Jun 23rd

Today, we prepare a monolayer of ATTO molecules to be scanned with the cantilever tip touching the surface of the sample. The goal is to find a molecule that shows quenching when the tip touches the molecule. In order to demonstrate this effect, we need to remove the SiO layer that is covering the tip. The SiO layer would block the transfer of electrons to the Si tip, thereby inhibiting quenching. To remove the SiO layer, a HF & NH4F solution was used. The cantilever was put into the HF solution for 1 minute to remove the SiO layer. Used harmful HF solution was remove by pipeting it into excess CaCl2 solution. A white precipitate of harmless CaF2 was produced. The sample was scanned with a red laser beam to visualise the fluorescent molecules. Next a molecule was picked and a smaller area around the molecule was re-scan to look for quenching effect. We picked several molecules to be re-scan. The first few molecules did not show quenching. Finally,we found a molecule that demonstrated a small quenching when the cantilever tip touches the molecule.