Pyridine-mediated B-B bond cleavage of tetrahydroxydiboron to synthesize n-doped SWCNTs with long-term air stability.

Neutral radicals, including carbon radicals, are highly useful chemical species for the functionalization of semiconducting materials to change their electrical and optical properties owing to their high reactivity. However, boron radicals have been limited to synthetic and reaction chemistry, with rare utilization in materials science. In this study, a mixture of tetrahydroxydiboron (B2(OH)4) and pyridine derivatives was found to act as an electron dopant for single-walled carbon nanotubes (SWCNTs) because of the electron transfer from pyridine-mediated boron radicals generated by B-B bond dissociation to neutral radicals. In particular, the radical formed from a mixture of B2(OH)4 and 4-phenylpyridine ((4-Phpy)B(OH)2·) efficiently doped electrons into the SWCNT films; thus, n-type SWCNTs with long-term air stability for more than 50 days at room temperature were prepared. Furthermore, the experimental and theoretical surface analyses revealed that the formation of stable cations from ((4-Phpy)B(OH)2·) and the efficient interaction with SWCNTs due to their high planarity served as the mechanism for their stable doping.

Electron doping of single-walled carbon nanotubes using pyridine-boryl radicals.

Pyridine-boryl (py-boryl) radicals serve as efficient electron-doping reagents for single-walled carbon nanotubes (SWCNTs). The doping mechanism comprises electron transfer from the py-boryl radical to the SWCNT. The formation of a stable py-boryl cation is essential for efficient doping; the captodative effect of the py-boryl cation is important to this process.