Core-shell and multilayered nanoparticles based on magnetite core with different metallic spacing and over-layers are prepared in one pot synthesis and characterized. The spacer layers were made from Au, Cu or Ag precursors. The nanoparticles were fabricated by a modified chemical seed based method. The obtained nanoparticles were examined by X-ray diffraction, Energy-dispersive X-ray spectroscopy, Transmission Electron Microscopy, Differential Scanning Calorimetry and Infrared spectroscopy. Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy and Magnetometry. Magnetization and Mössbauer measurements show that the presence of the metallic layers influences the magnetic state of the particles. XRD and EDX confirm layered structures of nanoparticles. Proposed synthesis allows for fabrication of layered particles with controlled morphology and register properties changes which are related to the nature of each subsequent layer. 相似文献
A homopolysaccharide fraction (PEP-1A) with desired immunomodulatory activity was isolated from culture broth of Parabacteroides distasonis. Structural characterization uncovered that PEP-1A had a molecular weight of 3.40 × 106 Da and possessed mannose merely. Comprehensive analysis of FT-IR, GC–MS and 1D/2D NMR confirmed that the structure of PEP-1A was expected as follows:
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Finally, the activity assays on RAW 264.7 macrophages showed that PEP-1A could promote proliferation, increase the production of reactive oxygen species (ROS), enhance the phagocytosis, and promote the secretion of nitric oxide (NO) and inflammatory cytokines including IL-1β, IL-6 and TNF-α. Furthermore, PEP-1A could give play to immunoregulation effect through NF-κB, MAPK and Akt signaling pathways. Collectively, the study of PEP-1A offers a molecular underpinning for the future application of PEP-1A as a potential immunostimulant. 相似文献
A zinc-nicotinate complex has been prepared by direct reaction of zinc acetate and nicotinic acid in the presence of template tetramethylethylenediamine and is characterized by elemental analysis, FTIR, and TGA/DTA. The Zn complex was a precursor for the synthesis of ZnO nanoparticles. A correlation of the thermal and spectral properties of the precursor complex with its structure has been discussed. Thermolysis under air was studied by thermogravimetry, and the resulting ZnO product was characterized by XRD and TEM, showing compact particles with a diameter of about 17–50?nm. 相似文献
Na2Ti3O7 and Na2Ti6O13 were synthesized by sol-gel method in order to obtain pure phases. Different heat-treatments were applied on powders and pellets of these materials. The effects were studied by XRD, dilatometry, TGA-DTA, SEM and electrochemical impedance spectroscopy. Pure Na2Ti3O7 was obtained at 973 K. Sintering at 1373 K caused a partial decomposition into Na2Ti6O13. The Na2Ti3O7 powder sintered at 1273 K showed polygonal microstructure. Na2Ti3O7 pellets sintered at 1323 K for 10 h exhibited large structures. This latter microstructure decreased the electrical conductivity of Na2Ti3O7. Pure Na2Ti6O13 was obtained at 873 K. Sintering at 1073 K caused a partial decomposition into TiO2 (rutile). Na2Ti6O13 pellets sintered at 1323 K for 10 h exhibited common shrinkage behavior. This shrinkage process increased the electrical conductivity of this material. The presence of TiO2 resulted in a oxygen partial pressure dependence of the electrical conductivity. 相似文献
A structural and electrical characterization of the system NiNb2−xTaxO6 (0≤x≤2) is presented. For x≤0.25 materials with the columbite-type structure typical of NiNb2O6 have been obtained whereas for x≥1 tri-rutile-like oxides were obtained. The electrical properties are similar in both cases; they are semiconducting with very low electrical conductivity and very high activation energy, though slight differences were found as a function of Ta content. Improvement of conductivity by reducing the stoichiometric materials could not be achieved due to decomposition. In this connection, partial substitution of Nb or Ta by Ti has been carried out in order to create oxygen vacancies. Tantalum was partially replaced by Ti to a significant extent in the tri-rutile structure inducing a slight increasing of conductivity. However, for the columbite case neither Nb nor Ta could be partially replaced. This behavior is quite different from that reported for other similar columbites such as MnNb2O6−δ, which exhibits high electrical conductivity upon substitution of niobium by titanium. 相似文献
