spectroscopic probes of h-bonding at aqueous interfaces...spectroscopic probes of h-bonding at...
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Alex BenderskiiDepartment of Chemistry & CEN University of Southern California
Spectroscopic Probes of HSpectroscopic Probes of H--bonding bonding at Aqueous Interfacesat Aqueous Interfaces
2OH
Water HWater H--bondsbondsWater H-bond network:
- H2
O liquid at room T-
high density
-
high viscosity-
solvation
properties
-
hydrophobic effect
at Interfacesat Interfaces
Aqueous interfaces:-
‘biological water’
-
environmental interfaces
-
electrochemistry-
heterogeneous catalysis
Spectroscopic Probes of HSpectroscopic Probes of H--bonding at Interfacesbonding at Interfaces
2
OHOH--stretchstretch HOH bendHOH bendOH
Rotational Dynamics of a Probe MoleculeRotational Dynamics of a Probe MoleculeStiopkinStiopkin et al.et al. NatureNature 474474, 192 (2011) , 192 (2011)
Vibrational spectrum of liquid waterVibrational spectrum of liquid water
Y. Marechal, J. Mol. Struct. 880
(2008) 38-43
HH--bond structures and dynamics at water surfacesbond structures and dynamics at water surfaces
““Free OHFree OH””
SFG line shapes SFG line shapes (SSP, PPP)(SSP, PPP)
Vibrational Vibrational couplingcoupling
InterferenceInterferencewith NR with NR backgroundbackground
Isotopic Isotopic dilutiondilution
Du, Superfine, Shen
PRL 70, 2313 (1993). PRL 86, 4799 (2001)
Richmond et.al.JPC B 107, 546 (2003)
HDHD--SFGSFG
Sovago
et al. PRL 100, 173901 (2008)Tian, Shen, JACS 2009,
131, 2790–2791
Free ODFree OD
of of HODHODHHODOD
Free OD at the Air/water interface: Free OD at the Air/water interface: isotopic dilutionisotopic dilution
Free ODFree OD
of of DD22
OODDODOD
D
O
H
D
O
D
C.-S.Tian
and Y.R. Shen, JACS 2009, 131, 2790–2791
Free OH and Free OD Free OH and Free OD stretchstretch
at the air/water interface of isotopic mixturesat the air/water interface of isotopic mixtures
HeterodyneHeterodyne--detected SFG (HDdetected SFG (HD--SFG)SFG)
Phase is locked across the spectrumPhase is locked across the spectrum SFG spectrum and phase recoveredSFG spectrum and phase recovered
0 0 D cela os +y Time DomainTime Domain Frequency DomainFrequency Domain
BroadBroad--Band Spectral Band Spectral InterferometryInterferometry
SFGSFG
LOLO
visIR
LOLO
KNbO4Monochromator
CCDτ 0
Stiopkin, I.V., Jayathilake, H.D.; Bordenyuk, A.N.; Benderskii, A.V. JACS 130, 2271 (2008).
Lepetit, Cheriaux, Joffre JOSA B 1995, 12, 2467Gallagher, Albrecht, Hybl, Landin, Rajaram,
Jonas JOSA B 1998, 15, 2338
2 2 2| | | | | | 2 | | cosHD SFG SFG LO SFG L SFG LO SFG LOOI E E E E E E
SSPSSPHDHD--SFG spectra at the air/water interface of DSFG spectra at the air/water interface of D22
O:HOD:HO:HOD:H22
OO
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Inte
nsity
(a.u
.)
2800276027202680Frequency (cm-1)
75% D2
O
50% D2
O
25% D2
O
100% D2
O
PPPPPP
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Inte
nsity
(a.u
.)
2800276027202680Frequency (cm-1)
FreeFree
OD of DOD OD of DOD vs. vs.
Free OD of HODFree OD of HOD
75% D2
O
50% D2
O
25% D2
O
100% D2
O
HOD D2
O HOD D2
O
νOD
(gas phase HOD) = 2728 cm-1
Δν
=17 cm-1
SSPSSP
0 20 40 60 80 1000
10
20
0.0
0.5
1.0
HO
D/D
2O F
ract
ion
D2O Concentration, %
Peak
Are
a, a
.u.
0 20 40 60 80 1002720
2730
2740
2750
D2O Concentration, %
Pea
k Fr
eque
ncy,
cm
-1
0 20 40 60 80 100
10
12
14
16
D2O Concentration, %
c
m-1
PPPPPP
0 20 40 60 80 1000
20
40
0.0
0.5
1.0
HO
D/D
2O F
ract
ion
D2O Concentration, %
Peak
Are
a, a
.u.
0 20 40 60 80 1002720
2730
2740
2750
D2O Concentration, %
Pea
k Fr
eque
ncy,
cm
-1
0 20 40 60 80 100
10
12
14
16
D2O Concentration, %
c
m-1
Δν
=17 cm-1
StiopkinStiopkin et al.et al.NatureNature 474474, 192 (2011) , 192 (2011)
D2
OHOD
GasGas--phase Dphase D22
OOνν11
= 2669.4 cm= 2669.4 cm--11
νν33
= 2787.9 cm= 2787.9 cm--11Local mode OD stretch Local mode OD stretch ODOD
= 2728 cm= 2728 cm--11
Coupling Coupling ≈≈
60 cm60 cm--11}}
Free ODFree OD
of of HODHODHHODOD
= 2728 cm= 2728 cm--11
Air/water interface HDAir/water interface HD--SFG resultsSFG resultsFree ODFree OD
of of DD22
OODDODOD
= 2745 cm= 2745 cm--1 1
17 cm17 cm--11
D
O
H
D
O
D
No shift upon isotopic dilutionNo shift upon isotopic dilution
(uncoupled)
Experiment (SSP)Experiment (SSP) Theory (SSP)Theory (SSP)
HOD DOD
DOD blue shifted from HOD
DOD broader than HOD
Peak at ~2680 cm-1
observed in DOD, suppressed in HOD
2650 2700 2750 2800
0.0
0.5
1.0
Im[
(2) S
SP]
(a.u
.)Frequency, cm-1
DOD HOD
0
1
2
2650 2700 2750 28000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Im[
(2) S
SP] (
a.u.
)
IR frequency (cm-1)
MD simulations + line shape calculationsMD simulations + line shape calculationsPiotr
A. Peieniazek, James L. Skinner, U. Wisconsin -
Madison
StiopkinStiopkin et al.et al. NatureNature 474474, 192 (2011) , 192 (2011)
The The other other (OD(OD))on the molecule with on the molecule with free ODfree OD
Max, Champados, J. Chem. Phys 116, 4626 (2002)
OH-stretch OD-stretch
Bulk FTIR of H2
O:HOD:D2
O mixtures
Corcelli, Lawrence, and SkinnerJ. Chem. Phys. 120, 8107 (2004)
2580 cm2580 cm--11
Vibrational spectrum of liquid waterVibrational spectrum of liquid water
Y. Marechal, J. Mol. Struct. 880
(2008) 38-43
HOH bendHOH bend
Small transition dipole: blessing in disguise?
Line shape not affected
by excitonic
effects
Water bend as a probe of HWater bend as a probe of H--bondsbonds
or is it, really??
H-bond strengthOH
νν22
(HOH
)
SFG spectrum of water bend at the A/W interfaceSFG spectrum of water bend at the A/W interface
Two Lorentzians
fits
SSPPPPGas (2) ( ) i m
NRm m m
bA e
i
1 (cm-1) 2 (cm-1)
SSP 1655b1
=161752b2
=3
PPP 1642b1
=211728b2
=7
Gas phase 1595
Unpublished
SFG spectrum of water bend at the A/W interfaceSFG spectrum of water bend at the A/W interface
1.1
1.0
0.9
0.8
0.7
0.6
PPP
intensity, a.u.
18501800175017001650160015501500IR frequency, cm-1
0.5
0.4
0.3
0.2
0.1
0.0
Lore
ntzi
an c
ompo
nent
s
PPP +20 oC
Gas phase
‘Free OH’
bend
‘H-bonded’
bend
Unpublished
Surface water bend: letSurface water bend: let’’s recall the stretchs recall the stretch
Du, Superfine, Shen
PRL 70, 2313 (1993); PRL 86, 4799 (2001)
ν(OH) frequency maps
‘free OH’
(narrow, blue-shifted)
H-bonded OH (red-shifted, broad, multiple species)
Non-Condon effects
Corcelli, SkinnerJPCA 2005, 109, 6154
Corcelli, SkinnerJPCA 2005, 109, 6154
OH
(cm-1)340032003000 3600 3800
1
3
2
OH-stretch
2
(cm-1)
180017001600 1900 2000
HOH bend
How to turn OHHow to turn OH--stretch into a bend spectrumstretch into a bend spectrum
ν2
=1590-0.26(3705-νOH
)(1) Flip frequency shift (2) Smaller shift(3) No Non-Condon effects –
dominant “free OH”
bend
2
(cm-1)180017001600 1900 2000
SFG spectrum of water bend at the A/W interfaceSFG spectrum of water bend at the A/W interface
1.1
1.0
0.9
0.8
0.7
0.6
PPP
intensity, a.u.
18501800175017001650160015501500IR frequency, cm-1
0.5
0.4
0.3
0.2
0.1
0.0
Lore
ntzi
an c
ompo
nent
s
PPP +20 oC
Gas phase
‘Free OH’
bend
‘H-bonded’
bend
Unpublished
WhatWhat’’s going on with the line width???s going on with the line width???
‘Free OH’
bend
(PPP): =37 cm-1
Bulk water: 45-50 cm-1
BendBend
0 20 40 60 80 100
10
12
14
16
D2O Concentration, %
c
m-1
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Inte
nsity
(a.u
.)
2800276027202680Frequency (cm-1)
StretchStretch
Free OH stretch
(PPP): =14 cm-1
Bulk water: 350-400 cm-1
1.1
1.0
0.9
0.8
0.7
1800170016001500IR frequency (cm-1)
1.0
0.9
0.8
0.7
0.6
0.5
0.16
0.12
0.08
0.04
1800170016001500IR frequency (cm-1)
0.16
0.12
0.08
0.04
PPPSSP
2
Unpublished
Water bend at the A/W interface: TWater bend at the A/W interface: T--dependencedependence1 .3
1 .2
1 .1
1 .0
0 .9
0 .8
0 .7
18501800175017001650160015501500IR f requency (cm -1)
1 .1
1 .0
0 .9
0 .8
0 .7
0 .6
0 .5
18501800175017001650160015501500IR f requency (cm -1)
PPP
SSP
20o
C
0o
C
20o
C
0o
C
Small changes in “free OH”
bend
Significant changes in “H-bonded”
bend –
suppressed at low T
Unpublished
Unpublished
Equilibrium orientational distribution
Orientational
anisotropy
E.g., rotational diffusion of a rigid rod
D D
D D
OrientationalOrientational
motion at surfaces/interfacesmotion at surfaces/interfaces
Orientational dynamics
Bulk
Interface
( ) 0
( ) 0
1.0
0.8
0.6
0.4
0.2
0.0
SFG
Inte
nsity
(a.u
.)
34003350330032503200IR frequency (cm-1)
SSP PPP SPS
OrientationalOrientational
dynamics in SFG line shapesdynamics in SFG line shapes
FrequencyFrequency--domain SFGdomain SFG
ΓΓSSP SSP =5.8 cm=5.8 cm--11
ΓΓSPS SPS =9.5 cm=9.5 cm--11
ΓΓrotrot
= 3.7 cm= 3.7 cm--11
~ 1 ~ 1 pspsDDrotrot
~~0.04 ps0.04 ps--11
CC−−H stretchH stretch
Unpublished
43
or ani iso
ani VH
iso VV VHI I I
OrientationalOrientational
Dynamics by Raman Dynamics by Raman --
PA in Bulk PA in Bulk
Rotational dynamics in water: TRotational dynamics in water: T--dependencedependence
3
92
Brot
K TR
7
6
5
4
3
2
1
0
Ram
an/S
FG ro
tatio
nal G
amm
a (c
m-1
)
340320300280260T (K)
800
600
400
200
0
Water fluidity x T
'SFG rot' (D2O surface) 'Raman rot' (H2O bulk) Fluidity x T (H2O) Fluidity x T (D2O)
Unpublished
PostdocsPostdocs::
Igor Igor StiopkinStiopkinSergey Sergey MalykMalykIan CraigIan CraigSean Roberts Sean Roberts
Grad. students:Grad. students:
ChampikaChampika
WeeramanWeeramanFadelFadel
ShalhoutShalhoutHimaliHimali
JayathilakeJayathilakeDavid ValleyDavid ValleyMikhail Mikhail VinaykinVinaykinPurminPurmin
DharDhar
NSF
Funding Funding
US AFOSR
Theory: water spectroscopyTheory: water spectroscopyProf. J. L. SkinnerProf. J. L. SkinnerDr. Dr. PiotrPiotr
PieniazekPieniazek(U. Wisconsin(U. Wisconsin--Madison)Madison)
AcknowledgmentsAcknowledgments