Using the Selective Functionalization of Metallic Single-Walled Carbon Nanotubes to Control Dielectrophoretic Mobility

The effect of sidewall functionalization on the dielectrophoretic mobility of single-walled carbon nanotubes is investigated using a 10-μm electrode gap and an alternating current electric field of 10 V and 10 Mhz. For nanotubes dispersed in aqueous solution using 1% sodium dodecyl sulfate, a high degree of alignment is observed for material deposited across the gap. Raman spectroscopy at 632.8- and 785-nm excitation indicates that both metallic and semiconducting nanotubes are deposited. An apparent increase in metallic modes in the 632.8-nm spectrum is shown to be related to sample morphology and the choice of control material for comparison, not separation or enrichment. Electrical transport measurements reveal both a gate-voltage dependence as well as current at zero gate voltage, which is consistent with a mixture of metallic and semiconducting pathways. Alternatively, fewer nanotubes deposit in the gap when the metallic nanotubes are selectively functionalized using 1-chlorobenzene diazonium. The results suggest that either the functionalization itself or an adsorbed reagent has reversed the sign of the Clausius−Mossotti factor for metallic nanotubes. This chemical method could be used as a means of selectively manipulating and depositing a heterogeneous mixture of nanotubes in solution into an array of uniform electronic type.