Magnetic Composite Microspheres Research Articles

Investigation on Formation Mechanism of Magnetic Nanoparticles-coated on Polystyrene Microspheres in Aqueous Solution of Anhydrous Ethylenediamine and Hexamethylene Tetramine

The monodispersed polystyrene (PS) microspheres were modified by concentrated sulfuric acid to obtain PS microspheres with negative charges, and then polystyrene/magnetic composite microspheres were fabricated by a simple and novel method in aqueous solution of anhydrous Ethylene diamine (EDA) and Hexamethylenetetramine (HMTA). Through serials of contrast experiments (based on different precursor ratios) and characteristic investigations of target samples, we have discovered the functions of EDA and HMTA, respectively. EDA not only acted as a weak base providing OH- ions, but also acted as a chelating combining with Fe2+ ions, which could control the concentration of Fe2+ ions, and resulted in the pure Fe3O4 nanoparticle coated on the surface of PS microspheres. Otherwise, the typical XRD peaks of FeOOH and Fe3O4 appeared, simultaneously, if HMTA played an action in the formation magnetic nanoparticles-coated PS microspheres. It indicated that HMTA could provide OH- ions and make Fe2+ to become FeOOH and Fe3O4, simultaneously, which could be confirmed the reaction mechanism suggested by us. Finally, the corresponding possible reaction mechanisms of EDA and HMTA for fabricating magnetic composite microspheres have been suggested in detail by combining SEM, XRD, FTIR analysis together.

The Adsorption Capacity of GONs/CMC/Fe₃O₄ Magnetic Composite Microspheres and Applications for Purifying Dye Wastewater.

Graphene oxide nanosheets (GONs)/carboxymethyl chitosan (CMC)/Fe3O4 magnetic composite microspheres (MCMs) were prepared by enclosing Fe3O4 particles with CMC and GONs in turn. The microstructures of GONs and GONs/CMC/Fe3O4 MCMs were characterized by FTIR, XRD, TEM, and SEM. The effects of GON content, pH value, and adsorption time on the adsorption capacity of the MCMs were investigated. The results show that the GONs/CMC/Fe3O4 MCMs have a greater specific surface area and a strong adsorption capacity for dye wastewater. Meanwhile, the adsorption mechanism was investigated, and the results accorded with the pseudo-second-order kinetic model and the Freundlich isotherm model. The search results indicate that GONs/CMC/Fe3O4 MCMs can be used to purify dye wastewater and has an important potential use in the practical purification of dye wastewater.

Fabrication of imidazolium-functionalized magnetic composite microspheres for selective recognition and separation of heme proteins

Imidazolium-functionalized magnetic composite microspheres were successfully synthesized, which exhibited high hemoglobin binding capacity (6321 mg g−1) and excellent selectivity.

Facile preparation of Fe3O4@MOF core-shell microspheres for lipase immobilization

In this article, a Fe3O4@MOF core-shell microsphere has been successfully prepared by growing MIL-100(Fe), three dimensional (3D) metal–organic frameworks (MOFs) onto Fe3O4 nanoparticles. The resultant composite microsphere exhibited both magnetic characteristics and large specific surface area, making them excellent candidates for enzyme immobilization. Candida rugosa lipase was immobilized as a model enzyme on core-shell microspheres. The results showed that the immobilized enzyme for hydrolysis of olive oil retained >65% of its initial activity at 65°C over 6h; and the residual activity still remained about 60% of the initial activity after the 10th catalysis run. Therefore, such MOF based core-shell magnetic composite microspheres showed promising applications as an enzyme immobilization support.

Dual-Mode Encoded Magnetic Composite Microsphere Based on Fluorescence Reporters and Raman Probes as Covert Tag for Anticounterfeiting Applications.

Utilizing fluorescence reporters and SERS probes as the security labels, a series of dual-mode encoded magnetic composite microspheres with micrometer size was designed and prepared for anticounterfeiting applications. At first, the micro-meter-sized melamine formaldehyde microspheres with different fluorescence molecules (FMF) were prepared by precipitation polymerization, and then the magnetite composite microspheres (FMF/MNPs) were fabricated by direct immobilization of magnetic nanoparticles (MNPs) onto the surface of FMF microspheres. After deposition of Ag nanoparticles (Ag-NPs) onto FMF/MNPs microspheres, the SERS probes were absorbed onto the surface of Ag-NPs, and then a protection layer of silica was coated on the composite microspheres by Stöber method. The combination of different fluorescence reporters and SERS probes greatly increased the encoding complexity and volume for high-level anticounterfeiting. The structure of the dual-encoded FMF/MNPs/Ag-NPs/SiO2 composite microspheres was characterized by FESEM, TEM, FLS(fluorescence spectrometer), XRD, VSM, UV-vis and EDS. The embedded magnetic nanoparticles enable the composite microspheres to be quickly isolated from the marked latex paint by magnet at the concentration of as low as 1 ppm, and the covert tag information can be read out even from one composite microsphere. In addition, the covert security information in the marked coating film can be also read out in situ and the existence of the composite microspheres does not influence the visible appearance of the coating film. All the above outstanding properties will make these dual-mode encoded composite microspheres as advanced security tags for next-generation anticounterfeiting applications.

Highly Sensitive and Reproducible SERS Performance from Uniform Film Assembled by Magnetic Noble Metal Composite Microspheres.

To realize highly sensitive and reproducible SERS performance, a new route was put forward to construct uniform SERS film by using magnetic composite microspheres. In the experiment, monodisperse Fe3O4@SiO2@Ag microspheres with hierarchical surface were developed and used as building block of SERS substrate, which not only realized fast capturing analyte through dispersion and collection under external magnet but also could be built into uniform film through magnetically induced self-assembly. By using R6G as probe molecule, the as-obtained uniform film exhibited great improvement on SERS performance in both sensitivity and reproducibility when compared with nonuniform film, demonstrating the perfect integration of high sensitivity of hierarchal noble metal microspheres and high reproducibility of ordered microspheres array. Furthermore, the as-obtained product was used to detect pesticide thiram and also exhibited excellent SERS performance for trace detection.

Preparation of light core/shell magnetic composite microspheres and their application for lipase immobilization

Fe3O4@P(GMA-DVB-MAA) magnetic composite microspheres were prepared by facile one-pot distillation–precipitation polymerization and were modified with amino groups for the immobilization of lipase.

Preparation of monodisperse cross-linked PS-DVB-GMA-amino-Fe3O4 magnetic microspheres with Cu (II) ions removal property

The monodisperse cross-linked PS-DVB-GMA-amino-Fe3O4 magnetic microspheres with functional group of amino were synthase by seed swelling method using PS microspheres as seeds, and glycidyl acrylate as monomer in the swelling polymerization; and then modified poly (styrene-glycidyl methacrylate) (PS-DVB-GMA) microspheres with ethylene diamine to form amino-groups; subsequently, Fe3O4 nanoparticles were grafted on the microspheres through in situ precipitation reaction. The morphology, composition, magnetic properties, and crystalline structure of the magnetic microspheres were characterized by scanning electron microscope with energy dispersive analysis of X-rays (SEM/EDX), transmission electron microscopy(TEM), vibrating sample magnetometer(VSM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) methods, respectively. The resulting PS-DVB-GMA-amino-Fe3O4 magnetic microspheres were tested for their ability to remove copper (II) ions from an aqueous solution in batch experiments. The effects of adsorption time and pH value on the adsorbed dosage of copper ions on magnetic microspheres was investigated. Besides, two adsorption isotherm models (i.e., the Langmuir and the Freundlich models) were used to fit the experimental isotherm adsorption data. The average size of microspheres was 5.92 μm with the PDI was 0.024. The composite magnetic microspheres could be easily separated from solution by magnetic decantation using a permanent magnet. The adsorption experiments demonstrate that copper ions adsorption onto the PS-DVB-GMA-amino-Fe3O4 magnetic microspheres reaches a maximum after the 45 min. The maximum adsorption capacities (q e = 76.8 mg/g) was reached at the pH value of 5.0 when the temperature was 25 °C, and by simulating the experimental data with the Langmuir, the maximum equilibrium absorption capacity of PS-DVB-GMA-amino-Fe3O4 magnetic microspheres was 134.0216 mg/g, showing a good adsorptive property to Cu (II).

Simultaneous removal of acid green 25 and mercury ions from aqueous solutions using glutamine modified chitosan magnetic composite microspheres

In this current work, the magnetic composite microsphere containing glutamine modified chitosan and silica coated Fe3O4 nanoparticles (CS-Gln-MCM) has been successfully prepared and extensively characterized, which is a kind of biodegradable materials. CS-Gln-MCM shows enhanced removal efficiency for both acid green 25 (AG25), an amphoteric dye, and mercury ions (Hg2+) from water in the respective while measured pH range compared with chitosan magnetic composite microsphere (CS-MCM) without modification. It is due to the fact that the grafted amino acid provides a variety of additional adsorption active sites and diverse adsorption mechanisms are involved. In AG25 and Hg2+ aqueous mixture, the modified adsorbents bear preferential adsorption for AG25 over Hg2+ in strong acidic solutions ascribed to multiple interactions between AG25 and CS-Gln-MCM, such as hydrogen bonding and electrostatic interactions. While, in weak acidic conditions, an efficient simultaneous removal is observed for different adsorption effects involved in aforementioned two pollutants. Besides, CS-Gln-MCM illuminates not only short equilibrium time for adsorption of each pollutant less than 20.0 min but also rapid magnetic separation from water and efficient regeneration after saturated adsorption. Therefore, CS-Gln-MCM bears great application potentials in water treatment.

Monodispers and Multifunctional Magnetic Composite Core Shell Microspheres for Demulsification Applications

AbstractIron oxide@Poly(Glycidylmethacrylate‐methyl methacrylate‐divinyl benzene) magnetic composite core shell microspheres Fe3O4@P(GMA‐MMA‐DVB) with epoxy group on the surface was designed and synthesized by solvothermal process followed by distillation polymerization. The surface epoxy group was modified with amino group of ethylene diamine (EDA) to prepare Fe3O4@P(GMA‐MMA‐DVB)/NH2 microspheres, and then effects of modification on the structure, interfacial behavior and hence demulsification of the amino modified epoxy coating were examined. The prepared magnetic microspheres were characterized using a laser particle size analyzer, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. Fourier transform infrared spectrometer analysis indicates the presence of epoxy group, amino group and Fe3O4 in the final Fe3O4@P(GMA‐MMA‐DVB) and Fe3O4@P(GMA‐MMA‐DVB)/NH2 magnetic core shell microspheres. Our experimental results show that Fe3O4@P(GMA‐MMA‐DVB)/NH2 magnetic core shell microspheres exhibit good interfacial and demulsification properties and able to remove emulsified water from stable emulsion. The resulting microspheres showed excellent magnetic properties and further these can be recycled and reused by magnetic separation.

Preparation of chitosan-graft-polyacrylamide magnetic composite microspheres for enhanced selective removal of mercury ions from water

A novel magnetic composite microsphere based on polyacrylamide (PAM)-grafted chitosan and silica-coated Fe3O4 nanoparticles (CS-PAM-MCM) was successfully synthesized by a simple method. The molecular structure, surface morphology, and magnetic characteristics of the composite microsphere were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), and scanning electron microscopy (SEM). The prepared CS-PAM-MCM was applied as an efficient adsorbent for the removal of copper(II), lead(II), and mercury(II) ions from aqueous solutions in respective single, binary, and ternary metal systems. Compared with chitosan magnetic composite microsphere (CS-MCM) without modification, CS-PAM-MCM showed improved adsorption capacity for each metal ion and highly selective adsorption for Hg from Pb and Cu. This improvement is attributed to the formation of stronger interactions between Hg and the amide groups of PAM branches for chelating effects. The adsorption isotherms of Hg/Cu and Hg/Pb binary metal systems onto CS-PAM-MCM are both well-described by extended and modified Langmuir models, indicating that the removal of the three aforementioned metal ions may follow a similar adsorption manner; that is, through a homogeneous monolayer chemisorption process. Furthermore, these magnetic adsorbents could be easily regenerated in EDTA aqueous solution and reused virtually without any adsorption capacity loss.

Synthesis of CoFe2O4/MCM-41/TiO2 composite microspheres and its performance in degradation of phenol

The core–shell structural magnetically separable catalyst CoFe2O4/MCM-41/TiO2 composite microspheres were synthesized, and the catalytic properties were systematically studied. Specifically, the preformed monodisperse magnetic CoFe2O4 particles were prepared by solvothermal method, the intermediate MCM-41 layer was prepared by the method of liquid crystal templating mechanism and subsequent TiO2 layer was synthesized by the method of esters precipitation. In this approach, the CoFe2O4/MCM-41/TiO2 composite microspheres synthesized under optimum condition were spherical particles, about 660nm in diameter. It consisted of mesoporous structure with a surface area of 682.83m2g−1, an average pore size of 2.93nm and excellent magnetic properties of 7.43emug−1. The photocatalytic activities were evaluated under simulated sunlight irradiation using the photocatalytic degradation of phenol as a model reaction. The prepared CoFe2O4/MCM-41/TiO2 composite microspheres showed higher photodegradation ability for phenol than Degussa P25. The degradation of phenol achieved up to 85% after 120min under simulated sunlight irradiation, and the composite microspheres could be recycled and reused. The synthesized magnetic hybrid composite microspheres displayed high photocatalytic efficiency and potential applications for cleaning polluted water with the help of magnetic separation.

Preparation and characterization of hollow magnetic composite nanoparticles for immobilized pectinase

The aims of the present work were to establish the magnetite core based nanometer microspheres of morphology concept of multifunctional core/shell nanometer microspheres which had the potential use as pectinase supporter. We had described the convenient method of synthesis and characterization of biodegradable/biocompatible Fe3O4/SiO2@CMCS. The larger aspect ratios of hollow materials could be taken up by cells in larger amounts and have higher internalization rates, which was of great significance for the enhancement of chemotherapy effectiveness. We investigated the enzymatic activity of pectinase adsorbing on novel hollow magnetic composite microspheres. The immobilized enzyme retained more than 50% of its initial activity over 40days, and the optimum temperature/pH also increased to the range of 50–60°C/3.0–5.0. The immobilized enzyme exhibited great operational stability, and more than 75% residual activity was observed after 10 batch reactions. Moreover, the Fe3O4/SiO2@Carboxymethyl chitosan (CMCS) support presented a very simple, mild and time-saving process for enzyme immobilization. This strategy of immobilizing pectinase made expensive enzymes economically viable, strengthening repeated usage of them because of their rapid and easy separation with a magnet.

Selective Capture and Quick Detection of Targeting Cells with SERS-Coding Microsphere Suspension Chip.

Circulating tumor cells (CTCs) captured from blood fluid represent recurrent cancers and metastatic lesions to monitor the situation of cancers. We develop surface-enhanced Raman scattering (SERS)-coding microsphere suspension chip as a new strategy for fast and efficient capture, recovery, and detection of targeting cancer cells. Using HeLa cells as model CTCs, we first utilize folate as a recognition molecule to be immobilized in magnetic composite microspheres for capturing HeLa cells and attaining high capturing efficacy (up to 95%). After capturing cells, the composite microsphere, which utilizes a disulfide bond as crosslinker in the polymer shell and as a spacer for linking folate, can recycle 90% cells within 20 min eluted by glutathion solution. Taking advantage of the SERS with fingerprint features, we characterize captured/recovered cells with the unique signal of report-molecule 4-aminothiophenol through introducing the SERS-coding microsphere suspension chip to CTCs. Finally, the exploratory experiment of sieving cells shows that the magnetic composite microspheres can selectively capture the HeLa cells from samples of mixed cells, indicating that these magnetic composite microspheres have potential in real blood samples for capturing CTCs.

Preparation of dithizone grafted poly(allyl chloride) core–shell–shell magnetic composite microspheres for solid-phase extraction of ultra-trace levels of Pb(ii), Cu(ii) and Cr(iii) ions

The novel dithizone grafted poly(ally chloride) core–shell–shell magnetic microspheres were prepared and applied to simultaneous detection of trace amounts of Pb(ii), Cu(ii) and Cr(iii) ions.

Adsorption of Humic Acid from Aqueous Solution Using Composite Magnetic Microspheres of Chitosan and Quaternary Ammonium Chitosan Derivative

Composite magnetic microspheres of chitosan (CTS) and quaternary ammonium chitosan derivative (HTCC) were prepared by inverse suspension method. Tripolyphosphate (TPP) and glutaraldehyde were used successively to co-crosslink the microsphere matrix. The morphology was analyzed using optical microscopy and scanning electron microscopy (SEM), while the chemical composition was characterized using Fourier transform infrared spectroscopy (FTIR). The adsorption of humic acid (HA) by the composite magnetic microspheres (CHMMs) was investigated in terms of adsorption capacity and kinetics in order to optimize preparation conditions. Both CTS/HTCC mass ratio and crosslinker dosage greatly affected the properties of the microspheres. A batch of CHMMs was prepared when the mass ratio of CTS and HTCC was 1:1 and TPP and glutaraldehyde were17% and 30% of total mass of CTS and HTCC, respectively. These CHMMs were between 150 and 800 μm. 85% HA was able to be removed in 60 min using this proposed absorbent. It was fast and efficient for HA removal from aqueous solution.

Fe3O4@SiO2@TiO2@Pt Hierarchical Core–Shell Microspheres: Controlled Synthesis, Enhanced Degradation System, and Rapid Magnetic Separation to Recycle

Magnetic composite microspheres consisting of a SiO2-coated Fe3O4 core, an ordered TiO2 hierarchically structured shell, and a Pt nanoparticle layer dispersed on the surface of the TiO2 nanoplatelets have been successfully synthesized using a facile and efficient method. The shells of TiO2 hierarchical microspheres were assembled from nanoplatelets, which exposed the high-energy {001} facets, and the Pt nanoparticles were evenly deposited on the surface of the TiO2 nanoplatelets, with a concentration of ∼1 wt %. The resulting composite microspheres exhibited flower-like hierarchical structures with a 202.42 m2 g–1 surface area and possessed superparamagnetic properties with a high saturation magnetization of 31.5 emu g–1. These features endow the obtained composite microspheres with a high adsorption capacity and strong magnetic responsivity that could be easily separated by an external magnetic field. The high photocatalytic activity toward Rhodamine B (RhB) degradation may be caused by the hierarchically structured TiO2 with exposed high-energy {001} facets and the Pt nanoparticle deposits on TiO2 surfaces, which would be efficient for the electron transfer reactions. In addition, the composite microspheres showed high recycling efficiency and stability over several separation cycles.

Polyacrylic acid brushes grafted from P(St-AA)/Fe3O4 composite microspheres via ARGET-ATRP in aqueous solution for protein immobilization

Recently, the atom transfer radical polymerization (ATRP) of acrylic monomers in many reaction systems has been successfully accomplished. However, its application in aqueous solution is still a challenging task. In this work, polyacrylic acid (PAA) brushes with tunable length were directly grafted from P(St-AA)/Fe3O4 composite microspheres in aqueous solution via an improved method, activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). This reaction was carried out in environment-friendly solvent. As well, this method overcame the sensitivity of the catalyst. Due to the strong coordination interaction of carboxyl groups, PAA brushes were employed for immobilizing gold nanoparticles, which were prepared via the in situ reduction of chloroauric acid. The PAA brushes modified magnetic composite microspheres decorating with gold nanoparticles were efficient for specific immobilization and separation of bovine serum albumin (BSA) from aqueous solution under the external magnetic field.

Synthesis of novel magnetic cellulose-chitosan composite microspheres and their application in laccase immobilization.

Novel magnetic cellulose-chitosan composite microspheres were prepared by sol-gel transition method using ionic liquids as solvent for dissolution and regeneration. Subsequently, the composite microspheres activated by glutaradehyde to immobilize enzyme. Which of their structure, properties and morphology were studied by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating-sample magnetometer showed Fe3O4 nanoparticles with mean size of -10 nm were successfully embedded in the composite microspheres. The microshpheres were examined to be with the mean size of 20 μm and good magnetic property with saturation magnetization of 30.1 emu g(-1). The effect of pH and temperature on the immobilization of laccase was also investigated. Compared with free laccase, the pH, thermal and operational stabilities of the immobilized laccase were improved and the activity recovery of immobilized laccase reached 80.6%. Immobilized laccase retained 88.9% activity after 12 reaction cycles. Therefore, the cellulose-chitosan composite microspheres were expected to be a novel support for enzyme immobilization.

Novel Ti4+-chelated magnetic nanostructured affinity microspheres containing N-methylene phosphonic chitosan for highly selective enrichment and rapid separation of phosphopeptides.

Magnetic composite particles immobilized with metal affinity ions show high potential in the phosphoproteome mass-spectrometric (MS) analysis. However, the preparation of this kind of material still suffers from a complicated synthesis procedure and high cost. In this work, the magnetic nanostructured composite microspheres (MPCS) incorporated into N-methylene phosphonic chitosan were first fabricated via a facile one-pot synthesis strategy and titanium ions (Ti4+) were subsequently immobilized onto the MPCS to form MPCS-Ti4+ affinity particles. The uniform spherical MPCS-Ti4+ affinity particles with abundant chelated titanium ions have a particle size distribution between 126 nm and 280 nm, and they display superparamagnetism with a saturation magnetization (Ms) value of 44.75 emu g-1. The amount of the immobilized Ti4+ ions was estimated to be 11.6 wt% by EDS. The MPCS-Ti4+ exhibited excellent dispersibility in aqueous solution, high affinity selectivity for phosphopeptides and quite fast magnetic separation within 10 s as well as good reusability. Thus, the prepared magnetic MPCS-Ti4+ nanostructured affinity materials will possess great potential in phosphoproteome research.