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.     

多元醇还原法制备片状六边形Fe3O4纳米颗粒

在表面活性剂油酸和油胺,液相环境二苄醚体系中,利用多元醇还原法,采用1,2-十二烷二醇还原前驱体乙酰丙酮铁Fe(acac)3,通过表面活性剂、金属前驱体以及液相环境的共同作用,制备出了单分散片状六边形Fe3O4纳米颗粒。分析了表面活性剂以及还原剂多元醇对纳米颗粒尺寸及形貌的影响。TEM表征结果显示：与未使用表面活性剂的情况相比,油酸和油胺的加入抑制了颗粒的生长,使颗粒尺寸从24.2 nm降低到10.7 nm;颗粒形貌多样化,出现了片状六边形形貌的Fe3O4纳米颗粒。磁性能检测表明： Fe3O4纳米颗粒具有高饱和磁化强度（Ms=88 emu/g）和零剩磁的特点,有望作为磁标记材料应用在生物检测上     

Metallic LiMo3Se3 nanowire film sensors for electrical detection of metal ions in water

LiMo 3Se 3 nanowire film sensors were fabricated by drop-coating a 0.05% (mass) aqueous nanowire solution onto microfabricated indium tin oxide electrode pairs. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM), the films are made of a dense network of 3-7 nm thick nanowire bundles. Immersion of the films in 1.0 M aqueous solutions of group 1 or 2 element halides or of Zn(II), Mn(II), Fe(II), or Co(II) chlorides results in an increase of the electrical resistance of the films. The resistance change is always positive and reaches up to 9% of the base resistance of the films. It occurs over the course of 30-240 s, and it is reversible for monovalent ions and partially reversible for divalent ions. The signal depends on the concentration of the electrolyte and on the size and charge of the metal cation. Anions do not play a significant role, presumably, because they are repelled by the negatively charged nanowire strands. The magnitude of the electrical response and its sign suggest that it is due to analyte-induced scattering of conduction electrons in the nanowires. An ion-induced field effect can be excluded based on gated conductance measurements of the nanowire films.     

Size-controlled synthesis of magnetite nanoparticles

Monodisperse magnetite nanoparticles have been synthesized by high-temperature solution-phase reaction of Fe(acac)3 in phenyl ether with alcohol, oleic acid, and oleylamine. Seed-mediated growth is used to control Fe3O4 nanoparticle size, and variously sized nanoparticles from 3 to 20 nm have been produced. The as-synthesized Fe3O4 nanoparticles have inverse spinel structure, and their assemblies can be transformed into gamma-Fe2O3 or alpha-Fe nanoparticle assemblies, depending on the annealing conditions. The reported procedure can be used as a general approach to various ferrite nanoparticles and nanoparticle superlattices.     

Monodisperse MFe2O4 (M = Fe, Co, Mn) nanoparticles

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)(3), with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe(3)O(4)) nanoparticles. Similarly, reaction of Fe(acac)(3) and Co(acac)(2) or Mn(acac)(2) with the same diol results in monodisperse CoFe(2)O(4) or MnFe(2)O(4) nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe(3)O(4) can be oxidized to Fe(2)O(3), as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.     

Solution self-assembly of magnetic light modulators from exfoliated perovskite and magnetite nanoparticles

Covalent linkage of oleic acid ligated Fe3O4 spheres (9 nm) with sheetlike [H1-xCa2Nb3O10] particles (300 x 300 x 2 nm) yields, depending on conditions, submicro- or microscale stacks, which on their surfaces are decorated with magnetite nanoparticles. Due to the optical anisotropy of the sheetlike Ca2Nb3O10 building blocks and due to the superparamagnetic nature of the Fe3O4 components, the nanostructured composites exhibit magnetically controllable birefringence and light-scattering properties in solution.     

Surfactant-assisted one-pot synthesis of superparamagnetic magnetite nanoparticle clusters with tunable cluster size and magnetic field sensitivity

Magnetic nanoparticles (MNPs) have many potential biomedical applications. Improvements in their magnetic properties and solubility are necessary for these applications to realize their full potential. In this study, MNPs in the form of raspberry-like magnetite (Fe(3)O(4)) nanoparticle clusters, consisting of tiny Fe(3)O(4) particles with a diameter of approximately 20 nm, were prepared under hydrothermal conditions at 200 °C in the presence of 3,4-dihydroxyhydroxysinnamic acid (DHCA). The primary particles were connected by DHCA molecules to form the clusters, which were well dispersed in water media because a COOH group from DHCA appeared on their surfaces. The cluster size could be tuned from 50 to 400 nm without changing the primary particle size by controlling the reaction time. Therefore, all prepared clusters displayed superparamagnetic properties at room temperature. In addition, the sensitivity of Fe(3)O(4) to an external magnetic field could also be controlled by the cluster size.     

Three-layer composite magnetic nanoparticle probes for DNA

A method for synthesizing composite nanoparticles with a gold shell, an Fe3O4 inner shell, and a silica core has been developed. The approach utilizes positively charged amino-modified SiO2 particles as templates for the assembly of negatively charged 15 nm superparamagnetic water-soluble Fe3O4 nanoparticles. The SiO2-Fe3O4 particles electrostatically attract 1-3 nm Au nanoparticle seeds that act in a subsequent step as nucleation sites for the formation of a continuous gold shell around the SiO2-Fe3O4 particles upon HAuCl4 reduction. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, but the magnetic properties of the Fe3O4 inner shell.     

NMR studies into colloidal stability and magnetic order in fatty acid stabilised aqueous magnetic fluids

We report the physico-chemical characterisation of fatty acid stabilised aqueous magnetic fluids, which are ideal systems for studying the influence of nanoparticle aggregation on the emergent magnetic resonance properties of the suspensions. Stable colloids of superparamagnetic magnetite, Fe(3)O(4), nanoparticle clusters in the 80 to 100 nm size range were produced by in situ nanoparticle growth and stabilisation, and by suspending pre-formed nanoparticles. NMR relaxation analysis shows that the magnetic resonance properties of the two types of suspension differ substantially and provides new insights into how the relaxation mechanisms are determined by the organisation of the nanoparticles within the clusters.     

Effect of additives on LiMo3Se3 nanowire film chemical sensors

Here we investigate the effect of lithium iodide and cetyltrimethylammonium (CTA) bromide additives on the ability of LiMo(3)Se(3) nanowire film sensors to bind and detect organic solvents electrically. Both additives decrease the electrical conductivity of the films. Lithium iodide increases the response of the films to both polar and nonpolar analytes. CTA increases the response of the films to nonpolar analytes but reduces the response to polar analytes. Quartz crystal microbalance measurements show that the modified electrical sensitivities of the films are due to altered analyte adsorption abilities of the films. These results show that the Li(+) ions are involved in analyte binding in native LiMo(3)Se(3) films and that a programming of LiMo(3)Se(3) nanowire film sensors is possible by replacing lithium cations with other receptors.     

Synthesis of bilayer oleic acid-coated Fe3O4 nanoparticles and their application in pH-responsive Pickering emulsions

Fe(3)O(4) nanoparticles coated with oleic acid bilayer (a diameter about 12 nm) were synthesized. The structure and composition of the particles were analyzed by TEM, FTIR and TGA. The TGA experiments of the bilayer-coated particles show a distinct two-stage mass loss. Partition experiments show that the modified Fe(3)O(4) nanoparticles are affected by aqueous dispersion pH and ion strength. Accordingly, the Pickering emulsions stabilized by modified Fe(3)O(4) particles are also sensitive to pH and ion strength. The phase inversion of the emulsions occurs when 1.0013.50. The phase inversion of emulsions also can be adjusted by the ion strength. In interfacial adsorption experiments, the hydrophobic Fe(3)O(4) nanoparticles form particle clusters, while the hydrophilic particles form uniform multilayers.     

以磁纳米粒为核的pH敏感型聚谷氨酸树状分子药物载体

报道了一种新的肽类树枝状分子改性磁性纳米药物载体.以天然氨基酸L-谷氨酸为原料,通过收敛法合成了聚(L-谷氨酸)树状分子,将多巴胺配体键合到聚(L-谷氨酸)树状分子上,用核磁(1H-NMR)、质谱(MS)对合成出的树状分子配体进行了表征,然后通过配体交换对四氧化三铁磁纳米粒表面进行多功能化.以阿霉素为模型药物通过pH敏...     

Biocompatible and biodegradable polymer nanofibers displaying superparamagnetic properties.

Superparamagnetic polymer nanofibers intended for drug delivery and therapy are considered here. Magnetite (Fe3O4) nanoparticles in the diameter range of 5-10 nm were synthesized in aqueous solution. Polymer nanofibers containing magnetite nanoparticles were prepared from commercially available poly(hydroxyethyl methacrylate), PHEMA, and poly-L-lactide (PLLA) by the electrospinning technique. Nanofibers with diameters ranging from 50 to 300 nm were obtained. Nanofibers containing up to 35 wt % magnetite nanoparticles displayed superparamagnetism at room temperature. The blocking temperature was about 50 K for an applied field of 500 Oe, and the saturation magnetization was 3.5 emu g(-1) and 1.1 emu g(-1) for Fe3O4/PHEMA and Fe3O4/PLLA nanofibers, respectively, and depended on the amount of Fe3O4 nanoparticles in the nanocomposites. To test such magnetic nano-objects for applications as drug carriers and drug-release systems we incorporated a fluorescent albumin with dog fluorescein isothiocyanate (ADFI).     

肿瘤靶向的磁性荧光IR780-Fe3O4纳米颗粒用于循环肿瘤细胞的检测

循环肿瘤细胞(Circulating tumor cells,CTCs)的简单、快速分离和检测是目前临床研究中面临的一项挑战.本研究制备了具有肿瘤靶向识别作用的磁性荧光IR780-Fe3 O4纳米颗粒,并将其用于CTCs的分离和检测.通过电镜、荧光光谱仪和超导量子干涉仪对合成的IR780-Fe3 O4纳米颗粒进行表征;采用激光共聚焦显微镜和流式细胞仪对IR780-Fe3 O4纳米颗粒对肿瘤细胞和正常细胞的靶向效果进行了分析;利用激光共聚焦显微镜对IR780-Fe3 O4纳米颗粒在MCF-7细胞中的位置进行定位;并根据IR780-Fe3 O4纳米颗粒孵育后肿瘤细胞的荧光强度绘制标准曲线.研究结果表明,IR780-Fe3 O4能很好地靶向多种CTCs.细胞定位实验进一步表明,IR780-Fe3 O4主要靶向识别肿瘤细胞的线粒体.通过Fe3 O4磁性纳米颗粒偶联IR780建立的这种方法可很好地区分肿瘤细胞和正常细胞,并对模拟血液中的CTCs进行了分离和检测.     

Synthesis of polymer-supported Fe3O4 nanoparticles and their application as a novel route for the synthesis of imidazole derivatives

Research on Chemical Intermediates - Cross-linked poly(4-vinylpyridine) supported Fe3O4 nanoparticles, abbreviated as [P4-VP]-Fe3O4NPs, were easily prepared as a new magnetic polymeric catalyst and...     

A magnetic MoS2-Fe3O4 nanocomposite as an effective adsorbent for dispersive solid-phase microextraction of lead(II) and copper(II) prior to their determination by FAAS

Microchimica Acta - The authors describe the preparation of a nanocomposite (mag-MoS2-Fe3O4) that was prepared from molybdenum disulfide (MoS2) and magnetic Fe3O4 nanoparticles by a hydrothermal...     

配体交换法制备水中高分散稳定性的多羧基修饰Fe3O4纳米颗粒

采用油相高温分解法制备了粒径可控且单分散的油溶性Fe3O4磁性纳米粒子(MNPs-OA), 并通过配体交换对其表面进行了亲水性修饰, 制备了柠檬酸(CA)、 N-(三甲氧基硅丙基)乙二胺三乙酸钠(SiCOOH)、 丁烷四羧酸(BTCA)和乙二胺四乙酸 (EDTA)四钠4种多羧基配体修饰的水溶性Fe3O4磁性纳米粒子(MNPs-CA, MNPs-SiCOOH, MNPs-BTCA 和MNPs-EDTA), 其中首次选用四羧基配体BTCA和EDTA四钠来修饰Fe3O4磁性纳米粒子(MNPs). 对油溶性MNPs和4种水溶性MNPs的形貌、 结构、 化学组成和磁性能进行了表征, 并对4种多羧基配体修饰的水溶性MNPs在水相中的稳定性和分散性进行了表征. 结果表明, 所得MNPs的平均粒径为15 nm, 具有超顺磁性, 配体交换后的水溶性MNPs具有良好的亲水性, 并在弱酸～碱性很宽的pH范围内具备良好的分散稳定性. 此类多羧基修饰的水溶性MNPs可与适当的阳离子聚电解质进行组装, 从而得到在磁靶向载体和磁共振造影(MRI)显影中具有良好应用前景的磁性自组装微囊.     

Porous Fe3O4 nanoparticles: synthesis and application in catalyzing epoxidation of styrene

A facile route was employed to synthesize porous magnetite via reaction of FeCl(3)·6H(2)O with N(2)H(4)·H(2)O in ethylene glycol without any structure-directing agent. The resultant Fe(3)O(4) particles were characterized by transmission electron microscopy, N(2) adsorption, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. It was demonstrated that the particle size varied in the range of 40-220 nm, and the pore size of particles was centered around 2 nm. The gases produced in the formation process of the particles played key role in the formation of the porous structure. The obtained porous magnetite was used as support to immobilize Au nanoparticles with size less than 2 nm with the assistance of L-cysteine. The as-prepared Fe(3)O(4) particles can effectively catalyze epoxidation of styrene, and the immobilization of Au nanoparticles on the Fe(3)O(4) support significantly improved the activity of the catalyst.     

Fe_3O_4/CdTe/聚氨酯纳米复合物的制备及其性能研究

由共沉淀法和Stober法制备了伯胺基功能化SiO2稳定的Fe3O4磁性纳米粒子Fe3O4@SiO2-NH2;Fe3O4@SiO2-NH2与二异氰酸酯及咪唑阳离子二醇、聚乙二醇的反应使其表面形成阳离子型聚氨酯稳定层;通过阳离子型聚氨酯与CdTe量子点表面修饰的巯基乙酸间的电荷相互作用,制备得到了Fe3O4/CdTe/聚氨酯纳米复合物.用X射线衍射(XRD)、红外吸收光谱(FTIR)、热重分析(TGA)、透射电子显微镜(TEM)、磁强计(VSM)、紫外吸收光谱(UV)、荧光发射光谱(PL)表征了该纳米复合物的结构与性能.结果表明,CdTe量子点均匀地分散在Fe3O4@SiO2磁性纳米粒子周围,所得纳米复合物在溶剂中分散均匀,不团聚,且具有超顺磁性,并保持了CdTe量子点的荧光性能.     

Magnetite nanorod thermotropic liquid crystal colloids: Synthesis, optics and theory

We have developed a facile method for preparing magnetic nanoparticles which couple strongly with a liquid crystal (LC) matrix, with the aim of preparing ferronematic liquid crystal colloids for use in magneto-optical devices. Magnetite nanoparticles were prepared by oxidising colloidal Fe(OH)(2) with air in aqueous media, and were then subject to alkaline hydrothermal treatment with 10moldm(-3) NaOH at 100°C, transforming them into a polydisperse set of domain magnetite nanorods with maximal length ～500nm and typical diameter ～20nm. The nanorods were coated with 4-n-octyloxybiphenyl-4-carboxylic acid (OBPh) and suspended in nematic liquid crystal E7. As compared to the conventional oleic acid coating, this coating stabilizes LC-magnetic nanorod suspensions. The suspension acts as a ferronematic system, using the colloidal particles as intermediaries to amplify magnetic field-LC director interactions. The effective Frederiks magnetic threshold field of the magnetite nanorod-liquid crystal composite is reduced by 20% as compared to the undoped liquid crystal. In contrast with some previous work in this field, the magneto-optical effects are reproducible on time scales of months. Prospects for magnetically switched liquid crystal devices using these materials are good, but a method is required to synthesize single magnetic domain nanorods.