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1.
有机磁合成化学研究进展 总被引:11,自引:0,他引:11
通过磁场对聚合反应、酯化反应、光还原反应和不对称合成等的影响,论述了有机磁化学的理论研究和应用进展。磁场在一定程度上影响有机反应的反应速率、产率、反应途径和产物构成。同时初步探讨了磁场影响化学反应速率的机理,并展望了磁化学的发展前景。 相似文献
2.
Magnetic nano- and microparticles in biotechnology 总被引:1,自引:0,他引:1
Both synthetic and biologically produced magnetic nano- and microparticles exhibit several types of responses to external
magnetic field which have been already employed in various areas of biosciences, biotechnology, medicine, environmental technology,
etc. This short review shows selected important biotechnological applications of magnetic particles, and the biological processes
leading to biogenic magnetic particles formation.
Presented at the 1st Nanomaterials and Nanotechnology Meeting, Nano Ostrava, Ostrava, Czech Republic, 1–4 September 2008. 相似文献
3.
G. A. Petrakovskii A. M. Vorotynov D. A. Velikanov Ya. G. Shiyan V. I. Ovcharenko V. N. Ikorskii G. V. Romanenko E. Yu. Fursova R. Szimczak 《Journal of Structural Chemistry》2006,47(3):447-452
Cu(hfac)2 chain polymer heterospin complexes with pyrazole-substituted nitronylnitroxides (LR, where R = Me, Et) with a composition Cu(hfac)2LR, exhibiting structural rearrangements with magnetic effects in the solid state at reduced temperatures, were studied by magnetic resonance. The magnetic resonance spectrum changes substantially for substituents of different types. The results of this study are discussed in the context of the cluster approach in view of the specific crystal structure of the compounds. 相似文献
4.
Fernando Vereda Dr. Juan de Vicente Prof. Roque Hidalgo‐Álvarez Prof. 《Chemphyschem》2009,10(8):1165-1179
Anisotropy counts: A brief review of the main physical properties of elongated magnetic particles (EMPs) is presented. The most important characteristic of an EMP is the additional contribution of shape anisotropy to the total anisotropy energy of the particle, when compared to spherical magnetic particles. The electron micrograph shows Ni‐ferrite microrods fabricated by the authors.
5.
Laura L. Vatta 《Macromolecular Symposia》2005,225(1):221-228
In the diamond industry, ferrofluids are used in ferrohydrostatic separators for the density separation of diamonds from gangue material. The size of the magnetic core of the coated particles forming the ferrofluid suspension is vital in ensuring the stability of the fluid. The particle size must be small enough such that sedimentation does not occur in a magnetic field gradient and under the influence of a gravitational field and such that magnetic agglomeration can be overcome. This paper discusses the particle size requirements for fluid stability under the influence of these effects. 相似文献
6.
Yabin Sun Xiaobin Ding Zhaohui Zheng Xu Cheng Xinhua Hu Yuxing Peng 《Macromolecular rapid communications》2007,28(3):346-351
Magnetic nanoadsorbents using Fe3O4 nanoparticles as cores and poly(methyl acrylic acid) (PMAA) as ionic exchange groups were prepared through our novel approach. Two steps were involved in this approach: the first was to functionalize the magnetic nanoparticles (MNPs) with methacrylate double bonds via the combination of ligand exchange and condensation of methacryloxypropyltrimethoxysilane(MPS); the second was to graft PMAA chains onto the surface of MNPs through radical polymerization. The success of the various surface functionalization steps was ascertained using FTIR and XPS. The as‐synthesized PMAA‐coated MNPs were effective in binding bovine serum albumin (BSA) with a high capacity of 1 300 mg · g−1.
7.
双层表面活性剂分散制备水基磁流体 总被引:20,自引:0,他引:20
Fe3O4 magnetic particles were synthesize by chemical co-precipitation. Sodium oleate and poly(ethylene glycol)-4000 were used as bilayer surfactants to envelope the ultra-fine Fe3O4 particles. Then stabilized water base magnetic fluid was obtained. Experiments indicated that surfactants and pH value of the solution had great effect on the stability and size of the magnetic fluid when Fe3O4 particles were synthesized and enveloped. It was the first time to employ this method to prepare magnetic fluid. Using laser diffraction particle size analyzer we found that the average diameter of magnetic fluid was lessen than 84 nanometer. Its magnetization was measured on magnetic balance and the result amounted to 3.84×103A·m-1. Further more, XRD and IR analysis measurements were employed to substantiate the existence of Fe3O4 and surfactant structure. The magnetic fluid can be used as tar-geted-part of nanometer targeted drug delivery system. 相似文献
8.
Microbial Cells with a Fe3O4 Doped Hydrogel Extracellular Matrix: Manipulation of Living Cells by Magnetic Stimulus 下载免费PDF全文
Xudian Shi Zhijun Shi Daming Wang Muhammad Wajid Ullah Guang Yang 《Macromolecular bioscience》2016,16(10):1506-1514
This study aims to develop an effective method to control motile microorganisms and enable their manipulation as functional ‘live micro/nano robots'. A novel strategy based on Fe3O4 nanoparticle‐doped alginate hydrogel is developed to fashion an artificial extracellular matrix (ECM) for microbial cells (e.g., Saccharomyces cerevisiae and Flavobacterium heparinum). During this strategy, a single layer of alginate hydrogel is coated around the microbial cells doped with Fe3O4 nanoparticles to form the alg‐mag‐cells. Transmission electron microscopy shows that Fe3O4 nanoparticles are uniformly distributed in the hydrogel shell. Together with maintaining the cell activity and metabolism, the hydrogel coated microbial cells demonstrate high magnetic responsiveness in an external magnetic field and are able to form micro‐scaled patterns using the magnetic template designed in this study. This strategy provides a building block to fabricate advanced biological models, medical therapeutic products, and non‐medical biological systems using different microorganisms.
9.
Polarized Neutron Diffraction as a Tool for Mapping Molecular Magnetic Anisotropy: Local Susceptibility Tensors in CoII Complexes 下载免费PDF全文
Dr. Karl Ridier Dr. Béatrice Gillon Dr. Arsen Gukasov Dr. Grégory Chaboussant Dr. Alain Cousson Prof. Dominique Luneau Dr. Ana Borta Dr. Jean‐François Jacquot Dr. Ruben Checa Yukako Chiba Prof. Hiroshi Sakiyama Prof. Masahiro Mikuriya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):724-735
Polarized neutron diffraction (PND) experiments were carried out at low temperature to characterize with high precision the local magnetic anisotropy in two paramagnetic high‐spin cobalt(II) complexes, namely [CoII(dmf)6](BPh4)2 ( 1 ) and [CoII2(sym‐hmp)2](BPh4)2 ( 2 ), in which dmf=N,N‐dimethylformamide; sym‐hmp=2,6‐bis[(2‐hydroxyethyl)methylaminomethyl]‐4‐methylphenolate, and BPh4?=tetraphenylborate. This allowed a unique and direct determination of the local magnetic susceptibility tensor on each individual CoII site. In compound 1 , this approach reveals the correlation between the single‐ion easy magnetization direction and a trigonal elongation axis of the CoII coordination octahedron. In exchange‐coupled dimer 2 , the determination of the individual CoII magnetic susceptibility tensors provides a clear outlook of how the local magnetic properties on both CoII sites deviate from the single‐ion behavior because of antiferromagnetic exchange coupling. 相似文献
10.
Bimetallic ferrimagnet [Cr(CN)6][Mn(R)-pnH(H2O)]H2O with crystallographical chirality of space group P212121 exhibits a giant third-order harmonic susceptibility at around 38 K. This anomaly appears as precursory magnetic phenomenon of the magnetic ordering. In order to investigate the effect of lattice distortion on this giant nonlinear magnetic response (NLMR) and finally elucidate the correlation between the structural chirality and the giant NLMR, we performed the ac susceptibility measurement for the single crystal in the situation of bringing about lattice distortion along the direction parallel to the a-axis. This giant NLMR was drastically suppressed even by slight strain, whereas the traces could be confirmed in the region up to 3.7 kbar. We conclude that the appearance of the giant NLMR requires crystal chirality well-regulated over the crystal. 相似文献
11.
M. B. Ferraro M. C. Caputo M. P. Bccar Varela P. Lazzeretti 《International journal of quantum chemistry》1998,66(1):31-45
A transformation of the transverse Coulomb vector potential was implemented to calculate molecular magnetic properties via the random-phase approximation (RPA) within the framework of a “longitudinal gauge.” In this gauge, the diamagnetic contribution to magnetic susceptibility is a tensor with equal diagonal components as in atoms, irrespective of molecular symmetry, whereas diagonal and average diamagnetic contributions to the nuclear magnetic shielding are the same as in the Coulomb gauge. Near-Hartree–Fock magnetic susceptibility and nuclear magnetic shielding tensors were evaluated for a set of small molecules, HF, H2O, NH3, and CH4, employing extended Gaussian basis sets. The peculiar features of the longitudinal gauge, and the fulfillment of a series of sum rules involving the virial operator, which must be satisfied to guarantee gauge invariance of total magnetic tensors, were exploited to check the degree of convergence of theoretical values and to estimate the corresponding Hartree–Fock limit for the properties. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 31–45, 1998 相似文献
12.
Multimetal‐Substituted Epsilon‐Iron Oxide ϵ‐Ga0.31Ti0.05Co0.05Fe1.59O3 for Next‐Generation Magnetic Recording Tape in the Big‐Data Era 下载免费PDF全文
Prof. Shin‐ichi Ohkoshi Dr. Asuka Namai Marie Yoshikiyo Dr. Kenta Imoto Kazunori Tamazaki Koji Matsuno Osamu Inoue Tsutomu Ide Kenji Masada Masahiro Goto Takashi Goto Takayuki Yoshida Tatsuro Miyazaki 《Angewandte Chemie (International ed. in English)》2016,55(38):11403-11406
From the viewpoints of large capacity, long‐term guarantee, and low cost, interest in magnetic recording tapes has undergone a revival as an archive storage media for big data. Herein, we prepared a new series of metal‐substituted ?‐Fe2O3, ?‐GaIII0.31TiIV0.05CoII0.05FeIII1.59O3, nanoparticles with an average size of 18 nm. Ga, Ti, and Co cations tune the magnetic properties of ?‐Fe2O3 to the specifications demanded for a magnetic recording tape. The coercive field was tuned to 2.7 kOe by introduction of single‐ion anisotropy on CoII (S=3/2) along the c‐axis. The saturation magnetization was increased by 44 % with GaIII (S=0) and TiIV (S=0) substitution through the enhancement of positive sublattice magnetizations. The magnetic tape media was fabricated using an actual production line and showed a very sharp signal response and a remarkably high signal‐to‐noise ratio compared to the currently used magnetic tape. 相似文献
13.
Lisboa-Filho P.N. Zenatti A. Casali G.M. Paskocimas C.A. Ortiz W.A. Leite E.R. Longo E. 《Journal of Sol-Gel Science and Technology》2002,24(3):241-245
Ti-oxide polycrystalline samples have been synthesized by the Pechini method and their low temperature magnetic properties have been characterized. The synthesis procedures allow the preparation of high-quality samples ensuring that the observed low temperature magnetic behavior is intrinsic to the system, not due to the polycrystalline nature of the samples. Magnetic susceptibility measurements showed that the anatase and rutile TiO2 exhibit a paramagnetic behavior. For the CoTiO3 samples, a totally reversible antiferromagnetic transition at 38 K is reported. 相似文献
14.
15.
On Approaching the Limit of Molecular Magnetic Anisotropy: A Near‐Perfect Pentagonal Bipyramidal Dysprosium(III) Single‐Molecule Magnet 下载免费PDF全文
You‐Song Ding Dr. Nicholas F. Chilton Prof. Dr. Richard E. P. Winpenny Prof. Dr. Yan‐Zhen Zheng 《Angewandte Chemie (International ed. in English)》2016,55(52):16071-16074
We report a monometallic dysprosium complex, [Dy(OtBu)2(py)5][BPh4] ( 5 ), that shows the largest effective energy barrier to magnetic relaxation of Ueff=1815(1) K. The massive magnetic anisotropy is due to bis‐trans‐disposed tert‐butoxide ligands with weak equatorial pyridine donors, approaching proposed schemes for high‐temperature single‐molecule magnets (SMMs). The blocking temperature, TB , is 14 K, defined by zero‐field‐cooled magnetization experiments, and is the largest for any monometallic complex and equal with the current record for [Tb2N2{N(SiMe3)2}4(THF)2]. 相似文献
16.
Abstract Heterocyclic scaffolds are important components in the structure of many drugs and natural products. They are well-known compounds because of their broad spectrum of pharmaceutical and biological activities. In this paper, we provide an overview of the utilization of copper complexes immobilized on magnetic nanoparticles as economical and efficient catalytic systems for the synthesis of heterocyclic molecules. 相似文献
17.
Knoevenagel condensation of aromatic aldehydes with active methylene compounds such as malononitrile, ethylcyanoacetate, benzimidazol‐2‐acetonitrile and benzothiazole‐2‐acetonitrile proceeded very smoothly, catalyzed by nano‐Fe3O4 encapsulated‐silica particles supported primary amine. Both reaction time and yield are satisfying. The advantages of this catalyst are ease of preparation, non‐toxicity, low cost, ease of handling and recyclability. 相似文献
18.
Hweiyan Tsai Chia-Yi Chen Yi-Hsuan Lu Ya-Yun Lai 《Green Chemistry Letters and Reviews》2018,11(4):399-403
A high-throughput and selective method for the determination of ?-dopa (levodopa) in complex formulations was developed. The method is based on the oxidation of ?-dopa to yield dopachrome using tyrosinase-labeled magnetic nanoparticles (TYR-MNPs) as the oxidation catalyst. TYR-MNP activity was retained at 75% after 20 reuse cycles, which is superior to previously reported systems that employ other substrates or cross-linkers for the immobilization of tyrosinase. In addition, the precision (< 3%), accuracy (recovery?=?95–102%), and selectivity of the newly developed quantitative-analysis method for ?-dopa in complex polypill formulations meets the pharmaceutical industry’s quality-control requirements; consequently this method can be applied to the routine analysis of complex formulations. The quality-control assay uses 96-well microplates, which reduces the required volume of reagents, and the tyrosinase can easily be recycled and reused using an in-house-prepared magnetic microplate, thereby rendering the proposed method economical and less wasteful than existing methods. 相似文献
19.
Abstract Heterocyclic scaffolds are important components in the structure of many drugs and natural products. They are well-known compounds because of their broad spectrum of pharmaceutical and biological activities. In this paper, we provide an overview of the utilization of nickel complexes immobilized on magnetic nanoparticles as attractive and efficient catalytic systems for synthesis of heterocyclic molecules. 相似文献