Remote Control of T Cell Activation Using Magnetic Janus Particles

We report a strategy for using magnetic Janus microparticles to control the stimulation of T cell signaling with single‐cell precision. To achieve this, we designed Janus particles that are magnetically responsive on one hemisphere and stimulatory to T cells on the other side. By manipulating the rotation and locomotion of Janus particles under an external magnetic field, we could control the orientation of the particle–cell recognition and thereby the initiation of T cell activation. This study demonstrates a step towards employing anisotropic material properties of Janus particles to control single‐cell activities without the need of complex magnetic manipulation devices.     

磁场对超细镍粉的磁性能及电磁屏蔽性能的影响

分别在水和乙二醇溶液中,于搅拌条件下采用液相还原法制备超细镍粉,研究反应过程中外加磁场对产物形貌及性能的影响。结果表明,水中得到的产品为刺球状颗粒,外加磁场对产物的形貌影响不大;乙二醇中得到类球形颗粒,加磁场后得到短链状结构。外加磁场使超细镍粉的饱和磁化强度值降低而矫顽力值升高。将水体系中得到的超细镍粉作为导电填料制备电磁屏蔽涂料,结果发现外加磁场条件下得到的超细镍粉/树脂复合涂料在130 MHz～1.5 GHz频段内具有更好的电磁屏蔽性能。     

晶体场与磁学性质

深入讨论了晶体场与材料磁学性质之间的关系并且给出了必要的数学推导。内容包括晶体场与轨道磁矩湮灭、磁各向异性的关系,以及通过波谱数据与磁学测量求晶体场参数。     

有机分子修饰铁粒子表面改善水基磁流变液的抗氧化性和稳定性

采用有机分子N-葡萄糖基乙二胺三乙酸(GED3A)修饰羰基铁(CI)粒子表面的方法, 制备了复合磁性粒子(CMPs)和水基磁流变(MR)液; 用扫描电镜(SEM)、振动样品磁强计(VSM)和带磁场供应和控制器的流变仪表征了CMPs及水基MR液的性能; 同时, 通过稳定性试验、空气氧化试验、酸腐蚀试验分别分析了水基MR液的分散稳定性和抗氧化性. 结果表明, 用此方法制备的CMPs具有良好的软磁性能, 饱和磁化强度(Ms)为182.2 emu·g-1, 矫顽力(Hc)为4.17 Oe, 剩磁(Mr)为0.1944 emu·g-1. 与原CI粒子水基MR液比较, 制备的水基MR液的沉降率下降了约24.4%; 在酸的浓度为0.02-0.10 mol·L-1范围内, 抗HCl氧化的能力提高了92.6%-95.7%, 抗HNO3氧化的能力提高了86.1%-93.8%.     

碗形胶体颗粒/阵列薄膜的制备及性能研究进展

随着科学技术和应用需求的快速发展, 对胶体颗粒形貌、尺寸和组分提出了越来越高的要求, 简单组成的球形颗粒已经难以满足需求. 微/纳米碗形胶体颗粒/阵列薄膜由于具有比表面积大、结构对称性下降等特点, 在纳米反应器、药物运载、高灵敏度传感器、数据储存、自组装等方面有着广阔的应用前景, 其研究、开发和应用已经成为微／纳米材料研究领域的热点. 概述了近十年来国内外碗形胶体颗粒/碗形阵列薄膜的研究进展, 按照无机和金属、聚合物两大类分别对碗形材料的各种制备方法进行了详细介绍, 目前主要有单层胶体晶体模板法、碗形阵列薄膜模板法、诱导生长法、异形颗粒法、中空微球内陷法、种子聚合法、溶剂处理法等; 按照材质种类, 分别对TiO₂, ZnO, Fe_xO_y, 贵金属、聚合物等碗形颗粒/阵列薄膜的结构与性能研究进行了概述, 指出了其潜在的应用领域; 并进一步展望了该领域未来的发展趋势.     

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.     

Extraction of Rutin and Rhoifolin by Inorganic Borate Functionalized Magnetic Particles

We demonstrate a facile approach for smart time‐saving extraction of active components of rutin and rhoifolin by a new kind of magnetic particles (MPs). The inorganic borate functionalized magnetic particles are quasi‐spherical with an average diameter of 200–220 nm. The MPs were characterized by scanning electron microscopy and X‐ray diffraction techniques. The inorganic boron content in MPs was confirmed by electron‐dispersive X‐ray spectroscopy. The extraction and release efficiency of MPs were investigated. The smart borate‐decorated magnetic particles show a specific extraction towards the active components containing cis‐1,2 diol moieties. Rutin and rhoifolin were extracted at 16.55 and 22.49 mg/g, respectively. The recycling test shows that MPs can be reused and maintain a significant efficiency for seven cycles. Hence, a novel structured and reusable magnetic nanomaterial for extracting rutin and rhoifolin was developed. This strategy of specific extraction will be an important method to obtain the active components with some structure features through designing various structured particles.     

Layered Black Phosphorus: Strongly Anisotropic Magnetic,Electronic, and Electron‐Transfer Properties

Layered elemental materials, such as black phosphorus, exhibit unique properties originating from their highly anisotropic layered structure. The results presented herein demonstrate an anomalous anisotropy for the electrical, magnetic, and electrochemical properties of black phosphorus. It is shown that heterogeneous electron transfer from black phosphorus to outer‐ and inner‐sphere molecular probes is highly anisotropic. The electron‐transfer rates differ at the basal and edge planes. These unusual properties were interpreted by means of calculations, manifesting the metallic character of the edge planes as compared to the semiconducting properties of the basal plane. This indicates that black phosphorus belongs to a group of materials known as topological insulators. Consequently, these effects render the magnetic properties highly anisotropic, as both diamagnetic and paramagnetic behavior can be observed depending on the orientation in the magnetic field.     

层层自组装修饰磁性纳米粒子及蛋白质吸附研究

采用层层自组装技术将聚天冬胺酸和聚乙二胺修饰到磁性纳米粒子表面上, 并研究了修饰后的磁性纳米粒子的zeta电势变化和对蛋白质的吸附. 先通过化学共沉淀的方法获得了四氧化三铁磁性纳米粒子, 然后利用层层自组装的方法对纳米粒子进行了修饰. 用TEM表征了纳米粒子的尺寸. 用红外光谱表征了修饰过程中磁性纳米粒子表面组成的变化情况. 研究了修饰过程对磁性纳米粒子的zeta电势的影响. zeta电势的正负和大小与表面连接的分子的带电性质有关. 磁性纳米粒子的等电点接近中性. 聚天冬胺酸修饰的磁性纳米粒子的Zeta电势为负值. 在聚乙二胺溶液的pH＝11时获得的双层修饰的磁性粒子的等电点接近9, 并且等电点随聚乙二胺溶液的pH的减小而减小. 结果也表明在pH＝7.4时具有不同表面电荷的磁性纳米粒子通过静电作用选择性地吸附蛋白质.     

Heterocoagulation in Bidisperse Magnetorheological Fluids Containing Like-Charged Nanosized and Micron Particles Without a Magnetic Field

Based on extended Derjaguin–Landau–Verwey–Overbeek theory, a heterocoagulation model is proposed for magnetorheological (MR) fluids containing like-charged nanosized and micron particles without a magnetic field. This model considers three major interactions, namely van der Waals attraction, electrical double layer (EDL) interaction, and steric repulsion. The EDL interaction has been identified as the most important factor. The surface potential ratio β (ψ₂/ψ₁) between two dissimilar particles with like charge plays an important role in controlling the change of EDL interaction. At higher β ratios, the EDL interaction becomes attractive when the surface separation falls within a certain range. Two groups of MR fluid samples have been used in experimental studies based on electroacoustic measurements. In the first group, the ratio and the sum of the zeta potentials between carbonyl iron particles and ceria were 4 and ?734.57 mV, respectively. In the second group, these parameters were 1.38 and ?108.17 mV, respectively. The experimental results suggested that the second group did not undergo heterocoagulation, whereas the first group showed extensive heterocoagulation. The difference in surface potentials between particles of two different phases has been found to be critical for determining the state of dispersion or heterocoagulation in concentrated MR fluid systems.     

铁酸钴纳米微粒的共沉淀法制备和磁性质(英)

The cobalt ferrite nanoparticles were prepared by coprecipitation in the presence of poly (N-vinylpyrrolidone) (PVP) and characterized by XRD, TEM, EDX and magnetometry. XRD results suggest the formation of pure cobalt ferrite. The mean particle sizes of CoFe₂O₄ samples annealed at 400 ℃ and 600 ℃ were ca. 6 and 25 nm, respectively as obtained by transmission electron microscopy (TEM). The magnetic measurements indicated that nano-particles obtained at 400 ℃ were superparamagnetic while that prepared at 600 ℃ were ferrimagnetic.     

热压/热变形纳米复合永磁体的制备和磁性能的研究

研究了热压热变形纳米复合永磁体制备的新工艺,探讨了制备高性能高各向异性块状纳米复合永磁体的新方法。以晶态纳米复合永磁粉末为原料,研究了热压热变形工艺参数与磁体密度和磁性能的关系。实验中制备出的热压热变形磁体的密度高达7.508g·cm-3,磁体的磁能积为61kJ·m-3。实验表明,温度是影响热压热变形磁体性能的重要因素。磁体在平行于压力方向的磁性能稍高于垂直于压力方向的磁性能,体现出微弱的各向异性。     

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.     

Estimation of the Thermophysical Properties of Pentaalkylguanidinium-Based Magnetic Ionic Liquids with Unusual Thermal Expansion Coefficient

The thermal expansion coefficient (α_exp.), the molecular volume (V_m), the entropy of surface formation (S_a), and the Gibbs energy of surface formation (E_a) of four pentaalkylguanidinium-based MILs [C_nTMG][FeCl₃Br] (n=2, 4, 6, 8) were calculated based on the density and surface tension data determined from 278.15 to 323.15 K. In terms of classical semiempirical methods, the standard molar entropy (S⁰), the lattice energy (U_POT), the molar enthalpy of evaporation ( , (298 K)), and the thermal expansion coefficient (α_est.) of the MILs were further estimated. The estimation results indicate that the classical semiempirical methods are suitable for estimating the thermophysical properties of the MILs, except the unusual α_exp., which were extremely larger than those of representative non-magnetic ionic liquids (ILs). We further optimized the estimation methods and discussed the potential reasons for the unusual thermal expansion coefficient of the MILs.     

Frozen‐In Magnetic Order in Uniaxial Magnetic Gels: Preparation and Physical Properties

We describe the preparation and characterization of uniaxial magnetic gels. Fibril formation of the embedded magnetic particles generates easily detectable magnetic and optical anisotropies. A finite magnetization is frozen‐in and leads to a ferromagnetic‐like response in small homogeneous external magnetic fields. We present, for the first time, frequency dependent measurements of the shear modulus G′. Despite their optical and magnetic anisotropy, the gels are mechanically isotropic.

The time‐dependent G′ for a ferrogel in the parallel orientation in a homogeneous field of 200 mT.     

Simulation of the Structure and the Dynamics of the Particles of MR Fluids in Rotating Magnetic Fields

By the numeric simulation of many particles in MR fluids, we can get the characteristic of the structure of MR fluids in rotating magnetic fields. During the simulation, the magnetic dipole model is used to simulate the force of magnetic fields on particles.