γ-Fe2O3 Nanorods Research Articles

Optimizing D-band center of tube brush-like CoZn13/Co/ZnO architecture with multiple-heterointerfaces enhancing ion/electron migration toward pseudocapacitive storage

The exploration of hierarchical heterostructures with heterointerfaces have proven indispensable for enhancing ion/electron migration of efficient energy storage. Herein, a fascinating design of CoZn13/Co/ZnO hierarchically porous nanostructures (CZCZ HPNs) with rich heterointerfaces concurrently encapsulated into N-doped carbon (NC), growing on three-dimensional Ni foam wrapped by N-doped graphene (denoted as CZCZ/NC HPNs) is showcased for pseudocapacitive storage. The ingeniously construction of CZCZ HPNs/NC features powerful built-in electric field (BIEF) introduced by well-defined heterointerface for boosting electronic/ionic transport dynamics, and unique porous hierarchical architectures for reinforcing the structural and electrochemical stability. Notably, combined with the differential charge density analysis, the BIEF in CZCZ/NC HPNs generated by two heterointerfaces of Co-ZnO and CoZn13-ZnO can offer additional driving forces for promoting electron transfer. The d band centers of different heterojunctions remarkably shift negatively in comparison with those of the monomers, indicative of lower electron/ion transfer energy barrier. Additionally, the CZCZ/NC HPNs as a positive electrode and porous γ-Fe2O3 nanorods wrapped by NC (γ-Fe2O3/NC) as a negative electrode are employed to assemble a soft-packed hybrid supercapacitor device with ultrahigh energy density of ∼107.2 Wh kg−1 at ∼399.9 W kg−1. This work highlights an in-depth fundamental understanding of underlying reaction mechanisms of the heterointerface and structures engineering in constructing other advanced electrodes in sustainable energy storage.

Surface engineering of hematite nanorods photoanode towards optimized photoelectrochemical water splitting

Rapid charge recombination in hematite (Fe2O3) during photoelectrochemical water splitting is a major obstacle to achieving high-efficiency photoelectrodes. Surface defect engineering is considered as a viable strategy for enhancing photoelectrochemical activity of oxide photoanodes. Herein, a one-dimensional (1D) defective γ-Fe2O3 nanorods (DFNRs) photoanode is prepared using solvothermal and high-temperature hydrogenation strategies. The as-prepared DFNRs possess superior visible-light absorption capacity and exhibit excellent photoelectrochemical performance (0.98 mA cm−2), with approximately three-fold higher photocurrent density than that of pristine Fe2O3 (FNRs, 0.32 mA cm−2). The enhanced activity of the DFNRs results from the moderate formation of oxygen vacancy defects, which promotes spatial charge separation and transfer at the DFNRs/electrolyte interface, as well as the 1D nanorod structure, which favors rapid charge transfer. The surface of γ-Fe2O3 with hydroxyl (OH) groups provides sufficient surface-active sites. This result suggests that surface-oxygen deficiency of γ-Fe2O3 can not only expand the light absorption range but also facilitating photo-generated charge carriers separation. This surface engineering strategy provides an alternative method for preparing stable and highly active metal oxide photoanodes for photoelectrochemical water splitting.

Optical and electrochemical properties of iron oxide and hydroxide nanofibers synthesized using new template-free hydrothermal method

We report the effect of hydrothermal synthesis conditions on the morphological, optical and electrochemical properties of as-prepared iron oxide (γ-Fe2O3) and hydroxide (α-FeOOH) nanostructures. The physico-chemical identification of these Fe-based nanostructures using X-ray diffraction, scanning/transmission electron microscopy, porosity and Raman spectroscopy analyses revealed a temperature-depended phase transformation. A maghemite and goethite iron-based nanostructured formation was observed in nanorod and trigonal nanofiber shape-like morphology with mean diameters ranging from 32 to 50 nm. The textural analysis of the nanofibers confirmed mesoporosity with a specific surface area of ~ 129 m2 g−1 (in γ-Fe2O3) and 23 m2 g−1 (in α-FeOOH). The electrochemical performance of the iron oxide and hydroxide nanofiber electrodes with and without the addition of activated carbon (AC) was also investigated. The sample electrodes composed of γ-Fe2O3, γ-Fe2O3/AC, α-FeOOH and α-FeOOH/AC showed remarkable specific capacities of 164 mAh g−1, 330 mAh g−1, 51 mAh g−1 and 69 mAh g−1 at 1 A g−1 gravimetric current. The influence of the phase transformation linked to the synthesis temperature, and the inclusion of an electric double-layer AC material into the nanofibers clearly demonstrates an enhancement in their energy-storage capability. Furthermore, the Fe-based nanofibers exhibited excellent cycling stability with good capacity retention of 73% and 99.8%, respectively, after 2000 cycles at a high 30 A g−1 gravimetric current as well as low resistance obtained by impedance spectroscopy analysis. The implication of the results depicts the potential of adopting these γ-Fe2O3 nanorods as suitable material electrodes in electrochemical energy-storage devices.

Effects of initial crystal structure of Fe2O3 and Mn promoter on effective active phase for syngas to light olefins

Although it is generally acknowledged that iron carbides are the active phase in Fischer-Tropsch synthesis (FTS), adjusting the formation of active phase and catalytic performance via the initial crystal structure of iron oxides has never been studied. Herein, we take one-dimensional pure phase α-Fe2O3 and γ-Fe2O3 nonporous nanorods to explore the effects of initial crystal phase of Fe2O3 on both formation of active phase and corresponding catalytic performance, in which the influence of diffusion limitation on selectivity can be ignored. In situ characterizations uncovered that the formation of iron carbides with high selectivity of light olefins strongly depends on the initial crystal phase of iron oxide and its induced metal-promoter interaction. Responding to the morphology effect and crystallographic phase effect, Mn located on surface of γ-Fe2O3 nanorods exhibit a low oxidation state due to a strong Fe-Mn interaction. This interaction was beneficial to the formation of C-poor iron carbide species at the metal-promoter interface during carburization. Hence, outstanding selectivity for light olefins (61.2%) was achieved on 0.5 Mn/γ-Fe2O3 nanorods catalyst at a CO conversion of 55.1% under industrially relevant conditions (320 °C, 1 MPa, H2/CO ratio of 1, and W/F = 5 gcat h mol−1). This finding enriches the fundamental understanding of active phase evolution and promoter effect in STO process and may guide the design of a catalyst with high selectivity.

Bio-activity of superparamagnetic maghemite nanorods capped with dl-alanine

The present research work explores an economic way of synthesizing maghemite (ᵞ-Fe2O3) nanorods through chemical coprecipitation method in which, ferric chloride was used, as one of the precursors and Sodium hydroxide as fuel with the assistance of dl-alanine, an organic surfactant. The obtained ᵞ-Fe2O3 nanorods have been characterized by X-ray diffraction, Fourier Transform Infrared Spectroscopy, Scanning electron microscopy, Transmission Electron Microscopy and Vibrating sample magnetometer techniques. X-ray diffraction results show that the synthesized ᵞ-Fe2O3 nanorods are in cubic spinel phase with improved crystalanity. The morphology and the size of the nanoparticles were confirmed by SEM as well as TEM. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of the sample have been performed. The FTIR spectra indicate the incorporation of dl-alanine on ᵞ-Fe2O3 nanorods. The saturation magnetization value of maghemite, measured by vibrating sample magnetometer corresponds to the typical superparamagnetic behavior. On examining the magnetic saturation (Ms) was found out to be 142emu/g, 57.7% higher than the bulk value, which is highly recommended for biomedical application. The antibacterial activity of ᵞ-Fe2O3 sample against gram-positive Streptococcus mutans, Staphylococus aures and gram-negative E.coli, Klebsiella pneumonia was investigated using Well diffusion method. The antifungal activity was tested by the same method against Aspergillus niger and Candida albicans. The MTT assay was employed to test the anticancerous activity of ᵞ-Fe2O3 against HT29 (coloncarcinoma) cell line. The sample shows positive control over antimicrobial species. The Lethal Dosage of the sample calculated to be 45.3149μg/ml, establishes its strong activity over HT29 cell line.

Pd@Fe2O3 Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth

Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe2O3 nanorods. The interfacial strain at the Pd−γ-Fe2O3 interface is minimized by the formation of an FexPd “buffer phase” facilitating the growth of the nanorods. The γ-Fe2O3 nanorods show a (111) orientation on the Pd(111) surface. Importantly, the Pd@γ-Fe2O3 hybrid nanomaterials exhibit enhanced peroxidase activity compared to ...

Hierachical Ni@Fe2O3 superparticles through epitaxial growth of γ-Fe2O3 nanorods on in situ formed Ni nanoplates.

One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water.

Constructing aligned γ-Fe2O3 nanorods with internal void space anchored on reduced graphene oxide nanosheets for excellent lithium storage

Unique 1D aligned γ-Fe2O3 nanorods with internal void spaces anchored on 2D rGO nanosheets were successfully constructed. The resultant nanocomposites of γ-Fe2O3/rGO exhibit excellent lithium storage properties.

Preparation and visible-light photocatalytic activity of α-Fe2O3/γ-Fe2O3 magnetic heterophase photocatalyst

Magnetic heterophase photocatalyst of α-Fe2O3/γ-Fe2O3 nanorods was prepared by a facile thermal decomposition and redox method. The nanorods were about 100nm in length and 20nm in diameter, and well-structured heterophase junctions were formed between α-Fe2O3 and γ-Fe2O3. Visible-light induced photodegradation of model dye rhodamine B was investigated by using the as-prepared α-Fe2O3/γ-Fe2O3 nanorods. The material exhibits a remarkably enhanced visible-light photocatalytic activity than the single-phase α-Fe2O3 or γ-Fe2O3 owing to its well-structured interfaces and suitable band configuration. The existence of magnetic γ-Fe2O3 facilitates the practical application of photocatalysts.

Solvent-mediated synthesis of magnetic Fe2O3 chestnut-like amorphous-core/γ-phase-shell hierarchical nanostructures with strong As(v) removal capability

In this paper, a magnetic adsorbent of iron oxide (Fe2O3) with a chestnut-like amorphous-core/γ-phase-shell hierarchical nanostructure (CAHN) has been synthesized in a rationally designed chemical reaction system, where the decomposition rate of Fe(CO)5 is controlled by the CO generated from the decomposition of N,N-dimethylformamide under the assistance of the hydrolysis of SnCl2·2H2O. By utilizing the current chemistry equilibrium dynamics, it is possible to kinetically modulate the nucleation and subsequent growth of Fe2O3 to form chestnut-like hierarchical nanostructures, in which single crystalline γ-Fe2O3 nanorods, with a diameter of 20 nm and a length of 300 nm, radially grow from the surfaces of amorphous and porous Fe2O3 sub-microspheres. The detailed possible formation mechanism of the Fe2O3 CAHNs is proposed according to the experimental results. The as-obtained Fe2O3 CAHNs show a strong adsorption capability for As(V), with a maximum adsorption capacity of 137.5 mg g−1, because of both the specific surface area, which can be as large as 143.12 m2 g−1, and the heterogeneous surface properties. Furthermore, their ferromagnetic properties make them easy to separate from water by magnetic separation. The adsorption process obeys the Freundlich isotherm model well, but not the Langmuir model, suggesting that a multilayered adsorption occurs on the surface of the Fe2O3 CAHNs. Our work may shed light on the design and preparation of high performance 3D hierarchically nanostructured adsorbents.

Synthesis of acicular iron oxide nanoparticles and their dispersion in a polymer matrix

An alternative forced hydrolysis approach for the synthesis of β-FeOOH of varying dimensions was achieved. The β-FeOOH particles were converted into γ-Fe2O3 in a colloidal process, which eliminated the agglomeration of γ-Fe2O3 particles. The acicular γ-Fe2O3 nanoparticles could be readily dispersed into an organic solvent. Preliminary studies have demonstrated that the dispersion of the γ-Fe2O3 nanorods in a polymer matrix is feasible leading to an organic-inorganic nanocomposite.