Size-controlled synthesis of Fe3O4 and Fe3O4@SiO2 nanoparticles and their superparamagnetic properties tailoring

Superparamagnetic properties and fine-tuning of colloidal Fe₃O₄nanoparticles are important for their widespread biomedical applications. Herein, colloidal Fe₃O₄nanoparticles(NPs) of different sizes(8–20 nm) were prepared,and their hydrophilization with SiO₂shell coating to be Fe₃O₄@SiO₂core-shell had been realized successively.The size of Fe₃O₄NPs was controlled by different heating rate...     

In vitro biological effects of magnetic nanoparticles

Magnetic nanoparticles (MNPs) have great potential for a wide use in various biomedical applications due to their unusual properties. It is critical for many applications that the biological effects of nanoparticles are studied in depth. To date, many disparate results can be found in the literature regarding nanoparticle-biological factors interactions. This review highlights recent developments in this field with particular focuses on in vitro MNPs-cell interactions. The effect of MNPs properties on cellular uptake and cytotoxicity evaluation of MNPs were discussed. Some employed methods are also included. Moreover, nanoparticle-cell interactions are mediated by the presence of proteins absorbed from biological fluids on the nanoparticle. Many questions remain on the effect of nanoparticle surface (in addition to nanoparticle size) on protein adsorption. We review papers related to this point too.     

Preparation and upconversion luminescence cell imaging of O-carboxymethyl chitosan-functionalized NaYF4:Yb3+/Tm3+/Er3+ nanoparticles

Upconversion luminescence nanoparticles (UCNPs) have shown promising applications in biomedical fields as luminescent probes because of their excellent advantages such as single excitation with multicolor emission, low autofluorescence, and deep penetration. But the biological applications of such nanomaterials are still restricted due to the unfavorable surface properties. In this work, we develop a facile one-pot hydrothermal route to obtain O-carboxymethyl chitosan (OCMC)-wrapped NaYF₄: Yb³⁺/Tm³⁺ /Er³⁺ red UCNPs which have been used for targeted cell luminescence imaging directly and efficiently. The successful coating of the UCNPs by OCMC has been confirmed by Fourier-transform infrared (FTIR) spectroscopy and dynamic light scattering (DLS) studies. Transmission electron microscopy (TEM), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and photoluminescence (PL) spectra have been used to characterize the size, composition and emission color of the samples, respectively. Due to the good biocompatibility, water-solubility, and strong UC luminescence, these hydrophilic nanocrystals will open up new avenues in further bioapplications.     

Enhancement of the efficiency of PEI/liposome transfection by magnetofectins formed via electrostatic self-assembly

One of the major challenges for successful gene therapy is improving the transfection efficiency of non-viral vectors. Magnetic nanoparticles (MNPs) have been developed as enhancers of non-viral vehicles. We prepared MNPs and modified them with polyethyleneimine (PEI), citric acid (CA) or carboxylmethyl-dextran (CMD). Both positively charged MNPs (MNPs@PEI) and negatively charged MNPs (MNPs@CA, MNPs@CMD) could spontaneously form transfection complexes (magnetofectins) with plasmid DNA and PEI/liposome via electrostatic self-assembly. Our results showed as-prepared magnetofectins apparently enhanced PEI/liposome transfection efficiency and/or gene expression level into COS-7 cells with reduced transfection time from 4 h to 15 min under a magnetic field in vitro. Meanwhile, the effect of magnetofection was cell line-dependant. These results suggest that charged MNPs could improve transfection efficiency for non-viral vectors by simply mixing with them and by exerting a magnetic force. Thus such MNPs provide a convenient platform for further applications of gene delivery.     

Embedding Co3O4 nanoparticles into graphene nanoscrolls as anode for lithium ion batteries with superior capacity and outstanding cycling stability

Co_3O_4 is a promising high-performance anode for lithium ion batteries(LIBs), but suffers from unsatisfied cyclability originating duo to low electrical conductivity and large volume expansion during charge and discharge process. Herein, we successfully constructed the Co_3O_4 nanoparticles embedded into graphene nanoscrolls(GNSs) as advanced anode for high-performance LIBs with large capacity and exceptional cyclability. The onedimensional(1 D) Co_3O_4/GNSs were synthesized via liquid nitrogen cold quenching of large-size graphene oxide nanosheets and sodium citrate(SC) modified Co_3O_4 nanoparticles, followed by freeze drying and annealing at400 °C for 2 h in nitrogen atmosphere. Benefiting from the interconnected porous network constructed by 1 D Co_3O_4/GNSs for fast electron transfer and rapid ion diffusion, and wrinkled graphene shell for significantly alleviating the huge volume expansion of Co_3O_4 during lithiation and delithiation. The resultant Co_3O_4/GNSs exhibited ultrahigh reversible capacity of 1200 mAh g~(-1) at 0.1 C, outperforming most reported Co_3O_4 anodes.Moreover, they showed high rate capability of 600 m Ah g-1 at 5 C, and outstanding cycling stability with a high capacity retention of 90% after 500 cycles. Therefore, this developed strategy could be extended as an universal and scalable approach for intergrating various metal oxide materials into GNSs for energy storage and conversion applications.     

水溶性磁性Fe_3O_4纳米粒子对小麦生长影响的研究

水溶性磁性Fe_3O_4纳米颗粒由于其良好的生物相容性、超顺磁性等特征,在生物领域常被用来作为磁性载体材料,其广泛的生产和应用增加了它们在环境中释放的可能性,需对其环境生物安全性进行评价.首先合成了水溶性磁性Fe_3O_4纳米纳米粒子,并用透射电子显微镜和马尔文粒度分析仪对其进行形貌分析和表征.然后在不同的浓度下(0、0.72、1.44、3.6 mg/mL)研究了水溶性磁性Fe_3O_4纳米粒子对小麦生长的影响,结果显示随着浓度的增加,磁性Fe_3O_4纳米纳米粒子对小麦生长的抑制越明显,造成生长抑制和根结构损伤.结果证明了水溶性磁性Fe_3O_4纳米颗粒对小麦植物存在一定的生物毒性,其环境排放应该严格限制.     

Synthesis of γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript>/Au magnetic composites for immobilization of bovine serum albumin

A method for the two-step synthesis of magnetic composites with a γ-Fe₂O₃ core, silica inner layer and numerous gold nanoparticles supported on the surface of the silica (γ-Fe₂O₃/SiO₂/Au) is described. First, thiol-functionalized γ-Fe₂O₃/SiO₂ composites and gold colloids are prepared by modifying γ-Fe₂O₃/SiO₂ composites with mercaptosilane and reduction of Au³⁺ to Au⁰ with citrate, respectively. Gold nanoparticles are then assembled on the surface of the thiol-functionalized γ-Fe₂O₃/SiO₂ composites to form γFe₂O₃/SiO₂/Au composites. The structure of the composite particles is confirmed by transmission electronic microscopy and powder X-ray diffraction. Immobilization studies with bovine serum albumin (BSA) demonstrate that the γ-Fe₂O₃/SiO₂/Au composites can be used to immobilize BSA, making them useful for biomedical and biological applications.     

In vitro bioactivity and cytocompatibility of porous scaffolds of bioactive borosilicate glasses

The bioactive borosilicate scaffolds （R2O-RO-B2O3-SiO2-P2O5） with four different contents of borate were fabricated by replication technique. The bioactivity, degradability and the cytotoxicity of the scaffolds were studied in this paper. The porosity of the scaffolds was found to be 73%-80%, and the pore size was in the range of 200-300 μm. The porous scaffolds immersed in 0.02 mol.L^-1 K2HPO4 solution were transformed into hydroxyapatite. And it is notable that the D-AIk-2B, D-AIk-3B-scaffolds were covered by hydroxyapatite layers after 7 h-immersion, which proved their high bioactivity. In the cell adhesion test, cells could be seen growing well on the scaffolds, showing stretched morphology and obvious pseudopodia, and only the high cumulative concentration of B ions released from the D-AIk-3B-scaffold samples had an inhibition effect on cell proliferation. But the inhibition effect could be alleviated by diluting the extract solution to a certain concentration （dilution ratio： 1：8）. Therefore, after suitable pretreatment, the porous borosilicate bioactive glass scaffold can be a desirable candidate for bone tissue engineering.     

A bulk metal/ceramic composite material with a cellular structure

Metal/ceramic composite materials can be divided into two groups: one is ceramic reinforced metal matrix composite, and the other is metal toughened ceramic matrix composite. The research on these materials mainly focuses on the mechanical properties due …     

Tailoring impedance match and enhancing microwave absorption of Fe3O4/ Bi24Fe2O39/Bi hollow porous microrods by controlling their composition

A self-assembly/precipitate conversion/decomposition process was developed for the controllable synthesis of Fe_3O_4/Bi_(24)Fe_2O_(39)/Bi hollow porous microrods(HPMRs).The results demonstrated that the crystal size,component,and performances of HPMRs could be effectively modulated via changing Fe~(2+)/Bi~(3+)molar ratio(γ).Fe_3O_4/Bi_(24)Fe_2O_(39)/Bi HPMRs exhibited ferromagnetic behavior at room temperature.As Bi and Bi_(24)Fe_2O_(39)contents increased withγ,the saturation magnetization M_sand attenuation constantly decreased,whereas coercivity H_cand impedance matching ratio increased.Compounding Fe_3O_4with small quantities of Bi and Bi_(24)Fe_2O_(39)into HPMRs can significantly enhance microwave absorption.Fe_3O_4/Bi_(24)Fe_2O_(39)/Bi HPMRs formed atγ=1:0.25 exhibited the optimum microwave absorption performance.The minimum R_Lwas-47.3 dB at8.72 GHz,corresponding to 2.4 mm sample thickness.The absorption band with the reflection loss below-20 dB was up to 14.0 GHz for the absorber with a thickness of 1.4-8.0 mm.The results demonstrate that the introduction of electromagnetic transparent materials(Bi_(24)Fe_2O_(39)or Bi)can improve the microwave absorption performances of Fe_3O_4 composites owing to enhanced impedance matching rather than attenuation constant.     

二维Ta4C3O2电子结构的拓扑性质

过渡金属碳化物和氮化物也被称为MXenes材料,是一类具有独特性质的新型二维材料.经第一性原理计算发现,二维Ta₄C₃O₂的电子结构可能具有拓扑性质,而Ta₄C₃已被成功制备,Ta₄C₃O₂可通过表面功能化实现制备.这些结果将为研究MXenes材料的拓扑性质提供有利借鉴,也为今后的实际应用奠定基础.     

Lithium-ion full cell with high energy density using nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode and SiO-C composite anode

A high-energy-density Li-ion battery with excellent rate capability and long cycle life was fabricated with a Ni-rich layered LiNi_0.8Mn_0.1Co_0.1O₂ cathode and SiO-C composite anode. The LiNi_0.8Mn_0.1Co_0.1O₂ and SiO-C exhibited excellent electrochemical performance in both half and full cells. Specifically, when integrated into a full cell configuration, a high energy density (280 Wh·kg-1) with excellent rate capability and long cycle life was attained. At 0.5C, the full cell retained 80% of its initial capacity after 200 charge/discharge cycles, and 60% after 600 cycles, indicating robust structural tolerance for the repeated insertion/extraction of Li+ ions. The rate performance showed that, at high rate of 1C and 2C, 96.8% and 93% of the initial capacity were retained, respectively. The results demonstrate strong potential for the development of high energy density Li-ion batteries for practical applications.     

Comparative study of different membranes as separators for rechargeable lithium-ion batteries

Membranes of polypropylene (PP), PP coated with nano-Al₂O₃, PP electrospun with polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), and trilayer laminates of polypropylene-polyethylene-polypropylene (PP/PE/PP) were comparatively studied. Their physical properties were characterized by means of thermal shrinkage test, liquid electrolyte uptake, and field emission scanning electron microscopy (FESEM). Results show that, for the different membranes as PP, PP coated with nano-Al₂O₃, PP electrospun with PVdF-HFP, and PP/PE/PP, the thermal shrinkages are 14%, 6%, 12.6%, and 13.3%, while the liquid electrolyte uptakes are 110%, 150%, 217%, and 129%, respectively. In addition, the effects on the performance of lithium-ion batteries (LiFePO₄ and LiNi_1/3Co_1/3Mn_1/3O₂ as the cathode material) were investigated by AC impedance and galvanostatic charge/discharge test. It is found that PP coated with Al₂O₃ and PP electrospun with PVdF-HFP can effectively increase the wettability between the cathode material and liquid electrolyte, and therefore reduce the charge transfer resistance, which improves the capacity retention and battery performance.     

Uptake kinetics of 3-buten-1-ol, 4-penten-1-ol and 3-methyl-3-buten-1-ol into sulfuric acid solutions

Unsaturated alcohols are important components in complex mixtures of oxygenated volatile organic compounds, and play a significant role in atmospheric chemistry. The uptake kinetics of 3-buten-1-ol (BO31), 4-penten-1-ol (PO41) and 3-methyl-3-buten-1-ol (MBO331) into 20 wt%-80 wt% H₂SO₄ solutions were studied, using a rotated wetted-wall reactor coupled to a differentially pumped single-photon ionization time of flight mass spectrometer (SPI-TOFMS). With increasing acidity, the uptake processes changed from reversible to irreversible (reactive). Reactive uptake was observed in 60 wt%-80 wt%, 50 wt%-80 wt% and 30 wt%-80 wt% H₂SO₄ solutions for BO31, PO41 and MBO331, respectively. Reactive uptake coefficients were acquired and are reported here for the first time. Reactivity order followed the trend: BO31<PO41<MBO331. An electrophilic addition mechanism of H₂SO₄ to the C=C double bond was used to explain this trend. Atmospheric implications were discussed, based on the reactive uptake coefficients. This heterogeneous reaction with sulfuric acid aerosols may be a potential degradation pathway of unsaturated alcohols, and should not be neglected.     

Formation and biocorrosion behavior of Zr-Al-Co-Nb bulk metallic glasses

Ni-and Cu-free Zr-Al-Co-Nb glassy alloys with different Nb and Co contents were synthesized by melt spinning and copper mold casting.The effects of Nb addition to partially replace Co in the Zr55Al20Co25 glassy alloy on the glass-forming ability,thermal properties,in-vitro biocorrosion behavior and surface wettability of the metallic glasses were investigated.Although addition of Nb up to 5 at.% slightly decreased the supercooled liquid region and the glass-forming ability(GFA),the alloys could be casted in a bulk glassy rod form with diameters up to 3mm.The Zr-Al-Co-Nb glassy alloys were spontaneously passivated with low passive current densities in phosphate buffered saline and Hanks’ solution.Substitution of "toxic" Co by Nb is effective in improved the corrosion resistance of the Zr-Al-Co glassy alloy.Water contact angle measurements showed that Nb addition increased the hydrophilicity of the glassy alloys,which may enhance cell adhesion of the alloys in biomedical applications.     

Mesoporous fibrous silicon nitride by catalytic nitridation of silicon

The catalytic effect of metal oxide/alumina whiskers(CeO_2, Mn_3O_4, NiO, Co_3O_4, Fe_2O_3, Cr_2O_3/AW) was evaluated on their ability to drive the nitridation of silicon and to generate mesoporous fibrous silicon networks.Silicon powder with different particles size along with the catalyst was nitridized at 1300 °C for 5 h in nitrogen and nitrogen diluted with 10 vol% ammonia atmospheres. Nitridation degree of silicon up to 99% was recorded using 1.5 wt% CeO_2 and Fe_2O_3 catalysts in nitrogen-ammonia atmosphere. The catalyzed samples contain submicronic silicon nitride fibres with a diameter of 400–500 nm and a length of up to few micrometers. The compressive strength of 46 ± 1 MPa was measured for silicon samples catalyzed with nickel oxide/alumina whiskers and nitridized in N_2/10 vol%NH_3 atmosphere. Porous silicon nitride networks were produced with 45–52% porosity, pore sizes in the range of 370–1200 nm and median pore in the range of 495–1655 nm.     

A novel non-enzymatic hydrogen peroxide sensor based on Co:ZnO modified electrodes

There is currently intense interest in the use of nanoparticles for a wide range of biomedical and technological applications. In this paper, the hierarchical Co doped ZnO nanoflowers were synthesized by a facile wet chemical method and explored as biosensing material. The as-modified novel hydrogen peroxide sensor exhibited a wide linear range(0.25–20 mM), highly reproducible response(R.S.D. of 2.7%) and long-term stability. The doping Co~(2+)ions carried out the oxidations rapidly and efficiently for the catalysis of hydrogen peroxide(H_2O_2). A high activity toward H_2O_2 in the presence of ascorbic acid(AA) and NaNO_2, which are only common for natural enzymes, has also been demonstrated. The good analytical performance, low cost and straightforward preparation method makes this doped semiconductor promising for a wide range of potential applications in medicine, biotechnology and environmental chemistry.     

Filter Paper-Derived Three-Dimensional Carbon Fibers Film Supported Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a Superior Binder-Free Anode Material for High Performance Lithium-Ion Batteries

Highly uniform and tight adhering of Fe₃O₄ particles on carbon fiber film (Fe₃O₄/CFF) is achieved through a simple in-situ thermal oxidation method. Particularly, 3D CFF with interconnected structure can shorten transfer path and buffer the volume expansion during charge-discharge cycling. Herein, the obtained Fe₃O₄/CFF anode exhibits a stable cycling performance and excellent high rate capability. The cell delivers a reversible capacity of 1 711 mAh·g^–1 at a current density of 100 mA·g^–1 after 100 cycles. Even at a high rate density of 2 A·g^–1, the specific capacity also can maintain 1 034 mAh·g^–1 after 100 cycles. The simplified fabrication is featured with low-cost and this binder-free perspective holds great potential in mass-production of high-performance metal oxide electrochemical devices.     

Preparation and magnetic properties of CoFe2O4/TiO2 composite films

Using （Ti（OC4H9）4） and metal chlorates as starting materials, CoFe2O4/TiO2 composite films were prepared by sol-gel method. The effects of heat treatment temperature and pH of the precursor on microstructure and magnetic properties were studied. The phase structure of the samples was examined by X-ray diffraction. The microstructure was examined by scanning electron microscope, atomic force microscope and polarized microscope. The magnetic property was measured by vibrating sample magnetometer. The results show that the crystals of different phases grow up independently. CoFe2O4 is uniformly embedded into the TiO2 matrix in the prepared composite films, and the growth of composite films is dependent on the heat treatment temperatures and PH of the precursor. The average size of CoFe2O4 crystal is 19 nm in Nanocomposite film prepared when the heat treatment temperature is 800℃ and the pH of the precursor is between 2 and 3. The magnetism of the composite films is enhanced as the heat treatment temperature increases.