Process for the simultaneous and selective preparation of single-walled and multi-walled carbon nanotubes

A process for the simultaneous and selective growth of single walled and multiwalled carbon nanotubes which comprises preparing a graphite electrode rod containing catalyst selected from Fe, Co, Ni and a mixture thereof, acting as an anode and another graphite electrode rod acting as a cathode each electrode having a distal and a proximal end, placing the above said two electrodes parallel to each other and their axis being substantially aligned such that their distal ends are at least 1 mm apart in a closed and evacuated arc discharge chamber, creating a DC-arc discharge inside the above said chamber by applying a DC-current voltage in the range of 10-50 V, at an arc current of 50-200 amp, under inert gas pressure of 120-500 torr followed by cooling the system by maintaining a temperature gradient by using a cooling coil around the arching electrodes, to obtain simultaneously the desired deposition of multiwalled carbon nanotubes at the cathode and the single walled carbon nanotubes in the chamber.