Prepared Cerium Oxide Research Articles

Evaluation of phytoactive contents and antibacterial activities of green synthesised cerium oxide nanoparticles using Melastoma sp. leaf extract as the capping agent

Simple and green methods of developing nanoparticles (NPs) have attracted the attention of researchers. Literature on utilising leaf extract to prepare cerium oxide (CeO2 NPs) is scarce. The present study synthesised leaf-mediated-CeO2 NPs to produce nanopowders of controllable sizes for further applications. The study is the first to report the optimised parameters (pH 7, 5 g/150 mL concentration of the leaf extract, and 3 h of reaction time) of procuring CeO2 NPs using Melastoma sp. leaf extract as the capping agent with excellent properties. The absorbance of the NPs suspension obtained in this study was recorded at approximately 252 nm with Ultraviolet–Visible (UV–Vis) Spectroscopy. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) were also utilised to characterise and confirm the CeO2 NPs prepared. The XRD spectra documented the purity of the NPs at specific diffraction patterns, while TEM revealed the spherical form of the NPs with a particle size of 16 nm. The formation of CeO2 NPs has been confirmed from the FTIR spectra procured, which exhibited a Ce–O peak at 555 nm. Phytochemical screening test and FT-IR analysis of leaf extract revealed the existence of flavonoids, terpenoids, sugars, saponins, quinones, and glycosides. The NPs suspensions of varying concentrations (control, 50, 100, 150, 200, and 250 μg/mL) were prepared and employed for evaluations against Gram-positive and -negative bacteria. Resultantly, CeO2 NPs demonstrated antibacterial activities against both bacteria types. The highest antibacterial activities were recorded against E. coli and K. pneumonia at 1.83 ± 0.137 and 1.83 ± 0.14 mm maximum inhibition zones, respectively, at 250 mg/uL of the NPs.

α-Glucosidase Inhibitory Activity and Cytotoxicity of CeO2 Nanoparticles Fabricated Using a Mixture of Different Cerium Precursors.

A mixture of three distinct cerium precursors (Ce(NO3)3·6H2O, CeCl3·7H2O, and Ce(CH3COO)3·H2O) was used to prepare cerium oxide nanoparticles (CeO2 NPs) in a polyol-mediated synthesis. Different ratios of diethylene glycol (DEG) and H2O were utilized in the synthesis. The properties of the synthesized CeO2 NPs, such as structural and morphological properties, were investigated to observe the effect of the mixed cerium precursors. Crystallite sizes of 7-8 nm were obtained for all samples, and all synthesized samples were confirmed to be in the cubic phase. The average particle sizes of the spherical CeO2 were between 9 and 13 nm. The successful synthesis of CeO2 can also be confirmed via the vibrational band of Ce-O from the FTIR. Antidiabetic properties of the synthesized CeO2 NPs were investigated using α-glucosidase enzyme inhibition assay, and the concentration of the synthesized CeO2 NPs was varied in the study. The biocompatibility properties of the synthesized CeO2 NPs were investigated via cytotoxicity tests, and it was found that all synthesized materials showed no cytotoxic properties at lower concentrations (62.5-125 μg/mL).

From Ce(OH)3 to Nanoscaled CeO2: Identification and Crystal Structure of a Cerium Oxyhydroxide Intermediate Phase

Cerium oxide is a pivotal compound in catalysis, both as a support and as an active phase. However, its fine features, such as the Ce(III) to Ce(IV) ratio, strongly depend on the protocol used to prepare it. While the literature contains tens of protocols to prepare cerium oxide nanoparticles from Ce(III) precursors, there is still an open question regarding the time at which the cerium oxidation occurs and the role of hydroxide phases in this process. This article identifies an oxyhydroxide phase of Ce(IV) as a key intermediate and proposes a crystal structure for it. For this purpose, phase-pure cerium trihydroxide (Ce(OH)3) nanorods (<20 nm) were first prepared by hydrothermal treatment of a cerium nitrate salt (Ce(NO3)3·6H2O) in the presence of KOH. Aging of this phase in air was monitored by X-ray absorption spectroscopy, which confirmed the formation of an intermediate Ce(IV) crystalline compound, unreferenced so far. Based on X-ray and neutron powder diffraction experiments combined with DFT calculations, we propose that this new phase is a cerium oxyhydroxide of the chemical formula CeO(OH)2, for which a structural model is proposed. Thermodiffraction experiments finally established that this compound is an observable intermediate in the synthesis of cerium dioxide CeO2 by calcination of Ce(OH)3 in air.

Effect of heat treatment on structural properties of CeO2 prepared by chemical-route method

The chemical-route auto combustion method was used to prepare Cerium oxide (CeO2) powder for different applications in the electronic and automobile sector. These experiments were carried out on two different cases, before and after calcination at 900 °C. The calcination process involves heating the samples to high temperatures to remove the impurities; we examined the different structural and morphological analyses to see whether the effect of heat treatment with the given temperature affected the sample. The structural analysis of the product material was performed using X-ray diffraction (XRD), scanning electron microscope (SEM), which provided morphological details, and the compositional analysis was confirmed using Energy Dispersive Spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR), which was used to determine the different functional groups present in the product material. Based on the XRD spectra, prepared CeO2 powder showed crystalline with cubic structure. The rise in crystalline size with respect to an increase in calcinated temperature was supported by the consistency between theoretical and experimental findings, SEM pictures show that the shape of the particles changes to a sphere-like structure with less aggregated as the temperature rises. The Ce-O stretching mode of CeO2 was demonstrated using FTIR data. the thermal treatment lowered the carbon s atomic fraction as anticipated, as seen by the EDS spectra of the annealed CeO2 samples.

Degradation of parathion methyl by reactive sorption on the cerium oxide surface: The effect of solvent on the degradation efficiency

A simple and easily scalable “wet” procedure was used to prepare nanocrystalline cerium oxide capable of destroying the toxic organophosphate pesticide parathion methyl. The synthetic procedure consists of the direct precipitation of cerous salt with aqueous ammonia in the absence of CO 2 . The prepared cerium oxide was able to decompose the organophosphate compounds both in nonpolar (e.g., heptane) and polar aprotic (e.g., acetonitrile) solvents. However, in solvents with hydrogen-bond donating ability, the –OH groups on the cerium oxide surface were solvated and inactivated. The preferential solvation model was used to express the experimental dependencies of the cerium oxide degradation efficiency on the composition of the water-acetonitrile mixture. In certain solvent systems, some empirical polarity scales, such as the alpha-scale or the Dimrodth-Richardt parameter E T (30), may be correlated with the degradation efficiency of cerium oxide.

Crystal Sizes and Energy Gaps of Cerium Oxide Using Co-Precipitation Method

Co-precipitation was used to prepare cerium oxide nano-particles. The effects of aging temperature and concentration of cobalt ion on the optical property, morphology, and particle size were investigated. The cerium oxide was prepared by adding ammonia solution into a mixed solution of cerium nitrate with cobalt nitrate solutions to obtain a large amount of precipitates and then aged further. Subsequently, the precipitates were kept in an oven for calcination keeping the temperature at 400?C for lasting 24 h. The average size of cerium oxide particles was obtained from the (111) peak in the X-ray diffraction pattern using the Scherrer equation. The crystal sizes obtained were found to be in the range of 11.82 - 13.47 nm. The results showed that the particle size decreased with an increase in the Co ion concentration and decreased with an increase in temperature. The SEM pictures show that the morphology for cerium oxide is granular and/or columnar. It can be seen from UV/Vis absorption spectrum that the maximum absorption peaks were in the range of 334 - 390 nm, depending on the operating conditions. The corresponding energy gaps were observed in the range of 3.18 - 3.71 eV. Subsequently, the Brus equation for the energy gap was discussed. Finally, particle size was correlated with the aging temperature and Co ion concentration.

Hybrid of cerium dioxide nanoparticles/reduced graphene oxide as an electrode material for supercapacitor applications

In this study, we prepared cerium oxide (CeO2) hybridized with reduced graphene oxide (rGO) nanosheets using the hydrothermal method. CeO2 and CeO2/rGO were evaluated as electrode materials for use in supercapacitor applications. The structure and morphology of the synthesized materials were investigated. Cyclic voltammetry tests determined a high specific capacitance of 581 F g−1 for CeO2/rGO at a scan rate of 10 mV s−1 in 2 M KOH. In addition, the CeO2/rGO electrode retained 91 % of its initial capacitance after 5000 consecutive cycles, thereby indicating its excellent electrochemical stability. The excellent stability of CeO2/rGO was due to a synergistic effect between CeO2 and rGO. CeO2 nanoparticles decorated on rGO facilitated the migration of electrolyte ions and provided electroactive sites for the faradic process. The rGO nanosheets increased the conductivity of the composite and enhanced its electrochemical stability.

Antibacterial and cytotoxic activities of cerium oxide nanoparticles prepared by laser ablation in liquid.

In this work, we have prepared cerium oxide (CeO2) nanoparticles (NPs) by laser ablation in water at different laser energies. The structural and optical properties of synthesized nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy, energy dispersive X-ray (EDX), and UV-Vis absorption. XRD results confirmed that the synthesized cerium oxide NPs were crystalline in nature with cubic structure. SEM investigations show that the nanoparticles having a spherical shape with diameter ranged from 26 to 37nm depending on the laser energy. The antibacterial activity and minimal inhibition concentration of synthesized CeO2 NPs against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa were examined. Bacterial adhesion test of cerium oxide NPs was also determined under different incubation temperatures. Cytotoxicity of CeO2 NP effect against the human throat cancer was studied. The cytotoxicity effect of CeO2 NPs synthesized at 160mJ on the cancer cells caused a free radical releasing which causing oxidative stress. The cytotoxicity effects of ceria NPs against human throat cancer (RD rhabdomyosarcoma cell line) and mouse fibroblast L cell (L20B cell line) growth were 33% and 13%, respectively.

Fluorescent and visual detection of methyl-paraoxon by using boron-and nitrogen-doped carbon dots

Methyl-paraoxon (MP) is a representative organophosphorus pesticide (OP), which is a huge threat to the safety of human beings. In this study, carbon dots doped with boron and nitrogen (B, N–CDs) were used as a fluorescent probe for MP detection. The prepared cerium oxide (CeO2) decompose MP efficiently into p-nitrophenol (p-NP) and phosphate group in the alkaline condition. The dissociative p-NP could reduce the fluorescent intensity of B, N–CDs through the inner filter effect (IFE). The pH value, incubation time, the amount of B, N–CDs and solvent effect were investigated and optimized for detection system. Under the optimum conditions, the limit of the detection was calculated to be 24.7 ng mL−1 with simple procedures. Tap water, lake water, Semen Coicis and Panax quinquefolius L. samples were used to test the recoveries of the detection system. The recoveries ranged from 94.68% to 107.28%. Furthermore, the fluorescence laminate was developed by painting B, N–CDs on the polyamide laminate. The MP residue could be observed directly under the 365 nm lamp, and linearity for MP by using the fluorescent laminates was ranged from 0.015 to 1.5 mM. The present work provides a rapid and dual-signal based method (fluorescent and visual) for routine detection of MP in real samples.

Effect of firing temperature on structural and electrical parameters of synthesized CeO2 thick films

In this work, the Ceria (CeO2) was synthesized by co-precipitation method. The thick films of synthesized CeO2 were prepared by screen printing technique. Films were fired at 350 °C, 400 °C, 450 °C for 2 h in muffle furnace. These films were characterized by XRD to investigate the structural properties of prepared material. The XRD confirmed the single phase cerium oxide nanoparticles. Scanning electron microscopy was utilized for the morphological parameters of prepared cerium oxide nanoparticles. The cubic shaped cerium nanoparticles with various diameters were observed from SEM images. The elemental composition of ceria was studied by EDS, where the perfect elemental composition of ceria was confirmed. The Fourier transform infra red spectroscopy was employed to find out metal- oxide vibrational bands in the cerium oxide nanoparticles. The effect of firing temperature was studied for cerium oxide calcined at 350 °C, 400 °C and 450 °C nanoparticles to study the various parameters such as Grain Size, Temperature Coefficient (TC), Stacking Fault Probability (α), Dislocation Density (ρ), Surface area, Activation Energy and RMS Microstrain (e).

Formation of cerium oxide hollow spheres and investigation of hollowing mechanism

Hollow structure materials have found important applications in many fields such as catalysis, energy storage and sensors. A facile and environmentally benign synthesis will favor their applications. Here we prepare a cerium oxide hollow structure with the size of micrometers through a simple one-step hydrothermal method. This process results in the formation of microspheres at 210 °C for only 2 h. Advantages of this method include no template, without surfactant-assistance or subsequent treatment during the synthesizing process. Explanation on the controlled crystal growth and hollowing mechanism via Ostwald Ripening is proposed elaborately based on the detailed experiment and observation. The FESEM images showed that the surface morphology of the sphere shell turned from initially smoothness into roughness with the increase of reaction time, relating to dissolution and re-deposition of nanoparticles onto inner and outside of the shell. The hollowing microstructure evolvement was vividly presented by observing samples taken out at different reaction stages, which makes visualization of Oswald ripening process. The prepared Cerium oxide microspheres were used to modify glassy carbon electrode, which acts as a sensor for sensitive determination of environmental hormone catechol (CC), demonstrating superior performance over the solid oxide. This work helps to deeply understand Ostwald ripening from a new perspective.

Role of pH on synthesis and characterization of cerium oxide (CeO2) nano particles by modified co-precipitation method

A facile synthesis has been made to prepare cerium oxide (CeO2) nano particles via modified co-precipitation method using different pH values viz, 9 to 12 in steps of 1. The as prepared powders have been systematically studied to analyze their structure, morphology and photoluminescence properties. The representative samples have been analyzed through TEM and XPS analyses. The crystallite size has been decreased upon increasing the pH of the environment. When pH of the solute reached 12, the particle size is reached to 27 nm, which is ascertained through TEM analysis.

Novel anti fouling mixed matrix CeO2/Ce7O12 nanofiltration membranes for heavy metal uptake

Nanofilraion membranes (NF) were fabricated by an incorporation of CeO2/Ce7O12 nanoparticles with various loads via phase inversion method. The prepared cerium oxide nanoparticles and fabricated mixed matrix membranes were recognized by using x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, surface charge studies and contact angle. The performances of the fabricated membranes were carried out using 100 mg/L/each aqueous solutions of Fe(NO3)3, Al2(SO4)3, Co(NO3)2, Cd(NO3)2, Cu(NO3)2. The antifouling properties of the mixed matrix membranes were studied using 300 mg/L humic acid as foulant. The morphologies of the fabricated membranes have been affected by the presence of CeO2/Ce7O12 nanoparticles, as fillers, in the casting solution. Since, the four mixed matrix fabricated membranes of different nanoparticles loads have different skin porosities and macro-void structures. The mixed matrix NF membrane of 1 wt% had the lowest irreversible fouling ratio (1.1%) and high antifouling potential with highest flux recovery after humic acid filtration with less change in the rejection. The absence of the used nanoparticales in treated water as well as non toxic properties indicates that the fabricated membranes are safe to be used for filtration.

Advanced treatment of sodium dithionite wastewater using the combination of coagulation, catalytic ozonation, and SBR

ABSTRACTA combined process of coagulation–catalytic ozonation–anaerobic sequencing batch reactor (ASBR)–SBR was developed at lab scale for treating a real sodium dithionite wastewater with an initial chemical oxygen demand (COD) of 21,760–22,450 mg/L. Catalytic ozonation with the prepared cerium oxide (CeO2)/granular activated carbon catalyst significantly enhances wastewater biodegradability and reduces wastewater microtoxicity. The results show that, under the optimum conditions, the removal efficiencies of COD and suspended solids are averagely 99.3% and 95.6%, respectively, and the quality of final effluent can meet the national discharge standard of China. The coagulation and ASBR processes remove a considerable proportion of organic matter, while the SBR plays an important role in post-polish of final effluent. The ecotoxicity of the wastewater is greatly reduced after undergoing the hybrid treatment. This work demonstrates that the hybrid system has the potential to be applied for the advanced treatment of high-strength industrial wastewater.

Synthesis effects on activity and stability of Pt-CeO2 catalysts for partial oxidation of methane

The objective of this study is to explore the effect of catalyst synthesis procedure on the activity of catalysts for partial oxidation of methane. In this aspect, Pt-nanoparticles supported CeO2 catalysts were prepared by Hydrothermal, co-precipitation, impregnation and by controlled deposition of platinum nanoparticles on hydrothermally prepared cerium oxide. Prepared catalysts were characterized by BET-surface area, X-ray diffraction, H2-Chemisorption, Transmission electron microscopy, Temperature programmed reduction, Inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. The study revealed that the catalyst preparation procedure plays a very crucial role on morphology, catalyst particle size, metal support interaction and activity of the catalysts. Catalytic activities were tested for partial oxidation of methane in the temperature range 350–800°C. The study revealed that the catalyst prepared by controlled deposition of Pt-nanoparticles on hydrothermally prepared cerium oxide showed better activity for partial oxidation of methane compared to the catalysts prepared by other conventional methods. Controlled deposition of Pt-nanoparticles generated better metal-support interaction compared to the catalysts prepared by conventional hydrothermal, co-precipitation and impregnation methods. All the catalysts showed excellent coke resisting ability but the deactivation of most of the catalyst was found to be caused by catalyst particles sintering and re-oxidation of the Pt particles during catalysis.

Structural, Optical, Morphological and Dielectric Properties of Cerium Oxide Nanoparticles

Cerium oxide (CeO2) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature.

Novel Synthesis of CeO2 Nanoparticles Within Formamide/Tri(ethyleneglycol)monododecyl Ether/n-Octane Nonaqueous Microemulsion Systems

The present study evaluates a new method to prepare Cerium oxide (CeO2) nanoparticles by formamide/tri(ethyleneglycol)monododecyl ether (C12E3)/n-octane oil-continuous nonaqueous microemulsion. The effect of the polar phase (formamide/water) on the phase behavior, drop size, and conductivity behavior of the reverse microemulsion were investigated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the phase and morphology of synthesized CeO2 nanoparticles. It was found that the CeO2 powders synthesized within nonaqueous microemulsions and aqueous microemulisons had an average particle size of 30–50 nm and 15–40 nm, respectively. The experimental results indicate the formation mechanism of CeO2 nanoparticles in formamide nonaqueous microemulsion and aqueous microemulsion is similar, and the formamide nonaqueous microemulsion can be used as nanoreactors for preparation of nanoparticles.

Effects of engineered cerium oxide nanoparticles on bacterial growth and viability.

Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear, due to a lack of standard methods for assessing such interactions. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. The growth and viability of the Gram-negative species Escherichia coli and Shewanella oneidensis, a metal-reducing bacterium, and the Gram-positive species Bacillus subtilis were examined relative to cerium oxide particle size, growth media, pH, and dosage. A hydrothermal synthesis approach was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined from MIC and CFU measurements, disk diffusion tests, and live/dead assays. For E. coli and B. subtilis, clear strain- and size-dependent inhibition was observed, whereas S. oneidensis appeared to be unaffected by the particles. Transmission electron microscopy along with microarray-based transcriptional profiling was used to understand the response mechanism of the bacteria. Use of multiple analytical approaches adds confidence to toxicity assessments, while the use of different bacterial systems highlights the potential wide-ranging effects of nanomaterial interactions in the environment.

An all chemical solution deposition approach for the growth of highly texturedCeO2 caplayers on La2Zr2O7-buffered long lengths of biaxially textured Ni–W substrates for YBCO-coatedconductors

A reel-to-reel, dip coating process has been developed to continuously deposit epitaxialLa2Zr2O7 (LZO)and CeO2 on 5 m long cube-textured {100} (001)Ni tapes. Recent results forLa2Zr2O7 and CeO2 buffer layers deposited on long lengths of Ni substrate for the realization ofYBa2Cu3O7−x (YBCO)-coated conductors are presented. The major achievement is thedevelopment of a new all chemical solution deposition (CSD) process leading to theformation of highly textured buffer layers at moderate annealing temperatures.Reproducible highly textured, dense and crack-free LZO buffer layers andCeO2 cap layers were obtained for annealing temperatures as low as900 °C in a reducingatmosphere (Ar–5 at.%-H2). The thickness of the LZO buffer layers was determined to be(200 ± 10) nm per single coating; prepared cerium oxide layers showed a thickness of60 nm ± 10 nm. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. ATc 0 ofT = 90.5 K andΔTc = 1.4 K was obtained onPLD-YBCO/CSD-CeO2 /CSD-LZO/Ni–5 at.% W, which shows the outstanding features of this new buffer layerarchitecture processed by CSD. The large layer thickness combined with lowannealing temperatures is the main advantage of this new process for low-cost bufferlayer deposition on Ni-RABiTS (rolling-assisted biaxially textured substrates).

H 2 reduction of CeO 2(111) surfaces via boundary RhO mediation

One of the unique features of cerium oxide is its ability to be reversibly converted into oxygen-deficient structures when it is exposed to a reducing atmosphere. Chemical processes on ceria surfaces serve as gateways in controlling such oxygen transfer. In this work, we have prepared cerium oxide films on which Rh is vapor-deposited and measured the Ce oxidation state following sequential exposure to oxygen and hydrogen. The difference between the fraction of Ce 4+ state of a ceria film resulting from room temperature O 2 exposure and the fraction following sequential H 2 exposure at 400 K was measured for various conditions. Our results show that to achieve an observable reduction by H 2 exposure, O 2 preexposure of the Rh-deposited ceria surface is needed. The H 2 reduction yield increases as the dose of Rh to CeO 2 surface increases. Although this reduction process is observed in as-grown Rh-deposited ceria films, ion sputtering of Rh-dosed ceria surfaces enhances the yield of H 2 reduction. The need of both Rh dose and oxygen preexposure for reduction of ceria by hydrogen suggests that oxygen removal from ceria films is catalyzed by RhO. A mechanism is proposed in which RhO in intimate contact with ceria transfers hydrogen to ceria lattice oxygen, followed by oxygen removal from the ceria surface through water desorption.