CeO2 nanoparticles synthesized by a microwave-assisted hydrothermal method: evolution from nanospheres to nanorods

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis of PTSH-modified CeO2 nanoparticles: Effect of the modifier on structure, optical properties, and dispersibility

CeO2 nanoparticles were synthesized by the precipitation method and modified with para-toluene sulfonic acid (PTSH), either in situ or post-synthesis. The presence of PTSH in the samples was confirmed by FTIR. PXRD and FTIR analyses showed that the post-synthesis PTSH modification altered the CeO2 structure, whereas the in situ modification maintained intact the crystalline structure and UV-vis absorbance properties. For both in situ and post-synthesis modifications, TEM images revealed the presence of nanoparticles that were 5nm in size. The dispersibility of the in situ PTSH-modified material in a hydrophilic ureasil-poly(ethylene oxide) matrix was investigated using SAXS measurements, which indicated that CeO2 nanoparticles modified with PTSH in situ were less aggregated within the matrix, compared to unmodified CeO2 nanoparticles. © 2013 Elsevier B.V.

Influence of solvent on the morphology and photocatalytic properties of ZnS decorated CeO2 nanoparticles

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of soaking time on the photoluminescence properties of cerium oxide nanoparticles

The structural and photoluminescence properties at room temperature of CeO2 nanoparticles synthesized by a microwave-assisted hydrothermal method (MAH) under different soaking times on KOH mineralizer added to a cerium ammonium nitrate aqueous solution were undertaken. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.

Photoluminescence properties of praseodymium doped cerium oxide nanoparticles

The structural and photoluminescent properties at room temperature of CeO2 nanoparticles synthesized by a Microwave-Assisted Hydrothermal Method (MAH) under different praseodymium contents was undertaken. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), UV-vis Spectroscopy (UV-vis), Fourier Transform Raman (FT-Raman) and Photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure while FT-Raman revealed a typical scattering mode of fluorite type. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.

Estudo das propriedades óticas e fotoluminescentes das nanopartículas do CeO2 modificadas com La pelo método hidrotermal assistido por microondas

Pós-graduação em Engenharia Mecânica - FEG

Preparation and characterization of ceria nanospheres by microwave-hydrothermal method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of mineralizer agents on the growth of crystalline CeO 2 nanospheres by the microwave-hydrothermal method

Cystalline ceria (CeO2) nanoparticles have been synthesized by a simple and fast microwave-assisted hydrothermal (MAH) under NaOH, KOH, and NH4OH mineralizers added to a cerium ammonium nitrate aqueous solution. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed-IR and Raman spectroscopies. Rietveld refinement reveals a cubic structure with a space group Fm3m while infrared data showed few traces of nitrates. Field emission scanning microcopy (FEG-SEM) revealed a homogeneous size distribution of nanometric CeO2 nanoparticles. The MAH process in KOH and NaOH showed most effective to dehydrate the adsorbed water and decrease the hydrogen bonding effect leaving a weakly agglomerated powder of hydrated ceria. TEM micrographs of CeO2 synthesized under MAH conditions reveal particles well-dispersed and homogeneously distributed. The MAH enabled cerium oxide to be synthesized at 100 °C for 8 min. © 2012 Elsevier B.V. All rights reserved.

Microstructural and morphological analysis of pure and Ce-doped tin dioxide nanoparticles

Structural morphological studies in pure and Ce-doped tin dioxide nanoparticles with high stability against particle growth were performed in samples, obtained using the polymeric precursor method and prepared at different annealing temperatures. A Ce-rich surface layer was used to control the particle size and stabilize SnO2 against particle growth. The formation of this segregated layer can contribute to a decreased surface energy, acting in the driving force, or reducing the surface mobility. Only the cassiterite SnO2 phase was observed below 1000 degreesC and a secondary phase (CeO2) was observed for the Ce-doped SnO2 at temperatures higher than 1000 degreesC, when de-mixing process occurs. The evolution of crystallite size, microstrain and morphology of the nanoparticles with annealing temperatures was investigated by X-ray diffraction (XRD), associated to Rietveld refinements, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Influence of the preparation method and the support on H2O 2electrogeneration using cerium oxide nanoparticles

This work describes the influence of the preparation method and the carbon support using a low contentof cerium oxide nanoparticles (CeO2/C 4%) on H2O2electrogeneration via the oxygen reduction reac-tion (ORR). For this purpose, the polymeric precursor (PPM) and sol-gel (SGM) methods with Vulcan XC72R (V) and Printex L6 (P) supports were employed. The materials were characterized by X-ray diffrac-tion (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TheXRD analysis identified two phases comprising CeO2and CeO 2-x. The smallest mean crystallite size wasexhibited for the 4% CeO2/C PPM P material, which was estimated using the Debye-Scherrer equation tobe 6 nm and 4 nm for the CeO2and the CeO 2-xphases, respectively, and was determined by TEM to be5.9 nm. XPS analysis was utilized to compare the oxygen content of the 4% CeO2/C PPM P to Printex L6.The electrochemical analysis was accomplished using a rotating ring-disk electrode. The results showedthat the 4% CeO2/C specimen, prepared by PPM and supported on Printex L6, was the best electrocatalystfor H2O2production in 1 mol L -1NaOH. This material showed the highest ring current, producing 88%H2O2and transferring 2.2 electrons per O 2molecule via the ORR at the lowest onset potential. Addition-ally, the ring-current of the 4% CeO2/C PPM P material was higher than that of Vulcan XC 72R and PrintexL6, the reference materials for H2O 2production, indicating the highest electrocatalytic activity for the 4%CeO2/C PPM P material. © 2013 Elsevier Ltd. All rights reserved.

Nanopartículas de CeO2 modificadas com Er obtidas pelo método hidrotermal microondas: estudo fotoluminescente

The development of nanostructured materials have aroused great interest of the industries all over the country, since they enable the development of devices that can be used as gate insulators on silicon transistors, electrochromic devices, solid electrolyte oxygen sensors and as a photoluminescent materials . In this project, it is proposed to investigate the optical properties of CeO2 modified with rare earth Er processed in hydrothermal-microwave. The synthesis of one-dimensional nanostructures (1D) was measured from dilute aqueous solutions of acids and salts of starting reagents in the presence of chemical basis, after these aqueous solutions were processed on hydrothermal-microwave to particle growth. The particles obtained after processing were characterized by X-ray Diffraction, Rietveld Analysis and Raman Spectroscopy. The particle morphology was observed by scanning electron microscopy with field emission gun. The synthesis of 1D nanostructures are evaluated for different surfactants and starting precursors (ceria different salts), pH, temperature and pressure which can modify the morphology of the nanostructures. Combining laboratory experiments and theoretical calculations it was desired to understand the organization of the nanoparticles and their resulting structure. Strict control of chemical homogeneity, crystal structure, microstructure and interaction of the CeO2 cluster with different surfactants using the Hartree-Fock method, was intended to obtain properties compatible with their use in catalysts and optical devices. The use of mineralizer agent KOH and 8 minutes of processing time synthesis conditions were chosen to evaluate the effect of Er dopant. It has been proved that this doping with rare earth increases the photoluminescent properties of the compound obtained without change the structural and morphological propreties of ceria

Estudo e desenvolvimento de filmes espessos de CeO2 obtidos por tape casting

Tape Casting proved to be an effective method for the production of thick films of CeO2 pure and doped with La. For this study, the nanoparticles used to form the slurry were synthesizes by the H-M method, at 100°C for 8 minutes, using KOH mineralizer. The slurry was made in aqueous solvent, requiring optimal control of surroundings conditions so that the produced tape has conditions to be studied. However, there's no toxicity or flammability in the film made by such solvent, being pleasing to the environment. The structural, optical and electrical properties of the films obtained by the Tape Casting process were studied by the methods of X-ray diffraction, scanning electron microscopy, specific surface area, Ultraviolet-visible spectroscopy and voltage-current measures, varying the electric field and frequency. From the results obtained by laboratory experiments, based on the literature, it was possible to reveal and understand some CeO2 features pure and doped with La

Evaluation of the Genotoxicity of Chitosan Nanoparticles for Use in Food Packaging Films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dynamics and Heterogeneity of Pb(II) Binding by SiO2 Nanoparticles in an Aqueous Dispersion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Polymeric alginate nanoparticles containing the local anesthetic bupivacaine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)