Search Results (18)

4-Acylpyrazolones are important ligands in analytical chemistry and technologies used for the separation and concentration of various metals. We have proposed a novel method for obtaining a material that consists of covalently immobilized functionalized ionic liquid on the surface of a mineral carrier featuring a coordination-active fragment of 4-acylpyrazolone. For its synthesis, we have introduced a strategy based on the quaternization of surface azolyl groups from 3-(1H-imidazol-1-yl)propyl silica with an alkylating reagent containing a 4-acylpyrazolone motif-4-(6-bromohexanoyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one. This method of covalent immobilization preserves the 1,3-dioxo fragment, which ensures the effective binding of metal ions. The success of this functionalization has been confirmed by IR and ¹³C NMR spectroscopy data, as well as by thermogravimetric analysis. The overall functional capacity was found to be 0.3 mmol/g. The potential of the synthesized organomineral material to concentrate five rare earth elements (REEs) representing the cerium (Eu(III), Sm(III)) and yttrium groups (Gd(III), Dy(III), Er(III)) has been demonstrated. It was shown that during extraction from multicomponent systems, both under static and dynamic preconcentration conditions, there is a competitive influence of analytes, and their separation can be evaluated under dynamic conditions based on dynamic output curves and calculated distribution coefficients. It was shown that for systems where Kd > 1.8, quantitative separation can be performed in a dynamic mode of sorption under selected conditions. Full article

Metal oxide nanoparticles (MONP/s) induce DNA damage, which is influenced by their physicochemical properties. In this study, the high-throughput CometChip and micronucleus (MicroFlow) assays were used to investigate DNA and chromosomal damage in mouse lung epithelial cells induced by nano and bulk sizes of zinc oxide, copper oxide, manganese oxide, nickel oxide, aluminum oxide, cerium oxide, titanium dioxide, and iron oxide. Ionic forms of MONPs were also included. The study evaluated the impact of solubility, surface coating, and particle size on response. Correlation analysis showed that solubility in the cell culture medium was positively associated with response in both assays, with the nano form showing the same or higher response than larger particles. A subtle reduction in DNA damage response was observed post-exposure to some surface-coated MONPs. The observed difference in genotoxicity highlighted the mechanistic differences in the MONP-induced response, possibly influenced by both particle stability and chemical composition. The results highlight that combinations of properties influence response to MONPs and that solubility alone, while playing an important role, is not enough to explain the observed toxicity. The results have implications on the potential application of read-across strategies in support of human health risk assessment of MONPs. Full article

The present study focuses on the electrochemical performance of polyethylene oxide (PEO)-polymethyl methacrylate (PMMA) blended plasticized nanocomposite solid polymer electrolytes (BPNSPEs) amid cadmium bromide (CdBr₂) as a dopant salt along with a cerium oxide (CeO₂) nanofiller. Incredibly thin nanofilms of BPNSPE were signalized through distinct methods of working in characterization studies, such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy and scanning electron micrography (SEM). The X-ray diffractograms (XRDs) confirmed the formation of the polymer electrolyte (PE) as well as a decrease in the degree of crystalline characteristics in the BPNSPE sample, and the particle dimension was calculated via the Debye–Scherer equation. The structural changes and formation of complexes were inspected by Fourier-transform infrared spectroscopy (FT-IR), and ocular absorbance scrutiny was accomplished by ultraviolet visible spectroscopy, whereas the morphological structure was interpreted by scanning electron microg-graphical images. The existing work is intended to increase the awareness of the significance of CeO₂ nanofillers with the BPNSPE arrangement, which is suitable for batteries and ionic devices. Full article

In this work, ceramic samples of cerium oxide doped with yttrium were investigated. The concentration of a dopant Y(NO₃)₃ varied from 5 to 25 wt% in the initial charge. In the course of the experiment, a simple method was developed to obtain ceramics with a porosity of ~20% via one-step annealing in air in a muffle furnace. For comparison, samples with two annealings were also synthesized to determine the effects of pores on electrical, structural, and mechanical characteristics. The obtained samples were examined via X-ray powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy, dielectric spectroscopy, and Vickers microhardness measurements. The substitution of Ce⁴⁺ ions with Y³⁺ ions led to a significant decrease in the lattice parameter, average crystallite size, and average grain size, with a simultaneous increase in the lattice defectivity, dielectric constant, electrical conductivity, and microhardness values. It is shown that samples with a dopant weight fraction of 0.05–0.15 and one-step annealing have favorable electrical and mechanical characteristics for energy applications as porous materials with ionic conductivity. Full article

As one of the most widely used nanomaterials, CeO₂ nanoparticles (NPs) might be released into the aquatic environment. In this paper, the interaction of CeO₂ NPs and Ce³⁺ ions (0~10 mg/L) with duckweed (Lemna minor L.) was investigated. CeO₂ NPs significantly inhibited the root elongation of duckweed at concentrations higher than 0.1 mg/L, while the inhibition threshold of Ce³⁺ ions was 0.02 mg/L. At high doses, both reduced photosynthetic pigment contents led to cell death and induced stomatal deformation, but the toxicity of Ce³⁺ ions was greater than that of CeO₂ NPs at the same concentration. According to the in situ distribution of Ce in plant tissues by μ-XRF, the intensity of Ce signal was in the order of root > old frond > new frond, suggesting that roots play a major role in the uptake of Ce. The result of XANES showed that 27.6% of Ce(IV) was reduced to Ce(III) in duckweed treated with CeO₂ NPs. We speculated that the toxicity of CeO₂ NPs to duckweed was mainly due to its high sensitivity to the released Ce³⁺ ions. To our knowledge, this is the first study on the toxicity of CeO₂ NPs to an aquatic higher plant. Full article

The rare-earth-doped zirconia-based solid electrolytes have gained significant interest in protonic ceramic fuel cell (PCFC) applications due to their high ionic conductivity. However, these solid electrolytes are susceptible to low conductivity and chemical stability at low operating temperatures, which are of interest in commercializing ceramic fuel cells. Thus, tailoring the structural properties of these electrolytes towards gaining high ionic conductivity at low/intermediate temperatures is crucial. In this study, Ce (cerium) and Nd (neodymium) co-doped barium zirconate perovskites, BaZr_(0.80-x-y)Ce_xNd_yY_0.10Yb_0.10O_3-δ (BZCNYYO) of various doping fractions (x, y: 0, 0.5, 0.10, 0.15), were synthesized (by the Pechini method) to systematically analyze their structural and conductivity properties. The X-ray diffraction patterns showed a significant lattice strain, and the stress inferences for each co-doped BZCNYYO sample were compared with Nd-cation-free reference samples, BaZrO₃ and BaZr_(0.80-x-y-z)Ce_xY_yYb_zO_3-δ (x: 0, 0.70; y: 0.20, 0.10; z: 0, 0.10). The comparative impedance investigation at low-to-intermediate temperatures (300–700 °C) showed that BaZr_0.50Ce_0.15Nd_0.15Y_0.10Yb_0.10O_3-δ offers the highest lattice strain and stress characteristics with an ionic conductivity (σ) of 0.381 mScm⁻¹ at 500 °C and activation energy (E_a) of 0.47 eV. In addition, this σ value was comparable to the best reference sample BaZr_0.10Ce_0.70Y_0.10Yb_0.10O_3-δ (0.404 mScm⁻¹) at 500 °C, and it outperformed all the reference samples when the set temperature condition was ≥600 °C. The result of this study suggests that Ce- and Nd-doped BZCNYYO solid electrolytes will be a specific choice of interest for developing intermediate-temperature PCFC applications with high ionic conductivity. Full article

Hydrogen peroxide acts as a byproduct of oxidative metabolism, and oxidative stress caused by its excess amount, causes different types of cancer. Thus, fast and cost-friendly analytical methods need to be developed for H₂O₂. Ionic liquid (IL)-coated cobalt (Co)-doped cerium oxide (CeO₂)/activated carbon (C) nanocomposite has been used to assess the peroxidase-like activity for the colorimetric detection of H₂O₂. Both activated C and IL have a synergistic effect on the electrical conductivity of the nanocomposites to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). The Co-doped CeO₂/activated C nanocomposite has been synthesized by the co-precipitation method and characterized by UV–Vis spectrophotometry, FTIR, SEM, EDX, Raman spectroscopy, and XRD. The prepared nanocomposite was functionalized with IL to avoid agglomeration. H₂O₂ concentration, incubation time, pH, TMB concentration, and quantity of the capped nanocomposite were tuned. The proposed sensing probe gave a limit of detection of 1.3 × 10⁻⁸ M, a limit of quantification of 1.4 × 10⁻⁸ M, and an R² of 0.999. The sensor gave a colorimetric response within 2 min at pH 6 at room temperature. The co-existing species did not show any interference during the sensing probe. The proposed sensor showed high sensitivity and selectivity and was used to detect H₂O₂ in cancer patients’ urine samples. Full article

This study investigated the effect of the remote activation of the ion exchangers Amberlite IR120 (H⁺ form) and AV-17-8 (OH⁻ form) in aqueous media to increase the sorption activity of the interpolymer system “Amberlite IR120H:AV-17-8” (X:Y, molar ratio of ionic groups) towards cerium ions from uranium-containing solutions. The sorption properties of the above-mentioned interpolymer system with molar ratios X:Y of 6:0, 5:1, 4:2, 3:3, 2:4, 1:5, and 0:6 were studied using the methods of conductometry, gravimetry, and inductively coupled plasma–optical emission spectrometry. The presented research revealed the dependence of the sorption activity of the interpolymer system “Amberlite IR120H:AV-17-8” (X:Y) on the acidity of the solution. At pH 2.0, the highest cerium ion sorption degree from the model solution (containing both cerium and uranium ions) by the interpolymer system “Amberlite IR120H:AV-17-8” (4:2) was 56% after 48 h of interaction, whereas the cerium ion sorption degrees by raw Amberlite IR120H (6:0) and raw AV-17-8 (0:6) were 30% and 0%, respectively. The increased sorption ability of the interpolymer system “Amberlite IR120H:AV-17-8” (4:2) might be associated with the achievement of the highest ionization degree by this system remotely activated in an aqueous medium. Moreover, the cerium ion desorption study demonstrated a 60% degree of desorption using 2M nitric acid as a desorbing agent (eluent). The obtained results demonstrate the potential of using the remote interaction effect for the activation of the ion exchangers in aqueous media as an interpolymer system for increased cerium ion sorption from uranium-containing solutions. Full article

Cerium oxide nanopowder (CeO_x) was prepared using the sol–gel method for the catalytic oxidation of N, N-dimethylformamide (DMF). The phase, specific surface area, morphology, ionic states, and redox properties of the obtained nanocatalyst were systematically characterized using XRD, BET, TEM, EDS, XPS, H₂-TPR, and O₂-TPO techniques. The results showed that the catalyst had a good crystal structure and spherelike morphology with the aggregation of uniform small grain size. The catalyst showed the presence of more adsorbed oxygen on the catalyst surface. XPS and H₂-TPR have confirmed the reduction of Ce⁴⁺ species to Ce³⁺ species. O₂-TPR proved the reoxidability of CeO_x, playing a key role during DMF oxidation. The catalyst had a reaction rate of 1.44 mol g⁻¹_cat s⁻¹ and apparent activation energy of 33.30 ± 3 kJ mol⁻¹. The catalytic performance showed ~82 ± 2% DMF oxidation at 400 °C. This work’s overall results demonstrated that reducing Ce⁴⁺ to Ce³⁺ and increasing the amount of adsorbed oxygen provided more suitable active sites for DMF oxidation. Additionally, the catalyst was thermally stable (~86%) after 100 h time-on-stream DMF conversion, which could be a potential catalyst for industrial applications. Full article

Finely dispersed (CeO₂)_0.95(Sm₂O₃)_0.05, (CeO₂)_0.90(Sm₂O₃)_0.10 and (CeO₂)_0.80(Sm₂O₃)_0.20 mesoporous powders with a specific pore volume of 0.080–0.092 cm³/g and a specific surface of 50–83 m²/g are synthesized by the co-precipitation of cerium and samarium hydroxides from the corresponding nitrate solutions. The prepared powders are used to obtain ceramic nanomaterials with a fluorite-like cubic crystal lattice with a coherent scattering region (CSR) of about 65–69 nm (1300 °C). The study of physicochemical and electrophysical properties of the prepared ceramics revealed the obtained materials featuring an open porosity of 2–6% and a predominantly ionic type of electric conductivity (ion transport numbers t_i = 0.85–0.73 in the temperature range 300–700 °C). The conductivity in solid solutions proceeds via a vacancy mechanism with σ_{700 °C}= 3.3·10⁻² S/cm. The synthesized ceramic materials are shown to be promising as solid oxide electrolytes in medium temperature fuel cells. Full article

Release of nanoceria (nCeO₂) into the environment has caused much concern about its potential toxicity, which still remains poorly understood for soil microorganisms. In this study, nanoceria and cerium (III) nitrate at different doses (10, 100 and 500 mg/kg) were applied to bok choy (Brassica rapa subsp. chinensis), grown in potting soil, to investigate the responses of soil bacterial communities to nanoceria (NC) and ionic cerium (IC) applications. The results showed that bacterial richness was slightly increased in all cerium treatments relative to the negative control without cerium amendment (CK), but a significant increase was only found in IC500. The patterns of bacterial community composition, predicted functions and phenotypes of all NC treatments were significantly differentiated from IC and CK treatments, which was correlated with the contents of cerium, available potassium and phosphorus in soil. The co-occurrence network of bacterial taxa was more complex after exposure to ionic cerium than to nanoceria. The keystone taxa of the two networks were entirely different. Predicted functions analysis found that anaerobic and Gram-negative bacteria were enriched under nanoceria exposure. Our study implies that Proteobacteria and nitrifying bacteria were significantly enriched after exposure to nanoceria and could be potential biomarkers of soil environmental perturbation from nanoceria exposure. Full article

A solid oxide fuel cell is a high-efficiency power device in hydrogen energy utilization. The durability and dynamic performance of metal-supported solid oxide fuel cells (MS-SOFCs) are superior to those of electrolyte- or electrode-supported cells, with many potential applications. Gadolinium-doped cerium (GDC) has a high oxygen ionic conductivity, making it suitable to act as the electrolyte in MS-SOFCs operating at 500–650 °C. However, the low-temperature sintering of GDC is difficult for MS-SOFCs. In this study, the factors affecting the low-temperature densification of GDC are analyzed based on an orthogonal experimental method. The shrinking rates of 16 experiments are determined. The effects of the particle diameter, pressure of the uniaxial press machine, sintering temperature, and fractions of aid and binder are estimated. The results of a range analysis indicate that the content of sintering aid has the greatest impact on the low-temperature densification of GDC, followed by the powder diameter and the uniaxial pressure. A maximum shrinking rate of 46.99% is achieved with a temperature of 1050 °C. Full article

Zeolitic Imidazolate Framework 67 (ZIF-67) and its derivates have attracted extensive interest for lithium-ion batteries (LIBs). Here, Cerium-doped cobalt phosphide@nitrogen-doped carbon (Ce-doped CoP@NC) with hollow polyhedron structure materials were successfully synthesized via ionic-exchange with Co and Ce ions using the ZIF-67 as a template followed with a facile low-temperature phosphorization treatment. Benefitting from the well-designed hollow polyhedron, steady carbon network, and Ce-doping structural merits, the as-synthesized Ce-doped CoP@NC electrode demonstrated superior performance as the anode in LIBs: a superior cyclability (400 mA h g⁻¹ after 500 cycles) and outstanding rate-capability (590 mA h g⁻¹, reverted to 100 mA g⁻¹). These features not only produced more lithium-active sites for LIBs anode and a shorter Li-ion diffusion pathway to expedite the charge transfer, but also the better tolerance against volume variation of CoP during the repeated lithiation/delithiation process and greater electronic conductivity properties. These results provide a methodology for the design of well-organized ZIFs and rare earth element-doped transition metal phosphate with a hollow polyhedron structure. Full article

Supramolecular systems based on transition metal complexes capable of reversible redox isomerization due to intramolecular electron transfer are one of the most interesting objects from the viewpoint of molecular switches’ design. In the present work, a comparative analysis of valence transformation of lanthanide complexes (Sm, Er, Tm and Yb) with donor-substituted bis-phthalocyaninates occurring during the formation and compression–extension of Langmuir monolayers was carried out using data of UV–Vis–NIR spectroscopy. It is shown that the numerical values of the Q-band positions in the absorption spectra for the extended monolayers of the complexes under study depend linearly on the ionic radius of the metal center, if the metals have an oxidation state of +2. This makes it possible to draw a direct analogy between the behavior of the studied compounds and analogous europium and cerium complexes, for which direct evidence of the valence tautomerism in such planar systems was obtained earlier. This led to the conclusion that the intramolecular electron transfer from the phthalocyanine ligand to the central metal ion [Ln³⁺(R₄Pc²⁻)(R₄Pc^•−)]⁰→[Ln²⁺(R₄Pc^•−)₂]⁰ occurs when solutions of donor-substituted bis-phthalocyaninates of samarium, erbium, thulium, and ytterbium are deposited onto the water subphase, and the reverse redox-isomeric transition is observed in most cases when the monolayer is compressed to high surface pressures. The first of these switches is related to the asymmetry of the air/water interface, and the second one is controlled by the lateral compression–expansion of the monolayer. It has been demonstrated that when bis-phthalocyanine monolayers of lanthanides with variable valence are transferred to solid substrates, the valence state of the metal center, and consequently, the redox-isomeric state of the complex, do not change. This means that we are able to form films with a predetermined state of the complex. Note that the redox-isomeric state of complexes should affect the entire range of physicochemical properties of such films. Full article

Ceria is one of the most important functional rare-earth oxides with wide industrial applications. Its amazing oxygen storage/release capacity is attributed to cerium’s flexible valence conversion between 4+ and 3+. However, there still exists some debate on whether the valence conversion is due to the Ce-4f electron localization-delocalization transition or the character of Ce–O covalent bonds. In this work, a mixed valence model was established and the formation energies of oxygen vacancies and electronic charges were obtained by density functional theory calculations. Our results show that the formation energy of oxygen vacancy is affected by the valence state of its neighboring Ce atom and two oxygen vacancies around a Ce⁴⁺ in CeO₂ have a similar effect to a Ce³⁺. The electronic charge difference between Ce³⁺ and Ce⁴⁺ is only about 0.4e. Therefore, we argue that the valence conversion should be understood according to the adjustment of the ratio of covalent bond to ionic bond. We propose that the formation energy of oxygen vacancy be used as a descriptor to determine the valence state of Ce in cerium oxides. Full article