electrochemistry in supramolecular science

Date 27.01.2009

Faculty of Mathematics

and Natural Sciences

Stratingh Institute for Chemistry

Electrochemistry in Supramolecular Science

Wesley R Browne

Supramolecular AIO course

Groningen, 1st /2nd of February

www.browne.fmns.rug.nl

Date 27.01.2009

faculty of mathematics

and natural sciences

stratingh institute for chemistry

Background1. Basic concepts in electrochemistry

2. Cyclic and thin layer voltammetry

3. Experimental conditions & Electrochemical cells

4. Spectroelectrochemistry

5. Other techniques

Applications1. Electrochemistry of SAMs and Electropolymers

2. Electrochemistry and molecular structure

3. Electrochemical STM

4. SERS on roughened electrodes

Date 27.01.2009

Faculty of Mathematics

and Natural Sciences

Stratingh Institute for Chemistry

Background

Date 27.01.2009




Basic concepts in electrochemistry

Potential

+

-

Energy level

of electrons Occupied

MO

Vacant

MO

Electrode Solution

Date 27.01.2009





Potential

+

-

Energy level


MO

Vacant

MO

Electrode Solution Electrode Solution

e-

Reduction: A + e- A-

Date 27.01.2009




Potential

+

-

Energy level


MO

Vacant

MO

Electrode Solution Electrode Solution

e-

Oxidation: A - e- A+


Date 27.01.2009




The Nernst Equation

Walther Hermann Nernst (25 June 1864 – 18 November 1941). German physical

chemist who is known for his theories behind the calculation of chemical affinity as

embodied in the third law of thermodynamics, for which he won the 1920 Nobel Prize

in chemistry. Nernst helped establish the modern field of physical chemistry and

contributed to electrochemistry, thermodynamics, solid state chemistry and

photochemistry. His career was cut short by his opposition to Hitler and the Nazi party

Red Ox + ne-

[ ]ln

[ ]

o

meas A

RT OxE E where F N e

nF red


http://upload.wikimedia.org/wikipedia/commons/7/71/Walther_Nernst.jpg

Date 27.01.2009




Electrode Solution

e-


[ ]ln

[ ]

o

meas

RT OxE E

nF red

Formally only at low concentrations, <10 mM

lno Oxmeas

red

RTE E

nF

Date 27.01.2009




0.4 0.6 0.8 1.0 1.2 1.420.0µ

10.0µ

0.0

-10.0µ

-20.0µ

-30.0µ

Compound

gets reduced

Compound

gets oxidized

START

Cu

rre

nt

/A

Potential vs SCE

Cyclic voltammetry is a powerful tool in following

redox processes in solution and on surfaces

Potential

+

-

Energy level


MO

Electrode Solution

Cyclic voltammetry

Pote

ntial

Time

Date 27.01.2009




1 -2 mm

Base of cell

Working electrode

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

-12.0µ

-10.0µ

-8.0µ

-6.0µ

-4.0µ

-2.0µ

0.0

2.0µ

4.0µ

6.0µ

Cu

rre

nt in

A

potential vs. SCE

0.001 V s-1

diffusion controlled

Co

nc

Potential

Cyclic voltammetry

Date 27.01.2009




1 -2 mm

Base of cell

Working electrode

Potential

Co

nc

Thin Layer Voltammetry

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

-12.0µ

-10.0µ

-8.0µ

-6.0µ

-4.0µ

-2.0µ

0.0

2.0µ

4.0µ

6.0µ

Cu

rre

nt in

A

potential vs. SCE

0.001 V s-1

pseudo thin layer

0.001 V s-1

diffusion controlled

Cyclic voltammetry

Date 27.01.2009




Diffusable species

Non-diffusion (surface confined)

3 1 15 *2 2 2(2.69 10 )p o oi n AD C v

5 2 *(9.39 10 )p oi n v A

Cyclic voltammetry

Date 27.01.2009




Two electrode cell

V

Power supplyi

Working electrodereference electrode

Experimental conditions & Electrochemical cells

Date 27.01.2009




Three electrode cell

V

Power supply i

Working

electrode

reference

electrode

counter

electrode

Current flow (ions not

electrons)

Potential

difference

N.B. iR drop = cell resistance


Date 27.01.2009




Four electrode cell

V

Power supply i

Working

electrode1

reference

electrode

counter

electrode

Current flow (ions not

electrons)N.B. iR drop = cell resistance

V

Working

electrode2


Date 27.01.2009




Electrodes

Reference electrodes

SCE (Hg/HgCl2/KClsat.aq.)

NHE (Pt/H2)

SCE (Hg/HgSO4/K2SO4sat.aq.)

Ag/Ag+ (non-aqueous)

Ag/AgCl electrode (aqueous)

Pseudo reference electrodes

Ag wire

Pt wire

Pd wire

Counter electrode

Typically platinum gauze or wire


Working electrodes

Pt wire/disc/gauze

Au wire/disc/bead/gauze (bead gives Au111

surface)

Glassy Carbon disc

Vitreous carbon (usually for bulk

electrolysis)

Diamond (boron doped)

ITO (indium tin oxide, transparent)

Hg (polarography)

Electrode size/shape

Mini – 0.1-1 cm2

Micro-/Ultramicro electrode 1-100 mm

IDE (interdigitated microelectrodes)

Date 27.01.2009




Solvents

Solvent window

Region in which solvent/electrolyte

are redox inactive. Depends also on

electrode type – e.g. platinum is

very active for H2 evolution whereas

Hg is not.

Solvent type

The more polar the better in order to

help dissociation of electrolyte and

increase conductivity.

N.B. Polarity is temperature

dependent. CH2Cl2 increases in

polarity with decreasing

temperature.


Electrolyte

In non-aqueous apolar media

TBAPF6, TOAHSO4, NaBArF (good for

electrochemistry in diethylether)

In non-aqueous polar media

KPF6, NaBF4 (can be a source of F-),

NaClO4 (can be explosive in very dry

solvent)

In aqueous media

KCl, NaCl, Na2SO4

Date 27.01.2009




UV.Vis Spectroelectrochemistry

Spectroelectrochemistry

Date 27.01.2009




FTIR Spectroelectrochemistry


Thin Gold Electrode

In transmission mode an adapted Liquid IR cell is very useful using CaF2 windows

See for example SPECACTM

Date 27.01.2009




Spectrograph

with CCD

Laser

sample

Basic Raman/fluorescence spectroscopic setup:


Date 27.01.2009




Raman spectro-electrochemistry of the polymer on a gold bead electrode. Signals are baseline corrected. Solvent

signals are present as a reference. At 0.2 Volts only solvent signals are observed as the neutral form of the polymer

doesn’t give resonance enhancement.

400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.3 V

0.3 V

Ab

s.

wavelenght (nm)

Date 27.01.2009




The electrode double layer

Electrode (positively charged)

Solution

Helmholtz or Stern

layer--

Specifically

adsorbed anion

= Solvent

molecule

+

Solvated cation

+

+Non-specifically

adsorbed anion

Outer

Inner

Diffuse layer


Date 27.01.2009




-15.0µ

-10.0µ

-5.0µ

0.0

5.0µ

10.0µ

15.0µ

20.0µ

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Dc3+

Dc2+

Potential (V vs SCE)

Curr

ent (A

)

Dc2+

Dc+

Dc

Desorption spike

Dc2+

Dc+

Dc

Dc3+

Dc2+

(qr)

Dc Dc2-

-10.0µ

-5.0µ

0.0

5.0µ

10.0µ

15.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0


Cu

rre

nt

(A)

Dc2+

Dc+

Dc

Dc2+

Dc+

Dc

Dc Dc2-

Adsorption to electrodes

Dr J. H. Jurenkamp, Ph.D. Thesis Groningen 2008


Date 27.01.2009




-10.0µ

-5.0µ

0.0

5.0µ

10.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Po


Cu

rre

nt

(A)

Pc3+

Pc2+

Po1+

Pc2+

Pc+

Pc

Pc3+

(Po3+

)

Pc Pc-

Pc2-

Pc Pc-

Pc2-

-10.0µ

-5.0µ

0.0

5.0µ

10.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Pc2-


Curr

ent (A

)Pc

3+ Pc

2+ Pc

+ Pc

Pc3+

Pc2+

Pc+

Pc

Pc2+

Pc Pc-

Pc2-

Pc Pc-

Pc2-

Pc3-

Pc2- Pc

3-


Other techniques

Date 27.01.2009




-10.0µ

-5.0µ

0.0

5.0µ

10.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Po


Curr

ent (A

)

Pc3+

Pc2+

Po1+

Pc2+

Pc+

Pc

Pc3+

(Po3+

)

Pc Pc-

Pc2-

Pc Pc-

Pc2-

-10.0µ

-5.0µ

0.0

5.0µ

10.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Pc2-


Curr

ent (A

)

Pc3+

Pc2+

Pc+

Pc

Pc3+

Pc2+

Pc+

Pc

Pc2+

Pc Pc-

Pc2-

Pc Pc-

Pc2-

Pc3-

Pc2- Pc

3-

-16.0µ

-12.0µ

-8.0µ

-4.0µ

0.0

4.0µ

8.0µ

12.0µ

16.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5


Curr

ent (A

)

-8.0µ

-4.0µ

0.0

4.0µ

8.0µ

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5


Curr

ent (A

)

Cyclic voltammetry of the open (left) and closed (right) form of PerSPer 7 (PerSPer open (Po), PerSPer closed (Pc)) in CH2Cl2 / 0.1 M TBAPF6 vs SCE at 0.1 V s-1.

Differential pulse voltammetry of the open (left) and closed (right) form of PerSPer 7 in CH2Cl2 / 0.1 M TBAPF6 vs SCE.


Other techniques – Differential Pulse Voltammetry

Date 27.01.2009




-16.0µ

-12.0µ

-8.0µ

-4.0µ

0.0

4.0µ

8.0µ

12.0µ

16.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5


Curr

ent (A

)

Other techniques – Differential Pulse Voltammetry

Pote

ntial

Time

Cyclic voltammetry

Pote

ntial

Time

Pulse voltammetry

Wait

Change potential

Sample current

-10.0µ

-5.0µ

0.0

5.0µ

10.0µ-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Po


Curr

ent (A

)

Pc3+

Pc2+

Po1+

Pc2+

Pc+

Pc

Pc3+

(Po3+

)

Pc Pc-

Pc2-

Pc Pc-

Pc2-

Date 27.01.2009




Applications

Date 27.01.2009




S SMe

Me

RRS SMe

Me

RR

UV

Vis

M. Irie, Chem. Rev., 2000, 100, 1685; H. Tian, S. Yang, Chem. Soc. Rev. 2004, 33, 85;

Date 27.01.2009




SSR R

SSR RSSR R S+S+R R

S.

+S.+R R

-e-

-2e-

hv313 nm

hv > 400 nm

+e-

-e-

+e-

isomerisation

-2e-

Date 27.01.2009




Self assembled monolayers and polymer

modified electrodes

Date 27.01.2009




S

S

CONH

Si(OEt)3

Toluene

S SO

O

O

Si (CH2)3CONH

Contact angle 80o

+ITO

J. Areephong, W. R. Browne, N. Katsonis, B. L. Feringa, Chem. Commun., 2006, 3930-3932.

Self assembled monolayers and

polymer modified electrodes

Electrochemistry of SAMs

Date 27.01.2009




S

S

CONH

Si(OEt)3

Toluene

S SO

O

O

Si (CH2)3CONH

Contact angle 30o

Contact angle 80o

+ITO

a) AFM image andb) phase contrast (1x1 mm2).


Date 27.01.2009




-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

-4.0µ

-2.0µ

0.0

2.0µ

4.0µ

6.0µ

8.0µ

10.0µ

12.0µ

14.0µ

16.0µ

Initial scan

2c 2c+ 2c

2+

2o2+

2c 2c+ 2c

2+

2c2+

2o

Curr

ent (A

)


-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

-10.0µ

0.0

10.0µ

20.0µ

30.0µ

Initial scan

1c-ITO 1c1+

-ITO

1c2+

-ITO

1c2+

-ITO

1o-ITO

Curr

ent

(A)


Solution SAM

J. Areephong, W. R. Browne, N. Katsonis, B. L. Feringa, Chem. Commun., 2006, 3930-3932.

S SMe

Me

RRS SMe

Me

RR

UV

Vis


Date 27.01.2009




-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5

30.0µ

20.0µ

10.0µ

0.0

-10.0µ

-20.0µ

-30.0µ

-40.0µ

Curr

ent (A

)


Photochemical switching of ITO switch modified electrode followed by electrochemistry

Photochemical switching - open/close cycling

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

5.0µ

10.0µ

15.0µ

20.0µ

25.0µ

30.0µ

35.0µ

40.0µ

b

a

Cu

rre

nt

(A)

Cycles


Date 27.01.2009




P. Wesenhagen, J. Areephong, T. Fernandez Landaluce, N. Heureux, N. Katsonis, J. Hjelm, P. Rudolf, W. R. Browne, B. L. Feringa, Langmuir, 2008, 24, 6334-6342.

Self assembled monolayers and

polymer modified electrodes

SS

OMeMeO

Polymerisable unit

Photochromic unit

Spacer

SS

OMeMeO

Electrochemistry of Redox polymers

Date 27.01.2009




300 400 500 600 7000.0

0.2

0.4

0.6

0.8

1.0

1.2

2o

2c

Ab

s

Wavelength in nm

a)

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.220.0µ

10.0µ

0.0

-10.0µ

-20.0µ

-30.0µ

-40.0µ

-50.0µ

-60.0µ

+e-

+e-

-2e-

-e-

2c

2c 2c+

2c+

2c2+

2c2+

2c2+

2o2+

Cu

rre

nt

in A

Potential in V vs SCE

2o

-e-

b)

SS

OMeMeO

Polymerisable unit

Photochromic unit

Spacer


Date 27.01.2009




0.0 0.3 0.6 0.9 1.2 1.530.0µ

20.0µ

10.0µ

0.0

-10.0µ

-20.0µ

-30.0µ

-40.0µ

Curr

ent

(A)

Potential V vs SCE


Date 27.01.2009




0.0 0.3 0.6 0.9 1.2 1.530.0µ

20.0µ

10.0µ

0.0

-10.0µ

-20.0µ

-30.0µ

-40.0µ

Curr

ent

(A)

Potential V vs SCE

0.0 0.2 0.4 0.6 0.8 1.0 1.2

40.0µ

20.0µ

0.0

-20.0µ

-40.0µ

Cu

rre

nt

(A)

Potential V vs SCE

0.0 0.2 0.4 0.6 0.8 1.0 1.20

5

10

15

20

25

30

35

40

Cu

rre

nt

in m

A

scan rate (V s-1)


Date 27.01.2009




SS

OMeMeO2o

-2e- S+S+

OMeMeO2o2+

S+S+

OMeMeO 2c2+

S+S+

OMeMeO

-2e-

++

2c4+

S+S+

poly-2c2+

1.2 V

1.5 V


Date 27.01.2009




>Limited layer thickness – lessons about conductivity of polymers

electrode

polymer

monomer monomer+

e-

monomermonomer+

e-polymer+

+

monomermonomer+

e-


Date 27.01.2009




S S

F6

S S

S S S S

F6

S

n

J. Areephong, T. Kudernac, J. J. D. de Jong, G. T. Carroll, D. Pantorotta, J. Hjelm, W. R.

Browne, B. L. Feringa, J. Am. Chem. Soc. 2008, 130, 12850-12851.


Date 27.01.2009




S S

F6

S S

S S

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

0.0

-5.0µ

-10.0µb)

Cu

rren

t (A

)



Date 27.01.2009




0.0 0.2 0.4 0.6 0.8 1.0 1.2

1.0n

0.0

-1.0n

-2.0n

-3.0n

-4.0n

a)

0.0 0.2 0.4 0.6 0.8 1.0 1.2

5.0n

4.0n

3.0n

2.0n

1.0n

0.0

-1.0n

-2.0n

-3.0n

-4.0n

-5.0n

-6.0n

Cu

rre

nt

in A

Potenial in V (vs SCE)

Cu

rre

nt in

A

Potenial in V (vs SCE)

0 5 10 15 20 25

-500.0p

0.0

500.0p

1.0n

1.5n

2.0n

2.5n

b)

Cu

rre

nt /A

cycle number

0.73

Cyclic voltammetric scanning electropolymerization of monomer in 0.1 M TBAPF6/CH2Cl2 cycled at 0.1 Vs-1 on gold micro electrode (10 mm diameter) Inset: Cyclic volatammogram of the polymer coated gold electrode in monomer-free 0.1 M TBAPF6/CH2Cl2

Increase in current at 0.73 V vs SCE with number of cycles.


Date 27.01.2009




Raman spectro-electrochemistry of the polymer on a gold bead electrode. Signals are baseline corrected. Solvent

signals are present as a reference. At 0.2 Volts only solvent signals are observed as the neutral form of the polymer

doesn’t give resonance enhancement.

Date 27.01.2009




-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

20.0µ

10.0µ

0.0

-10.0µ

-20.0µ

-30.0µ

Cu

rre

nt (A

)


S S

F6

S SS

S

S

H3C

F6

S

S S CH3

SS

S S

F6

S SS

S

UV

Vis


Date 27.01.2009




Electrochemistry & molecular structure

Date 27.01.2009




Yan-Li Zhao; William R. Dichtel; Ali Trabolsi; Sourav Saha; Ivan Aprahamian;

J. Fraser Stoddart; J. Am. Chem. Soc. 2008, 130, 11294-11296.

Cyclic voltammetry of [2]rotaxane (black, 1.1 mM) and

dumbbell 6(red, 1.1 mM) in 0.1 M LiClO4/H2O at scan rate =

100 mV s−1.

Date 27.01.2009




X

X

Anti-folded

Orthogonal

Syn-folded

X

X

X

X

X

X

Twisted

See for example: Mills, N. S.; Benish, M. A.; Ybarra, C. J. Org. Chem. 2002, 67, 2003-2012., Levy, A.;

Biedermann, P. U.; Cohen, S.; Agranat, I. J. Chem. Soc., Perkin Trans. 2, 2001, 2329-2341.

Bistricyclic aromatic enylidenes

Date 27.01.2009




S

S

Me

Me

Date 27.01.2009




250 300 350 400 450 500 5500.00

0.05

0.10

0.15

0.20

0.25

Abs

Wavelength /nm

Abs LumS

S

Me

Me

Date 27.01.2009




-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.42.0µ

0.0

-2.0µ

-4.0µ

-6.0µ

-8.0µ

-10.0µ

-12.0µ

Curr

ent in

A

potential vs. SCEAt 1 mV s-1 in CH3CN/TBAPF6, GC (WE), Pt (CE), SCE (RE)

S

S

R

R

Anti-folded

Kissinger, P. T.; Holt, P. T.; Reilley, C. N. J. Electro. Anal. Chem. 1971, 33, 1-12.

Evans, D. H.; Busch, R. W. J. Am. Chem. Soc. 1982, 104, 5057-5062.

Date 27.01.2009




0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.46.0µ

4.0µ

2.0µ

0.0

-2.0µ

-4.0µ

-6.0µ

Curr

ent / A

V vs. SCE

S

S

S

S

1.21 V- 2e-

0.36 V+ 2e-

R

R

R

R

Thin layer Cyclic voltammetry

Date 27.01.2009




300 400 500 600 7000.0

0.2

0.4

0.6

0.8

1.0

Abs (

AU

)

Wavelength /nm

Electrochromism

S

S

S

S

R

R

R

R

Date 27.01.2009




300 400 500 600 7000.0

0.2

0.4

0.6

0.8

1.0

Abs (

AU

)

Wavelength /nm

Fluorescence – blue/red

Date 27.01.2009




400 600 800 10000.00

0.05

0.10

0.15

0.20

12+

1A 12+

1A 12+

1.15 V1.15 V 0.35 V0.35 V 0.35 VA

bso

rba

nce

Time / s (1 s = 10 mV)

Date 27.01.2009




400 600 800 10000.00

0.05

0.10

0.15

0.20

12+

1B 1A 12+

1B 1A 12+

1B

1.15 V1.15 V 0.35 V0.35 V 0.35 VA

bsorb

ance

Time / s (1 s = 10 mV)


Date 27.01.2009




250 300 350 400

0.00

0.05

0.10

0.15

0.20

0.25

Ab

s

Wavelength /nm

S

S

hv

R

R

Anti-foldedSyn-folded

S

S

R

R

Date 27.01.2009




250 300 350 400

0.00

0.05

0.10

0.15

0.20

0.25

Abs

Wavelength /nm

S

S

hv

R

R

Anti-foldedSyn-folded

S

S

R

R

Date 27.01.2009




S

S

hv

MeO

OMe

Anti-folded

Syn-folded

S

S

MeO

OMe0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0.0

-1.0µ

-2.0µ

-3.0µ

-4.0µ

-5.0µ

-6.0µ

Curr

ent (A

)

Potential (V vs. SCE)

Date 27.01.2009




0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0.0

-1.0µ

-2.0µ

-3.0µ

-4.0µ

-5.0µ

-6.0µ

Curr

ent (A

)

Potential (V vs. SCE)

S

S

hv

MeO

OMe

Anti-folded

Syn-folded

S

S

MeO

OMe

Date 27.01.2009




Cyclic voltammetry of 1A before (black) and after conversion to 1B (blue) by irradiation with 365 nm light and after thermal reversion

of the photoproduct to 1A (red). Initial scan direction cathodic, scan rate 0.1 V s-1.

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

6.0µ

4.0µ

2.0µ

0.0

-2.0µ

-4.0µ

-6.0µ

-8.0µ

-10.0µ

-12.0µ

Cu

rre

nt

(A)


Date 27.01.2009




S

S

S

S

S

S

1.21 V- 2e-

0.36 V+ 2e-

hv

R R

R

R R

R

Anti-foldedBlue fluorescent

OrthogonalRed fluorescent

Syn-foldednon-fluorescent

1.10 V- 2e-

W. R. Browne, M. M. Pollard, B. de Lange, A. Meetsma, B. L. Feringa, J. Am. Chem. Soc., 2006, 126, 12412

Date 27.01.2009




Electrochemical STM

ii

Ref electrodeAuxillary electrode

moleculesubstrate

STM tip

Han Vos (Dublin city University)

Johan Hjelm (University of Denmark)

Date 27.01.2009




>Electrochemical STM

Tim Albrecht, Adrian Guckian, Alexander M. Kuznetsov, Johannes G. Vos, and Jens

Ulstrup, J. Am. Chem. Soc., 2006, 128, 17132–17138

Date 27.01.2009




Date 27.01.2009




>Electrochemical STM

Date 27.01.2009




Self-assembled monolayers

Surface Enhanced Raman Spectroscopy

on roughened gold electrodesYvonne Halpin (Dublin City University)

Hella Logtenberg (RUG)

Date 27.01.2009




Surface enhanced Raman spectroscopy

› Surface coverage = 6.5 * 10-12 mol/cm2

› Raman spot size = 100 µm2

› Roughly we are looking at 6.5 * 10-18 mol analyte

SERS effect:

› Raman enhancement

by surface plasmon

› Charge transfer effect

between metal and monolayer

0

0.7

0.2

0.4

0.6

200 900400 600 800

Abs

Wavelength [nm]

Date 27.01.2009




SERS on electrodes

>Au-beads (electrochemically cleaned and roughened)

>Prepare SAM from solution

>Raman microscope

>785 nm and 633 nm excitation

Date 27.01.2009




Roughened bead

5x 20x 50x

Date 27.01.2009




Recommended Texts

Electrochemical Methods- Fundamentals and applications, Allen J. Bard, Larry R. Faulkner

Electrode Dynamics - (Oxford Chemistry Primers) by A. C. Fisher

Electrochemistry for Chemists- by Donald T. Sawyer, Andrzej Sobkowiak, and Julian L. Roberts

Supramolecular Electrochemistry- By Angel E. Kaifer

Experimental Electrochemistry for Chemists- by Donald T. Sawyer

Date 27.01.2009




Any questions?

electrochemistry in supramolecular science

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