Structural, Magnetic, and Catalytic Evaluation of Spinel Co, Ni, and Co-Ni Ferrite Nanoparticles Fabricated by Low-Temperature Solution Combustion Process

Bioinspired ferromagnetic NiFe2O4 nanoparticles: Eradication of fungal and drug-resistant bacterial pathogens and their established biofilm

Nickel ferrite nanoparticles (NiFe2O4 NPs) were synthesized using the medicinally important plant Aloe vera leaf extract, and their structural, morphological, and magnetic properties were characterized by x-ray diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), and vibrating sample magnetometer (VSM). The synthesized NPs were soft ferromagnetic and spinel in nature, with an average particle size of 22.2 nm. To the best of our understanding, this is the first comprehensive investigation into the antibacterial, anticandidal, antibiofilm, and antihyphal properties of NiFe2O4 NPs against C. albicans as well as drug-resistant gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and gram-negative multidrug resistant Pseudomonas aeruginosa (MDR-P. aeruginosa) bacteria. NiFe2O4 NPs showed potent antimicrobial activity (MIC 1.6-2 mg/mL) against the test pathogens. NiFe2O4 NPs at 0.5 mg/mL suppressed biofilm formation by 49.5-53.1 % in test pathogens. The study found that the NPs not only prevent the formation of biofilm, but also eliminate existing mature biofilms by 50.5-75.79 % at 0.5 mg/mL, which was further validated by SEM. SEM examination revealed a reduction in the number of cells that form biofilms and adhere to the surface. Additionally, it considerably impeded the colonization and aggregation of the biofilm strains on the glass surface. Light microscopic examination demonstrated that NPs effectively prevent the expansion of hyphae, filaments, and yeast-to-hyphae transformation in C. albicans, resulting in a substantial decrease in their ability to cause infection. Moreover, SEM images of the treated cells exhibited the presence of wrinkles, deformities, and impaired cell walls, which suggests an alteration and instability of the membrane. This study demonstrated the efficacy of the greenly manufactured NPs in suppressing the proliferation of candida, drug-resistant bacteria, and their preexisting biofilms, as well as yeast-to-hyphae transformation. Therefore, these NPs with broad spectrum applications could be utilized in health settings to mitigate biofilm-related health conditions caused by pathogenic microbial strains.

Enhancing Zn (II) recovery efficiency: Bi-divalent nickel-cobalt ferrite spinel NiXCo1-xFe2O4 as a Game-changing Adsorbent-an experimental and computational study

This study presents a comprehensive investigation into NiXCo1-xFe2O4 (x = 0.5) spinel nanoparticles synthesized through a one-pot hydrothermal method using Co(NO3)2.6H2O and Ni(NO3)2.6H2O salts. XRD, FTIR, FESEM, and VSM analyses confirmed a cubic structure of NiXCo1-xFe2O4 (x = 0.5) nanoparticles without impurities. These nanoparticles exhibit efficient Zn (II) adsorption characteristics, following Langmuir isotherm and pseudo-second-order kinetics. The maximum adsorption capacity was measured to be 666.67 mg g-1 at pH = 7, with mechanisms involving both electrostatic attraction and cation exchange. Desorption studies indicate more than 75% Zn (II) recovery in an acidic environment (pH = 2) after three cycles. Computational analysis was used to validate the experimental results through Molecular Dynamics simulations, initially focusing on NiXCo1-xFe2O4 (x = 0.5). Further exploration involved variations in x at 0.25 and 0.75 to identify the optimal Ni and Co ratio in this bivalent cation spinel ferrite. Computational analyses reveal the superior performance of NiXCo1-xFe2O4 (x = 0.75) in Zn (II) removal, supported by radial distribution analysis, VdW energy, Coulombic energy, mean square displacement (MSD), root mean square displacement (RMSD), and interaction energy. This comprehensive study provides valuable insights into the adsorption behavior and structural stability of NiXCo1-xFe2O4 nanoparticles, showcasing potential applications in Zn (II) removal.

Gold Nanodots-Anchored Cobalt Ferrite Nanoflowers as Versatile Tumor Microenvironment Modulators for Reinforced Redox Dyshomeostasis

Given that tumor microenvironment (TME) exerts adverse impact on the therapeutic response and clinical outcome, robust TME modulators may significantly improve the curative effect and increase survival benefits of cancer patients. Here, Au nanodots-anchored CoFe2O4 nanoflowers with PEGylation (CFAP) are developed to respond to TME cues, aiming to exacerbate redox dyshomeostasis for efficacious antineoplastic therapy under ultrasound (US) irradiation. After uptake by tumor cells, CFAP with glucose oxidase (GOx)-like activity can facilitate glucose depletion and promote the production of H2O2. Multivalent elements of Co(II)/Co(III) and Fe(II)/Fe(III) in CFAP display strong Fenton-like activity for·OH production from H2O2. On the other hand, energy band structure CFAP is superior for US-actuated 1O2 generation, relying on the enhanced separation and retarded recombination of e-/h+ pairs. In addition, catalase-mimic CFAP can react with cytosolic H2O2 to generate molecular oxygen, which may increase the product yields from O2-consuming reactions, such as glucose oxidation and sonosensitization processes. Besides the massive production of reactive oxygen species, CFAP is also capable of exhausting glutathione to devastate intracellular redox balance. Severe immunogenic cell death and effective inhibition of solid tumor by CFAP demonstrates the clinical potency of such heterogeneous structure and may inspire more relevant designs for disease therapy.

Regulating Surface Dipole Moments of TiO2 for the pH-Universal Cathodic Fenton-Like Process

Although electro-Fenton (EF) processes can avoid the safety risks raised by concentrated hydrogen peroxide (H2O2), the Fe(III) reduction has always been either unstable or inefficient at high pH, resulting in catalyst deactivation and low selectivity of H2O2 activation for producing hydroxyl radicals (•OH). Herein, we provided a strategy to regulate the surface dipole moment of TiO2 by Fe anchoring (TiO2-Fe), which, in turn, substantially increased the H2O2 activation for •OH production. The TiO2-Fe catalyst could work at pH 4-10 and maintained considerable degradation efficiency for 10 cycles. Spectroscopic analysis and a theoretical study showed that the less polar Fe-O bond on TiO2-Fe could finely tune the polarity of H2O2 to alter its empty orbital distribution, contributing to better ciprofloxacin degradation activity within a broad pH range. We further verified the critical role of the weakened polarity of H2O2 on its homolysis into •OH by theoretically and experimentally investigating Cu-, Co-, Ni-, Mn-, and Mo-anchored TiO2. This concept offers an avenue for elaborate design of green, robust, and pH-universal cathodic Fenton-like catalysts and beyond.

Sensing the invisible: Ultra-low-level electrochemical detection of the microbe (Pseudomonas aeruginosa) on cobalt ferrite-doped silver nanocomposite (CoFe2O4/AgNPs) surfaces

This study introduces an efficient electrochemical method for rapidly identifying the pathogen Pseudomonas aeruginosa (P. aeruginosa), which poses threats to individuals with compromised immune systems and cystic fibrosis. Unlike conventional techniques such as polymerase chain reaction, which fails to detect modifications in the resistant properties of microbes due to environmental stress, our proposed electrochemical approach offers a promising alternative. The characterisation analyses, involving microscopic and spectroscopic methods, reveal that the nanocomposite exhibits a crystalline structure, specific atomic vibrational patterns, a cubic surface shape, and distinct elemental compositions. This sensor demonstrates exceptional detection capabilities for P. aeruginosa, with a linear range of 1-23 CFU mL-1 and a low detection limit of 4.0 × 10-3 CFU mL-1. This research not only explores novel electrochemical techniques and the CoFe2O4/AgNPs nanocomposite but also their practical implications in food science, highlighting their relevance across various food samples, water, and soil.

Tuning the magnetic properties of hard-soft Ba0.5Sr0.5Fe10Al2O19and Ni0.1Co0.9Fe2O4nanocomposites via one pot sol-gel auto combustion method for permanent magnet applications

Permanent magnets generate magnetic fields that can be sustained when a reverse field is supplied. These permanent magnets are effective in a wide range of applications. However, strategic rare-earth element demand has increased interest in replacing them with huge energy product (BH)max. Exchange-coupled hard/soft ferrite nanocomposites have the potential to replace a portion of extravagant rare earth element-based magnets. In the present, we have reported the facile auto combustion synthesis of exchange-coupled Ba0.5Sr0.5Fe10Al2O19and Ni0.1Co0.9Fe2O4nanocomposites by increasing the content of soft ferrite over the hard fromx= 0.1 to 0.4 wt%. The XRD combined with Rietveld analysis reflected the presence of hexaferrite and spinel ferrite without the existence of secondary phases. The absorption bands from the Fourier transform infrared spectrum analysis proved the presence of M-O bonds in tetrahedral sites and octahedral sites. Rod and non-spherical images from TEM represent the hexaferrite and spinel ferrite. The smoothM-Hcurve and a single peak of the switching field distribution curve prove that the material has undergone a good exchange coupling. The nanopowders displayed an increase in saturation magnetization and a decrease in coercivity with the increases in the spinel content. The prepared nanocomposites were showing higher energy products. The composite with the ratiox= 0.2 displayed a higher value of (BH)maxof 13.16 kJ m-3.

CTAB-Assisted Synthesis of FeNi Alloy Nanoparticles: Effective and Stable Electrocatalysts for Urea Oxidation Reactions

Development of highly efficient electrocatalysts for treating urea-rich wastewater is an important problem in environmental management and energy production. In this work, an iron-nickel alloy (Fe-Ni alloy) was synthesized via soft-template cetyltrimethylammonium bromide (CTAB)-assisted precipitation using low-temperature calcination. The as-synthesized nanoalloy was characterized by X-ray diffraction (XRD), which revealed the formation of a face-centered cubic (FCC) structure of the Fe-Ni alloy; field emission-scanning electron microscopic (FE-SEM) analysis revealed the spherical shape of the Fe-Ni alloy; high-resolution transmission electron microscopy (HR-TEM) revealed the average size to be ∼33.09 nm; and X-ray photoelectron spectroscopy (XPS) showed the presence of Fe, Ni, C, and O components and their chemical composition and valence states in the Fe-Ni alloy. The electrochemical urea oxidation reaction (UOR) was investigated by conducting linear sweep voltammetry (LSV) tests on the synthesized electrocatalysts with different Ni/Fe ratios in alkaline electrolytes with urea. The potential required to reach a current density of 10 mA cm-2 is 1.27 V vs RHE, which demonstrates the higher electrochemical activity of the Fe-Ni alloy compared to other individual compounds. This could be due to CTAB which improved the structural stability and synergetic and electronic effects in the nanoscale. This study will further contribute to renewable energy generation technology with long-term energy sustainability and also opens up great potential for reducing water pollution.

Biosynthesis of ternary NiCoFe2O4 nanoflowers: investigating their 3D structure and potential use in gene delivery

Multicomponent nanoparticle systems are known for their varied properties and functions, and have shown potential as gene nanocarriers. This study aims to synthesize and characterize ternary nickel-cobalt-ferrite (NiCoFe2O4) nanoparticles with the potential to serve as gene nanocarriers for cancer/gene therapy. The biogenic nanocarriers were prepared using a simple and eco-friendly method following green chemistry principles. The physicochemical properties of the nanoparticles were analyzed by X-ray diffraction, vibrating sample magnetometer, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller. To evaluate the morphology of the nanoparticles, the field emission scanning electron microscopy with energy dispersive X-Ray spectroscopy, high-resolution transmission electron microscopy imaging, and electron tomography were conducted. Results indicate the nanoparticles have a nanoflower morphology with a mesoporous nature and a cubic spinel structure, where the rod and spherical nanoparticles became rose-like with a specific orientation. These nanoparticles were found to have minimal toxicity in human embryonic kidney 293 (HEK-293 T) cells at concentrations of 1 to 250 µg·mL-1. We also demonstrated that the nanoparticles could be used as gene nanocarriers for delivering genes to HEK-293 T cells using an external magnetic field, with optimal transfection efficiency achieved at an N/P ratio of 2.5. The study suggests that biogenic multicomponent nanocarriers show potential for safe and efficient gene delivery in cancer/gene therapy.

Synergistic effects of mixing and strain in high entropy spinel oxides for oxygen evolution reaction

Developing stable and efficient electrocatalysts is vital for boosting oxygen evolution reaction (OER) rates in sustainable hydrogen production. High-entropy oxides (HEOs) consist of five or more metal cations, providing opportunities to tune their catalytic properties toward high OER efficiency. This work combines theoretical and experimental studies to scrutinize the OER activity and stability for spinel-type HEOs. Density functional theory confirms that randomly mixed metal sites show thermodynamic stability, with intermediate adsorption energies displaying wider distributions due to mixing-induced equatorial strain in active metal-oxygen bonds. The rapid sol-flame method is employed to synthesize HEO, comprising five 3d-transition metal cations, which exhibits superior OER activity and durability under alkaline conditions, outperforming lower-entropy oxides, even with partial surface oxidations. The study highlights that the enhanced activity of HEO is primarily attributed to the mixing of multiple elements, leading to strain effects near the active site, as well as surface composition and coverage.

Investigation of Structural, Dielectric and Optical Properties of Polyaniline-Magnesium Ferrite Composites

A study on the influence of magnesium ferrite nanoparticles on the optical and dielectric attributes of Polyaniline has been conducted. Magnesium nano Ferrite powder is synthesized by the self-propagating solution combustion method. Polyaniline-Magnesium nano ferrite composites are synthesized by chemical oxidative polymerization of aniline with the addition of Magnesium nanoparticles. The samples are characterized with XRD and UV-Vis spectrometer, in the wavelength range of 200-800 nm and studied for optical properties. Dielectric properties are studied in the frequency range of 50 Hz to 5 MHz. X-ray diffraction reveals single phase formation of Magnesium ferrite, whereas Polyaniline shows an amorphous nature. In the XRD of the composites, we see the crystalline peaks of ferrite becoming more intense with the addition of ferrite and whereas the peak of Polyaniline diminishes. The crystallite size is quantified with the Debye-Scherrer formula, and it increases as the content of ferrite in the composites increases. The micro-strain decreases in the composites as the percentage of ferrite enhances in the composites. In the UV-Vis absorption spectra of composites, the peaks of Polyaniline shift to higher wavelength and there is also an absorption band in the spectra of composites corresponding to that of Magnesium ferrite particles. Both direct and indirect band gaps are calculated with the Tauc plot, and both the optical band gap decrease as the percentage of ferrite increases in the composite. The dielectric loss and dielectric constant both decrease with frequency in all the samples, and the dielectric response are in good agreement with Maxwell-Wagner model. Ferrite-polymer composites with both conducting and magnetic properties are considered useful for electromagnetic shielding and microwave absorption.

Combustion Synthesis of Magnetic Nanomaterials for Biomedical Applications

Combustion synthesis is a green, energy-saving approach that permits an easy scale-up and continuous technologies. This process allows for synthesizing various nanoscale materials, including oxides, nitrides, sulfides, metals, and alloys. In this work, we critically review the reported results on the combustion synthesis of magnetic nanoparticles, focusing on their properties related to different bio-applications. We also analyze challenges and suggest specific directions of research, which lead to the improvement of the properties and stability of fabricated materials.

Effect of High-Anisotropic Co2+ Substitution for Ni2+ on the Structural, Magnetic, and Magnetostrictive Properties of NiFe2O4: Implications for Sensor Applications

This work reports on the effect of substituting a low-anisotropic and low-magnetic cation (Ni²⁺, 2μ_B) by a high-anisotropic and high-magnetic cation (Co²⁺, 3μ_B) on the crystal structure, phase, microstructure, magnetic properties, and magnetostrictive properties of NiFe₂O₄ (NFO). Co-substituted NFO (Ni_1-xCo_xFe₂O₄, NCFO, 0 ≤ x ≤ 1) nanomaterials were synthesized using glycine-nitrate autocombustion followed by postsynthesis annealing at 1200 °C. The X-ray diffraction measurements coupled with Rietveld refinement analyses indicate the significant effect of Co-substitution for Ni, where the lattice constant (a) exhibits a functional dependence on composition (x). The a-value increases from 8.3268 to 8.3751 Å (±0.0002 Å) with increasing the "x" value from 0 to 1 in NCFO. The a-x functional dependence is derived from the ionic-size difference between Co²⁺ and Ni²⁺, which also induces grain agglomeration, as evidenced in electron microscopy imaging. The chemical bonding of NCFO, as probed by Raman spectroscopy, reveals that Co(x)-substitution induced a red shift of the T_2g(2) and A_1g(1) modes, and it is attributed to the changes in the metal-oxygen bond length in the octahedral and tetrahedral sites in NCFO. X-ray photoelectron spectroscopy confirms the presence of Co²⁺, Ni²⁺, and Fe³⁺ chemical states in addition to the cation distribution upon Co-substitution in NFO. Chemical homogeneity and uniform distribution of Co, Ni, Fe, and O are confirmed by EDS. The magnetic parameters, saturation magnetization (M_S), remnant magnetization (M_r), coercivity (H_C), and anisotropy constant (K₁) increased with increasing Co-content "x" in NCFO. The magnetostriction (λ) also follows a similar behavior and almost linearly varies from -33 ppm (x = 0) to -227 ppm (x = 1), which is primarily due to the high magnetocrystalline anisotropy contribution from Co²⁺ ions at the octahedral sites. The magnetic and magnetostriction measurements and analyses indicate the potential of NCFO for torque sensor applications. Efforts to optimize materials for sensor applications indicate that, among all of the NCFO materials, Co-substitution with x = 0.5 demonstrates high strain sensitivity (-2.3 × 10^-9 m/A), which is nearly 2.5 times higher than that obtained for their intrinsic counterparts, namely, NiFe₂O₄ (x = 0) and CoFe₂O₄ (x = 1).

Towards hard-magnetic behavior of CoFe2O4 nanoparticles: a detailed study of crystalline and electronic structures, and magnetic properties

We have used the coprecipitation and mechanical-milling methods to fabricate CoFe₂O₄ nanoparticles with an average crystallite size (d) varying from 81 to ∼12 nm when changing the milling time (t _m) up to 180 min. X-ray diffraction and Raman-scattering studies have proved the samples crystalizing in the spinel structure. Both the lattice constant and residual strain tend to increase when t _m(d) increases (decreases). The analysis of magnetization data has revealed a change in the coercivity (H _c) towards the hard-magnetic properties. Specifically, the maximum H _c is about 2.2 kOe when t _m = 10 min corresponding to d ≈ 29 nm; beyond this t _m(d) value, H _c gradually decreases. Meanwhile, the increase of t _m always reduces the saturation magnetization (M _s) from ∼69 emu g^-1 for t _m = 0 to 35 emu g^-1 for t _m = 180 min. The results collected as analyzing X-ray absorption data have indicated a mixed valence state of Fe^2+,3+ and Co²⁺ ions. We think that the migration and redistribution of these cations between the tetrahedral and octahedral sites together with lattice distortions and defects induced by the milling process have impacted the magnetic properties of the CoFe₂O₄ nanoparticles.

Enhancing the Performance of Quantum Dot Light-Emitting Diodes Using Solution-Processable Highly Conductive Spinel Structure CuCo2O4 Hole Injection Layer

Charge imbalance in quantum-dot light-emitting diodes (QLEDs) causes emission degradation. Therefore, many studies focused on improving hole injection into the QLEDs-emitting layer owing to lower hole conductivity compared to electron conductivity. Herein, CuCo₂O₄ has a relatively higher hole conductivity than other binary oxides and can induce an improved charge balance. As the annealing temperature decreases, the valence band maximum (VBM) of CuCo₂O₄ shifts away from the Fermi energy level (E_F), resulting in an enhanced hole injection through better energy level alignment with hole transport layer. The maximum luminance and current efficiency of the CuCo₂O₄ hole injection layer (HIL) of the QLED were measured as 93,607 cd/m² and 11.14 cd/A, respectively, resulting in a 656% improvement in luminous performance of QLEDs compared to conventional metal oxide HIL-based QLEDs. These results demonstrate that the electrical properties of CuCo₂O₄ can be improved by adjusting the annealing temperature, suggesting that solution-processed spinel can be applied in various optoelectronic devices.

Controlled Electrophoretic Deposition Strategy of Binder-Free CoFe2O4 Nanoparticles as an Enhanced Electrocatalyst for the Oxygen Evolution Reaction

The kinetic-sluggish oxygen evolution reaction (OER) is the main obstacle in electrocatalytic water splitting for sustainable production of hydrogen energy. Efficient water electrolysis can be ensured by lowering the overpotential of the OER by developing highly active catalysts. In this study, a controlled electrophoretic deposition strategy was used to develop a binder-free spinel oxide nanoparticle-coated Ni foam as an efficient electrocatalyst for water oxidation. Oxygen evolution was successfully promoted using the CoFe₂O₄ catalyst, and it was optimized by modulating the electrophoretic parameters. When optimized, CoFe₂O₄ nanoparticles presented more active catalytic sites, superior charge transfer, increased ion diffusion, and favorable reaction kinetics, which led to a small overpotential of 287 mV for a current density of 10 mA cm^-2, with a small Tafel slope of 43 mV dec^-1. Moreover, the CoFe₂O₄ nanoparticle electrode exhibited considerable long-term stability over 100 h without detectable activity loss. The results demonstrate promising potential for large-scale water splitting using Earth-abundant oxide materials via a simple and cheap fabrication process.

Thiolated gamma-cyclodextrin-polymer-functionalized CeFe3O4 magnetic nanocomposite as an intrinsic nanocatalyst for the selective and ultrasensitive colorimetric detection of triacetone triperoxide

Explosives are powerful destructive weapons used by criminals and terrorists across the globe and their use within military installation sites poses serious environmental health problems. Existing colorimetric sensors for triacetone triperoxide (TATP) relies on detecting its hydrolysed H₂O₂ form. However, such detection strategy limits the practicability for on-site TATP sensing. In this work, we have developed a novel peroxidase mimic catalytic colorimetric sensor for direct recognition of TATP. Ceria (Ce)-doped Fe₃O₄ nanoparticles (CeFe₃O₄) were synthesized via the hot-injection organic synthetic route in the presence of metal precursors and organic ligands. Thereafter, the organic-capped CeFe₃O₄ nanoparticles were surface-functionalized with amphiphilic polymers (Amp-poly) to render the nanoparticle stable, compact and biocompatible. Thiolated γ-cyclodextrin (γ-CD) was adsorbed on the Amp-poly-CeFe₃O₄ nanocomposite (NC) surface to form a γ-CD-Amp-poly-CeFe₃O₄ NC. γ-CD served both as a receptor and as a catalytic enhancer for TATP. Hemin (H), used as a catalytic signal amplifier was adsorbed on the γ-CD-Amp-poly-CeFe₃O₄ NC surface to form a γ-CD-Amp-poly-CeFe₃O₄-H NC that served as a functional nanozyme for the enhanced catalytic colorimetric detection of TATP. Under optimum experimental reaction conditions, TATP prepared in BIS-TRIS-Trisma Ac-KAc-NAc buffer, pH 3, was selectively and ultrasensitively detected without the need for acid hydrolysis based on the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine by H₂O₂ in the presence of the γ-CD-Amp-poly-CeFe₃O₄-H hybrid nanozyme. The obtained limit of detection of ∼0.05 μg/mL when compared with other published probes demonstrated superior sensitivity. The developed peroxidase mimic γ-CD-Amp-poly-CeFe₃O₄-H catalytic colorimetric sensor was successfully applied to detect TATP in soil, river water and tap water samples.

Tuning the Structural and Magnetic Properties of the Stuffed Framework Structures MeFe2O4 (Me = Ni, Ca, and Sr)

Spinel ferrite nanoparticles (NPs), have received a lot of attention in medical applications. Therefore, facile synthesis of ferrite NPs of numerous shapes and sizes using the citrate autocombustion technique was utilized in this article. A series of ferrite with the general formula MeFe2O4 [Me = nickle (Ni), calcium (Ca), and strontium (Sr)] are synthesized with varying average ionic radii and cation disorder on the A-site. The structural and morphological characterization of the prepared samples was performed using XRD, HRTEM, FESEM, EDAX, XPS, and Raman analyses. The phase transformation from cubic (Ni) to orthorhombic (Ca) to monoclinic (Sr) was also revealed by XRD. Accordingly, HRTEM images demonstrated nanoparticles in orthorhombic and monoclinic shapes, which are inconsistent with XRD analyses. The coercive field HC for monoclinic SrFe2O4 is ≈ 42 times larger than the Hc for NiFe2O4 with a cubic structure. This deviation in HC compared to the cubic shape particles can be coupled to the shape anisotropy present in SrFe2O4 and refers to the presence of a preferred magnetization direction within the material. The use of monoclinic SrFe2O4 NPs as antifungal activity agents is noteworthy due to their advantages in terms of surface area, efficacy, and biodegradability.

Solution combustion synthesis: the relevant metrics for producing advanced and nanostructured photocatalysts

The current developments and progress in energy and environment-related areas pay special attention to the fabrication of advanced nanomaterials via green and sustainable paths to accomplish chemical circularity. The design and preparation methods of photocatalysts play a prime role in determining the structural, surface characteristics and optoelectronic properties of the final products. The solution combustion synthesis (SCS) technique is a relatively novel, cost-effective, and efficient method for the bulk production of nanostructured materials. SCS-fabricated metal oxides are of great technological importance in photocatalytic, environmental and energy applications. To date, the SCS route has been employed to produce a large variety of solid materials such as metals, sulfides, carbides, nitrides and single or complex metal oxides. This review intends to provide a holistic perspective of the different steps involved in the chemistry of SCS of advanced photocatalysts, and pursues several SCS metrics that influence their photocatalytic performances to establish a feasible approach to design advanced photocatalysts. The study highlights the fundamentals of SCS and the importance of various combustion parameters in the characteristics of the fabricated photocatalysts. Consequently, this work deals with the design of a concise framework to link the fine adjustment of SCS parameters for the development of efficient metal oxide photocatalysts for energy and environmental applications.

Impact of Ga3+ Ions on the Structure, Magnetic, and Optical Features of Co-Ni Nanostructured Spinel Ferrite Microspheres

Co-Ni ferrite is one of the crucial materials for the electronic industry. A partial substitution with a rare-earth metal brings about modification in crystal lattice and broadens knowledge in the discovery of new magnetic material. Current work reports a Ga³⁺ substitution in the Co-Ni ferrite with composition Co_0.5Ni_0.5Fe_2-xGa_xO₄ (where x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0), herein referred to as spinel ferrite microspheres (CoNiGa-SFMCs). The samples were crystallized hydrothermally showing a hollow sphere morphology. The crystal phase, magnetic, morphology, and optical behaviour were examined using various microscopy and spectroscopic tools. While the XRD confirmed the phase of SFMCs, the crystallite size varied between 9 and 12 nm. The Tauc plot obtained from DRS (diffuse reflectance spectroscopy) shows the direct optical energy bandgap (E_g) of the products, with the pristine reading having the value of 1.41 eV E_g; the band gap increased almost linearly up to 1.62 eV along with rising the Ga³⁺ amount. The magnetic features, on the other hand, indicated the decrease in coercivity (H_c) as more Ga³⁺ is introduced. Moreover, there was a gradual increase in both saturation magnetization (M_s) and magnetic moment (nB) with increasing amount of Ga³⁺ till x = 0.6 and then a progressive decline with increases in the x content; this was ascribed to the spin-glass-like behavior at low temperatures. It was detected that magnetic properties correlate well with crystallite/particle size, cation distribution, and anisotropy.

Hyaluronic acid coated spinel ferrite for combination of chemo and photodynamic therapy: Green synthesis, characterization, and in vitro and in vivo biocompatibility study

In this project, different photosensitizers were prepared using different ratios of nickel, manganese, and iron. Then, multiple analysis were performed to evaluate their efficiency, and the most suitable one was used to be coated by hyaluronic acid to improve the nano-platform's biocompatibility and target ability. Moreover, another chemical targeting agent (riboflavin) was used to further improve the target ability of the prepared nano-platform. Different spectroscopies and thermal analysis were used to determine the physical and chemical characteristics of the prepared nano-platform. Also, in order to determine the biocompatibility of the nano-platform, in vitro and in vivo tests such as blood hemolysis, blood aggregation and lethal dose were performed. Then, an anti-cancer agent (curcumin) was loaded on the selected nano-platform to makes us able utilizing the synergistic effect of chemotherapy and photodynamic therapy simultaneously. Finally, the cell cytotoxicity results showed that the prepared nano-platform had a great anti-cancer potential which can make it a great candidate as a dual photo and chemo therapy agent for treatment of breast cancers.

The effect of fuel on the physiochemical properties of ZnFe2O4 synthesized by solution combustion method

The synthesis of ZnFe2O4 nanoparticles was performed using the solution combustion method with three types of fuel, namely urea, glycine, and ethylenediamine tetra-acetic acid (EDTA) with precursors (Zn(NO3)2.6H2O and Fe(NO3)3.9H2O. The combustion process was conducted in an open space at 300 °C for ± 1 h, resulting in a brownish-black ZnFe2O4. Meanwhile, the fuel type used in the process affects the physicochemical properties of ZnFe2O4. XRD analysis showed that ZnFe2O4 synthesized using urea, glycine, and EDTA had spinel structures with crystal sizes of 10.19, 20.34, and 27.21 nm, respectively. The FTIR spectra of ZnFe2O4 synthesized using the three fuel types had Zn-O and Fe-O stretching vibrations. Furthermore, the morphology of ZnFe2O4 synthesized using urea was more homogeneous than glycine and EDTA. The saturation magnetization of ZnFe2O4 synthesized using EDTA was 54.63 emu/g compared to glycine and urea, 50.93 and 44.73 emu/g, respectively. Finally, the surface area of synthesized ZnFe2O4 using urea, glycine, and EDTA were 116.4, 100.6, and 94.2 m2/g, respectively.

Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment

In this review, the most recent advances in the field of magnetic composite photocatalysts with integrated plasmonic silver (Ag) is presented, with an overview of their synthesis techniques, properties and photocatalytic pollutant removal applications. Magnetic attributes combined with plasmonic properties in these composites result in enhancements for light absorption, charge-pair generation-separation-transfer and photocatalytic efficiency with the additional advantage of their facile magnetic separation from water solutions after treatment, neutralizing the issue of silver’s inherent toxicity. A detailed overview of the currently utilized synthesis methods and techniques for the preparation of magnetic silver-integrated composites is presented. Furthermore, an extended critical review of the most recent pollutant removal applications of these composites via green photocatalysis technology is presented. From this survey, the potential of magnetic composites integrated with plasmonic metals is highlighted for light-induced water treatment and purification. Highlights: (1) Perspective of magnetic properties combined with plasmon metal attributes; (2) Overview of recent methods for magnetic silver-integrated composite synthesis; (3) Critical view of recent applications for photocatalytic pollutant removal.

Recyclable magnetically retrievable nanocatalysts for C–heteroatom bond formation reactions

During recent years, magnetic separation has proven to be a highly indispensable and sustainable tool for facile separation of catalysts from the reaction medium with the aid of only an external magnetic force that precludes the requirement of energy intensive, solvent based centrifugation or filtration techniques. Extensive research in the area of catalysis has clearly divulged that while designing any catalyst, the foremost features that need to be paid due attention to include high activity, ready recoverability and good reusability. Fortunately, the magnetic nanocatalysts involving a superparamagnetic core material that could comprise of iron oxides such as magnetite, maghemite or hematite or mixed ferrites (CoFe2O4, CuFe2O4) have offered bright prospects of designing the ideal catalysts by proving their efficacy as strong support material that could be further engineered with various tools of nanotechnology and efficiently catalyze various C–heterobond formation reactions. This chapter provides succinct overview of all the approaches utilized for fabricating different types of magnetic nanoparticles and strategies adopted for imparting them durability. The prime forte however remains to exclusively showcase the applications of the various types of magnetic nanocatalysts in C–O, C–N, C–S and miscellaneous (C–Se, C–Te) bond formation reactions which are anticipated to benefit the synthetic community on a broad spectrum by helping them rationalize and analyze the key features that need to be taken into account, while developing these magical nanostructured catalytic systems for boosting the green bond formation reactions/transformations.

Robust and sustainable Mg1-xCexNiyFe2-yO4 magnetic nanophotocatalysts with improved photocatalytic performance towards photodegradation of crystal violet and rhodamine B pollutants

This study aims at manufacturing Ce³⁺/Ni²⁺ ions doped Mg nanoferrites by the sol-gel method for the photocatalytic degradation of rhodamine B and crystal violet pollutants under visible natural sunlight. The particle size of synthesized nanoferrites was calculated through XRD, Hall-William plots, and TEM analysis, which perfectly agree with each other. FTIR study investigated the existence of stretching vibrations in M - O (metal-oxygen) complexes at the tetrahedral (A-site) and octahedral sites (B-site). The Raman spectra of synthesized nanophotocatalysts show the presence of four vibrational modes (E_g + 2T_2g + A_1g), providing suitable information of occupancy of Mg²⁺, Ce³⁺, Ni^2+, and Fe³⁺ ions at the interstitial sites of undoped and Ce³⁺/Ni²⁺ doped MgFe₂O₄ crystal structure. The synthesized MGF3 nanophotocatalyst performs well with degradation of 97.674% crystal violet (CV) and 90.05% rhodamine B (RhB) under natural sunlight in 60 min. The experimental results showed that doped MgFe₂O₄ nanoferrites have a high tendency to photodegrade the RhB and CV dyes in an aqueous form. The pseudo-first-order equation reflects the best photocatalytic process kinetics and studied the feasibility of RhB and CV dyes adsorption on the doped and undoped MgFe₂O₄ nanoferrites. The results show good support for adsorption by the spontaneous photodegradation process. The excellent photocatalytic activity of synthesized nanoferrites under natural sunlight verifies them as a potential candidate for the photodegradation of organic dyes. Finally, the antibacterial activity of magnetic nanoferrites was examined against S. aureus and E. Coli. The studies demonstrated that synthesized magnetic nanoferrites were more effective against S. aureus.

Impact of Sm3+ and Er3+ Cations on the Structural, Optical, and Magnetic Traits of Spinel Cobalt Ferrite Nanoparticles: Comparison Investigation

In this study, we investigated a comparison of the structure, morphology, optic, and magnetic (room temperature (RT)) features of Er³⁺ and Sm³⁺ codoped CoFe₂O₄ (CoErSm) nanospinel ferrite (NSFs) (x ≤ 0.05) synthesized via hydrothermal (H-CoErSm NSFs) and sonochemical (S-CoErSm NSFs) approaches. The formation of all products via both synthesis methods has been validated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), along with energy-dispersive X-ray (EDX) and transmission electron microscopy (TEM) techniques. The single phase of the spinel structure (except for the Hyd sample with x = 0.03) was evidenced by XRD analysis. The D _XRD (crystallite size) values of H-CoErSm and S-CoErSm NSFs are in the 10-14.7 and 10-16 nm ranges, respectively. TEM analysis presented the cubic morphology of all products. A UV-visible percent diffuse reflectance (DR %) study was performed on all products, and E _g (direct optical energy band gap) values varying in the 1.32-1.48 eV range were projected from the Tauc plots. The data of RT magnetization demonstrated that all prepared samples are ferromagnetic in nature. M-H data revealed that rising the contents of cosubstituent elements (Sm³⁺ and Er³⁺ ions) caused an increase in M _s (saturation magnetization) and H _c (coercive field) in comparison to pristine samples. Although concentration dependence is significant (x > 0.02), no strict regularity (roughly fluctuating) has been ruled out in M _s values for doped samples prepared via the hydrothermal method. However, sonochemically prepared samples demonstrated that M _s values increase with increasing x up to x = 0.04 and then decrease with the further rise in cosubstituent Sm³⁺ and Er³⁺ ions. The calculated values of M _s and H _c were found to be greater in H-CoErSm NSFs compared to those in S-CoErSm NSFs. The present investigation established that the distribution of cations and the variation in crystallite/particle sizes are efficient to control the intrinsic properties of all samples.

Gold-coated iron oxide core–shell nanostructures for the oxidation of indoles and the synthesis of uracil-derived spirooxindoles

Synthesis of isatins and uracil-based spirooxindoles catalysed by Au/Fe3O4 core–shell nanoparticles under mild conditions and low reaction times.

Revealing long-lived electron–hole migration in core–shell α/γ-Fe2O3/FCP for efficient photoelectrochemical water oxidation

A γ/α-Fe2O3/FCP photoanode with rapid interfacial hole injection and long-lived charge separation states (∼50.64 ps) showed that the synergistic effect of a phase junction and FeCo Prussian blue (FCP) could optimize the kinetics in water oxidation.

Large-scale synthesis of mixed valence K3[Fe2S4] with high dielectric and ferrimagnetic characteristics

Large scale, high purity synthesis of K3[Fe2S4] which indicates soft ferrimagnetic, high dielectric and semiconductive characteristics.

Mechanistic studies on the conversion of NO gas on urea-iron and copper metal organic frameworks at low temperature conditions: in situ infrared spectroscopy and Monte Carlo investigations

Nitrogen oxide (NOx) emissions from high-temperature combustion processes under fuel-lean conditions continue to be a challenge for the energy industry. Selective catalytic reduction (SCR) is possible using metal oxides and zeolites. There is still a need to identify catalytic materials that are efficient in reducing NOx to environmentally benign nitrogen gas at temperatures lower than 200 °C. Metal-organic frameworks (MOFs) have emerged as a class of highly porous materials with unique physical and chemical properties. This study is motivated by the lack of systematic investigations on SCR using MOFs under industrially relevant conditions. Here, we investigate the extent of NO conversion with two commercially available MOFs, Basolite F300 (Fe-BTC) and HKUST-1 (Cu-BTC), mixed with solid urea as a source for the reductant, ammonia gas. For comparison, experiments were also conducted using cobalt ferrite (CoFe2O4) as a non-porous counterpart to relate its reactivity to those obtained from MOFs. Fourier-transform infrared spectroscopy (FTIR) was utilized to identify the gas and surface species in the temperature range of 115–180 °C. Computational analysis was performed using Monte Carlo simulations to quantify the adsorption energies of different surface species. The results show that the rate of ammonia production from the in situ solid urea decomposition was higher using CoFe2O4 than Fe-BTC and Cu-BTC and that there was very limited conversion of NO on the mixed solid urea-MOF systems due to site blocking. The main conclusions from this study are that MOFs have limited ability to convert NO under low-temperature conditions and that surface regeneration requires additional experimental steps.

High-Performance, Lightweight, and Flexible Thermoplastic Polyurethane Nanocomposites with Zn2+-Substituted CoFe2O4 Nanoparticles and Reduced Graphene Oxide as Shielding Materials against Electromagnetic Pollution

The development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2-12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material.

Photooxidative decomposition and defluorination of perfluorooctanoic acid (PFOA) using an innovative technology of UV-vis/ZnxCu1-xFe2O4/oxalic acid

Per- and polyfluoroalkyl substances (PFAS) are a large group of perfluorinated organic molecules that have been in use since the 1940s for industrial, commercial, and consumer applications. PFAS are a growing concern because some of them have shown persistent, bioaccumulative and toxic effects. Herein, we demonstrate an innovative technology of UV-vis/Zn_xCu_1-xFe₂O₄/oxalic acid for the degradation of perfluorooctanoic acid (PFOA) in water. The magnetically retrievable nanocrystalline heterogeneous ferrite catalysts, Zn_xCu_1-xFe₂O₄ were synthesized using a sol-gel auto-combustion process followed by calcination at 400 °C. The combination of Zn_xCu_1-xFe₂O₄ and oxalic acid generate reactive species under UV light irradiation. These reactive species are then shown to be capable of the photodegradation of PFOA. The degree of degradation is tracked by identifying transformation products using liquid chromatography coupled with quadrupole time-of-flight mass spectroscopy (LC-QTOF-MS).

Preparation of NiFe2O4 Nanoparticles by Solution Combustion Method as Photocatalyst of Congo red

NiFe2O4 nanoparticles had been successfully synthesized by solution combustion method using urea fuel (organic precursor). The synthesized NiFe2O4 were characterized by X-ray diffraction (XRD), Scanning electron microscopy-Electron Dispersive X-ray Spectroscopy (SEM-EDs), Transmission Electron Microscopy (TEM), Fourier Transform Infra-Red (FTIR), Vibrating Sample Magnetometer (VSM), UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS), and Point of Zero Charge (pHpzc). NiFe2O4 nanoparticles irradiated with visible light were employed to degrade Congo red dye with the following variable: solution pH (3–8), H2O2 concentration (0.5–3 mM), and Congo red concentration (100–600 mg/L). XRD analysis results showed that the NiFe2O4 nanoparticles had a cubic spinel structure. The particle sizes are in the range of 10–40 nm. The magnetic properties of NiFe2O4 nanoparticles determined using VSM showed a magnetization saturation value of 47.32 emu/g. UV-Vis DRS analysis indicated that NiFe2O4 nanoparticles had an optical band gap of 1.97 eV. The success of synthesis was also proven by the EDS analysis results, which showed that the synthesized NiFe2O4 nanoparticles composed of Ni, Fe, and O elements. The removal efficiency of Congo red dye was 96.80% at the following optimum conditions: solution pH of 5.0, H2O2 concentration of 2 mM, Congo red dye concentration of 100 mg/L, and contact time of 60 min. The study of the photodegradation kinetics follows a pseudo-first order reaction with a rate constant value of 0.0853 min−1. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Sunlight powered degradation of pentoxifylline Cs0.5Li0.5FeO2 as a green reusable photocatalyst: Mechanism, kinetics and toxicity studies

The degradation of Pentoxifylline (PXF) was achieved successfully by green energy in a built-in solar photocatalytic system using hybrid LiCs ferrites (Li_0.5Cs_0.5FeO₂) as magnetically recoverable photocatalysts. Kinetics showed a first-order reaction rate with maximum PXF removal of 94.91% at mildly acidic pH; additionally, the ferromagnetic properties of catalyst allowed recovery and reuse multiple times, reducing costs and time in degradation processes. The degradation products were identified by HPLC-MS and allowed us to propose a thermodynamically feasible mechanism that was validated through DFT calculations. Additionally, toxicity studies have been performed in bacteria and yeast where high loadings of Cs showed to be harmful to Staphylococcus aureus (MIC≥ 4.0 mg/mL); Salmonella typhi (MIC≥ 8.0 mg/mL) and Candida albicans (MIC≥ 10.0 mg/mL). The presented setup shows effectiveness and robustness in a degradation process using alternative energy sources for the elimination of non-biodegradable pollutants.

Photocatalytic activation of peroxymonosulfate (PMS) by novel mesoporous Ag/ZnO@NiFe2O4 nanorods, inducing radical-mediated acetaminophen degradation under UVA irradiation

A new mesoporous Ag/ZnO@NiFe₂O₄ nanorod was prepared by a facile, low-cost, and environmentally friendly strategy from a bimetallic Fe₂Ni-MIL-88 metal organic framework (MOF), as an effective catalyst and peroxymonosulfate (PMS) photo-activator. The structural, morphological, optical, and magnetic properties, as well as the material composition were investigated by XRD, FE-SEM, EDX, HR-TEM, XPS, DRS, PL, EIS, VSM, N₂ adsorption-desorption and ICP-AES analysis. 1.0% w/w loading of Ag nanoparticles on ZnO_0.04@NiFe₂O₄ led to the best catalytic activity for PMS activation under UVA in acetaminophen (ACT) degradation. The maximum degradation efficiency for ACT was 100% within 15 min (at pH = 7.0), with a first-order rate constant of 0.368 min^-1. The calculated quantum yield (1.3 × 10^-3 molecule/photon) of the optimum catalyst was 2.05, and 5.63 times higher than its simple constituents, ZnO_0.04@NiFe₂O₄ and NiFe₂O₄, respectively. Among the various inorganic ions, Cl^- and HCO₃^- showed significant inhibition effect in 1.0%w/w Ag/ZnO_0.04@NiFe₂O₄/PMS/UVA system, due to radical quenching effects. Based on scavenger experiments, HO^• and SO₄^•- were the dominant reactive species in photocatalytic process coupled with PMS. Due to presence of the Fe³⁺/Fe²⁺, and Ni²⁺/Ni³⁺ reaction cycles in the as-made catalyst, the reaction rate of PMS activation was greatly enhanced. Moreover, the formation of a hetero-junction structure with NiFe₂O₄ and ZnO promoted the charge separation of the photo-generated electron/hole pairs. Finally, the major intermediates produced during the reaction were detected by LC-MS analysis, and a plausible mechanism for the photocatalytic degradation of ACT was proposed and discussed in detail.

Catalytically Active CoFe2O4 Nanoflowers for Augmented Sonodynamic and Chemodynamic Combination Therapy with Elicitation of Robust Immune Response

A hypoxic and acidic tumor microenvironment (TME) plays a significant role in cancer development through complex cellular signaling networks, and it is thus challenging to completely eradicate tumors via monotherapy. Here, PEGylated CoFe₂O₄ nanoflowers (CFP) with multiple enzymatic activities, serving as bioreactors responsive to TME cues, were synthesized via a typical solvothermal method for augmented sonodynamic therapy (SDT) and chemodynamic therapy (CDT) with elicitation of robust immune response. The CFP occupying multivalent elements (Co^2+/3+, Fe^2+/3+) exhibited strong Fenton-like and catalase-like activity. In another aspect, CFP itself is a brand-new sonosensitizer for high-performance SDT based on ultrasound-triggered electron (e^-)/hole (h⁺) pair separation from the energy band with promptness and high efficiency. With efficient enrichment in tumorous tissue as revealed by magnetic resonance imaging, CPF could generate ^•OH for CDT relying on Fenton-like reactions. Moreover, catalase-mimicking CFP could react with endogenous H₂O₂ to generate molecular oxygen, and high O₂ level may promote the production of ¹O₂ for SDT. What's more, the reactive oxygen species obtained from combined SDT/CDT could efficiently trigger immunogenic cell death through a synergistic therapy based on the elicitation of antitumor immunity with the aid of an immune checkpoint blockade for the sake of suppressing primary and distant tumors as well as lung metastasis. Taken together, this paradigm delivers useful insights for developing in-coming nanocomposites based on cobalt ferrite for cancer theranostics.

Recent Advances in Synthesis and Applications of MFe2O4 (M = Co, Cu, Mn, Ni, Zn) Nanoparticles

In the last decade, research on the synthesis and characterization of nanosized ferrites has highly increased and a wide range of new applications for these materials have been identified. The ability to tailor the structure, chemical, optical, magnetic, and electrical properties of ferrites by selecting the synthesis parameters further enhanced their widespread use. The paper reviews the synthesis methods and applications of MFe₂O₄ (M = Co, Cu, Mn, Ni, Zn) nanoparticles, with emphasis on the advantages and disadvantages of each synthesis route and main applications. Along with the conventional methods like sol-gel, thermal decomposition, combustion, co-precipitation, hydrothermal, and solid-state synthesis, several unconventional methods, like sonochemical, microwave assisted combustion, spray pyrolysis, spray drying, laser pyrolysis, microemulsion, reverse micelle, and biosynthesis, are also presented. MFe₂O₄ (M = Co, Cu, Mn, Ni, Zn) nanosized ferrites present good magnetic (high coercivity, high anisotropy, high Curie temperature, moderate saturation magnetization), electrical (high electrical resistance, low eddy current losses), mechanical (significant mechanical hardness), and chemical (chemical stability, rich redox chemistry) properties that make them suitable for potential applications in the field of magnetic and dielectric materials, photoluminescence, catalysis, photocatalysis, water decontamination, pigments, corrosion protection, sensors, antimicrobial agents, and biomedicine.

Structural and Magnetic Properties Study of Fe2O3/NiO/Ni2FeO4 Nanocomposites

In the current work, the nanocomposites that consist chiefly of three components—α-Fe2O3, NiO and Ni2FeO4, in two different ratios 2:2:1 (FNN-221) and 2:1:1 (FNN-211), respectively—were produced. The synthesis was done in two steps by following the chemical co-precipitation and mechanical ball-milling route. The presence of individual phase was identified from the XRD data without the detection of any additional impurities. The phase fraction of each component estimated from the profile fitting of XRD patterns were found to be 41.2%, 39.7%, 19.1% in FNN-221 sample and 49.5%, 26.4%, 24.1% for FNN-211 sample, respectively, which were consistent with the experimental values. The total magnetization at 300 K was obtained to be 13.41 emu/g and 10.95 emu/g for FNN-221 and FNN-211 samples, respectively. In FNN-211 compound the zero field coercivity (HC) expanded towards the higher field values thereby signifying the exchange bias behavior. Furthermore, the exchange bias field (Hex) for FNN-211 was obtained as 35.1 Oe.

Improving photocatalytic efficiency of MnFe2O4 ferrites via doping with Zn2+/La3+ ions: photocatalytic dye degradation for water remediation

The interference of industrial effluents such as dyes, surfactants, metals, polycyclic aromatic hydrocarbons, and pharmaceutical waste has become a severe global problem for human health due to their carcinogenic, mutagenic, and toxic properties. Ferrites were considered promising photocatalysts for the degradation of organic and inorganic dyes. This study mainly focused on improving the photocatalytic performance of MnFe₂O₄ nanoferrites via doping of Zn²⁺ and La³⁺ ions. The zinc and lanthanum substituted Mn_1-xZn_xLa_yFe_2-yO₄ nanoferrites were prepared by the sol-gel auto-combustion technique for the degradation of organic textile malachite green dye (MGD) under the natural solar irradiation. The synthesized nanoferrites were investigated for their structural properties, surface morphology and elemental analysis, optical studies, magnetic properties, and photocatalytic performance by XRD, FESEM/EDX, FTIR/Raman spectrum, vibrating sample magnetometer, and UV-visible spectrophotometer, respectively. The substitution of zinc and lanthanum improved the photocatalytic efficiency of nanoferrites, and about 96% of MGD was degraded by Mn_0.97Zn_0.03La_0.04Fe_1.96O₄ after 60 min of irradiation. The results showed the pseudo-first-order kinetics for dye degradation using undoped and Zn/La-doped MnFe₂O₄ photocatalysts.

Selectivity of Mixed Iron-Cobalt Spinels Deposited on a N,S-Doped Mesoporous Carbon Support in the Oxygen Reduction Reaction in Alkaline Media

One of the practical efforts in the development of oxygen reduction reaction (ORR) catalysts applicable to fuel cells and metal-air batteries is focused on reducing the cost of the catalysts production. Herein, we have examined the ORR performance of cheap, non-noble metal based catalysts comprised of nanosized mixed Fe-Co spinels deposited on N,S-doped mesoporous carbon support (N,S-MPC). The effect of the chemical and phase composition of the active phase on the selectivity of catalysts in the ORR process in alkaline media was elucidated by changing the iron content. The synthesized materials were thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). Detailed S/TEM/EDX and Raman analysis of the phase composition of the synthesized ORR catalysts revealed that the dominant mixed iron-cobalt spinel is accompanied by minor fractions of bare cobalt and highly dispersed spurious iron oxides (Fe2O3 and Fe3O4). The contribution of individual phases and their degree of agglomeration on the carbon support directly influence the selectivity of the obtained catalysts. It was found that the mixed iron-cobalt spinel single phase gives rise to significant improvement of the catalyst selectivity towards the desired 4e- reaction pathway, in comparison to the reference bare cobalt spinel, whereas spurious iron oxides play a negative role for the catalyst selectivity.