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OXIDATION AND REPLACEMENT OF OLEIC ACID AT THE AIR/WATER INTERFACE TO UNDERSTAND
FAT-COATED AEROSOLS
Laura F. Voss, Kandice L. Harper, Gang Ma, Christopher M. Hadad, & Heather C. Allen
Department of ChemistryThe Ohio State University
Columbus, Ohio
FundingCamille and Henry Dreyfus Postdoctoral Program in Environmental ChemistryNSF-ATM NSF-Ohio State EMSI NSF-CHE CAREER Beckman Young Investigator Award
• 3.3 billion metric tons of salt spray enters the atmosphere yearly
• Inverse micelle first proposed by Gill et al. (1983), furthered by Ellison, Tuck, & Vaida (1999)
• Field samples of marine and continental aerosols collected and analyzed by Tervahattu et al. (2002, 2005)
Dobson et al., PNAS., 97, 11864, 2000
Fat-Coated Aerosols
Tervahattu et al., J. Geophys. Res., 107, D7, 4053, 2002; D16, 4319,
2002.
TOF-SIMS Analysis of Coated Aerosols
C16C18
palmitic acid cis-oleic acid
Tervahattu et al., J. Geophys. Res., 107, D7, 4053, 2002.
Oleic Acid Monolayers
• Studied using sum frequency generation spectroscopy• Oxidation of oleic acid by ozone• Replacement of oxidation products by less soluble species
Sum Frequency Generation
Spectroscopy
2 ps, 800
100 fs, IR
800nm + IR= sum
300 cm- 1 bandwidth spectrum from every laser pulse
815810805800795790785
visible wavelength (nm)
ground state
IR excited state
virtual state
En
erg
y
3050300029502900285028002750
Incident infrared (cm-1
)
3200310030002900280027002600
Incident infrared (cm-1
)
25
20
15
10
5
0
surf
ace
pres
sure
(m
N/m
)
80706050403020
Å2/molecule
Coupling BBSFG with Langmuir trough allows simultaneous collection of spectroscopic and thermodynamic data.
Langmuir Isotherms
Concurrent Langmuir Isotherm & SFG:Oleic Acid
25
20
15
10
5
0
surface pressure (mN
/m)
8006004002000
time (seconds)
Concurrent Langmuir Isotherm & SFG:Oleic Acid
25
20
15
10
5
0
surface pressure (mN
/m)
8006004002000
time (seconds)
Oleic Acid Compression Snapshots
0.10
0.05
0.00
305030002950290028502800
Incident infrared (cm-1
)
30
20
10
0
surfa
ce p
ress
ure
(mN/
m)
80706050403020Å
2/molecule
0.10
0.05
0.00
BBSF
G in
tens
ity (a
.u.)
0.10
0.05
0.00
a
b
c
abc
0.5
0.4
0.3
0.2
0.1
0.0
BB
SF
G in
ten
sity
(a.
u.)
305030002950290028502800
Incident infrared (cm-1
)
CH2
SS
CH3
SS
CH2
FR
CH3
FR
=CH olefinic stretch
Oleic Acid Monolayer
R1
R2
+
+
··
··
··
·· · ·
+
··
oleic acid primary ozonide
nonanal
oxononanoicacid
(a)
(b)
(a)
(b)
azelaic acid
octanoic acid
nonanoic acid
Oleic Acid-Ozone Reaction Snapshots
0.10
0.05
0.00
305030002950290028502800
Incident infrared (cm-1
)
0.10
0.05
0.00
0.10
0.05
0.00
BB
SFG
inte
nsity
(a.u
.)
0.10
0.05
0.00
0.10
0.05
0.00
T=0 min
T=1 min
T=10 min
T=2 min
T=30 min
CH2 SSCH3 SS
CH3 FRCH2
FR
R1
R2
Voss et al., J. Geophys. Res. submitted
Oleic Acid Oxidation on 0.6 M NaClT=0 min
T=1 min
T=10 min
T=2 min
T=30 min
CH2 SSCH3 SS
CH3 FRCH2
FR
R1
R2
0.10
0.05
0.00
305030002950290028502800
Incident infrared (cm-1
)
0.10
0.05
0.00
BB
SF
G in
ten
sity
(a.
u.)
0.10
0.05
0.000.10
0.05
0.00
0.10
0.05
0.00
nonanoic acid octanoic acidazelaic acidnonanal 9-oxononanoic acid
product solubility
in water,
g/L
nonanal 0.096
nonanoic acid 0.28
octanoic acid 0.79
azelaic acid 2.4
9-oxononanoic acid
19
Oleic Acid-Ozone Reaction Products
0.10
0.05
0.00
BB
SF
G i
nte
ns
ity
(a
.u.)
305030002950290028502800
Incident infrared (cm-1
)
0.10
0.05
0.00
nonanal
oleic acid monolayer after 2 minute of ozone
Nonanal vs. Oxidation of Oleic Acid
0.10
0.05
0.00
305030002950290028502800
Incident infrared (cm-1
)
0.10
0.05
0.00
BB
SF
G in
ten
sit
y (
a.u
.)
oleic acid monolayer after 1 minute of ozone
oleic acid monolayer in disordered liquid state
Compression Data vs. Oxidation of Oleic Acid
Oleic Acid-Ozone Reaction
Oleic Acid Monolayer Replaces
d31-Palmitic Acid Monolayer
Monolayer Replacement
Voss et al., J. Chem. Phys. B. submitted
1.0
0.8
0.6
0.4
0.2
0.0
220021002000
Incident infrared (cm-1
)
1.0
0.8
0.6
0.4
0.2
0.0
BB
SF
G in
ten
sity
(a
.u.)
0.3
0.2
0.1
0.0
300029002800
Incident infrared (cm-1
)
0.3
0.2
0.1
0.0
d
CD3 SS
CD3 FR
CD3 AS
CH3 FR
CH2 FR
CH3 SS
CH2 SS
=CHolefinicstretch
Monolayer Replacement
Voss et al., J. Chem. Phys. B. submitted
1.0
0.8
0.6
0.4
0.2
0.0
220021002000
Incident infrared (cm-1
)
1.0
0.8
0.6
0.4
0.2
0.0
BB
SF
G in
ten
sity
(a
.u.)
0.3
0.2
0.1
0.0
300029002800
Incident infrared (cm-1
)
0.3
0.2
0.1
0.0
d
CD3 SS
CD3 FR
CD3 AS
CH3 FR
CH2 FR
CH3 SS
CH2 SS
=CHolefinicstretch
1.0
0.8
0.6
0.4
0.2
0.0BB
SF
G i
nte
ns
ity
(a
.u.)
220021002000
Incident infrared (cm-1
)
0.3
0.2
0.1
0.0
300029002800
Incident infrared (cm-1
)
After Oxidation
d31-Palmitic Acid Monolayer Reforms
Conclusions
• No spectroscopic evidence of oxidation products at the air/water interface
• Least soluble surfactants at interface• Dissolved surfactants replace reaction products• Results same on 0.6 molar sodium chloride solution
Acknowledgements
FundingCamille and Henry Dreyfus Postdoctoral Program in Environmental ChemistryNSF-ATM NSF-Ohio State EMSI NSF-CHE CAREER Beckman Young Investigator Award
Jeremy Beck
Mohamad F. Bazerbashi
Allen Group
Hadad Group
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