German scientists design the world’s first light-activated molecular-level switch

Light-Activated Molecular Switch-2

Nanoelectronics is a fast growing field in the world of science. The need for smaller and more energy-efficient electronic devices has led to the development of one-dimensional nanowires, single electron transistors and even nanoscopic sensors. A few months back, scientists, from the University of Rochester and the Swiss Federal Institute of Technology, created a nanoscale photonic circuit that allows concomitant passage of light and electricity. This time around, a team of German researchers has successfully designed a fully-functioning molecular switch that can be turned on, with the help of light.

The research, recently published in the Advanced Science journal, was conducted by scientists, working at the Germany-based University of Konstanz and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). One of the biggest hurdles, for the team, was to find a molecule that can selectively transmit electricity, much like a switch. After countless hours of research, Dr. Jannic Wolf, of the University of Konstanz, came upon a specific diarylethene compound that exhibited similar properties. A photochromic substance, diarylethene undergoes chemical changes when exposed to light of particular frequencies. The three-nanometer-wide contraption also includes a set of gold nanowires, which are in turn attached to each side of the compound. Dr Artur Erbe, a physicist working at HZDR, said:

We developed a nanotechnology at the HZDR that relies on extremely thin tips made of very few gold atoms. We stretch the switchable diarylethene compound between them.

In the absence of incident light, part of the ring-shaped molecule remains open, thus acting as an insulator. By contrast, the different parts of the structure reconnect upon exposure to light. When closed, the device conducts electricity, quite easily. This is because the molecule, while possessing a strong bond between the individual atoms, is capable of suspending this connection, and restoring it, under the application of external energy. What is more, the breakthrough marks the first time that scientists have been able to switch a molecule on, in order to transmit current. Dr Erbe believes that such developments, in the field of molecular electronics, would eventually pave the way for smaller and more technologically-advanced gadgets. He said:

Single molecules are currently the smallest imaginable components capable of being integrated into a processor… For the first time ever we could switch on a single contacted molecule and prove that this precise molecule becomes a conductor on which we have used the light beam. We have also characterized the molecular switching mechanism in extremely high detail, which is why I believe that we have succeeded in making an important step toward a genuine molecular electronic component.

In order to test the efficacy of the contraption, the scientists first suspend the molecule in a fluid, inside a test tube. According to the group, exposure to UV light causes the compound to switch from its open to its closed state. However, turning off the molecule, to discontinue the current flow, is currently not possible. Nonetheless, Dr. Erbe is confident that the team will soon come up with a solution for the problem. He said:

Our colleagues from the HZDR theory group are computing how precisely the molecule must rotate so that the current is interrupted. Together with the chemists from Konstanz, we will be able to accordingly implement the design and synthesis for the molecule.

A significant milestone in the development of full-functioning nanocircuitry, the research will likely lead to substantial advancements in the fields of molecular electronics and nanotechnology. Speaking about the potential applications of the technology, Dr. Erbe said:

DNA molecules are, for instance, able to arrange themselves into structures without any outside assistance. If we succeed in constructing logical switches from self-organizing molecules, then computers of the future will come from test-tubes.

Light-Activated Molecular Switch-1

Source: University of Konstanz / Advanced Science

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