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Hematite ([alpha]-Fe.sub.2O.sub.3) is supposed to be one of the most promising photoanode candidates for solar-driven water splitting. However, the photoelectrochemical (PEC) performance of [alpha]-Fe.sub.2O.sub.3 is limited by fast recombination of carriers. In this work, we demonstrate that the recombination of [alpha]-Fe.sub.2O.sub.3 films could be suppressed by forming the heterojunction structure with cubic-In.sub.2O.sub.3. By utilizing the magnetron sputtering method, the In.sub.2O.sub.3/[alpha]-Fe.sub.2O.sub.3 films were prepared when the In concentration exceeded its solubility in [alpha]-Fe.sub.2O.sub.3 matrix, which was confirmed by the XRD and TEM analysis. The dependence of charge separation on heterojunction structure was evidenced by Mott-Schottky and EIS analyses. It was found that the enhanced separation of holes and electrons in [alpha]-Fe.sub.2O.sub.3 films contributed to higher PEC performance.

Among the transition metal oxides, hematite (α-Fe[sub.2]O[sub.3]) has been widely used in the preparation of memristors because of its excellent physical and chemical properties. In this paper, α-Fe[sub.2]O[sub.3] nanowire arrays with a preferred orientation along the [110] direction were prepared by a facile hydrothermal method and annealing treatment on the FTO substrate, and then α-Fe[sub.2]O[sub.3] nanowire array-based Au/α-Fe[sub.2]O[sub.3]/FTO memristors were obtained by plating the Au electrodes on the as-prepared α-Fe[sub.2]O[sub.3] nanowire arrays. The as-prepared α-Fe[sub.2]O[sub.3] nanowire array-based Au/α-Fe[sub.2]O[sub.3]/FTO memristors have demonstrated stable nonvolatile bipolar resistive switching behaviors with a high resistive switching ratio of about two orders of magnitude, good resistance retention (up to 10[sup.3] s), and ultralow set voltage (V[sub.set] = +2.63 V) and reset voltage (V[sub.reset] = −2 V). In addition, the space charge-limited conduction (SCLC) mechanism has been proposed to be in the high resistance state, and the formation and destruction of the conductive channels modulated by oxygen vacancies have been suggested to be responsible for the nonvolatile resistive switching behaviors of the Au/α-Fe[sub.2]O[sub.3]/FTO memristors. Our results show the potential of the Au/α-Fe[sub.2]O[sub.3]/FTO memristors in nonvolatile memory applications.

Natural hydrogen is a promising clean energy resource, but locating subsurface accumulations remains challenging. Aeromagnetic anomalies are increasingly utilized as a rapid and cost‐effective tool for geological hydrogen prospection, particularly associated with magnetite formation during abiotic geochemical hydrogen generation through serpentinization. In this study, we investigate an alternative hydrogen‐induced source of magnetic anomalies, the hematite to magnetite reduction, in hematite‐bearing rocks within hydrogen reservoirs or along migration pathways. We exposed hematite‐rich granites and reservoir sandstones to hydrogen at a temperature of 200°C for 10–18 days, and measured their magnetic properties before and after. Superparamagnetic to (stable) single‐domain (SP‐SSD) magnetite formed during the reaction, leading to magnetic susceptibility enhancement of up to three orders of magnitude in the sandstones, whereas the granite exhibited only minor increase. These results provide proof‐of‐concept for hydrogen‐induced hematite‐to‐magnetite reduction at low temperatures, potentially generating localized aeromagnetic anomalies, detectable in exploration surveys.

The large uncertainty in the mineral dust direct radiative effect (DRE) hinders projections of future climate change due to anthropogenic activity. Resolving modeled dust mineral speciation allows for spatially and temporally varying refractive indices consistent with dust aerosol composition. Here, for the first time, we quantify the range in dust DRE at the top of the atmosphere (TOA) due to current uncertainties in the surface soil mineralogical content using a dust mineral-resolving climate model. We propagate observed uncertainties in soil mineral abundances from two soil mineralogy atlases along with the optical properties of each mineral into the DRE and compare the resultant range with other sources of uncertainty across six climate models. The shortwave DRE responds region-specifically to the dust burden depending on the mineral speciation and underlying shortwave surface albedo: positively when the regionally averaged annual surface albedo is larger than 0.28 and negatively otherwise. Among all minerals examined, the shortwave TOA DRE and single scattering albedo at the 0.44–0.63 µm band are most sensitive to the fractional contribution of iron oxides to the total dust composition. The global net (shortwave plus longwave) TOA DRE is estimated to be within −0.23 to +0.35 W/sq. m. Approximately 97 % of this range relates to uncertainty in the soil abundance of iron oxides. Representing iron oxide with solely hematite optical properties leads to an overestimation of shortwave DRE by +0.10 W/sq. m at the TOA, as goethite is not as absorbing as hematite in the shortwave spectrum range. Our study highlights the importance of iron oxides to the shortwave DRE: they have a disproportionally large impact on climate considering their small atmospheric mineral mass fractional burden (∼2 %). An improved description of iron oxides, such as those planned in the Earth Surface Mineral Dust Source Investigation (EMIT), is thus essential for more accurate estimates of the dust DRE.

Hematite- and cinnabar-based paint mock-ups prepared with either rabbit glue or egg yolk binder were artificially aged in an SO[sub.2]-rich atmosphere, as a model system for investigating the deterioration of tempera paints exposed to an industrial atmosphere. The overall research aim was to identify the type of degradation occurring in tempera paints and the different alteration mechanisms related to the physical, mineralogical and chemical characteristics of the paint. Tempera mock-ups were prepared by mixing binder (egg yolk or rabbit glue) and pigment (cinnabar of different particle sizes or hematite) and were then exposed to SO[sub.2] for 2 months in accelerated aging tests. The colour, gloss, reflectance, roughness and micro-texture of the surfaces of the mock-ups were determined before and after the tests. In addition, chemical and mineralogical changes were determined by X-ray Powder Diffraction (XRPD), Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) analysis. Colorimetric changes were confirmed, mainly in the cinnabar-based paints containing egg yolk, and in the hematite-based paints containing rabbit glue. Neoformed mineral phases have not been detected by XRPD, but precipitation of gypsum on the exposed surfaces has been confirmed by SEM. For cinnabar-based paints, the amount of sulfate-rich deposits was higher on egg yolk mock-ups than on rabbit glue samples, though the opposite was observed for the hematite-based paints. This confirmed the influence of the binder composition and pigment-binder tandem in the susceptibility to SO[sub.2] deposition. Pigment particle size did not have a clear influence on the physical and chemical changes in the tempera mock-ups during the ageing tests.

The IOCG deposit at Olympic Dam (South Australia) is hosted within the Roxby Downs Granite, which displays a weakly mineralised contact to the orebody (hereafter ‘outer shell’). In a mineralogical-geochemical characterisation of Fe-oxides from the outer shell, we show silician magnetite (Si-magnetite) and HFSE-bearing hematite define the early stages of alkali-calcic alteration. This association forms in the presence of hydrothermal K-feldspar and calc-silicates via overprinting of magmatic magnetite and ilmenite breakdown. Geochemical modelling, at ≥ 400 °C, shows such reactions occur at pH-fO2 conditions coinciding with shifts from K-feldspar to sericite, and ilmenite to rutile stability. The subsequent Si-magnetite+siderite association forms down-T in the absence of K-feldspar. Transition from granular to bladed morphologies in Si-magnetite is part of a series of Fe-oxide interconversions, followed by formation of zoned, U-W-Sn-Mo-bearing hematite. Enrichment in REE, Y and U in Si-magnetite and the prevalence of U-W-Sn-Mo-bearing hematite support a granite-derived fluid. Combined, petrographic and geochemical evidence show a transition among Fe-oxides from the outer shell to the orebody attributable to the evolution of the same fluid. Unusual massive magnetite intervals and Fe-oxide nodules in granite are considered due to either the presence of inherited lithologies, metasomatic products, or the result of magnetite-rich, crystal mush forming in the melt. We propose a model, corroborated by recently published data including high-precision U-Pb dating of magmatic zircon and hydrothermal hematite, in which an ‘outer shell’ is initiated at the 6–8 km depth of granite emplacement during volatile release from fluids ponding at intrusion margins. Granite cupola collapse at shallower levels (2–3 km?) follows via uplift along faults, facilitating intense brecciation and ore formation.

Poly(triazine imide) is a non-metal semiconductor material with remarkable photocatalytic properties, which was successfully employed for selective photoreactions. Currently, pristine forms of semiconductors are inefficient and rarely used as such. Instead, various composites are being composed on their base in search of more efficient means for photo-activated processes, such as hydrogen evolution, pollution remediation and selective photoreactions. In pursuit of a more efficient photoactive material catalyzing selective photooxidation of an alcohol to an aldehyde, we screened various compositions of PTI and hematite obtained in hydrothermal conditions. Although conversion rates exhibited by the best sample of the composites did not exceed those of pristine PTI, selectivity of the process was improved to 98% at the conversion rate of 99%.

Antibiotic contamination in water and soil has been widely investigated. However, there is still no effective removal method for antibiotics from water or soil environments. Therefore, the single and competitive sorption dynamics of ionizable tetracycline (TC), sulfamethazine (SMZ), norfloxacin (NOR), erythromycin (ERY), and chloramphenicol (CAP) adsorbed by NaOH-activated and hematite-modified biochars were investigated. NaOH-activated biochar (NAB) showed much better antibiotic sorption than the hematite-modified biochar (HMB). The affinity coefficient of NAB for TC, NOR, and ERY were at least 100 times higher than that of the HMB. The sorption rate of the five target antibiotics was faster in the single-solute systems than in the ternary-solute systems. Sorption capacity was inhibited in the competitive system for all five antibiotics adsorbed by either the NaOH-activated or hematite-modified biochars. Antibiotic sorption by the biochars was governed by electrostatic interactions, π-π electron donor-acceptor (EDA) interactions, and hydrogen bonding. All five antibiotics showed similar adsorption trends in pH treatments of both biochars. However, the sorption capacity slightly increased from pH 7 to pH 9 in HMB compared with those in NAB, as the metal ions from the hematite modification provided cation bridging combinations to negatively charged antibiotics at a high pH value. These observations are useful for producing NaOH-activated biochar as an engineered sorbent to reduce the bioavailability of antibiotics in water and soil. The results are important for the application of biochars to use as soil amendments in the remediation of antibiotic co-pollution in agricultural water or soils.

Nanoparticles (NPs) and nanomaterials (NMs) are now widely used in a variety of applications, including medicine, solar energy, drug delivery, water treatment, and pollution detection. Hematite (α-Fe2O3) nanoparticles (Hem-NPs) were manufactured in this work by utilizing a cost-effective and ecofriendly approach that included a biomass filtrate of A. niger AH1 as a bio-reducer. The structural and optical properties of Hem-NPs were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV-visible and Fourier-transform infrared (FTIR) spectroscopies. The results revealed that all of the studied parameters, as well as their interactions, had a significant impact on the crystallite size. The average diameter size of the biosynthesized Hem-NPs ranged between 60 and 80 nm. The antimicrobial and photocatalytic activities of Hem-NPs were investigated. The antimicrobial results of Hem-NPs revealed that Hem-NPs exhibited antibacterial activity against E. coli, B. subtilis, and S. mutans with MICs of 125, 31.25, and 15.62 µg/mL, respectively. Moreover, Hem-NPs exhibited antifungal activity against C. albicans and A. fumigatus, where the MICs were 2000 and 62.5 µg/mL, respectively. The efficiency of biosynthesized Hem-NPs was determined for the rapid biodegradation of crystal violet (CV) dye, reaching up to 97 percent after 150 min. Furthermore, Hem-NPs were successfully used more than once for biodegradation and that was regarded as its efficacy. In conclusion, Hem-NPs were successfully biosynthesized using A. niger AH1 and demonstrated both antimicrobial activity and photocatalytic activity against CV dye.