| Oct 22, 2024 |
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(Nanowerk News) Researchers have achieved a significant breakthrough in the synthesis of carbon nanotubes (CNTs) by developing a novel catalyst that allows for precise control over their atomic arrangement, known as chirality. This advancement paves the way for the creation of innovative semiconductor devices, addressing a challenge that has remained unresolved for over 30 years.
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The team consisting of researchers across Japan, led by Associate Professor Toshiaki Kato from the Advanced Institute for Materials Research (WPI-AIMR), has successfully synthesized CNTs with a chiral index of (6,5) at an ultra-high purity of over 95%.
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These findings were published in ACS Nano (“Synthesis of Ultrahigh-Purity (6,5) Carbon Nanotubes Using a Trimetallic Catalyst”).
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| (a) Relationship between binary catalyst (Ni+X) and (6,5)CNTs purity. A plot of (6,5)CNTs purity against the atomic number of the second factor (X) used in the binary catalyst. (b) Relationship between the fluorescence (PL) intensity (∝synthesized amount) of the ternary catalyst (NiSn+Y) and (6,5)CNTs. PL intensity dependence of (6,5)CNTs on the third factor (Y). (c-e) (c) Fluorescence-excitation (PLE) map, (d) UV-visible-NIR absorption spectrum, and (e) fitting results of CNTs synthesized under optimal synthesis conditions using a NiSnFe ternary catalyst. (Image: Toshiaki Kato)
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“A carbon nanotube is basically a sheet of carbon rolled into a hollow tube,” explains Kato, “While it sounds simple, CNTs are highly sought after for properties such as their exceptional conductivity, optical characteristics, and mechanical strength.”
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It’s no wonder they’re nicknamed the “king of nanomaterials.” This laundry list of desirable traits makes them a promising option for a truly broad number of applications – from constructing aircrafts and spaceships to developing biomedical devices.
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“The inability to control CNT chirality has been a major barrier to their industrial application, so this project was undertaken to find a catalyst that could consistently produce the desired target,” says Kato. Thus far, single-chirality synthesis with a purity of over 90% has only been achieved for (14,4) and (12,6) chiralities.
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| (a) Scanning transmission electron microscopy (STEM) image of NiSnFe catalyst and its atomic structure analysis results, and (b) Elemental mapping results for the same particles. (Image: Toshiaki Kato)
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By introducing a new catalyst composed of nickel (Ni), tin (Sn), and iron (Fe), the researchers have opened a new pathway for chirality-controlled synthesis. This NiSnFe catalyst acts as a highly specialized growth catalyst, enabling the selective synthesis of (6,5) chirality CNTs. Furthermore, these chirality-pure bundle structures of (6,5) CNTs show more than a 20-fold increase in their photoluminescence lifetime, compared to isolated (6,5) CNTs. This technique could potentially be used in the future to achieve other chiralities as well.
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The research team anticipates that their findings will lead to significant advancements in how semiconductor devices are manufactured and utilized.
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