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Probing charge heterogeneities with AFM Torbjörn Pettersson, Esben Thormann and Per Claesson torbjorn.pettersson@surfchem.kth.se Showing 1 - 15 of 15 items

Tags: forc | surfac | imag | method | bentonit | charg | plan | curv

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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