Spectral and morphological characteristics of synthetic nanophase iron (oxyhydr)oxides

Nonclassical crystallization of goethite nanorods in limpet teeth by self-assembly of silica-rich nanoparticles reveals structure-mechanical property relations

The intricate organization of goethite nanorods within a silica-rich matrix makes limpet teeth the strongest known natural material. However, the mineralization pathway of goethite in organisms under ambient conditions remains elusive. Here, by investigating the multi-level structure of limpet teeth at different growth stages, it is revealed that the growth of goethite crystals proceeds by the attachment of amorphous nanoparticles, a nonclassical crystallization pathway widely observed during the formation of calcium-based biominerals. Importantly, these nanoparticles contain a high amount of silica, which is gradually expelled during the growth of goethite. Moreover, in mature teeth of limpet, the content of silica correlates with the size of goethite crystals, where smaller goethite crystals are densely packed in the leading part with higher content of silica. Correspondingly, the leading part exhibits higher hardness and elastic modulus. Thus, this study not only reveals the nonclassical crystallization pathway of goethite nanorods in limpet teeth, but also highlights the critical roles of silica in controlling the hierarchical structure and the mechanical properties of limpet teeth, thus providing inspirations for fabricating biomimetic materials with excellent properties.

Systematic evaluation of methods for iron-impregnation of biochar and effects on arsenic in flooded soils

There is a need for innovative strategies to decrease the mobility of metal(loids) including arsenic (As) and cadmium (Cd) in agricultural soils, including rice paddies, so as to minimize dietary exposure to these toxic elements. Iron (Fe)-modified biochars (FBCs) are used to immobilize As and Cd in soil-water systems, but there is a lack of clarity on optimal methods for preparing FBCs because there are only limited studies that directly compare BCs impregnated with Fe under different conditions. There is also a lack of information on the long-term performance of FBCs in flooded soil environments, where reductive dissolution of Fe (oxy)hydroxide phases loaded onto biochar surfaces may decrease the effectiveness of FBCs. This study uses material characterization methods including FTIR, SEM-EDX, BET, and adsorption isotherm experiments to investigate the effects of Fe-impregnation methods (pH, pyrolysis sequence, and sonication) on the morphology and mineralogy of Fe loaded onto the biochar surface, and to FBC adsorbent properties for arsenate (As(V)), arsenite (As(III)), and Cd. Acidic impregnation conditions favored the adsorption of As(III) onto amorphous Fe phases that were evenly distributed on the biochar surface, including within the biochar pore structure. The combination of sonication with acidic Fe-impregnation conditions led to the best adsorption capacities for As(V) and As(III) (4830 and 11,166 μg As g-1 biochar, respectively). Alkaline Fe-impregnation conditions led to the highest Cd adsorption capacity of 3054 μg Cd g-1 biochar, but had poor effectiveness as an As adsorbent. Amending soil with 5% (w/w) of an acid-impregnated and sonicated FBC was more effective than an alkaline-impregnated FBC or ferrihydrite in decreasing porewater As concentrations. The acid-impregnated FBC also had greater longevity, decreasing As by 54% and 56% in two flooded phases, probably due to the greater stability of Fe(III) within the biochar pore structure that may have a direct chemical bond to the biochar surface. This study demonstrates that FBCs can be designed with selectivity towards different As species or Cd and that they can maintain their effectiveness under anaerobic soil conditions. This is the first study to systematically test how impregnation conditions affect the stability of FBCs in soils under multiple drying-rewetting cycles.

Photovoltaic amorphous feroxyhyte nanostructures synthesized by atmospheric AC microplasma

Feroxyhite (δ-FeOOH) nanomaterials were successfully synthesized through the atmospheric AC microplasma method at room temperature from ferrous sulfate aqueous solutions. Various syntheses conditions, including electric voltage, electric field strength, ferrous concentration, hydrogen peroxide concentration, and reaction duration, were systematically investigated. The synthesized products were characterized through x-ray diffraction, UV-vis absorption spectroscopy, photoluminescence spectroscopy, infra-red spectroscopy, and electron microscopy. The bandgap of the produced materials were strongly dependent of the ferrous concentration while the product ratio was dependent on all experimental conditions. The synthesis mechanism was thoroughly discussed. The synthesized nanomaterials were amorphous nanospheres, showing superparamagnetic properties at room temperature. The synthesized oxyhydroxide is a potential photovoltaic material besides its reported applications in photocatalysts and supercapacitors. The application of this synthesis technique could be extended to synthesize other oxy-hydroxide nanomaterials for renewable energy applications facilely, scalablely, cost-effectively, and environmentally.

A multispectroscopic approach for ultra-trace sensing of prostate specific antigen (PSA) by iron nanocomposite fabricated on graphene nanoplatelet

Herein we report an easy, rapid and cost-effective method for spectroscopic sensing of a prostate cancer biomarker prostate specific antigen (PSA) using a novel nanocomposite. The material is a synthetic quinoxaline derivative-based iron nanocomposite fabricated on graphene nanoplatelet surface (1d-Fe-Gr). Presence of graphene enhanced the efficacy of synthesized 1d-Fe-Gr to sense PSA in serum medium with an impressive limit of detection (LOD) value of 0.878 pg/mL compared to 1d-Fe alone (LOD 17.619 pg/mL) using UV-visible absorption spectroscopy. LOD of PSA by 1d-Fe-Gr using Raman spectroscopy is even more impressive (0.410 pg/mL). Moreover, presence of interfering biomolecules like glucose, cholesterol, bilirubin and insulin in serum improves the detection threshold significantly in presence of 1d-Fe-Gr which otherwise cause LOD values of PSA to elevate in control sets. In presence of these biomolecules, the LOD values improve significantly as compared to healthy conditions in the range 0.623-3.499 pg/mL. Thus, this proposed detection method could also be applied efficiently to the patients suffering from different pathophysiological disorders. These biomolecules may also be added externally during analyses to improve the sensing ability. Fluorescence, Raman and circular dichroism spectroscopy were used to study the underlying mechanism of PSA sensing by 1d-Fe-Gr. Molecular docking studies confirm the selective interaction of 1d-Fe-Gr with PSA over other cancer biomarkers.

Fe(III) (oxyhydr)oxide reduction by the thermophilic iron-reducing bacterium Desulfovulcanus ferrireducens

Some thermophilic bacteria from deep-sea hydrothermal vents grow by dissimilatory iron reduction, but our understanding of their biogenic mineral transformations is nascent. Mineral transformations catalyzed by the thermophilic iron-reducing bacterium Desulfovulcanus ferrireducens during growth at 55°C were examined using synthetic nanophase ferrihydrite, akaganeite, and lepidocrocite separately as terminal electron acceptors. Spectral analyses using visible-near infrared (VNIR), Fourier-transform infrared attenuated total reflectance (FTIR-ATR), and Mössbauer spectroscopies were complemented with x-ray diffraction (XRD) and transmission electron microscopy (TEM) using selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) analyses. The most extensive biogenic mineral transformation occurred with ferrihydrite, which produced a magnetic, visibly dark mineral with spectral features matching cation-deficient magnetite. Desulfovulcanus ferrireducens also grew on akaganeite and lepidocrocite and produced non-magnetic, visibly dark minerals that were poorly soluble in the oxalate solution. Bioreduced mineral products from akaganeite and lepidocrocite reduction were almost entirely absorbed in the VNIR spectroscopy in contrast to both parent minerals and the abiotic controls. However, FTIR-ATR and Mössbauer spectra and XRD analyses of both biogenic minerals were almost identical to the parent and control minerals. The TEM of these biogenic minerals showed the presence of poorly crystalline iron nanospheres (50-200 nm in diameter) of unknown mineralogy that were likely coating the larger parent minerals and were absent from the controls. The study demonstrated that thermophilic bacteria transform different types of Fe(III) (oxyhydr)oxide minerals for growth with varying mineral products. These mineral products are likely formed through dissolution-reprecipitation reactions but are not easily predictable through chemical equilibrium reactions alone.

Solid waste collagen-associated fabrication of magnetic hematite nanoparticle@collagen nanobiocomposite for emission-adsorption of dyes

The strategic utilization of hazardous particulate waste in eliminating environmental pollution is an important research hotspot. Herein, abundantly available hazardous solid collagenic waste of leather industry is converted into stable hybrid nanobiocomposite (HNP@SWDC) comprising magnetic hematite nanoparticles (HNP) and solid waste derived collagen (SWDC) via co-precipitation method. The structural, spectroscopic, surface, thermal, and magnetic properties; fluorescence quenching; dye selectivity; and adsorption are explored via microstructural analyzes of HNP@SWDC and dye adsorbed-HNP@SWDC using ¹H nuclear magnetic resonance, Raman, ultraviolet-visible, Fourier-transform infrared (FTIR), X-ray photoelectron, and fluorescence spectroscopies; thermogravimetry; field-emission scanning electron microscopy; and vibrating-sample magnetometry (VSM). The intimate interaction of SWDC with HNP and elevated magnetic properties of HNP@SWDC are apprehended via amide-imidol tautomerism associated nonconventional hydrogen bondings, disappearance of goethite specific -OH def. in HNP@SWDC, and VSM. The as-fabricated reusable HNP@SWDC is employed for removing methylene blue (MB) and rhodamine B (RhB). Chemisorption of RhB/MB in HNP@SWDC via ionic, electrostatic, and hydrogen bonding interactions alongside dimerization of dyes are realized by ultraviolet-visible, FTIR, and fluorescence studies; pseudosecond order fitting; and activation energies. The adsorption capacity = 46.98-56.14/22.89-27.57 mg g^-1 for RhB/MB is noted using 0.01 g HNP@SWDC within 5-20 ppm dyes and 288-318 K.

Spectral Detection of Nanophase Iron Minerals Produced by Fe(III)-Reducing Hyperthermophilic Crenarchaea

Mineral transformations by two hyperthermophilic Fe(III)-reducing crenarchaea, Pyrodictium delaneyi and Pyrobaculum islandicum, were examined using synthetic nanophase ferrihydrite, lepidocrocite, and akaganeite separately as terminal electron acceptors and compared with abiotic mineral transformations under similar conditions. Spectral analyses using visible-near-infrared, Fourier-transform infrared attenuated total reflectance (FTIR-ATR), Raman, and Mössbauer spectroscopies were complementary and revealed formation of various biomineral assemblages distinguishable from abiotic phases. The most extensive biogenic mineral transformation occurred with ferrihydrite, which formed primarily magnetite with spectral features similar to biomagnetite relative to a synthetic magnetite standard. The FTIR-ATR spectra of ferrihydrite bioreduced by P. delaneyi also showed possible cell-associated organics such as exopolysaccharides. Such combined detections of biomineral assemblages and organics might serve as biomarkers for hyperthermophilic Fe(III) reduction. With lepidocrocite, P. delaneyi produced primarily a ferrous carbonate phase reminiscent of siderite, and with akaganeite, magnetite and a ferrous phosphate phase similar to vivianite were formed. P. islandicum showed minor biogenic production of a ferrous phosphate similar to vivianite when grown on lepidocrocite, and a mixed valent phosphate or sulfate mineral when grown on akaganeite. These results expand the range of biogenic mineral transformations at high temperatures and identify spacecraft-relevant spectroscopies suitable for discriminating mineral biogenicity.

Exploring the secondary mineral products generated by microbial iron respiration in Archean ocean simulations

Marine chemical sedimentary deposits known as Banded Iron Formations (BIFs) archive Archean ocean chemistry and, potentially, signs of ancient microbial life. BIFs contain a diversity of iron- and silica-rich minerals in disequilibrium, and thus many interpretations of these phases suggest they formed secondarily during early diagenetic processes. One such hypothesis posits that the early diagenetic microbial respiration of primary iron(III) oxides in BIFs resulted in the formation of other iron phases, including the iron-rich silicates, carbonates, and magnetite common in BIF assemblages. Here, we simulated this proposed pathway in laboratory incubations combining a model dissimilatory iron-reducing (DIR) bacterium, Shewanella putrefaciens CN32, and the ferric oxyhydroxide mineral ferrihydrite under conditions mimicking the predicted Archean seawater geochemistry. We assessed the impact of dissolved silica, calcium, and magnesium on the bioreduced precipitates. After harvesting the solid products from these experiments, we analyzed the reduced mineral phases using Raman spectroscopy, electron microscopy, powder x-ray diffraction, and spectrophotometric techniques to identify mineral precipitates and track the bulk distributions of Fe(II) and Fe(III). These techniques detected a diverse range of calcium carbonate morphologies and polymorphism in incubations with calcium, as well as secondary ferric oxide phases like goethite in silica-free experiments. We also identified aggregates of curling, iron- and silica-rich amorphous precipitates in all incubations amended with silica. Although ferric oxides persist even in our electron acceptor-limited incubations, our observations indicate that microbial iron reduction of ferrihydrite is a viable pathway for the formation of early iron silicate phases. This finding allows us to draw parallels between our experimental proto-silicates and the recently characterized iron silicate nanoinclusions in BIF chert deposits, suggesting that early iron silicates could possibly be signatures of iron-reducing metabolisms on early Earth.

Thermally-induced color transformation of hematite: insight into the prehistoric natural pigment preparation

Since the prehistoric era, hematite has been known as a reddish color pigment on rock art, body paint, and decorating substances for objects discovered almost worldwide. Recently, studies about purple hematite used in prehistoric pigment have been done vigorously to investigate the origin of the purple pigment itself. These previous studies indicate that the differentiation of crystallinity, crystal size, morphology, and electronic structure can cause the color shift, resulting in purple hematite. In this study, we conducted a detailed study of the sintering temperature effects on the formation of hematite minerals. This study aims to reveal the structural, crystallography, and electronic transformation in hematite due to heating treatment at various temperatures. The hematite was synthesized using precipitation to imitate the primary method of hematite formation in nature. The sintering process was carried out with temperature variations from 600 °C to 1100 °C and then characterized by crystallographic and structural properties (XRD, Raman Spectroscopy, FTIR), particle size (TEM), as well as electronic properties (DRS, XANES). The crystallinity and particle size of hematite tend to increase along with higher sintering temperatures. Moreover, we noted that the octahedral distortion underwent an intensification with the increase in sintering temperature, which affected the electronic structure of hematite. Specifically, the 1s → 3d transition exhibited lower energy for hematite produced at a higher temperature. This induced a shift in the absorbed energy of the polychromatic light that led to a color shift within hematite, from red to purple. Our finding emphasizes the importance of electronic structure in explaining hematite pigment’s color change rather than relying on simple reasons, such as particle size and crystallinity. In addition, this might strengthen the hypothesis that the prehistoric human created a purple hematite pigment through heating.

Coupling X-ray Absorption and Raman Spectroscopies to Characterize Iron Species in a Karst Pedosedimentary Record

The identification of iron (Fe) forms throughout a sediment sequence was investigated by X-ray Absorption Near Edge Spectroscopy (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) at the Fe K-edge, paired with Raman micro-spectroscopy. The contribution of different organic and inorganic Fe-bearing compounds was quantified by Linear Combination Fitting (LCF) carried out on both XANES and EXAFS spectra. Fe-XANES showed that the Fe(II)/Fe(III) ratio of different Fe-bearing minerals in sediments can be quantified with reasonable accuracy. The main Fe species detected were ferrihydrite, goethite, hematite, clay minerals (smectite, illite, nontronite), and Fe(III)-organic matter (Fe(III)-OM). A more accurate quantification of ferrihydrite was possible with LCF conducted on Fe-EXAFS spectra. With the exception of hematite, the concentration of these mineral species does not have a clear trend with depth, probably because water infiltration caused continuous Fe reduction and oxidation cycles in these sediments. From an analytical perspective, Fe oxide compounds can be difficult to identify or distinguish unless multiple techniques are used. X-ray diffraction (XRD; previous work) and Raman spectroscopy turn out to be not particularly useful in identifying ferrihydrite, while they are best suited for a broad mineralogical analysis that requires integrative spectral studies for an accurate Fe speciation. In detail, XANES and EXAFS allowed for the detection of Fe-bearing clay minerals and a more refined identification of Fe species, including Fe(III)-OM. Thermal analysis was useful to confirm some mineralogical components observed using both XRD (data previously published) and Raman spectroscopy (e.g., goethite, todorokite). In conclusion, this study underlines how a multi-technique approach is required to investigate peculiar environments such as karst pedosequences.

Multivariate metal-organic framework MTV-MIL-101 via post-synthetic cation exchange: is it truly achievable?

The post-synthetic exchange (PSE) method is a well-proven route to replace, modify, and add different functionalities to metal-organic frameworks (MOFs). Particularly, the solvent-assisted cation substitution (SACS) technique has been reported to prepare mixed-metal multivariate metal-organic frameworks (MTV-MOFs). However, such a technique does not apply to all types of MOFs. In 2013, Szilágyi et al. reported the achievement of the mixed-metal MTV-MIL-101 framework via PSE. Since then, a debate has been taking place about the validity of these findings. On the other hand, the attainment of the mixed-metal MIL-101 was reported to be obtainable through the direct synthesis, which is, to some, the only way to achieve it. Here, we settle this dispute by investigating Szilágyi's method not only as described, but also at extended conditions of time and different metal precursors: all attempts were vain. However, by reconsidering the refluxing solvent (dimethylformamide "DMF" instead of water) and the applied reaction conditions (110 °C-20 h), mixed-metal MIL-101(Cr/Fe) was achieved via a simple PSE method.

Desulfovulcanus ferrireducens gen. nov., sp. nov., a thermophilic autotrophic iron and sulfate-reducing bacterium from subseafloor basalt that grows on akaganéite and lepidocrocite minerals

A deep-sea thermophilic bacterium, strain Ax17^T, was isolated from 25 °C hydrothermal fluid at Axial Seamount. It was obligately anaerobic and autotrophic, oxidized molecular hydrogen and formate, and reduced synthetic nanophase Fe(III) (oxyhydr)oxide minerals, sulfate, sulfite, thiosulfate, and elemental sulfur for growth. It produced up to 20 mM Fe²⁺ when grown on ferrihydrite but < 5 mM Fe²⁺ when grown on akaganéite, lepidocrocite, hematite, and goethite. It was a straight to curved rod that grew at temperatures ranging from 35 to 70 °C (optimum 65 °C) and a minimum doubling time of 7.1 h, in the presence of 1.5–6% NaCl (optimum 3%) and pH 5–9 (optimum 8.0). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain was 90–92% identical to other genera of the family Desulfonauticaceae in the phylum Pseudomonadota. The genome of Ax17^T was sequenced, which yielded 2,585,834 bp and contained 2407 protein-coding sequences. Based on overall genome relatedness index analyses and its unique phenotypic characteristics, strain Ax17^T is suggested to represent a novel genus and species, for which the name Desulfovulcanus ferrireducens is proposed. The type strain is Ax17^T (= DSM 111878^T = ATCC TSD-233^T).

Newly-synthesized iron-oxide nanoparticles showed synergetic effect with citric acid for alleviating arsenic phytotoxicity in soybean

In the current investigation, we presented the success of the modified hydrothermal method for synthesizing the iron-oxide nanoparticles (Fe2O3-NPs) efficiently. These NPs were further characterized by using different techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) micrographs, energy-dispersive X-ray spectroscopy (EDAX)/Mapping pattern, Raman Spectroscopy Pattern, ultra violet (UV) and Photoluminescence (PL). All these analyses revealed highly pure nature of Fe2O3-NPs with no internal defects, and suggested its application for plant growth improvement. Therefore, we further investigated the separate as well as combined effects of the Fe2O3-NPs and citric acid (CA) in the alleviation of arsenic (As) toxicity in the soybean (Glycine max L.), by evaluating the different plant growth and metabolic attributes. Results of our study revealed that As-induced growth inhibition, reduction of photosynthesis, water use efficiency (WUE), and reactive oxygen species (ROS) accumulation whereas application of the Fe2O3-NPs and CA significantly reversed all these adverse effects in soybean plants. Moreover, the As-stress induced malondialdehyde (MDA) and hydrogen peroxide (H2O2) production were partially reversed by the Fe2O3-NPs and CA in the As-stressed plants by 16% and 10% (MDA) and 29% and 12% (H2O2). This might have resulted due to the Fe2O3-NPs and CA induced activities of the antioxidant defense in plants. Overall, the Fe2O3-NPs and CA supplementation separately and in combination positively regulated the As tolerance in soybean; however, the effect of the combined application on the As tolerance was more profound relative to the individual application. These results suggested the synergetic effect of the Fe2O3-NPs and CA on the As-tolerance in soybean. However, in-depth mechanism underlying the defense crosstalk between the Fe2O3-NPs and CA needs to be further explored.

Fe(II) Redox Chemistry in the Environment

Iron (Fe) is the fourth most abundant element in the earth's crust and plays important roles in both biological and chemical processes. The redox reactivity of various Fe(II) forms has gained increasing attention over recent decades in the areas of (bio) geochemistry, environmental chemistry and engineering, and material sciences. The goal of this paper is to review these recent advances and the current state of knowledge of Fe(II) redox chemistry in the environment. Specifically, this comprehensive review focuses on the redox reactivity of four types of Fe(II) species including aqueous Fe(II), Fe(II) complexed with ligands, minerals bearing structural Fe(II), and sorbed Fe(II) on mineral oxide surfaces. The formation pathways, factors governing the reactivity, insights into potential mechanisms, reactivity comparison, and characterization techniques are discussed with reference to the most recent breakthroughs in this field where possible. We also cover the roles of these Fe(II) species in environmental applications of zerovalent iron, microbial processes, biogeochemical cycling of carbon and nutrients, and their abiotic oxidation related processes in natural and engineered systems.

Morphology-Tunable Synthesis of Intrinsic Room-Temperature Ferromagnetic γ-Fe2O3 Nanoflakes

Intrinsic two-dimensional (2D) magnetic materials with room-temperature ferromagnetism and air stability are highly desirable for spintronic applications. However, the experimental observations of such 2D or ultrathin ferromagnetic materials are rarely reported owing to the scarcity of these materials in nature and for the intricacy in their synthesis. Here, we report a successful controllable growth of ultrathin γ-Fe₂O₃ nanoflakes with a variety of morphologies tunable by the growth temperature alone using a facile chemical vapor deposition method and demonstrate that all ultrathin nanoflakes still show intrinsic room-temperature ferromagnetism and a semiconducting nature. The γ-Fe₂O₃ nanoflakes epitaxially grown on α-Al₂O₃ substrates take a triangular shape at low temperature and develop gradually in lateral size, forming eventually a large-scale γ-Fe₂O₃ thin film as the growth time increases due to a thermodynamic control process. The morphology of the nanoflakes could be tuned from triangular to stellated, petaloid, and dendritic crystalloids in sequence with the rise of precursor temperature, revealing a growth process from thermodynamically to kinetically dominated control. Moreover, the petaloid and dendritic nanoflakes exhibit enhanced coercivity compared with the triangular and stellated nanoflakes, and all the nanoflakes with diverse shapes possess differing electrical conductivity. The findings of such ultrathin, air-stable, and room-temperature ferromagnetic γ-Fe₂O₃ nanoflakes with tunable shape and multifunctionality may offer guidance in synthesizing other non-layered magnetic materials for next-generation electronic and spintronic devices.

Magnetic chitosan stabilized palladium nanostructures: Potential catalysts for aqueous Suzuki coupling reactions

This work describes the preparation of palladium-based catalyst supported on magnetic chitosan (Pd@IO-Chitosan) for Suzuki Miyaura C-C coupling reaction. The Pd@IO-Chitosan catalyst was characterized using different spectroscopic and microscopic techniques such as Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), X-ray powder diffraction (XRD), X-ray Absorption Near Edge Structure (XANES) Spectroscopy and X-ray photoelectron spectroscopy (XPS). Pd@IO-Chitosan was further analysed by thermogravimetric analysis (TGA) in order to determine its thermal behavior. The catalyst comprised Pd, PdO species stabilised by chitosan that facilitated Suzuki coupling reactions. Palladium loading as low as 0.0055 mol% was found to be effective for aqueous Suzuki cross-couplings with excellent yields of over 99%. The catalyst could be recycled and reused at least 12 times with no significant decrease in its catalytic activity.

Dual-Functional Iron Oxide Nanoparticles Coated with Polyvinyl Alcohol/5-Fluorouracil/Zinc-Aluminium-Layered Double Hydroxide for a Simultaneous Drug and Target Delivery System

Iron oxide nanoparticles are suitable for biomedical applications owing to their ability to anchor to various active agents and drugs, unique magnetic properties, nontoxicity, and biocompatibility. In this work, the physico-chemical and magnetic properties, as well as the cytotoxicity, of Fe₃O₄ nanoparticles coated with a polymeric carrier and loaded with a 5-fluorouracil (5-FU) anti-cancer drug are discussed. The synthesized Fe₃O₄ nanoparticles were coated with polyvinyl alcohol and Zn/Al-layered double hydroxide as the drug host. The XRD, DTA/TG, and FTIR analyzes confirmed the presence of the coating layer on the surface of nanoparticles. The results showed a decrease in saturation magnetization of bare Fe₃O₄ nanoparticles after coating with the PVA/5FU/Zn/Al-LDH layer. In addition, the presence of the coating prevented the agglomeration of nanoparticles. Furthermore, the pseudo-second-order equation governed the kinetics of drug release. Finally, the coated nanoparticles showed stronger activity against liver cancer cells (HepG2) compared to that of the naked 5-FU drug, and displayed no cytotoxicity towards 3T3 fibroblast cell lines. The results of the present study demonstrate the potential of a nano delivery system for cancer treatment.

Microbe-Mineral Interaction and Novel Proteins for Iron Oxide Mineral Reduction in the Hyperthermophilic Crenarchaeon Pyrodictium delaneyi

Understanding iron reduction in the hyperthermophilic crenarchaeon Pyrodictium delaneyi provides insight into the diversity of mechanisms used for this process and its potential impact in geothermal environments. The ability of P. delaneyi to reduce Fe(III) oxide minerals through direct contact potentially using a novel cytochrome respiratory complex and a membrane-bound molybdopterin respiratory complex sets iron reduction in this organism apart from previously described iron reduction processes.

Dissimilatory iron reduction by hyperthermophilic archaea occurs in many geothermal environments and generally relies on microbe-mineral interactions that transform various iron oxide minerals. In this study, the physiology of dissimilatory iron and nitrate reduction was examined in the hyperthermophilic crenarchaeon type strain Pyrodictium delaneyi Su06. Iron barrier experiments showed that P. delaneyi required direct contact with the Fe(III) oxide mineral ferrihydrite for reduction. The separate addition of an exogenous electron shuttle (anthraquinone-2,6-disulfonate), a metal chelator (nitrilotriacetic acid), and 75% spent cell-free supernatant did not stimulate growth with or without the barrier. Protein electrophoresis showed that the c-type cytochrome and general protein compositions of P. delaneyi changed when grown on ferrihydrite relative to nitrate. Differential proteomic analyses using tandem mass tagged protein fragments and mass spectrometry detected 660 proteins and differential production of 127 proteins. Among these, two putative membrane-bound molybdopterin-dependent oxidoreductase complexes increased in relative abundance 60- to 3,000-fold and 50- to 100-fold in cells grown on iron oxide. A putative 8-heme c-type cytochrome was 60-fold more abundant in iron-grown cells and was unique to the Pyrodictiaceae. There was also a >14,700-fold increase in a membrane transport protein in iron-grown cells. For flagellin proteins and a putative nitrate reductase, there were no changes in abundance, but a membrane nitric oxide reductase was more abundant on nitrate. These data help to elucidate the mechanisms by which hyperthermophilic crenarchaea generate energy and transfer electrons across the membrane to iron oxide minerals.

IMPORTANCE Understanding iron reduction in the hyperthermophilic crenarchaeon Pyrodictium delaneyi provides insight into the diversity of mechanisms used for this process and its potential impact in geothermal environments. The ability of P. delaneyi to reduce Fe(III) oxide minerals through direct contact potentially using a novel cytochrome respiratory complex and a membrane-bound molybdopterin respiratory complex sets iron reduction in this organism apart from previously described iron reduction processes. A model is presented where obligatory H₂ oxidation on the membrane coupled with electron transport and either Fe(III) oxide or nitrate reduction leads to the generation of a proton motive force and energy generation by oxidative phosphorylation. However, P. delaneyi cannot fix CO₂ and relies on organic compounds from its environment for biosynthesis.

Plasticenta: First evidence of microplastics in human placenta

Microplastics are particles smaller than five millimeters deriving from the degradation of plastic objects present in the environment. Microplastics can move from the environment to living organisms, including mammals. In this study, six human placentas, collected from consenting women with physiological pregnancies, were analyzed by Raman Microspectroscopy to evaluate the presence of microplastics. In total, 12 microplastic fragments (ranging from 5 to 10 μm in size), with spheric or irregular shape were found in 4 placentas (5 in the fetal side, 4 in the maternal side and 3 in the chorioamniotic membranes); all microplastics particles were characterized in terms of morphology and chemical composition. All of them were pigmented; three were identified as stained polypropylene a thermoplastic polymer, while for the other nine it was possible to identify only the pigments, which were all used for man-made coatings, paints, adhesives, plasters, finger paints, polymers and cosmetics and personal care products.

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions

Although gas exsolution is a major driving force behind explosive volcanic eruptions, viscosity is critical in controlling the escape of bubbles and switching between explosive and effusive behavior. Temperature and composition control melt viscosity, but crystallization above a critical volume (>30 volume %) can lock up the magma, triggering an explosion. Here, we present an alternative to this well-established paradigm by showing how an unexpectedly small volume of nano-sized crystals can cause a disproportionate increase in magma viscosity. Our in situ observations on a basaltic melt, rheological measurements in an analog system, and modeling demonstrate how just a few volume % of nanolites results in a marked increase in viscosity above the critical value needed for explosive fragmentation, even for a low-viscosity melt. Images of nanolites from low-viscosity explosive eruptions and an experimentally produced basaltic pumice show syn-eruptive growth, possibly nucleating a high bubble number density.

Pulsed Laser Deposition of In0.1Ga0.9N Nanoshapes by Nd:YAG Technique

In0.1Ga0.9N thin film was grown on a cheap glass substrate by the Nd:YAG pulsed laser deposition technique. The In0.1Ga0.9N thin films show the semi-crystalline structure as observed with X-ray diffraction (XRD). The surface morphology has a non-dense layer with both scattered nanospheres and agglomerated particles. These nanospheres tended to grow randomly on the glass substrate, as observed with field emission scanning electron microscopy (FESEM). The direct bandgap energy for In0.1Ga0.9N thin film was 2.08 eV, which is calculated using photoluminescence (PL) measurements. The Raman measurements illustrated two sets of phonon modes as A1(LO) and E2 high vibrational modes that are observed. The resonance behavior of the A1(LO) mode is experimentally verified and studied under laser light energy of 532 nm.

Effect of Sulfuric Acid Patination Treatment on Atmospheric Corrosion of Weathering Steel

The requirements for the formation of a protective patina on conventional weathering steels (WS) are well known in the scientific literature related to civil structures. However, these criteria are not always given due consideration when WS is used in cultural heritage, as in the case of sculptural work. An artificial patina was produced simulating artists’ working procedures using a direct patination technique, applying a solution of 10% H2SO4 on WS specimens. These were exposed for two years in the urban atmosphere of Madrid along with weathering steel specimens without artificial patina, called natural patina. The patinas generated have been analyzed using colorimetry, micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thickness measurements.The artificial patina color formed hardly differs from the color that the natural patina acquires from practically the beginning of its formation in the atmosphere of Madrid. After two years, the atmospheric corrosion rate of patinated WS is lower than 6 µm/year. The sulfuric acid treatment accelerates the protective ability of the patina with respect to the natural patina according to the ratio goethite to lepidocrocite (α/γ). Chromium-rich goethite is located in the inner part of the artificial patina as well as chromium-rich ferrihydrite. Ferrihydrite may act as a precursor of nanophasic goethite.

Reduction and Morphological Transformation of Synthetic Nanophase Iron Oxide Minerals by Hyperthermophilic Archaea

Fe(III) (oxyhydr)oxides are electron acceptors for some hyperthermophilic archaea in mildly reducing geothermal environments. However, the kinds of iron oxides that can be used, growth rates, extent of iron reduction, and the morphological changes that occur to minerals are poorly understood. The hyperthermophilic iron-reducing crenarchaea Pyrodictium delaneyi and Pyrobaculum islandicum were grown separately on six different synthetic nanophase Fe(III) (oxyhydr)oxides. For both organisms, growth on ferrihydrite produced the highest growth rates and the largest amounts of Fe(II), although P. delaneyi produced four times more Fe(II) (25 mM) than P. islandicum (6 mM). Both organisms grew on lepidocrocite and akaganéite and produced 2 and 3 mM Fe(II). Modest growth occurred for both organisms on goethite, hematite, and maghemite where ≤1 mM Fe(II) was produced. The diameters of the spherical mineral end-products following P. delaneyi growth increased by 30 nm for ferrihydrite and 50–150 nm for lepidocrocite relative to heated abiotic controls. For akaganéite, spherical particle sizes were the same for P. delaneyi-reacted samples and heated abiotic controls, but the spherical particles were more numerous in the P. delaneyi samples. For P. islandicum, there was no increase in grain size for the mineral end-products following growth on ferrihydrite, lepidocrocite, or akaganéite relative to the heated abiotic controls. High-resolution transmission electron microscopy of lattice fringes and selected-area electron diffraction of the minerals produced by both organisms when grown on ferrihydrite showed that magnetite and/or possibly maghemite were the end-products while the heated abiotic controls only contained ferrihydrite. These results expand the current view of bioavailable Fe(III) (oxyhydr)oxides for reduction by hyperthermophilic archaea when presented as synthetic nanophase minerals. They show that growth and reduction rates are inversely correlated with the iron (oxyhydr)oxide crystallinity and that iron (oxyhydr)oxide mineral transformation takes different forms for these two organisms.

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca-, Na-, Mg- and Fe-chloride brines and multi-component (Fe2 (SO4)3 ± Ca, Na, Mg, Fe, Cl, HCO3) brines at ∼21°C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe-chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials.