An NMR-relaxation study of the effect of albumin on aggregation of magnetic iron oxide nanoparticles

The dependence of the aggregation of magnetic iron oxide nanoparticles in aqueous suspensions under the action of human serum albumin is analyzed based on the data of proton magnetic relaxation. It is shown that albumin adsorption on magnetic nanoparticles gives rise to the formation of a protein corona and clusters of magnetic nanoparticles, decreasing the aggregation stability of the suspension in a 7.1-T magnetic field. Clustering of magnetic iron oxide nanoparticles enhances the relaxation efficiency of magnetic suspensions during NMR measurements.     

Magnetoanalysis of micro/nanoparticles: a review

Application of magnetic field on the separation and analysis of nano/microparticles is a growing subject in analytical separation chemistry. The migration phenomenon of a particle under inhomogeneous magnetic field is called magnetophoresis. The migration velocity depends on the magnetic susceptibility and the size of a particle. Therefore, magnetophoresis allows us to determine the magnetic susceptibility of particles, and to separate particles based on the magnetic properties. Magnetic separation of ferromagnetic particles in liquid has been utilized for a long time. For example, a high gradient magnetic separation under the non-uniform magnetic field generated by ferromagnetic mesh has been utilized in a wide region from chemical industry to bioscience. Recent progress on magnetic nanoparticles and microfluidic devices has made it possible to extend the range of application. Furthermore, it has been demonstrated that the very sensitive measurement of the magnetic susceptibility of microparticles can be performed by observing magnetophoretic velocity. In this review, we mainly introduce novel separation and detection methods based on magnetophoresis, which have been invented in this decade, and then new principles of particle migration under magnetic field are presented.     

Adsorption of Eu(III) on iron oxide/multiwalled carbon nanotube magnetic composites

Iron oxide/multiwalled carbon nanotube magnetic composites (denoted as magnetic composites) were synthesized and characterized in detail. The magnetic composites can be separated from aqueous solution easily by using magnetic separation method. The application of magnetic composites in the removal of Eu(III) from large volumes of aqueous solutions was studied. The results indicated that the sorption of Eu(III) on the magnetic composites was strongly dependent on pH values and weakly dependent on ionic strength. The sorption of Eu(III) on the magnetic composites was mainly dominated by inner-sphere surface complexation. The linear sorption isotherms of Eu(III) suggested that Eu(III) sorption on the magnetic composites was far from saturation. The large sorption capacity and the easy magnetic separation method indicate that the magnetic composites may be a promising suitable material in nuclear waste management in future.     

Effects of structural transformations in magnetic emulsions

Structural transformations and relevant changes in the magnetic and optical properties of magnetosensitive emulsions based on magnetic fluids are experimentally studied. Peculiarities of the changes in the magnetic susceptibility of emulsions associated with the deformation of their microdroplets and the effect of phase inversion (the transformation of dispersions of magnetic droplets in nonmagnetic media into dispersions of nonmagnetic droplets in magnetic fluids) are established. Optical effects occurring in magnetic emulsions under the combined action of a shear flow and a magnetic field are studied. It is concluded that optically active composition media may be developed on the basis of magnetic fluids.     

镝钴铁氧磁流体的制备与性质研究(英文)

为了提高磁流体的抗氧化能力,制备了镝钴铁氧磁流体.利用古埃磁天平研究了温度对磁性和稳定性的影响;研究了稀土镝磁性能的改性、表面活性剂的表面改性,并从理论上进行了分析.利用X射线衍射仪(XRD)、透射电镜(TEM)对制得的磁粒子的组成、结构及粒径进行了分析.     

Nanodrop of an Ising magnetic fluid on a solid surface

The density functional theory of inhomogeneous simple fluids is extended to an Ising magnetic fluid in contact with a solid surface, which is subjected to an external uniform or nonuniform magnetic field. The system is described by two coupled integral equations regarding the magnetic moment and fluid density distributions. The dependence of the contact angle that a nanodrop makes with the solid surface on the parameters involved in the magnetic interactions between the molecules of fluid and between the molecules of fluid and an external magnetic field is calculated. For the uniform magnetic field, the contact angle increases with increasing magnetic field, approaching an asymptotic value that depends on the strength of the fluid-fluid magnetic interactions. In the nonuniform field generated by a permanent magnet, the contact angle first increases with increasing magnetic field B(M) and then decreases, with the decrease being almost linear for large values of B(M). The obtained results are in qualitative agreement with the experimental data on the contact angle of magnetic drops on a solid surface available in the literature.     

磁场对Schiff碱配合物模拟甲烷单加氧酶催化性能的影响

生命体中存在许多双金属酶 ,其结构和作用机制目前尚不清楚 ,为了模拟甲烷单加氧酶的催化作用 ,我们将催化活性较高的金属卟啉、稳定性较高的 Schiff碱及双核结构结合起来 ,设计合成了一系列“类卟啉型”Schiff碱双核配合物 ,并将这些双核配合物模拟酶催化亚碘酰苯 (Ph IO)单加氧化环己烷反应 ,发现其催化活性及抗氧化稳定性类似于四芳基金属卟啉 [1～ 3 ] ;还发现在模拟酶催化环己烷氧化反应中双核配合物中的两个金属离子间存在协同作用 [4 ] .外加磁场对一般热化学反应影响较小 [5～ 7] ,而在催化反应中的磁场效应更明显 [5,8] .为了较…     

Preparation and Performance of Dual-functional Magnetic Phase-change Microcapsules

The fabrication of desired anti-magnetic materials for irradiation shielding remains a challenge to date. In this work, a new type of dual-functional magnetic shielding phase change microcapsules with paraffin as the core, melamine-formaldehyde (MF) resin as the shell and doped with magnetic particles in the shell were successfully prepared by in situ polymerization. The magnetic particles were dispersed in the shell layer by coating a hydrophilic emulsifier on the surface. These microcapsules were specifically applied to the field of magnetic shielding by the screen printing method. The effect of magnetic particles on the performance of phase-change microcapsules was examined by differential scanning calorimetry and thermogravimetric analyses. The magnetic type and magnetic strength of the microcapsules were studied by the vibrating sample magnetometer. Moreover, the effects of different magnetic particles (Fe₃O₄, CrO₂) on the performance of phase change microcapsules and the magnetic strength of microcapsules were compared. The results showed that these two kinds of magnetic particles can greatly improve the phase change latent heat, thermal stability, and thermal conductivity of the microcapsules. Finally, the great magnetic shielding role of these microcapsules was demonstrated in both static and pulsed magnetic fields through the screen printing of magnetic shielding ink on wallpaper. Incorporating 0.5 g Fe₃O₄ inside of microcapsules, specifically, the magnetic intensity was effectively reduced by ∼250 Oe within a short distance in the static field. We expect that these magnetic microcapsules hold great potential for the shielding of irradiations via the screen printing on various substrates.     

磁场对微生物生长及苯酚降解影响的研究

以Fe3O4磁粉和稳恒弱磁场作为磁场来源,研究了不同磁场条件对微生物/细菌生长及苯酚降解的影响。结果表明,1~4g/L磁粉加量对微生物生长有促进作用,使之提前进入对数增长期;投加量为4g/L时效果最好,加量超过6g/L会抑制微生物生长;磁粉添加使微生物生长静止期稳定性有所下降。适量磁粉和弱磁场作用可促进苯酚与微生物共代谢,能明显提高苯酚的去除率。4g/L磁粉、100mT恒弱磁场作用下,22h对苯酚的去除率分别可达96%、90%,无磁场对照组仅为85%。     

Effect of the magnetic field on the melting transition of Ga and In by nW-stabilized DSC

The melting transition of Ga and In was measured by using a nW-stabilized differential scanning calorimeter working in a magnetic bore. The magnetic effect on the thermometer was about 18 mK at 5 T, which was corrected for the measurement of the magnetic effect on the melting transition of Ga and In. The melting temperatures of Ga and In with the magnetic field of 5 T were obtained to be 8.3 and 10.2 mK, respectively higher than those without the magnetic field. These results show that the solid phase to be relatively more stable under the magnetic field. The calculated temperature shifts of the melting transition due to the magnetic field using the magneto-Clapeyron equation and the reference data of magnetic susceptibility were negative values for both Ga and In, being contradictory to the experimental results.     

磁场对316L不锈钢微生物腐蚀行为的影响

采用循环极化、微生物分析法、扫描电镜及表面能谱分析等方法,研究了磁场对316L不锈钢在含硫酸盐还原菌(SRB)的土壤模拟溶液中的腐蚀行为。结果表明,磁场可以抑制SRB的生长;未外加磁场时316L不锈钢表面膜层以局部堆积为主,加有磁场时,局部堆积明显减小,膜层均匀致密的排列于基体表面;无论有或没有外加磁场,316L不锈钢表面均发生钝化膜破裂型点蚀,未外加磁场时的点蚀电位低于加有磁场时的。在相同的浸泡时间,未外加磁场时循环极化滞后环面积明显比加有磁场时的大,说明磁场可以有效抑制316L不锈钢点蚀的形成与发展,降低316L不锈钢的点蚀诱发能力。     

Quantitative Evaluation of the Total Magnetic Moments of Colloidal Magnetic Nanoparticles: A Kinetics‐based Method

A kinetics‐based method is proposed to quantitatively characterize the collective magnetization of colloidal magnetic nanoparticles. The method is based on the relationship between the magnetic force on a colloidal droplet and the movement of the droplet under a gradient magnetic field. Through computational analysis of the kinetic parameters, such as displacement, velocity, and acceleration, the magnetization of colloidal magnetic nanoparticles can be calculated. In our experiments, the values measured by using our method exhibited a better linear correlation with magnetothermal heating, than those obtained by using a vibrating sample magnetometer and magnetic balance. This finding indicates that this method may be more suitable to evaluate the collective magnetism of colloidal magnetic nanoparticles under low magnetic fields than the commonly used methods. Accurate evaluation of the magnetic properties of colloidal nanoparticles is of great importance for the standardization of magnetic nanomaterials and for their practical application in biomedicine.     

Some Aspects of Magnetic Filtration Theory for Removal of Fine Particles from Aqueous Suspensions

The magnetic filtration theory was evaluated to intensify the filtration of industrial fluids by magnetic filters. Effects of filtration velocity and external magnetic field intensity on filter performance were investigated and the dependence of the logarithmic efficiency coefficient on filtration velocity was questioned. It was concluded that change in the magnetic susceptibility of the dispersion particles, caused by external magnetic field, and change in the flow rate properties of the liquid alongside the filter pores are the most essential factors to be considered in the design, development, and modeling of magnetic filtration systems in various industrial areas.     

Pt/TiO2上苯和乙烯光催化氧化过程的磁场效应

以Pt/TiO₂为催化剂和365 nm紫外光为光源, 在低于0.2 T的磁场强度范围考察了磁场对苯和乙烯光催化氧化反应的影响. 实验发现, 当用紫外灯管作光源并靠近磁场磁极或者置于磁场磁极间隙内照射反应器时, 磁场可显著提高气相苯和乙烯的光催化转化率和矿化率; 而当光源远离磁场磁极而通过光导纤维传导照射到反应器上时, 磁场对这两个反应没有促进作用. 在前一种情况下, 紫外灯管的发光强度随磁场的增强而提高, 磁场对这两个光催化降解反应的促进作用被证实是由于磁场提高了紫外灯管的发光强度, 进而为反应提供了更多的光能和使反应温度升高所致；在后一种光照方式下, 由于光源不受磁场影响, 磁场对这两个光催化反应不产生影响. 这一研究结果表明, 在所研究磁场强度范围, 磁场对气-固相光催化反应没有任何本征影响.     

磁场对醋酸乙烯酯乳液聚合反应的影响

迄令为止,有关磁场对化学反应影响的研究,主要是小分子自由基反应,而对聚合反应的研究甚少。1981年周朝华、苏致兴报道了磁场对聚甲基丙烯酸甲酯立体构型的影响。随后,N.J.Turro研究了磁场对苯乙烯乳液聚合的影响。结果表明,磁场对苯乙烯的聚合速率及聚合物分子量有影响。 本文首次报道磁场对醋酸乙烯酯乳液聚合反应速率,聚合物分子量及热稳定性的影响。     

Theoretical study of magnetic properties of ammonia molecule in nonuniform magnetic field

The interaction Hamiltonian within the Bloch gauge for the potentials of the electromagnetic field has been used to define magnetic multipole moment operators and operators for the magnetic field of electrons acting on the nuclei of a molecule in the presence of nonhomogeneous external magnetic field. Perturbation theory has been applied to evaluate the induced electronic moments and magnetic field at the nuclei. Multipole magnetic susceptibility and nuclear magnetic shielding tensors have been introduced to describe the contributions arising in nonuniform fields, and their origin dependence has been analyzed. Extended numerical tests on the ammonia molecule in a static, nonuniform magnetic field have been carried out, using the random-phase approximation within the framework of accurate Hartree-Fock zero-order wavefunctions, and allowing for both angular momentum and torque formalisms in the calculation of paramagnetic contributions.     

The effect of magnetic field on conductive films

Conductive paints consisting of nickel powder (conductive material), solvent, and binder polymer were treated in a magnetic field. The efficiency of magnetic treatments on conductivity of coating films was evaluated. The effect of the following factors on conductivity of composite films by magnetic treatment was studied: metal powder concentration, magnetic flow density, time difference between film preparation and magnetic treatment, drying time of paint films, and effect of distance between terminals. Results showed that the volume resistivity of paint films treated magnetically was lower than that for untreated films at each nickel content. Magnetic treatment provided high conductivity even at low magnetic flow density, and conductivity increased with magnetic flow density.     

Adhesion of Pseudomonas fluorescens on magnetic surfaces

The adhesion of Pseudomonas fluorescens (ATCC 700830) to perpendicularly polarized magnetic surfaces was recently discovered. The findings have found that the magnetic free surfaces from different magnetic polarities have different profound effects on the P. fluorescens bacterial adhesion to its surfaces. These phenomena can be explained by the surface magnetic effect, which was found to affect the surface free energy. An in situ experiment, by contrast microscopy and under static conditions, was conducted to determine the influence of magnetic surfaces, that are polarized under different external magnetizing field strengths, on bacterial adhesion. The effect of different magnetic polarities on the surface free energy has also been investigated.     

Controlling the magnetic field distribution on the micrometer scale and generation of magnetic bead patterns for microfluidic applications

As is well known, controlling the local magnetic field distribution on the micrometer scale in a microfluidic chip is significant and has many applications in bioanalysis based on magnetic beads. However, it is a challenge to tailor the magnetic field introduced by external permanent magnets or electromagnets on the micrometer scale. Here, we demonstrated a simple approach to controlling the local magnetic field distribution on the micrometer scale in a microfluidic chip by nickel patterns encapsulated in a thin poly(dimethylsiloxane) (PDMS) film under the fluid channel. With the precisely controlled magnetic field, magnetic bead patterns were convenient to generate. Moreover, two kinds of fluorescent magnetic beads were patterned in the microfluidic channel, which demonstrated that it was possible to generate different functional magnetic bead patterns in situ, and could be used for the detection of multiple targets. In addition, this method was applied to generate cancer cell patterns.