Identification of Ferrous-Ferric Fe3O4 Nanoparticles in Recombinant Human Ferritin Cages

AbstractRecombinant ferritin is an excellent template for the synthesis of magnetic nanoparticles. This paper describes carefully performed experiments both to identify ironoxides within nanoparticles and to measure the number of iron atoms in the cores of recombinant human H-chain ferritin (HFn), based on spectroscopy techniques. Using electron energy-loss spectroscopy (EELS) analysis, magnetite (Fe3O4) has been unequivocally identified as the ironoxide formed within HFn cores under special preparation conditions. Atom counting analysis by EELS and high-angle annular dark-field imaging further allowed the correlation of the particle sizes to the real Fe atom numbers in a quantitative manner. These results help clarify some structural confusion between magnetite and maghemite (γ-Fe2O3), and also provide standard data for the number of Fe atoms within Fe3O4 particles of a given size, whose use is not limited to cases of magnetite synthesized in the cores of recombinant human ferritin.

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3d Reconstruction of Sub-Nm Beam Profiles in STEM

Microscopy and Microanalysis ◽

10.1017/s1431927600027793 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 344-345

Author(s):

G. Möbus ◽

R.E. Dunin-Borkowski ◽

C.J.D. Hethėrington ◽

J.L. Hutchison

Keyword(s):

Electron Beam ◽

Chemical Analysis ◽

Energy Loss ◽

Intensity Distribution ◽

Dark Field ◽

Beam Forming ◽

Dark Field Imaging ◽

Annular Dark Field ◽

Electron Energy Loss ◽

Field Imaging

Introduction:Atomically resolved chemical analysis using techniques such as electron energy loss spectroscopy and annular dark field imaging relies on the ability to form a well-characterised sub-nm electron beam in a FEGTEM/STEM [1-2]. to understand EELS+EDX-signal formation upon propagation of a sub-nm beam through materials we first have to assess precisely the beam intensity distribution in vacuum and find conditions for the best obtainable resolution.Experimental Details:Modern TEM/STEM instruments combine features of both imaging and scanning technology. The beam forming capability approaches closely that for dedicated STEMs, while CCD recording devices allow us to measure the beam profile by direct imaging at magnifications up to 1.5 M. The recording of a “z-section” series through the 3D intensity distribution of the cross-over can therefore be realised by recording of a “condenser focal series”.

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Structure and Chemistry across Interfaces at Nanoscale of a Ge Quantum Well Embedded within Rare Earth Oxide Layers

Microscopy and Microanalysis ◽

10.1017/s1431927611000559 ◽

2011 ◽

Vol 17 (5) ◽

pp. 759-765 ◽

Cited By ~ 5

Author(s):

Tanmay Das ◽

Somnath Bhattacharyya

Keyword(s):

Rare Earth ◽

Solid Phase ◽

Rare Earth Oxide ◽

Dark Field ◽

X Ray ◽

Dark Field Imaging ◽

Transmission Electron ◽

Annular Dark Field ◽

Electron Energy Loss ◽

Field Imaging

AbstractStructure and chemistry across the rare earth oxide-Ge interfaces of a Gd2O3-Ge-Gd2O3 heterostructure grown on p-Si (111) substrate using encapsulated solid phase epitaxy method have been studied at nanoscale using various transmission electron microscopy methods. The structure across both the interfaces was investigated using reconstructed phase and amplitude at exit plane. Chemistry across the interfaces was explored using elemental mapping, high-angle annular dark-field imaging, electron energy loss spectroscopy, and energy dispersive X-ray spectrometry. Results demonstrate the structural and chemical abruptness of both the interfaces, which is most essential to maintain the desired quantum barrier structure.

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Atomic-Scale Imaging of Dopant Atom Distributions Within Silicon δ-Doped Layers

MRS Proceedings ◽

10.1557/proc-589-173 ◽

1999 ◽

Vol 589 ◽

Cited By ~ 1

Author(s):

R. Vanfleet ◽

D.A. Muller ◽

H.J. Gossmann ◽

P.H. Citrin ◽

J. Silcox

Keyword(s):

Dark Field ◽

Atomic Scale ◽

Dopant Atom ◽

Specimen Preparation ◽

Dark Field Imaging ◽

Dramatic Difference ◽

Annular Dark Field ◽

Dopant Atoms ◽

Electron Energy Loss ◽

Field Imaging

AbstractWe report measurements of the distribution of Sb atoms in σ-doped Si, over a wide 2-D concentration range. Both annular dark-field imaging and electron energy loss spectroscopy proved sufficiently sensitive to locate Sb atoms at the atomic scale. Improvements in both detector sensitivities and specimen preparation were necessary to achieve these results, which offer a surprising explanation for the dramatic difference in electrical activity between 2-D and 3-D dopant distributions at the same effective volume concentrations. The prospects for the general identification of individual dopant atoms will be discussed.

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Measurement of Effective Extinction Distances in Zone Axis Silicon

Microscopy and Microanalysis ◽

10.1017/s1431927600016597 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 654-655

Author(s):

Z. Yu ◽

R.R. Vanfleet ◽

J. Silcox

Keyword(s):

Cross Section ◽

Dark Field ◽

Zone Axis ◽

Ion Milling ◽

Low Loss ◽

Dark Field Imaging ◽

Annular Dark Field ◽

Many Sources ◽

Electron Energy Loss ◽

Field Imaging

Extinction distances for two beam conditions are readily available through many sources, but under more complex zone axis conditions extinction distances are not well known. The use of thickness fringes as an approximate thickness estimate under zone axis conditions, such as in high resolution Annular Dark Field imaging, can be a useful tool. We have measured thickness vs. fringe number under zone axis conditions using low loss Electron Energy Loss Spectroscopy (EELS). Work was done on the Cornell UHV HB501 STEM.Several orientations of silicon were glued together and thinned in cross section by the wedge technique. Additional thinning was done by low angle ion milling. Surface oxide was removed with an HF etch before loading into the microscope.Each piece of silicon was tilted to the zone axis condition and low loss EELS spectra was taken at selected points. The thickness fringes were numbered with the following convention: the center of the first black fringes close to the edge is 1 and the center of the second black fringe is 2, etc.

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