As-synthesized Fe3O4 Research Articles

Citrus sinensis assisted biogenic synthesis and physicochemical properties of Fe3O4 nanoparticles for antibacterial activity

The biogenic synthesis of Fe3O4 nanoparticles was boosted by the use of a recently found organic acid produced from Citrus sinensis. Fe3O4 nanoparticles were synthesized at 350 °C and 450 °C, and their physical and chemical properties were studied using a number of different characterisation techniques. Crystalline structure and phase were determined by X-ray diffraction (XRD) analysis of as-synthesized and annealed Fe3O4 nanoparticles. This finding demonstrates that the Fe3O4 nanoparticles have a unique, cubic spinel structure with only one phase. With the use of well-established formulae, we were able to calculate the crystallite size and lattice parameter of the synthesized Fe3O4 nanoparticles, and found that their size increased as a function of the annealing temperature, from 11 nm to 34 nm. The FTIR method was used to analyse the as-synthesized and annealed Fe3O4 nanoparticles for functional groups, molecular structure, and chemical bonding. Metallic components at 465, 551 and 1628 cm−1 were found after analysing the three samples. Field Emission Scanning Electron Microscopy (FESEM) was used to analyse the surface morphology and grain size fluctuations of Fe3O4 nanoparticles, while Energy Dispersive X-ray Spectroscopy (EDX) was used to study the elemental composition. Fe3O4 nanoparticles' thermal characteristics change depending on the annealing temperature. The antibacterial efficacy of Fe3O4 nanoparticles, manufactured using green methods, was assessed against two different types of bacteria: Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative).

Performance of a rotating packed bed with blade packings in synthesizing nano-sized Fe3O4 particles

Nano-sized Fe3O4 particles were continuously synthesized in the rotating packed bed with blade packings where the rotational speed was set at 1800 rpm, the liquid flow rate of aqueous FeCl2/FeCl3 was kept at 0.5 L/min, and the liquid flow rate of aqueous NaOH was maintained at 0.5 L/min with the chemical co-precipitation route that the synthesis temperature was fixed at 25 °C, the FeCl2 concentration was fixed at 0.15 mol/L, the FeCl3 concentration was fixed at 0.3 mol/L, and the NaOH concentration was fixed at 1.2 mol/L. The average crystallite size and mean particle size of the as-synthesized nano-sized Fe3O4 particles were 12.7 nm and 10.9 nm, respectively. The rate of continuous synthesis of nano-sized Fe3O4 particles was 23.6 kg/day. The as-synthesized nano-sized Fe3O4 particles exhibited a superparamagnetic characteristic at 25 °C. Furthermore, the saturation magnetization of the as-synthesized nano-sized Fe3O4 particles was 66.4 emu/g. The as-synthesized nano-sized Fe3O4 particles had the Type-IV isotherm for N2 adsorption-desorption with a BET specific surface area of 109.4 m2/g. The maximum Orange G adsorption capacity of the as-synthesized nano-sized Fe3O4 particles at 25 °C and pH 3 was 55.0 mg/g. This maximum Orange G adsorption capacity was much higher than that (5.7 mg/g) of the commercial nano-sized Fe3O4 particles that were purchased from Sigma-Aldrich (SA-Fe3O4) because the as-synthesized nano-sized Fe3O4 particles had a smaller mean particle size than SA-Fe3O4. Accordingly, the as-synthesized nano-sized Fe3O4 particles are a promising magnetic adsorbent in the removal of Orange G from water.

Sustainable production of bio-propionic acid: Facet-mediated C-O bond cleavage of Fe3O4 nano-crystallites

The disclosure of structure-dependent activity is always of great significance to rationalize the design of catalyst for achieving an excellent catalytic performance. Three clearly shaped and structured α-Fe2O3 crystallites (nano-truncated hexagonal bipyramids (THB), nano-cubes (QC) and nano-spheres (RC)) were used as precursors to successfully synthesize their counterparts of three Fe3O4 nano-crystallites, marked as THB-R, QC-R and RC-R, respectively, which remained consistent in shape. HRTEM images reveal that the three as-synthesized Fe3O4 nano-crystallites expose different facets, in which (311) plane is exclusively exposed in RC-R, and the mixed planes of (111) and (222) are exposed in THB-R and QC-R. DFT calculations reveal that the Fe site located at the exposed (311) plane is more preferential to selectively adsorb α‑hydroxyl group (α-C-OH) in lactic acid (LA) molecule than the other two exposed planes of (111) and (222) on basis of adsorption energy of LA molecule, leading to a high activity on CO cleavage. The thermoanalysis of sample further indicates that the Fe site in RC-R is covered with less organic polymer or coke, than QC-R and THB-R, endowing an excellent activity and stability during the catalytic reaction. At 380 °C and LA LHSV of 16 h−1 under the inert atmosphere, the catalyst offered a satisfactory propionic acid selectivity of nearly 70%, and its catalytic performance hardly decayed within 34 h on stream.

Green biosynthesis of Fe3O4 nanoparticles using Chlorella vulgaris extract for enhancing degradation of 2,4 dinitrophenol

ObjectivesThis study aimed to provide the excellent role of Chlorella vulgaris extract as a green, reducing agent for improving and enhancing the effectiveness and performance of as-prepared NPs, which is higher than bare Fe3O4. MethodsThe extract of the algal cell of Chlorella vulgaris is used as a green, reducing agent was used to prepare green Fe3O4 NPs to improve and enhance the degradation effectiveness of 2,4 dinitrophenol (2,4 DNP) in their aqueous solution using UV irradiation. The as-synthesized bare Fe3O4 and green Fe3O4 NPs were characterized using UV–VIS spectroscopy, TEM, SEM, EDX, XRD, and FT-IR spectroscopy to determine bandgap energy, particle size, structural morphology, crystallite nature, phase structure, elemental compositions, and existed functional group. ResultsSEM and TEM images indicated that the as-synthesized NPs have a regular spherical shape with a mean size ranging between 13.68 and 31.71 nm. The energy bandgap (Eg) indicated the green Fe3O4 NPs have low values (2.73 and 2.3 eV) than bare Fe3O4 (2.89 eV). The maximum degradation of 2,4 DNP was achieved at pH = 8, 90 min contact time, 0.35 g/L catalyst dose, and 100 mg/L 2,4 DNP concentration. ConclusionThe degradation results proved that green Fe3O4 NPs have more effectiveness than bare Fe3O4 NPs.

Synthesis of Superparamagnetic Fe3O4 Nano-Adsorbent Using an Energy-Saving and Pollution-Reducing Strategy for the Removal of Xylenol Orange Dye in Water

The superparamagnetic Fe3O4 nanoparticles as an absorbent with a size distribution of 4.8–6.4 nm were synthesized using a simple one-pot hydrothermal strategy at 200 °C for 24 h, where iron citrate and distilled were the sum total of raw materials. The as-synthesized Fe3O4 powders showed rapid and efficient adsorption for xylenol orange with a saturated adsorption amount of 42.5 mg/g according to Langmuir linear fitting, and the adsorption reaction between xylenol orange adsorbate and Fe3O4 adsorbent was mostly completed within 10 min. The Fe3O4 nanoparticles not only had superparamagnetism with a saturation magnetization value of 54.9 emu/g at 15 kOe but also possessed strong magnetic response, making them easy to separate easily from aqoeous solution under the attraction of magnet. In this work, the Fe3O4 particles can be totally attracted toward the magnet within 15 s, leaving the suspension a clear solution.

Construction of Fe3O4@β-CD/g-C3N4 nanocomposite catalyst for degradation of PCBs in wastewater through photodegradation and heterogeneous Fenton oxidation

Herein, a multifunctional magnetic β-cyclodextrin/graphitic carbon nitride catalyst (Fe3O4@β-CD/g-C3N4) was fabricated for PCBs degradation in wastewater. The catalysts were investigated using various characterization methods including X-ray diffractometry, field emission scanning electron microscopy, vibrating sample magnetometry and UV–Vis diffuse reflectance spectroscopy et al. As-synthesized Fe3O4@β-CD/g-C3N4 displayed the superior catalytic activity, and the degradation efficiency of six PCBs was 77%–98% at 55 min, with pseudo-first order reaction rate constants were in the range of 0.027–0.065 min−1. The super synergy of photodegradation and heterogeneous Fenton oxidation was 2.1–4.6 times more efficient than that photodegradation or heterogeneous Fenton oxidation alone. Fe3O4@β-CD/g-C3N4 could be reused for at least 6 cycles without significant deterioration to its catalytic activity. Several reaction intermediates were identified using GC-MS/MS. The products of the last stage of the reaction were alkanes, aldehyde, ketone and ester, which were formed via ring opening, dechlorinating and isomerization reactions. For PCBs degradation, •OH played a major role, •O2− played a secondary role, 1O2, h± and e− played minor roles based on reactive species trapping experiments. The catalytic performance of the Fe3O4@β-CD/g-C3N4 − H2O2 − visible light system towards degradation of PCBs in river water and municipal wastewater was 89–100% and 69–92%, respectively, which means the Fe3O4@β-CD/g-C3N4 has great potential for environmental remediation.

Rheological performances and enhanced sedimentation stability of mesoporous Fe3O4 nanospheres in magnetorheological fluid

In this study, hierarchically structured mesoporous Fe3O4 nanospheres were synthesized using a solvothermal method and the application of the obtained Fe3O4 nanospheres in magnetorheological (MR) fluid was investigated in detail. The morphology, microstructure and magnetic properties of the as-synthesized Fe3O4 nanospheres were examined through different characterization techniques, such as SEM, TEM, XRD, XPS, BET and SQUID. The results of rheological measurements revealed that the prepared homogeneous MR fluid based on mesoporous Fe3O4 nanospheres showed typical MR performances, exhibiting a rapid and reversible transition from a liquid-like to a solid-like state under the action of an external magnetic field. More importantly, it should be noted that the Fe3O4 nanospheres-based MR fluid demonstrated enhanced a sedimentation stability as compared to that of carbonyl iron (CI) particles-based MR fluid. This finding was probably assigned to the particular mesoporous structure and the decreased density mismatch between two components of MR fluid.

Investigation of Physicochemical and Cytotoxic Potential of Ocimum basilicum Leaf Extract Mediated Magnetite Nanoparticles: In Vitro

In this report, an environment friendly and cost effective green synthesis method of magnetite nanoparticles (Fe3O4 NPs) was introduced. Fe3O4 NPs were successfully synthesized by green route using Ocimum basilicum leaf extract. The structural investigation of Fe3O4 NPs using X-Ray diffraction technique revealed the cubic crystallinity with Fd3m space group, which was confirmed with an aid of Rietveld refinement. No secondary phases (such as Fe2O3 and FeO) were observed, which confirmed the high purity of synthesized Fe3O4 NPs. The characteristics peak at 3320 cm−1 displayed the phenolic constituents of Ocimum basilicum leaf extract and peak at 665 cm−1 illustrated the Fe–O bending, which confirmed the formation of Fe3O4 NPs. Ocimum basilicum leaf extract mediated Fe3O4 NPs possess spherical morphology with an average particle size ~ 15 nm as depicted by transmission electron microscopy (TEM). The magnetic potential of Ocimum basilicum leaf extract mediated Fe3O4 NPs was also carried out by using a vibration sample magnetometer (VSM), which revealed the superparamagnetic behavior of Fe3O4 NPs. Cytotoxicity of the as-synthesized Fe3O4 NPs nanoparticles was also examined on the human breast cancer cell line, which illustrated the efficacy of the synthesized nanoparticles with a low value of IC50 (~ 17.75 µg/ml). The results displayed the potent anticancerous effect of Ocimum basilicum leaf extract capped Fe3O4 NPs, which made these nanoparticles suitable for a drug-loaded vehicle for the drug delivery system for biomedical applications.

Drug delivery system based on magnetic iron oxide nanoparticles coated with (polyvinyl alcohol-zinc/aluminium-layered double hydroxide-sorafenib)

The structural, physicochemical, morphological, and magnetic properties of magnetic drug nanoparticles prepared using polymer, layered double hydroxide (LDHs) and drug as the coating agent and magnetic iron oxide nanoparticles (MNPs) as the core were systematically studied. Firstly, a co-precipitation method was employed to synthesize the Fe3O4 nanoparticles. Then, the surface was coated with polyvinyl alcohol, Zn/Al-LDH and sorafenib (SO). XRD and FTIR studies indicate that the core has the crystal structure of the iron oxide. The TGA results supported the existence of both the core and the shell. The saturation magnetization of the as-synthesized Fe3O4 nanoparticles was found to be reduced from 80 to57 emu/g when the nanoparticles were coated with polyvinyl alcohol, Zn/Al-LDH and the drug sorafenib. HRTEM images revealed that the mean dimension of the naked Fe3O4 nanoparticles is around 30 nm. Further structural characterizations showed that the addition of the shell led to the formation of uniform particles with a particle size distribution of about 95 nm. The kinetics of drug release from the nanoparticles was found to be governed by the pseudo-second-order equation. Cell viability assays clearly showed that the magnetic iron oxide nanoparticles coated with polyvinyl alcohol-sorafenib-Zn/Al-layered double hydroxide were found to be more potent than sorafenib alone against HepG2 liver cancer cells, while displayed no cytotoxicity against 3T3 fibroblasts. These results show that the coated Fe3O4 magnetite nanoparticles are a good candidate as a drug delivery carrier to be further explored for biomedical applications.

Solvothermal synthesis of Fe3O4 nanospheres for high-performance electrochemical non-enzymatic glucose sensor

Ferroferric oxide (Fe3O4) nanospheres have been synthesized via a facile solvothermal procedure to serve as an electrode material for high performance non-enzymatic glucose sensor. The as-synthesized Fe3O4 nanospheres with a uniform size from 16 to 18 nm, which can increase the reaction contact area and the active sites in the process of glucose detection. Benefiting from the particular nanoscale structure, the Fe3O4 nanospheres obviously enhanced the activity of electrocatalytic oxidation towards glucose. When the Fe3O4 nanospheres material was used for non-enzymatic glucose sensor, several electrochemical properties including the high sensitivity 6560 μA mM−1 cm−2 (0.1–1.1 mM), limit of detection 33 μM (S/N = 3) and good long-term stability were well demonstrated. Furthermore, Fe3O4 nanospheres electrode confirmed the excellent performance of selectivity in glucose detection with the interfering substances existed such as urea, citric acid, ascorbic acid, and NaCl. Due to the excellent electrocatalytic activity in alkaline solution, the Fe3O4 nanospheres material can be considered as a promising candidate in blood glucose monitoring.

Multifunctional Electrochemical Properties of Synthesized Non-Precious Iron Oxide Nanostructures

Magnetic Fe3O4 nanostructures for electrochemical water splitting and supercapacitor applications were synthesized by low temperature simple wet-chemical route. The crystal structure and morphology of as-acquired nanostructures were examined by powder X-ray diffraction and transmission electron microscopy. Magnetic measurements indicate that the as-synthesized Fe3O4 nanostructures are ferromagnetic at room temperature. The synthesized nanostructures have a high-specific surface area of 268 m2/g, which affects the electrocatalytic activity of the electrode materials. The purity of the as-synthesized nanostructures was affirmed by Raman and X-ray Photoelectron studies. The electrochemical activity of the magnetic iron oxide nanoparticles (MIONPs) for the hydrogen evolution reaction (HER) and supercapacitors were investigated in alkaline medium (0.5 M KOH) versus Ag/AgCl at room temperature. The electrocatalysts show low onset potential (~0.18 V) and Tafel slope (~440 mV/dec) for HER. Additionally, the specific capacitance of MIONPs was investigated, which is to be ~135 ± 5 F/g at 5 mV/s in 1 M KOH.

Preparation and electromagnetic wave absorption properties of carbon nanotubes loaded Fe3O4 composites

Carbon nanotubes loaded Fe3O4 (CNTs-loaded Fe3O4) composites synthesized via a common chemical vapor deposition method showed excellent electromagnetic wave absorption performance. The effect of different Fe3O4 content on the electromagnetic parameters and wave absorption properties of the CNTs-loaded Fe3O4 composites was investigated. The results indicated that the CNTs-loaded Fe3O4 composites with the content of 42.4% Fe3O4 exhibited the best absorption property among the as-synthesized CNTs-loaded Fe3O4 composites. The minimum RL value reached −35.9 dB at 7.12 GHz with a thickness of 3 mm. More significantly, the effective bandwidth less than −10 dB was 4.32 GHz with a thickness of 1.5 mm. Compared with pure CNTs or Fe3O4, the impedance matching of CNTs-loaded Fe3O4 composites is markedly improved. The absorbing mechanism is mainly due to the synergistic effect of improved impedance matching, interface scattering, dielectric loss and magnetic loss. CNTs-loaded Fe3O4 composites with excellent electromagnetic wave absorption performance contribute to the development of light and highly efficient electromagnetic wave absorbing materials.

Rapid and sensitive determination of neomycin and kanamycin in measles, mumps, and rubella vaccine via high‐performance liquid chromatography–tandem mass spectrometry using modified super-paramagnetic Fe3O4 nanospheres

A simple magnetic dispersive solid-phase extraction (MDSPE) methodology based on mesoporous Fe3O4@ succinic acid nanospheres and high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) has been developed to determine kanamycin (KNM) and neomycin (NEO) contents in Measles, Mumps, and Rubella (MMR) vaccine products. The monodispersed mesoporous Fe3O4 nanospheres with self-assembled carboxyl terminated shell have been prepared via a simple solvothermal method. These as-synthesized mesoporous Fe3O4 nanospheres showed a high magnetic saturation value (Ms = 46 emu g−1) and large specific surface area (111.12 m2 g−1) which made them potential candidates as sorbents in magnetic solid-phase extraction. The adsorption experimental data fitted well with the Freundlich-Langmuir isotherm and followed a pseudo-second-order kinetic model. Moreover influential parameters on extraction efficiency were investigated and optimized. Under optimal conditions, the limits of detection for KNM and NEO were 1.0 and 0.1 ng mL−1, respectively. Recovery assessments using real samples exhibited recoveries in the range of 96.0 ± 4.3 to 101.5 ± 7.1 %, with relative standard deviations of <10.7% (for intra- day) and <14.6% (for inter- day). The proposed method was successfully applied for different spiked and un-spiked MMR vaccine samples. The presented extraction method provides a fast, selective, robust and practical platform for the detection of KNM and NEO in MMR vaccine samples.

Peroxydisulfate activation by in-situ synthesized Fe3O4 nanoparticles for degradation of atrazine: Performance and mechanism

Herein activation of persoxydisulfate (PDS) was achieved by in-situ synthesized Fe3O4 nanoparticles (NPs) from a sacrificial iron anode in an electrochemical (EC) cell. The as-synthesized Fe3O4 NPs were characterized to be in spherical and in the nano size. The performance of the process, EC-Fe3O4/PDS, was investigated in terms of atrazine (ATZ) degradation. Optimum process conditions were determined as initial pH of 5, electrolyte (Na2SO4) concentration of 1 mM, a current density of 1.67 A m−2, PDS concentration of 0.5 mM and initial ATZ concentration of 10 mg L–1. At optimum conditions, the EC-Fe3O4/PDS process could effectively degrade 80% of ATZ in an aqueous solution within a short reaction time of 20 min. The electrical energy consumption of the process was found to be quite low with 0.0307 kWh/m3. Based on the LC/MS analysis, the degradation pathway of ATZ with seven transformation products was proposed. Finally, a possible mechanism of the EC-Fe3O4/PDS process was put forward, which includes the activation of PDS and the role of radicals in the degradation of ATZ. In conclusion, the combination of Fe3O4 NPs catalyzed PDS oxidation with the EC process was very effective in the degradation of ATZ to dechlorinated final products. The strong synergistic effect makes this process superior to conventional methods due to the high degradation efficiency with low electrical energy and chemical consumption. Application of this method, with very low current density, may not only minimize the electrical energy consumption but also help reduce the sludge production due to the lower iron dissolution.

Microwave-Assisted Combustion Synthesis of Fe3O4 Undoped and Cr-Doped Fe3O4 Nanoparticles: Morphological, Structural, Optical, and Magnetic Behavior

Cr-doped Fe3O4 nanoparticles have been efficiently synthesized by microwave combustion approach to evaluate structural, magnetic, and optical properties. The as-synthesized Fe3O4 nanopowders structural, optical, morphological, and magnetic properties assessment was carried out by employing X-ray diffraction analysis, optical spectroscopic technique, scanning electron microscope, and vibrating-sample magnetometer. The X-ray diffraction (XRD) analysis studied the structural properties of the nanoparticles and confirms structure of the Fe3O4 and Cr-doped Fe3O4 crystal structure. The magnetic hysteresis loops of the samples indicated that the samples are ferromagnetism in nature. The ferromagnetism behavior of the samples is also discussed.

Novel sonochemical synthesis of Fe3O4 nanospheres decorated on highly active reduced graphene oxide nanosheets for sensitive detection of uric acid in biological samples.

In this study, a super-active Iron (II, III) oxide nanospheres (Fe3O4 NPs) decorated reduced graphene oxide (rGOS) nanocomposite was developed. Fe3O4 NPs were stabilized on rGOS through electrostatic interactions in the aqueous medium. This process involves an ultrasound assisted reduction reaction of the GOS. The as-synthesized Fe3O4 NPs@rGOS was characterized through the HRTEM, SEM, XRD, Raman, elemental mapping and EDX analysis. The Fe3O4 NPs@rGOS modified GCE was developed for the determination of biomarker. Uric acid is important biomarker based on gout and kidney stone with high adverse effect in human body. The results obtained showed that the modified electrode Fe3O4 NPs@rGOS shows good electrochemical reduction peak compared to bare electrode and control electrodes. The Fe3O4 NPs@rGOS modified sensor linear range 0.02-783.6 µM was observed with nanomolar LOD 0.12 nM. In addition, the modified Fe3O4 NPs@rGOS/GCE sensor has been applied to determination of uric acid concentration in urine and blood serum samples. Furthermore, advantages of the modified sensor are high stability, repeatability and reproducibility.

Size-controlled synthesis of superparamagnetic magnetite nanoclusters for heat generation in an alternating magnetic field

We report the size-controlled synthesis of monodisperse magnetite (Fe3O4) nanoclusters by a facile and economic solvothermal route by using polyacrylic acid (PAA) as the coordinative ligand. In comparison with previous reports, nanocluster sizes were tuned over a broad range of 640–250 nm while retaining the superparamagnetic behaviour in the present study. The nanocluster sizes are varied by changing the amounts of PAA as well as water added in the reaction medium during the solvothermal treatment. As-synthesized Fe3O4 nanoclusters are characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The radio frequency alternating magnetic field induced heating studies indicate that the as-synthesized Fe3O4 nanoclusters are promising candidates for magnetic fluid hyperthermia applications. In the case of magnetic nanoclusters, consisting of individual superparamagnetic nanocrystals, the field induced heating occurs at two different length scale, viz. Neel-Brown relaxation of the individual superparamagnetic nanocrystals (length scale <10 nm) and Brownian relaxation of the entire nanoclusters (length scale ~250 nm or higher). Experimental findings indicate that the heating efficiency of the magnetic nanoclusters vary significantly with variations in the relaxation time at both length scales. The heating efficiency of the magnetic nanoclusters is also found to increase linearly with the square of the external field amplitudes, in accordance with the linear response theory.

Implementation of magnetic Fe3O4@ZIF-8 nanocomposite to activate sodium percarbonate for highly effective degradation of organic compound in aqueous solution

Here, as-synthesized Fe3O4 nanoparticles were incorporated into the zeolitic imidazolate framework (ZIF-8) lattice to activate sodium percarbonate (SPC) for degradation of methylene blue (MB). The reaction rate constant of Fe3O4@ZIF-8/SPC process (0.0632min−1) at acidic conditions (pH=3) was more than six times that of the Fe3O4/SPC system (0.009min−1). Decreasing the solute concentration, along with increasing SPC concentration and Fe3O4@ZIF-8 nanocomposite (NC) dosage, favored the catalytic degradation of MB. The Fe3O4@ZIF-8 NC after fifteen consecutive treatment processes showed the excellent stability with a negligible drop in the efficiency of the system (<10%). The reaction pathway was obtained via GC–MS analysis.

Hydrothermal Synthesis of Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@C Spheres as Anode Material for Lithium-Ion Batteries

Fe3O4@C spheres were synthesized by hydrothermal reaction at 190°C followed by a low temperature heat annealing at 600 °C and applied as an anode material for lithium-ion batteries. The samples were characterized by XRD and SEM. The electrochemical performances of as-synthesized Fe3O4@C were systemically investigated. A reversible capacity of 873 mAh g-1 is obtained in the second cycle at 400 mA g-1. More importantly, the discharge specific capacity can still maintain at about 767 mAh g-1 after 80 cycles. Moreover, Fe3O4@C spheres electrode shows satisfactory rate capability even at a rate up to 2000 mA g-1. Thus, the results demonstrate that Fe3O4@C spheres show encouraging application potential to be an advanced anode material for lithium storage

Self-Template Etching Synthesis of Urchin-Like Fe3O4 Microspheres for Enhanced Heavy Metal Ions Removal

Hierachical Fe3O4 microspheres with superparamagnetic properties are attractive for their superior structural, water-dispersible, and magnetic separation merits. Here self-template etching route was developed to create optimal porous structure in superparamagnetic Fe3O4 microspheres by using the oxalic acid (H2C2O4) as etching agent. A plausible formation mechanism of the urchin-like Fe3O4 microspheres was proposed based on systematic investigation of the etching process, which involved two stages including pore-forming step based on size-selective etching and pore-expanding step based on further etching. The as-synthesized Fe3O4 microspheres exhibited urchin-like structure with specific surface area and pore-size tunable, water-dispersible, and superparamagnetic properties. The optimal urchin-like Fe3O4 microspheres demonstrated superior performance including fast magnetic separation and high removal capabilities for the heavy metals ions like Pb2+ (112.8 mg g-1) and Cr(VI) (68.7 mg g-1). This work will shed new light on the synthesis of urchin-like microspheres for superior performance.