Molecular light chain: hybrid electronics for customized circuits

Molecular electronics could enable more powerful, smaller and faster electronic components in the future. Well-known components such as transistors, capacitors and resistors consist of individual molecules or groups of molecules. A team of researchers from the Swiss Federal Laboratories for Materials Science and Technology (Empa) in Switzerland and the Max Planck Institute for Polymer Research in Mainz has now taken an important step in this direction. They have combined graphene ribbons with special molecular compounds. The results have been published in the journal "Nature Chemistry".

Molecular zigzag wires

For their study, the researchers attached special molecules with a metal center to a graphene nanoribbon. This enabled the team to link the chemical and physical properties of the molecules to electronic components.

The graphene nanoribbons consist of a two-dimensional layer of carbon atoms with a width of just a few nanometers. Its electrical and magnetic properties depend on the structure of the ribbon. In their study, the research team created nanoribbons with zigzag edges. They docked special molecules to the edges of the graphene ribbon at regular intervals, alternating left and right. The graphene thus acted like a molecular, electrically and magnetically conductive cable between the molecules.

The molecules are so-called porphyrins. Porphyrins are chemical structures that also occur in nature, for example in the haemoglobin of human blood or in the chlorophyll of plants. The molecules form an organic ring of carbon, in the middle of which individual metal ions can be anchored. The team tested zinc, iron and gold, for example.

The type of metal ion bound determines the properties of the structure. "Our system is a construction kit that can be used to adjust different properties," says Roman Fasel, head of Empa's "nanotech@surfaces" laboratory and lead author of the study. The team produced the complex molecules under high vacuum at several hundred degrees Celsius on a gold surface.

Applications in quantum technology

As a next step, the team wants to insert different metal centers into the porphyrins and investigate their effect. They also hope to test a broader graphene band to offer the molecules a more versatile electronic basis.

The team sees potential applications for its components in quantum technology. "Our graphene ribbon with the porphyrins could function as a series of interconnected qubits," says Fasel.

As porphyrins often act as dyes in nature, for example in chlorophyll or haemoglobin, they can also emit light – like a string of molecular lights. The wavelength then depends on the magnetic properties of the system, meaning that information could be read on the basis of slight color changes.

Conversely, the porphyrins could also be excited by light to influence the properties of the graphene or act as chemical sensors.

(nie)