Reduction-controlled viologen in bisolvent as an environmentally stable n-type dopant for carbon nanotubes.
Various viologens have been used to control the doping of single-walled carbon nanotubes (SWCNTs) via direct redox reactions. A new method of extracting neutral viologen (V(0)) was introduced using a biphase of toluene and viologen-dissolved water. A reductant of sodium borohydride transferred positively charged viologen (V(2+)) into V(0), where the reduced V(0) was separated into toluene with high separation yield. This separated V(0) solution was dropped on carbon nanotube transistors to investigate the doping effect of CNTs. With a viologen concentration of 3 mM, all the p-type CNT transistors were converted to n-type with improved on/off ratios. This was achieved by donating electrons spontaneously to CNTs from neutral V(0), leaving energetically stable V(2+) on the nanotube surface again. The doped CNTs were stable in water due to the presence of hydrophobic V(0) at the outermost CNT transistors, which may act as a protecting layer to prevent further oxidation from water.
Kim
Soo Min
SM
BK21 Physics Division, Center for Nanotubes and Nanostructured Composites, Sungkyunkwan Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
Jang
Jin Ho
JH
Kim
Ki Kang
KK
Park
Hyeon Ki
HK
Bae
Jung Jun
JJ
Yu
Woo Jong
WJ
Lee
Il Ha
IH
Kim
Gunn
G
Loc
Duong Dinh
DD
Kim
Un Jeong
UJ
Lee
Eun-Hong
EH
Shin
Hyeon-Jin
HJ
Choi
Jae-Young
JY
Lee
Young Hee
YH