Dispersibility, Shape and Magnetic Properties of Nano-Fe₃O₄Particles

Nano-Fe3O4 particles were prepared by a two-step microemulsion method, the influence of molar ratio of water to NP-5 (R), alkali concentration and temperature on dispersibility and shape of the nanoparticles were discussed. Magnetic studies were also carried out using VSM in this paper. It was found that the optimum preparation parameters are R = 6.0, alkali concentration = 2.5 mol.L–1, initial total iron concentration as 0.88 mol.L–1, and the temperature being 30°C, the prepared nano magnetite particles have uniform size and good dispersibility with a crystal structure belonging to cubicFe3O4 and lattice parameters of a = 8.273 ?. The results of magnetic studies show, magnetic properties of particles are influenced by dispersibility of nanoparticles which depends on size of clusters. The better dispersibility of nanoparticles leads to more ordered inner magnetic vector, and so the stronger magnetic behavior of nano-Fe3O4 particles.

Application of Polymerizable Surfactant in the Preparation of Polystyrene/Nano-Fe_3O_4 Composite

Monooctadecyl maleate, as a polymerizable surfactant, was synthesized by the mono-esterification of maleic anhydride and octadecanol, and was utilized to surface-modify nano-Fe3O4 particles. A polymerizable magnetic fluid was obtained by directly dispersing modified nano-Fe3O4 particles into styrene monomer, and the polystyrene/nano-Fe3O4 composite was prepared through free radical polymerization of polymerizable magnetic fluid. The structure and dispersion status in different dispersion phases of modified nano-Fe3O4 particles were studied by Fourier transform infrared （FTIR） spectrometry, X-ray diffraction （XRD） and transmission electron microscopy （TEM）, respectively. The experimental results show that the nano-Fe3O4 particles modified by monooctadecyl maleate with the size of about 7-10 nm can be uniformly dispersed into styrene and fixed in the composite during the procedure of polymerization. Thermogravimetric analysis （TGA） and vibrating sample magnetometry （VSM） indicate that the thermal stability of polystyrene/nano-Fe3O4 composite is improved compared to that of pure polystyrene, and the composite is a sort of superparamagnetic materials.

Preparation and Analysis of Fe3O4 Magnetic Nanoparticles Used as Targeted-drug Carriers

Fe3O4 magnetic nanoparticles were prepared by the aqueous co-precipitation of FeCl3-6H2O and FeCl2-4H2O with addition of ammonium hydroxide. The conditions for the preparation of Fe3O4 magnetic nanoparticles were optimized, and Fe3O4 magnetic nanoparticles obtained were characterized systematically by means of transmission electron microscope （TEM）, dynamic laser scattering analyzer （DLS） and X-ray diffraction （XRD）. The results revealed that the magnetic nanoparticles were cubic shaped and dispersive, with narrow size distribution and average diameter of 11.4 nm. It was found that the homogeneous variation of pH value in the solution via the control on the dropping rate of aqueous ammonia played a critical role in size distribution. The magnetic response of the product in the magnetic field was also analyzed and evaluated carefully. A 32.6 mT magnetic field which is produced by four ferromagnets was found to be sufficient to excite the dipole moments of 0.05 g Fe3O4 powder 2 cm far away from the ferromagnets. In conclusion, the Fe3O4 magnetic nanoparticles with excellent properties were competent for the magnetic carders of targeted-drug in future application.

Removing Cd^(2+) by Composite Adsorbent Nano-Fe_3O_4/Bacterial Cellulose

A new composite adsorbent, nano-Fe3O4/bacterial cellulose（BC）, was prepared through blending method. The process of adsorbing Cd2＋ including its isotherm and kinetics measured was studied. The results show that the adsorption efficiency is improved because of huge surface area and surface coordination of nano-Fe3O4 particles. Its adsorption capacity is 27.97 mg/g and the maximum of Cd2＋ removal is 74%. The adsorption kinetics can be described by pseudo-second rate model and the adsorption equilibrium by Langmuir type. The superparamagnetism of nano-Fe3O4 particles can help to solve the difficult separation of single BC adsorbent and lead to the quick separation of composite adsorbent from the liquid if a magnetic field was applied. Cd2＋ can be desorbed effectively by EDTA and HCl from the composite adsorbent, which can make it be reused.

Preparation of Calcium Cross-linked Nano-Fe3O4 Modified Zeolite Microspheres for Cu^2+ Adsorption from Wastewater

Artificial zeolite was modified by nano-Fe3O4 for development of functional adsorbents.Subsequently,adsorbents such as calcium cross-linked nano-Fe3O4 microspheres (Ca-MS),calcium cross-linked nano-Fe3O4 modified zeolite microspheres (Ca-MZS) and iron cross-linked nano-Fe3O4 modified zeolite microspheres (Fe-MZS) were prepared and compared for their adsorption performance.The effects of adsorbent dosage,solution pH,initial concentration and ion content on the removal of Cu^2+ from wastewater are investigated,and the adsorption kinetics and isotherms for the adsorbent materials were analyzed.The experimental results indicate that for the initial concentration of Cu^2+ of 30 mg/L,the adsorption is noted to be most stable.The optimal initial pH for adsorbing Cu^2+ is observed to be 5.5.At an optimal dosage of Ca-MZS of 900 mg/L,the adsorption capacity is measured to be 28.25 mg/g,along with the removal rate of 72.49%.The addition of Na+ and K+ affects the adsorption of Cu^2+.For the Na^+ and K^+ concentration of 0.2 mmol/L,the Cu^2+ removal rate by Ca-MZS drops to 11.94% and 22.12%,respectively.As compared with the adsorbents such as Natural Zeolite (NZ),Ca-MS and Fe-MZS,Ca-MZS demonstrates the best removal effect in solution,where the removal rate reaches 84.27%,with the maximum adsorption capacity of 28.09 mg/g.The Cu^2+ adsorption kinetics of Ca-MZS is observed to follow the Elovich kinetic model,with the adsorption isotherm data fitting the Freundlich isotherm model by using the non-linear method.

Photosynthetic Toxicity and Oxidative Damage Induced by nano-Fe3O4 on <i>Chlorella vulgaris</i>in Aquatic Environment

With the rapid development of nanotechnology and widespread use of nanoproducts, concerns have arisen regarding the ecotoxicity of these materials. In this paper, the photosynthetic toxicity and oxidative damage induced by nano Fe3O4 on a model organism, Chlorella vulgaris (C. vulgaris) in aquatic environment, were studied. The results showed that Nano-Fe3O4 was toxic to C. vulgaris and affected its content of chlorophyll a, malonaldehyde and glutathione, CO2 absorption, net photosynthetic rate, superoxide dismutase activity and inhibition of hydroxyl radical generation. At higher concentrations, compared with the control group, the toxicity of nano-Fe3O4 was significantly different. It suggested that nano-Fe3O4 is ecotoxic to C. vulgaris in aquatic environment.

A simple method for purification of genomic DNA from whole blood using Fe_3O_4/Au composite particles as a carrier

Objective： To establish a method of genomic DNA extraction from whole blood using Fe3O4/Au composite particles as a carrier. Methods： Two crucial conditions （sodium chloride concentration and amount of the magnetic particles） were optimized and 8 different human whole blood samples were used to purify genomic DNA under the optimal condition. Then agarose gel electrophoresis and polymerase cbain reaction （PCR） were performed. Results： The optimal binding condition was 1.5 mol/L NaC1/10% PEG, and the optimal amount of Fe3O4/Au composite particles was 600μg. The yields of the genomic DNA from 100μl of different whole blood samples were 2-5 μg, and the ratio of A260/A280 was in the range of 1.70-1.90. The size of genomic DNA was about 23 kb and the PCR was valid. Conclusion： The purification system using Fe3O4/Au composite microparticles has advantages in high yield, high purity, ease of operating, time saving and avoiding centrifugation. The purified sample was found to function satisfactorily in PCR amplification.

Synthesis and Characterization of Superparamagnetic Fe₃O₄@SiO₂Core-Shell Composite Nanoparticles

The Fe3O4@SiO2 composite nanoparticles were obtained from as-synthesized magnetite (Fe3O4) nanoparticles through the modified St?ber method. Then, the Fe3O4 nanoparticles and Fe3O4@SiO2 composite nanoparticles were characterized by means of X-ray diffraction (XRD), Raman spectra, scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). Recently, the studies focus on how to improve the dispersion of composite particle and achieve good magnetic performance. Hence effects of the volume ratio of tetraethyl orthosilicate (TEOS) and magnetite colloid on the structural, morphological and magnetic properties of the composite nanoparticles were systematically investi-gated. The results revealed that the Fe3O4@SiO2 had better thermal stability and dispersion than the magnetite nanoparticles. Furthermore, the particle size and magnetic property of the Fe3O4@SiO2 composite nanoparticles can be adjusted by changing the volume ratio of TEOS and magnetite colloid.

EFFECT OF SOLVENT ON THE MAGNETIC INTERACTIONS BETWEEN Fe_3O_4 PARTICLES AND SURFACTANTS

Mossbauer spectra for 5 nm Fe3O4 particles coated with different surfactants (the polar end groups as -COONa and -SO3Na) were measured and show a significant influence on superparamagnetic relaxation with and without the solvent. Some phenomena were explained by the superparamagnetism and the surfactant hydrophilicity.

Preparation of Fe_3O_4/PS Magnetic Particles by Dispersion Polymerization

Fe_3O_4/PS magnetic particles with core/shell structure has been prepared in the presence of Fe3O4 magnetic fluid in ethanol/water mixture.Magnetic particles with diameter size range from 5. 54 t0 187. 32 μm were obtained by different reaction conditions.Some parameters such as ethanol, PEG and monomer which affect particle size diameter and size distribution are discussed briefly in this paper.

Fabrication and Investigation of the Magnetic Properties of Co and Co3O4 Nanoparticles

The nanoparticles exhibit some novel optical and magnetic properties, which are different from its bulk material. Cobalt oxide has been known as a semi-conductor compound of p type with a Spinel structure. Therefore, they are used as gas sensor and absorbent of solar energy. Furthermore, they are employed as an effective catalyzer in environmental clearing. In the thermal gradation method, carbonyl cobalt Co2(CO)8 is often used as a precursor, though cobalt carbonyl is very toxic and expensive. Magnetic compounds have been among interesting issues for human beings for over 4000 years. In large societies, magnetic compounds including computer disks, credit cards, speakers, coolers, automatic doors, and many other devices can be observed on a daily basis. The structure and morphology of as-prepared Co3O4 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The TEM images showed that the product nanoparticles consisted of dispersive quasi- spherical particles with a narrow size distribution ranged from 5 to 15 nm and an average size around 10 nm. The magnetic measurements confirmed that the Co3O4 nanoparticles show a little ferromagnetic behavior which could be attributed to the uncompensated surface spins and finite size effects. The ferromagnetic order of the Co3O4 nanoparticles is raised with increasing the decomposition temperature.

Preparation and mechanical properties of in situ Al_2O_3/Al composites by adding NH_4AlO(OH)HCO_3

Aluminium matrix composite reinforced by Al2O3 particles was produced by adding NH4AlO（OH）HCO3 into molten aluminum.The mechanical properties and wear behavior of the as-fabricated composites were studied.The results show that during stirring γ-Al2O3 particles were formed via decomposition reaction of NH4AlO（OH）HCO3,and the distribution of Al2O3 particles is more uniform in the matrix aluminum than directly added Al2O3 into molten aluminum.The density and the hardness values of the as-fabricated composites increase with increasing the particle volume fraction,while the tensile strength of the composites decreases with increasing the volume fraction of the Al2O3 particles.The wear rate of the composites decreases with increasing the volume fraction of the particle and loading.The in situ formed Al2O3/Al composite by adding NH4AlO（OH）HCO3 shows more superior mechanical and wear behaviors than that prepared by directly adding Al2O3 particles.

吡罗昔康在纳米Fe_3O_4-石墨烯复合修饰玻碳电极上的电化学行为及电分析研究

采用纳米Fe3 O4粒子（ nano-Fe3 O4）和石墨烯（ Reduced Graphene Oxide,RGO）制备了nano-Fe3 O4-RGO复合材料修饰玻碳电极（nano-Fe3O4-RGO/GCE）,采用循环伏安法（cyclic voltammetry,CV）,方波伏安法（square wave voltammetry,SWV）,计时电流法（ chronoamperometry,CA）,计时库仑法（ chronocoulometry,CC）研究了吡罗昔康（ Piroxicam,PC）在此复合修饰电极上的电化学行为及电化学动力学性质。实验结果表明,与GCE相比, nano-Fe3 O4-RGO/GCE对PC的电化学氧化作用有显著的促进作用,其氧化峰电流显著增加；对各种实验条件进行了优化,测得峰电流Ipa与PC浓度在2．0×10^-6～2．0×10^-4 mol·L^-1范围内呈良好的线性关系,检出限（S/N=3）为5．3×10^-7 mol·L^-1,加标回收率为100．0%～104．0%。该方法快速,灵敏,并将nano-Fe3O4-RGO/GCE用于市售吡罗昔康片剂的测定,结果符合定量测定要求。

纳米Fe_3O_4/离子液体电解质的制备及其性能研究

采用简单易制的1-丁基-3-甲基咪唑氯盐作为离子液体,纳米Fe_3O_4作为胶凝剂制备准固态电解质。用油酸钾对纳米Fe_3O_4进行改性,考察纳米Fe_3O_4改性前后、不同质量比纳米Fe_3O_4对准固态电解质的影响。利用X射线衍射仪、扫描电子显微镜、傅里叶红外光谱仪、电化学工作站等对样品进行表征。结果表明,纳米Fe_3O_4改性后导致准固态电解质的电导率下降,当纳米Fe_3O_4含量为4%时,电导率最高;当纳米Fe_3O_4含量为12%时,I_3^-在Pt电极上的还原速度最快。

Effect of Al2O3np on the Properties and Microstructure of B4Cp/Al Composites

Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 particle (Al2O3np) reinforced B4Cp/Al + Al2O3np composites were prepared by powder metallurgy method. The Monte Carlo particle transport program (MCNP) was used to determine the influence of Al2O3np on the thermal neutron absorptivity of composites. The universal material testing machine and scanning electron microscope (SEM) were used to study the mechanical properties, microstructure and fracture morphology of B4Cp/Al composites. The results indicated that the neutron absorption properties of B4Cp/Al composites were not affected by the addition of nano-Al2O3 particles in the range of 1 wt%-15 wt%. The addition of Al2O3np can obviously reduce the grain size of B4Cp/Al matrix metals thus improve the tensile strength of the composites. The addition threshold of Al2O3np is about 2.5 wt%. Both B4Cp and Al2O3np change the fracture characteristics of the composites from toughness to brittleness, and the latter is more important.

Preparation of Micron Co₃O₄by Liquid-Phase Precipitation

Co3O4 powder has a wide range of applications in the fields of catalysts, magnetic materials and electrochemistry. Especially after the 1990s, the demand for lithium ion battery industry has grown tremendously. The traditional wet preparation of Co3O4 powder cannot meet the requirements of the battery industry. Exploring suitable methods and theories for controlling particle size and morphology is of great significance for the preparation of battery-grade Co3O4 powder. CoCl2 was used as the cobalt source, NH4HCO3 was used as the precipitant, and the precursor was prepared and further calcined to obtain Co3O4 powder. The results show that the molar ratio is the main factor affecting the precursor phase in the preparation of Co3O4 in CoCl2-NH4HCO3 system. The suitable process conditions for the system are a molar ratio of NH4HCO3 to CoCl2 of 4.5:1, a concentration of CoCl2 of 13 g/L, a reaction temperature of 600C, and a reaction time of 10 hours. The median diameter of Co3O4 prepared by the reaction conditions is about 9 μm.

拉贝洛尔在nano-Fe_3O_4-多壁碳纳米管复合修饰玻碳电极上的电催化氧化及电分析方法

目的:研究拉贝洛尔(labetalol,LBT)在nano-Fe3O4与多壁碳纳米管(Multi-walled carbon nanotubes,MWCNTs)复合修饰玻碳电极(nano-Fe3O4-MWCNTs/GCE)上的电化学行为及电化学动力学性质,建立LBT电化学定量测定方法。方法:循环伏安法(Cyclic Voltammetry,CV),计时电流法(Chronoamperometry,CA),方波伏安法(Square Wave Voltammetry,SWV)以及电化学交流阻抗谱(EIS)。结果:在nano-Fe3O4-MWCNTs/GCE上LBT发生了一受扩散控制的不可逆电化学氧化过程。考查了实验条件对LBT伏安行为的影响,测定了LBT在nano-Fe3O4-MWCNTs/GCE上的电极反应过程动力学参数。用SWV法测得LBT氧化峰电流与其浓度在1.0#10-5$1.0#10-3mol.L-1呈线性关系,检出限(S/N=3)为1.0#10-5mol.L-1。并用本方法对市售LBT片进行了电化学定量测定,RSD在0.4%～0.9%之间,加标回收率在99.70%～103.0%之间。结论:nano-Fe3O4-MWCNTs/GCE对LBT电化学氧化具有良好的催化作用,该方法可用于市售LBT片中LBT含量的电化学定量测定。

Preparation and characterization of Fe_(3)O_(4)/Au composite particles

Using Fe3O4 nano-particles as seeds, a new type of Fe3O4/Au composite particles with core/shell structure and diameter of about 170 nm was prepared by reduction of Au3+ with hydroxylamine in an aqueous solution. Particle size analyzer and transmission electron micro-scope were used to analyze the size distribution and microstructure of the particles in different conditions. The result showed that the magnetically responsive property and suspension stability of Fe3O4 seeds as well as reduction conditions of Au3+ to Au0 are the main factors which are crucial for obtaining a colloid of the Fe3O4/Au composite particles with uniform particle dispersion, excellent stability, homogeneity in particle sizes, and effective response to an external magnet in aqueous suspension solutions. UV-Vis analysis revealed that there is a characteristic peak of Fe3O4/Au fluid. For particles with d(0.5)=168 nm, the lmax is 625 nm.

Controlled synthesis and magnetic properties of Fe_3O_4 walnut spherical particles and octahedral microcrystals

Magnetite Fe3O4 walnut spherical particles and octahedral microcrystals were suc- cessfully synthesized from K4 [Fe (CN) 6], K3 [Fe (CN) 6] and NaOH reagents via a simple hydrothermal process. And the uniform morphology of octahedral micro- crystals was obtained in the presence of ethylene glycol. The morphology and structure of products were characterized by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the Fe3O4 walnut spherical particles and octahedral microcrystals were single crystals with the face-center cubic structure and with size distributions from 2.2 to 8.6 μm and 1.6 to 12.5 μm, respectively. Their magnetic properties were detected by a vibrating sample magnetometer at room temperature. The walnut spherical parti- cles exhibited a ferromagnetic behavior with the coercive force (Hc), saturation magnetization (Ms) and remanent magnetization (Mr) being 150.57 Oe, 97.634 and 12.05 emu/g, respectively. For the octahedral microcrystals they were 75.28 Oe, 101.90 and 6.69 emu/g, respectively. Different sizes of walnut spherical particles were controlled synthesized through adjusting the NaOH concentration. It was found that ethylene glycol molecules have a significant effect on the formation of Fe3O4 octahedra. A possible mechanism was also proposed to account for the growth of these Fe3O4 products

Oxidative-damage effect of Fe3O4 nanoparticles on mouse hepatic and brain cells in vivo

To assess the biological safety of Fe3O4 nanoparticles （NPs）, the oxidative-damage effect of these NPs was studied. Twenty-five Kunming mice were exposed to Fe3O4 NPs by intraperitoneai injection daily for 1 week at doses of 0, 10, 20, and 40 mg.kg1. Five Kunming mice were also injected with 40 mg.kg 1 ordinary Fe3O4 particles under the same physiological conditions. Biomarkers of reactive oxygen species （ROS）, glutathione （GSH）, and malondialdehyde （MDA） in the hepatic and brain tissues were detected. Results showed that no significant difference in oxidative damage existed at concentrations lower than 10 mg.kg i for NPs compared with the control group. Fe3O4 NP concentration had obvious dose-effect relationships （P〈 0.05 or P 〈 0.01） with ROS level, GSH content, and MDA content in mouse hepatic and brain tissues at〉20 mg.kg 1 concentrations. To some extent, ordinary Fe3O4 particles with 40mg.kg -1 concentration also affected hepatic and brain tissues in mice. The biological effect was similar to Fe3O4 NPs at 10 mg. kg-1 concentration. Thus, Fe3O4 NPs had significant damage effects on the antioxidant defense system in the hepatic and brain tissues of mice, whereas ordinary Fe3O4 had less influence than Fe3O4 NPs at the same concentration.