Core-shell Magnetic Structure Research Articles

Facile in situ synthesis and characterization of Fe@Si/zeolite Na composites with magnetic core–shell structures from natural materials for enhanced curcumin loading capacity

Curcumin is a natural polyphenol that is used in various traditional medicines. However, its inherent properties, such as its rapid degradation and metabolism, low bioavailability, and short half-life, are serious problems that must be resolved. To this end, a drug carrier incorporating natural magnetic cores in a zeolite framework was developed and applied to the loading of curcumin in ethanol solutions. In this system, curcumin is encapsulated in a zeolite Na (ZNA) magnetic core–shell structure (Fe@Si/ZNA), which can be easily synthesized using an in situ method. Synthesis of Fe3O4 nanoparticles was carried out from natural materials using a co-precipitation method. Analysis of the prepared magnetic core–shell structures and composites was carried out using vibrating-sample magnetometery, Fourier transform infrared spectroscopy, transmission electron microscopy, and x-ray diffraction. The cumulative loading of curcumin in the ZNA composite with 9% nanoparticles was found to reach 90.70% with a relatively long half-life of 32.49 min. Stability tests of curcumin loading in the composite showed that adding magnetic particles to the zeolite framework also increased the stability of the composite structure. Adsorption kinetics and isotherm studies also found that the system follows the pseudo-second-order and Langmuir isotherm models.

Crystal Structure, Morphology, and Magnetic Properties of Magnetic Nanocomposites with Iron Oxide Core and Zinc Oxide/Titanium Oxide Shell

In this work, we successfully synthesized a magnetic nanocomposite material (Fe3O4@ZnO/TiO2) with an iron oxide core and a zinc oxide/TiO2 shell (Fe3O4@ZnO/TiO2). The purpose of this study was to characterize the Crystal Structure, Morphology, and Magnetic Properties of Magnetic Nanocomposites with Iron Oxide Core and Zinc Oxide/Titanium Oxide Shell. The crystal structure of the sample was analyzed using X-ray diffraction, which identified three distinct phases: Fe3O4, ZnO, and TiO2. These phases respectively exhibited cubic spinel, hexagonal wurtzite, and tetragonal crystal structures. Transmission Electron Microscopy (TEM) characterization confirmed that the sample had a magnetic core–shell structure, with superparamagnetic properties and excellent stability owing to its spinel cubic structure, which is the primary magnetic material structure of the sample. The successful formation of the Fe3O4@ZnO/TiO2 nanocomposite represents a significant advancement in the synthesis of materials. This could serve as a basis for further investigations into magnetic materials, opening up possibilities for their application across diverse fields.

Design of a ternary magnetic composite based on a covalent organic framework and Ag nanoparticles for simultaneous photodegradation of organic pollutants under LED light irradiation: Application of BBD-RSM modeling and resolution of spectral overlap of analytes

Designing novel photocatalysts is crucial in improving pollutant removal and promoting a cleaner and healthier environment. The main objective of this study was to create a novel magnetic core-shell structure that could be used for photocatalytic applications. To achieve this goal, we used CoFe2O4 magnetic nanoparticles as the core and a covalent organic framework (COF) as the shell, which was designed to have magnetic properties and a suitable surface for further functionalization. To improve its photocatalytic properties, we added silver nanoparticles (Ag NPs) by a facile light-assisted reduction process to create a ternary composite. The presence of Ag NPs is expected to result in a broader absorption range of light and more effective degradation of pollutants through plasmonic sensitization and the transfer of bandgap energy into the visible light spectra. We characterized the prepared composite using various chemical and physical techniques, and then examined its ability to remove two stable organic pollutants, methylene blue (MB) dye and 4-nitrophenol (4-NP), simultaneously. The strong spectral overlap between these pollutants posed a challenge for conventional spectroscopic methods to accurately measure their concentration. To overcome this, a rapid and new method, namely extended ratio subtraction method (EXRSM), was utilized to separate and remove the spectral overlap. We further optimized the reaction conditions using response surface methodology (RSM) modeling techniques. Our findings indicated that the designed composite was capable of degrading organic pollutants under the visible light radiation of an LED lamp.

Magnetic Nanoclusters Stabilized with Poly[3,4-Dihydroxybenzhydrazide] as Efficient Therapeutic Agents for Cancer Cells Destruction.

Magnetic structures exhibiting large magnetic moments are sought after in theranostic approaches that combine magnetic hyperthermia treatment (MH) and diagnostic magnetic resonance imaging in oncology, since they offer an enhanced magnetic response to an external magnetic field. We report on the synthesized production of a core-shell magnetic structure using two types of magnetite nanoclusters (MNC) based on a magnetite core and polymer shell. This was achieved through an in situ solvothermal process, using, for the first time, 3,4-dihydroxybenzhydrazide (DHBH) and poly[3,4-dihydroxybenzhydrazide] (PDHBH) as stabilizers. Transmission electron microscopy (TEM) analysis showed the formation of spherical MNC, X-ray photoelectronic spectroscopy (XPS) and Fourier transformed infrared (FT-IR) analysis proved the existence of the polymer shell. Magnetization measurement showed saturation magnetization values of 50 emu/g for PDHBH@MNC and 60 emu/g for DHBH@MNC with very low coercive field and remanence, indicating that the MNC are in a superparamagnetic state at room temperature and are thus suitable for biomedical applications. MNCs were investigated in vitro, on human normal (dermal fibroblasts-BJ) and tumor (colon adenocarcinoma-CACO2, and melanoma-A375) cell lines, in view of toxicity, antitumor effectiveness and selectivity upon magnetic hyperthermia. MNCs exhibited good biocompatibility and were internalized by all cell lines (TEM), with minimal ultrastructural changes. By means of flowcytometry apoptosis detection, fluorimetry, spectrophotometry for mitochondrial membrane potential, oxidative stress, ELISA-caspases, and Western blot-p53 pathway, we show that MH efficiently induced apoptosis mostly via the membrane pathway and to a lower extent by the mitochondrial pathway, the latter mainly observed in melanoma. Contrarily, the apoptosis rate was above the toxicity limit in fibroblasts. Due to its coating, PDHBH@MNC showed selective antitumor efficacy and can be further used in theranostics since the PDHBH polymer provides multiple reaction sites for the attachment of therapeutic molecules.

Off-Diagonal Magnetoimpedance in Annealed Amorphous Microwires with Positive Magnetostriction: Effect of External Stresses

It was observed recently that the giant magnetoimpedance (GMI) effect in Fe-rich glass-coated amorphous microwires with positive magnetostriction can be improved significantly by means of post-annealing. The increase in the GMI is attributed to the induced helical magnetic anisotropy in the surface layer of the microwire, which appears after the annealing. The application of external stresses to the microwire may result in changes in its magnetic structure and affect the GMI response. In this work, we study theoretically the influence of the tensile and torsional stresses on the off-diagonal magnetoimpedance in annealed amorphous microwires with positive magnetostriction. The static magnetization distribution is analyzed in terms of the core–shell magnetic structure. The surface impedance tensor is obtained taking into account the magnetoelastic anisotropy induced by the external stresses. It is shown that the off-diagonal magnetoimpedance response exhibits strong sensitivity to the magnitude of the applied stress. The obtained results may be useful for sensor applications of amorphous microwires.

Constructing magnetic iron-based core-shell structure and dielectric nitrogen-doped reduced graphene oxide nanocomposite for enhanced microwave absorption performance

A ferromagnetic nanocomposite Fe3O4@Fe/Fe4N/CFe15.1-NrGO, which is composed of elemental iron-based, iron nitride-based and iron carbide-coated ferroferric oxide core-shell structured nanospheres and nitrogen-doped partially-reduced graphene oxide (NrGO), has been successfully prepared by combining an initial hydrothermal processing, subsequent reducing agent impregnation and final solid-state thermal reduction. And then, we investigate the microwave absorption performance of Fe3O4@Fe/Fe4N/CFe15.1-NrGO nanocomposite in paraffin dispersion. When the loading mass of Fe3O4@Fe/Fe4N/CFe15.1-NrGO is 9.0 wt% in paraffin dispersion, the minimum reflection loss (RLmin) of microwave is as high as −30.5 dB at the thickness of 1.5 mm, and the corresponding effective absorption bandwidth (EAB < -10 dB) of 4.4 GHz (13.6 ∼ 18.0 GHz) is the 27.5% of the entirely measuring bandwidth from (2.0 ∼ 18.0 GHz). The excellent microwave absorbing performances of nanocomposite Fe3O4@Fe/Fe4N/CFe15.1-NrGO may be attributed to the following twoaspects: (i) the interfacial polarization of the core-shell structure of spheroidal iron-based constituents and the interface between an iron-based nanosphere and dielectric lamellar NrGO and (ii) a synergistic effect between dielectric properties of lamellar-structured NrGO and the magnetic properties of core-sell structured Fe3O4@Fe/Fe4N/CFe15.1. This electromagnetic absorber with core-shell structure and dielectric graphene properties can satisfy the requirements of ideal absorbers, such as strong absorption ability, broad absorption bandwidth, thin absorber thickness and low density. In addition, this work also provides a promising strategy to synthesize multivariate two-dimensional nanocomposite with light-weight and high absorption performance.

Resolving magnetic contributions in BiFeO3 nanoparticles using First order reversal curves

BiFeO3 (BFO) nanoparticles (NPs) were studied using First-Order Reversal Curve (FORC) and temperature-dependent magnetometry measurements. The BFO NPs were fabricated by a sol–gel method, while the crystal structure and the average particle radius were obtained by powder X-ray diffraction analysis and Small-Angle X-Ray Scattering (SAXS) measurements, respectively. The NP size varies below and above the typical bulk BFO spin cycloid length (λ= 62 nm). Below λ, the NPs show ferromagnetic-like hysteresis loops where the saturation magnetization decreases while nanoparticle size rises. This magnetic behavior changes for NP size over λ, which only exhibits a paramagnetic contribution. The FORC distributions indicate the presence of two competing size-dependent contributions to the observed magnetic signal Also, the FORC distributions show that in the ferromagnetic regime there are two competing size-dependent contributions to the observed magnetic signal. Our results suggest the existence of a magnetic core–shell structure in NPs below λ, possibly driven by the strong spin–lattice coupling.

Chemiluminescence sensing of adenosine using DNA cross-linked hydrogel-capped magnetic mesoporous silica nanoparticles

At present, a host of high-sensitivity and selective tumor marker detection methods play a central role in various research fields and assay platforms. Here, a method for DNA cross-linked hydrogel-capped magnetic core-shell structure mesoporous silica nanoparticles (Fe3O4@nSiO2@mSiO2) based on target stimulus was proposed. Specifically, Fe3O4@nSiO2@mSiO2 nanoparticles with nucleic acid promoter units were prepared. The promoter induces the predesigned modified polyacrylamide DNA strand to carry out hybridization chain reaction on the surface of Fe3O4@nSiO2@mSiO2 nanoparticles, forming a hydrogel coating on the surface of Fe3O4@nSiO2@mSiO2 nanoparticles. Under the stimulation of adenosine, Fe3O4@nSiO2@mSiO2 released the signal molecule luminol. Simultaneously, the MIL-101（Fe）material, a signal amplification molecule, was released from the DNA hydrogel. Compared with the traditional gated mesoporous silica system, the DNA hydrogel-coated Fe3O4@nSiO2@mSiO2 is not easy to leak and has a higher loading capacity. In addition, the optical background of DNA hydrogels is low, combined with MOFs materials, even about 1.4 × 10−10 M adenosine can be detected in this biosensor. Based on the combination of DNA hydrogels, MOFs conjugates and gating systems, the construction of biosensors will be more eye-catching, which will expand new ideas for biosensor platform manufacturing.

Constructing Magnetic Iron-Based Core-Shell Structure and Dielectric Nitrogen-Doped Reduced Graphene Oxide Nanocomposite for Enhanced Microwave Absorption Performance

Constructing Magnetic Iron-Based Core-Shell Structure and Dielectric Nitrogen-Doped Reduced Graphene Oxide Nanocomposite for Enhanced Microwave Absorption Performance

Templated Mesoporous Silica Outer Shell for Controlled Silver Release of a Magnetically Recoverable and Reusable Nanocomposite for Water Disinfection.

In this work, we encapsulated Fe3O4@SiO2@Ag (MS-Ag), a bifunctional magnetic silver core-shell structure, with an outer mesoporous silica (mS) shell to form an Fe3O4@SiO2@Ag@mSiO2 (MS-Ag-mS) nanocomposite using a cationic CTAB (cetyltrimethylammonium bromide) micelle templating strategy. The mS shell acts as protection to slow down the oxidation and detachment of the AgNPs and incorporates channels to control the release of antimicrobial Ag+ ions. Results of TEM, STEM, HRSEM, EDS, BET, and FTIR showed the successful formation of the mS shells on MS-Ag aggregates 50-400 nm in size with highly uniform pores ∼4 nm in diameter that were separated by silica walls ∼2 nm thick. Additionally, the mS shell thickness was tuned to demonstrate controlled Ag+ release; an increase in shell thickness resulted in an increased path length required for Ag+ ions to travel out of the shell, reducing MS-Ag-mS' ability to inhibit E. coli growth as illustrated by the inhibition zone results. Through a shaking test, the MS-Ag-mS nanocomposite was shown to eradicate 99.99+% of a suspension of E. coli at 1 × 106 CFU/mL with a silver release of less than 0.1 ppb, well under the EPA recommendation of 0.1 ppm. This high biocidal efficiency with minimal silver leach is ascribed to the nanocomposite's mS shell surface characteristics, including having hydroxyl groups and possessing a high degree of structural periodicity at the nanoscale or "smoothness" that encourages association with bacteria and retains high Ag+ concentration on its surface and in its close proximity. Furthermore, the nanocomposite demonstrated consistent antimicrobial performance and silver release levels over multiple repeated uses (after being recovered magnetically because of the oxidation-resistant silica-coated magnetic Fe3O4 core). It also proved effective at killing all microbes from Long Island Sound surface water. The described MS-Ag-mS nanocomposite is highly synergistic, easy to prepare, and readily recoverable and reusable and offers structural tunability affecting the bioavailability of Ag+, making it excellent for water disinfection that will find wide applications.

Photocatalytic activation of peroxydisulfate by magnetic Fe3O4@SiO2@TiO2/rGO core–shell towards degradation and mineralization of metronidazole

In the present work, the degradation of metronidazole (MNZ) antibiotic by photocatalytic activation of peroxydisulfate (PDS) was studied in a batch environment. In this regard, TiO2 nanoparticles (NPs) with magnetic core–shell structure were anchored on the reduced graphene oxide (rGO) to fabricate the Fe3O4/SiO2/TiO2@rGO nanocomposite (FST@rGO) and applied as a recoverable heterogeneous catalyst along with ultraviolet (UV) light for activation of PDS. The nanocomposite was synthesized successfully by the sol–gel method and then characterized by using FESEM, EDS, XRD, Raman, EIS, BET, TEM, VSM, PL, and UV–VIS techniques. The degradation rate of MNZ was evaluated as a function of different concentrations of catalyst, PDS, and MNZ as well as the solution pH to determine the optimum operational conditions. Photocatalytic activity of TiO2 toward the degradation of MNZ was enhanced significantly after its magnetization by core–shell structure. Activated PDS exhibited excellent performance for degradation of MNZ in the wide range of pH. Under optimum conditions (pH:7, PDS:3 mM and FST@rGO:0.1 g L-1), >94% of MNZ and 58% of total organic carbon (TOC) were removed within 60 min. Based on trapping tests, HO•, 1O2, holes, and SO4•− species were identified as major reactive species during the MNZ degradation process. After four cycles of reuse the FST@rGO was able to remove 63.5% of MNZ, revealing relative reusability potential of the nanocomposite. In summary, integration of UV light and FST@rGO toward the activation of PDS could be introduced as a promising technique for application in environmental objectives, due to the good performance in the degradation/mineralization, easily separation, and high reusability potential of catalyst.

Magnetic core-shell structure in-situ encapsulated in bamboo-derived carbon skeleton for efficient microwave absorption

A fast renewable bamboo source is first adopted to synthesize carbon-based magnetic composites as efficient and sustainable microwave absorbers through a carbothermal in-situ growth process. The magnetic core-shell particles uniformly encapsulated in porous carbon skeleton can promote magnetic loss and graphitization of carbon shell. The gradient graphitization of graphitic shells and disordered framework is favorable for conductive loss and polarization relaxation. By controlling the magnetic content, the microstructure, magnetic property, graphitization and absorbing performance of the composites can be delicately manipulated. As expected, the strong reflection loss surpassing − 40 dB is achieved at both high frequency of 14.1 GHz (1.9 mm) and low frequency of 5.5 GHz. Meanwhile, a wide effective bandwidth of 4.7 GHz covering from 6.6 GHz to 11.3 GHz is achieved. This work demonstrates that the combination of bamboo carbon with magnetic cores could provide a perspective for refining low frequency and thin thickness characteristics for plant-derived microwave absorption.

Spherical Nucleic Acid Mediated Functionalization of Polydopamine-Coated Nanoparticles for Selective DNA Extraction and Detection.

Magnetic nanoparticles have been widely used for the separation of biomolecules for biological applications due to the mild and efficient separation process. In previous studies, core-shell magnetic nanoparticles (NPs) were designed for DNA extraction without much sequence specificity. In this work, to achieve highly selective DNA extraction, we designed a core-shell magnetic structure by coating polydopamine (PDA) on Fe3O4 NPs. Without divalent metal ions, PDA does not adsorb DNA at neutral pH. The Fe3O4@PDA NPs were then functionalized with spherical nucleic acids (SNA) to provide a high density of probe DNA. Fe3O4@PDA@SNA was also compared with when a linear SH-DNA was covalently attached to the NPs surface, showing a higher density of the probe SNA than SH-DNA can be loaded on the NPs in a remarkably shorter time. Nonspecific DNA extraction was thoroughly inhibited by both probes. DNA extraction by the Fe3O4@PDA@SNA was more effective as well as 5-fold faster than by the Fe3O4@PDA@SH-DNA, probably due to the favorable standing conformation of DNA strands in SNA. Moreover, extraction by Fe3O4@PDA@SNA showed high robustness in fetal bovine serum, and the same design can be used for selective detection of DNA. Finally, the method was also demonstrated on silica NPs and WS2 nanosheets for coating with PDA and SNA. Altogether, our findings revealed an interesting and general surface modification strategy using PDA@SNA conjugates for sequence-specific DNA extraction.

Synthesis and surface modification of magnetic Fe3O4@SiO2 core-shell nanoparticles and its application in uptake of scandium (III) ions from aqueous media.

The main objective of this work is to produce an eco-friendly and economically nano-adsorbent which can separate scandium metal ions Sc from a model aqueous phase prior to applying these adsorbents in industrial filed. The magnetic core-shell structure Fe3O4@SiO2 nanoparticles were synthesized by modified Stöber method and functionalized with (3-aminopropyl) triethoxysilane APTES as a coupling agent and ethylenediaminetetraacetic acid (EDTA) as a ligand. Magnetic nano support adsorbents exhibit many attractive opportunities due to their easy removal and possibility of reusing. The ligand grafting was chemically robust and does not appreciably influence the morphology or the structure of the substrate. To evaluate the potential, the prepared hybrid nanoparticles were used as nano-adsorbent for Sc ions from model aqueous solutions due to the fact that rare earth elements (REEs) have a strong affinity for oxygen and nitrogen donors. The iron oxide nanoparticles were prepared by co-precipitation method at pH 10 and pH 11 to get the best morphology and nanoscale dimensions of iron oxide magnetic nanoparticles. The particle size, morphology, specific surface area, and surface modification were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), and X-ray powder diffraction (XRD). The results showed that the Fe3O4 nanoparticles with average particle size of 15 ± 3 nm were successfully synthesized at pH 11, and 25 °C. Moreover, the prepared Fe3O4 nanoparticles were coated with amorphous SiO2 and functionalized with amino and carboxyl groups. The adsorption study conditions of Sc are as follows: the initial concentrations of the Sc model solution varied 10-50 mg/L, 20 mL volume, 20-80 mg of the Fe3O4@SiO2-COO adsorbent, pHrange of 1-5, and 5 h contact time at 25 °C temperature. The adsorption equilibrium was represented with Langmuir, Freundlich, and Temkin isotherm models. Langmuir model was found to have the correlation coefficient value in good agreement with experimental results. However, the adsorption process followed pseudo-second-order kinetics.

Magnetic covalently immobilized nickel complex: A new and efficient method for the Suzuki cross‐coupling reaction

In this study, an efficient procedure was reported to prepare Fe3O4@SiO2magnetic nanoparticles (MNPs) with immobilized nickel NPs. In order to increase the activity of this catalyst, creatine as a ligand with high content of nitrogen atoms was linked onto the magnetic core–shell structure. Then, Ni(II) ions were coordinated on the surface of the silica‐coated MNPs and reduced to Ni(0) NPs to obtain the final catalyst. The catalytic activity of the prepared catalyst was studied for the synthesis of biaryl derivatives via the Suzuki–Miyaura cross‐coupling reaction in high yields. The catalyst could also be recovered and reused with no loss of activity over five successful runs.

A facile, two-step synthesis and characterization of Fe 3 O 4 -L Cysteine -graphene quantum dots as a multifunctional nanocomposite.

In this research, a facile, two-step synthesis of Fe3O4–LCysteine–graphene quantum dots (GQDs) nanocomposite is reported. This synthesis method comprises the preparation of GQDs via hydrothermal route, which should be conjugated to the LCysteine functionalized core–shell magnetic structure with the core of about 7.5-nm iron oxide nanoparticle and 3.5-nm LCysteine shell. LCysteine, as a biocompatible natural amino acid, was used to link magnetite nanoparticles (MNPs) with GQDs. X-ray powder diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray were used to investigate the presence and formation of MNPs, {text{L}}_{{{text{Cysteine}}}} functionalized MNPs, and final hybrid nanostructure. Morphology and size distribution of nanoparticles were demonstrated by scanning electron microscopy and transmission electron microscopy. Finally, the magnetic and optical properties of the prepared nanocomposite were measured by vibrating sample magnetometer, ultraviolet–visible, and photoluminescence spectroscopy. The results show that Fe3O4–LCysteine–GQDs nanocomposite exhibits a superparamagnetic behavior at room temperature with high saturation magnetization and low magnetic coercivity, which are 28.99 emu/g and 0.09 Oe, respectively. This nanocomposite also shows strong and stable emission at 460 nm and 530 nm when it is excited with the 235 nm wavelength. The magnetic GQDs structure also reveals the absorption wavelength at 270 nm. Therefore, Fe3O4–LCysteine–GQDs nanocomposite can be considered as a potential multifunctional hybrid structure with magnetic and optical properties simultaneously. This nanocomposite can be used for a wide range of biomedical applications like magnetic resonance imaging (MRI) contrast agents, biosensors, photothermal therapy, and hyperthermia.

Laccase immobilization on core-shell magnetic metal-organic framework microspheres for alkylphenol ethoxylate compound removal

An amino-functionalized magnetic core-shell structure metal-organic framework (MOF), Fe3O4-NH2@MIL-100 (Fe), has been successfully constructed by a step-by-step method. The composite microspheres exhibited excellent magnetic characteristics, large surface area, and pore size, which were employed for the Trametes versicolor laccase immobilization. The immobilized laccase exhibited high activity recovery (72.05%) and significantly improved stability. The reactive activity remained 75% of its initial activity after storage for 4 weeks. Additionally, when the ambient reached 80 °C, the good stability enabled the immobilization laccase to keep 33% residual activity even after 6 h storage. Application of the immobilized laccase for environmental pollutant alkylphenol polyethoxylate (APEO) removal was also investigated. The results showed the immobilized laccase can remove 100% octylphenol polyethoxylate (OPEO) and 98.16% nonylphenol polyethoxylate (NPEO) in 200 min, and can still achieve 63.42% and 46.17% removal efficiency for OPEO and NPEO after reusing four cycles, respectively. The novel MOF based core-shell magnetic composite microspheres introduced by this study showed promising applications as laccase immobilization support, and both the immobilized laccase and its support had great potential in wastewater treatment.

Selective enrichment-release of trace dibutyl phthalate via molecular-imprinting based photo-controlled switching followed by high-performance liquid chromatography analysis.

A novel intelligent photo-controlled molecularly imprinted polymers were synthesized, based on the magnetic core-shell structure, with 4-[(4-methacryloyloxy) phenylazo] benzenesulfonic acid as the functional monomer and ethylene glycol dimethyl acrylate as the cross-linking agent. Subsequently, a series of light-controlled enrichment-release performance showed that it only took about 30 and 10min to reach the equilibrium photosensitive characteristic peak, respectively. The photo-controlled polymers could intelligently select target molecules, the maximum adsorption capacity for dibutyl phthalate was 3.88mg/g. However, the adsorption capacity for its structural analogue dicyclohexyl phthalate was only 0.88mg/g. The Freundlich and Langmuir isothermal equations were discussed for the specific enrichment process. Finally, the photo-controlled molecularly imprinted polymers were successfully applied to the selective detection of dibutyl phthalate, with the recovery rate of 95.4-98.4%. It could be used for the analysis of trace dibutyl phthalate in actual samples.

Photocatalytic degradation of MB dye by the magnetically separable 3D flower-like Fe3O4/SiO2/MnO2/BiOBr-Bi photocatalyst

The flower-like Fe3O4/SiO2/MnO2/BiOBr-Bi magnetic composite photocatalyst was prepared in this work. The combination of BiOBr and Bi metal with flower-like MnO2 constituted a heterojunction structure, which increased the specific surface area of the photocatalyst and promoted the separation of photo-generated carriers, resulting in the enhanced catalytic performance. The morphologies and the compositions of the photocatalyst were characterized in detail. Under simulated light, the degradation of organic dye methylene blue (MB) was used to research the photocatalytic activity. In the case of 15 mg photocatalyst, it was found that the photocatalytic degradation efficiency to the MB solution was 95.23% within 150 min. Moreover, the degradation rate of MB could still reach 81.11% after four cycles. The design of flower-like composites with magnetic core-shell structure provided a new method for fabricating photocatalysts having excellent catalytic performance and cyclic stability.

A Core–Shell Model for Magnetoimpedance in Stress-Annealed Fe-Rich Amorphous Microwires

The magnetoimpedance effect in a stress-annealed Fe-rich amorphous microwire with induced magnetic anisotropy in a surface region is studied theoretically. The static magnetization distribution within the microwire is described in the framework of the core–shell magnetic structure. It is assumed that the microwire has an axial magnetic anisotropy in the inner core and a helical anisotropy in the external shell appearing due to the stress-annealing. Both the diagonal and off-diagonal magnetoimpedance responses are found in terms of the surface impedance tensor. The influence of the bias current on the magnetoimpedance is analyzed. The obtained theoretical dependences are shown to be in a qualitative agreement with the results of recent experimental studies of the magnetoimpedance effect in stress-annealed Fe-rich glass–coated amorphous microwires.