Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

Abstract

In the present study, monodispersed CeO2 nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.

Molecular dynamics simulations of the effect of shape and size of SiO2 nanoparticle dopants on insulation paper cellulose

“…[1][2][3][4] In recent years, molecular dynamics simulations have been used to investigate the properties of polymers doped and modified by nanoparticles. [5][6][7][8][9][10][11][12][13] Simulations have demonstrated improvements in the mechanical properties of modified polymer materials, with the incorporation of smaller nanoparticles tending to yield larger increases in the Young's modulus.…”

Dual-Site Cooperation for High Benzyl Alcohol Oxidation Activity of MnO2 in Biphasic MnOx–CeO2 Catalyst Using Aerial O2 in the Vapor Phase

“…The broadening of the peaks with a gradual decrease in the intensity indicates a decrease of the crystallite size for CeO 2 and MnO 2 in the MnO x –CeO 2 catalyst with increasing MnO x content. Raman peak broadening has been previously noted to be due to the smaller crystallite size of CeO 2 . On the other hand, vibrational peaks at 570 and 627 cm –1 (A g symmetry) related to Mn–O symmetric vibrations and a peak at 182 cm –1 related to MnO 6 octahedra translation motion correspond to α-MnO 2 (space group I 4/ m ) phase. , The MnO 2 -related peaks are broad and indicate a highly nanocrystalline nature of the oxide.…”

“…Raman peak broadening has been previously noted to be due to the smaller crystallite size of CeO 2 . 64 On the other hand, vibrational peaks at 570 and 627 cm −1 (A g symmetry) related to Mn−O symmetric vibrations and a peak at 182 cm −1 related to MnO 6 octahedra translation motion correspond to α-MnO 2 (space group I4/m) phase. 65,66 The MnO 2 -related peaks are broad and indicate a highly nanocrystalline nature of the oxide.…”

Entangled spintronic modulated high‐performance Ce 2 O 3 small polaron surface state‐based water splitting cells

“…32 In such many kinds of metal-oxide-semiconductor materials, cerium oxide nanoparticles have been found as the semiconductor material with high application potential in spintronic devices. 33 Since the stable oxygen vacancies are generated in the cerium oxide matrix, 34 the oxidation states of Ce +4 and Ce +3 form permanent redox reactions as polaron which raises the charge mobility 35 and be utilized to spintronic excitation. CeO 2-x NPs thin films showed a similar mechanism with Zhang-Rice by unpaired electron occupied small polaron surface state.…”

“…From reference, d orbital of Ni ions demonstrated the unpaired electron which is the Zhang‐Rice singlet 31 for excited spintronic by absorbing the angular momentum, spin, and orbital quantum information of polarized incident light 32 . In such many kinds of metal‐oxide‐semiconductor materials, cerium oxide nanoparticles have been found as the semiconductor material with high application potential in spintronic devices 33 . Since the stable oxygen vacancies are generated in the cerium oxide matrix, 34 the oxidation states of Ce +4 and Ce +3 form permanent redox reactions as polaron which raises the charge mobility 35 and be utilized to spintronic excitation.…”