Ce Nitrate Research Articles

Fabrication of ultrafine cerium oxide nanoparticles as an aqueous colloidal solution with single-molecular dispersant via shear agitation reactor or one-pot hydrolysis

Herein, ultrafine CeO2 nanoparticles are synthesized using monomolecular amino acids as dispersants. Monomolecular amino acids are suitable dispersants for the dispersion of nanoparticles with a diameter of 1 nm. Batch-type room-temperature hydrolysis (RTH) synthetic method, which takes advantage of the low decomposition pH of Ce (IV) nitrate, and a shear agitation (SA) reactor, which is highly versatile for multicomponent systems of colloidal synthesis, are used. After adding glycine, ultrafine CeO2 colloids of sizes 1.1 and 1.2 nm are obtained via the batch-type RTH synthesis method and SA reactor, respectively. The smallest CeO2 colloid size is 0.7 nm, which earned at the close concentration of the saturation of glycine using the batch-type RTH method. Because RTH can slowly hydrolyze Ce (IV) nitrate over several hours, we were able to observe the initial stage of nucleation (0.7 nm), which passes instantaneously in the SA reactor. Furthermore, glycine was found to be particularly effective in stabilizing the surface of cerium oxide due to its high adsorption capacity. Therefore, cerium oxide, which is amorphous in the synthesis stage, remained amorphous up to 100 °C due to glycine adsorption, neutralized the colloidal dispersion to form precipitates, and crystallized at room temperature after glycine was removed by washing treatment, resulting in a fluorite structure with a crystallite diameter of 1.5 nm. This crystallite diameter is maintained after heat treatment at 200 °C for 30 min.

Simple Synchronous Dual-Modification Strategy with Zr4+ Doping and CeO2 Nanowelding to Stabilize Layered Ni-Rich Cathode Materials

A Ni-rich layered oxide, one promising cathode for lithium-ion batteries (LIBs), exhibits the advantages of low cost and high capacity but suffers from rapid capacity loss due to bulk structural instability and surface side reactions. Herein, a simple synchronous dual-modification strategy with Zr4+ doping and CeO2 nanowelding is proposed to address such issues. Utilizing the migration energy difference of Zr and Ce ions in layered structures, one-step high-temperature sintering of LiNi0.8Co0.1Mn0.1O2 particles with Zr and Ce nitrate distributions enables simultaneous doping of Zr ions in the bulk and CeO2 surface modification. Therein, Zr ions in the bulk occupying the Li sites can improve the Li+ diffusion rate and stabilize the crystal structure, while CeO2 on the surface provides nanowelding between the grain boundaries and resistance to electrolyte erosion. Theoretical calculations and a series of structure/composition characterizations (i.e., neutron scattering, in situ X-ray diffraction, etc.) validated the proposed strategy and its role in stabilizing the Ni-rich cathodes. The synergistic effect of Zr4+ doping and CeO2 nanowelding enables an impressive initial capacity of 187.2 mAh g–1 (2.7–4.3 V vs Li/Li+) with 86.1% retention after 200 cycles at 1 C and rate capabilities of 146.6 and 127.3 mAh g–1 at 5 and 10 C, respectively. Upon increasing the testing temperature to 60 °C, the dual-modified Ni-rich cathode exhibits an initial discharge capacity of 203.5 mAh g–1 with a good retention of 80.8% after 100 cycles at 0.5 C. The present strategy utilizing the migration energy difference of metal ions to achieve synchronous bulk doping and surface modification will offer fresh insights to stabilize layered cathode materials for LIBs, which can be widely used in other kinds of batteries with various cathode materials.

THE CERIUM OXIDE GENERATED RADICAL ELIMINATION PROPERTIES OF PEG-NANOCERIA

Reactive oxygen species (ROS) have been linked to cellular degeneration, irreversible DNA damage, and various diseases. Cerium oxide nanoparticles have shown promising medical applications for their SOD mimetic activity to catalyze the breakdown of various ROS. Increasing the biocompatibility, longevity of residence, and rate of internalization of nanoceria are essential to increase its range of biomedical applications. Polyethylene glycol’s (PEG) hydrophilic, nonimmunogenic, and antioxidative properties make it an ideal coating for increasing cerium nanoparticle’s applicability. Gelatin’s low cost and versatility have made it widely employed as an antioxidant drug carrier in a variety of physiological systems. Because of gelatin’s susceptibility to ROS denaturation and well-researched structure, it is a useful tool for assessing conformational damage in applications that involve acute oxidative stress. PEG-nanoceria of various molar weights was synthesized from Ce (III) nitrate and incorporated into gelatin hydrogels that were exposed to hydrogen peroxide to provide oxidative stress damage. This study aims to assess changes to gelatin conformation were assessed using Fourier transform infrared spectroscopy. PEGNanoceria showed radical damage mitigation in hydrogels as evident by the decreased change in transmittance over its nonPEG counterpart. There was notably exceptional damage mitigation in the amide A and amide II regions. These promising findings suggest more research should be done to examine polymer-coated nanoceria’s antioxidative properties in more biologically relevant models.

Analysis of the Ce(III) chloride, Ce(III) nitrate, and Ce(III) propionate as corrosion inhibitor of the aluminum alloys in NaCl solution

AbstractGreen corrosion inhibitors, Ce(III) chloride, Ce(III) nitrate, and Ce(III) propionate, were tested in NaCl solution with the aim to evaluate their inhibitory effect on 7049 aluminum alloy and to propose a mechanism of their inhibitive action. Corrosion properties of the formed inhibitor layer were analyzed using electrochemical impedance spectroscopy, while the pit formation resistance was analyzed using potentiodynamic polarization tests. Morphology of the formed pits was evaluated by scanning electron microscope/energy‐dispersive spectroscopy analysis. It was shown that Ce(III) propionate in NaCl solution has a noticeably higher protective ability than Ce(III) chloride and Ce(III) nitrate. The presence of cerium, propionate anions, and Al–O bonds in the inhibitive layer on the 7049 aluminum alloy surface was confirmed by X‐ray photoelectron spectroscopy analysis. This indicates the formation of Ce propionate complexes and bonds via oxygen atoms from carboxylate anions with the metal surface. Density‐functional theory methods were used for the geometry optimization of possible Ce propionate complexes as corrosion inhibitors.

Luminescent properties of Ln(III) complexes with 2-[(phenylamino)methylene]-5,5-dimethyl-cyclohexane-1,3-dione as an antenna

Seven lanthanide-based coordination compounds with 2-[(phenylamino)methylene]-5,5-dimethyl-cyclohexane-1,3-dione were synthesized: [Eu(HL)2(NO3)3] (1), [Sm(HL)2(NO3)3] (2), [Ce(HL)2(NO3)3] (3), [Tm(HL)2Cl3]·H2O (4), [Tb(HL)2Cl3]·H2O (5), [Dy(HL)2(H2O)(NO3)3] (6) and [Gd(HL)2Cl3]·H2O (7). The obtained Eu(III), Sm(III) and Ce(III) nitrate complexes was established to be isostructural just like Tm(III), Tb(III) and Gd(III) chloride ones. Using X-ray diffraction analysis, the structures of cerium and samarium were determined, which occurred to be polymer chains. On the contrary, the dysprosium compound was mononuclear. Ligand was shown to emit in blue region with quantum yield near 12%. For lanthanide complexes of Eu(III), Sm(III), and Tb(III), during the energy transfer from the ligand triplet state to the central atom, characteristic bands of the metal ion are observed in the emission spectra. The lifetimes and quantum yields of luminescence for these complexes were also determined. For other compounds, no energy transfer is observed due to lower energy of ligand triplet state than corresponding emitting state of the lanthanide ions.

Influence of cerium salt concentration, co-solvents and water on the efficiency of supercritical CO2 extraction

The extraction of cerium from cotton substrate, as a matrix model, using supercritical CO2 modified with phosphorus extractant and co-solvent/water in wise proportions, has been investigated. Using a recently developed isobutyl amidophosphonate extractant, the aim of this study was to emphasize how besides the usually considered operating parameters (flow rate, pressure and temperature), the efficiency of supercritical CO2 extraction of cerium depends on the concentration of cerium nitrate deposits on the substrate (between 0.27 and 261 mg gcotton−1) and on the presence and composition of co-solvent/water mixture as well. The variations of the extraction efficiency with the nature of the Ce nitrate deposits (aggregates or homogenous layers) are explained by using a deposition model confirmed using SEM and coupled with SAXS data. Extraction is promoted when Ce nitrates deposits are in the form of segregated aggregates instead of homogeneous layers. Phase equilibrium data for CO2-ethanol-amidophosphonate and CO2-isopropanol-amidophosphonate ternary systems have been measured at 40 °C and 25 MPa to investigate the benefit of using a co-solvent. Extraction experiments show that adding a co-solvent and carefully adjusting the water concentration up to 30%wt are crucial to obtain high mass extraction yields, here up to 82%.

MCC: Specific of preparation, correlation of the phase composition and electrodynamic properties

Metal-carbon composites (MCC) were produced by the dissolving of the Fe, Co and Ce nitrates in phenol–formaldehyde resin with further pyrolysis (under heating up to 800 °C). Concentrations of the metal compositions in final MCC were 2, 7 and 15 wt%. Phase composition of the final MCC samples was determined using XRD and Mössbauer spectroscopy. It was established phase separation in metallic compounds under pyrolysis process due to chemical interaction with phenol–formaldehyde decomposition products. The main phases for composites were: Fe3O4 (for MCC-Fe); Co (for MCC-Co) and CeO2 (for MCC-Ce). Average crystal size for metal-based fillers was 28, 24–35 and 3.5 nm for Fe-; Co and Ce-based composites respectively. The electrodynamic properties of the MCCs in the Extremely High Frequency range (30–50 GHz) were studied as function of the filler concentration. The frequency dependences of the permittivity and permeability (real and imaginary parts) of the investigated composites were measured. The nature of the MCC electrodynamic properties was discussed in detail in terms of polarization losses.

Effect of process parameters on YAG:Ce phosphor properties obtained by co-precipitation method

In the present paper we have studied the influence of the process parameters and the possibility of adapting a urea based co-precipitation process by using different types of surfactants in order to improve the optical properties of YAG:Ce phosphors. Practically, the process is based on the concomitant precipitation of the metal cations with the formation of a gelatinous precipitate between the cation salts (Y, Al or Ce nitrate) and a precipitating agent (urea) in basic medium and in the presence of surfactants, followed by maturation, filtration, washing, drying steps for the formation of the precursor, completed with the final thermal treatment at 1000 °C. In order to find the optimal synthesis conditions, we compared the effect of the different parameters on the structural properties (using as characterization techniques FTIR spectrometry, TG-DSC and XRD), morphological (SEM) and optical (PL). The analysis of phosphors samples confirmed utility of the use of the PEG or CTAB surfactants and flux agents, the need of an optimum temperature of 1000 °C for the synthesis of (Y1-xCex)3A5O12, with x = 0.05.

The Effect of Pre-Treatment on Corrosion Properties, Surface Chemistry and Interfacial Properties of Sol-Gel Coating on Aluminium and Aluminium Alloys

Hybrid sol-gel coatings are amongst the most promising environmentally friendly replacements for chromate conversion coatings for corrosion protection of aluminium alloys (1). However, there is still a lack of understanding about the importance of the pre-treatment of the substrate prior to sol-gel coating deposition. The goal of this study is to improve the understanding of the effect of different pre-treatments on corrosion, surface chemistry and interfacial properties of sol-gel coating on aluminium (Al) and aluminium alloys AA7075 and AA2024.The hybrid sol-gel coating used in the present study is based on alkoxysilane precursors (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and tetraethyl orthosilicate (TEOS) (2). A wide variety of Ce-based chemistries are found to be effective corrosion inhibitors for aluminium alloys and can be incorporated into sol-gel coatings to achieve active corrosion protection in case of a coating defect (1). The corrosion inhibitor studied in the present work is cerium nitrate Ce(NO3)3. Due to oxygen reduction at cathodic sites during initial stages of corrosion, OH-ions are formed increasing the local pH, establishing the condition for local precipitation of cerium oxide/hydroxide reducing the cathodic and hence corrosion kinetics of the substrate (3).It is known that adhesion increases with the hydroxyl fraction at the surface of the substrate, resulting in stronger bonding between aluminium and the silicone from hybrid sol-gel coatings, resulting in better corrosion protection properties of coatings (1). For that purpose, alkaline (KOH), acidic (HNO3) and pseudoboehmite (DI boiling water) pre-treatments were used to control the formation of oxide layers with different hydroxyl fractions, prior to hybrid sol-gel coating deposition.General observations, morphology and composition, of differently pre-treated samples were obtained by scanning electron microscopy equipped with electron dispersive spectroscopy (SEM/EDS). SEM analysis confirmed the significant effect of pre-treatment on the morphology of Al, AA7075 and AA2024. Surface compositional maps, carried out with EDS, were recorded to obtain the elemental distribution after different pre-treatments. EDS showed that AA7075 and AA2024 are enriched with copper after alkaline pre-treatment because of the galvanic coupling between copper and aluminium matrix resulting in preferential and accelerated corrosion of the aluminium matrix during the pre-treatment process (4).Surface oxide chemistry of differently pre-treated samples was studied by X-ray photoelectron spectroscopy (XPS). The hydroxyl fraction of differently pre-treated Al, AA7075 and AA2024 were calculated from O1s and C1s peaks fitting. A relatively high hydroxyl fraction is observed after pseudoboehmite pre-treatment (DI boiling water) for all substrates (Figure 1), which is in accordance with earlier studies (5).Electrochemical impedance spectroscopy (EIS) of different pre-treated substrates Al, AA2024 and AA7075, with the sol-gel coating on the top, is measured to study the effect of pre-treatment on corrosion protection properties of the deposited sol-gel coatings. The results show the highest low-frequency impedance modulus values after pseudoboehmite pre-treatment, for all substrates (Fig. 2).Finally, we determined the effect of differently pre-treated sol-gel coatings on the dry and wet adhesion of overlaying epoxy-based adhesive Araldite®, by using pull off tests. Furthermore, the delamination kinetics of this adhesive on all pre-treated substrates coated with sol-gel is measured by using scanning Kelvin probe (SKP). Results show that a high hydroxyl fraction resulting from the pseudoboehmite pre-treatment, provides the best corrosion protection properties and the highest adhesion after sol-gel coating application for all studied substrates. Roughness measurements also confirmed that surface chemistry has a dominant effect on adhesion compared to surface roughness.The financial support was provided by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 707404.

Foliar application of rare earth elements on soybean (Glycine max (L)): Effects on biometrics and characterization of phytotoxicity

This study aims at investigating the effects of foliar application of aqueous solutions of La3+ and Ce3+ nitrates on soybean plants (Glycine max). First, we observe that Triton HW 1000 surfactant at 0.01 vol% reduces droplets contact angle and increases their drying time. Under greenhouse conditions, the foliar treatments do not affect chlorophyll content, plant height, number of leaves, number of pods, number of seeds per pod, and average seed weight. However, the treatments induce phytotoxicity since foliar injuries appear after the spraying. Microprobe X-ray fluorescence spectroscopy combined to scanning electron microscopy shows that the leaf lesions are positively correlated to accumulation of Ce and La on the leaf surface and also promote structural alteration to the epidermal cells. X-ray absorption near edge structure shows that the La and Ce nitrates are partially bio transformed into oxides by the leaves which might explain the harmful effects.

Ce Cation Migration and Diffusivity in Perfluorosulfonic Acid Fuel Cell Membranes

Cerium enhances the durability of polymer electrolyte membrane (PEM) fuel cells by scavenging reactive radical species which are generated during operation. However, during cell fabrication, conditioning, discharge, and during fuel cell operation, Ce dissolves and is transported within the membrane-electrode-assembly (MEA) due to gradients in ionic potential (migration),1–3 ionic concentration (diffusivity),1,4 and ionomer hydration (convection).5,6 Ce migration is detrimental because (i) its accumulation in the CL ionomer can diminish the electrode’s proton conductivity, which results in sub-optimal performance, especially at high current density7,8; and (ii) its depletion may leave an ionomer region more susceptible to radical attack. Therefore, it is necessary to quantify these transport mechanisms under a range of operating conditions in order to understand their effects on cell performance/durability and determine the necessity of further Ce stabilization. To understand the effects of potential gradients and relative humidity (RH) on Ce migration, ex situ experiments were performed using Nafion™ NR-211 (Ion Power, Inc.) which was doped in-house using Ce(III) nitrate to ~5% ion-exchanged Ce. PEM specimens were operated in 4-electrode H2 pump mode in a standard conductivity cell (Scribner Associates) under a range of temperatures and RHs. The evolution of Ce profiles as a function of charge transfer was quantified using X-ray fluorescence, which were fit using our previously-developed transient, 1-D transport model in order to decouple the competing effects of migration and diffusion.1 The model was updated to capture convection due to hydration gradients, as well as variations in λ (defined as nH2O/nSO3 -) and conductivity as a function of Ce exchange fraction. As shown in Figure 1a, diffusion experiments performed in the absence of potential gradients showed excellent agreement with simultaneous 2-parameter migration and diffusivity fitting of a single migration experiment, validating the efficiency and effectiveness of this technique. Figure 1 shows modeled values for (a) diffusivity and (b) migration over a range of temperatures and λs. Convection experiments were also conducted using a differential RH cell, adapted from the GM/Giner design.9 Since no potential gradient is present here, the convection coefficients were fit by employing the isothermal diffusivity-λ relations determined from the H2 pump experiments. Results of all three transport coefficients will be presented over a range of relevant operating conditions and 2-D cell model results demonstrating the impact on cell performance will be discussed. The findings of these studies may also be analogously applied to Co and Fe cations, which dissolve from Pt-Co electrocatalysts and system balance of plant components, respectively, and are expected show transport characteristics in PFSA. Acknowledgement: This research is supported by the U.S. Department of Energy Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium (Fuel Cells Program Manager: Dimitrios Papageorgopoulos and Technical Development Manager: Greg Kleen). References A. M. Baker, S. K. Babu, R. Mukundan, S. G. Advani, A. K. Prasad, D. Spernjak, and R. L. Borup, J. Electrochem. Soc., 164, 1272–1278 (2017).A. M. Baker, D. Torraco, E. J. Judge, D. Spernjak, R. Mukundan, R. L. Borup, S. G. Advani, and A. K. Prasad, ECS Trans., 69, 1009–1015 (2015).Y. Cai, J. M. Ziegelbauer, A. M. Baker, W. Gu, R. S. Kukreja, A. Kongkanand, M. F. Mathias, R. Mukundan, and R. L. Borup, J. Electrochem. Soc., 165, F3132–F3138 (2018).F. D. Coms and A. B. McQuarters, ECS Trans., 86, 395–405 (2018).A. M. Baker, R. Mukundan, D. Spernjak, E. J. Judge, S. G. Advani, A. K. Prasad, and R. L. Borup, J. Electrochem. Soc., 163, F1023–F1031 (2016).Y.-H. Lai, K. M. Rahmoeller, J. H. Hurst, R. S. Kukreja, M. Atwan, A. J. Maslyn, and C. S. Gittleman, J. Electrochem. Soc., 165, F3217–F3229 (2018).D. Banham, S. Y. Ye, T. Cheng, S. Knights, S. M. Stewart, M. Wilson, and F. Garzon, J. Electrochem. Soc., 161, F1075–F1080 (2014).E. L. Redmond, S. M. Wriston, and J. L. Szarka III, ECS Trans., 80, 633–641 (2017).S. Kumaraguru, "Durable High Power Membrane Electrode Assembly with Low Pt Loading," Fuel Cell R&D Annual Merit Review Proceedings, (2018). Figure 1

PHASE RELATION STUDIES IN THE ZrO2-CeO2-Dy2O3 SYSTEM AT 1500 °С

The systems containing ceria, dysprosium and zirconia are perspective for the development of energy saving technological solutions and solid oxide fuel cells (SOFC). Ceramics based on ZrO 2 is used as a high temperature electrolyte for SOFC. The solid solutions based on CeО 2 are the most perspective electrolytes, operating at moderate temperatures, because of their ionic conductivity and high sensitivity to changes of oxygen partial pressure is much higher than ones of ZrO 2 stabilized with Y 2 O 3 (YSZ). In the present work, first the phase equilibria and physicochemical properties for solid solutions in the ternary ZrО 2 -CeО 2 -Dy 2 O 3 system at temperature 1500 °С (150 h) in air were studied by X-ray diffraction in the overall concentration range of compositions. Cerium oxide nitrate Ce(NO 3 ) 3 ∙6H 2 O and zirconium oxide nitrate ZrO(NO 3 ) 2 ×2Н 2 О of grade «ch» (above 98%, dysprosium oxide (99.99 % produced by Merck Corp.) and analytical-grade nitric acid were used as the starting materials. Samples were prepared with a concentration step of 1-5 mol % from nitrate solutions with subsequent evaporation and decomposіtion of nitrates into oxides through annealing at 1200 °С for 2 h. Powders were pressed in pellets (diameter 5 mm, height 4 mm) under a pressure of 10-30 MPа. XRD analysis of samples was performed by powder procedure on a DRON-3 apparatus at ambient temperature under CuКa radiation. Scanning step was 0.05-0.1 degrees in the range 2θ = 15–90°. Lattice parameters were calculated by the least square method using the LATTIC computer code with an error of not lower than 0.0001 nm for the cubic phase. Any new phase in the ternary system was revealed at 1500 °С. The structure of the boundary binary systems defines the phase equilibria in the ZrО 2 -CeО 2 -Dy 2 O 3 system. Solid solutions based on tetragonal (Т) modification ZrО 2 , cubic (С) modification Dy 2 O 3 and cubic with fluorite-type structure (F) modifications СеО 2 (ZrО 2 ) were determined.

Extraction of cerium(III) with N, N′-dimethyl-N, N′-dioctyl-diglycolamide in [Bmim][PF6] compared in 40% octanol/kerosene

ABSTRACT The extraction of Ce(III) nitrate has been investigated by using N, N′-dimethyl-N, N′-dioctyl-diglycolamide (DMDODGA = L) as extractant with 1-Butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) as diluent in comparison with 40% octanol/kerosene. DMDODGA in two different diluents shows good extraction ability for Ce(III), but the trends are quite different depending on the concentrations of the ligand in solvent phase and nitric acid in aqueous phase. The slope analysis method is used to obtain the stoichiometric ratio of the extracted complexes. 1:3 complex of Ce(III) to DMDODGA may be formed in both systems, while 1:2 complex may be also formed in DMDODGA-40% octanol/kerosene system. The extraction of Ce(III) is by the cation exchange mechanism in DMDODGA-[Bmim][PF6] system. Unlike the expected positively charged 1:3 complex of Ce(III) formed in the DMDODGA-40% octanol/kerosene system, the 1:2 complex is assumed to be a neutral complex with two DMDODGA molecules bonding to Ce(III). In addition, the stronger interaction between the C = O groups of L and Ce(III) in the DMDODGA-[Bmim][PF6] system than in the DMDODGA-40% octanol/kerosene system is confirmed by IR spectroscopy.

EIS investigation of a Ce‐based posttreatment step on the corrosion behaviour of Alclad AA2024 anodized in TSA

In the aircraft industry, anodizing and posttreatment steps use Cr (VI) compounds, which, despite offering good corrosion resistance and self‐healing properties, are highly toxic and carcinogenic. Ce compounds are recognized as efficient corrosion inhibitors for Al alloys, and several works report self‐healing ability for these chemicals. In this investigation, the corrosion resistance of Alclad AA2024‐T3 alloy anodized in tartaric‐sulphuric acid (TSA) bath and posttreated in a solution comprising cerium nitrate without and with hydrogen peroxide was evaluated. The purpose is to investigate the potentiality of using hydrothermal treatment in Ce nitrate solution as candidate to replace Cr (VI) posttreatment. The aim is to provide a posttreatment step which, while improving the corrosion resistance, does not plug the mouths of the pores maintaining the adhesion properties of the porous anodic layer. Microstructural characterization was carried out by SEM‐EDS whereas corrosion resistance was evaluated by EIS. The surface analysis showed that the posttreatments, all performed at 50°C, kept the open structure of the pores. EIS analysis showed that the posttreatments performed in the H2O2 solution for short immersion times were the most effective in improving the corrosion resistance of the samples, whereas electrical equivalent circuit (EEC) fitting of the data indicated sealing of the porous layer during the immersion of the different samples in the test solution. SEM‐EDS analysis of the samples posttreated in the H2O2 containing solution, prior and after the corrosion test, showed the presence of Ce oxy‐hydroxide randomly deposited on the sample surface, indicating that Ce could be incorporated/stored in the anodic layer.

Anion structural effects on interaction of rare earth element ions with Dowex 50W X8 cation exchange resin

The effect of the anion in the original rare earth element (REE) solution on the reversible ion exchange of Ce nitrate and Ce sulfate with the Dowex 50W X8 was investigated using attenuated total reflection infrared (ATR-IR) spectroscopy, continuous flow reactor studies coupled with inductively coupled plasma mass spectroscopy (ICP-MS), and density functional theory (DFT). The simulated IR spectrum at the DFT B3LYP/6-31G(d) level was compared to the experimental results to characterize the IR spectrum, molecular interactions, and bonding of the ion exchanged species. The continuous liquid flow reactor studies show a capacity of 0.72 mmol/g sorbent for the Ce nitrateand 0.96 mmol/g sorbent for the Ce sulfate with the Dowex 50W X8. The flow reactor studies reveal the type of solute anion (SO4(2–) or NO3(−)) associated with the REE during cation exchange significantly affects the sorption capacity of the Dowex 50W X8 ion exchange resin. The calculated REE binding energy (BE) and the DFT optimized structures suggest that the differences in sorption capacity is the result of the formation of different types of partially ion-exchanged Ce2(3+)2SO4(2–) and Ce(3+) 3NO3(−). These results suggest that the solute anion affects the equilibrium constants of the Dowex resin by the formation of a charged layer capable of retaining the counterion. Modifying the sulfonic acid site (H+) in the Dowex 50W X8 with the NH4+ counterion does not affect the sorption capacity and retention times of the Ce nitrate and Ce sulfate species. These results suggest that the counterions and co-ions having a finite size, may limit access to the Dowex sulfonate active site where the type of REE cation as a nitrate or sulfate in solution may significantly modify the sorption capacity of the ion exchange resin. Similar results are obtained during sorption with nitrates and sulfates of Sm and Yb.

Effect of Sol Concentration, Aging and Drying Process on Cerium Stabilization Zirconium Gel Produced by External Gelation

Cerium Stabilized Zirconium gel has been prepared using external gelation process. As the raw materials was used ZrO(NO3)2 and Ce(NO3)4 nitrate salt which was dissolved with water into Zr-Ce nitrate mixture. The concentration of the nitrate salt mixture in the sol solution was varied by varying the concentration of zirconium and cerium nitrate in the sol solution and the addition of PVA and THFA to produce a sol with a viscosity of 40-60 cP. The viscosity range of 40-60cP is the viscosity of the sol solution that was easy to produce a good gel in the gelation apparatus. Sol solution was casted in a gelation column equipped with following tools: a 1 mm diameter drip nozzle which was vibrated to adjust the best frequency and amplitude of vibration, a flow meter to measure the flow rate of sol, flowing of NH3 gas to presolidification process. Gelation column was contained NH4OH solution as gelation medium and gel container to collect gel product. Gel obtained from the gelation process than processed with ageing, washing, drying and calcinations to get round gel and not broken at calcinations up to 500°C. The parameters observed in this research are variation of Zr nitrate concentration, Ce nitrate concentration, ratio of Zr and Ce in the sol and ageing and drying process method which was appropriate to get a good gel. From the gelation processes that has been done, it can be seen that with the presolidification process can be obtained a round gel and without presolidification process, produce not round gel. In the process of ageing to get not broken gel, ageing was done on the rotary flask so that during the ageing, gels rotate in gelation media. Gels, then be washed by dilute ammonium nitrate, demireralized water and iso prophyl alcohol. The washed gel was then dried by vacuum drying to form pores on the gel which become the path for the gases resulting from decomposition of the gel to exit the gel. Vacuum drying can prevent cracking because the pores allow the gel to release the decomposition of the material during heating. Larger the concentration of nitric metal in sol solution, yields a gel with a larger diameter of gels. This research allows us to plan the diameter of the sintered particles to be made.

Size controlled ultrafine CeO2 nanoparticles produced by the microwave assisted route and their antimicrobial activity

Cerium oxide (CeO2) nanoparticles (NPs) have a wide range of biological and biomedical applications. This work describes a new methodology for producing ultrafine, highly uniform NPs with controlled sizes using the chemical microwave assisted route. The size of CeO2-NPs decreased from 10 to 5 nm by increasing the molar ratio of cerium nitrate Ce(NO3)3.(6H2O) to that of hexamethylenetetramine (C6H12N) from 1:20 to 20:20. Detailed information about their structural characterization was obtained from the XRD, UV-visible, photoluminescence, Raman spectroscopy, SEM, TEM and AFM. These CeO2-NPs were tested as antimicrobial agent against Gram-negative (Escherichia.coli), Gram-positive (Bacillus.subtilis) bacteria and yeast (Saccharomyces cerevisiae). The obtained results showed significant inhibition of these strain even at low concentration of CeO2-NPs. The CeO2-NPs with the molar ratio 5:20 had the most effective inhibition against E.coli (~70%) at a concentration of 20 µL. The CeO2-NPs with the ratio 12:20 were found to be the most effective against B.subtilis (inhibition ~68%). On the other hand, CeO2-NPs synthesized with the 20:20 molar ratio caused the highest inhibition for S. cerevisiae (~60%). It is observed that at higher NPs concentration (i.e., >20 µL) the inhibition of these strains decreased. The antimicrobial activity may be attributed to the penetrating power of CeO2-NPs size beside the generated oxygen species radicals that caused inhibition of bacterial growth.

Modulating the Catalytic Activity of Cerium Oxide Nanoparticles with the Anion of the Precursor Salt.

In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by presence of counterions. We first employed various precursor cerium (III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•2- from reduction of NO3- in CNPs synthesized from Ce(III) nitrate). Physicochemical properties of these CNPs, e.g., dispersion stability, hydrodynamic size, signature surface chemistry, SOD-mimetic activity, and oxidation potentials were found to be significantly affected by the anions of the precursor salts. CNPs synthesized from Ce(III) nitrate and Ce(III) chloride exhibited higher extent of SOD-mimetic activities. Therefore, these CNPs were studied extensively employing in-situ UV-Visible spectroelectrochemistry and changing the counterion concentrations affected the oxidation potentials of these CNPs. Thus, the physicochemical and antioxidant properties of CNPs can be modulated by anions of the precursor. Furthermore, our ESR studies present evidence of the formation of guanine cation radical (G•+) in 5'-dGMP via UV-photoionization at 77 K in the presence of CNPs synthesized from Ce(III) nitrate and chloride and CNPs act as the scavenger of radiation-produced electrons.

Green chemical approach towards the synthesis of CeO2 doped with seashell and its bacterial applications intermediated with fruit extracts

Nanomaterials of CeO2 with A. vera were synthesized by using simple chemical method. Grapes drops are used as an oxidizing agent. Structural and morphological studies of nanomaterials of cerium oxide (CeO2), were studied for combustion method of preparation. The precursor solution was initialized by a hydrothermal reaction. Cerium hydroxyl carbonate precursors which involves cerium (III) nitrate Ce(NO3)3. 6 H2O with (1.0M) of seashell powder, 3% A. vera, extracts, grapes and pomegranate drops and this complex solution was used to produce the CeO2 powder particles. We have prepared another sample with 5% of Aloe vera extract and found that 3% Aloe vera extract has lesser grain size and enhanced band gap values, so the article explained the sample analysis of combination with 3% extract of Aloe vera. The product has the rod pattern which was the unusual features appear to originate from the unique crystal chemistry aspects. From the optical absorption spectrum, it has been shown that the CeO2 rods have 3.847eV of direct band gap energy. The minimum inhibitory concentration (MIC) values of the synthesized compounds exhibited activity towards various microbial pathogens such as B. subtilis (15μg/mL), S. aureus (50μg/mL), S. epidermidis (20μg/mL), E. faecalis (25μg/mL) and towards E. coli (100μg/mL), K. pneumoniae (50μg/mL) and P. aeruginosa (75μg/mL) respectively. The tests on bacterial activities confirmed that the CeO2 rods are suitable hand for the biological applications. The seashell structure and the phytochemical contents of A. vera might enhance its bacterial activities.

Study the Catalytic Activity of CeO2 Catalyst for the Oxidative Degradation of Orange G Dye in Aqueous Solution

The oxidative degradation of Orange G dye by nanosized CeO2 catalyst has been performed in this study. The catalyst was prepared by precipitation method. Various characterization techniques were carried out to study the physical and chemical properties of the synthesized catalyst. The XRD result confirms well the formation of CeO2 cubic phase. The FTIR result showed the effect of calcination temperature for CeO2 was clearly observed due to reduction in band intensity compared to uncalcined Ce nitrate sample. Meanwhile, the diffused reflection spectra recorded reflection spectra at 414 nm with an energy gap of 3.2 ev. The decolorization of Orange G dye by oxidation process were carried out under various conditions such as, the effects of H2O2 dosage , pH, catalyst dosage and the temperature of reaction. The optimum conditions for the highest decolorization efficiency (100%) were achieved at 10 mg/L of orange G dye with catalyst dosage of 1.5 g/L, pH 2, reaction temperature of 65 °C and 0.1 mL H2O2.