Luminescent Lanthanide Research Articles

Lanthanide Luminescence to Mimic Molecular Logic and Computing through Physical Inputs

AbstractThe remarkable advances in molecular logic reported in the last decade demonstrate the potential of luminescent molecules for logical operations, a paradigm‐changing concerning silicon‐based electronics. Trivalent lanthanide (Ln3+) ions, with their characteristic narrow line emissions, long‐lived excited states, and photostability under illumination, may improve the state‐of‐the‐art molecular logical devices. Here, the use of monolithic silicon‐based structures incorporating Ln3+ complexes for performing logical functions is reported. Elementary logic gates (AND, INH, and DEMUX), sequential logic (KEYPAD LOCK), and arithmetic operations (HALF ADDER and HALF SUBTRACTOR) exhibiting a switching ratio >60% are demonstrated for the first time using nonwet conditions. Additionally, this is the first report showing sequential logic and arithmetic operations combining molecular Ln3+ complexes and physical inputs. Contrary to chemical inputs, physical inputs may enable the future concatenation of distinct logical functions and reuse of the logical devices, a clear step forward toward input–output homogeneity that is precluding the integration of nowadays molecular logic devices.

Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals.

In this work, we describe a protocol for a novel application of hyperspectral imaging (HSI) in the analysis of luminescent lanthanide (Ln3+)-based molecular single crystals. As representative example, we chose a single crystal of the heterodinuclear Ln-based complex [TbEu(bpm)(tfaa)6] (bpm=2,2'-bipyrimidine, tfaa- =1,1,1-trifluoroacetylacetonate) exhibiting bright visible emission under UV excitation. HSI is an emerging technique that combines 2-dimensional spatial imaging of a luminescent structure with spectral information from each pixel of the obtained image. Specifically, HSI on single crystals of the [Tb-Eu] complex provided local spectral information unveiling variation of the luminescence intensity at different points along the studied crystals. These changes were attributed to the optical anisotropy present in the crystal, which results from the different molecular packing of Ln3+ ions in each one of the directions of the crystal structure. The HSI herein described is an example of the suitability of such technique for spectro-spatial investigations of molecular materials. Yet, importantly, this protocol can be easily extended for other types of luminescent materials (such as micron-sized molecular crystals, inorganic microparticles, nanoparticles in biological tissues, or labelled cells, among others), opening many possibilities for deeper investigation of structure-property relationships. Ultimately, such investigations will provide knowledge to be leveraged into the engineering of advanced materials for a wide range of applications from bioimaging to technological applications, such as waveguides or optoelectronic devices.

Bioactive, luminescent erbium-doped hydroxyapatite nanocrystals for biomedical applications

Diagnosis and imaging play an essential key role in primary detection, screening, and image-guided smart nanomedicine for healthcare solutions. This study illustrates the successful fabrication of luminescent lanthanide (erbium)-doped hydroxyapatite (Er-HAp) by one step facile wet-chemical precipitation method. The chemical compositions, morphology, optical, and biological properties were systematically characterized using relevant different structural, compositional analytical instrumentation and cytotoxicity assays. After erbium doping, synthesized luminescent nano-structured materials exhibited elongated morphology, with well dispersed <50 nm size distribution. The photoluminescence (PL) study confirmed three emission bands assigned to 4F3/2 → 4I15/2 (purple), 4F7/2 → 4I15/2 (blue), and 4S3/2 → 4I15/2 (green) transition states, respectively. In vitro bioactivity and optical imaging studies conducted in osteoblast like MG-63 cells confirmed the nontoxic luminescent behavior of the synthesized nanomaterials.

Divergent Adsorption-Dependent Luminescence of Amino-Functionalized Lanthanide Metal-Organic Frameworks for Highly Sensitive NO2 Sensors.

A novel gas sensing mechanism exploiting lanthanide luminescence modulation upon NO2 adsorption is demonstrated here. Two isostructural lanthanide-based metal-organic frameworks (MOFs) are used, including an amino group as the sensitive recognition center for NO2 molecules. The transfer of energy from the organic ligands to Ln is strongly dependent on the presence of NO2, resulting in an unprecedented photoluminescent sensing scheme. Thereby, NO2 exposition triggers either a reversible enhancement or a decrease in the luminescence intensity, depending on the lanthanide ion (Eu or Tb). Our experimental studies combined with density functional theory and complete active space self-consistent field calculations provide an understanding of the nature and effects of NO2 interactions within the MOFs and the signal transduction mechanism.

Water-soluble luminescent lanthanide complexes based on C6-DTTA-appended 5-aryl-2,2′-bipyridines

By using a number of synthetic approaches new lanthanide cations ligands based on 5-aryl-2,2′-bipyridines bearing diethylenetriamine tetracarboxylic acid (DTTA) residue at the C6-position of the pyridine moiety were synthesized. By using these ligands the water soluble lanthanide complexes (Ln = Eu, Tb, Sm, Dy) were prepared, and their photophysical properties were studied. For the europium complexes the luminescence quantum yields up to 12.8% and luminescence lifetime up to 1.09 ms were observed. For the terbium complexes of all the ligands a very weak luminescence with quantum yields not higher than 0.43% were observed. The influence of the nature of the bipyridine ligands on the photophysical properties of the lanthanide complexes was also discussed.

Cancer Stem Cell Target Labeling and Efficient Growth Inhibition of CD133 and PD-L1 Monoclonal Antibodies Double Conjugated with Luminescent Rare-Earth Tb3+ Nanorods

Rare-earth nanomaterials are being widely applied in medicine as cytotoxicity agents, in radiation and photodynamic therapy, as drug carriers, and in biosensing and bioimaging technology. Terbium (Tb), a rare-earth element belonging to the lanthanides, has a long luminescent lifetime, large stock displacement, narrow spectral width, and biofriendly probes. In cancer therapy, cancer stem cell (CSC)-targeted treatment is receiving considerable attention due to these cells’ harmful characteristics. However, CSCs remain barely understood. Therefore, to effectively label and inhibit the growth of CSCs, we produced a nanocomplex in which TbPO4·H2O nanorods were double conjugated with CD133 and PD-L1 monoclonal antibodies. The Tb3+ nanomaterials were created in the presence of a soft template (polyethylene glycol 2000). The obtained nanomaterial TbPO4·H2O was hexagonal crystal and nanorod in shape, 40–80 nm in diameter, and 300–800 nm in length. The nanorods were further surfaced through tetraethyl orthosilicate hydrolysis and functionalized with amino silane. Finally, the glutaraldehyde-activated Tb3+ nanorods were conjugated with CD133 monoclonal antibody and PD-L1 monoclonal antibody on the surface to obtain the nanocomplex TbPO4·H2O@silica-NH2+mAb^CD133+mAb^PD-L1 (TMC). The formed nanocomplex was able to efficiently and specifically label NTERA-2 cells, a highly expressed CD133 and PD-L1 CSC cell line. The conjugate also demonstrated promising anti-CSC activity by significant inhibition (58.50%) of the growth of 3D tumor spheres of NTERA-2 cells (p &lt; 0.05).

Construction of visible luminescent lanthanide coordination compounds with different stacking modes based on a carboxylate substituted terpyridyl derivative ligand

Five new binuclear lanthanide coordination compounds, namely, Eu2(L)6(H2O)2·2(HL) (1), Ln2(L)6(H2O)2·5H2O (Ln = Sm (2), Eu (3), Gd (4), Tb (5)) (HL = 4′-(2-carboxyphenyl)-2,2′:6′,2″-terpyridine) were prepared under hydrothermal methods. Compounds 1–5 exhibit binuclear structures, and further packed by the hydrogen bonding interactions to form different supramolecular structures. These lanthanide compounds present typical visible luminescence and good thermal stabilities. The difference of luminescent intensity in 1-Eu and 3-Eu is caused by the rigidity of compounds.

A mini-review on recent progress of new sensitizers for luminescence of lanthanide doped nanomaterials

Trivalent lanthanide (Ln3+) doped luminescent nanocrystals are promising for applications ranging from biosensor, lasing, super-resolution nanoscopy, information security and so on. Although the utility prospect is of great attractions, the light absorption of these lanthanide doped nanocrystals is inherently weak due to the electric dipole-forbidden 4f → 4f transitions. Even worse, the quantum yields of upconverison nanocrystals are very low, which will unavoidably hinder their further applications. In a typical lanthanide luminescent nanosystem, both sensitizers as light absorption centers and activators as light emitting centers are necessary and important for desired luminescence properties. Among various sensitization systems, only Yb3+ and Nd3+ are considered as the most efficient sensitizers. Thus, the corresponding excitation wavelengths are strictly limited around 980 and 808 nm. To enrich excitation wavelengths and boost luminescence intensity, exploring more sensitization units that possess larger absorption cross section, higher efficiency of energy transfer process and independent excitation is imperative and beneficial for the demands of different applications, such as broadened absorption in near infrared (NIR) region for higher conversion efficiency of solar cells, prolonged excitation wavelength to second near infrared windows region (NIR II, 1,000–1,700 nm) for in vivo fluorescence imaging with deeper tissue depth and higher spatial resolution, more orthogonal excitations and emissions to improve optical multiplexing, and so on. Therefore, in the review, we primarily conclude several major energy transfer mechanisms from sensitizers to activators. Then we present three kinds of sensitizers, including lanthanide ions, organic dyes and quantum dots (QDs), and introduce the newly designed sensitization system that allows us to exploit superior excitation wavelength and amplify luminescence intensity. Finally, several future challenges and opportunities for the sensitizing strategies are discussed in hope of directing and broadening the applications of lanthanide nanosystem.

Luminescence of divalent lanthanide doped BaBrI single crystal under synchrotron radiation excitations

Luminescence excitation spectra of BaBrI single crystals doped by divalent lanthanide ions are studied using synchrotron radiation excitations from the MAX IV 1.5 GeV storage ring. The energy of the edge and the formation of core cation exciton as well as the energy threshold of the multiplications of electronic excitations is found. It was clearly established the energy transfer from intrinsic luminescence centers to Sm2+ and Eu2+ ions.

Nanotoxicological study of downconversion Y2 O3 :Eu3+ luminescent nanoparticles functionalized with folic acid for cancer cells bioimaging.

Luminescent lanthanide downconversion nanoparticles (DCNPs) provide a combination of high luminescence intensity, sharp emission peaks with narrow bandwidth and a large Stokes' shift, leading to high-performance biomedical applications mainly for imaging. The purpose of this study is to present a nanotoxicological study of DCNPs Y2 O3 codoped with Eu3+ and functionalized with folic acid (FA). These assessments include cytotoxicity, genotoxicity, hemocompatibility, and in vitro inflammatory studies. We demonstrated by flow cytometry and confocal microscope the internalization of FA-DCNPs in breast cancer and melanoma cells. They were synthesized by sol-gel method and coated with a thin silica shell to make them biocompatible; also they were functionalized with amino groups and FA ligands that bind to the folate receptors (FR) located on the surface of the cancer cells studied. This functionalization enables the DCNPs to be internalized into the cancer cells via endocytosis by the conjugation FA-FR. The DCNPs were characterized with transmission electron microscope, Fourier transform infrared spectroscopy and photoluminescence. The nanotoxicological assessments demonstrated that both nanoparticles (bare and functionalized) are no cytotoxic and no genotoxic at the tested concentrations (0.01-20 μg/mL) in three cell lines (breast, skin cancer, and osteoblasts). Also they are hemocompatible and do not exert nitric oxide production in vitro by macrophages. The FA-DCNPs were clearly localized into the cell cytoplasm with bright red luminescence. Thus, herein we present a complete nanotoxicological study of FA-DCNPs Y2 O3 codoped with Eu3+ and we conclude that these nanoparticles are biocompatible and can be further used for cancer cells bioimaging.

Crystal Structure Dependence of the Energy Transfer from Tb(III) to Yb(III) in Metal–Organic Frameworks Based in Bispyrazolylpyridines

Luminescent mixed lanthanide metal−organic framwork (MOF) materials have been prepared from two polyheterocyclic diacid ligands, 2,6-bis(3-carboxy-1-pyrazolyl)pyridine and 2,6-bis(4-carboxy-1-pyrazolyl)pyridine. The crystal structures of the two organic molecules are presented together with the structures for the MOFs obtained by hydrothermal synthesis either with Yb(III) or mixed Tb(III)/Yb(III) ions. Different coordination architectures result from each ligand, revealing also important differences between the lanthanides. The mixed lanthanide metal−organic frameworks also present diverse luminescent behavior; in the case of 2,6-bis(4-carboxy-1-pyrazolyl)pyridine, where no coordinated water is present in the metal environment, Tb(III) and Yb(III) characteristic emission is observed by excitation of the bispyrazolylpyridine chromophore.

Construction, energy transfer, tunable multicolor and luminescence enhancement of YF3:RE3+(RE=Eu, Tb)/carbon dots nanocomposites

Carbon dots (CDs) have displayed giant potential in carbon-based multifunctional nanomaterials owing to their outstanding optical properties. The nanocomposites combining CDs with rare-earth (RE) luminescence materials have increasingly attracted more and more attention due to the dual-mode optical properties. In this work, YF3:Eu3+,Tb3+/CDs nanocomposites were synthesized via hydrothermal method. The phase structure, surface functional groups, morphology and elements distribution of the samples were measured by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (SEM) and Energy-dispersive X-ray spectrometer (EDS), respectively. Besides, optical properties have also been systematically studied by photoluminescence spectra. The energy transfer of YF3:Eu3+/CDs nanocomposites from CDs to Eu3+ was proved. The YF3:Ln3+/CDs nanocomposites realized luminescence enhancement and tunable multicolor. Furthermore, using CDs as the blue light source, YF3:Eu3+ as the red light source and YF3:Tb3+ as the green light source, the YF3:Eu3+,Tb3+/CDs nanocomposites can achieve white light emission with CIE coordinate (0.3117, 0.2791) upon ultraviolet-light (318 nm) excitation, suggesting that this nanocomposites can be highly applied to the bioimaging and solid-state laser.

Tripyridinophane Platform Containing Three Acetate Pendant Arms: An Attractive Structural Entry for the Development of Neutral Eu(III) and Tb(III) Complexes in Aqueous Solution.

We report a detailed characterization of Eu3+ and Tb3+ complexes derived from a tripyridinophane macrocycle bearing three acetate side arms (H3tpptac). Tpptac3- displays an overall basicity (∑ log KiH) of 24.5, provides the formation of mononuclear ML species, and shows a good binding affinity for Ln3+ (log KLnL = 17.5-18.7). These complexes are also thermodynamically stable at physiological pH (pEu = 18.6, pTb = 18.0). It should be noted that the pGd value of Gd-tpptac (18.4) is only slightly lower than that of commercially available MRI contrast agents such as Gd-dota (pGd = 19.2). Moreover, a very good selectivity for these ions over the endogenous cations (log KCuL = 14.4, log KZnL = 12.9, and log KCaL = 9.3) is observed. The X-ray structure of the terbium complex shows the metal coordinated by the nine N6O3 donor set of the ligand and one inner-sphere water molecule. DFT calculations result in two Eu-tpptac structures with similar bond energies (ΔE = 0.145 eV): one structure in which the water is coordinated to the metal ion and one structure in which the water molecule is farther away from the ion, bound to the ligand with an OH-π bond. By detailed luminescence experiments, we demonstrate that the europium complex in aqueous solution presents a hydration equilibrium between nine-coordinate, dehydrated [Eu-tpptac]0 and ten-coordinate, monohydrated [Eu-tpptac(H2O)]0 species. A similar trend is observed for the terbium complex. Despite the presence of this hydration equilibrium, the H3tpptac ligand sensitizes Eu3+ and Tb3+ luminescence efficiently in buffered water at physiological pH. Particularly, the terbium complex displays a long excited-state lifetime of 2.24 ms and an overall quantum yield of 33% with a brightness of 3600 M-1 cm-1. Such features of Ln3+ complexes of H3tpptac indicate that this platform appears to be particularly appealing for the further development of luminescent lanthanide labels.

Two-dimensional lanthanide coordination polymer nanosheets for detection of FOX-7.

Despite the recent surge of interest in two-dimensional (2D) inorganic nanosheets derived from photoactive coordination polymers of lanthanide ions having interesting optical properties, research in this area is still in its infancy. Luminescent lanthanide ions, Eu(iii) or/and Tb(iii), as well as a bis-terpyridine ligand (L), were used in this study as the building blocks for the synthesis of the archetypical layered structure of coordination polymers (CPs) (L·Eu/L·Tb). 2D-nanosheets were obtained through exfoliation of the layered precursor of CPs in a suitable solvent system following a sonication-assisted strategy. These nanosheets exhibit lateral sizes on the micrometer scale (0.3–1 μm) and an ultrathin thickness of 2–6.5 nm. 1,1-Diamino-2,2-dinitroethene or FOX-7 is an insensitive high explosive; in a binder mixture, it exhibits a slightly superior detonation velocity of 8870 m s−1 in comparison to RDX. The insensitive nature of FOX-7 makes it a key component for the development of low vulnerable high explosive compositions for further application in weaponry. The growing demand for FOX-7, for use as a suitable replacement of conventional explosives, is of serious concern to human security. Achieving rapid and efficient detection of this unexplored explosive is a challenging task. In the present study, the developed luminescent nanosheets were used for the first time for micromolar level detection of FOX-7 both in solution and in the solid state. A visually distinct color change of the nanosheets from red (L·Eu) and green (L·Tb) to colorless was witnessed upon UV light irradiation during the detection process. Notably, the solid-state detection technique could be exploited for developing a commercial spray kit for quick onsite screening of this important explosive.

Структура, летучесть и люминесценция аддуктов фенантролина с трис-дипивалоилметанатами лантаноидов

Синтезирована серия трис-дипивалоилметанатов Ln(III) с фенантролином состава Ln(thd)3Phen (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Установлено, что все аддукты изоструктурны с ранее известными комплексами La(thd)3Phen, Tb(thd)3Phen и Dy(thd)3Phen. Определены кристаллические структуры комплексов Sm(thd)3Phen (I) и Eu(thd)3Phen (II) при 150(2) K (пр. гр. P-1, a = 10.8590(5) Å, b = 12.3049(6) Å, с = 18.4479(10) Å, α = 80.210(2)°, β = 87.499(2)°, γ = 68.799(2)°, V = 2264.3(2) Å3, Z = 2; пр. гр. P-1, a = 10.8788(3) Å, b = 12.3009(3) Å, с = 18.4309(5) Å, α = 80.3644(9)°, β = 87.5440(10)°, γ = 68.7376(8)°, V = 2265.7(1) Å3, Z = 2 соответственно). Кристаллические структуры I и II являются молекулярными и состоят из изолированных молекул Ln(thd)3Phen (Ln = Sm(III), Eu(III)). Наибольшие квантовые выходы люминесценции для данной серии аддуктов установлены для Eu(thd)3Phen (10 %) и Sm(thd)3Phen (1.5 %). Термогравиметрические исследования (ТГ) показали, что летучесть аддуктов слабо уменьшается от Pr(thd)3Phen до Yb(thd)3Phen; их точки плавления близки к известным по литературным данным.

A Short Review on Rare Earth Doped NaYF4 Upconverted Nanomaterials for Solar Cell Applications

The enhancement of upconversion luminescence (UCL) of rare earth (RE) doped upconversion nanomaterials which facilitates anti-Stokes emission is particularly important and urgently required for a broad range of applications. The fascinating properties such as anti-Stokes shifts, long life times and sharp emissions exhibits potential application in various areas. The UC is one of the exciting processes in the RE ions in which one can get the emission of high energy ultra-violet (UV) and visible (Vis) photons with the help of low energy near infrared (NIR) photons. In this mini review, we have discussed fundamental concepts of NaYF4 host for UC emission. The NaYF4 host has been selected due to its low phonon energy and composition stability. We have also demonstrated that the introduction of core shell and plasmonic nanostructure which has a critical effect on UCL. The recent advances in plasmon-enhanced UCL in RE doped NaYF4 are also noted. Finally, the recent solar cell applications of RE doped NaYF4 nanocomposite phosphor materials are introduced

稀土掺杂光功能玻璃及器件应用（特邀）

The luminescence and laser properties of rare earth are produced by the transition of 4f electrons between different energy levels. Due to its special properties, rare earth ions doped optical-functional glass have played important roles in high power laser system, whether as active or passive components. Nd3+, Er3+ doped phosphate laser glass, which have high rare earth ion doping concentration, preparation characteristics with large size and high uniformity, can be used in high energy laser as an important gain medium material; Volume Bragg grating based on Ce3+-doped Photo-Thermo-Refractive glass, is a multifunctional optical components in high power laser system, owing to its excellent wavelength and angular selectivity, high diffraction efficiency, high thermal stability and high damage threshold. In this paper the latest progress of Nd3+, Er3+ doped phosphate laser glass and Volume Bragg grating base on Ce3+-doped Photo-Thermo-Refractive glass were reported.

Luminescent pro-nitroxide lanthanide complexes for the detection of reactive oxygen species.

The DOTA-based ligand H3L (5) appended with a pro-nitroxide moiety has been synthesized. The europium and ytterbium complexes 5Ln show metal-centred luminescence. They react with ROS in aqueous media to give a transient iminonitroxide and a stable nitronylnitroxide radical authenticated by EPR, with change in luminescence.

Manipulating Upconversion Luminescence of Rare Earth by Photonic Crystals

Manipulating Upconversion Luminescence of Rare Earth by Photonic Crystals

Joining the journey to near infrared (NIR) imaging: the emerging role of lanthanides in the designing of molecular probes

The recent developments and prospects of near-infrared molecular probes based on luminescent lanthanide coordination complexes in bioimaging are described, which is important to emphasise the importance of lanthanide chemical biology.