导电聚苯胺与磁性CoFe2O4纳米复合物的制备与表征

在利用HNO3酸化处理CoFe2O4磁性纳米粒子使其表面离子化、分散性得到改善的基础上, 采用原位聚合法制备了具有电磁功能的聚苯胺/CoFe2O4 (PANI/CoFe2O4)纳米复合物. 借助TEM, XRD, FT-IR, TG, 四探针电导率仪、VSM(振动样品磁强计)等分析手段研究了复合物的形貌、结构、热稳定性及电磁性能. 结果表明, 处理过的CoFe2O4磁性纳米粒子可形成分散均匀的PANI/CoFe2O4纳米复合物, CoFe2O4以25 nm左右的粒子分散于聚苯胺基体中; PANI与CoFe2O4之间存在化学键合作用, 正是这种作用使复合物热稳定性得以提高; 复合物同时具有导电性和磁性能, 且随CoFe2O4含量变化而变化.     

导电聚苯胺与磁性CoFe2O4纳米复合物的合成及其电磁性能

在利用HNO3处理CoFe2O4磁性纳米粒子使其表面离子化、分散性得到改善的基础上, 采用苯胺在其表面原位聚合, 制备了具有电磁功能的聚苯胺(PANI)/CoFe2O4纳米复合物. 借助TEM、XRD、FT-IR、四探针电导率仪和VSM(振动样品磁强计)等分析手段研究了复合物的形貌、结构及其电磁性能. 结果表明, CoFe2O4以25 nm左右的粒子分散于聚苯胺基体中, 被其完全包覆, CoFe2O4与PANI之间存在化学键合作用; 复合物同时具有电性能和磁性能, 其导电率随CoFe2O4含量增加而降低, 饱和磁化强度随之升高, 而矫顽力在所研究的范围内则先增大而后又减小, 且均高于CoFe2O4的矫顽力.     

花生酸单分子膜诱导PbS晶体取向生长的研究

以花生酸单分子膜为模板，诱导沉积了PbS半导体纳米粒子，粒径为30～50 nm.实验发现， 由于花生酸单分子膜的诱导作用， 使得PbS晶体在膜上发生取向生长，可以形成三角形、四边形和棒状的PbS纳米粒子.通过改变单分子膜的表面压，考察了表面压对PbS晶体取向生长的影响，结合透射电镜及电子衍射实验，对PbS晶体的生长机制进行了初步的分析和探讨.     

多级结构还原氧化石墨烯包覆的钴铁氧体的合成及电化学性能

以水滑石为前驱体合成微米花/纳米片多级结构过渡金属复合氧化物CoFe2O4,一种高性能锂离子电池负极材料。 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对其进行结构表征,发现得到的复合氧化物为单一晶相,且具有多级结构。 电化学性能测试表明,得到的负极材料具有高比容量和倍率性能。 通过还原氧化石墨烯(rGO)对CoFe2O4进行表面包覆制备CoFe2O4/rGO,其循环稳定性得到大幅度提高。     

纳米复合固体超强酸SO42-/CoFe2O4的制备和表征

采用纳米化学制备技术合成了新型的纳米复合团体超强酸催化剂ＳＯ４２－／ＣｏＦｅ２Ｏ４。用ＸＲＤ、ＴＥＭ、ＸＰＳ、红 外光谱和比表面测定等技术研究了该催化剂的结构形态,结果表明：所研制的ＳＯ４２－／ＣｏＦｅ２Ｏ４催化剂为晶态纳 米粒子（＜ ５０ｎｍ）,比表面积很大（１５７ｍ２· ｇ－１）,ＳＯ４２－与氧化物的金属离子呈无机双齿螯合状配位化合物的结 合形式。以乙酸乙酯合成为模型反应考察了该催化剂的催化活性,比较了酸性和酸强度,推断出该催化剂的酸 强度Ｈ０＜－１４．５。     

Synthesis of highly crystalline and monodisperse maghemite nanocrystallites without a size-selection process.

The synthesis of highly crystalline and monodisperse gamma-Fe(2)O(3) nanocrystallites is reported. High-temperature (300 degrees C) aging of iron-oleic acid metal complex, which was prepared by the thermal decomposition of iron pentacarbonyl in the presence of oleic acid at 100 degrees C, was found to generate monodisperse iron nanoparticles. The resulting iron nanoparticles were transformed to monodisperse gamma-Fe(2)O(3) nanocrystallites by controlled oxidation by using trimethylamine oxide as a mild oxidant. Particle size can be varied from 4 to 16 nm by controlling the experimental parameters. Transmission electron microscopic images of the particles showed 2-dimensional and 3-dimensional assembly of particles, demonstrating the uniformity of these nanoparticles. Electron diffraction, X-ray diffraction, and high-resolution transmission electron microscopic (TEM) images of the nanoparticles showed the highly crystalline nature of the gamma-Fe(2)O(3) structures. Monodisperse gamma-Fe(2)O(3) nanocrystallites with a particle size of 13 nm also can be generated from the direct oxidation of iron pentacarbonyl in the presence of oleic acid with trimethylamine oxide as an oxidant.     

配位-氧化聚合-水热法制备聚苯胺/CoFe_2O_4纳米复合物及其微波吸收性能

采用"配位-氧化聚合-水热法"制备了本征态聚苯胺/CoFe2O4二元纳米复合物,再以磺基水杨酸掺杂获得聚苯胺/CoFe2O4电磁复合物.考察了反应物配比及掺杂酸浓度对产物电磁性能的影响.通过透射电子显微镜(TEM)、X射线衍射(XRD)、红外光谱(FTIR)及电磁测量等手段对聚苯胺/CoFe2O4的形貌、结构及性能进行了表征.结果表明,复合物呈现多级结构,其中CoFe2O4为立方体状,平均粒径小于20 nm.当CoFe2O4的质量分数为8.86%时,复合物的电导率约为0.43 S/cm;当聚苯胺/CoFe2O4复合物厚度为2 mm时,在16.01 GHz处最大反射损耗为-16.71 dB,小于-10 dB的带宽达4.68 GHz;而当聚苯胺/CoFe2O4复合物厚度为3.2 mm时,在9.23 GHz处最大反射损耗达-51.81 dB,小于-10 dB的带宽为3.69 GHz,表明具有良好的吸波性能.     

Adsorption of cobalt ferrite nanoparticles within layer-by-layer films: a kinetic study carried out using quartz crystal microbalance

The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe(2)O(4)--10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe(2)O(4) nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe(2)O(4)/PSS bilayers (n) and/or by changing the CoFe(2)O(4) nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe(2)O(4) nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe(2)O(4) nanoparticles while growing multilayers of CoFe(2)O(4)/PSS was conducted using colloidal suspensions with CoFe(2)O(4) concentration in the range of 10(-8) to 10(-6) (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe(2)O(4) nanoparticles within the CoFe(2)O(4)/PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe(2)O(4) nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film thickness increasing from about 20 to 120 nm while shifting from 3 to 10 CoFe(2)O(4)/PSS bilayers, using the 8.9 × 10(-6) (moles of cobalt ferrite per litre) suspension.     

Hydrothermal synthesis of magnetic CoFe2O4 nanoparticles and CoFe2O4/MWCNTs nanocomposites for U and Pb removal from aqueous solutions

Journal of Radioanalytical and Nuclear Chemistry - Magnetite CoFe2O4 nanoparticle and CoFe2O4/MWCNT nanocomposite adsorbents with high specific surface area, high adsorption capacity, and easily...     

磁电CoFe2O4/BaTiO3纳米管的溶胶-凝胶模板法合成和表征

用溶胶-凝胶模板法合成了 CoFe2O4)/BaTiO3(CFO/BTO)复合纳米管,管的直径约为 100、200 和 300 nm,其长度约为100 μm.x射线衍射(xRD)和选区电子衍射(sAED)都显示复合纳米管中同时存在尖晶石相的CoFe2O4(CFO)和钙钛矿相的 BaTiO3(BTO),进一步的透射电子显微镜(TEM)研究证实合成的纳米复合物具有明显的管状结构.磁、电研究表明,该复合纳米管的磁性与纯 CFO 纳米管的磁性相当;而铁电性与纯BTO纳米管的铁电性相当.     

磁电CoFe2O4/BaTiO3纳米管的溶胶-凝胶模板法合成和表征

用溶胶-凝胶模板法合成了CoFe2O4/BaTiO3(CFO/BTO)复合纳米管, 管的直径约为100、200和300 nm, 其长度约为100 μm. X射线衍射(XRD)和选区电子衍射(SAED)都显示复合纳米管中同时存在尖晶石相的CoFe2O4 (CFO)和钙钛矿相的BaTiO3(BTO), 进一步的透射电子显微镜(TEM)研究证实合成的纳米复合物具有明显的管状结构. 磁、电研究表明, 该复合纳米管的磁性与纯CFO纳米管的磁性相当; 而铁电性与纯BTO纳米管的铁电性相当.     

Synthesis and coating of cobalt ferrite nanoparticles: a first step toward the obtainment of new magnetic nanocarriers

Monodisperse and stable cobalt ferrite (CoFe2O4) nanoparticles (5.4 nm) have been produced, coated with mono- and difunctional phosphonic and hydroxamic acids, and fully characterized (using thermogravimetric analysis (TGA), dynamic light scattering (DLS), IR spectroscopy, transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) measurements). Cobalt leakage of the coated nanoparticles has been also studied. Magnetic measurements show the possible applications in hyperthermia at low frequencies, and for this reason, water-soluble coated CoFe2O4 can be seen as a first step toward the obtainment of novel systems for biomagnetic applications.     

Vast magnetic monolayer film with surfactant-stabilized Fe3O4 nanoparticles using Langmuir-Blodgett technique

Although several methods (e.g., self-assembly, spin coating, etc.) have been explored for making a monolayer film of nanoparticles, the monolayer on a substrate is typically smaller than 1 micromx1 microm in certain regions. The approach is not ideally suitable for generating a highly ordered and close-packed homogeneous vast monolayer of nanoparticles, which is potentially important for applications. In this report, the preparation of the vast monolayer films of Fe3O4 nanoparticles with a wide range such as that over 3.25 micromx3.95 microm is reported. Their TEM images showed a two-dimensional assembly of Fe3O4 nanoparticles, demonstrating the uniformity of these nanoparticles. The formation of a Langmuir monolayer of the oleic acid-coated Fe3O4 nanoparticles mixed with stearic acid molecules at the air/water interface and its stability were studied with a pressure-area isotherm curve. TEM and BAM studies demonstrated that increasing surface pressure resulted in a transition from well-separated domains of nanoparticles complex to well-compressed, monoparticulate layers.     

The effective peroxidase-like activity of chitosan-functionalized CoFe2O4 nanoparticles for chemiluminescence sensing of hydrogen peroxide and glucose

Here, we report a highly simple and general protocol for functionalization of the CoFe(2)O(4) NPs with chitosan polymers in order to make CoFe(2)O(4) NPs disperse and stable in solution. The functionalized CoFe(2)O(4) NPs (denoted as CF-CoFe(2)O(4) NPs) were characterized by scanning electron microscope (SEM), thermogravimetric (TG), X-ray diffraction (XRD) and FT-IR spectra. It was found that the CoFe(2)O(4) NPs were successfully decorated and uniformly dispersed on the surface of chitosan without agglomeration. The CF-CoFe(2)O(4) NPs were found to increase greatly the radiation emitted during the CL oxidation of luminol by hydrogen peroxide. Results of ESR spin-trapping experiments demonstrated that the CF-CoFe(2)O(4) NPs showed catalytic ability to H(2)O(2) decomposition into ˙OH radicals. On this basis, a highly sensitive and rapid chemiluminescent method was developed for hydrogen peroxide in water samples and glucose in blood samples. Under optimum conditions, the proposed method allowed the detection of H(2)O(2) in the range of 1.0 × 10(-9) to 4.0 × 10(-6) M and glucose in the range of 5.0 × 10(-8) to 1.0 × 10(-5) M with detectable H(2)O(2) as low as 500 pM and glucose as low as 10 nM, respectively. This proposed method has been successfully applied to detect H(2)O(2) in environmental water samples and glucose in serum samples with good accuracy and precision.     

球形SnO2 纳米微粒的合成及形成机理分析

以SnCl4*5H2O为主要原料,用溶剂热技术在油酸体系中成功地合成了球形SnO2纳米微粒,在无水乙醇体系中合成了菱形的SnO2纳米微粒.通过X射线粉末衍射(XRD),选区电子衍射(SAED)和透射电镜(TEM)对两种产物进行了表征,并对两种产物的形成机理进行了分析.透射电镜(TEM)结果表明: 在油酸体系中得到了平均尺寸约为 3.5 nm的球形SnO2纳米微粒,此微粒趋向于特殊高的比表面积,适合于作气敏探测器材料方面的应用.     

Correlation between spin-orbital coupling and the superparamagnetic properties in magnetite and cobalt ferrite spinel nanocrystals

The superparamagnetic properties of CoFe2O4 and Fe3O4 nanocrystals have been systematically investigated. The observed blocking temperature of CoFe2O4 nanocrystals is at least 100 deg higher than that of the same sized Fe3O4 nanocrystals. The coercivity of CoFe2O4 nanocrystals at 5 K is over 50 times higher than the same sized Fe3O4 nanocrystals. The drastic difference in superparamagnetic properties between the similar sized spherical CoFe2O4 and Fe3O4 (or FeFe2O4) spinel ferrite nanocrystals was correlated to the coupling strength between electron spin and orbital angular momentum (L-S) in magnetic cations. Compared to the Fe2+ ion, the effect of much stronger spin-orbital coupling at Co2+ lattice sites leads to a higher magnetic anisotropy and results in the dramatic discrepancy of superparamagnetic properties between CoFe2O4 and Fe3O4 nanocrystals. These results provide some insight to the fundamental understanding of the quantum origin of superparamagnetic properties. Furthermore, they suggest that it is possible to control the superparamagnetic properties through magnetic coupling at the atomic level in spinel ferrite nanocrystals for various applications.     

纳米CoFe2O4催化剂催化转化乙醇制氢

采用溶胶-凝胶法制备了纳米CoFe_2O_4催化剂并用于乙醇裂解和部分氧化制氢反应. CoFe_2O_4催化剂对乙醇催化裂解反应表现出较低的催化活性, 其主要原因可能是催化剂表面积碳以及催化剂粒径的长大. 而纳米CoFe_2O_4催化剂对乙醇部分氧化制氢反应具有良好的催化性能. TPR和XRD结果表明尖晶石结构的CoFe_2O_4相在乙醇部分氧化反应过程中发生了结构变化, 部分生成了CoFe合金相. 另外, 催化剂的粒径没有明显增大. 推测纳米CoFe_2O_4催化剂具有良好催化性能是尖晶石结构的CoFe_2O_4和合金相的协同作用所致.     

合成醇催化剂中组分间的相互作用

近年来,CO/H_2催化合成低碳混合醇的研究受到广泛的关注。低碳混合醇可作为掺合汽油的助溶剂、燃料和代油品,一经分离则是非常重要的化工原料,应用价值很大。催化剂是合成过程的关键,七十年代以来该领域研究取得很大进展,如美国Dow公司开发的MoS_2体系,意大利Sham公司研制的“甲基燃料”合成催化剂及法国IFP开发的混合氧化物型“乙基燃料”合成催化剂等,引起人们的极大重视。催化剂的表面     

静电纺丝法制备定向排列的铁氧体纳米纤维

以聚乙烯吡咯烷酮(PVP)和金属硝酸盐为原料,采用改进的静电纺丝法制备了直径均匀、表面光滑、定向排列的Co0.8Zn0.2Fe2O4/PVP纳米纤维前驱体,经热处理后得到定向排列的铁氧体纳米纤维.对前驱体纤维的热分解过程及Co0.8Zn0.2Fe2O4(CZFO)的结构、物相及形貌进行了表征.结果表明,在空气中经550～950℃热处理3 h后均得到纯相、结晶良好的尖晶石型钴锌铁氧体;在2000 r/min转速下收集的复合纤维形貌最佳,直径约300 nm;经750℃热处理后纤维直径约为70 nm,室温下测得饱和磁化强度为66.1 A.m2/kg,矫顽力达到最大值6.6 A/m,表明钴锌尖晶石型铁氧体单畴临界尺寸约为44 nm.与CoFe2O4相比,CZFO的饱和磁化强度升高,矫顽力下降,并且CZFO的纤维与粉末的磁特性有明显的区别.     

Role of urea in the preparation of highly porous nanocomposite aerogels

The preparation of highly porous CoFe2O4-SiO2 nanocomposite aerogels was successfully achieved by a novel sol-gel procedure involving urea-assisted co-gelation of the precursor phases. This method allows fast gelation, giving rise to an aerogel with 97% porosity. The formation of CoFe2O4 nanocrystals homogeneously distributed within the matrix occurs after calcination at 750 degrees C and is complete at 900 degrees C. Despite the high temperature required for the formation of the CoFe2O4 nanocrystals, the high porosity typical of aerogels is still retained.