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Reduction-Controlled Viologen in Bisolvent as an Environmentally Stable n-Type Dopant for Carbon Nanotubes

2008; American Chemical Society; Volume: 131; Issue: 1 Linguagem: Inglês

10.1021/ja807480g

1943-2984

Soo Min Kim, Jin Ho Jang, Ki Kang Kim, Hyeon Ki Park, Jung Jun Bae, Woo Jong Yu, Il Ha Lee, Gunn Kim, Dinh Loc Duong⧫, Un Jeong Kim, Eun‐Hong Lee, Hyeon‐Jin Shin, Jae‐Young Choi, Young Hee Lee,

Supercapacitor Materials and Fabrication

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.