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Snapshot of a molecular switch

Scanning probe microscopes – like the scanning tunneling microscope, and the atomic force microscope – give us valuable information about individual molecules. One of the most interesting areas of research are molecular switches, which can be switched from one configuration to another.

The key to a molecular switch is to know what is required to switch it. Normally this is described by a potential energy barrier. To determine the potential energy above an adsorbate with a normal AFM requires a series of images at various heights. But molecular switches can change configurations as the tip height changes, making this analysis problematic.

We used lateral force microscopy, where only a single image is required to determine the potential energy. We investigated copper phthalocyanine – a molecule used for OLEDs – on a metal surface and determined the potential energy barrier of the switching.

This is the first demonstration of lateral force microscopy capturing the “snapshot” of a molecular switch, and we believe this technique will be applied to more systems to better understand the dynamics and stability of molecular switches.

For more information, see Weymouth, Riegel, Simmet, Gretz and Giessibl “Lateral Force Microscopy Reveals the Energy Barrier of a Molecular Switch” ACS Nano (2021).

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