Nanoparticle Surface Characterization by X-Ray Photoelectron Spectroscopy

http://www.phi.com/Interface/PHI%20Interface%20Spring%2005.pdf

What is Nanotechnology?

Nanoscale science: investigates the properties of matter in the critcal range of 1nm – 100 nm.

Nanotechnology: Is building and using devices from 1 nm – 100 nm.

Nano = 10-9

What Leads to Unsual Properties?

Any solid or liquid has 2 components:

•surface

•bulk

The Macroscopic Case

One drop of water:

100,000 bulk molecules per

1 surface molecule

Another Example...

•2 surface layers vs. ~10,000,000 internal layers

•2 surface layers vs. ~5,000,000 internal layers

•Percentage of surface:

0.000002% vs 0.000004%

Shrinking Down to the Nanoscale

5%

10%

50%

100%

Properties of surface atoms/molecules now

affect the overall properties.

C60

Properties Change According to Size!

Different sizes of gold particles = different optical properties.

• Nano is all about surface!• Surfaces are thin.• Most surface coatings are

organic.

Boyen, H.-G.; Kastle, G.; Weigl, F. et al. Science 2002, 297, 1533-1536.

Nanoparticle Surfaces: What’s the Problem?

http://www.almaden.ibm.com/st/scientific_services/materials_analysis/xps/

XPS: How Does it Work?

X-Ray

ejected electron

KEelectron = hX-ray – BEelectron

XPS Spectrometer: Basic Components

Settle, F., ed. Handbook of Instrumental Techniques for Analytical Chemistry. Prentice Hall. 1997.

300 295 290 285 280 275

0

200

400

600

800

1000

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Co

un

ts /

s

C(1s) Binding Energy (eV)

Peak Position Area % C1s Carbon- ID

1 285.50 1457.1 52% Pristine C60

2 287.45 489.75 18% Mono-oxidized C

3 289.73 836.67 30% Di-oxidized C