Free and partially encapsulated manganese ferrite nanoparticles in multiwall carbon nanotubes

Abstract

Free and partially encapsulated manganese ferrite (MnFe2O4) nanoparticles are synthesized and characterized regarding structure, surface, and electronic and magnetic properties. The preparation method of partially encapsulated manganese ferrite enables the formation of a hybrid nanoparticle/tube system, which exhibits properties of manganese ferrite nanoparticles inside and attached to the external surface of the tubes. The effect of having manganese ferrite nanoparticles inside the tubes is observed as a shift in the X-ray diffraction peaks and as an increase in stress, hyperfine field, and coercivity when compared to free manganese ferrite nanoparticles. On the other hand, a strong charge transfer from the multiwall carbon nanotubes is attributed to the attachment of manganese ferrite nanoparticles outside the tubes, which is detected by a significant decrease in the σ band emission of the ultraviolet photoemission spectroscopy signal. This is followed by an increase in the density of states at the Fermi level of the attached manganese ferrite nanoparticles in comparison to free manganese ferrite nanoparticles, which leads to an enhancement of the metallic properties.

Effect of Transition Metals (Mn, Co, Ni, and Zn) in Size-Controlled Metal Ferrite Nanocrystals on the Electrocatalytic Oxygen Evolution Reaction

“…The surface electronic structure and elemental valence in the samples MnFO, CoFO, NiFO, and ZnFO NCs were characterized using XPS analysis (Figure ). The deconvoluted peaks of MnFO, for the Mn 2p 3/2 and Mn 2p 1/2 spectra, were well-fitted into four peaks, located at 640.04, 641.35, 650.254, and 651.995 eV, respectively, attributed to Mn 2+ (Figure a) . In Figure b, the Fe 2p 3/2 and Fe 2p 1/2 prominent peaks were assigned to Fe 3+ at 710.35 and 724.05 eV, with satellite peaks at 717.45, 719.05, 731.9, and 733.3 eV .…”

“…The deconvoluted peaks of MnFO, for the Mn 2p 3/2 and Mn 2p 1/2 spectra, were well-fitted into four peaks, located at 640.04, 641.35, 650.254, and 651.995 eV, respectively, attributed to Mn 2+ (Figure 4a). 26 In Figure 4b, the Fe 2p 3/2 and Fe 2p 1/2 prominent peaks were assigned to Fe 3+ at 710.35 and 724.05 eV, with satellite peaks at 717.45, 719.05, 731.9, and 733.3 eV. 15 Similarly, in the case of CoFO, the Co 2p 3/2 spectra were fitted into two peaks at 780.78 and 783.98 eV, attributed to Co 2+ ions present in octahedral (B-site) and tetrahedral (A-site) sites of the spinel structure, respectively, 15 with additional satellite peaks appearing at 787.88 and 790.58 eV.…”