Fe Nanoparticles Research Articles

Polyimide-based triazine-cored covalent organic frameworks supported metal (Fe, Ni, Ru and Rh) nanoparticles for high-efficiency electrocatalytic hydrogen evolution

Covalent organic frameworks (COFs) have great potential in electrocatalytic hydrogen evolution reaction (HER). Nevertheless, it is a challenging task to fabricate COF-based electrocatalysts with low overpotential and high stability for HER in acidic media. Herein, a series of polyimide-based triazine-cored COFs (PIT-COFs) with different aromatic diimides are designed to support metal (Fe, Ni, Ru and Rh) nanoparticles for electrocatalytic HER. PIT-COFs are obtained by the reaction between melamine and aromatic (benzene, biphenyl, naphthalene and perylene) diimides. PIT-COFs based on perylenediimide show the optimal electrocatalytic HER activity in acidic media due to its large π-conjugated structure. Rh@COFMA-PT has a low overpotential value of 70 mV at 10 mA cm−2 and a small Tafel slope of 56.58 mV dec−1, which surpasses numerous previously published HER electrocatalysts. Furthermore, Rh@COFMA-PT exhibits good electrocatalytic stability and still keeps high activity after 3000 cycles. The conjugated nitrogen-rich structures of PIT-COFs and their ability to effectively anchor metal nanoparticles as active sites significantly promote the electron and proton transport during the electrocatalytic HER process. This work offers a guideline for developing effective and stable COF-based HER electrocatalysts with abundant active sites.

Fire-Induced Multiple Changes in Electron Transfer Properties of Peat Soil Organic Matter: The Role of Functional Groups, Graphitic Carbon, and Iron.

Peatland fires induced changes in electron transfer properties and relevant electroactive structures of peat soil organic matter (PSOM) remain ambiguous, impeding comprehension of postfire biogeochemical processes. Here, we revealed temperature-dependent electron exchange capacity (EEC) of PSOM dynamics through simulated peat soil burning (150-500 °C), which extremely changed postfire microbial Fe-nanoparticles reduction and methanogenesis. EEC diminished significantly (60-75% loss) due to phenolic-quinone moieties depletion with increasing temperature, regardless of oxygen availability. The final EEC in oxic burning surpassed that of anoxic burning by 1.5 times, attributed to additional quinones from oxygen incorporation. Notably, EEC exhibited heat resistance up to 200 °C and stabilized above 350 °C. Additionally, fire reshaped the EEC-relevant redox-active moieties. Heterocyclic-N generated from burning predominantly contributed to the electron-accepting capacity (EAC) alongside quinones, while phenolic moieties and bonded Fe(II) enhanced the electron-donating capacity (EDC). However, the preferential binding of heterocyclic-N to Fe(II) restricted the EDC of Fe(II). Interestingly, the decrease in EAC declined its electron-shuttling effects in microbial Fe nanoparticle reduction, but fire-induced graphitic carbon formation increased the electrical conductivity (EC) of PSOM, promoting electron transfer. Further, enhanced EC may facilitate methanogenesis in postfire peatlands. These findings advance our understanding of elemental biogeochemical cycles and greenhouse emission mechanisms in postfire peatlands.

Highly-improved microwave absorption performance of LaFeO3/Fe@CNTs nanocomposites through in-situ synthesis of Fe@CNTs

In order to enhance the microwave absorption performance, the multi-phase nanocomposites composed of magnetic medium and carbon nanotubes (CNTs) is designed and developed based on impedance matching. In this paper, LaFeO3/Fe@CNTs nanocomposites are prepared in situ using LaFeO3 as catalysts and C2H2 as carbon sources with CVD method, and then the microstructures, magnetic properties and microwave absorption performance are investigated in detail. The specific surface area of LaFeO3/Fe@CNTs nanocomposites increases greatly from 16.39 m3/g for LFC0 to 52.29 m3/g for LFC5 with the increasing CNTs content due to the enhanced heterogeneous interfaces. Ms also increases from 0.68 emu/g for LFC0 to 10.24 emu/g for LFC5 from magnetic Fe nanoparticles. LFC5 exhibits the best microwave absorption properties with the minimum reflection loss of -38.758 dB and a broad effective absorption bandwidth of 2.32 GHz at 2.5 mm. Impedance matching is balanced by permittivity from CNTs and permeability from Fe nanoparticles. Owing to the conductive CNTs with more defects, the dielectric loss and eddy current loss both increases to some extent. The synergistic loss mechanism of magnetic Fe nanoparticles and dielectric CNTs result in impedance matching and outstanding microwave attenuation.

Synthesis, modification, characterization, and in vitro evaluation of chitosan-hyaluronic acid coated MIL-100 (Fe) nanoparticles for methotrexate delivery in rheumatoid arthritis

Synthesis, modification, characterization, and in vitro evaluation of chitosan-hyaluronic acid coated MIL-100 (Fe) nanoparticles for methotrexate delivery in rheumatoid arthritis

Synthesis and Characterization of Iron Nanoparticles from a Bioflocculant Produced by Pichia kudriavzevii Isolated from Kombucha Tea SCOBY

The intriguing characteristics of nanoparticles have fueled recent advancement in the field of nanotechnology. In the current study, a microbial-based bioflocculant made from the SCOBY of Kombucha tea broth was purified, profiled, and utilized to biosynthesize iron nanoparticles as a capping and reducing agent. UV–visible absorption spectroscopy, transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and TGA were used to characterize the Fe nanoparticles. The FT-IR spectra showed functional groups such as hydroxyl, a halogen (C-Br), and carbonyl, and the alkane (C-H) functional groups were present in both samples (bioflocculant and FeNPs) with the exception of the Fe-O bond, which represented the successful biosynthesis of FeNPs. The TEM investigation revealed that the sizes of the produced iron nanoparticles were between 2.6 and 6.2 nm. The UV-vis spectra revealed peaks at 230 nm for the bioflocculant and for the as-fabricated FeNPs, peaks were around 210, 265, and 330 nm, which confirms the formation of FeNPs. X-ray diffraction presented planes (012), (104), (110), (113), (024), (116), and (533) and these planes correspond to 17.17, 32.58, 33.75, 38.18, 45.31, 57.40, and 72.4° at 2Ө. The presence of Fe nanoparticles presented with 0.82 wt% from the EDX spectrum of the biosynthesized FeNPs. However, Fe content was not present from the bioflocculant. SEM images reported cumulus-like particles of the bioflocculant, while that of FeNPs were agglomerated and hexagonal with sizes between 18 and 50 nm. The TGA of FeNPs showed thermal stability by retaining above 60% of its weight at high temperatures. It can therefore be deduced that the purified bioflocculant produced by a yeast Pichia kudraivzevii can be utilized to synthesize FeNPs with the current simple and effective method.

Design and development of green electrode using graphene oxide modified with L-hypip coated with iron NPs for enantioselective electro-organic cyanation in the presence of NaCl electrolyte

This study presents the development of a cost-effective and eco-friendly electrode for the enantioselective electro-organic synthesis of (R)-2‑hydroxy-2-phenylpropanenitriles 4(a-l) with yields ranging from 88 % to 98 %. The electrode is constructed using graphene oxide (GO) modified with (2S,3R)-3-hydroxypiperidine-2-carboxylic acid (L-Hypip) as a cheap enantioselective organic linker and coated with iron (Fe) nanoparticles, referred to as GOHypip@Fe. This design aims to facilitate the efficient synthesis of (R)-2‑hydroxy-2-phenylpropanenitrile derivatives 4(a-l). Sodium chloride (NaCl), a readily available and inexpensive electrolyte, is employed to enhance the electrochemical reaction rate. The electrode underwent thorough characterization and identification using SEM, EDS, XPS, XRD, TGA, BET, CV, and FT-IR analyses. Its cost-effectiveness and eco-friendly nature highlight its potential for sustainable electro-organic synthesis processes. The synthesized (R)-2‑hydroxy-2-phenylpropanenitriles 4(a-l) were identified and characterized through melting point, 1HNMR, and CHN analyses.

Structural and magnetic properties of high magnetization FexCo100-x nanoparticles investigated at the nanoscale: Unveiling the origin of the observed anisotropy

In this work the authors have performed the synthesis of FexCo100-x (0<x<100) alloy nanoparticles (NPs) with different compositions, as well as pure Fe and Co NPs for comparison, by a chemical reduction technique. The subsequent characterization demonstrated excellent quality NPs with the expected bcc cubic (for Fe and FeCo alloys) and hcp hexagonal (for Co NPs) structures showing a room temperature magnetization as high as 235 emu/g for the Fe66Co34 composition alloy. Nevertheless, this soft magnetic character is accompanied by determined values of effective anisotropy as high as 2 MJ/m3. Aiming to deep into the properties of these FeCo alloys as well as to unveil the origin of that observed high anisotropy value, we now present an extensive study at the nanoscale of the synthesized Fe, Co and FexCo100-x alloy nanoparticles by using nuclear techniques as neutron powder diffraction, EXAFS and XANES spectroscopies. Mössbauer spectroscopy revealed that the FeCo alloys are in an A2 disordered solid solution. The obtained results, combined with AFM/MFM images, have demonstrated that despite the cubic bcc structure observed for all FeCo alloys (in excellent concordance with the pure Fe one) the NPs show a "flaky" shape of 50–60 nm size (diameter) but only 3–4 nm thickness, giving rise to a strong shape anisotropy contribution to the observed total effective anisotropy.

Exploring sustainable synthesis paths: a comprehensive review of environmentally friendly methods for fabricating nanomaterials through green chemistry approaches.

This comprehensive review delves into the burgeoning field of nanotechnology, where the synthesis of nanoparticles (NPs) is strategically tailored to specific applications. Embracing the principles of green chemistry, nanotechnology increasingly utilizes environmentally friendly materials, such as plant extracts or microorganisms, as capping or reducing agents and solvents in the synthesis process. Notably, plant-based synthesis demonstrates enhanced stability and faster rates compared to microorganisms. The synthesized materials exhibit unique properties ranging from antimicrobial and catalytic effects to antioxidant activities and they are finding applications across diverse fields. Green synthesis processes, characterized by mild conditions in terms of temperature and reagents, stand in stark contrast to traditional chemical synthesis methods. This review focuses on the synthesis of various metal and metal oxide NPs, including Ag, Au, Zn, Fe, Mg, Ti, Sn, Cu, Cd, Ni, Co, and Ag NPs and their oxides, using plant extracts and microorganisms. We provide a comprehensive analysis of the advantages, disadvantages, and applications associated with each synthesis method. Additionally, we explore the future prospects of green synthesis and its limitations and challenges, offering insights into its evolving role in nanotechnology.

Self-Adaptive Magnetic Liquid Metal Microrobots Capable of Crossing Biological Barriers and Wireless Neuromodulation.

Magnetic liquid-bodied microrobots (MRs) possess nearly infinite shape adaptivity. However, they currently confront the risk of structure instability/crushes during shape-morphing in tiny biological environments. This article reports that magnetic liquid metal (LM) MRs (LMMRs) show high structure stability and robust magnetic maneuverability. In this protocol, Fe nanoparticles are encapsulated inside less-than-10-μm LM microdroplets by establishing interfacial chemical potential barriers, yielding LMMRs. Their robust magnetic maneuverability originates from the magnetically controlled assembly of Fe nanoparticles inside LM and distinct liquid-solid interaction. With the self-adaptive shape-recovering capabilities even after 50% deformation, LMMRs can implement vertical climbing over walls up to 400% of its body length and traverse channels with the size of its two-thirds. The in vitro and in vivo experiments have both verified the effective magneto-mechanical stimulation of LMMRs upon neurons after their shape-adaptive crossing the blood-brain barrier under a driven magnetic field. Our work provides a promising strategy for wireless therapies with MRs by safely and effectively overcoming biological barriers.

Improved Thermoelectric Performance in n–type Bi2(Te,Se)3 Alloys through the Incorporation of Fe Nanoparticles

Improved Thermoelectric Performance in n–type Bi₂(Te,Se)₃ Alloys through the Incorporation of Fe Nanoparticles

Localized heating coupling with radical oxidation eliminating antibiotic resistance genes (ARGs) in interfacial photothermal Fenton-like disinfection process

Conventional oxidative disinfection processes are inefficient in eliminating intracellular antibiotic resistance genes (iARGs) due to the barrier of the cell membrane and the competitive reaction of cellular constituents within antibiotic-resistant bacteria (ARB), resulting in the widespread prevalence of ARGs in recycled water. This study presented the first application of localized heating coupling with advanced oxidation to destroy the resistant Escherichia coli cells and improved subsequent iARGs (blaTEM-1) degradation in a novel photothermal Fenton-like disinfection process. The Fe-Mn@CNT microfiltration membrane, comprising carbon nanotubes wrapped with Fe and Mn nanoparticles (Fe-Mn@CNT), was employed as a nanomaterial for photothermal conversion and H2O2 activation. The highly efficient absorption of full-spectrum photons by CNTs enabled the Fe-Mn@CNT membrane to concentrate light to generate localized intense heat, resulting in the destruction of ARB nearby, and the subsequent release of iARGs. Interfacial heat favored Fe-Mn-induced H2O2 activation, leading to the production of more ·OH, which in turn promoted the oxidation for ARG degradation and ARB cell damage. The results of the acetylcysteine quenching experiments indicated that interfacial heating and radical oxidation-induced accumulation of intracellular reactive oxygen species contributed to the elimination of about 1-log iARGs through direct attack. The integrity of the cell membrane, the morphology of ARB and the variation of i/e ARG copy numbers were observed to reveal that the introduction of interfacial heating aggravated the cell lysis and accelerated the iARGs release, resulting in the inactivation of 7.27-log ARB and the elimination of 4.64-log iARGs and 2.23-log eARGs. Localized heating coupling with ·OH oxidation achieved a 143 % increase in iARGs removal compared to the conventional Fenton-like oxidation. The interfacial photothermal Fenton-like disinfection process exhibited remarkable material stability, robust disinfection performance, and effective suppression of horizontal gene transfer, underscoring its immense potential to mitigate the risk of ARG dissemination in reclaimed water systems.

Leaching and vertical distribution of Fe and Zn citrate nanoparticles in Indian red soil

This research aims to address common constraints in the effective utilization of plant nutrients in soil, such as fixation, mobility, leaching, and reactions with soil colloids. To mitigate these issues, Fe and Zn citrate nanoparticles were synthesized and applied as nanochelators in a reconstructed soil profile column. We evaluated the mobility, release, and leaching behaviors of these nanoparticles. Results revealed that, no leaching of Fe and Zn citrate nanoparticles occurred even after a 90-day incubation. The release profiles exhibited a peak at 60 and 90 days for Fe and Zn respectively. In the mobility studies, Fe and Zn availability was highest in the 0–15 cm soil depth. Fe citrate and Zn citrate nanoparticles demonstrated the highest availability at 264.7 mg/kg and 86.26 mg/kg of soil, respectively as compared with commercial samples. The superior performance of Fe and Zn citrate nanoparticles was observed in terms of reduced leaching and improved accessibility, indicating their potential as efficient and environmentally-friendly plant nutrient sources. The study concludes that Fe and Zn citrate nanoparticles are stable nutrient sources that can enhance plant use efficiency with minimal environmental impact.

Atomically dispersed Fe-N4 sites in activation of peroxymonosulfate for wastewater purification: Mechanism of non-radical pathways and their quantification

Single-atom catalysts are promising alternatives to homogeneous and heterogeneous catalysts in the advanced oxidation processes for contaminant degradation; however, quantifying the exact contribution of nonradical reactive oxygen species has remained challenging. Herein, Fe single atoms anchored on nitrogen-doped carbonaceous substrates (Fe SAs-N-C) were synthesized for peroxymonosulfate (PMS) activation toward pollutant degradation. Fe SAs-N-C achieved high activity within 30 min, which is 17.20 and 5.08 times higher than those of N-C catalysts without or with Fe nanoparticles, respectively. A synergistic mechanism of singlet oxygen (1O2) and electron transfer for dominating pollutant degradation was revealed. The former contributed 78.50 % while the latter contributed 21.50 % in pollutant elimination. Density functional theory calculations uncovered that the O atom in −SO4 moiety of PMS was adsorbed on the Fe atoms, leading to the OH bond elongation and generating 1O2. While the absorbed O atom in OO bond near to −SO4 moiety of PMS tended to enlarge the OO bond and accelerate the electron transfer. The adsorbed PMS was prone to being decomposed into 1O2 due to a lower energy barrier (0.43 eV) of 1O2 rate-determining step than that of electron transfer (0.95 eV). Fe-N4 sites are both electron transfer channels and 1O2 formation sites. This work provides insights into the quantitative contributions of non-radical active species to pollutant degradation.

Microwaves in ferromagnetic composites Fe/Epoxy with aggregates of nanoparticles: Theory and experiment

Microwave transmission through plates of a composite material containing spherical Fe nanoparticles in an epoxyamine matrix and reflection from plates have been studied. Measurements were carried out at the frequencies from 26 to 32 GHz in the magnetic fields up to 12 kOe. The ferromagnetic resonance phenomenon in the composite has been investigated. The theory of electromagnetic waves transmitting through a composite material containing ferromagnetic particles, taking into account aggregating the particles, has been developed. A good agreement of calculation results and experimentally obtained field dependences of the transmission and reflection coefficients, as well as microwaves dissipation, has been achieved.

Ultrasmall Fe‐Nanoclusters‐Anchored Carbon Polyhedrons Interconnected with Carbon Nanotubes for High‐Performance Zinc‐Air Batteries

The catalytic activity of metal catalyst is closely related to its particle size. Yet, the size effect in electrocatalytic oxygen reduction reaction (ORR), an important reaction for metal‐air batteries and fuel cells, has not been clearly studied. Herein, a two‐step anchoring method is utilized to control the Fe catalyst in forms of nanoparticles (NPs), ultrasmall nanoclusters (NCTs), and isolated atoms as well as stabilized and dispersed by carbon polyhedrons interconnected with carbon nanotubes (CNTs). The uniformly distributed Fe NCTs displays superior ORR performance compared with Fe NPs, isolated Fe atoms, and commercial Pt/C. The brilliant ORR activity of Fe NCTs is a result of its unique electron structure and abundant edge and corner active sites. Due to the porous structure of carbon polyhedrons and high electron conductivity of CNTs, Fe NCTs also delivers an excellent discharge performance in zinc‐air battery with a peak power density of 213.3 mW cm−2 and long‐term stability. In these findings, a new strategy for the design of metal NCTs catalysts applied in various catalytic reactions is opened up.

Ni–Fe Nanoparticles Supported on UiO-66-X Catalyst for Hydrogenation of Fatty Acid Esters to Alcohols

Ni–Fe Nanoparticles Supported on UiO-66-X Catalyst for Hydrogenation of Fatty Acid Esters to Alcohols

Magnetic bimetallic nanoparticles confined growth for enhancement of electromagnetic loss in void@Fe@SiO2/Co/C particles

The dispersion of diverse magnetic metallic in a single particle plays an important role in microwave absorption; however, its contribution is not clear due to the challenge of controllable synthesis of magnetic bimetallic nanoparticles in one micro/nanostructure. Herein, a series of magnetic bimetallic nanoparticles separately confined growth in a hollow multi-shell microsphere with proper impedance matching characteristic were prepared, which can be used as theoretical models to elucidate magnetic coupling effect between diverse magnetic metallic nanoparticles in a single particle on electromagnetic attenuation. The coupling effect of magnetic Co and Fe nanoparticles dispersed in different shell effectively enhance the microwave absorption performance of void@Fe@SiO2/Co/C particles with minimum reflection loss (RLmin) of −62.3 dB (RL=-20 dB, 99 % absorption) at a thickness of 2.05 mm, provoking the maximum radar cross-section (RCS) reduction value of perfect electric conductor (PEC) 37.37 dBm2. Meanwhile, broad effective bandwidth (EBW, RL≤-10 dB, ≥90 % absorption) response of 7.04 GHz at a thickness of 2.44 mm was achieved. These findings can provide guidance for the designation of novel magnetic broadband microwave absorbing materials (MAMs).

Operando electron spin probes for the study of battery processes

Operando electron spin probes, namely magnetometry and electron paramagnetic resonance (EPR), provide real-time insights into the electrochemical processes occurring in battery materials and devices. In this work, we describe the design criteria and outline the development of operando magnetometry and EPR electrochemical cells. Notably, we show that a clamping mechanism, or springs, are needed to achieve sufficient compression of the battery stack and an electrochemical performance on par with that of a standard Swagelok-type cell. The tandem use of operando EPR and magnetometry allows us to identify five distinct and reversible redox processes taking place on charge and discharge of the intercalation-type LiNi0.5Mn0.5O2 Li-ion cathode. While redox processes in conversion-type electrodes are notoriously difficult to investigate using standard characterization methods (e.g. X-ray based) and/or post mortem analysis, due to the formation of poorly crystalline and metastable reaction intermediates and products during cycling, we show that operando magnetometry provides unique insight into the kinetics and reversibility of Fe nanoparticle formation in the Na3FeF6 electrode for Na-based batteries. Step increases in the cell magnetization upon extended cycling indicate the build-up of Fe nanoparticles in the system, hinting at only partially reversible charge–discharge processes. The broad applicability of the tools developed herein to a range of electrode chemistries and structures, from intercalation to conversion electrodes, and from crystalline to amorphous systems, makes them particularly promising for the development of electrochemical energy storage technologies and beyond.

Enhancement of oxygen flux through Nb-doped La0.4Sr0.6FeO3-δ ceramic hollow fiber membranes by Fe exsolution

In recent years, numerous studies have focused on the use of mixed ionic-electronic conducting oxides for coupled oxygen separation and catalytic reactions in membrane reactors. A promising strategy for the efficient fabrication of oxygen separation membranes involves modification of the membrane surface via exsolved metal nanoparticles decoration. Here, we present a detailed characterization of the structural and transport properties of a novel membrane material La0.4Sr0.6Fe0.95Nb0.05O3−δ (LSFNb5). The exsolution of Fe nanoparticles was observed after heating of LSFNb5 in a reducing atmosphere (5 % Н2/Ar) and was confirmed by X-ray diffraction analysis, Mössbauer spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The formation of Fe nanoparticles on the surface of LSFNb5 hollow fiber membrane in the reduction process leads to the enhancement of oxygen fluxes and reduces the apparent activation energy. Kinetic parameters for oxygen transport through LSFNb5 hollow fiber membrane estimated using two different models, are in good agreement with the experimental results. Furthermore, LSFNb5 hollow fiber membrane demonstrates stable performance both before and after surface treatment.

Nanoengineered pure Fe in a citrate matrix (Fe–CIT) with significant and tunable magnetic properties

This work demonstrates the synthesis and characterization of Fe nanoparticles surrounded by a citrate (CIT) matrix prepared at various temperatures and concentrations of metal, capping agent and reducing agent at standard conditions. We study the effect of reactant ratio and reaction temperature on the magnetization of the produced nanoparticles and their crystal structure. We found that for optimal metal concentrations, magnetic saturation increases with increase in the concentration of capping and reducing agents but decreases as the temperature of the reaction increases. Synthesis conditions were tailored to reveal nucleation of particles with average sizes ranging from 24 to 105 nm and a spherical shape. The ultra-high saturation magnetization of 228 emu g-1obtained for samples prepared at a metal precursor concentration of 27.8 mol l-1was attributed to the formation of small magnetic domains. Energy band gap measurements revealed a band gap energy for the Fe nanoparticles in the CIT matrix which is associated with CIT concentration and/or possible formation of a few thin layers of iron oxide shell and does not have a significant effect on the magnetic properties of the samples. Herein, we demonstrate that the synthesis parameters are crucial for the nucleation of Fe-CIT nanoparticles tailoring their magnetizatic properties as well as their potential for different applications.