Papers by Keyword: γ-Fe₂O₃

Abstract: Apatite Nucleus (AN) was attached on the surfaces of maghemite (γ-Fe₂O₃) particles and soaked them in SBF. By this treatment, formation of bonelike apatite was induced by AN and the apatite covered the whole surface of the γ-Fe₂O₃ particles. Urease was immobilized on the surfaces of microcapsules and collected by a neodymium magnet. The immobilized urease has an ability of a urea decomposition in an aqueous solution.

Abstract: During the synthesis of γ-Fe₂O₃ nanoparticles by a chemically-induced transition method in FeCl₂ solution, Cu modification was attempted by adding CuCl/NaOH or CuCl₂/NaOH to the solution. The as-prepared products were characterized using VSM, TEM, EDS, XRD, and XPS. When adding a NaOH solution with a certain concentration, the components of the as-prepared products changed in relation to the copper salt used. When CuCl 2.5 × 10^-3 M was used, γ-Fe₂O₃/CuFeO₂ composite nanoparticles coated by FeCl₃·6H₂O and with an average size of 11.47 nm were formed. When the CuCl concentration increased to 5 × 10^-2 M, a mixture of γ-Fe₂O₃/CuFeO₂ and Cu (OH)Cl nanoparticles was formed. When 5 × 10^-2 M CuCl₂ was used, the final product contained γ-Fe₂O₃ nanoparticles, coated with FeCl₃·6H₂O, and Cu (OH)Cl nanoparticles. The magnetization of the as-prepared products depends on the content of the γ-Fe₂O₃ and CuFeO₂ ferrites.

Abstract: Structural, magnetic and magneto-optical properties of borate glasses co-doped with Fe and the lager radius ions are presented. Maghemite, γ-Fe₂O₃, nanoparticles arise in the glasses as a result of their thermal treatment in different regimes. Magnetization FC and ZFC temperature dependences demonstrate the superparamagnetic behavior of the particles with the blocking temperature below the room temperature. The EMR spectra measurements revealed a significant anisotropy with a large contribution of the nanoparticles’ surface anisotropy. The FR maximum centered near 700 nm is a characteristic feature of the investigated glasses.

Abstract: When pH or temperature of simulated body fluid (SBF) is raised, fine particles of calcium phosphate are precipitated. We found that this fine particle actively induces hydroxyapatite from body fluid or SBF and named the particle Apatite Nucleus (AN). In this study, we attached AN on the surface of γ-Fe₂O₃ nanoparticles and soaked them in SBF. By this treatment, hydroxyapatite was induced from AN and covered the whole surface of the γ-Fe₂O₃ nanoparticles, then hydroxyapatite microcapsule encapsulated γ-Fe₂O₃ was fabricated. We dispersed the microcapsules in urease solution, and collected the microcapsules by neodymium magnet. It was indicated that the urease was adsorbed to the hydroxyapatite microcapsules and collected by the magnetism of γ-Fe₂O₃ successfully.

Abstract: Functional ceramic nanopowders with emphasis on biomedical applications were engineered by gas-phase condensation using the CO₂ laser vaporization (LAVA) technique. Europium doped strontium aluminate nanoparticles (NP) were prepared from a SrO/α-Al₂O₃/Eu₂O₃ powder mixture. Excited with ultraviolet radiation (UV), the as-prepared amorphous NP revealed red photoluminescence emission. After annealing in reductive atmosphere crystalline SrAl₂O₄:Eu²⁺ nanopowder was obtained showing strong green emission at UV excitation. Ferrimagnetic iron oxide (Fe_xO_y) nanopowders were prepared starting from α-Fe₂O₃ powder. In oxygen-free condensation atmosphere γ-Fe₂O₃ NP were obtained. Oxygen as condensation gas yielded γ-and ε-Fe₂O₃ NP. Superparamagnetic NP were prepared starting from α-Fe₂O₃/SiO₂ mixtures. Depending on the mixing ratio γ-Fe₂O₃ nanocrystallites embedded in a SiO₂ glass matrix or γ-Fe₂O₃-SiO₂ Janus NP were obtained. These NP provide a reactive SiO₂ interface for subsequent functionalizing. The co-vaporization of α-Al₂O₃ as the main proportion and t-ZrO₂ yielded zirconia-toughened-alumina NP. Reinforcing effects of Al₂O₃-ZrO₂ dispersion ceramics will be increased using NP with an intraparticle dispersion of these phases. Future applications of the LAVA prepared NP include biological fluorescence labeling, and drug targeting, magnetic resonance imaging, and hyperthermic cancer therapy, as well as sintering of load bearing ceramic implants, respectively.

Abstract: In this paper graphene is used to improve absorption rate of nano-titanium dioxide under visible light, meanwhile titanium dioxide is doped with superparamagnetism nano-powder of γ-Fe2O3 to modify the recovery of the photocatalyst. Gradually the increasing content of grapheme promotes the removal efficiency and correspondingly. Excitation condition is reduced and the photocatalysis property under visible light is improved and recycle rate of the titanium dioxide is effective promoted after the dispose. The effect of photocatalytic degradation of methylene blue is used to evaluate the photocatalytic activity. The methylene blue degradation rate raised from 53.4% to 85.9% with the increasing graphene load from 5% to 20% under visible light. The degradation efficiency of methylene blue decreased to 15% without the graphene load. The recovery rate of the photocatalyst can achieve 95% above. Graphene oxide works as the electron acceptor and photosensitizer to efficiently enhance the dye photodecomposition.

Abstract: Maghemite (γ-Fe_{Subscript text}2O_{Subscript text}3) and hematite (α-Fe2O3) nanoparticles with various dominant exposure crystal planes were prepared by several different methods. The structure and the reducibility of these materials were investigated by XRD, Raman and H2-TPR technologies, and their catalytic performance for propene oxidation was also discussed. The maghemite (γ-Fe_{Subscript text}2O_{Subscript text}3) showed a better reducibility than hematite (α-Fe_{Subscript text}2O_{Subscript text}3), but its activity for propene oxidation is relatively lower. The exposure crystal plane of hematite has a significant influence on its catalytic activity for propene oxidation. Among the prepared four samples, the hematite-1 sample showed the best activity. The selective growth of any planes with a relative low density of Fe atoms for the α-Fe_{Subscript text}2O_{Subscript text}3 catalyst would lead to an obvious decrease in the catalytic activity.

Abstract: Magnetic catalyst was made of magnetic core and surface coating layer and obtained a core-shell complex materials. The magnetic γ-Fe₂O3 core has a relatively higher saturation magnetization, coercivity and good thermal stability even at 500°C. In order to prevent magnetic core forming spinel structure and migrating of Fe³⁺, a layer of silicon dioxide was coated by sol-gel method. During the process iron atoms scattered in –Si-O-Si- network and produced a γ-Fe₂O₃@SiO₂ structure. Finally, the γ-Fe₂O₃@SiO₂ powder was put into the alumina sol and evenly sprayed into a column of oil, after calcination the carrier of alumina layer was prepared.

Abstract: Coating of
-Fe2O3 nanoparticles with SiO2 layer by wet chemical synthesis and its applications to protein separation and purification were investigated. The average particle size of
-Fe2O3 core was 20 nm and SiO2 layer thickness was 5 nm. The band of OH- radicals on SiO2 layer was detected between 3600 and 3200 cm-1 in wave numbers, which showed that the surface property of coated nanoparticles was similar to that of conventional fumed silica. Finally, the feasibility of
-Fe2O3/SiO2 nanoparticles for magnetic separation media in various bio processes was discussed in terms of structural and functional properties such as pore structure and magnetic properties.