Diodes and resistors were assembled from proteins that use quantum effects

Chemists Ryan Chiechi and Xingkai Qiu of North Carolina State University used two different types

fullerenes (molecular closed polyhedra made of carbon). These cells were placed on gold substrates and immersed in a solution of the first chloroplast photosystem. 

Scientists have shown that various fullerenesinduced the proteins of the first photosystem to self-assemble on surfaces into specific shapes, creating diodes and resistors. To complete the circuit, contacts from gallium-indium liquid metal eutectic were printed on top. 

Image: Xinkai Qiu, Ryan C. Chiechi, Nature Communications

“Where we needed resistors, we appliedone type of fullerene on the electrodes, on which the first photosystem is assembled independently, and where we needed diodes, we applied another type. The oriented photosystem I proteins rectify the current, which means that the electrons only move in one direction,” says Chiechi.

The researchers connected protein structures to artificial electrodes and created simple logic circuits that used electron tunneling to modulate current.

These proteins scatter the wave function of electrons,mediating tunneling in ways that are still not fully understood. As a result, despite the thickness of 10 nm, this circuit operates at the quantum level, functioning in the tunnel mode. And because we're using a group of molecules rather than individual molecules, the structure is stable. In fact, we can print electrodes on top of these circuits and create devices.

Ryan Chiechi, professor of chemistry at North Carolina State University, study co-author

To demonstrate their development, chemists createdsimple diode-based AND/OR gates and incorporated them into pulse modulators that can encode information by turning one input signal on or off depending on the voltage of another input. Logic circuits based on the proteins of the first photosystem could switch an input signal with a frequency of 3.3 kHz. This, the researchers note, although not comparable in speed to modern logic circuits, is one of the best results for molecular circuits.

Scientists believe that these protein-based circuits could lead to the development of electronic devices that improve, replace, or extend the functionality of classical semiconductors.

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