Iron Oxide Phases Research Articles

Relationship between thermal dehydroxylation and aluminium extraction from a low-grade kaolinite: Role of clay chemistry and crystallinity

The presented research investigates the impact of clay crystallinity and iron oxide content on thermal dehydroxylation of kaolinite and thus the impact on aluminium dissolution. Two clay samples with different crystallinity and purity levels (designated low-grade for the impurity rich and disordered kaolin, and high grade for the highly crystalline and relatively pure kaolin) underwent thermal treatment from ambient temperature to 850 °C in 50 °C increments, followed by acid digestion to recover aluminium. Infrared spectroscopy and X-ray diffraction were used to characterise the clays after thermal treatment and following acid digestion to gain insights into the chemistry of the process. Lower temperatures were required to achieve complete thermal dehydroxylation for the low-grade kaolin at 450 °C, in comparison to high-grade kaolin, which was complete at 650 °C. Solid-state 27Al Nuclear magnetic resonance (NMR) highlighted the emergence of Al(IV) at 600 °C and Al(V) at 650 °C, the latter of which corresponded to the complete thermal dehydroxylation of the kaolinite and was the main aluminium species responsible for aluminium dissolution. The iron oxide phases present within the low-grade kaolin resulted in phase transformation to insoluble aluminium spinels at lower temperatures (750 °C), which caused a reduction in the acid solubility of aluminium and iron. However, there were benefits associated with aluminium recovery from the low-grade kaolin, namely, less energy being required to achieve complete thermal dehydroxylation for aluminium dissolution. This finding holds significance for the utilisation of low-grade kaolin by industry, such as for production of new commodities such as high purity alumina.

Microstructure and physical properties of ε-Fe2O3 thin films fabricated by pulsed laser deposition

ε-Fe2O3 has attracted intense interest in the field of magnetoelectric materials due to its promising physical properties. The epitaxial growth of ε-Fe2O3 thin films is challenging since it is a metastable phase of iron oxide. In this study, ε-Fe2O3 (001) thin films are epitaxially grown on SrTiO3 (111) substrates by pulsed laser deposition (PLD). The crystal structure, valence state, and microstructure of the ε-Fe2O3 thin films are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is revealed that the oxygen pressure, deposition and annealing temperatures, and laser beam energy affect significantly the epitaxial growth of ε-Fe2O3 thin films. The orientation relationship between films and substrates is ε-Fe2O3 (001)[010] // SrTiO3 (111)[1¯10]. The magnetic hysteresis loops tested by a superconducting quantum interference device and UV–Vis reflection spectra suggest that the ε-Fe2O3 thin film with thickness of ∼ 20 nm has a strong magnetic anisotropy, a coercivity of 600 Oe, and an indirect band gap of 3.26 eV.

Photodegradation of methyl orange under solar irradiation on Fe-doped ZnO nanoparticles synthesized using wild olive leaf extract

Abstract Fe-doped ZnO nanoparticles (NPs) with different Fe contents (0.1–5.0 wt%) were prepared using extract of wild olive leaves growing in Saudi Arabia (region of Abha). The biosynthesized NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL). Characterization results showed that undoped ZnO and Fe-doped ZnO powders were crystallized in the wurtzite structure with a small shift for the doped samples. Neither Fe3O4 nor another iron oxide phase was observed in the samples, which proves the incorporation of Fe into the ZnO lattice. Doping has a pronounced effect on the physical and optical properties. Indeed, the size of the crystallites, the energy of the bandgap as well as the intensity of the PL emission decreased with the Fe content. Photocatalytic tests revealed that the doped samples degraded methyl orange (MO) more efficiently than pure ZnO and pure Fe3O4. Moreover, the photocatalytic activity improved with increasing Fe content. The best photocatalyst of the series (Fe–ZnO-5) was found degrading MO by 92.1%, in 90 min in a pseudo-first order reaction.

Mechanistic Insight into Hydrocarbon Synthesis via CO2 Hydrogenation on χ-Fe5C2 Catalysts.

Converting CO2 into value-added chemicals and fuels is one of the promising approaches to alleviate CO2 emissions, reduce the dependence on nonrenewable energy resources, and minimize the negative environmental effect of fossil fuels. This work used density functional theory (DFT) calculations combined with microkinetic modeling to provide fundamental insight into the mechanisms of CO2 hydrogenation to hydrocarbons over the iron carbide catalyst, with a focus on understanding the energetically favorable pathways and kinetic controlling factors for selective hydrocarbon production. The crystal orbital Hamiltonian population analysis demonstrated that the transition states associated with O-H bond formation steps within the path are less stable than those of C-H bond formation, accounting for the observed higher barriers in O-H bond formation from DFT. Energetically favorable pathways for CO2 hydrogenation to CH4 and C2H4 products were identified which go through an HCOO intermediate, while the CH* species was found to be the key C1 intermediate over χ-Fe5C2(510). The microkinetic modeling results showed that the relative selectivity to CH4 is higher than C2H4 in CO2 hydrogenation, but the trend is opposite under CO hydrogenation conditions. The major impact on C2 hydrocarbon production is attributed to the high surface coverage of O* from CO2 conversion, which occupies crucial active sites and impedes C-C couplings to C2 species over χ-Fe5C2(510). The coexistence of iron oxide and carbide phases was proposed and the interfacial sites created between the two phases impact CO2 surface chemistry. Adding potassium into the Fe5C2 catalyst accelerates O* removal from the carbide surface, enhances the stability of the iron carbide catalyst, thus, promotes C-C couplings to hydrocarbons.

Silver distribution and binding mode as key determinants of the antimicrobial performance of iron oxide/silver nanocomposites

The emerging threat of bacterial resistance to antibiotics prompts the urgent search for biomaterials for the treatment of infectious disease. Here we report on the synthesis and characterization of a multiphasic nanocomposite comprising magnetic iron oxide and silver nanoparticles. The method of synthesis involved the combustion of a metalorganic complex and reduction of the silver ions that were exchanged and/or adsorbed on the surface of iron oxide. Different physical and chemical treatments coupled to the reduction process, including ultrasound and Lugol's iodine solution, respectively, homogenized the distribution of the silver nanoparticles on the iron oxide phase. Remarkably, using ascorbic acid as a reductant enhanced the magnetic properties of the material as a result of the reduction of the magnetic matrix alongside the silver cations. The treatment with ultrasound detached large amounts of silver from the iron oxide phase and resulted in the lowest amount of silver incorporated in the nanocomposite. Despite that, this treatment led to the highest antibacterial activity against both Gram-positive and Gram-negative strains, indicating that the homogeneity of the distribution of silver on the iron oxide matrix is a more important determinant of the antibacterial performance than the amount of silver incorporated in the material. At the same time, the treatment with Lugol's iodine equally increased the distribution homogeneity, but induced excessive ion exchange and crystal lattice substitutions, thereby adversely affecting the antibacterial performance. This has indicated that the mode of binding silver to iron oxide can compensate for the positive effects of homogeneous distribution with respect to the antibacterial performance.

Multi-Modal Identification of Feldspar and Iron Oxide Phases in Granite Using Raman Spectroscopy in the Electron Microscope

Multi-Modal Identification of Feldspar and Iron Oxide Phases in Granite Using Raman Spectroscopy in the Electron Microscope

A Geochemical and Mineralogical Study of the Sediments Transported through Wadi Al-Qassab and Wadi Al-Murr, South Mosul City, Northern Iraq

The Wadi Al-Qassab and Wadi Al-Murr are the main valleys in the west of the town of Qaiyarah, extending almost parallel in the northwest-southeast direction and descending from the topographically high areas located to the west towards the Tigris River in the east. Wadi Al-Qassab extends in the area sandwiched between the mountains (Attshan, Nuegett and Eklayan) in the north of the valley and the mountains (Jawan, Najmah and Qaiyarah) south of the valley which represents anticlines. While Wadi Al-Murr extends to the south of the mountains (Najmah and Qaiyarah). These two valleys are active during the rainy season due to the wide catchment area, especially for Wadi Al-Qassab, which several seasonal tributaries flow. The structural situation reflected by the Qaiyarah and Najma anticlines helps reveal many types of rocks belonging to the Fat'ha and Injana formations, as well as the sediments that cover the area mainly derived from the rocks of these two formations. The two valleys' sediments were classified as sand and gravelly sand that will contribute to the groundwater recharge during the rainy season. The average mineral compositions of the sediments (according to X-ray data and chemical composition of major and minor oxides) in the valleys of Al-Murr and Al-Qassab were estimated to be silicate minerals (such as quartz, clay minerals and feldspar minerals) estimated at 62.78% and 59.89%, carbonate minerals (main calcite) 26.14% and 31.97%, the evaporite minerals that included gypsum mineral 5.46% and 2.87% and halite 0.62% and 0.36%, in addition to the iron oxide phases of 4.69% and 4.41%, respectively. Most of the trace elements have been associated with clay minerals, either in the form of substitution and/or adsorption, and some of them are maybe as resistant minerals inherited from the source rocks from which they were derived. Chemical analysis shows that there are no significant indicators of hydrocarbon pollutions that may enrich the area with some organometallic compounds in valley sediments due to the emitted refinery gases and fine hydrocarbon particles.

Extraction of rare earth and cobalt from leach residue of Nd-Fe-B waste by reductive leaching with iron powder

After recovering rare earth from neodymium–iron–boron (Nd–Fe–B) magnet waste via oxidation roasting–hydrochloric acid leaching, extracting rare earths and cobalt from remaining leach residue, containing about 0.67% (w/w) RE and 0.36% Co, is environmentally and economically important. However, extracting valuable elements from low–grade minerals remains challenging. The purpose of this study is to accelerate the dissolution of rare earths and cobalt from leach residue of Nd–Fe–B waste (MWLR) under low acidity by adding iron as a reductant, which is conducive to destroying the main phase iron oxide. To optimize the leaching process of MWLR in a sulfuric acid system, the effects of reaction temperature, reaction time, sulfuric acid dosage, solid/liquid (S/L) ratio, reductant addition time and reductant dosage were investigated. Circa 87.9% Fe, 99.7% Co, 99.4% Nd, 73.2% Pr and 87.9% Ce were leached. Furthermore, kinetic results indicated that the leaching process, controlled by a combination of internal diffusion and surface chemical reaction, changed to a surface chemical reaction control in the presence of Fe added as the reductant. This research proposed and verified a way to extract low–grade rare earths and cobalt from MWLR, and investigated the mechanism of reductive leaching process.

An integrated investigation of the crystalline, rheological and physical properties of corrosion products in cementitious materials

This paper discusses the behaviour of the rheological behaviour of corrosion products (produced in the laboratory) in a high alkaline environment to understand hydraulic-induced fracture by corrosion products in reinforced concrete. A mixture of iron powder, sodium chloride, calcium hydroxide, and water was used to produce corrosion products. The development of corrosion products was studied at 2, 4, 6, and 8-week intervals. Imaging techniques, along with rheological characterization methods, were conducted to understand the viscoelastic flow behaviour of corrosion products. The results show that corrosion products exhibited different rheologic properties throughout the corrosion process. Three iron oxide phases (Magnetite, Goethite, and Lepidocrocite) were detected throughout the initiation and propagation stages of corrosion in the laboratory. The corrosion products obtained for each study period behaved as colloidal materials, demonstrating all the characteristics of shear-thinning materials. As a result of chemical and particle disintegration, the viscosity of corrosion products decreased with the applied shear rate. In addition, the experimental data showed that the density and particle size of corrosion products decreased with time. These results can be used to understand the progress of corrosion's damage in reinforced concrete.

All Shapes and Phases of Nanometer-Sized Iron Oxides Made from Natural Sources and Waste Material via Green Synthesis Approach: A Review

Iron oxides are old but gold. Stacks of review articles have been published with regard to sounding the magnificence of iron oxides for many applications. Nevertheless, no existing review papers discuss more specifics on how to fabricate nanometer-sized iron oxides, which, in fact, we can obtain them directly from natural sources and wastes via green technology. Direct synthesis of nanometer-sized iron oxides from natural sources and wastes could simply make them less expensive, and, of course, significantly decrease the energy requirement in the synthesis process, lower time synthesis consumption, and be environmentally benign. Here, we compile and synthesize all information on nanometer-sized iron oxides, starting from their phase diversity and their low-dimensional forms such as in zero-, one-, two-, and three-dimensional (0D, 1D, 2D, and 3D, respectively) shapes. Furthermore, the synthesis of nanometer-sized iron oxides from natural sources and waste materials via green synthesis is explained comprehensively, followed by the elucidation of the prospect and challenges of each synthesis method. Lastly, the recent applications and potential commercialization of nanometer-sized iron oxides synthesized from natural sources and waste materials from the point of view of green technology are also listed in this review article.

Magnetite‐Free Sn‐Doped Hematite Nanoflake Layers for Enhanced Photoelectrochemical Water Splitting

In the present work, we report on a preparation strategy for hematite phase-pure photoanodes consisting of Sn-doped hematite nanoflakes/hematite thin film bilayer nanostructure (Sn-HB). This approach is based on a two-step annealing process of pure iron films deposited on FTO substrates by advanced magnetron sputtering. While the high density hematite ultrathin nanoflakes (HNs) with detrimental iron oxide layers (Fe 3 O 4 and/or FeO) are generated during the first annealing step at 400 °C for two hours, the second thermal treatment at 800 °C for 15 minutes oxidises all the undesired iron oxide phases to a photoactive hematite layer as well as is providing efficient Sn doping of a drop-casted SnCl 4 in order to increase the conductivity. The optimized Sn-HB shows an ~11 times higher photocurrent density (0.71 mA/cm 2 at 1.23 V RHE ) compared with a reference hematite photoanode produced from iron foil under the same conditions.

CO2 hydrogenation to olefins on supported iron catalysts: Effects of support properties on carbon-containing species and product distribution

Catalytic utilizing of CO2 into valuable olefins on Fe-based catalysts is a feasible way to mitigate the pressure of carbon neutrality. Herein, by investigating the effects of support (SiO2, Al2O3, CNT, and ZrO2) on the structure and catalytic performance of iron catalysts, we have found that ZrO2 supported catalysts are more beneficial to olefin selectivity and chain growth. The optimization catalytic performance of FeNa/ZrO2 displays C2-C7 olefin selectivity of 68.2% (O/P = 8.0) with a space time yields (111.4 g Kgcat-1h−1) at XCO2 = 32.7%, 320 ⁰C, 2.0 MPa, CO2/H2/Ar = 1:3:3, and 9000 mL g-1h−1. Characterizations show that the support regulates the composition of the iron oxide phase and the iron carbide phase and induces to form the highest content of Fe5C2 on the spent FeNa/ZrO2, which is probably caused by the carbon rich surface and lower disorder of carbon species. Besides, the higher intensity of CO2 and CO adsorption and lower intensity of H2 adsorption is confirmed on the surface of the FeNa/ZrO2 catalysts, leading to a higher ratio of C/H on the surface of the spent catalysts and consequently inhibiting the hydrogenation of olefins. Therefore, the O/P is 8 times as many as that on the FeNa/SiO2 and FeNa/Al2O3. Understanding the effect of support on CO2 hydrogenation to olefins over iron-based catalysts would be significant for precisely designing new catalysts.

Synthesis and characterization of α-Fe2O3 nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

P-type and n-type metal oxide semiconductors are widely used in the manufacture of gas sensing materials, due to their excellent electronic, electrical and electrocatalytic properties. Hematite (α-Fe2O3) compound has been reported as a promising material for sensing broad types of gases, due to its affordability, good stability and semiconducting properties. In the present work, the efficient and easy-to-implement sol-gel method has been used to synthesize α-Fe2O3 nanoparticles (NPs). The TGA-DSC characterizations of the precursor gel provided information about the phase transformation temperature and the mass percentage of the hematite NPs. X-ray diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy data analyses indicated the formation of two iron oxide phases (hematite and magnetite) when the NPs are subjected to thermal treatment at 400 °C. Meanwhile, only the hematite phase was determined for thermal annealing above 500 °C up to 800 °C. Besides, the crystallite size shows an increasing trend with the thermal annealing and no defined morphology. A clear reduction of surface defects, associated with oxygen vacancies was also evidenced when the annealing temperature was increased, resulting in changes on the electrical properties of hematite NPs. Resistive gas-sensing tests were carried out using hematite NPs + glycerin paste, to detect quaternary ammonium compounds. Room-temperature high sensitivity values (S r ∼ 4) have been obtained during the detection of ∼1 mM quaternary ammonium compounds vapor. The dependence of the sensitivity on the particle size, the mass ratio of NPs with respect to the organic ligand, changes in the dielectric properties, and the electrical conduction mechanism of gas sensing was discussed.

Applying Saudi clay deposits for treatment of household water at the point-of-use

This research aims to beneficiate the clay deposits abundant in the Al Baha district to produce ceramic filters for “point-of-use” household water treatment technology to remove dissolved solids from water that is no longer valid for drinking purposes to meet the needs of the community through a safe household and industrial water supply after further treatment purposes. In addition, it helps to reduce the expenses of citizens earmarked to buy drinking water. A sample of laterite, clay, and kaolin from Al Baha district was thermally treated at 800 °C, acid treated with HCl, analyzed by XRD, FTIR, and SEM, and tested for treatment of household water. The temperature, pH, electrical conductivity (EC), and total dissolved solids (TDS) were measured. In the application step for point-of-use water treatment of household water, the treated materials were introduced in calcined kaolin filters and commercial polypropylene filters. Based on the results of household water treatment with raw and treated clay materials, the raw clay materials, has poor adsorption capacity. The thermal treatment of clay samples dehydrates the clay minerals into sintered aluminosilicates and enhances the conversion of poorly crystallized iron oxide to α-Fe2O3 without improving the adsorption capacity of clay materials. However, the acid treatment of the clay samples removes iron-bearing minerals leaving behind amorphous aluminosilicate matter characterized with improved adsorption capacity. It was concluded that the acid treatment of clay material by concentrated HCl acid completely leaches iron oxide phases and broke down and disintegrated the clay minerals into the amorphous matter with enhanced the adsorption capacity. The combination of selected acid-treated laterite, clay, and charcoal for the household water treatment filter at the point of use in the calcined kaolin filter and the polypropylene filter reduced the TDS content by 40–42%.

Zn-Doped Iron Oxide Thin Films Prepared by Spray Pyrolysis Technique and Characterized for Use as an Efficient Photocatalyst for Methyl Green Organic Dye

Ultrasonic Spray Pyrolysis (USP) technique was used to prepare undoped and (2, 4, 6 and 10 at. %) Zn-doped iron oxide (FexOy:Zn) thin films for use in photocatalytic applications. The effect of Zn ion substitution on structural, optical, and electrical properties was studied. The X-ray diffraction patterns showed that there are two different phases of iron oxide, a hematite phase (α‑Fe2O3) and a magnetite phase (Fe3O4) that crystallized in the prepared samples. The nominal fractions of α‑Fe2O3 and Fe3O4 phases changed from 74 % to 42 % for the hematite phase and from 26 % to 58 % for the magnetite phase and this confirmed that the Zn doping favored the growth of Fe3O4 phase. The crystallite size decreased from 15.43 nm to 8.99 nm, while the micro-strain changed from 0.0056 to 0.0215 and the dislocation density from 0.0099 nm‑2 to 0.0639 nm‑2. The unit cell parameters were also improved when the doping rate was changed. Optical measurements showed that the energy gap decreased from 2.26 eV to 2.16 eV, the film thickness changed from 569 nm to 479 nm while the refractive index increased from 2.99 to 3.51 and the Urbach energy from 544 meV to 558 meV. Electrical measurements performed by the two-point probe method showed that the electrical conductivity increased directly with increasing Zn concentration reaching 18.5 10‑15 (Ω.cm)‑1 with 10 at. % Zn concentration. The variation of the electrical conductivity curves versus the sample heating temperature as well as the activation energy showed a semiconductor behavior of the films. Zinc doped iron oxide thin films exhibit 51.85 % photocatalytic degradation efficiency for methyl green organic dye.

How magnetic field affects catalytic CO2 hydrogenation over Fe-Cu/MCM-41: In situ active metal phase—reactivity observation during activation and reaction

In this work, a systematic investigation of external magnetic field affecting metal phase transformation of Fe-Cu/MCM-41 catalysts both during activation and reaction, and their performances by means of CO2 conversion and C2 + C3 hydrocarbons selectivity were for the first time examined in-situ using time-resolved X-ray absorption spectroscopy (TRXAS) and an online quadrupole mass spectrometer. The in-situ XANES result confirmed that FeO and Fe3O4 are major active forms of the catalyst. With magnetic flux intensities of 28.91–58.59 mT, iron oxide phases, specifically Fe3O4 and FeO, within the catalysts were stabilized and maintained. The CO2 conversion was increased for 1.03 – 1.09 times, while the concentrations of C2 + C3 hydrocarbons were considerably improved by 24.03 – 35.37 times compared to those without magnetic field. The reaction steps of CO2 hydrogenation were theoretically confirmed on the isolated catalysts using M06-L with the 6-31G(d,p) + LANL2DZ mixed basis set based on the results from LCF analysis. Fe4, Fe4O4, and Fe2Cu2 clusters were used to represent the active species of pristine Fe and iron oxide (FeO) and bimetallic Fe-Cu catalyst, respectively. It was found that CO2 hydrogenation could take place via the bimolecular route in which adsorbed CO2 on the Fe center was hydrogenated by dissociative adsorption of H2 on the Cu center—promoting chain growth probability of CO2 to form C2 + C3 hydrocarbons due to the active iron oxides (Fe3O4 and FeO) were maintained by magnetic field during the reaction.

Lanthanum substitution effect on the structural, optical, and dielectrical properties of nanocrystalline BaFe2O4 ferrites

The effects of varying the amount of lanthanum infusion on the barium ferrite characteristics were investigated in this study. An orthorhombic structure formed as a majority phase and traces of barium lanthanum iron oxide as segregated phases in the ferrites composites. The optical bandgap energy values of the BaLaxFe2−xO4 nanoferrites were 3.50–3.72 eV. SEM confirmed that the prepared nanoferrites had spherical morphology with size of 66.50–81.50 nm. The dielectric parameters of BaLaxFe2−xO4 nanoferrites were studied in the specified spectrum, which revealed the La doped barium nanoferrites had a low dielectric constant and conductivity properties compared to the barium nanoferrites. The saturation magnetization (60.03–25.98 emu g−1) and coercivity (454.85–80.65 Oe) of the prepared nanoferrites were improved due to an effect of La3+ ions. Accordingly, the observed optical bandgap energy, dielectric constant, and magnetism could be employed in high-frequency magneto-optoelectronic systems.

Antimicrobial potential of four mica drugs and their chemical and mineralogical properties

BackgroundMica drugs, a group of herbo-metallic traditional preparations comprising biotite mica as the major mineral ingredient, are prescribed for skin disorders and respiratory ailments and other chronic conditions in South Asian countries, particularly India and Sri Lanka. Mica-based drugs (Abhrak drugs) are subjected to unique and varied preparation procedures and the bioactivity of the drugs can be affected by drug-processing conditions, the ingredients used and the mica composition. The current study aimed to evaluate and compare, on the basis of their physical and chemical characteristics, the antimicrobial potential of two commercial mica drugs AbBb (Abhrak bhashma) and AbCh (Abhrak Chenhuram) and two mica drugs ABL1 (Abhrak Bhasma Laboratory Prepared 1) and ABL2 (Abhrak Bhasma Laboratory Prepared 2) prepared in the laboratory under different conditions.MethodsAntimicrobial activity of all four drugs was assessed at 10 mg/ml concentration against Pseudomonas aeruginosa, Escherischia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Candida albicans using well diffusion assay, agar dilution assay and Miles and Misra method. Major and trace metal constituents of the drug samples were measured using atomic absorption spectrometry. Mineralogical properties, bacteria-mineral interactions, morphological changes in microbes and the surface characteristics of the drugs were determined using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM).ResultsThe drugs ABL1, ABL2 and AbBh exhibited antimicrobial activity against only Gram-positive organisms (S. aureus and MRSA) when tested with Miles and Misra method (broth method). Mineralogical studies (XRD) revealed that biotite mica was altered into secondary clay minerals and iron oxides in the commercial drug AbCh while the other three drugs had altered mica and iron oxide phases. The essential elements (Na, K, Ca and Mg) required for microbial functions were present in varying extents in all four drugs while they were present in exceedingly high amounts in AbCh having comparatively high cation-exchange capacity, consistent with the observation that AbCh was inactive against all the microbes tested. The three drugs (ABL1, ABL2 and AbBh) showing antimicrobial activity contained comparatively high amounts of Fe, Zn and Cu that are known to display antimicrobial properties at high concentrations. SEM studies revealed that the drug particles adhered and entrapped the bacterial species, presumably modifying the physiochemical characteristics of the bacteria and eventually causing lethality.ConclusionThree of the four mica drugs inhibited the tested Gram-negative bacteria and the antibacterial activity of the mica drugs depends on their constituents and the methods of preparation.

Structural, Magnetic, and Dielectric Spectroscopy Investigations of Multiferroic Composite Based on Perovskite–Spinel Approach

Multiferroic composite materials with the nominal composition (La0.8Gd0.2FeO3)1−x(Mn0.5Cu0.5Fe2O4)x, x = 0.0≤x≤1 were prepared using the co-precipition method. XRD, FTIR and Raman were utilized to investigate the structure phase, microstructural characteristics, vibrational bands. The optical properties were analyzed; the VSM was used to investigate the magnetic properties of the composites. Broadband dielectric spectroscopy is employed to investigate the dielectric and electrical performance of the prepared multiferroic composites. Rietveld refinement of the XRD patterns confirmed the orthorhombic phase for lanthanum gadolinium iron oxide (La0.8Gd0.2FeO3) and cubic phase for manganese copper ferrite (Mn0.5Cu0.5Fe2O4). The crystallite size of LGFO phase pointed out that it increases with increasing the MCFO phase, while the microstrain found to decline. The FTIR results elucidated the tetrahedral and octahedral bands. The deduced optical properties revealed that the samples have optical energy gap in the range 4.18 −4.5 eV. The magnetic properties revealed that the composites exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure. The frequency dependence of permittivity ε′(f) and real part of complex conductivity, σ′(f) exhibits a development of a net of micro-capacitors like behavior that stores charge carriers.

Triphasic Metal Oxide Photocatalyst for Reaction Site‐Specific Production of Hydrogen Peroxide from Oxygen Reduction and Water Oxidation

AbstractThe search for photocatalysts allowing the highly active, selective, and stable conversion of molecular oxygen into hydrogen peroxide is of worldwide interest. Here, the authors report the efficient conversion of O2 into H2O2 with ≈100% selectivity and stable cycle stability by a triphasic metal oxide photocatalyst with a cobalt hydroxide carbonate nanosheet phase for water oxidation as well as iron oxide and titanium oxide phases of a core‐shell morphology for charge transfer and oxygen reduction, denoted as CFT. The different surface energies of 0.78 (anatase) and 0.93 J m‐2 (rutile) for titanium oxide and 1.39 J m‐2 for iron oxide result in a core‐shell morphology. The band gaps for iron oxide (2.02 eV), titanium oxide (≈3 eV), and cobalt hydroxide carbonate (3.80 eV) sites reveal that the CFT photocatalyst allows visible‐to‐UV light absorption. The 18O2 isotope‐labeling experiments prove that the core‐shell structure promotes hole transfer toward the water oxidation site. Additionally, the hole‐induced H2O2 decomposition at the oxygen reduction site is efficiently hindered. Moreover, the photogenerated electrons transfer toward the oxygen reduction site to produce H2O2 from O2 with ≈10‐fold higher activity than those by conventional single‐ or dual‐phase photocatalysts, while giving robust cycle stability.