Abstract
Electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM) was used to compare the iron oxidation state at the surface and interior of γ-Fe2O3 nanoparticles produced by the combustion process under fuel conditions leading to low and high soot concentrations. These experiments were performed in the nanoprobe mode, which allowed for very high spatial resolution (the probe size was 1.4 nm). Here, low soot concentrations were obtained in a laminar ethylene-air diffusion flame seeded with iron pentacarbonyl, while high soot concentrations were achieved with the addition of acetylene to this fuel mixture. The studies showed that the surface oxidation state of iron was lowered with the addition of acetylene, although the core composition remained the same. This was indicated by changes in both the iron L23- and the oxygen K-edges at the surface of the particles. These highly spatially-resolved measurements showed a chemical shift of both the L3 and L2 iron lines, accompanied by significant reduction of the L3:L2-intensity ratio, indicating Fe2+ at the particle surface. Reduction in the pre-edge peak of the oxygen K-edge at the particle surface also indicated iron reduction at the surface. These results suggest that the surface oxidation state, and therefore gas-sensing properties, of combustion-synthesized iron oxide nanoparticles is highly dependent on flame conditions. Furthermore, this study shows that EELS is an important research tool for the investigation of nanoscale gas-sensors, allowing differentiation of composition and oxidation state at the interior and surface of individual nanostructures in these materials.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 19-23 |
| Number of pages | 5 |
| Journal | Sensors and Actuators, B: Chemical |
| Volume | 109 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jul 24 2005 |
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Keywords
- EELS
- Gas-sensing
- Iron oxide
- Oxidation state
- White lines
ASJC Scopus subject areas
- Analytical Chemistry
- Electrochemistry
- Electrical and Electronic Engineering
Cite this
Surface oxidation state of combustion-synthesized γ-Fe 2O3 nanoparticles determined by electron energy loss spectroscopy in the transmission electron microscope. / Jasinski, Jacek; Pinkerton, Kent E; Kennedy, Ian M.; Leppert, Valerie J.
In: Sensors and Actuators, B: Chemical, Vol. 109, No. 1, 24.07.2005, p. 19-23.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Surface oxidation state of combustion-synthesized γ-Fe 2O3 nanoparticles determined by electron energy loss spectroscopy in the transmission electron microscope
AU - Jasinski, Jacek
AU - Pinkerton, Kent E
AU - Kennedy, Ian M.
AU - Leppert, Valerie J.
PY - 2005/7/24
Y1 - 2005/7/24
N2 - Electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM) was used to compare the iron oxidation state at the surface and interior of γ-Fe2O3 nanoparticles produced by the combustion process under fuel conditions leading to low and high soot concentrations. These experiments were performed in the nanoprobe mode, which allowed for very high spatial resolution (the probe size was 1.4 nm). Here, low soot concentrations were obtained in a laminar ethylene-air diffusion flame seeded with iron pentacarbonyl, while high soot concentrations were achieved with the addition of acetylene to this fuel mixture. The studies showed that the surface oxidation state of iron was lowered with the addition of acetylene, although the core composition remained the same. This was indicated by changes in both the iron L23- and the oxygen K-edges at the surface of the particles. These highly spatially-resolved measurements showed a chemical shift of both the L3 and L2 iron lines, accompanied by significant reduction of the L3:L2-intensity ratio, indicating Fe2+ at the particle surface. Reduction in the pre-edge peak of the oxygen K-edge at the particle surface also indicated iron reduction at the surface. These results suggest that the surface oxidation state, and therefore gas-sensing properties, of combustion-synthesized iron oxide nanoparticles is highly dependent on flame conditions. Furthermore, this study shows that EELS is an important research tool for the investigation of nanoscale gas-sensors, allowing differentiation of composition and oxidation state at the interior and surface of individual nanostructures in these materials.
AB - Electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM) was used to compare the iron oxidation state at the surface and interior of γ-Fe2O3 nanoparticles produced by the combustion process under fuel conditions leading to low and high soot concentrations. These experiments were performed in the nanoprobe mode, which allowed for very high spatial resolution (the probe size was 1.4 nm). Here, low soot concentrations were obtained in a laminar ethylene-air diffusion flame seeded with iron pentacarbonyl, while high soot concentrations were achieved with the addition of acetylene to this fuel mixture. The studies showed that the surface oxidation state of iron was lowered with the addition of acetylene, although the core composition remained the same. This was indicated by changes in both the iron L23- and the oxygen K-edges at the surface of the particles. These highly spatially-resolved measurements showed a chemical shift of both the L3 and L2 iron lines, accompanied by significant reduction of the L3:L2-intensity ratio, indicating Fe2+ at the particle surface. Reduction in the pre-edge peak of the oxygen K-edge at the particle surface also indicated iron reduction at the surface. These results suggest that the surface oxidation state, and therefore gas-sensing properties, of combustion-synthesized iron oxide nanoparticles is highly dependent on flame conditions. Furthermore, this study shows that EELS is an important research tool for the investigation of nanoscale gas-sensors, allowing differentiation of composition and oxidation state at the interior and surface of individual nanostructures in these materials.
KW - EELS
KW - Gas-sensing
KW - Iron oxide
KW - Oxidation state
KW - White lines
UR - http://www.scopus.com/inward/record.url?scp=22944447168&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=22944447168&partnerID=8YFLogxK
U2 - 10.1016/j.snb.2005.03.013
DO - 10.1016/j.snb.2005.03.013
M3 - Article
AN - SCOPUS:22944447168
VL - 109
SP - 19
EP - 23
JO - Sensors and Actuators, B: Chemical
JF - Sensors and Actuators, B: Chemical
SN - 0925-4005
IS - 1
ER -