Pictured here is a stationary (left) versus a spinning (right) rotor molecule. At very low temperatures (close to absolute zero) it is possible to stop the rotation of molecules because the molecules do not have enough energy to spin. Energy applied to the stationary molecule in the form of heat or electrical current can induce rotation. When supplied with energy, the molecule will spin around a central axle, similar to a propeller. In the bottom-left corner of each image are schematics. In this schematic, blue=sulfur, yellow=carbon, white=hydrogen and gray=gold atoms.
On the left is a still from a scanning tunneling microscope (STM) movie showing what happens when a single molecule moves to close to a chain of molecules. A schematic representation of what is happening in the STM movie is shown on the right.
In the schematic representation, a single molecule (on the right) rotates very close to a chain of two molecules (on the left). After a few frames, the rotor moves toward the chain. The molecules in the chain begin to interact with the rotor, and rotation of the single molecule is hindered. After a few more frames the spinning molecule is pulled onto the chain and it stops spinning altogether. In the schematic, blue=sulfur, yellow=carbon, white=hydrogen and gray=gold atoms. [Note: Each frame in the movie took ~2 minutes to acquire.]
This research, supported by a grant from the National Science Foundation (CHE 08-44343), was conducted in the lab of Professor E. Charles H. Sykes in the chemistry department at Tufts University. For further information about this research, including a video, visit http://ase.tufts.edu/chemistry/sykes/Sykes%20Lab%20Research%20Group.html.
More About This Image
As devices become smaller and smaller, moving parts are needed on a more miniature (nano) size scale. One such component that will be required to build nanoscale machines is the rotor. Just as gears and ratchets are used in everyday life to produce motion, making nanoscale counterparts will be a crucial step towards building tiny machines out of molecules. These nanomachines can be found throughout our bodies in the form of proteins, which complete tasks such as cellular motion or muscle contraction. However, very little is known about how to harness the motion of individual molecules in order to perform similar tasks.
Professor Sykes has found a group of molecules with which to study the basic properties and mechanics of rotation. In order to turn a rotor into a useful machine, Sykes' group will need to be able to use a fuel source to drive mechanical motion. Their molecular rotors can be spun using heat or an electrical current as the fuel. While heat provides an easy source of energy, rotation by this method is random and uncontrollable. However, recently Sykes found that by exciting vibrations of the chemical bonds between individual atoms, it is possible to rotate molecules on command. This capability will make the complicated task of powering nanomachines much easier for future studies of directed motion.
(Date of Images: 2007-2009)
Credit: Heather L. Tierney, April D. Jewell and E. Charles H. Sykes, Chemistry Department, Tufts University