Scattering Experiments

1
Scattering Experiments
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Coherence Length
Structural coherence length found for small
regions from TEM images SAXS Structural Lcoh
average SANS Structural and Magnetic Lcoh
averages
3
Small Angle X-ray Scattering
Braggs Law
Observe diffraction from planes of particles at
small angles
Both the lattice symmetry and the shape of
diffracting object contribute to the intensity
I(q)
Ignore scattering by the surfactant coating
? the radius R Rcore
4
3D Arrays Structures from SAXS
x10.3 nm
0
Shape factor, d8.5 nm
-2
d8.5 nm
-4
-6
-8
Both hcp and fcc arrays observed
Shcp(q)P(q)
Shcp(q)P(q)
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3D Arrays Made Over 4 Weeks
Interparticle spacing slightly reduced
x9.6 nm
d8.5 nm

• Average intensity
• Sharpest peak

Spots due to 3 hcp supercrystals- Large Lcoh
6
Nanoparticle Crystals vs Disordered Assemblies
SAXS patterns of 8.5 nm Fe nanoparticle FCC
nanoparticle crystals and rapidly quenched
assemblies
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