Lanthanide-based Materials Research Articles

Probing the electronic structure, optical, and transport nature of lanthanide-based ternary materials: A First-principles perspective

High thermal stability and adjustable optoelectronic properties are the unique characteristics of lanthanide-based materials. The complex interplay between unique electronic, optical, and thermoelectric characteristics of lanthanide-based ternary chalcogenides is investigated by first principles modeling. The cohesive energy values were anticipated to be −4.54 eV/atom for PrSF and −4.87 eV/atom for PrSBr suggesting PrSBr to have the greatest bonding properties and is the most stable material. The computed formation energies range from −1.3 to −3.0 (eV/f. u), demonstrating their stability. The inclusion of bromine, a more electronegative element than fluorine, produces unique hybridization patterns and spin polarization effects. Compared to PrSBr, PrSF bonding employs more effective orbital hybridization, resulting in a greater band gap. PrSF has a higher frequency dielectric constant compared to PrSBr. The absorption edges in the ε2(ω) result from optical transitions between the Pr-f, S-p, F-p, and Br-p states. As the temperature rises, the Seeback coefficients for PrSF and PrSBr decrease exponentially. The thermal conductivity spectra of PrSF and PrSBr materials exhibit a linear increase across the temperature range. As temperature rises, the concentration of carriers and mobility increases, resulting in increased electrical conductivity values.

Multifunctional 1D lanthanide-based coordination polymers exhibiting single-chain magnets and fluorescence detection

Given the extensive applications of lanthanide-based materials in optics, electricity, magnetism, biomedicine, and other fields, the strategic development of multifunctional lanthanide-based molecular materials through meticulous design of organic ligands and rational selection of Ln3+ ions with distinct characteristics holds significant importance. In this work, a series of 1D chain lanthanide-based polymers {Ln(L)3(H2O)2}n (Ln = Eu for 1, Gd for 2, Tb for 3, Dy for 4) were successfully synthesized by using monomethyl isophthalate (HL) to control the hydrolysis of Ln3+ ions. Magnetic results revealed a weak paramagnetic interaction in 2, an antiferromagnetic coupling in 3, and an intriguing single-chain magnets behavior in 4. Compound 4 characterized an effective energy barrier of 38.08 K without a direct current field. Additionally, compounds 1, 3 and 4 exhibited photoluminescence behaviors, and the photoluminescence quantum yield (PLQY) of 1 was as high as 56 %. Compound 3 exhibited efficient detection of acetylacetone (acac) and nitroarenes through luminescence quenching, achieving the low limits of detection (LOD) of 0.068 μM for acac, 0.142 μM for Nitrobenzene, 0.260 μM for 4-Chloronitrobenzene and 0.276 μM for p-Nitrobenzoic acid. This study successfully prepared multifunctional lanthanide polymers, incorporating magnetic, optical, and sensing properties, by precisely controlling the hydrolysis of Ln3+ ions using organic ligands. These findings not only enrich the repertoire of multifunctional lanthanide-based materials but also broaden their applications in diverse domains.

Ultrastrong up-conversion luminescence in inert-active-inert sandwich structure with critical inert-core size

Lanthanide-based up-conversion materials exhibit abundant emission colors under infrared excitation; however, enhancing their up-conversion luminescence efficiency remains a hot topic and a challenge. Here, we show ultra-strong up-conversion luminescence in an inert-active-inert sandwich structure with critical core sizes. It is observed that the emission intensity of the sandwich structure (NaYF4@NaYbF4:0.5 %Tm@ NaYF4) is equal to ∼ 129 times of that in the NaYF4@NaYbF4:0.5 %Tm core/shell nanoparticles and 64 times of that in the NaYbF4:0.5 %Tm@Y core/shell nanoparticles. Moreover, it is more than a tenfold enhancement compared to the well-known classic core–shell structures (NaYF4:20 %Yb, 0.5 %Tm@NaYF4). By restricting the activator to 2D planes, their interactions with vacancies that are randomly distributed in 3D space are minimized. As a result, the energy transfer rate of Yb3+ defects is suppressed in this sandwich structure, while further effectively maintaining or enhancing the energy transfer from Yb3+ to the activator. Worth mentioning is that the strongest up-conversion luminescence is observed in the inert-active-inert sandwich structure with a critical inert core size of approximately 85 nm, which is in good agreement with the inflexion point of the calculated the effective excitation volume per unit cross-section.

Developing highly reliable Ag@NaYF4 hybrid structures for efficiently improving optical property

Here, we report a rational method for constructing a composite functional surface-enhanced Raman scattering (SERS) substrate, which is prepared by modifying the surfaces of β-NaYF4:Yb3+/Er3+ microtubes (MTs) with Ag nanoparticles (NPs). A single Ag@NaYF4 MT hybrid structure (Ag@NaYF4 MTHS) improves SERS activity compared to a typical substrate consisting of pure Ag NPs deposited on glass slide and exhibits excellent Raman signal response to various probe molecules (4-nitrothiophenol (4-NTP), crystal violet (CV), and Rhodamine 6G (Rh6G)). Furthermore, the Ag@NaYF4 MTHS substrate presents good catalytic performance and the plasmon-driven catalytic kinetics process is successfully monitored by using in situ SERS spectroscopy technique. This study provides valuable insights for designing multifunctional hybrid structures that incorporate containing noble metallic and lanthanide-based materials. These composite structures hold significant potential for advancing applications in photocatalysis, sensor, and in situ bio/chemical-analysis.

Luminescent lanthanide-based molecular materials: applications in photodynamic therapy.

Luminescent lanthanide molecular compounds have recently attracted attention as potential photosensitizers (PSs) for photodynamic therapy (PDT) against malignant cancer tumours because of their predictable systemic toxicity, temporospatial specificity, and minimal invasiveness. A photosensitizer exhibits no toxicity by itself, but in the presence of light and oxygen molecules, it can generate reactive oxygen species (ROS) to cause damage to proteins, nucleic acids, lipids, membranes, and organelles, which can induce cell apoptosis. This review focuses on the latest developments in luminescent lanthanide-based molecular materials as photosensitizers and their applications in photodynamic therapy. These molecular materials include lanthanide coordination complexes, nanoscale lanthanide coordination polymers, and lanthanide-based nanoscale metal-organic frameworks. In the end, the future challenges in the development of robust luminescent lanthanide molecular materials-based photosensitisers are outlined and emphasized to inspire the design of a new generation of phototheranostic agents.

Physical and Chemical Characteristics of the Chromium and the Cerium Group Lanthanide-Based New Materials

Physical and Chemical Characteristics of the Chromium and the Cerium Group Lanthanide-Based New Materials

Orotic acid-capped Tb(III)-doped calcium sulphate nanorods for the selective detection of tryptophan.

Lanthanide-based luminescent materials have gained huge attention due to their applications in optoelectronic devices, sensing, bio-imaging, anti-counterfeiting, and more. In this work, we report a luminescence-based sensor for the detection of tryptophan using orotic acid-capped Tb3+-doped CaSO4 nanorods (NRs). Orotic acid (OA) was found to play a dual role as a capping agent to control the growth of the nanorods and as a sensitizer for Tb3+ ions. The resulting nanorods exhibited excellent dispersibility and strong photoluminescence signals characteristic of Tb3+ ions in the visible region. Nearly 10-fold enhancement in the emission intensity was noted through OA sensitization compared to direct excitation of Tb3+ ions (acceptors). Interestingly, the strong emission intensity of the NRs reduced significantly with the addition of tryptophan. In contrast, hardly any change was noted with the addition of other amino acids and metal ions, suggesting greater selectivity for tryptophan. Moreover, there is barely any notable interference from other amino acids toward the detection of tryptophan. The limit of detection is found to be ∼0.61 μM. Finally, the sensing study was extended to biological samples to detect tryptophan present in blood plasma, urine, and saliva samples. The nanorods demonstrated high detection abilities, indicating the potential of the developed materials for biomedical applications.

Lanthanide hydrogels with tunable circularly polarized luminescence (CPL) via supramolecular chirality induction

“Supramolecular chirality induction” from cholate assembly, along with non-covalent sensitization of various lanthanide emission, provides an efficient induction of tunable CPL in lanthanide-based soft materials.

Cross Relaxation Enables Spatiotemporal Color-Switchable Upconversion in a Single Sandwich Nanoparticle for Information Security.

Smart control of ionic interaction dynamics offers new possibilities for tuning and editing luminescence properties of lanthanide-based materials. However, it remains a daunting challenge to achieve the dynamic control of cross relaxation mediated photon upconversion, and in particular the involved intrinsic photophysics is still unclear. Herein, this work reports a conceptual model to realize the color-switchable upconversion of Tm3+ through spatiotemporal control of cross relaxation in the design of NaYF4:Gd@NaYbF4:Tm@NaYF4 sandwich nanostructure. It shows that cross relaxation plays a key role in modulating upconversion dynamics and tuning emission colors of Tm3+. Interestingly, it is found that there is a short temporal delay for the occurrence of cross relaxation in contrast to the spontaneous emission as a result of the slight energy mismatch between relevant energy levels. This further enables a fine emission color tuning upon non-steady state excitation. Moreover, a characteristic quenching time is proposed to describe the temporal evolution of cross relaxation quantitatively. These findings present a deep insight into the physics of ionic interactions in heavy doping systems, and also show great promise in frontier applications including information security, anti-counterfeiting and nanophotonics.

Enhancing the Circularly Polarized Luminescence of Europium Coordination Polymers by Doping a Chromophore Ligand into Superhelices.

Lanthanide-based molecular materials showing efficient circularly polarized luminescence (CPL) activity with a high quantum yield are attractive due to their potential applications in data storage, optical sensors, and 3D displays. Herein we present an innovative method to achieve enhanced CPL activity and a high quantum yield by doping a chromophore ligand into a coordination polymer superhelix. A series of homochiral europium(III) phosphonates with a helical morphology were prepared with the molecular formula S-, R-[Eu(cyampH)3-3n(nempH)3n]·3H2O (S/R-Eu-n, n = 0-5%). The doping of chromophore ligand S- or R-nempH2 into superhelices of S/R-Eu-0% not only turned on the CPL activity with the dissymmetry factor |glum| on the order of 10-3 but also increased the quantum yield by about 14-fold. This work may shed light on the development of efficient CPL-active lanthanide-based coordination polymers for applications.

On the calculation of lanthanide systems. The spectral parameters of praseodymium trivalent ion

In this work, taking the Pr(III) ion as a suitable case study, the authors test the capacity of a series of Gaussian Type Orbitals (GTOs) basis sets to account for the atomic spectra of lanthanide ions. An extended relevance of this assessment can be found in modeling the luminescence of lanthanide-based materials. It was selected the Pr(III) case because it shows a rather rich collection of experimental data, emerging from the f2 and fd configurations. The energy barycenters of spectral multiplets can be equated analytically in terms of the so-called Slater-Condon parameters. By multi-configurational ab initio procedures, with basis sets from existing GTO repositories, the calculated f→f transitions are moderately higher than the experimental values, while the relative energies of Fd states undergo both under- and over-estimation. The GTO shortcomings, that are impacting the accuracy, were debated, the critical perspective spreading the seeds of future development.

MnOx In Situ Growth-Induced Luminescence and Oxidase-Like Feature Bimodulation of CePO4:Tb Nanorods: Toward Ascorbic Acid-Related Bioanalysis in a "One-Stone-Two-Birds" Manner.

Nanozyme-based multimode detection is a useful means to improve the accuracy and stability of analytical methods. However, both multifunctional nanozymes and related multimodal sensing strategies are still very scarce. Besides, they require complex processes to fabricate and operate. To fill this gap, here we propose a spontaneous interfacial in situ growth strategy to prepare a new bifunctional material (CePO4:Tb@MnOx) featuring good oxidase-like activity and green photoluminescence for the dual-mode colorimetric/luminescence determination of ascorbic acid (AA)-related biomarkers specifically. CePO4:Tb@MnOx was gained through the controllable redox reaction between KMnO4 and CePO4:Tb nanorods. It was interestingly found that MnOx in situ growth not only significantly enhanced the enzyme-like activity but also could reversibly regulate the luminescence of CePO4:Tb via a dual quenching mechanism. More interestingly, CePO4:Tb@MnOx exhibited a distinctive response toward AA against other reducing species. A double-coordination regulation mechanism was further verified to clarify the catalytic activity and luminescence switching behaviors in CePO4:Tb@MnOx. Based on these findings, a dual-mode colorimetric/luminescence approach was established for AA sensing in a "one-stone-two-birds" manner, providing excellent selectivity, sensitivity, and practicability. Furthermore, the determination of AA-related biomarkers, including acid phosphatase activity and organophosphorus residue, was also validated by the sensing principle. Our work not only deepens the understanding of the coordinated regulation of the luminescence and enzyme-like features in lanthanide-based materials but also offers a novel way to design and develop multifunctional nanozymes for advanced bioanalytical applications.

Recent Progress in Photonic Upconversion Materials for Organic Lanthanide Complexes.

Organic lanthanide complexes have garnered significant attention in various fields due to their intriguing energy transfer mechanism, enabling the upconversion (UC) of two or more low-energy photons into high-energy photons. In comparison to lanthanide-doped inorganic nanoparticles, organic UC complexes hold great promise for biological delivery applications due to their advantageous properties of controllable size and composition. This review aims to provide a summary of the fundamental concept and recent developments of organic lanthanide-based UC materials based on different mechanisms. Furthermore, we also detail recent applications in the fields of bioimaging and solar cells. The developments and forthcoming challenges in organic lanthanide-based UC offer readers valuable insights and opportunities to engage in further research endeavors.

Exploring Ln(III)-Ion-Based Luminescent Species as Down-Shifters for Photovoltaic Solar Cells.

In this work, we have compiled our research on lanthanide-based luminescent materials for use as down-shifter layers in photovoltaic (PV) mini-modules. The complexes we have prepared (C1-17), with formulas [Eu2(phen)2(bz)6] (C1), [Eu2(bphen)2(bz)6] (C2), [Eu(tta)3bphen] (C3), [Eu(bta)3pyz-phen] (C4), [Eu(tta)3pyz-phen] (C5), [Eu(bta)3me-phen] (C6), [Er(bta)3me-phen] (C7), [Yb(bta)3me-phen] (C8), [Gd(bta)3me-phen] (C9), [Yb(bta)3pyz-phen] (C10), [Er(tta)3pyz-phen] (C11), [Eu2(bz)4(tta)2(phen)2] (C12), [Gd2(bz)4(tta)2(phen)2] (C13), [EuTb(bz)4(tta)2(phen)2] (C14), [EuGd(bz)4(tta)2(phen)2] (C15), [Eu1.2Gd0.8(bz)4(tta)2(phen)2] (C16), and [Eu1.6Gd0.4(bz)4(tta)2(phen)2] (C17), can be grouped into three families based on their composition: Complexes C1-6 were synthesized using Eu3+ ions and phenanthroline derivatives as the neutral ligands and fluorinated β-diketonates as the anionic ligands. Complexes C7-11 were prepared with ligands similar to those of complexes C1-6 but were synthesized with Er3+, Yb3+, or Gd3+ ions. Complexes C12-17 have the general formula [M1M2(bz)4(tta)2(phen)2], where M1 and M2 can be Eu3+, Gd3+, or Tb3+ ions, and the ligands were benzoate (bz-), 2-thenoyltrifluoroacetone (tta-), and 1,10-phenanthroline (phen). Most of the complexes were characterized using X-ray techniques, and their photoluminescent properties were studied. We then assessed the impact of complexes in the C1-6 and C12-17 series on the EQE of PV mini-modules and examined the durability of one of the complexes (C6) in a climate chamber when embedded in PMMA and EVA films. This study emphasizes the methodology employed and the key findings, including enhanced mini-module efficiency. Additionally, we present promising results on the application of complex C6 in a bifacial solar cell.

Self-Assembly of Triple-Stranded Lanthanide Molecular Quasi-Lantern Containing 2,2'-Bipyridine Receptor: Luminescence Sensing and Magnetic Property.

Ln2L3-type supramolecular architectures have received significant attention recently due to their unique magnetism and optical properties. Herein, we report the triple-stranded Ln2L3-type lanthanide molecular quasi-lanterns, which are fabricated by the deprotonation self-assembly of a linear ligand featuring a β-diketone chelating claw and 2,2'-bipyridine (bpy) moiety with lanthanide ions (Ln = Eu3+ and Dy3+). The crystal structure analysis indicates that Eu3+ and Dy3+ ions are all coordinated by eight oxygen donors but in different coordination geometries. The eight oxygen donors in Eu2L3 and Dy2L3 are arranged in a square antiprism and triangular dodecahedron geometry, respectively. Taking into account the fact that the bpy moiety has a strong coordination affinity for transition metal ions, luminescence sensing toward Cu2+ ions has been demonstrated with Eu2L3, bearing a detection of limit as low as 2.84 ppb. The luminescence sensing behavior of Eu2L3 is ascribed to the formation host-guest complex between Eu2L3 and Cu2+ ions with a 1:2 binding ratio. Dynamic AC susceptibility measurements for Dy2L3 reveal the relaxation of magnetization in it. This work provides a potential way for design and fabrication of lanthanide-based molecular materials with functions endowed by the ligands.

Insight into Eu3+-Doped Phase-Change K3Lu(PO4)2 Phosphate toward Data Encryption.

Adjusting the local coordination environment of lanthanide luminescent ions can modulate their crystal-field splittings and broaden their applications in the relevant optical fields. Here, we introduced Eu3+ ions into the phase-change K3Lu(PO4)2 phosphate and found that the temperature-induced reversible phase transitions of K3Lu(PO4)2 (phase I ⇆ phase II and phase II ⇆ phase III, below room temperature) give rise to an obvious photoluminescence (PL) difference of Eu3+ ions. The Eu3+ emission mainly focused on the 5D0 → 7F1 transition in phase III but manifested comparable 5D0 → 7F1,2 transitions in the two low-temperature phases. On this basis, the change of Eu3+-doped concentration led to the phase evolution in Eu3+:K3Lu(PO4)2, which could stabilize two types of low-temperature polymorphs to the specific temperature by controlling the doping content. Finally, we proposed a feasible information encryption strategy based on the PL modulation of Eu3+:K3Lu(PO4)2 phosphors, which was caused by the temperature hysteresis of the relevant phase transition, exhibiting good stability and reproducibility. Our findings pave an avenue for exploring the optical application of lanthanide-based luminescent materials by introducing phase-change hosts.

Photo-responsive Single-Molecule Magnet Showing 0D to 1D Single-Crystal-to-Single-Crystal Structural Transition and Hysteresis Modulation.

Photo-responsive lanthanide-based single-molecule magnets (SMM) hold great promise for future switching and memory devices. Herein, we report a dysprosium phosphonate [DyIII (SCN)2 (NO3 )(depma)2 (4-hpy)2 ] (1Dy), which features a supramolecular framework containing layers of hydrogen-bonding network and pillars of π-π interacted anthracene units. The photocycloaddition reaction of anthracene pairs led to a rapid and reversible single-crystal-to-single-crystal (SC-SC) structural transition to form the 1D coordination polymer [DyIII (SCN)2 (NO3 )(depma2 )(4-hpy)2 ]n (2Dy), accompanied by photoswitchable SMM properties with the reduction of effective energy barrier by half and the narrowing of the butterfly-like hysteresis loop. The diluted sample showed a photo-induced switch of the blocking temperature (TB ) from 3.8 K for 1Dy@Y to 2.6 K for 2Dy@Y. This work may inspire the construction of lanthanide-based molecular materials with targeted photo-responsive magnetic properties.

Water-Soluble Cationic Eu3+-Metallopolymer with High Quantum Yield and Sensitivity for Intracellular Temperature Sensing.

Lanthanide-based (Ln3+) luminescent materials are ideal candidates for use in fluorescence intracellular temperature sensing. However, it remains a great challenge to obtain a Ln3+-ratiometric fluorescence thermometer with high sensitivity and quantum yield in an aqueous environment. Herein, a cationic Eu3+-metallopolymer was synthesized via the coordination of Eu(TTA)3·2H2O with an AIE active amphipathic polymer backbone that contains APTMA ((3-acrylamidopropyl) trimethylammonium) and NIPAM (N-isopropylacrylamide) units, which can self-assemble into nanoparticles in water solution with APTMA and NIPAM as the hydrophilic shell. This polymer exhibited highly efficient dual-emissive white-light emission (Φ = 34.3%). Particularly, when the temperature rises, the NIPAM units will transform from hydrophilic to hydrophobic in the spherical core of the nanoparticle, while the VTPE units are moved from inside the nanoparticle to the shell, activating its nonradiative transition channel and thereby decreasing its energy transfer to Eu3+ centers, endowing the Eu3+-metallopolymer with an extremely high temperature sensing sensitivity within the physiological temperature range. Finally, the real-time monitoring of the intracellular temperature variation is further conducted.

A susceptible coordination hybrid based terbium sensibilization coupled ESIPT effects for pattern discrimination of analogues.

Multianalyte detection and analogue discrimination are extremely valuable frontier areas for their wide applications in environmental, medical, clinical and industrial analyses. Nowadays, researchers rack their brains on how to develop excellent multianalyte chemosensors that have presented huge challenges in designing high-efficient fluorescent sensing materials and constructing high-throughput detection methods. In this paper, we propose a novel strategy to utilize the dual-emission fluorescent detection platform as a lab-on-a-molecule, arising from the disalicylaldehyde-coordinated hybrid H2Qj3/Tb based terbium sensibilization coupled excited-state intramolecular proton transfer effects. Using the statistical analysis (PCA and HCA) for sensing signals of three fluorescence channels (431, 543 and 583nm), we demonstrate this elaborate chemosensor with multianalyte detection of three species (solvents, anions and cations) and pattern discrimination of analogues. As a result, the H2Qj3/Tb shows great lab-on-a-molecule characters for each set of species, resulting in the easier identification of many critical analytes (e.g., H2O, NO2- and Fe3+) and discrimination of analogues. In addition, it is also proven to be able to provide reliable content determination for an analyte, especially the NO2- (LOD=0.37μM), and discrimination for mixed analogues. A combination of easy-to-implement preparation procedure and data analysis technique makes this work promising for not only designing similar lanthanide-based materials but also realizing more high-efficient multianalyte sensing systems towards various potential applications.

Noncentrosymmetric Lanthanide-Based MOF Materials Exhibiting Strong SHG Activity and NIR Luminescence of Er3+: Application in Nonlinear Optical Thermometry

Optically active luminescent materials based on lanthanide ions attract significant attention due to their unique spectroscopic properties, nonlinear optical activity, and the possibility of application as contactless sensors. Lanthanide metal-organic frameworks (Ln-MOFs) that exhibit strong second-harmonic generation (SHG) and are optically active in the NIR region are unexpectedly underrepresented. Moreover, such Ln-MOFs require ligands that are chiral and/or need multistep synthetic procedures. Here, we show that the NIR pulsed laser irradiation of the noncentrosymmetric, isostructural Ln-MOF materials (MOF-Er3+ (1) and codoped MOF-Yb3+/Er3+ (2)) that are constructed from simple, achiral organic substrates in a one-step procedure results in strong and tunable SHG activity. The SHG signals could be easily collected, exciting the materials in a broad NIR spectral range, from ≈800 to 1500 nm, resulting in the intense color of emission, observed in the entire visible spectral region. Moreover, upon excitation in the range of ≈900 to 1025 nm, the materials also exhibit the NIR luminescence of Er3+ ions, centered at ≈1550 nm. The use of a 975 nm pulse excitation allows simultaneous observations of the conventional NIR emission of Er3+ and the SHG signal, altogether tuned by the composition of the Ln-MOF materials. Taking the benefits of different thermal responses of the mentioned effects, we have developed a nonlinear optical thermometer based on lanthanide-MOF materials. In this system, the SHG signal decreases with temperature, whereas the NIR emission band of Er3+ slightly broadens, allowing ratiometric (Er3+ NIR 1550 nm/SHG 488 nm) temperature monitoring. Our study provides a groundwork for the rational design of readily available and self-monitoring NLO-active Ln-MOFs with the desired optical and electronic properties.