Selective Surface Charge Sign Reversal on Metallic Carbon Nanotubes for Facile Ultrahigh Purity Nanotube Sorting

Jing Wang, Tuan Dat Nguyen, Qing Cao, Yilei Wang, Marcus Y.C. Tan, Mary B. Chan-Park

Research output: Contribution to journalArticlepeer-review


Semiconducting (semi-) single-walled carbon nanotubes (SWNTs) must be purified of their metallic (met-) counterparts for most applications including nanoelectronics, solar cells, chemical sensors, and artificial skins. Previous bulk sorting techniques are based on subtle contrasts between properties of different nanotube/dispersing agent complexes. We report here a method which directly exploits the nanotube band structure differences. For the heterogeneous redox reaction of SWNTs with oxygen/water couple, the aqueous pH can be tuned so that the redox kinetics is determined by the availability of nanotube electrons only at/near the Fermi level, as predicted quantitatively by the Marcus-Gerischer (MG) theory. Consequently, met-SWNTs oxidize much faster than semi-SWNTs and only met-SWNTs selectively reverse the sign of their measured surface zeta potential from negative to positive at the optimized acidic pH when suspended with nonionic surfactants. By passing the redox-reacted nanotubes through anionic hydrogel beads, we isolate semi-SWNTs to record high electrically verified purity above 99.94% ± 0.04%. This facile charge sign reversal (CSR)-based sorting technique is robust and can sort SWNTs with a broad diameter range.

Original languageEnglish (US)
Pages (from-to)3222-3232
Number of pages11
JournalACS Nano
Issue number3
StatePublished - Mar 22 2016
Externally publishedYes


  • carbon nanotubes
  • charge sign reversal
  • gel chromatography
  • purification
  • sorting

ASJC Scopus subject areas

  • General Materials Science
  • General Engineering
  • General Physics and Astronomy


Dive into the research topics of 'Selective Surface Charge Sign Reversal on Metallic Carbon Nanotubes for Facile Ultrahigh Purity Nanotube Sorting'. Together they form a unique fingerprint.

Cite this