Magnetic composites based on hybrid spheres of aluminum oxide and superparamagnetic nanoparticles of iron oxides

Abstract

a b s t r a c tMaterials containing hybrid spheres of aluminum oxide and superparamagnetic nanoparticles of iron oxides were obtained from a chemical precursor prepared by admixing chitosan and iron and aluminum hydroxides. The oxides were first characterized with scanning electron microscopy, X-ray diffraction, and Mössbauer spectroscopy. Scanning electron microscopy micrographs showed the size distribution of the resulting spheres to be highly homogeneous. The occurrence of nano-composites containing aluminum oxides and iron oxides was confirmed from powder X-ray diffraction patterns; except for the sample with no aluminum, the superparamagnetic relaxation due to iron oxide particles were observed from Mössbauer spectra obtained at 298 and 110 K; the onset six line-spectrum collected at 20 K indicates a magnetic ordering related to the blocking relaxation effect for significant portion of small spheres in the sample with a molar ratio Al:Fe of 2:1.

Magneto-sensitive hybrid nanocomposites of water-soluble sodium alginate cross-linked with calcium ions and maghemite

“…FeO-Fe 2 O 3 and/or maghemite Fe 2 O 3 . By using the Scherrer equation [44] an average size of crystallites was estimated as 9±1 nm that was in excellent agreement with the TEM data.…”

Synthesis of copper on iron/aluminum oxide mesoporous spheres and application on denitrification reaction

“…This result was similar to the different supports (10FeAl, 30FeAl, 50FeAl) and the Mössbauer spectra for the 50FeAl sample taken at low temperatures confirm its superparamagnetic state [44], indicating that the incorporation of copper oxide in the composition of the solid did not change the superparamagnetic properties of the material.…”

“…TEM images indicate the presence of a heterogeneous material which is consistent with the method of preparation for the copper-based sample (wet impregnation), whereas the metal is randomly deposited on the support containing aluminum and iron oxide synthesized by hybrid spheres route, thus, generating particles of different sizes [44]. These results corroborate with the X-ray diffraction profiles, which point to the presence of nanoparticles in the solids, Fig.…”

“…It was detected an increase of the quadrupole shift (QS) parameter (0.94 ± 0.05 mm s À1 ) for the Cu50FeAl sample compared to the support 50FeAl (0.91 mm s À1 ) [44], suggesting an increase in the superparamagnetic fraction of the material. These results corroborate previous research [45,46], which indicate that metals such as nickel and copper potentiate magnetic properties of the iron oxide.…”

Magnetic Nanosystem for Cancer Therapy Using Oncocalyxone A, an Antitomour Secondary Metabolite Isolated from a Brazilian Plant

“…The diffraction patterns showed that the main reflection peaks at {111}, {220}, {311}, {400}, {422}, {511}, {440}, {533} and {553} can be well indexed with the reference pattern of the Fe 3 O 4 inverse cubic spinel structure (JCPDS card # 08-4611) with spatial group Fd3M. The crystal size calculated by using the Scherrer’s equation [23] showed a magnetite nanoparticle average size of about 11 nm.…”