In recent years, graphene‐incorporated micro‐/nanocomposites represent one of the hottest developing directions for the composite materials. However, a large number of active nanoparticles (NPs) are still in the unprotected state in most constructed graphene‐containing designs, which will seriously impair the effects of the graphene additives. Here, a fully protected Fe3O4‐based micro‐/nanocomposite (G/Fe3O4@C) is rationally developed by carbon‐boxing the common graphene/Fe3O4 microparticulates (G/Fe3O4). The processes and results of full protection are tracked in detail and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, and nitrogen absorption–desorption isotherms, as well as scanning and transition electron microscopy. When used as the anode for lithium‐ion batteries, the fully protected G/Fe3O4@C exhibits the best lithium‐storage properties in terms of the highest rate capabilities and the longest cycle life compared to the common G/Fe3O4 composites and commercial Fe3O4 products. These much improved properties are mainly attributed to its novel structural features including complete protection of active Fe3O4 nanoparticles by the surface carbon box, a robust conductive network composed of nitrogen‐doped graphene nanosheets, ultra‐small Fe3O4 NPs of 4–5 nm, abundant mesopores to accommodate the volume variation during cycling, and micrometer‐sized secondary particles. 相似文献
A three steps synthesis route is proposed to generate thermosensitive and magnetically responsive γ‐Fe2O3@Wax@SiO2 sub‐micrometer capsules with a paraffinic core and a solid and brittle shell. The process integrates Pickering‐based emulsions, inorganic and sol–gel chemistries to promote monodisperse in size wax droplets, γ‐Fe2O3 nanoparticles and mineralization of the wax/water interfaces. Hybrid capsules are obtained with an average size around 800 nm, representing the first example of sub‐micrometer capsules generated employing Pickering emulsions as templates. Cetyltrimethylammonium bromide (CTAB) cationic surfactant added during mineralization at concentrations between 0.17 and 1.0 wt% impacts the shell density. The shell density seems to improve its mechanical strength while affording a low wax expansion volume without breaking for CTAB concentrations above 1.0 wt%. At lower CTAB concentration (0.17 wt%), the silica shell becomes less bulky and cannot resist the wax dilatation induced by the solid‐to‐liquid phase transition imposed by hyperthermia. The magnetically induced heating provided by the internal magnetic moments is sufficient to melt the wax core, expanding its volume, inducing thereby the surrounding silica shell rupture. Such γ‐Fe2O3@Stearic Acid@Wax@SiO2 sub‐micrometer capsules allow a sustained wax release with time, whereby 20% of the wax is released after 50 min of alternating magnetic field treatment. 相似文献
The facile hydrothermal synthesis of polyethyleneimine (PEI)‐coated iron oxide (Fe3O4) nanoparticles (NPs) doped with Gd(OH)3 (Fe3O4‐Gd(OH)3‐PEI NPs) for dual mode T1‐ and T2‐weighted magnetic resonance (MR) imaging applications is reported. In this approach, Fe3O4‐Gd(OH)3‐PEI NPs are synthesized via a hydrothermal method in the presence of branched PEI and Gd(III) ions. The PEI coating onto the particle surfaces enables further modification of poly(ethylene glycol) (PEG) in order to render the particles with good water dispersibility and improved biocompatibility. The formed Fe3O4‐Gd(OH)3‐PEI‐PEG NPs have a Gd/Fe molar ratio of 0.25:1 and a mean particle size of 14.4 nm and display a relatively high r2 (151.37 × 10?3m ?1 s?1) and r1 (5.63 × 10?3m ?1 s?1) relaxivity, affording their uses as a unique contrast agent for T1‐ and T2‐weighted MR imaging of rat livers after mesenteric vein injection of the particles and the mouse liver after intravenous injection of the particles, respectively. The developed Fe3O4‐Gd(OH)3‐PEI‐PEG NPs may hold great promise to be used as a contrast agent for dual mode T1‐ and T2‐weighted self‐confirmation MR imaging of different biological systems. 相似文献
With increasing miniaturization, it is extremely important to maintain the magnetization stability at small scale. Herein, more efforts and interests focus on the interface of magnetic core and semiconductor shell to obtain desired magnetic and/or luminescent properties. Here, Fe3O4 nanocubes are synthesized via a thermal decomposition followed by coating ZnO nanocrystals. To create a large interface, large Fe3O4 nanocubes with 78 ± 3 nm average side‐length are synthesized through adjusting the ratio of iron precursor to stabilizer. The average diameter of the particular ZnO nanostructures coated on the nanocubic Fe3O4 is around 10 ± 2 nm. In addition to the photoluminescent properties of the ZnO‐coated nanostructures, core‐shell Fe3O4@ZnO nanostructures demonstrate enhanced UV absorption at 360 nm, which has a 20 nm blueshift compared to bulk ZnO. The superparamagnetic properties of Fe3O4@ZnO core–shell hybrid nanocrystals at room temperature are dominated by the ferromagnetic properties when the temperature is lower than the Blocking temperature, 235.7 K. The observed exchange bias and temperature‐dependent magnetization can result from the interfacial interphase between ZnO and Fe3O4. The anisotropy contributed by the interfacial interphase allows the nanostructures to maintain stable magnetization in miniaturized devices. 相似文献
The use of carbon shells offers many advantages in surface coating or surface modification due to their surface with activated
carboxyl and carbonyl groups. In this study, the Fe3O4@C@YVO4:Eu3+ composites were prepared through a simple sol–gel process. Reactive carbon interlayer was introduced as a key component,
which separates lanthanide-based luminescent component from the magnetite, more importantly, it effectively prevent oxidation
of the Fe3O4 core during the whole preparation process. The morphology, structure, magnetic, and luminescent properties of the composites
were characterized by transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, X-ray photoelectron
spectra, VSM, and photoluminescent spectrophotometer. As a result, the Fe3O4@C/YVO4:Eu3+ composites with well-crystallized and core–shell structure were prepared and the YVO4:Eu3+ luminescent layer decorating the Fe3O4@C core–shell microspheres are about 10 nm. In addition, the Fe3O4@C@YVO4:Eu3+ composites have the excellent magnetic and luminescent properties, which allow them great potential for bioapplications such
as magnetic bioseparation, magnetic resonance imaging, and drug/gene delivery. 相似文献
A new type of multifunctional plasmonic nanoparticles, cobalt‐doped Fe2O3@polydopamine‐Au (Co‐Fe2O3@PDA‐Au), is fabricated via coating PDA through self‐polymerization onto Co‐Fe2O3 and further loading gold nanoparticles by in situ reduction onto the surface of PDA shell. Benefiting from the universal adhesive ability of PDA and negative zeta potetntial of the composite, the Co‐Fe2O3@PDA‐Au shows strong adsorptivity for cationic dyes. The presence of gold nanoparticle with the diameter of 15 nm in the Co‐Fe2O3@PDA‐Au system promotes surface‐enhanced Raman scattering (SERS) activity with an impressive detection limit of 1 × 10?6 m . Thanks to the synergistic effect of the light harvesting of PDA, the surface plasmon resonance of Au, and the electron conductibility of PDA and Au, the Co‐Fe2O3@PDA‐Au exhibits an enhanced photocatalytic activity comparing with unmodified Co‐Fe2O3. All the above‐mentioned functions enable Co‐Fe2O3@PDA‐Au to be a multifunctional material system for various applications toward environmental pollutants. 相似文献
In this study, the magnetically recyclable Fe3O4@C/BiOBr heterojunction with enhanced visible light-driven photocatalytic ability was obtained by two-step solvothermal method. The phase, morphology, and structure of the samples were investigated by XRD, FESEM, HRTEM, and XPS. The Fe3O4@C/BiOBr heterojunction was composed of Fe3O4@C sphere and BiOBr microsphere with diameters of 200 nm and 1000 nm, respectively. The photocatalytic performance of Fe3O4@C/BiOBr composite for RhB was examined under visible light irradiation. The photocatalytic activity of Fe3O4@C/BiOBr composite was much higher than that of pure BiOBr and Fe3O4@C. After 35 min of irradiation, 97% of RhB could be removed with the Fe3O4@C/BiOBr photocatalyst. Based on radical trapping experiments of active species, the mechanism of enhanced photocatalytic performance was proposed. In addition, the superparamagnetic property of the photocatalyst not only allows its easy recyclability by an external magnetic field but also maintains high photocatalytic activity after five cyclic experiments.
Magnetic iron oxide coated in hydrogenation silica (Fe3O4@HSiO2) is constructed as both a tumor drug carrier and a magnetic resonance (MR) contrast agent. Colchicine (COLC) is loaded in Fe3O4@HSiO2 with the highest amount of 28.3 wt% at pH 9. The release performance of COLC can be controlled by pH, as the porous HSiO2 shell can partially shed at pH below 3.0 to facilitate the release of COLC. MR imaging (MRI) tests prove that Fe3O4@HSiO2 at pH 3.0 (H+‐Fe3O4@HSiO2) shows a stronger MR contrast enhancement than Fe3O4. Cytotoxicity experiment indicates that Fe3O4@HSiO2 has excellent biocompatibility and magnetic targeting performance. Additionally, COLC‐loaded Fe3O4@HSiO2 (Fe3O4@HSiO2–COLC) displays a higher inhibition effect on tumor cells under a magnetic field than free COLC. The visibility upon MRI, high targeting, and pH‐controlled release characteristics of Fe3O4@HSiO2–COLC are favorable to achieve the aim of reducing side effects to normal tissues, making Fe3O4@HSiO2–COLC an attractive drug delivery system for nanomedicine. 相似文献
The development of cancer photothermal therapies, many of which rely on photothermal agents, has received significant attention in recent years. In this work, various ligands‐stabilized magnetite (Fe3O4) particles are fabricated and utilized as a photothermal agents for in vivo tumor‐imaging‐guided photothermal therapy. Fe3O4 particles stabilized by macromolecular ligands as, e.g. polyethylene glycol (PEG), exhibit a superior and more stable photothermal effect compared to Fe3O4 particles stabilized by small molecules like citrate, due to their stronger ability of antioxidation. In addition, the photothermal effect of Fe3O4 particles is revealed to increase with size, which is attributed to the redshift of Vis‐NIR spectra. Fe3O4 particles injected intravenously into mice can be accumulated in the tumor by the application of an external magnetic field, as revealed by magnetic resonance imaging. In vivo photothermal therapy test of PEG‐stabilized Fe3O4 further achieves better tumor ablation effect. Overall, this study demonstrates efficient imaging‐guided photothermal therapy of cancer that is based on Fe3O4 particles of optimized size and with optimized ligands. It is expected that the ligand‐directed and size‐dependent photothermal effect will provide more approaches in the design of novel materials. 相似文献
Mössbauer spectroscopy revealed that a central hyperfine interaction doublet and an additional sextet characterized the appearance of new phases in the mechanically alloyed Fe2O3–Al and Fe2O3–Co systems. In the Fe2O3–Al system, the intensity of the central super paramagnetic doublet which represents small particles of iron, increased with increasing milling time from 5 to 30 h of mechanical alloying. The magnetic sextet characterizing hematite vanished in the room temperature Mössbauer spectra of samples produced after 25 h of mechanically alloying the 50% Fe2O3 and 50% Al system. In general XRD peak broadening was observed as a result of extensive material structural distortion and formation of small particles. Fe, Al2O3 and mixed iron–aluminium oxide phases were identified in the XRD patterns with a small persistence of the iron oxide up to 20 h of mechanically alloying the 1:1 system Al–Fe2O3. In the 50% Co–50% Fe2O3 system, a 55% abundant new phase CoFe2O4 was observed, from the Mössbauer spectra of the system. The presence of this new phase was confirmed by the XRD analysis. The high energy ball milling of WC–Fe2O3 revealed a more effective grinding compared to hematite alone. The hematite particles were reduced to nanosized particles. 相似文献
Development of advanced theranostics for personalized medicine is of great interest. Herein, a multifunctional mesoporous silica‐based drug delivery carrier has been developed for efficient chemo/photothermal therapy. The unique Au nanoframes@mSiO2 spheres are elaborately prepared by utilizing Ag@mSiO2 yolk–shell spheres as the template through spatially confined galvanic replacement method. Compared with the Ag@mSiO2 yolk–shell spheres, the resultant Au nanoframes@mSiO2 spheres show a strong and broad near‐infrared (NIR) absorbance in the 550–1100 nm region, high surface areas, and good biocompatibility. When irradiated with a NIR laser with a power intensity of 1 W cm?2 at 808 nm, they can become highly localized heat sources through the photothermal effect. Moreover, the photothermal effect of the Au nanoframes can significantly promote the fast release of doxorubicin. The in vitro studies show obvious synergistic effects combining photothermal therapy and chemotherapy in the Au nanoframes@mSiO2 spheres against Hela cells. It is believed that the as‐obtained multifunctional vehicles provide a promising platform for the combination of hyperthermia and chemotherapy for cancer treatment application. 相似文献
A scalable synthesis of magnetic core–shell nanocomposite particles, acting as a novel class of magnetic resonance (MR) contrast agents, has been developed. Each nanocomposite particle consists of a biocompatible chitosan shell and a poly(methyl methacrylate) (PMMA) core where multiple aggregated γ‐Fe2O3 nanoparticles are confined within the hydrophobic core. Properties of the nanocomposite particles including their chemical structure, particle size, size distribution, and morphology, as well as crystallinity of the magnetic nanoparticles and magnetic properties were systematically characterized. Their potential application as an MR contrast agent has been evaluated. Results show that the nanocomposite particles have good stability in biological media and very low cytotoxicity in both L929 mouse fibroblasts (normal cells) and HeLa cells (cervical cancer cells). They also exhibited excellent MR imaging performance with a T2 relaxivity of up to 364 mMFe?1 s?1. An in vivo MR test performed on a naked mouse bearing breast tumor indicates that the nanocomposite particles can localize in both normal liver and tumor tissues. These results suggest that the magnetic core–shell nanocomposite particles are an efficient, inexpensive and safe T2‐weighted MR contrast agent for both liver and tumor MR imaging in cancer therapy. 相似文献
The reduction of 4‐nitrophenol (Nip) into 4‐aminophenol (Amp) by NaBH4, which is catalyzed by both binary and ternary yolk–shell noble‐metal/SnO2 heterostructures, is reported. The binary heterostructures contain individual Au or Ag nanoparticles (NPs) and the ternary heterostructures contain both Au and Ag NPs. The Au@SnO2 yolk–shell NPs are synthesized via a silica seeds‐mediated hydrothermal method. Subsequently, the Au@SnO2@Ag and Au@SnO2@Au yolk–shell–shell (YSS) NPs are synthesized, whereby SnO2 is located between the Au and Ag NPs. The morphology, composition, and optical properties of the as‐prepared samples are analyzed. For the binary heterostructures, the rate of the reduction reaction increases with decreasing particle size. The catalytic results demonstrate the synergistic effect of Au and Ag in the ternary metal–semiconductor heterostructures, which is beneficial to the catalytic reduction of Nip into Amp. Both the binary and ternary heterostructures exhibit significantly better catalytic performances than the corresponding bare Au and Ag NPs. It is envisaged that the current synthesized strategy will promote further interest in the field of bimetal NP‐based catalysis. 相似文献