Ultra-high purity carbon nanotubes are basically divided into two categories

Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Despite the obvious commonalities, there are significant differences in the physical properties of single-walled carbon nanotubes and multi-walled carbon nanotubes due to structural differences.

The most important feature that distinguishes single-walled carbon nanotubes is that the tube wall has only one layer. In other words, single-walled carbon nanotubes can be described as seamless hollow cylindrical tubes formed by rolling up a single layer of graphene sheets. This is why they are often called single-layer graphene nanotubes.

Unlike single-walled carbon nanotubes, multi-walled carbon nanotubes can be regarded as concentric arrangements of single-walled carbon nanotubes, that is, multiple layers of graphene sheets are seamlessly rolled up into a tube shape.

These differences between single-walled carbon nanotubes and multi-walled carbon nanotubes lead to very different performance of the material when they are added to the material, and have a corresponding impact on the material.

For example, the Young's modulus of single-walled carbon nanotubes (sometimes referred to as the elastic modulus related to the ability of a material to withstand changes in length under tension or compression) is almost an order of magnitude higher than that of multi-walled carbon nanotubes.

Multi-walled carbon nanotubes can be seen as a set of single-walled carbon nanotubes of different diameters, ranging from 2 layers to more than a dozen layers, with an interlayer spacing of about 0.343nm. Each layer of nanotubes is a cylindrical surface composed of hexagonal planes formed by a carbon atom fully bonded with the surrounding three carbon atoms through sp2 hybridization. The diameter of the carbon nanotubes ranges from a few nanometers to tens of nanometers, and the length can reach several microns, with a large aspect ratio.

When multi-walled carbon nanotubes begin to form, the layers between layers can easily become trap centers and capture various defects, so the walls of multi-walled tubes are usually covered with small hole-like defects. The interlayer spacing of multi-walled carbon nanotubes is about 0.34nm, the outer diameter ranges from a few nanometers to hundreds of nanometers, and the smallest inner diameter found is 0.4 nm. The length is generally in the micrometer range, and the longest can reach several millimeters.

There is no relevant report indicating that multi-walled carbon nanotubes can kill bacteria. The capacitance of multi-walled carbon nanotubes is generally 102F/g. A summary of some differences between multi-walled carbon nanotubes and single-walled carbon nanotubes, but both have excellent mechanical properties, electrical conductivity, thermal properties, hydrogen storage properties, etc.