Probing charge heterogeneities with AFM Torbjörn Pettersson, Esben Thormann and Per Claesson
torbjorn.pettersson@surfchem.kth.se
Probing charge heterogeneities with AFM Torbjörn Pettersson, Esben Thormann and Per Claesson
torbjorn.pettersson@surfchem.kth.se
AFM
Imaging
Normal force
Imaging
1 x 1 mm (gold particle)
Normal force
Normal force
Time Z sensor Z movement Approach Retraction Time Deflection Deflection Approach Retraction
Force profiles in different salt concentrations
Force profiles when surface charge is varied
Probe size – sensing neighbouring charges
Our plans
Method 1
Force curve – raster
Our plans
Scan size 15 nm. Height image.
A single defect in molecular lattice of PDA crystal is visible. Method 2
High-resolution images
Sample preparation
Disperse bentonite in aqueous solution
Prepare -charged surface (amin-silan modification of silica)
Adsorbe bentonite sheets on the surface
Sample preparation -Problems
Remove excess of amin-silane from the surface
Bentionite might not adsorb as a homogeneous layer
Bentonite can release from surface with high salt concentration in the solution
Force curve raster -Problems
Find bentonite on the surface
Lateral drift
Huge amount of data to analyse
Electrostatic repulsion vs. hydration forces
High resolution imaging -Problems
Need smooth surface
Our plans
Method 1
Force curve – raster Method 2
High-resolution images
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