Scalable and Selective Dispersion of Semiconducting Arc-Discharged Carbon Nanotubes by Dithiafulvalene/Thiophene Copolymers for Thin Film Transistors

Abstract

We report a simple and scalable method to enrich large quantities of semiconducting arc-discharged single-walled carbon nanotubes (SWNTs) with diameters of 1.1-1.8 nm using dithiafulvalene/thiophene copolymers. Stable solutions of highly individualized and highly enriched semiconducting SWNTs were obtained after a simple sonication and centrifuge process. Molecular dynamics (MD) simulations of polymer backbone interactions with and without side chains indicated that the presence of long alkyl side chains gave rise to the selectivity toward semiconducting tubes, indicating the importance of the roles of the side chains to both solubilize and confer selectivity to the polymers. We found that, by increasing the ratio of thiophene to dithiafulvalene units in the polymer backbone (from pDTFF-1T to pDTFF-3T), we can slightly improve the selectivity toward semiconducting SWNTs. This is likely due to the more flexible backbone of pDTFF-3T that allows the favorable wrapping of SWNTs with certain chirality as characterized by small-angle X-ray scattering. However, the dispersion yield was reduced from pDTFF-1T to pDTFF-3T. MD simulations showed that the reduction is due to the smaller polymer/SWNT contact area, which reduces the dispersion ability of pDTFF-3T. These experimental and modeling results provide a better understanding for future rational design of polymers for sorting SWNTs. Finally, high on/off ratio solution-processed thin film transistors were fabricated from the sorted SWNTs to confirm the selective dispersion of semiconducting arc-discharge SWNTs.

Semiconducting single-walled carbon nanotubes sorting with a removable solubilizer based on dynamic supramolecular coordination chemistry

“…As shown in Fig. 4h, sem-SWNTs with (n,m) ¼ (6,5), (7,5), (7,6), (8,3), (8,4), (8,6), (8,7), (9,4), (9,5), (9,7), (10,2), (10,3), (10,5), (10,6), (11,3), (11,4), (11,6) and (12,2) were found to exist in the solution. In order to evaluate the extraction efficiency for each (n,m) chirality of the tubes, we calculated the relative contents of each SWNT based on the calibrated PL intensity using the method reported by Oyama et al 57 The calibrated contents of the SWNT species deduced from the PL mapping are shown in Supplementary Table 1, in which SWNTs with (n,m) ¼ (7,6), (8,6), (9,4) and (10,2) were enriched for the sample using CP-Zn.…”

“…Not only their structural characteristics, but also opto-electronic properties derived from their diameters and chiral indices, denoted as (n,m)SWNTs, are important for a deep understanding of their fundamental intrinsic properties [1][2][3][4][5][6][7][8][9][10] . Highly purified semiconducting SWNTs (sem-SWNTs) not containing metallic SWNTs (met-SWNTs) are specifically required for electronic devices, such as field-effect transistors [11][12][13][14] and photovoltaic applications 15,16 because the met-SWNTs decrease and reduce the efficiency of their associated devices 17,18 . Hence, the separation/purification of SWNTs according to their chirality is one of the most important issues in the science of carbon nanotubes.…”

“…In order to preserve the intrinsic SWNT properties, the latter method has an advantage over the former one. Recently, various methods for the separation of sem-and met-SWNTs including wrapping by SWNT solubilizers, such as DNAs 20,21 and p-conjugated or non-conjugated copolymers 11,[22][23][24] , density gradient ultracentrifugation 25,26 and gel chromatography techniques 12,14,[27][28][29][30][31][32][33][34][35][36][37][38][39] , have been reported. However, the reported techniques are rather complex and the efficiency is not very high.…”

Dispersant selection for nanomaterials: Insight into dispersing functionalized carbon nanotubes by small polar aromatic organic molecules

“…solution [9][10][11]. Up to date, two methods are applied to suspend CNTs, i.e., covalent [12] and non-covalent stabilization [13][14][15][16][17].…”

High performance transistors via aligned polyfluorene-sorted carbon nanotubes

“…12,13 Recent advances in the post-synthetic sorting and isolation of s-SWCNTs show promise to overcome this challenge. 11,14,15 Density gradient ultracentrifugation, 16 anion exchange chromatography, 17 dextran-based chromatography, 18 polymer wrapping, [19][20][21][22] and two-phase separation 23 have made it possible to isolate s-SWCNTs that are >99% semiconducting. The improved electronic-type purity has made it possible to increase on/off conductance modulation and on-conductance but a trade-off remains because metallic SWCNTs present in these materials are still limiting even at parts per hundred or thousand concentrations.…”