transfer is based on matched energy gap instead of conventional overlapped spectra. We further utilize Yb 3+ doped YbNP@MnO x as NIR-II luminescence lifetime sensor to realize in vitro quantitative redox visualization with relative errors under 5% after mouse skin coverage. Furthermore, HepG2 cells and tumors with high redox state have been accurately distinguished by NIR-II luminescence lifetime imaging. The quantified intracellular and intratumoral glutathione (GSH) levels are highly consistent with the commercial kit results, illustrating the reliable redox visualization ability under bio-tissue.

Luminescence lifetime is a crucial parameter in photophysical studies that bears essential physical and chemical information and that is used to quantify a variety of phenomena, from the determination of quenching mechanisms to temperature sensing and bioimaging. The current perception of lifetime measurement is that it is a trivial and fast experiment. However, despite this apparent simplicity, measuring luminescence decay and fitting the obtained data to a suitable model can be far more intricate. In this perspective, the influence of experimental parameters and fitting procedures on the determination of lifetimes are investigated and, through carefully chosen examples, it is shown that large variations, up to 10%, can be induced by varying parameters such as the data acquisition time, the baseline evaluation, or the mathematical fitting model. In order to present to a wider audience, detailed mathematical descriptions are kept out of the manuscript.

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Developing robust oxygen evolution reaction (OER) catalysts for proton exchange membrane water electrolysis (PEMWE) demands concurrent mitigation of insufficient activity and structural instability in acidic media. Herein, we propose a spin-state engineering strategy enabled by rare-earth doping to resolve the intrinsic activity-stability trade-off dilemma. Incorporation of rare-earth cations (Sm3+, Nd3+, Ho3+) into MnCo2O4.5 enhances Co-O covalency and 4f-3d coupling, increasing the crystal-field splitting and driving the Co sublattice from a purely high-spin Co2+/Mn4+ toward a mixed-spin Co3+/Mn4+configuration, within which the intermediate-spin Co3+ state can stably exist. This spin-state modulation occurs alongside lattice distortion and oxygen-vacancy formation, which together reinforce the spinel framework and mitigate excessive Co overoxidation. The coupled electronic-structural effects lower the adsorption energy barrier, thereby alleviating structural reconstruction. The optimized Sm-MnCo2O4.5 catalyst exhibits a low overpotential of 212 mV at 10 mA cm-2 and sustains operation for 1200 h. When integrated into a PEM electrolyzer, it delivers 0.5 A cm-2 at 1.73 V for over 300 h. This work establishes rare-earth-mediated spin-state modulation as a fundamental design principle for sustainable non-noble-metal acidic OER catalysts.

In quantum information processing, the implementation of qudits─multilevel qubits where d is the number of levels─has been a major challenge that, if resolved, could lead to the acceleration of certain computational tasks. Spin transport measurements demonstrate that tris(phthalocyaninato)-dinuclear rare-earth(III) molecules offer a promising platform for nuclear spin qudits with an increased Hilbert space. However, the absence of radicals in these systems has so far hindered studies on the coupling between lanthanide ions and conduction electrons. In this study, we report the synthesis of (phthalocyaninato)bis(porphyrinato)-dinuclear rare-earth(III) complexes functionalized with thiomethyl groups. The tailored oxidation of the neutral complexes facilitated their conversion to air-stable radicals. CASSCF calculations and static magnetic measurements revealed a radical-lanthanide exchange coupling constant of JLn-Rad = -0.45 cm-1. Dynamic magnetic measurements demonstrated a shift in the magnetic properties due to exchange interaction, namely from field-induced single-molecule magnets (SMMs) to zero-field SMMs. The findings of this study, along with the strong bonding affinity of thiomethyl groups to gold electrodes, highlight the potential of these molecules as novel materials for the implementation of nuclear spin qudits with an increased Hilbert space.

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Magneto-optical coupling provides a powerful alternative to crystal field engineering for modulating Mn2+ luminescence. However, precise control over Mn–Mn coupling is hindered by the complex spin-electron super-exchange interactions. Herein, we report a symmetry-broken Mn(II) chloride dimer, (C10H20O5Mn)(CH3CN)MnCl4, synthesized through a crown-ether-assisted supramolecular strategy. The dimer features a 7-coordinated pentagonal bipyramid and a 4-coordinated tetrahedron linked by a distorted Mn–Cl–Mn bridge (129°), which promotes rare spin-canted Mn–Mn coupling and creates a novel Mn–Mn luminescent center. This center exhibits a red emission at 638 nm with an unusually short lifetime of 0.42 ms, which is attributed to the relaxation of spin-forbidden d–d transitions. Notably, the emission undergoes a 30 nm blue-shift upon heating (5–305 K) due to the thermal suppression of spin-canting, and a 40 nm blue-shift under applied pressure (0–20 MPa) resulting from reduced orbital overlap. This dual-responsive luminescence originates from spin-canted weak ferromagnetism, which induces a rearrangement of energy-levels by separating antibonding orbitals. Using this effect, we have demonstrated an optical manometer for real-time underwater depth sensing. These findings highlight spin-canted Mn(II) dimers as a promising platform for stimuli-responsive luminescence and reveal a new mechanism for d–d transition modulation. A symmetry-broken Mn(II) dimer enables the dual-stimuli-responsive luminescence through spin-canted Mn‒Mn coupling, providing a new mechanism for modulating d-d transitions and serving an optical manometer for sensing.

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All inorganic lead halide perovskite (CsPbX3) has become a hot topic in chiral optics for its high quantum yield and tunable luminescence. The environmental degradation tendency and lack of magneto-optical coupling mechanism of lead-based perovskite severely restrict its chirality integrated application. Rare-earth ions (such as Gd3+, Eu3+), with their unique 4f electronic configuration, not only passivate the lattice defects to improve stability but also expand the spectral response range through electronic localization effects. In this study, we proposed a strategy to introduce magneto-optical active rare-earth ions (Gd3+, Eu3+) into the CsPbX3 lattice to form nanosheets (NSs), and oriented assembled into large scale chiral films with tailorable chiroptical activity ranging from 300 to 700 nm and achieved tailoring a multicolor circularly polarized luminescence (CPL) system with angle dependent polarization switching characteristics. Chiral Gd3+:CsPbBr3 NSs films and chiral Eu3+:CsPb(Br/Cl)3 NSs films exhibited significantly increased luminescence asymmetry factor of |glum| up to 10-2 and also displayed enhanced magnetic circular dichroism (MCD) responses. We further developed an optical encryption system based on multidimensional regulation of components/polarization/wavelength, enabling dynamic programmable information storage and providing a new material platform for spin photon devices, quantum communication, and high-end anti-counterfeiting technology.

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Here, we report the synthesis of two new sets of dibismuth-bridged rare earth molecules. The first series contains a bridging diamagnetic Bi22– anion, (Cp*2RE)2(μ-η2:η2-Bi2), 1-RE (where Cp* = pentamethylcyclopentadienyl; RE = Gd (1-Gd), Tb (1-Tb), Dy (1-Dy), Y (1-Y)), while the second series comprises the first Bi23– radical-containing complexes for any d- or f-block metal ions, [K(crypt-222)][(Cp*2RE)2(μ-η2:η2-Bi2•)]·2THF (2-RE, RE = Gd (2-Gd), Tb (2-Tb), Dy (2-Dy), Y (2-Y); crypt-222 = 2.2.2-cryptand), which were obtained from one-electron reduction of 1-RE with KC8. The Bi23– radical-bridged terbium and dysprosium congeners, 2-Tb and 2-Dy, are single-molecule magnets with magnetic hysteresis. We investigate the nature of the unprecedented lanthanide–bismuth and bismuth–bismuth bonding and their roles in magnetic communication between paramagnetic metal centers, through single-crystal X-ray diffraction, ultraviolet–visible/near-infrared (UV–vis/NIR) spectroscopy, SQUID magnetometry, DFT and multiconfigurational ab initio calculations. We find a πz* ground SOMO for Bi23–, which has isotropic spin–spin exchange coupling with neighboring metal ions of ca. −20 cm–1; however, the exchange coupling is strongly augmented by orbitally dependent terms in the anisotropic cases of 2-Tb and 2-Dy. As the first examples of p-block radicals beneath the second row bridging any metal ions, these studies have important ramifications for single-molecule magnetism, main group element, rare earth metal, and coordination chemistry at large.

We report the first inverse-sandwich complexes containing rare earth (REIII) metal ions that captured a toluene dianion between them. Toluene-bridged complexes [{(Me3Si)2NC(NiPr)2}2RE]2(μ-η6:η6-C6H5Me) (RE = Y (1), Dy (2), and Er (3)) were synthesized via chemical reductions of chloride-bridged RE complexes in which each tripositive metal is stabilized by two guanidinate ligands. Compounds 1–3 were unambiguously characterized by crystallography, NMR, UV–vis, and IR spectroscopy, magnetometry, and computations. The bond metrics from single-crystal X-ray diffraction analysis revealed a planar, cyclohexadienediide-like structure for the ligated arene, indicative of a dianionic toluene. The 1H NMR spectrum of 1 exhibits upfield-shifted resonances representing increased shielding from excess electrons, further validating its dianionic nature. DFT calculations afforded similar bond metrics, and natural bond orbital (NBO) analysis uncovered ionic bonding interactions between the bridging toluene and the yttrium centers, supporting the assignment of a −2 charge to the toluene. UV–vis spectroscopy highlighted that the electronic excitations primarily stem from toluene- and guanidinate-based orbitals. The Dy and Er congeners were further probed by SQUID magnetometry, with 3 revealing weak magnetic exchange coupling between the ErIII centers. These findings highlight the ability of reduced arenes to serve as bridging ligands in multimetallic rare earth architectures.

Temperature-sensitive luminescent materials have aroused great interest for practical applications in optical sensors. Layered rare-earth hydroxides (LRHs) possess rich interlayer chemistry and adjustable composition; thus, they are the promising candidates for designing functional materials, usually through an ion exchange process. Herein, the intercalation of neutral TbIII complex rather than ion exchange was successfully performed in situ into the gallery of Y/Eu binary LRHs by using a hydrothermal process. Interestingly, the swollen LRHs are chameleon luminophores, exhibiting color emissions from green to pink that were tunable through variations in temperature ranging from 77 to 450 K. Because of the highly sensitive and temperature-dependent emissions, novel optical temperature sensors for 1D and 2D thermal imaging were fabricated by employing the chameleon luminophores, which displayed luminescence capable of reversibly undergoing repeated thermocycles. The present work opens up new fields in layered inorganic materials.

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Molecular lanthanide phosphonates [Ln2 (H3 tpmm)2 (H2 O)6 ] ⋅ xH2 O (Ln=Eu, EuP; Ln=Tb, TbP) were synthesized. Single-crystal X-ray diffraction confirmed that EuP has a sandwich-like dinuclear structure, in which the Eu(III) center adopts a {EuO8 } distorted dodecahedral geometry. XRPD patterns prove that TbP and EuP are isomorphous and isostructural. EuP and TbP are highly thermally stable approaching 450 °C and exhibit red- and green-light emissions from the characteristic 4 f-4 f transition of the Eu3+ and Tb3+ , respectively. Interestingly, luminescence modulation is achieved for the chemically mixed Eu/Tb phosphonate analogues, c-Eux Tb2 -x P (x=1.5, 1, 0.5), and physically mixed Eu/Tb phosphonate materials, p-yEuP : zTbP (y : z=3 : 1, 1 : 1, 1 : 3), with varying the excitation wavelength. Of particular note, near-white-light emission is also achieved for c-EuTbP, p-EuP : TbP, and p-EuP : 3TbP when excited at 365 nm. Therefore, these dinuclear molecular lanthanide phosphonates emitting excitation wavelength and Eu3+  : Tb3+ ratio dependent luminescence might be potential candidates for color-tunable luminescence materials and white-light-emitting materials. On the other hand, the bright green-light emission makes TbP to be an excellent reusable luminescence sensor for selective detection of Fe3+ with Stern-Volmer quenching constant (KSV ) of 9.66×103  M-1 and detection limit (DL) of 0.42 μM through absorption competition caused luminescence quenching effect.

The development of novel rare earth fluorescent materials and the exploration of their applications have consistently been focal points of research in the fields of materials science and chemistry. In this work, a novel rare earth composite material with good photo-fluorescence properties and self-supporting has been prepared via a simple ultrasonic solvent reaction method. Initially, the Phen moieties is immobilized onto the surface of a self-supporting fiberglass paper using ICPTES, followed by the coordination of Eu(TTA)3 moieties with Phen moieties through a convenient ultrasonic solvent reaction. The resulting GF–Phen–Eu(TTA)3 has been characterized using FTIR, UV-Vis DRS, fluorescence measurements, and so on. The results indicate that the composite material exhibits strong fluorescent emission and presents a vivid red color under ultraviolet light. Further research has shown that the fluorescence of GF–Phen–Eu(TTA)3 strips demonstrated a pronounced quenching effect in response to some transition metal ions (1 mM). Hence, the rare earth composite materials presented here can be utilized not only for the production of optical materials, but also for the development of fluorescence sensing strips.

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Solvothermal reaction of 5,5'-(pyridine-2,6-diylbis(oxy))diisophthalic acid (H4L) with europium(III) or terbium(III) nitrates in acetonitrile-water (1:1) at 120 °C gave rise to isostructural 2D coordination polymers, [Ln(HL)(H2O)3]∞ (NIIC-1-Eu and NIIC-1-Tb), the layers of which are composed by eight-coordinated lanthanide(III) ions interconnected by triply deprotonated ligands HL3-. The layers are packed in the crystal without any specific intermolecular interactions between them, allowing the facile preparation of stable water suspensions, in which NIIC-1-Tb exhibited top-performing sensing properties through luminescence quenching effect with exceptionally low detection limits towards Fe3+ (LOD 8.62 nM), ofloxacin (OFX) antibiotic (LOD 3.91 nM) and cotton phytotoxicant gossypol (LOD 2.27 nM). In addition to low detection limit and high selectivity, NIIC-1-Tb features fast sensing response (within 60-90 seconds), making it superior to other MOF-based sensors for metal cations and organic toxicants. The photoluminescence quantum yield of NIIC-1-Tb was 93%, one of the highest among lanthanide MOFs. Mixed-metal coordination polymers NIIC-1-EuxTb1-x demonstrated efficient photoluminescence, the color of which could be modulated by the excitation wavelength and time delay for emission monitoring (within 1 millisecond). Furthermore, an original 2D QR-coding scheme was designed for anti-counterfeiting labeling of goods based on unique and tunable emission spectra of NIIC-1-Ln coordination polymers.

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A dual-emissive optical material as a ratiometric fluorescent probe has been demonstrated to be remarkably superior in precise and quantitative analyses. Herein, a novel dual-emissive fluorescent probe Eu-BDC-OH was designed and successfully synthesized using Eu3+ and 2-hydroxyterephthalic acid (H2BDC-OH) at room temperature. Eu-BDC-OH has a three-dimensional interpenetrating network structure with a large number of exposed hydroxyl functional groups, providing abundant active sites for molecular recognition. In particular, the as-obtained Eu-BDC-OH serves as a unique fluorescent probe, and the double emission peaks of both the ligand and Eu3+ are completely quenched by Fe3+. However, it is worth noting that the dual emissions of Eu-BDC-OH enable the ratiometric detection of Fe2+, which leads to an increase in ligand emission and a decrease in Eu3+ emission, accompanied by a distinct red to blue color transition. The relative fluorescence intensity ratio (I618 nm/I433 nm) decreased linearly with increasing Fe2+ concentration in the 0-50 μM range with a superior detection limit of 0.32 μM. In this work, a fluorescent probe based on a MOF was developed for the recognition of Fe2+ and Fe3+, providing a promising strategy for the synthesis of novel dual-emission materials by integrating suitable luminescent ligands with lanthanide metal ions.

We report a detailed study of the photophysical properties of EuIII and TbIII complexes with two ligands based on a 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane platform containing either four pyridine-2yl-methyl (L1) or four hydroxyethyl (L2) pendant arms. The [TbL1]3+ and [TbL2]3+ complexes present moderate luminescence quantum yields upon excitation through the ligand bands (φH2O = 7.4 and 21%, respectively). The [EuL2]3+ complex displays a relatively low quantum yield in H2O (φH2O = 1.6%) that increases considerably in D2O (φD2O = 5.3%), which highlights the strong quenching effect of the four ligand O-H oscillators. The emission spectrum of [EuL1]3+ is rather unusual in that it shows a relatively high intensity of the 5D0 → 7F5,6 transitions, which appears to be also related to the distorted D4d symmetry of the coordination polyhedron. Surprisingly, the quantum yield of the [EuL1]3+ complex is very low (φH2O = 0.10%), considering the good protection of the EuIII coordination environment offered by the ligand. Cyclic voltammograms recorded from aqueous solutions of [EuL1]3+ display a reversible curve with a half-wave potential of -620 mV (versus Ag/AgCl), while [EuL2]3+ presents a reduction peak at more negative potential (-1040 mV). Thus, the L1 ligand provides a rather good stabilisation of divalent Eu compared to the L2 analogue, suggesting that the presence of a low-lying ligand-to-metal charge-transfer (LMCT) state might be responsible for the low quantum yield determined for [EuL1]3+. A density functional theory (DFT) study provides very similar energies for the ligand-centered excited singlet (1ππ*) and triplet (3ππ*) states of [EuL1]3+ and [EuL2]3+. The energy of the 9LMCT state of [EuL1]3+ was estimated to be 20 760 cm-1 by using all-electron relativistic calculations based on the DKH2 approach, a value that decreases to 15 940 cm-1 upon geometry relaxation.

Two lanthanide–glutarate coordination polymers, viz. : {[Eu(C5H6O4)(H2O)4]Cl}n, (1) and [Tb(C5H7O4)(C5H6O4)(H2O)2]n, (2) have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and X-ray crystallography. In 1, the Eu(III) ions are coordinated by four O atoms from two bidentate chelating carboxylate groups, one O atom from a bridging carboxylate group and four O atoms from water molecules adopting an EuO9 distorted tri-capped trigonal prismatic coordination geometry. In 2, the Tb(III) ions are coordinated by six O atoms from three bidentate chelating carboxylates, one O atom from a bridging carboxylate and two O atoms from water molecules to generate distorted tri-capped trigonal prismatic TbO9 polyhedron. In both compounds, the metal polyhedra share edges, producing centrosymmetric Ln2O2 diamonds, and are linked into [001] chains by bridging glutarate di-anions. The crystal structures are consolidated by O–H···O and O–H···Cl hydrogen bonds in 1, and O–H···O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the 5D0 → 7FJ (J = 1–4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the 5D4 → 7FJ (J = 0–6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe3+ ions due to luminescence quenching compared with other metal ions, which include; Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+. Compounds 1 and 2 also show high luminescence quenching sensitivity for 4-nitrophenol over the other aromatic and nitroaromatic compounds, namely; bromobenzene, 1,3-dimethylbenzene, nitrobenzene, 4-nitrotolune, 4-nitrophenol, 2,6-dinitrophenol and 2,4,6-trinitrophenol.

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The maximum permissible concentration (m.p.c.) of Cu2+ ions in drinking water, as set by the World Health Organization (WHO) is m.p.c. (Cu2+)WHO = 30 μM, whereas the US Environmental Protection Agency (EPA) establishes a more restrictive value of m.p.c. (Cu2+)EPA = 20 μM. Herein, we develop-for the first time ever-a family of m.p.c. (Cu2+) "visual" pass/fail sensors based on water-soluble lanthanide-containing single-chain nanoparticles (SCNPs) exhibiting an average hydrodynamic diameter less than 10 nm. Both europium (Eu)- and terbium (Tb)-based SCNPs allow excessive Cu2+ to be readily detected in water, as indicated by the red-to-transparent and green-to-transparent changes, respectively, under ultra-violet (UV) light irradiation, occurring at 30 μM Cu2+ in both cases. Complementary, dysprosium (Dy)-based SCNPs show a yellow color-to-transparent transition under UV light irradiation at approximately 15 μM Cu2+. Eu-, Tb- and Dy-containing SCNPs prove to be selective for Cu2+ ions as they do not respond against other metal ions, such as Fe2+, Ag+, Co2+, Ba2+, Ni2+, Hg2+, Pb2+, Zn2+, Fe3+, Ca2+, Mn2+, Mg2+ or Cr3+. These new m.p.c. (Cu2+) "visual" pass/fail sensors are thoroughly characterized by a combination of techniques, including size exclusion chromatography, dynamic light scattering, inductively coupled plasma-mass spectrometry, as well as infrared, UV and fluorescence spectroscopy. This article is protected by copyright. All rights reserved.

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The luminescent coarse-, micro- and nanocrystalline europium(III) terephthalate tetrahydrate (Eu2bdc3·4H2O) metal-organic frameworks were synthesized by the ultrasound-assisted wet-chemical method. Electron micrographs show that the europium(III) terephthalate microparticles are 7 μm long leaf-like plates. According to the dynamic light scattering technique, the average size of the Eu2bdc3·4H2O nanoparticles is equal to about 8 ± 2 nm. Thereby, the reported Eu2bdc3·4H2O nanoparticles are the smallest nanosized rare-earth-based MOF crystals, to the best of our knowledge. The synthesized materials demonstrate red emission due to the 5D0–7FJ transitions of Eu3+ upon 250 nm excitation into 1ππ* state of the terephthalate ion. Size reduction results in broadened emission bands, an increase in the non-radiative rate constants and a decrease in both the quantum efficiency of the 5D0 level and Eu3+ and the luminescence quantum yields. Cu2+, Cr3+, and Fe3+ ions efficiently and selectively quench the luminescence of nanocrystalline europium(III) terephthalate, which makes it a prospective material for luminescent probes to monitor these ions in waste and drinking water.

Fluorescence Correlation Spectroscopy (FCS) has been extensively used to measure equilibrium binding constants (K) or association and dissociation rates in many reversible chemical reactions across chemistry and biology. For the majority of investigated reactions, the binding constant was on the order of ~100 M^(-1), with dissociation constants faster or equal to 103 s^(-1), which ensured that enough association/dissociation events occur during the typical diffusion-determined transition time of molecules through the FCS detection volume. However, complexation reactions involving metal ions and chelating ligands exhibit equilibrium constants exceeding 104 M^(-1). In the present paper, we explore the applicability of FCS for measuring reaction rates of such complexation reactions, and apply it to binding of iron, europium and uranyl ions to a fluorescent chelating ligand, calcein. For this purpose we exploit the fact that the ligand fluorescence becomes strongly quenched after binding a metal ion, which results in strong intensity fluctuations that lead to a partial correlation decay in FCS. We also present measurements for the strongly radioactive ions of 241Am3+, where the extreme sensitivity of FCS allows us to work with sample concentrations and volumes that exhibit close to negligible radioactivity levels. A general discussion of the applicability of FCS to the investigation of metal-ligand binding reactions concludes our paper.

Aerogels hold great promise as the lightweight replacement in materials fields. Dynamic fluorochromic aerogels that possess reversible stimuli-responsiveness are particularly attractive recently for the new design opportunities in practical solid-state lighting and wide applications in advanced sensors/probe. In this study, we report a reversibly multi-responsive white-light emitting (WLE) aerogel prepared with co-doped lanthanide, thymidine and carbon dots. By precisely modulating the stoichiometric ratio of lanthanide complexes and carbon dots, broad-spectrum output from purple to red is obtained, including pure white light (CIE (0.33, 0.32)). Freeze-drying process contributes to the elimination of hydration between water molecules and lanthanide ions, further preventing the quenching of lanthanide luminescence and preserving the high quantum yield (47.4%) of our aerogel. Moreover, the dynamic coordination bond between lanthanide (europium and terbium) and thymidine endows aerogel with reversible responsiveness upon five different stimuli, including halide anions, metal ions, pH, temperature and humidity. We envision that our WLE aerogel illustrate considerable potential using in various fields such as display device, advanced sensor and environmentally friendly probe where multi-responsiveness is required.

The interaction between polyelectrolytes and metal ions is governed by different types of interactions, leading to the formation of different phases, from liquid state to weak gels, through an appropriate choice of metal ion/polyelectrolyte molar ratio. We have found that lanthanide ions, europium(III) and terbium(III), are able to form polymer composites with poly(sodium acrylate). That interaction enhances the luminescent properties of europium(III) and terbium(III), showing that Eu3+/poly(sodium acrylate) (PSA) and Tb3+/PSA composites have a highly intense red and green emission, respectively. The effect of cations with different valences on the luminescent properties of the polymer composites is analyzed. The presence of metal ions tends to quench the composite emission intensity and the quenching process depends on the cation, with copper(II) being by far the most efficient quencher. The interaction mechanism between lanthanoid ions and PSA is also discussed. The composites and their interactions with a wide range of cations and anions are fully characterized through stationary and non-stationary fluorescence, high resolution scanning electronic microscopy and X-ray diffraction.