The characteristics of multi-walled carbon nanotubes by a two-step separation scheme via dielectrophoresis

The unique properties of carbon nanotubes (CNTs) have led to demonstration of many applications. For good performance, the uniformity in the CNT property is very important. Among many purification schemes, dielectrophoresis (DEP) separation is non-destructive and often employed to separate CNTs. In this study, a two-step DEP separation scheme was developed to purify multi-walled carbon nanotubes (MWCNTs). This process is performed by either positive or negative DEP force followed successively by another positive or negative DEP force. The purification degree is characterized by the I_D/I_G ratio. The results show that the affinity in the first step primarily determines the overall separation degree. This indicates the operation frequency (DEP affinity) rather than the number of steps is the critical factor in DEP separation.