Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Evaluating structure selection in the hydrothermal growth of FeS₂ pyrite and marcasite.

ABSTRACT: While the ab initio prediction of the properties of solids and their optimization towards new proposed materials is becoming established, little predictive theory exists as to which metastable materials can be made and how, impeding their experimental realization. Here we propose a quasi-thermodynamic framework for predicting the hydrothermal synthetic accessibility of metastable materials and apply this model to understanding the phase selection between the pyrite and marcasite polymorphs of FeS₂. We demonstrate that phase selection in this system can be explained by the surface stability of the two phases as a function of ambient pH within nano-size regimes relevant to nucleation. This result suggests that a first-principles understanding of nano-size phase stability in realistic synthesis environments can serve to explain or predict the synthetic accessibility of structural polymorphs, providing a guideline to experimental synthesis via efficient computational materials design.

SUBMITTER: Kitchaev DA

PROVIDER: S-EPMC5171653 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Evaluating structure selection in the hydrothermal growth of FeS2 pyrite and marcasite.

Kitchaev Daniil A DA Ceder Gerbrand G

Nature communications 20161214

While the ab initio prediction of the properties of solids and their optimization towards new proposed materials is becoming established, little predictive theory exists as to which metastable materials can be made and how, impeding their experimental realization. Here we propose a quasi-thermodynamic framework for predicting the hydrothermal synthetic accessibility of metastable materials and apply this model to understanding the phase selection between the pyrite and marcasite polymorphs of Fe ...[more]

PMID: 27966547

Similar Datasets

Symmetry-defying iron pyrite (FeS?) nanocrystals through oriented attachment.

Project description:Iron pyrite (fool's gold, FeS?) is a promising earth abundant and environmentally benign semiconductor material that shows promise as a strong and broad absorber for photovoltaics and high energy density cathode material for batteries. However, controlling FeS? nanocrystal formation (composition, size, shape, stoichiometry, etc.) and defect mitigation still remains a challenge. These problems represent significant limitations in the ability to control electrical, optical and electrochemical properties to exploit pyrite's full potential for sustainable energy applications. Here, we report a symmetry-defying oriented attachment FeS? nanocrystal growth by examining the nanostructure evolution and recrystallization to uncover how the shape, size and defects of FeS? nanocrystals changes during growth. It is demonstrated that a well-controlled reaction temperature and annealing time results in polycrystal-to-monocrystal formation and defect annihilation, which correlates with the performance of photoresponse devices. This knowledge opens up a new tactic to address pyrite's known defect problems.

| S-EPMC3697776 | biostudies-literature

Pyrite formation from FeS and H2S is mediated through microbial redox activity.

Project description:The exergonic reaction of FeS with H2S to form FeS2 (pyrite) and H2 was postulated to have operated as an early form of energy metabolism on primordial Earth. Since the Archean, sedimentary pyrite formation has played a major role in the global iron and sulfur cycles, with direct impact on the redox chemistry of the atmosphere. However, the mechanism of sedimentary pyrite formation is still being debated. We present microbial enrichment cultures which grew with FeS, H2S, and CO2 as their sole substrates to produce FeS2 and CH4 Cultures grew over periods of 3 to 8 mo to cell densities of up to 2 to 9 × 106 cells per mL-1 Transformation of FeS with H2S to FeS2 was followed by 57Fe Mössbauer spectroscopy and showed a clear biological temperature profile with maximum activity at 28 °C and decreasing activities toward 4 °C and 60 °C. CH4 was formed concomitantly with FeS2 and exhibited the same temperature dependence. Addition of either penicillin or 2-bromoethanesulfonate inhibited both FeS2 and CH4 production, indicating a coupling of overall pyrite formation to methanogenesis. This hypothesis was supported by a 16S rRNA gene-based phylogenetic analysis, which identified at least one archaeal and five bacterial species. The archaeon was closely related to the hydrogenotrophic methanogen Methanospirillum stamsii, while the bacteria were most closely related to sulfate-reducing Deltaproteobacteria, as well as uncultured Firmicutes and Actinobacteria. Our results show that pyrite formation can be mediated at ambient temperature through a microbially catalyzed redox process, which may serve as a model for a postulated primordial iron-sulfur world.

| S-EPMC6452648 | biostudies-literature

One-Stage Hydrothermal Growth and Characterization of Epitaxial LaMnO3 Films on SrTiO3 Substrate.

Project description:Epitaxial LaMnO3 thin films were grown on SrTiO3 substrate using a one-stage hydrothermal route from La(NO3)3, MnCl2 and KMnO4 in an aqueous solution of 10 M KOH at 340 °C. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) indicate full coverage of LaMnO3 on the substrate. X-ray diffraction in the symmetric ω/2θ mode suggests the film has an out-of-plane preferred orientation along the [001] direction of the substrate. The LaMnO3 epitaxial thin film growth mechanism is proposed based on the analysis of the atomic sharp interface formed between LaMnO3 and the SrTiO3 substrate, as seen by aberration-corrected scanning transmission electron microscopy (AC-STEM) imaging in combination with electronic energy loss spectroscopy (EELS). Compared with the conventional vapor deposition methods, the one-stage hydrothermal route opens up a new way to fabricate complex oxide epitaxial heterostructures.

| S-EPMC9457439 | biostudies-literature

FeS/FeS2 nanoscale structures synthesized in one step from Fe(ll) dithiocarbamate complexes as a single source precursor.

Project description:Nanoscale FeS and FeS2 mixed phases were synthesized by one-pot decomposition of (N-anil-N-piperldtc)Fe1 as FeS#1), (N-piperldtc)Fe2 as FeS#2) and (N-anildtc)Fe3 as FeS#3) complexes as precursors, with the help of tri-n-octylphosphine oxide (TOPO) coordinating solvent. Their morphology, stability, size, optical and structural characteristics were observed using various material characterization instruments. In comparison to the FeS#2 nano-flower shape, FeS#1 and FeS#3 have a uniform nano-rod shape. A one-step decomposition pattern was obtained from the thermal gravimetric analysis (TGA) results with 3% final mass residual. The high-resolution transmission electron microscopy (HRTEM) image reveals an aggregation and size diameter of around 14.47-30.25 nm for the three samples. The optical response between 3.8 and 4.2 eV from the three samples shows that they are inconsiderable materials for solar cells application. The diffraction peaks for the three samples matched well with the FeS/FeS2. These nanoscale materials can be used in a variety of applications, including lithium-ion batteries, biosensors, hydrogen evolution, and multifunctional nanocomposite materials.

| S-EPMC9755493 | biostudies-literature

Evaluating the psychometric properties of the iconographical falls efficacy scale (ICON-FES).

Project description:OBJECTIVE:This study aims to analyze the construct and content validity of the Iconographical Falls Efficacy Scale (Icon-FES) in order to measure the fear of falling in community-dwelling older adults. METHODS:The Icon-FES was applied to 333 older adults. An exploratory factor analysis was performed to assess internal consistency. Item response theory (IRT) and confirmatory factor analysis (CFA) were used to evaluate the consistency of the questionnaire and whether it corresponded satisfactorily to the construct "concern about falling." Concurrent validity with the Falls Efficacy Scale-International (FES-I) and convergent validity with the Senior Fitness Test (SFT) were also assessed. Receiving operator characteristic (ROC) curves were used to determine the sensitivity and specificity. RESULTS:The structural model of the 30-item and 10-item Icon-FES showed some theoretical fragility. The final model of the new short version of the Icon-FES consisted of 13 items, yielding a theoretically satisfactory structural model. Validity analyses indicated that the 13-item Icon-FES had a moderate relationship with the SFT, a strong relationship with the FES-I, and good sensitivity and specificity for a history of falls. CONCLUSION:The 13-item Icon-FES has excellent psychometric properties for measuring fear of falling in community-dwelling older adults. It can be recommended as a screening tool for fear of falling for both research and clinical purposes.

| S-EPMC7061319 | biostudies-literature

Hydrothermal control, characterization, growth mechanism, and photoluminescence properties of highly crystalline 1D Eu(OH)3 nanostructures.

Project description:Six types of 1D Eu(OH)3 nanostructures with typical morphologies, including short hexagonal prism, long hexagonal prism, coiling rod, short rod, long rod, and nanobunch, were synthesized via the hydrothermal route using EuCl3 and NaOH as raw materials. The morphologies, sizes, structures, and compositions of the as-prepared products were characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and Fourier transform infrared spectroscopy. The effects of different reaction conditions on the morphology and size of the products were also investigated, and the relevant growth mechanism was assessed. Results showed that the geometric features of Eu(OH)3 are affected by the precursor pH and reaction time and temperature; among these factors, precursor pH played a key role in controlling the morphologies of the resulting Eu(OH)3 nanostructures. The fluorescence properties of the six Eu(OH)3 nanostructures were analyzed, and typical photoluminescence emission peaks due to the 5D0-7F J (J = 1-4) transition of Eu3+ were noted. Moreover, the intensity of the emission peak of the products at 616 nm was slightly weaker than that at 592 nm. This finding reflects the high site symmetry of Eu3+ in the Eu(OH)3 nanostructures.

| S-EPMC9056699 | biostudies-literature

Air-Stable 2D Intrinsic Ferromagnetic Ta3FeS6 with Four Months Durability.

Project description:2D ferromagnetic materials provide an important platform for the fundamental magnetic research at atomic-layer thickness which has great prospects for next-generation spintronic devices. However, the currently discovered 2D ferromagnetic materials (such as, CrI3, Cr2Ge2Te6, and Fe3GeTe2) suffer from poor air stability, which hinders their practical application. Herein, intrinsic long-range ferromagnetic order in 2D Ta3FeS6 is reported, which exhibits ultrahigh stability under the atmospheric environment. The intrinsic ferromagnetism of few-layer Ta3FeS6 is revealed by polar magneto-optical Kerr effect measurement, which exhibits giant MOKE response and has Curie temperature of ≈80 K. More importantly, few-layer Ta3FeS6 nanosheet exhibits excellent air stability and its ferromagnetism remains unchanged after 4 months of aging under the atmosphere. This work enriches the family of 2D ferromagnetic materials, which will facilitate the research progress of spintronics.

| S-EPMC7675181 | biostudies-literature

Effective Mass for Holes in Paramagnetic, Plasmonic Cu5FeS4 Semiconductor Nanocrystals.

Project description:The impact of a magneto-structural phase transition on the carrier effective mass in Cu5FeS4 plasmonic semiconductor nanocrystals was examined using Magnetic Circular Dichroism (MCD). Through MCD, the sample was confirmed as p-type from variable temperature studies from 1.8 - 75 K. Magnetic field dependent behavior is observed, showing an asymptotic behavior at high field with an m∗ value 5.98 m∗∕me at 10 T and 2.73 m∗∕me at 2 T. Experimentally obtained results are holistically compared to SQUID magnetization data and DFT results, highlighting a dependency on vacancy driven polaronic coupling, magnetocrystalline anisotropy, and plasmon coupling of the magnetic field all contributing to an overall decrease in the hole mean free path dependent on the magnetic field applied to Cu5FeS4.

| S-EPMC10410696 | biostudies-literature

Quantifying Fenton reaction pathways driven by self-generated H2O2 on pyrite surfaces.

Project description:Oxidation of pyrite (FeS2) plays a significant role in the redox cycling of iron and sulfur on Earth and is the primary cause of acid mine drainage (AMD). It has been established that this process involves multi-step electron-transfer reactions between surface defects and adsorbed O2 and H2O, releasing sulfoxy species (e.g., S2O32-, SO42-) and ferrous iron (Fe2+) to the solution and also producing intermediate by-products, such as hydrogen peroxide (H2O2) and other reactive oxygen species (ROS), however, our understanding of the kinetics of these transient species is still limited. We investigated the kinetics of H2O2 formation in aqueous suspensions of FeS2 microparticles by monitoring, in real time, the H2O2 and dissolved O2 concentration under oxic and anoxic conditions using amperometric microsensors. Additional spectroscopic and structural analyses were done to track the dependencies between the process of FeS2 dissolution and the degradation of H2O2 through the Fenton reaction. Based on our experimental results, we built a kinetic model which explains the observed trend of H2O2, showing that FeS2 dissolution can act as a natural Fenton reagent, influencing the oxidation of third-party species during the long term evolution of geochemical systems, even in oxygen-limited environments.

| S-EPMC5337962 | biostudies-literature

Low-Temperature Hydrothermal Growth of ZnO Nanowires on AZO Substrates for FACsPb(IBr)3 Perovskite Solar Cells.

Project description:Electron and hole transport layers (ETL and HTL) play an essential role in shaping the photovoltaic performance of perovskite solar cells. While compact metal oxide ETL have been largely explored in planar n-i-p device architectures, aligned nanowires or nanorods remain highly relevant for efficient charge extraction and directional transport. In this study, we have systematically grown ZnO nanowires (ZnO NWs) over aluminum-doped zinc oxide (AZO) substrates using a low-temperature method, hydrothermal growth (HTG). The main growth parameters were varied, such as hydrothermal precursors concentrations (zinc nitrate hexahydrate, hexamethylenetetramine, polyethylenimine) and growing time, in order to finely control NW properties (length, diameter, density, and void fraction). The results show that ZnO NWs grown on AZO substrates offer highly dense, well-aligned nanowires of high crystallinity compared to conventional substrates such as FTO, while demonstrating efficient FACsPb(IBr)3 perovskite device performance, without the requirement of conventional compact hole blocking layers. The device performances are discussed based on NW properties, including void fraction and aspect ratio (NW length over diameter). Finally, AZO/ZnO NW-based devices were fabricated with a recent HTL material based on a carbazole moiety (Cz-Pyr) and compared to the spiro-OMeTAD reference. Our study shows that the Cz-Pyr-based device provides similar performance to that of spiro-OMeTAD while demonstrating a promising stability in ambient conditions and under continuous illumination, as revealed by a preliminary aging test.

| S-EPMC9229726 | biostudies-literature