Ceric Ammonium Research Articles

Synthesis of nanocrystalline CeO2 particles by different emulsion methods

Cerium oxide nanoparticles were synthesized using three different methods of emulsion: (1) reversed micelle (RM); (2) emulsion liquid membrane (ELM); and (3) colloidal emulsion aphrons (CEAs). Ammonium cerium nitrate and polyoxyethylene-4-lauryl ether (PE4LE) were used as cerium and surfactant sources in this study. The powder was calcined at 500 °C to obtain CeO2. The effect of the preparation procedure on the particle size, surface area, and the morphology of the prepared powders were investigated. The obtained powders are highly crystalline, and nearly spherical in shape. The average particle size and the specific surface area of the powders from the three methods were in the range of 4–10 nm and 5.32–145.73 m2/g, respectively. The CeO2 powders synthesized by the CEAs are the smallest average particle size, and the highest surface area. Finally, the CeO2 prepared by the CEAs using different cerium sources and surfactant types were studied. It was found that the surface tensions of cerium solution and the type of surfactant affect the particle size of CeO2.

In-situ Attainment of Paramagnetic Behaviour of Poly(Amino-Acetanalide) during Synthesis

Polyaniline and its derivatives have gained significant interest because of their unique electronic property, simple synthesis process and their environmental stability. We report on the cerium (IV) ammonium nitrate mediated synthesis of poly (amino-acetanilide), PAA, using an interfacial polymerization technique in which PAA serves as a guest of the cerium (III) ion, a paramagnetic species produced during the synthesis condition. The cerium (III) ionic species bonded with the chain nitrogen of the PAA and the supramolecular system show the paramagnetic behavior throughout the experimental temperature range 400-1.9 K.

Hollandite as a Functional and Structural Model for the Biological Water Oxidizing Complex: Manganese-Calcium Oxide Minerals as a Possible Evolutionary Origin for the CaMn4 Cluster of the Biological Water Oxidizing Complex

Oxygen evolution was observed upon mixing either hollandite, which has been proposed as a structural model for the biological water oxidizing complex, or hausmannite with an aqueous solution of cerium (IV) ammonium nitrate. Oxygen evolution from water during irradiation with visible light (λ > 400 nm) was also observed upon adding either hollandite or hausmannite to an aqueous solution containing tris (2,2′-bipyridyl)ruthenium(II) chloride and chloro pentaammine cobalt(III) chloride in acetate buffer. These experiments showed that hollandite is a good catalyst for oxygen evolution in presence of cerium (IV) ammonium nitrate or tris (2,2′-bipyridyl)ruthenium (III). Thus, hollandite is not only a structural but also a functional model for the biological water oxidizing complex. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the free supplemental file.

Emergence of Paramagnetism in Organic Macromolecules during Synthesis

Paramagnetism in polyaniline can be generated during synthesis if cerium (IV) ammonium nitrate (CAN) is used as a polymerizing (oxidizing) agent. During the reaction, in situ formation of Ce3+ ions are doped in the spherical polyaniline particles and show paramagnetic behavior throughout the experimental temperature range (400–1.9 K). The result indicated that the Ce3+ ions covalently functionalized with the chain nitrogen of the polyaniline.

Glucosylceramide synthase in the fat body controls energy metabolism in Drosophila

Glucosylceramide synthase (GlcT-1) catalyzes the synthesis of glucosylceramide (GlcCer), the core structure of major glycosphingolipids (GSLs). Obesity is a metabolic disorder caused by an imbalance between energy uptake and expenditure, resulting in excess stored body fat. Recent studies have shown that GSL levels are increased in obese rodents and that pharmacologically reducing GSL levels by inhibiting GlcCer synthesis improves adipocyte function. However, the molecular mechanism underlying these processes is still not clearly understood. Using Drosophila as a model animal, we report that GlcT-1 expression in the fat body, which is equivalent to mammalian adipose tissue, regulates energy metabolism. Overexpression of GlcT-1 increases stored nutrition (triacylglycerol and carbohydrate) levels. Conversely, reduced expression of GlcT-1 in the fat body causes a reduction of fat storage. This regulation occurs, at least in part, through the activation of p38-ATF2 signaling. Furthermore, we found that GlcCer is the sole GSL of the fat body, indicating that regulation of GlcCer synthesis by GlcT-1 in the fat body is responsible for regulating energy homeostasis. Both GlcT-1 and p38-ATF2 signaling are evolutionarily conserved, leading us to propose an evolutionary perspective in which GlcT-1 appears to be one of the key factors that control fat metabolism.

Sol-Gel Combustion Synthesis of Nanocrystalline Cerium (IV) Oxide Powders

CeO2nano-sized crystalline powders were prepared by sol-gel combustion method from ammonium cerium nitrate and citric acid, and the dependences of the particle size of synthesized powder on the precursor gel were investigated. The precursor gels and the synthesized powders were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray scattering (XRD). The colloid particle with nanometer size was firstly observed by FE-SEM, and its size variation had the same tendency as that of CeO2powders with the varying of the ratio of metal ions to citric acid. Furthermore, the probable reasons for the effect of gel structure on properties of nano-sized ceria powders prepared by sol-gel combustion were explained.

Cerium(IV) Ammonium Nitrate–Mediated Oxidation of Mono-aryl-substituted Methylenecyclobutanes: A Convenient Method for the Synthesis of Spirocyclobutyl-1,2-dioxethanes

Cerium(IV) ammonium nitrate (CAN)-mediated oxidation of methylenecyclobutanes was investigated. Compared with the similar reactions of methylenecyclopropanes, the reaction products were quite different. Instead of the desired ring-enlarged product cyclopentanones, a cyclobutyl ring-intact product, spirocyclobutyl-1,2-dioxethane, was obtained. The structures of these spiroheterocycle-containing compounds are interesting, and the reactions are potentially valuable in both organic synthesis and mechanism research.

Studies on the Graft Copolymer of 2,3-Glycidyl Trimethyl Ammonium Chloride onto Chitosan with Ultrasonic

Under the action of ultrasonic, the graft copolymer is synthesized by grafting 2, 3- glycidyl trimethyl ammonium chloride onto chitosan with ammonium cerium nitrate as initiator, and the main factors which influences this reaction are selected. The results show the optimum reactive conditions while chitosan: 2, 3- glycidyl trimethyl ammonium chloride is 1:3, pH 7.0, 70°C, the reactive time 3h, and the concentration of initiator 0.5mmol/L. Finally, the product of graft copolymer is analyzed by chemical titration, infrared analysis (IR), differential scanning calorimetry (DSC), elemental analysis, and XRD.

Monodisperse CeO2 Nanoparticles and Their Oxygen Storage and Release Properties

Monodisperse polyhedral nanoparticles (NPs) and nanorods (NRs) of cerium dioxide, CeO2, were synthesized by thermal decomposition of ammonium cerium(IV) nitrate, (NH4)2Ce(NO3)6, at 180 °C in an organic solution of oleylamine (OAm) and/or oleic acid (OA). The 4 nm CeO2 NPs were synthesized in diphenyl ether solution of OAm and OA with the molar ratio of Ce/OAm/OA = 1:3:3, while the 6 nm CeO2 NPs were made in 1-octadecene solution of OAm with Ce/OAm = 1:6. The NRs were formed in 1-octadecene with Ce/OAm/OA = 1:3:1.5. The CeO2 NPs were assembled on γ-Al2O3 via polyvinylpyrrolidone and were annealed at 500 °C under air to remove organic coating. They were well-dispersed on Al2O3 and showed the increased oxygen storage capacity compared to the physical mixture of aggregated CeO2 and γ-Al2O3 powder. The reported CeO2 NPs are promising for oxygen storage and release applications.

Cerium (IV) Ammonium Nitrate (CAN) Mediated Reactions IV. A Highly Efficient Synthesis of N,N’-Diarylsubstituted Formamidines in Water at Ambient Temperature

A green, simple and highly efficient synthesis of N,N-diarylsubstituted formamidines has been developed employs reaction of triethylorthoformate (TEO) with aromatic amines catalyzed by cerium (IV) ammonium nitrate (CAN) in water at ambient temperature. This method offers the advantages of proceeding under environmentally friendly technique with high yields and simplicity either in conducting the reaction or handling the products.

Spectrofluorimetric methods of stability-indicating assay of certain drugs affecting the cardiovascular system

Two stability-indicating spectrofluorimetric methods have been developed for the determination of ezetimibe and olmesartan medoxomil, drugs affecting the cardiovascular system, and validated in the presence of their degradation products. The first method, for ezetimibe, is based on an oxidative coupling reaction of ezetimibe with 3-methylbenzothiazolin-2-one hydrazone hydrochloride in the presence of cerium (IV) ammonium sulfate in an acidic medium. The quenching effect of ezetimibe on the fluorescence of excess cerous ions is measured at the emission wavelength, λ em , of 345 nm with the excitation wavelength, λ ex , of 296 nm. Factors affecting the reaction were carefully studied and optimized. The second method, for olmesartan medoxomil, is based on measuring the native fluorescence intensity of olmesartan medoxomil in methanol at λ em = 360 nm with λ ex = 286 nm. Regression plots revealed good linear relationships in the assay limits of 10–120 and 8–112 g/ml for ezetimibe and olmesartan medoxomil, respectively. The validity of the methods was assessed according to the United States Pharmacopeya guidelines. Statistical analysis of the results exposed good Student’s t-test and F-ratio values. The introduced methods were successfully applied to the analysis of ezetimibe and olmesartan medoxomil in drug substances and drug products as well as in the presence of their degradation products.

Synthesis and Pigmental Properties of Nickel Phosphates by the Substitution with Tetravalent Cerium Cation

In this paper, we report the preparation of nickel phosphate in aqueous solution and its use as inorganic pigment. Because cerium phosphate is insoluble in acidic and basic solution, the addition of cerium was tried to improve the acid and base resistance of nickel phosphate pigment. The cerium substituted nickel phosphates were prepared from phosphoric acid, nickel nitrate, and ammonium cerium nitrate solution. The additional effects of tetravalent cerium cation were studied on the chemical composition, particle shape and size distribution, specific surface area, color, acid and base resistance of the precipitates and their thermal products.

Kinetic spectrophotometric methods for the determination of artificial sweetener (sucralose) in tablets

Two simple and sensitive kinetic spectrophotometric methods for the determination of sucralose are described. The first method is based upon a kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 30 min. The absorbance of the green coloured manganate ions produced was measured at 610 nm. The second method is based on the reaction of sucralose with cerium (IV) ammonium sulfate in the presence of perchloric acid with the subsequent measurement of the excess unreacted cerium (IV) ammonium sulfate at 320 nm at a fixed time of 30 min in a thermostated water bath at 60 ± 1 °C. This principle is adopted to develop a kinetic method for sucralose determination. The absorbance concentration plots in both methods were rectilinear over the range 4-16 and 10-30 µg ml(-1) , for the first and second methods, respectively. The different experimental parameters affecting the development and stability of the colours were carefully studied and optimized. The determination of sucralose by rate constant method, fixed concentration method, and fixed-time method was also feasible with calibration equations obtained but the latter method was found to be more applicable. The two methods have been applied successfully to commercial tablets.

Electrospray ionization mass spectrometry of a cerium(III) phosphomolybdate complex: Condensed and gas-phase cluster chemistry

Electrospray ionization quadrupole ion trap mass spectrometry (ESI-QIT/MS) of the ammonium cerium(III) phosphomolybdate complex (NH 4) 11[Ce(III)(PMo 11O 39) 2] in aqueous media has revealed a concentration-dependent behavior. Under fixed instrumental parameters, the Ce-containing polyoxomolybdate complexes H 2Ce(III)P 2Mo 22O 75 3− and Ce(III)PMo 11O 38 2− are the primary species present at 11 mM (pH = 4.3); at 0.7 mM (pH = 3.6), Ce(III)PMo 10O 35 2− is the predominant species, Ce(III)PMo 11O 38 2− is quite diminished, and H 2Ce(III)P 2Mo 22O 75 3− is absent. As a result of the complex isotopic fingerprints from multiple molybdenums, compositions of such ions are difficult to assign—successive collision induced dissociation (CID) of large ions produced smaller ions for which calculated and experimental isotopic patterns could be compared. The oxidation state of Ce and the number of counter cations on negative complexes was discerned from spectra of ions containing 1H + and 7Li +. The overall result is an ESI method applicable to phosphomolybdate complexes containing redox sensitive f-block metal ions such as Ce(IV) and Pu(III/IV). Dissociation studies also gave insight into favored fragmentation pathways, and generated gas ions with empirical formulae similar to known condensed-phase ions. Deconvolution of concentration- and pH-dependent solution behavior via ESI/MS and 31P NMR spectroscopy showed speciation dependent on solution concentration, not on pH.

Synthesis, characterization of ceria-coated silica particles and their chemical mechanical polishing performance on glass substrate

Nano-sized ceria particles were coated on the silica surface by the precipitation method using ammonium cerium nitrate and urea as precipitant with poly(vinylpyrrolidone) (PVP) as assistant. The structures and compositions of ceria-coated silica particles were characterized using X-ray diffraction (XRD), field-emission scanning microscopy (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. The results show that nano-size ceria particles were coated uniformly around the surface of silica particles when PVP was used as assistant during coating process, while without PVP, the ceria particles were grown sparsely on the silica particle surface and many ceria particles grow up through independent nucleation in the solution. Then, the chemical mechanical polishing (CMP) behaviors of the as-prepared ceria-coated silica particles on glass substrate were investigated. The CMP test results suggest that the as-prepared ceria-coated silica particles exhibit higher removal rate than pure silica particles without deteriorating the surface quality. In addition, online coefficient of friction (COF) was conducted during the polishing process. The COF data indicate that the COF values of ceria-coated silica particles are larger than those of pure silica particles due to their surface properties.

Development and validation of fixed‐time method for the determination of isoxsuprine hydrochloride in commercial dosages forms

The main aim of this work was to develop a kinetic spectrophotometric method for the quantitative analysis of isoxsuprine hydrochloride in commercial tablets. The method is based on the reaction of isoxsuprine hydrochloride (ISx) with hydroxylamine hydrochloride and ammonium cerium (IV) nitrate in sulphuric acid medium at room temperature which resulted in the formation of yellow-coloured product peaking at 380 nm. The reaction is followed spectrophotometrically by measuring the absorbance as a function of time. Fixed time method (ΔA = A₄-A₂, where A₂ and A₄ refer to absorbance measurements taken at 2 and 4 min, respectively) was adopted for constructing the calibration curve which was found to be linear over the concentration range of 30-80 µgmL⁻¹ with molar absorptivity of 5.95 × 10³ L mol⁻¹ cm⁻¹. The method has been applied successfully to the determination of isoxsuprine hydrochloride in tablets. Statistical comparison (point and interval hypothesis tests) of the results showed that there is no significant difference between the proposed method and reference method.

ChemInform Abstract: Cerium(IV) Ammonium Nitrate Promoted Oxidative Cyclization of Dimethyl 4-Pentenylmalonate.

ChemInform Abstract: Cerium(IV) Ammonium Nitrate Promoted Oxidative Cyclization of Dimethyl 4-Pentenylmalonate.

Characterization and synthesis of Ce-incorporated mesoporous molecular sieves under microwave irradiation condition

Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized by microwave irradiation method from sodium silicate and ammonium cerium (IV) nitrate precursors and using cetyltrimethyl ammonium bromide (CTAB) as template. The resulting samples were characterized by means of XRD, TEM, FT-IR, UV-Vis, XPS and N2 physical adsorption, respectively. The effect of the Si/Ce molar ratio on the textural properties of CeMCM-41 was investigated. The results reveal that the CeMCM-41 was successfully synthesized. The resultant mesoporous materials have specific surface areas in the range of 602–1,216 m2/g and pore sizes in the range of ca. 2.6–2.9 nm. The structural properties are related to the amount of cerium incorporation. The surface area and pore volume of the resulting CeMCM-41 were gradually reduced as the cerium content in the sample increased, and the mesoporous ordering diminished.

ChemInform Abstract: A Chiral, Oxidatively Cleavable Auxiliary in Conjugate Additions of Lithium Amides. Preparation of Enantiomerically Pure β-Amino Acid Derivatives.

Abstract Addition of enantiomerically pure 4-methoxyphenethyl-substituted lithium amides to α,β-unsaturated esters leads to β-amino acid derivatives 4-7 with selectivities > 95: 5. The auxiliary can be cleaved by oxidation with cerium(IV) ammonium nitrate (CAN) and subsequent hydrolysis of the resulting mixture of imines.

ChemInform Abstract: Synthesis of a New Class of C2‐Symmetrical Biheteroaryls by Ammonium Cerium(IV) Nitrate Mediated Dimerization of 2‐(Furan‐3‐yl)pyrroles.

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