Experimental demonstration of a single-molecule electric motor

ROM 2012-2
Author: Heather L. Tierney, Colin J. Murphy, April D. Jewell, Ashleigh E. Baber, Erin V. Iski, Harout Y. Khodaverdian, Allister F. McGuire, Nikolai Klebanov and E. Charles H. Sykes
Institute: Department of Chemistry, Tufts University, Medford, Massachusetts 02155-5813, USA E. Charles H. Sykes: charles.sykes@tufts.edu
Publication: Tierney, H.L. et al. Experimental demonstration of a single-molecule electric motor. Nature Nanotechnology 6, 625-629 (2011). www.nature.com/nnano
Instrument: LT STM

For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor.

Electrons from an Omicron low-temperature scanning tunnelling microscope (LT-STM) are use to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.