In vitro biological evaluations of Fe3O4 compared with core–shell structures of chitosan-coated Fe3O4 and polyacrylic acid-coated Fe3O4 nanoparticles

Research on Chemical Intermediates - Today the use of magnetic nanoparticles (MNPs) is widely investigated because of their biocompatibility and nontoxicity. The objective of this study was to...     

Optical and magnetic properties of small-size core–shell Fe3O4@C nanoparticles

Core–shell Fe₃O₄@C magnetic nanoparticles which are of great interest for research have a widely applied prospect. However, people know little about the optical and magnetic properties of the small-size Fe₃O₄@C nanoparticles due to the difficulty of uniformly coating small size Fe₃O₄ nanoparticles. In this paper, the influence of carbon shell coating on the optical and magnetic properties of small size Fe₃O₄ nanoparticles was presented. Carbon coating can strengthen the absorption intensity in the UV–visible light region through the introduction of oxygen defects on the surface of the nanoparticles by nitric acid treatment. Fe₃O₄ and Fe₃O₄@C nanoparticles both display typical superparamagnetic behavior in the high-temperature regime and a blocked state at low temperature from hysteresis loop, zero-field cooled and field cooled curves. Carbon coating reduce the surface uniaxial anisotropy, thus the average blocking temperature <T_B> decreases from 59 K of Fe₃O₄ nanoparticles to 50 K of Fe₃O₄@C nanoparticles.     

Characterization and preparation of core–shell type nanoparticle for encapsulation of anticancer drug

The aim of this study is to prepare delivery vehicles of paclitaxel using low molecular weight water-soluble chitosan (LMWSC) and evaluate them as an anticancer drug delivery system. LMWSC was modified with methoxy polyethylene glycol (LMWSC-MPEG, ChitoPEG), and then it was conjugated with cholesterol (LMWSC-MPEG-Chol). Core–shell type LMWSC-MPEG-Chol nanoparticles (LMWSC-NPs) were prepared by the dialysis method, and the core–shell structure was confirmed by ¹H NMR analysis. To this polymer, paclitaxel was encapsulated and core–shell type nanoparticles were prepared. The release tests indicated that release of paclitaxel from the core–shell type nanoparticles and its transport across the dialysis membrane was slower than dialysis of free paclitaxel. In a cytotoxicity study using CT26 cell, the paclitaxel-encapsulated core–shell type nanoparticles (LMWSC-NPs) showed a toxicity against tumor cells similar to paclitaxel itself. The results of a tumor inhibition test with CT26 implanted upon mouse tumor models in vivo indicated that the application of a dose of 10 mg/kg of LMWSC-NPT showed a superior survival rate, and a slower tumor growth than when paclitaxel alone was administered, although the tumor growth and survival rate were not significantly changed at a dose of 2 mg/kg. The LMWSC-NPT dose above 10 mg/kg showed a superior antitumor activity.     

Facile deposition of gold nanoparticles on core–shell Fe3O4@polydopamine as recyclable nanocatalyst

A simple and green method for the controllable synthesis of core–shell Fe₃O₄ polydopamine nanoparticles (Fe₃O₄@PDA NPs) with tunable shell thickness and their application as a recyclable nanocatalyst support is presented. Magnetite Fe₃O₄ NPs formed in a one-pot process by the hydrothermal approach with a diameter of ∼240 nm were coated with a polydopamine shell layer with a tunable thickness of 15–45 nm. The facile deposition of Au NPs atop Fe₃O₄@PDA NPs was achieved by utilizing PDA as both the reducing agent and the coupling agent. The satellite nanocatalysts exhibited high catalytic performance for the reduction of p-nitrophenol. Furthermore, the recovery and reuse of the catalyst was demonstrated 8 times without detectible loss in activity. The synergistic combination of unique features of PDA and magnetic nanoparticles establishes these core–shell NPs as a versatile platform for potential applications.     

Picolinimidoamide-Cu(II) complex anchored on Fe3O4@SiO2 core–shell magnetic nanoparticles: an efficient reusable catalyst for click reaction

A Cu(II) complex supported on Fe₃O₄@SiO₂ core–shell magnetic nanoparticles (MNPs) was prepared and characterized by FT-IR, XRD, SEM, EDX, TEM, VSM, TGA, and AAS analysis. The load of Cu on picolinimidoamide ligand anchored on Fe₃O₄@SiO₂ core–shell MNPs was determined as 1.22, 1.54, and 1.70 wt% using AAS, EDX and TGA analyses, respectively. Synthesized Cu(II) complex on Fe₃O₄@SiO₂ MNPs efficiently catalyzed a click reaction between alkyl halides, alkynes, and sodium azide to synthesize corresponding triazoles in high to excellent yields. The catalyst was recovered using an external magnetic field, and recycled for subsequent reactions without substantial loss of efficiency.     

Preparation of Mn2O3 catalyst with core–shell structure via spray pyrolysis assisted with glucose

A novel core–shell Mn₂O₃ catalyst is obtained by facile spray pyrolysis assisted with glucose acting as a structure-directing agent. The detail characterizations include X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms, and the thermogravimetric method (TG/DTA). In the probe test of the aqueous degradation of methylene blue (MB), the high catalytic peroxidization activity of core–shell Mn₂O₃ catalyst, compared to the commercial Mn₂O₃, is attributed to the high crystallization of α-Mn₂O₃, the large surface area that resulted from the core–shell structure with porous architecture, and the special core–shell structure that acted as a micro-reactor.     

An experimental study on stability and rheological properties of magnetorheological fluid using iron nanoparticle core–shell structured by cellulose

Journal of Thermal Analysis and Calorimetry - In this study, silicone oil as the base fluid and carbonyl iron powder with the average particle size of 2.7&nbsp;µm as the disperse phase was...     

Crucial factors affecting the physicochemical properties of sol–gel produced Fe3O4@SiO2–NH2 core–shell nanomaterials

Multifunctional nanomaterials with task-specific physicochemical properties, especially core?Cshell nanostructures with Fe₃O₄ core and NH₂-functional shells (Fe₃O₄@SiO₂?CNH₂), have been extensively investigated as high-performance adsorbents, catalysts and catalyst supports; and in most cases the controllable sol?Cgel technique is the choice for fabrication of this kind of widely applied materials. Herein, we demonstrated that mono-dispersed and spherical Fe₃O₄@SiO₂?CNH₂ nanomaterials with magnetic response core, NH₂-functional shell structure can be facilely prepared by co-condensation of TEOS with APTMS using a versatile sol?Cgel process. It was shown that the proper usage of APTMS and appropriate pre-hydrolysis time of TEOS were crucial and key steps for formation of highly uniform and desirable amino loading Fe₃O₄@SiO₂?CNH₂ materials. The TEOS pre-hydrolysis and the critical time (around 90?min) before the addition of APTMS prove to be vital for uniform structure evolution, while the appropriate concentration of APTMS (~2.28?mmol?L^?1 in our system) leads to well-dispersed materials with relatively high loading of amino functionality. The as-prepared Fe₃O₄@SiO₂?CNH₂ magnetic nanoparticles prepared under optimum conditions possessing superparamagnetic behavior, uniform core?Cshell structure (~200?nm in diameter), relatively large BET surface area (~138?m²/g) and high incorporation of amino-functionality (~2.90?wt?%).     

Fe3O4@SiO2@Propyl–ANDSA: as a new catalyst for one-pot synthesis of 4H-chromene

Research on Chemical Intermediates - This work describes a new method for a one-pot multicomponent condensation of a variety of aldehydes with dimedone and malononitrile in water, providing a...     

Luminescent core–shell Fe3O4@Gd2O3:Er3+, Li+ composite particles with enhanced optical properties

Bifunctional magneto-optical nanocomposites with Fe₃O₄ nanoparticles as a core and erbium and lithium codoped gadolinium (Gd₂O₃:Er³⁺, Li⁺) as the shell were synthesized successfully using a simple urea homogeneous precipitation method. The fabricated Fe₃O₄@Gd₂O₃:Er³⁺, Li⁺ particles were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy and quantum design vibrating sample magnetometry. The upconversion emission intensity was enhanced significantly comparing to that without Li⁺ ions. These bifunctional composites are expected to be potentially applied for drug delivery, cell separation and bioimaging.     

Influence of elastomeric core–shell impact modifiers on mechanical properties of cellulose diacetate resin

Cellulose diacetate (CDA) plasticized with triacetine was blended by melting extrusion with two different kind of elastomeric core–shell impact modifiers: methyl methacrylate (MMA, shell) grafted onto styrene–butadiene–rubber (SBR, core) (MSBR) and MMA (shell) grafted onto butyl acrylate rubber (BAR, core) (MBAR). The different CDA/MSBR and CDA/MBAR blends were characterized by mechanical properties and morphological observation with various impact modifier contents. The highest impact strength was observed in the case of the blend with 5 wt% of MSBR and 3 wt% of MBAR, respectively. The tensile strength and Young’s modulus of CDA blends were decreased with increasing both MSBR and MBAR. According to SEM observation, MBAR was dispersed more effectively in CDA matrix than that of MSBR, thus indicating improved impact strength.     

Hierarchical core/shell Fe3O4@SiO2@γ-AlOOH@Au micro/nanoflowers for protein immobilization

A facile synthesis of monodispersed microparticles composed of superparamagnetic Fe(3)O(4) cores, SiO(2) shell, hierarchical γ-AlOOH periphery with Au nanoparticles is reported. These particles are found to be useful for protein immobilization and bear resemblance to daisy flowers, and are hereafter termed "nanoflowers".     

Green synthesis of 3,4-disubstituted isoxazol-5(4H)-ones using ZnO@Fe3O4 core–shell nanocatalyst in water

An effective and environmentally benign methodology for the synthesis of isoxazol-5(4H)-one derivatives has been developed using a ZnO@Fe₃O₄ core–shell nanocatalytic system. The one-pot, multicomponent reaction of an aromatic/heterocyclic aldehyde, hydroxylamine hydrochloride and ethyl acetoacetate under aqueous conditions at slightly elevated temperature resulted in the formation of title compounds in extremely good yields. The present new protocol is environmentally friendly as it offers heterocyclization with some interesting promising features such as safety, atom efficiency, low cost, mild conditions, minimal waste, catalyst recyclability, water as a solvent, easy workup and possession of excellent functional group tolerance for the synthesisis of structurally diverse isoxazole derivatives. All products were characterized by spectral and analytical methods. A representative title derivative was studied for its structure by single crystal X-ray diffraction method.     

Core–shell magnetic Fe3O4/CNC@MOF composites with peroxidase-like activity for colorimetric detection of phenol

Rapid and accurate detection of phenolic wastewater from industries has created global concern. Herein, core–shell magnetic cellulose nanocrystal supported MOF (Fe₃O₄/CNC@ZIF-8) with robust peroxidase-like activity was synthesized with tannic acid as modifier and bridge. The peroxidase-mimic catalytic activity of as-prepared Fe₃O₄/CNC@ZIF-8 was further investigated using o-phenylenediamine (OPD) as peroxidase substrates in the presence of H₂O₂. Moreover, the experimental conditions were optimized and the kinetic analysis results showed that Fe₃O₄/CNC@ZIF-8 had higher affinity towards both the substrate OPD and H₂O₂ than horseradish peroxidase (HRP). Finally, a phenol colorimetric assay with a linear range of 2–200 µM and a detection limit of 0.316 µM was constructed. The catalytic mechanism of Fe₃O₄/CNC@ZIF-8 with phenol was further investigated by fluorescence test and the generated ·OH was proved to act a crucial role to produce quinoid radicals. Additionally, the synthesized magnetic material had excellent stability and recyclability and ease to separation. These results suggest that the Fe₃O₄/CNC@ZIF-8 may be one of the promising candidates as peroxidase mimic for colorimetric detection of phenol.

     

Preparation and characterization of SO4 2−/Fe2O3–TiO2–Nd2O3 catalyst

This paper reports on the preparation of SO₄ ^2?/Fe₂O₃–TiO₂–Nd₂O₃ (SFTN) by combustion method. The effect of Nd content on catalytic activity was investigated. The prepared materials doped and undoped by Nd were compared by means of TG-DTG, XRD, FT-IR, NH₃-TPD and TEM techniques. Results indicated that the introduction of Nd improved the catalytic activities of the catalysts. Catalytic activity of SFTN was the highest with 98.3 % menthol conversion when Nd content was at 2 wt%. The introduction of Nd stabilized the coordination bond between the sulfate irons and the metallic oxides, helping in the formation of solid acid sites, enhancing the dispersion of catalyst particles, and inhibiting the growth of catalyst particles under heating.     

Hydrophobic modification of cellulose fibres by cationic-modified polyacrylate latex with core–shell structure

In cellulose fibre-based green packaging, the poor resistance or barrier against water or water vapour has remained as one of the key challenges. In this work, cationic polymer latex, butyl acrylate-co-styrene/2-ethylhexylacrylate-co-methyl methacrylate (BA-co-St/EHA-co-MMA), with core–shell structure was especially synthesized and used as a wet-end additive to render the fibre or paper hydrophobic. TEM observation confirmed that the latex particles obtained indeed possessed desired characteristic of core–shell structure. The experimental results showed that the cationic polymer was especially suitable for use in papermaking processes due to its high retention with cellulose fibres. The surface modification of the natural fibre by the adsorption of cationic latex on the fibre surfaces potentially created the thin films of polymers on fibre surfaces. The resulting paper is highly hydrophobic with improved barrier property, as demonstrated by the high contact angles and relatively low WVTR value. Moreover, the mechanical properties of paper were maintained or even improved in the presence of an appropriate level of the latex.     

Electrochemical Sensor Based on Magnetic Fe3O4–Reduced Graphene Oxide Hybrid for Sensitive Detection of Binaphthol

Russian Journal of Electrochemistry - Naphthol is an environmental pollutant with highly toxic and corrosive. Naphthol can be absorbed by the body easily through the skin, and can cause serious...     

Synthesis of nanocomposite with a core—shell structure based on Fe3O4 magnetic nanoparticles and iron glycerolate

Russian Chemical Bulletin - An original method for preparation of nanoparticles with a core—shell structure based on Fe3O4 magnetic nanoparticles (MNPs) and iron glycerolate was proposed. The...