Fe-O Bond Research Articles

Electron redistribution and proton transfer induced by atomically fully exposed Cu-O-Fe clusters coupled with single-atom sites for efficient oxygen electrocatalysis

Single-atom catalysts have garnered significant attention by showing sparkling performance in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the air cathode side of energy devices such as metal-air batteries and fuel cells. This work presents a novel catalyst, AC-CuFe-NC, that incorporates Fe-doped CuO atomic clusters (CuOFe) synergistically with single-atom sites. The AC-CuFe-NC demonstrates outstanding ORR performance (half-wave potential of 0.92 V) and an oxygen overpotential gap between ORR and OER as low as 0.61 V, which is among the top reported performances. Combined with in situ ATR-SEIRAS and DFT calculations, it is shown that the synergistic CuOFe atomic clusters are effective in inducing the electronic structure redistribution of the Fe single-atom site, modulating oxygen adsorption energy, and lowering ORR barriers. More importantly, it is revealed that the synergistic adsorption of clusters and single-atom sites establishes hydrogen bonds between the oxygenated intermediates and the electrolyte H2O molecules. The constructed hydrogen bond can provide a pathway for efficient proton transport as supported by kinetic isotope experiments, leading to a substantial enhancement in reaction kinetics. Additionally, the oxygenated intermediates are stabilized, and the Fe-O bond is elongated during the final step of ORR, thereby facilitating the desorption of OH*. The excellent bifunctional electrocatalytic performance of AC-CuFe-NC enable it to show promising application in rechargeable Zn-air batteries. The innovative catalyst structure and synergistic mechanism demonstrated in this study shed light on the development of high-performance catalysts in energy devices.

Simultaneous elimination of antibiotic-resistant bacteria and antibiotic resistance genes by different Fe-N co-doped biochars activating peroxymonosulfate: The key role of pyridine-N and Fe-N sites

The coexistence of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in the environment poses a potential threat to public health. In our study, we have developed a novel advanced oxidation process for simultaneously removing ARGs and ARB by two types of iron and nitrogen-doped biochar derived from rice straw (FeN-RBC) and sludge (FeN-SBC). All viable ARB (approximately 108 CFU mL−1) was inactivated in the FeN-RBC/ peroxymonosulfate (PMS) system within 40 min and did not regrow after 48 h even in real water samples. Flow cytometry identified 96.7 % of dead cells in the FeN-RBC/PMS system, which verified the complete inactivation of ARB. Thorough disinfection of ARB was associated with the disruption of cell membranes and intracellular enzymes related to the antioxidant system. Whereas live bacteria (approximately 200 CFU mL−1) remained after FeN-SBC/PMS treatment. Intracellular and extracellular ARGs (tetA and tetB) were efficiently degraded in the FeN-RBC/PMS system. The production of active species, primarily •OH, SO4•- and Fe (IV), as well as electron transfer, were essential to the effective disinfection of FeN-RBC/PMS. In comparison with FeN-SBC, the better catalytic performance of FeN-RBC was mainly ascribed to its higher amount of pyridine-N and Fe0, and more reactive active sites (such as CO group and Fe-N sites). Density functional theory calculations indicated the greater adsorption energy and Bader charge, more stable Fe-O bond, more easily broken OO bond in FeN-RBC/PMS, which demonstrated the stronger electron transfer capacity between FeN-RBC and PMS. To encapsulate, our study provided an efficient and dependable method for the simultaneous elimination of ARGs and ARB in water.

Enhanced Fe(OH)2-driven reductive Dechlorination via shortened Fe-O bonds and colloidal medium

Fe2+ is usually adsorbed to the surface of iron-bearing clay, and iron (hydr)oxide in groundwater. However, the reductive activity of Fe(OH)2, a prevalent intermediate during the transformation of Fe2+, remains unclear. In this study, high-purity Fe(OH)2 was synthesized and tested for its activity in the degradation of carbon tetrachloride (CT). XRD data confirm that the synthesized material is a pure Fe(OH)2 crystal, exhibiting sharp peaks of (001) and (100) facets. Zeta potential analysis confirms that the off-white Fe(OH)2 is a colloidal suspension with a positive charge of ∼+35-50 mV. FTIR spectra reveal the formation of a coordination compound Fe2+ with OH−/OD−, derived from NaOH/OD. SEM and HRTEM results demonstrate that the Fe(OH)2 crystal has a regular octahedral structure with a size of ∼30-70 nm and average lattice spacings of 2.58 Å. Mössbauer spectrum verifies that the Fe2+ in Fe(OH)2/Fe(OD)2 is hexacoordinated with six Fe-O bonds. XAFS data demonstrate that the Fe-O bonds become shorter as the OH−:Fe(II) ratios increase. DFT results indicate that the (100) crystal face of Fe(OH)2 more readily transfers electrons to CT. In addition to being adsorbed to iron compounds, structural Fe2+ compounds such as Fe(OH)2 could also accelerate the electron transfer from Fe2+ to CT through shortened Fe-O bonds. The rate constant of CT reduction by Fe(OH)2 is as high as 0.794 min−1 when the OH−:Fe(II) ratio is 2.5 in water. This study aims to enhance our understanding of the structure-reactivity relationship of Fe2+ compounds in groundwater, particularly in relation to electron transfer mechanisms.

Precisely constructing orbital coupling-modulated iron dinuclear site for enhanced catalytic ozonation performance

The advancement of atomically precise dinuclear heterogeneous catalysts holds great potential in achieving efficient catalytic ozonation performance and contributes to the understanding of synergy mechanisms during reaction conditions. Herein, we demonstrate a "ship-in-a-bottle and pyrolysis" strategy that utilizes Fe2(CO)9 dinuclear-cluster to precisely construct Fe2 site, consisting of two Fe1-N3 units connected by Fe-Fe bonds and firmly bonded to N-doped carbon. Systematic characterizations and theoretical modeling reveal that the Fe-Fe coordination motif markedly reduced the devotion of the antibonding state in the Fe-O bond because of the strong orbital coupling interaction of dual Fe d-d orbitals. This facilitates O-O covalent bond cleavage of O3 and enhances binding strength with reaction intermediates (atomic oxygen species; *O and *OO), thus boosting catalytic ozonation performance. As a result, Fe dinuclear site catalyst exhibits 100% ozonation efficiency for CH3SH elimination, outperforming commercial MnO2 catalysts by 1,200-fold. This research provides insights into the atomic-level structure-activity relationship of ozonation catalysts and extends the use of dinuclear catalysts in catalytic ozonation and beyond.

A novel magnetic graphene-loaded biochar gel for the remediation of arsenic- and antimony-contaminated mining soil

Metalloid co-contamination such as arsenic (As) and antimony (Sb) in soils has posed a significant threat to ecological balance and human well-being. In this study, a novel magnetic graphene-loaded biochar gel (FeBG) was developed, and its remediation potential for the reclamation of AsSb spoiled soil was assessed through a six-month soil incubation experiment. Results showed that the incorporation of iron substances and graphene imparted FeBG with enhanced surface characteristics, such as the formation of a new FeO bond and an enlarged surface area compared to the pristine biochar (BC) (80.5 m2 g−1 vs 57.4 m2 g−1). Application of FeBG significantly decreased Na2HPO4-extractable concentration of As in soils by 9.9 %, whilst BC addition had a non-significant influence on As availability, compared to the control. Additionally, both BC (8.2 %) and FeBG (16.4 %) treatments decreased the Na2HPO4-extractable concentration of Sb in soils. The enhanced immobilization efficiency of FeBG for As/Sb could be attributed to FeBG-induced electrostatic attraction, complexation (Fe–O(H)–As/Sb), and π-π electron donor-acceptor coordination mechanisms. Additionally, the FeBG application boosted the activities of sucrase (9.6 %) and leucine aminopeptidase (7.7 %), compared to the control. PLS-PM analysis revealed a significant negative impact of soil physicochemical properties on the availability of As (β = −0.611, P < 0.01) and Sb (β = −0.848, P < 0.001) in soils, in which Sb availability subsequently led to a suppression in soil enzyme activities (β = −0.514, P < 0.01). Overall, the novel FeBG could be a potential amendment for the simultaneous stabilization of As/Sb and the improvement of soil quality in contaminated soils.

Rational Design and Synthesis of Fe-Doped Co-Based Coordination Polymer Composite Photocatalysts for the Degradation of Norfloxacin and Ciprofloxacin.

The solar light-responsive Fe-doped Co-based coordination polymer (Fe@Co-CP) photocatalyst was synthesized under mild conditions. [Co(4-padpe)(1,3-BDC)]n (Co-CP) was first constructed using mixed ligands through the hydrothermal method. Then, Fe was introduced into the Co-CP framework to achieve the enhanced photocatalytic activity. The optimal Fe@Co-CP-2 exhibited excellent catalytic degradation performance for norfloxacin and ciprofloxacin under sunlight irradiation without auxiliary oxidants, and the degradation rates were 91.25 and 92.66% in 120 min. These excellent photocatalytic properties were ascribed to the generation of the Fe-O bond, which not only enhanced the light absorption intensity but also accelerated the separation efficiency of electrons and holes, and hence significantly improved the photocatalytic property of the composites. Meanwhile, Fe@Co-CP-2 displayed excellent stability and reusability. In addition, the degradation pathways and intermediates of antibiotic molecules were effectively analyzed. The free radical scavenging experiment and ESR results confirmed that •OH, •O2-, and h+ active species were involved in the catalytic degradation reaction; the corresponding mechanisms were deeply investigated. This study provides a fresh approach for constructing Fe-doped Co-CP-based composite materials as photocatalysts for degradation of antibiotic contaminants.

Green synthesis of iron (III) oxide (Fe3O4) Nanoparticles Using Citrus sinensis Peel Extract for the Removal of Ciprofloxacin in Water

Ciprofloxacin is a widely used antibiotic that can contaminate water sources and pose environmental and health risks. Therefore, the objective of this paper is to explore the green synthesis of iron (III) oxide nanoparticles using Citrus sinensis peel extract for the removal of ciprofloxacin in water using standard techniques. The adsorption of ciprofloxacin on the nanoparticles was investigated under different conditions, such as pH, initial concentration of adsorbate, contact time, and different adsorbent doses. The adsorption data were fitted to different isotherm and kinetic models to understand the adsorption mechanism and parameters. The results of characterization revealed the particles to be of nanocrystalline structure with a cubic crystal shape, negative surface charge, and a high thermal stability with elemental composition primarily of Fe and O; it has z- average of 42.60, with Fe-O bond at 693.30cm-1 and UV-Visible absorbance at 221nm. The maximum adsorption capacity with ciprofloxacin was 29.21 mg/g (97.45%) at pH of 7 and room temperature of 25 °C. The results of the adsorption data indicated that the adsorption followed the Langmuir isotherm model and the pseudo-second-order kinetic model, suggesting a monolayer adsorption on a homogeneous surface with a finite number of identical sites. The synthesized nanoparticles showed a high efficiency and selectivity for the removal of ciprofloxacin from water, demonstrating it potential as an eco-friendly and low-cost adsorbent for water purification.

Urease-producing bacteria enhance the adsorption of Cd on organo-Fe hydroxide coprecipitates

Microorganisms, organic carbon, and iron oxides are important active components in soil that control the availability of heavy metals. In the extensive cultivation areas based on wheat–maize rotation, returning corn straw to the field increases the content of dissolved organic carbon (DOC) in the soil, affecting heavy metal adsorption by iron oxides and thereby threatening the safety of wheat. However, the effects and underlying mechanisms of maize straw-derived DOC on Cd adsorption by ferrihydrite (Fh) are unclear, and the effects of functional strains on Cd adsorption by organo-Fe hydroxide coprecipitates (OFCs) need further study. The effect of DOC on the adsorption of Cd by Fh was studied through batch solution adsorption experiments. Moreover, the mechanisms underlying the synergistic adsorption of Cd by the urease-producing bacterium Enterobacter sp. TJ6 and OFC were studied in adsorption experiments via scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that DOC inhibited the adsorption of Cd by OFC, while strain TJ6 enhanced the adsorption of Cd by OFC. Fe-OH and Fe-O bonds on the surface of Fh were important Cd adsorption sites. DOC affected the adsorption of Cd by Fe-OH and Fe-O, thereby inhibiting the adsorption of Cd by OFC. DOC also served as a reducing agent, reducing Fe2O3 on the surface of OFC to FeO and thus inhibiting OFC adsorption of Cd. The mechanisms by which strain TJ6 enhanced Cd adsorption by OFC included the following: 1) strain TJ6 utilized its own oxidation ability to oxidize FeO on the surface of OFC to Fe2O3, promoting the secondary precipitation of Cd during the redox process and enhancing the Cd adsorption capacity of OFC; and 2) strain TJ6 immobilized Cd2+ through ion exchange between Cd2+ and H+ in surface amino groups. In conclusion, this study has revealed the mechanism by which urease-producing bacteria regulate the adsorption of Cd by OFC and provides a theoretical basis for safe straw return to Cd-polluted farmland. This study also provides technical approaches and bacterial resources for the remediation of heavy metal-contaminated soil under straw return.

Enhanced degradation of Direct Red 80 dye via Fenton-like process mediated by cobalt ferrite: generated superoxide radicals and singlet oxygen.

Azo dyes, widely used in the textile industry, contribute to effluents with significant organic content. Therefore, the aim of this work was to synthesize cobalt ferrite (CoFe2O4) using the combustion method and assess its efficacy in degrading the azo dye Direct Red 80 (DR80). TEM showed a spherical structure with an average size of 33 ± 12nm. Selected area electron diffraction and XRD confirmed the presence of characteristic crystalline planes specific to CoFe2O4. The amount of Co and Fe metals were determined by ICP-OES, indicating an n(Fe)/n(Co) ratio of 2.02. FTIR exhibited distinct bands corresponding to Co-O (455cm-1) and Fe-O (523cm-1) bonds. Raman spectroscopy detected peaks associated with octahedral and tetrahedral sites. For the first time, the material was applied to degrade DR80 in an aqueous system, with the addition of persulfate. Consistently, within 60min, these trials achieved nearly 100% removal of DR80, even after the material had undergone five cycles of reuse. The pseudo-second-order model was found to be the most fitting model for the experimental data (k2 = 0.07007 L mg-1min-1). The results strongly suggest that degradation primarily occurred via superoxide radicals and singlet oxygen. Furthermore, the presence of UV light considerably accelerated the degradation process (k2 = 1.54093 L mg-1min-1). The material was applied in a synthetic effluent containing various ions, and its performance consistently approached 100% in the photo-Fenton system. Finally, two degradation byproducts were identified through HPLC-MS/MS analysis.

Ultra-stable aqueous nickel-ion storage achieved by iron-ion pre-introduction assisted hydrated vanadium oxide cathode

Aqueous Nickel-ion batteries (ANIBs) are attracting growing attention for next-generation energy storage devices, but their development is hindered by deficient satisfactory cathode materials and undefined reaction mechanisms. Herein, a novel layered vanadium oxide with Fe3+-ions pillars (Fe0.29V2O5·0.57H2O, FVO) is developed and innovatively used for effective Ni2+ ion storage. The large interlayer spacing and abundant oxide vacancies of FVO can provide broad ion migration channels and rich ion storage sites. The pre-intercalated Fe3+-ions can firmly support the integrity of the layered structure by Fe-O bonds to achieve excellent cycle stability. RGO is further introduced to construct the FVO@G composite can improve the conductivity and stability of the FVO electrode. As a result, the FVO@G electrode exhibits exceptional Ni2+ storage performance of 169.8 mAh g−1 at 0.5C and ultrahigh capacity retention of 91.9% after 320 cycles at 10C. The Ni2+ storage mechanism in FVO@G is clarified by in-situ XRD and ex-situ Raman, ex-situ XPS techniques, the results show that FVO@G undergoes a phase transition accompanied by an expansion of the interlayer spacing upon the first charging, and the electrodes display a high degree of structural reversibility and a negligible volume expansion during the subsequent cycles. Furthermore, density functional theory (DFT) calculations show that FVO provides efficient diffusion paths along the b-axis with ultrafast transport kinetics. This work is a significant step in ANIBs research and provides valuable insights for the design of high-performance ANIBs cathode material.

Facile green fabrication of magnetite nanoparticles using an aqueous flower extract of Murraya paniculata (L) Jack for an efficient removal of organic dye pollutant, antibacterial activities

This article reports, the plant-mediated synthesis of Magnetite nanoparticles achieved by utilising an aqueous flower extract of Murraya paniculata (L) Jack (FMPM NPs). The active compounds are phenols, alkaloids, flavones and terpenoids in the aqueous flower extract of Murraya paniculata act as ligating agents to synthesize novel green superparamagnetic magnetite nanoparticles by the coprecipitation method. As prepared FMPM NPs have been characterized by a range of spectroscopic and microscopic techniques. All spectroscopic and microscopic results confirmed the occurrence of pure FMPM NPs. Fourier transform-infrared spectroscopy (FTIR) shows the presence of a Fe-O bond and the band gap was found to be 2.57 eV for FMPM NPs. The surface area of the synthesized nanoparticles was 70.31 m2/g evaluated by BET analysis. The elemental analysis has been performed by the XPS technique. The XRD pattern revealed the crystal size of 14.12 nm of FMPM NPs. TEM images show the spherical shaped FMPM NPs with an average particle size of 11.58 nm. SEM results clearly show spherically shaped FMPM NPs. The superparamagnetic character of FMPM NPs is revealed by the VSM curve and saturation magnetization (Ms) value of 58 emu/g. FMPM NPs used for photocatalytic activity, tested against gram positive, gram negative and antifungal bacteria. As prepared FMPM NPs. showed 93 % removal efficiency of Fast sulphon black-F dye pollutant. Moreover, FMPM NPs efficiently inhibit the growth of Enterococcus faecalis and Penicillium chrysogenum. The current research is for the fabrication of magnetite nanoparticles utilising novel green source and examining their applications.

Rapid mechanochemical synthesis of high-performance Na4Fe2.94Al0.04(PO4)2(P2O7)/C cathode material for sodium-ion storage

Na4Fe3(PO4)2(P2O7) is regarded as a promising cathode material for sodium-ion batteries due to its affordability, non-toxic nature, and excellent structural stability. However, its electrochemical performance is hampered by its poor electronic conductivity. Meanwhile, most of the previous studies utilized spray-drying and sol–gel methods to synthesize Na4Fe3(PO4)2(P2O7), and the large-scale synthesis of the cathode material is still challenging. This study presents a composite cathode material, Na4Fe2.94Al0.04(PO4)2(P2O7)/C, prepared via a straightforward ball-milling technique. By substituting Al3+ minimally into the Fe2+ site of NFPP, Fe defects are introduced into the structure, hindering the formation of NaFePO4 and thereby enhancing Na-ion diffusion kinetics and conductivity. Additionally, the average length of AlO bonds (2.18 Å) is slightly smaller than that of FeO bonds (2.19 Å), contributing to the superior structural stability. The smaller ionic radii of Al3+ induce lattice contraction, further enhancing the structural stability. Moreover, the surface of material particles is coated with a thin layer of carbon, ensuring excellent electrical conductivity and outstanding structure stability. As a result, the Na4Fe2.94Al0.04(PO4)2(P2O7)/C cathode exhibits excellent electrochemical performance, leading to high discharge capacity (128.1 mAh g−1 at 0.2 C), outstanding rate performance (98.1 mAh g−1 at 10 C), and long cycle stability (83.7 % capacity retention after 3000 cycles at 10 C). This study demonstrates a low-cost, ultra-stable, and high-rate cathode material prepared by simple mechanical activation for sodium-ion batteries which has application prospects for large-scale production.

Synthesis and characterization of Magnetic Fe3O4/SiO2 composite for Environmental Sanitation

The synthesis and characterization of the Fe3O4/SiO2 composite using the co-precipitation method have been conducted. Magnetite (Fe3O4) possesses magnetic properties capable of removing catalyst and dye waste. Silica is excellently suited as a material for magnetic coatings. The Fe3O4/SiO2 composite was characterized using XRD to identify the crystal phase and lattice structure parameters. Morphological analysis and elemental mapping of the sample were carried out using SEM-EDS, and FTIR was used to identify the functional groups. The XRD characterization results show that the Fe3O4/SiO2 composite crystallizes well, with identified peaks at angles of 2θ = 30.18°; 36.86°; 43.14°; 53.52°; 57.08°. The FTIR test results indicate the presence of SI-O-Si bonds, characteristic of the SiO2 peak, and Fe-O bonds, which are indicative of Fe3O4. The homogeneous morphologies are demonstrated by the SEM-EDS image.

Formation of Fe4+ based on the Fe-O bond lengths in perovskite Eu1-xSrxFeO3

The physical properties of high oxidation state of transition metal oxide compounds have attracted many research interest for its potential applications. A systematic investigation of Fe4+ in Eu1-xSrxFeO3 with x = 0, 0.1, 0.2, 0.3, and 0.4 has been carried out in polycrystalline form obtained using sol-gel method. The single phase of Eu1-xSrxFeO3 is observed up to x = 0.3. The X-Ray powder pattern for low Sr content of x = 0.1, is best refined by using EuFeO3 crystal structure with Sr occupied the Eu-site. On the other hand, for higher Sr contents, two phases of EuFeO3 and Eu1/3Sr2/3FeO3 are required to obtained the best refinement. The result of the refinements shows that the volume and the average bond lengths of Fe-O decreases as increasing the Sr content. These results are consistent to support the existence of Fe4+ upon Sr doping in Eu1-xSrxFeO3. For the Sr content of x = 0.1, an anomalous change of the volume is observed.

Green Synthesis of Magnetite Nanoparticles Using &lt;i&gt;Moringa oleifera&lt;/i&gt; and their Electro-Optic Surface Plasmon Resonance Properties

The application of an external electric field to the surface plasmon resonance (SPR) system of green-synthesized magnetite (Fe3O4) nanoparticles (MNPs) is very promising for increasing the SPR detection signal. Electro-optic surface plasmon resonance (EOSPR) behavior of MNPs has been successfully carried out. The EOSPR system was investigated using the Kretschmann configuration with the prism/Au thin film/MNPs/air layer arrangement and applying an electric voltage of 0 V, 2 V, 4 V, and 6 V. In this study, we synthesized MNPs using the green synthesis approach from moringa oleifera extract. The benefits of green synthesis include being safe, affordable, clean, and ecologically friendly processes. X-ray diffraction results obtained crystal size of the MNPs is about 9.2 nm with inverse spinel face-centered cubic crystal structure. Fourier transforms infrared characterization showed the presence of Fe-O bonds at wave numbers 569 cm-1 and 629 cm-1, indicating that MNPs were successfully formed. The saturation magnetization of the samples is 55.3 emu/g. The SPR angle of the SPR system Prism/Au thin film/air without the addition of MNPs is 44.66°. After being deposited by MNPs and induced by a voltage of 0 V, 2 V, 4 V, and 6 V, the SPR angles changed to 44.87°, 44.90°, 44.95° and 45.12°. The addition of MNPs and an external electric field causes the SPR angle to increase. The results of this study can provide new insights into the development of optical devices that can be manipulated electrically and have the potential for future biosensor applications.

Agro-Waste Sweet Pepper Extract-Magnetic Iron Oxide Nanoparticles for Antioxidant Enrichment and Sustainable Nanopackaging.

This study synthesizes magnetic iron oxide nanoparticles from agro-waste sweet pepper extract, exploring their potential as antioxidant additives and in food preservation. Iron (III) chloride hexahydrate is the precursor, with sweet pepper extract as both a reducing and capping agent at pH 7.5. Characterization techniques, including microscopy and spectroscopy, analyze the sweet pepper extract-magnetic iron oxide nanoparticles. Antioxidant capacities against 2,2-diphenyl-1-picrylhydrazyl are assessed, incorporating nanoparticles into banana-based bioplastic for grape preservation. Microscopy reveals cubic and quasi-spherical structures, and spectroscopy confirms functional groups, including Fe-O bonds. X-ray diffraction identifies cubic and monoclinic magnetite with a monoclinic hematite presence. Sweet pepper extract exhibits 100% inhibitory activity in 20 min, while sweet pepper extract-magnetic iron oxide nanoparticles show an IC50 of 128.1 µg/mL. Furthermore, these nanoparticles, stabilized with banana-based bioplastic, effectively preserve grapes, resulting in a 27.4% lower weight loss rate after 144 h compared to the control group (34.6%). This pioneering study encourages institutional research into the natural antioxidant properties of agro-waste sweet pepper combined with magnetic iron and other metal oxide nanoparticles, offering sustainable solutions for nanopackaging and food preservation. Current research focuses on refining experimental parameters and investigating diverse applications for sweet pepper extract-magnetic iron oxide nanoparticles in varied contexts.

Structural and magneto-optical investigations of citrate sol–gel derived barium hexaferrite nanocrystalline powder

Magneto-optical measurements enable the identification of Fe2+ and Fe3+ in the R and S blocks of BaFe12O19 M-hexaferrite powder obtained by sol-gel processing, followed by thermal annealing at 900 C for 3 hours. The ferromagnetic phase is evidenced by the spin-majority configuration (Fe3+) due to their unpaired electrons between d-d orbitals, while the Fe2+ in the low spin possesses diamagnetic behavior strongly dependent on the surrounded crystal field. Additionally, the irradiation with gamma rays changes the ratio between Fe2+/Fe3+, mainly on the surface of BaFe12O19 nanocrystals. These changes were confirmed by X-ray Photoelectron Spectroscopy measurements, in which the concentration of Fe2+ increased from 69% to 82%, while the one of Fe3+ decreased from 31% to 18%. he thermoluminescent measurements reveal the same changes of Fe3+ in Fe2+ by electron capturing during irradiation, which is released as a red emission after recombination processes. The changes are explained by the increasing of some Fe-O bonds along the c-axis, mainly due to breaking a part of these bonds. The X-ray analysis confirms the changing of the parameters for the BaFe12O19 hexagonal structure.

Mechanistic Insights into the Selectivity for Arsenic over Phosphate Adsorption by Fe3+-Cross-Linked Chitosan Using DFT.

Fe3+-cross-linked chitosan exhibits the potential for selectively adsorbing arsenic (As) over competing species, such as phosphate, for water remediation. However, the effective binding mechanisms, bond nature, and controlling factor(s) of the selectivity are poorly understood. This study employs ab initio calculations to examine the competitive binding of As(V), P(V), and As(III) to neat chitosan and Fe3+-chitosan. Neat chitosan fails to selectively bind As oxyanions, as all three oxyanions bind similarly via weak hydrogen bonds with preferences of P(V) = As(V) > As(III). Conversely, Fe3+-chitosan selectively binds As(V) over As(III) and P(V) with binding energies of -1.9, -1, and -1.8 eV for As(V), As(III), and P(V), respectively. The preferences are due to varying Fe3+-oxyanion donor-acceptor characteristics, forming covalent bonds with distinct strengths (Fe-O bond ICOHP values: - 4.9 eV/bond for As(V), - 4.7 eV/bond for P(V), and -3.5 eV/bond for As(III)). Differences in pKa between As(V)/P(V) and As(III) preclude any preference for As(III) under typical environmental pH conditions. Furthermore, our calculations suggest that the binding selectivity of Fe3+-chitosan exhibits a pH dependence. These findings enhance our understanding of the Fe3+-oxyanion interaction crucial for preferential oxyanion binding using Fe3+-chitosan and provide a lens for further exploration into alternative transition-metal-chitosan combinations and coordination chemistries for applications in selective separations.

Decreasing of Magnetic Saturation of Yttrium Doped Cobalt Ferrite Prepared by the Sol-Gel Auto-Combustion

In this research, a nano-sized cobalt ferrite material doped with Yttrium has been successfully fabricated using the sol-gel method of automatic combustion with variations in low sintering temperatures of 200, 300 and 400 °C. The results of refinement of XRD data using the Rietveld method show that the Yttrium-doped cobalt ferrite compound with a Yttrium concentration molarity of 0.1 possess a cubic crystal system and Fd-3m space group. The increasing annealing temperatures also increase the crystallite size of Yttrium-doped cobalt ferrite with the highest magnitude of 16.05 nm. The FTIR results of the samples indicated the presence of Co-O bonds around wave number 385 cm−1 and Fe-O bonds around wave number 582 cm−1 which are characteristic of the presence of cobalt ferrite compounds. From the VSM measurement results, it can be seen that there is a decrease in magnetic saturation with an increase in annealing temperature. The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization. Image from SEM results showed samples have nanoparticle crystallite size. Evaluation of potential photocatalyst applications using a UV-Visible Spectrophotometer (UV-Vis). For Yttrium doped cobalt ferrite at 200 °C, the best degradation efficiency of Congo Red findings showed a magnitude of 76.10 %; the results are confirmed by the occurrence of the smallest crystallite size (15.11 nm). HIGHLIGHTS Preparation of yttrium-doped cobalt ferrite by the sol-gel auto-combustion method with various annealing temperatures The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization Yttrium-doped cobalt is applied for photocatalytic Congo Red dye in water with the best performance according to the smallest crystallite size GRAPHICAL ABSTRACT

Effect of Interfacial Action on the Generation and Transformation of Reactive Oxygen Species in Tripolyphosphate-Enhanced Heterogeneous Fe3O4/O2 Systems.

It has been reported that tripolyphosphate (TPP) can enhance the oxygenation of natural Fe(II)-containing minerals to produce reactive oxygen species (ROS). However, the molecular structure of the TPP-Fe(II) mineral surface complex and the role of this complex in the generation and transformation of ROS have not been fully characterized. In the present study, a heterogeneous magnetite (Fe3O4)/O2/TPP system was developed for the degradation of p-nitrophenol (PNP). The results showed that the addition of TPP significantly accelerated the removal of PNP in the Fe3O4/O2 system and extended the range of effective pH to neutral. Experiments combined with density functional theory calculations revealed that the activation of O2 mainly occurs on the surface of Fe3O4 induced by a structural Fe(II)-TPP complex, where the generated O2•- (intermediate active species) can be rapidly converted into H2O2, and then the •OH generated by the Fenton reaction is released into the solution. This increases the concentration of •OH produced and the efficiency of •OH produced relative to Fe(II) consumed, compared with the homogeneous system. Furthermore, the binding of TPP to the surface of Fe3O4 led to stretching and even cleavage of the Fe-O bonds. Consequently, more Fe(II)/(III) atoms are exposed to the solvation environment and are available for the binding of active O2 and O2•-. This study demonstrates how common iron minerals and O2 in the natural environment can be combined to yield a green remediation technology.