Ce 3d Research Articles

Effective purification of phosphate from water using ultra-small hydrated cerium oxides encapsulated inside gel-type polymer

Deep removing phosphate from waters is crucial in managing eutrophication, and adsorption has been widely regarded as an effective option. However, it is still lack of adsorbents with high reactivity and applicability. Herein, a novel nanocomposite HCO@N201 was introduced by impregnating hydrated cerium oxides (HCO) NPs inside a gel-type polymer N201. Due to the unique pore structure of N201 that contained plenty of micropores of <5 nm, the in-situ generated HCO NPs were regulated to sub-5 nm level (with the average size of 3.99 ± 0.06 nm), much smaller than the HCO NPs formed inside the widely-used macroporous host D201 (27.64 ± 2.55 nm). Adsorption isotherms demonstrated that HCO@N201 exhibited the saturated adsorption capacity of 218.43 mg/g toward phosphate, reaching to 1.52 times that of the macroporous analogue HCO@D201 (144.04 mg/g). In addition, HCO@N201 exhibited highly enhanced decontamination performance in terms of adsorption selectivity, stability, and reusability. XPS analyses of O 1s and Ce 3d spectra indicated that HCO@N201 possessed elevated proportions of surface hydroxyl groups (−OH, 53.35 %) and Ce(III) species (38.13 %) than HCO@D201 (37.31 % and 29.13 % for –OH and Ce(III) species, respectively). Various techniques including FT-IR, SEM-EDS, and STEM-HAADF have also been applied to deeply explore the internal mechanism of decontamination. In cyclic fixed-bed operations, HCO@N201 could consistently produce approximately 1150 bed volumes (BV) of clean water from the influent containing ∼2 mg/L of phosphate, exceeding twice that of HCO@D201. This study may provide a promising phosphate purifier with high reactivity and applicability.

Construction of antimicrobial CeO2/Fe2O3 nanomaterials with enzyme-like activity and study of their mechanisms

This study employed rare earth element, Ce, and elemental Fe to prepare antimicrobial nanocomposites with enzyme-like activity. The materials were characterized by SEM, EDS, and XRD, as well as antimicrobial and drug resistance properties were tested. XPS analysis revealed a change in the valence state of Ce 3d in CeO2/Fe2O3 on addition of Fe. Furthermore, UV–vis spectral results showed that the band gap of the composite material decreased after composite formation. The creation of a heterogeneous structure was a significant factor responsible for enhancing the antimicrobial performance. The study analyzed the peroxidase (POD) activity of the materials using UV–vis spectroscopy. Results showed that the enzyme activity of the composites was significantly enhanced, compared to the individual materials. This enhancement combined with H2O2 to induce the production of ROS, resulted in a significant increase in the antimicrobial effect. The antimicrobial rate of the composite material exceeded 90 % at 250 µg/mL concentration. The antibacterial mechanism revealed that it primarily operated through synergistic effects of ROS, ionic dissolution, and damage by adsorption. It also had an apparent inhibitory effect on bacterial micro-organisms in water, which has wider application prospects.

RCSB protein Data Bank: exploring protein 3D similarities via comprehensive structural alignments.

Tools for pairwise alignments between 3D structures of proteins are of fundamental importance for structural biology and bioinformatics, enabling visual exploration of evolutionary and functional relationships. However, the absence of a user-friendly, browser-based tool for creating alignments and visualizing them at both 1D sequence and 3D structural levels makes this process unnecessarily cumbersome. We introduce a novel pairwise structure alignment tool (rcsb.org/alignment) that seamlessly integrates into the RCSB Protein Data Bank (RCSB PDB) research-focused RCSB.org web portal. Our tool and its underlying application programming interface (alignment.rcsb.org) empowers users to align several protein chains with a reference structure by providing access to established alignment algorithms (FATCAT, CE, TM-align, or Smith-Waterman 3D). The user-friendly interface simplifies parameter setup and input selection. Within seconds, our tool enables visualization of results in both sequence (1D) and structural (3D) perspectives through the RCSB PDB RCSB.org Sequence Annotations viewer and Mol* 3D viewer, respectively. Users can effortlessly compare structures deposited in the PDB archive alongside more than a million incorporated Computed Structure Models coming from the ModelArchive and AlphaFold DB. Moreover, this tool can be used to align custom structure data by providing a link/URL or uploading atomic coordinate files directly. Importantly, alignment results can be bookmarked and shared with collaborators. By bridging the gap between 1D sequence and 3D structures of proteins, our tool facilitates deeper understanding of complex evolutionary relationships among proteins through comprehensive sequence and structural analyses. The alignment tool is part of the RCSB PDB research-focused RCSB.org web portal and available at rcsb.org/alignment. Programmatic access is available via alignment.rcsb.org. Frontend code has been published at github.com/rcsb/rcsb-pecos-app. Visualization is powered by the open-source Mol* viewer (github.com/molstar/molstar and github.com/molstar/rcsb-molstar) plus the Sequence Annotations in 3D Viewer (github.com/rcsb/rcsb-saguaro-3d).

Resonance photoemission in pure and Tb doped CePO4 luminescent nanowires

The resonance photoemission spectroscopy (RPES) studies on pure and Terbium doped CePO4 nanowires (NWs) are reported here with the supporting characterizations using structural, optical and morphological properties. The NWs with varying Terbium (Tb) doping concentrations were synthesized using chemical synthesis route. Photoluminescence (PL) showed high PL emission intensity in the visible wavelength range indicating strong green luminescence due to efficient Ce3+ to Tb3+ energy transfer. The PL intensity increased up to a doping concentration of 15 wt% Tb3+, beyond which it decreased due to concentration quenching or cross-relaxation effect. Based on PL studies, pure, 5 wt% (the lowest doping amount) and 15 wt% (that shows the highest PL) doped samples were chosen for RPES studies. To understand the comparative contribution of Ce3+ and Ce4+ in the valence band, RPES measurements performed around the Ce 4d →4 f resonance threshold indicated strong presence of Ce 4 f states in pure CePO4 NWs, which reduced upon 5 wt% Tb doping in CePO4 NWs. At 15 wt% Tb3+ doping, the sample did not show resonance of Ce 4 f feature, which may be because Tb3+ ions have replaced Ce3+ ions in the CePO4 lattice. The results are crucial to understand the relative participation of Ce3+ and Ce4+ oxidation states in the valence band, which is an important factor in defining the optical properties of the material that determine the PL intensity.

Impact of the states in the electronic structure of the intermediate-valence superconductor CeIr3

The electronic structure of the f-based superconductor was studied by photoelectron spectroscopy. The energy distribution of the states were revealed by the resonant photoelectron spectroscopy. The states were mostly distributed in the vicinity of the Fermi energy, suggesting the itinerant character of the states. The contribution of the states to the density of states (DOS) at the Fermi energy was estimated to be nearly half of that of the states, implying that the states have a considerable contribution to the DOS at the Fermi energy. The core-level and x-ray absorption spectra were analyzed based on a single-impurity Anderson model. The number of the states in the ground state was estimated to be , which is much larger than the values obtained in the previous studies (i.e. ).

Unusual spectral features in square-net based nonsymmorphic Kondo lattice system, CeCuX2 (X = As/Sb)

We study the electronic structure of a nonsymmorphic Kondo lattice system, CeCuX2 (X = As/Sb), a promising class of correlated topological materials important for advanced technology. While both the materials show Kondo behavior in their transport properties, CeCuSb2 is antiferromagnetic and no magnetic order is observed in CeCuAs2. We studied high-quality single-crystalline samples employing hard x-ray photoemission spectroscopy. The sample cleaving exposes the square-net structured pnictogen layers. The CeCuSb2 valence band indicates a highly metallic phase. The spectral intensity at the Fermi level in CeCuAs2 is weak, revealing close to semi-metallic behavior of the system. The Ce 3d spectra exhibit multiple features; the intensity of the features changes with the change in surface sensitivity of the technique, suggesting significant differences in the surface and bulk electronic structure. The bulk spectra of the Kondo system do not exhibit the typical f0-feature often observed in such materials. Instead, a distinct feature is observed at the lower binding energy side of the well-screened peak; the signature of this feature is manifested in the spectra from high-quality single-crystalline samples. This is outstanding and calls for physics beyond existing theories of correlated systems.

Oxidative Desorption of Adsorbed Sulfur on Platinum Surfaces Modified with Cerium Species

In polymer electrolyte membrane fuel cells, hydrogen oxidation and oxygen reduction reaction occur at platinum (Pt) catalyst surface. Pollutants in air and hydrogen fuel, especially, sulfur (S) species, often strongly adsorb on the Pt surface, resulting in reduced electrochemically active surface area, namely poisoning effect. Because such poisoning causes the significant deterioration of cell performance and durability, understanding and control of adsorption behavior of S species are very important. Thus, it is necessary to develop a new method or material for recovery from S poisoning in anode.In this study, a Pt(111) single crystal electrode was modified with a Ce species and its electrochemical property was compared with a bare Pt electrode. The modification with Ce species was accomplished by immersion in a Ce (NO3)3 + HClO4 aqueous solution with bubbling Ar + H2 gas through the solution for 1 h or applying the potential at -0.2 V in a Ce (NO3)3 + HClO4 aqueous solution. The modification of Pt(111) electrode with Ce species drastically changed the electrochemical responses; hydrogen adsorption/desorption waves become smaller and adsorption/desorption waves of hydroxy group disappeared because of the presence of adsorbed Ce species. Adsorbed species was identified as a Ce3+ ion by XANES spectrum.After the bare Pt(111) electrode was immersed in an aqueous solution containing sodium sulfide, three types of adsorbed S species, HS and S/Sn were detected by XPS. HS was reductively desorbed from Pt electrode surface at potential cycling between 0.0 and 0.2 V vs. RHE (-0.2 and 0.0 V vs. Ag/AgCl). S/Sn species remained during this potential cycling but oxidatively desorbed when the positive limit of potential cycling was 0.6 V vs. RHE (0.8 V vs. Ag/AgCl). The hydrogen adsorption/desorption current gradually increased as repeating potential cycling between 0.0 and 1.0 V vs. RHE (-0.2 V and 0.8 V vs. Ag/AgCl).After the Ce-modified Pt(111) electrode was immersed in an aqueous solution containing sodium sulfide, an anodic current assignable to the oxidative desorption of S species appeared at 0.3 V. The peak current decreased as repeating potential cycling between 0.0 and 0.7 V vs. RHE (-0.2 V and 0.5 V vs. Ag/AgCl). After this potential cycling, the peak area of S2p region of XPS spectra decreased as well as Ce 3d peak. The oxidative desorption of S and Sn on the Ce-modified Pt(111) electrode took place at 0.5 V vs RHE (0.3 V vs. Ag/AgCl) which is much more negative than that of bare Pt(111) electrode (1.0 V vs. RHE (0.8 V vs. Ag/AgCl)). Thus, modification of Pt(111) electrode with Ce species promoted the oxidative desorption of S species.

Enhanced Oxygen Storage Capacity of Porous CeO2 by Rare Earth Doping.

CeO2 is an important rare earth (RE) oxide and has served as a typical oxygen storage material in practical applications. In the present study, the oxygen storage capacity (OSC) of CeO2 was enhanced by doping with other rare earth ions (RE, RE = Yb, Y, Sm and La). A series of Undoped and RE-doped CeO2 with different doping levels were synthesized using a solvothermal method following a subsequent calcination process, in which just Ce(NO3)3∙6H2O, RE(NO3)3∙nH2O, ethylene glycol and water were used as raw materials. Surprisingly, the Undoped CeO2 was proved to be a porous material with a multilayered special morphology without any additional templates in this work. The lattice parameters of CeO2 were refined by the least-squares method with highly pure NaCl as the internal standard for peak position calibrations, and the solubility limits of RE ions into CeO2 were determined; the amounts of reducible-reoxidizable Cen+ ions were estimated by fitting the Ce 3d core-levels XPS spectra; the non-stoichiometric oxygen vacancy (VO) defects of CeO2 were analyzed qualitatively and quantitatively by O 1s XPS fitting and Raman scattering; and the OSC was quantified by the amount of H2 consumption per gram of CeO2 based on hydrogen temperature programmed reduction (H2-TPR) measurements. The maximum [OSC] of CeO2 appeared at 5 mol.% Yb-, 4 mol.% Y-, 4 mol.% Sm- and 7 mol.% La-doping with the values of 0.444, 0.387, 0.352 and 0.380 mmol H2/g by an increase of 93.04, 68.26, 53.04 and 65.22%. Moreover, the dominant factor for promoting the OSC of RE-doped CeO2 was analyzed.

Ce doped LaAlO3 pigments with high NIR reflectance and modification of thermal aging properties of polyvinyl chloride

Based on the modified weather resistance of PVC plastics, a series of La1-xCexAlO3 inorganic pigments were synthesized in this study. A single La1-xCexAlO3 (x varies from 0.00 to 0.20) phase replacement solid solution of rhombohedral crystal structure with the addition of more Ce3+ doping. The sample pigments demonstrated a curved rod to spherical particle morphology change as Ce doping amount increased. The analysis by X-ray photoelectron spectroscopy (XPS) demonstrated that the cerium ion chemical valence states in the synthesized samples were + 3 and + 4. The carrier concentration and electron trap theory can be used to understand the variation in near-infrared reflectance of La1-xCexAlO3 pigment powder from 72.55% to 83.35%. Electric charge transfer (La 3d ↔ Ce 3d) can be used to describe how the La1-xCexAlO3 pigment shifts from white to orange to yellow. When PVC plastic is modified with pigment, the near-infrared reflectance varies from 52.87% to 61.63%. Inner surface temperature of La1-xCexAlO3/PVC composite plastics can be lowered by 8.5–13.7 °C, and the weather resistance of the modified PVC plastic is greatly increased. In conclusion, the modification of PVC plastics with La1-xCexAlO3 inorganic pigments can significantly reduce the surface temperature of plastics and prolong their service life.

Temperature dependence of ferromagnetic behavior in ceria nanoparticles with cubic morphology

Cerium IV oxide (CeO2) is a semiconductor material composed of a rare-earth metal that has been extensively studied due to present ferromagnetic behavior at room temperature and the possibility of being used in the production of information systems devices. The origin of this ferromagnetism is still far from clear up to now and there are scarce works about their temperature dependence. In this work, we report a systematic study of the temperature dependence of the magnetic properties of ceria nanoparticles with cubic morphology using magnetization measurements and electron paramagnetic resonance (EPR) spectroscopy. The material was characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-Ray excited Photoelectron Spectroscopy (XPS) techniques. A bimodal size distribution of CeO2 (100) NPs with an average size of 28.5 nm and 11 nm was obtained. XPS data for Ce 3d indicated that the relative surface amounts of Ce4+ and Ce3+ species were 74.10 % and 25.90 %, while for O 1 s the relative surface proportion found was 71.48 % for species oxygenated located in the crystalline lattice of the nanomaterial and 28.51 % of adsorbed hydroxyl oxygen (Ce – OH). The zero-field-cooled/field-cooled (ZFC/FC) curves of χ(T) and the M(H) curves as a function at different temperatures indicated ferromagnetic and paramagnetic behavior. The temperature dependence of the broad line in EPR spectra showed a magnetic transition at approximately 50 K, which can be attributed to the condensation of surface oxygen and the extinction of oxygen vacancies. This result reinforces the relationship between oxygen vacancies and ferromagnetic behavior in CeO2 nanoparticles.

Utilizing N-hydroxy-9-octadecenamide as a collector in flotation separation of bastnaesite and fluorite

Bastnaesite ((Ce,La,Pr,Nd)CO3F) is a significant light rare earth mineral found in nature, known for its fine-grained properties. Flotation is commonly employed for the recovery of fine-grained bastnaesite particles. Collectors serve as an essential flotation reagent that enhance the surface hydrophobicity of target minerals. A novel collector, N-hydroxy-9-octadecenamide (N-OH-9-ODA), was synthesised in this study. N-OH-9-ODA exhibits superior selectivity compared to the traditional collector oleic acid in the flotation separation of bastnaesite and fluorite. The experimental and computational results indicate that N-OH-9-ODA exhibits superior selectivity due to its higher adsorption affinity for bastnaesite surface compared to fluorite surface. The zeta potential and the binding energies of the Ce 3d peaks in the X-ray photoelectron spectrum (XPS) of bastnaesite surface exhibit significant shifts. Conversely, fluorite surface demonstrates minimal alterations in its zeta potential and the binding energies of the Ca 2p peaks in its XPS after its interaction with N-OH-9-ODA.

Superparamagnetic and antimicrobial biosynthesis of Ce/NiO nanomaterials for biomedical applications

Nanomaterials have been used in advanced biomedical applications due to their superparamagnetic and antimicrobial properties. The adequate superparamagnetic and antimicrobial capacity has improved the nanomaterials applicability in biomedical applications. Herein, superparamagnetic and antibacterial Ce doped NiO nanomaterials were developed by dissolving cerium(III) nitrate and nickel(II) nitrate at different concentrations (1-X, X = 0.001, 0.002 and 0.003, and 0.099, 0.098 and 0.097 M, respectively) using Azadirachta Indica extract as a nucleation agent. The oxidation states Ni(2p), Ce(3d) and O(1s) of the nanomaterials were investigated by XPS spectra. The XRD patterns determined that the Ce doped NiO nanomaterials exhibit face-centred​ cubic structures. FE-SEM illustrates the surface structure of the nanomaterials, which have non-uniform spherical particles. Photoluminescence spectra reveal multi-emission centres​ created in the nanostructure. In addition, the electrical and magnetic behaviours of the Ce-doped NiO nanomaterials were investigated to determine the dielectric polarization and magnetic properties. The nanomaterials’ superparamagnetic behaviour was studied using a vibrating sample magnetometer at ambient temperature. Additionally, nanostructures’ bacterial activity significantly inhibited Staphylococcus Aureus and Klebsiella Pneumoniae. This investigation indicates that forming a nanostructure has significant advantages in biomedical applications.

Detection of Acute Optic Neuritis using Contrast-Enhanced 3-Dimensional Cube T1-Weighted Imaging: A Preliminary Study.

At a field strength of 3 T, CE 3D Cube T1-weighted and conventional CE 2D T1- weighted MR images were retrospectively analyzed for 32 patients (64 optic nerves) with clinically confirmed acute ON. The study cohort included 36 pathological nerves. Image assessments including the overall image quality, clarity of the optic nerve, and visual contrast enhancement were performed by two blinded neuroradiologists using a 4-point scale. The sensitivity, specificity, and accuracy of the conventional 2D T1WI and 3D Cube T1WI were calculated according to the clinical diagnosis. The application of 3D Cube T1WI improved the overall image quality compared to 2D Ax T1WI and 2D Cor T1WI (P < 0.05). The clarity of the optic nerve and the visual contrast enhancement were higher for the 3D Cube T1WI compared to the 2D Ax T1WI and 2D Cor T1WI for at least one reader. The sensitivity, specificity, and accuracy were 89%, 86%, 88% for the 3D Cube T1WI respectively, and 75%, 79%, 77% for the conventional 2D T1WI respectively. The lesions detected by the conventional 2D T1WI were all detected by the 3D Cube T1WI. Our data show that whole-brain imaging with CE 3D Cube T1WI is a viable alternative for the detection of acute ON without sacrificing scanning efficiency.

Quasiparticle State in 4f Localized Ferromagnet CeRu2Ge2 Studied by Soft X-ray Photoemission Spectroscopy

The electronic state of 4f localized ferromagnet CeRu2Ge2 has been investigated by angle-resolved photoemission spectroscopy (ARPES) experiments using soft x rays. The band structure and Fermi surfaces consisting of non-4f bands are almost consistent with a calculation based on the density-functional theory for LaRu2Ge2, thus confirming a localized character of the 4f electrons. On the other hand, the Ce 3d–4f resonant ARPES experiments demonstrated that the 4f spectral function is dominated by f1 components in the vicinity of the Fermi level and thus is different from that expected for a localized electron system. We also revealed that the intensities of the f1 components have almost no temperature dependence up to at least 100 K, which is two orders of magnitude larger than the Kondo temperature of CeRu2Ge2.

Diagnostic value of contrast-enhanced 3D FLAIR sequence in acute optic neuritis.

Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) sequence of the brain has the potential for detecting optic nerve abnormality. This study aimed to compare the diagnostic value of whole-brain contrast-enhanced three-dimensional FLAIR with fat suppression (CE 3D FLAIR FS) sequence in detecting acute optic neuritis to dedicated orbit MRI and clinical diagnosis. Twenty-two patients with acute optic neuritis who underwent whole-brain CE-3D-FLAIR FS and dedicated orbit MRI were retrospectively included. The hypersignal FLAIR of the optic nerve on whole-brain CE-3D-FLAIR FS, enhancement, and hypersignal T2W on orbit images were assessed. The optic nerve to frontal white matter signal intensity ratio on CE-FLAIR FS was calculated as maximum signal intensity ratio (SIR) and mean SIR. Twenty-six hypersignals of optic nerves were found on CE-FLAIR FS from 30 pathologic nerves. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CE FLAIR FS brain and dedicated orbital images for diagnosing acute optic neuritis were 77%, 93%, 96%, 65%, and 82% and 83%, 93%, 96%, 72%, and 86%, respectively. Optic nerve to frontal white matter SIR of the affected optic nerves was higher than that of normal optic nerves. Using a cutoff maximum SIR of 1.24 and cutoff mean SIR of 1.16, the sensitivity, specificity, PPV, NPV, and accuracy were 93%, 86%, 93%, 80%, and 89% and 93%, 86%, 93%, 86%, and 91%, respectively. The hypersignal of the optic nerve on whole-brain CE 3D FLAIR FS sequence has qualitative and quantitative diagnostic potential in patients with acute optic neuritis.

Layer-resolved electronic behavior in a Kondo lattice system, CeAgAs2

We investigate the electronic structure of an antiferromagnetic Kondo lattice system CeAgAs2 employing hard x-ray photoemission spectroscopy. CeAgAs2, an orthorhombic variant of HfCuSi2 structure, exhibits antiferromagnetic ground state, Kondo like resistivity upturn and compensation of magnetic moments at low temperatures. The photoemission spectra obtained at different photon energies suggest termination of the cleaved surface at cis-trans-As layers. The depth-resolved data show significant surface-bulk differences in the As and Ce core level spectra. The As 2p bulk spectrum shows distinct two peaks corresponding to two different As layers. The peak at higher binding energy correspond to cis-trans-As layers and is weakly hybridized with the adjacent Ce layers. The As layers between Ce and Ag-layers possess close to trivalent configuration due to strong hybridization with the neighboring atoms and the corresponding feature appear at lower binding energy. Ce 3d core level spectra show multiple features reflecting strong Ce-As hybridization and strong correlation. Intense f 0 peak is observed in the surface spectrum while it is insignificant in the bulk. In addition, we observe a features at binding energy lower than the well-screened feature indicating the presence of additional interactions. This feature becomes more intense in the bulk spectra suggesting it to be a bulk property. Increase in temperature leads to a spectral weight transfer to higher binding energies in the core level spectra and a depletion of spectral intensity at the Fermi level as expected in a Kondo material. These results reveal interesting surface-bulk differences, complex interplay of intra- and inter-layer covalency, and electron correlation in the electronic structure of this novel Kondo lattice system.

Enhanced redox properties of Gd-doped CeO2–TiO2 induced by oxygen vacancies and disordered structure

The redox properties of Gd-doped CeO2–TiO2 (xGd = 0.03, 0.09, and 0.15) was related to the oxygen defects and the local atomic structure. As the gadolinium doping concentration increased, a low-angle shift of the CeO2 (111) peak was observed. The EPR spectrum of the gadolinium-doped sample had an oxygen vacancy peak, indicating the oxygen vacancies induced by gadolinium. The O 1s core-level spectra showed that the ratio of oxygen vacancies gradually increased with the gadolinium doping concentration, and the Gd 4d and Ce 3d core-level spectra showed that Gd3+ reduced Ce4+ to Ce3+. An EXAFS analysis of the local atomic structures around Ce and Gd showed an increase in the Ce–O and Ce-(Ce,Gd) bond lengths and peak broadening occurred upon gadolinium doping, indicating bond disordering. The same Ce–O and Gd–O bond lengths suggested that the gadolinium was substituted for the cerium site. Surface chemisorption characterization was carried out by analyzing O2-TPD and H2-TPR profiles: the peaks for oxygen desorption and hydrogen reduction gradually shifted to lower temperatures as the dopant concentration increased. The quantities of desorbed oxygen and reduced hydrogen also increased. These enhanced redox properties resulted from disordered Ce3+-VO∙∙-Gd3+ acting as a surface active site, which promoted the redox reaction.

Phytosynthesized Cu‐Doped Cerium Oxide Nanoparticles for Antibacterial Application

Herein, phytosynthesized copper doped cerium oxide nanoparticles (NPs) are synthesized and their application potential in antibacterial activity is investigated. The compensative effect of Cu2+ occupying Ce4+/Ce3+ site and redox conversion of Ce4+ to Ce3+ are found to facilitate the antibacterial activity of the doped NPs. The preliminary characterizations are done using X‐ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and energy‐dispersive analysis of X‐ray spectroscopy. The particle size distribution curves from field‐emission scanning data give the mean particle sizes to be ≈20.4, 19.9, and 18.8 nm, respectively, for pure, lightly doped, and heavily doped NPs. The transmission electron microscopy manifests tetra‐ and hexa‐shaped particles, indicating the presence of Ce2O3/Ce1−x Cu x O2 along with ceria in pure and lightly doped and an additional presence of CuO in the heavily doped. The X‐ray photoelectron spectra of Ce 3d deconvolute to 10 peaks corresponding to Ce3+ and Ce4+ yielding Ce3+/Ce4+ % ratio &lt;1 and Cu 2p and O 1s spectra are fitted to assess variation in Cu% and oxygen vacancies with doping. The Cu‐doped CeO2 samples show a commendable improvement over pure ceria, in the antibacterial activity against pathogenic bacteria Escherichia coli, Staphylococcus aureus, and Bacillus cereus.

Determination of the Primary Excitation Spectra in XPS and AES

This paper reviews a procedure that allows for extracting primary photoelectron or Auger electron emissions from homogeneous isotropic samples. It is based on a quantitative dielectric description of the energy losses of swift electrons travelling nearby surfaces in presence of stationary positive charges. The theory behind the modeling of the electron energy losses, implemented in a freely available QUEELS-XPS software package, takes into account intrinsic and extrinsic effects affecting the electron transport. The procedure allows for interpretation of shake-up and multiplet structures on a quantitative basis. We outline the basic theory behind it and illustrate its capabilities with several case examples. Thus, we report on the angular dependence of the intrinsic and extrinsic Al 2s photoelectron emission from aluminum, the shake-up structure of the Ag 3d, Cu 2p, and Ce 3d photoelectron emission from silver, CuO and CeO2, respectively, and the quantification of the two-hole final states contributing to the L3M45M45 Auger electron emission of copper. These examples illustrate the procedure, that can be applied to any homogeneous isotropic material.

Alleviation of O2 competition with NO in electrochemical reduction through nanoceria supported on LSM cathode

• Nano-sized ceria infiltrated on LSM can alleviate negative impact of oxygen on NO electrochemical reduction. • Higher OSC of LSM-GDC(nano) and oxygen vacancies regeneration under polarization favors to extend the limit of oxygen tolerance. • Besides OSC, gas or chemical diffusion is another key kinetic limit to improve performance. Inhibition of O 2 competing with NO will promote NO electrochemical abatement, and further will facilitate its application in the purification of exhaust emitted from a gasoline engine. This study discovered that (La 0.75 Sr 0.25 ) 0.95 MnO 3 cathode with nano-sized Ce 0.9 Gd 0.1 O 1.95 (GDC) particles (denoted as LSM-GDC(nano)) in solid-state cell can alleviate the negative impact of oxygen content on NO conversion. When oxygen content increases gradually from 0 to 1%, NO conversions decrease to 60% and 30% for LSM-GDC(nano) and LSM-GDC cathodes, respectively. In comparison with LSM-GDC, the abundance of oxygen vacancies available for oxygen adsorption in LSM-GDC(nano) is responsible for higher OSC values under polarization. Postmortem XPS spectra of Ce 3d for the cathodes further confirm that Ce 4+ reduction- into Ce 3+ under polarization can regenerate oxygen vacancies, and that the redox cycle of Ce 4+ /Ce 3+ between polarization and external atmosphere takes place during electrochemical reduction of NO. The DRT method precisely reveals that LSM-GDC(nano) improves adsorption and dissociation of O 2 significantly, which is also confirmed by DFT calculations. However, the limit of gas/chemical diffusion is still prominent in the presence of relatively higher oxygen content, even at higher applied voltages.