EPR and Magnetic Susceptibility Investigations of Fe Containing TeO2-B2O3-SrF2 Glasses

1. IntroductionTellurite-borate vitreous systems[1] and binajry tellurite oxide systems containing transition metal ions[2]were investigated in detail due to their interestingproperties having a number of applications in microelectronics. They are optical glajsses with high refraction index (n>2) and a good iR transmission,being suitable as laser and opto-acoustical materials. Tellurite systems containing FeZO3 were studied to reveal their electrical properties as well asthe structural onesl…     

Evaluation of CaO-SiO2-P2O5-Na2O-Fe2O3 bioglass-ceramics for hyperthermia application

Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO x (52-x)SiO2 x 4P2O5 x xFe2O3 x 3Na2O (2 < or = x < or = 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050 degrees C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x > or = 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them.     

Preparation and characterization of Ni-nitrilotriacetic acid bearing poly(methacrylic acid) coated superparamagnetic magnetite nanoparticles

Stable superparamagnetic magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in the presence of poly(methacrylic acid) (PMAA) in aqueous solution. The polymer coated Fe3O4 nanoparticles were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis, and vibrating sample magnetometry (VSM) techniques. These measurements reveal the presence of magnetite nanoparticles with a size of approximately 8 nm inside the PMAA matrix. The magnetization value of these superparamagnetic nanoparticles at room temperarure and 7 T was measured as about 40 emu/g. PMAA-coated Fe3O4 nanoparticles were further assembled with Ni-chelate through a reaction between a primary amine-bearing NTA (nitrilotriacetic acid) ligand and carboxy-functional groups of PMAA. NTA-PMAA-coated magnetite nanoparticles were then loaded with nickel ions and characterized using FTIR. The average amount of binded Ni on the surface of the NTA-modified PMAA coated Fe3O4 was calculated as 1.65 +/- 0.3 x 10(-6) mol nickel(II) ions per g of the magnetic particles from the inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements.     

Mesoporous silica-magnetite nanocomposite synthesized by using a neutral surfactant

Magnetite nanoparticles coated by mesoporous silica were synthesized by an alternative chemical route using a neutral surfactant and without the application of any functionalization method. The magnetite (Fe(3)O(4)) nanoparticles were prepared by precipitation from aqueous media, and then coated with mesoporous silica by using nonionic block copolymer surfactants as the structure-directing agents. The mesoporous SiO(2)-coated Fe(3)O(4) samples were characterized by x-ray diffraction, Fourier-transform infrared spectroscopy, N(2) adsorption-desorption isotherms, transmission electron microscopy, (57)Fe M?ssbauer spectroscopy, and vibrating sample magnetometry. Our results revealed that the magnetite nanoparticles are completely coated by well-ordered mesoporous silica with free pores and stable (～8?nm thick) pore walls, and that the structural and magnetic properties of the Fe(3)O(4) nanoparticles are preserved in the applied synthesis route.     

纳米磁性四氧化三铁的制备及表征

采用化学共沉淀法制备了纳米磁性Fe3O4粒子.选用NH3@H2O作为沉淀剂,加入到Fe2+和Fe3+的混合溶液中,制得了纳米磁性Fe3O4粒子.考察了Fe2+和Fe3+溶液浓度、沉淀剂的浓度、Fe2+/Fe3+/OH-、温度及搅拌速度等因素对产物粒径及性能的影响,并对其进行了初步的性能表征.     

Microwave properties of polymer composites containing combinations of micro- and nano-sized magnetic fillers

We investigated the microwave absorbing properties of composite bulk samples with nanostructured and micron-sized fillers. As magnetic fillers we used magnetite powder (Fe3O4 with low magnetocrystalline anisotropy) and strontium hexaferrite (SrFe12O9 with high magnetocrystalline anisotropy). The dielectric matrix consisted of silicone rubber. The average particle size was 30 nm for the magnetite powder and 6 micro/m for the strontium hexaferrite powder. The micron-sized SrFe12O19 powder was prepared using a solid-state reaction. We investigated the influence of the filler concentration and the filler ratio (Fe3O4/SrFe12O19) in the polymer matrix on the microwave absorption in a large frequency range (1 / 18 GHz). The results obtained showed that the highly anisotropic particles become centers of clusterification and the small magnetite particles form magnetic balls with different diameter depending on the concentration. The effect of adding micron-sized SrFe12O19 to the nanosized Fe3O4 filler in composites absorbing structures has to do with the ferromagnetic resonance (FMR) shifting to the higher frequencies due to the changes in the ferrite filler's properties induced by the presence of a magnetic material with high magnetocrystalline anisotropy. The two-component filler possesses new values of the saturation magnetization and of the anisotropy constant, differing from those of both SrFe12O1919 and Fe3O4, which leads to a rise in the effective anisotropy field. The results demonstrate the possibility to vary the composite's absorption characteristics in a controlled manner by way of introducing a second magnetic material.     

Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2

A magnetic adsorbent, amine-functionalized silica magnetite (NH(2)/SiO(2)/Fe(3)O(4)), has been synthesized to behave as an anionic or cationic adsorbent by adjusting the pH value of the aqueous solution to make amino groups protonic or neutral. NH(2)/SiO(2)/Fe(3)O(4) were used to adsorb copper ions (metal cation) and Reactive Black 5 (RB5, anionic dye) in an aqueous solution in a batch system, and the maximum adsorption were found to occur at pH 5.5 and 3.0, respectively. The adsorption equilibrium data were all fitted the Langmuir isotherm equation reasonably well, with a maximum adsorption capacity of 10.41 mg g(-1) for copper ions and of 217 m g g(-1) for RB5. A pseudo-second-order model also could best describe the adsorption kinetics, and the derived activation energy for copper ions and RB5 were 26.92 kJ mol(-1) and 12.06 kJ mol(-1), respectively. The optimum conditions to desorb cationic and anionic adsorbates from NH(2)/SiO(2)/Fe(3)O(4) were provided by a solution with 0.1M HNO(3) for copper ions and with 0.05 M NaOH for RB5.     

The one-pot synthesis of dextran-based nanoparticles and their application in in-situ fabrication of dextran-magnetite nanocomposites

The dextran-based nanoparticles containing carboxyl groups were synthesized by a one-pot approach, without using any organic solvents and surfactants. The resultant dextran-based nanoparticles was used as a host for the growing and organization of Fe(3)O(4) nanoparticles. The approach consists of the mixture of ferrous/ferric ions aqueous solution and host nanoparticles and subsequent coprecipitation of ferrous/ferric ions in basic medium. The magnetic nanocomposite material obtained was characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), X-ray diffraction techniques (XRD) and vibrating sample magnetometry (VSM). The data demonstrate that the carboxyls which can capture cationic ferrous/ferric by electronic interaction in the dextran-based hosts plays a crucial role in fabricating nanocomposites with a homogeneous spatial distribution of magnetite nanoparticles. The magnetic nanocomposites exhibit comparable saturation magnetizations to that of reported Fe(3)O(4) nanoparticles, and therefore display great potential in a large scope of biomedical fields.     

静电纺丝法制备PAN/Fe3O4磁性纳米纤维

采用化学共沉淀法制备纳米四氧化三铁,选用曲拉通X-100为分散剂,利用静电纺丝法制备PAN/Fe3O4磁性纳米复合材料。X射线衍射仪(XRD)验证了四氧化三铁在复合纳米纤维中的存在。同时使用扫描电镜(SEM)和透射电镜(TEM)对复合纳米纤维的微观形貌和Fe3O4在纤维中的分布进行了观察,利用热重(TGA)对纳米复合材料的热稳定性进行分析;通过磁性实验分析了纳米复合材料的磁性性能。结果表明,所制备PAN/Fe3O4磁性纳米纤维成型良好,且Fe3O4磁性颗粒在纤维中分散均匀,其与PAN是物理复合。纳米复合材料具有一定磁性,并可由磁性颗粒的加入量进行控制。     

Paraoxonase 1-bound magnetic nanoparticles: preparation and characterizations

This is most probably the first time that covalently binding of Human serum paraoxonase 1 (PON1) to superparamagnetic magnetite nanoparticles via carbodiimide activation was investigated and presented in this study. PON1 was purified from human serum using ammonium sulfate precipitation and hydrophobic interaction chromatography (Sepharose 4B, L-tyrosine, 1-Napthylamine) and magnetic iron oxide nanoparticles were prepared by co-precipitation Fe(+2) and Fe(+3) ions in an ammonia solution at room temperature. X-ray diffraction (XRD) and the magnetic measurements showed that the nanoparticles are magnetite and superparamagnetic, respectively. Direct measurements by dynamic light scattering revealed that the hydrodynamic size was 16.76 nm with polydispersity index (PDI: 0.234). The analysis of Fourier transform infrared spectroscopy revealed that the PON1 was properly bound to magnetic nanoparticles replacing the characteristic band of -NH2 at 1629 cm(-1) with the protein characteristic band at 1744 cm(-1) and 1712 cm(-1). Magnetic measurements determined that PON1-bound nanoparticles have also favorable superparamagnetic properties with zero coercivity and remanence though a slightly smaller saturation magnetization due to the decrease of magnetic moment in the volume friction. The kinetic measurements indicated the PON1-bound nanoparticles retained 70% of its original activity and exhibited an improved stability than did the free enzyme. The PON1 enzyme is seen to be quite convenient to bind superparamagnetic nanoparticles as support material.     

超临界CO2中聚丙烯酸丁酯/Fe3O4复合物的制备及应用

通过超临界二氧化碳(scCO2)沉淀聚合法制备了磁性聚丙烯酸丁酯(PBA/Fe3O4)复合物。首先经共沉淀法制备油酸(OA)改性的纳米Fe3O4颗粒,然后以丙烯酸丁酯(BA)为反应单体,偶氮二异丁腈(AIBN)为引发剂,二甲基丙烯酸乙二醇酯(EGDMA)为交联剂,正己烷为助溶剂,在scCO2中制备了PBA/Fe3O4复合物。对复合物进行了红外光谱、透射电镜、热重分析、X射线衍射表征和磁性能测试,结果显示OA-Fe3O4与PBA复合。对磁性复合物进行吸油性能测试,当反应压力为17MPa,改性纳米Fe3O4用量为6.7%时,反应生成的PBA/Fe3O4复合物对柴油的吸附量达7g/g,利用磁铁可对吸油复合物进行回收,经CO2再生后可重复使用10次,复合物对柴油的吸附量仍维持在5g/g以上。     

PLLA-PEG-PLLA/Fe_3O_4磁性微球的制备及性能

以聚乙二醇为引发剂,L-丙交酯为单体,开环聚合得到聚乳酸-聚乙二醇三嵌段共聚物(PLLA-PEG-PLLA),采用溶剂挥发法制备了PLLA-PEG-PLLA/Fe_3O_4磁性微球,并通过扫描电镜对其形态进行了表征。利用振动样品磁强计和Tg研究了微球的磁含量和磁性能,结果发现,相同粒径不同磁含量的磁性微球,磁含量越高,升温速率越快,当磁含量为70.57%时,升温速率最快,能达到磁热疗的有效温度42℃。对于磁含量相同,粒径不同的微粒,粒径越小,升温速率越快,粒径约为10μm时升温速率最快。     

Synthesis and characterization of magnetic adsorbent prepared by magnetite nanoparticles and zeolite from coal fly ash

Magnetite nanoparticles were prepared by partial oxidation of Fe(II) ions of an aqueous suspension of hydroxysulfate green rust which was obtained by precipitation of Fe(II) ions. This magnetite was mixed with zeolite synthesized from coal fly ash to obtain the magnetic adsorbent and the final product characterization was made. By analysis of scanning electron microscopy and X-ray diffraction, images of clusters of magnetite nanoparticles were observed and crystallite sizes of 17 nm were determined, respectively. In thermal analysis, the weight ratio of 1:3 for magnetite-zeolite in the magnetic adsorbent was measured and a non-magnetic product at 974 °C was found in both magnetite and magnetic adsorbent. Magnetization measurements described small hysteresis from the clusters of magnetite nanoparticles. Fourier Transform Infrared spectroscopy analysis indicated that the synthesized zeolite is a hydroxy sodalite and evidences of formation of the magnetic adsorbent were observed. The performance of magnetic separation technique was evaluated and it was comparable to the centrifugation process. The magnetic adsorbent indicated a potential application for adsorption of dye Reactive Orange 16 from aqueous solution.     

Characteristic of a novel composite inorganic polymer coagulant-PFAC prepared by hydrochloric pickle liquor

A novel magnetic nano-adsorbent has been developed by the covalent binding of polyacrylic acid (PAA) on the surface of Fe(3)O(4) nanoparticles and the followed amino-functionalization using diethylenetriamine (DETA) via carbodiimide activation. Transmission electron microscopy image showed that the amino-functionalized Fe(3)O(4) nanoparticles were quite fine with a mean diameter of 11.2+/-2.8 nm. X-ray diffraction analysis indicated that the binding process did not result in the phase change of Fe(3)O(4). Magnetic measurement revealed they were nearly superparamagnetic with a saturation magnetization of 63.2 emu/g Fe(3)O(4). The binding of DETA on the PAA-coated Fe(3)O(4) nanoparticles was demonstrated by the analyses of Fourier transform infrared (FTIR) spectroscopy and zeta potential. After amino-functionalization, the isoelectric point of PAA-coated Fe(3)O(4) nanoparticles shifted from 2.64 to 4.59. The amino-functionalized magnetic nano-adsorbent shows a quite good capability for the rapid and efficient adsorption of metal cations and anions from aqueous solutions via the chelation or ion exchange mechanisms. The studies on the adsorption of Cu(II) and Cr(VI) ions revealed that both obeyed the Langmuir isotherm equation. The maximum adsorption capacities and Langmuir adsorption constants were 12.43 mg/g and 0.06 L/mg for Cu(II) ions and 11.24 mg/g and 0.0165 L/mg for Cr(VI) ions, respectively.     

（BiAl）YIG薄膜的生长感生磁各向异性

从理论和实验上分析了Ｆｅ＾３＋和Ｆｅ＾２＋对（ＢｉＡ）ＹＩＧ薄膜的生长感各向异性的贡献，掺Ｂｉ导致的生长磁感生各向异性，来源于Ｅｉ＾３＋改变了Ｆｅ＾３＋的零场劈裂，其大小取决于Ｂｉ＾３＋含量及在十二面体位的择优分布，高价离子和氧空位形成的Ｆｅ＾２＋在八面体位的择优分布，对生长感生磁各向异性也有贡献。     

Effects of ferrous ions on the reductive dechlorination of trichloroethylene by zero-valent iron

The surface characteristics of zero-valent iron (ZVI) and the efficiency of reductive dechlorination of trichloroethylene (TCE) in the presence of ferrous ions were studied. The experimental results indicated that the acid-washing of a metallic iron sample enhanced the efficiency of TCE degradation by ZVI. This occurred because acid-washing changed the conformation of oxides on the surface of iron from maghemite (gamma-Fe(2)O(3)) to the more hydrated goethite (alpha-FeOOH), as was confirmed by XPS analysis. However, when ferrous ions were simultaneous with TCE in water, the TCE degradation rate decreased as the concentration of ferrous ion increased. This was due to the formation of passive precipitates of ferrous hydroxide, including maghemite and magnetite (Fe(3)O(4)), that coated on the surface of acid-washed ZVI, which as a result inhibited the electron transfer and catalytic hydrogenation mechanisms. On the other hand, in an Fe(0)-TCE system without the acid-washing pretreatment of ZVI, ferrous ions were adsorbed into the maghemite lattice which was then converted to semiconductive magnetite. Thus, the electrons were transferred from the iron surface and passed through the precipitates, allowing for the reductive dechlorination of TCE.     

Fe_x(In_2O_3)_(1-x)磁性颗粒膜的结构及光学性质

用射频溅射法制备了金属 /半导体 Fex(In2 O3) 1-x 颗粒膜。实验结果表明 :纳米尺度的Fe颗粒比较均匀地分布在非晶态母体In2 O3 中。退火可使In2 O3 晶化。该样品在室温下表现出超顺磁驰豫 ,符合Langevin方程。光学测量表明 :嵌Fe的磁性颗粒膜 ,其电子的带间跃迁由In2 O3 的直接跃迁变为间接跃迁 ,基本吸收边红移 ;随磁性增强 ,局域态尾变宽 ,带隙变窄     

The Faraday effect of natural and artificial ferritins

Measurements of the Faraday rotation at room temperature over the light wavelength range of 300-680?nm for horse spleen ferritin (HSF), magnetoferritin with different loading factors (LFs) and nanoscale magnetite and Fe(2)O(3) suspensions are reported. The Faraday rotation and the magnetization of the materials studied present similar magnetic field dependences and are characteristic of a superparamagnetic system. The dependence of the Faraday rotation on the magnetic field is described, excluding HSF and Fe(2)O(3), by a Langevin function with a log-normal distribution of the particle size allowing the core diameters of the substances studied to be calculated. It was found that the specific Verdet constant depends linearly on the LF. Differences in the Faraday rotation spectra and their magnetic field dependences allow discrimination between magnetoferritin with maghemite and magnetite cores which can be very useful in biomedicine.     

Green fabrication of agar-conjugated Fe3O4 magnetic nanoparticles

Magnetic nanoparticles are of great interest both for fundamental research and emerging applications. In the biomedical field, magnetite (Fe(3)O(4)) has shown promise as a hyperthermia-based tumor therapeutic. However, preparing suitable solubilized magnetite nanoparticles is challenging, primarily due to aggregation and poor biocompatibility. Thus methods for coating Fe(3)O(4) NPs with biocompatible stabilizers are required. We report a new method for preparing Fe(3)O(4) nanoparticles by co-precipitation within the pores of agar gel samples. Permeated agar gels were then dried and ground into a powder, yielding agar-conjugated Fe(3)O(4) nanoparticles. Samples were characterized using XRD, FTIR, TGA, TEM and SQUID. This method for preparing agar-coated Fe(3)O(4) nanoparticles is environmentally friendly, inexpensive and scalable.