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
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
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
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.
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.
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
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.
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
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
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