Carbon nanotubes and metal particle-containing carbon nanotubes are provided. The carbon nanotubes have increased surface area. A method of cutting carbon nanotubes is also provided. According to the method, the dispersion properties of the carbon nanotubes are improved by simplifying the structural changes and/or surface modifications of the carbon nanotubes, thereby enabling insertion of an active substance into the inner walls of the carbon nanotubes and increasing the insertion efficiency.