Researchers claim to have developed ‘smallest conceivable switch’

For a very long time miniaturization was the magic word in electronics. Dr. Willi Auwaerter and Professor Johannes Barth, along with their team of physicists on the Technische Universitaet Muenchen (TUM), have now presented a singular molecular switch within the journal Nature Nanotechnology. Decisive for the functionality of the switch is the placement of a single proton in a porphyrin ring with an inside diameter of under half a nanometer. The physicists can set four distinct states on demand.

Porphyins are ring-shaped molecules that may flexibly change their structure, making them useful for a big selection of applications. Tetraphenylporphyrin isn’t any exception: It loves to tackle a saddle shape and isn’t limited in its functionality when that’s anchored to a metal surface. The molecule holds has a couple of hydrogen atoms which can change their positions between two configurations each. At room temperature this process occurs continuously at an exceptionally rapid rate.

Of their experiment, the scientists suppressed this spontaneous movement by cooling the sample. This allowed them to urge and observe all the process in one molecule using a scanning tunneling microscope. This sort of microscope is especially best for the duty since – unlike other methods – it may be used not just to find out the initial and final states, but additionally allows the physicists to manipulate the hydrogen atoms directly. In an extra step they removed probably the most two protons from the interior of the porphyrin ring. The remainder proton could now tackle anyone of 4 positions. A tiny current that flows throughout the fine tip of the microscope stimulates the proton transfer, setting a particular configuration within the process.

Although the respective positions of the hydrogen atoms influence neither the fundamental structure of the molecule nor its bond to the metallic surface, the states aren’t identical. This small but significant difference, taken at the side of the truth that the method could be arbitrarily repeated, forms the idea of a switch whose state may be changed as much as 500 times per second. A single tunneled electron initiates the proton transfer.

The molecular switch has a surface area of just one square nanometer, making it the smallest switch implemented thus far. The physicists are thrilled by their demonstration and also are more than happy about new insights into the mechanism behind the proton transfer on account of their study. Knud Seufert played a key role along with his experiments: “To function a four-state switch by moving a single proton within a molecule is actually fascinating and represents a real leap forward in nano-scale technologies.”