A number of materials are studied in the field of magnetic hyperthermia. In general, the most promising ones appear to be iron oxide particle nanosystems. This is also indicated in some clinical trial studies where iron-based oxides were used. On the other hand, the type of material itself provides a number of variations on how to tune hyperthermia indicators. In this paper, magnetite nanoparticles in various forms were analyzed. The nanoparticles differed in the core size as well as in the form of their arrangement. The arrangement was determined by the nature of the surfactant. The individual particles were covered chemically by dextran; in the case of chain-like particles, they were encapsulated naturally in a lipid bilayer. It was shown that in the case of chain-like nanoparticles, except for relaxation, a contribution from magnetic hysteresis to the heating process also appears. The influence of the chosen methodology of magnetic field generation was also analyzed. In addition, the influence of the chosen methodology of magnetic field generation was analyzed. The application of a rotating magnetic field was shown to be more efficient in generating heat than the application of an alternating magnetic field. However, the degree of efficiency depended on the arrangement of the magnetite nanoparticles. The difference in the efficiency of the rotating magnetic field versus the alternating magnetic field was much more pronounced for individual nanoparticles (in the form of a magnetic fluid) than for systems containing chain nanoparticles (magnetosomes and a mix of magnetic fluid with magnetosomes in a ratio 1:1). 相似文献
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.
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
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.
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
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
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
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
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
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
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
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