By Josh Perry, Editor
Scientists from Tokyo Metropolitan University (Japan) used templates for building carbon nanotubes to produce nanowires of transition metal monochalcogenide (TMM) that are only three atoms in diameter, are 50 times longer that previous attempts, and can be studied in isolation.
This is a schematic and electron microscopy images of single wires of molybdenum telluride formed inside carbon nanotubes. (Tokyo Metropolitan University)
According to a report from the university, the researchers preserved the properties of a ‘1-D’ object and saw that the single wires would twist when unsettled, which they believe indicates unique mechanical properties that could be used for switching in nanoelectronics.
Transition metal monochalcogenides consist of a transition metal plus a group 16 element and have been studied for 30 years as a potential in nanowires, but experiments were limited to small quantities, bundled, and short. The bundling was particularly ineffective, as it masked the properties of 1-D wires, but now researchers have found a method for isolating nanowires.
“They used tiny, open-ended rolls of single-layered carbon, or carbon nanotubes (CNTs), to template the assembly and reaction of molybdenum and tellurium into wires from a vapor,” the report explained. “These nanometer-sized CNT ‘test tubes’ were also shown to be not chemically bound to the wires, effectively preserving the properties expected from isolated TMM wires. Importantly, they effectively ‘protected’ the wires from each other, allowing for unprecedented access to how these 1D objects behave in isolation.”
Transmission electron microscopy (TEM) was used to demonstrate a twisting effect when the nanowires were exposed to electron beams.
The research was recently published in Nano Letters. The abstract read:
“The successful isolation of single layers from two-dimensional (2D) van der Waals (vdW)-layered materials has opened new frontiers in condensed matter physics and materials science. Their discovery and unique properties laid the foundation for exploring 1D counterparts.
“However, the isolation of 1D vdW-wired materials has thus far remained a challenge, and effective techniques are demanded. Here we report the facile synthesis of isolated transition-metal monochalcogenide MoTe nanowires by using carbon nanotubes (CNTs) as molds. Individual nanowires are perfectly separated by CNTs with a minimal interaction, enabling detailed characterization of the single wires.
“Transmission electron microscopy revealed unusual torsional motion of MoTe nanowires inside CNTs. Confinement of 1D vdW-wired materials to the nanotest tubes might open up possibilities for exploring unprecedented properties of the nanowires and their potential applications such as electromechanical switching devices.”