Synthesis of Ceria Nanoparticles With Controlled Morphology (original) (raw)
Nanoceria prepared by electron beam evaporation
NANOCOM ..., 2022
Cerium oxide nanoparticles (nanoceria) are currently one of the most investigated nanomaterials because of their attractive properties used in biomedical applications, catalysis, fuel cells, and many others. These attractive properties are connected with the Ce 3+ and Ce 4+ valency state ratio. In the nanoparticle form, cerium oxides contain a mixture of Ce 3+ and Ce 4+ on the nanoparticle surfaces. Switching between these two states requires oxygen vacancies. Therefore, nanoceria's inherent ability to act as an antioxidant in an environmentally-dependent manner and a "redox switch" to confer auto-regenerating capabilities by automatically shifting between Ce 4+ and Ce 3+ oxidation states is significantly affected by surface morphology. Regarding this demanded behavior, we aimed to characterize synthesized nanoparticle surface quality and its influence on the cerium oxidation states. The received results were used to evaluate the synthesis method's suitability for suggested utilization. We used nanoparticles prepared by electron beam evaporation. This unique physical method includes nanoparticle creation through the fast cooling process followed by breaking radiation damaging nanoparticle surfaces to create surface off-stoichiometry. We prepared a sample containing clusters of a mixture of ultrasmall nanoparticles and approximately 100 nm particles. X-ray diffraction confirmed the CeO2 phase in both components. To extract the finest component, we used centrifugal size fractionation. We received 200 nm clusters of 2-10 nm nanoparticles. Nanoparticle shapes and facet types were analyzed using transmission electron microscopy methods. We found out most nanoparticles were formed with truncated octahedrons containing {1,1,1} and {1,0,0} facet types and truncated cuboctahedrons containing {1,1,1}, {1,0,0}, and additional {1,1,0} facets. No octahedron (without truncation) containing only {1,1,1} facets was observed. Nanoparticle shapes containing {1,1,0} and {1,0,0} are suitable for redox activity. Some amount of irregular shapes, beneficial for redox activity, was also observed. Spectroscopy methods confirmed Ce 3+ content.
Microemulsion route to the synthesis of nanoparticles
Pure and Applied Chemistry, 2008
Nanoparticles of several titanates and zirconates in the range of 20-60 nm have been obtained using the reverse micellar route. Important oxides like CeO 2 (mixture of nanorods; 7 nm diameter and 30 nm length and nanoparticles; 10 nm), ZrO 2 (3-4 nm) and SnO 2 (8 nm) have also been synthesized. Nanorods and nanoparticles of CaCO 3 in all three forms (aragonite, vaterite, and calcite) have been obtained using reverse micelles as nanoreactors. The specific reactions vary depending on the nature of the target nanomaterial. For synthesis of ternary oxides like BaTiO 3 , a modified and convenient route using microemulsions (avoiding Ba-alkoxide) has evolved. Monophasic tin dioxide (SnO 2 ) was obtained when liquid NH 3 was used as precipitating agent. Transmission electron microscopy (TEM) studies show that the SnO 2 nanoparticles are highly uniform and particle size was found to be 6-8 nm at 500 °C. The gas sensing characteristics of SnO 2 have also been investigated using n-butane, which shows high sensitivity and fast recovery time. Reverse micelles have been used, for the first time, to mimic the conditions suitable for the room-temperature synthesis of the high-temperature and -pressure orthorhombic phase of calcium carbonate (aragonite). Other forms of calcium carbonate (vaterite and calcite) could be obtained by varying the atmospheric conditions. At a lower temperature (5°C), homogeneous and monodisperse spheres of vaterite are obtained. The spherical particles aggregate after longer aging (168 h) to form nanorods, and the self-assembly is clearly seen at various stages by electron microscopy images. The samples were well characterized using powder X-ray diffraction (PXRD), line-broadening studies, TEM, variation in the dielectric properties with frequency and temperature, were measured on disks sintered at high temperature.
Adsorption, 2005
New nanoporous resin (NPR), based on organic xerogel compounds, was prepared at 150 W C by sol-gel method from pyrogallol and formaldehyde mixtures in water using perchloric acid as catalyst. NPR was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and nitrogen porosimetry. The metal uptake characteristics were explored using well-established and effective parameters including pH, contact time, initial metal ion concentration and temperature. Optimum adsorptions of Cr(VI) and Cd(II) were observed at pH 3 and 4, respectively. Langmuir model gave the better fit for Cd(II) whereas for Cr(VI), Freundlich model was better than the other models to fit the experimental data. Kinetic studies revealed that the adsorption of Cd(II) was very fast compared to Cr(VI), and its data are well fitted by the pseudo-second-order kinetic model. The thermodynamic properties, i.e. ΔG W , ΔH W and ΔS W , showed that adsorption of Cr(VI) and Cd(II) onto NPR was endothermic, spontaneous and feasible in the temperature range of 27-55 W C.
Microwave-assisted synthesis of ceria nanoparticles
Materials Research Bulletin, 2005
Cuprous oxide (Cu 2 O) nano-crystallites with different sizes were prepared via electrolysis method and characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM). Its photo-catalytic activities in the degradation of methyl orange as the model pollutant using UV light as an energy source were investigated. The XRD patterns showed that the sizes of Cu 2 O nano-crystallite decreased with the increasement of cetyltrimethyl ammonium bromide (CTAB) being added into the electrolyte, which were ranging from 27 nm to 48 nm. The progress of photocatalytic degradation of the methyl orange was observed by monitoring the concentration change of the methyl orange solution. The highest decolorization ratio of 90% was observed for the sample prepared by addition of 0.05 g/L CTAB after photo-degradating 50 mg/L of methyl orange solution for 70 min. The mechanism of photo-degradation was discussed.
Synthesis of nanocrystalline ceria by thermal decomposition and soft-chemistry methods
Scripta Materialia, 2004
Nanocrystalline ceria synthesized by different methods have been characterized using TGA-EGA-MS, XRD and HR-TEM. All samples showed stable cubic fluorite structure down to 6 nm particle size. A reduction in lattice parameter with particle size was observed. Effects of synthesis conditions on nano-ceria and grain growth with annealing temperature are discussed.
A surfactant-stabilized microemulsion method was used to prepare nano-sized particles (<10 nm) of cubic-CeO 2 exposing surfaces of not only highest specific areas (142-201 m 2 /g) ever reported for polycrystalline ceria, but also high thermal stability at 800 • C. Three different surfactants, a non-ionic, an anionic and a cationic, were used to form the microemulsions. Then, N 2 sorptiometry and pore volume distribution calculations, were used to reveal microporous and mesoporous structures of these cerias as a function of surfactant type. Transmission electron microscopy was used to visualize consequent particle behaviors. Suggestions have been made as to the textural attributes of the high surface area and thermal stability. Accordingly, cationic surfactants, in the presence or absence of added non-ionic surfactant, are seen to assist in producing cerias of promising surface textural properties for the chemical makeup of combustion catalysts.
Ceria Nanoparticles Synthesized by a Polymer Precursor Method
We report a novel synthesis technique of ceria nanoparticles by a sol-gel type chemical process using poly-vinyl alcohol (PVA) as a capping as well as a reducing agent. The as-synthesized CeO2 nanoparticles were characterized by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The XRD analysis reveals the fluorite type face centered cubic structure in the ceria nanoparticles with an average crystallite size of 6 nm and 9 nm for the samples calcined at 350°C and 400°C, respectively.
Materials Chemistry and Physics, 2012
h i g h l i g h t s < Ce 0.95 Zr 0.05 O 2 nanopowders synthesized by solegel and template methods. < Influence of the synthesis method on structural and microstructural features. < Analysis of the thermoluminescence response. < Study of application on dosimetry field. a b s t r a c t Ce 0.95 Zr 0.05 O 2 nanopowders have been prepared by a standard Pechini-type solegel process and by using polymethyl methacrylate (PMMA) colloidal crystals as template. The effects of these different synthesis routes, on the structure and microstructural features of the nanopowders, were evaluated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area measurements. For both preparation routes, the XRD analysis has shown that a cubic fluorite structure is formed with a crystallite size of w45e50 nm. The SEM images indicate that the powder obtained by the solegel Pechini-type process, is constituted by aggregated nanoparticles with relatively uniform shape and size, whereas the powder synthesized as inverse opal exhibits the formation of macropores with a mean size of w130 nm. The specific surface areas of the powder samples obtained by the Pechini-type solegel and inverse opal methods are w56 m 2 g À1 and w90 m 2 g À1 respectively. Additionally, the thermoluminescence (TL) signal of the synthetized samples has been measured in order to examine its potential application in the field of dosimetry of ionizing radiations.
2010-JAC-Characterization of nanometric multidoped ceria powders.pdf
The ceria solid solutions doped with rare earth cations were synthesized by two methods and the microstructural and morphological characterization of powders was performed. The results obtained by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) method and Raman spectroscopy were studied and discussed. The results showed that finer powders have not only higher specific surface area, smaller particles and crystallite sizes, but also larger lattice parameters in the case of both single and multidoped solid solutions.