Molecular motors on surfaces studied by scanning tunnelling microscopy
Place: Conference room, IMDEA Nanociencia.
Artificial molecular motors that convert external energy into controlled motion have seen great developments in the last decades . While many studies exist in solution, little is known how such functional molecules behave on a surface. However, such a solid support can be advantageous as it offers fixed points of reference as well as confinement in two dimensions, making it easier to study the directionality of their motion.
We have studied so-called Feringa motors on various surfaces by low-temperature scanning tunnelling microscopy (STM). On Cu(111) these molecules adsorb in three different conformations, which are related to the states of the motor cycle in solution. The relative stability of the in-solution motor states is reversed on the surface. It was found that rotations of individual molecules can be induced over rather long distances up to about 100 nm by voltage pulses with the STM tip. Importantly, these rotations show high directionality (clockwise or anticlockwise), which will be discussed in view of their specific chemical structure and adsorption.
 W. R. Browne and B. L. Feringa, Nat. Nanotech. 1, 25 (2006).