In Situ Environmental Cell–Transmission Electron Microscopy Study of Microbial Reduction of Chromium(VI) Using Electron Energy Loss Spectroscopy

2001 ◽  
Vol 7 (6) ◽  
pp. 470-485 ◽  
Author(s):  
Tyrone L. Daulton ◽  
Brenda J. Little ◽  
Kristine Lowe ◽  
Joanne Jones-Meehan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Energy Loss ◽  
Transmission Electron Microscope ◽  
Transmission Electron ◽  
Environmental Cell ◽  
Cell Transmission ◽  
Electron Energy Loss

AbstractReduction of Cr(VI) by the bacterium, Shewanella oneidensis (previously classified Shewanella putrefaciens strain MR-1), was studied by absorption spectrophotometry and in situ, environmental cell–transmission electron microscopy (EC-TEM) coupled with electron energy loss spectroscopy (EELS). Bacteria from rinsed cultures were placed directly in the environmental cell of the transmission electron microscope and examined under 100 Torr pressure. Bright field EC-TEM images show two distinct populations of S. oneidensis in incubated cultures containing Cr(VI)O42−: those that exhibit low image contrast and heavily precipitateencrusted cells exhibiting high image contrast. Several EELS techniques were applied to determine the oxidation state of Cr associated with encrusted cells. The encrusted cells are shown to contain a reduced form of Cr in oxidation state +3 or lower. These results demonstrate the capability to determine the chemistry and valence state of reduction products associated with unfixed, hydrated bacteria in an environmental cell transmission electron microscope.

Microbial Reduction of Chromium(VI): In-Situ Environmental Cell Transmission Electron Microscopy Study Using Electron Energy Loss Spectroscopy

2001 ◽  
Vol 7 (S2) ◽  
pp. 134-135
Author(s):  
Tyrone L. Daulton ◽  
Brenda J. Little ◽  
Kristine Lowe ◽  
Joanne Jones-Meehan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Shewanella Oneidensis ◽  
Transmission Electron ◽  
Environmental Cell ◽  
Electron Energy Loss

The geochemistry and toxicity of chromium is controlled by its valence state. Chromium is a redox active 3d transition metal with a wide range (− to +6) of possible oxidation states; however only Cr(III) and Cr(VI) are stable. Hexavalent Cr(VI) can be readily reduced to the trivalent state by Fe2+, S2−, organic compounds, wetland plants, and several species of microorganisms. The associated mechanisms of Cr(VI) reduction are technologically and biologically important because they convert a toxic, mobile element into a less toxic, immobile form.Reduction of Cr(VI) by the bacterium, Shewanella oneidensis (previously classified Shewanella putrefaciens strain MR-1), was studied by absorption spectrophotometry and in-situ, environmental cell (EC) - transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS). Shewanella oneidensis (S. oneidensis), a gram-negative, facultative bacterium is capable of respiring aerobically and anaerobically using a variety of compounds, including O2, Fe(III), Mn(IV), NO2−, NO3−, SO2, SO32−, thiosulfate (S2O32−), trimethyamine oxide, fumarate, U(VI), and Cr(VI) as terminal electron acceptors.

Investigation of Switching Mechanism in HfO2-Based Oxide Resistive Memories by In-Situ Transmission Electron Microscopy and Electron Energy Loss Spectroscopy

2017 ◽  
Author(s):  
T. Dewolf ◽  
D. Cooper ◽  
N. Bernier ◽  
V. Delaye ◽  
A. Grenier ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Hafnium Dioxide ◽  
Switching Mechanism ◽  
Transmission Electron ◽  
Electron Energy Loss

Abstract Forming and breaking a nanometer-sized conductive area are commonly accepted as the physical phenomenon involved in the switching mechanism of oxide resistive random access memories (OxRRAM). This study investigates a state-of-the-art OxRRAM device by in-situ transmission electron microscopy (TEM). Combining high spatial resolution obtained with a very small probe scanned over the area of interest of the sample and chemical analyses with electron energy loss spectroscopy, the local chemical state of the device can be compared before and after applying an electrical bias. This in-situ approach allows simultaneous TEM observation and memory cell operation. After the in-situ forming, a filamentary migration of titanium within the dielectric hafnium dioxide layer has been evidenced. This migration may be at the origin of the conductive path responsible for the low and high resistive states of the memory.

scholarly journals Electron Energy Loss Spectroscopy for Aqueous in Situ Scanning Transmission Electron Microscopy

2011 ◽  
Vol 17 (S2) ◽  
pp. 778-779 ◽  
Author(s):  
K Jungjohann ◽  
J Evans ◽  
I Arslan ◽  
N Browning
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

In-Situ Transmission Electron Microscopy of the Etching of Silicon (111) Surfaces by Oxygen

1991 ◽  
Vol 238 ◽  
Author(s):  
J. M. Gibson ◽  
F. M. Ross
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Oxide Layer ◽  
Transmission Electron Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Surface Steps ◽  
Transmission Electron

ABSTRACTSilicon (111) surfaces have been etched in-situ in a ultra-high vacuum transmission electron microscope. Surface steps are observed to flow during etching, so that Si atoms are removed only from steps. This is in contrast to the behavior during the formation of an oxide layer reported previously. The nucleation of steps and their interaction with surface impurities is described.

The structural transitions of C60 nanowhiskers under an electric field characterized by in situ transmission electron microscopy and electron energy-loss spectroscopy

Nanoscale ◽  
2014 ◽  
Vol 6 (12) ◽  
pp. 6585-6589 ◽  
Author(s):  
Chao Li ◽  
Bingzhe Wang ◽  
Yuan Yao ◽  
Guangzhe Piao ◽  
Lin Gu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electric Field ◽  
Energy Loss ◽  
Electron Energy ◽  
Structural Transformation ◽  
Electron Energy Loss Spectroscopy ◽  
Transmission Electron ◽  
Electron Energy Loss

The structural transformation path of C60 nanowhiskers under an electric field studied using in situ TEM is reported.

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