Soluble self-doped single-walled carbon nanotube

Abstract

Treatment of single-walled carbon nanotube (SWNT) having carboxylic acid chloride groups at the open end, SWNT–(COCl) n , with polyethyleneimine (PEI) caused amidation reaction between the COCl group and the amine groups of PEI to give functionalized SWNTs. The products were separated into soluble and insoluble parts in chloroform, 1 and 2, respectively. IR data revealed that all the COCl groups reacted with amine groups of PEI to provide 1, whereas unreacted COCl groups remained in 2. 1 was photoluminescent and electrochemically active in the solution. Electron spin resonance (ESR) spectrum of 1 indicated formation of a radical cation on N atoms of PEI. An electric junction, Pt/P3HexTh/ 1/Hg, where P3HexTh is poly(3-hexylthiphene) which usually shows p-type electrically conducting properties, was fabricated. The junction shows rectification of electric current, and this rectification is attributed to the formation of a p–n junction between P3HexTh and 1. These data supported a view that 1 served as an n-type electrically conducting material. Optical and thermal properties of 1 and 2 were also investigated.