scholarly journals Bacterial production of vanadium ferrite spinel (Fe,V)3O4 nanoparticles

2020 ◽  
Vol 84 (4) ◽  
pp. 554-562
Author(s):  
Victoria S Coker ◽  
Gerrit van der Laan ◽  
Neil D Telling ◽  
Jonathan R Lloyd ◽  
James M Byrne ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Magnetite Nanoparticles ◽  
Bacterial Production ◽  
Magnetic Circular Dichroism ◽  
Microbial Reduction ◽  
Geobacter Sulfurreducens ◽  
X Ray ◽  
Redox Boundary ◽  
X Ray Absorption ◽  
Ferrite Spinel

AbstractBiogenic nanoscale vanadium magnetite is produced by converting V(V)-bearing ferrihydrites through reductive transformation using the metal-reducing bacterium Geobacter sulfurreducens. With increasing vanadium in the ferrihydrite, the amount of V-doped magnetite produced decreased due to V-toxicity which interrupted the reduction pathway ferrihydrite–magnetite, resulting in siderite or goethite formation. Fe L2,3 and V L2,3 X-ray absorption spectra and data from X-ray magnetic circular dichroism analysis revealed the magnetite to contain the V in the Fe(III) Oh site, predominately as V(III) but always with a component of V(VI), present a consistent V(IV)/V(III) ratio in the range 0.28 to 0.33. The bacteriogenic production of V-doped magnetite nanoparticles from V-doped ferrihydrite is confirmed and the work reveals that microbial reduction of contaminant V(V) to V(III)/V(IV) in the environment will occur below the Fe-redox boundary where it will be immobilised in biomagnetite nanoparticles.

scholarly journals Magnetic spectroscopy of nanoparticulate greigite, Fe3S4

2017 ◽  
Vol 81 (4) ◽  
pp. 857-872 ◽  
Author(s):  
Richard A. D. Pattrick ◽  
Victoria S. Coker ◽  
Masood Akhtar ◽  
M. Azad Malik ◽  
Edward Lewis ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Oxidation State ◽  
Magnetic Circular Dichroism ◽  
Covalent Character ◽  
X Ray ◽  
Positive Feature ◽  
A Site ◽  
Intermediate Oxidation ◽  
X Ray Absorption ◽  
Ferrite Spinel

AbstractSynthesis of Ni and Zn substituted nano-greigite, Fe3S4, is achieved from single source diethyldithiocarbamato precursor compounds, producing particles typically 50–100 nm in diameter with plate-like pseudohexagonal morphologies. Up to 12 wt.% Ni is incorporated into the greigite structure, and there is evidence that Zn is also incorporated but Co is not substituted into the lattice. The FeL3X-ray absorption spectra for these materials have a narrow single peak at 707.7 eV and the resulting main X-ray magnetic circular dichroism (XMCD) has the same sign at 708.75 eV. All XMCD spectra also have a broad positive feature at 711 eV, a characteristic of covalent mixing. The greigite XMCD spectra contrast with the three clearly defined XMCD site specific peaks found in the ferrite spinel, magnetite. The FeL2,3X-ray absorption spectra and XMCD spectra of the greigite reflect and reveal the high conductivity of greigite and the very strong covalency of the Fe–S bonding. The electron hopping between Fe3+and Fe2+on octahedral sites results in an intermediate oxidation state of the Fe in the Ohsite of Fe2.5+producing an effective formula of [Fe3+↑]A-site[2Fe2.5+↓]B-siteS42–]. The NiL2,3X-ray absorption spectra and XMCD reveal substitution on the Ohsite with a strongly covalent character and an oxidation state <Ni1.5+in a representative formula [Fe3+↑]A[[(2 – x)Fe2.5+↓][Nix1.5+]]BS42–.

scholarly journals Magnetic circular dichroism in the soft-x-ray absorption spectra of Mn-based magnetic intermetallic compounds

1997 ◽  
Vol 56 (10) ◽  
pp. 6021-6030 ◽  
Author(s):  
A. Kimura ◽  
S. Suga ◽  
T. Shishidou ◽  
S. Imada ◽  
T. Muro ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Intermetallic Compounds ◽  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
X Ray ◽  
X Ray Absorption ◽  
Circular Dichroïsm

scholarly journals Controlled cobalt doping in biogenic magnetite nanoparticles

2013 ◽  
Vol 10 (83) ◽  
pp. 20130134 ◽  
Author(s):  
J. M. Byrne ◽  
V. S. Coker ◽  
S. Moise ◽  
P. L. Wincott ◽  
D. J. Vaughan ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Magnetic Circular Dichroism ◽  
Cobalt Content ◽  
Microbial Reduction ◽  
Geobacter Sulfurreducens ◽  
Cobalt Doping ◽  
Effective Anisotropy ◽  
Cobalt Iron ◽  
Potential Use ◽  
Ferrite Spinel

Cobalt-doped magnetite (Co x Fe 3 − x O 4 ) nanoparticles have been produced through the microbial reduction of cobalt–iron oxyhydroxide by the bacterium Geobacter sulfurreducens . The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe 2+ site with Co 2+ , with up to 17 per cent Co substituted into tetrahedral sites.

scholarly journals Bayesian spectroscopy of synthesized soft X-ray absorption spectra showing magnetic circular dichroism at the Ni-L3, -L2 edges

2021 ◽  
Vol 1 (1) ◽  
pp. 75-86
Author(s):  
Taiga Yamasaki ◽  
Kazunori Iwamitsu ◽  
Hiroyuki Kumazoe ◽  
Masato Okada ◽  
Masaichiro Mizumaki ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
X Ray ◽  
X Ray Absorption ◽  
Circular Dichroïsm

scholarly journals Magnetic Coupling in Spin-Valves from Magnetic Circular Dichroism

1995 ◽  
Vol 403 ◽  
Author(s):  
P. J. Bedrossian ◽  
J. G. Tobin ◽  
G. D. Waddill ◽  
A. F. Jankowski ◽  
T. C. Anthony ◽  
...  
Keyword(s):  
Thin Film ◽  
Circular Dichroism ◽  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
Magnetic Coupling ◽  
Spin Valves ◽  
Magnetic Polarization ◽  
X Ray ◽  
X Ray Absorption ◽  
Circular Dichroïsm

AbstractWe demonstrate the detection of Magnetic X-ray Circular Dichroism (MXCD) from commercial, thin-film spin valves. Measured x-ray absorption spectra on these devices indicate magnetic polarization of the ferromagnetic constituents, Fe, Co, and Ni.

scholarly journals Measuring spectroscopy and magnetism of extracted and intracellular magnetosomes using soft X-ray ptychography

2016 ◽  
Vol 113 (51) ◽  
pp. E8219-E8227 ◽  
Author(s):  
Xiaohui Zhu ◽  
Adam P. Hitchcock ◽  
Dennis A. Bazylinski ◽  
Peter Denes ◽  
John Joseph ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
Phase Spectrum ◽  
X Ray ◽  
Scanning Transmission ◽  
Left And Right ◽  
The Individual ◽  
And Function ◽  
X Ray Absorption ◽  
Phase Spectra

Characterizing the chemistry and magnetism of magnetotactic bacteria (MTB) is an important aspect of understanding the biomineralization mechanism and function of the chains of magnetosomes (Fe3O4nanoparticles) found in such species. Images and X-ray absorption spectra (XAS) of magnetosomes extracted from, and magnetosomes in, wholeMagnetovibrio blakemoreistrain MV-1 cells have been recorded using soft X-ray ptychography at the Fe 2p edge. A spatial resolution of 7 nm is demonstrated. Precursor-like and immature magnetosome phases in a whole MV-1 cell were visualized, and their Fe 2p spectra were measured. Based on these results, a model for the pathway of magnetosome biomineralization for MV-1 is proposed. Fe 2p X-ray magnetic circular dichroism (XMCD) spectra have been derived from ptychography image sequences recorded using left and right circular polarization. The shape of the XAS and XMCD signals in the ptychographic absorption spectra of both sample types is identical to the shape and signals measured with conventional bright-field scanning transmission X-ray microscope. A weaker and inverted XMCD signal was observed in the ptychographic phase spectra of the extracted magnetosomes. The XMCD ptychographic phase spectrum of the intracellular magnetosomes differed from the ptychographic phase spectrum of the extracted magnetosomes. These results demonstrate that spectro-ptychography offers a superior means of characterizing the chemical and magnetic properties of MTB at the individual magnetosome level.

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