Rapid synthesis and characterization of maghemite nanoparticles

Fe2O3-SiO2 nanocomposites were prepared by a sol-gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3-SiO2 sols were gelated at various temperatures ranging from 50 degrees C to 70 degrees C, and subsequently they were calcined in air at 400 degrees C for 4 hours. The structure and the magnetic properties of the prepared Fe203-SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3-SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 degrees C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10 K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 degrees C, respectively. At the gelation temperature of 70 degrees C, gamma-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9 +/- 2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.     

表面活性剂对FePt纳米颗粒形貌的影响

分别以乙酰丙酮铁(Fe(acac)3)和氯铂酸(H2PtCl6.6H2O)作为Fe源和Pt源,乙二醇作为还原剂和溶剂,通过多元醇还原法制备出单分散的FePt纳米颗粒,并研究了表面活性剂油酸油胺和CTAB对FePt纳米颗粒形貌和磁性能的影响。通过X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁强计(VSM)对纳米颗粒进行表征。结果表明,表面活性剂油酸油胺和CTAB修饰的FePt纳米颗粒均为面心立方(FCC)结构,分散性良好,粒径分布较未使用表面活性剂时变窄;油酸油胺修饰的FePt形貌主要是球形,但是有四方形纳米结构出现;而CTAB修饰的FePt形貌有蠕虫状产生。VSM结果显示其矫顽力都趋近于零,呈现超顺磁性。     

Synthesis and Characterization of Dendrimer-Encapsulated Iron and Iron-Oxide Nanoparticles

In this paper, a series of iron (Fe) containing nanoparticles were prepared by employing PAMAM (Poly(amidoamine), dendrimers with different generations (G0?CG3) as templates and sodium borohydride as a reducing agent. The products have been characterized by TEM, FT-IR, XRD, VSM, TGA, and XPS. XRD analysis reveal low crystallinity of formed particles within the dendrimers, however, crystallinity of the nanoparticles was observed to increase with increasing generation of dendrimers. Dominant phases were determined as magnetite (Fe₃O₄ or maghemite, ??-Fe₂O₃). XPS analysis revealed the chemical composition of nanoparticles as iron oxide which indicated the oxidation of Fe species subsequent to the reduction process, in agreement with XRD analysis. The magnetization curves have superparamagnetic nonhysteretic characteristic at lower fields and with nonsaturation characteristic at high fields. Magnetic evaluation of samples with the 20:1?molar ratio of Fe:PAMAM showed decreasing superparamagnetic character and decreasing saturation magnetisation with increasing generation of dendrimers.     

Direct synthesis of maghemite,magnetite and wustite nanoparticles by flame spray pyrolysis

Magnetic iron-oxide nanoparticles have been prepared by flame spray pyrolysis (FSP) under controlled atmosphere. This way controlled and direct flame synthesis of Fe₂O₃ (maghemite), Fe₃O₄ (magnetite) and FeO (wustite) particles is possible by a scalable process. The Fe oxidation state was controlled by varying the fuel to air ratio during combustion as well as by varying the valence state of the applied Fe precursor. The as-prepared materials were characterized by electron microscopy, nitrogen adsorption, X-ray diffraction and Raman spectroscopy. Magnetic properties were investigated with SQUID, which unravelled superparamagnetic behaviour for all materials and typical features for the corresponding crystal structures and particle sizes. Maximum magnetisation was achieved for a mixture of maghemite and magnetite.     

超顺磁性纳米Fe3O4的热分解法制备及表征

以单甲氧基聚乙二醇、对甲苯磺酰氯、邻苯二甲酰亚胺钾等为原料,根据盖布瑞尔合成法原理,合成了一端为氨基的单甲醚聚乙二醇(mPEG-NH2)。并以其为还原剂,聚乙二醇(PEG)为溶剂,利用热分解法制备了水分散性的超顺磁性纳米Fe3O4。采用红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)、热重分析(TG)、超导量子干涉仪(SQUID)和纳米粒度与Zeta电位分析仪等测试技术对其性能进行表征,实验结果表明,所制得的纳米Fe3O4粒子结晶度高,粒度均匀,分散良好,平均粒径为(12.2±1.6)nm,具有超顺磁性,饱和磁化强度为54 emu/g,在中性水溶液中其表面带正电,Zeta电位为+33 mV。TG测试结果表明,Fe3O4纳米粒子表面有机物的含量约为28%,Fe3O4的产率为57%左右。     

磁性羧甲基化壳聚糖纳米粒子的制备与表征

以化学共沉淀法制备了Fe3O4纳米粒子,壳聚糖经羧甲基化改性后接枝在Fe3O4颗粒表面,得到了磁性羧甲基化壳聚糖(Fe3O4/CMC)纳米粒子.利用透射电镜(TEM)、X射线衍射(XRD)、傅立叶红外光谱(FT-IR)及磁性测试对产物进行了表征.TEM表明Fe3O4纳米粒子被CMC包覆,粒径约10 nm;XRD分析表明复合纳米粒子中磁性物质为Fe3O4;FT-IR表明壳聚糖发生羧甲基反应以及在Fe3O4表面的接枝反应.Fe3O4/CMC纳米粒子具有超顺磁性,比饱和磁化强度25.73 emu/g,有良好的磁稳定性.     

Synthesis and characterization of copper nanoparticles

Reduction of copper salt by sodium citrate/SFS and myristic acid/SFS leads to phase pure Cu nanoparticles. However, a similar reaction with hydrazine hydrate (HH) and sodium formaldehyde sulfoxylate (SFS) in polymer afforded only a mixture of Cu₂O and Cu. Copper nanoparticles so-prepared were characterized by UV-Visible spectroscopy, X-ray diffraction measurements (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Freshly prepared solutions showed an absorption band at about 600 nm due to surface plasmon resonance (SPR). XRD analysis revealed all relevant Bragg's reflection for fcc crystal structure of copper metal. The particle size by use of Scherrer's equation is calculated to be about 30 nm. TEM showed nearly uniform distribution of the particles in PVA.     

雾化-热分解法合成氧化铁纳米粒子及其磁性能

建立了将五羰基铁超声雾化、分段加热分解-氧化及产物收集-修饰一体化的氧化铁纳米粒子合成装置,研究了不同温度参数对纳米粒子的相组成和形貌的影响,并通过在雾化液及收集液中添加修饰剂以控制合成纳米粒子的粒径和分散性。采用XRD、TEM和SQUID对合成的纳米粒子进行了表征。成功合成了不同结晶性和分散性的球形γ-Fe2O3纳米粒子。随着粒径减小,合成纳米粒子由顺磁性过渡到超顺磁性。     

磁性羟基磷灰石复合物的制备与表征

为探索磁性颗粒在治疗因缺乏骨骼应有的应力刺激而导致骨质疏松方面的潜在应用,研究制备了兼具良好生物活性和超顺磁性的羟基磷灰石(HA)/Fe3O4复合物。以化学沉积法合成的纳米Fe3O4浆料为底物,在Ca、P溶液中通过尿素酶催化水解尿素缓慢升高pH值,从而使HA逐渐在Fe3O4上沉积,形成具有一定核壳结构的磁性HA复合物。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线能量色散谱仪(EDX)、振动样品磁强计(VSM)和磁铁对底物及试样进行了表征。结果表明,以纳米Fe3O4浆料为底物,一定浓度含氯化钠的Ca、P溶液(Ca、P原子比为5∶3,Ca、Fe原子比为5∶3)为媒介,在37℃水浴中,反应48h,可制得具有较好磁性能的HA复合物,其饱和磁化强度可达7.23A.m2/kg,剩磁为0.073A.m2/kg,矫顽力为261.08A/m。     

新型磁性离子交换吸附TiO_2@Fe_3O_4/聚吡咯树脂复合材料制备及其吸附性能

首先采用溶胶-凝胶法制备TiO_2@Fe_3O_4核壳结构的磁性纳米粒子,然后与聚吡咯(PPy)采用原位聚合法制备TiO_2@Fe_3O_4/PPy磁性离子交换吸附剂。通过TEM、SEM对样品的形貌及粒径进行表征,用XRD表征分析物相,FTIR表征样品的表面性质,用VSM测定磁性能,由紫外-可见分光光度计测定吸光度,并对孔雀石绿溶液进行吸附性能测试。结果表明,PPy与TiO_2@Fe_3O_4纳米粒子复合后形貌未变,团聚现象明显改善,磁强度为5.384emu·g~(-1),具有超顺磁性。在pH=7,温度为298K条件下,用0.05g TiO_2@Fe_3O_4/PPy吸附剂对25mL 20mg·L~(-1)孔雀石绿溶液(MG)进行吸附,饱和吸附容量为312.50mg·g~(-1),且30min内去除率可达到99.1%。与活性炭相比较,TiO_2@Fe_3O_4/PPy磁性离子交换吸附树脂可以进行大面积动态交换与吸附,吸附性能优于活性炭。     

Facile synthesis of monodisperse superparamagnetic Fe3O4/PMMA composite nanospheres with high magnetization

Monodisperse superparamagnetic Fe(3)O(4)/polymethyl methacrylate (PMMA) composite nanospheres with high saturation magnetization were successfully prepared by a facile novel miniemulsion polymerization method. The ferrofluid, MMA monomer and surfactants were co-sonicated and emulsified to form stable miniemulsion for polymerization. The samples were characterized by DLS, TEM, FTIR, XRD, TGA and VSM. The diameter of the Fe(3)O(4)/PMMA composite nanospheres by DLS was close to 90 nm with corresponding polydispersity index (PDI) as small as 0.099, which indicated that the nanospheres have excellent homogeneity in aqueous medium. The TEM results implied that the Fe(3)O(4)/PMMA composite nanospheres had a perfect core-shell structure with about 3 nm thin PMMA shells, and the core was composed of many homogeneous and closely packed Fe(3)O(4) nanoparticles. VSM and TGA showed that the Fe(3)O(4)/PMMA composite nanospheres with at least 65% high magnetite content were superparamagnetic, and the saturation magnetization was as high as around 39 emu g(-1) (total mass), which was only decreased by 17% compared with the initial bare Fe(3)O(4) nanoparticles.     

Fabrication of nanocomposite particles with superparamagnetic and luminescent functionalities

A new kind of superparamagnetic luminescent nanocomposite particles has been synthesized using a modified Stöber method combined with an electrostatic assembly process. Fe₃O₄ superparamagnetic nanoparticles were coated with uniform silica shell, and then 3-aminopropyltrimethoxysilane was used to terminate the silica surface with amino groups. Finally, negatively charged CdSe quantum dots (QDs) were assembled onto the surface of the amino-terminated SiO₂/Fe₃O₄ nanoparticles through electrostatic interactions. X-ray diffraction (XRD), transmission electron microscopy (TEM), microelectrophoresis, UV-vis absorption and emission spectroscopy and magnetometry were applied to characterize the nanocomposite particles. Dense CdSe QDs were immobilized on the silica surface. The thickness of silica shell was about 35 nm and the particle size of the final products was about 100 nm. The particles exhibited favorable superparamagnetic and photoluminescent properties.     

Fe3O4纳米粒子的制备与超顺磁性

采用红外光谱、X射线衍射、透射电子显微镜和振动样品磁强计对用化学共沉淀法制备出的纳米Fe3O4粒子进行了形貌、结构及磁性能表征.其中,红外和XRD测试结果表明制备出的Fe3O4粒子的物态和晶相结构;透射电子显微镜照片表明制备出的纳米四氧化三铁成球性好,且大部分四氧化三铁粒子的粒径在10nm左右;磁化曲线表明制备出的Fe3O4粒子无剩磁和矫顽力,具有超顺磁性.并且,将制备出的纳米Fe3O4粒子和块状Fe3O4的磁性能进行对比,探讨了Fe3O4由块状的亚铁磁性向纳米级的超顺磁性转变的原因.     

Wet-chemical green synthesis of L-lysine amino acid stabilized biocompatible iron-oxide magnetic nanoparticles

In this paper, we report a novel method for the synthesis of L-Lysine (lys) amino acid coated maghemite (gamma-Fe2O3) magnetic nanoparticles (MNPs). The facile and cost effective method permitted preparation of the high-quality superparamagnetic gamma-Fe2O3 MNPs with hydrophilic and biocompatible nature. For this work, first we synthesized magnetite phase Fe3O4/lys by wet chemical method and oxidized to y-Fe2O3 in controlled oxidizing environment, as evidenced by XRD and VSM magnetometry. The crystallite size and magnetization of gamma-Fe2O3/lys MNPs was found to be 14.5 nm, 40.6 emu/gm respectively. The surface functionalization by L-lysine amino acid and metal-ligand bonding was also confirmed by FTIR spectroscopy. The hydrodynamic diameter, colloidal stability and surface charge on MNPs were characterized by DLS and zeta potential analyser.     

Ni doped Fe3O4 magnetic nanoparticles

In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.     

Magnetic hollow mesoporous silica nanospheres: facile fabrication and ultrafast immobilization of enzymes

Hollow mesoporous silica nanospheres with large pore size of around 11 nm have been synthesized by a structural difference based selective etching strategy, and the highly dispersed hydrophobic Fe3O4 nanoparticles with a particle size of 5 nm were then impregnated into hollow cores of nanospheres through these large pores by a vacuum impregnation technique. The structural characteristics of obtained magnetic composites were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Selected Area Electron Diffraction (SAED), Ultraviolet-visible (UV-Vis) and Vibrating Sample Magnetometer (VSM). The results show that the obtained Fe3O4-hollow mesoporous silica composites exhibit superparamagnetic property with saturation magnetization value of 4.17 emu/g. Furthermore, the obtained supports show ultrafast immobilization of hemoglobin and the immobilized enzymes are not denatured, indicating that the superparamagnetic hollow mesoporous silica spheres are excellent support for immobilization of enzymes with magnetic recycling property.     

一步法制备L10相FePt纳米颗粒

以乙酰丙酮铁(Fe(acac)3)和氯铂酸(H2PtCl6.6H2O)分别作Fe源和Pt源,三缩四乙二醇(TEG)作溶剂和还原剂,聚乙烯基吡咯烷酮(PVP)作表面活性剂,通过多元醇还原法制备出单分散的FePt纳米颗粒。通过X射线衍射仪(XRD)及透射电子显微镜(TEM)分析表明,所制备的FePt纳米颗粒形状近似球形,分散性较好,平均颗粒粒径约为5.5nm。通过振动样品磁强计(VSM)分析显示所制备FePt纳米颗粒矫顽力为37.64kA/m,这意味着FePt纳米颗粒部分转变为面心四方相(L10相)。     

A novel route to prepare Fe3O4/P(MAA-co-NVP) cross-linked magnetic composite microspheres with core-shell architecture by surface-initiated radical dispersion polymerization

A novel route was proposed to design and construct a magnetic composite microsphere with a controllable and regular core-shell architecture, which consists of Fe3O4 nanoparticles chemical-covalently encapsulated with pH-smart poly(methacrylic acid-co-N-vinyl pyrrolidone) (P(MAA-co-NVP)) cross-linked copolymers by a surface-initiated radical dispersion polymerization approach. The multistep surface treatment was employed to improve the dispersity and surface-chemical reactivity of Fe3O4 nanoparticles, involving introduction of active -NH2 groups, coupling of 1,1-methylene bis-(4-isocyanato-cyclohexane) and immobilizing of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl) propionamide]. The structure and morphological characterization were carried out by FTIR, TEM, SEM and XRD etc. The neat Fe3O4 nanoparticles take on an aggregated spherical shape with an average diameter of about 12 nm, while Fe3O4/P(MAA-co-NVP) magnetic microspheres assume regularly monodispersed spheres with a mean dimension of ca. 0.8 microm. The dimension of the microspheres is abruptly increased with increasing pH values of the media. The microspheres exhibit superparamagnetic properties. It is expected that this type of novel microspheres can be employed as a magnetic targeted and pH-sensitive drug carrier.     

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。     

Synthesis and characterization of environment friendly and multifunctional Fe3O4 magnetic nanoparticles

In this study, the size-uniform (5-6 nm), nearly spherical, and well-dispersed aqueous Fe3o4 magnetic nanoparticles were prepared by an improved chemical coprecipitation method. The DDAT-terminated (S-1-Dodecyl-S'-(alpha,alpha'-dimethyl-alpha"-acetic acid) trithiocarbonate) polymethacrylic (PMA-DDAT) was chosen as the apt surfactant, and the terminal DDAT can be used as a high efficient RAFT chain-transfer agent for further functionalization. Then, the functionalized Fe3O4 reacted with 4-amino-2,2,6,6-tetramethyl-piperidine-oxyl (4-NH2-TEMPO) to give the spin labeling magnetic nanoparticles. Finally, the multifunctional MNPs was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), Fourier transform infrared spectrometer (FT-IR), and vibrating-sample magnetometer (VSM). The obtained highly water-soluble, superparamagnetic, and multifunctional magnetic nanoparticles should find potential applications in biomedical research.