Preparation of carbon coated Fe3O4 nanoparticles and their application for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples

The carbon coated Fe₃O₄ nanoparticles (Fe₃O₄/C) were synthesized by a simple hydrothermal reaction and applied as solid-phase extraction (SPE) sorbents to extract trace polycyclic aromatic hydrocarbons (PAHs) from environmental water samples. The Fe₃O₄/C sorbents possess high adsorption capacity and extraction efficiency due to strong adsorption ability of carbon materials and large surface area of nanoparticles, and only 50 mg of sorbents are required to extract PAHs from 1000 mL water samples. The adsorption attains equilibrium rapidly and analytes are eluted with acetonitrile readily. Salinity and solution pH have no obvious effect on the recoveries of PAHs, which avoids fussy adjustment to water sample before extraction. Under optimized conditions, the detection limits of PAHs are in the range of 0.2–0.6 ng L⁻¹. The accuracy of the method was evaluated by the recoveries of spiked samples. Good recoveries (76–110%) with low relative standard deviations from 0.8% to 9.7% are achieved. This new SPE method provides several advantages, such as high extraction efficiency, high breakthrough volumes, convenient extraction procedure, and short analysis times. To our knowledge, this is the first time that Fe₃O₄/C nanoparticles are used for the pretreatment of environmental water samples.     

Barium alginate caged Fe3O4@C18 magnetic nanoparticles for the pre-concentration of polycyclic aromatic hydrocarbons and phthalate esters from environmental water samples

The hydrophobic octadecyl (C₁₈) functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄@C₁₈) were caged into hydrophilic barium alginate (Ba²⁺-ALG) polymers to obtain a novel type of solid-phase extraction (SPE) sorbents, and the sorbents were applied to the pre-concentration of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) pollutants from environmental water samples. The hydrophilicity of the Ba²⁺-ALG cage enhances the dispersibility of sorbents in water samples, and the superparamagnetism of the Fe₃O₄ core facilitates magnetic separation. With the magnetic SPE technique based on the Fe₃O₄@C₁₈@Ba²⁺-ALG sorbents, it requires only 30 min to extract trace levels of analytes from 500 mL water samples. After the eluate is condensed to 0.5 mL, concentration factors for both phenanthrene and di-n-propyl-phthalate are over 500, while for other analytes are about 1000. The recoveries of target compounds are independent of salinity and solution pH under testing conditions. Under optimized conditions, the detection limits for phenanthrene, pyrene, benzo[a]anthracene, and benzo[a]pyrene are 5, 5, 3, and 2 ng L⁻¹, and for di-n-propyl-phthalate, di-n-butyl-phthalate, di-cyclohexyl-phthalate, and di-n-octyl-phthalate are 36, 59, 19, and 36 ng L⁻¹, respectively. The spiked recoveries of several real water samples for PAHs and PAEs are in the range of 72-108% with relative standard deviations varying from 1% to 9%, showing good accuracy of the method. The advantages of the new SPE method include high extraction efficiency, short analysis time and convenient extraction procedure. To the best of our knowledge, it is unprecedented that hydrophilic Ba²⁺-ALG polymer caged Fe₃O₄@C₁₈ magnetic nanomaterial is used to extract organic pollutants from large volumes of water samples.     

Surface modified Fe3O4 nanoparticles as a protein delivery vehicle

We report a one-step synthesis of Fe₃O₄ nanoparticles coated with PEG. The formation of the Fe₃O₄ core and the polymer coating took place simultaneously. Furthermore, these nanoparticles were modified with 3-APTES, providing a -NH₂ functional group, and applied in the immobilization of lysozyme. In this paper, the modified magnetic nanoparticles acting as a general agent to immobilize proteins are around 10 nm in size. The protein immobilization can be adjusted flexibly by changing either the amount of glutaraldehyde or the buffer solution.     

Ultrasonic synthesis of polyaniline nanotubes containing Fe3O4 nanoparticles

Polyaniline (PANI) nanotubes containing Fe₃O₄ nanoparticles were synthesized under ultrasonic irradiation of the aqueous solutions of aniline, ammonium peroxydisulfate (APS), phosphoric acid (H₃PO₄), and the quantitative amount of Fe₃O₄. It was found that the obtained samples had the morphologies of nanotubes. TEM images and selected area electronic diffractions showed that Fe₃O₄ nanoparticles were embedded in PANI nanotubes. We thought that the mechanism of the formation of PANI/Fe₃O₄ nanotubes could be attributed to the ultrasonic irradiation and the H₃PO₄-aniline salt template. The molecular structure of PANI/Fe₃O₄ nanotubes were characterized by Fourier transform infrared spectroscopy (FTIR), UV-vis absorption spectra and X-ray diffraction (XRD). The conductivity and magnetic properties of the PANI nanotubes containing Fe₃O₄ nanoparticles were also investigated.     

Synthesis of Fe3O4\SiO2\Ag nanoparticles and its application in surface-enhanced Raman scattering

To obtain a recyclable surface-enhanced Raman scattering (SERS) material, we developed a composite of Fe₃O₄\SiO₂\Ag with core\shell\particles structure. The designed particles were synthesized via an ultrasonic route. The Raman scattering signal of Fe₃O₄ could be shielded by increasing the thickness of the SiO₂ layer to 60 nm. Dye rhodamine B (RB) was chosen as probe molecule to test the SERS effect of the synthesized Fe₃O₄\SiO₂\Ag particles. On the synthesized Fe₃O₄\SiO₂\Ag particles, the characteristic Raman bands of RB could be observed when the RB solution was diluted to 5 ppm (1×10⁻⁵ M). Furthermore, the synthesized particles could keep their efficiency till four cycles.     

Fast synthesis of dopamine-coated Fe3O4 nanoparticles through ligand-exchange method

A fast approach was described for the synthesis of water-dispersible monodisperse dopamine-coated Fe₃O₄ nanoparticles（DA-Fe₃O₄） with uniform size and shape via ligand-exchange of oleic acid on Fe₃O₄ using only 2 min.The prepared DA-Fe₃O₄ nanoparticles were characterized by transmission electron microscopy,Fourier transform infrared spectrometry,and vibrating sample magnetometer.The results indicated that the resulting DA-Fe₃O₄ nanoparticles had an average diameter of about 19.2 nm. The magnetic saturation value of the prepared DA-Fe₃O₄ nanoparticles was determined to be 72.87 emu/g,which indicating a well-established superparamagnetic property.     

超声法制备Au/Fe_3O_4及其催化还原4-硝基苯酚性能

通过简易的超声法以及原位还原法成功制备出了负载型可再生Au/Fe_3O_4催化剂。利用3-氨丙基三乙氧基硅烷(APTES)作为有机桥键,将Au固定在Fe_3O_4的表面,得到单分散磁性Au/Fe_3O_4。Au0在氨基的作用下不会团聚,因此具有较高的催化活性及稳定性。XRD、HRTEM、EDS和XPS等测试结果表明Au/Fe_3O_4已被成功制备。将其用于催化还原4-硝基苯酚得到4-氨基苯酚,表现出较高的催化活性,速率常数可达0.225 6 min~(-1)。重复性实验表明该催化剂具有良好的稳定性,反应9个循环之后,催化还原反应的转化率仍可达到94%。     

超声法制备Au/Fe3O4及其催化还原4-硝基苯酚性能

通过简易的超声法以及原位还原法成功制备出了负载型可再生Au/Fe₃O₄催化剂。利用3-氨丙基三乙氧基硅烷（APTES）作为有机桥键,将Au固定在Fe₃O₄的表面,得到单分散磁性Au/Fe₃O₄。Au⁰在氨基的作用下不会团聚,因此具有较高的催化活性及稳定性。XRD、HRTEM、EDS和XPS等测试结果表明Au/Fe₃O₄已被成功制备。将其用于催化还原4-硝基苯酚得到4-氨基苯酚,表现出较高的催化活性,速率常数可达0.225 6 min^-1。重复性实验表明该催化剂具有良好的稳定性,反应9个循环之后,催化还原反应的转化率仍可达到94%。     

Preparation and mechanism of Fe3O4/Au core/shell super-paramagnetic microspheres

In the presence of Fe₃O₄ nano-particles, a new type of super-paramagnetic Fe₃O₄/Au microspheres with core/shell structures was prepared by reduction of Au³⁺ with hydroxylamine. The formation mechanism of the core/shell microspheres was studied in some detail. It was shown that the formation of the complex microspheres can be divided into two periods, that is, surface reaction-controlled process and diffusion-controlled process. The relative time lasted by either process depends upon the amount of Fe₃O₄ added and the initial concentration of Au³⁺. XPS analysis revealed that along with increasing in coating amount, the strength of the characteristic peaks of Au increased, and the Auger peaks of Fe weakened and even disappeared. Size distribution analysis showed that the core/shell microspheres are of an average diameter of 180 nm, a little bit larger than those before coating.     

Magnetically separable Fe3O4 nanoparticles: an efficient catalyst for the synthesis of propargylamines

Magnetically separable Fe₃O₄ nanoparticles endow with an efficient and economic route for the synthesis of propargylamines by the three-component coupling of aldehyde, amine, and alkyne through C-H activation. The reaction is especially effective for reactions involving aliphatic aldehydes and no additional co-catalyst or activator is required. High catalytic activity and ease of recovery using an external magnetic field are additional eco-friendly attributes of this catalytic system. The catalyst was recycled for five times without a significant loss of catalytic activity.     

Hydrothermal synthesis of monodisperse Fe3O4 nanoparticles based on modulation of tartaric acid

In this paper, monodisperse Fe₃O₄ nanoparticles with single crystalline structure were synthesized via a facile environment-friendly method. And the size of the nanoparticles ranges from 10 nm to 15 nm. As-synthesized Fe₃O₄ were characterized by X-ray diffraction instrument (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectrometer and field emission transmission electron microscope (FE-TEM). The effect of tartaric acid (TA) amount on products was investigated by XRD and TEM. The results indicated that TA could commendably modulate the crystalline phase, morphology and size of nanometer Fe₃O_4. A possible generated mechanism of Fe₃O₄ crystals was proposed in virtue of UV–vis absorption spectra. Besides, the magnetic properties of as-synthesized Fe₃O₄ were detected.     

Alginate-Coated Fe3O4 Hollow Microspheres for Drug Delivery

Novel hollow Fe₃O₄ nanoparticles for drug delivery were synthesized via a one-step templatefree approach. These nanoparticles were obtained by modifing the Fe₃O₄ nanoparticles with 3-aminopropyltrimethoxy silane, and then grafting alginate onto the surface of amine magnetic. The hollow structure of Fe₃O₄ spheres was characterized by TEM, XRD, and XPS. The M-H hysteresis loop indicated that the magnetic spheres exhibit superparamagnetic characteristics at room temperature. Daunorubicin acting as a model drug was loaded into the carrier, and the maximum percent of envelop and load were 28.4% and 14.2% respectively. The drug controlled releasing behaviors of the carriers were compared in different pH media.     

A highly selective magnetic sensor with functionalized Fe/Fe3O4 nanoparticles for detection of Pb2+

A magnetic sensor for detection of Pb~(2+) has been developed based on Fe/Fe_3O_4 nanoparticles modified by3-(3,4-dihydroxyphenyl)propionic acid(DHCA). The carboxyl groups of DHCA have a strong affinity to coordination behavior of Pb~(2+) thus inducing the transformation of Fe/Fe_3O_4 nanoparticles from a dispersed to an aggregated state with a corresponding decrease, then increase in transverse relaxation time(T_2) of the surrounding water protons. Upon addition of the different concentrations of Pb~(2+) to an aq. solution of DHCA functionalized Fe/Fe_3O_4 nanoparticles(DHCA-Fe/Fe_3O_4 NPs)([Fe] = 90 mmol/L), the change of T_2 values display a good linear relationship with the concentration of Pb~(2+) from 40 μmol/L to 100 μmol/L and from 130 μmol/L to 200 μmol/L, respectively. Owing to the especially strong interaction between DHCA and Pb~(2+), DHCA-Fe/Fe_3O_4 NPs exhibited a high selectivity over other metal ions.     

Fabrication of graphene/Fe3O4@polythiophene nanocomposite and its application in the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples

Polythiophene (PT) was used as a surface modifier of graphene/Fe₃O₄ (G/Fe₃O₄) composite to increase merit of it, and also overcome some limitations and disadvantages of using G/Fe₃O₄ alone as solid phase extraction (SPE) sorbent. An in-situ chemical polymerization method was employed to prepare G/Fe₃O₄@PT nanocomposites. Application of this newly designed material in the magnetic SPE (MSPE) of polycyclic aromatic hydrocarbons (PAHs), as model analytes, in the environmental water samples was investigated. The characterization of the hybrid material was performed using transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, Fourier transform-infrared (FT-IR) spectroscopy and vibrating sample magnetometry. Seven important parameters, affecting the extraction efficiency of PAHs, including: amount of adsorbent, adsorption and desorption times, type and volume of the eluent solvent, initial sample volume and salt content of the sample were evaluated. The optimum extraction conditions were obtained as: 4 min for extraction time, 20 mg for sorbent amount, 100 mL for initial sample volume, toluene as desorption solvent, 0.6 mL for desorption solvent volume, 6 min for desorption time and 30% (w/v) for NaCl concentration. Good performance data were obtained at the optimized conditions. Detection limits were in the range of 0.009–0.020 μg L⁻¹ in the real matrix. The calibration curves were linear over the concentration ranges from 0.03 to 80 μg L⁻¹ with correlation coefficients (R²) between 0.995 and 0.998 for all the analytes. Relative standard deviations were ranged from 4.3 to 6.3%. Appropriate recovery values, in the range of 83–107%, were also obtained for the real sample analysis.     

Oxygen fugacity for stoichiometric magnetite Fe3O4-hercinite FeAl2O4 solid solutions

The Frenkel defect model is applied to determine the oxygen fugacity that corresponds to the preparation of magnetite-hercinite solid solutions with an exact 4:3 oxygen:cation ratio. The result are presented in graphic form for .     

线性麦芽糊精聚合物功能化Fe3O4纳米复合物药物载体的合成和应用

采用共沉淀法制备得到了线性麦芽糊精聚合物功能化的Fe₃O₄磁性纳米粒子(LM-SP-MNPs),通过傅里叶变换红外光谱、透射电子显微镜、热重分析等技术对其结构、形貌进行了表征。 其粒径大小为(12±2) nm。 选取抗癌药物盐酸阿霉素(DOX)作为模型药物,运用荧光光谱法研究了LM-SP-MNPs的载药性能和释放行为,探讨了pH值对LM-SP-MNPs药物释放性能的影响。 最适pH条件下,LM-SP-MNPs对盐酸阿霉素的最大吸附量约为357.1 mg/g,吸附等温线符合Freundlich等温吸附模型。 LM-SP-MNPs与盐酸阿霉素的复合物(DOX@LM-SP-MNPs),在37 ℃的条件下药物在酸性条件下的释放效率大于中性条件。 pH=5.3时,盐酸阿霉素在7 h内的累积释放率为26.9%。 此外,细胞毒性试验表明,LM-SP-MNPs具有良好的生物相容性,而DOX@LM-SP-MNPs和肝癌细胞共培养后可以明显杀死HepG2肝癌细胞。     

Fe3O4 nanoparticles/ethyl acetoacetate system for the efficient catalytic oxidation of aldehydes to carboxylic acids

A new methodology for the oxidation of aldehydes promoted by commercially available Fe₃O₄ nanoparticles (Fe₃O₄ NPs) activated by ethyl acetoacetate was developed. The use of ethyl acetoacetate as additive was crucial to achieve high reactivities. All reactions were realized under solvent free conditions, using air or tBuOOH as oxidants. Finally, the separation and reuse of the magnetically recoverable nanoparticles make this methodology very practical, simple and economical.     

Facile synthesis of multifunctional multiwalled carbon nanotubes/Fe3O4 nanoparticles/polyaniline composite nanotubes

With an average diameter of 100-150 nm, composite nanotubes of polyaniline (PANI)/multiwalled carbon nanotubes (MWNTs) containing Fe₃O₄ nanoparticles (NPs) were synthesized by a two-step method. First, we synthesized monodispersed Fe₃O₄ NPs (d=17.6 nm, σ=1.92 nm) on the surface of MWNTs and then decorated the nanocomposites with a PANI layer via a self-assembly method. SEM and TEM images indicated that the obtained samples had the morphologies of nanotubes. The molecular structure and composition of MWNTs/Fe₃O₄ NPs/PANI nanotubes were characterized by Fourier transform infrared spectra (FTIR), energy dispersive X-ray spectrometry (EDX), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and Raman spectra. UV-vis spectra confirmed the existence of PANI and its response to acid and alkali. As a multifunctional material, the conductivity and magnetic properties of MWNTs/Fe₃O₄ NPs/PANI composites nanotubes were also investigated.     

Pt/Au/Fe3O4的制备及其电化学性能

以制得的纳米Fe₃O₄颗粒作为载体,用还原法将还原出的Au与Pt分别负载到Fe₃O₄颗粒表面,制得纳米Pt/Au/Fe₃O₄复合材料。对Pt/Au/Fe₃O₄进行紫外可见光吸收光谱、透射电子显微镜、X射线衍射及光电子能谱等物理表征,结果表明,Au与Pt均匀地沉积到了Fe₃O₄纳米颗粒表面。对纳米Pt/Au/Fe₃O₄复合材料进行循环伏安扫描,当H₂PtCl₆的加入量达到8 mL时,Pt/Au/Fe₃O₄催化性能最佳;正扫电流峰i_p与扫描速率的平方根v^1/2线性相关,Pt/Au/Fe₃O₄催化氧化甲醇的过程受扩散控制;对催化剂进行201次循环伏安扫描,催化剂仍然能保持较好的催化性能且稳定性良好。因此,所合成催化剂Pt/Au/Fe₃O₄是一种具有良好化学稳定性的阳极催化剂材料。     

Synthesis of pyranopyrazoles using magnetic Fe3O4 nanoparticles as efficient and reusable catalyst

Magnetic Fe₃O₄ nanoparticles as a heterogeneous catalyst, were found to be efficient for the synthesis of a series of pyranopyrazoles by a four component reaction of a mixture of hydrazine hydrate, ethyl acetoacetate, aldehydes/ketones and malononitrile in water at room temperature. The products were attributed to the nanosize of about 16 nm in which the catalyst could act as a nanoreactor. The present protocol offers the advantages of clean reaction, short reaction time, high yield, easy purification and economic availability of the catalyst.