Length-controllable catalyzing-synthesis and length-corresponding properties of FeCo/Pt nanorods

Newly designed magnetic-alloy/noble-metal FeCo/Pt nanorods have been first reported and fabricated through a length-controllable catalyzing-synthesis process in which the growth of FeCo nanorods was induced on Pt nanotips. The length of FeCo/Pt nanorods depends on the number of platinum nanotips. The proposed synthesis mechanism was corroborated by scanning electron microscopy, transition electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. With the decrease of Fe content in Fe(x)Co(96-x)/Pt(4) nanoalloys from 77 to 15, the morphology changes from nanorods with different lengths to nanoparticles. The analysis of the magnetic hysteresis loops indicated that the magnetic saturation and coercivity were strongly dependent on the length of the nanorods in which maximum saturation magnetization and minimum coercivity were obtained for Fe(77)Co(19)/Pt(4) nanorods with the length of ～2.5 μm. In particular, FeCo/Pt exhibited length-dependent reactivity towards 1,1,2,2-tetrachloroethane, and Fe(77)Co(19)/Pt(4) nanorods with the length of ～2.5 μm yielded the greatest dechlorination rate. Moreover, Pt can enhance the dechlorination of 1,1,2,2-tetrachloroethane.     

A Simple Chemical Method for Synthesis of NiFe2O4 Nanoparticles and Polystyrene-Based Magnetic Nanocomposites

Magnetic NiFe₂O₄ (NiFe) nanoparticles were synthesized via a facile chemical reaction between Ni(NO₃)₂ and Fe(NO₃)₃. Different percents of NiFe nanoparticles were then added to polystyrene (PS) matrix. Nanoparticles were characterized using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. The nanoparticles exhibit ferromagnetic behaviour at room temperature, with a saturation magnetization of 20.8 emu/g and a coercivity of 99.6 Oe. Preparation of NiFe₂O₄ -PS nanocomposite leads to decrease in the coercivity.     

Two-, three-, and four-component magnetic multilayer onion nanoparticles based on iron oxides and manganese oxides

Magnetic multilayered, onion-like, heterostructured nanoparticles are interesting model systems for studying magnetic exchange coupling phenomena. In this work, we synthesized heterostructured magnetic nanoparticles composed of two, three, or four components using iron oxide seeds for the subsequent deposition of manganese oxide. The MnO layer was allowed either to passivate fully in air to form an outer layer of Mn(3)O(4) or to oxidize partially to form MnO|Mn(3)O(4) double layers. Through control of the degree of passivation of the seeds, particles with up to four different magnetic layers can be obtained (i.e., FeO|Fe(3)O(4)|MnO|Mn(3)O(4)). Magnetic characterization of the samples confirmed the presence of the different magnetic layers.     

Generalized synthesis of metal phosphide nanorods via thermal decomposition of continuously delivered metal-phosphine complexes using a syringe pump

We synthesized uniform-sized nanorods of transition metal phosphides from the thermal decomposition of continuously delivered metal-phosphine complexes using a syringe pump. MnP nanorods with dimensions of 8 nm x 16 nm and 6 nm x 22 nm sized were synthesized by the thermal decomposition of Mn-TOP complex, which was prepared from the reaction of Mn(2)(CO)(10) and tri-n-octylphosphine (TOP), using a syringe pump with constant injection rates of 10 and 20 mL/h, respectively. When Co-TOP complex, which was prepared from the reaction of cobalt acetylacetonate and TOP, was reacted in a mixture solvent composed of octyl ether and hexadecylamine at 300 degrees C using a syringe pump, uniform 2.5 nm x 20 nm sized Co(2)P nanorods were generated. When cobaltocene was employed as a precursor, uniform Co(2)P nanorods with 5 nm x 15 nm were obtained. When Fe-TOP complex was added to trioctylphosphine oxide (TOPO) at 360 degrees C using a syringe pump and then allowed to age at 360 degrees C for 30 min, uniform-sized FeP nanorods with an average dimension of 12 nm x 500 nm were produced. Nickel phosphide (Ni(2)P) nanorods with 4 nm x 8 nm were synthesized successfully by thermally decomposing the Ni-TOP complex, which was synthesized by reacting acetylacetonate [Ni(acac)(2)] and TOP. We measured the magnetic properties of these nanorods, and some of the nanorods exhibited different magnetic characteristics compared to the bulk counterparts.     

Synthesis and shape-tailoring of copper sulfide/indium sulfide-based nanocrystals

Heterostructured Cu2S-In2S3 nanocrystals with various shapes and compositions were synthesized by a high-temperature precursor-injection method using the semiconductor nanocrystal Cu1.94S as a catalyst. The intrinsic cationic deficiencies formed at high temperature by Cu ions made the Cu1.94S nanocrystal a good candidate for catalyzing the nucleation and subsequent growth of In 2S3 nanocrystals, eventually leading to the formation of heterostructured Cu2S-In2S3 nanocrystals. Gelification of the reaction systems, which were composed of different types of nanocrystal precursors and solvent, was found to be a very effective measure for controlling the growth kinetics of the heterostructured particles. Consequently, matchsticklike Cu2S3-In2S3 heterostructured nanorods, teardroplike quasi-core/shell Cu2S@In2S3 nanocrystals, and pencil-like In2S3 nanorods were successfully obtained by manipulating the gelification of the reaction system; this formed a solid experimental basis for further discussion of the growth mechanisms for differently shaped and structured nanocrystals. By reaction with 1,10-phenanthroline, a reagent that strongly and selectively binds to Cu(+), a compositional transformation from binary matchsticklike Cu2S-In2S3 nanorods to pure In2S3 nanorods was successfully achieved.     

碳包覆纳米铁镍磁性颗粒的合成

通过在双温控的化学气相沉积炉中热解四吡啶并卟啉铁镍混合物,合成了碳包覆铁镍纳米颗粒。原料中四吡啶并卟啉铁镍的质量比为7∶3;扫描电镜和透射电镜的结果显示碳包覆铁镍纳米颗粒形貌均匀,直径为100~300 nm;能谱结果显示碳包覆铁镍纳米颗粒是由铁、镍和碳组成;拉曼光谱证明产物有大量的缺陷存在,可能是由于球状结构上的碎片引起的;此外,磁性能测试表明室温下,碳包覆铁镍纳米颗粒有很高的饱和磁化强度,为56.3 emu·g^-1;而其产物的矫顽力趋近于零,呈超顺磁性,适合用于催化剂载体。     

Light-induced selective deposition of metals on gold-tipped CdSe-seeded CdS nanorods

We introduce a facile approach for the selective deposition of metals on Au-tipped CdSe-seeded CdS nanorods that exploits the transfer of electrons from CdS to the Au tips upon UV excitation. This light-induced deposition method was used for the deposition of Pd under mild conditions, which produced a Pd/Au alloyed tip while preserving the rest of the semiconductor nanoarchitecture. The highly site-selective deposition method was extended to the deposition of Fe, yielding monodispersed, structurally complex Au core/Fe(x)O(y) hollow shell-tipped semiconductor nanorods. These structurally well-defined rods were found to exhibit magnetic functionality. The synthetic strategies described in this work expand on the range of metals that can be deposited on heterostructured semiconductor nanorods, opening up new avenues for the hierarchical buildup of structural complexity and therefore multifunctionality in nanoparticles.     

镍钴锌纳米铁氧体的制备及磁热性能

以乙酰丙酮盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了纳米Ni0.5-xCoxZn0.5Fe2O4(x=0,0.1,0.2,0.3和0.4)铁氧体.通过X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FTIR)和振动样品磁强计(VSM)等对样品的结构、形貌和磁性能进行了表征.结果表明,所得纳米Ni0.5-xCoxZn0.5Fe2O4铁氧体的分散性较好,尺寸均一.在室温下产物的剩磁和矫顽力均较小,表现出亚铁磁性.纳米Ni0.3Co0.2Zn0.5Fe2O4铁氧体的饱和磁化强度达到41.34 A·m2·kg-1,其在交变磁场中升温可达到55℃,表现出较好的磁热性能.     

Magnetic properties of electrodeposited Ni‒P alloys with varying phosphorus content

The effect thermal treatment has on the magnetic properties (magnetization, saturation magnetization, and coercivity) of Ni?P alloys prepared via electrodeposition is studied. The process of amorphous Ni?P alloys devitrification is investigated by differential scanning calorimetry. The effects of chemical composition and thermal treatment on magnetic properties of the alloys are revealed.     

阴离子柱撑磁性镍铝水滑石的制备及表征

将磁性基质与镍铝类水滑石组装制备磁性镍铝水滑石。研究了磁性基质含量、焙烧温度对水滑石磁学性能及结构的影响。并采用SEM、XRD、FT-IR、DSC-TG及VSM(vibrating sample magnetometer)等测试技术对制备的水滑石的结构和磁学性能进行了表征。结果表明,磁性基质的引入赋予镍铝类水滑石以超顺磁性,磁性基质含量对样品的磁性能起决定性作用,磁性镍铝水滑石的比饱和磁化强度随磁性基质含量的增加而增加;XRD分析结果表明,磁性基质的引入没有改变水滑石的典型层状结构且随着磁性基质含量的增多,磁性镍铝水滑石的特征衍射峰的衍射强度有所降低,n(Ni2 )/n(Fe2 )达到20时,XRD谱图中开始出现Fe3O4晶相的衍射峰;前驱体经1073K焙烧后出现尖晶石晶相;DSC-TG分析结果表明,磁性基质的引入没有改变水滑石2个阶段吸热的特征,这与XRD的检测结果一致。     

One-pot hydrothermal synthesis of heterostructured ZnO/ZnS nanorod arrays with high ethanol-sensing properties

ZnO/ZnS heterostructured nanorod arrays with uniform diameter and length were synthesized from zinc substrates in a one-pot procedure by using a simple hydrothermal method. Structural characterization by HRTEM indicated that the heterostructured nanorods were composed of parallel segments of wurtzite-type ZnO and zinc-blende ZnS, with a distinct interface along the axial direction, which revealed the epitaxial relationship, ZnO (1010) and ZnS (111). The as-prepared ZnO/ZnS nanorods showed only two green emissions at around 523?nm and 576?nm. We also found that the nanorods exhibited high sensitivity to ethanol at relatively low temperatures, owing to their smaller size and structure.     

Synthesis and characterization of highly magnetized nanocrystalline Co(30)Fe(70) alloy by chemical reduction

Co(30)Fe(70) nanoparticles with mean particle size of about 8 nm were successfully synthesized by the chemical reduction of cobalt chloride and iron chloride with borohydride as a reducing agent in aqueous solution. The composition and size of the Co(30)Fe(70) nanoparticles were optimized by controlling the molar ratio of starting materials, reaction time, and dropping rate of aqueous reducing agent. As alloy powders prepared by chemical reduction tend to be amorphous in the as-synthesized state, the as-precipitated Co(30)Fe(70) nanoparticles were heat-treated to achieve crystallinity at the different temperatures for 1 h. The Co(30)Fe(70) nanocrystallite by chemical reduction shows excellent soft magnetic behavior, such as high permeability, negligible coercivity, and high saturation magnetization like that of Co(30)Fe(70) bulk.     

反相微乳液助水热法可控合成FeNi3合金纳米结构

利用水热法处理表面活性剂/正辛烷/正己醇/水四元微乳体系成功合成FeNi3合金纳米结构. 通过改变表面活性剂的用量和类型来调控产物粒径与形貌. 当表面活性剂为聚乙二醇4000(PEG4000)时, 产物为球状, 粒径约为75 nm. 当表面活性剂为十六烷基三甲基溴化铵(CTAB)时, 产物为海胆状.单个海胆状颗粒是由许多纳米棒构成, 其直径约为42 nm, 长度为0.4-1.2 μm. 利用X射线粉末衍射(XRD), 穆斯堡尔谱, 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 选区电子衍射(SAED), 多功能磁天平(MMVFTB)等测试手段对产物的组成、形貌和磁性能进行了表征. 球状和海胆状的FeNi3样品在室温下呈现典型的铁磁性特征, 其饱和磁化强度(Ms)值分别为114.4和97.4 emu·g-1, 矫顽力(Hc)值分别为94.0和329.0 Oe.     

Electrospinning preparation, characterization and magnetic properties of cobalt-nickel ferrite (Co(1-x)Ni(x)Fe2)O4) nanofibers

Uniform Co(1-)(x)Ni(x)Fe(2)O(4) (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanofibers with average diameter of 110 nm and length up to several millimeters were prepared by calcination of electrospun precursor nanofibers containing polymer and inorganic salts. The as-spun and calcined nanofibers were characterized in detail by TG-DTA, XRD, FE-SEM, TEM, SAED and VSM, respectively. The effect of composition of the nanofibers on the structure and magnetic properties were investigated. The nanofibers are formed through assembling magnetic nanoparticles with poly(vinyl pyrrolidone) as the structure-directing template. The structural characteristics and magnetic properties of the resultant nanofibers vary with chemical composition and can be tuned by adjusting the Co/Ni ratio. Both lattice parameter and particle size decrease gradually with increasing nickel concentration. The saturation magnetization and coercivity lie in the range 29.3-56.4 emu/g and 210-1255 Oe, respectively, and both show a monotonously decreasing behavior with the increase in nickel concentration. Such changes in magnetic properties can mainly be attributed to the lower magnetocrystalline anisotropy and the smaller magnetic moment of Ni(2+) ions compared to Co(2+) ions. Furthermore, the coercivity of Co-Ni ferrite nanofibers is found to be superior to that of the corresponding nanoparticle counterparts, presumably due to their large shape anisotropy. These novel one-dimensional Co-Ni ferrite magnetic nanofibers can potentially be used in micro-/nanoelectronic devices, microwave absorbers and sensing devices.     

Synthesis of Pt@Fe2O3 nanorods as MRI probes for in vivo application

Magnetic Fe(2)O(3) nanorods with low cell toxicity were successfully synthesized via a wet-chemical method. In vivo studies with a rabbit model show that the nanorods exhibit excellent T(2) signal enhancement. This work demonstrates that magnetic nanorods may provide a new type of MR enhancement agent for use in biomedical applications.     

Shape-dependent magnetic properties of low-dimensional nanoscale Prussian blue (PB) analogue SmFe(CN)6.4H2O

Unique nanorods and nanobelts of Prussian blue (PB) analogue SmFe(CN)6.4H2O have been successfully synthesized by using reverse micelles as colloidal soft templates; magnetic studies show that the shape of the low-dimensional nanoscale material is a dominating factor for its coercivity due to the effect of shape anisotropy.     

形貌可控纳米SrFe_(12)O_(19)的制备及其磁性能

以FeCl3为原料,NaOH作为沉淀剂,通过化学沉淀法,制备出球状的Fe(OH)3中间体,同时以FeCl2为原料,采用化学沉淀法,分别使用NH3·H2O、Na2CO3和NaOH作为沉淀剂制得了不同形貌的中间体,利用柠檬酸法在中间体表面包裹锶的柠檬酸络合物,煅烧后分别制得了球形、纺锤体及棒状的纳米SrFe12O19.利用X射线衍射(XRD)和透射电镜(TEM)等测试手段对不同形貌的纳米SrFe12O19进行表征,并利用振动样品磁强计(VSM)对磁性能进行研究.结果表明:在用化学沉淀-柠檬酸法制备SrFe12O19的过程中,铁盐的种类以及沉淀剂的碱性对中间体的物相和SrFe12O19的形貌有着至关重要的影响.当原料为Fe3+时,制得了球形的纳米SrFe12O19;当原料为Fe2+时,利用碱性不同的沉淀剂可制得不同形貌的纳米SrFe12O19.随着沉淀剂碱性的增加,所得SrFe12O19的长径比增加,形貌各向异性增加.SrFe12O19的矫顽力(Hc)主要取决于粒子的各向异性,各向异性越大,矫顽力越大,饱和磁化强度(Ms)随着样品的各向异性的增加也有所增加,以FeCl2为原料,NaOH作为沉淀剂时制得的棒状SrFe12O19的矫顽力和饱和磁化强度最大分别为458.2kA·m-1和64.2A·m2·kg-1.     

A novel one-dimensional cyano-bridged Ni3Fe2 ferromagnet constructed from bimetallic molecular squares

Reaction of the complex [Ni(rac-CTH)](2+) (rac-CTH = rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) with [Fe(CN)(6)](3-) leads to a novel cyano-bridged Ni(3)Fe(2) complex, [[Ni(rac-CTH)](3)[Fe(CN)(6)](2)](4). The structure consists of an alternating arrangement of [Fe(CN)(6)Ni(rac-CTH)](2) squares and trans-planar [Ni(rac-CTH)](2+) units bridged by cyanide groups to give a neutral 1D chain running along the a axis. Magnetic measurements reveal the occurrence of ferromagnetic coupling between Fe(III) and Ni(II) ions and 3D magnetic ordering at 3 K due to interchain interactions. Canting of the moments is inferred from the low value of the magnetization of the saturation below T(c).     

Co3O4 纳米棒的溶剂热合成及形成机理分析

Co3O4 nanorods have been synthesized at 160℃ for 10 h in the solution of oleic and n-cetane by an emulsion-solvothermal method using Co（NO3）2·6H2O as starting materials. The as-prepared product was characterized by X-ray powder diffraction（XRD）,transmission electron microscope（TEM）,and vibrating sample magnetometer（VSM）. The formation mechanism of the prepared product was analyzed based on formation of rod-like micelles of oleic acid. Cobalt ions can migrate into the micelle core for the nucleation and growth of Co3O4 . The results show that the as-prepared Co3O4 nanorods are with the average size 25×100 nm and in the cubic phase. The magnetic susceptibility meets about linearly with the applied magnetic field at room temperature,and the coercivity （Hc）and remanent magnetization（Ms）values of the product at room temperature are 353 Oe and 0.4 emu/g,respectively. This simple route is also expanded to synthesize other materials with the rod-like morphology.     

Effect of hydrogen reduction temperature on the microstructure and magnetic properties of Fe–Ni powders

The effect of hydrogen reduction temperature on the properties of Fe–Ni powders was described. The mixed powders of Fe-oxide and NiO were prepared by chemical solution mixing of nitrates powders and calcination at 350 °C for 2 h in air. The calcined powders formed small agglomeration with an average particle size of 100 nm. The microstructure and magnetic properties were investigated by using X-ray diffractometry, thermogravimetry, differential thermal analyzer, and vibrating sample magnetometer. Microstructure and thermal analysis revealed that the Fe-oxide and NiO phase were changed to FeNi₃ phase in the temperature range of 245–310 °C, and by heat-up to 690 °C the FeNi₃ phase was transformed to γ-FeNi phase. The reduced powder at 350 °C showed saturation magnetization of 76.3 emu/g and coercivity of 205.5 Oe, while the reduced powders at 690 °C exhibited saturation magnetization of 84.0 emu/g and coercivity of 14.0 Oe. The change of magnetic properties was discussed by the observed microstructural features.