Eu Cd Research Articles

The economic costs of cadmium non‐tariff measures for smallholder cocoa farmers in Ecuador

AbstractWhile there is a growing number of studies on the export‐ and firm‐level implications of non‐tariff measures for developing countries, there is little evidence on the trickle‐down effects on the farm level. In this paper, we analyse the recent regulations of the European Union regarding the maximum allowed cadmium (Cd) contents for cocoa‐derived products. We assess the potential economic costs associated with these Cd regulations for smallholder cocoa farmers in Ecuador. We rely on data from a nationwide survey among 1392 cocoa producers and a contingent valuation method to estimate producers' willingness to convert cocoa orchards to other land uses in case cocoa bean Cd levels exceed the limit. We estimate that farmers' economic cost of abandoning cocoa production is, on average, about 4400 US$ per hectare. Combining this value with a Cd distribution map and cocoa production statistics, we estimate that abandoning cocoa cultivation in areas with bean Cd concentrations above the 0.6 mg/kg target comes at a total economic cost of about 750 million US$. We conclude that the potential total economic cost of the EU Cd standard at the producer level in Ecuador could be very large if compliance strategies are not implemented to minimise welfare loss.

Europium-cadmium organic framework with zwitterionic ligand exhibiting tunable luminescence, CO2 adsorption and dye degradation

Porous lanthanide-transition heterometallic metal-organic frameworks (MOFs) as a subclass of porous hybrid materials have attracted considerable attention as a new advance in the research on MOFs. However, rationally designing and constructing heterometallic MOFs with desirable properties remains a challenging task. In this work, involving the heterometallic cooperative crystallization method, a novel europium-cadmium MOF based on a zwitterionic carboxylate ligand, [EuCd(pbbp)2(SO4)2Cl2(H2O)3] (1), (H2pbbp·2Cl ​= ​1,1'-(1,4-phenylene-bis(methylene))-bis(3-carboxy pyridinium) dichloride), has been solvothermally synthesized. Complex 1 was characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. The structure of complex 1 consists of Eu–Cd heterometallic chains with one-dimensional channels. Complex 1 shows interesting excitation-dependent luminescence at room temperature. The gas adsorption studies show that complex 1 exhibits highly selective adsorption of CO2 over N2 and H2 under ambient conditions, which may be caused by the stronger interaction of CO2 with the positively charged pyridinium functional groups. In addition, the photocatalytic activity studies indicate that complex 1 shows good activity in rhodamine B dye degradation.

Cadmium mobility in a circular food-to-waste-to-food system and the use of a cultivated mushroom (Agaricus subrufescens) as a remediation agent

Cadmium (Cd) and its mobility and toxicity in the food chain receives considerable public and scientific attention. Levels in soil have been increasing, partly caused by mineral fertiliser use. In many areas in the EU, intake of Cd is not far from the maximum tolerable level. Now, urban and more circular approaches to food production are being promoted, in which waste materials substitute growing media and fertilizers. Can this make the situation worse, or is it, on the contrary, possible to extract Cd from the cycle using practical microbial methods? Cd concentration, availability and accumulation in materials and crops in a closed greenhouse system was investigated first. Secondly, we tested if fungal remediation was able to remove a significant amount of Cd.A sequential extraction analysis showed how anaerobic digestion and composting changed chemical Cd availability. Cd levels in the system were comparable to agricultural soils. The vegetable crops did not accumulate Cd. However, the culture of the edible mushroom Agaricus subrufescens in the greenhouse had a strong effect on Cd mobility: It extracted 80% of the Cd from the growing medium into the mushrooms, mostly at the start of fruiting. These early Cd enriched mushrooms can be treated as special waste, while the later harvest complied with EU Cd limits for foodstuffs and can potentially be consumed. Thus, growing this mushroom species in an integrated waste-to-crop system can be a cost-efficient way to remediate Cd from the food chain.

A triplet state energy transfer material design concept enables enhanced visualization applications

A triplet energy transfer approach to fabricate Eu–CD nanomaterials to improve sensor and visualization effects for –OH-related environmental changes.

Exploratory Work in the Quaternary System of Ca⁻Eu⁻Cd⁻Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions.

Investigation of the quaternary system, Ca–Eu–Cd–Sb, led to a discovery of the new solid solutions, Ca1−xEuxCd2Sb2, with the CaAl2Si2 structure type (x ≈ 0.3–0.9, hP5, Pm1, a = 4.6632(5)–4.6934(3) Å, c = 7.630(1)–7.7062(7) Å), Ca2−xEuxCdSb2 with the Yb2CdSb2 type (x ≈ 0.6, oS20, Cmc21, a = 4.646(2) Å, b = 17.733(7) Å, c = 7.283(3) Å), and Eu11−xCaxCd6Sb12 with the Sr11Cd6Sb12 type (x ≈ 1, mS58, C2/m, a = 32.407(4) Å, b = 4.7248(5) Å, c = 12.377(1) Å, β = 109.96(1)°). Systematic crystallographic studies of the Ca1−xEuxCd2Sb2 series indicated expansion of the unit cell upon an increase in the Eu content, in accordance with a larger ionic radius of Eu2+ vs. Ca2+. The Ca2−xEuxCdSb2 composition with x ≈ 0.6 adopts the non-centrosymmetric space group, Cmc21, although the parent ternary phase, Ca2CdSb2, crystallizes in the centrosymmetric space group, Pnma. Two non-equivalent Ca sites in the layered crystal structure of Ca2−xEuxCdSb2 get unevenly occupied by Eu, with a preference for the interlayer position, which offers a larger available volume. Similar size-driven preferred occupation is observed in the Eu11−xCaxCd6Sb12 solid solution with x ≈ 1.

Human exposure to heavy metals and possible public health risks via consumption of wild edible mushrooms from Slovak Paradise National Park, Slovakia

The contamination level of 92 samples (12 species) of wild edible mushrooms and underlying substrates with heavy metals (Cd, Cu, Hg, Pb and Zn) in the Slovak Paradise National Park that borders with a region of historical mining and processing of polymetallic ores, were determined. The collected samples were analyzed using of atomic absorption spectrophotometry. The metals were determined separately in hymenophore (H) and rest of fruit bodies (RFB). Bioaccumulation factor as well as ratio of metal content in H and RFB were calculated. Cadmium and lead contents in hymenophore exceeded statutory limits of the EU (Cd: 0.5 mg/kg dry weight (dw), Pb: 1.0 mg/kg dw) for edible mushrooms in 96% and 83% of the samples, respectively. The risk from the consumption of the collected mushroom species was calculated based on the provisionally tolerable weekly intake (PTWI) values, and the highest health risk arising with consumption of particularly Macrolepiota procera, Marasmius oreades and Russula vesca from the observed area was demonstrated. It was shown that average weekly consumption of tested mushrooms species results the threat of exceeding of PTWI limits in the case of cadmium values (by 164%, 86% and 4% of PTWI for M. oreades, R. vesca and R. puellaris, respectively) and of mercury (by 96% of PTWI for M. procera) but not lead.

A self-assembling lanthanide molecular nanoparticle for optical imaging.

Chromophores that incorporate f-block elements have considerable potential for use in bioimaging applications because of their advantageous photophysical properties compared to organic dye, which are currently widely used. We are developing new classes of lanthanide-based self-assembling molecular nanoparticles as reporters for imaging and as multi-functional nanoprobes or nanosensors for use with biological samples. One class of these materials, which we call lanthanide "nano-drums", are homogeneous 4d-4f clusters approximately 25 to 30 Å in diameter. These are capable of emitting from the visible to near-infrared wavelengths. Here, we present the synthesis, crystal structure, photophysical properties and comparative cytotoxicity data for a 32 metal Eu-Cd nano-drum [Eu(8)Cd(24)L(12)(OAc)(48)] (1). We also explored the imaging capabilities of this nano-drum using epifluorescence, TIRF, and two-photon microscopy platforms.

Structural variability versus structural flexibility. A case study of Eu9Cd4+xSb9 and Ca9Mn4+xSb9 (x ≈ (1)/2).

The focus of this article is on the synthesis and structural characterization of the new ternary antimonides Eu(9)Cd(4+x)Sb(9) and Ca(9)Mn(4+x)Sb(9) (x ≈ (1)/2). Although these compounds have analogous chemical makeup and formulas, which may suggest isotypism, they actually belong to two different structure types. Eu(9)Cd(4.45(1))Sb(9) is isostructural with the previously reported Eu(9)Zn(4.5)Sb(9) (Pbam), and its structure has unit cell parameters a = 12.9178(11) Å, b = 23.025(2) Å, and c = 4.7767(4) Å. Ca(9)Mn(4.41(1))Sb(9) crystallizes in the orthorhombic space group Pnma with unit cell dimensions a = 12.490(2) Å, b = 4.6292(8) Å, and c = 44.197(8) Å and constitutes a new structure type. The two structures are compared and contrasted, and the structural relationships are discussed. Exploratory work aimed at the arsenic-based analogues of either type led to the identification of Ca(9)Zn(4.46(1))As(9), forming with the latter structure [a = 11.855(2) Å, b = 4.2747(8) Å, and c = 41.440(8) Å]. Differential thermal analysis and electrical resistivity measurements, performed on single crystals of Ca(9)Zn(4+x)As(9), indicate high thermal stability and semiconducting behavior. Magnetic susceptibility measurements on Eu(9)Cd(4+x)Sb(9) samples confirm the expected Eu(2+) ([Xe]4f(7)) ground state.

Eu9Cd4-xCM2+x-y□ySb9: Ca9Mn4Bi9-type structure stuffed with coinage metals (Cu, Ag, and Au) and the challenges with classical valence theory in describing these possible zintl phases.

The synthesis, crystal structure, magnetic properties, and europium Mössbauer spectroscopy of the new members of the 9-4-9 Zintl family of Eu(9)Cd(4-x)CM(2+x-y)□(y)Sb(9) (CM = coinage metal: Au, Ag, and Cu) are reported. These compounds crystallize in the Ca(9)Mn(4)Bi(9) structure type (9-4-9) with the 4g interstitial site almost half-occupied by coinage metals; these are the first members in the 9-4-9 family where the interstitial positions are occupied by a monovalent metal. All previously known compounds with this structure type include divalent interstitials where these interstitials are typically the same as the transition metals in the anionic framework. Single-crystal magnetic susceptibility data indicate paramagnetic behavior for all three compounds with antiferromagnetic ordering below 10 K (at 100 Oe) that shifts to lower temperature (<7 K) by applying a 3 T magnetic field. (151)Eu Mössbauer spectra were collected on polycrystalline powder samples of Eu(9)Cd(4-x)CM(2+x-y)□(y)Sb(9) at 50 and 6.5 K in order to evaluate the valence of Eu cations. Although the Zintl formalism states that the five crystallographically distinct Eu sites in Eu(9)Cd(4-x)CM(2+x-y)□(y)Sb9 should bear Eu(2+), the Mössbauer spectral isomer shifts are clearly indicative of both 2+ and 3+ valence of the Eu cations with the Cu- and Au-containing compounds showing higher amounts of Eu(3+). This electronic configuration leads to an excess of negative charge in these compounds that contradicts the expected valence-precise requirement of Zintl phases. The spectra obtained at 6.5 K reveal magnetic ordering for both Eu(2+) and Eu(3+). The field dependence of Eu(2+) indicates two distinct magnetic sublattices, with higher and lower fields, and of a small field for Eu(3+). The site symmetry of the five Eu sites is not distinguishable from the Mössbauer data.

Pentaeuropium dicadmium pentaantimonide oxide, Eu5Cd2Sb5O

The title compound, Eu5Cd2Sb5O adopts the Ba5Cd2Sb5F-type structure (Pearson symbol oC52), which contains nine crystallographically unique sites in the asymmetric unit, all on special positions. One Eu, two Sb, and the Cd atom have site symmetry m..; two other Eu, the third Sb and the O atom have site symmetry m2m; the remaining Eu atom has 2/m.. symmetry. Eu atoms fill penta­gonal channels built from corner-sharing CdSb4 tetra­hedra. The isolated O atom, i.e., an oxide ion O2−, is located in a distorted tetra­hedral cavity formed by four Eu cations.

Thermoelectric properties of Eu(Zn1−xCdx)2Sb2

The thermoelectric performance of EuZn(2)Sb(2) and EuCd(2)Sb(2) was optimized by mixed occupation of the transition metal position. Samples in the solid solution Eu(Zn(1-x)Cd(x))(2)Sb(2) with the CaAl(2)Si(2)-type crystal structure (space group Pm1) were prepared from the elements for compositions with x = 0, 0.1, 0.3, 0.5 and 1. The thermoelectric properties were investigated after densification of the products by spark plasma sintering (SPS). The samples show low electrical resistivity, high thermopower and a low lattice thermoconductivity. The highest ZT value of 1.06 at 650 K is obtained for x = 0.1.

Synthesis, Structural Characterization, Electronic Structure, and Magnetic Properties of the Zintl Phase Eu10Cd6Bi12

A new transition-metal-containing Zintl phase, Eu(10)Cd(6)Bi(12), was synthesized by combining the elements in excess molten Cd. Single-crystal X-ray diffraction studies indicated that this compound crystallizes in the orthorhombic space group Cmmm (No. 65) with a=7.840(2), b=24.060(7), and c=4.7809(14) A. The crystal structure of Eu(10)Cd(6)Bi(12) can be viewed as a stacking of a series of [Cd(6)Bi(12)] double layers, which are arranged alternately along the b axial direction. The layers are composed of corner- and edge-shared CdBi(4) tetrahedra, a common feature in the crystal chemistry of many transition-metal Zintl phases. Electronic-band-structure calculations confirm the closed-shell configuration of all constituent elements and corroborate the electron count inferred by the Zintl formalism, that is, [Eu(2+)](10)[Cd(2+)](6)[Bi(3-)](8)[Bi(2-)](4). Magnetic-susceptibility measurements confirm the divalency of europium and show the existence of a long-range antiferromagnetic order of the Eu spins below 12.3 K.

Superstructure of EU4CD25: a quasicrystal approximant.

The quasicrystal approximant Eu(4)Cd(25), formerly designated EuCd(6), was synthesized and characterized by means of single-crystal X-ray diffraction. Superstructure reflections corresponding to an F-centered cubic unit cell with a doubled cell-parameter relative to the I-centered cubic sub-cell could be observed in the diffraction data. This gives the largest cubic unit cell reported to date among binary alloys. The superstructure exhibits structural features that are found in all the RE-Cd(6) approximants as well as a further ordering between vacant/occupied Cd(8) cubes and oriented Cd(4) tetrahedra, which causes the superstructure. A reversible high-temperature phase-transition was observed at 782 K by means of DSC.

Structural, luminescence, and NMR studies of the reversible binding of acetate, lactate, citrate, and selected amino acids to chiral diaqua ytterbium, gadolinium, and europium complexes.

The nature of the ternary complexes formed in aqueous media at ambient pH on reversible binding of acetate, lactate, citrate, and selected amino acids and peptides to chiral diaqua europium, gadolinium, or ytterbium cationic complexes has been examined. Crystal structures of the chelated ytterbium acetate and lactate complexes have been defined in which the carboxylate oxygen occupies an "equatorial" site in the nine-coordinate adduct. The zwitterionic adduct of the citrate anion with [EuL1] was similar to the chelated lactate structure, with a 5-ring chelate involving the apical 3-hydroxy group and the alpha-carboxylate. Analysis of Eu and Yb emission CD spectra and lifetimes (H2O and D2O) for each ternary complex, in conjunction with 1H NMR analyses of Eu/Yb systems and 17O NMR and relaxometric studies of the Gd analogues, suggests that carbonate, oxalate, and malonate each form a chelated (q = 0) square-antiprismatic complex in which the dipolar NMR paramagnetic shift (Yb, Eu) and the emission circular polarization (gem for Eu) are primarily determined by the polarizability of the axial ligand. The ternary complexes with hydrogen phosphate, with fluoride, and with Phe, His, and Ser at pH 6 are suggested to be monoaqua systems with Eu/Gd with an apical bound water molecule. However, for the ternary complexes of simple amino acids with [YbL1]3+, the enhanced charge demand favors a chelate structure with the amine N in an apical position. Crystal structures of the Gly and Ser adducts confirm this. In peptides and proteins (e.g. albumin) containing Glu or Asp residues, the more basic side chain carboxylate may chelate to the Ln ion, displacing both waters.