Surfactant Used for Nanotube Growth

Scientists Use Surfactants to Create 'Inert' Templates for Nanotube Growth   Researchers from Tokyo Metropolitan University used a surfactant to disperse and coat insulating boron nitride nanotubes onto surfaces without bundling them. The team demonstrated that thermal treatment could remove the surfactant to reveal clean nano-scale templates; coaxial nanotubes can then be created on the template using a variety of materials through chemical vapor deposition. The ability to coat nanotubes onto "inert" insulating structures provides scientists with unprecedented access to the properties of novel nanotube materials. Advances in nanotechnology have made nanotubes and nanolayers more readily obtainable for materials scientists. However, examining them individually is not straightforward. Since they typically exist in bundles or in bulk, determining their exotic optical and electronic properties arising from reduced dimensionality is difficult. Recent studies have shown that nanotube materials can be grown on the surface of a carbon nanotube and can provide well-separated structures that could potentially be characterized. However, carbon nanotubes have conductive properties and strongly absorb light, making it difficult to distinguish the electrical and optical properties of the coated material from those of the original nanotube. Assistant Professor Yusuke Nakanishi, Assistant Professor Yohei Yomogida and Associate Professor Yasumitsu Miyata from Tokyo Metropolitan University used insulating boron nitride nanotubes as templates this time. This is far from an easy task, as boron nitride nanotubes are known to be highly adhesive. While they can be dispersed with a surfactant that helps keep the tubes separate, it was uncertain whether the surfactant could be removed to reveal a clean template. However, the research team succeeded in finding a surfactant that does not adhere to the tubes; they also developed a vacuum thermal treatment that produces clean, well-isolated insulating nanotube templates. Using chemical vapor deposition, a variety of materials can be coated on the surface of the templates. The new tube wraps around the original BN tubes, creating a structure resembling a nano-scale coaxial cable. Since BN is an insulating material, the electrical properties of any coated material can be examined in unprecedented depth. This includes a property known as chirality, which relates to the "handedness" in the structure of atoms in the nanotube that leads to the formation of a series of exotic electronic properties. The research team believes that "nano test tubes" could in principle be used to template the growth of a variety of different materials. The team achieved success with molybdenum disulfide and carbon materials, and it appears feasible to accomplish this with many more substances. When combined with the optical and electrical inertness of BN templates, the project promises not only materials discovery, but also unlimited access to exotic physicochemical properties. The work was published in ACS Nano.     Source More information: Shinpei Furusawa et al, Surfactant-Assisted Isolation of Small-Diameter Boron-Nitride Nanotubes for Molding One-Dimensional van der Waals Heterostructures, ACS Nano (2022). DOI: 10.1021/acsnano.2c06067 / Journal information: ACS Nano / Provided by Tokyo Metropolitan University / https://phys.org/news/2022-10-scientists-surfactant-inert-templates-nanotube.html