In episode 20 of our Make-It-Move segment, a terfluorene bobsleigh makes an appearance on a flat silver surface in a scanning tunneling arena. As described by Civita et al. (DOI)in the journal Science the slim and elongated terfluorene molecule (think fluorene trimer) has bromine substituents front and back for STM visibility and methyl legs that lift it from the ground. It is well known a STM tip can move molecules around on many different surfaces but for the particular combination of probe and surface, expectations were raised.
When a molecule was scanned that had aligned itself with the 110 direction of the silver crystal surface, it was found to be very mobile in such a way that only a blurry line was registered instead of the clearly defined molecule. As if superman makes a fly-by. More observations: the molecule stayed on the same track and was unable to hop to another track, only when the bromine headlights were removed it could reverse direction. In another experiment a molecule was dragged to one position, then the STM tip was raised and moved to another position 150 nanometers away. When the tip was lowered again it attracted the molecule which swiftly closed the distance. In another setup one tip was the sender and another was the receiver by switching voltages. Measurements of absolute velocities of different molecules are announced.
Previous make-it-move episodes: 19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1