High-Yield Separation of Metallic and Semiconducting Single-Wall Carbon Nanotubes by Agarose Gel Electrophoresis

Abstract

We have developed a novel separation method of metallic and semiconducting single-wall carbon nanotubes (SWCNTs) using agarose gel electrophoresis. When the SWCNTs were isolated with sodium dodecyl sulfate (SDS) and embedded in agarose gel, only the metallic SWCNTs separated from the starting gel by an electric field. After 20 min, almost all SWCNTs applied to gel electrophoresis were separated into two fractions, containing $95% semiconducting and $70% metallic nanotubes. The difference in the response to the electric field between metallic and semiconducting SWCNTs can be explained by the higher affinity of semiconducting SWCNTs to agarose than to SDS. # S ingle-wall carbon nanotubes (SWCNTs) have attracted a great deal of attention towards versatile applications, especially in the field of electronics, such as field effect transistors (FETs). 1,2) However, asproduced SWCNTs always contain both metallic and semiconducting SWCNTs, which is one of the most crucial problems preventing useful application of SWCNTs. There are several reports on the separation of metallic and semiconducting SWCNTs (MS separation) by dielectrophoresis, 3) amine extraction, 4) polymer wrapping, 5,6) selective oxidation, 7) and density-gradient ultracentrifugation; 8,9) however, problems in yield, purity, cost, etc. for industrial production of metallic and semiconducting SWCNTs are present in these methods. 10) Here, we report a novel separation method of metallic and semiconducting SWCNTs by agarose gel electrophoresis (AGE) that has high scalability for industrial application.Various SWCNTs synthesized by laser vaporization (LV1, 1:2 AE 0:1 nm in diameter; LV2, 1:4 AE 0:1 nm), high-pressure carbon monoxide processing (HiPco, R500, Carbon Nanotechnology, 1:0 AE 0:3 nm), and arc discharge (electric arc, APJ, Meijou Nano Carbon, 1:4 AE 0:1 nm) were used in this study. LV1 and LV2 SWCNTs were synthesized by conventional laser-oven technique and were highly purified as previously reported. 11) The growth temperatures were 1050 C for LV1-and 1250 C for LV2-SWCNTs. HiPco and arc SWCNTs were used without any purification steps. An SWCNT-dispersed solution was prepared as follows. SWCNTs were dispersed in 2% sodium dodecyl sulfate (SDS; 99%, Sigma-Aldrich) at 0.3 mg/ml and sonicated using a tip-type ultrasonic homogenizer (Taitec VP-30S) for 5.7 h at a duty cycle of 70% (total on-time: 4 h). In the case of arc SWCNTs, the sonication time was prolonged to 22.9 h (total on time: 16 h). The solution was centrifuged to remove bundles and impurities (16;100 Â g for 15 h at 25 C), and the resulting supernatant was collected as an SWCNT dispersion, where SWCNTs were coated with the surfactant.Agarose was chosen for the matrix of gel electrophoresis because agarose gel has been used for the separation of DNA which is almost the same size as SWCNTs. In the case of DNA, they are separated by a difference of length, where a network of the gel functions as a molecular sieve at the separation step and fixes the separated objects after the separation. 12) ...

Selective suspension in aqueous sodium dodecyl sulfate according to electronic structure type allows simple separation of metallic from semiconducting single-walled carbon nanotubes

“…For this reason, separation of m-from s-SWNTs has become a fl ourishing subfi eld and in fact enrichment of m/s-SWNTs has been achieved by various techniques including (AC) dielectrophoresis [1], density gradient centrifugation [2], and (DC) agarose gel electrophoresis [3]. A recent review article on separation methods in general, including separation of m-from s-SWNTs, gives a good overview of efforts to date [4].…”

From metal/semiconductor separation to single‐chirality separation of single‐wall carbon nanotubes using gel

“…Recently, novel M/S separation methods have been developed using agarose gel [15][16][17][18][19][20]. Agarose is a biopolymer obtained from algae and is a gel-forming linear polysaccharide with a 1,3-β-D-galactose and 1,4-α-L-3,6-anhydro-galactose repeat unit.…”

“…The size and shape of DNA is very similar to those of SWCNTs. Thus, agarose gel electrophoresis was first applied to separate SWCNTs, and the M/S separation was successful [15]. In addition, the electric field was determined not to be required for the separation [16], and the continuous column method was developed [17].…”

“…The network of the gel functions as a molecular sieve and sorts analytes by differences in molecular weight or length. For the separation of the SWCNTs, the agarose gel was prepared in a glass tube [15]. A SWCNT dispersion that was prepared by sonication in a sodium dodecyl sulfate (SDS) aqueous solution and was followed by centrifugation was placed on the gel (Fig.…”

“…Intriguingly, only the bluish-gray M-SWCNTs migrated across the gel; the greenish S-SWCNTs did not migrate. In addition to the high yield, the separation duration was shortened to approximately 20 min, and the purities of the S-and MSWCNTs in fractions i and ii were also improved to 95% and 70%, respectively [15]. tempted to separate M-and S-SWCNTs without an electric field [16].…”