Luminescent Lanthanide Research Articles

Smart Applications of Lanthanide Chelates-based Luminescent Probes in Bio-Imaging.

Luminescent Lanthanide (III) (Ln(III)) bioprobes (LLBs) have been extensively used in the last two decades as intracellular molecular probes in bio-imaging for the efficient revelation of analytes, to signal intracellular events (enzymes/protein activity, antigen-antibody interaction), target specific organelles, and determine parameters of particular biophysical interest, to gain important insights on pathologies or diseases. The choice of using a luminescent Ln(III) coordination compound with respect to a common organic fluorophore is intimately connected to how their photophysical sensitization (antenna effect) can be finely tuned and especially triggered to respond (even quantitatively) to a certain biophysical event, condition or analyte. While there are other reviews focused on how to design chromophoric ligands for an efficient sensitization of Ln(III) ions, both in the visible and NIR region, this review is application-driven: it is a small collection of particularly interesting examples where the LLB's emissive information is acquired by imaging the emission intensity and/or the fluorescence lifetime (fluorescence lifetime imaging microscopy, FLIM).

Hydrogen-Bond-Regulated Tb3+-Centered Emission in a ZnII-TbIII Heterometallic Compound for Water Sensing in Ethanol and Gasoline.

Luminescent lanthanide compounds stand out for their distinctive characteristics including narrow emission bands, substantial Stokes shifts, high quantum yields, and unique luminescent colors. However, Ln3+ is highly susceptible to vibrational quenching from X-H (X = O/N) high-energy oscillators in the embedded organic antenna, resulting in significant nonradiative energy dissipation of the 5D excited states of Ln3+. Herein, we introduce a strategy based on supramolecular interactions to modulate the nonradiative transitions in a new ZnII-TbIII heterometallic compound, [ZnTb(HL)2(NO3)Cl2]·2CH3CN·H2O (ZnTb), based on a phenyl-substituted pyrazolinone-modified salicylamide-imide ligand (H2L). The regulation mechanisms are explored in detail both experimentally and theoretically. With the N,N'-dimethylformamide (DMF)-boosted Tb3+ luminescence, ZnTb⊃DMF (1 mg of ZnTb + 2 mL of DMF) realizes a rapid (3s) and sensitive detection of water in DMF with a detection limit of 0.021%. Further, ZnTb⊃DMF can detect trace amounts of water in ethanol and ethanol gasoline with a low detection limit of 0.023% and 0.048%. In addition, portable paper strips of ZnTb⊃DMF are prepared to improve its practicability, which can afford real-time and faster (1 s) in situ visual sensing of trace amounts of water in common organic solvents and ethanol gasoline with sensitivity comparable to the titration results. This study provides a new idea for the lanthanide luminescence modulation and application in the field of fluorescence sensing.

A Luminescent Lanthanide MOF for the Selective and Ultra‐High Sensitivity Detection of Caffeic Acid

ABSTRACTA novel metal–organic framework (MOF) [Eu3L4(CH3COO) (H2O)7]·(CH3CN)5 (1) based on the ligand H2L (3′,5′‐di(1H‐1,2,4‐triazole‐1‐yl)‐[1,1′‐biphenyl]‐3,5‐dicarboxylic acid) has been synthesized by the hydrothermal method. A complete characterization of 1 was conducted, employing a range of techniques including crystallography, PXRD, SEM, FTIR spectroscopy, and TGA analysis. The fluorescence sensing behavior of 1 was examined in a solution of N,N‐dimethylformamide (DMF). The results demonstrated that 1 exhibited a pronounced “turn‐off” fluorescence phenomenon in the presence of caffeic acid (CA). Despite the interference of 11 potential substances, 1 was still capable of effectively recognizing CA. The luminescence intensity ratio of 1 showed a strong linear relationship with CA concentration in the range 0–5 μM. The Ksv value was 2.49 × 105 M−1. Additionally, the detection mechanism was studied using PXRD, SEM, UV–Vis, and fluorescence lifetime methods.

A Multifaceted Luminescent Europium(III) Probe for the Discrimination of Nucleoside Phosphates and Detection of Organophosphate Nerve Agents.

The nucleotides play multiple fundamental roles that are essential in biochemical enzymatic reactions and signaling pathways. Many diseases are closely associated with their dysregulation. Therefore, reliable and sensitive optical probes to discriminate various nucleotides are essential in biochemistry, drug discovery, and disease diagnosis. Furthermore, developing reliable, easy-to-use optical sensors for extremely toxic organophosphonates/nerve-agents is critical to counter public health threats. Luminescent lanthanide(III) complexes have emerged as promising optical bioprobes owing to intraconfigurational f → f transitions. Herein, we present strategically designed Eu(III) probes: [Eu(THC)(X)3]Cl (Eu.1) and [Eu(TBC)(X)3]Cl/Br (Eu.2) containing pentadentate terpyridine dicarboxylates: 4'-(3,4,5-trihydroxyphenyl)-[2,2':6',2″-terpyridine]-6,6″-dicarboxylic acid (THC) and 4'-phenyl-[2,2':6',2″-terpyridine]-6,6″-dicarboxylic acid (TBC) and X = solvent. The Eu.1 probe is systematically evaluated for discrimination of various NPs and as a luminescent chemodosimetric probe for diethyl chlorophosphate (DCP) as a G-series nerve agent mimic. The time-delayed luminescence is used for discrimination between various adenine-based NPs under physiological conditions. The Eu.1 probe shows high affinity and selectivity for ADP enabling continuous monitoring of the ADP/ATP ratio in a simulated enzymatic reaction. Additionally, Eu.1 acted as a chemodosimetric probe for DCP. The interaction produces a change in the sensitization pathway, enhancing the Eu(III)-based luminescence with a ppb level of detection of DCP (LOD = 758 ppb). Our innovative approach expands applications of lanthanide luminescence for probing nucleotides and the detection of lethal nerve agents.

Dual–resonance enhancement and polarization control of upconversion luminescence of NaYF4:Yb,Er nanoparticles on 2D metal gratings

In this work, we report enhancement and polarization control of multi–color (green/red) upconversion luminescence (UCL) of lanthanide–doped (NaYF4:Yb,Er) nanoparticles by dual–resonance modes of surface plasmons (SP) on two–dimensional (2D) metal gratings in orthogonal directions. Investigations are performed for the SP resonance modes to be tuned, by adjusting the grating periods, to match any one or two of the green–UCL, red–UCL and excitation wavelengths. It is shown that, for the upconversion nanoparticles (UCNPs) on the 2D gratings with both of the dual resonance modes matching the green–/red–UCL or excitation wavelength, enhancements of the UCLs are roughly doubled, compared with their one–dimensional (1D) counterparts. And when the dual resonance modes match the green– or red–UCL and the excitation wavelength, enhancements of the UCLs are further greatly improved, in spite that the resonance modes for the excitation and emission light are in orthogonal directions. As the emitted UCL photons are largely coupled with the dual SP resonance modes, the radiated green– and red–UCL light can be distinguished by their linear polarization states in orthogonal directions. It is also indicated that polarization of the excitation light can influence the polarization of the UCL light when coupled with the SP resonance modes.

Mechanically sensitive luminescence of dinuclear lanthanide(III) complexes linked by biphenylene moieties with varying conformational freedom

Mechanically sensitive luminescence of dinuclear lanthanide(III) complexes linked by biphenylene moieties with varying conformational freedom

Achieving bi-function of enhanced CO2 gas sensing and orange-red light emission of La2O2CO3 1D nanostructures via Eu3+ doping

Bi-functional nanomaterials with gas sensing and luminescence are more attractive and promising compared with the counterpart single functional nanomaterials, and have become a hotspot subject. Herein, La2O2CO3 and La2O2CO3:Eu3+ one-dimensional (1D) nanostructures including nanofibers, hollow nanofibers and nanobelts are rationally designed and are synthesized by a facile electrospinning via regulating spinning parameters. Excellent bi-functionalities of enhanced CO2 gas sensing and intense orange-red light emission are achieved via Eu3+ doping in 1D La2O2CO3 nanostructures. CO2 sensors based on La2O2CO3:Eu3+ 1D nanostructures display superior selectivity, high response, short response/recovery time and good reproducibility. With respect to response time (2 s) and recovery time (9s), the La2O2CO3:Eu3+ hollow nanofibers sensor is the best of the presently reported La2O2CO3-based CO2 sensors. The enhanced CO2 sensing mechanism of La2O2CO3:Eu3+ 1D nanostructures can be contributed to the lattice distortion and increase of OH- groups due to Eu3+ doping. Meanwhile, La2O2CO3:Eu3+ 1D nanostructures emit bright orange-red light under 274-nm UV light excitation. The luminescent characteristics are easily adjusted by varying the doping concentrations of Eu3+ ions and changing the morphology of 1D nanostructures. Rationally devised and prepared La2O2CO3:Eu3+ 1D nanostructures with different morphologies can better meet the applications in CO2 gas sensing and rare earth luminescence fields. The preparation strategy of 1D nanostructures is established and the formation mechanism is advanced. The design concepts and fabrication methods established in this work can be extended to prepare other 1D nanostructured materials, promoting the developments of 1D bi-functional nanostructures in the fields of gas sensing and luminescence.

Theoretical insights into the vibrational spectra and chemical bonding of Ln(III) complexes with a tripodal N4O3 ligand along the lanthanide series.

This study provides new theoretical insights into the vibrational spectra of Ln(III) complexes, along the lanthanide series by utilizing the LModeAGen protocol and integrating cutting-edge topological ideas. It provides a quantitative interpretation of the vibrational spectra of [Ln(trensal)] complexes at the B3LYP/MWBn(Ln)/6-311++G** (n from 46 (La) to 60 (Lu)) level using the characterization of normal modes from the local vibrational mode theory. This involves decomposing normal vibrational modes related to the complex formation, distortions in the coordination sphere, and C-H vibrations into local mode contributions, offering particularly promising results aimed at the design of highly luminescent lanthanide complexes. This study also delivers key theoretical insights into the chemical bonding of the coordination sphere of [Ln(trensal)] by combining the local vibrational mode theory and the bond overlap model to achieve relationships between bond properties, including those of the Badger-type. Altogether, we present the theoretical framework necessary to quantitatively interpret the vibrational spectra of [Ln(trensal)] complexes along the lanthanide series and gain a better understanding of the lanthanide-ligand chemical bonds, thereby enhancing our understanding of their chemistry and guiding future design efforts.

Mild Focused Ultrasound-Induced Microscopic Heating of Nanoparticles Observed by Lanthanide Luminescence for Precise Sonothermal Cancer Therapy.

Focused ultrasound (FUS) is a recognized tool that can be used clinically for the thermal ablation of tumors. However, excessive heat can cause side effects on the ultrasound transmission path and normal tissues around the tumor. To address the issue, this work detected for the first time the effect of microscopic heating of nanoparticles under the action of FUS through the luminescence intensity ratio (LIR) and luminescence lifetime of temperature-responsive lanthanide-doped nanoparticles. When FUS is applied to the tissue embedded with nanoparticles, the increase in the microscopic temperature of the nanoparticles synchronously monitored by LIR is more obvious than the increase in the macroscopic temperature. Based on this phenomenon, the intensity of focused ultrasound can be finely regulated to avoid overheating while ensuring a therapeutic effect. This work achieves the measurement of the microscopic heating of nanoparticles under FUS, which is of great significance for the development of sonothermal cancer therapy.

Facile Synthesis of Ln-Doped Hydrogen-Bonded Organic Frameworks with Rare-Earth-Characteristic Long Persistent Luminescence.

Tunable luminescence-assisted information storage and encryption holds increasing significance in today's society. A promising approach to incorporating the benefits of both organic long persistent luminescent (LPL) materials and rare-earth (RE) luminescence lies in utilizing organic host materials to sensitize RE luminescence, as well as employing Förster resonance energy transfer from hydrogen-bonded organic framework (HOF) phosphorescence to RE compound luminescence. This work introduces a one-pot, in situ pyrolytic condensation method, achieved through high-temperature melting calcination, to synthesize lanthanide ion-doped HOF materials. This method circumvents the drawback of molecular triplet energy annihilation, enabling the creation of organic LPL materials with RE characteristics. The HOF material serves as the host, exhibiting blue phosphorescence and cyan LPL. By fine-tuning the doping amount, the composite material U-Tb-100 achieves green LPL with a luminescent quantum yield of 56.4 %, and an LPL duration of approximately 2-3 s, demonstrating tunable persistence. Single-crystal X-ray diffraction, spectral analysis, and theoretical calculation unveil that U-Tb-100 exhibits exceptional quantum yield and long-lived luminescence primarily due to the efficient sensitization of U monomer to RE ions and the PRET process between U and RE complexes. This ingenious strategy not only expands the repertoire of HOF materials but also facilitates the design of multifunctional LPL materials.

Luminescence Color Control Based on Inter Molecular Excited Energy Transfer Induced by Electrochromic Reaction

Electrochemical switching of luminescence color, i.e., electrofluorochromism, has received increasing attention because of its extensive applications. We have reported photo- and electrochemical- functional materials enabling dual reflective and emissive function by combining EC materials and luminescent lanthanide(III) complex. This modulation of emission is caused by control of photoexcitation energy transfer from the luminescent lanthanide(III) complex to EC material. In this study, we investigate the combination of a luminescent EC molecule and a blue luminescent molecule to achieve electrochemical control of luminescence color by controlling the energy transfer through an electrochromic reaction. We employed a functional leuco dye (Yellow-1), which shows yellow coloration and green emission by electrochemical oxidation, and 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT), which shows strong blue luminescence upon photoexcitation. Using this combination, the blue photoluminescence of the BBT molecule can be electrochemically modulated by the EC reaction of the Yellow-1 molecule, allowing the control of the luminescence color between blue and green emissions through electrochemical reactions.

Strong Red Luminescence in Europium Complexes Solution for Anti-Counterfeiting Applications.

Eu3+-activated phosphors with distinct photoluminescence properties are well-suited for diverse applications, including lighting, sensing, and imaging. Despite their potential, the large-scale and energy-efficient production of Eu3+-doped phosphors remains a significant challenge for industrial applications. This research delves into the luminescent performance of Eu3+ ions in nitrate solutions at room temperature by employing detailed spectroscopic characterization. Results reveal vibrant red luminescence at 594 nm and 616 nm in europium nitrate solutions, irrespective of concentration or solvent. We proposed a luminescent mechanism based on the formation of coordination complexes in nitrate solution. Furthermore, the investigation highlights the superior performance of NH2- over CH2-ligands in mitigating the deactivation of Eu3+ emissive state induced by OH- oscillators in H2O solvent, leading to enhanced photoluminescence. Particularly, europium nitrate solutions without lengthy preparation exhibit ligand-dependent luminescent feature, showcasing potential applications in anti-counterfeiting and coordination group structure detection. This study here not only enhances our understanding of rare earth luminescence mechanisms, but also broadens the range of rare earth luminescent materials.

Luminescent rare earth complexes of Ce3+, Eu2+and Yb2+with spiro-bis(pyrazolyl)borate ligands containing C–H···M interactions

Luminescent rare earth complexes based on interconfigurational 5d-4f transition have characteristics of adjustable emission spectra and short excited state lifetimes, showing potential applications in display, lighting and other fields. In this work, nine Ce3+, Eu2+ and Yb2+ complexes with spiro-bis(pyrazolyl)borate ligands, where pyrazolyl stands for pyrazolyl, 3-methylpyrazolyl, or 3,5-dimethylpyrazolyl, were designed and synthesized. Ce3+ complexes show emission colors of blue, with photoluminescence quantum yields (PLQYs) of 94%–100%; Eu2+ complexes show emission colors of yellow-green, with PLQYs of 60%–78%; Yb2+ complexes show emission colors of orange or red, with PLQYs of 3%–4%. In addition, the crystal structures and theoretical calculation results show C–H···M interactions between bridge-head H atoms of the spirane and central metal ions in these complexes. It is found that the introduction of spirane with large steric hindrance and the existence of C–H···M interactions can improve the stability of the complexes in air atmosphere.

Elucidating Polyphosphate Anion Binding to Lanthanide Complexes Using EXAFS and Pulsed EPR Spectroscopy.

Reversible anion binding to lanthanide complexes in aqueous solution has emerged as an effective method for anion sensing. Through careful design of the organic ligand, luminescent lanthanide complexes capable of binding biologically relevant anions in a bidentate or monodentate manner can be realized. While single-crystal X-ray diffraction analyses and NMR spectroscopy have revealed the structural geometry of several host-guest complexes, the challenge remains in designing preorganized lanthanide receptors with enhanced anion selectivity for broader applications in diagnostics and bioimaging. To address this challenge, innovative and complementary methods to investigate host-anion binding geometry are becoming increasingly important. Herein, we demonstrate the combined use of Eu L3-edge extended X-ray absorption fine structure (EXAFS) and electron paramagnetic resonance (EPR) spectroscopy to elucidate the binding of nucleoside phosphates (ATP, ADP, and AMP) to a cationic lanthanide complex. We establish that ATP unequivocally binds the lanthanide center in a bidentate manner in water, while ADP adopts both bidentate and monodentate modes, and AMP binds in a monodentate manner. This interdisciplinary approach provides deeper insight into lanthanide host-guest chemistry in solution, laying the groundwork for designing emissive probes that undergo specific anion-induced structural changes and elicit desired optical responses upon binding.

Regulating Energy Transfer Pathways to Construct Multicolor Luminescent Lanthanide Metal–Organic Frameworks and Their Multiorder Anticounterfeiting Barcodes and Antibiotic Sensing

Regulating Energy Transfer Pathways to Construct Multicolor Luminescent Lanthanide Metal–Organic Frameworks and Their Multiorder Anticounterfeiting Barcodes and Antibiotic Sensing

Green syntheses of novel luminescent lanthanide compounds based on pentafluorobenzoate

Green syntheses employing aqueous solutions of lanthanide chloride, NaOH, and pentafluorobenzoic acid were successfully developed and produced pure dinuclear α-Ln compounds, [Ln(L)3(H2O)4]2·2H2O (L: pentafluorobenzoate) and new ones: η-Ln, Na[Ln(L)3(H2O)4]·L·2H2O, and θ-Ln, with Ln: Eu(III), Gd(III), and Tb(III). The synthesis becomes even greener when mechanochemistry is employed because it is quantitative, solvent-free, fast (30 min), and energy efficient. The θ-Ln compounds still have unknown composition and structure, so its description and properties are not explored. The η-Ln compounds are 1-D coordination polymer with only one bridging L, which leads to a large Ln···Ln distance (6.865 Å). Heteronuclear α-Ln0.50Ln0.50′ and η-LnxLn1−x′ compounds, with x = 0.05, 0.25, 0.50, and 0.75, Ln, Ln′: Eu, Tb, and Gd, have been synthesized by mixing the proper proportion of the lanthanide chlorides in the initial solution. The η-EuxTb1−x materials present Tb(III) → Eu(III) energy transfer, which confers interesting luminescent and photophysical properties with relevant potential applications. The color of the emission under UV irradiation can be tuned by the composition of the η-EuxTb1−x materials as well as by the excitation wavelength. In addition, it was observed a significant increase (ca. 35–260 %) of the D05 Eu(III) emission lifetime in the η-EuxTb1−x compounds by varying the excitation wavelength.

Micronuclear battery based on a coalescent energy transducer.

Micronuclear batteries harness energy from the radioactive decay of radioisotopes to generate electricity on a small scale, typically in the nanowatt or microwatt range1,2. Contrary to chemical batteries, the longevity of a micronuclear battery is tied to the half-life of the used radioisotope, enabling operational lifetimes that can span several decades3. Furthermore, the radioactive decay remains unaffected by environmental factors such as temperature, pressure and magnetic fields, making the micronuclear battery an enduring and reliable power source in scenarios in which conventional batteries prove impractical or challenging to replace4. Common radioisotopes of americium (241Am and 243Am) are α-decay emitters with half-lives longer than hundreds of years. Severe self-adsorption in traditional architectures of micronuclear batteries impedes high-efficiency α-decay energy conversion, making the development of α-radioisotope micronuclear batteries challenging5,6. Here we propose a micronuclear battery architecture that includes a coalescent energy transducer by incorporating 243Am into a luminescent lanthanide coordination polymer. This couples radioisotopes with energy transducers at the molecular level, resulting in an 8,000-fold enhancement in energy conversion efficiency from α decay energy to sustained autoluminescence compared with that of conventional architectures. When implemented in conjunction with a photovoltaic cell that translates autoluminescence into electricity, a new type of radiophotovoltaic micronuclear battery with a total power conversion efficiency of 0.889% and a power per activity of 139 microwatts per curie (μW Ci-1) is obtained.

Upconversion and NIR-II luminescent rare earth nanoparticles combined with machine learning for cancer theranostics.

How to develop contrast agents for cancer theranostics is a meaningful and challenging endeavor, and rare earth nanoparticles (RENPs) may provide a possible solution. In this study, we initially modified RENPs through the application of photodynamic agents (ZnPc) and targeted the bevacizumab antibody for cancer theranostics, which was aimed at improving the therapeutic targeting and efficacy. Subsequently, we amalgamated anthocyanin with the modified RENPs, creating a potential cancer diagnosis platform. When the spectral data were obtained from the composite of cells, the crucial information was extracted through a competitive adaptive reweighted sampling feature algorithm. Then, we employed a machine learning classification model and classified both the individual spectral data and fused spectral data to accurately predict distinctions between breast cancer and normal tissue. The results indicate that the amalgamation of fusion techniques with machine learning algorithms provides highly precise predictions for molecular-level breast cancer detection. Finally, in vitro and in vivo experiments were carried out to validate the near-infrared luminescence and therapeutic effectiveness of the modified nanomedicine. This research not only underscores the targeted effects of nanomedicine but also demonstrates the potent synergy between optical spectral technology and machine learning. This innovative approach offers a comprehensive strategy for the integrated treatment of breast cancer.

Harnessing Spatiotemporal-Specific Tumorous Exosome Dynamics: Ultra-Sensitive Lanthanide Luminescence Detection Strategy Enabled by Exosomal Membrane Engineering for Melanoma Immunotherapy Monitoring.

Focused on the newly secreted tumorous exosomes during melanoma immunotherapy, this work has pioneered an ultra-sensitive spatiotemporal-specific exosome detection strategy, leveraging advanced exosomal membrane engineering techniques. The proposed strategy harnesses the power of amplified lanthanide luminescence signals on these exosomes, enabling precise and real-time monitoring of the efficacy of melanoma immunotherapy. The methodology comprises two pivotal steps. Initially, Ac4ManNAz-associated metabolic labeling is employed to evolve azide groups onto the membranes of newly secreted exosomes with remarkable selectivity. These azide groups serve as versatile clickable artificial tags, enabling the precise identification of melanoma exosomes emerging during immunotherapy. Subsequently, lanthanide-nanoparticle-functionalized polymer chains are controllably grafted onto the exosome surfaces through click chemistry and in situ Fenton-RAFT polymerization, serving as robust signal amplifiers. When integrated with time-resolved fluorescence detection, this strategy yields detection signals with an exceptionally high signal-to-noise ratio, enabling ultra-sensitive detection of PD-L1 antigen expression levels on the spatiotemporal-specific exosomes. The detection strategy boasts a wide linear concentration range spanning from 1.7 × 104 to 1.7 × 109 particles/mL, with a remarkable theoretical detection limit of 1.28 × 103 particles/mL. The remarkable enhancements in detection sensitivity and accuracy facilitate the evaluation of the efficacy of immunotherapeutic interventions in the mouse B16 melanoma model, notably revealing a substantial disparity in PD-L1 levels between immunotherapy-treated and untreated groups (P < 0.01) and further emphasizing the cumulative therapeutic effect that intensifies with repeated treatments (P < 0.001).

Efficient photosensitized luminescence from Eu3+ in inert nanocrystals via ligand coordination

Abstract Luminescent lanthanide ions incorporated in sodium yttrium fluoride nanocrystals are promising as new luminescent materials in optoelectronics and bioimaging since the nonradiative transition is significantly suppressed due to the absence of high-energy vibrational modes. To prepare optically and electrically active nanocrystals, we explored organic ligands that allow efficient triplet energy transfer to Eu3+ incorporated into nanocrystals, resulting in an efficient photosensitization effect in colloidal solutions and films. Further, we applied these emitting nanocrystals to light-emitting devices and observed the electroluminescence.