The crystal structures of 11 lanthanide terephthalate tetrahydrates have been refined using laboratory X-ray powder diffraction data and optimized using density functional techniques. The lattice parameters and R–O bonds exhibit expected trends based on the cation size. The R–O bond distances in the Rietveld-refined structures are similar. However, in the density functional theory (DFT)-optimized structures, the bond distances break into two distinct groups, longer and shorter R–O bonds. This indicates that the bond distance restraints imposed upon the refined structures may have a greater impact than is expected from their weights. The aromatic carboxyl groups were not completely planar, but it is known that the carboxyl groups can rotate to accommodate hydrogen bonding and coordination to the metal. Both water molecules coordinated to the lanthanides act as hydrogen bond donors, but only one of the three unique carboxyl groups acts as an acceptor.

Polyhedral YVO4: Ln3+ (Ln = Eu, Sm, Yb/Er, Yb/Tm) microcrystals were fabricated via a facile sol–gel auto-combustion method using NH4VO3 as vanadium source in the presence of glycine. The X-ray diffraction patterns were well matched with pure YVO4, and the doped lanthanide ions did not change the host structure. The YVO4 microcrystals annealed from 500 to 1000 °C for 3 h were polyhedral and ranged in particle size from 0.1 to 2 μm. The luminescence properties of YVO4: Ln3+ (Ln = Eu, Sm, Yb/Er, Yb/Tm) samples indicated that all of the YVO4: Ln3+ samples exhibited typical emission spectra of Ln3+ cations, suggesting that the Ln3+ cations were well doped in YVO4 and could be excited efficiently through matrix absorption. In addition, the corresponding mechanisms of emission and energy transfer in the YVO4: Ln3+ are proposed.

Small luminescent Y2O3:Eu3+ particles were prepared by a hydrothermal method first, and then, Y2O3:Eu3+/C3N4 nanocomposites were further prepared by a chemisorption method. The luminescent Y2O3:Eu3+/C3N4 nanocomposites are not only a promising down-conversion luminescent material, but also it could be used to improve the efficiencies of dye-sensitized solar cells (DSSCs). Especially, the morphology of Y2O3:Eu3+ has great influence on the performance of DSSCs. Compared with Y2O3:Eu3+ nanorods, the introduction of small Y2O3:Eu3+ particles into the cells is conducive to the improvement of cell efficiency. The efficiencies of TiO2-Y2O3:Eu3+–C3N4 composite cells were not only higher than those of pure TiO2 cells but also higher than those of TiO2-Y2O3:Eu3+ or TiO2-C3N4 composite cells, resulting in the enhancement of the average efficiency of the TiO2-Y2O3:Eu3+–C3N4 composite cell from 7.16% to 8.14%, with 14% improvement over the pure TiO2 cell. The enhancement of the efficiency can be attributed to the synergetic effect of small Y2O3:Eu3+ particles and C3N4.

Near infrared (NIR) optical imaging has demonstrated significant potential as an effective modality for cancer molecular imaging. Among various NIR probes currently under investigation, upconversion nanophosphors (UCNPs) possess great promise due to their anti-Stokes emission and sequential photon absorption which result in superior detection sensitivity and a simple imaging setup, respectively. Here we investigated the utility of this imaging modality to detect tumor cells expressing the epidermal growth factor receptor (EGFR) using affibody functionalized nanophosphors and a custom built imaging system. Initially, aqueous dispersible NaYF4: Tm+3, Yb+3 UCNPs were synthesized and their photophysical properties were characterized. Then, their luminescence response as a function of concentration and their depth resolving capability in a tissue-simulating phantom were examined. Finally, we demonstrated the use of bioconjugated UCNPs for imaging EGFR-expressing tumors both in vitro and in vivo. Our data suggests that NIR imaging with UCNPs may be useful for noninvasive imaging of tumors.

Previously known to form only under high pressure synthetic conditions, here we report that the T′-type 214-structure cuprate based on the rare earth atom Tb is stabilized for ambient pressure synthesis through partial substitution of Pd for Cu. The new material is obtained in purest form for mixtures of nominal composition Tb1.96Cu0.8Pd0.2O4. The refined formula, in orthorhombic space group Pbca, with a = 5.5117(1) Å, b = 5.5088(1) Å, and c = 11.8818(1) Å, is Tb2Cu0.83Pd0.17O4. An incommensurate structural modulation is seen along the a axis by electron diffraction and high resolution imaging. Magnetic susceptibility measurements reveal long-range antiferromagnetic ordering at 7.9 K, with a less pronounced feature at 95 K; a magnetic moment reorientation transition is observed to onset at a field of approximately 1.1 T at 3 K. The material is an n-type semiconductor.

Previously, it has been suggested that metal ions complexed to humic acid in the environment might show slower dissociation than those added to humic substances in the laboratory, which has serious implications for the transport of radionuclides in the environment. The dissociation of lanthanide and anthropogenic actinide ions from humic substance complexes has been studied as a function of humic concentration and metal ion:humic concentration ratio. The results suggest that the apparently slower kinetics observed for metal ions complexed in the environment are probably due to the large humic concentrations that are used in those studies. Further, there is no evidence that the dissociation rate constant varies at very low metal ion concentrations. Although humic samples size-fractionated by ultrafiltration showed that more metal may be bound non-exchangeably, there was no evidence for different rate constants. Ultrafiltration of Eu(III)/humic acid mixtures did show a shift in Eu from smaller to larger fractions over a period of two days. Therefore, the results suggest that dissociation rate constants determined in the laboratory at metal ion concentrations higher than those expected in the environment may be used in predicting radionuclide mobility, provided that the humic acid concentration is in the range expected at the site.

The apparent diffusion coefficients of La, Nd, Eu, Dy, Er, and Lu in compacted bentonites were investigated at various bicarbonate concentrations. The apparent diffusion coefficients of these lanthanides tended to decrease with increasing dry density. At bicarbonate concentrations below 0.25 M, lanthanum had the largest diffusion coefficient (ca. 10-13 m2/s) at 1.0 Mg/m3, and the diffusion coefficient decreased with increasing atomic number. On the other hand, at bicarbonate concentrations above 0.25 M, lutetium had the largest diffusion coefficient, and the diffusion coefficient decreased with decreasing atomic number. In particular, lanthanum and neodymium had diffusion coefficients below 10-14 m2/s, even at 1.0 Mg/m3. The diffusion coefficient of europium was around 10-13 m2/s at 1.0 Mg/m3 and was influenced less by the bicarbonate concentration. The diffusion coefficient of lutetium increased from 2 × 10-14 to 10-12 m2/s as the bicarbonate concentration was increased to 1.0 M. The concentration of carbonate ion in the pore water of bentonite is estimated to be much lower than that in solutions in contact with bentonite from the viewpoints of solubility and chemical species of lanthanides.

Lanthanide nanoparticles had the possibility to couple many imaging techniques into a sole labeling agent has awaken high expectations on personalized medicine or <<Theranostics>>. This is possible due to their intrinsic physic – chemical properties. Combining different imaging techniques physicians may provide a better treatment and perform surgical procedures that might increase the survival rate of patients. Hence, there is an enormous opportunity area for the development of lanthanide multimodal nanoparticles. For this study, we synthesized Gd – Gd2O3 nanoparticles at room temperature by reduction method assisted by Tannic acid, and later we doped them with different ratios of Eu. The nanoparticles were analyzed through high resolution microscopy (HRTEM), Raman Spectroscopy, luminescence, and magnetic characterizations. We found small nanoparticles with a mean size of 5 nm, covered in a carbonaceous layer. In addition, different emissions were detected depending on Eu concentration. Finally, the magnetization vs. temperature recorded under zero field cooled (ZFC) and field cooled (FC) conditions exhibit an antiferromagnetic to ferromagnetic phase transition in samples with Gd2O3, and hysteresis loops recorded at 100 Oe and 2 K showed a relevant magnetization without magnetic remanence. Hence, these nanomaterials have interesting properties to be tested in biocompatibility assays.

Luminescent biolabels are being eagerly investigated as a means of detecting cancer cells by bioimaging. Upconversion nanoparticles are a promising option to be used as biolabels for cancer cell detection. This process uses a near infrared beam (NIR λ = 980 nm) as the excitation source to upconvert the energy into light in the visible region. The present study, used Y2O3:Yb3+, Er3+ (1%, 10% mol) and Gd2O3:Yb3+, Er3+ (1%, 10% mol) capable of emitting red photons of λ = 660 nm. The nanoparticles were previously functionalized with aminosilanes and folic acid (UCNP-NH2-FA). Folic acid binds to the folate receptor on the surface of MCF-7 breast cancer cells, and this binding promotes internalization of the UCNPs via endocytosis. The UCNPs were characterized by TEM, EDS, and Fourier transform infrared. Cytotoxicity was also analyzed using the MTT (methy-134 thiazolyltetrazolium) colorimetric assay. The UCNPs-NH2-FA was noncytotoxic to the studied cancer cells and they were clearly localizable within the cell cytoplasm via confocal microscope.

The resolution of the electron microscope is now largely limited by the performance of its electron source when various aberrations in the electron imaging system, especially spherical aberrations, are corrected. A nanowire tip could be an ideal point electron source, where electrons are emitted from a small physical area. In this article, we review recent advances in electric-field-induced electron emission using a single nanowire, specifically, single-crystalline lanthanum hexaboride (LaB6) nanowire, compared to the state-of-the-art contemporary tungsten cold-field electron emitter W(310) as well as single atom tip and single-carbon nanotube emitters. Owing to its low work function, improved emission stability, and high emission brightness, the LaB6 nanowire as a cold-field-emission electron source offers a new and exciting opportunity for developing the next generation of electron microscopes.

Terbium and ytterbium co-doped aluminum oxynitride thin films were grown onto silicon substrates using radiofrequency magnetron sputtering. Aluminum oxynitride samples doped with 4.6 at. % of Yb3+ and co-doped with 0.4 at. % of Tb3+ were obtained. The prepared samples were annealed from 150°C to 850°C in steps of 100°C. By using energy dispersive X-ray analysis we measured the sample composition and the doping concentration. The emission intensities at different annealing temperatures were characterized using photoluminescence measurements upon excitation at 325 nm. The 5D4 → 7F5 main transition of Tb3+ and the characteristic near infrared emission at 980 nm of Yb3+ were recorded. In order to study the luminescence behavior of the samples in terms of a down conversion process, we have plotted the integrated areas of the main transition peaks versus the annealing temperature.

In this work, calcium fluoride (CaF2) and Tb3+-doped calcium fluoride (CaF2:Tb3+) thin films were prepared by electrochemical methods. According to EDS and XRD results, CaF2 thin films undergo through a phase transformation from cubic CaF2:Tb3+ to NaTbF4 when Tb3+ concentration in the electrolytic bath is increased. So that, peaks showed a very clear shifting towards lower angles. On the other hand, optical absorption results showed the typical range of transparency from IR to UV, and from photoluminescence (PL) spectra results it can be observed that it is possible to identify the f-f transition of Tb3+. The PL at low temperature allows finding the quenching concentration when the PL intensity decreases at the highest doping concentration value. However, the results also showed that the transition of Tb3+ does not seem to be affected by the coexistence of the secondary phases such as cubic NaTbF4. In the case of RE-doped CaF2 thin films materials, they can be used with a double purpose for solar cell applications, not only as antireflecting coating, but also as a host for lanthanide doping for down conversion of light. These properties could be very useful for photovoltaic applications, so that the spectral range of light conversion could be increased to achieve higher conversion efficiency values.

La2Hf2O7 and La2Mo2O9 as potential electrolytes for solid oxide fuel cells (SOFCs) have been investigated through first-principles calculations to understand the mechanism of ion motion. In La2Hf2O7, three unique types of positions that can form anion-Frenkel (a-Fr) pairs have been screened out and a reasonable continuous diffusion path constructed by these migration sites has also been suggested as the dominant cause of ion conduction. On the other side, excellent ion conductivity in La2Mo2O9 is more based on the short-range disorder induced by mobile structure. The thermodynamic properties comparison of La2Mo2O9 and La2Hf2O7 shows that the formation of a-Fr pairs in La2Mo2O9 will start at lower temperature because of higher degree of structural disorder and less constraints on oxygen ions.

The upconversion nanoparticles (UCNPs) possess the ability to absorb near infrared energy (980 nm) and upconvert it to emit in the visible spectra. In this research, the UNCPs emit in red (660 nm) due to the electronic transitions between two rare earth ions: Er3+ and Yb3+, this process is called energy transfer upconversion (ETU). The UCNPs were functionalized with aminosilanes and folic acid receptors (UCNP-FR) and analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy and luminescence measurements. UCNPs-FR of Y2O3 have a particle size of 70 ± 10 nm and the Gd2O3 have a 50 ± 10 nm particle size. Both showed a good luminescence spectrum in comparison with the bare ones. Cytotoxicity of different amounts between 0.001 µg/ml to 1 µg/ml of bare and functionalized UCNPs was measured with the colorimetric assay MTT in three cancer cell lines: human cervical adenocarcinoma (HeLa), human breast cancer cells MB-MDA-231. Some concentrations of bare UCNPs were cytotoxic for cancer cells; however after their functionalization they resulted to be non-cytotoxic. The functionalized UCNPs were able to bind to folate receptors which are overexpressed in cervical and breast cancers cells. It was demonstrated by confocal microscopy, that the functionalized UCNPs were internalized into the cancer cells, confirming that they can be used as biolabels for breast and cervical cancer cells.

In the context of management of the wastes arising from the reprocessing of spent nuclear fuel, studies have been conducted into the solvent extraction kinetics of lanthanide fission products by TODGA and the effects of solvent phase acidity on the effectiveness of this organic extractant molecule. In this study we observe an increase in organic phase viscosity increasing acidity and, potentially by consequence, that the rate of cerium extraction is summarily decreased.

The liquidus temperature (TL) of rare earth (RE) was determined for alumino-borosilicate glasses for treating americium and curium that have been studied previously. Their work covers a wide range of glass composition with various crystalline phases as primary phase. Present work is aimed at understanding the effect of glass composition on TL for waste glasses designed for vitrifying RE oxides wastes. In a sufficiently narrow composition region, this effect can be represented by a first-order model fitted measured TL versus composition data. Test glasses were formulated by varying of component fractions one-at-a-time. The glasses contained SiO2, B2O3, and Al2O3 as glass formers and Nd2O3 with CeO2 as simulated RE waste. Twenty glasses were made to investigate crystallization as a function of temperature and glass composition. The primary crystalline phase was Ce-borosilicate (Ce3BSi2O10), secondary phases were Al-containing crystals (Al2O3 and Al10Si2O19), and crystalline CeO2. A first-order model was fitted to crystal fraction versus glass composition data. Generally, SiO2 and B2O3 tend to suppress crystallization, Al2O3 has little effect, and, as expected, RE components (Nd2O3 and CeO2) promote it. The correlation coefficient, R2, was 0.89 for the primary crystalline phase TL as a linear function of composition.

Spectroscopic imaging and statistical analysis of NIR-to-visible upconversion luminescence (UCL) from β-NaYF4:Yb3+:Er3+ upconverting nanoparticles (UCNPs) supported on a series of random Ag nanowire aggregates reveals a density dependent UCL enhancement. Statistical analysis of the spectrally resolved upconversion images shows a non-linear dependence of upconversion luminescence enhancement with Ag nanowire surface coverage. A maximum average enhancement of 5.8× was observed for 58% surface coverage. Based on the empirically determined trend with density, it is estimated that up to 20× upconversion luminescence enhancement can be achieved at 100% surface coverage, even at high excitation intensity. This projection is commensurate with the 20× enhancement ratio observed for select locations within the imaged micro-ensemble. Time-resolved emission of the UC luminescence from UCNPs on the Ag nanowire aggregates confirms the surface plasmon effects on the UCNPs kinetics. Such Ag nanowire aggregates show potential as a scalable and relatively simple metal-enhanced upconversion substrate.

ErxYb(3-x)Q9 (1, x = 1, 2), NdYb2Q9 (2), NdEr2Q9 (3) and NdErYbQ9 (4), have been obtained through a simple molecular strategy, by controlling reactant stoichiometry. In 2-4, the templating effect of the molecular framework allows to control the metal distribution across the coordination sites where the central position is occupied by the larger Nd ion and the terminal ones by the almost vicariants Yb3+ and Er3+, drastically reducing molecular speciation. Remarkably, 4 represents the first example of a discrete molecular entity containing three different Ln ions simultaneously emitting in three different spectral regions in the NIR, upon single visible wavelength excitation. Highly transparent and homogeneous doped silica glasses have been prepared, which show the same optical properties of the incorporated complex in solution.

Single crystals of Ln(NO3)3·Bpy2 where Ln = Eu, Gd, Nd, Tm, Er, La and Yb were fabricated and characterized. Materials have good optical quality, can be excited at UV or the rare earth ion transitions, demonstrate efficient luminescence and are suitable for thin film fabrication. Fabrication approaches and possible applications are discussed.

We employ a combination of the density-functional theory and the dynamical mean-field theory to study the electronic structure of selected rare-earth sesquioxides and dioxides. We concentrate on the core-level photoemission spectra, in particular, we illustrate how these spectra reflect the integer or fractional filling of the 4f orbitals. We compare the results to our earlier calculations of actinide dioxides and analyze why the core-level spectra of actinide compounds display a substantially reduced sensitivity to the filling of the 5f orbitals.