Synthesis of Fe3O4 nanoparticles with tunable and uniform size through simple thermal decomposition

A novel and facile method with low cost has been developed to fabricate Fe3O4 nanoparticles (NPs) with tunable and uniform sizes by the thermal decomposition of iron oleate complex. The synthesis of iron oleate complex was carried out using a reaction between oleic acid and FeCl3 x 6H2O at low temperature. The decomposition of iron oleate complex occurs when the complex added in the solution of octadecene (ODE) and trioctylamine (TOA) with simple heat treatment. The X-ray diffraction pattern of a resulting sample indicated that Fe3O4 NPs formed during the decomposition of iron oleate complex. Preparation conditions including reaction time and temperature, the concentration of the complex, and the ratio of TOA and ODE strikingly affected the size and size distribution of resulting Fe3O4 NPs. Under optimal preparation conditions, the size of Fe3O4 NPs was adjusted (less than 20 nm in average diameter). The analysis of samples by a Fourier transform infrared spectroscopy confirmed the formation of iron oleate complex. Because the Fe3O4 NPs revealed a superparamagnetic property as well as tunable and uniform sizes, the NPs will be utilizable for further applications. This simple strategy with low cost has to give a useful enlightenment for the design and fabrication of magnetic oxide.     

A facile route to sonochemical synthesis of magnetic iron oxide (Fe3O4) nanoparticles

A facile sonochemical approach was applied for the large scale synthesis of iron oxide magnetic nanoparticles (NPs) using inexpensive and non-toxic metal salts as reactants. The as-prepared magnetic iron oxide NPs has been characterized by XRD, TEM, EDS, and VSM. X-ray diffraction (XRD) and EDS analysis revealed that Fe₃O₄ NPs have been successfully synthesized in a single reaction by this simple method. Transmission electron microscopy (TEM) data demonstrated that the particles were narrow range in size distribution with 11 nm average particle size. Moreover, TEM measurements also show that the synthesized nanoparticles are almost spherical in shape. The magnetization curve from vibrating sample magnetometer (VSM) measurement shows that as-synthesized NPs were nearly superparamagnetic in magnetic properties with very low coercivity, and magnetization values were 80 emu/g, which is very near to the bulk value of iron oxide. The estimated value of mass susceptibility of as-synthesized nanoparticles is Xg = 5.71 × 10^− 4 m³/kg.     

A facile synthesis of PEG-coated magnetite (Fe3O4) nanoparticles and their prevention of the reduction of cytochrome c

We report here a facile and green synthetic approach to prepare magnetite (Fe(3)O(4)) nanoparticles (NPs) with magnetic core and polyethylene glycol (PEG) surface coating. The interaction of the bare and PEG-coated Fe(3)O(4) NPs with cytochrome c (cyt c, an important protein with direct role in the electron transfer chain) is also reported in this study. With ultrasonication as the only peptization method and water as the synthesis medium, this method is easy, fast, and environmentally benign. The PEG coated NPs are highly water dispersible and stable. The bare NPs have considerable magnetism at room temperature; surface modification by PEG has resulted in softening the magnetization. This approach can very well be applicable to prepare biocompatible, surface-modified soft magnetic materials, which may offer enormous utility in the field of biomedical research. Detailed characterizations including XRD, FTIR, TG/DTA, TEM, and VSM of the PEG-coated Fe(3)O(4) NPs were carried out in order to ensure the future applicability of this method. Although the interaction of bare NPs with cyt c shows reduction of the protein, efficient surface modification by PEG prevents its reduction.     

Facile one-pot preparation, surface functionalization, and toxicity assay of APTS-coated iron oxide nanoparticles

We report a facile approach to synthesizing 3-aminopropyltrimethoxysilane (APTS)-coated magnetic iron oxide (Fe(3)O(4)@APTS) nanoparticles (NPs) with tunable surface functional groups for potential biomedical applications. The Fe(3)O(4) NPs with a mean diameter of 6.5?nm were synthesized by a hydrothermal route in the presence of APTS. The formed amine-surfaced Fe(3)O(4)@APTS NPs were further chemically modified with acetic anhydride and succinic anhydride to generate neutral (Fe(3)O(4)@APTS?Ac) and negatively charged (Fe(3)O(4)@APTS?SAH) NPs. These differently functionalized NPs were extensively characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry analysis, zeta potential measurements, and T(2) relaxometry. The cytotoxicity of the particles was evaluated by in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric viability assay of cells along with microscopic observation of cell morphology. The hemocompatibility of the particles was assessed by in vitro hemolysis assay. We show that the hydrothermal approach enables an efficient modification of APTS onto the Fe(3)O(4) NP surfaces and the formed NPs with different surface charge polarities are water-dispersible and colloidally stable. The acetylated Fe(3)O(4)@APTS?Ac NPs displayed good biocompatibility and hemocompatibility in the concentration range of 0-100?μg?ml(-1), while the pristine Fe(3)O(4)@APTS and Fe(3)O(4)@APTS?SAH particles started to display slight cytotoxicity at a concentration of 10?μg?ml(-1). The findings from this study suggest that the Fe(3)O(4)@APTS NPs synthesized by the one-pot hydrothermal route can be surface modified for various potential biomedical applications.     

Composites of aminodextran-coated Fe3O4 nanoparticles and graphene oxide for cellular magnetic resonance imaging

Formation of composites of dextran-coated Fe(3)O(4) nanoparticles (NPs) and graphene oxide (Fe(3)O(4)-GO) and their application as T(2)-weighted contrast agent for efficient cellular magnetic resonance imaging (MRI) are reported. Aminodextran (AMD) was first synthesized by coupling reaction of carboxymethyldextran with butanediamine, which was then chemically conjugated to meso-2,3-dimercaptosuccinnic acid-modified Fe(3)O(4) NPs. Next, the AMD-coated Fe(3)O(4) NPs were anchored onto GO sheets via formation of amide bond in the presence of 1-ethyl-3-(3-dimethyaminopropyl) carbodiimide (EDC). It is found that the Fe(3)O(4)-GO composites possess good physiological stability and low cytotoxicity. Prussian Blue staining analysis indicates that the Fe(3)O(4)-GO nanocomposites can be internalized efficiently by HeLa cells, depending on the concentration of the composites incubated with the cells. Furthermore, compared with the isolated Fe(3)O(4) NPs, the Fe(3)O(4)-GO composites show significantly enhanced cellular MRI, being capable of detecting cells at the iron concentration of 5 μg mL(-1) with cell density of 2 × 10(5) cells mL(-1), and at the iron concentration of 20 μg mL(-1) with cell density of 1000 cells mL(-1).     

Synthesis and characterization of core∕shell Fe(3)O(4)∕ZnSe fluorescent magnetic nanoparticles

We report on the successful preparation and characterization of fluorescent magnetic core∕shell Fe(3)O(4)∕ZnSe nanoparticles (NPs) with a spherical shape by organometallic synthesis. The 7 nm core∕3 nm shell NPs show good magnetic and photoluminescence (PL) responses. The observed PL emission∕excitation spectra are shifted to shorter wavelengths, compared to a reference ZnSe NP sample. A dramatic reduction of PL quantum yield is also observed. The temperature dependence of the magnetization for the core∕shell NPs shows the characteristic features of two coexisting and interacting magnetic (Fe(3)O(4)) and nonmagnetic (ZnSe) phases. Compared to a reference Fe(3)O(4) NP sample, the room-temperature Néel relaxation time in core∕shell NPs is three times longer.     

Reduction of hexavalent chromium by Pannonibacter phragmitetus LSSE-09 coated with polyethylenimine-functionalized magnetic nanoparticles under alkaline conditions

A novel cell separation and immobilization method for Cr (VI)-reduction under alkaline conditions was developed by using superparamagnetic Fe(3)O(4) nanoparticles (NPs). The Fe(3)O(4) NPs were synthesized by coprecipitation followed by modification with sodium citrate and polyethyleneimine (PEI). The surface-modified NPs were monodispersed and the particle size was about 15 nm with a saturation magnetization of 62.3 emu/g and an isoelectric point (pI) of 11.5 at room temperature. PEI-modified Fe(3)O(4) NPs possess positive zeta potential at pH below 11.5, presumable because of the high density of amine groups in the long chains of PEI molecules on the surface. At initial pH 9.0, Pannonibacter phragmitetus LSSE-09 cells were immobilized by PEI-modified NPs via electrostatic attraction and then separated with an external magnetic field. Compared to free cells, the coated cells not only had the same Cr (VI)-reduction activity but could also be easily separated from reaction mixtures by magnetic force. In addition, the magnetically immobilized cells retained high specific Cr (VI)-reduction activity over six batch cycles. The results suggest that the magnetic cell separation technology has potential application for Cr (VI) detoxification in alkaline wastewater.     

交联P（St-r-AA）包覆Fe3O4粒子的制备及对Cu2＋的吸附

用乳液聚合的方法合成了交联P（St-r-AA）包覆的Fe3O4粒子,研究了该类粒子对Cu2＋离子的吸附性能。透射电镜（TEM）表明,交联的P（St-r-AA）包覆的Fe3O4磁性粒子粒径约100 nm;X射线衍射（XRD）分析表明,磁性粒子中磁性物质为尖晶石结构的Fe3O4;红外光谱（FT-IR）表明,Fe3O4表面的...     

Investigation on mechanism of growth arrest induced by iron oxide nanoparticles in PC12 cells

Iron oxide nanoparticles (Fe3O4 NPs) have recently received increasing interest in the biotechnology and life science. However, little is known about the nanoneurotoxicity of Fe3O4 NPs following exposure to neurons. This study was to elucidate the cytotoxicity and DNA damage of Fe3O4 NPs on PC12 cells line which derived from Rattus norvegicus pheochromocytoma. The cell viability was observed by MTS assay and cell cycle status was analyzed using flow cytometry. DNA damage related gene (P53) and its downstream targets (P21 and GADD45) were determined by semiquantitative RT-PCR. The results showed that exposure to Fe3O4 NPs at dosage levels between 25 and 200 microg/ml decreased cell viability respectively. The nanoparticles treatment caused cell cycle arrest in G2/M phase and the mRNA levels of P53 increased when PC12 cells were incubated with different concentrations Fe3O4 NPs. However, P21 and GADD45, the downstream targets of P53, were not affected. In summary, exposure to Fe3O4 NPs resulted in a dose-dependent cytotoxicity in cultured PC12 cells that was associated with increased P53 gene expression and much attention should be paid to the potential impact of Fe3O4 NPs on the central nervous system.     

Electronic structure studies of nanoferrite Cu(x)Co(1-x)Fe2O4 by X-ray absorption spectroscopy

Pure and mixed cobalt copper ferrites are of great interest due to their widespread application in electronics and medicine. We report on the electronic structure of a nanoferrite Cu(x)Co(1-x)Fe2O4 (0.0 < or = x < or = 1.0) system studied by X-ray absorption spectroscopy. These magnetic nanoferrites (average crystallite size approximately 31-43 nm) were synthesized by an auto combustion method and are characterized by high resolution X-ray diffraction and near edge X-ray absorption fine structure measurements at the O K and Co, Cu, and Fe L-edges. The O K-edge spectra suggest that there is a strong hybridization between O 2p and 3d electrons of Co, Cu and Fe cations and Fe L3,2-edge spectra indicate that Fe ions coexist in mixed valence states (Fe3+ and Fe2+) at tetrahedral and octahedral sites of the spinel structure. Copper and cobalt ions are distributed in the divalent state in octahedral sites of the spinel structure. The origin of high saturation magnetization and coercivity in cobalt-copper ferrites are explained in light of these results.     

Electrospun magnetic poly(l-lactide) (PLLA) nanofibers by incorporating PLLA-stabilized Fe3O4 nanoparticles

Magnetic poly(l-lactide) (PLLA)/Fe₃O₄ composite nanofibers were prepared with the purpose to develop a substrate for bone regeneration. To increase the dispersibility of Fe₃O₄ nanoparticles (NPs) in the PLLA matrix, a modified chemical co-precipitation method was applied to synthesize Fe₃O₄ NPs in the presence of PLLA. Trifluoroethanol (TFE) was used as the co-solvent for all the reagents, including Fe(II) and Fe(III) salts, sodium hydroxide, and PLLA. The co-precipitated Fe₃O₄ NPs were surface-coated with PLLA and demonstrated good dispersibility in a PLLA/TFE solution. The composite nanofiber electrospun from the solution displayed a homogeneous distribution of Fe₃O₄ NPs along the fibers using various contents of Fe₃O₄ NPs. X-ray diffractometer (XRD) and vibration sample magnetization (VSM) analysis confirmed that the co-precipitation process had minor adverse effects on the crystal structure and saturation magnetization (Ms) of Fe₃O₄ NPs. The resulting PLLA/Fe₃O₄ composite nanofibers showed paramagnetic properties with Ms directly related to the Fe₃O₄ NP concentration. The cytotoxicity of the magnetic composite nanofibers was determined using in vitro culture of osteoblasts (MC3T3-E1) in extracts and co-culture on nanofibrous matrixes. The PLLA/Fe₃O₄ composite nanofibers did not show significant cytotoxicity in comparison with pure PLLA nanofibers. On the contrary, they demonstrated enhanced effects on cell attachment and proliferation with Fe₃O₄ NP incorporation. The results suggested that this modified chemical co-precipitation method might be a universal way to produce magnetic biodegradable polyester substrates containing well-dispersed Fe₃O₄ NPs. This new strategy opens an opportunity to fabricate various kinds of magnetic polymeric substrates for bone tissue regeneration.     

Tuning exchange bias in core/shell FeO/Fe3O4 nanoparticles

Monodisperse 35 nm FeO nanoparticles (NPs) were synthesized and oxidized in a dry air atmosphere into core/shell FeO/Fe(3)O(4) NPs with both FeO core and Fe(3)O(4) shell dimensions controlled by reaction temperature and time. Temperature-dependent magnetic properties were studied on FeO/Fe(3)O(4) NPs obtained from the FeO NPs oxidized at 60 and 100 °C for 30 min. A large exchange bias (shift in the hysteresis loop) was observed in these core/shell NPs. The relative dimensions of the core and shell determine not only the coercivity and exchange field but also the dominant reversal mechanism of the ferrimagnetic Fe(3)O(4) component. This is the first time demonstration of tuning exchange bias and of controlling asymmetric magnetization reversal in FeO/Fe(3)O(4) NPs with antiferromagnetic core and ferrimagnetic shell.     

Immobilization of functional oxide nanoparticles on silicon surfaces via Si-C bonded polymer brushes

A method for immobilizing and mediating the spatial distribution of functional oxide (such as SiO2 and Fe3O4) nanoparticles (NPs) on (100)-oriented single crystal silicon surface, via Si-C bonded poly(3-(trimethoxysilyl)propyl methacrylate) (P(TMSPM)) brushes from surface-initiated atom transfer radical polymerization (ATRP) of (3-(trimethoxysilyl)propyl methacrylate) (TMSPM), was described. The ATRP initiator was covalently immobilized via UV-induced hydrosilylation of 4-vinylbenzyl chloride (VBC) with the hydrogen-terminated Si(100) surface (Si-H surface). The surface-immobilized Fe3O4 NPs retained their superparamagnetic characteristics and their magnetization intensity could be mediated by adjusting the thickness of the P(TMSPM) brushes.     

Superparamagnetic sub-5 nm Fe@C nanoparticles: isolation, structure, magnetic properties, and directed assembly

A method for isolating single crystalline sub-5 nm carbon coated iron nanoparticles (Fe@C NPs) from a carbon nanotube matrix has been developed. The isolation of such particles allows for their characterization by high resolution electron microscopy methods and SQUID magnetometry. While the NPs are superparamagnetic at room temperature, at 10 K they exhibit a coercivity nearly 30 times greater than that of commercial Fe3O4 NPs of comparable size. A novel nanotemplate directed assembly method for manipulating the particles at the individual particle level is also reported.     

Fast microwave synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Ag magnetic nanoparticles using Fe<Superscript>2+</Superscript> as precursor

A simple and quick microwave method to prepare high performance magnetite nanoparticles (Fe₃O₄ NPs) directly from Fe has been developed. The as-prepared Fe₃O₄ NPs product was fully characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the as-prepared Fe₃O₄ NPs are quite monodisperse with an average core size of 80 × 5 nm. The microwave synthesis technique can be easily modified to prepare Fe₃O₄/Ag NPs and these NPs possess good magnetic properties. The formation mechanisms of the NPs are also discussed. Our proposed synthesis procedure is quick and simple, and shows potential for large-scale production and applications for catalysis and biomedical/biological uses.     

Dumbbell-like PtPd-Fe(3)O(4) Nanoparticles for Enhanced Electrochemical Detection of H(2)O(2)

Dumbbell-like Pt(x)Pd(100-x)-Fe(3)O(4) nanoparticles (NPs) were synthesized and studied for electrocatalytic reduction and sensing of H(2)O(2). In 0.1 M phosphate buffered saline (PBS) solution, the 4-10 nm Pt(x)Pd(100-x)-Fe(3)O(4) NPs showed the Pt/Pd composition-dependent catalysis with Pt(48)Pd(52)-Fe(3)O(4) NPs having the best activity. The Pt(48)Pd(52)-Fe(3)O(4) NPs were tested for H(2)O(2) detection, and their H(2)O(2) detection limit reached 5 nM, which was suitable for monitoring H(2)O(2) generated from Raw 264.7 cells. These dumbbell-like PtPd-Fe(3)O(4) NPs are the most sensitive probe ever reported and can be used to achieve real-time quantitative detection of H(2)O(2) in biological environment for biological and biomedical applications.     

葡聚糖包覆纳米Fe3O4颗粒的研究

采用化学共沉淀法制备了葡聚糖包覆的纳米Fe3O4颗粒,平均粒径为6nm,包覆层厚度约为3～5nm,纳米Fe3O4粒径分布较窄.红外光谱分析可知,葡聚糖与纳米Fe3O4主要以氢键结合,结合Zeta电位和热重分析,分散作用主要是空间位阻作用,葡聚糖的包覆量约为10%.吸光度测试表明,随着葡聚糖用量的增加,悬浮液的稳定性提高.用量为25%时,悬浮液在室温下静止1周,无分层现象.包覆样的饱和磁化强度为60emu/g,具有良好的超顺磁性.     

Optically transparent magnetic nanocomposites based on encapsulated Fe(3)O(4) nanoparticles in a sol-gel silica network

Composite Fe(3)O(4)-SiO(2) materials were prepared by the sol-gel method with tetraethoxysilane and aqueous-based Fe(3)O(4) ferrofluids as precursors. The monoliths obtained were crack free and showed both optical and magnetic properties. The structural properties were determined by infrared spectroscopy, x-ray diffractometry and transmission electron microscopy. Fe(3)O(4) particles of 20?nm size lie within the pores of the matrix without any strong Si-O-Fe bonding. The well established silica network provides effective confinement to these nanoparticles. The composites were transparent in the 600-800?nm regime and the field dependent magnetization curves suggest that the composite exhibits superparamagnetic characteristics.     

Facile and green synthesis of cobalt oxide nanoparticles using ethanolic extract of Trigonella foenumgraceum (Fenugreek) leaves

Cobalt oxide nanoparticles (Co₃O₄ NPs) were successfully synthesized using ethanolic extract of Trigonella foenumgraceum L. (fenugreek) leaves as a green, potentially low cost, and easily biosynthesized method. The organic bioactive compounds present in fenugreek leaves extract acted as both reducing agents and stabilizing agents for synthesizing metal NPs from cobalt chloride hexahydrate as a precursor. As evidence from UV/Visible spectroscopy, energy dispersive spectroscopy (EDS), and X-ray diffraction analysis (XRD) studies, high alkaline pH was found favorable for the preparation of pure and crystallized single-phase Co₃O₄ NPs. The interaction of biomolecules from fenugreek leaves extract with Co₃O₄ NPs was defined by Fourier transform infrared spectroscopy (FTIR) analysis and X-ray photoelectron spectroscopy (XPS). The hydrodynamic size and surface charge of the biosynthesized NPs were measured using light-scattering (DLS) and zeta potential analyses; revealed the formation of negative charged Co₃O₄ NPs with uniform hydrodynamic size distribution. According to transmission electron microscopy (TEM) analysis, quasi-spherical Co₃O₄ NPs were synthesized with an average size of 13.2 nm under the modified condition of pH 12 and reaction time of 2 h through inexpensive, environmental friendly benign synthesis process without the use of any additional toxic chemical.     

One-dimensional SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers and enhancement magnetic property

SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers of diameters about 100 nm with mass ratio 1:1 have been prepared by the electrospinning and calcination process. The SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrites are formed after calcined at 700 degrees C for 2 hours. The composite ferrite nanofibers are fabricated from nanosized Ni(0.5)Zn(0.5)Fe2O4 and SrFe12O19 ferrite grains with a uniform phase distribution. The ferrite grain size increases from about 11 to 36 nm for Ni(0.5)Zn(0.5)Fe12O4 and 24 to 56 nm for SrFe12O19 with the calcination temperature increasing from 700 to 1100 degrees C. With the ferrite grain size increasing, the coercivity (Hc) and remanence (Mr) for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers initially increase, reaching a maximum value of 118.4 kA/m and 31.5 Am2/kg at the grain size about 40 nm (SrFe12O19) and 24 nm (Ni(0.5)Zn(0.5)Fe2O4) respectively, and then show a reduction tendency with a further increase of the ferrite grain size. The specific saturation magnetization (Msh) of 63.2 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers obtained at 900 degrees C for 2 hours locates between that for the single SrFe12O19 ferrite (48.5 Am2/kg) and the single Ni(0.5)Zn(0.5)Fe2O4 ferrite (69.3 Am2/kg). In particular, the Mr value 31.5 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers is much higher than that for the individual SrFe12O19 (25.9 Am2/kg) and Ni(0.5)Zn(0.5)Fe2O4 ferrite (11.2 Am2/kg). These enhanced magnetic properties for the composite ferrite nanofibers can be attributed to the exchange-coupling interaction in the composite.