Pure Cerium Oxide Research Articles

Precision engineering of surface defects of cerium oxide nanostructured fine particles for the multiplexed detection of electrolytes and glucose inside tissue models

The development of biosensors for the detection of glucose and electrolytes has become a crucial field of research nowadays due to the increasing incidence of long-term conditions. Specifically, the use of cerium oxide as a selective material for the detection of glucose is raising interest as an alternative to enzymatic sensors due to their stability and low-cost. This work demonstrates for the first time a significant improvement in the selectivity of glucose sensors based on cerium oxide nanostructured fine particles through doping with nickel ions and using pulse voltammetry for the sensing. By using nickel-doped cerium oxide fine particles, the sensitivity of the devices improved by 10-fold, and the selectivity when testing the devices against lactate increased by 68.5 % as compared to pure cerium oxide fine particles, with a limit of detection in the micromolar level. Crystallographic and compositional properties that led to such increase in sensitivity were determined, as a result of a presence of oxygen defects and amorphous domains at the surface of fine particles. This device could be adapted for the simultaneous measurement of glucose and sodium ions. The pulse voltametric approach enhanced the sensitivity of the sensors towards sodium ions, which reached a super-Nernstian sensitivity of 111 mV Log[Na+]-1, with a response time of 2 mins, and has been used for the testing of the electrodes in a practical environment using a skin-inspired material. This technology will pave the way for the development of miniaturised non-invasive wearable sensors real-time measurement of glucose and electrolytes in patients.

Synthesis and photocatalytic properties of Cerium(IV) oxide graphene oxide composites

Semiconductor photocatalytic technology is a simple, efficient, and low-cost method for environmental pollution remediation. Cerium dioxide (CeO2), as a promising oxidative degradation photocatalyst, can solve the problems of energy shortage and environmental pollution. In this paper, cerium dioxide/graphene oxide composites were successfully synthesized by a one-pot hydrothermal method, achieving a degradation rate of 88.96 % for rose red dye in 150 min, and the introduction of reduced graphene oxide effectively improves the photocatalytic performance of pure cerium oxide.

Improvement of chemical mechanical polishing performance by introducing N–Si bond via external coating of cerium oxide with ZIF-8

Cerium oxide (CeO2) nanoparticles are widely used as abrasives in chemical mechanical polishing (CMP), an essential process for obtaining Si wafers with excellent surface quality. While CeO2 nanoparticles form Ce–O–Si bonds, which exhibit good CMP performance, their low activity results in a low removal rate. To address this issue, a two-step ultrasonic dispersion method was employed to prepare a uniform nuclear@shell CeO2@ZIF-8. The process of chemical bond generation in CMP was studied using spherical aberration-corrected transmission electron microscopy and X-ray photoelectron spectroscopy. In comparison to pure cerium oxide, the formation of Ce–O–Si bond was observed, and notably, the emergence of N–Si bond originating from the N of the ZIF-8 shell was identified. Coupled with the increased Ce3+ content, these developments enhanced CMP performance. The material removal rate (MRR) of the CeO2@ZIF-8 abrasives was 151.507 nm/min, which is 89.72 % higher than that of the pure CeO2 abrasives. Moreover, the surface roughness, as determined via AFM testing, was reduced to 0.231 nm within the confines of a 5.0 × 5.0 μm² region. Therefore, this study introduces a novel concept for CMP research by developing a CeO2@ZIF-8 compound abrasive to create a new N–Si bond.

Fabrication of CeO2/CaO nanocomposite as ultraviolet screening agent and its application in sunscreen

In order to improve CeO2 ultraviolet absorption performance and transparency, this paper puts forward that different proportions of calcium oxide are doped during the formation of CeO2. Doping calcium ions with larger ion size and lower valence leads to the formation of oxygen defects by inhibiting the precipitation of oxygen from cerium oxide and keeps the fluorite structure of cerium oxide stable. The effects of CaO doping on the crystal structure, morphology, and optical characteristics of CeO2 were analyzed by XRD, SEM, TEM, TGA, XPS, UV–vis spectrophotometry. The pH of sunscreen, spread ability and some physical as well as chemical evaluations were carried out, while to study its UV protection performance the sunscreen SPF test was performed. The UV–vis results revealed that CeO2/20%CaO showed highly efficient UV absorption capacity. After adding calcium oxide, the catalytic activity of the material is reduced, due to which the generation of free radicals is demoted, and the harm to human body is decreased. After the addition of 3 wt% nanomaterials into sunscreen, the sun protection factor（SPF ）values of pure cerium oxide and CeO2/20%CaO are 1.95 and 2.81, and their sun protection coefficient is increased by 69.39%. Therefore, it is an ideal candidate as a component of ultraviolet screening agent in sunscreens and provides a new idea for the research direction of cerium oxide in anti-ultraviolet applications.

Cerium oxide nanoparticles: Chemical properties, biological effects and potential therapeutic opportunities (Review).

The chemistry of pure cerium oxide (CeO2-x) nanoparticles has been widely studied since the 1970s, especially for chemical catalysis. CeO2-x nanoparticles have been included in an important class of industrial metal oxide nanoparticles and have been attributed a range of wide applications, such as ultraviolet absorbers, gas sensors, polishing agents, cosmetics, consumer products, high-tech devices and fuel cell conductors. Despite these early applications in the field of chemistry, the biological effects of CeO2-x nanoparticles were only explored in the 2000s. Since then, CeO2-x nanoparticles have gained a spot in research related to various diseases, especially the ones in which oxidative stress plays a part. Due to an innate oxidation state variation on their surface, CeO2-x nanoparticles have exhibited redox activities in diseases, such as cancer, acting either as an oxidizing agent, or as an antioxidant. In biological models, CeO2-x nanoparticles have been shown to modulate cancer cell viability and, more recently, cell death pathways. However, a deeper understanding on how the chemical structure of CeO2-x nanoparticles (including nanoparticle size, shape, suspension, agglomeration in the medium used, pH of the medium, type of synthesis and crystallite size) influences the cellular effects observed remains to be elucidated. In the present review, the chemistry of CeO2-x nanoparticles and their impact on biological models and modulation of cell signalling, particularly focusing on oxidative and cell death pathways, were investigated. The deeper understanding of the chemical activity of CeO2-x nanoparticles may provide the rationale for further biomedical applications towards disease treatment and drug delivery purposes.

Samarium doped cerium oxide nanoparticles under extreme temperatures and its photocatalysis activity on tetracycline

In this work, we report the characterization and application of cerium oxide (CeO2) doped with samarium (Sm). The physical and chemical properties of these Sm-CeO2 are discussed in comparison with their pure cerium oxide counterparts. Raman spectroscopy measurements under extreme temperature conditions showed that the vibrational optical modes at 267 cm−1, 458 cm−1, 555 cm−1 and 603 cm−1, except for the mode 555 cm−1, exhibited a red shift with increasing temperature with different temperature coefficients θ = ∂ω/∂T. The first-order temperature coefficient θ of the mode 458 cm−1 is ∼ (−0.01154 ± 4.4 × 10−4 cm−1/K). In contrast, the second-order mode coefficient at ∼267 cm−1 which equal ∼ (−0.04949 ± 2 × 10−3 cm−1/K) is higher, as well as that of modes 555 cm−1 and 603 cm−1 which are equivalent to ∼ (−0.01339 ± 2.6 × 10−3 cm−1/K) and (−0.00575 ± 1.89 × 10−3 cm−1/K). If based on the evolution of the analyzed Raman spectra that no structural phase transition of the crystal was observed for high and low temperatures, only a conformational change at temperatures of 553 and 733 K, which may be associated with the formation of oxygen vacancies in the lattice of Sm-CeO2. We also show the efficiency of the Sm-CeO2 sample for applications in Photocatalysis demonstrated through the removal of the Tetracycline (TC) drug in comparison with the pure CeO2 sample. The photocatalytic experiments showed a significant increase in TC removal efficiency in a remarkable synergistic effect between adsorption and photocatalysis, leading to approximately 83 % TC removal for Sm-CeO2.

Europium-doped cerium oxide nanoparticles: investigating oxygen vacancies and their role in enhanced photocatalytic and magnetic properties.

In this study, pure and europium-doped (2%, 4%, 6%, and 8%) cerium oxide (CeO2) nanoparticles (NPs) were employed for efficient dye removal through photocatalytic approach. XRD and TEM confirmed the formation of pure CeO2 nanoparticles, while XPS and Raman spectroscopy were used to analyze the electronic properties and lattice defects, such as oxygen vacancies. The presence of lattice defects, which increased with the concentration of Eu, was found to be responsible for the enhanced degradation of Rose Bengal dye (82.4% for 8% Eu-doped sample) in 75min. FTIR confirmed the chemical composition of the synthesized sample. The band at 617cm-1, corresponding to the symmetrical stretching vibration mode of (Ce-O-Ce) or (Ce-O-Eu). The magnetic properties of synthesized samples were examined using VSM, revealing an increase from 4.48 to 11.0emu/g in magnetization. This enhancement was attributed to F-center exchange mechanism (FCE), resulting from the presence of oxygen vacancies. These findings contribute to the development of advanced materials for sustainable wastewater treatment and spintronics.

Facile catalytic construction of one-pot two-component 1,3,4-oxadiazole derivatives over Zn promoted Cu/CeO3 catalysts in semi-aqueous condition

Novel Zn promoted Cu/CeO3 catalysts was investigated to the green 1,3,4-oxadiazole synthesis via two component condensation of 2-aminobenzhydrazide and aldehydes in semi-aqueous environment. FT-IR, XRD, SEM, Raman, XPS, and BET have been used to examine catalyst through structural investigation. To determine the catalyst's use, some 1, 3,4-Oxadizole compounds were produced with varied catalyst concentrations in semi-aqueous circumstances. It was thoroughly investigated how pure Cerium oxide, Zinc nitrate and Copper nitrate affect the yield and reaction time of 1, 3,4-Oxadizole derivatives. The model compound under optimized condition afforded maximum yield (96%) in just 45 min. The goal of current research is to create a cheap, reusable catalyst that can be easily handled, produces a lot of products, and reacts quickly. The produced organic molecules were further examined using FT-IR and NMR techniques to identify the synthesized compounds. Furthermore, the novel catalyst can be characterized using several analytical techniques for both the fresh and recycled ones, demonstrating that there is no activity or stability loss during four reaction cycles.

New perspective of ceria nanodots for precise tumor therapy via oxidative stress pathway

Ceria-based nanomaterials have aroused major attentions among the biomedical application research field in recent years. Most of the researches have mainly focused on promoting the functional healing therapies of normal cells/organs with cerium oxide compounds, while the applications of ceria-based materials employed on cancer curing processes have been merely mentioned. To explore the possible capabilities of cerium oxide nanomaterials exterminating tumor cells, innovatively, we synthesized the eco-friendly pure cerium oxide nanodots (CNDs), proving the prominent ability of CNDs used in tumor chemotherapy (CDT) via Fenton reaction with the highly presence of H2O2 (acidic pH) in tumor tissues. CNDs reacted with the self-produced H2O2 of tumor cells, which generated piled up toxic hydroxyl radical (·OH). The accumulated virulent ·OH restrained the growth of cancer cells intensively. This peroxidase-like activity, provided a distinguished paradigm for effective cancer curing treatment. We also verified the biosafety of CNDs applied on normal cells. Notably, not only did CNDs be harmless to normal cells, but also it protected them from the damages of reactive oxygen species (ROS). In normal cells/tissues, under the microenvironment of neutral pH and low level of H2O2, the CNDs could effectively function as an annihilator inhibiting ROS. They reduced the damages caused by ROS, exhibiting catalase-like activity. The research we studied, which estimated CNDs thoroughly, has provided a new perspective to the future researches of the cerium oxide biomaterial applications.

Cerium Oxide Nanoparticles with Entrapped Gadolinium for High T 1 Relaxivity and ROS-Scavenging Purposes.

Gadolinium chelates are employed worldwide today as clinical contrast agents for magnetic resonance imaging. Until now, the commonly used linear contrast agents based on the rare-earth element gadolinium have been considered safe and well-tolerated. Recently, concerns regarding this type of contrast agent have been reported, which is why there is an urgent need to develop the next generation of stable contrast agents with enhanced spin–lattice relaxation, as measured by improved T1 relaxivity at lower doses. Here, we show that by the integration of gadolinium ions in cerium oxide nanoparticles, a stable crystalline 5 nm sized nanoparticulate system with a homogeneous gadolinium ion distribution is obtained. These cerium oxide nanoparticles with entrapped gadolinium deliver strong T1 relaxivity per gadolinium ion (T1 relaxivity, r1 = 12.0 mM–1 s–1) with the potential to act as scavengers of reactive oxygen species (ROS). The presence of Ce3+ sites and oxygen vacancies at the surface plays a critical role in providing the antioxidant properties. The characterization of radial distribution of Ce3+ and Ce4+ oxidation states indicated a higher concentration of Ce3+ at the nanoparticle surfaces. Additionally, we investigated the ROS-scavenging capabilities of pure gadolinium-containing cerium oxide nanoparticles by bioluminescent imaging in vivo, where inhibitory effects on ROS activity are shown.

Design and fabrication of carbon spheres-supported cerium oxide heterostructured composites for enhanced photocatalytic activity

The effective separation of photogenerated electron-hole (e−/h+) pairs play a key role in photocatalytic processes. Herein, the carbon spheres (CS) supported pure or Y-doped cerium oxide (CeO2) heterostructured photocatalysts were designed and fabricated via a facile and green chemical approach, aiming to improve the photocatalytic performances of CeO2 materials. The physiochemical properties of the CS/CeO2 and CS/Ce0.9Y0.1O2-δ products were characterized via X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, Raman spectroscopy, and Flourier-transform infrared spectroscopy. The photocatalytic performances were evaluated by the photodegradation of methylene blue dyes under ultraviolet and visible light irradiations. Compared to commercial CeO2 nanoparticles, the CS-coupled CeO2 heterostructured photocatalysts presented significantly enhanced photooxidation activities over MB. Under visible-light irradiation, the CS/Ce0.9Y0.1O2-δ photocatalysts achieved the most outstanding photodegradation efficiency of 99.9% with a high rate constant of 6.25 × 10−2/min. In addition, the developed CS/CeO2 photocatalysts were highly recyclable and did not show significant loss in photoactivity. The improved photocatalytic activity was attributed to the binary heterojunction formation created by the combination of CS and CeO2, the efficient interfacial separation of photogenerated e−/h+ charges, and the enriched tervalent cerium and oxygen vacancy induced by the Y3+ incorporated in CeO2. The possible photocatalytic mechanism toward MB dyes of the proposed CS-coupled CeO2 was also discussed. The developed photocatalysts are expected to be a promising material system in photochemical applications.

Influence of the concentration of capping agent on synthesizing and analyses of Ceria nano‐filler using modified co‐precipitation technique

AbstractThe pure crystalline cerium oxide (CeO2) nanoparticles were synthesized using optimized content of Ce(NO3)3. 6H2O with varying concentrations of sodium hydroxide (NaOH) (0.5, 1, 1.5, and 2 M) as a precipitation agent in presence of 2.5 wt% poly(vinylpyrrolidone) PVP. All the samples are prepared via the modified coprecipitation technique. The synthesized materials have been analyzed using X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR), laser Raman, high‐resolution scanning electron microscope (HR‐SEM), and photo luminescence (PL) analyses. The optimized sample was identified with the help of the above studies that could be analyzed through transverse electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS) studies. The cubic structure with the Fm‐3 m space group has been confirmed through XRD (JCPDS: 81‐0792) and Raman analyses. The FT‐IR and energy dispersive X‐ray spectroscopy (EDX) analyses ascertain the occurrence of Ce and O species. The as‐prepared CeO2 filler (0, 3, 6, 9, and 12 wt%) is dispersed through the optimized polymer electrolyte Poly (styrene‐co‐methyl methacrylate) P(S‐MMA) (27 wt%)–lithium perchloride (LiClO4) (8 wt%)–ethylene carbonate + propylene carbonate (EC + PC) (1;1 of 65 wt%) complex system using solution casting technique. P(S‐MMA) (27 wt%)–LiClO4 (8 wt%)–EC + PC (1;1 of 65 wt%)–6 wt% of CeO2 shows the high ionic conductivity 8.13 × 10−4 S cm−1.

Cerium oxide (CeO2-x) nanoparticles with high Ce3+ proportion synthesized by pulsed plasma in liquid

Cerium oxide (CeO2-x) nanoparticles were synthesized using a simple one-step method known as the pulsed plasma in liquid (PPL). XRD analysis showed the production of pure cubic cerium oxide (Fm 3‾ m). HRTEM and XANES analysis confirmed the monophase cubic CeO2-x, and exclude the presence of the hexagonal Ce2O3 and/or mix phase of CeO2/Ce2O3 in the particle layers. HRTEM analysis showed that most particles were about 3 nm in diameter. XPS analysis showed that the cerium oxide nanoparticles synthesized by the PPL method had a higher Ce3+ proportion (42.2%) than some commercial powders, and also higher than the previous reported nanoparticles. The present cerium oxide nanoparticles showed high visible light-induced photocatalytic activity in the degradation of methyl orange (MO) and better polishing characteristics of quartz glass, compared to commercial samples. These results may attribute to the high Ce3+-ion content and/or the small particle size.

Infinite dilution in doped ceria and high activation energies

Oxygen ion diffusion determines the performance of materials in energy conversion, energy storage and catalysis. For nominally pure cerium oxide, experiments measure high activation enthalpies while calculations predict low activation enthalpies. Moreover, for doped oxides, e.g. doped ceria, experiments show a high activation enthalpy for both pure ceria and for high dopant fractions, leading to a minimum in activation enthalpy for small dopant fractions. While for high dopant fractions the increase in activation enthalpy is correlated with the association of oxygen vacancies and dopant ions, which are both created by doping, the minimum in activation enthalpy is assumed in the literature to be related to the maximum in ionic conductivity at similar dopant fractions. In this study, density functional theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations are combined in order to calculate the ionic conductivity and activation enthalpy in doped oxides. We show that the experimental ionic conductivity and activation energy in nominally pure cerium oxide is dominated by impurities. We resolve the discrepancy between activation enthalpies of nominally pure oxides in experiments as opposed to calculations. This will lead to a more comprehensive understanding of the oxygen ion conductivity and its underlying atomistic mechanisms. Moreover, such a focus will be of great benefit to the future development of sustainable and efficient materials.

The ionic conductivity of Sm‐doped ceria

AbstractThe oxygen ion conductivity of polycrystalline samples of Sm‐doped ceria and of Gd‐doped ceria is studied as a function of doping fraction and temperature using impedance spectroscopy allowing the separation of bulk and grain boundary conductivity. The introduction of a fine spacing for the Sm dopant fraction allows the clear identification of the dopant fraction leading to the largest bulk conductivity. At 267°C, the largest bulk conductivity is shown for Ce0.93Sm0.07O1.965. With increasing temperature, indications of an increase in the dopant fraction, which leads to the maximum in conductivity, are found. For the grain boundary conductivity, the maximum appears at larger dopant fractions compared to the bulk conductivity. The largest total conductivity for both dopants is again found for Sm‐doped ceria. In literature, different syntheses and sample preparation methods led to larger total conductivities for Gd‐doped ceria. In this work, we demonstrate that the variation of sintering conditions leads to scattering in the conductivity over one order of magnitude. Finally, we demonstrate that, in nominally pure cerium oxide, impurities dominate the ionic conductivity.

Synthesis and characterization of pure and Cu doped CeO2 nanoparticles: photocatalytic and antibacterial activities evaluation

This article reports the effect of pure CeO2 and Cu (1%, 3% and 5 mol %) doped CeO2 Nanoparticles (NPs) have been prepared by very simple and improved co-precipitation method. Synthesized NPs has been subjected to several analytical methods, viz. XRD, TEM and UV-Vis spectral analysis. XRD data analysis confirmed that face cubic structure and average size are found to be in the range 5-10nm. Particle size and morphological studies as observed from TEM exhibits almost identical cubical shaped particles with average size 5-8nm. The tuning of band gap energy has been observed from UV-Visible absorption spectrum of cerium oxide NPs upon Cu (1%, 3%, and 5mol %) incorporation. Degradation of the methylene blue (MB) through photocatalysis has been observed for pure and Cu (1%, 3% and 5 mol%) CeO2 nanoparticles under solar spectrum. In addition, pure and Cu (1%, 3% and 5 mol %) cerium oxide nanoparticles has also been subjected to antibacterial response using different strains.

Effect of copper substitution on structural, optical and humidity-sensing characteristics of cerium oxide nanoparticles

Cerium (pure) and copper-substituted cerium oxide nanoparticles were synthesized by microwave oven method. Powder X-ray diffraction showed that particle size was reduced with increases in copper content, termed the “particle size effect”. Scanning electron microscopy and transmission electron microscopy (TEM) images showed that particle formation was spherical. Miniature sizes of nanoparticles were in the range ~4–10 nm and were identified from typical TEM microstructures. Absorption peaks were reduced as result of copper content and binding energy was also reduced, which decreased the particle size. The particle size effect produced significant changes in humidity sensing, copper-substituted cerium oxide nanoparticles had better humidity-sensing behavior than pure cerium oxide. Reproducibility of the sensor produced notable sensing characteristics.

Synthesis and Characterization of Pure and Gd-Doped CeO2 Nanoparticles

CeO₂ and Gd-doped CeO₂ nanoparticles were synthesized by microwave-assisted method. The structural properties of cerium oxide were analyzed by XRD. The XRD pattern confirmed the cubic structure of cerium oxide. The morphology and size of the CeO₂ and Gd-doped CeO₂ nanoparticles were analyzed by SEM and TEM analysis. From the SEM and TEM images it was confirmed that the pure cerium oxide exhibited the spherical morphology whereas Gd-doped CeO₂ shows rod like morphology as it was confirmed by SEM and TEM images. Raman spectra confirm the F2g mode of vibration of cerium oxide and it was slightly shifted in the Gd-doped cerium oxide sample due to incorporation of Gd.<div><br></div>

A mechanical and modelling study of magnetron sputtered cerium-titanium oxide film coatings on Si (100)

Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce2O3 and rutile form of TiO2 with SiO2 present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1 GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000 °C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti = 68%:32% has a new additional minor oxide phase above 800 °C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7–95.7° contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration.

Effect of Epoxy/Al2O3/CeO2 Coating on Corrosion Rate and Mechanical Properties of Mild Steel

In any industry like a power station, corrosion is a natural process that commonly happens and one of the problems that need to be considered. The example is in the underground pipeline where sea water is transported for cooling purposes. This study mainly on corrosion rate and mechanical properties of coating material on mild steel. Theoretically, Metal can get the higher rate of corrosion when exposed to the surrounding environment. Corrosion can cause to a lot of unwanted conditions, including failures in functions and higher maintenance cost as well as it is too risky for safety. The objective of this project is to study the corrosion rate and mechanical properties of the coating material of pure epoxy, aluminum oxide (Al2O3) and cerium oxide (CeO2) on mild steel. Different composition of epoxy/ Al2O3/CeO2 coating tested on mild steel specimen. There is three experimental conduct which is a Gamry test for corrosion rate and impact and hardness test for mechanical tests. As a conclusion, the results from the tests show that the coated mild steel of Al2O3-CeO2-epoxy obtained the best value in term of corrosion resistance and mechanical properties.