Synthesis of Ceria Nanoparticles With Controlled Morphology (original) (raw)
Related papers
Journal of Colloid and Interface Science, 2006
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.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
Given the scientific and technological interest in cerium oxide (ceria), in this paper nanoparticles of ceria (ceria-NPs) were synthesized using a modified polymer complex process (modified Pechini), while varying the pH of the system. This methodology made it possible to obtain, in a reproducible and controlled way, nanoparticles of ceria (<100nm) of a high chemical purity at low temperatures. The precalcined cerium solid obtained at 350°C was characterized using differential thermal analysis (DTA), thermogravimetric analysis (TG) and IR spectroscopy. Very little organic phase was found in the respective spectra, indicating that the inorganic phase, cerium oxide, is predominant. Carbonaceous residues still present in the solids were removed by heating at temperatures above 500°C and the samples obtained were characterized using X-ray diffraction (XRD), IR, UV-visible absorption and diffuse reflectance spectroscopies, and Transmission Electron Microscopy (TEM). The diffractograms of the samples showed that the only crystalline phase present was CeO2. From the results of UV-vis absorption and diffuse reflectance spectroscopy, two important energy values were obtained, 3.8 eV and 3.4 eV. These could be attributed to the energy gap value (3.8 eV) and to a possible "mid-gap" (3.4 eV). Furthermore, on increasing the synthesis pH, a reduction in particle size results, the particle being between 10 and 20 nm, with a spheroidal shape. By looking at the different stages of the synthesis process, a mechanism is proposed to explain how nanoparticles of ceria are formed.
Physical Chemistry Chemical Physics, 2011
Experimental details Characterization. Particle size and morphology were investigated by High Resolution Transmission Electron Microscopy (HRTEM). The sample was prepared as follows: 0.5 mg of ceria powder were suspended in isopropanol (2 ml) and sonicated. For analysis a drop of this dispersion was deposited onto a holey formvar/carbon copper grid. Observation was carried out using a Field Emission Transmission Elentron Microscope, JEM-2200FS, 200 kV, with 0.19 nm resolution in TEM mode and 0.1 nm resolution in STEM mode and spheric abberration correction in STEM mode. Surface area and pore analysis were carried out at liquid nitrogen temperature with a Micromeritics ASAP 2020 Surface area and Porosity Analyzer. Before analysis the samples were outgassed at 150 o C for 12 h. Powder X-ray diffraction (XRD) patterns were recorded on a Schimadzu XRD-7000 diffractometer using Cu Kα radiation (λ = 1.5418 Å, 40 kV, 40 mA) at a scanning speed of 0.10 degrees min-1 in the 6-60 degrees 2Θ range inside an in-situ cell accessory. In situ calcination of the samples was carried out using the same apparatus in the 50-1000 o C temperature range. DR-UV-Vis spectra were recorded at room temperature on a Analytik Jena Specord 250 spectrophotometer with an integrating sphere for reflectance measurements and Spectralon as the reflectance standard. DR-UV-Vis spectra of the catalysts were recorded in reflectance units and were transformed in Kubelka-Munk remission function F(R). Fourier transform infrared (FTIR) spectra were measured with a Thermo Electron Nicolet 4700 FTIR spectrometer with a Smart Accessory for diffuse reflectance measurements. The IR spectra were scanned in the region of 4000-400 cm‾ 1 at the resolution of 4 cm‾ 1. The final spectra are an accumulation of 200 scans. Raman analysis was carried out with a Horiba Jobin Yvon-Labram HR UV-Visible-NIR Raman Microscope Spectrometer, with a DL 785-100 laser at 633, 514 and 488 nm and a catalytic cell for sample heating. In-situ measurements were carried out in the range 50-550 o C by heating the samples with a rate of 10 o C/min and keeping a plateau of 10 minutes for collecting the spectra. X-ray photoelectron spectra (XPS) was measured in a Specs setup operating at a base pressure of low 10-10 mbar. Samples are constituted from powders dispersed onto carbon tapes. A flood gun operating at 1 eV energy and 0.1 mA electron current was used to ensure sample neutralization. XPS spectra were recorded by using unmonochromatized Mg K radiation (h = 1253.6 eV) and a Phoibos hemispherical energy analyzer of 150 mm radius operating at 30 eV pass energy for individual electron distribution curves (EDCs). Within these conditions, previous calibrations have shown an overall full width at half maximum (FWHM) of Ag 3d 5/2 lines of 1.37 eV. Photoluminescence measurements. The photoluminescence (PL) measurements were carried out using a Fluoromax 4 spectrofluorometer (Horiba) operated in both the fluorescence and the phosphorescence mode. The repetition rate of the xenon flash lamp was 25 Hz, the integration window varied between 300 ms and 3 s, the delay after flash varied between 0.03 and 10 ms, and up to 100 flashes were accumulated per data point. The slits were varied from 0.001 nm to 10 nm in excitation as well as emission. PL decays were measured by using the "decay by delay" feature of the phosphorescence mode. Time resolved emission spectra (TRES) were recorded at room temperature using a wavelength tunable Nd:YAG-laser/OPO system (Spectra Physics/GWU) operated at 20 Hz as excitation light source and an intensified CCD camera (Andor Technology) coupled to a spectrograph (MS257
RASAYAN Journal of Chemistry
In this study, ceria nanoparticles were synthesized via one of the simplest methods, which is the precipitation method. The effects of three different ethanol/DI water ratios (i.e. 1:1; 1:4; 0:1) and post-heat treatments (i.e. drying only and drying + calcination) on the crystal structure and morphology of the ceria nanoparticles have been investigated. The characterization of the ceria nanoparticles was conducted using X-Ray Diffractometer (XRD) for the crystal structure and Transmission Electron Microscopy (TEM) for the morphology. From XRD analysis results, the comparison of the highest XRD intensity peaks (at 2θ = 28.6°) of the ceria nanoparticles samples showed that all the ceria nanoparticles samples with drying + calcination treatment were higher than the ones with drying treatment only. Additionally, the XRD peaks were analyzed using a well-known Scherrer’s equation to determine the average crystallite size of the ceria nanoparticles. It was found that the ceria nanoparticle...
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.