Metal Precursors Research Articles

Synthesis of Metal Complexes of Substituted Isonicotinohydrazide and their Catalytic and Biological Activities

Coordination chemistry has fascinated and inspired chemists all over the world due to an increasing academic, industrial, and biological interest in metal complexes of organic chelating ligands. Among the chelating ligands, Schiff bases have attracted the attention of chemists due to ease of preparation and complexation. Numerous reports showed that a large number of isatin and its Schiff base metal complexes have excellent catalytic activity in a variety of reactions at mild reaction conditions and are used as homogeneous catalysts. Copper-based isatin complexes have found much attention because of their biological relevance. In this study, we report the synthesis of Schiff base metal complexes of substituted isonicotinohydrazide. The Schiff base, (C14H10N4O2) is prepared by condensing isoniazid with isatin. The complexes were synthesized in good yield from easily available metal precursors and characterized by UV-visible and FTIR spectroscopy. The Cu complex shows excellent activity for the C-N coupling reaction of the amination of aryl halides. All four complexes show better antibacterial activity as compared to their corresponding [M (acac)n] complexes. In addition to this, the Co and Cu complexes such as [Co(C14H10N4O2)3] and Cu(C14H10N4O2)3] respectively show negative growth, towards Fusarium, and Aspergillus i.e. showing antifungal activity. The results were compared with the standard acetyl-acetone complexes of the same metals.

Cost-Effective Single-Step Synthesis of Metal Oxide-Supported Ni Catalyst for H2-Production Through Dry Reforming of Methane

AbstractPreparing catalysts from cheap metal precursors in a single pot are an appealing method for reducing catalytic preparation costs, minimizing chemical waste, and saving time. With regards to the catalytic conversion of dry reforming of methane, it offers the prospect of significantly reducing the cost of H2 production. Herein, NiO-stabilized metal oxides like Ni/TiO2, Ni/MgO, Ni/ZrO2, and Ni/Al2O3 are prepared at two different calcination temperatures (600 °C and 800 °C). Catalysts are characterized by X-ray diffraction, Raman spectroscopy, surface area-porosity analysis, Temperature program experiments, infrared spectroscopy, and thermogravimetry analysis. The MgO-supported Ni catalyst (Ni/MgO-600), ZrO2-supported Ni catalyst (Ni/ZrO2-600), and Al2O3-supported Ni (Ni/Al2O3-600) catalyst calcined at 600 °C show initial equal H2 yields (~ 55%). The population of CH4 decomposition sites over ZrO2-supported Ni catalyst remains highest, but H2-yield drops to 45% against high coke deposition. The catalytic activity remains constant over the Ni/MgO-600 catalyst due to the enrichment of “surface interacted CO2-species”. MgO-supported Ni catalyst calcined at 800 °C undergoes weak interactions of NiO-M′ (M′ = support), serious loss of CH4 decomposition sites and potential consumption of H2 by reverse water gas shift reaction, resulting in inferior H2 yield. H2-yield remains unaffected over an Al2O3-supported Ni catalyst even against the highest coke deposition due to the formation of stable Ni (which exsolves from NiAl2O4) and proper matching between carbon formation and rate of carbon diffusion.

Extracellular synthesis of silver nanoparticle using yeast extracts: antibacterial and seed priming applicationss.

The evolution and rapid spread of multidrug-resistant (MDR) bacterial pathogens have become a major concern for human health and demand the development of alternative antimicrobial agents to combat this emergent threat. Conventional intracellular methods for producing metal nanoparticles (NPs) using whole-cell microorganisms have limitations, including binding of NPs to cellular components, potential product loss, and environmental contamination. In contrast, this study introduces a green, extracellular, and sustainable methodology for the bio-materialization of silver NPs (AgNPs) using renewable resource cell-free yeast extract. These extracts serve as a sustainable, biogenic route for both reducing the metal precursor and stabilizing the surface of AgNPs. This method offers several advantages such as cost-effectiveness, environment-friendliness, ease of synthesis, and scalability. HR-TEM imaging of the biosynthesized AgNPs revealed an isotropic growth route, resulting in an average size of about ~ 18nm and shapes ranging from spherical to oval. Further characterization by FTIR and XPS results revealed various functional groups, including carboxyl, hydroxyl, and amide contribute to enhanced colloidal stability. AgNPs exhibited potent antibacterial activity against tested MDR strains, showing particularly high efficacy against Gram-negative bacteria. These findings suggest their potential role in developing alternative treatments to address the growing threat of antimicrobial resistance. Additionally, seed priming experiments demonstrated that pre-sowing treatment with AgNPs improves both the germination rate and survival of Sorghum jowar and Zea mays seedlings. KEY POINTS: •Yeast extract enables efficient, cost-effective, and eco-friendly AgNP synthesis. •Biosynthesized AgNPs showed strong antibacterial activity against MDR bacteria. •AgNPs boost seed germination and protect against seed-borne diseases.

Rapid High-Temperature Liquid Shock Synthesis of High-Entropy Alloys for Hydrogen Evolution Reaction.

High-entropy-alloy nanoparticles (HEA-NPs) show great potential as electrocatalysts for water splitting, fuel cells, CO2 conversion, etc. However, fine-tuning the surface, morphology, structure, and crystal phase of HEA remains a great challenge. Here, the high-temperature liquid shock (HTLS) technique is applied to produce HEA-NPs, e.g., PtCoNiRuIr HEA-NPs, with tunable elemental components, ultrafine particle size, controlled crystal phases, and lattice strains. HTLS directly applied Joule heating on the liquid mixture of metal precursors, capping agents, and reducing agents, which is feasible for controlling the morphology and structure such as the atomic arrangement of the resulting products, thereby facilitating the rationally designed nanocatalysts. Impressively, the as-obtained PtCoNiRuIr HEA-NPs delivered superior activity and long-term stability for the hydrogen evolution reaction (HER), with low overpotentials at 10 mA cm-2 and 1 A cm-2 of only 18 and 408 mV, respectively, and 10000 CV stable cycles in 0.5 M H2SO4. Furthermore, in the near future, by combining the HTLS method with artificial intelligence (AI) and theoretical calculations, it is promising to provide an advanced platform for the high-throughput synthesis of HEA nanocatalysts with optimized performance for various energy applications, which is of great significance for achieving a carbon-neutral society with an effective and environmentally friendly energy system.

Mercury removal performance of sulfated MnCe catalyst prepared by tobacco waste combustion synthesis

MnOx-CeO2 is a promising catalyst for Hg0 removal from coal flue gas at ∼150 °C but exhibits insufficient catalytic activity. Even though sulfation enhances the catalytic activity of MnOx-CeO2, gas-phase sulfation leads to SO2 poisoning and catalyst deactivation. In this study, we developed a liquid-phase sulfation strategy involving the direct combustion of cigarette butts soaked in a solution of sulfate and metal precursors to directly synthesize sulfated MnCe catalyst (SMC). SMC was characterized via N2 adsorption–desorption isotherms, SEM-EDS, XRD, XPS, and Hg-TPD. Both the MnCe catalyst and SMC exhibited good Hg0 oxidation efficiencies (66.46 % and 88.76 %, respectively) at 150 °C. The enhanced performance of SMC was attributed to the generation of abundant chemically adsorbed oxygen species on the SMC surface during sulfation. Moreover, the synergistic effect between the Ce4+ and Mn4+ species contributed to the improved catalytic performance of SMC. This strategy not only provides a one-step synthesis of sulfated catalysts but also has potential applications in Hg0 removal from coal flue gas in coal-fired power plants.

Wearable Plasmonic Sensors Engineered via Active-Site Maximization of TiVC MXene for Universal Physiological Monitoring at the Molecular Level.

Two-dimensional transition metal carbon/nitrides (MXenes) are promising candidates to revolutionize next-generation wearable sensors as high-performance surface-enhanced Raman scattering (SERS) substrates. However, low sensitivity of pure MXene nanosheets and weak binding force or uncontrolled in situ growth of plasmonic nanoparticles on hybrid MXene composites limit their progress toward universal and reliable sensors. Herein, we designed and manufactured a highly sensitive, structurally stable wearable SERS sensor by in situ fabrication of plasmonic nanostructures on the flexible TiVC membranes via the maximization of chemically reducing sites using alkaline treatment. DFT calculations and experimental characterization demonstrated that the hydroxyl functional groups on the surface of MXenes can facilitate the reduction of metal precursors and the nucleation of gold nanoparticles (AuNPs) and can be covalently attached to AuNPs. Thus, the fabricated flexible TiVC-OH-Au sensor satisfied the rigorous mechanical requirements for wearable sensors. In addition, combining the electromagnetic (EM) enhancement from dense AuNPs formed by the activation of nucleation sites and charge transfer (CT) between target molecule and substrate induced by the abundant DOS near the Fermi level of TiVC, the fabricated sensor exhibits ultrasensitivity, long-term stability, good signal repeatability, and excellent mechanical durability. Moreover, the proof-of-concept application of the wearable SERS sensor in sweat sensing was demonstrated to monitor the content of nicotine, methotrexate, nikethamide, and 6-acetylmorphine in sweat at the molecular level, which was an important step toward the universality and practicality of the wearable sensing technology.

Synthesis of Metallic Nanostructures Using Ionizing Radiation and Their Applications.

This paper reviews the radiation-induced synthesis of metallic nanostructures and their applications. Radiolysis is a powerful method for synthesizing metallic nanoparticles in solution and heterogeneous media, and it is a clean alternative to other existing physical, chemical, and physicochemical methods. By varying parameters such as the absorbed dose, dose rate, concentrations of metallic precursors, and nature of stabilizing agents, it is possible to control the size, shape, and morphology (alloy, core-shell, etc.) of the nanostructures and, consequently, their properties. Therefore, the as-synthesized nanoparticles have many potential applications in biology, medicine, (photo)catalysis, or energy conversion.

Synthesis of biogenic silver and gold nanoparticles from Anemopsis californica extract with antibacterial and cytotoxic activities

Silver (Ag) and gold (Au) nanoparticles, have gained attention for their unique properties and diverse applications, including medicine and antimicrobial agents. To meet the demand for eco-friendly synthesis methods, we explored plant-mediated nanoparticle synthesis using Anemopsis californica extracts. The Anemopsis californica leaves were used to extract bioactive compounds with water, methanol, and isopropanol. These extracts served as reducing and stabilizing agents for Ag and Au nanoparticle synthesis. The process involved mixing the extract, a metallic precursor solution, and deionized water in specific volume ratios, resulting in nanoparticles denoted as W-(Ag or Au), M-(Ag or Au), and I-(Ag or Au) for water, methanol, and isopropanol, respectively. The synthesized nanoparticles ranged from 5 to 30 nm in size and displayed various shapes. UV-Vis spectroscopy confirmed their presence with surface plasmon resonance bands. Antibacterial tests on Staphylococcus aureus and Escherichia coli showed significant antibacterial effects of Ag nanoparticles, especially those synthesized in methanol. In contrast, Au nanoparticles had limited antibacterial impact, regardless of the solvent. Cytotoxicity evaluations with macrophage cells indicated that Ag nanoparticles were more cytotoxic than Au nanoparticles, with the synthesis solvent influencing cytotoxicity. The observed antibacterial effects of Ag nanoparticles align with their reputation as potent antimicrobial agents, particularly against Gram-positive strains. The limited antibacterial impact of Au nanoparticles suggests differences in their antibacterial mechanisms. Varying cytotoxicity between Ag and Au nanoparticles underscores the significance of the chosen synthesis method in shaping nanoparticle properties.

Monolithic metal-based/porous carbon nanocomposites made from dissolved cellulose for use in electrochemical capacitor

Porous metal-based carbon nanocomposites, with a monolithic shape, were prepared by a one-pot synthesis from dissolved cellulose and metallic salts using a simple, cheap, and environmentally friendly route. Their potential performances as electrochemical capacitors were tested with three metal precursors (M = Cu, Mn, and Fe) with two loadings and in an asymmetric cell for the Fe-based carbon material. Interestingly, here soluble metal precursors were not deposited on a hard cellulose template but mixed in a precooled concentrated NaOH solution where cellulose was previously dissolved, allowing for a good dispersion of the metallic species. After a freezing step where concomitant cellulose regeneration and pore ice-templating phenomena took place, followed by a carbonization step, the mixture led to a porous carbon monolith embedding well-dispersed metal-based nanoparticles having a diameter below 20 nm and present as metallic, oxide, or carbide phase(s) according to the element M. These materials were characterized by different physicochemical techniques and electrochemical tests. Their performances as supercapacitors are discussed in light of the specific behaviour of the metal-based phase and its influence on the carbon matrix properties such as mesopore formation and carbon graphitization. An asymmetric energy storage cell assembled with a Fe-based carbon electrode against a carbon xerogel electrode derived from a phenolic resin shows specific energy and power of 18.3 Wh kg−1 at 5 mA cm−2 and 1.6 kW kg−1 at 25 mA cm−2, respectively.

Thermodynamic Guidelines for the Mechanosynthesis or Solid-State Synthesis of MnFe2O4 at Relatively Low Temperatures.

Herein, thermodynamic assessment is proposed to screen suitable precursors for the solid-state synthesis of manganese ferrite, by mechanosynthesis at room temperature or by subsequent calcination at relatively low temperatures, and the main findings are validated by experimental results for the representative precursor mixtures MnO + FeO3, MnO2 + Fe2O3, and MnO2 +2FeCO3. Thermodynamic guidelines are provided for the synthesis of manganese ferrite from (i) oxide and/or metallic precursors; (ii) carbonate + carbonate or carbonate + oxide powder mixtures; (iii) other precursors. It is also shown that synthesis from metallic precursors (Mn + 2Fe) requires a controlled oxygen supply in limited redox conditions, which is hardly achieved by reducing gases H2/H2O or CO/CO2. Oxide mixtures with an overall oxygen balance, such as MnO + Fe2O3, act as self-redox buffers and offer prospects for mechanosynthesis for a sufficient time (>9 h) at room temperature. On the contrary, the fully oxidised oxide mixture MnO2 + Fe2O3 requires partial reduction, which prevents synthesis at room temperature and requires subsequent calcination at temperatures above 1100 °C in air or in nominally inert atmospheres above 750 °C. Oxide + carbonate mixtures, such as MnO2 +2FeCO3, also yield suitable oxygen balance by the decomposition of the carbonate precursor and offer prospects for mechanosynthesis at room temperature, and residual fractions of reactants could be converted by firing at relatively low temperatures (≥650 °C).

Investigation of the influence for S-ions incorporated into the Ag2ZnSnSe4 photoelectrodes on their light-enhanced activities in aqueous salt-water solution

BackgroundLarge-scale application in solar salt-water splitting is an important way to reduce the influence of environmental problem without any decrease in the usage of energy. To develop the photoelectrochemical (PEC) salt-water splitting is thus a promising way for further industrial application. MethodsThe Ag2ZnSnSe4 (AZTSe) and their S-ions incorporating samples were produced by the post selenization/sulfurization of Ag/Sn/Zn sandwich metal precursors with the suitable amount of sulfur + selenium powder mixtures at 410 ℃ for 90 min under nitrogen atmosphere. The PEC tests using samples as photoelectrode were then carried out. Significant findingsThe maximum light-enhanced activity of pristine AZTSe and their S-ions incorporated samples was 3.65 and 2.37 mA/cm2 as the applied voltage of 1.23 V vs. RHE (relative hydrogen electrode) in a 0.5 M sodium chloride electrolyte, respectively. Electrochemical impedance and intensity-modulated photocurrent spectra of samples represented that the S-ions incorporated into AZTSe sample could reduce the photo-corrosion reaction on sample surface because of the decrease in the number of light-induced holes occupied on sample surface. Our report proposed the systemic evaluation on the influence of S-ions incorporated into AZTSe sample for light-enhanced salt-water splitting.

Solvent Influence in the Synthesis of Lead(II) Complexes Containing Benzoate Derivatives

A series of lead(II) complexes incorporating benzoate derivative ligands was prepared: [Pb(2MeOBz)2]n (1), [Pb(2MeOBz)2(H2O)]n (2), [Pb2(1,4Bzdiox)4(DMSO)]n (3), [Pb(1,4Bzdiox)2(H2O)]n (4), [Pb(Pip)2(H2O)]n (5), and [Pb(Ac)(Pip)2(MeOH)]n (6) (2MeOBz: 2-methoxybenzoate; 1,4Bzdiox: 1,4-benzodioxan-5-carboxylate; DMSO: dimethylsulfoxide; Ac: acetate; Pip: piperonylate; MeOH: methanol). All compounds were characterized via elemental analysis, ATR-FTIR spectroscopy, and powder XRD. In addition, the crystal structures of some compounds were elucidated. Compounds 1 and 2, involving 2-methoxybenzoate, were closely related, only differing in the presence of one extra aqua ligand found for the latter. However, this implies key changes in the studied properties, e.g., 2 shows solid-state luminescence that displays a different color as a function of the crystal orientation, while 1 does not. The crystal structure of 2 revealed a 1D coordination polymer. A similar relationship was found between compounds 3 and 4, incorporating 1,4-benzodioxan-5-carboxylate. In this pair, only 4, with aqua ligands, displayed a greenish-yellow-color solid-state luminescence. Furthermore, two new lead(II) piperonylate complexes, 5 and 6, were obtained from the reaction between lead(II) acetate and piperonylic acid. In water, all acetate ligands in the metal precursor were displaced and [Pb(Pip)2(H2O)]n (5) was isolated, while in methanol, a mixed acetate–piperonylate complex, [Pb(Ac)(Pip)2(MeOH)]n (6), was precipitated. Considering only conventional Pb-O bonds, the crystal structure of 6 was described as a 1D coordination polymer, although, additionally, the chains were associated via tetrel bonds, defining an extended 2D architecture.

Hollow-cathode plasma deposited vanadium oxide films: Metal precursor influence on growth and material properties

Due to its different polymorphs, including vanadium pentoxide (V2O5) and vanadium dioxide (VO2), the vanadium oxide (VOX) compound is an immensely interesting material with many important applications. While atomic layer deposition (ALD) is among the possible VOX film synthesis methods, literature reports have majorly utilized thermal-ALD, which reveals as-grown amorphous VOX films. Further post-deposition annealing process is needed to crystallize these films. High-temperature crystallization indeed limits the use of low-temperature compatible materials, processes, and substrates. In this work, we report on the low-temperature crystalline VOX film growth in a hollow-cathode plasma-enhanced atomic layer deposition reactor using two different vanadium precursors, tetrakis(ethylmethylamino)vanadium and vanadium(V) oxytriisopropoxide. Oxygen plasmas were used as co-reactants at a substrate temperature of 150 °C. Along with the purpose of investing in the impact of metal precursors on VOX film growth, we also studied Ar-plasma in situ and thermal ex situ annealing to investigate possible structural enhancement and phase transformation. In situ Ar-plasma annealing was performed with 20 s, 20 SCCM Ar-plasma, while post-deposition ex situ annealing was carried out at 500 °C and 0.5 mTorr O2 pressure. In situ ellipsometry was performed to record instant film thickness variation and several ex situ characterizations were performed to extract the optical, structural, and electrical properties of the films. The outcomes of the study confirm that both metal precursors result in as-grown crystalline V2O5 films at 150 °C. On the other hand, post-deposition annealing converted the as-grown crystalline V2O5 film to VO2 film. Finally, we have also successfully confirmed the metal-to-insulator transition property of the annealed VO2 films via temperature-dependent structural and electrical measurements.

Anchoring highly dispersed metal nanoparticles by strong electrostatic adsorption (SEA) on a dealuminated beta zeolite for catalysis

Enhanced interaction between metal precursors and silanol nests was demonstrated on a silanol-rich dealuminated beta zeolite by strong electrostatic adsorption, leading to the formation of highly dispersed Ni nanoparticles for effective catalysis.

Diverse structural reactivity patterns of a POCOP ligand with coinage metals.

We have utilised the 4,6-di-tert-butyl resorcinol bis(diphenylphosphinite) (POCOP) ligand for exploring its coordination ability towards group 11 metal centres. The treatment of the bidentate ligand 1 with various coinage metal precursors afforded a wide range of structurally diverse complexes 2-12, depending upon the metal precursors used. This furnishes several multinuclear Cu(I) complexes with dimeric (2) and tetrameric cores (3, 4, and 5). The tetrameric stairstep complex 4 shows thermochromic behaviour, whereas the dimeric complex 2 and tetrameric complex 3 show luminescence properties at cryogenic temperatures. Interestingly, the halide substitution reaction of the dimeric complex 2 with KPPh2 produces a unique mixed phosphine-based tetrameric Cu(I) complex, 5. Treatment of the POCOP ligand with [CuBF4(CH3CN)4] in the presence of 2,2'-bipyridine afforded heteroleptic complex 6, consisting of tri- and tetra-coordinated cationic Cu(I) centres. Furthermore, we could also isolate cubane (8) and stairstep (9) complexes of Ag(I). The cationic Au(I) complex (12) was obtained from the dinuclear Au(I) complex of POCOP, 11. Complex 12 revealed the presence of a strong intramolecular aurophilic interaction with an Au⋯Au bond distance of 3.1143(9) Å. Subsequently, the photophysical properties of these complexes have been studied. All the complexes were characterised by single-crystal X-ray diffraction studies, routine NMR techniques, and mass spectroscopy.

Ni-Fe bimetallic catalysts with high dispersion supported by SBA-15 evaluated for the selective oxidation of benzyl alcohol to benzaldehyde.

A wetness impregnation method was used to impregnate the substrate with a substantial quantity of oleic acid together with a metal precursor, leading to significantly dispersed Ni-Fe bimetallic catalysts based on mesoporous SBA-15. Using a wide variety of characterization methods, such as XRD, BET, and TEM Analysis, the physiochemical properties of the catalyst were determined. The addition of the metal does not have any effect on the structural characteristics of the SBA-15 catalyst, as validated by transmission electron microscopy (TEM), which shows that the prepared SBA-15 supported catalyst has a hexagonal mesoporous structure. The catalytic capabilities of the Ni-Fe-SBA-15 catalysts were evaluated in the conversion of BzOH using tert-butyl hydroperoxide (TBHP) as an oxidant and acetonitrile as a solvent. The Ni/Fe-SBA-15 (NFS-15) catalytic composition is the best of the developed catalysts, with a maximum conversion of 98% and a selectivity of 99%. In-depth investigations were conducted into the molar ratio of TBHP to BzOH, the dosage of the catalyst, the reaction rate, temperature, and solvent. The recycling investigations indicate that the synthesized Ni/Fe-SBA-15 (NFS-15) catalyst seems to be more durable up to seven successive cycles.

Silver nanoclusters stabilized with PVP-BSA conjugate: Optical properties approach

<abstract> <p>The objective of this research was to synthesize fluorescent silver nanoclusters (NC Ag-BSA/PVP) using polyvinylpyrrolidone polymer (PVP) as a stabilizer in conjunction with bovine serum albumin protein (BSA). The nanoclusters were prepared using a wet chemistry reduction technique with two distinctive pathways: the addition of PVP after BSA and the addition of PVP after the metal precursor. The optical properties of the materials were studied in samples with different BSA/PVP molar ratios and varying amounts of metal/reductant. The impact of protein and polymer amounts on fluorescence was determined. The materials were characterized using X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray energy dispersive spectroscopy (EDS), dynamic light scattering (DLS), fluorescence spectroscopy, and UV-Vis-NIR spectroscopy.</p> <p>It was observed that increasing the BSA/PVP ratio resulted in higher fluorescence intensity at λ = 450 nm and a decrease at λ = 600 nm. Regarding the metal/reductant ratio, the amount of metal ions impacted the intensity obtained at λ = 600 nm. The experiments revealed that BSA had the largest effect on fluorescence intensity at λ = 450 nm, with little effect on fluorescence intensity regardless of the amount of polymer used. Due to its one-step synthesis and favorable reaction conditions, the NC Ag-BSA/PVP obtained under the proposed methodology holds promise as an optical marker material. The use of the stabilizing duo BSA-PVP, as well as the proposed amounts in this research, serves as a precedent for developing new experimental syntheses of colloidal nanoparticles.</p> </abstract>

Chemical engineering of cationic distribution in spinel ferrite nanoparticles: the effect on the magnetic properties.

A set of ∼9 nm CoFe2O4 nanoparticles substituted with Zn2+ and Ni2+ was prepared by thermal decomposition of metallic acetylacetonate precursors to correlate the effects of replacement of Co2+ with the resulting magnetic properties. Due to the distinct selectivity of these cations for the spinel ferrite crystal sites, we show that it is possible to tailor the magnetic anisotropy, saturation magnetization, and interparticle interactions of the nanoparticles during the synthesis stage. This approach unlocks new possibilities for enhancing the performance of spinel ferrite nanoparticles in specific applications. Particularly, our study shows that the replacement of Co2+ by 48% of Zn2+ ions led to an increase in saturation magnetization of approximately 40% from ∼103 A m2 kg-1 to ∼143 A m2 kg-1, whereas the addition of Ni2+ at a similar percentage led to an ∼30% decrease in saturation magnetization to 68-72 A m2 kg-1. The results of calculations based on the two-sublattice Néel model of magnetization match the experimental findings, demonstrating the model's effectiveness in the strategic design of spinel ferrite nanoparticles with targeted magnetic properties through doping/inversion degree engineering.

Synthesis of metallic high-entropy alloy nanoparticles.

The theoretically infinite compositional space of high-entropy alloys (HEAs) and their novel properties and applications have attracted significant attention from a broader research community. The successful synthesis of high-quality single-phase HEA nanoparticles represents a crucial step in fully unlocking the potential of this new class of materials to drive innovations. This review analyzes the various methods reported in the literature to identify their commonalities and dissimilarities, which allows categorizing these methods into five general strategies. Physical minimization of HEA metals into HEA nanoparticles through cryo-milling represents the typical top-down strategy. The counter bottom-up strategy requires the simultaneous generation and precipitation of metal atoms of different elements on growing nanoparticles. Depending on the metal atom generation process, there are four synthesis strategies: vaporization of metals, burst reduction of metal precursors, thermal shock-induced reduction of metal precursors, and solvothermal reduction of metal precursors. Comparisons among the methods within each strategy, along with discussions, provide insights and guidance for achieving the robust synthesis of HEA nanoparticles.

Movable-type printing method to fabricate ternary FeCoNi alloys confined in porous carbon towards oxygen electrocatalysts for rechargeable Zn-air batteries.

Transition metal-based carbon catalysts are a promising class of electrocatalysts to enhance the efficiency of energy conversion and storage devices. However, it remains a challenging task to develop multi-metal alloy catalysts. Herein, ternary FeCoNi alloy nanoparticles (NPs) confined in nitrogen-doped carbon (NC) catalysts were fabricated via a facile movable-type printing method, where a range of transition metals confined in NC catalysts was prepared using the same technique except for the adjustment of the metal precursors. Due to the unique electronic structure and significant active sites of the medium-entropy alloy, the FeCoNi-NC catalysts demonstrated highly efficient bifunctional electrocatalytic activities for the oxygen reduction (E1/2 = 0.838 V) and evolution (Eoverpotential = 330 mV, 10 mA cm-2) reactions, which were comparable to those of Pt/C and RuO2. Moreover, the FeCoNi-NC-based liquid rechargeable ZABs displayed a substantial power density of 231.2 mW cm-2, and the homemade flexible ZABs also exhibited outstanding activity and cycling durability. Thus, this movable-type printing method is suitable for constructing a variety of multi-metal-based catalysts for metal air batteries.