Single-walled carbon nanotubes have many applications in electronics and new touch-screen devices and are typically black or a dark grey in color. To spice up this technology, researchers at Aalto University in Finland have devised a technique to produce large quantities of pristine, single-walled carbon nanotubes in select shades of the rainbow.

Color is incorporated during fabrication instead of applying purifying techniques to finished tubes. The direct synthesis scheme yields large quantities of clean sample materials and avoids damage to the product in the purifying phase.

The use of aerosols of metal and carbon and low doses of carbon dioxide allows the researchers to carefully manipulate and control the nanotube structure directly from the fabrication process. The green, brown and silvery grey thin films produced could find application in vari-colored touch screens or solar cells that display novel optical properties.

An advanced electron diffraction technique revealed that the thin films have very narrow chirality distributions, meaning that the orientation of the honeycomb-lattice of the tubes' walls is almost uniform throughout the sample. The chirality governs the electrical properties of carbon as well as the color of nanotubes.

The research is published in the Journal of the American Chemical Society.

Colorful carbon nanotube thin films produced in the fabrication reactor. Source: Aalto UniversityColorful carbon nanotube thin films produced in the fabrication reactor. Source: Aalto University

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