Carbon Functional Groups Identification and Source … · 2016-04-13 · NEXAFS • Near-edge X-Ray...
Transcript of Carbon Functional Groups Identification and Source … · 2016-04-13 · NEXAFS • Near-edge X-Ray...
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Carbon Functional Groups Identification and Source Apportionment of Fine Particulate Matter
withC(1s) NEXAFS Spectroscopy
Artur BraunDept. of Chemical & Materials Engineering
Consortium for Fossil Fuel SciencesUniversity of Kentucky, Lexington KY, USA
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Acknowledgement• F.E. Huggins, N. Shah, G.P. Huffman, Univ. of Kentucky• K.E. Kelly, A. Sarofim, Univ. of Utah• B.S. Mun, Berkeley Nat’l Lab, Advanced Light Source• S. Wirick, C. Jacobsen, SUNY SB & Brookhaven Nat’l Lab, NSLS• M. Maricq, Ford Motor Company• W. Linak, US EPA Nat’l Risk Management Research Center• W. Harrison, USAF Wright Patterson AFB• J. Mcdonald, Lovelace Respiratory Research Institute• S. di Stasio, Istituto Motori, Napoli, Italy• A. Kubatova, EERC Univ. of North Dakota• M. Heuberger-Vernooij, EMPA
NSF Grant # CHE-0089133. NEXAFS was performed at Beamline 9.3.2 at theALS and Beamline X1A at the NSLS.
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Direct correlation: Particle concentration ~ Mortality ratio
Suspected role in global climate forcing
Airborne fine particulate matter - Feinstaub
970
975
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985
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995
1000
0
10
20
30
40
50
1 2 3 4 5 6
Surv
ivor
s/10
00 p
erso
n ye
ars
Fine particles (μg/m3)
City
Portage, WI1Topeka, KS2Watertown, MS3Harriman, TN4St. Louis5Steubenville, OH6
Soot takes center stageW.L. Chameides, M. Bergin;Science (2002) 297 2214
“The 6 Cities Study”D.W. Dockery et.al., New Engl. J. of Medicine (1993):329/24 1753-1759.
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NEXAFS
• Near-edge X-Ray Absorption Fine Structure Spectroscopy• For the analysis of soot molecular structure• Element specific – here we focus on the carbon
X-ray spectroscopy has been used for PM speciation before, but notfor carbon speciation !
Environm. Sci. & Technol. 41 (2007) 173.
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C(1s) NEXAFS spectroscopy
- J. Stöhr, NEXAFS Spectroscopy, Springer, 1992, NY.- S.C.B. Myneni, Rev. Miner. Geochem. 49 (2002) 485.- A. Braun, J. Env. Monitoring., 2005, 7(11), 1059.
di Stasio, Braun. Energy & Fuels 2006, 20(1), 187 pp.
Element specific
• Sensitive to molecular structure
• Soot shows strong peak at 285 eVfrom C=C double bonds such as graphite or PAH
• Surface functional groups, SOM
• Goal: molecular fingerprint for sourceattribution
• Quantitative ?0
1
2
3
4
5
280 290 300 310 320 330
NEX
AFS
abs
orpt
ion
[a.u
.]
Energy [eV]
ethylene soot
carbon black
diesel soot
graphite
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280 285 290 295 300
NEX
AFS
inte
nsity
[a.u
.]
Energy [eV]
SRM 1650Graphite SL-25
Environm. Sci. & Technol. 41 (2007) 173.
280 300 320 340 360 380 400
NEX
AFS
inte
nsity
[a.u
.]
Energy [eV]
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NEXAFS of idle and load diesel soot
0.00
0.50
280 285 290 295
1.00
1.50
Energy [eV]
C-HC=O
C=C COOH
C-OHIdle
Load soot contains more graphitic material. Idle soot contains significantly more aliphatic material, incl. volatiles, residual oil, fuel, soluble organic matter,… .
phen
olic
arom
atic
alip
hatic
load
quin
oide
alky
late
d
Carbon 43/12 (2005), 2588
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8282 284 286 288 290 292 294
Energy [eV]
C=C C=O
COOH
C-OH
C=Cgraphite-like
p-benzoquinoneNIST SRM 2975NIST SRM 1650
Utah, 2200 rpm
1800 rpm
1500 rpm
FTP 75
CNT
Utah, weathered
Exciton
Utah, generic
Comparison of various DPM samples
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282 284 286 288 290 292 294Energy [eV]
LRRI
UND
DRY
MOIST
LEX
MIX
C=C
C-OH
COOH
C=O
C-H
NEX
AFS
abs
orpt
ion
[a.u
.]
Wood Smoke Studies
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.5 1 1.5 2 2.5 3 3.5
C-OHAromatic
Estimated Dry Time [yr]
LRRI MOISTLEX
MIXDRY
Rel
ativ
e Pe
ak H
eigh
t
Kreosote from dry wood and moist woodyields entirely different spectra
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10282 284 286 288 290 292 294
Energy [eV]
LEX/LAW 103
LEX/LAW 86
LEX/Whalen
SRM NIST 1648
NEX
AFS
abs
orpt
ion
[a.u
.]
NEX
AFS
abs
orpt
ion
[a.u
.]
280 282 284 286 288 290 292 294
NIST 1648 Urban
LRRI Woodsmoke
FTP-75 day 3 DEP
90% DEP
50% DEP
10% DEP
Energy [eV]
Can We „Model“ Urban PM ?
c · Woodsmoke + (1-c) · DEP = Urban ?
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0.72
0.76
0.8
0.84
0.88
0.92
0.96
0 10 20 30 40 50 60 70Weathering time [days]
PAHs Graphite
rela
tive
C=C
pea
kra
tio
DPM exposed to air, humidity, sun light for 2 monthsNEXAFS peak heights changeAromatic C=C peak decreases , then increasesPAHs decomposed ?
Diesel PM Weathering Study
282 284 286 288 290 292 294Energy [eV]
DEP
CNT
weathered
as received
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Scanning Transmission X-ray Micro-spectroscopy
STXM is X-ray microscopy with chemical contrastResolution: ~ 100 nm, and chemical contrast of ~ 0.1 eVSoot core and extracts have different spectral characteristics
Spectrum = soot coreSpectrum = extract
Spectrum = graphiteand differential
Fuel (2004) 10 7/8, 997
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Potential tool for in-situ reaction studies !(ozone + soot, etc…)
Photochemistry and De-carboxylation
0.6
0.7
0.8
0.9
1
1.1
1.2
282 284 286 288 290 292 294
Energy [eV]
C=C C=O
COOH
C-OH
Exposure time t = 120 msec
600 msec
600 msec
120 msec
0.5
1
1.5
100 200 300 400 500 600 700Exposure time [msec]
R2CO
3
Intense X-ray beam of the STXM microscope generates nascent oxy-gen from air.
Upon irradiation, COOH carboxyl peak intensity decreases, and new peak evolves - probably from an organo-carbonate.
Alginic acidAtm. Environment 40/30 (2006) 5837and Special Issue in J. Electron Spectr. & Related Phenomena on Radiation Damages; in press
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Diesel Soot
25 °C extract
282 284 286 288 290 292 294282 284 286 288 290 292 294
Energy [eV]
Urban PM
25 °C extract
282 284 286 288 290 292 294Energy [eV]
Wood Smoke
25 °C extract
C=C
C=C
C-O
H
C=O
C-O
H
C-O
H
C=O
C=O
CO
OH
CO
OH
CO
OH
C=C
NEX
AFS
abs
orpt
ion
[a.u
.]PM and extracts may have entirely different,if not controversal spectral characteristics
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Diesel exhaust PM generated with oxidizer has higher genotoxicity
0.8
0.9
1.0
1.1
1.2
1.3
1.4
527 DEC 603 Ref
Incr
ease
in g
enot
oxic
ity
(pro
duct
ion
of b
-gal
acto
sida
se)
Incr
ease
in
geno
txic
ity
Total water extracts (25°-300°C)
280 285 290 295 300
527 DEC
603 Ref
Energy [eV]
A. Kubatova, A Braun, in preparationDe Marini et al., Bio-assay directed fractionation and mutagenicity of exhaust particles, Env. Health Persp. 2004, 112(8), 814-819
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Thank you
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Carbon, 43(1), (2005) 117-124.
NEXAFS vs. EELS
EELS and NEXAFS have similar spectra. TEM microscopes often come with an EELS spectrometer. But EELS spectra from TEM look blurred, almost entirely useless for quantitative studies.280 285 290 295 300
Inte
nsity
[a.u
.]
Energy [eV]
NEXAFS BL 9.3.2 ALS(Total Electron Yield)
NEXAFS BL 9.3.2 ALS(Sample current)NEXAFS BL X1A NSLS(STXM)
EELS in connectionwith TEM
Diesel soot powder from oxygenateddiesel fuel under load engine
Note: this concerns not ISEELS such as the ones by Hitchcock & coworkers
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0
0.5
1
1.5
280 285 290 295 300
ferrocenereference
Energy [eV]
C(1s) NEXAFS confirms WAXS results:catalytic suppression of soot formation by ferrocene
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Suggested NEXAFS Peak Assignments for DPM Extract
Energy [eV]
NE
XA
FS in
tens
ity [a
.u.]
282 284 286 288 290 2920
1.05
2.1CO3
2-
COOH
C-OH
C=OC=C
C-H
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C=C
CO
HC
OO
H
Energy [eV]280 284 300288 296292
Different PM samples show complex patterns in NEXAFS which cannot be easily attributed to the PM polarity
NE
XA
FS in
tens
ity [a
.u.]
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NEXAFS of soot, oil, and fuel
0
0.5
1
1.5
280 285 290 295 300Photon energy [eV]
Soot
C=C
C-H
Oil
Mix A
Diesel
284 285 286
287 287.5 288
Spectra of soot, lubricant, fuel.
Allows for chemical speciation of samples, and determination of oxidation states.
Fuel (2004) 10 7/8 997-1000.
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Catalytic suppression of soot formation in diesel engines
280 285 290 295 300
Diesel soot / ferrocene doped fuelGraphite SL 25Diesel soot / Ford motor vehicle
NEX
AFS
inte
nsity
[a.u
.]
Energy [eV]
FerroceneMetastable molecule = ironatom sandwiched between two cyclopentadienyl rings.
Dramatic decrease of C=C bond contribution in soot; increase in aliphatics
Mixing diesel fuel with ferrocene
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Soot Extracts
280 285 290 295 300
Energy [eV]
25oC
50oC
100 oC
150 oC200 oC
250 oC
Soot powder
Diesel soot and extractsFord Motor Company
Separation of diesel soot into solid core and volatile fractions with sub-critical water facilitates subsequent decomposition of NEXAFS spectra.
0
0.5
1
1.5
2
280 285 290 295 300Energy [eV]
Extract
Residual
Soot as prepared
Extracts do contain material with C=C bonds
From reference diesel fuel
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Soot ResidualsSeparation of diesel soot into solid core and volatile fractionswith sub-critical water facilitates subsequent decomposition of NEXAFS spectra.
280 285 290 295 300
25C 527250C 527300C 527
Energy [eV]
Soot Residuals
At low temperatures polar species like carboxylates and quinones are extracted.
282 284 286 288 290 2920
1.05
2.1
Energy [eV]
R2CO
3
COOH
C-OH
C=OC=C
C-H
benzo-quinone
Proposed peak assignment for extracts.
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Correlation of Toxicological Results and Spectra ?
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
0 50 100 150 200 250 300 350
527/DEC603/Reference
Extraction Temperature [oC]
0.20.30.40.50.60.70.80.9
1
0 50 100 150 200 250 300 350
603 Ref527 DEC
Extract Temperature oC
Cell cultures exposed to a series of subcritical water extracts. Protein fold increase is a measure for toxic response.
A. Kubatova, A Braun, in preparation
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Spectra of some solid carbon samples
280 285 290 295 300
Graphite SL 25Diesel soot / Ford motor vehicleFurnace deposits / Beech woodEthylene soot / Bunsen burnerNIST Urban PM
NEX
AFS
inte
nsity
[a.u
.]
Energy [eV]
Systematic and significant differences in the spectra depending on their origin
Soot spectra contain significant intensity from C=C bonds ~ 285 eV.Urban PM and wood creosote spectra contain significant intensity from aliphatics ~ 287 eV.
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0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.5
2
2.5
3
3.5
270 280 290 300 310 320
Urban_PM_summary
SC averaged NIST 1648 pellet
tey averaged NIST 1648 pellet
corrected energy
0.55
0.6
0.65
0.7
0.75
0.62
0.64
0.66
0.68
0.7
0.72
0.74
0.76
0.78
280 285 290 295 300
Urban_PM_summary
LAW 103 LAW 86
energy
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
270 275 280 285 290 295 300 305
FTP-75 day 3LRRINIST 1648composition
Energy