Fe Nanoparticles Research Articles

Clove bud extract mediated green synthesis of bimetallic Ag–Fe nanoparticles: Antimicrobial, antioxidant and dye adsorption behavior and mechanistic insights of metal ion reduction

Metal nanoparticle synthesis by metal ion reduction from plant extract has paid immense attention to researchers owing to its low cost, easy synthesis and eco-friendly nature compared to other biological methods. Compared to monometallic nanoparticles, syntheses of bimetallic nanoparticles have great importance due to the possibility of better performance of bimetallic nanoparticles compared to their monometallic counterpart. To explore this possibility, we synthesized bimetallic Ag–Fe nanoparticles of different compositions using aqueous phase co-reduction of Ag+ and Fe3+ metal ions in different ratios by clove (Syzygium aromaticum) flower bud extract. Prepared nanoparticles were characterized by Ultraviolet–visible spectroscopy, powder X-ray diffraction and Scanning Electron Microscopic studies, etc. All bimetallic nanoparticles exhibited multifaceted applications as antimicrobial agents, antioxidants and dye adsorbents. Among the different nanoparticles, bimetallic nanoparticles having Ag–Fe ratio 80:20 exhibit better performance for antimicrobial and dye adsorption activity than mono as well as other bimetallic nanoparticles. As depicted by the powder X-ray diffraction study, the synergy between metals is attributed to the prevention of oxidation of silver to silver oxide in the presence of iron. However, antioxidant activity is directly related to silver content as both silver and silver oxide exhibit almost similar antioxidant properties. The synergy between the metals in bimetallic nanoparticles provided the opportunity to enhance the activity of nanomaterials for various applications along with lowering the cost. Besides the synthesis and activity study of bimetallic nanoparticles, we tried to provide theoretical evidence for the mechanism of metal ion reduction by Eugenol (a major phytochemical present in the clove extract). Structural optimization and thermodynamic parameter calculation using DFT methods suggest that eugenol is preferred to oxidize itself and theoretically calculated reduction potential is ∼ -3.40V at 300K in the gaseous phase.

Synergistic effect of sub-5 nm Fe nanoparticles supported on nanoporous carbon for catalyzing hydrogen storage properties of Mg(BH4)2

This study investigates synergistic effects of sub-5 nm Fe nanoparticles (FeNPs) supported on mesoporous carbon (MC) for catalyzing hydrogen storage properties of Mg(BH4)2 (MBH). The study compares two methods for dispersing Fe NPs in MC: (i) ultrasonication nanoconfinement (un) and (ii) post-nanoconfinement (pn) via stirring. Based on the results, it is found that the ultrasonication nanoconfinement method can effectively disperse the FeNPs with 5 nm in MC support (FeNP-un-MC), later which can efficiently confine MBH (FeNP-un-MC@MBH system). The hydrogen (H2) desorption properties of the FeNP-un-MC@MBH system were found to be better than that of post-confinement-mediated FeNP-pn-MC@MBH system. For instance, H2 started to desorb from the FeNP-un-MC@MBH system at only 66 °C (Tonset) and reached its peak at ∼153 °C, compared to 270 °C (Tonset) and its peak ∼350 °C for pure MBH, respectively. The ultrasonication-mediated nanoconfined FeNP-un-MC@MBH system released a total of 7.01 wt% H2 within 90 min at 350 °C. The study shows that the activation energy (Ea) of FeNP-un-MC@MBH is 19.57 kJ/mol, achieved due to the improved dehydrogenation kinetics of MBH. These improvements are due to the synergistic effects of nano-compartmentalization and highly dispersed Fe NP catalyst sites in the MC support. The research emphasizes the promising application of ultrasonication-mediated nanoconfined Fe NPs in mesoporous carbon which can be used as an effective catalyst for enhancing the hydrogen storage properties of metal-based hydrides (MBH).

Investigating the stability of Ni and Fe nanoparticle distribution and the MWCNT structure in the dry reforming of methane.

Catalysts based on Ni and Fe nanoparticles deposited selectively on carbon nanotubes were investigated before and after the dry methane reforming. Three catalysts were synthesized and evaluated, varying the concentration of Ni inside and Fe outside the carbon tubes. BET analysis revealed that the acid treatment opened the ends of the nanotubes and resulted in a higher surface area. Transmission electron microscopy (TEM) showed 24 layers with inner diameter ranging from 4 to 6nm and outer diameter ranging from 16 to 22nm. Raman spectroscopy confirmed that after calcination at high temperature the structure of the nanotubes was maintained. X-ray diffraction (XRD) analysis of the catalysts confirmed the presence of NiO (2.6-3.2nm) and Fe2O3 (4.3nm) crystallites. The catalytic tests presented high activity in dry methane reform (DRM). The catalysts 10Ni@CNT and 10Ni@CNT/5Fe presented conversions of CH4 (63 and 67%) and CO2 (72 and 88%), respectively, at 800°C, under atmospheric pressure. Analysis after the reaction showed an increasing ratio of ID/IG, which indicates the formation of defects. The Raman analysis showed that even after calcination at high temperatures the structures of the nanotubes were mostly preserved, and TEM images showed that during the reaction, there were formation of nanotubes occurring randomly.

Pd–Ni–Fe Nanoparticles Supported on UiO-66 for Selective Hydrogenation of Fatty Acid Methyl Esters to Alcohols

Pd–Ni–Fe Nanoparticles Supported on UiO-66 for Selective Hydrogenation of Fatty Acid Methyl Esters to Alcohols

Heterogeneous Interface Engineering of Bi‐Metal MOFs‐derived ZnFe2O4–ZnO‐Fe@C Microspheres via Confined Growth Strategy Toward Superior Electromagnetic Wave Absorption

AbstractHeterogeneous interface regulation plays an important role in tailoring the intrinsic electromagnetic (EM) properties for obtaining excellent EM wave absorption, which still faces huge challenge. In this work, bi‐metal MOFs‐derived ZnFe2O4–ZnO‐Fe@C (ZZFC) microspheres with custom‐built heterogeneous interfaces are successfully fabricated via a confined growth strategy. Bi‐metal Fe–Zn–ZIF with tailored coordination structure and chemical bonding are first selected as the precursor template. After undergoing the annealing process, the metal Fe2+ host is converted into magnetic Fe nanoparticles (NPs). The Zn2+ host is transformed into semiconductor zinc oxide (ZnO) with increasing (101) crystal‐oriented growth. At the same time, metal hosts Fe2+ and Zn2+ are further reacted to synthesize the zinc ferrite (ZnFe2O4). Formed Fe nanoparticles catalyze organic ligands to constitute graphitized carbon layers, which confine the further growth of ZnFe2O4, ZnO, and Fe NPs. Combined with the well impendence and synergy absorption mechanism (magnetic loss, interface polarization, and conduction loss), optimized magnetic–dielectric ZnFe2O4–ZnO‐Fe@C microspheres exhibit outstanding EM wave absorption with the minimum reflection loss −66.5 dB at only 2.0 mm thickness. Bi‐metal MOF‐derived magnetic–dielectric absorption materials with tailored heterogeneous interfaces provide a new sight to design an efficient EM wave absorption system.

Double perovskite decorated with in situ exsolved Fe nanoparticles as active catalyst for CO2 electrolysis

The double perovskite (Pr0.5Ba0.5)1.8Fe1.8Mn0.2O5-δ decorated with in situ exsolved Fe nanoparticles (Fe@PBFM) was used as the cathode in a solid oxide electrolysis cell (SOEC) to convert CO2 to CO and exhibited high efficiency and stability. This catalyst is synthesized from the simple perovskite (Pr0.5Ba0.5)0.9Fe0.9Mn0.1O3-δ (PBFM) by annealing it under an H2-N2 atmosphere at 850 °C for 15 h. The cell fabricated with the Fe@PBFM cathode shows a higher current density of 1.6 A/cm2 at 850 °C and 1.8 V than the cell with the unreduced PBFM. The increased current density can be attributed to the in situ exsolved Fe nanoparticles and generation of the Fe@PBFM double perovskite. Furthermore, the cell containing this active catalyst exhibits stable CO2 electrolysis performance for 100 h at a stable voltage of 1.3 V, suggesting that Fe@PBFM is an attractive candidate as SOEC cathode for CO2 electrolysis.

Dielectric and Humidity Sensing Properties in Iron Nanoparticle Substituted Polyaniline Composite

The existence of graphene-based Polyaniline nanocomposite has been demonstrated to be exceptional host matrices for entrapping nano-sized particles, and its composites are widely used in a variety of applications such as transducers, sensors, electrodes, microwave absorption, and thermoelectric applications. The purpose of this study is to investigate the dielectric properties and humidity sensing response of a Fe doped PANI/Graphene (PAFG) composite synthesized in-situ polymerization using adhathoda vasica plant extract. The FT-IR, XRD, and SEM-EDX techniques were used to characterize the sample. The dielectric measurements were performed at 298K over a wide frequency range 5x101 to 5x106 Hz. Humidity response studies were performed at room temperature. Iron nanoparticles distributed homogeneously in the PANI matrix were ascertained from IR spectral data. At room temperature, the dielectric properties of the synthesized DS-4 powder outperform those of the synthesized pristine PANI and Fe nanoparticles, with superior dielectric constant and high dielectric loss. When the synthesized iron decorated composite was exposed between 10% and 97% RH, the electrical resistance decreased, which is attributed to the polarization process affecting electrical conductivity within these materials. The PAFG-40% composite exhibited high sensitivity at low humidity levels ranging from 30% to 70% RH.

Bimetal-oxide (Fe/Co) modified bagasse-waste carbon coated on lead oxide-battery electrode for metronidazole removal

Current study covers the preparation and application of a commercial modified lead oxide battery electrode (LBE) in electrochemical oxidation (ECO) of metronidazole (MNZ) in an aqueous phase. Modified electrode is prepared by doping of bimetal-oxide (Fe and Zn) nanoparticles (NPs) & single metal-oxide (Fe/Zn) on bagasse-waste carbon (bwc) which is further coated on LBE. The modified LBE electrode surface was examined for metal-oxide NPs through X-ray diffraction analysis (XRD). Different electrodes are prepared by varying combinations of two metal-oxide based on molar ratio and tested for electrochemical characterization and MNZ removal test. Based on large oxygen evolution potential in a linear sweep volumetry (LSV) analysis and high MNZ removal rate, the best electrode has been represented as Fe1:Co2-bwc/LBE which contains Fe & Co molar ratio of 1:2. Moreover, equilibrium attained at faster rate in degradation process of MNZ, where pseudo first order kinetics of 2.29 × 10−2 min−1 was obtained under optimized condition of (MNZ:100 mg/L, pH:7, CD: 30 mA/cm2 and electrolyte: 0.05 M Na2SO4). Maximum MNZ removal, total organic carbon removal (TOC), mineralization current efficiency (MCE) & energy consumption (EC) of 98.7%, 85.3%, 62.2% & 96.143 kW h/kg-TOC removed are found in 180 min of treatment time for Fe1:Co2-bwc/LBE electrode. Accelerated service life test confirms that the stability of modified electrode is enhanced by 1.5 times compared to pristine LBE. Repeatability test confirms that modified LBE (Fe1:Co2-bwc/LBE) can be utilized up to 3 times.

Pt–Fe Nanoparticles Dispersed on Mesoporous Silica as Selective Catalysts for Dehydrogenation of Isobutane

Pt–Fe Nanoparticles Dispersed on Mesoporous Silica as Selective Catalysts for Dehydrogenation of Isobutane

CARBON NANOSPHERE SYNTHESIZED FROM MAIZE COB-HAIR FOR ARSENIC ADSORPTION FROM WATER

Carbon Nanospheres (CNS) are synthesized by pyrolyzing Maize cob-hair using the CVD method for two hours, at 10000C in presence of Ni, Fe, or Co nanometals as the catalyst. The morphology of carbon nanomaterial was characterized by the HRSEM images. The XRD pattern and the Raman spectrum confirmed the graphitic nature of the carbon. Surface area measurement of CNM was done by the Methylene Blue test method. The impact of catalyst was noted on the surface area of the carbon nanosphere; the maximum being 95.018 m2/g when Fe nanoparticle was used as catalyst, 83.141 m2/g when Ni was used, and a minimum of 21.379 m2/g in presence of Co. These carbon nanospheres were used for Arsenic adsorption from water. Adsorption of Arsenic was assessed by Chand Pasha et al’s method. It was found that after 12 hrs of exposure, CNS with 95 m2/g surface area could adsorb 32% arsenic; CNS (of 23.8m2/g surface area adsorbed 31% whereas CNS (surface area of 21.379m2/g. could adsorb only 16% arsenic. The arsenic adsorption capacity was found to be affected by the available surface area.

Tumor targeted cancer membrane-camouflaged ultra-small Fe nanoparticles for enhanced collaborative apoptosis and ferroptosis in glioma.

Glioma is recognized as the most common and aggressive primary brain tumor in adults. Owing to the occurrence of drug resistance and the failure of drug to penetrate the blood-brain barrier (BBB), there is no effective strategy for the treatment of glioma. The main objective of this study was to develop a biomimetic glioma C6 cell membrane (C6M) derived nanovesicles (DOX-FN/C6M-NVs) loaded with doxorubicin (DOX) and ultra-small Fe nanoparticles (FN) for accomplishing the effective brain tumor-targeted delivery of DOX and improving anti-cancer efficacy via inducing collaborative apoptosis and ferroptosis. The findings revealed that employing C6M-NVs as a carrier significantly improved the therapeutic efficacy by enabling evasion of immune surveillance, facilitating targeted drug delivery to tumor sites, and minimizing cardiotoxicity and adverse effects associated with DOX. DOX-FN/C6M-NVs exhibited more potent anti-tumor effects as compared with free DOX by promoting DOX-mediated apoptosis and accelerating ferroptosis via the mediation of FN. This study suggested that DOX-FN/C6M-NVs as the potential inducer of ferroptosis and apoptosis conferred effective tumor suppression in the treatment of glioma.

Application of Iron Nanoparticles Synthesized from a Bioflocculant Produced by Yeast Strain Pichia kudriavzevii Obtained from Kombucha Tea SCOBY in the Treatment of Wastewater.

Studying the production of Iron (Fe) nanoparticles using natural substances is an intriguing area of research in nanotechnology, as these nanoparticles possess biocompatibility and natural stability, which make them useful for a variety of industrial applications. The study utilized Fe nanoparticles that were synthesized using a bioflocculant and applied to eliminate different kinds of pollutants and dyes found in wastewater and solutions. The study involved the generation of Fe nanoparticles through a bioflocculant obtained from Pichia kudriavzevii, which were evaluated for their flocculation and antimicrobial capabilities. The impact of the Fe nanoparticles on human embryonic kidney (HEK 293) cell lines was studied to assess their potential cytotoxicity effects. An array of spectroscopic and microscopic methods was employed to characterize the biosynthesized Fe nanoparticles, including SEM-EDX, FT-IR, TEM, XRD, UV-vis, and TGA. A highly efficient flocculating activity of 85% was achieved with 0.6 mg/mL dosage of Fe nanoparticles. The biosynthesized Fe nanoparticles demonstrated a noteworthy concentration-dependent cytotoxicity effect on HEK 293 cell lines with the highest concentration used resulting in 34% cell survival. The Fe nanoparticles exhibited strong antimicrobial properties against a variety of evaluated Gram-positive and Gram-negative microorganisms. The efficiency of removing dyes by the nanoparticles was found to be higher than 65% for the tested dyes, with the highest being 93% for safranine. The Fe nanoparticles demonstrated remarkable efficiency in removing various pollutants from wastewater. In comparison to traditional flocculants and the bioflocculant, biosynthesized Fe nanoparticles possess significant potential for eliminating both biological oxygen demand (BOD) and chemical oxygen demand (COD) from wastewater samples treated. Hence, the Fe nanoparticles synthesized in this way have the potential to substitute chemical flocculants in the treatment of wastewater.

Tailored microwave absorption performance through interface evolution by in-situ reduced Fe nanoparticles on the surface of FeSiAl microflake

Poor impedance matching and low-frequency magnetic resonance are great challenge for Fe-based micron-scale materials as microwave absorber in GHz range. Here, we propose in situ interface engineer strategy for tailoring the interface through in situ reduced Fe nanoparticles and introduce planar anisotropy for flattening particles with high aspect ratio during high-energy vertical ball milling process, which can synchronously enhance impedance matching and exceed Snoke’s limit. With increasing milling time, the interface experiences the following in situ evolution: the nano oxide layer-micro particles interface, the partial interface between nano oxide layer and Fe nanoparticles, the integrity Fe nanoparticles-oxide layer interface, the nano oxide layer-microflake interface. Meanwhile, the aspect ratio is up to 74.93. The evolution of interface and high aspect ratio can effectively tailor permittivity and permeability. Due to the novel microstructure that FeSiAl flake are covered by ∼ 30 nm oxide layer containing ∼ 10 nm Fe nanoparticles, natural resonance induced by planar anisotropy, eddy current loss of metallic microflake, relaxation loss induced by interface polarization, conductive loss from electric resistivity together led to good microwave absorption performance (effective absorbing bandwidth of 3.12 GHz at 3.2 mm and minimal reflection loss of −44.47 dB at 7.44 GHz and 3.3 mm). The present finding might highlight for developing the composite absorbers with multi loss type coupling across nano-micro scales.

Adding Fe/dicyandiamide to Co-MOF to greatly improve its ORR/OER bifunctional electrocatalytic activity

Exploring efficient non-precious metal oxygen electrocatalysts for oxygen reduction/evolution reactions (ORR/OER) is of great importance in electrochemical energy conversion devices like metal-air battery. Among them, carbon-based composites derived from metal-organic framework (MOF) exhibit excellent catalytic performance in ORR/OER. In this paper, Co-MOF-67 was firstly prepared, and then mixed with FeCl3·6 H2O and dicyandiamide, followed by a one-step pyrolysis to obtain bamboo-like nitrogen-doped carbon nanotubes. For the samples, Fe and Co nanoparticles were encapsulated in the front end of the carbon nanotubes and the presence of new (n)-diamond carbon was unexpectedly found. The obtained catalyst (FeCo@CNTs-60) has an onset potential of 1.04 V for ORR in alkaline solution, which is close to the commercial Pt/C (40 wt% Pt) of 1.05 V. The onset potential of 1.02 V in quasi-neutral solution exceeds that of Pt/C of 0.99 V. In addition, FeCo@CNTs-60 exhibited a low potential difference of 0.81 V between OER and ORR potentials. The alkaline zinc-air batteries, fabricated with the sample as the electrocatalyst of air electrode, exhibit higher peak power density and stability than Pt/C, while the rechargeable batteries present superior cycling discharge/charge stability at 5 mA·cm−2 and 10 mA·cm−2. In particular, the battery with FeCo@CNTs-60 was conducted for continuous over 1300 h of ultra long-term cycle charging / discharging test at a current density of 5 mA·cm−2, and it reveals excellent stability with high voltage efficiency and also presents superior cycle charging / discharging stability after replacing the Zn plates and electrolyte.

Magnetic ordering boost excellent thermoelectric performance of flexible films

The poor electrical transport performance of flexible thermoelectric (TE) films is a major bottleneck for the development of in-plane heat dissipation technology based on Peltier effect. Herein, ordered Fe nanoparticles (Fe-NPs) and in-situ Fe3O4 nanoparticles (Fe3O4-NPs) as magnetic functional elements (MFEs) were embedded into Bi0·5Sb1·5Te3 (BST)/epoxy flexible films in order to enhance the TE performance. The remarkable increases in electrical conductivity of BST/MFEs/BST/epoxy flexible films have been confirmed to originate from the carrier mobility increases. The retention of large Seebeck coefficient is attributed to the negative magnetoresistance (MR−) induced by spin-dependent scattering and weak localization effect from MFEs. As a result, the maximum power factor of BST/MFEs/BST/epoxy flexible films increased by 45%, and the maximum cooling temperature difference enhanced by 1.6 times. This work reveals that the ordered MFEs can significantly boost the electro-thermal conversion performance of flexible TE films and the magnetoresistance theory can reveal the scattering mechanism of charge carriers in thermo-electromagnetic flexible films.

Fe-NPs and Zn-NPs: Advancing Aquaculture Performance Through Nanotechnology.

Aquaculture is a growing industry facing several challenges, including disease control, water quality management, and sustainable feed production. One potential solution to these challenges is the use of trace elements such as iron (Fe) and zinc (Zn), either in their conventional form or as nanoparticles (NPs). Aquatic animals need these micronutrients for normal growth, physiological processes, and overall health. In marine species, iron boosts development, immunity, and disease resistance. At the same time, zinc enhances metabolism, synthesizes essential enzymes, and produces hormones that play a part in defenses, growth, reproduction, and antioxidative activities. According to this review, species-specific requirements by different Fe and Zn compounds have all emphasized the impacts on animal growth and development, antioxidant capacity, reproductive efficiency, and immunological response. However, NPs of Fe and Zn have been found to have higher bioavailability and efficacy than conventional forms. This work examines the effects of applications of Fe and Fe nanoparticles (Fe-NPs) and Zn and Zn nanoparticles (Zn-NPs) in aquaculture. However, the source of Fe and Zn in aquaculture species and administration volume may significantly impact efficacy. Nanotechnology boosts the positive benefits of Fe and Zn by converting them to their nanoforms (Fe-NPs) and (Zn-NPs), which are better used by animals and have a broader intake range. As a result, Fe-NPs and Zn-NPs offer an effective method for using nutrients in aquaculture.

The Role of Carbon Nanotube Deposit in Catalytic Activity of FeOX-Based PECVD Thin Films Tested in RWGS Reaction

While the reverse water-gas shift (RWGS) reaction holds great promise as a method of converting CO2 to CO and subsequently into valuable fuels, achieving its commercial viability requires the development of highly efficient, selective, durable, and low-cost catalysts. Recently, thin-film nanocatalysts produced through plasma deposition (PECVD) have garnered significant attention in this domain. Among them, FeOx-based catalytic films deposited using Fe(CO)5 as a precursor, under reduced pressure (4–5 Pa) and a 13.56 MHz glow discharge, have demonstrated particular interest. Our study shows that by appropriately tuning the parameters of the plasma deposition process, it is feasible to generate nanocatalyst films exhibiting exceptional CO2 conversion (38% at 673 K) and CO selectivity (97%). Moreover, the study has revealed the formation of a carbon deposit containing carbon nanotubes (CNTs) during the RWGS reaction, significantly increasing the catalytic activity of the films. Through an analysis involving X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electron microscopy techniques (SEM and HRTEM), we have determined that CNTs not only serve as carriers for highly catalytically active Fe nanoparticles but also create nanoscale heterojunctions (p-n) with Fe2O3 nanoparticles, thereby enhancing their catalytic effect. This paper attempts to elucidate the differences and changes in the surface structure of FeOx-based films dictating the catalytic activity, which stems from both the conditions of plasma deposition and the environmental impact during the catalytic process.

Coexisting Fe single atoms and nanoparticles on hierarchically porous carbon for high-efficiency oxygen reduction reaction and Zn-air batteries

Fe single-atom catalysts still suffer from unsatisfactory intrinsic activity and durability for oxygen reduction reaction (ORR). Herein, the coexisting Fe single atoms and nanoparticles on hierarchically porous carbon (denoted as Fe-FeN-C) are prepared via a Zn5(OH)6(CO3)2-assisted pyrolysis strategy. Theoretical calculation reveals that the Fe nanoparticles can optimize the electronic structures and d-band center of Fe active center, hence reducing the reaction energy barrier for enhancing intrinsic activity. The Zn5(OH)6(CO3)2 self-sacrificial template not only can promote the formation of Fe single atoms, but also contributes to the construction of microporous/mesoporous/macroporous structures. Therefore, the obtained Fe-FeN-C exhibits impressive ORR activity with a half-wave potential of 0.921 V, which far exceeds Pt/C. With Fe-FeN-C as the cathode catalyst, the assembled Zn-air batteries delivered a maximum power density of 206 mW cm−2 and a long-cycle life over 400 h.

Evidence for suppression of collective magnetism in Fe-Ag granular multilayers

Evidence for the suppression of collective magnetic behavior of dipolarly interacting Fe nanoparticles is found in Fe-Ag granular multilayers. Interaction of Fe particles separated by an Ag layer is studied as a function of the nominal thickness of the Ag layer. The surprisingly increasing interaction with increasing Ag-layer thickness, verified by memory-effect measurements, is explained by the formation of pinholes in the Ag layer at small Ag thicknesses, allowing direct ferromagnetic coupling between the Fe particles. This coupling may hinder the frustration of superspins favored by dipolar interactions. At larger Ag thicknesses, the Ag layer is continuous without pinholes and frustration leads to the appearance of the superspin-glass state. The effect of increasing interactions correlates well with the growing deviation at low temperatures of the measured field-cooled (FC) magnetization from the interaction-free FC curve calculated by a model based on the relaxation of two-level systems. Similar phenomenon is reported in a recently published paper (Sánchez et al., Small2022, 18, 2106762) where a dense nanoparticle system is studied. Here the collective magnetic behavior of the particles due to dipolar interactions is suppressed when the anisotropy energy of the individual particles exceeds a certain threshold.

Encapsulation of Methanotrophs within a Polymeric Matrix Containing Copper- and Iron-Based Nanoparticles to Enhance Methanol Production from a Simulated Biogas.

The production of renewable energy or biochemicals is gaining more attention to minimize the emissions of greenhouse gases such as methane (CH4) and carbon dioxide for sustainable development. In the present study, the influence of copper (Cu)- and iron (Fe)-based nanoparticles (NPs), such as Cu, Fe3O4, and CuFe2O4, was evaluated during the growth of methanotrophs for inoculum preparation and on the development of a polymeric-matrix-based encapsulation system to enhance methanol production from simulated biogas (CH4 and CO2). The use of simulated biogas feed and the presence of NP-derived inoculums produce a remarkable enhancement in methanol production up to 149% and 167% for Methyloferula stellata and Methylocystis bryophila free-cells-based bioconversion, respectively, compared with the use of pure CH4 as a control feed during the growth stage. Furthermore, these methanotrophs encapsulated within a polymeric matrix and NPs-based systems exhibited high methanol production of up to 156%, with a maximum methanol accumulation of 12.8 mmol/L over free cells. Furthermore, after encapsulation, the methanotrophs improved the stability of residual methanol production and retained up to 62.5-fold higher production potential than free cells under repeated batch reusability of 10 cycles. In the presence of CH4 vectors, methanol production by M. bryophila improved up to 16.4 mmol/L and retained 20% higher recycling stability for methanol production in paraffin oil. These findings suggest that Cu and Fe NPs can be beneficially employed with a polymeric matrix to encapsulate methanotrophs and improve methanol production.