Scientists from the University of California, Berkeley, and Lawrence Berkeley National Laboratory (Berkeley Lab) have devised a technique to selectively grow carbon nanotubes with specific atomic structures known as chiralities. This breakthrough, described in a study published in the journal Nature, advances the control and understanding of nanotube properties which is crucial for their practical applications in nanoelectronics, optics, and energy technologies.

Carbon nanotubes are cylindrical structures made of carbon atoms arranged in a hexagonal lattice. Due to their unique properties, including high electrical and thermal conductivity, mechanical strength, and chemical stability, nanotubes have attracted significant research interest for various potential applications.

However, the realization of these applications relies on achieving precise control over the atomic structure of nanotubes, particularly chiralities. Chirality refers to the way carbon atoms twist as they wrap around to form a tube, and it influences the nanotube's electronic and optical properties. Researchers have previously observed more than 170 different chiralities, but controlling the growth of specific ones has been a challenge.

To address this challenge, the Berkeley Lab team developed a growth technique called "supercritical fluid chemical vapor deposition with continuous solution feeding." This method involves continuously introducing a precursor solution into a chemical vapor deposition (CVD) reactor under supercritical conditions—high temperature and pressure that make the solution behave like a gas.

The continuous feeding of the precursor ensures a consistent supply of carbon atoms, while the supercritical conditions promote uniform growth of nanotubes.

Using this technique, the researchers selectively grew single-chirality carbon nanotubes with controlled diameters and lengths. They showcased their approach by growing nanotubes with five different chiralities, demonstrating the versatility of their method. The growth selectivity was made possible by fine-tuning the precursor composition and the growth conditions.

According to the study, the selective growth of carbon nanotubes opens up new possibilities for fundamental studies of the structure-property relationships and for optimizing nanotube performance in targeted applications. For instance, specific chiralities show promise for electronic devices, optoelectronics, and field-effect transistors. Carbon nanotubes can also serve as a basis for nanocomposites with tailored mechanical and electrical properties.

By mastering the ability to synthesize nanotubes with specific atomic structures, the researchers provide a significant step forward in unlocking the potential of these nanosized wonders for advanced technological applications.