Nanotubes

Nanotubes List

Nanotubes were first reported by Japanese scientist Iijimar in 1991. The nanotubes are 104 times thinner than a human hair, but they are 100 times harder than steel and have excellent thermal conductivity. As conductors, the conductive ability of nanotubes is much better than metal and can be made into computer chips. The nanotubes also have superconducting properties at extremely low temperatures, allowing them to conduct electricity without interference. The walls can be as thin as a single atom, and the length of nanotubes can be thousands of times thicker than the width, giving them a variety of functions. Because of the unique physical and chemical properties, nanotubes have shown good application prospects in many fields, which is the focus of current researches.

Applications:

• Sensor field: Sensors made by nanotubes have low cost, low energy consumption, good sensitivity and selectivity, which are widely used as gas sensors to realize remote monitoring of NO₂, O₂, NH₃ and other gases. Compared with metal oxide semiconductor sensor, the nanotube gas sensor has a faster reaction rate and better sensitivity. Moreover, nanotube gas sensor works at room temperature, and can be used repeatedly.

Figure 1. Carbon nanotube sensor detects nitrosamines in the air.

• Hydrogen storage field: As a high - quality clean energy, hydrogen is attracting more and more attention. However, because of the low density of hydrogen, storage and transportation has become a bottleneck for hydrogen utilization. If compressed into liquid storage, conditions are harsh and energy consuming is high. Using the gap between the walls and layers, nanotubes are ideal for storing hydrogen.
• Catalyst field: In the field of catalysts, nanotubes can be used as catalysts alone or as catalyst carriers. Moreover, taking advantages of good stability, unique adsorption properties, excellent electronic properties, large specific surface area and small diameter size, nanotubes are ideal catalyst carriers.

Figure 2. An example of nanotube applied in catalyst field.

• The others: Nanotubes also can be used in other fields, including emission material, lithium ion battery, adsorbent, composite reinforcement, supercapacitor electrode and the others.

Classification:

According to the composition, nanotubes can be classified into the following categories:

• Carbon nanotube: Carbon nanotubes are one - dimensional nanomaterials with light weight and good mechanical properties. In addition, carbon nanotubes are strong enough to make thin springs that can be used as shock absorbers in cars and trains, greatly reducing their weight.
• TiO2 nanotubes: The TiO₂ nanotube is one of the directionally arranged tubular nanotubes. As an important inorganic functional material, TiO₂ has a broad application prospect in the storage and utilization of solar energy, photoelectric conversion and other aspects.
• Silicon nanotubes: Silicon nanotubes have semiconductor properties and are easily compatible with the microelectronics industry, which have important applications in field effect transistors and nano - electronic integrated circuits.
• The others: Nanotubes also include polymer nanotubes, boron - nitrogen nanotubes and the others.

References

1. Maggie He, Robert G. Croy, John M. Essigmann, et al. Chemiresistive Carbon Nanotube Sensors for N -Nitrosodialkylamines[J]. ACS sensor, 2019.
2. Gu X, Qi W, Xu X, et al. Covalently functionalized carbon nanotube supported Pd nanoparticles for catalytic reduction of 4-nitrophenol[J]. Nanoscale, 2014.