scholarly journals Biomineralization of Cu2S Nanoparticles by Geobacter sulfurreducens

2020 ◽  
Vol 86 (18) ◽  
Author(s):  
Richard L. Kimber ◽  
Heath Bagshaw ◽  
Kurt Smith ◽  
Dawn M. Buchanan ◽  
Victoria S. Coker ◽  
...  
Keyword(s):  
Biogeochemical Cycling ◽  
Geobacter Sulfurreducens ◽  
Edge Structure ◽  
Colloidal Transport ◽  
Content Type ◽  
Anoxic Conditions ◽  
X Ray ◽  
Sulfate Reducing ◽  
Wide Range ◽  
X Ray Absorption

ABSTRACT Biomineralization of Cu has been shown to control contaminant dynamics and transport in soils. However, very little is known about the role that subsurface microorganisms may play in the biogeochemical cycling of Cu. In this study, we investigate the bioreduction of Cu(II) by the subsurface metal-reducing bacterium Geobacter sulfurreducens. Rapid removal of Cu from solution was observed in cell suspensions of G. sulfurreducens when Cu(II) was supplied, while transmission electron microscopy (TEM) analyses showed the formation of electron-dense nanoparticles associated with the cell surface. Energy-dispersive X-ray spectroscopy (EDX) point analysis and EDX spectrum image maps revealed that the nanoparticles are rich in both Cu and S. This finding was confirmed by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses, which identified the nanoparticles as Cu2S. Biomineralization of CuxS nanoparticles in soils has been reported to enhance the colloidal transport of a number of contaminants, including Pb, Cd, and Hg. However, formation of these CuxS nanoparticles has only been observed under sulfate-reducing conditions and could not be repeated using isolates of implicated organisms. As G. sulfurreducens is unable to respire sulfate, and no reducible sulfur was supplied to the cells, these data suggest a novel mechanism for the biomineralization of Cu2S under anoxic conditions. The implications of these findings for the biogeochemical cycling of Cu and other metals as well as the green production of Cu catalysts are discussed. IMPORTANCE Dissimilatory metal-reducing bacteria are ubiquitous in soils and aquifers and are known to utilize a wide range of metals as terminal electron acceptors. These transformations play an important role in the biogeochemical cycling of metals in pristine and contaminated environments and can be harnessed for bioremediation and metal bioprocessing purposes. However, relatively little is known about their interactions with Cu. As a trace element that becomes toxic in excess, Cu can adversely affect soil biota and fertility. In addition, biomineralization of Cu nanoparticles has been reported to enhance the mobilization of other toxic metals. Here, we demonstrate that when supplied with acetate under anoxic conditions, the model metal-reducing bacterium Geobacter sulfurreducens can transform soluble Cu(II) to Cu2S nanoparticles. This study provides new insights into Cu biomineralization by microorganisms and suggests that contaminant mobilization enhanced by Cu biomineralization could be facilitated by Geobacter species and related organisms.

Phosphorus L 2,3-edge XANES: overview of reference compounds

2009 ◽  
Vol 16 (2) ◽  
pp. 247-259 ◽  
Author(s):  
Jens Kruse ◽  
Peter Leinweber ◽  
Kai-Uwe Eckhardt ◽  
Frauke Godlinski ◽  
Yongfeng Hu ◽  
...  
Keyword(s):  
Spectral Features ◽  
Edge Structure ◽  
Complex Samples ◽  
Distinctive Features ◽  
X Ray ◽  
Wide Range ◽  
Element Speciation ◽  
Unknown Composition ◽  
Almost All ◽  
X Ray Absorption

Synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy is becoming an increasingly used tool for the element speciation in complex samples. For phosphorus (P) almost all XANES measurements have been carried out at the K-edge. The small number of distinctive features at the P K-edge makes in some cases the identification of different P forms difficult or impossible. As indicated by a few previous studies, the P L 2,3-edge spectra were richer in spectral features than those of the P K-edge. However, experimentally consistent spectra of a wide range of reference compounds have not been published so far. In this study a library of spectral features is presented for a number of mineral P, organic P and P-bearing minerals for fingerprinting identification. Furthermore, the effect of radiation damage is shown for three compounds and measures are proposed to reduce it. The spectra library provided lays a basis for the identification of individual P forms in samples of unknown composition for a variety of scientific areas.

Microstructure of TiC/Amorphous Hydrocarbon Nanocomposite Coatings

2000 ◽  
Vol 6 (S2) ◽  
pp. 440-441
Author(s):  
D. M. Cao ◽  
J. C. Jiang ◽  
B. Feng ◽  
W. J. Meng
Keyword(s):  
Inductively Coupled Plasma ◽  
High Hardness ◽  
Ceramic Surface ◽  
Edge Structure ◽  
X Ray ◽  
Inductively Coupled ◽  
Transmission Electron ◽  
Wide Range ◽  
Mechanical Components ◽  
X Ray Absorption

Application of an appropriate ceramic surface coating to mechanical components such as bearings and gears can provide longer life and increased performance reliability. Metal-containing hydrocarbon (Me-C:H) coatings possess high hardness, together with low friction and low wear rate. They have also been suggested to adhere better to metallic substrates. This combination of attractive mechanical/tribological properties makes Me-C:H coatings potentially useful for surface modification of a wide range of mechanical components.Using the technique of inductively coupled plasma (ICP) assisted vapor deposition[1], we have synthesized Ti-containing hydrocarbon (Ti-C:H) coatings with a wide range of Ti compositions[2]. Coating mechanical properties such as modulus and hardness have been measured by the technique of nanoindentation and correlated to Ti and hydrogen compositions[2,3].We have performed detailed microstructural examination of Ti-C:H coatings by transmission electron microscopy (TEM), Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, and X-ray Absorption Near Edge Structure (XANES) spectroscopy.

scholarly journals X-Ray Absorption Near-Edge Structure (XANES) Spectroscopy Study of the Interaction of Silver Ions with Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli

2013 ◽  
Vol 79 (20) ◽  
pp. 6385-6390 ◽  
Author(s):  
Gudrun Lisa Bovenkamp ◽  
Ulrike Zanzen ◽  
Katla Sai Krishna ◽  
Josef Hormes ◽  
Alexander Prange
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Listeria Monocytogenes ◽  
Silver Ions ◽  
Xanes Spectroscopy ◽  
Gram Positive ◽  
Edge Structure ◽  
Content Type ◽  
X Ray ◽  
X Ray Absorption

ABSTRACTSilver ions are widely used as antibacterial agents, but the basic molecular mechanism of this effect is still poorly understood. X-ray absorption near-edge structure (XANES) spectroscopy at the AgLIII, SK, and PKedges reveals the chemical forms of silver inStaphylococcus aureusandEscherichia coli(Ag+treated). The AgLIII-edge XANES spectra of the bacteria are all slightly different and very different from the spectra of silver ions (silver nitrate and silver acetate), which confirms that a reaction occurs. Death or inactivation of bacteria was observed by plate counting and light microscopy. Silver bonding to sulfhydryl groups (Ag-S) in cysteine and Ag-N or Ag-O bonding in histidine, alanine, anddl-aspartic acid was detected by using synthesized silver-amino acids. Significantly lower silver-cysteine content, coupled with higher silver-histidine content, in Gram-positiveS. aureusandListeria monocytogenescells indicates that the peptidoglycan multilayer could be buffering the biocidal effect of silver on Gram-positive bacteria, at least in part. Bonding of silver to phosphate groups was not detected. Interaction with DNA or proteins can occur through Ag-N bonding. The formation of silver-cysteine can be confirmed for both bacterial cell types, which supports the hypothesis that enzyme-catalyzed reactions and the electron transport chain within the cell are disrupted.

Tribological behaviours of surface-modified serpentine powder as lubricant additive

2016 ◽  
Vol 68 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Yawen Zhang ◽  
Zhipeng Li ◽  
Jincan Yan ◽  
Tianhui Ren ◽  
Yidong Zhao
Keyword(s):  
Thermo Gravimetric Analysis ◽  
Lubricant Additives ◽  
Aliphatic Acid ◽  
Gravimetric Analysis ◽  
Edge Structure ◽  
Content Type ◽  
X Ray ◽  
Grafting Ratio ◽  
Surface Modified ◽  
X Ray Absorption

Purpose – The aim of this paper is to study the tribological performance and self-repairing performance of surface-modified nanoscale serpentine powders as lubricant additives in the mineral base oil (5-CST). Design/methodology/approach – Fourier transform infrared spectroscopy spectra and thermo-gravimetric analysis of both modified and unmodified serpentine were performed to analyse their grafting ratio and suspension after modified using a long-chain naphthene aliphatic acid. The tribological properties of surface-modified serpentine as lubricant additives in 5-CST were evaluated and the worn surfaces were investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES). Findings – The results show that the serpentine particles have high grafting ratio, improving the dispersity in 5-CST. When the serpentine concentration of 1.00 weight per cent is used as additives in 5-CST, friction coefficient reduces by 14.80 per cent under 294 N and wear scar diameter (WSD) decreases by 11.82 per cent. The results of X-ray absorption near edge structure and XANES show that the adsorption and tribochemical reactions occur to form self-repairing lubrication films. Originality/value – The paper illustrates a tribofilm form on the rubbed surface, which is responsible for the decrease in friction and wear, mainly containing iron oxides, silicon oxides, magnesium oxides and organic compounds. The results are useful for further applications in advanced environmental friendly lubricating oils and additives.

Tribofilms Generated From ZDDP and DDP on Steel Surfaces: Part 1 — Growth, Wear and Morphology

2005 ◽  
Author(s):  
Z. Zhang ◽  
E. S. Yamaguchi ◽  
M. Kasrai ◽  
G. M. Bancroft
Keyword(s):  
Atomic Force Microscopy ◽  
Photoelectron Spectroscopy ◽  
Zinc Dialkyldithiophosphate ◽  
Edge Structure ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Wide Range ◽  
Steel Surfaces ◽  
X Ray Absorption

The growth and morphology of tribofilms, generated from zinc dialkyldithiophosphate (ZDDP) and an ashless dialkyldithiophosphate (DDP) over a wide range of rubbing times (10 seconds to 10 hours) and concentrations (0.1 to 5 wt % ZDDP), have been examined using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption near edge structure (XANES) spectroscopy at the O, P and S K-edges, and the P, S, and Fe L-edges. The physical aspects of the growth and morphology of the tribofilms will be presented here (Part I) and the chemistry of the films will be discussed in (Part II).

X-ray absorption spectroscopy principles and practical use in materials analysis

2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Wolfgang Grünert ◽  
Konstantin Klementiev
Keyword(s):  
Fine Structure ◽  
Structural Analysis ◽  
Disordered Systems ◽  
Structural Information ◽  
Research Strategies ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Wide Range ◽  
X Ray Absorption

AbstractThe X-ray Absorption Fine Structure (XAFS) with its subregions X-ray Absorption Near-edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) is a powerful tool for the structural analysis of materials, which is nowadays a standard component of research strategies in many fields. This review covers a wide range of topics related to its measurement and use: the origin of the fine structure, its analytical potential, derived from the physical basis, the environment for measuring XAFS at synchrotrons, including different measurement geometries, detection modes, and sample environments, e. g. for in-situ and operando work, the principles of data reduction, analysis, and interpretation, and a perspective on new methods for structure analysis combining X-ray absorption with X-ray emission. Examples for the application of XAFS have been selected from work with heterogeneous catalysts with the intention to demonstrate the strength of the method providing structural information about highly disperse and disordered systems, to illustrate pitfalls in the interpretation of results (e. g. by neglecting the averaged character of the information obtained) and to show how its merits can be further enhanced by combination with other methods of structural analysis and/or spectroscopy.

scholarly journals U(VI) Reduction by Diverse Outer Surfacec-Type Cytochromes of Geobacter sulfurreducens

2013 ◽  
Vol 79 (20) ◽  
pp. 6369-6374 ◽  
Author(s):  
Roberto Orellana ◽  
Janet J. Leavitt ◽  
Luis R. Comolli ◽  
Roseann Csencsits ◽  
Noemie Janot ◽  
...  
Keyword(s):  
Outer Surface ◽  
Geobacter Sulfurreducens ◽  
Outer Cell ◽  
Wild Type ◽  
Energy Dispersion Spectroscopy ◽  
Edge Structure ◽  
Content Type ◽  
X Ray ◽  
Transmission Electron ◽  
Pilin Protein

ABSTRACTEarly studies withGeobacter sulfurreducenssuggested that outer-surfacec-type cytochromes might play a role in U(VI) reduction, but it has recently been suggested that there is substantial U(VI) reduction at the surface of the electrically conductive pili known as microbial nanowires. This phenomenon was further investigated. A strain ofG. sulfurreducens, known as Aro-5, which produces pili with substantially reduced conductivity reduced U(VI) nearly as well as the wild type, as did a strain in which the gene for PilA, the structural pilin protein, was deleted. In order to reduce rates of U(VI) reduction to levels less than 20% of the wild-type rates, it was necessary to delete the genes for the five most abundant outer surfacec-type cytochromes ofG. sulfurreducens. X-ray absorption near-edge structure spectroscopy demonstrated that whereas 83% ± 10% of the uranium associated with wild-type cells correspond to U(IV) after 4 h of incubation, with the quintuple mutant, 89% ± 10% of uranium was U(VI). Transmission electron microscopy and X-ray energy dispersion spectroscopy revealed that wild-type cells did not precipitate uranium along pili as previously reported, but U(IV) was precipitated at the outer cell surface. These findings are consistent with those of previous studies, which have suggested thatG. sulfurreducensrequires outer-surfacec-type cytochromes but not pili for the reduction of soluble extracellular electron acceptors.

Pluri-millenial evolution of uranium speciation in lacustrine sediments

2020 ◽  
Author(s):  
Pierre Lefebvre ◽  
Alkiviadis Gourgiotis ◽  
Arnaud Mangeret ◽  
Pierre Le Pape ◽  
Olivier Diez ◽  
...  
Keyword(s):  
Contaminated Soils ◽  
Sediment Cores ◽  
Lacustrine Sediments ◽  
Storage Conditions ◽  
Edge Structure ◽  
Anoxic Conditions ◽  
X Ray ◽  
Long Term Storage ◽  
X Ray Absorption

<p>Uranium (U) is a toxic radionuclide which environmental dissemination must be limited. In this regard, understanding U immobilization mechanisms in reducing environments is essential for improving the management of radioactive waste and the remediation of contaminated sites. In particular, determining the long-term behavior of non-crystalline U(IV) species in (sub-)surface conditions is of growing importance, as these environmentally-relevant species have been recently showed to play a major role in U mobility. For this purpose, we investigated the evolution of U speciation over a pluri-millennial period in naturally U-enriched sediments from Lake Nègre (alt. 2354 m, Mercantour, France) as an analogue of contaminated systems. Several sediment cores were sampled at 24 m of water depth and preserved under anoxic conditions. Bottom sediments were dated back to 8700 cal BP. These organic- and Si-rich sediments display increasing U concentration with depth, from 350 to more than 1000 µg/g. Sequential ultrafiltration of surface waters and uranium isotopic ratios (<sup>238</sup>U/<sup>235</sup>U and (<sup>234</sup>U/<sup>238</sup>U)) of sediments and waters suggest that the deposition mode of U did not vary significantly with time, thus giving the opportunity to follow the effect of diagenesis on U speciation over more than 1000 years. Uranium L<sub>III</sub>-edge X-Ray Absorption Near-Edge Structure (XANES) analysis shows that U is rapidly reduced in the upper sediment layers and is fully reduced at depth. Preliminary Extended X-Ray Absorption Fine Structure (EXAFS) spectroscopy data at the U L<sub>III</sub>-edge reveals that U speciation evolved with depth in the sediment core, suggesting an effect of diagenesis in anoxic conditions on U solid speciation. Our results may help to design long-term storage conditions that are able to enhance the formation of poorly soluble U species in U-contaminated soils and sediments.</p>

scholarly journals Quantifying redox heterogeneity in single-crystalline LiCoO2 cathode particles

2020 ◽  
Vol 27 (3) ◽  
pp. 713-719 ◽  
Author(s):  
Chenxi Wei ◽  
Yanshuai Hong ◽  
Yangchao Tian ◽  
Xiqian Yu ◽  
Yijin Liu ◽  
...  
Keyword(s):  
X Rays ◽  
Particle Engineering ◽  
Charge Heterogeneity ◽  
White Line ◽  
Edge Structure ◽  
Single Crystalline ◽  
X Ray ◽  
Chemical Complexity ◽  
Wide Range ◽  
X Ray Absorption

Active cathode particles are fundamental architectural units for the composite electrode of Li-ion batteries. The microstructure of the particles has a profound impact on their behavior and, consequently, on the cell-level electrochemical performance. LiCoO2 (LCO, a dominant cathode material) is often in the form of well-shaped particles, a few micrometres in size, with good crystallinity. In contrast to secondary particles (an agglomeration of many fine primary grains), which are the other common form of battery particles populated with structural and chemical defects, it is often anticipated that good particle crystallinity leads to superior mechanical robustness and suppressed charge heterogeneity. Yet, sub-particle level charge inhomogeneity in LCO particles has been widely reported in the literature, posing a frontier challenge in this field. Herein, this topic is revisited and it is demonstrated that X-ray absorption spectra on single-crystalline particles with highly anisotropic lattice structures are sensitive to the polarization configuration of the incident X-rays, causing some degree of ambiguity in analyzing the local spectroscopic fingerprint. To tackle this issue, a methodology is developed that extracts the white-line peak energy in the X-ray absorption near-edge structure spectra as a key data attribute for representing the local state of charge in the LCO crystal. This method demonstrates significantly improved accuracy and reveals the mesoscale chemical complexity in LCO particles with better fidelity. In addition to the implications on the importance of particle engineering for LCO cathodes, the method developed herein also has significant impact on spectro-microscopic studies of single-crystalline materials at synchrotron facilities, which is broadly applicable to a wide range of scientific disciplines well beyond battery research.

scholarly journals Sorption and Distribution of Copper in Unsaturated Pseudomonas putida CZ1 Biofilms as Determined by X-Ray Fluorescence Microscopy

2011 ◽  
Vol 77 (14) ◽  
pp. 4719-4727 ◽  
Author(s):  
Guangcun Chen ◽  
Xincai Chen ◽  
Yuanqiang Yang ◽  
Anthony G. Hay ◽  
Xiaohan Yu ◽  
...  
Keyword(s):  
Fluorescence Microscopy ◽  
Pseudomonas Putida ◽  
Temporal Distribution ◽  
Thick Layer ◽  
Edge Structure ◽  
Content Type ◽  
X Ray ◽  
Copper Phosphate ◽  
Pseudomonas Putida Cz1 ◽  
X Ray Absorption

ABSTRACTThe spatial and temporal distribution of metals in unsaturatedPseudomonas putidaCZ1 biofilms was determined using synchrotron-based X-ray fluorescence microscopy (XRF). It was found that Fe, Mn, and Ca were mainly distributed near the air-biofilm interface of a biofilm grown on 40 mM citrate, while there were two Fe-, Mn-, and Ca-rich layers within a biofilm grown on 10 mM citrate. The sorption of copper by biofilm grown in medium containing 10 mM citrate was rapid, with copper being found throughout the biofilm after only 1 h of exposure. Copper initially colocalized with Fe and Mn element layers in the biofilm and then precipitated in a 40-μm-thick layer near the air-biofilm interface when exposed for 12 h. Cu K-edge X-ray absorption near edge structure (XANES) analysis revealed that Cu was primarily bound with citrate within the biofilm, and the precipitate formed in the biofilm exposed to copper for 12 h was most similar to copper phosphate. LIVE/DEAD staining revealed that cells at the biofilm-membrane interface were mostly alive even when the copper concentration reached 80.5 mg copper g−1biomass. This suggests that the biofilm matrix provided significant protection for cells in this area. These results significantly improve our understanding of metal acquisition, transportation, and immobilization in unsaturated biofilm systems.

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