Aligning single-wall carbon nanotubes with an alternating-current electric field

TLDR: In this article, single-wall carbon nanotubes (SWCNTs) were highly aligned by an external electric field and the results suggest that the alignment of SWCNT shows significant dependencies on the frequency and the magnitude of the applied electric field.

Abstract: Single-wall carbon nanotubes (SWCNTs) were highly aligned by an external electric field. The results suggest that the alignment of SWCNTs shows significant dependencies on the frequency and the magnitude of the applied electric field. The electric field with 5 MHz straightened out the SWCNTs and created highly oriented samples with fewer large particles. We also discussed the mechanism and applications.

Figures

FIG. 3. Tapping-mode AFM images of the aligned SWCNT samples.~a! Aligned by applying an ac electric field with a frequency of 5 MHz and a voltage of 10 V peak to peak.~b! Aligned by applying an ac electric field with a frequency of 500 Hz and a voltage of 10 V peak to peak.

FIG. 2. SEM images of the SWCNT samples aligned in different conditions. ~a! Aligned by applying an ac electric field with a frequency of 5 MHz and a voltage of 10 V peak to peak.~b! Aligned by applying an ac electric field with a frequency of 5 MHz and a voltage of 6 V peak to peak. ~c! Aligned by applying an ac electric field with a frequency of 500 Hz and a voltage of 10 V peak to peak.

Frequently asked questions

Q1. What is the effect of the dc electric field on the nanotubes?

The SWCNTs used in this work were aggregated on the anode when the dc electric field was applied, which indicates that the nanotubes were negatively charged. 

Q2. Why is the dipole moment stronger in the direction parallel to the tube axis?

Because of the structure anisotropy of the carbon nanotubes, the dipole moment in the direction parallel to the tube axis is quite stronger than that in the perpendicular direction. 

Q3. What is the effect of the electric field on the alignment of carbon nanotubes?

When the frequency of the electric field was decreased to 500 Hz, there were many aggregations of the SWCNTs existing within the electrode gaps. 

Q4. What is the reason for the selective deposition of carbon nanotubes?

The selective deposition of the carbon nanotubes is probably attributed to the structure defects or the charge of the carbon nanotubes, which could be made in the sample preparing process. 

Q5. What is the reason why the carbon nanotubes are aligned?

Based on the above alignment mechanism, it seems to be reasonable that carbon nanotubes with a perfect structure will move towards both the anode and the cathode because of the concentration of the electric field at the edges of the electrodes. 

Q6. What is the name of the paper?

Redistribution subject to AIP license or copyright, see http://apl.aip.org/apl/copyright.jspac electric field with a frequency of 5 MHz and a magnitude of 10 V peak to peak. 

Q7. How can the authors rationalize the results of the alignment experiment?

For this alignment, the results could be rationalized by considering the electronic polarization induced in carbon nanotubes by the electric field.