It is widely acknowledged that the majority of acute environmental issues can be attributed directly to human activity. Since the inception of human settlements, the production of waste has been a common occurrence. In addition to the production of natural waste products, the advent of the Industrial Revolution has resulted in a significant increase in the generation of artificial waste. It is therefore imperative, from an environmental standpoint, to implement effective measures to reduce these pollutants. One method of reducing the impact of organic environmental pollutants is to photochemically convert them with europium, particularly trivalent europium. As demonstrated in this proof of concept using a range of model pollutants, it is possible to break down environmentally relevant pollutants, including nitriles, carbamates and halogenated compounds, with trivalent europium salts into environmentally friendly organic compounds.

Europium is one of the most reactive lanthanides and humans use it in many different applica-tions, but we still know little about its potential toxicity and cellular response to its exposure. Two strains of the eukaryotic microorganism model Tetrahymena thermophila adapted to high concentrations of two Eu(III) compounds (EuCl3 or Eu2O3) were obtained and compared to a control strain and cultures treated with both compounds. In this ciliate, EuCl3 is more toxic than Eu2O3. LC50 values show that this microorganism is more resistant to these Eu(III) compounds than other microorganisms. Oxidative stress originated mainly by Eu2O3 is minimized by overexpression of genes encoding important antioxidant enzymes. The overexpression of metallothionein genes under treatment with Eu(III) compounds supports the possibility that this lanthanide may interact with the -SH groups of the cysteine residues from metallothi-oneins and/or displace essential cations of these proteins during their homeostasis function. Both lipid metabolism (lipid droplets that fuse with europium-containing vacuoles) and au-tophagy are involved in the cellular response to europium stress. Bioaccumulation, together with a possible biomineralization to europium phosphate, seems to be the main mechanism of Eu(III) detoxification in these cells.

Lanthanides and actinides are emerging contaminants, but little is known about their uptake and distribution by plants and their interactions in the rhizosphere. To better understand the fate of these metals in plants, we assessed the bioassociation of 2, 20 and 200 µM Eu(III) by five hydroponically grown crops endemic to Europe. The metal’s concentration and its speciation was monitored by inductively coupled plasma mass spectrometry and laser spectroscopy, whereas root exudation was investigated by chromatographic methods. It has been shown, that Eu(III) bioassociation is a two-stage process, involving rapid biosorption followed by accumulation in root tissue and distribution to the stem and leaves. Within 96 h of exposure time, the plant induces a change of Eu(III) speciation in the liquid medium, from a predominant Eu(III) aquo species, as calculated by thermodynamic modelling, to a species with longer luminescence lifetime. Root exudates such as citric, malic, and fumaric acid were identified in the cultivation medium and affect Eu(III) speciation in solution, as was shown by a change in the thermodynamic model. These results contribute to a comprehensive understanding of the fate of lanthanides in the biosphere and provide a basis for further investigations with the chemical analogues Cm(III) and Am(III).

Complexes of triply positive europium ion with organic ligands are popular objects for studying photophysical properties. This is related not only to the bright red emission of this 4f element, but also to some spectroscopic peculiarities of its luminescence: the first excited spin-orbit level (7F1) lies only about 300 cm−1 above the ground state (7F0), so that at room temperature its population is around 25–30%. However, such electronic structure of Eu(III) provides its paramagnetism under ordinary conditions. This fact is often ignored by researchers, which is shortsighted from the materials science point of view. A comprehensive and systematic study of the magnetic behavior for the Eu(III) molecular coordination compounds is a challenging task for the development of new polyfunctional materials. The present work presents synthesis, single crystal XRD analysis results, and a magnetic study for the firstly prepared europium(III) complexes with two neutral scorpionate ligands: trispyrazolylmethane (HCPz3) and its methylated analog, tris(3,5-dimethyl-1-pyrazolyl)methane (HC(PzMe2)3). The values of the spin-orbit coupling parameter obtained for Eu-trication by a theoretical approximation of the experimental magnetic susceptibility data are compared with those known for the scarce amount of the magnetically studied molecular compounds.

A novel multicomponent glasses with nominal compositions of (50-x)MoO3:xWO3:25La2O3:25B2O3, x = 0, 10, 20, 30, 40, 50 mol% doped with 3 mol % Eu2O3 were prepared using a conventional melt quenching method. Their structure, thermal behavior and luminescent properties were investigated by Raman spectroscopy, differential thermal analysis and photoluminescence spectroscopy. Physical parameters as density, molar volume, oxygen molar volume and oxygen packing density were determined. Glasses are characterized with high glass transition temperature. Raman analysis revealed that the glass structure is built up mainly from tetrahedral (MoO4)2- and (WO4)2- units providing Raman bands of around 317 cm-1, 341-352 cm-1, 832-820 cm-1 and 928-935 cm-1. At the same time with the replacement of MoO3 with WO3 some fraction of WO6 octahedra are produced, which number increases with the increasing WO3 content. A strong red emission from the 5D0 level of Eu3+ ions was registered under near UV (395 nm) excitation using the 7F0 →5L6 transition of Eu3+. PL emission gradually increases with increasing WO3 content evidencing that WO3 is more appropriate component than MoO3. The integrated fluorescence intensity ratio R (5D0 →7F2/5D0 →7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites.

In this study we have investigated the effect of the addition of Nb2O5 (up to 5 mol%) on the structure and luminescent properties of ZnO-B2O3 glass doped with 0.5 mol % Eu2O3 by using of infrared (IR), Raman and photoluminescence (PL) spectroscopy. Physical properties as molar volume, oxygen packing density and glass transition temperature were determined using the results of differential thermal analyisis (DTA) and Archimedes principle for density. IR and Raman spectra revealed that niobium ions incorporate into the base zinc borate glass as NbO4 trtraherda and NbO6 octahedra. A strong red emission from the 5D0 level of Eu3+ ions was registered under near UV (392 nm) excitation using the sharp 7F0 - 5L6 transition of Eu3+. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. The higher Еu3+ luminescence emission observed in zinc borate glasses containing 1÷5 mol% Nb2O5 compared to the Nb2O5-free zinc borate glass evidences that Nb2O5 is suitable component for modification of host glass structure and improving the emission intensity.

In this study, we report a novel synthesis of hydrophobic silica aerogel powder composites, functionalized and binary-doped with [Tb(phen)₂](NO₃)₃ and [Eu(phen)₂](NO₃)₃ nanocrystals, employing a two-step sol-gel methodology. The investigation delves into the structural elucidation, optical properties and thermal conductivity of these functionalized Tb(III)-Eu(III) composites. Our analysis encompasses diffuse reflectance spectra, along with excitation and luminescence spectra, highlighting the quantum yields of composites with varying chemical composition. Remarkably, these samples exhibit a strong luminescence, with distinct hues of red or green color upon the specific doping type and level. The detailed examination of excitation spectra and quantum yields unequivocally establishes robust energy transfer mechanisms from the 1,10-phenanthroline molecule to the lanthanide ions. Notably, our study uncovers a Tb³⁺→Eu³⁺ energy transfer phenomenon within the binary functionalized samples, providing compelling evidence for a structural formation process occurring within the mesoporous framework of the aerogel powders.

The present contribution is focused on the relation preparation – structure – optical properties of hybrid silica and zirconia powders containing Eu(III) complexes: [Eu(ntac)₃][pphendcn] and [Eu(phen)₂](NO₃)₃. Methods for functionalization of silica and zirconia microparticles, based on adsorption of 1,10-phenantroline and [Eu(ntac)₃][pphendcn], and doping with [Eu(phen)₂](NO₃)₃ nanoparticles are proposed to obtain of red emitting hybrid composites with quantum efficiency 20 – 50 %. The optical properties of rare earth ions incorporated in silica and zirconia composites are used to explore the site symmetry (D₂, C_2v or lower) of the Eu³⁺ optical centers in the hybrid composites. Quantum yields of the investigated sol-gel micropowders and quantification of their optical spectra are presented.

Europium is the most-studied and least-well-understood rare earth ion (REI) dopant in GaN. While attempting to increase the efficiency of red GaN light-emitting diodes (LEDs) by implanting Eu⁺ into p-type GaN templates, the Strathclyde University group, in collaboration with IST Lisbon and Unipress Warsaw, discovered hysteretic photochromic switching (HPS) in the photoluminescence spectrum of doubly doped GaN(Mg):Eu. Our recent work, summarised in this contribution, has used time-, temperature- and light-induced changes in the Eu intra-4f shell emission spectrum to deduce the microscopic nature of the Mg-Eu defects that form in this material. As well as shedding light on the Mg acceptor in GaN, we propose a possible role for these emission centres in quantum information and computing.

The results of the study of the interaction between the CeF3+EuF3 system and the salt melt NaCl–KCl by spectroscopic methods are presented. It was established that no significant changes occur with CeF3 ions upon dissolution in the NaCl–KCl melt. Instead, the transition of EuF3 into solution-melt, both individually and in the CeF3+EuF3 system, is accompanied by oxidation-reduction reactions with the formation of Eu2+. Diffuse reflection spectra of the samples – both bottom (insoluble sediment) and upper parts of the solidified salt melt in the UV range indirectly indicate the excitation of photoluminescence of Ce3+ and Eu2+ ions. On the other hand, the presence of absorption bands in the near-IR range of the spectrum (1900-2300 cm−1) confirms the preservation of a certain proportion of Eu3+ ions in the salt melt. The influence of various factors (composition of the solidified salt melt sample, excitation wavelength, previous and subsequent heat treatment, and composition of the medium) on the nature of the excitation and emission spectra of the samples was studied. A very intense 5d-4f luminescence of Ce3+ and Eu2+ ions (at 330 and 430 nm, respectively), mainly in the upper part of salt melts, and much weaker 4f-4f luminescence of Eu3+ ions were observed. Certain parameters were optimized to reduce the proportion of luminescence of Ce3+ and, especially, Eu3+ ions and to increase the luminescence of Eu2+ ions. Solidified salt solutions-melts of the NaCl–KCl–CeF3–EuF3 system are promising materials for the creation of solar ultraviolet radiation detectors.

Nanoporous films of Eu-doped organosilicate glass (OSG) have been synthesized using sol-gel technology and spin-coating, employing evaporation-induced self-assembly (EISA), on silicon wafers. The Eu doping is achieved by dissolution of Eu(NO3)3·6H2O in the precursor solution. The deposited films are characterized by using Fourier transform infrared (FTIR) spectroscopy, ellipsometric porosimetry (EP), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. It is observed that Eu doping makes the films more hydrophilic and reduces the pore size and open porosity. The reduction Eu3+ → Eu2+ occurs in the pores of OSG films, which is confirmed by depth profiling XPS. However, Eu3+ still presents on the film’s top surface. Presence of Eu3+ and Eu2+ gives characteristic luminescence emission in the range of 600‒630 nm (Eu3+) and 290‒400 nm (Eu2+). The Eu2+/Eu3+ concentrations ratio depends on CH3 groups concentration in the films. Moreover, concentration of Eu2+ ions in the pores can be reduced by exposure in inductively coupled (ICP) oxygen plasma. The observed shift of the luminescence spectra towards the UV region, in comparison to previously reported Eu-doped organosilicate films, can be attributed to the energy transfer occurring between the host material and Eu2+ ions.

Traditional photodynamic therapy (PDT), a clinical cancer therapeutic approach using light in killing cancer cells, is often limited by insufficient light penetration, inefficient photosensitizer energy transfer, and inadequate oxygen in hypoxic tumors. Employing X-ray to activate photosensitizer in PDT can potentially overcome these limitations. Here, we compared protocols to synthesize a novel nano-photosensitizer composed of a europium-doped yttrium oxide core with a silica shell (Y₂O₃:Eu@SiO₂) which can be utilized in such therapeutic method, i.e., X-ray activated PDT (XPDT). Transmission electron microscopy (TEM) and dihydroethidium (DHE) were utilized to evaluate the effects of various synthesis conditions on the characteristics of Y₂O₃:Eu@SiO₂ and their ability to generate reactive oxygen species (ROS). The in vivo tumor suppression effects of the Y₂O₃:Eu@SiO₂ were assessed by ¹⁸F-fluorothymidine position emission tomography (¹⁸F-FLT PET) in human ovarian cancer xenografts using radiation sensitive CAOV3 and radiation resistant SKOV3 cell lines. Our data revealed a positive correlation between nanoparticle condensation time and core size as well as a negative correlation between urea concentrations and core size. Addition of cetyltrimethylammonium bromide (CTAB) during core synthesis enhanced particle dispersion. Two silica coating conditions showed the greatest efficiency in the enhancement of ROS generation. Furthermore, our in vivo study revealed suppression of tumor growth by Y₂O₃:Eu@SiO₂ administration when compared to non-treated control. Silica shell provides flexibility to conjugate moieties that specifically target to cancers. This nano-photosensitizer demonstrates the significant promise for overcoming limitations of conventional PDT and combating various cancers in clinical applications.