Nanoresistors and Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) can conduct electricity under ambient conditions. In a hands-on activity, students react Br2 and I2 with SWNTs and demonstrate that the dopants lower the resistance of SWNTs. In two other activities they demonstrate that Cl2 (generated by reacting Clorox and hydrochloric acid) and NaOH, when reacted with the tubular carbon structures, increase the resistance of SWNTs. This is due to the conversion of sp2-hybridized carbon atoms to functionalized carbon atoms (C–OH, C–Cl) that assume sp3 hybridization, thus causing the SWNT to lose their conductivity. In an appendix, a simple demonstration involving ten forms of carbon allotropes reacting with nitric acid (or not reacting!) is discussed.