Yes, Carbon nanotubes were synthesized by high thermal chemical vapor deposition method in which Fe catalyst was placed inside the quartz tube and ethanol was decomposed inside the same. Such process consists of three steps; firstly the formation of a precursor consisting of some metal nanoparticles that provides the nucleation point at high temperatures then dissociation of gas takes place. Later the carbon atoms are deposited on the nucleation point and the growth will start in two ways: in root growth the catalyst will be placed at the bottom of the tubes and in tip growth the catalyst will be at the top of the tubes. Therefore carbon atom was deposited on Fe catalyst by growth mechanism and MWCNTs were formed. The nanotube synthesized using Fe was filtered by DMF treatment method in which the prepared film was dipped inside the DMF so that Fe nano catalyst may be dissolved and pure nanotubes were found on the film. A quartz tube was placed in a single zone furnace providing a temperature plateau of about 1 m length at temperatures between 700 and 850 °C. The annealing of the catalyst films was made in situ in the quartz tube, followed by the growth of the MWCNTs by ethanol decomposition. The reactor tube was heated with

about 20 °C/min in air or with N2 flow until the desired temperature was obtained. The deposition was done by bubbling N2 through an ethanol reservoir at room temperature. The flow rate of the N2 could be varied between 10 and 100

sccm/min. All treatments in the quartz tube were made at atmospheric pressure.

DOI 10.1007/s10904-016-0442-3

Yes Funsho Kolawole , non-metals dopants are usually nitrogen and boron, doping with oxygen, silicon and sulfur has also been reported.

Everything depends on the synthesis method and the precursors.

Regarding of doping with metals, it has recently been possible to dope diamond-like carbon with Al, Ti or Nb using a hybrid technique “magnetron sputtering-RFPECVD”.

Coatings 2018, 8, 370; doi:10.3390/coatings8100370

DOI:10.1016/j.tsf.2016.04.048

So yes, it is possible to dope the graphitic diamond-like structure with heteroatoms but you mostly see this characteristic on thin films, i think it would harder to dope a sp3 carbon crystal (maybe in the borders).