Migration Of Eu Research Articles

Surface activation of calcium tungstate by europium doping for improving photocatalytic performance: Towards lanthanide site photocatalysis

• The Eu doping on surface of CaWO 4 raises the d -band center to improve the adsorption. • The better crystallization promotes the charge mobility to the surface of CaWO 4 . • The surface adsorption and charge mobility synergistic ally improve the photocatalysis. Lanthanides doping can improve the performance of photocatalysts due to the enhanced optical absorption or charge separation. Here, we demonstrate the important role of lanthanide in photocatalysis in terms of surface reactivity. The Eu 3+ on the surface of CaWO 4 , especially for the 1st-layer lattice, substantially raised the surface energy by heightening the d -band center, so that the adsorption ability at the surface was improved. Calcination at a proper temperature promoted the mobility of more excited charge carrier to the Eu 3+ sites on the catalyst surface. The synergistic effect of the enhanced adsorption ability and carrier mobility improved the photocatalytic performance as in the case of CaWO 4 calcined at 600 °C, where Rhodamine B, Ciprofloxacin and nitroblue tetrazolium were degraded at the highest rate among all the CaWO 4 samples. Our study provides important insights into lanthanide site photocatalysis (i.e. migration of Eu 3+ into the inner part of the crystal contributed to photoluminescence rather than catalysis).

Improving light converting properties with wettability of polyethylene film by rare earth complex Eu(GI)3Phen

ABSTRACT Modern agriculture needs multifunctional greenhouse films to meet different needs. A novel method for improving light converting properties and wettability of polyethylene film was developed in this paper. Glycerin monostearic acid itaconic acid diester (GI) with a carboxyl group and double band was synthesized. Rare earth complex Eu(GI)3Phen with Eu3+ as central ion has been obtained. Subsequently, a simple strategy of grafting it onto LLDPE backbone was employed to delay the migration of Eu(GI)3Phen. The fluorescence spectrum indicated that the modified film emitted red light. Meanwhile, the accelerated dripping time of modified film was extended to 12 days.

Crystal Chemistry and Luminescence Properties of Eu-Doped Polycrystalline Hydroxyapatite Synthesized by Chemical Precipitation at Room Temperature

Europium-doped hydroxyapatite Ca10(PO4)6(OH)2 (3% mol) powders were synthesized by an optimized chemical precipitation method at 25 °C, followed by drying at 120 °C and calcination at 450 °C and 900 °C. The obtained nanosized crystallite samples were investigated by means of a combination of inductively coupled plasma (ICP) spectroscopy, powder X-ray diffraction (PXRD), Fourier Transform Infrared (FTIR), Raman and photoluminescence (PL) spectroscopies. The Rietveld refinement in the hexagonal P63/m space group showed europium ordered at the Ca2 site at high temperature (900 °C), and at the Ca1 site for lower temperatures (120 °C and 450 °C). FTIR and Raman spectra showed slight band shifts and minor modifications of the (PO4) bands with increasing annealing temperature. PL spectra and decay curves revealed significant luminescence emission for the phase obtained at 900 °C and highlighted the migration of Eu from the Ca1 to Ca2 site as a result of increasing calcinating temperature.

Assessment of gynaecological and general history parameters inpregnant women in long term refugee camps in Greece: results from a pilot program

Objective:The purpose of the present article is to present preliminary data related to the gynecological history and current health status of pregnant refugees that reside in long-term refugee camps in Greece. Materials and Methods: The study was funded by the European program “PHILOS – Emergency health response to refugee crisis” of the Greek Ministry of Health, implemented by the Hellenic Center for Disease Control and Prevention (HCDCP), funded by the Asylum, Migration and Integration Fund (AMIF) of EU’s DG Migration and Home Affairs.Refugee pregnant women who resided in long-stay refugee camps of the mainland in Greece in 2017 were recruited. Results: Overall, 456 pregnant women were enrolled in the present study with a mean age of 27.5±6.9 years (median 27, range 17-48 years). 182 women (39.8%) were primigravidae. Mean gravidity was 2.4 (median 2, range 1-11). Among them 105 had a previous delivery, 75 women had 2 previous deliveries, 50 women had 3 previous deliveries and 14 had four previous deliveries. Of those, only six women had access to prenatal screening.Twenty-three women (5%) reported that had at least an artificial abortion performed (median 1, range 1-4) and 87 women (19.0%) had at least one spontaneous abortion (median 1, range 1-6).Two hundred and three women (44.5%) reported the use of a contraceptive method. Among them withdrawal (pull-out method) was the most prevalent accounting for almost half cases (36.9%), by followed by condom, intrauterine devices (IUD) and oral contraceptives. No differences were observed after checking the potential differences among the different age groups (p=.234). Conclusions: Refugee women that reside in long term refugee camps have limited access to national healthcare systems concerning their gynecological and obstetrical assessment. Future studies, should specifically target these problems to help structure specific healthcare plans that will ensure maternal and fetal well-being.

Damage recovery and dopant migration of Eu+ ion implanted KTiOAsO4 crystals

Damage formation and annealing of Eu implanted KTiOAsO4 crystals is investigated. Ion implantation was done with 400 keV Eu2+ ions and an ion fluence of 5 × 1015 ions/cm2 at room temperature. The damage of as-implanted and annealed samples was analysed by Rutherford backscattering spectrometry in channelling configuration using 2.1 MeV He+ ions. After implantation, a thick RBS-amorphous layer is obtained. The damage in the Eu2+ implanted KTiOAsO4 layer decreases significantly after annealing at 700° C for 30 min in Ar atmosphere. Interestingly, the Eu peak firstly migrated to the surface after annealing at 600° C for 30 min, and then appeared narrower after annealing at 700° C for 30 min. Furthermore, arsenic loss by evaporation and titanium enrichment at the surface are observed during the annealing process.

Migration behaviour of Europium implanted into single crystalline 6H-SiC

Migration behaviour of Europium (Eu) implanted into 6H-SiC was investigated using Rutherford backscattering spectroscopy (RBS), RBS in a channelling mode (RBS-C) and scanning electron microscopy (SEM). Eu ions of 360 keV were implanted into 6H-SiC at 600 °C to a fluence of 1 × 1016 cm−2. The implanted samples were sequentially annealed at temperatures ranging from 1000 to 1400 °C, in steps of 100 °C for 5 h. RBS-C showed that implantation of Eu into 6H-SiC at 600 °C retained crystallinity with some radiation damage. Annealing of radiation damage retained after implantation already took place after annealing at 1000 °C. This annealing of radiation damage progressed with increasing annealing temperature up to 1400 °C. A shift of Eu towards the surface took place after annealing at 1000 °C. This shift became more pronounced and was accompanied by loss of Eu from the surface at annealing temperatures >1000 °C. This shift was accompanied by broadening of Eu peak/Fickian diffusion after annealing at temperatures >1100 °C. The migration of Eu occurring concurrently with the annealing of radiation damage was explained by trapping and de-trapping of Eu by radiation damage.

RETRACTED: Investigation of Eu(III) immobilization on γ-Al2O3 surfaces by combining batch technique and EXAFS analyses: Role of contact time and humic acid

Abstract Aluminum (hydr)oxides play an important role in the regulation of the composition of soil/water, sediment/water and other natural water systems. In this study, the interactions among Eu(III), humic acid (HA) and γ-Al 2 O 3 were investigated using a combination of batch and extended X-ray absorption fine structure (EXAFS) techniques. Experiments were performed with varying contact times (2, 15, 60 and 180 d) at a pH of 6.5 for both the binary γ-Al 2 O 3 /Eu(III) and the ternary γ-Al 2 O 3 /HA/Eu(III) systems. In addition, two representative pH values (pH 6.5 for a near-neutral condition and pH 8.5 for an alkalescence condition) were selected to determine the sequestration mechanisms of Eu(III) in the ternary γ-Al 2 O 3 /HA/Eu(III) systems. To verify the specific binding modes and corresponding chemical species, a coordination geometry calculation and a quantitative comparison between the HA binding site concentration and the initial Eu(III) concentration were conducted along with EXAFS data analysis. The microstructure and thermodynamic stability of the formed Eu(III) species were dependent on various environmental parameters. For the binary γ-Al 2 O 3 /Eu(III) systems, quantitative analysis results of EXAFS spectra suggested the presence of two Eu(III) species within a contact time of 15 d. Using a coordination geometry calculation, the R Eu–Al values at ∼3.28 A and ∼3.99 A corresponded to the formation of edge-shared and corner-shared surface complexes, respectively. For samples reacted longer than 15 d, the appearance of an additional Eu–Eu shell at ∼3.50 A was indicative of a structural rearrangement process, leading to the formation of thermodynamically stable surface polynuclear complexes. For the ternary γ-Al 2 O 3 /HA/Eu(III) systems, the EXAFS-derived structural parameters indicated the formation of 1:1 type B ternary complexes and binary corner-shared complexes at pH 6.5 after 2 d. In contrast, the Eu(III) sequestration mechanisms at pH 8.5 were mainly attributed to the formation of 1:2 type A ternary complexes and binary edge-shared complexes. Considering the high proton dissociation constant of strong HA phenolic sites (8.8) and the high metal loading in the present study, the weak HA carboxylic sites are predominantly involved in Eu(III) complexation at pH 6.5 and 8.5. The time-dependent variation tendency of the Eu(III) chemical species formed in the ternary systems may arise from Eu(III)-induced HA agglomeration, binding of Eu(III) ions on stronger HA binding sites and migration of Eu(III) ions to less sterically accessible sites in the HA macromolecule structures. The adsorbed HA could accelerate Eu(III) immobilization at the γ-Al 2 O 3 /water interfaces and could enhance the thermodynamic stability of the formed chemical species. The findings presented in this study could provide important microcosmic information for the prediction of the long-term behaviors of Eu(III) and the relevant Ln/An(III) in a geological environment rich in aluminum hydr(oxides).

Laboratory determination of migration of Eu(III) in compacted bentonite–sand mixtures as buffer/backfill material for high-level waste disposal

For the safety assessment of geological disposal of high-level radioactive waste (HLW), the migration of Eu(III) through compacted bentonite–sand mixtures was measured under expected repository conditions. Under the evaluated conditions, advection and dispersion is the dominant migration mechanism. The role of sorption on the retardation of migration was also evaluated. The hydraulic conductivities of compacted bentonite–sand mixtures were K=2.07×10−10–5.23×10−10cm/s, The sorption and diffusion of Eu(III) were examined using a flexible wall permeameter for a solute concentration of 2.0×10−5mol/l. The effective diffusion coefficients and apparent diffusion coefficients of Eu(III) in compacted bentonite–sand mixtures were in the range of 1.62×10–12–4.87×10–12m2/s, 1.44×10–14–9.41×10–14m2/s, respectively, which has a very important significance to forecast the relationship between migration length of Eu(III) in buffer/backfill material and time and provide a reference for the design of buffer/backfill material for HLW disposal in China.

Thermal treatment effects on degradation of BaMgAl 10O 17:Eu 2+ phosphor for PDP

The thermal degradation mechanism of the BaMgAl 10O 17:Eu 2+ (BAM) phosphor used in plasma display panel (PDP) is not yet fully clarified. We studied the dependency of the luminance and chromaticity y-value of BAM phosphor on baking temperature, handling time, atmosphere and thermal treating process. The luminance and chromaticity y-value increased after baking at around 400 °C but decreased at 600 °C or higher temperatures. The thermal degradation was obviously aggravated in oxidative atmosphere. The shift of y-value was reversed when thermal treated in non-oxidative atmosphere. We considered that the mechanism of thermal degradation of BAM phosphor was firstly due to the migration of Eu 2+ ions and then due to the effect of oxygen. We also proposed a post-treatment for BAM phosphor to reduce the thermal degradation during panels’ fabrication.

Vertical distribution and diel migration of euphausiids from Oyashio Current to Kuroshio area off northeastern Japan

The vertical distribution of dominant euphausiid species was investigated in the offshore waters of north- eastern Japan in April and September 1998 and November 1999 using MOCNESS-I net samples. In total, 32 eu- phausiid species in eight genera were identified in the study area. Subarctic Euphausia pacifica and Thysanoessa in- spinata occurred over a wide range, although mainly in the Oyashio and cooler transitional areas, and the former made a relative contribution of 78% to the total numerical abundance of euphausiids. At night, these species tended to stay near the surface in the Oyashio area and in deeper layers in warmer areas. During the daytime, they tended to stay in deeper layers in the warmer areas, although E. pacifica stayed in deeper layers even in the Oyashio area where the chlorophyll a concentration was low. T. inspinata did not perform clear diel vertical migration. Except for these subarc- tic species, five warm-water species of Euphausia were abundant among the epipelagic euphausiids. At night, these species tended to stay at a wide range of depths from the surface to subsurface layers in the warmer Kuroshio area, but were concentrated near the surface in the transitional area. During the daytime, they stayed in deeper layers in the Kuroshio area. Diel vertical migration of euphausiids seems to be strongly affected by water temperature, but other fac- tors such as phytoplankton abundance may also be important. The possible effects of diel vertical migration of eu- phausiids on euphausiid fisheries are discussed.

Photoluminescence degradation and color shift studies of annealed BaMgAl 10O 17:Eu 2+ phosphor

The photoluminescence (PL) in UV and VUV regions, such as excitation and emission spectra, PL intensity, full-width at half-maximum (FWHM) and chromaticity coordinates, of pre- and post-annealed BaMgAl 10O 17:Eu 2+ (BAM) samples were investigated. The observed more PL degradation under VUV excitation was assigned to the formation of defects (extinction centers or new Eu 2+ centers) which decreased the luminance efficiency of Eu 2+ in mirror plane. The increasing y value of chromaticity coordinates that appeared in annealed samples under 147 nm excitation was attributed to the migration of Eu 2+ from mirror plane to spinel block, which induced long wavelength emission. Therefore, besides the well-accepted oxidation mechanism, the migration of Eu 2+ also led to the decrease of blue luminescent centers, and there by is responsible for the PL degradation, too. The conclusion of this work revealed a more full-scale and precise mechanism of thermal degradation than the conventional one.

Sorption and desorption of Eu(III) on alumina

Effects of ionic strength and of fulvic acid on the sorption of Eu(III) on alumina were investigated by using a batch technique. The experiments were carried out at T=25±1 °C, pH 4-6 and in the presence of 1M NaCl. The results indicate that sorption isotherms of Eu(III) are linear at low pH values. The sorption-desorption of Eu(III) on alumina at pH 4.4 is reversible, but a sorption-desorption hysteresis is found at pH 5.0. Fulvic acid has an obvious positive effect on the sorption of Eu(III) on alumina at low pH values. The migration of Eu(III) in alumina was studied by using column experiments and 152+154Eu(III) radiotracer at pH 3.8. For column experiments, Eu(III) sorbed on alumina can be desorbed completely from the solid surface at low pH values. The findings are relevant to the evaluation of lanthanide and actinide ions in the environment.

Diffusion of Eu(III) in compacted bentonite—effect of pH, solution concentration and humic acid

The effect of pH, Eu(III) solution concentration and humic acid on the diffusion of Eu(III) in compacted bentonite ( ρ b=1000±30 kg/m 3) was studied with “in-diffusion” method at an ionic strength of 0.1 M NaClO 4. The results ( K d values from the first slice and theoretical calculation, apparent and effective diffusion coefficients) derived from the new capillary method are in good agreement with the literature data under similar conditions, and fit the Fick's second law very well. The results suggest that the diffusion of Eu(III) is dependent on pH values and independent on solution concentration in our experimental conditions. Humic acid forms precipitation/complexation with Eu(III) at the surface of compacted bentonite and thus deduces the diffusion/transport of Eu(III) in compacted bentonite. The K d values in compacted bentonite are in most cases lower than those in powdered bentonite obtained from batch experiments. The difference between the K d values from powdered and compacted bentonite is a strong function of the bulk density of the bentonite. The results suggest that the content of interlaminary space plays a very important role to the diffusion, sorption and migration of Eu(III) in compacted bentonite.

Evaluation of Eu(III) migration in compacted bentonite

The distribution coefficient of Eu(III) derived from batch experiments is used to predict the migration of Eu(III) in compacted bentonite with time. The effect of the dispersion coefficient and the pore water velocity on the migration of Eu(III) are also taken into account. It was found that the dispersion coefficient does not influence the migration, while the variation of the distribution coefficient and the water velocity affected the behavior of Eu(III) in compacted bentonite. Most of the europium is retained in the first several meters. So, 30 m of backfill bentonite may be sufficient to prevent the release of Eu(III) to the environment.

Model Study of Migration Behavior in Floods of 241Am and 152Eu Associated with Humus Compounds in Floodplain Soils of the Yenisei River

It is demonstrated in model experiments that in the presence of Ca ions (typomorphous cations of water of the Yenisei River) fulvic acids of floodplain soils and associated radionuclides (Am, Eu) form poorly soluble mixed Ca, Fe, Al(Am, Eu) fulvates. As a result, under the flooding conditions the migration of Am and Eu in the form of solubilized organomineral complexes is practically totally suppressed. With decreasing pH in the model system from 8 to 6 the mobility of the radionuclides noticeably increases.

Site-selective emission spectra of Eu 3+:Ca 5(PO 4) 3F

The room temperature site-selective fluorescence and excitation spectra of Eu 3+:FAP powder samples as well as the decay times of the observed emission lines associated with the 5D 0→ 7F 0,1,2 transitions have been measured. In sample I, prepared by the thermally stimulated diffusion of Eu 2O 3 in the solid state, Eu 3+ reside only in the Ca(II) location which has C s symmetry. Experimental values for the Stark energy levels have been determined for three well-separated sites. Sites A and B exhibit very similar spectral features attributed to the presence of the charge-compensating O 2− ion in the F − position in the FAP lattice, whereas for Eu 3+ in site C the charge is most probably compensated by vacancies according to 3Ca 2+→2Eu 3++Vacancy substitution. In sample II, prepared by precipitation of Eu 3+(1%):FAP from solution, Eu 3+ substitute for calcium in the Ca(I) position exclusively and three sites with C 3 symmetry have been identified. Substitution of 3Ca 2+/2Eu 3+ is the most probable charge-compensation mechanism. Heating of sample II stimulates the migration of Eu 3+ from the Ca(I) position to the low symmetry Ca(II) site.

Luminescence of Eu 3+ in La 1− xEu xTa 7O 19 (0< x⩽1) solid solution

The luminescence properties of Eu 3+ in La 1− x Eu x Ta 7O 19 solid solution were examined systematically. In the structure the nearest neighbours of La 3+ sites doped with Eu 3+ ions are arranged two-dimensionally with proper separations of about 0.62 nm. An intense emission peak is observed at 610 nm together with supplementary weak peaks. All the peaks can be ascribed to 5 D j → 7 F j′ (j = 0,1; j′=0,1,2,3,4) transitions of Eu 3+. The emission of the 5D 0 → 7F 2 transition becomes intense and saturates with the Eu 3+ concentration. As a result, the profile of the concentration quenching implies that energy migration of excited Eu 3+ hardly takes place in La 1− x Eu x Ta 7O 19 solid solution.