Preparation and clinical application of immunomagnetic latex

Magnetic poly(methyl methacrylate) (PMMA)/poly(methyl methacrylate‐co‐methacrylic acid) [P(MMA–MAA)] composite polymer latices were synthesized by two‐stage soapless emulsion polymerization in the presence of magnetite (Fe₃O₄) ferrofluids. Different types and concentrations of fatty acids were reacted with the Fe₃O₄ particles, which were prepared by the coprecipitation of Fe(II) and Fe(III) salts to obtain stable Fe₃O₄ ferrofluids. The Fe₃O₄/polymer particles were monodisperse, and the composite polymer particle size was approximately 100 nm. The morphology of the magnetic composite polymer latex particles was a core–shell structure. The core was PMMA encapsulating Fe₃O₄ particles, and the shell was the P(MMA–MAA) copolymer. The carboxylic acid functional groups (COOH) of methacrylic acid (MAA) were mostly distributed on the surface of the composite polymer latex particles. Antibodies (anti‐human immunoglobulin G) were then chemically bound with COOH groups onto the surface of the magnetic core–shell composite latices through the medium of carbodiimide to form the antibody‐coated magnetic latices (magnetic immunolatices). The MAA shell composition of the composite latex could be adjusted to control the number of COOH groups and thus the number of antibody molecules on the magnetic composite latex particles. With a magnetic sorting device, the magnetic immunolatices derived from the magnetic PMMA/P(MMA–MAA) core–shell composite polymer latex performed well in cell‐separation experiments based on the antigen–antibody reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1342–1356, 2005     

Study on the properties and stability of ionic liquid-based ferrofluids

Ionic liquid (IL)-based ferrofluids have been prepared dispersing both bare and sterically stabilized CoFe₂O₄ nanoparticles. The precipitated particles were characterized by X-ray diffraction, scanning electronic microscopy, transmission electron microscopy, Fourier transform infrared, and vibrating sample magnetometry studies. The water-absorbing property of ferrofluids at ambient temperature was estimated by weight and viscosity measurements. Colloidal dispersion stability of the ferrofluids was evaluated by particle suspension percentage. Experimental results indicate that interparticle electrostatic repulsion is not effective in stabilizing bare magnetic particles in IL. There is no significant increase on the dispersion stability when the particles were coated with a monolayer of oleic acid. The reason could be caused by the incompatibility between the nonpolar tail of surfactant and carrier liquid. When excess oleic acid was added into IL, stable magnetic colloid was achieved by a steric stabilization layer coated to be compatible with the IL.     

Synthesis of Iron Oxide Nanoparticles Used as MRI Contrast Agents: A Parametric Study

Colloidal iron oxides play an important role as magnetic resonance imaging (MRI) contrast agents. The superparamagnetic particles actually used are constituted by solid cores (diameter of 5-15 nm), generally coated by a thick polysaccharidic layer (hydrodynamic radii of 30-100 nm), and formulated by direct coprecipitation of iron salts in the presence of polymeric material. To better control the synthesis, we attempted to formulate new stable uncoated superparamagnetic nanoparticles. Colloids were generated by coprecipitation of an aqueous solution of iron salts and tetramethylammonium hydroxide (TMAOH) solution. The influence of parameters such as media composition, iron media, injection fluxes, Fe and TMAOH concentrations, temperature, and oxygen on size, magnetic and magnetic resonance relaxometric properties, and colloidal stability of particles were evaluated. We have determined the relative importance of these parameters as well as the optimal conditions for obtaining uncoated stable particles with an average size of 5 nm and interesting relaxivities. The interpretation of the observed limits takes into account diffusibilities of reactants and product, feeding rates of reactants, and surface properties of nanoparticles. A model of synthesis, related to spontaneous emulsification of suspensions, is proposed. Copyright 1999 Academic Press.     

Saturation Magnetization and Law of Approach to Saturation for Self-formed Ionic Ferrofluids Based on MnFe2O2 Nanoparticles

The magnetization curves of MnFe₂O₂ nanoparticles and self-formed ferrofluids based on these particles have been measured at room temperature. The median size of the particlesis 13.67 nm. The specific saturation magnetization is less than the theoretical value for theferrofluids. In the high field range from 5 kOe to 10 kOe, the higher the particle volume fraction is, the steeper the slope of the magnetization curves is when it approaches saturation.The behavior of the saturation magnetization and the law of approach to saturation are due to the presence of self-assembled aggregates of ring-like micelle structures which form in the absence of the magnetic field and field-induced aggregates, respectively. The field-induced aggregates have a dissipative structure, so that at high field, the law of approach to saturation magnetization is different from the one described using Langevin paramagnetism theory. The large particles in the ferrofluids result in apparent hysteresis.     

Preparation of PMAA-coated Dysprosium Ferrite Ferrofluids and Study on the Superparamagnetism

IntroductionFerrofluids[1] consistof ultramicroscopic ferro-and ferrimagnetic particles coated with a monolayeror a bilayer of surfactant molecules,which are col-loidally dispersed in a carrier liquid.Under the in-fluence of an external magnetic field,such ferroflu-ids exhibit certain novel phenomena and severalphysical properties of theirs are modified.For ex-ample,ferrofluids are stable in the gravitationaland magnetic fields and behave not only as solidshaving a large saturation magnetizati…     

Preparation and properties of monodisperse latex spheres with controlled magnetic moment for field-induced colloidal crystallization and (dipolar) chain formation

We report the preparation and properties of monodisperse magnetic poly(methyl methacrylate) latex spheres that exhibit field-induced colloidal crystallization to exotic morphologies controlled by the geometry of the gradient. The magnetic moment of the novel magnetic spheres is due to an inner core of magnetite particles. These particles, obtained from a conventional ferrofluid, first form a monodisperse emulsion with a silane coupling agent, after which they are directly incorporated in PMMA latex synthesized by standard emulsion polymerization. Scattering from the latex shell dominates over light absorption by the magnetic cores such that visible Bragg reflections of the magnetic crystals can be clearly observed. Concentrated nearly white latex fluids may exhibit near a magnet the warped equilibrium menisci known from the usually dark magnetite ferrofluids. Of the many possible applications, we briefly discuss the subsequent growth and melting of crystals by a slowly oscillating gradient, the formation of radial lattices, and the formation of ordered magnetic dots in PMMA latex films.     

Design and synthesis of novel magnetic core-shell polymeric particles

A novel synthetic strategy was developed for the preparation of magnetic core-shell (MCS) particles consisting of hydrophobic poly(methyl methacrylate) cores with hydrophilic chitosan shells and gamma-Fe2O3 nanoparticles inside the cores via copolymerization of methyl methacrylate from chitosan in the presence of vinyl-coated gamma-Fe2O3 nanoparticles. The magnetic core-shell particles were characterized with transmission electron microscopy, field-emission scanning electron microscopy, particle size and zeta-potential measurements, vibrating sample magnetometry, and atomic force microscopy, respectively. The MCS particles were less than 200 nm in diameter with a narrow size distribution (polydispersity = 1.09) and had a good colloidal stability (critical coagulation concentration = 1.2 M NaCl at pH 6.0). Magnetization study of the particles indicated that they exhibited superparamagnetism at room temperature and had a saturation magnetization of 2.7 A m2/kg. The MCS particles were able to form a continuous film on a glass substrate, where magnetic nanoparticles could evenly disperse throughout the film. Thus, these new materials should be extremely useful in various applications.     

聚硅氮烷包敷纳米铁磁粉PSZFe的合成及其雷达波吸收性能研究

金属磁性材料是一类很重要的雷达波吸收材料 ,而纳米铁磁粉是其中的姣姣者 ,具有质量轻、居里温度高、磁化强度高 (可以是铁氧体磁性材料的 2～ 3倍 ) [1,2 ] 、矫顽力大、雷达波吸收性能好和频带宽等优点[3 ] ;但由于其颗粒太细 ,暴露在空气中即被强烈氧化 ,实际应用很困难 ,对其进行包敷处理是一种很有效的抗氧化腐蚀方法 .聚硅氮烷(PSZ)做为纳米铁磁粉包敷层有很多优点 :包敷层所要求的化学和力学性能可以通过调整氯硅烷单体的比例以及反应条件而实现[4] ;包敷层具有高致密性、高疏水性 ,从而使潮气、水和氧气很难侵入 ;包敷层耐热性好…     

Micelle-like particles based on self-assembly of rod-like FPEEK and coil-like PVA

The self-assembly of a rod-like polymer [hydroxyl-terminated trifluoromethylphenyl-substituted fluorinated poly(ether ether ketone) (FPEEK)] and a coil-like polymer (polyvinyl alcohol, PVA) in water has been studied. It was found that this polymer pair could form micelle-like particles. Hydrogen bonding between the hydroxy groups of rod-like FPEEK and coil-like PVA, and parallel packing of the rod-like FPEEK are the main factors affecting the formation of micelle-like particles. Over a broad range, when the FPEEK/PVA mass ratio or the tetrahydrofolate/H₂O volume ratio is decreased, the diameter of micelle-like particles is decreased. The diameters (around 250 nm) of micelle-like particles measured by scanning electron microscopy and dynamic light scattering are similar, but are different from that measured by transmission electron microscopy (around 150 nm). Thus, it can be concluded that micelle-like particles have a core–shell structure and the cores of micelles are composed of FPEEK, and that the shells of micelles are composed of PVA. When polyethylene glycol was used instead of PVA, micelle-like particles were also formed, but the average diameter was bigger than that of the particles formed by PVA and FPEEK. This work was supported by the National Nature Science Foundation of China (50203004).     

Micellar factors which play a role in the control of the nanosize particles of cobalt ferrite

Cobalt and iron (II) dodecylsulfate [Co(DS)₂ and Fe(DS)₂] form oil in water micelles. They have been used to make nanosize magnetic particles. The size of the particles is controlled by the surfactant concentration. The average size of the particles is determined by transmission electron microscopy, X-ray diffraction by small angle X-rays scattering and from simulation of magnetization curves. It varies from 2 to 5 nm, with less than 30% in polydispersity. By XANES, an increase in the formal oxidation degree of iron and cobalt ions with the increase in surfactant concentration has been observed. This could be correlated to the increase in the particle size with surfactant concentration.     

铁系胶体催化剂各组分相互作用的研究

已知催化剂 FeCl3 Al(i Bu)3 Phen(邻菲罗啉 )在加氢汽油介质中对丁二烯聚合有较高的活 性 [1－ 2],作者曾研究了 FeCl3 Al(i Bu)3 Phen体系催化剂的相态,证明该体系为胶体催化剂 [3]. 　　Bushick[4]较早地使用电导率研究烷基铝氯化钛体系离子特性与聚合速率的关系 .至今尚未见从胶体角度研究本体系各组分之间相互作用的报导 . 　　本文是把电导率作为胶体的电学性质之一进行研究的 .主要研究了 FeCl3 Al(i Bu)3 Phen胶体催化剂体系单、多组分溶液的电导率与浓度的关系,结合相应的紫外可见光谱分析结果,…     

On the Theory of the Dynamic Properties of Dense Magnetic Fluids: Polydisperse Media

The theoretical model was proposed for determining functions of the dynamic response of moderately concentrated ferrofluids on the external magnetic field and their rheological properties. Ferrofluids are considered to be polydisperse colloidal systems with the interacting (albeit individual) particles. The model is based on the regular approximation of virial expansion in powers of the particle concentration and on the well-known effective field method. The effect of system polydispersity and the magnetodipole and hydrodynamic interactions between particles on the macroscopic and dynamic properties of ferrofluids was estimated. Calculations demonstrated that the interparticle interaction results in an increase in the dynamic functions of uniform ferrocolloids up to several tens of percents.     

Synthesis and characterization of perovskite-type La1-yCayMn1-xB″xO3±δ nanomaterials (B″ = Ni,Fe; x = 0.2, 0.5; y = 0.4, 0.25)

Perovskite-type nanomaterials of the compositions La_1-yCa_yMn_1-xB″_xO_3±δ with B’’ = Ni, Fe; x = 0.2, 0.5 and y = 0.4, 0.25 were prepared using two different preparation routes (synthesis by precipitation and the PVA/sucrose method) at 500 °C–700 °C. The calcined products of the syntheses were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and physisorption measurements. The materials from the PVA/sucrose method contain particles with diameters from 33 nm to 48 nm, generate specific surface areas up to 33 m²/g and form pure compared to 45 nm–93 nm and up to 18 m²/g from precipitation method which contain a significant amount of sodium ions. The agglomeration process was analyzed for one nanomaterial (B’’ = Fe, x = 0.2, y = 0.4) from the PVA/sucrose method using temperature dependent XRD showing only a slight growth (4.3%) of nanoparticles at 600 °C. The materials from the PVA/sucrose method turned out to be more suitable as electrode materials in electrochemical applications (SOFC, sensors) because of smaller particle sizes, higher specific surface areas and purity.     

Synthesis and utilization of monodisperse hollow polymeric particles in photonic crystals

We developed a process to fabricate 150-700 nm monodisperse polymer particles with 100-500 nm hollow cores. These hollow particles were fabricated via dispersion polymerization to synthesize a polymer shell around monodisperse SiO(2) particles. The SiO(2) cores were then removed by HF etching to produce monodisperse hollow polymeric particle shells. The hollow core size and the polymer shell thickness, can be easily varied over significant size ranges. These hollow polymeric particles are sufficiently monodisperse that upon centrifugation from ethanol they form well-ordered close-packed colloidal crystals that diffract light. After the surfaces are functionalized with sulfonates, these particles self-assemble into crystalline colloidal arrays in deionized water. This synthetic method can also be used to create monodisperse particles with complex and unusual morphologies. For example, we synthesized hollow particles containing two concentric-independent, spherical polymer shells, and hollow silica particles which contain a central spherical silica core. In addition, these hollow spheres can be used as template microreactors. For example, we were able to fabricate monodisperse polymer spheres containing high concentrations of magnetic nanospheres formed by direct precipitation within the hollow cores.     

Synthesis of cationic core-shell latex particles

Surfactant-free seeded (core-shell) polymerization of cationic polymer colloids is presented. Polystyrene core particles with sizes between 200 nm and 500 nm were synthesized. The number average diameter of the colloidal core particles increased with increasing monomer concentration. Cationic shells were introduced by co-polymerizing styrene with the cationic monomers (vinylbenzyl)trimethylammonium chloride (VBTMAC), [(2-methacryloyloxy)ethyl] trimethylammonium chloride (METMAC) and [(2-(acryloyloxy)ethyl] trimethylammonium chloride (AETMAC) onto the polystyrene cores. The cationic monomer AETMAC, undocumented to our knowledge in colloid synthesis, produced the best cationic shells and could be incorporated at much higher concentrations in the shell compared to the commonly used VBTMAC and METMAC, which yielded undesired polyelectrolyte side products already at relatively low cationic monomer concentrations. In shell formation, feed concentrations of AETMAC between 1.3 mol% (2.4 wt%) and 10.7 mol% (20 wt%) in styrene could be employed, allowing us to control colloid surface charge density over a wide range. The influence of various polymerization parameters (initiator concentration, cross-linking agent, and ionic strength) on the co-polymerization process with AETMAC is discussed. Core-shell particles were characterized using HR-SEM, potentiometric titration and zeta potential measurements.     

核壳结构磁性镁铝复合氧化物亚微米粒子的制备与表征

首先采用溶剂热法制备粒径均匀分散性良好的Fe3O4亚微米粒子,在对其包覆上一层碳膜进行表面修饰后,采用共沉淀法将硝酸根插层LDHs包覆到磁性粒子的表面,然后500℃焙烧2 h得到磁性镁铝复合氧化物亚微米粒子。这种磁性镁铝复合氧化物亚微米粒子具有以镁铝复合氧化物为壳层,Fe3O4为核的核壳结构,其中壳层厚度为20 nm左右,对其进行二次包覆后壳层厚度可达到50 nm左右,并可以方便的通过重复包覆焙烧过程进行调节,从而实现磁性镁铝复合氧化物亚微米粒子的控制制备。同时,磁性镁铝复合氧化物亚微米粒子具有较强的磁性,其比饱和磁化强度为23.3 emu·g-1,对其进行二次包覆并焙烧后为20.1 emu·g-1。     

Carbon encapsulated magnetic nanoparticles produced by hydrothermal reaction

Carbon encapsulated magnetic nanoparticles(CEMNs)were synthesized by heating an aqueous glucose solution containing Fe-Au(Au coated Fe nanoparticles)nanoparticles at 160-180℃ for 2 h.This novel hydrothermal approach is not only simple but alsoprovides the surface of CEMNs with functional groups like-OH.The formation of carbon encapsulated magnetic nanoparticles wasnot favored when using pure Fe nanoparticles as cores because of the oxidation of Fe nanoparticles by H2O during the reaction and,therefore,the surfaces of the naked Fe nanoparticles had to be coated by Au shell in advance.TEM,XRD,XPS and VSMmeasurments characterized that they were uniform carbon spheres containing some embedded Fe-Au nanoparticles,with asaturation of 14.6 emu/g and the size of the typical product is$350 nm.     

Preparation of non-contact ordered array of polystyrene colloidal particles by using a metallic thin film of fused hemispheres

A thin metallic bilayer consists of fused hollow hemispheres of 930 nm in diameter is fabricated by sputter deposition of Ti and Fe at 50 and 5 nm of thickness, respectively, onto an array of spherical polystyrene colloidal particles. The fused metal hemispheres are utilized to assemble polystyrene colloidal particles of smaller diameters (800 nm) into non-contact two-dimensional periodic array by trapping them in the metallic wells.     

Synthesis and real-time magnetic manipulation of a biaxial superparamagnetic colloid

Superparamagnetic colloidal plates were synthesized from tetrabutylammonium stabilized Ca(2)Nb(3)O(10) nanosheets and oleic acid-stabilized Fe(3)O(4) nanoparticles. Modification with 3-aminopropyltrimethoxysilane produces amine-terminated Ca(2)Nb(3)O(10) with an amine concentration of 0.43 +/- 0.06 groups per Ca(2)Nb(3)O(10) unit as follows from spectroscopic quantification with trinitrobenzenesulfonic acid as a dye. Treatment of the modified sheets in THF/ethanol with 5.3 nm oleic acid-stabilized magnetite nanoparticles yields pseudo-2D assemblies that consist of 2 nm thick nanosheets decorated on both sides with a dense collection (9.3 +/- 0.5 x 10(3) particles per square micrometer per side) of magnetite particles. In noncoordinating or weakly coordinating solvents, these composite particles further aggregate into stacked aggregates with a mean edge length of 1.6 +/- 0.7 microm and a thickness of 79 +/- 30 nm. The colloidal plates were characterized by elemental analysis, X-ray powder diffraction, and infrared and UV/vis spectroscopy. SQUID measurements show that films of the aligned particles are superparamagnetic at room temperature. The magnetic hysteresis that is observed at 5 K reveals that the plates have a magnetic anisotropy with the easy axis in the plane of the plates and the hard axis perpendicular to it. Calculations show that the magnetic anisotropy is a direct consequence of the two-dimensional distribution of the magnetic nanoparticles on the sheets. Optical microscopy reveals that when suspended in ethanol or THF, the colloidal plates can be rotated in real time with a variable external magnetic field (200 Oe). Magnetic alignment of the particles in suspensions also produces asymmetric light scattering patterns and magnetic birefringence. These effects and the observed magneto-orientational properties make the biaxial colloids interesting as components in displays and as magnetic actuators.     

醇／水混合液分离用聚乙烯醇复合膜的渗透汽化特性

制备了聚乙烯醇（ＰＶＡ）／聚丙烯睛（ＰＡＮ）渗透汽化复合膜，研究了交联剂用量、底膜结构、进料液组成、操作温度等因素对膜的渗透汽化性能的影响．发现ＰＶＡ／ＰＡＮ复合膜对水／醇混合液表现为水优先透过，进料液中乙醇浓度在６０～９９ｗｔ％的范围内，渗透通量Ｊｔ与温度之间符合Ａｒｒｈｅｎｉｕｓ关系，选择分离系数αＷ／Ｅ也随温度上升而增大．进料液为９５ｗｔ％的乙醇／水混合液时，７５℃下Ｊｔ高达３００～４５０ｇ／ｍ２ｈ，αＷ／Ｅ为８００～１１００．对异丙醇／水、异丁醇／水及甘油／水混合体系，复合膜显示出更为优秀的透过、分离性能．就膜的化学、物理结构与其渗透汽化性能间的关系进行了讨论．