Toward tip-enhanced Raman spectroscopy at the solid/liquid interface

Towardtip-enhanced Raman spectroscopy

at the solid/liquid interface

Katrin F. Domke, Bruno Pettinger

Fritz Haber Institute of the Max Planck SocietyDepartment of Physical Chemistry

Berlin, Germany

STM and Raman …

… and potential control

-1.2 -0.8 -0.4 0.0 0.4

-2

-1

0

1

**

physisorbed phasechemisorbed phase

E / V vs. Ag/Ag+

j /

cm-2

Cyclic voltammogram provided by Constanze Donner, Free University Berlin.

TERSSLi at potential-controlled surfaces

adenineopen circuit: -0.08 V

?-1.2 -0.8 -0.4 0.0 0.4

-2

-1

0

1

**

Cyclic voltammogram provided by Constanze Donner, Free University Berlin.

TERSSLi at potential-controlled surfaces

adeninecontrolled potential

FHI experimental set-up

working in air

Problem with old set-up

+TERS modified EC-STM

refractive indicesair: 1

glass: 1.5water: 1.33

focus too big,no signal

glasses don‘t fit, no roomcorrection?

Parabolic-mirror approach

electrode potential control

parabolic mirror

STM tip, insulated for EC measurements

sample

CE RE

in: excitation laser beamout:scattered light

4 mm

16 mm

Optical path

fibre in (633 nm)

fibre out (multimode)HeNelaser

spectrometer

beam expander

STM head

glass plate

parabolic mirror

TERSSLi set-up

Technical support: Klaus Grabitz

New STM head

500 x 500 nm2

200 x 200 nm2

Pt(111) bead crystal2 mm diameter

crystals prepared byJuan M. Feliu, Alicante, Spain

Si signal in air/water

(for comparison: 10 000 cts/s with old setup)

Tip coating I

Tip coating I

Tip coating II

To come …

50 x 50 nm2

25 x 25 nm2

Metal organyls: Co(II) porphyrines/toluene at Au(111)

flat, well-ordered?

nanocrystal?nice focus??