The device, developed by researchers at King’s College London and published in Nature Nanotechnology, uses quantum effects to convert electrons flowing around a circuit into a controlled stream of “hot electrons” and light.
Hot electrons are highly energetic, making them very useful in chemical research, according to Dr Pan Wang, the paper’s lead author.
“Hot electrons can allow chemical reactions to occur between two molecules which would not normally react,” he said.
The device consists of two materials, eutectic gallium indium and gold nanorods, which are separated by an air gap of less than 1nm.
When a voltage is applied across the device, it causes a flow of electrons from the eutectic gallium indium electrode to the gold nanorods.
Although an air gap would usually prevent the electrons from flowing between the two materials, at distances of less than 1nm quantum mechanical rules apply, meaning the electrons are able to “tunnel” through.
This tunnelling means that the electrons arrive at the nanorod tips in the form of hot electrons.
What’s more, a small number of the tunnelling electrons also excite particles known as plasmons in the material, emitting light.
This process is typically very inefficient, said Wang. “But by using a gold nanorod array for one of the electrodes, we can provide billions of tunnel junctions, improving the electron-to-plasmon conversion efficiency,” he said. “This makes the emitted light visible to the naked eye.”
The device could be used in electronics to optically transmit information in the form of 1s and 0s by rapidly switching the light on and off. In this way it could be used to replace semiconductor lasers, which are becoming too bulky as the size of electronics equipment shrinks.
As well as chemical research, the hot electrons produced by the device could also be used in sensing. Since the tunnel junctions in the material are very sensitive to change, any new substance produced by a chemical reaction will alter their properties, changing the flow of electrons through the device. In this way it could be used to monitor chemical reactions, or to detect the presence of hydrogen leaks in fuel cell production, for example.
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