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

Heterogeneous 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.     

A Photo-Therapeutic Nanocomposite with Bio-Responsive Oxygen Self-Supplying Combats Biofilm Infections and Inflammation from Drug-Resistant Bacteria

The use of non-antibiotic strategies to combat refractory drug-resistant bacterial infections, especially biofilms and accompanying inflammation, has recently aroused widespread interest. Herein, a photo-therapeutic nanocomposite with bio-responsive oxygen (O₂) self-supplying is introduced by integrating manganese dioxide (MnO₂) nanozymes onto photosensitizer (indocyanine green, ICG)-loaded mesoporous polydopamine nanoparticles (MPDA), namely MI-MPDA NPs. MI-MPDA can activate O₂ generation in the infection microenvironment, thereby effectively alleviating biofilm hypoxia. Under near-infrared light (NIR) irradiation, continuous O₂ supplying further boosts the level of singlet oxygen (¹O₂), enabling robust biofilm elimination through O₂-potentiated photodynamic/photothermal therapy. Interestingly, MI-MPDA down-regulates the factor expression of inflammatory signaling pathways through MnO₂-mediated reactive oxygen species scavenging, which ameliorates the inflammatory condition. Meanwhile, O₂ supplying prevents the M1-phenotype switch of macrophages from the overexpression of hypoxia-inducible factor-1α (HIF-1α), thereby prompting macrophage reprogramming toward pro-regenerative M2-phenotype. In the mouse models of subcutaneous implant-associated infection caused by methicillin-resistant Staphylococcus aureus (MRSA) biofilms and burn infection caused by Pseudomonas aeruginosa biofilms, NIR-irradiated MI-MPDA not only effectively eliminates the formed biofilms, but also alleviates the oxidative stress and accompanying inflammation, and drives the cascade reaction of immunomodulation-wound healing. Overall, this O₂-potentiated photo-therapeutic strategy provides a reliable tool for combating biofilm infections and inflammation from drug-resistant bacteria.     

Self‐Mineralized Photothermal Bacteria Hybridizing with Mitochondria‐Targeted Metal–Organic Frameworks for Augmenting Photothermal Tumor Therapy

A photothermal bacterium (PTB) is reported for tumor‐targeted photothermal therapy (PTT) by using facultative anaerobic bacterium Shewanella oneidensis MR‐1 (S. oneidensis MR‐1) to biomineralize palladium nanoparticles (Pd NPs) on its surface without affecting bacterial activity. It is found that PTB possesses superior photothermal property in near infrared (NIR) regions, as well as preferential tumor‐targeting capacity. Zeolitic imidazole frameworks‐90 (ZIF‐90) encapsulating photosensitizer methylene blue (MB) are hybridized on the surface of living PTB to further enhance PTT efficacy. MB‐encapsulated ZIF‐90 (ZIF‐90/MB) can selectively release MB at mitochondria and cause mitochondrial dysfunction by producing singlet oxygen (¹O₂) under light illumination. Mitochondrial dysfunction further contributes to adenosine triphosphate (ATP) synthesis inhibition and heat shock proteins (HSPs) down‐regulated expression. The PTB‐based therapeutic platform of PTB@ZIF‐90/MB demonstrated here will find great potential to overcome the challenges of tumor targeting and tumor heat tolerance in PTT.     

Engineering Fe–Fe3C@Fe–N–C Active Sites and Hybrid Structures from Dual Metal–Organic Frameworks for Oxygen Reduction Reaction in H2–O2 Fuel Cell and Li–O2 Battery

Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe₃C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe₃C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm^?2 in peak power density) and an aprotic Li–O₂ battery (8749 mAh g^?1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe₃C contribution to the catalyst performance, suggesting Fe₃C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.     

Tumor Microenvironment‐Responsive Mesoporous MnO2‐Coated Upconversion Nanoplatform for Self‐Enhanced Tumor Theranostics

The insufficient blood flow and oxygen supply in solid tumor cause hypoxia, which leads to low sensitivity of tumorous cells and thus causing poor treatment outcome. Here, mesoporous manganese dioxide (mMnO₂) with ultrasensitive biodegradability in a tumor microenvironment (TME) is grown on upconversion photodynamic nanoparticles for not only TME‐enhanced bioimaging and drug release, but also for relieving tumor hypoxia, thereby markedly improving photodynamic therapy (PDT). In this nanoplatform, mesoporous silica coated upconversion nanoparticles (UCNPs@mSiO₂) with covalently loaded chlorin e6 are obtained as near‐infrared light mediated PDT agents, and then a mMnO₂ shell is grown via a facile ultrasonic way. Because of its unique mesoporous structure, the obtained nanoplatform postmodified with polyethylene glycol can load the chemotherapeutic drug of doxorubicin (DOX). When used for antitumor application, the mMnO₂ degrades rapidly within the TME, releasing Mn²⁺ ions, which couple with trimodal (upconversion luminescence, computed tomography (CT), and magnetic resonance imaging) imaging of UCNPs to perform a self‐enhanced imaging. Significantly, the degradation of mMnO₂ shell brings an efficient DOX release, and relieve tumor hypoxia by simultaneously inducing decomposition of tumor endogenous H₂O₂ and reduction of glutathione, thus achieving a highly potent chemo‐photodynamic therapy.     

Synthesis and Electronic Properties of Thermoelectric and Magnetic Nanoparticle Composite Materials

Application of a magnetic field greatly enhances the thermoelectric efficiency of bismuth-antimony (Bi-Sb) alloys. We synthesized a hybrid of Bi-Sb alloy and magnetic nanoparticles, expecting improvement of the thermoelectric performance due to the magnetic field generated by the nanoparticles. Powder x-ray diffraction and magnetic measurements of the synthesized hybrid Bi_0.88Sb_0.12(FeSb)_0.05 sample indicated that the ferromagnetic FeSb nanoparticles, with a size of about 30 nm, were distributed in the main phase of the Bi-Sb alloy. The FeSb nanoparticles act as soft ferromagnets in the diamagnetic host Bi-Sb alloy. The electrical resistivity ρ of the host Bi_0.88Sb_0.12 sample decreased concomitantly with decreasing temperature, showing a shoulder at 80 K. In contrast, ρ for the hybrid sample was enhanced below 100 K because of carrier scattering by the nanoparticles. The temperature dependence of the Seebeck coefficient S was also altered by the nanoparticle addition. In contrast, the addition of magnetic nanoparticles only slightly influenced the thermal conductivity κ. These results indicate that the addition of magnetic nanoparticles to thermoelectric materials modulates the electronic structures but does not influence the lattice system.     

Sol–Gel Synthesis of Robust Metal–Organic Frameworks for Nanoparticle Encapsulation

A new type of composite material involving the in situ immobilization of tin oxide nanoparticles (SnO₂‐NPs) within a monolithic metal–organic framework (MOF), the zeolitic imidazolate framework (ZIF)‐8 is presented. SnO₂@_monoZIF‐8 exploits the mechanical properties, structural resilience, and high density of a monolithic MOF, while leveraging the photocatalytic action of the nanoparticles. The composite displays outstanding photocatalytic properties and represents a critical advance in the field of treating toxic effluents and is a vital validation for commercial application. Crucially, full retention of catalytic activity is observed after ten catalytic cycles.     

Steering Local Electronic Configuration of Fe–N–C-Based Coupling Catalysts via Ligand Engineering for Efficient Oxygen Electroreduction

Fe–N–C materials are prospective candidates to displace platinum-group-based oxygen reduction reaction (ORR) catalysts, but their application is still impeded by the conundrums of unsatisfactory activity and stability. Herein, a feasible strategy of ligand engineering of the metal-organic framework is proposed to steer the local electronic configuration of Fe–N–C-based coupling catalysts by incorporating engineered sulfur functionalities. The obtained catalysts with rich Fe-N₄ sites and FeS nanoparticles are embedded on N/S-doped carbon (denoted as FeS/FeNSC). In this unique structure, the engineered FeS nanoparticles and oxidized sulfur synergistically induce electron redistribution and modulate electronic configuration of Fe-N₄ sites, contributing to substantially accelerated kinetics and improved activity. Consequently, the optimized FeS/FeNSC catalyst displays outstanding ORR performance with a half-wave potential of 0.91 V, better four electron pathway selectivity, lower H₂O₂ yield, and superior long-term stability. As a proof-of-concept, zinc-air batteries based on FeS/FeNSC deliver high capacity of 807.54 mA h g⁻¹, a remarkable peak power density of 256.06 mW cm⁻², and outstanding cycling stability over 600 h at 20 mA cm⁻². This study delivers an efficacious approach to manipulate the electronic configuration of Fe–N–C catalysts toward elevated catalytic activity and stability for various energy conversion/storage devices.     

Single‐Atom Fe‐Nx‐C as an Efficient Electrocatalyst for Zinc–Air Batteries

Highly efficient non‐noble metal electrocatalysts are vital for metal–air batteries and fuel cells. Herein, a noble‐metal–free single‐atom Fe‐N _x‐C electrocatalyst is synthesized by incorporating Fe‐Phen complexes into the nanocages in situ during the growth of ZIF‐8, followed by pyrolysis at 900 °C under inert atmosphere. Fe‐Phen species provide both Fe²⁺ and the organic ligand (Phen) simultaneously, which play significant roles in preparing single‐atom catalysts. The obtained Fe‐N_x‐C exhibits a half‐wave potential of 0.91 V for the oxygen reduction reaction, higher than that of commercial Pt/C (0.82 V). As a cathode catalyst for primary zinc–air batteries (ZABs), the battery shows excellent electrochemical performances in terms of the high open‐circuit voltage (OCV) of 1.51 V and a high power density of 96.4 mW cm^?2. The rechargeable ZAB with Fe‐N_x‐C catalyst and the alkaline electrolyte shows a remarkable cycling performance for 300 h with an initial round‐trip efficiency of 59.6%. Furthermore, the rechargeable all‐solid‐state ZABs with the Fe‐N_x‐C catalyst show high OCV of 1.49 V, long cycle life for 120 h, and foldability. The single‐atom Fe‐N_x‐C electrocatalyst may function as a promising catalyst for various metal–air batteries and fuel cells.     

A Versatile Prodrug Strategy to In Situ Encapsulate Drugs in MOF Nanocarriers: A Case of Cytarabine‐IR820 Prodrug Encapsulated ZIF‐8 toward Chemo‐Photothermal Therapy

Zeolitic imidazolate framework‐8 (ZIF‐8) is an attractive metal organic framework (MOF) in drug delivery. Strong interaction between drugs and ZIF‐8 is essential for high drug loadings through in situ construction of MOFs. However, only limited drugs with unique functional groups (? COOH, ? SO₃H, et al.) can interact with ZIF‐8 and be encapsulated satisfactorily so far. Drugs without these functional groups are difficult to be loaded due to the lack of strong interaction. Herein a versatile prodrug strategy is proposed to solve the problems encountered by MOFs. Cytarabine (Ara) is chosen as a model drug since it cannot be loaded in ZIF‐8 satisfactorily by itself. New indocyanine green (IR820) is utilized to bond with Ara for the formation of prodrug (Ara‐IR820) and endows the prodrug with fluorescence imaging‐guided chemo‐photothermal therapy, in which sulfonic groups strengthen the interaction between prodrug and ZIF‐8. This prodrug loaded ZIF‐8 is further functionalized with hyaluronic acid (HA) to result in active‐targeting HA/Ara‐IR820@ZIF‐8 nanoparticles. The in vitro and in vivo results demonstrate its excellent visual cancer therapy with tumor‐targeted and pH‐responsive release behavior. This design offers a new concept to solve the drug loading problem of MOFs, exhibiting a flexible strategy to expand the biomedical applications of MOFs.     

Microwave Arcing Induced Formation and Growth Mechanisms of Core/Shell Metal/Carbon Nanoparticles in Organic Solutions

Well‐graphitized core/shell iron/carbon nanoparticles (Fe@CNPs) were formed in toluene solutions containing Fe(CO)₅‐C_60/70 via an novel microwave arcing process. High temperature γ‐Fe phase was found to be stable at room temperature when encapsulated inside graphene shells. In the absence of C_60/70, the structures of graphene shells are poor. Pre‐synthesized Co nanoparticles were used as templates for the growth of graphene shells in toluene‐C_60/70 solutions. Via acid etching and removal of the central core Co nanoparticles, hollow carbon nanoparticles could be obtained. Further thermal annealing by focused microwave irradiation leads to merging of small core/shell metal/carbon nanoparticles into large ones, as well as conversion of body centered cubic (bcc) α‐Fe to face centered cubic (fcc) γ‐Fe. The possible growth mechanisms of core/shell metal/carbon nanoparticles were discussed.     

Magnetic-Activated Nanosystem with Liver-Specific CRISPR Nonviral Vector to Achieve Spatiotemporal Liver Genome Editing as Hepatitis B Therapeutics

Chronic hepatitis B infection remains incurable due to the stable presence of various forms of hepatitis B virus (HBV) genome, especially the HBV covalently closed circular DNA (cccDNA). The emergence of clustered regularly interspaced short palindromic repeat (CRISPR) technology provides a new opportunity to potentially cure the HBV infection. However, the efficiency and specificity remain unsatisfactory, especially for nonviral CRISPR/Cas9 delivery. To tackle these, a liver-specific CRISPR/Cas9 magnetic nanosystem FMNP_pAG333/sgXPP is constructed based on fluorinated polyethylenimine-coated magnetic nanoparticles and liver-specific ApoE.HCR.hAAT promoter-driven Cas9-T2A-EGFP plasmid with dual sgRNAs. The elaborate system enables magnetic field-induced spatially specific distribution and hepatocyte-specific promoter-driven liver-specific gene editing. Moreover, this CRISPR/Cas9 magnetic nanosystem is designed to disrupt the two conserved sites in X opening reading frame and Pol opening reading frame of the HBV genome, thereby significantly inactivating the HBV genome without showing off-target effects. Treatment with FMNP_pAG333/sgXPP for 7 days reduces serum HBsAg levels by 76% with a total editing efficiency of ≈20% in the two conserved sites. Collectively, this study demonstrates spatiotemporal liver genome editing as well as the feasibility of applying a nonviral CRISPR/Cas9 vector for HBV treatment, which may open up a new application for CRISPR therapeutics.     

Shining Light on Multidrug-Resistant Bacterial Infections: Rational Design of Multifunctional Organosilver-Based AIEgen Probes as Light-Activated Theranostics for Combating Biofilms and Liver Abscesses

The intricate environment of biofilms provides a heaven for bacteria to escape antibiotic eradication, leading to persistent chronic infections. Therefore, it is urgently needed to develop effective therapies to combat biofilm-associated infections. To address this problem, a series of antimicrobial agents are designed and synthesized utilizing triphenylamine imidazole silver complexes ( TPIMS ). Due to the photoactivated release of Ag⁺ coupled with aggregation-induced emission (AIE) properties and efficient ¹O₂ generation, TPIMS exhibits excellent visual diagnostic capabilities and potent broad-spectrum antimicrobial activity, showing antimicrobial efficacy against both Gram (+) and Gram (−) bacteria. Additionally, TPIMS shows extraordinary antibacterial performance and biofilm resistance against methicillin-resistant Staphylococcus aureus (MRSA), with reduced potential for resistance thanks to the synergistic effect of phototoxicity and dark toxicity. Notably, among the TPIMS variants tested, TPIMS-8 has demonstrated exceptional curative ability against resistant bacterial biofilm infections in vivo with minimal side effects. Furthermore, it is applied to clinical samples from infected patients and the results indicated that TPIMS-8 is able to achieve excellent bacterial-specific detection and superior killing of drug-resistant bacteria even in complex systems, demonstrating its great potential for clinical applications. This study presents a promising foundation for the development of advanced antimicrobial therapeutics targeting multidrug-resistant bacteria and biofilm-associated infections.     

Design and Synthesis of “All‐in‐One” Multifunctional FeS2 Nanoparticles for Magnetic Resonance and Near‐Infrared Imaging Guided Photothermal Therapy of Tumors

The ideal theranostic nanoplatform for tumors is a single nanoparticle that has a single semiconductor or metal component and contains all multimodel imaging and therapy abilities. The design and preparation of such a nanoparticle remains a serious challenge. Here, with FeS₂ as a model of a semiconductor, the tuning of vacancy concentrations for obtaining “all‐in‐one” type FeS₂ nanoparticles is reported. FeS₂ nanoparticles with size of ≈30 nm have decreased photoabsorption intensity from the visible to near‐infrared (NIR) region, due to a low S vacancy concentration. By tuning their shape/size and then enhancing the S vacancy concentration, the photoabsorption intensity of FeS₂ nanoparticles with size of ≈350 nm (FeS₂‐350) goes up with the increase of the wavelength from 550 to 950 nm, conferring the high NIR photothermal effect for thermal imaging. Furthermore, this nanoparticle has excellent magnetic properties for T₂‐weighted magnetic resonance imaging (MRI). Subsequently, FeS₂‐350 phosphate buffer saline (PBS) dispersion is injected into the tumor‐bearing mice. Under the irradiation of 915‐nm laser, the tumor can be ablated and the metastasis lesions in liver suffer significant inhibition. Therefore, FeS₂‐350 has great potential to be used as novel “all‐in‐one” multifunctional theranostic nanoagents for MRI and NIR dual‐modal imaging guided NIR‐photothermal ablation therapy (PAT) of tumors.     

Accelerating Proton and Electron Transfer Enables Highly Active Fe─N─C Catalyst for Electrochemical CO2 Reduction

Atomically dispersed Fe─N─C catalysts display great potential for efficient CO production in the field of electrochemical CO₂ reduction (ECR), but still suffer from unsatisfactory activity limited by the slow proton and electron transfer during the ECR process. Here, a superior Fe─N─C electrocatalyst is designed by anchoring the individual FeN₄ sites and Fe nanoparticles onto highly conductive carbon nanotubes. The resultant catalyst displays a commendable CO partial current density of 16.01 mA cm⁻² with a turnover frequency of 3519.6 h⁻¹ at −0.65 V in an H-type cell, and also exhibits CO selectivity > 90% under high current density over 120 mA cm⁻² in a flow cell. This remarkable activity exceeds a host of previously reported Fe─N─C catalysts. The findings indicate that the carbon nanotube facilitates CO production due to its strong capability of electron transport and charge transfer. In situ spectroscopic analysis, controlled experiments, and theoretical calculations reveal that Fe nanoparticles effectively promote water dissociation and the subsequent protonation step, accelerate the formation of ^*COOH intermediate, and thus greatly enhance the ECR activity.     

Impact of <Emphasis Type="Italic">In Situ</Emphasis> Generated Ag<Subscript>2</Subscript>Te Nanoparticles on the Microstructure and Thermoelectric Properties of AgSbTe<Subscript>2</Subscript> Compounds

A series of ternary (Ag₂Te) _x (Sb₂Te₃)_100−x (x = 44 to 54) bulk materials with in situ generated Ag₂Te nanoparticles were prepared from high-purity elements by combining the melt-quench technique with the spark plasma sintering technique. The influence of the Ag₂Te nanoparticles on the thermoelectric transport properties, and the mechanism of nanoparticle formation were investigated. With increasing x, the concentration of the Ag₂Te nanoparticles increased monotonically, but their diameter remained nearly unchanged. Due to the possible carrier energy filtering effect caused by the Ag₂Te nanoparticle inclusions, the Seebeck coefficient of the sample with x = 50 was two times higher than that of the sample prepared by the melting method. Moreover, notable scattering of mid-to-long wavelength phonons arising from the evenly distributed Ag₂Te nanoparticles led to a large reduction of the lattice thermal conductivity. All these effects led to the enhancement of the ZT value of the x = 50 sample (AgSbTe₂) compared with the single-phase sample (x = 44).     

Antifungal‐Inbuilt Metal–Organic‐Frameworks Eradicate Candida albicans Biofilms

Fungal biofilms cause a major clinical problem with a shrinking armamentarium for treatment. Here, the design and synthesis of voriconazole‐inbuilt zinc 2‐methylimidazolates frameworks (V‐ZIF) is reported. Voriconazole is built in through coordination‐binding between zinc and voriconazole. These metal–organic‐frameworks with inbuilt voriconazole, reduce inadvertent voriconazole‐leakage, yield a zero‐order release kinetics of voriconazole, aid antifungal penetration in Candida albicans biofilms, and prevent Candida aggregation yielding better dispersal. Once accumulated in an acidic C. albicans biofilm, voriconazole dissociates from the metal–organic framework to cause membrane‐damage and killing of inhabiting fungi. Moreover, in a murine model, the V‐ZIFs eradicate open‐wound infections caused by C. albicans better than voriconazole in solution, with negligible side effects to the healthy tissues of major organs. Thus, V‐ZIFs may provide a welcome addition to the antifungal armamentarium currently available for the treatment of fungal biofilms.     

Hierarchically Structured Magnetic Nanoconstructs with Enhanced Relaxivity and Cooperative Tumor Accumulation

Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub‐micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra‐small super‐paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r ₂ ≈ 835 mm ^?1 s^?1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r ₂ relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter‐particle magnetic dipole interactions. In tumor bearing mice, the silicon‐based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg^?1 animal) as compared to current practice.     

Combustion synthesis of Mg–Er ferrite nanoparticles: Cation distribution and structural,optical, and magnetic properties

Rare earth ion (Er³⁺)-doped magnesium ferrite nanoparticles of basic composition MgFe_2−xEr_xO₄ (x=0, 0.02, 0.04, and 0.06) were synthesized for the first time by a combustion method with use of glycine as fuel. The synthesized nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-diffuse reflectance spectroscopy, and vibrating sample magnetometer analysis in order to study the structural, compositional, morphological, and magnetic changes with addition of dopant. The X-ray diffraction pattern revealed a single phase with cubic spinel structure, and from the Scherrer formula and the Williamson–Hall formula, the average grain sizes ranged from 35 to 56 nm and from 31 to 54 nm, respectively. The lattice parameter (a) increases with the increase of the Er³⁺ concentration x in the lattice. The cation distributions among the tetrahedral (A) and octahedral (B) sites of spinel-type Er-doped magnesium ferrites were also investigated. The Fourier transform infrared spectroscopy spectra of synthesized samples illustrate that the higher-frequency bands lying in the range from 550 to 620 cm⁻¹ and the lower-frequency bands lying in the range from 410 to 450 cm⁻¹ are associated with the asymmetric stretching modes of the AB₂O₄ type of spinel transition metal oxides. Information about the chemical elements and oxidation states of the samples was obtained from high-resolution core-level X-ray photoelectron spectroscopy spectra of Mg 1s, Fe 2p, Er 4d, and O 1s. Further information about the morphology of the nanoparticles was obtained by scanning electron microscopy. From UV-diffuse reflectance spectroscopy studies, the optical band gaps were found to range from 1.81 to 1.96 eV. The magnetic hysteresis curves clearly indicate the soft ferromagnetic nature of the samples. Various magnetic properties such as saturation magnetization, coercivity, and remanent magnetization obtained from M–H loops were observed to increase with Er³⁺ substitution.     

Self-Templated Hierarchically Porous Carbon Nanorods Embedded with Atomic Fe-N4 Active Sites as Efficient Oxygen Reduction Electrocatalysts in Zn-Air Batteries

Iron-nitrogen-carbon materials are being intensively studied as the most promising substitutes for Pt-based electrocatalysts for the oxygen reduction reaction (ORR). A rational design of the morphology and porous structure can promote the accessibility of the active site and the reactants/products transportation, accelerating the reaction kinetics. Herein, 1D porous iron/nitrogen-doped carbon nanorods (Fe/N-CNRs) with a hierarchically micro/mesoporous structure are prepared by pyrolyzing the in situ polymerized pyrrole on the surface of Fe-MIL-88B-derived 1D Fe₂O₃ nanorods (MIL: Material Institut Lavoisier). The Fe₂O₃ nanorods not only partially dissolve to generate Fe³⁺ for initiating polymerization but serve as templates to form the 1D structure during polymerization. Furthermore, the pyrrole coated Fe₂O₃ nanorod architecture prevents the porous structure from collapsing and protects Fe from aggregation to yield atomic Fe-N₄ moieties during carbonization. The obtained Fe/N-CNRs display exceptional ORR activities (E_1/2 = 0.90 V) and satisfactory long-term durabilities, exceeding those for Pt/C. Furthermore, the unprecedented Fe/N-CNRs catalytic performance is demonstrated with Zn-air batteries, including a superior maximum power density (181.8 mW cm⁻²), specific capacity (998.67 W h kg⁻¹), and long-term durability over 100 h. The prominent performance stems from the unique 1D structure, hierarchical pore system, high surface area, and homogeneously dispersed single-atom Fe-N₄ moieties.