Molecules comprise clusters of atoms and are the product of the nature and arrangement of those atoms within. Where oxygen molecules we breathe feature the same repeating type of atom, sugar molecules are made of carbon, oxygen and hydrogen.
To create precisely the chemical interactions between atoms they desire, scientists have been working on a concept known as "selective chemistry" for some time. This could cause the development of sophisticated chemicals and machinery that can be tailored for specific purposes.
The 2016 Nobel Prize in Chemistry was awarded to Dutch scientist Ben Feringa for his development of a molecular car propelled by molecular motors spinning at 12 million revolutions per second. These so-called molecular machines were the subject of the award. To specifically target cancer cells, scientists have also developed molecular pumps, small gear wheels, and molecular submarines, to name a few examples.
This new study's authors compare “putting Lego bricks in a washing machine and hope that the quintillions of molecules somehow manage to assemble themselves into the intended product.” Their latest research hopes to rely more on deliberate control of the chemical bonding process and less on chance.
The study focuses on molecules known as structural isomers, which share the same atomic structure but differ in the way those atoms are connected to one another. The researchers showed they could specifically rearrange the chemical interactions by applying different voltage pulses using the tip of a scanning probe microscope. It was possible to change a molecule with a 10-membered carbon ring in the middle into, for instance, a molecule with a 4- and 8-member ring or a molecule with two 6-member rings in the middle.
The scientists discovered these processes were also reversible, allowing them to flip between different molecular configurations in a controlled way by arbitrarily breaking and forming the various connections. The team claims that this type of "selective chemistry" is unique.
Leo Gross, an IBM Research scientist and the senior author of the study, said “it is the first time that selectivity different bonds can be formed in a single molecule. By the magnitude of the voltage pulse applied on the molecule in the center, we can choose if we want to create the molecule on the right or the one on the left (see above left).”
Although molecular machinery is still in its infancy, technology that allows for more precise control over these kinds of structures may drastically speed up their development.
The movement of molecules or nanoparticles, the creation and manipulation of nanostructures, and the facilitation of chemical reactions are just a few of the activities that molecular machines may be used, according to Gross. Future uses could involve medication delivery, chemical synthesis, nanoelectromechanical systems, and single-electron molecular devices.