Iron Films Research Articles

Electrochemical behaviour of tungsten nitride thin film in phosphate buffer saline solution for application in bioelectronics

ABSTRACT Micro-supercapacitor with tungsten nitride electrode has the potential to be used in bioelectronics for fast power supply. This study examines the electrochemical behaviour of magnetron-sputtered tungsten nitride (W2N) thin film in phosphate buffer saline (PBS) solution to evaluate their corrosion rate as electrodes in micro-supercapacitors used in bioelectronics. The electrochemical behaviour of W2N was analysed using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The corrosion rate of W2N was compared with commercially pure titanium (CP-Ti) and magnetron-sputtered pure iron (Fe) film. Our results show that the corrosion current density of W2N was ∼6 times higher than CP-Ti and ∼2.5 times lower than Fe. Additionally, the charge transfer resistance of W2N was 18 times lower than that of CP-Ti and 1.3 times higher than Fe. Overall, the corrosion rate of W2N was significantly higher than CP-Ti and slightly lower than Fe. In summary, the findings suggest that W2N could be a potential candidate for micro-supercapacitor electrodes in bioelectronics. However, further studies are required to fully evaluate the biodegradation behaviour of W2N in vivo.

Industrial by-products (ferrous sulfate minerals and stone powder) can serve as amendments to remediate Cd-As paddy soil, alleviating Cd-As accumulation in rice

Our previous research has shown that industrial by-products such as ferrous sulfate mineral and stone powder as amendments can remediate Cadmium (Cd) and arsenic (As) soil. However, their role in the soil-rice system is unknown. Therefore, this article explored the effects of the combined use of industrial by-products and commercial conditioners on the accumulation of Cd-As in weakly alkaline and acidic soil-rice systems. Potted experiments shown that SL (stone powder+ferrous sulfate mineral) and SLW (stone powder+ferrous sulfate mineral+Weidikang conditioner) could reduce the availability of Cd-As in soil by adjusting soil pH and CEC, increase iron film content on the root surface, strengthening the “barrier” for fixing Cd-As. Brown rice Cd was lower than the national food safety standard of 0.20 mg kg−1 (GB2762–2022). 1 % SLW could reduce brown rice As from 1.24 mg kg−1 to 0.83 mg kg−1. The results of field experiments confirmed the conclusion of pot experiments. SL and SLW not only reduced the accumulation of Cd-As in rice but also significantly increased rice yield by 16.58 % and 11.68 %, respectively. Compared to the two types of conditioning agents sold in the market, the material costs have been reduced by 79.1 % -86.5 % and 12.4 % -43.3 %, respectively. In summary, this study demonstrates that ferrous sulfate minerals and stone powder could efficiently remediate Cd-As pollution in paddy soil under different acid-base conditions, providing an application example for the resource utilization of industrial by-products for the remediation of Cd-As pollution in paddy soil.

Applicability of energy-theta mapping in resonant soft X-ray reflectometry to probe depth dependence of oxidation state and crystallographic environment in iron oxide multilayers

In the present paper we discuss applicability of the synchrotron method of resonant x-ray reflectometry to non-destructive depth profiling of multilayer heterostructures with low optical contrast between the sublayers. The two-dimensional mapping approach comprising evaluation and measurement of reflectance as a function of photon energy and grazing angle is shown to provide a convenient way to effectively utilize the enhancement of optical contrast between the sublayers that exists at the absorption edges of chemical elements due to particular spectral shape peculiarities related to oxidation state, crystallographic environment and magnetization. In the present study the evaluation of the resonant X-ray reflectivity maps is performed using a specially developed modeling and fitting software. Estimation of the photon energy / grazing angle combinations at which the reflectance is most sensitive to the minor changes in the physical properties of the sublayers is illustrated by the example of ferroic-on-semiconductor nanoscale heterostructures composed of nanoscale film of metallic iron oxidized from either top or bottom side. The subtle differences in resonant soft x-ray reflectance caused by variation of the oxide film thickness, oxidation state and crystallographic environment are discussed. The presented approach is applicable to a large class of heterostructures composed of sublayers that can be distinguished only by the differences in their near edge X-ray absorption fine structure.

The Use of External Fields (Magnetic, Electric, and Strain) in Molecular Beam Epitaxy-The Method and Application Examples.

Molecular beam epitaxy (MBE) is a powerful tool in modern technologies, including electronic, optoelectronic, spintronic, and sensoric applications. The primary factor determining epitaxial heterostructure properties is the growth mode and the resulting atomic structure and microstructure. In this paper, we present a novel method for growing epitaxial layers and nanostructures with specific and optimized structural and magnetic properties by assisting the MBE process using electromagnetic and mechanical external stimuli: an electric field (EF), a magnetic field (MF), and a strain field (SF). The transmission of the external fields to the sample is realized using a system of specialized sample holders, advanced transfers, and dedicated manipulators. Examples of applications include the influence of MFs on the growth and anisotropy of epitaxial magnetite and iron films, the use of EFs for in situ resistivity measurements, the realization of in situ magneto-optic measurements, and the application of SFs to the structural modification of metal films on mica.

Reduction of Ferric Chloride in Yeast Growth Media, by Sugars and Aluminum

Iron compounds can be used in antimicrobial applications by exploiting the toxicity of divalent iron to living organisms due to the Fenton reaction. In this study, the growth inhibitory effects of ferrous sulfate FeSO4·7H2O and ferric chloride FeCl3·6H2O were observed on Metschnikowia clade and Saccharomyces cerevisiae yeast cells. The relatively high amount of reduced Fe3+ to Fe2+ in the growth medium determined by Mössbauer spectroscopy may contribute to the antimicrobial activity of ferric chloride. In order to test the reducing ability of sugars in the growth media of yeasts, the reaction of ferric chloride FeCl3·6H2O with sugars was investigated. In mixtures of FeCl3·6H2O and fructose, approximately two thirds of Fe3+ can be reduced to Fe2+. When the mixture of FeCl3·6H2O and fructose is placed on the surface of aluminum foil, an iron film is formed on the surface of the aluminum due to the reduction by both fructose and aluminum. The relative amount of Fe3+ which was reduced to Fe0 reached 68%.

Unconventional parametric spin-wave pumping in single-crystal iron films

Unconventional parametric spin-wave pumping in single-crystal iron films

Fabrication of Nanostructures Consisting of Composite Nanoparticles by Open-Air PLD

We present a two-step physical method for the fabrication of composite nanoparticle-based nanostructures. The proposed method is based on the pulsed laser deposition (PLD) technique performed sequentially in vacuum and in air. As a first step, thin-alloyed films of iron with noble metal were deposited by PLD in vacuum. The films were prepared by ablation of a mosaic target formed by equal iron and gold sectors. As a second step, the as-prepared alloyed films were ablated in air at atmospheric pressure as the laser beam scanned their surface. Two sets of experiments were performed in the second step, namely, by applying nanosecond (ns) and picosecond (ps) laser pulses for ablation. The structure, microstructure, morphology, and optical properties of the samples obtained were studied with respect to the laser ablation regime applied. The implementation of the ablation process in open air resulted in the formation of nanoparticle and/or nanoparticle aggregates in the plasma plume regardless of the ablation regime applied. These nanoparticles and/or nanoaggregates deposited on the substrate formed a complex porous structure. It was found that ablating FeAu films in air by ns pulses resulted in the fabrication of alloyed nanoparticles, while ablation by ps laser pulses results in separation of the metals in the alloy and further oxidation of Fe. In the latter case, the as-deposited structures also contain core–shell type nanoparticles, with the shell consisting of Fe-oxide phase. The obtained structures, regardless of the ablation regime applied, demonstrate a red-shifted plasmon resonance with respect to the plasmon resonance of pure Au nanoparticles.

Features of the Tanalyk gold placer and its primary sources (the Baymak ore-placer cluster, Southern Urals)

The article presents the results of a study of the Tanalyk placer, which is part of the Baymak ore-placer cluster. It is shown that gold is predominantly bright yellow in color and has lump-shaped, wedge-shaped, plate-shaped and wire-rod-shaped forms. In terms of granulometric composition, it belongs to the large and medium class and is characterized mainly by medium roundness. The uniformity of morphological varieties of gold in different lithological and stratigraphic horizons indicates the inheritance of gold from ancient deposits to young ones.
 Placer gold is of high quality and has a fairly consistent composition; the main impurity here is silver, the content of which varies from 0.2 to 9%. The average fineness of gold in the placer in the following areas: Baymak pond – 938, Shurinsky log – 935, Aktash log – 943, Tanalyk (lines 1502-1559) – 917. Hypergene new formations on the surfaces of gold grains are represented by high-fineness rims. A common feature for gold of all size classes is the presence in the depressions and on their surface of films of iron and manganese hydroxides, crusts of fine-grained quartz, chlorite, and less commonly biotite, in which a large number of microparticles of very high-fine gold measuring 0.1–0.5 μm were found.
 The typomorphism of schlich gold, its composition and features of the internal structure indicate that the main source of gold was gold-quartz mineralization in the zones of wall-metasomatites of the Kul-Yurt-Tau gold-pyrite deposit, gold-polymetallic and gold-barite deposits Grafskoye, Troitsk and Novo-Troitsk. The junction points of diagonal neotectonically active lineaments with meridional magma- and ore-supplying faults form polychronic and polygenic through ore-concentrating structures. Dispersed gold occurrences in these structures are placer-forming and serve as the main source of the formation of large placers.

Strong Magnetic–Dielectric Synergistic Gradient Metamaterials for Boosting Superior Multispectral Ultra‐Broadband Absorption with Low‐Frequency Compatibility

AbstractThe construction of 3D porous structures and metamaterials (MMs) is the most promising approaches to achieve broadband electromagnetic wave (EMW) absorption. However, it is still a huge challenge to achieve multispectral ultra‐broadband EMW absorption properties compatible with low‐frequency band (L‐ and S‐band) due to its ultralong wavelength and strong bypass capability. Herein, magnetic–dielectric synergistic gradient MMs (MDSGM) consisting of oriented flaky carbonyl iron (FCI) film and periodical RGO/CNT/CNF aerogel (GTFA) array are demonstrated. Benefiting from the synergistic effect of strong magnetic–dielectric loss, structural loss, and excellent impedance matching, MDSGM harvests an exciting multispectral ultra‐broadband EMW absorption performance with a remarkable effective absorption bandwidth covering the whole measured frequency of 1–40, 50–110 GHz, and 0.1–2.0 THz for the first time. The minimum RL (RLmin) reaches −40.24 dB and average RL is up to −19.3 dB (98.8% EMW being absorbed) in microwave band. Moreover, this multispectral ultra‐broadband EMW absorption property is less affected by the incident angle. This work pioneered realization of multispectral ultra‐broadband EMW absorption compatible with low‐frequency, which provides a great thrust for the development of stealth technology in the upcoming smart era.

Antibacterial activities of titanium dioxide (TiO2) nanotube with planar titanium silver (TiAg) to prevent orthopedic implant infection

BackgroundOrthopedic implant infection has become a common catastrophic complication after various orthopedic implants, which can lead to prolonged use of antibiotics and even surgical failure. The quality of care (QoC) of orthopedic implant infection is very important.MethodsTitanium dioxide (TiO2) nanotube array with planar TiAg was prepared, and their antibacterial rates were tested. 400 patients hospitalized in the Department of Orthopedics of Wuhan Fourth Hospital from May 2019 to May 2020 were selected as controls (before QoC evaluation system of orthopedics), and 400 patients hospitalized from June 2020 to June 2021 were selected as observation group (after QoC evaluation system of orthopedics).ResultsRegardless of Staphylococcus aureus or Escherichia coli, the antibacterial rate of TiO2 nanotube array with planar TiAg was clearly higher than that of pure iron film on the 10th and 20th days (P < 0.05). The accuracy of hospitalization assessment, disease assessment, adverse event intervention, nursing record filing and nursing satisfaction in observation group were higher as against controls (P < 0.05).ConclusionThe TiO2 nanotube array with planar TiAg has good antibacterial property, which can effectively prevent orthopedic implant infection. The construction of QoC evaluation system for orthopedic specialists can effectively improve the QoC of orthopedic specialists.

Effect of organic component (tartrate) addition on cerium nitrate's ability to inhibit corrosion of mild steel in NaCl solution

Cerium tartrate (CeTar), produced in this study by precipitating cerium nitrate with potassium sodium tartrate (KNaTar), was examined as a corrosion inhibitor. Weight loss tests show inhibition efficiency of 71.7% with Ce(NO3)3 and 88.7% with CeTar inhibitor for one-month exposure to mild steel in 7 g/L NaCl solution. The inhibition efficiency drops to 28.6% with the former and remains around 87% with the latter inhibitor after six months of exposure. Similar results from electrochemical testing indicate that the inhibition efficiency decreases by adding cerium nitrate. Still, the cerium tartrate inhibitor demonstrates a nearly constant inhibition efficiency for up to 30 d, i.e., ≈90%. Electrochemical impedance spectroscopy (EIS) performed in these cases shows the following results: (i) with cerium nitrate, a film of iron and cerium oxide, which on prolonged exposure diminishes, and (ii) with cerium tartrate, the formation of a bimetallic film (Fe-tartrate-Ce) and a mixture of cerium hydroxide and iron oxide that protects steel for a longer duration. These inferences are based on the analyses of scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron (XPS), and Raman spectroscopy results.

Microstructure and Magnetism of Heavily Helium-Ion Irradiated Epitaxial Iron Films

This study reports on the microstructure and magnetism of pure iron irradiated with high doses of helium ions. Iron alloys are important structural materials used as components in fusion reactors, and a comprehensive database of their various properties has been developed. But little has been investigated on magnetic properties, in particular, the effects of high doses and helium cavities are lacking. Single-crystal iron films, with a thickness of 200 nm, were prepared using the ultra-high vacuum evaporation method. These films were then irradiated with 30 keV He+ ions at room temperature up to a dose of 18 dpa. X-ray diffraction measurements and cross-sectional transmission electron microscope observations revealed significant microstructural changes, including a large lattice expansion perpendicular to the film plane and the formation of high-density cavities after irradiation. However, the saturation magnetization and the shape of the magnetization curve showed almost no change, indicating the robustness of the magnetic properties of iron.

Design and Processing as Ultrathin Films of a Sublimable Iron(II) Spin Crossover Material Exhibiting Efficient and Fast Light-Induced Spin Transition.

Materials based on spin crossover (SCO) molecules have centered the attention in molecular magnetism for more than 40 years as they provide unique examples of multifunctional and stimuli-responsive materials, which can be then integrated into electronic devices to exploit their molecular bistability. This process often requires the preparation of thermally stable SCO molecules that can sublime and remain intact in contact with surfaces. However, the number of robust sublimable SCO molecules is still very scarce. Here, we report a novel example of this kind. It is based on a neutral iron(II) coordination complex formulated as [Fe(neoim)2], where neoimH is the ionogenic ligand 2-(1H-imidazol-2-yl)-9-methyl-1,10-phenanthroline. In the first part, a comprehensive study, which covers the synthesis and magnetostructural characterization of the [Fe(neoim)2] complex as a bulk microcrystalline material, is reported. Then, in the second part, we investigate the suitability of this material to form thin films through high-vacuum sublimation. Finally, the retainment of all present SCO capabilities in the bulk when the material is processed is thoroughly studied by means of X-ray absorption spectroscopy. In particular, a very efficient and fast light-induced spin transition (LIESST effect) has been observed, even for ultrathin films of 15 nm.

Corrosion-driven droplet wetting on iron nanolayers

The classical Evans’ drop describes a drop of aqueous salt solution, placed on a bulk metal surface where it displays a corrosion pit that grows over time producing further oxide deposits from the metal dissolution. We focus here on the corrosion-induced droplet spreading using iron nanolayers whose semi-transparency allowed us to monitor both iron corrosion propagation and electrolyte droplet behavior by simple optical means. We thus observed that pits grow under the droplet and merge into a corrosion front. This front reached the triple contact line and drove a non radial spreading, until it propagated outside the immobile droplet. Such chemically-active wetting is only observed in the presence of a conductive substrate that provides strong adhesion of the iron nanofilm to the substrate. By revisiting the classic Evan’s drop experiment on thick iron film, a weaker corrosion-driven droplet spreading is also identified. These results require further investigations, but they clearly open up new perspectives on substrate wetting by corrosion-like electrochemical reactions at the nanometer scale.

Microbe interactions drive the formation of floating iron films in circumneutral wetlands

Floating iron (Fe) films are widely found in wetlands that can form oxic-anoxic boundaries under circumneutral conditions. These films play a crucial role in the redox transformations and bioavailability of nutrients and trace metals. Current studies mainly focus on chemical oxidation during Fe film formation under circumneutral conditions. The functional microorganisms and associated microbial processes involved in Fe film formation have yet to be investigated in detail. Here, we investigated the microbial communities and involved microbial processes for the formation of floating Fe films in wetlands. Ferrihydrite was the dominant Fe(III) phase in films, accompanied by moderate levels of carbon and silicon. The Fe species and microbial analysis indicated that Fe films contain mixed-valent Fe and can form biotically. Microbial community analysis showed that the dominant genera in these Fe films were Fe-oxidizing and reducing bacteria and methanotrophs, including Leptothrix, Ferriphasclus, Gallionella, Geobacter and Methylococcales. Leptothrix, Ferriphasclus and Gallionella, as classical Fe(II)-oxidizing bacteria (FeOB), can oxidize Fe(II) with limited oxygen and form special structures that are consistent with Fe film morphology. Geobacter can provide a source of Fe(II) for FeOB growth, and Methylococcales can perform methane oxidation to provide energy for Fe cycling. The high ratios of Gallionella- and Geobacter-related microorganisms and carbon fixation genes proved the contribution of potential of Fe cycling and autotrophic microbial communities to the formation of Fe films. The diversity of microbial community suggested that Fe(II) oxidation could trigger carbon fixation, while Fe(III) reduction accelerated Fe and carbon cycling through anaerobic respiration and autotrophic chemosynthesis. These results highlight the contribution of these multiple microbial processes to Fe and carbon cycling during the formation of floating Fe films in wetlands. However, further studies are required to fully elucidate the interaction of functional microorganisms involved in floating film formation and their biogeochemical role in wetlands.

Effects of Equal Amounts Silicon Fertilizer Application on Soil Bioavailability of Cadmium and Cadmium Uptake by Rice

Cadmium (Cd) contamination of paddy fields is a global concern, as it can cause the accumulation of Cd in food. To explore the effects of equal application of silicon fertilizers on the bioavailability of cadmium and soil Cd uptake at different growth stages of rice, a field experiment was conducted with five silicon fertilizers under the same silicon dose (225 kg·hm-2). The results revealed that the Cd contents in roots, stems, and leaves increased with the extension of the rice growth stage. The application of silicon fertilizers reduced the Cd contents in roots, stems, and leaves in brown rice by 14.9%, 28.2%, and 12.2%, respectively. Compared with that in the control, the Cd content of brown rice in the SiCaMgFe and SiW treatments was decreased by 21.1% (P<0.05) and 21.2% (P<0.05), respectively. Similarly, Cd content in iron plaque (DCB-Cd) increased with the extension of the rice growth period, which accounted for 15.8%-42.8% of the total Cd content in roots, and the DCB-Cd content was different in each stage of rice. The content of exchangeable Cd (Exc-Cd) in soil at the mature stage of rice decreased by 36.4%, and the other fractions increased by 12.5%-48.2%. The results showed significant negative correlations between the Cd contents and Si in roots, DCB-Cd and soil available Cd and available Si, Exc-Cd and Car-Cd, and soil available Cd and pH value. Cd content in roots was positively correlated with DCB-Cd. With the equal dose of silicon fertilizer, the treatments of SiCaMgFe and SiW could effectively reduce the Cd content in rice. The application of silicon fertilizer promoted the transfer of Exc-Cd to Carb-Cd by increasing the soil pH value and the soil available Si content, meanwhile reducing the soil available Cd, Exc-Cd contents, the adsorption of Cd by the iron film on the root surface, and the adsorption capacity of iron plaque and root, thereby reducing the absorption of Cd by rice.

Computer simulation of Fe epitaxial films on a Cu(100) substrate

The article addresses the problem of modeling thin epitaxial iron films on a Cu (100) substrate by calculating the surface potential. The purpose of the simulation is to determine the film structure. The model uses the paired Lennard-Jones potential to describe the interatomic interaction. We calculate the surface potential of the copper substrate using the first 10 surface atomic layers. The iron atoms in the first layer are placed in the minima of the surface potential. The surface potential of the monoatomic iron layer and the 9 copper layers underneath determine the position of the second iron layer. The position of atoms in the following layers is formed on the basis of similar calculations. Calculations show that the copper substrate stabilizes the fcc crystal lattice in the iron film at low temperatures. Bulk iron samples at low temperatures have a bcc crystal lattice. The period of the iron lattice along the substrate is equal to the period of the copper lattice. The crystal lattice period of iron perpendicular to the substrate has an intermediate value between the values for copper and for γ-ferrum. The interface effect causes additional vertical deformations in the first two layers of iron above the substrate.

Lasing in Zn-doped GaAs nanowires on an iron film

In this work, we demonstrate optically pumped lasing in highly Zn-doped GaAs nanowires (NWs) lying on an iron film. The conically shaped NWs are first covered with an 8 nm thick Al2O3 film to prevent atmospheric oxidation and mitigate band-bending effects. Multimode and single-mode lasing have been observed for NWs with a length greater or smaller than 2 μm, respectively. Finite difference time domain calculations reveal a weak electric field enhancement in the Al2O3 layer at the NW/iron film interface for the lasing modes. The high Zn acceptor concentration in the NWs provides enhanced radiative efficiency and enables lasing on the iron film despite plasmonic losses. Our results open avenues for integrating NW lasers on ferromagnetic substrates to achieve new functionalities, such as magnetic field-induced modulation.

Topology-induced chiral photon emission from a large-scale meron lattice

AbstractMerons are a class of topologically protected particle-like structures created in in-plane magnetized magnetic films. The structures can act as information carriers and could be used for magnetic storage. However, the development of such applications is hampered by limitations in the size, thermal stability and magnetic-field requirements of the systems. Here we report the construction of millimetre-scale meron lattices that are stable at room temperature and under zero magnetic field. Our system is based on a trilayer structure composed of a thin iron film sandwiched between films of palladium and magnesium oxide (Pd/Fe/MgO) on a gallium nitride wafer. It is fabricated using a molecular-beam epitaxy approach that is assisted by a high magnetic field, which leads to a strong Dzyaloshinskii–Moriya interaction. The lattices can be used for chirality transfer from merons to electrons and then to photons, and we show that the meron lattices can be used as spin injectors in nitride-based light-emitting diodes. The topology-induced spin light-emitting diode can provide 22.5% circularly polarized electroluminescence at room temperature and under zero magnetic field.

Design and Numerical Analysis of Ultra-Broadband Absorber with Chimney Type Structure

In this study, a novel ultra-broadband absorber is suggested and numerically analyzed to demonstrate that the suggested absorber can achieve an average absorbance of 98.6% in the visible to near-infrared wavelength range (496–2100 nm). The structure of the proposed new ultra-wideband absorber consists of four thin films of silicon dioxide (SiO2), iron (Fe), magnesium fluoride (MgF2), and chromium (Cr). We have examined the structure’s electromagnetic field intensity distribution at numerous selected optical wavelengths and the influence of various structural parameters on the absorption performance of the absorber to offer a physical mechanism underlying the ultra-broadband absorption effect. Furthermore, in the presence of high-performance absorption, the structure has the effect of stabilizing absorption at large angles of incidence and is polarization-independent at vertical angles of incidence. The study also assesses the solar absorption capability of this structure, indicating that the structure has potential applications in solar absorption, such as solar energy collection and conversion, solar power generation, and thermal emitters.