By p- or n-type nanotubes, do you mean ones that are intrinsically doped with e.g. nitrogen or boron? If so, to my knowledge (I have been working with doped nanotubes for close to 6 years) there are no commercial vendors anywhere for the world for doped single-walled carbon nanotubes.

If you mean extrinsic doping, there might be some functionalised tubes on sale, but I am not so sure any has air-stable n-type doping - just exposing single-walled tubes to normal atmosphere will somewhat p-type dope them over several weeks. Usually intentional doping is done on your specific substrate or device by chemical and other treatments after depositing noral tubes.

Dear Toma,

Thank you so much for your response. We are interested in intrinsically doped n- and p-type CNTs. So there is not any commercial product, I would be more than grateful if you could introduce me some papers which have recipes for doping CNTs intrinsically. 

Regards

I can do that, yes. But perhaps you could open a new question about that so my answer would be more discoverable by other people with similar interests?

Amir,

Judging from very meager experience with nanotubes, Toma Susi is correct in his statements, especially about n- to p-doping. I will be curious to see the references.

Thanks for your responses. I will open a new question about the doping Carbon Nanotubes intrinsically as Toma suggested.

PS: Toma, I was wondering if you could put those references in the new question which I am planning to open.  

Sure, I will write a detailed answer there!

Try to check this list of suppliers:

http://www.nanochemistry.it/CNTsuppliers.html