CeO₂nanoparticles synthesized by a microwave-assisted hydrothermal method: evolution from nanospheres to nanorods

Abstract

Ceria (CeO 2 ) plays a vital role in emerging technologies for environmental and energy-related applications. The catalytic efficiency of ceria nanoparticles depends on its morphology. In this study, CeO 2 nanoparticles were synthesized by a microwave-assisted hydrothermal method under different synthesis temperatures. The samples were characterized by X-ray diffraction, transmission electron microscopy, Raman scattering spectroscopy, electron paramagnetic resonance spectroscopy and by the Brunauer-Emmett-Teller method. The X-ray diffraction and Raman scattering results indicated that all the synthesized samples had a pure cubic CeO 2 structure. Rietveld analysis and Raman scattering also revealed the presence of structural defects due to an associated reduction in the valence of the Ce 4+ ions to Ce 3+ ions caused by an increasing molar fraction of oxygen vacancies. The morphology of the samples was controlled by varying the synthesis temperature. The TEM images show that samples synthesized at 80 C consisted of spherical particles of about 5 nm, while those synthesized at 120 C presented a mix of spherical and rod-like nanoparticles and the sample synthesized at 160 C consisted of nanorods with 10 nm average diameter and 70 nm length. The microwave-assisted method proved to be highly efficient for the synthesis of CeO 2 nanoparticles with different morphologies.

Raman and Fluorescence Spectroscopy of CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7

“…CeO 2 has the fluorite type cubic crystal structure that exhibits only one allowed Raman mode, T 2 g. It emanates from the Ce-O-Ce symmetric vibration [4,14]. In the present study, the Raman spectra from 442 nm, 514 nm, and 633 nm excitation were consistent, having a single Raman band observed at a shift of 465 cm −1 ( Figure 1).…”

“…Denning and Ross proposed that a number of factors contribute to changes of the Raman band position including phonon confinement, strain, particle size effect, and defects [16]. Raman band shifts caused by differences in particle sizes have been reported by a number of authors [5,14,19]. Differences in particle size have led to variation in phonon relaxation and thus caused band position shifts in the lattice area of the spectra [19].…”

Low-defect CeO2 films synthesis by combined spray pyrolysis using different precursors

“…In addition, the small deviations of their peak positions when compared to the 466 cm À1 value reported for single crystals may also be an assessment of film quality. The red shift of the Raman modes can be explained by the decrease in the film crystallite size, which shifts the peak position to lower energies at the same time that leads to an increase on the line width of the mode [12,13,35,36]. Also in agreement with the XRD data, the stronger intensity of the F 2g peak for CCp sample would indicate a better crystallinity for the films submitted to addition of precursor powder during thermal annealing.…”

Microwave-assisted hydrothermal synthesis of magnetite nanoparticles with potential use as anode in lithium ion batteries

“…extensively used for the preparation of pure phase of several material with different applications such as, copper oxide (CuO) 17,18 , zinc oxide (ZnO) [19][20][21] hafnium oxide (HfO 2 ) 22 and cerium oxide (CeO 2 ) 23,24 . In this paper, we report a simple strategy to synthesize magnetite nanoparticles (Fe 3 O 4 ) by microwave hydrothermal method in a short time of processing without further treatment.…”