Carbon nanotube
Carbon nanotubes are nanoscale tubes with remarkable strength and conductivity.
Wikipedia / Wikimedia Commons
A carbon nanotube (CNT) is a nanoscale cylinder composed entirely of carbon, placing it among the element’s allotropes. There are two main types: single-walled carbon nanotubes (SWCNTs), which measure roughly 0.5 to 2.0 nanometres across—about one hundred-thousandth the width of a human hair—and can be thought of as a rolled-up sheet of graphene; and multi-walled carbon nanotubes (MWCNTs), which consist of several SWCNTs nested inside one another like concentric tubes. Double- and triple-walled versions are considered special cases of MWCNTs. Thanks to their nanostructure and the strength of carbon–carbon bonds, these tubes can possess extraordinary tensile strength and thermal conductivity. Some SWCNTs are highly conductive electrically, while others behave as semiconductors. They can also be chemically altered. These traits make them promising for electronics, optics, composite materials (where they might supplement or replace carbon fibres), nanotechnology (including nanomedicine), and other areas of materials science.
The remarkable properties predicted for SWCNTs were enticing, but no method to synthesize them existed until 1993, when two independent teams—Iijima and Ichihashi at NEC, and Bethune and colleagues at IBM—found that co-vaporizing carbon with transition metals like iron or cobalt could catalyze the formation of SWCNTs. This breakthrough spurred research that greatly improved the efficiency of catalytic production and led to an explosion of work characterizing SWCNTs and seeking their applications.
The question of who first discovered carbon nanotubes is debated. A 2006 editorial in the journal *Carbon* by Marc Monthioux and Vladimir Kuznetsov traced the history. Much of the scientific and popular literature credits Sumio Iijima of NEC with the 1991 discovery of hollow, nanometre-sized graphitic tubes. His paper ignited widespread excitement and inspired research into many applications. However, the timeline extends much earlier. In 1952, L. V. Radushkevich and V. M. Lukyanovich published clear images of 50-nanometre carbon tubes in the *Journal of Physical Chemistry of Russia*. Their work went largely unnoticed because it was in Russian and Western access to Soviet publications was limited during the Cold War. Monthioux and Kuznetsov argued that Radushkevich and Lukyanovich deserve credit for discovering that carbon filaments could be holl
- field
- Materials science, nanotechnology
- known_for
- Hollow carbon tubes with nanoscale diameters, exceptional strength and conductivity
- discovery_controversy
- Multiple claims from 1952 onward; Iijima's 1991 paper sparked widespread interest
Lore & Background
The true identity of the discoverers of carbon nanotubes is a subject of some controversy. In 1952, L. V. Radushkevich and V. M. Lukyanovich published clear images of 50-nanometre diameter tubes made of carbon, but this discovery was largely unnoticed due to Cold War limitations. In 1976, Morinobu Endo observed hollow tubes of rolled up graphite sheets, later known as single-walled carbon nanotubes. In 1979, John Abrahamson presented evidence of carbon nanotubes at a conference, and in 1981, Soviet scientists suggested that their 'carbon multi-layer tubular crystals' were formed by rolling graphene layers into cylinders.
Helping to create the initial excitement associated with carbon nanotubes were Iijima's 1991 discovery of multi-walled carbon nanotubes in arc-burned graphite rods, and independent predictions that single-walled nanotubes would exhibit remarkable conducting properties. In 1993, Iijima and Ichihashi at NEC, and Bethune and colleagues at IBM independently discovered that co-vaporising carbon and transition metals could catalyse SWCNT formation, triggering an explosion of research. In 2020, archaeological excavation in Keezhadi, India, revealed ~2600-year-old pottery whose coatings appear to contain carbon nanotubes.
Reader's Guide
Carbon nanotubes represent a pivotal class of nanomaterials whose history is marked by multiple independent discoveries and ongoing controversy. The earliest known observations date to 1952, but widespread scientific attention only began after Iijima's 1991 paper on multi-walled nanotubes. The subsequent development of catalytic methods to produce single-walled nanotubes in 1993 enabled systematic study and application. Their unique structure—a hexagonal lattice rolled into a cylinder—gives rise to exceptional tensile strength, thermal conductivity, and variable electrical properties ranging from metallic to semiconducting. These characteristics make them promising for electronics, optics, composite materials, and nanomedicine. The discovery of naturally occurring carbon nanotubes in ancient pottery coatings suggests their durability over millennia. Despite decades of research, the field continues to evolve, with debates over priority of discovery and ongoing efforts to harness their properties for practical technologies. The arc discharge technique, known for producing fullerenes, played a role in both multi- and single-wall nanotube discoveries, extending a series of serendipitous findings in carbon science.
Did You Know?
- Carbon nanotubes are allotropes of carbon with diameters in the nanometre range.
- The first clear images of carbon nanotubes were published in 1952 by Radushkevich and Lukyanovich.
- In 2020, ~2600-year-old pottery from Keezhadi, India, was found to contain carbon nanotubes in its coatings.
- Single-walled carbon nanotubes have diameters about a 100,000th the width of a human hair.
More in Discovery and invention controversies 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record