Oxidation State Of Cerium Research Articles

Ratiometric fluorescent composites united metal-organic frameworks sensing system for detection of methyl-paraoxon

Organophosphorus pesticide residues pose significant risks to human health, but conventional analytical methods are costly and complex. To address this, we developed a new environmentally friendly technique using a simple hydrothermal method to create a ratiometric fluorescent composite (RFC) with two distinct signals: blue and orange. This RFC allowed for rapid detection and quantitative analysis of organophosphorus pesticides. The composite incorporated a cerium-based metal–organic framework (Ce-UiO-66), which could degrade methyl paraoxon (MP) due to the two oxidation states of cerium. The resulting degradation product, p-nitrophenol (p-NP), specifically quenched the blue fluorescence of the RFC via the inner filter effect (IFE), while the orange fluorescence remained unaffected, ensuring consistency under microenvironmental and spectrometer conditions. This innovative approach was sensitive, with a detection limit of 0.55 μM, selective, and repeatable, offering a new strategy for pesticide analysis and safety evaluation of edible and medicinal plant and water samples.

Probing the structural, mechanical, biomineralization, resorbability and biocompatibility characteristics of ZrO2–CaSiO3 composite dependent on cerium substitutions

Composites comprising mechanically stronger ceramic and bioactive alongside resorbable ceramic are a most welcomed choice in load-bearing bone replacement. In this pursuit, the present study aims to investigate the varied levels of cerium additions in the ZrO2–CaSiO3 composite. The influence of cerium concentration on the structural, mechanical, apatite formation, resorbability and in-vitro biological behaviour of the ZrO2–CaSiO3 composite has been undertaken in the current study. Sol-gel synthesis technique has been adopted to yield composite powders and the structural behaviour of the resultant has been performed using various analytical techniques. The results envisaged the crucial role of Ce3+ concentration in accomplishing a phase stable t/c-ZrO2-α-CaSiO3 composite after heat treatment at 1300 °C. XPS analysis revealed the presence of dual oxidation state (+3 and + 4) of cerium in the composite powders and a homogeneous mixture of the composite has been determined from morphological analysis. Mechanical properties determined from nanoindentation indicated better strength displayed by the composite than the natural bone. The immersion tests conducted in simulated body fluids indicated the development of apatite crystals on the composite. Resorbability and biocompatibility tests demonstrated the virtuous appropriateness of the 30 wt% Ce3+/Ce4+ doped t/c-ZrO2-α-CaSiO3 composite for load-bearing bone replacement.

Investigation of cerium as a surrogate for tetravalent actinides in monazite-type compounds

The incorporation of tetravalent cerium into the monazite structure via Ca(II)-coupled substitution was investigated using a solid state and a co-precipitation route for the synthesis of the La1-2xCaxCexPO4 solid solution. Based on powder XRD measurements and elemental mappings an optimised synthesis procedure was developed that averts the formation of secondary phases and allows the stabilisation of tetravalent cerium with a ratio of up to 0.21 Ce(IV)/Ce(III). In-situ HERFD-XANES measurements at the Ce L3 edge at up to 800°C were performed to study the cerium oxidation state during the phase transformation from rhabdophane to monazite, revealing an unexpected non-linear behaviour as well as a charge-directing effect of the lanthanum cation.

Cerium-oxide functionalized iron scaffolds: A synergistic approach for enhanced degradation and reduced cytotoxicity

Biodegradable scaffolds play a crucial role in biomedical restoration. These are three-dimensional (3D) structures that can provide support for the development of newly formed bone tissues. Among the studied metallic biodegradable scaffolds, those composed of iron (Fe) are notable for their high mechanical resistance. However, the slow degradation rate of Fe and the potential cytotoxicity of its degradation products pose challenges to effective osseointegration. Cerium oxide was incorporated into Fe scaffolds to overcome these two inherent limitations.We employed the dynamic hydrogen bubbling template (DHBT) technique, utilizing a citric acid-based electrolyte, to produce iron scaffolds. This same technique was used to embed cerium oxide nanoparticles (CNFe), whereas electrodeposition was used to create a thin cerium oxide coating over the scaffolds (CCFe). The oxidation state of cerium oxide in the functionalized scaffolds was scrutinized through surface characterization techniques. Ensuring similar porosities, we evaluated the degradation of the different distinct scaffolds using electrochemical techniques.The impact of cerium incorporation within or over the scaffolds on their degradation and cell viability was correlated with cerium oxidation states and the nature of the resulting degradation products. The synergistic implications of adding cerium to the iron scaffolds were thoroughly explored, and their potential benefits in future clinical settings were discussed.

Investigation of biological efficacy assessment of cobalt-doped cerium oxide nanocomposites against pathogenic bacteria, fungi, and lung cancer cells

This paper presents the fabrication of cobalt doped-cerium oxide nanocomposites (Co/CeO2 NCs) by solid combustion method. Synthesized cobalt doped CeO2 nanocomposites and pure CeO2 were confirmed by UV–Visible spectrophotometer, Fourier transform infrared spectrometer (FTIR), X-ray diffraction study (XRD), BET analysis and transmission electron microscope coupled with energy dispersive spectroscopy (TEM-EDS). The bandgap energies of CeO2, 0.25, 0.50 and 0.75%Co/CeO2 NCs were 3.02, 2.98, 2.81 and 2.80 eV, respectively. The 50 % inhibitory concentration (IC50) values of CeO2, 0.25, 0.50, and 0.75 % of Co-doped CeO2 were 57.02, 38.65, 35.33 and 39.87 μg/mL, respectively. The oxidation state of Cobalt and Cerium was confirmed by X-ray photoelectron spectrum. The Co/CeO2 NCs exhibited a zone of inhibition against bacteria and fungi. Thus, Co/CeO2 NCs can be used as a biomaterial for controlling pathogenic bacteria, fungi and lung cancer cell lines.

Realization of Organocerium-Based Fullerene Molecular Materials Showing Mott Insulator-Type Behavior.

Electron-rich organocerium complexes (C5Me4H)3Ce and [(C5Me5)2Ce(ortho-oxa)], with redox potentials E1/2 = -0.82 V and E1/2 = -0.86 V versus Fc/Fc+, respectively, were reacted with fullerene (C60) in different stoichiometries to obtain molecular materials. Structurally characterized cocrystals: [(C5Me4H)3Ce]2·C60 (1) and [(C5Me5)2Ce(ortho-oxa)]3·C60 (2) of C60 with cerium-based, molecular rare earth precursors are reported for the first time. The extent of charge transfer in 1 and 2 was evaluated using a series of physical measurements: FT-IR, Raman, solid-state UV-vis-NIR spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and magnetic susceptibility measurements. The physical measurements indicate that 1 and 2 comprise the cerium(III) oxidation state, with formally neutral C60 as a cocrystal in both cases. Pressure-dependent periodic density functional theory calculations were performed to study the electronic structure of 1. Inclusion of a Hubbard-U parameter removes Ce f states from the Fermi level, opens up a band gap, and stabilizes FM/AFM magnetic solutions that are isoenergetic because of the large distances between the Ce(III) cations. The electronic structure of this strongly correlated Mott insulator-type system is reminiscent of the well-studied Ce2O3.

Investigating cerium redox changes between aluminosilicate glass and melt: A multispectroscopic approach.

Redox control of glasses is paramount both to their fusion process and to obtaining the desired properties of high technological glasses. However, the link between melting parameters, such as temperature, furnace atmosphere, or quenching rate, and the redox state of the final products is poorly understood. In this work, in situ x-ray absorption near-edge structure (XANES) data at Ce L3-edge data were acquired at high temperatures on cerium-containing sodium aluminosilicate glasses, allowing the determination of thermodynamic constants necessary to predict the cerium redox state over a wide temperature range (900-1500 °C). The results obtained were compared to the Raman spectra of samples quenched at different temperatures. Our findings demonstrate that the quench performed was fast enough to block the cerium oxidation state, meaning the redox measured at room temperature is representative of a high temperature state. This was further verified by room temperature Raman spectroscopy, where a relationship was found between the spectra and melting conditions. Wet chemical analysis, XANES at Ce L3-edge, Raman spectroscopy, and optical absorption spectroscopy were successfully used to determine the redox state of cerium in aluminosilicates.

Using Ex Situ and In Situ HERFD-XANES to Reveal the Superior Oxidation and Reduction Cycling of Ceria Nanocubes Dispersed in Silica Aerogel.

The oxygen storage capacity of ceria-based catalytic materials is influenced by their size, morphology, and surface structure, which can be tuned using surfactant-mediated synthesis. In particular, the cuboidal morphology exposes the most reactive surfaces; however, when the capping agent is removed, the nanocubes can agglomerate and limit the available reactive surface. Here, we study ceria nanocubes, lanthanum-doped ceria nanocubes, and ceria nanocubes embedded inside a highly porous silica aerogel by high-energy resolution fluorescence detection-X-ray absorption near edge spectroscopy at the Ce L3 edge. In situ measurements showed an increased reversibility of redox cycles in ceria nanocubes when embedded in the aerogel, demonstrating enhanced reactivity due to the retention of reactive surfaces. These aerogel nanocomposites show greater improvement in the redox capacity and increased thermal stability of this catalytic material compared to the surfactant-capped nanocubes. Ex situ measurements were also performed to study the effect of lanthanum doping on the cerium oxidation state in the nanocubes, indicating a higher proportion of Ce4+ compared to that of the undoped ceria nanocubes.

The Role of Cerium Valence in the Conversion Temperature of H2Ti3O7 Nanoribbons to TiO2-B and Anatase Nanoribbons, and Further to Rutile.

CeO2-TiO2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO2 nanostructures decorated with CeO2 nanoparticles at the surface. As the precursor, we used H2Ti3O7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF-STEM mapping of the Ce4+-modified nanoribbons revealed a thin continuous layer at the surface of the H2Ti3O7 nanoribbons, while Ce3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO2 nanoparticles on the surface of the TiO2 nanoribbons, whose size increased with the calcination temperature. The use of Ce4+ raised the temperature required for converting H2Ti3O7 to TiO2-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.

Spherical CeO2 synthesized by molten-salt with unique fast variable valence properties for lithium-ion battery anode

As an important rare earth oxide, fluorite CeO2 is widely used in lithium ion batteries because it can quickly and directly change the oxidation state of cerium from Ce3+ to Ce4+. In this work, the ball milling method and the molten salt approach were both used to successfully produce amorphous carbon-coated CeO2 composite. The CeO2@C composite has excellent rate characteristics, high reversibility, and cycling stability. In contrast to the pure CeO2 electrode, the reversible capacity of CeO2@C remains at 264.8 mAh/g after 100 cycles at 100 mA g−1, with a capacity retention rate of 79.3%. The CeO2@C specific capacity is returned to 257.2 mAh/g, accounting for 89% of the initial capacity, after large current fluctuations and returning to the initial current density.

Effect of Re Addition on the Water–Gas Shift Activity of Ni Catalyst Supported by Mixed Oxide Materials for H2 Production

Water–gas shift (WGS) reaction was performed over 5% Ni/CeO2, 5% Ni/Ce-5% Sm-O, 5% Ni/Ce-5% Gd-O, 1% Re 4% Ni/Ce-5% Sm-O and 1% Re 4% Ni/Ce-5% Gd-O catalysts to reduce CO concentration and produce extra hydrogen. CeO2 and M-doped ceria (M = Sm and Gd) were prepared using a combustion method, and then nickel and rhenium were added onto the mixed oxide supports using an impregnation method. The influence of rhenium, samarium and gadolinium on the structural and redox properties of materials that have an effect on their water–gas shift activities was investigated. It was found that the addition of samarium and gadolinium into Ni/CeO2 enhances the surface area, reduces the crystallite size of CeO2, increases oxygen vacancy concentration and improves Ni dispersion on the CeO2 surface. Moreover, the addition of rhenium leads to an increase in the WGS activity of Ni/CeMO (M = Sm and Gd) catalysts. The results indicate that 1% Re 4% Ni/Ce-5% Sm-O presents the greatest WGS activity, with the maximum of 97% carbon monoxide conversion at 350 °C. An increase in the dispersion and surface area of metallic nickel in this catalyst results in the facilitation of the reactant CO adsorption. The result of X-ray absorption near-edge structure (XANES) analysis suggests that Sm and Re in 1% Re 4% Ni/Ce-5% Sm-O catalyst donate some electrons to CeO2, resulting in a decrease in the oxidation state of cerium. The occurrence of more Ce3+ at the CeO2 surface leads to higher oxygen vacancy, which alerts the redox process at the surface, thereby increasing the efficiency of the WGS reaction.

Selective Discrimination between CO and H2 with Copper-Ceria-Resistive Gas Sensors.

The production of hydrogen and the utilization of biomass for sustainable concepts of energy conversion and storage require gas sensors that discriminate between hydrogen (H2) and carbon monoxide (CO). Mesoporous copper-ceria (Cu-CeO2) materials with large specific surface areas and uniform porosity are prepared by nanocasting, and their textural properties are characterized by N2 physisorption, powder XRD, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The oxidation states of copper (Cu+, Cu2+) and cerium (Ce3+, Ce4+) are investigated by XPS. The materials are used as resistive gas sensors for H2 and CO. The sensors show a stronger response to CO than to H2 and low cross-sensitivity to humidity. Copper turns out to be a necessary component; copper-free ceria materials prepared by the same method show only poor sensing performance. By measuring both gases (CO and H2) simultaneously, it is shown that this behavior can be utilized for selective sensing of CO in the presence of H2.

Role of the Gd2O3 increment on the cerium oxidation state and luminescence behavior in the CeF3 doped silicoborate glass

This study aimed to investigate the effect of Gd2O3 on the cerium oxidation state and studied their luminescence in the silicoborate glass. Glass samples of a silicoborate glass containing cerium fluoride were prepared by doping the glass with varying amounts of Gd2O3 in the chemical formula xGd2O3: 40Na2O: 5SiO2: (54.5)B2O3: 0.5CeF3 (x = 0.0, 2.5, 5.0, 7.5, and 10.0 mol%). Density and refractive index tend to increase with increasing Gd2O3 content, whereas molar volume decreases. High-resolution XPS spectra confirm the chemical composition in the glass structure and found that the B1s and O1s regions illustrated more BO4 and bridging oxygen, respectively. X-ray absorption near edge structure (XANES) at the Ce LIII-edge was used to investigate the proportion between trivalent cerium (Ce3+) and tetravalent cerium (Ce4+). The ratio of Ce3+/Ce4+ decreased with the addition of Gd2O3. A higher concentration of Gd2O3 content showed more Ce4+ related to the reduction of photoluminescence and X-ray-induced luminescence spectra. Alpha-induced luminescence was used to calculate the light yield of the 7.5Gd:0.5CeF glass. Decay time was measured by pulsed light sources at 286 nm and X-ray excitation.

A systematic study on synthesis of CeO2 nanoparticles by various routes

Cerium oxide (CeO2), also known as, ceria, is a well-known n-type semiconductor material. It finds potential roles in various field applications such as catalysis, sensing and antibacterial. It is widely used as a photocatalyst for treatment of waste water pollutants, because of the variable oxidation state of cerium i.e. +3, and +4. Many reports are available in literature which deals with the synthesis and properties of CeO2. The properties of CeO2 are highly dependent on the synthesis conditions such as precursors, additives, calcination temperature and type of synthesis route. In this review article, synthesis of CeO2 by various chemical routes are discussed in detail.

MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy.

The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of cerium's redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO2 and CeZrOx nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce3+/Ce4+ redox properties are investigated by H2-TPR experiments exploited by in situ FT-IR and Ce M5-edge AP-NEXAFS spectroscopy. In the latter case, Ce3+ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce3+ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce3+ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce3+ quantification are discussed.

Synthesis and Characterization of a Bridging Cerium(IV) Nitride Complex.

Complexes featuring lanthanide-ligand multiple bonds are rare and highly reactive. They are important synthetic targets to understand 4f/5d-bonding in comparison to d-block and actinide congeners. Herein, the isolation and characterization of a bridging cerium(IV)-nitride complex: [(TriNOx)Ce(Li2μ-N)Ce(TriNOx)][BArF4] is reported, the first example of a molecular cerium-nitride. The compound was isolated by deprotonating a monometallic cerium(IV)-ammonia complex: [CeIV(NH3)(TriNOx)][BArF4]. The average Ce═N bond length of [(TriNOx)Ce(Li2μ-N)Ce(TriNOx)][BArF4] was 2.117(3) Å. Vibrational studies of the 15N-isotopomer exhibited a shift of the Ce═N═Ce asymmetric stretch from ν = 644 cm-1 to 640 cm-1, and X-ray spectroscopic studies confirm the +4 oxidation state of cerium. Computational analyses showed strong involvement of the cerium 4f shell in bonding with overall 16% and 11% cerium weight in the σ- and π-bonds of the Ce═N═Ce fragment, respectively.

Isolation and redox reactivity of cerium complexes in four redox states.

The chemistry of lanthanides is limited to one electron transfer reactions due to the difficulty of accessing multiple oxidation states. Here we report that a redox-active ligand combining three siloxides with an arene ring in a tripodal ligand can stabilize cerium complexes in four different redox states and can promote multielectron redox reactivity in cerium complexes. Ce(iii) and Ce(iv) complexes [(LO3)Ce(THF)] (1) and [(LO3)CeCl] (2) (LO3 = 1,3,5-(2-OSi(OtBu)2C6H4)3C6H3) were synthesized and fully characterized. Remarkably the one-electron reduction and the unprecedented two-electron reduction of the tripodal Ce(iii) complex are easily achieved to yield reduced complexes [K(2.2.2-cryptand)][(LO3)Ce(THF)] (3) and [K2{(LO3)Ce(Et2O)3}] (5) that are formally "Ce(ii)" and "Ce(i)" analogues. Structural analysis, UV and EPR spectroscopy and computational studies indicate that in 3 the cerium oxidation state is in between +II and +III with a partially reduced arene. In 5 the arene is doubly reduced, but the removal of potassium results in a redistribution of electrons on the metal. The electrons in both 3 and 5 are stored onto δ-bonds allowing the reduced complexes to be described as masked "Ce(ii)" and "Ce(i)". Preliminary reactivity studies show that these complexes act as masked Ce(ii) and Ce(i) in redox reactions with oxidizing substrates such as Ag+, CO2, I2 and S8 effecting both one- and two-electron transfers that are not accessible in classical cerium chemistry.

Cerium oxide nanosheets-based tertiary composites (CeO2/ZnO/ZnWO4) for supercapattery application and evaluation of faradic & non-faradic capacitive distribution by using Donn's model

Batteries and supercapacitors are trending energy storage devices nowadays but the low energy density of supercapacitors and modest power density of batteries limit their applications for practical usage. Recently a new class of energy storage devices called supercapattery has emerged as an ultimate energy storage device which shows a hybrid storage mechanism of both battery and supercapacitor. In the present work, CeO2-based binary and tertiary composites have been prepared by the facile hydrothermal method, characterized by different techniques, and applied as an electrode in supercapacitors and supercapattery. The X-ray diffraction patterns and EDX confirm the successful synthesis of tertiary composites with the average crystallite size of 26 nm while the SEM images show the randomly orientated nanosheets of CeO2 loaded with ZnO and ZnWO4 over it. The XPS spectrum depicts the presence of variable oxidation states of cerium (Ce+2 and Ce+4) in the tertiary composites. The electrochemical performance shows the highest specific capacity (496.9 Cg−1) for tertiary composite. The supercapattery device is fabricated by using mixed (AC/Ternary composite) as a working electrode and AC as a cathode which is separated by filter paper. The evaluation of capacitive and battery mechanisms shows the dominant feature of diffusive and surface-controlled processes at lower and high scan rates respectively due to varying diffusion time of electrolyte species. The fabricated device shows the energy density and power density of 56.92 Whkg−1 and 2000 Wkg−1 at a current density of 0.5 mAg−1 respectively with 88 % cyclic stability and 82 % coulombic efficiency.

Nano-sized cerium vanadium oxide as corrosion inhibitor: A microstructural and release study

• A simple chemical route to synthesize cerium vanadate. • Mixed nanostructure. • Cerium vanadate is an effective corrosion inhibitor for ferrous alloys. • It forms a layer on the steel surface. • Self-healing and smart corrosion inhibitor. The synthesized, nano-sized cerium vanadate is proposed as a self-healing corrosion inhibitor for ferrous alloys (e.g., automotive high strength steel (HSS) and mild steel (MS)). Cerium vanadate prepared at two different pH conditions (neutral and basic) showed similar corn-like morphology with nanorod structure. UV-Vis spectroscopy studies revealed that the release rate of cerium vanadate-B (basic condition) was higher than cerium vanadate-N (neutral condition) in 0.1 M NaCl solution. The specimen exposed to 0.1 M NaCl containing a supersaturated solution of cerium vanadate-B (1000 ppm) revealed 8 times and 6 times lower corrosion current density values for HSS and MS respectively than that of the one without corrosion inhibitor. There was a gradual increase in the film resistance ( R film ) on both HSS and MS observed as a function of exposure time in corrosive medium containing cerium vanadate-B inhibitor. An order higher impedance values were observed for both HSS and MS immersed for 168 h, highlighting the self-healing effect of the cerium vanadate compound. The X-ray photoelectron spectroscopy results showed the presence of multivalent oxidation states of both cerium and vanadium species. The inhibiting action is attributed to the high solubility of cerium vanadate in the corrosive medium to form a film on the metal surface. The dissolution/solubility of the corrosion inhibitor was more favorable in neutral to alkaline conditions than in acidic conditions.

Synergistic effect of doping and defect in achieving white light emission and oxygen reduction catalysis in Ce1-xSmxPO4

Multifunctional materials owing to their efficacy to perform more than one job have attracted the attention of global materials science community to resolve the issue of material crunch and reduce the work load. Here, in this work, we have demonstrated the suitability of CePO4:Sm3+ (CPOS) phosphor for white light luminophore and oxygen reduction catalyst. Raman spectroscopy confirmed the stabilization of monoclinic phase for CPOS. White light emission with correlated color temperature (CCT) favoring cool white feature in CPOS is endowed by inefficient host to dopant energy transfer (HDET). X-ray photoelectron spectroscopy (XPS) suggested presence of both Ce3+ and Ce4+ in CPOS with later in lower fraction. XPS results also showed the presence of surface oxygen in CPOS which along with mixed oxidation state of cerium on the surface may be aiding CPOS to work as electrocatalysts for oxygen reduction reaction (ORR). The best electrocatalytic performance was achieved with 1.0% Sm doped sample which has higher concentration of oxygen associated with Ce (IV) on the surface.