In a world-first, researchers at University College London have created individual 2D phosphorene nanoribbons, which could play an important role in future battery technologies.
Phosphorene is the phosphorous equivalent of graphene, and was first isolated in 2014. Since then, more than 100 theoretical studies have predicted new properties that could emerge from narrow ribbons of this material.
A new study published in Nature reports how researchers from UCL, Bristol, Virginia and Lausanne were able to form quantities of high-quality ribbons of phosphorene from crystals of black phosphorous and lithium ions.
"It's the first time that individual phosphorene nanoribbons have been made. Exciting properties have been predicted and applications where phosphorene nanoribbons could play a transformative role are very wide-reaching," said UCL’s Dr Chris Howard.
The ribbons have a height of one atomic layer, and are between 4 and 50 nanometres wide, and up to 75 micrometres long. "By using advanced imaging methods, we've characterised the ribbons in great detail, finding they are extremely flat, crystalline and unusually flexible," said Mitch Watts, first author on the study.
“Most are only a single layer of atoms thick but, where the ribbon is formed of more than one layer of phosphorene, we have found seamless steps between 1-2-3-4 layers where the ribbon splits. This has not been seen before and each layer should have distinct electronic properties," he explained.
Phosphorene nanoribbons have a greater range of widths and lengths than nanoribbons produced from other materials such as graphene, and could be produced at scale in a liquid. According to the researchers, potential areas of use include batteries, solar cells and thermoelectric devices for converting waste heat to electricity. They could also be used in quantum computing.
“We were trying to make sheets of phosphorene so were very surprised to discover we'd made ribbons,” said Howard. The process involves mixing black phosphorous with lithium ions dissolved in liquid ammonia at -50 degrees C. After 24 hours the ammonia is replaced with an organic solvent.
“For nanoribbons to have well-defined properties, their widths must be uniform along their entire length, and we found this was exactly the case for our ribbons," Howard continued.
Further research will study the fundamental properties of the nanoribbons, and explore their potential use in energy storage and electronic transport.
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