spectroscopic probes of h-bonding at aqueous interfaces...spectroscopic probes of h-bonding at...

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