A novel class of molecular motors that rotate in the same direction at high speeds upon exposure to sunlight have been developed. This novel behaviour holds promise in new nano-engineering applications.
Bild: Artenauta / fotolia.com
Molecular motors are chemical compounds that are developed to carry out directional movements with respect to a particular stimulus. These compounds are capable of converting energy into mechanical motion and are used in the development of nanomachines. Substances whose 3D structure can be modified by light exposure serve as good candidates for molecular ‘engine blocks’.
However, all the light-activated molecular motors described so far utilize UV light as a power source. But this severely restricts their potential range of application, as its high-energy photons may have deleterious effects on the nanomachinery as a whole
- Dr. Henry Dube, LMU
In order to overcome the detrimental effects of the high-energy photons associated with UV light, a new class of molecular rotor was developed by the researchers that can be powered by visible light. When compared to UV radiation visible light is significantly less energetic and therefore does not negatively impact the operation of molecular machines.
The hemithioindigo molecule is a photoswitch that serves as the basis of the unique molecular motor. It contains two organic molecules joined by a carbon double bond. When exposed to sunlight, the hemithioindigo structure isomerises resulting in directional rotatation about the central double bond.
Lower energies of visible light can be used to acheive fast rotatation of the hemithioindigo-based motors in comparison to other light-powered motors. The research team demonstrated that the molecule rotates unidirectionally at speeds of up to 1000 times per second at room temperature.
We ourselves were surprised that the motor works so well, for it is known that many molecular motors do not steadily rotate in one direction, but also revolve in the opposite sense to some degree,” says Dube. “Given the complexity involved in the design of such motor molecules, it is really astonishing to that we gained complete control over the direction of rotation at the first attempt.
- Dr. Henry Dube, LMU
Since visible light can be used to power the novel molecule, it is much more versatile when compared to the other radiation-activated molecular motors. However whilst this is certainly a step in the right direction. Dube and the team at LMU were quick to point out that more research is needed before anything resembling an operational molecular machine is synthesised.
But we have a long way to go before molecular motors can be integrated into more complex nanomachines to perform functions that are more complicated than the directed rotatory movement we have now demonstrated. The long-term goal in this field is the miniaturization of working machines down to the size range of organic molecules. Such nanomachines would provide unprecedented precision in the processing or targeted modification of matter at the molecular scale, opening up entirely new opportunities in many areas of research
- Dr. Henry Dube, LMU