honed tube

Image: Chemical vapor deposition of molybdenum disulfide onto highly segregated boron nitride nanotubes to form coaxial nanotube structures. learn more
Tokyo, Japan. Researchers at Tokyo Metropolitan University used a surfactant to disperse insulating boron nitride nanotubes and apply them to surfaces without clumping. The team demonstrated that heat treatment can remove the surfactant to open up a pure nanoscale matrix; chemical vapor deposition can then use a range of materials to form coaxial nanotubes on a matrix. The ability to deposit nanotubes on “inert” insulating structures has given scientists unprecedented insight into the properties of new nanotube materials.
Breakthroughs in nanotechnology have made nanotubes and nanosheets more accessible to materials scientists. But studying them in isolation is far from easy. Since they are often coupled or clustered together, it is difficult to target the exotic optical and electronic properties that result from their reduced dimensionality.
Recent research has shown that nanotube materials can be grown on the surface of carbon nanotubes, providing well separated structures that can be characterized. But carbon nanotubes are conductive and highly absorbent, making it difficult to distinguish the electrical and optical properties of the coated material from those of the original nanotubes.
Now, a team led by Associate Professors Yusuke Nakanishi, Associate Professor Yohei Yomogida, and Associate Professor Yasumitsu Miyata from Tokyo Metropolitan University have used insulating boron nitride (BN) nanotubes as templates for nanotube growth. It was no easy task: Boron nitride nanotubes are known for their stickiness. Although they can be dispersed with a surfactant to help separate the tubes, it is not clear if the surfactant can be removed to give a clean template. Now the team has found a surfactant that doesn’t stick to the tubes, and they’ve also vacuum-heat-treated it, leaving clean, well-isolated patterns of insulating nanotubes.
Using chemical vapor deposition, a number of materials can be applied to the template. The new tube is wrapped around the original BN tube, forming what looks like a nanoscale coaxial cable. It is important to note that since BN is an insulating material, the electrical properties of any coating material can be studied to unprecedented depth. This includes a property called chirality, “chirality” in the structure of atoms in nanotubes, which creates a number of exotic electronic properties.
In principle, the team believes their “nanotubes” could be used to simulate the growth of various materials. They’ve already had success with molybdenum disulfide and carbon, and there’s room for more. Combined with the optical and electrical inertia of their BN template, their new platform promises not only material discovery, but unlimited access to its exotic physical and chemical properties.
This work was supported by JSPS KAKENHI Grant Numbers JP19H02543, JP19K15392, JP20H00220, JP20H02572, JP20H02573, JP20H02605, JP20KK0114, JP21H05232, JP21H05234, JP22H00280, JP22H00283, JP22H01911, JP22K04886, JP22H04957, JP22H05468, and JP22H05469, JST CREST Grant Numbers JPMJCR17I5, JPMJCR20B1, и JPMJCR20B5, и номер гранта программы JST FOREST JPMJFR213X.
Separation of small-diameter boron nitride nanotubes using surfactants to form one-dimensional van der Waals heterostructures
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