Surface Of Fe3O4 Nanoparticles Research Articles

Immobilization of alpha-L-rhamnosidase on a magnetic metal-organic framework to effectively improve its reusability in the hydrolysis of rutin

α-L-Rhamnosidase (Rha) is a biotechnologically important enzyme that degrades biomass containing natural rhamnoside. Herein, the recombinant Rha was successfully immobilized on magnetic metal-organic frameworks (MOFs), and used to hydrolyze rutin. Magnetic MOFs were constructed by binding Cu2+ and PABA to the surface of Fe3O4 nanoparticles coated with a polydopamine film through coordinate covalent bonds, and the enzyme was attached to the MOFs using the cross-linking agents EDC/NHS. The immobilized enzyme Rha@MOF reached an activity of 25.09 U/g with a lower apparent Km value compared with the free enzyme. The conversion rate of 20 g/L rutin was 91.42%, corresponding to an isoquercitrin productivity of 12.78 g/L/h. Rha@MOF also exhibited significantly improved reusability; the conversion rate was still 73.55% after 30 cycles at 60 °C. These results indicated that the magnetic MOF-immobilized enzyme was a feasible biocatalyst for the conversion of flavonoids with low aqueous solubility.

Magnetic solid-phase extraction for speciation of mercury based on thiol and thioether-functionalized magnetic covalent organic frameworks nanocomposite synthesized at room temperature

A simple and practical magnetic solid-phase extraction high-performance liquid chromatography-inductively coupled plasma mass spectrometry (MSPE-HPLC-ICP-MS) method for extraction and determination of trace mercury species, including inorganic mercury (IHg), monomethylmercury (MeHg) and ethylmercury (EtHg), was developed. The MSPE adsorbent, urchin-like thiol and thioether-functionalized magnetic covalent organic frameworks (Fe3O4@COF-S-SH), was synthesized by coating covalent organic frameworks (COFs) on the surface of Fe3O4 nanoparticles at room temperature and then easily grafting 1,2-Ethanedithiol on the COFs. The as-prepared Fe3O4@COF-S-SH has strong adsorption capacity for IHg, MeHg and EtHg, with excellent static adsorption capacity: 571, 559 and 564 mg g−1, respectively. The parameters influencing the extraction and enrichment had been optimized, including pH, adsorption and desorption time, composition and amount of the eluent, co-existing ions and dissolved organic materials etc. Under the optimized condition, the limit of detection (3δ) of the proposed method were 0.96, 0.17 and 0.47 ng L−1 for IHg, MeHg and EtHg, and the developed method has high actual enrichment factors of 370, 395, 365-fold for IHg, MeHg and EtHg based on 200 mL samples, respectively. The high accuracy and reproducibility has been proved by the spiked recoveries (96.0‒108 %) in real water samples and determination of the certified reference material. Both the adsorption and desorption process can be completed within 5 min. The proposed method with simple operation, short pre-concentration time and high sensitivity has been successfully applied to mercury speciation at trace levels in the samples with complicated matrices, including underground water, surface water, sea water and fish samples.

A novel method for in situ encapsulation of curcumin in magnetite-silica core-shell nanocomposites: A multifunctional platform for controlled drug delivery and magnetic hyperthermia therapy

In this study, we developed a novel strategy for in situ encapsulation of hydrophobic drugs such as curcumin into the magnetite-mesoporous silica nanocomposites with a core-shell structure. In the proposed method, a modified reverse microemulsion system was used for silica formation on the surface of curcumin-loaded Fe3O4 nanoparticles (Cur@Fe3O4 NPs) to render mesoporous silica-coated Cur@Fe3O4 NPs (SiO2/Cur@Fe3O4 NPs). The prepared SiO2/Cur@Fe3O4 NPs with a core-shell structure had a spherical shape with a mean particle size less than 100 nm. The heating efficacy of the prepared nanocomposites was examined for application in magnetic hyperthermia therapy by exposing them to different biological safe alternating magnetic fields. The maximum specific absorption rate (SAR) obtained by the prepared sample, was found to be 22.11 WgFe3O4−1at the magnetic field intensity of 28 kA m−1 and frequency of 120 kHz.. Also, the prepared nanocomposites exhibited a pH-responsive drug release behavior. The in vitro drug release studies showed that, only 8.9% of curcumin was releasedwas from SiO2/Cur@Fe3O4 NPs at pH 7.4, while about 40% of drug was released at pH 5.0, after 5 days. Moreover, the in vitro cytotoxicity analysis showed that, by encapsulation of curcumin in the prepared nanocomposites, the cytotoxicity of the drug was significantly increased against breast cancer MCF-7 cells, compared to the free drug, so that, at curcumin concentration of 40 μg mL−1, the viability of MCF-7 cells incubated with free curcumin was 62.0%, whereas by encapsulation of curcumin in SiO2/Cur@Fe3O4 NPs the viability was decreased to 26.7% (Pvalue ≤ 0.005).

Crystallization- and morphology-tunable Fe3O4@C core–shell composites decorated on carbon nanotube skeleton with tailorable electromagnetic wave absorption behavior

Herein, a scalable method is developed to fabricate carbon nanotube (CNT)/Fe3O4@C composites, in which the crystallization and morphology of the carbon shell on the surface of Fe3O4 nanoparticles can be controlled by manipulating the synthesis conditions of chemical vapor deposition technology. Owing to the synergic dissipation effect of the core–shell structure, as well as the excellent conductive loss induced by the CNT skeleton, the CNT/Fe3O4@C composite shows a minimum reflection loss of −50.1 dB at 9.7 GHz and an effective bandwidth of 4.6 GHz. This study provides new insight into preparing core–shell-structured microwave absorbers with excellent performance.

Titanium decorated iron oxide (Ti@Fe2O3) regulates the proliferation of bovine muscle satellite cells through oxidative stress

In the present study, the titanium decorated iron oxide (Ti@Fe2O3) nanocomposites are synthesized using the chemical method. The as-prepared nanocomposite was characterized for successful formulation and the elemental spectra showed the composition of Fe (44%), Ti (0.71%) and O (55%) is confirmed the homogenous distribution. Crystallographic spectra depict the strong peaks corresponding to the of TiO2 and Fe2O3 nanoparticles planes with minor shift variation due to the formulation of Ti on the surface of Fe2O3 nanoparticles and it is also confirmed with SAED analysis. The X-ray photoelectron spectroscopy (XPS) analysis of Ti@Fe2O3) nanocomposite confirms the existence of elements such as Fe, O and Ti. Further, the morphology of the composite showed the well-defined encapsulation and aggregation of TiO2 nanoparticles on the surface of Fe2O3 nanoparticles. Further, the TiO2 nanoparticles showed less cytotoxic activity against bovine satellite cells, as well the nanocomposite increased the growth of bovine satellite cells comparing with control cells. Further, the morphological analysis showed the significant changes in TiO2 nanoparticles treated cells and the nanocomposite induces the myotube formation due to the increased ROS level in bovine satellite cells. Moreover, the nanocomposite regulates the expression of genes IGF-1, TGF-β, MSTN, CASP3, CASP2 and proteins such as CALP1, CALP2, MyoD, MyoG which are responsible for the growth, proliferation, and differentiation of satellite cells. Together, the prepared Ti@Fe2O3 nanocomposites afford additional support for the applications of nanomaterials in skeletal muscle repair and tissue regeneration engineering.

Cartilage Mimics Adaptive Lubrication.

The natural cartilage layer exhibits excellent interface low friction and good load-bearing properties based on the mechanically controlled adaptive lubrication mechanism. Understanding and imitating such a mechanism is important for developing high-load-bearing water-lubrication materials. Here, we report the successful preparation of thermoresponsive layered materials by grafting a poly(3-sulfopropyl methacrylate potassium salt) (PSPMA) polyelectrolyte brush onto the subsurface of an initiator-embedded high strength hydrogel [poly(N-isopropylacrylamide-co-acrylic acid-co-initiator/Fe3+)] [P(NIPAAm-AA-iBr/Fe3+)]. The top soft hydrogel/brush composite layer provides aqueous lubrication, while the bottom thermoresponsive hydrogel layer exhibits adaptive load-bearing capacity that shows tunable stiff or modulus in response to the temperature above and below the lower critical solution temperature (LCST, 32.5 °C). An obvious friction-reduction feature is realized above the LCST, resulting from the dynamic increase of the bottom layer mechanical modulus. Furthermore, in situ lubrication-improvement behavior is achieved upon applying a near-infrared (NIR) laser onto the surface of Fe3O4 nanoparticle (NP)-integrated layered materials. Such a typical lubrication-regulated behavior can be attributed to the synergy effect of the improved load-bearing capacity of the bottom layer and the enhanced lubrication behavior of the top layer with an increase in the polyelectrolyte brush chain density, which is similar to the mechanically controlled adaptive lubrication mechanism of the natural cartilage layer. Current research results provide an inspiration for developing novel biomimetic lubrication materials with considerable load-bearing capacity and also propose a strategy for designing intelligent/stable friction-actuation devices.

Effects of different amin-based core-shell magnetic NPs on CO2 capture using NMP solution at high pressures

In this work, different modified magnetic nanoparticles (NPs) including Fe3O4–NH2, Fe3O4-proline, Fe3O4-lysine, Fe3O4@SiO2–NH2, Fe3O4@SiO2-proline, and Fe3O4@SiO2-lysine were synthesized to enhance the properties of Fe3O4 NPs in carbon dioxide (CO2) absorption via functionalizing various chemical agents on the surfaces of Fe3O4 NPs. For the investigation of CO2 absorption improvement, the NPs at different weight percents were dispersed in aqueous N-Methyl-2-pyrrolidone (NMP) solution (50 wt%) as a very strong physical absorbent of CO2; and the nano/NMP solutions were in direct contact with CO2 at a high-pressure batch setup. The impressions of different NPs, the initial pressure of CO2 and mass nanoparticle concentration on CO2 absorption were elucidated. The experimental results revealed that Fe3O4, Fe3O4–NH2 and Fe3O4-proline nanofluids were not stable at high concentrations. So, they increased the CO2 absorption rate just up to 7.64%, 15.14% and 15.88% as compared to the base fluid. However, Fe3O4-lysine, Fe3O4@SiO2–NH2, Fe3O4@SiO2-proline and Fe3O4@SiO2-lysine nanofluids by applying chemical agents as a sort of stabilizer and chemical reactant of CO2, improved the equilibrium CO2 absorption up to 19.41%, 23%, 25.53% and 28.49%, respectively.

Ultrasound Imaging Based on Magnetic Lipid Microbubble Contrast Agent with Fe₃O₄ Nanoparticles.

To construct magnetic microbubbles with dual response characteristics of ultrasound and magnetic field. The surfactant-based microbubble ultrasound contrast agent (ST68) was prepared using acoustic cavitation. Magnetic Fe₃O₄ nanoparticles having a negative charge on the surface were prepared by the polyol method. The microbubbles were used as the template, and the magnetic microbubbles were prepared by alternating deposition of polyethyleneimine and magnetic Fe₃O₄ nanoparticles on the surface of microbubbles using electrostatic attraction for a layer-by-layer selfassembly. An in vitro ultrasound contrast device was set up to compare the ultrasound images of the silicone tube in the device before and after the injection of human magnetic microbubbles (3×10/M), and to observe the movement of the magnetic microbubbles after the magnetic field was applied to the silicone tube. To evaluate the contrast effect of magnetic microbubbles in vivo, we compared the renal ultrasound images of New Zealand white rabbits before and after injection of human magnetic microbubbles. The surface of Fe₃O₄ nanoparticles displayed a stable negative charge (-24.6±67 mV). More than 98% of the assembled magnetic microbubbles were smaller than 8 μm, which met the basic size requirement for an ultrasound contrast agent. There was no echo signal in the silicone tube before the injection of magnetic microbubbles. Following injection, a solid echo was detected in the silicone tube. After the application of the magnetic field, the magnetic microbubbles migrated in the direction of magnetic field. Contrast-enhanced ultrasound did not image the kidney before the injection of magnetic microbubbles, while the kidney shadow was clear following injection. Magnetic targeted microbubbles and contrast-enhanced ultrasound provide good imaging, which lays the foundation for further studies of magnetic targeted microbubble contrast agents in diagnosis and treatment.

In situ Fe3O4 nanoparticles coating of polymers for separating hazardous PVC from microplastic mixtures

Poly(vinyl chloride) (PVC) poses great challenges to the recycling of plastic wastes since it highly deteriorates the properties of other plastics and induces the formation of hazardous chlorinated dioxins and furans. For the first time, we developed a novel hydrophilization method of polymers, the in situ magnetite (Fe3O4) nanoparticles (NPs) coating, to facilitate the flotation separation of PVC from microplastic mixtures. A homogeneous Fe3O4 NPs layer was selectively fabricated on the surface of non-PVC microplastics via a facile in situ coprecipitation method. This obviously decreased the contact angle of non-PVC microplastics by approximately 30° due to the plenty of hydroxyl groups on the surface of Fe3O4 NPs. However, the fabrication was not observed on the surface of PVC due to the weak interaction between Fe3+/Fe2+ and the surface of PVC. In this regard, the application of in situ Fe3O4 NPs coating in the flotation separation of PVC was systematically optimized using Box-Behnken design of response surface methodology. Quadratic models were generated to predict the floatability of microplastics, ascertain the effect of independent and interacted parameters, and numerically optimize the separation efficiency. Under optimum conditions, the Removalrate, Purity, and Recovery of PVC were 100.0%, 99.6%, and 100.0%, respectively. This study provides novel insights into the surface hydrophilization of polymers and shows promising prospects for facilitating the recycling of plastic wastes.

Decorated Au NPs on agar modified Fe3O4 NPs: Investigation of its catalytic performance in the degradation of methylene orange, and anti-human breast carcinoma properties

This work describes an eco-friendly approach for in situ immobilization of Au nanoparticles on the surface of Fe3O4 nanoparticles, with help of Agar and ultrasound irradiations, without using any toxic reducing and capping agents. The structure, morphology, and physicochemical properties were characterized by various analytical techniques such as Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), inductively coupled plasma (ICP) and vibrating sample magnetometer (VSM). The desired catalyst showed great efficiency in the reductive degradation of methylene orange (MO) dye over NaBH4 at room temperature. The MO was fully reduced in only 70 s and achieved rate constant of 9.6 × 10−2 s−1. The catalyst was reused for 10 runs without significant loss in catalytic activity. Cell viability of Fe3O4/agar/Au NPs was very low against breast adenocarcinoma (MCF7), breast carcinoma (Hs 578Bst), infiltrating ductal cell carcinoma (Hs 319.T), and metastatic carcinoma (MDA-MB-453) cell lines without any cytotoxicity on the normal cell line. According to the above findings, the Fe3O4/agar/Au NPs may be administrated for the treatment of several types of human breast carcinoma in humans.

Electrochemical assay of protein kinase activity based on the Fe3O4@PNE-Ti4+ functionalized PDMS microchip

A new strategy for the sensitive assay of protein kinase activity has been constructed using Fe3O4@PNE-Ti4+ nanocomposite as stationary phase in microchip electrophoresis. Through the self-polymerization of norepinephrine in weak alkaline solution, a thin poly(norepinephrine) (PNE) film can be spontaneously formed on the surface of Fe3O4 nanoparticles (NPs) to produce Fe3O4@PNE NPs. Due to the good magnetic property, Fe3O4@PNE NPs can be easily fixed in poly(dimethylsiloxane) (PDMS) channel under external magnetic field. On the other hand, the catechol hydroxyl groups in PNE can chelate Ti4+ to form Fe3O4@PNE-Ti4+ in PDMS channel. When peptides are phosphorylated by protein kinase A (PKA) in the presence of adenosine 5′-triphosphate (ATP), the Fe3O4@PNE-Ti4+ packed in PDMS channels can specifically coordinate with the phosphorylated sites of phosphopeptides, but the non-phosphorylated peptides cannot bind with Ti4+. Thus, the retention time of the phosphorylated peptides in the Fe3O4@PNE-Ti4+ packed PDMS channel was increased, and phosphorylated peptides and non-phosphorylated peptides can be separated successfully. Due to the high loading of Ti4+ on the Fe3O4@PNE, this strategy can be used for the enrichment of phosphorylated peptides and electrochemical assay of PKA activity. This method can also be used for quantitative analysis of PKA activity in cell lysate, indicating its potential application in clinical diagnosis.

Fabrication of composite Fe3O4 nanoparticles coupled by thermo-responsive and fluorescent Eu complex on surface

Stimuli-responsive luminescent hybrid nanoparticles consisting of a magnetite Fe3O4 core and a hydrophilic outer shell were synthesized. The shell was a thermo-responsive Eu(III) complex shell, which was synthesized as follows: first, 3-Methacryloxypropyl-trimethoxysilane (MEMO)-co-poly(N-isopropylacrylamide) (NIPAM) (MEMO-co-PNIPAM) copolymer was prepared by free radical polymerization. Subsequently, the copolymer chelated with Europium(III) ions to form a luminescent polymeric layer. Finally, the polymeric shell was grafted onto the Fe3O4 nanoparticles surface through chemical action. The sizes of fabricated nanoparticles with core–shell structure were controlled at about 30-45 nm. The as-synthesized nanocomposite particles had excellent fluorescence performance and thermo-responsive behavior, which possessed high color purity and produced red-emission at 613 nm. The lower critical solution temperature (LCST) of thermo-sensitive magnetic nanoparticles was at around 37–38 °C. Cell viability assays suggested that these nanoparticles showed excellent biocompatibility and fluorescence-intensity in vitro.

Lipid/Hyaluronic Acid-Coated Doxorubicin-Fe3O4 as a Dual-Targeting Nanoparticle for Enhanced Cancer Therapy.

Development of a delivery system to lower systemic toxicity and enhance doxorubicin (DOX) antitumor efficacy against multi-drug resistant (MDR) tumors is of great clinical significance. Here, lipid/hyaluronic acid (HA)-coated DOX-Fe3O4 was characterized to determine its optimal safety and efficacy on a tumor. DOX was first conjugated onto the Fe3O4 NPs surface, which was subsequently coated with phosphatidylcholine (PC) lipids, which consisted of a tumor cell-targeting HA ligand, to generate a dual-targeting nanoparticle (NP). DOX-Fe3O4 synthesis was validated by the Fourier-transform infrared (FT-IR) analysis results. Core-shell PC/HA@DOX-Fe3O4 formation, which had an average particle size of 48.2nm, was observed based on the transmission electron microscopy (TEM) and dynamic laser light scattering (DLS) results. The saturation magnetization value of PC/HA@DOX-Fe3O4 was discovered to be 28emu/g using vibrating-sample magnetometry. Furthermore, the designed PC/HA@DOX-Fe3O4 achieved greater MCF-7/ADR cellular uptake and cytotoxicity as compared with DOX. In addition, PC/HA@DOX-Fe3O4 exhibited significant DOX tumor-targeting capabilities and enhanced tumor growth inhibition activity in the xenograft MCF-7/ADR tumor-bearing nude mice following magnetic attraction and ligand-mediated targeting, with less cardiotoxicity. Therefore, PC/HA@DOX-Fe3O4 is a potential candidate for MDR tumor chemotherapy. Graphical abstract.

Fe<sub>3</sub>O<sub>4</sub>.SiO<sub>2</sub>: A Study of Structural and Magnetic Properties in Various Volume of Tetraethyl Orthosilicate

Magnetic nanofluids are a category of nanomaterial which exhibit simultaneously liquid and superparamagnetic properties. These nanofluids are magnetic nanoparticles stably dispersed in liquid carrier. Magnetic nanoparticles with and without SiO2 encapsulation have been successfully synthesized by co-precipitation method from ferrous and ferric precursors dispersed in various liquid. Fe3O4 nanoparticles were investigated by Zeta Potential and HR-TEM to determine the stability of nanoparticles, average particles size and microstructure of nanoparticles. From zeta potential measurements, is was found that the value of zeta potential for Fe3O4 dispersed in ethanol was ± 0,9 mV, while dispersed in di-water was ± 31,1 mV, indicating that nanoparticles Fe3O4 are more stable in DI-water. The increasing of zeta potential indicated the adsorption of negatively charged hydroxyl group to the surface of Fe3O4 nanoparticles. From XRD measurements, it was found that crystal quality of Fe3O4.SiO2 sintering at 80 °C decreased by increasing the volume of tetraethyl orthosilicate (TEOS), while that samples sintering at 1000 °C have a good crystal quality with hexagonal phase of a-Fe2O3.SiO2. From SQUID measurements, it was found that samples of Fe3O4.SiO2 sintering at 80 °C with TEOS volumes of 1 ml and 2 ml showed a paramagnetic like while samples of a-Fe2O3.SiO2 sintering at 1000 °C with the same TEOS volume showed ferrimagnetic properties.

OXYGEN REDUCTION ON THE SURFACE OF Fe3O4&Au NANOCOMPOSITES

Functional materials based on ferromagnetics and noble metals are attractive due to their unique optical, catalytic and magnetic properties. Nowadays these materials find their application in various fields of science and technology: medicine, biotechnology, chemistry, physics and energy sector. The aim of the present work is to study the electrochemical characteristics of the oxygen reduction on the surface of Fe3O4&Au nanocomposites. The formation of the composite particles took place on the surface of a rotating steel disk which was in contact with HAuCl4 aqueous solution and air. Initial gold concentration was varied from 0.2 to 10.0 mg/l. Oxygen reduction was studied on a floating gas diffusion electrode (pressed carbon black P803 + 30 % PTFE) with surface, modified by prepared Fe3O4&Au nanocomposites, in 1 M KOH solution at 20 ºC. Electrochemical measurements were carried out using a PI-50-1.1 potentiostat.
 Tafel slopes of the stationary polarization curves ∂E/∂lgj of oxygen reduction on the electrode modified by composites formed at с(Au3+) from 0.2 to 5.0 mg/l lay in the ranges: b1 = 0.048 – 0.060 V, b2 = 0.119 – 0.131 V. When nanocomposites were obtained at с(Au3+) from 7.0 to 10 mg/l these values were: b1 = 0.042 –0.061 V, b2 = 0.079 – 0.105 V. It was concluded that oxygen reduction mechanism is multistep and includes formation of the hydrogen peroxide as intermediate. Obtained b1 and b2 values indicate that electrode process me-chanism changes when current density grows.
 The largest exchange current (8.51∙10–3 A/g) was achieved when electrode was modified by composite formed at с(Au3+) = 1.0 mg/l, whereas when the composite formed at с(Au3+) = 10.0 mg/l was used, the j0 value was smallest. Perhaps, the increase in the initial Au3+ concentration during nanocomposite formation led to an increase in the number of separate gold clusters on the surface of Fe3O4 nanoparticles and to raise of composite catalytic activity. But when с(Au3+) exceeded 1.0 mg/l the core-shell Fe3O4&Au composites with compact gold shell were formed. Such coreshall composites had lower catalytic activity in the oxygen reduction than composites with separate gold clusters on the surface of Fe3O4 particles.

Synthesis and characterization of new bent-core liquid crystal with a ferroelectric-like switching / modified magnetite nanocomposite

A new bent-core liquid crystal (LC) compound 4-Cyano-1,3-phenylenebis[4-(4-(S)-2-Dodecyloxypropionyloxyphenoxycarbonyl)benzoate] (CyPDB) consisting of O-dodecyl lactate substituted terephthalate based rod-like units which were located at 1,3-positions of 4-cyanoresorcinol central unit has been synthesized and LC/1.0% modified Fe3O4 nanocomposite has been prepared. The effects of being the doped with 1.0% modified Fe3O4 (magnetite) nanoparticles on mesomorphic properties of the new bent-core liquid crystal, which exhibits an enantiotropic SmA phase with a ferroelectric-like switching, were investigated by differential scanning calorimetry, optical polarizing microscopy and electro-optic studies. The surface of Fe3O4 (magnetite) nanoparticles was modified with a silane surfactant, octadecyltrimethoxysilane (OTMS), used as a compatibilizer for the attractive interaction of liquid crystal molecule with Fe3O4 nanoparticles. The size, morphology and distribution of modified Fe3O4 (magnetite) nanoparticles in LC host were investigated by using Transmission Electron Microscope (TEM) and Scanning Electron Microscopy (SEM). The magnetic properties of nanocomposite were studied using a vibrating-Sample Magnetometer (VSM).

Phase inversion synthesis of Fe3O4@NC composites with superior lithium storage performance

The N-doped carbon coated Fe3O4 composites (Fe3O4@NC) are successfully fabricated on a polyacrylonitrile (PAN) phase inversion method and subsequently annealing. Compared with common electrospinning method, needing delicate equipment and strict reaction conditions, this method is facile and ingenious to synthesize PAN-based composites or carbon-coated materials. Applied to lithium ion batteries (LIBs) anode, the Fe3O4@NC composite exhibits a large specific capacity of 981 mAh g−1 at 0.2 A g−1 after 500 cycles, an outstanding rate capability and a superior long-term high-rate cycling performance (632 mAh g−1 at 1 A g−1 after 900 cycles). Its excellent electrochemical performance is attributed to the thin carbon layers on the surface of Fe3O4 nanoparticles, which can not only enhance the electron conductivity, but also buffer the volume change of Fe3O4 nanoparticles during lithiation/delithiation. Moreover, the doped nitrogen atoms derived from PAN can lead to more defects in electrode material, which benefits to the electrochemical performance of Fe3O4@NC composites.

Continuous high-efficient degradation of organic pollutants based on sea urchin-like Fe3O4/ZnO/ZnSe heterostructures in photocatalytic magnetically fixed bed reactor

In this study, a sea urchin-like Fe3O4/ZnO/ZnSe hierarchical heterostructured photocatalyst was successfully prepared via a convenient synthetic strategy and combined with a newly designed photocatalytic magnetically fixed bed reactor (PMFBR) to continuously photodegrade pollutants under simulated solar light irradiation. In the experiment, ZnO nanorods were first grafted onto the surfaces of hollow Fe3O4 nanoparticles, and then ZnSe nanoparticles were uniformly distributed on the ZnO nanorods, the obtained Fe3O4/ZnO/ZnSe composite exhibited three-dimensional structure and excellent magnetic response. Through citing PMFBR, a stable and homogeneously distributed heterogeneous catalyst, efficient light distribution, and good mass transfer of reactants were achieved. As a result, the Fe3O4/ZnO/ZnSe composite in the PMFBR showed excellent photocatalytic capacity with a continuous process. The combination of the magnetic photocatalyst and PMFBR transformed the reaction mode from cumbersome intermittent operation to a simple continuous-flow photocatalytic style. It is hoped that this continuous photocatalytic system could provide a new idea for large-scale wastewater treatment.

Au@Ag core-shell nanoparticles for microRNA-21 determination based on duplex-specific nuclease signal amplification and surface-enhanced Raman scattering.

Anovel surface-enhanced Raman scattering (SERS) analysis strategy has been designedcombining Au@DTNB@Ag core-shell nanoparticles (DTNB attachment on gold nanoparticles, then encapsulated in Ag shell nanoparticles named as ADANPs) and duplex-specific nuclease signal amplification (DSNSA) platform. Firstly, ADANPs and magnetic substrate of Fe3O4 nanoparticles were covalently attached to the 3'- and 5'- end of capture probe (CP) targeting miRNA-21. Upon the addition of target miRNA-21, these heteroduplexes were specifically cleaved by DSN and resulted in ADANPs that were released from the surface of Fe3O4 nanoparticles (Fe3O4 NPs). At the same time, miRNA-21 remained intact and can rehybridize another DNA probe to trigger the signal-amplifying reaction. Based onthis principle, the developed SERS method exhibited good linearity in the range 0 to 1nM for miRNA-21 with a limit of detection (LOD) of 0.084fM and has an ability to differentiate even a single-base mismatched sequence on the target sequence or other miRNA sequence. The results provide a novel SERS method which can successfully been applied to the miRNA-21 detection in human serum. Graphical abstract a shows the synthesis of Fe3O4 NPs and the conjugation of Au@DTNB@Ag NPs (ADANPs) for the detection of miRNA-21, b shows the operating principle of DSN-assisted signal amplification strategy for miRNA detection based on Fe3O4@CP@ADA NPs.

Polystyrene Magnetic Nanocomposites as Antibiotic Adsorbents.

There are different ways for antibiotics to enter the aquatic environment, with wastewater treatment plants (WWTP) considered to be one of the main points of entrance. Even treated wastewater effluent can contain antibiotics, since WWTP cannot eliminate the presence of antibiotics. Therefore, adsorption can be a sustainable option, compared to other tertiary treatments. In this direction, a versatile synthesis of poly(styrene-block-acrylic acid) diblock copolymer/Fe3O4 magnetic nanocomposite (abbreviated as P(St-b-AAc)/Fe3O4)) was achieved for environmental applications, and particularly for the removal of antibiotic compounds. For this reason, the synthesis of the P(St-b-AAc) diblock copolymer was conducted with a reversible addition fragmentation transfer (RAFT) method. Monodisperse superparamagnetic nanocomposite with carboxylic acid groups of acrylic acid was adsorbed on the surface of Fe3O4 nanoparticles. The nanocomposites were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) analysis. Then, the nanoparticles were applied to remove ciprofloxacin (antibiotic drug compound) from aqueous solutions. The effects of various parameters, such as initial drug concentration, solution pH, adsorbent dosage, and contact time on the process were extensively studied. Operational parameters and their efficacy in the removal of Ciprofloxacin were studied. Kinetic and adsorption isothermal studies were also carried out. The maximum removal efficiency of ciprofloxacin (97.5%) was found at an initial concentration of 5 mg/L, pH 7, adsorbent’s dosage 2 mg/L, contact time equal to 37.5 min. The initial concentration of antibiotic and the dose of the adsorbent presented the highest impact on efficiency. The adsorption of ciprofloxacin was better fitted to Langmuir isotherm (R2 = 0.9995), while the kinetics were better fitted to second-order kinetic equation (R2 = 0.9973).