information about xps with cdots

1. www.usra.edu
X-Ray Photoelectron Spectroscopy
(XPS)
Applied to Soot
&
What It Can Do for You
Randy L. Vander Wal,
Vicki Bryg & Michael D. Hays
USRA The U.S. EPA
Acknowledgements:
1. Former funding through NASA NRA 99-HEDs-01 (RVW) and the U.S. EPA
2. Soot samples supplied by the U.S. EPA, Sandia National Labs
3. Vicki Bryg, Patrick Rodgers, Y.L.Chen, David R. Hull and Dr. Chuck
Mueller, Sandia National Labs

2. Results Regarding Soot Nanostructure
Soot Nanostructure: (Definition)
* Soot Nanostructure refers to carbon lamella (layer plane) length, orientation,
separation and tortuosity.
* Nanostructure is variable, dependent upon temperature, residence time and
fuel identity.
Fringe Analysis Algorithm: (Quantification)
* Lattice fringe analysis can be used to analyze HRTEM image data and
quantify carbon nanostructure through statistical analysis.
Oxidation Rates: (Implications)
* Oxidation rates are dependent upon nanostructure - suggests using
nanostructure to control (accelerate) oxidation.
* Source apportionment via analysis of nanostructure?
* Health consequences related to nanostructure?
* Environmental impact dependent upon nanostructure?

3. Pure Hydrocarbon
Application I:
Emissions Reduction
Oxygenated Additive

4. Fringe Length Analysis
Reference Fuel-n-hexadecane + heptamethylnonane
25
20
15
10
5
0
0.00 0.72 1.44 2.16 2.88 3.60 4.32 5.04 5.76
Fringe Length (nm)
Diethylene glycol ether (DGE)
25
20
15
10
5
0
0.00 0.72 1.44 2.16 2.88 3.60 4.32 5.04 5.76
Fringe Length (nm)
Fringe Tortuosity Analysis
Reference Fuel- n-hexadecane + heptamethylnonane
20
15
10
5
0
1.00 1.12 1.24 1.36 1.48 1.60 1.72 1.84 1.96
Fringe Tortuosity
Diethylene glycol ether (DGE)
20
15
10
5
0
1.00 1.12 1.24 1.36 1.48 1.60 1.72 1.84 1.96
Fringe Tortuosity

5. Smoke Meter (Engine Out)

6. Microscopic and Spectroscopic Analysis
Techniques for Soot Characterization
HRTEMHRTEM
(high resolution transmission(high resolution transmission
electron microscopy)electron microscopy)
Microscopy TechniqueMicroscopy Technique
Physical StructurePhysical Structure
(nanostructure)(nanostructure)
XPS
(X-ray photoelectron
spectroscopy)
Spectroscopy Technique
Chemical Composition
(& bonding states)

7. Outline - XPS
1. Motivation & Background
2. Introduction to XPS
3. Analytical capabilities:
A. Elemental Composition (Identification of source; wear, etc.)
B. Carbon Oxidation State - Oxygen Functional Groups
(Oxidation conditions)
* Consistency of samples within the same class
* Distinctness between different classes of samples
C. Carbon (nano)structure
4. Conclusions

8. Introduction to X-Ray Photoelectron Spectroscopy
(XPS)
* XPS provides information about elemental composition
and
oxidation state of the surface.
* A monochromatic X-ray beam of known energy displaces an
electron from a K-shell orbital.
* The kinetic energy of the emitted electron is measured in an
electron spectrometer.
* The binding energy Eb = hv – Ek
is characteristic of the atom and orbital from which the electron is
emitted.

9. Introduction to XPS (continued)
* A low-resolution wide-scan (survey) spectrum serves as the basis
for the determination of the elemental composition of samples.
* At higher resolution, chemical shifts are observed depending upon
oxidation state.
Ek = hv - Eb
X-ray
e-
Eb

10. Outline
1. Motivation & Background
2. Introduction to XPS
3. Analytical capabilities:
A. Elemental Composition (Identification of source; wear, etc.)
B. Carbon Oxidation State - Oxygen Functional Groups
(Oxidation conditions)
* Consistency of samples within the same class
* Distinctness between different classes of samples
C. Carbon (nano)structure
4. Conclusions

11. Low-Resolution Survey Scan - Jet Aircraft Emissions

12. Low-Resolution Survey Scan - Diesel Engine Soot

13. 6.0
5.0
4.0
%
3.0
2.0
1.0
0.0
XPS - Survey Elemental Analysis
S
Plant OFB
Wildfire
Jet Engines
Industrial OFB
Biodiesel A
Residential OFF
Biodiesel B
Biodiesel Soot
Na N Ca P
Elements

14. Outline
1. Motivation & Background
2. Introduction to XPS
3. Analytical capabilities:
A. Elemental Composition (Identification of source; wear, etc.)
B. Carbon Oxidation State - Oxygen Functional Groups
(Oxidation conditions)
* Consistency of samples within the same class
* Distinctness between different classes of samples
C. Carbon (nano)structure
4. Conclusions

15. Identify Oxygen Functional Groups
C-C sp2
Carbonyls
Phenols
Plasmon
Carboxylic
-C-OH Phenol
-C=O Carbonyl
-C-OOH Carboxylic

16. %Area
Oil Fired Boiler versus Residential Oil Fired Furnace
%Area
50
40
30
20
10
0
C1s Peak Histogram
80
C1s Peak Histogram
C-C sp2
60
C-C sp2
Fullerenic
40
-C-OH
C-C sp3
-C=O
0
20
-C-OOH -C-OOH
C-C sp3
-C=O
Industrial OFB1
Industrial OFB2
Res. OFF1
Res. OFF2
281.6 283.2 284.4 285.2 286.3 288.2 289.5 281.6 283.2 284.4 285.2 286.3 288.2 289.5
C1s Peak Position (eV) C1s Peak Position (eV)

17. 0
10
20
30
40
50
60
%Area
Comparison Between Biodiesel Soots
C1s Peak Histogram
Biodiesel 15&16
Biodiesel 17&18
0
20
40
60
80
100
C1s Peak Histogram
%Area
C-C sp2
-C-OH -C-OOH
C-C sp2
-C-OH
-C=O
Fullerenic
Biodiesel 13
Biodiesel 14
281.6 283.2 284.4 285.2 286.3 288.2 289.5 282.8 283.6 284.8 285.8 287 288.8
C1s Peak Position (eV) C1s Peak Position (eV)

18. Comparative Peak Intensities - Oxygen Functional Groups
Average C1s Peaks
(normalized)
Diesel Soot
Plant OFB
Wildfire%
Jet Engine%
Industrial OFB
Residential OFF
Biodiesel A
Biodiesel B
281.4
283.4
284.2
284.7
285.0
285.9
286.3
C1s position (eV)
286.6
287.4
288.8
289.5
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

19. Outline
1. Motivation & Background
2. Introduction to XPS
3. Analytical capabilities:
A. Elemental Composition (Identification of source; wear, etc.)
B. Carbon Oxidation State - Oxygen Functional Groups
(Oxidation conditions)
* Consistency of samples within the same class
* Distinctness between different classes of samples
C. Carbon (nano)structure
4. Conclusions

20. Motivation for Alternative Analysis Techniques
1. Lattice Fringe Analysis is time consuming
2. Analysis can be difficult to apply (in some cases)
Hmmm….

21. Identify Types of Carbon Nanostructure
C-C sp2
Carbonyls
Phenols
Fullerenic
Carboxylic
C-C sp3

22. Identify Types of Carbon Nanostructure
Carbonyls
Phenols
Carboxylic
C-C sp3 C-C sp2
Fullerenic

23. Identify Types of Carbon Nanostructure
C-C sp2
Carbonyls
Phenols
Fullerenic
Carboxylic
C-C sp3

24. AverageIntensity
(rawdata)
281.4
283.1
283.6
284.2
284.4
284.6
285.0
285.7
286.0
286.3
286.5
286.8
287.4
287.9
288.8
289.5
Comparative Peak Intensities - Carbon Nanostructure
12000
Average XPS peaks
10000
Diesel Soot
Plant OFB
8000
Wildfire
Jet engines
Industrial OFB6000
Residential OFF
Biodiesel A
4000 Biodiesel B
2000
0
Peak positions

25. High Resolution Scan - C1s Region - HOPG Edge Planes
C-C sp2
C-C sp3
Carboxylic
Phenols
Carbonyl
Graphitic
Defects

26. High Resolution Scan - C1s Region - HOPG Layer Planes
C-C sp2
C-C sp3
Phenols
Graphitic
Defects

27. XPS Sensitivity to Carbon Nanostructure
C-C sp2
C-C sp3
Phenols
C-C sp2
C-C sp3
Carboxylic
Phenols
Carbonyl

28. * Developing Correlations with Carbon Reactivity*
Sample:
Edge Sites Basal Plane
Intensity Sum Intensity Sum
Planar Graphite
( ~ 284 eV, sp2)
1749
13%
11265
87%
Edge Graphite
( ~ 285 eV, sp3)
4021
37%
6723
63%
Ratio (G/D) 0.35 1.38
Edge site carbons can be nearly 10-fold more reactive than basal plane sites

29. Goal & Result
HRTEM & Lattice Fringe Analysis
XPS Carbon nanostructure Oxidative Reactivity

30. Conclusions
1. XPS analysis can identify & quantify trace elements.
Utility: Can be used to identify source based on specific elements
present and their distribution.
* Track fuel and/or oil elements
* Analysis of engine wear
2. XPS can identify oxygen groups by bonding type; C-OH, C=O, and
C-OOH. These reflect the soot oxidation history.
Utility: Identify the occurrence and degree of oxidation, such as
the soot cake within a DPF
3. XPS can identify the types of carbon present, sp2, sp3 and fullerenic
Therein it can provide a complimentary method to HRTEM and image
analysis.
Utility: Correlate nanostructure with soot reactivity, and changes
new fuels, e.g. biodiesel

31. Graphitic
Normal Particle
DPF
Soot
Hollow
Interiors
outer shell
Normal Particle Normal Particle
Partially Oxidized Partially Oxidized
Application III:
DPFs

32. Application II: Source Specific Nanostructure
Wildfire Emissions Oil Fired Boiler
Comparison between carbon lamella;
short, disconnected versus longer range structure and order

33. Jet Aircraft Engine Exhaust
Fullerenic
Structure

34. Jet Engine Emission Diesel Emission Wildfire Emission
a1-1c-ROI_14 e2-3a-roi_1c4-hb-ROI_1
252525
202020
151515
101010
555
000
0.00 0.72 1.44 2.16 2.88 3.60 4.32 5.04 5.76 0 0.72 1.44 2.16 2.88 3.6 4.32 5.04 5.76 0.00 0.72 1.44 2.16 2.88 3.60 4.32 5.04 5.76
Fringe Length (nm) Fringe Length (nm) Fringe Length (nm)
C4-HB-SEPSKEL_1 A1-1C-SEPSKEL_1 E2-3A-ROI_1_4
25 25
25
202020
151515
101010
555
000
0.32 0.35 0.37 0.40 0.43 0.46 0.48 0.32 0.35 0.37 0.40 0.43 0.46 0.48 0.32 0.35 0.37 0.40 0.43 0.46 0.48
Fringe Separation (nm) Separation Distance (nm) Separation Distance (nm)
Separation Distance (nm)
c4-hb-tort_1 a1-1c-tort_1 e2-3a-_1
202020
151515
101010
555
000
1.00 1.12 1.24 1.36 1.48 1.60 1.72 1.84 1.96 1.00 1.12 1.24 1.36 1.48 1.60 1.72 1.84 1.96 1.00 1.12 1.24 1.36 1.48 1.60 1.72 1.84 1.96
Tortuosity Tortuosity Tortuosity

35. Average C1s Peaks Average C1s Peaks
Intensitiies and Locations Intensitiies and Locations
AverageIntensity
2500
2000
1500
1000
500
0 0
500
1000
1500
2000
281.4 283.6 284.4 285.2 286.4 287 288.8
Bio 13-18
AverageIntensity
Average Peak Position (eV)
281.4 283.6 284.4 285.2 286.4 287 288.8
Bio 13-14
Average Peak Position
0
2000
4000
6000
8000
1 104
Average C1s Peaks
Intensitiies and Locations
BBB2&WVU
AverageIntensity
Biodiesel 1 Biodiesel 2
Ordinary
diesel
Averaged by Intensity
Averaged by Position
281.4 283.6 284.4 285.2 286.4 287 288.8
Average Peak Position (eV)