A nanotube is a nanometer-scale hollow tube.
| BCN nanotube | Composed of boron, carbon, and nitrogen atoms. Exhibit a high and stable capacitance, which exceeds CNT, and are used in supercapacitors which store 10 to 100 times more energy than electrolytic capacitors. |
| BN nanotube | Composed of boron and nitride. Can withstand 900 °C, as opposed to CNTs at 400 °C, and bond better to polymers, and are also capable of absorbing radiation. Used in biomedical applications such as cancer treatment. |
| Carbon nanotube (CNT) | Remarkable electrical and thermal conductivity, and high tensile strength because of the adamantine strength of the bonds between carbon atoms. Used in as electronics, optics, composite materials, nanotechnology, superconducting, and many applications of materials science such as in megastructures like the space elevator.
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| DNA nanotube | A 2d lattice which curves back upon itself, used in bio computers. |
| GaNNT | Gallium nitride nanotube used as light emitting diodes, and to produce microchips with faster processing speeds. |
| Silicon nanotube | Used as nanowires because they act as charge or energy carriers over relatively long distances in a material. Also used in lithium-ion batteries and light emission. |
| Inorganic nanotube | Especially tungsten sulfide nanotubes. Inorganic nanotubes have advantages over CNTs, such as high crystallinity, good uniformity and dispersion, and electrical conductivity. They are not as strong as CNTs under tensile stress, but stronger under compression, leading to impact-resistant applications such as bulletproof vests. They have good adhesion to a number of polymers, making them "polyfillers" in lower strength materials such as concrete. |
| Tunneling nanotube (TNT) | A natural tubular membrane connection between cells. Involved in cell-to-cell communication, transfer of nucleic acids between cells in a tissue, and the spread of pathogens or toxins such as HIV. |
| Titanium nanotube | Can be converted into inorganic nanotubes and nanowires. |