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Complexes emitting in the blue spectral region are attractive materials for developing white-colored light sources. Here, we report the luminescence properties of novel coordination compounds based on the trivalent group 3, 13 metals, and the 1-phenyl-3-methyl-4-cyclohexylcarbonyl-pyrazol-5-onate (Q CH ) ligand. [M(Q CH ) 3 ] (M = Al, Ga, and In), [M(Q CH ) 3 (H 2 O)] (M = Sc, Gd, and Lu), [Lu(Q CH ) 3 (DMSO)], and [La(Q CH ) 3 (H 2 O)(EtOH)] complexes were synthesized and structurally characterized by a single-crystal X-ray diffraction study. It has been found that the luminescence quantum yields of the ligand increase by one order of magnitude upon metal coordination. A significant correspondence between the energies of the ligand's excited states and the luminescence quantum yields to the metal ion's atomic numbers was found using molecular spectroscopy techniques. The replacement of the central ion with the heavier one leads to a monotonic increase in singlet state energy, while the energy of the triplet state is similar for all the complexes. Time-resolved measurements allowed us to estimate the intersystem crossing (ISC) rate constants. It was shown that replacing the Al 3+ ion with the heavier diamagnetic Ga 3+ and In 3+ ions decreased the ISC rate, while the replacement with the paramagnetic Gd 3+ ion increased the ISC rate, which resulted in a remarkably bright and room-temperature phosphorescence of [Gd(Q CH ) 3 (H 2 O)].

We present a systematic study on the properties of Na(Y,Gd)F 4 -based upconverting nanoparticles (UCNP) doped with 18% Yb 3+ , 2% Tm 3+ , and the influence of Gd 3+ (10-50 mol% Gd 3+ ). UCNP were synthesized via the solvothermal method and had a range of diameters within 13 and 50 nm. Structural and photophysical changes were monitored for the UCNP samples after a 24-month incubation period in dry phase and further redispersion. Structural characterization was performed by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as dynamic light scattering (DLS), and the upconversion luminescence (UCL) studies were executed at various temperatures (from 4 to 295 K) using time-resolved and steady-state spectroscopy. An increase in the hexagonal lattice phase with the increase of Gd 3+ content was found, although the cubic phase was prevalent in most samples. The Tm 3+ -luminescence intensity as well as the Tm 3+ -luminescence decay times peaked at the Gd 3+ concentration of 30 mol%. Although the general upconverting luminescence properties of the nanoparticles were preserved, the 24-month incubation period lead to irreversible agglomeration of the UCNP and changes in luminescence band ratios and lifetimes., (© 2022. The Author(s).)

There is a large interest in luminescent materials for application as temperature sensors. In this scenario, we investigate the performance of neodymium-doped alkaline-earth fluoride (Nd 3+ :MF 2 ; M=Ba, Ca, Sr) crystalline powders prepared by combustion synthesis for optical temperature-sensing applications based on the luminescence intensity ratio (LIR) technique. We observe that the near-infrared luminescence spectral profile of Nd 3+ changes with the temperature in a way that its behavior is suitable for optical thermometry operation within the first biological window. We also observe that the thermometric sensitivities of all studied samples change depending on the spectral integration range used in the LIR analysis. Nd 3+ :CaF 2 presents the largest sensitivity values, with a maximum absolute sensitivity of 6.5×10 -3 /K at 824 K and a relative sensitivity of 1.71 %/K at human-body temperature (310 K). The performance of CaF 2 for optical thermometry is superior to that of β-NaYF 4 , a standard material commonly used for optical bioimaging and temperature sensing, and on par with the most efficient oxide nanostructured materials. The use of thermometry data to help understand structural properties via Judd-Ofelt intensity standard parameters is also discussed., (© 2021 Wiley-VCH GmbH.)

Functional molecule-based solids built of metal complexes can reveal a great impact of external stimuli upon their optical, magnetic, electric, and mechanical properties. We report a novel molecular material, {[Eu III (H 2 O) 3 (pyrone) 4 ][Co III (CN) 6 ]}· n H 2 O ( 1 , n = 2; 2 , n = 1), which was obtained by the self-assembly of Eu 3+ and [Co(CN) 6 ] 3- ions in the presence of a small 2-pyrrolidinone (pyrone) ligand in an aqueous medium. The as-synthesized material, 1 , consists of dinuclear cyanido-bridged {EuCo} molecules accompanied by two H-bonded water molecules. By lowering the relative humidity (RH) below 30% at room temperature, 1 undergoes a single-crystal-to-single-crystal transformation related to the partial removal of crystallization water molecules which results in the new crystalline phase, 2 . Both 1 and 2 solvates exhibit pronounced Eu III -centered visible photoluminescence. However, they differ in the energy splitting of the main emission band of a 5 D 0 → 7 F 2 origin, and the emission lifetime, which is longer in the partially dehydrated 2 . As the 1 ↔ 2 structural transformation can be repeatedly reversed by changing the RH value, the reported material shows a room-temperature switching of detailed luminescent features including the ratio between emission components and the emission lifetime values.

The excitation of lanthanides with visible light to promote photochemical reactions has garnered interest in recent years. Lanthanides serve as initiators for photochemical reactions because they exhibit visible-light-promoted 4f→5d transitions that lead to emissive states with electrochemical potentials that are more negative than the corresponding ground states. The lanthanides that have shown the most promising characteristics for visible-light promoted photoredox are Sm II , Eu II , and Ce III . By understanding the effects that ligands have on the 5d orbitals of Sm II , Eu II , and Ce III , luminescence and reactivity can be rationally modulated using coordination chemistry. This review briefly overviews the photochemical reactivity of Sm II , Eu II , and Ce III with visible light; the properties that influence the reactivity of these ions; and the research that has been reported towards modulating their photochemical-relevant properties using visible light and coordination chemistry.

New metal-organic frameworks (MOF) with lanthanum(III), cerium(III), neodymium(III), europium(III), gadolinium(III), dysprosium(III), and holmium(III)] and the ligand precursor 1,3,5- tris( 4 -carboxyphenyl)- 2,4,6 -trimethylbenzene (H 3 L) were synthesized under solvothermal conditions. Single crystal x-ray analysis confirmed the formation of three-dimensional frameworks of [LnL(H 2 O) 2 ] n ·xDMF·yH 2 O for Ln = La, Ce, and Nd. From the nitrogen sorption experiments, the compounds showed permanent porosity with Brunauer-Emmett-Teller (BET) surface areas of about 400 m 2 /g, and thermal stability up to 500 °C. Further investigations showed that these Ln-MOFs exhibit catalytic activity, paving the way for potential applications within the field of catalysis.

Deep tissue imaging in the second near-infrared (NIR-II) window holds great promise for widespread fundamental research. However, inhomogeneous signal attenuation due to tissue absorption and scattering hampers its application for accurate in vivo biosensing. Here, lifetime-based in situ hepatocellular carcinoma (HCC) detection in NIR-II region is presented using a tumor-microenvironment (peroxynitrite, ONOO - )-responsive lanthanide-cyanine Förster resonance energy transfer (FRET) nanosensor. A specially designed ONOO - -responsive NIR-II dye, MY-1057, is synthesized as the FRET acceptor. Robust lifetime sensing is demonstrated to be independent of tissue penetration depth. Tumor lesions are accurately distinguished from normal tissue due to the recovery lifetime. Magnetic resonance imaging and liver dissection results illustrate the reliability of lifetime-based detection in single and multiple HCC models. Moreover, the ONOO - amount can be calculated according to the standard curve., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this study, we report the luminescence color tuning in the lanthanide metal-organic framework (LnMOF) ([La(bpdc)Cl(DMF)] ( 1 ); bpdc 2- = [1,1'-biphenyl]-4,4'-dicarboxylate, DMF = N , N -dimethylformamide) by introducing dual emission properties in a La 3+ MOF scaffold through doping with the blue fluorescent 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylate (dabpdc 2- ) and the red emissive Eu 3+ . With a careful adjustment of the relative doping levels of the lanthanide ions and bridging ligands, the color of the luminescence was modulated, while at the same time the photophysical characteristics of the two chromophores were retained. In addition, the photophysical properties of the parent MOF ( 1 ) and its doped counterparts with various dabpdc 2- /bpdc 2- and Eu 3+ /La 3+ ratios and the photoinduced energy transfer pathways that are possible within these materials are discussed. Finally, the temperature dependence study on the emission profile of a doped analogue containing 10% dabpdc 2- and 2.5% Eu 3+ ( 7 ) is presented, highlighting the potential of this family of materials to behave as temperature sensors., Competing Interests: The authors declare no conflict of interest.

This study investigates the significantly different luminescent and chiroptical properties of tetracycline (TC) when coordinated to Eu(III). The approach involves understanding the 1) speciation of TC and 2) conformation and species formed between Eu(III) and TC in a ratio of 1 : 1 in a dimethylformamide (DMF) solution and as a function of the pH value. By identifying the conformational changes of the various 1 : 1 Eu(III) : TC species, the results from this study explain information on the local microenvironment about the Eu(III) metal center. In particular, 5 D 0 ← 7 F 0 Eu(III) laser excitation spectroscopy was employed to distinguish the different types of species found in solution in order to understand the interaction between Eu(III) and TC. On the other hand, circularly polarized luminescence (CPL) spectroscopy was used to understand the structural changes within the 1 : 1 Eu(III) : TC complex that could be related to the chirality of the Eu(III)-containing species. The CPL spectrum serves as a "fingerprint" to indicate the conformational changes within the 1 : 1 Eu(III) : TC complex as a result of the chiroptical signal arising from the various Eu(III) : TC species., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The ability of several chelating mycotoxins to form coordination complexes with the lanthanide metals europium and terbium was explored. The mycotoxins examined included ochratoxin A, citrinin, cyclopiazonic acid (CPA), kojic acid, and tenuazonic acid (TeA). Of these compounds, TeA and CPA resulted in the greatest luminescence. Parameters influencing luminescence of TeA were investigated further. These included the type of lanthanide and its concentration, certain environmental factors, and the effect of competing metal cations. Of the two lanthanide metals, the terbium coordination complex (TeA-Tb 3+ ) showed greater luminescence relative to the europium complex (TeA-Eu 3+ ). The effects of solvent type, water content, and pH on the TeA-Tb 3+ system suggested that optimal conditions for luminescence were in 90% methanol with 10% aqueous buffer at pH 3. In competitive assays, the luminescence of the TeA-Tb 3+ complex decreased as the concentration of competing metal cations increased. Among the cations tested, Cu 2+ was the best inhibitor followed by Al 3+ , Au 3+ , Fe 3+ , Co 2+ , Mn 2+ , Mg 2+ , and Ca 2+ . Two cations, Na + and K + , showed no significant inhibition. This is the first report to describe the coordination of the metal-chelating mycotoxin TeA with lanthanides and the ability of TeA to serve as an "antenna" for the efficient transfer of energy to the lanthanide with resulting luminescence. Understanding the ability of mycotoxins such as TeA to chelate metals provides insight into how they exert their toxic effects.

Solid-state functional luminescent materials arouse an enormous scientific interest due to their diverse applications in lighting, display devices, photonics, optical communication, low energy scintillation, optical storage, light conversion, or photovoltaics. Among all types of solid luminophors, the emissive coordination polymers, especially those based on luminescent trivalent lanthanide ions, exhibit a particularly large scope of light-emitting functionalities, fruitfully investigated in the aspects of chemical sensing, display devices, and bioimaging. Here, we present the complete overview of one of the promising families of photoluminescent coordination compounds, that are heterometallic d-f cyanido-bridged networks composed of lanthanide(3+) ions connected through cyanide bridges with polycyanidometallates of d-block metal ions. We are showing that the combination of cationic lanthanide complexes of selected inorganic and organic ligands with anionic homoligand [M(CN)x] n- (x = 2, 4, 6 and 8) or heteroligand [M(L)(CN)4] 2- (L = bidentate organic ligand, M = transition metal ions) anions is the efficient route towards the emissive coordination networks revealing important optical properties, including 4f-metal-centred visible and near-infrared emission sensitized through metal-to-metal and/or ligand-to-metal energy transfer processes, and multi-coloured photoluminescence switchable by external stimuli such as excitation wavelength, temperature, or pressure., Competing Interests: The authors declare no conflict of interest.

DNA-sensitized Tb 3+ luminescence spectroscopy is a powerful method for probing nucleic acids and developing biosensors. Its performance in organic solvents has yet to be explored. In this study, Tb 3+ luminescence with nucleosides, nucleotides and DNA oligonucleotides in various organic solvents is studied. Tb 3+ emission with single nucleotides is quenched up to 88% in dimethyl formamide (DMF), while its emission with nucleosides is enhanced. For the four 15-mer DNA homopolymers, the strongest absolute emission enhancement was achieved with C 15 . Similar emission properties are observed in other solvents including DMF, DMSO, acetonitrile methanol, ethanol, isopropanol and ethylene glycol. A few DNAzymes are tested as random DNA sequences all showing 1.4-6.9-fold emission enhancement in ethanol. A previously reported optimized sequence in water (G 3 T) 5 is further enhanced by the solvents. Using this sequence, a detection limit of 5.5 nm Hg 2+ is achieved in 25% ethanol solution. A similar Hg 2+ sensitivity is also observed in a lake water mixed with ethanol. Luminescence lifetime is longer in DMF than in water. This study indicates that DNA-sensitized Tb 3+ luminescence can be measured in water miscible solvents and most likely, with even stronger emission than that in water., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Ciprofloxacin, a fluoroquinolone antibiotic, is widely used for the treatment of bacterial infection in humans due to its broad antibacterial spectrum. An excessive use or overdose of ciprofloxacin on the other hand can cause several adverse effects not only to humans but also to microorganisms. Unabsorbed ciprofloxacin in the body is mostly excreted through urine and finally goes to the environment, providing a drug resistance pressure on bacteria. Hence a simple and efficient detection method of ciprofloxacin is necessary, which, for example, can be used to analyze ciprofloxacin content in urine. Although ciprofloxacin itself shows inherent fluorescence, direct fluorescent detection of ciprofloxacin in raw urine sample is difficult due to autofluorescence of urine by other components. Herein we report that a Tb(III) complex of DO3A (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) can be efficiently sensitized by ciprofloxacin to emit luminescence separately from the urine autofluorescence wavelength region. Tb-DO3A shows excellent sensitivity with a detection limit of three parts per billion in aqueous buffer solution. Further, Tb-DO3A is used to detect ciprofloxacin with high sensitivity and selectivity in a raw urine sample without any purification or separation procedures in the concentrations ranging from 1 µg·mL -1 to 50 µg·mL -1 . The direct measurement of ciprofloxacin excreted in urine may be used to control overdose of the drug., Competing Interests: The authors declare no conflict of interest.

The enthusiasm for research on lanthanide-doped upconversion nanoparticles is driven by both a fundamental interest in the optical properties of lanthanides embedded in different host lattices and their promise for broad applications ranging from biological imaging to photodynamic therapy. Despite the considerable progress made in the past decade, the field of upconversion nanoparticles has been hindered by significant experimental challenges associated with low upconversion conversion efficiencies. Recent experimental and theoretical studies on upconversion nanoparticles have, however, led to the development of several effective approaches to enhancing upconversion luminescence, which could have profound implications for a range of applications. Herein we present the underlying principles of controlling energy transfer through lanthanide doping, overview the major advances and key challenging issues in improving upconversion luminescence, and consider the likely directions of future research in the field., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Multicolor upconversion (UC) luminescence of NaYF4:Yb(3+)/Er(3+) nanoparticles (NPs) was successfully tuned by simply controlling the NaF dosage. Unlike UC nanocrystals previously reported in the literature with multicolor emission obtained by varying the rare-earth dopants, the current work developed a new approach to tune the UC emission color by controlling the NaF concentration without changing the ratio and dosage of rare-earth ions. TEM and powder XRD were used to characterize the shape, size, and composition of the UC luminescent nanocrystals. The luminescence images, emission spectra, and multicolor emission mechanism of the NPs have also been demonstrated. As a result of the excellent ability of this new method to manipulate color emission, this will open up new avenues in the areas of bioprobes, light-emitting devices, color displays, lasers, and so forth. To demonstrate their biological applications, the water-stable, biocompatible, and bioconjugatable NaYF4:Yb(3+)/Er(3+) @poly(acrylic acid) NPs were synthesized by this developed strategy and applied in targeted-cell UC luminescence imaging., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

"Trinity Sliotar" family: Chiral ligands containing pyridyl and naphthalene moieties were synthesized and characterized. These ligands were successfully used for the synthesis of Eu(III) bundles where chirality of the ligand is successfully transferred onto the lanthanide centre resulting in circularly polarized red luminescence., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Magnetic circularly polarized luminescence (MCPL) is a technique based on the differential emission of left and right circularly polarized light induced by a magnetic field. This technique is the emission counterpart of to the widely explored magnetic circular dichroism. In this work, the first demonstration of MCPL is presented in heterometallic lanthanide(III) systems by using two molecular cluster aggregates, {Eu1Tb19} and {Eu3Tb17}. The results presented here indicate the potential that MCPL holds for obtaining highly tuned magneto‐optical materials for various applications, such as anti‐counterfeiting materials. Additionally, the findings suggest that magnetic interactions between the ions modulate the dissymmetry factor, opening the possibility of the development of highly tunable MCPL materials. [ABSTRACT FROM AUTHOR]

Triple‐stranded helical lanthanide MOFs with CO2 adsorption properties were investigated. Lanthanide MOFs ([Eu0.1Tb0.9(hfa)3(dpa)]n) are composed of lanthanide luminophores (Eu(III) and/or Tb(III) ions), fluorinated antenna ligands (hfa: hexafluoroacetylacetonate), and polyamide‐type linker ligands (dpa: 4‐(diphenylphosphoryl)‐N‐(4‐(diphenylphosphoryl)phenyl)benzamide). The cylindrical structure was characterized by single‐crystal X‐ray analysis, thermogravimetric analysis, and gas adsorption measurements. The inner surfaces of the cylindrical channels were covered with the fluorine atoms of the hfa ligands. The emission intensity ratio (IEu/ITb) in [Eu0.1Tb0.9(hfa)3(dpa)]n is affected by the CO2 gas adsorption behavior. The change in IEu/ITb value was caused by the intermolecular interactions between the CO2 gas molecules and the fluorinated ligands, resulting in an electronic structural change of the lowest triplet excited state in the photosensitized hfa ligands. [ABSTRACT FROM AUTHOR]

Molecular scaffolds are ideal for investigating upconversion (UC) at the highest spatial resolution and to create precisely controllable luminescent materials. Such control may be the key to overcoming the limitations of brightness and reproducibility found in UC micro‐ and nanoparticles. Cooperative UC can significantly increase luminescence brightness and bulk studies showed that highest efficiencies can be obtained by sensitizer‐to‐activator ion ratios ≥ 2, that is, via high probabilities of sensitizing the emitting lanthanide ion. Using nonanuclear molecular complexes, the authors demonstrate both experimentally and theoretically that interion distances are more relevant and that the highest UC efficiencies are actually attained for sensitizer‐to‐activator ion ratios around 1. By modeling accretive and cooperative sensitization UC, energy migration, and fitting experimental data, it is revealed that cooperative sensitization is predominant for the determination of UC luminescence intensities, whereas energy migration defines UC luminescence kinetics. The implementation of interion distances and different energy transfer mechanisms into advanced modeling of experimental UC data will be paramount for designing brighter and better UC materials. [ABSTRACT FROM AUTHOR]

Isostructural binuclear complexes [Ln2L2(hfac)6] (Ln = Eu, Tb; hfac– = hexafluoroacetylacetonate ion) are synthesized by the interaction of [Ln(hfac)3(H2O)2] with 3,6-bis(diphenylphosphinyl)pyridazine (L). According to the single-crystal XRD data, two Ln(hfac)3 moieties in the complexes are connected by two O,O´-bidentate-bridging ligands L, and the coordination polyhedron Ln@O8 has the geometry of a triangular dodecahedron. The Eu3+ and Tb3+ complexes exhibit characteristic lanthanide-centered photoluminescence in the solid state at 297 K with luminescence quantum yields of 31% and 2% and excited state lifetimes of 707 and 30 μs, respectively, thus indicating that luminescence sensitization by the ligand environment is more effective for Eu3+ than for Tb3+. [ABSTRACT FROM AUTHOR]

Lanthanide nanoparticle (LnNP) scintillators exhibit huge potential in achieving radionuclide‐activated luminescence (radioluminescence, RL). However, their structure–activity relationship remains largely unexplored. Herein, progressive optimization of LnNP scintillators is presented to unveil their structure‐dependent RL property and enhance their RL output efficiency. Benefiting from the favorable host matrix and the luminescence‐protective effect of core–shell engineering, NaGdF4 : 15 %Eu@NaLuF4 nanoparticle scintillators with tailored structures emerged as the top candidates. Living imaging experiments based on optimal LnNP scintillators validated the feasibility of laser‐free continuous RL activated by clinical radiopharmaceuticals for tumor multiplex visualization. This research provides unprecedented insights into the rational design of LnNP scintillators, which would enable efficient energy conversion from Cerenkov luminescence, γ‐radiation, and β‐electrons into visible photon signals, thus establishing a robust nanotechnology‐aided approach for tumor‐directed radio‐phototheranostics. [ABSTRACT FROM AUTHOR]

This study is focused on determining the refractive index as a crucial parameter for evaluating the intrinsic quantum yield and the ligand sensitisation efficiency in solid‐state trivalent lanthanide coordination compounds. For this, eight trivalent europium complexes with phenyl‐terpyridine ([EuX3(ptpy)(L)], X=Cl− or NO3−, ptpy=4′‐phenyl‐2,2′ : 6′,2′′‐terpyridine, L=H2O or other molecules) were examined. Their refractive indices were determined using the Becke lines test by immersing transparent material in a series of media with known refractive indices. Using the set of media presented here, determining crystalline materials′ refractive indices from 1.41 to 1.73 with a step of 0.01 is possible. Assessment of the refractive indices of the complexes mentioned above allowed a comprehensive analysis of their photophysical properties in the solid state. Moreover, this method can be extrapolated for other solid‐state materials, offering valuable insights in the broader field of photophysics. In addition to photoluminescence investigations, the compounds presented were characterised by single‐crystal X‐ray diffraction (SCXRD), powder X‐ray diffraction (PXRD), Hirschfeld surface area analysis, UV‐Vis reflectance spectroscopy, hydrolysis sensitivity analysis, and simultaneous thermogravimetry and differential thermal analysis coupled with mass‐spectrometry (STA‐MS). [ABSTRACT FROM AUTHOR]

Supramolecular metallogels combine the rheological properties of gels with the color, magnetism, and other properties of metal ions. Lanthanide ions such as Eu(III) can be valuable components of metallogels due to their fascinating luminescence. In this work, we combine Eu(III) and iminodiacetic acid (IDA) into luminescent hydrogels. We investigate the tailoring of the rheological properties of these gels by changes in their metal:ligand ratio. Further, we use the highly sensitive Eu(III) luminescence to obtain information about the chemical structure of the materials. In special, we take advantage of computational calculations to employ an indirect method for structural elucidation, in which the simulated luminescent properties of candidate structures are matched to the experimental data. With this strategy, we can propose molecular structures for different EuIDA gels. We also explore the usage of these gels for the loading of bioactive molecules such as OXA, observing that its aldose reductase activity remains present in the gel. We envision that the findings from this work could inspire the development of luminescent hydrogels with tunable rheology for applications such as 3D printing and imaging‐guided drug delivery platforms. Finally, Eu(III) emission‐based structural elucidation could be a powerful tool in the characterization of advanced materials. [ABSTRACT FROM AUTHOR]

Photochromic luminescent glass-ceramics attract lots of attention as an optical storage medium owing to their large storage capacity, reversible luminescence modulation, simple operation, etc. Herein, a kind of phosphosilicate glass containing AgBr nanoparticles was designed and prepared, which can realize the color reversible transformation between light yellowish-green and brown by alternating 365 nm light illumination and thermal treatment at 300 °C. The mechanism of photochromism and bleaching of the glass is related to the generation and decomposition of Ag0 clusters. Relying on the re-absorption effect, the emission intensity of Eu3+ ions could be reversibly regulated, showing the maximum luminescence contrast of 74 %. A good fatigue resistance and reproducibility of transmittance and luminescence modulation could be observed in cycle measurements, demonstrating its potential in the optical memory field. [ABSTRACT FROM AUTHOR]

Abstract We are reporting on the use of a low‐coordinate YbIII amide with near‐ideal planar trigonal [Yb{N(SiMe3)2}3] (1) and on a bipyramidal trigonal derivative [Yb{N(SiMe2H)2}3 ⋅ (thf)2] (2) that constitute quintessential cases to investigate luminescent and magnetic properties otherwise usually blurred on less symmetrical compounds. These compounds represent the first experimental objects that allow for the confirmation of the recent conjecture about best‐performing SMM built on the archetypal prolate lanthanide ion. We have performed a combined theoretical, luminescent, and magnetic study on these molecules. For 1, a spectacular split of the 2F7/2 ground state of 1312 cm−1 is measured by low‐temperature near‐infra‐red luminescence as well as the calculated pure wavefunction composition of the low‐lying Kramers doublets, making this complex a textbook example of a prolate SMM. These results are corroborated by comparison with 2, that exhibits as expected a 50 % decrease of the ground state splitting compared to 1. Yet, we show that these remarkable features are insufficient to promote SMM behavior, and Orbach relaxation is unlikely to occur even on such an ideal low‐coordinate SMM without control of spin‐phonon coupling.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO15)8(LnO15)4(O)(C5H8O2)6(EtOH)2(CH3CN)2-2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb[sup 3+] and Tb[sup 3+]/Eu[sup 3+]-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the [sup 5]D4 Stark components, while the mixed Tb[sup 3+]/Eu[sup 3+] analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb[sup 3+]-to-Eu[sup 3+] energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the [sup 5]D4^[sup 7]F5 (Tb[sup 3+]) and [sup 5]D0^[sup 7]F2 (Eu[sup 3+]) transitions in the range 11-373 K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11-373 K with a maximum relative sensitivity of 2.0% K[sup -1] at 373 K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications. [ABSTRACT FROM AUTHOR]

Cyclen‐peptide bioconjugates are usually prepared in multiple steps that require individual preparation and purification of the cyclic peptide and hydrophilic cyclen derivatives. An efficient strategy is discovered for peptide cyclization and functionalization toward lanthanide probe via three components intermolecular crosslinking on solid‐phase peptide synthesis with high conversion yield. Multifunctionality can be conferred by introducing different modular parts or/and metal ions on the cyclen‐embedded cyclopeptide. As a proof‐of‐concept, a luminescent Eu3+ complex and a Gd3+‐based contrasting agent for in vitro optical imaging and in vivo magnetic resonance imaging, respectively, are demonstrated through utilizing this preparation of cyclen‐embedded cyclic arginylglycylaspartic acid (RGD) peptide. [ABSTRACT FROM AUTHOR]

Silver and lanthanide (Tm3+, Yb3+) doped oxyfluoride glasses have been prepared by melt-quenching method. The absorption of the glasses was measured in the range from 350 to 550 nm revealing the absorption edges of Ag nanoclusters and Tm3+ transition. The photoluminescence spectra of the glasses were detected in the range from 400 to 1100 nm under excitation in the range from 300 to 500 nm. The photoluminescence excitation spectra showed that Ag nanoclusters and Tm3+ ions can effectively harvest energy in UV-range and convert to visible and infrared (through emission by Yb3+ ions) ranges making the glasses perspective as white light emitters and solar spectrum downconverters. [ABSTRACT FROM AUTHOR]

Nanoparticles of Zn2SiAl2O4 infused with Dy3+ were produced through a traditional co-precipitation approach. We investigated the particles' structural attributes and physical characteristics using tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), UV–Vis absorption spectroscopy, and photoluminescence (PL) spectrometry. The XRD outcomes validated the crystalline nature of the nanoparticles and showed the effective replacement of Dy3+ ions in the place of Zn2+ ions within the matrix and with increasing Dy concentration from 0.5 % to 1.25 %, the crystallite size decreased from 84 nm to 53 nm. The SEM visuals offered clarity on the shape, dimension, and spread of these particles. FTIR analysis further confirmed the composition and structure of the nanoparticles by identifying the chemical bonds and functional groups. UV–visible absorption spectroscopy revealed increase in the optical energy bandgap from 4.45 eV to 4.55 eV with increasing Dy3+ content, indicating potential for optical applications. The photoluminescence spectrometry results featured a prominent transition at approximately 646 nm, suggest that the phosphor has the capability to function as a vivid yellow light emitter and demonstrate their potential for application in optoelectronics, photonics, and luminescent materials.

For the first time, glass in the ZrF4–BaF2–NaPO3–Er(Nd)F3 system was obtained and investigated by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), 19F and 31P MAS NMR, luminescence spectroscopy, and electron microscopy. It has been found that the addition of 2.5–20 mol% NaPO3 increases the glass thermal stability factor (ΔT) and extends the Tx – Tg interval. Ionic mobility in a fluoride sublattice has been studied depending on the composition of the glass at different temperatures. It has been established that at the studied concentrations of NaPO3 and Er(Nd)F3 additives, the structure of the studied glasses is similar to the structure of fluorozirconate glasses, although some phosphate ions can be incorporated into the glass network. The NMR data indicate a weak interaction of fluorozirconate and phosphate glass networks and low degree of depolymerization of phosphate chains. Heat treatment and NaPO3 additives decrease the luminescence intensity of Er3+ and Nd3+ ions in the visible region. Isothermal heating in the Tg – Tc1 temperature range causes formation of sphere-like nanoparticles of BaZrF6 composition. Their sizes are 5–90 nm. Fluorozirconate phosphate glasses doped with erbium or neodymium ions can be considered as potential precursors for glass ceramics. [ABSTRACT FROM AUTHOR]

Materials doped with the luminescent Eu3+ ion are attracting an ever-increasing amount of attention due to their potential applications in solid-state lighting, display devices, solar cells, or bioanalytics. But, why Eu3+? Unlike other lanthanides, its electronic features make the calculation of some physicochemical parameters quite straightforward, since they can be extracted directly from the emission spectrum. Highly appreciated for its reddish emission, the luminescent ion has also been widely used as a site-sensitive structural probe. With this in mind, this paper aims to offer easy guidance with helpful advice on how to interpret measurements of the emission spectra. It also presents the most useful tools for saving time, and gives a focused and practical explanation of the theoretical concepts involved. [Display omitted] [ABSTRACT FROM AUTHOR]

Currently, lanthanide (Ln3+) doped Pb‐free double perovskites (DPs) suffer from competitive emissions of the self‐trapped exciton (STE) and Ln3+. Herein, a new type of Nd3+‐doped Cs2AgInCl6 DPs with Na+/Bi3+ co‐alloying is developed. Benefiting from Na+/Bi3+‐induced local structural modification, both STE broadband visible luminescence and Nd3+ near‐infrared (NIR) emissions are boosted via free exciton sensitization. Specifically, a total 648‐fold enhancement in emitting intensities compared to the Na+/Bi3+‐free counterpart is realized, with a significantly improved NIR photoluminescence quantum yield (PLQY) from 0.16% to 30.3%. First‐principles density functional theory calculations, Raman spectra, and steady/transient‐state PL spectra verify the modification of local site symmetry, breakdown of parity‐forbidden absorption, and reduction of electron‐phonon coupling via Na+/Bi3+ doping. Finally, a compact vis–NIR broadband light‐emitting diode (LED) is designed by coupling the Na/Bi/Nd: Cs2AgInCl6 DP with a commercial ultraviolet LED chip, which shows promising applications in spectroscopic analyses and multifunctional lighting. [ABSTRACT FROM AUTHOR]

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11–373 K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11–373 K with a maximum relative sensitivity of 2.0% K−1 at 373 K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

The study is devoted to the development of the concept of targeted delivery of pharmacological agents. A nanocomposite (NC) – (LaF3:Tb/Citr@RuBiNic), which is formed by luminescent nanoparticles (ScNPs) – LaF3: Tb/Citr and a photosensitive substance – [Ru(bpy)2(nic)2]2+ (where bpy = 2,2′ bipyridine and nic = nicotine (3-[(2S)-1-methylpyrrolidin-2-yl] pyridine) – (RuBiNic), in response to X-ray irradiation, emits quanta of visible light, as a result is released of a pharmacological agent – nicotine from the NC surface. In principle, when implementing the methods of photopharmacology, or photodynamic therapy, it allows controlling the desired physiological or therapeutic effect in a specific place and at the right time with high specificity of influence.To conduct research, LaF3:Tb/Citr nanoparticles were synthesized, and RuBiNic was used as a model photosensitive substance. The size and morphology (TEM), surface (FTIR-spectroscopy), thermogravimetric (TG/DTG/DTA) and X-ray structural analysis were carried out, SSA value and acid-base characteristics of the surface were determined. In the static mode at 25°С, the processes of adsorption immobilization of the RuBiNic complex on the surface of nanoparticles in the medium of an aqueous solution were investigated. Diffuse kinetics models, pseudo-first- and pseudo-second-order kinetics models, Langmuir and Freundlich models were used to quantitatively describe the equilibrium adsorption processes. The kinetics of RuBiNic adsorption is characterized by a mixed-diffusion mechanism. The pseudo-second-order model was also found to have a higher correlation coefficient than the pseudo-first-order model, confirming the chemisorption process. The data of fitting the adsorption isotherm according to the Langmuir adsorption model (r2 = 0.99) indicate chemisorption of RuBiNic on the surface of ScNPs LaF3:Tb/Citr with a maximum adsorption capacity of 7.47 mg⋅g−1.The obtained data are useful for optimizing the conditions of adsorption immobilization of molecules of photosensitive substances on the surface of phosphors based on lanthanum fluoride. The LaF3:Tb/Citr@RuBiNic system shows potential for future applications in photopharmacology and X-ray photodynamic therapy.

Two compounds, Na3[Eu(DPA)3] ⋅ 14H2O and [Eu(DPA)(HDPA)(H2O)2] ⋅ 4H2O, were created and the structure determined using single crystal X‐ray diffraction. The single crystal luminescence properties were compared and related to the Eu3+ coordination geometry. The formation of single crystals from solutions of Eu(CF3SO3)3 and H2DPA was found change with the pH value of the H2DPA solution. Mixtures of Na3[Eu(DPA)3] ⋅ 14H2O and [Eu(DPA)(HDPA)(H2O)2] ⋅ 4H2O were observed with a pH ratio between the two structures. While visual inspection showed that all samples contained both Na3[Eu(DPA)3] ⋅ 14H2O and [Eu(DPA)(HDPA)(H2O)2] ⋅ 4H2O, the PXRD and luminescence data did not immediately reveal that the samples were pure. Having discovered that the samples were indeed mixtures, quantification was attempted by Rietveld refinement of the PXRD data, and the luminescence spectra were compared to those from single crystals. As the data was not found to reveal that the samples were mixtures, even though we knew that this was the case, we must urge caution when inferring structure‐property relationships from powder samples. In this case we were able to isolate monophasic systems and do a comparative study, but this requires that the samples are identified as mixtures. [ABSTRACT FROM AUTHOR]

Lanthanide-doped nanoparticles, featuring sharp emission peaks with narrow bandwidth, exhibit high downconversion luminescence intensity, making them highly valuable in the fields of bioimaging and drug delivery. High-crystallinity Y2O3 nanoparticles (NPs) doped with Er3+ ions were functionalized by using a pegylation procedure to confer water solubility and biocompatibility. The NPs were thoroughly characterized using transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), and photoluminescence measurements. The pegylated nanoparticles were studied both from a toxicological perspective and to demonstrate their internalization within HCT-116 cancer cells. Cell viability tests allowed for the identification of the "optimal" concentration, which yields a detectable fluorescence signal without being toxic to the cells. The internalization process was investigated using a combined approach involving confocal microscopy and ICP-MS. The obtained data clearly indicate the efficient internalization of NPs into the cells with emission intensity showing a strong correlation with the concentrations of nanoparticles delivered to the cells. Overall, this research contributes significantly to the fields of nanotechnology and biomedical research, with noteworthy implications for imaging and drug delivery applications. [ABSTRACT FROM AUTHOR]

We report the synthesis of a new pyrene, dipicolinic acid‐based ligand (L1H) and its corresponding multi‐emissive and multifunctional europium complex [Eu(L1)3] that is capable of single component color switchable emission from red to blue and also white. At high concentration (10 mM) the single component system results in near pure white emission (CIE coordinates x,y=0.329, 0.324). Furthermore, the system showed ratiometric oxygen sensing with oxygen significantly quenching the pyrene centered emission but not the Eu3+ emission, resulting in an overall emission color change from blue to red on increasing oxygen content. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The reaction of DyCl3⋅6H2O with a rigid diacylhydrazone ligand (H2L) afforded a trinuclear precursor [Dy3L2Cl3(H2O)2(CH3OH)]Cl2⋅3CH3OH (1). The replacement of the Cl– ions and the coordinating solvents by the aryloxides ligands (Lx)– yields three trinuclear complexes [Dy3L2(Lx)5]⋅nsol (x = 1,2‐naphthol (2); x = 2,7‐hydroxycoumarin (3); and x = 3, phenol (4)). In complexes 2—4, two end Dy3+ centers adopt almost identical N4O4 coordination sphere of D6h geometry while the central one adopts N4O5 coordination sphere in Cs geometry. Magnetic measurements reveal weak antiferromagnetic interactions in the hydrated samples 2e—4e and two‐step slow relaxation process under zero dc field with effective energy barriers Ueff of 439 and 91 K, 353 and 40 K, 466 and 89 K for SR and FR in 2e—4e, respectively. Such dynamic magnetic behaviour for 4 persists in the magnetically diluted sample of 4@Y. Complex 4 possesses the short Dy‐Oaryloxide bond distance of 2.055(18) Å, and the largest Ueff among the reported linear trinuclear dysprosium complexes. Moreover, the functionalized aryloxides ligands (Lx)– show photoluminescence via intramolecular energy transfer, making 2e—4e luminescent Dy3+ SMMs with high energy barriers. [ABSTRACT FROM AUTHOR]

The possibility to precisely control reaction outcomes for pursuing materials with well-defined features is a main endeavor in the development of inorganic materials. Confining reactions within a confined space, such as nanoreactors, is an extremely promising methodology which allows to ensure control over the final properties of the material. An effective room temperature inverse miniemulsion approach for the controlled synthesis of undoped and Eu3+-doped calcium molybdate crystalline nanophosphors was developed. The advantages and the efficiency of confined space in terms of controlling nanoparticle features like size, shape, and functional properties are highlighted by systematically comparing miniemulsion products with calcium molybdate particles obtained without confinement from a typical batch synthesis. A relevant beneficial impact of space confinement by miniemulsion nanodroplets is observed on the control of size and shape of the final nanoparticles, resulting in 12 nm spherical nanoparticles with a narrow size distribution, as compared to the 58 nm irregularly shaped and aggregated particles from the batch approach (assessed by TEM analysis). Further considerable effects of the confined space for the miniemulsion samples are found on the doping effectiveness, leading to a more homogeneous distribution of the Eu3+ ions into the molybdate host matrix, without segregation (assessed by PXRD, XAS, and ICP-MS). These findings are finally related to the photoluminescence properties, which are evidenced to be closely dependent on the Eu3+ content for the miniemulsion samples, as an increase of the relative intensity of the direct f–f excitation and a shortening of the lifetime (from 0.901 ms for 1 at. % to 0.625 ms for 7 at. % samples) with increasing Eu3+ content are observed, whereas no relationship between these parameters and the Eu3+ content is evidenced for the batch samples. All these results are ascribed to the uniform and controlled crystallization occurring inside each miniemulsion nanodroplet, as opposed to the less controlled nucleation and growth for a classic nonconfined approach. [ABSTRACT FROM AUTHOR]

We report the synthesis of Ln3+ nitrate [Ln(Tpm)(NO3)3] ⋅ MeCN (Ln=Yb (1Yb), Eu (1Eu)) and chloride [Yb(Tpm)Cl3] ⋅ 2MeCN (2Yb), [Eu(Tpm)Cl2(μ‐Cl)]2 (2Eu) complexes coordinated by neutral tripodal tris(3,5‐dimethylpyrazolyl)methane (Tpm). The crystal structures of 1Ln and 2Ln were established by single crystal X‐ray diffraction, while for 1Yb high resolution experiment was performed. Nitrate complexes 1Ln are isomorphous and both adopt mononuclear structure. Chloride 2Yb is monomeric, while Eu3+ analogue 2Eu adopts a binuclear structure due to two μ2‐bridging chloride ligands. The typical lanthanide luminescence was observed for europium complexes (1Eu and 2Eu) as well as for terbium and dysprosium analogues ([Ln(Tpm)(NO3)3] ⋅ MeCN, Ln=Tb (1Tb), Dy (1Dy); [Ln(Tpm)Cl3] ⋅ 2MeCN, Ln=Tb (2Tb), Dy (2Dy)). [ABSTRACT FROM AUTHOR]

Halide double perovskites [A2MIMIIIX6] are an important class of materials that have garnered substantial interest as non‐toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs2NaLnI6 (Ln=Ce, Nd, Gd, Tb, Dy). The complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported. [ABSTRACT FROM AUTHOR]

Six new complexes of the ligand HQcy (-4-(cyclohexanecarbonyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one) and Ln3+ ions with emission in the near-infrared (Nd3+) or visible and near-infrared (Sm3+, Pr3+) spectral regions were synthesized and characterized using various methods, including single crystal X-ray diffraction. The study demonstrated that both tris complexes [LnQcy3(H2O)(EtOH)] and tetrakis-acids [H3O][LnQcy4] can be synthesized by varying the synthetic conditions. The photochemical properties of the complexes were investigated experimentally and theoretically using various molecular spectroscopy techniques and Judd–Ofelt theory. The objective was to quantitatively and qualitatively disclose the influence of complex stoichiometry on its luminescence properties. The study showed that the addition of an extra ligand molecule (in the tetrakis species) increased molar extinction by up to 2 times, affected the shape of photoluminescence spectra, especially of the Pr3+ complex, and increased the quantum yield of the Sm3+ complex by up to 2 times. The results obtained from this study provide insights into the luminescent properties of lanthanide coordination compounds, which are crucial for the design and development of novel photonic materials with tailored photophysical properties. [ABSTRACT FROM AUTHOR]

The key to developing smart light‐emitting systems lies in the ability to tune luminescence with only modest changes in the chemical environment. Divalent europium‐based luminophores are unique materials that access emissions ranging from the blue to red regions of the visible spectrum. Early studies demonstrate the tunability of the emission of EuII in solid‐state host lattices, and recent research has shown that altering counter anions, solvents, and ligands also enables tuning of the emission of EuII. These findings are supported by numerous publications, and mechanistic studies shed light on the underlying theories behind the tunable emissions of EuII. The purpose of this article is to present the most recent hypotheses and understanding regarding the effect of counter anions, solvents, and ligands on luminescence properties of EuII based systems. [ABSTRACT FROM AUTHOR]

To develop novel luminescent materials for optical temperature measurement, a series of Yb3+- and Er3+-doped Ca3Sc2Si3O12 (CSS) upconversion (UC) phosphors were synthesized by the sol–gel combustion method. The crystal structure, phase purity, and element distribution of the samples were characterized by powder X-ray diffraction and a transmission electron microscope (TEM). The detailed study of the photoluminescence emission spectra of the samples shows that the addition of Yb3+ can greatly enhance the emission of Er3+ by effective energy transfer. The prepared Yb3+ and Er3+ co-doped CSS phosphors exhibit green emission bands near 522 and 555 nm and red emission bands near 658 nm, which correspond to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. The temperature-dependent behavior of the CSS:0.2Yb3+,0.02Er3+ sample was carefully studied by the fluorescence intensity ratio (FIR) technique. The results indicate the excellent sensitivity of the sample, with a maximum absolute sensitivity of 0.67% K−1 at 500 K and a relative sensitivity of 1.34% K−1 at 300 K. We demonstrate here that the temperature measurement performance of FIR technology using the CSS:Yb3+,Er3+ phosphor is not inferior to that of infrared thermal imaging thermometers. Therefore, CSS:Yb3+,Er3+ phosphors have great potential applications in the field of optical thermometry. [ABSTRACT FROM AUTHOR]

Strong circularly polarized luminescence (CPL) at 1550 nm is reported for lanthanide complexes supported by Vanol; these are the first examples of coordination of Vanol to lanthanides. A change in the ligand design from a 1,1'‐bi‐2‐naphthol (in Binol) to a 2,2'‐bi‐1‐naphthol (in Vanol) results in significantly improved dissymmetry factors for (Vanol)3ErNa3 (|glum|=0.64) at 1550 nm. This is among the highest reported dissymmetry factors to date in the telecom C‐band region, and among the highest for any lanthanide complexes. Comparative solid‐state structural analysis of (Vanol)3ErNa3 and (Binol)3ErNa3 suggests that a less distorted geometry around the metal center is in part responsible for the high chiroptical metrics of (Vanol)3ErNa3. This phenomenon was further evidenced in the analogous ytterbium complex (Vanol)3YbNa3 that also exhibit a significantly improved dissymmetry factor (|glum|=0.21). This confirms and generalizes the same observation that was made in other visibly emitting, six‐coordinate lanthanide complexes. Due to their strong CPL at 1550 nm, the reported complexes are potential candidates for applications in quantum communication technologies. More importantly, our structure‐CPL activity relationship study provides guidance towards the generation of even better near‐infrared CPL emitters. [ABSTRACT FROM AUTHOR]

Lead halide perovskite nanocrystals (NCs) have recently drawn considerable attention in the fields of materials science and nanotechnology. However, a major drawback of these NCs is the reliance on toxic lead, which hinders widespread application. Herein, a new class of lead‐free perovskite NCs, that is, lanthanide double perovskite (Ln‐DP) NCs, with f‐orbital‐induced optical properties, is introduced. The Pr‐, Ce‐, Tb‐, Eu‐, Sm‐, and Yb‐based Ln‐DP NCs display narrow d→f and f→f emissions ranging from the UV‐C to the near‐infrared spectral region. Experimental data and calculations reveal that the emissive Ln‐DP NCs exhibit small molecule‐like electronic absorptions: f→d atomic transitions or ligand‐to‐metal charge transfer transitions. Last, it is demonstrated that by alloying Ln compositions in the DP NCs, new materials with unique and improved optical properties can be obtained. These Ln‐DP NCs are promising for optical sensing and lighting, and as components in optoelectronic and/or magneto‐fluorescent devices. [ABSTRACT FROM AUTHOR]