April 23, 2024

Scientists are working to develop methods to engineer materials at the molecular level as devices continue to be constructed on a smaller scale. This breakthrough was published in Nature Communications. It results from the collaboration between researchers from the RIKEN Cluster for Pioneering Research (RIKEN Center for Advanced Photonics) and collaborators. The dry transfer technique, which uses no solvent, allows for the precisely positioning of optical-quality carbon nanotubes.

Carbon nanotubes are a promising material with potential applications in light-emitting diodes, single-electron transistors, and single-photon sources. These tubes are made of graphene and twisted in specific ways. This is what allows the desired properties to emerge. Creating devices with selected properties involves precise manipulation of their orientation and position. This property is called “chirality,” which describes the degree of twisting. However, it is difficult to control the molecules accurately as solvents, and high-temperature treatments can make them dirty. This will affect their optical properties.

The researchers sought a solution to this problem by looking for a way of engineering nanotubes without using solvents. Anthracene, an oil-derived chemical, was used as a sacrifice material. They carried the nanotube around on anthracene scaffolding, then heated the anthracene to sublimate it, leaving it in pristine optical condition. The researchers also created a method to monitor the photoluminescence of nanotubes throughout the transfer. This ensured that the right nanotube would be placed in the correct location.

The researchers confirmed that the nanotubes left after the dry transfer had bright photoluminescence up to 5,000 times brighter than the original molecule. This makes them suitable for optical devices. The group could also position the nanotube precisely on top of a miniature optical resonator, increasing the light emission properties.

Keigo Otsuka, the first author of the paper and member of the RIKEN Cluster of Pioneering Research, stated that “we believe that this technology could not only contribute to the creation nanodevices out of carbon nanotubes with desired characteristics but also to higher-order systems that are based upon the free combination of atomic layers materials and other nanostructures.”

Yuichiro Kato is the leader of the group. He says that “beyond that,” this technology can contribute to developing atomically defined technologies beyond nanotechnology. In which materials with precise structures at the atomic level are used to build functions that differ from existing materials, they are used as building blocks.

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