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51.
Nanowires of SrFe12O19 with diameters of 100 nm and lengths of 2.5 μm have been successfully synthesized in a hydrothermal cell at 180 °C with an 0.35 T magnetic field applied. The growth behavior of the nanoparticles was compared with that under zero magnetic field. The X-ray diffraction patterns indicate that both of the two processes result in formation of pure SrFe12O19, however transmission electron microscope observations show that the morphology of the particles changed from flake-like in zero magnetic field into nanowires in a magnetic field. Compared to the sample obtained under zero magnetic field, the as-prepared one exhibits a higher saturation magnetization. The possible underlying mechanism responsible for the morphology change and the magnetic properties improvement were discussed. 相似文献
52.
Dr. Tong Han Dr. Xing Cao Dr. Hsiao-Chien Chen Junguo Ma Yuan Yu Yuhuan Li Wei Xu Dr. Kaian Sun Aijian Huang Dr. Zheng Chen Prof. Chen Chen Prof. Hongjun Zhang Prof. Bangjiao Ye Prof. Qing Peng Prof. Yadong Li 《Angewandte Chemie (International ed. in English)》2023,62(49):e202313325
Photocatalytic organic functionalization reactions represent a green, cost-effective, and sustainable synthesis route for value-added chemicals. However, heterogeneous photocatalysis is inefficient in directly activating ammonia molecules for the production of high-value-added nitrogenous organic products when compared with oxygen activation in the formation of related oxygenated compounds. In this study, we report the heterogeneous photosynthesis of benzonitriles by the ammoxidation of benzyl alcohols (99 % conversion, 93 % selectivity) promoted using BiOBr nanosheets with surface vacancy associates. In contrast, the main reaction of catalysts with other types of vacancy sites is the oxidation of benzyl alcohol to benzaldehyde or benzoic acid. Experimental measurements and theoretical calculations have demonstrated a specificity of vacancy type with respect to product selectivity, which arises from the adsorption and activation of NH3 and O2 that is required to promote subsequent C−N coupling and oxidation to nitrile. This study provides a better understanding of the role of vacancies as catalytic sites in heterogeneous photocatalysis. 相似文献
53.
A novel bat-like ZnO nanostructure was synthesized on the silicon substrate by simple ther-mal evaporation of zinc powders without any catalyst. Each bat-like nanorod ("nanobat") is composed of a hexagonal head, a continuous neck and a thin handle. High-resolution transmission electron microscopy and selected area electron di raction results reveal the single-crystalline feature and the growing direction along [0001] of the nanobat. The vapor-solid mechanism was found suitable to explain the growth process of the nanobat and a schematic model was proposed in detail based on the experimental results. 相似文献
54.
《Particuology》2023
Current evidence of concept analyses recommending nanotechnology for biomedical uses abounds in recent research. The area of biotechnology interfaces with nanostructures, reconfigures their composition, and alters their characteristics; which influences the dispersion of the particles, the biotransformation they cause, and their potential toxic effect. It is vital to link the idea of the lifecycle of nanostructures to the biological impacts and use methodologies to identify, estimate, and track the gradual bioprocessing of nanostructures in vivo, from a body-wide level to a nanoscopic size. This is necessary because understanding how nanostructures processing, degradation, persistence, and recycling predict potential exposure risks. The safe implementation of nanotechnology-based products in biomedical applications necessitates an extensive understanding of the recycling and transformations of nanomaterials in a living organism. Long-term fate in the body is crucial, as it governs potential environmental risks to human health. Strategies may be used to manage the long-term outcome of nanostructures in an organism since, in addition to composition, their design also affects how long they last and how easily they degrade. The lifespan of nanoparticles, a flexible and biocompatible category of nanostructures that have made it into clinical trials, is the subject of this article. Strategies may be used to manage the long-term outcome of nanoparticles in an organism since, in addition to composition, their design also affects how long they last and how easily they degrade. This review explained the safety of nanoscale materials, biotransformation, and the multifunctional recycling mechanism of nanostructures. 相似文献
55.
Sol was prepared by the mixing of tetra-η-butyle titanat, ethyl aceto acetate, and ethanol in an optimized condition. Polished 316L specimens were coated with the sol by dip-coating method. The influences of drying condition, withdrawal speed, calcination temperature, addition of dispersant, and pH of sol on TiO2 nanostructure coating were investigated. Choosing of alcohol as drying atmosphere hindered the crack formation. The relation between coating thickness and withdrawal speed was evaluated. The optimum temperature to create a uniform distribution of nanoparticles of anatase was derived as 400 °C. Average roughness of coating was found about 10.61 nm by AFM analysis. Dispersant addition promoted formation of a uniform film as well as prevention of agglomeration. Acidic sol provided smaller particles than neutral sol. 相似文献
56.
Liandong Deng Yinglei Zhai Shutao Guo Fengmin Jin Zhaopeng Xie Xiaohua He Anjie Dong 《Journal of nanoparticle research》2009,11(2):365-374
P((MAA-co-DMAEMA)-g-EG) polyampholyte nanogels (PANGs) were prepared by distillation-dispersion copolymerization of poly(ethylene
glycol) methyl ether methacrylate (MPEGMA), N,N-dimethylaminoethyl methacrylate (DMAEMA), and methacrylic acid (MAA) using acetonitrile (AN) as dispersion medium. The results
of FTIR spectra indicate that the composition of P((MAA-co-DMAEMA)-g-EG) PANGs is consistent with the designed structure.
The results of TEM and laser particle size analyzer (LPSA) show that P((MAA-co-DMAEMA)-g-EG) PANGs present spherical morphology
and a bimodal size distribution after and before swelling. P((MAA-co-DMAEMA)-g-EG) PANGs have typically amphoteric characters
responding to pH, whose isoelectric point (IEP) increases with decreasing the ratio of MAA/DMAEMA and equilibrium swelling
degree (ESD) is greater than that at IEP when the pH value is distant from IEP. P((MAA-co-DMAEMA)-g-EG) PANGs also represent
ionic strength sensitivity. Using the water-soluble chitosan (CS, Mn = 5 kDa) as model drug, in vitro release indicates that
CS can be effectively incorporated into PANGs and the release rate of CS at pH 1.89 is an order of magnitude greater than
that at pH 8.36. P((MAA-co-DMAEMA)-g-EG) PANGs may be useful in biomedicine, especially in oral drug delivery of biomacromolecule. 相似文献
57.
Hongxia Chen Daning Shi Jingshan Qi Baolin Wang 《Physica E: Low-dimensional Systems and Nanostructures》2009,42(1):32-37
We investigate the energetic, electronic, and mechanical properties of the pristine, hydrogen, and water adsorbed ZnS nanowires using the all-electron density functional theory. We found that water adsorption is energetically favorable and makes the band gap change from indirect to direct for the smallest nanowire. The Young's moduli of the pristine and water adsorbed nanowires are larger, but those of the hydrogen adsorption nanowires are smaller than that of bulk ZnS. The physical origin of the different tendencies can be attributed to the different surface relaxations of three kinds of ZnS nanowires. 相似文献
58.
Zhao Juan 《Journal of magnetism and magnetic materials》2009,321(1):43-46
In this paper, nanosized particles of (La0.47Gd0.2)Sr0.33MnO3 perovskite-type oxides were successfully synthesized at a relatively low calcinated temperature at 800 °C for 10 h using amorphous molecular alloy as precursor. X-ray diffraction (XRD) and electron diffraction (ED) revealed that the resulting product is of pure single-phase rhombohedral structure. The Curie temperature TC and magnetic entropy change (MCE) in (La0.47Gd0.2)Sr0.33MnO3 polycrystalline nanoparticles are determined and compared to those of similar systems prepared by the conventional solid-state reaction method. The Curie temperature TC is shifted to 298 k, and a relatively large MCE with a broad peak around Curie temperature is observed in (La0.47Gd0.2)Sr0.33MnO3 polycrystalline particles. These results suggested that this material is a suitable candidate as working substance in magnetic refrigeration near room temperature. 相似文献
59.
S.P. Crane C. Bihler S.T.B. Goennenwein R. Ramesh 《Journal of magnetism and magnetic materials》2009,321(4):L5
Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe2O4 pillars in a multiferroic BiFeO3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars. 相似文献
60.
C.H. Lin S.Y. Chen N.J. Ho D. Gan P. Shen 《Journal of Physics and Chemistry of Solids》2009,70(12):1505-1510
The α-Cr2O3 single-crystal nanocondensates were fabricated by pulsed laser ablation in air and characterized by analytical electron microscopy regarding shape-dependent local internal stress of the anisotropic crystal. The nanocondensates formed predominantly as rhombohedra with well-developed surfaces and occasionally hexagonal plate with thin edges and blunt corners. Such nanocondensates showed Raman shift for the CrO6 polyhedra, indicating a local compressive stress up to ca. 4 GPa on the average. Careful analysis of the lattice fringes revealed a local compressive stress (0.5% strain) at the thin edge of the hexagonal plates and a local tensile stress (0.3–1.0% strain) near the relaxed , , and (0 0 0 1) surfaces of truncated rhombohedra. The combined effects of nanosize, capillarity force at sharp edge, and specific surface relaxation account for the retention of a local internal compressive stress built up in an anisotropic crystal during a very rapid heating–cooling process. 相似文献