Hierarchical Iron Oxide Research Articles

Hierarchical iron oxide nanocomposite: Bundle-like morphology, magnetic properties and potential biomedical application

Controlled spatial arrangements of superparamagnetic iron oxide nanoparticles (SPIONs) in complex nanostructures determine fine tuning of physico-chemical properties which, in turn, may lead to new practical applications. We report here on newly observed properties of hierarchical SPIONs nanostructure with bundle-like morphology, also known as nanobundles. Colloidal chemical processes and sol-gel synthesis were used for the synthesis of nanobundles, i.e. i) self-assembly of SPIONs into magnetic nanoparticle clusters, ii) their magnetic assembly to the nanochains, and finally iii) formation of bundle-like hierarchical nanostructure. An XRPD measurements show spinel crystal structure of maghemite/magnetite nanoparticles, EDS analysis reveals Fe, Si and O as main elements whereas SEM/TEM analysis show silica-coated magnetic nanoclusters (∼100 nm) and their hierarchical assemblies with bundle-like morphology of ∼8 μm length and ∼1 μm width. TEM analysis revealed core-shell nature of iron oxide nanoparticle clusters with their size of around 80 nm that were coated by an amorphous silica shell with thickness of ∼15 nm. The nanoclusters in the core are constructed of maghemite/magnetite nanoparticle assembly with primary iron oxide nanoparticle size about 10 nm. The magnetization M data as a function of an applied external magnetic field H were successfully fitted by the Langevin function, whence the magnetic moment μp = 19256 μB, and the diameter d = 9.6 nm of nanoparticles were determined. Microsized bundle-like particles are superparamagnetic, magnetically guidable and possess high transverse relaxivity of r2 = 397.8 mM−1s−1. Magnetic properties and such high value of transverse relaxivity holds promise for nanobundles application in MRI imaging (MRI contrast agent), as nanobundles may enhance the magnetic field in their surroundings and enhance proton relaxation processes. Our nanobundles can open new opportunities in the biomedical applications, magnetic separation, photonic crystals and magnetic liquid manipulation and can be inspiration for synthesizing novel self-assembled nanoparticle structures.

Thermally oxidized steel mesh for oil-water separation application and its automation device

Automatic oil-water separating equipment based on nanostructured hierarchical iron oxide grown on steel mesh by thermal oxidation method is presented. The iron oxide was rather amorphous but is highly hydrophobic due to the presence of the hierarchical nanostructure. The semi-permeable property emerged from this nanostructure made the oxidized steel mesh suitable as a membrane to separate oil from water. The membrane was assembled in an oil-water separator equipment, that equipped with Internet of Things (IoT) devices, that consisting of sensors, a microcontroller, and actuators. They are connected to the Blynk IoT Platform, via a Wi-Fi connection. The built equipment and IoT implementation allow users to perform the oil-water separation process automatically and the real-time process can be monitored, even from a smart phone application. The oil-water separator is shown to have an excellent capability to separate water from oil, with efficiency reaching >96% and can be repeatedly use.

Biological behavior of nanoparticles with Zr-89 for cancer targeting based on their distinct surface composition.

Nano-sized materials with properties that enable their internalization into target cells using passive targeting systems have been utilized with radioisotopes to track their pharmacokinetics in the body. Here, we report the incorporation of novel chelator-free Zr-89 using a hierarchical iron oxide nanocomposite (89Zr-IONC). Characterization revealed that it had a rice-shape with a mean width of 160 nm. The surface of the 89Zr-IONCs was coated by polyethyleneimine (PEI) and polyvinylpyrrolidone (PVP) to improve the cancer target efficacy. The biological behavior of the nanoparticles coated with the polymers differed significantly by the surface composition. Positron emission tomography measurements by the labeled Zr-89 effectively confirmed the cancer target capability and the fate of distribution in the body. We found that only PVP coated 89Zr-IONC reached the tumor region while non-coated and PEI coated 89Zr-IONC tended to be undesirably entirely cleared in the liver and spleen. The 89Zr-incorporated iron oxide nanocomposite is significantly stable for radiolabeling despite various surface modifications, allowing the potential carrier to specifically target cancer cells. The strategy of utilizing the biocompatible PEI and PVP surface coating system for negative charged nanoparticles such as iron oxide will afford enhanced biological application.

Architecting hierarchical shell porosity of hollow prussian blue-derived iron oxide for enhanced Li storage.

Delicate architecture of active material enables improving the performacne of lithium ion batteries. Environmental-friendly Fe2 O3 anode has high theoretical specific capacity (1007 mAh g-1 ) in lithium ion batteries, but suffers from structural collapsing and poor electronic conductivity. Herein, we design an unique hierarchical iron oxide by regulating the initial precursor prussian blue and targeting hollow-shell structures with full consideration of temperature controls. Among them, Fe2 O3 with a sheet-crossing structure at 650°C, affords obvious advantages of improved electronic conductivity, short ionic diffusion length, prevented particle agglomeration, and buffer volume change. Thus, we achieve a superior discharge specific capacity of 611 mAh g-1 at 500 mA g-1 . Regulating hierarchical structure of prussian blue-assisted oxides enables effectively enchancing Li storge performance. LAY DESCRIPTION: Nanoparticle self-assembly, one of bottom-up methods is often used to prepare hollow hierarchical structures, whereas it suffers from low productivity and insufficient stability. Hence, we designed a unique hierarchical iron oxide by top-down method with regulating the initial precursor PB and targeting hollow-shell structures through full consideration of temperature controls. Delicate architecture of active material enables improving the performacne of lithium ion batteries. Environmental-friendly Fe2 O3 anode has high theoretical specific capacity (1007 mAh g-1 ) in lithium ion batteries, but suffers from structural collapsing and poor electronic conductivity. Hence, we prepared Prussian Blue (PB) materials with different sizes and calcined them at different temperatures. We found that no matter what the size of PB, the sheet-crossing morphology appeared at 650°C, and the interlaced morphology was the key to improve the performance of lithium batteries. If the size of PB precursor is too large or too small, it has adverse effects on lithium batteries. Only when the size and calcination temperature of PB precursor reach the optimum state, the best performance can be obtained. The calcination PB-K-3 at 650°C has a unique hierarchical structure of sheet-crossing. An obvious advantages include the prevention of particle agglomeration, short ionic diffusion lengths, and buffering volume changes. As a consequence, 611 mAh g-1 was obtained at the current density of 500 mA g-1 . In addition, we observed the structural changes of electrode plates at different reaction potentials, according to the reaction equation of Fe2 O3 +xLi+ +xe→Lix Fe2 O3 . With the proceeding charge process, the voltage increases from 0.01 to 3 V, the lithium ions gradually comes out of the iron oxide electrode surface. Whereas the discharging process reverses the aforementioned phenomena. Even if the changing volumes, however, the shape of cubic blocks for the PB-K-3 is preserved at different potentials. Taking these advantages into account, our designed MOFs-derived struture was an effective way to prepare hollow hierarchical structure with enhanced Li storage performacne. Such work is expected to facilitate the design of new electrode structure of lithium batteries.

A novel route to the formation of 3D nanoflower-like hierarchical iron oxide nanostructure

The present work reports the formation of 3D nanoflower-like morphology of iron alkoxide via the anodization of Fe sheet in ethylene glycol (EG) electrolyte. XRD, FESEM, EDX, XPS, Raman and FTIR are applied to characterize the samples. SEM results show that the as-anodized sample is composed of 3D nanoflowers with hierarchical nanosheets beneath it. The average width of the nanoflower petal is ∼25 nm and the length is about 1 μm. The 3D nanoflowers are transformed into spherical nanoparticles (NPs) with uniform size when calcined at elevated temperature. XRD and Raman results indicate that the 3D nanoflowers consist of akaganeite, which transforms into magnetite and hematite by annealing. XPS and FTIR results confirm that the nanoflowers contain significant amounts of F, C and OH, which are drastically decreased after annealing. The formation of 3D nanoflower-like morphology can be attributed to EG. A possible formation mechanism of 3D nanoflowers and their transformation into NPs is proposed. We showed that the morphology of the as-anodized iron oxide can be tailored simply by changing the electrolyte. The anodization of Fe sheet in glycerol-based electrolyte under identical conditions produced nanotubes.

Effect of synthesis parameters on tuning of phase and shape of hierarchical iron oxides and selective application as supercapacitor

The synthetic strategy for iron oxides with diverse superstructures has become one of the most promising researches due to their advance and synergistic application in energy and environment field. Self-assembling of nanostructure to structural hierarchy in general enhances mass transportation, reducing resistance to diffusion, and high surface areas for adsorption and electrochemical reaction, and thus much effort has been devoted to the exploration of various novel synthesis schemes for high-throughput synthesis processes with a choice of starting materials. In this strategy, we utilize metal-organic solvent solutions as the starting material for synthesizing functional hierarchical iron oxide materials without further addition of base for hydrolysis reactions. The process is templates/surfactant less which makes the process simple without intact of other impurities in desired structure. The agglomerations of the particles are also controlled due to acidic pH condition adopted during synthesis. All the experiments were done at a moderate temperature (~ < 100 °C) with a variation of time and concentration. The reaction parameters are optimized to get uniform and highly dispersed flower or spindle-shaped 3D hierarchical goethite phase and thereof we evaluate the electrochemical capacitance using cyclic voltammetry technique. One of the pure iron oxide samples shows specific capacitance value of 243.2 Fg−1 and exhibited 26 Wh Kg−1 energy density at 0.5 Ag−1 current density.

Development of hierarchical Fe3O4 magnetic microspheres as solid substrates for high sensitive immunoassays.

Improving the detection sensitivity of enzyme linked immunosorbent assay (ELISA) is of the utmost importance for meeting the demand of early disease diagnosis. In this work, a sensitive solid substrate for ELISA, i.e., hierarchical iron oxide magnetic microspheres, Fe3O4@mSiO2@poly[poly(ethylene glycol) methacrylate-co-glycidyl methacrylate], was developed via a novel surface-initiated photoiniferter-mediated polymerization (SI-PIMP) strategy. The magnetic microspheres consist of a magnetic Fe3O4 core that gives a high magnetic response, a 3D backbone, a mesoporous SiO2 middle layer, that facilitates microsphere stability and provides anchoring sites, and polymer brushes, that serve as an antifouling and oriented antibody immobilization layer. As a result, the as-prepared microspheres possess a high antibody loading capacity, an enhanced detection signal and a dramatically improved sensitivity, resulting in a 25-fold improvement over conventional ELISA solid substrates.

3D hierarchical nanostructures of iron oxides coatings prepared by pulsed laser deposition for photocatalytic water purification

3D hierarchical nanostructured hematite (α-Fe2O3) coatings containing various shapes were developed by pulsed laser deposition (PLD). A cold pressed, homogeneous mixture of Fe and H3BO3 (Fe+H3BO3) was used as a target in PLD to deposit the coatings in O2 atmosphere. Phase explosion phenomenon provided by laser ablation on the target, allowed to form rough, porous and embedded metallic Fe particulates coating with H3BO3 as background on a glass substrate. Subsequent thermal annealing of the as deposited Fe+H3BO3 coating at 600°C, led to formation of crystalline, hierarchical 3D nanostructured features with nanowires, nanorods, and nanosheets grown from the spherical particulates. Characterization by XRD, Micro-Raman, XPS, SEM and KPM analysis provided information on the systematic phase and morphology transformation from metallic Fe to hierarchical Iron oxide. Stress-induced phase segregation and stress release process during thermal annealing are suggested as the growth mechanism for the nanostructures. Photocatalytic activity measurements were studied with the coating in presence of Methylene Blue dye through Photo-Fenton process. To understand the effect of precursors, morphology, and synthesis technique (physical and chemical), similar hematite nanostructures were also prepared by thermal annealing of as deposited metallic Fe coating, hematite nanoparticles assembled coating by PLD, and by hydrothermal chemical method respectively. All these coatings showed less photocatalytic activity as compared to the hematite coating obtained from thermal annealing of Fe+H3BO3 sample. A series of various parameters such as effect of H2O2 concentration, effect of pH, water medium and recyclability tests for 10 times were performed, and all revealed promising results in terms of enhanced activity and high mechanical stability of the coatings. Presence of various 3D hierarchical nanostructures, high aspect ratio, more exposed active sites, increased interactions between catalyst surface and reactant dye molecules, and enhanced charge carrier separation, with immobilized stable coating form developed by PLD contributed to achieve the enhanced and stable photocatalytic activity.

Synthesis of hierarchical iron oxide nanostructures from primary nanoparticles and their morphology control via hydrolysis

Flower-like hierarchical iron oxide structures have attracted much research attention due to their large surface area, easy separation and re-use, and ability to adsorb toxic ions. However, harsh synthetic conditions such as the use of surfactants and autoclave reactors limit their broader application. Moreover, control over the porosity and morphology of such structures has not yet been investigated. Facile preparation of hierarchical Fe-glycolate particles is possible using pre-prepared (Fe, Ti) oxide nanoparticles without the use of surfactants or autoclave reactors as they act as both precursors and intermediate seeds for self-assembly. The porosity and morphology of the particles are controlled via variable rates of hydrolysis. Replacement of bulky glycolates with smaller water molecules induces surface area and porosity changes in the hierarchical structures. Hierarchical magnetite particles are obtained from the Fe-glycolate and hydrolyzed particles after reductive annealing, and exhibit different surface areas, porosities and magnetic properties. Porosity-controlled magnetites from hydrolyzed particles also show greater adsorption for removing toxic arsenate ions in water.

Synthesis and magnetism of hierarchical iron oxide particles

Abstract The hierarchical polyhedral α-Fe2O3 oxide particles, and hierarchical spherical CoFe2O4 oxide particles in the microsized ranges have been successfully prepared via modified polyol methods with NaBH4 and heat treatment process. An exact comparison was presented in the soft magnetic properties and structures of new hierarchical α-Fe2O3 and CoFe2O4 oxide particles. To study Fe-based oxide microparticles, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometer have been used to characterize their microstructures and magnetic properties according to the preparation processes. The hierarchical α-Fe2O3 and CoFe2O4 oxide microparticles with oxide grain and grain boundary textures were perfectly formed under heat treatment at high temperature without any chemical self-assembly methods. For this exciting research, the various kinds of homogeneous hierarchical Fe-based oxide particles can be successfully produced in the large amount for commercialization. It is discovered that MS of hierarchical CoFe2O4 particles is much larger than that of hierarchical α-Fe2O3 particles about 93 times. The coordination numbers of Co and Fe cations at tetrahedral and octahedral sites lead to determine its magnetic behavior. Finally, hierarchical Fe-based oxide particles are proposed for promising and potential candidates for energy and environment related technologies associated with safety and sustainability.

The synthesis of hierarchical porous iron oxide with wood templates

Synthesis of hierarchical iron oxide with controllable porous structure by wood templates is presented in this paper. These wood-templated iron oxides (Fe 2O 3) with special hierarchical pore size from 20 nm up to 50 μm were prepared with inorganic precursor solution in four kinds of wood templates. Different characterization techniques such as SEM, FESEM, field emission topography SEM, EDAX, XRD, TEM and N 2 adsorption were used to investigate the structures of iron oxide in different length scales. We demonstrate that the structures of the iron oxide synthesized here are hierarchical porous derived from their wood templates. Moreover, the pore size distribution of wood-templated iron oxide shows dependence on the calcination temperature and wood template.