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.     

The grafting and release behavior of doxorubincin from Fe(3)O(4)@SiO(2) core-shell structure nanoparticles via an acid cleaving amide bond: the potential for magnetic targeting drug delivery

Fe(3)O(4)@SiO(2) core-shell structure nanoparticles were first prepared and characterized by TEM, FTIR, XPS and XRD. Subsequently the widely used anticancer agent doxorubincin (DOX) was successfully grafted to the surface of the core-shell nanoparticles via an amide bond with the aid of a spacer arm we synthesized. The spacer arm met two needs: one end can couple to the core-shell nanoparticles' surface while the other end was the active?-COOH group, which can react with the?-NH(2) group of DOX molecules. The synthesized spacer arm and the conjugation of the drug with nanoparticles through amidation were confirmed by FTIR. The DOX-loading efficiency determined by UV-vis spectrometer was 86.5%. Drug release experiments displayed a pH-dependent behavior that DOX was cleaved from the nanoparticles easily under low pH conditions in the presence of protease and that most of the conjugated doxorubincin were released within the first 12?h. The prepared DOX-grafted Fe(3)O(4)@SiO(2) core-shell structure nanoparticles showed a superparamagnetic property with a saturation magnetization value of 49.3?emu?g(-1), indicating a great potential application in the treatment of cancer using magnetic targeting drug-delivery technology.     

Fe3O4 magnetic nanoparticles as peroxidase mimetics and their applications in H2O2 and glucose detection

Artificial enzyme mimetics are a current research interest because natural enzymes bear some serious disadvantages, such as their catalytic activity can be easily inhibited and they can be digested by proteases. A very recently study reported by Yan et al. has proven that Fe(3)O(4) magnetic nanoparticles (MNPs) exhibit an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, though MNPs are usually thought to be biological and chemical inert (Gao, L. Z.; Zhuang, J.; Nie, L.; Zhang, J. B.; Zhang, Y.; Gu, N.; Wang, T. H.; Feng, J.; Yang, D. L.; Perrett, S.; Yan, X. Y. Nat. Nanotechnol. 2007, 2, 577-583). In the present work, we just make use of the novel properties of Fe(3)O(4) MNPs as peroxidase mimetics reported by Yan et al. to detect H(2)O(2). The Fe(3)O(4) MNPs were prepared via a coprecipitation method. The as-prepared Fe(3)O(4) MNPs were then used to catalyze the oxidation of a peroxidase substrate 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) by H(2)O(2) to the oxidized colored product (see eq 1) which provides a colorimetric detection of H(2)O(2). As low as 3 x 10(-6) mol/L H(2)O(2) could be detected with a linear range from 5 x 10(-6) to 1 x 10(-4) mol/L via our method. More importantly, a sensitive and selective method for glucose detection was developed using glucose oxidase (GOx) and the as-prepared Fe(3)O(4) MNPs. The detection platforms for H(2)O(2) and glucose developed in the present work not only further confirmed that the Fe(3)O(4) MNPs possess intrinsic peroxidase-like activity but also showed great potential applications in varieties of simple, robust, and easy-to-make analytical approaches in the future.     

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.     

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.     

Glutaraldehyde mediated conjugation of amino-coated magnetic nanoparticles with albumin protein for nanothermotherapy

A novel bioconjugation of amino saline capped Fe3O4 magnetic nanoparticles (MNPs) with bovine serum albumin (BSA) was developed by applying glutaraldehyde as activator. Briefly, Fe3O4 MNs were synthesized by the chemical co-precipitation method. Surface modification of the prepared MNPs was performed by employing amino saline as the coating agent. Glutaraldehyde was further applied as an activation agent through which BSA was conjugated to the amino-coated MNPs. The structure of the BSA-MNs was confirmed by FTIR analysis. Physico-chemical characterizations of the BSA-MNPs, such as surface morphology, surface charge and magnetic properties were investigated by Transmission Electron Microscopy (TEM), zeta-Potential and Vibrating Sample Magnetometer (VSM), etc. Magnetic inductive heating characteristics of the BSA-MNPs were analyzed by exposing the MNPs suspension (magnetic fluid) under alternative magnetic field (AMF). The results demonstrate that BSA was successfully conjugated with amino-coated MNs mediated through glutaraldehyde activation. The nanoparticles were spherical shaped with approximately 10 nm diameter. Possessing ideal magnetic inductive heating characteristics, which can generate very rapid and efficient heating while upon AMF exposure, BSA-MNPs can be applied as a novel candidature for magnetic nanothermotherapy for cancer treatment. In vitro cytotoxicity study on the human hepatocellular liver carcinoma cells (HepG-2) indicates that BSA-MNP is an efficient agent for cancer nanothermotherapy with satisfied biocompatibility, as rare cytotoxicity was observed in the absence of AMF. Moreover, our investigation provides a methodology for fabrication protein conjugated MNPs, for instance monoclonal antibody conjugated MNPs for targeting cancer nanothermotherapy.     

Synthesis and characterization of SiO2/(PMMA/Fe3O4) magnetic nanocomposites

Magnetic silica nanocomposites (magnetic nanoparticles core coated by silica shell) have the wide promising applications in the biomedical field and usually been prepared based on the famous St?ber process. However, the flocculation of Fe3O4 nanoparticles easily occurs during the silica coating, which limits the amount of magnetic silica particles produced in the St?ber process. In this paper, PMMA/Fe3O4 nanoparticles were used in the St?ber process instead of the "nude" Fe3O4 nanoparticles. And coating Fe3O4 with PMMA polymer beforehand can prevent magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of tetraethoxysilane (TEOS) by the steric hindrance. The results show that the critical concentration of magnetic nanoparticles can increase from 12 mg/L for "nude" Fe3O4 nanoparticles to 3 g/L for PMMA/Fe3O4 nanoparticles during the St?ber process. And before the deposition of silica shell, the surface of PMMA/FeO4 nanoparticles had to be further modified by hydrolyzing them in CH3OH/NH3 x H2O mixture solution, which provides the carboxyl groups on their surface to react further with the silanol groups of silicic acid.     

Fe3O4/Ni复合纳米颗粒的制备及其微波吸收特性

采用电爆炸技术,合成了粒径约为70nm 的Ni纳米颗粒,以3-巯基丙基三甲氧基硅烷偶联剂(MPTS)对Ni颗粒进行表面改性,利用共沉淀法对改性Ni颗粒进行包覆得到核-壳结构的复合纳米颗粒。将获得的复合纳米颗粒作为微波吸收剂, 并以不同比例分散到热固性酚醛树脂中,涂刷在200mm×200mm的金属板上,用RAM反射率远场RCS测量法研究了微波吸收特性。研究表明,核-壳结构Fe₃O₄/Ni复合颗粒作为微波吸收剂,在相同质量比条件下,其微波吸收性能明显优于纯Ni纳米颗粒或Fe₃O₄纳米颗粒的情况,并且在Fe₃O₄/Ni核-壳结构复合纳米颗粒中随着镍含量的提高,微波吸收增强,而随着Fe₃O₄含量的增加,微波吸收频段向高频段移动。     

A facile synthesis of Cu(2)O/SiO(2) and Cu/SiO(2) core-shell octahedral nanocomposites

We report here a simple approach to the synthesis of Cu(2)O/SiO(2) core-shell nanocomposites in water solution. The Cu(2)O cores have a perfect octahedral structure with uniform size of about 200-300?nm. A compact SiO(2) shell 9?nm in thickness is located at the surfaces of Cu(2)O octahedra, and it is composed of fine SiO(2) nanoparticles. During the depositing of the SiO(2) particles, as we presumed, dynamic absorbing and disengaging of Na(+) at the interface of Cu(2)O octahedra and the solution made it possible for the formation of Cu-O-Si bonds between core and shell in the composites. The existence of Cu-O-Si bonds in our core-shell composite can be substantiated by peak changes at?1236 and 1080?cm(-1) in the FT-IR spectra. This is the reason why the SiO(2) shell is so compact and uniform. Moreover, these Cu(2)O/SiO(2) core-shell octahedra were further used as precursors, depending on a simple disproportionation reaction of Cu(2)O in acid, to easily achieve Cu/SiO(2) movable multicore-shell octahedral nanocomposites. In the final Cu/SiO(2) core-shell composite, the thin SiO(2) octahedral shell was held, inside of which formed several free Cu nanoparticles 50-80?nm in size. Studies on the Cu(2)O/SiO(2) core-shell octahedral composites and Cu/SiO(2) movable multicore-shell octahedral nanocomposites would be a good thing not only for fundamental research but also for applications.     

Synthesis of size-controlled Fe3O4@SiO2 magnetic nanoparticles for nucleic acid analysis

We present a systematic study on the preparation, characteration and potential application of Fe3O4 and Fe3O4@SiO2 nanoparticles. Fe3O4 nanoparticles of controllable diameters were successfully synthesized by solvothermal system with tuning pH. The magnetic properties of nanoparticles were measured by vibration sample magnetometer. Fe3O4@ SiO2 nanoparticles were obtained via classic St?ber process. Streptavidin coated Fe3O4@SiO2 nanoparticles were prepared by covalent interaction. The quantity of streptavidin bound to nanoparticles was determined by UV-Vis spectrometer. To evaluate the binding efficiency and capacity of nucleic acid on nanoparticles, the capture of biotinylated oligonucleotide on streptavidin coated Fe3O4@SiO2 nanoparticles at different concentration was estimated by fluorescence detection. Both Fe3O4 and Fe3O4@SiO2 nanoparticles exhibited well crystallization and magnetic properties. The maximal amount of streptavidin immobilized onto the Fe3O4@SiO2 nanoparticles was 29.3 microg/mg. The saturation ratio of biotinylated oligonucleotides captured on streptavidin coated Fe3O4@SiO2 nanoparticles was 5 microM/mg within 20 minutes, indicating that FeO4@SiO2 nanoparticles immobilized by streptavidin were excellent carriers in nucleic acid analysis due to their convenient magnetic-separation property. Therefore, the synthesized Fe3O4 and Fe3O4@SiO2 nanoparticles with controllable size and high magnetic saturation have shown great application potentials in nucleic acid research.     

Enhancing cancer therapeutics using size-optimized magnetic fluid hyperthermia

Magnetic fluid hyperthermia (MFH) employs heat dissipation from magnetic nanoparticles to elicit a therapeutic outcome in tumor sites, which results in either cell death (>42?°C) or damage (<42 °C) depending on the localized rise in temperature. We investigated the therapeutic effect of MFH in immortalized T lymphocyte (Jurkat) cells using monodisperse magnetite (Fe(3)O(4)) nanoparticles (MNPs) synthesized in organic solvents and subsequently transferred to aqueous phase using a biocompatible amphiphilic polymer. Monodisperse MNPs, ～16 nm diameter, show maximum heating efficiency, or specific loss power (watts/g Fe(3)O(4)) in a 373 kHz alternating magnetic field. Our in vitro results, for 15 min of heating, show that only 40% of cells survive for a relatively low dose (490 μg Fe/ml) of these size-optimized MNPs, compared to 80% and 90% survival fraction for 12 and 13 nm MNPs at 600 μg Fe/ml. The significant decrease in cell viability due to MNP-induced hyperthermia from only size-optimized nanoparticles demonstrates the central idea of tailoring size for a specific frequency in order to intrinsically improve the therapeutic potency of MFH by optimizing both dose and time of application.     

Non-aqueous synthesis of water-dispersible Fe3O4-Ca3(PO4)2 core-shell nanoparticles

The Fe(3)O(4)-Ca(3)(PO(4))(2) core-shell nanoparticles were prepared by one-pot non-aqueous nanoemulsion with the assistance of a biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO), integrating the magnetic properties of Fe(3)O(4) and the bioactive functions of Ca(3)(PO(4))(2) into single entities. The Fe(3)O(4) nanoparticles were pre-formed first by thermal reduction of Fe(acac)(3) and then the Ca(3)(PO(4))(2) layer was coated by simultaneous deposition of Ca(2+) and PO(4)(3-). The characterization shows that the combination of the two materials into a core-shell nanostructure retains the magnetic properties and the Ca(3)(PO(4))(2) shell forms an hcp phase (a = 7.490 ?, c = 9.534 ?) on the Fe(3)O(4) surface. The magnetic hysteresis curves of the nanoparticles were further elucidated by the Langevin equation, giving an estimation of the effective magnetic dimension of the nanoparticles and reflecting the enhanced susceptibility response as a result of the surface covering. Fourier transform infrared (FTIR) analysis provides the characteristic vibrations of Ca(3)(PO(4))(2) and the presence of the polymer surfactant on the nanoparticle surface. Moreover, the nanoparticles could be directly transferred to water and the aqueous dispersion-collection process of the nanoparticles was demonstrated for application readiness of such core-shell nanostructures in an aqueous medium. Thus, the construction of Fe(3)O(4) and Ca(3)(PO(4))(2) in the core-shell nanostructure has conspicuously led to enhanced performance and multi-functionalities, offering various possible applications of the nanoparticles.     

磁性纳米钌催化剂的制备及对聚苯乙烯催化加氢的催化性能

通过化学共沉淀法制备了Fe3O4,利用硅酸钠水解、缩合制备了具有核壳结构SiO2/Fe3O4复合纳米粒子。利用红外光谱(FT-IR)、扫描电镜(SEM)、X射线衍射(XRD)以及振动样品磁强计(VSM)技术对其进行了表征。将所得的磁性纳米SiO2/Fe3O4用有机硅改性的聚乙烯吡咯烷酮进行表面修饰,利用原位还原RuCl3的方法将金属Ru负载到磁性载体上,制备了磁性纳米催化剂Ru/PVP/SiO2/Fe3O4。探讨了所得催化剂对聚苯乙烯氢化反应的催化性能,考察了反应压力、温度、时间以及溶剂等对催化性能的影响。结果表明,随着反应温度的升高、压力的增加,催化活性提高;当反应温度为393K、氢气压力为8 MPa、反应时间为5 h时,聚苯乙烯氢化度可以达到90%以上。     

Preparation and photocatalytic properties of nanometer-sized magnetic TiO2/SiO2/CoFe2O4 composites

Magnetic TiO2/SiO2/CoFe2O4 nanoparticles (TiO2/SCFs) were prepared by a sol-gel process in a reverse microemulsion combined with solvent-thermal technique. TiO2/SCFs were characterized by Fourier transform infrared spectrometry, thermogravimetric analysis-differential scanning calorimetry, X-ray diffraction, Raman spectrometry, TEM, BET specific surface area measurement, and magnetic analysis. Structure analyses indicated that TiO2/SCFs presented a core-shell structure with TiO2 uniformly coating on SiO2/CoFe2O4 nanomagnets (SCFs) and typical ferromagnetic hysteresis. TiO2/SCFs showed larger specific surface area and better photocatalytic activities than TiO2 and TiO2/CoFe2O4 photocatalysts prepared by the same method. The doping interaction between TiO2 and CoFe2O4 reduced thanks to the inert SiO2 mesosphere.     

Controlled synthesis of core-shell iron-silica nanoparticles and their magneto-dielectric properties in polymer composites

Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO(2)) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO(2) nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (ε) and magnetic permeability (μ) of the polymer composite increased with increasing amount of Fe@SiO(2) nanoparticle doping. The dielectric loss (tanδ) was near 0.020 at a frequency of 1 GHz.     

Magnetic Fe3O4@chitosan nanoparticle: synthesis, characterization and application as catalyst carrier

A novel method was developed to prepare Fe3O4@CS beads with core-shell structure using a double-crosslinking process. Before the coating process, an unique crosslinking agent, glutaraldehyde (GA), was adsorbed onto the surface of Fe3O4 in advance, so the subsequent CS can uniformly coat around the magnetic core processed from the strong interaction between GA and CS, forming a perfect core-shell structure. The obtained Fe3O4@CS beads were followed by the Pd deposition through in-situ reduction method, and the prepared composite catalyst was applied exemplarily in synthesizing nabumetone to check its reusing property. The nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and the magnetic hysteresis loop determination method. This novel composite catalyst showed admirable potential in reusable catalysis.     

磁性分子筛催化剂的制备及其性能

以改性Fe3O4颗粒为核,采用溶胶-凝胶法在Fe3O4核表面包覆SiO2壳层,并在SiO2孔道内负载纳米TiO2颗粒,得到易于固-液分离、平均直径为90~150 nm的具有核壳结构的Fe3O4-TiO2-MCM-41光催化剂复合颗粒,采用透射电镜、X射线衍射、X射线光电子能谱等手段对样品进行表征,并对该催化剂的光催化性能进行测试。结果表明:所制备的磁性分子筛催化剂在紫外光下对苯酚的降解率达94.12%,对重金属离子Cr6+的吸附能达到95.05%。     

Fe3O4磁性纳米颗粒的合成与接枝聚合修饰（英文）

以氨水作为沉淀剂并控制溶液的pH值,采用Fe3+和Fe2+共沉淀法制得了磁性四氧化三铁纳米颗粒。合成的磁性纳米颗粒通过高分辨透射电镜、X射线衍射仪、傅里叶变换红外光谱仪进行了表征。四氧化三铁纳米颗粒的粒径约为10nm,其表面含有丰富的羟基。为了增强磁性四氧化三铁纳米颗粒和聚合物基质之间的相互作用,在纳米颗粒的表面接枝上乙烯基单体。傅里叶变换红外光谱仪和热重分析仪的测试结果显示,聚合物链共价结合在纳米颗粒表面。表面接枝聚合后,四氧化三铁纳米颗粒由极性转变为非极性。     

磁性核壳Fe3O4/P(GMA-DVB)-SH-Au复合催化剂的制备及催化性能

首先通过水热法合成了单分散空心Fe3O4磁球,之后利用蒸馏沉淀聚合将P(GMA-DVB)聚合物层包覆在Fe3O4磁球表面形成Fe3O4/P(GMA-DVB)核壳结构,巯基化处理后吸附Au纳米粒子,得到磁性核壳Fe3O4/P(GMA-DVB)-SH-Au复合催化剂。利用TEM,SEM,FTIR,XRD,TGA,VSM及UV-vis对其进行表征,并考察该催化剂在催化还原4-硝基苯酚反应中的催化性能。结果表明合成的材料粒径均匀,球形度规整,核壳结构明显,在催化反应中,Fe3O4/P(GMA-DVB)-SH-Au表现出优异的催化性能,而且经过连续8次循环使用后,催化效率仍可保持80%以上。     

One-step solvothermal synthesis of Fe3O4@C core-shell nanoparticles with tunable sizes

We report the synthesis of Fe3O4@C core-shell nanoparticles (FCNPs) by using a facile one-step solvothermal method. The FCNPs consisted of Fe3O4 particles as the cores and amorphous uniform carbon shells. The content of Fe3O4 is up to 81.6 wt%. These core-shell nanoparticles are aggregated by primary nanocrystals with a size of 10-12 nm. The FCNPs possess a hollow interior, high magnetization, excellent absorption properties and abundant surface hydroxyl groups. A possible growth mechanism of the FCNPs is proposed. The role of glucose in regulating the grain size and morphology of the particles is discussed. The absorption properties of the FCNPs towards Cr(VI) in aqueous solution is investigated. We demonstrate that the FCNPs can effectively remove more than 90 wt% of Cr(VI) from aqueous solution.