Small Amount Of Fe3 Research Articles

Effects of Al Substitution for Fe in Na₅FeSi₄O₁₂ (5.1.8) Glasses: Structure and Crystallization

In this study, the effects of substituting Al for Fe in 5Na2O∙(Al2O3)x∙(Fe2O3)1-x∙8SiO2 glass, x=0 to 1, and Na5AlxFe1-xSi4O12 (5.1.8) crystal, were investigated using thermal analysis, Fe K-edge X-ray absorption, X-ray diffraction, Raman spectroscopy, and Electron Probe Microanalysis. In both glass and crystallized glass, nearly all the Fe was tetrahedrally coordinated Fe3+, as expected from the high concentration of Na2O. The substitution of Al for Fe in the glasses caused the glass transition temperature to increase as polymerization increased, as evidenced by Raman, likely due to both field strength differences of Al vs Fe and a small amount of Fe2+ network modifier present with Fe. After heat treatment at 700 °C for 24 hours, the glasses had crystallized, forming Na2SiO3 and NaAlSiO4 in compositions with high Al concentrations and the 5.1.8 crystal in compositions with high Fe concentrations. Through electron microprobe, it was determined that <0.04 formula unit Al incorporated into the 5.1.8 crystal, i.e. Na5Fe0.96Al0.04Si4O12. The 5.1.8 crystal only formed when Fe concentration was higher than Al in the starting glass.

Phosphorus removal from steelmaking slag by selective leaching in the steel pickling waste liquor

Steelmaking slag and steel pickling waste liquor (SPWL) are two kinds of by-products in steel plants. The existence of phosphorus (P) in steelmaking slag is the main factor affecting its reuse within the steelmaking process. To remove P from steelmaking slag with a low-cost method, selective leaching was proposed by using SPWL as a leaching agent. SPWL generally contains a small amount of Fe3+ ions, and thus the effect of Fe3+ content in SPWL on the dissolution behavior (especially P element) of steelmaking slag was investigated, as well as the pH value and steelmaking slag type. The dissolution ratios of P from various slags in the SPWL containing 500 ppm Fe3+ exceeded 95 % at pH 1.5 while those of Fe, Mn, and Al were very low, exhibiting satisfied selective leaching of P. Increasing pH value and Fe3+ content (in SPWL) resulted in a decreasing P dissolution ratio while exerting an insignificant effect on the dissolution of other elements. The FeHPO4+ was predicted as the predominant species during leaching and the transformation of FeHPO4+ to FePO4 could be present. When the SPWL containing 800 ppm Fe3+ was used, FePO4 was observed in the residues after leaching at pH 2.0, resulting in a worse removal of P from slag. However, the residues including massive valuable components had an extremely low P content after leaching in the SPWL containing 500 ppm Fe3+ at pH 1.5, which can be used as a flux in the metallurgical process. To ensure a high P removal rate from steelmaking slag and to prevent FePO4 precipitation during leaching, a relatively low pH and Fe3+ content in the SPWL are necessary.

Variable Iron Mineralogy and Redox Conditions Recorded in Ancient Rocks Measured by In Situ Visible/Near‐Infrared Spectroscopy at Jezero Crater, Mars

AbstractUsing relative reflectance measurements from the Mastcam‐Z and SuperCam instruments on the Mars 2020 Perseverance rover, we assess the variability of Fe mineralogy in Noachian/Hesperian‐aged rocks at Jezero crater. The results reveal diverse Fe3+ and Fe2+ minerals. The igneous crater floor, where small amounts of Fe3+‐phyllosilicates and poorly crystalline Fe3+‐oxyhydroxides have been reported, is spectrally similar to most oxidized basalts observed at Gusev crater. At the base of the western Jezero sedimentary fan, new spectral type points to an Fe‐bearing mineral assemblage likely dominated by Fe2+. By contrast, most strata exposed at the fan front show signatures of Fe3+‐oxides (mostly fine‐grained crystalline hematite), Fe3+‐sulfates (potentially copiapites), strong signatures of hydration, and among the strongest signatures of red hematite observed in situ, consistent with materials having experienced vigorous water‐rock interactions and/or higher degrees of diagenesis under oxidizing conditions. The fan top strata show hydration but little to no signs of Fe oxidation likely implying that some periods of fan construction occurred either during a reduced atmosphere era or during short‐lived aqueous activity of liquid water in contact with an oxidized atmosphere. We also report the discovery of alternating cm‐scale bands of red and gray layers correlated with hydration and oxide variability, which has not yet been observed elsewhere on Mars. This could result from syn‐depositional fluid chemistry variations, possibly as seasonal processes, or diagenetic overprint of oxidized fluids percolating through strata having variable permeability.

Rhenium substitution effects on the structural, morphological and magnetic properties of bismuth ferrite BiFe(1-x)RexO3

In order to fully realize room temperature multiferroicity, a release of remnant magnetization in the BiFeO3 (BFO) system is still needed. Herein, we describe novel Re-substituted BiFe1-xRexO3 compounds that were synthesized using an aqueous sol-gel procedure when ethylene glycol was used as a complexing agent. Rhenium substitution was used to disrupt the modulated magnetic structure due to its aliovalent nature and maintain electroneutrality in case of Bi evaporation. Obtained compounds were investigated using X-ray powder diffraction (XRD) analysis coupled with Rietveld refinement, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), as well as magnetometry measurements. The obtained data revealed that only tiny amounts of Re (≤0.75 %) can be introduced instead of Fe ions while maintaining a single-phase structure. Larger inclusions lead to the formation of two impurity phases with Pbam and I213 space groups. However, the typical R3c bismuth ferrite crystal structure remained dominant. SEM analysis indicated that the inclusion of Re ions into the crystal structure caused an increase in average particle size. XPS analysis confirmed the designed chemical compositions of the samples as well as the small amount of Fe2+, which is formed to compensate for the Re ions in the 6+ and 7+ states. Magnetometry measurements revealed that even sub 1 % of Re substitution led to a presence of non-zero remnant magnetization, which reaches 0.0449 Am2kg−1 at room temperature in the compound with x = 0.0075.

Electrochemical characteristic analysis for surface passivation layer of galena and chalcopyrite in acid corrosion

The surface passivation layer of galena and chalcopyrite after sulfuric acid corrosion can enlarge the difference in their floatability. The floatability test shows that sulfuric acid corrosion strongly inhibits galena’s floatability but has no effect on chalcopyrite. Scanning electron microscope and energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Eh-pH diagram analysis showed that the galena surface was oxidized to form a coarse passivation layer of PbSO4, while the chalcopyrite surface dissolved only a small amount of Fe2+ ions and formed a dense sulfide layer (Cu(1-x)Fe(1-y)S2). Open circuit potential (OCP), polarization curve, and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the surface passivation layer on galena and chalcopyrite after sulfuric acid corrosion. The electrochemical analysis results showed that the electrostatic potential increased and the electrochemical activity decreased on the galena and chalcopyrite surface due to corrosion action; the current density of corroded galena was stable around 17.41 μA·cm−2 and the surface oxidation reaction can be further carried out, while the current density of corroded chalcopyrite was reduced from 17.91μA·cm−2 to 9.01 μA·cm−2, and the surface reaction was gradually inhibited; the double electric layer resistance (Rt) and the resistance (Rp) for the passivation layer of corroded galena both decreased significantly, and the passivation layer could be further generated from the surface to the interior, while the Rt and Rp of corroded chalcopyrite increased significantly and prevented the dissolution of internal components. The electrochemical analysis results were consistent with each other and confirmed by SEM-EDS and XPS conclusion. In addition, the corrosion-flotation process has been used to achieve high-efficiency separation of the galena-chalcopyrite mixture.

Study on the Effectiveness of Sulfate Reducing Bacteria to Remove Heavy Metals (Fe, Mn, Cu, Cr) in Acid Mine Drainage

Aiming at the problem of environmental pollution caused by heavy metals such as Fe, Mn, Cu, and Cr, Sulfate Reducing Bacteria (SRB) were enriched in mining soil. SRB was added to AMD containing different concentrations of Fe, Mn, Cu, and Cr by batch experiments to explore the potential of SRB for treating heavy metals in AMD. Testing combining Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM-EDS), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) revealed the mechanism by which heavy metal ions were removed by SRB. The results showed that SRB had a strong ability to remove total Fe in the concentration range of 0–300 mg/L, and the removal percentage of total Fe reached to 92.16–93.17%. SRB had a good removal effect on total Cu, in the concentration range of 0–20 mg/L, and the removal percentage of total Cu reached to 79.79–81.80%. SRB had a good removal effect on total Cr as well; SRB activity would probably not be inhibited for total Cr concentrations below 500 mg/L. The ability to solidify different heavy metal ions using SRB was as follows: total Cr > total Fe > total Mn > total Cu. When SRB removed Fe2+ there was precipitation at the same time, appearing as black granules. This precipitation consisted mainly of FeS, and contained small amounts of Fe3(PO4)2-8H2O, FeCO3, Fe(OH)2, Fe(OH)3, and Fe2S as well.

The importance of moisture in regulating soil organic carbon content based on a comparison of “enzymic latch” and “iron gate” in Zoige Plateau peatland

Due to the enormous amount of carbon (C) stored in peatlands, understanding the regulator of soil organic carbon (SOC) in peatlands is critical for global C cycling. Currently, “enzymic latch” and “iron gate” are the frequently debated mechanisms that propose phenol oxidase (PHO) and Fe2+ as important regulators driving SOC cycling in peatland. Therefore, this study compared “enzymic latch” and “iron gate” in the same peatland (Zoige Plateau, the largest peatland in China) to figure out the crucial regulator of SOC content via investigating the interrelationships among soil properties, C-related enzymes, phenolics, and iron (Fe) oxides. Moreover, waterlogged and non-waterlogged soils were chosen to take samples in both dry and wet season to understand the potential role of moisture in regulating SOC content. It was found that the contents of dissolved organic C, phenolics, SOC, Fe oxides, and β-glucosidase (BG) activities in waterlogged soils were higher than those in non-waterlogged soils. Compared to the dry season, soils in the wet season had higher phenolics, SOC, and Fe oxides contents. Also, this study observed an insignificant relationship between PHO and SOC (p > 0.05) and the small amounts of Fe2+ to total Fe (<2‰) in soils. Meanwhile, the highest effect of moisture (0.89) and negligible effect of PHO (0.04) and Fe2+ (-0.08) on SOC based on pathway analysis suggested that moisture might be the crucial regulator of SOC. Furthermore, pathway analysis implied that moisture could indirectly affect SOC by adjusting BG (p < 0.05) and soluble phenolics (p < 0.05). This study provided valuable information for understanding the importance of moisture in driving C cycling and helping against soil C loss by moisture management in Zoige Plateau.

Surface Mechanism of Fe3+ Ions on the Improvement of Fine Monazite Flotation With Octyl Hydroxamate as the Collector.

Froth flotation of fine minerals has always been an important research direction in terms of theory and practice. In this paper, the effect and mechanism of Fe3+ on improving surface hydrophobicity and flotation of fine monazite using sodium octyl hydroxamate (SOH) as a collector were investigated through a series of laboratory tests and detection measurements including microflotation, fluorescence spectrum, zeta potential, and X-ray photoelectron spectroscopy (XPS). Flotation tests have shown that fine monazite particles (−26 + 15 μm) cannot be floated well with the SOH collector compared to the coarse fraction (−74 + 38 μm). However, adding a small amount of Fe3+ to the pulp before SOH can significantly improve the flotation of fine monazite. This is because the addition of Fe3+ promotes the adsorption of SOH and greatly improves the hydrophobicity of the monazite surface. This can result in the formation of a more uniform and dense hydrophobic adsorption layer, as shown by the fluorescence spectrum and zeta potential results. From the XPS results, Fe3+ reacts with surface O atoms on the surface of monazite to form a monazite–Osurf–Fe group that acts as a new additional active site for SOH adsorption. A schematic model was also proposed to explain the mechanism of Fe3+ for improving surface hydrophobicity and flotation of fine monazite using octyl hydroxamate as a collector. The innovative point of this study is using a simple reagent scheme to float fine mineral particles rather than traditional complex processes.

X-ray absorption and Mössbauer spectra, and microwave absorption of (Co, Mn)-doped SrFe12O19 hexaferrites

Polycrystalline SrCo1·2Fe10·8O19 (SCFO) and SrMn1·2Fe10·8O19 (SMFO) samples were prepared by the normal ceramic technique. Powder X-ray diffraction patterns indicated the crystallization in the M-type hexaferrite structure of the samples. X-ray absorption analyses proved Co2+ and Mn3+,4+ ions existing in SCFO and SMFO, respectively. Though Fe3+ is dominant in both the compounds, small amounts of Fe2+ and Fe4+ are present in SCFO and SMFO, respectively. Mössbauer spectra analyses also confirmed the dominance of Fe3+ in both the samples. Additionally, Fe3+ ions in the 12 k, 4f1, 4f2, and 2a sites could be attributed to the high-spin state (S = 5/2). A large QS value for the sextet assigned to the 2b site indicated that in this case Fe3+ could be in the low-spin state (S = 1/2) or there was the addition of Fe2+ (or Fe4+) when Fe in SrFe12O19 was partially replaced by Co2+ (or Mn3+,4+). The mixture of transition-metal ions with different oxidation states influenced the magnetic properties and microwave shielding ability. At frequencies f = 10–18 GHz, we have found SCFO showing the lowest reflection loss with RL = −11.1 dB at 13.2 GHz and the thickness t = 2.2 mm. With an absorption bandwidth of 0.7 GHz, and about 92% microwave energy being absorbed, SCFO is considered as a potential candidate for microwave shielding applications.

Nano zero valent iron encapsulated in graphene oxide for reducing uranium

Nano zero-valent iron (Fe0) has been widely used to remove Uranium (U(VI)). In order to enhance the performance of Fe0 toward U(VI) removal, the Fe0 was assembled into graphene oxide (GO) sheets via 3-aminopropyl triethoxysilane (APTES) as Fe0/APTES-GO composites. The Fe0/APTES-GO composites were triumphantly prepared, characterized and analyzed by means of Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) together with Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). SEM and TEM-EDS results manifested that Fe0 particles were encapsulated into rolled-up GO, which greatly improved the stability of Fe0. Batch experiment showed that only a small amount of Fe2+ was leached in the first two leaching cycles of Fe0/APTES-GO composites. The removal capacity of Fe0/APTES-GO composites was up to 1357.99 mg/g at pH = 4.1 and T = 50 °C, which was mainly attributed to the reducing activity of Fe0 and an abundance of functional groups (i.e., –COOH, C–OH and –OH) on the Fe0/APTES-GO composites. The electrostatic potential (ESP) from the calculation also supported that U(VI) tended to be reduced at the back side of the GO-Fe0 cluster.

Iron (III) cross-linked thermoplastic nitrile butadiene elastomer with temperature-adaptable self-healing property

Fe cross-linked thermoplastic carboxylated nitrile butadiene rubber (XNBR) materials using Fe-COOH coordination as dynamic cross-links are reported. The transparent and brown Fe cross-linked XNBR (Fe/XNBR) elastomer was prepared by drying of Fe/XNBR organogels, which were fabricated by simple mixing of Fe3+ ethanol solution and XNBR dioxane solution. Tensile tests showed that only a small amount of Fe3+ ions (e.g., COOH/Fe=1/0.086, mol/mol) made the Fe/XNBR had even better tensile strength and stretchability than 2 phr sulphur vulcanized XNBR. Dynamic mechanical analysis demonstrated that the Fe-COOH interaction not only increased the moduli at higher temperatures, but also made the glass transition temperature high-temperature-shifted. In-situ infrared spectra measurements suggested that higher temperatures (e.g, 100°C) generated more trifunctional Fe-COOH cross-links and made the Fe-COOH interaction highly dynamic. The dynamic nature of the Fe-COOH interaction and generation of more trifunctional cross-links at high temperatures endowed fast self-healing and re-molding properties to the Fe/XNBR elastomers. Our result as a proof-of-concept illustrated a simple and cost-efficient way to fabricate self-healable thermoplastic elastomers using metal-ligand coordination in commercial rubbers.

ESI-TOF MS analysis and DNA cleavage activity of complexes formed by luteolin and five metal ions in hot water

Luteolin is a common flavonoid in plants and exhibits a variety of biological activities. In this study, luteolin was reacted in hot water with five trace metal elements found in plants, and the products were tested by electrospray-ionization time-of-flight mass spectrometry (ESI-TOF MS). Luteolin formed complexes with Ca2+, Mg2+, and Zn2+ in both 2:1 and 3:1 ratios, in addition to a complex with Cu2+ in a 2:1 ratio. A luteolin-iron (III) complex was also formed in a 2:1 ratio, and a small amount of Fe2+ was produced to form a luteolin-iron (II) complex in a 2:1 ratio. The formed luteolin-Cu2+ complex exhibited significant DNA cleavage activity in a time- and concentration-dependent manner, while no or little such activity was observed for luteolin or Cu2+ alone. Therefore, complexes of luteolin and trace metal elements may exist in cooked foods and medicinal plant decoctions, which could influence associated health and therapeutic effects.

A Fe3+-crosslinked pyrogallol-tethered gelatin adhesive hydrogel with antibacterial activity for wound healing.

In this work, a tunicate-inspired gelatin-based hydrogel is prepared by simply mixing 2,3,4-trihydroxybenzaldehyde (THB)-tethered gelatin solution with a small amount of Fe3+ ions via the Schiff-base reaction and simultaneous formation of hexavalent Fe-complexes. The resulting hydrogel (termed GelTHB-Fe) exhibits not only tunable gelation time, rheological properties and self-healing ability by adjusting the composition, but also robust adhesion to a variety of materials, with an average adhesion strength of 136.7 kPa, 147.3 kPa, 153.7 kPa, 92.9 kPa, and 56.5 kPa to PMMA, iron, ceramics, glass and pigskin, respectively. Intriguingly, the pyrogallol moieties impart an antibacterial activity to the GelTHB-Fe hydrogel, which is shown to reduce infection and promote wound healing in a diabetic rat model. This GelTHB-Fe hydrogel holds great potential as a promising tissue adhesive.

Semiconductor-Microbial Mechanism of Selective Dissolution of Chalcocite in Bioleaching.

Chalcocite-dominant secondary copper ore with a high pyrite content had a rapidly increased iron concentration in the middle and later periods of bioleaching, which increased the difficulty of separating copper and iron ions in the leaching solution. In the two aspects of microbial community succession and energy band theory, the selective dissolution mechanism of chalcocite in this type of copper ore was analyzed and illustrated using experiments and first-principles calculations. The results showed that controlling the solution potential at a lower level was beneficial to the selective leaching of chalcocite, while bacteria promoted the leaching of pyrite and chalcocite simultaneously by oxidizing Fe2+ to Fe3+ in the solution. Below 700 mV of solution potential, the bacterial community, mainly consisting of Acidithiobacillus and Sulfobacillus, had a stronger promotion on the selective dissolution of chalcocite. The solution energy level of bioleaching was higher than ideal pyrite but lower than ideal chalcocite, which resulted in the accumulation of electrons on the surface of pyrite and the formation of holes at the top of the chalcocite valence band. When bacteria assisted the oxidation of Fe2+ to Fe3+ and caused the raise of the solution potential, the difference between the solution energy level and the top of the pyrite valence band would be smaller than the width of the pyrite energy gap. Below 700 mV, the assistance of Acidithiobacillus and Sulfobacillus on the oxidation of Fe2+ was weak. Chalcocite would be selectively dissolved by oxygen and a small amount of Fe3+ in the solution. Because of the existence of Fe, Cu, and S vacancies in real minerals, the atomic activity in the Cu–S bond and the Fe–S bond enhanced, and the reaction difficulty between chalcocite, pyrite, and electron acceptors in the solution reduced. The solution potential should be controlled at 600 mV or less to ensure the selective dissolution of chalcocite.

Inorganic Polymers From CaO-FeOx-SiO2 Slag: The Start of Oxidation of Fe and the Formation of a Mixed Valence Binder

Belonging to the family of alternative cementitious materials, inorganic polymers are rising in importance because of the drive to decrease CO2 emissions of concrete production. A synthetic Fe-rich slag resembling industrial copper or lead slags, was mixed with a sodium silicate activating solution. 57Fe Mossbauer spectra analyses indicate that the oxidation reactions are taking place simultaneously with the polymerization reactions. The slag contains Fe2+ states and a small amount of Fe3+. During polymerization a new octahedral Fe2+ state is formed, while oxidation is manifested through the appearance of an additional Fe3+ state. The reactions continue after setting, lowering the relative contributions of the slag in the Mossbauer and FTIR spectra of the samples. The Na+/Fe3+ molar ratio in the mixture that makes up the binder after 28 days is approximately 1, suggesting the participation of tetrahedral Fe3+ in the silicate framework, charge balanced by Na+.

Exploring the links between bacterial communities and magnetic susceptibility in bulk soil and rhizosphere of beech (Fagus sylvatica L.)

Soil magnetic properties are sensitive indicators of pedogenetic processes. Although many of the processes that increase soil magnetism are well documented, the role of microbial communities and the metabolic characteristics of Fe-reducing bacteria are still largely unknown. For this work, two soils with contrasting magnetic properties were identified in a beech forest on Monte Zuccarello (central Italy). Samples of bulk soil and rhizosphere were obtained from A (0–7 cm), AB (7–16 cm), Bw1 (16–22 cm) and Bw2 (22–29 cm) horizons of both soils, and were analysed for their physicochemical characteristics, the amount of magnetic minerals, and the composition of total and culturable bacterial communities, focusing on siderophore-producing bacteria (SPB). Analyses confirmed that the magnetic soil (MS) have a higher content of maghemite and magnetite association, compared to non-magnetic soil (NMS). Since the formation of maghemite can occur through different processes, we investigated on the possible role of soil bacteria in the formation of this magnetic mineral. As soil maghemite generally contains small amounts of Fe2+, the formation of which has been attributed to the combustion of organic matter, SPB have been isolated and identified. MS samples showed the highest number of SPB (mainly Micrococcaceae, Bacillaceae, and Pseudomonadaceae), suggesting a significant increase in Fe-reducing bacteria. High-throughput sequencing analysis revealed a separation in terms of the total composition of the bacterial community between bulk and rhizosphere of both MS and NMS, dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Verrucomicrobia phyla. Interestingly, Gamma and Delta Proteobacteria, as well as Nitrospirae, were usually more abundant in MS than in NMS, confirming that the MS was predominantly characterized by groups of magnetotactic bacteria and SPB, and potentially contributing to enhance the soil magnetic properties.

Electronic structure by X-ray absorption spectroscopy and observation of field induced unusually slow spin relaxation from magnetic properties in pyrochlore Eu2−xFexTi2O7

X-ray absorption spectroscopy (XAS) as well as x-ray magnetic circular dichroism (XMCD) and magnetization of hybrid pyrochlore Eu2-xFexTi2O7 were investigated, where the rare earth Eu (4f) was replaced with transition metal Fe (3d) to introduce competing 4f-3d interactions. It is confirmed that the valence states of Eu and Fe ions are formally trivalent while that of Ti ions are tetravalent (3d0). The analysis yielded that the tetravalent Ti ions occupy octahedral sites with distorted Oh symmetry which is triggered by the presence of vacant 8a anionic site adjacent to TiO6 octahedra. Further study with Fe doping revealed that it essentially reduces the octahedral distortion by introducing anionic disorder (migration of 48f oxygen ions to 8a site). Analysis of O K edge XAS spectra further confirmed the Fe substitution causing the systematic change in the ligand (O2-) coordination of the Ti4+ cations. On the other hand, a new field induced transition (with Fe doping) at low temperature T* (4 K<T*< 8 K) in ac susceptibility with unusually slow spin relaxation was observed. The transition shifted towards higher temperatures both with increasing applied field and Fe concentration. However, the single ion spin freezing (Tf ~35 K) appears to be suppressed with Fe substitution. Interestingly, small amount of Fe3+ ion substitution showed significant enhancement in the dc magnetization at lower temperatures (<100 K). Analysis further indicated rise of dipolar FM exchange interaction with Fe doping.

Lanthanum loaded graphitic carbon nitride nanosheets for highly sensitive and selective fluorescent detection of iron ions

A facile synthesis of lanthanum (La) loaded graphitic carbon nitride nanosheets (CNNS) was developed in this study. The obtained La-CNNS exhibited an intense emission peak at 255nm, owing to fluorescence enhancement effect of introduced La on the surface of CNNS. La-CNNS showed excitation-independent behavior and blue shift compared with CNNS. It displayed great fluorescence quenching via photoinduced electron transfer (PET) when a small amount of Fe3+ was added. The probe exhibited a wide linear response concentration range (0.1–20μM) to Fe3+ with a detection limit of 0.0232μM. The La-CNNS fluorescence probe was highly selective and suitable for Fe3+ analysis in natural water samples.

Mineralogical study of brown olivine in Northwest Africa 1950 shergottite and implications for the formation mechanism of iron nanoparticles

AbstractMartian meteorites, in particular shergottites, contain darkened olivine (so‐called “brown olivine”) whose color is induced by iron nanoparticles formed in olivine during a shock event. The formation process and conditions of brown olivine have been discussed in the Northwest Africa 2737 (NWA 2737) chassignite. However, formation conditions of brown olivine in NWA 2737 cannot be applied to shergottites because NWA 2737 has a different shock history from that of shergottites. Therefore, this study observed brown olivine in the NWA 1950 shergottite and discusses the general formation process and conditions of brown olivine in shergottites. Our observation of NWA 1950 revealed that olivine is heterogeneously darkened between and within grains different from brown olivine in NWA 2737. XANES analysis showed that brown olivine contains small amounts of Fe3+ and TEM/STEM observation revealed that there is no SiO‐rich phase around iron metal nanoparticles. These observations indicate that iron nanoparticles were formed by a disproportionation reaction of olivine (3Fe2+olivine → Fe0metal + 2Fe3+olivine + Volivine, where Volivine means a vacancy in olivine). Some parts of brown olivine show lamellar textures in SEM observation and Raman peaks in addition to those expected for olivine, implying that brown olivine experienced a phase transition (to e.g., ringwoodite). In order to induce heterogeneous darkening, heterogeneous high temperature of about 1500–1700 K and shock duration of at least ~90 ms are required. This heterogeneous high temperature resulted in high postshock temperature (&gt;900 K) inducing back‐transformation of most high‐pressure phases. Therefore, in spite of lack of high‐pressure phases, NWA 1950 (= Martian meteorites with brown olivine) experienced higher pressure and temperature compared to other highly shocked meteorite groups.

Cation distribution in CuFe2O4 nanoparticles: Effects of Ni doping on magnetic properties

The Cu1−xNixFe2O4 nanoparticles (with x = 0, 0.3, 0.5, 0.7, and 1) were synthesized by using spray co-precipitation method at annealing temperature Ta = 900 °C in air for 5 h. The crystal structure, microstructure, oxidation state, and magnetic properties of the samples were characterized by using X-ray diffraction, synchrotron X-ray diffraction, scanning electron microscopy, X-ray absorption spectroscopy, and vibrating sample magnetometer. It was shown that all the samples have cubic structure. Lattice constant and grain size decrease, while the Curie temperature TC increases with increasing of Ni2+ content. A small amount of Fe2+ was found in all the samples. Cation distribution was determined by using a combination of magnetization measurements, extended X-ray absorption fine structure analysis, and Rietveld refinement from synchrotron X-ray diffraction data. It was indicated that Ni2+ ions occupy in octahedral site only, while Cu2+ ions distribute in both tetrahedral and octahedral sites. The variation of magnetic parameters is discussed based on Ni2+ concentration, grain size, the cation distribution, surface effect, and the presence of Fe2+ ion in the samples.