Double Wall CNT

Double Wall CNT List

Carbon nanotubes were discovered in 1991. Since then, with excellent electrical, optical and mechanical properties, carbon nanotubes have been considered to be one of the most promising members of the carbon family. According to the number of graphite layers, carbon nanotubes can be divided into single wall CNTs and multi wall CNTs. Double wall CNTs are the simplest multi wall CNTs. Double wall CNTs are seamless and hollow coaxial tubular structures formed by curling two layers of graphite in accordance with a certain spiral angle. The diameter of the inner wall is between 0.8 nm and 1.1 nm and the diameter of the outer wall is between 1.6 nm and 1.8 nm. In addition, the spacing between inner and outer layers ranges from 0.34 nm to 0.39 nm. In general, double wall CNTs are more stable and have smaller energy gap than single wall CNTs, so they have better electrical conductivity.

Figure 1. The structure of double wall CNT.

Applications:

• Laser field: In recent years, using saturable absorber to design ultrashort laser pulses at picosecond or femtosecond scales has become one of the hot research topics. Double wall CNT is a new kind of saturable absorber, which is one-dimensional nanomaterial. With the good electrical conductivity and excellent stability, double wall CNT has wide applications in the field of ultrashort pulse laser field. For example, a low threshold mode-locked laser has been successfully designed based on double wall CNT.
• Lighting field: At present, the world is facing an energy crisis, and the competition among countries in energy is becoming increasingly fierce. As the phenomenon of electric tension becomes more and more prominent, improving the luminous efficiency of electric light source to save energy has become an important task in the field of lighting. Based on the excellent physical and chemical properties, double wall CNT can be used as the filament of electric bulbs to improve the luminous efficiency and achieve the purpose of energy saving.
• The others: In addition, double wall CNTs also have a wide range of applications in other fields, including photodetectors, hydrogen storage, field effect transistors, catalysts, biological fields and the others.For example, based on the characteristic of large specific surface area, double wall CNTs have good adsorption capacity for gases, so they can be used as gas storage devices, which is of great significance for hydrogen storage field.

Figure 2. The structure of photodetectors that designed by double wall CNT.

Classification:

According to the solubility, double wall CNTs can be divided into water-soluble double wall CNTs and non-water-soluble double wall CNTs.

• Water-soluble double wall CNTs: Water-soluble double wall CNTs have high solubility and good biocompatibility in aqueous solutions, and they have been widely used in the field of biology.
• Non-water-soluble double wall CNTs: The solubility of non-water-soluble double wall CNTs in aqueous phase is low and other means are usually required to disperse them.

References

1. Rafique I, Kausar A, Anwar Z, et al. Exploration of Epoxy Resins, Hardening Systems, and Epoxy/Carbon Nanotube Composite Designed for High Performance Materials: A Review[J]. Polymer-Plastics Technology and Engineering, 2016, 55(3):312-333.
2. Novel photodetectors based on double-walled carbon nanotube film/TiO2 nanotube array heterodimensional contacts[J]. Nano Research, 2011, 4(9):901-907.