The switch is as fundamental to electronics as the covalent bond is to chemistry: Switches make and break currents, whereas bonds make and break molecules. By covalently tethering a diarylethene to two graphene electrodes, scientists have harnessed the bond-breaking and bond-making process to create a single-molecule switch. The robust switch works at room temperature and is stable for more than a year.
In its open state, when there is no direct bond between the diarylethene’s thiophene units, the molecule acts as an insulator. But shine ultraviolet light on it, and a bond will form between the two thiophenes, making it possible for the molecule to conduct electricity. Visible light breaks the bond and returns the molecule to its insulating state.
Researchers had known that diarylethene molecules could behave as molecular switches, but previous examples of such switches weren’t necessarily reversible and tended to degrade over time. Covalently linking the molecule to graphene electrodes with appropriately sized linkers helped the research team, led by Peking University’s Xuefeng Guo and H. Q. Xu and University of Pennsylvania’s Abraham Nitzan, to create a successful switch (Science 2016, DOI: 10.1126/science.aaf6298)
The molecular switch could be a key component for ever-shrinking electronic devices. It could also guide the creation of devices that interface organic and inorganic materials.