High Purity Isolation and Quantification of Semiconducting Carbon Nanotubes via Column Chromatography

Abstract

The isolation of semiconducting carbon nanotubes (CNTs) to ultrahigh (ppb) purity is a prerequisite for their integration into high-performance electronic devices. Here, a method employing column chromatography is used to isolate semiconducting nanotubes to 99.9% purity. The study finds that by modifying the solution preparation step, both the metallic and semiconducting fraction are resolved and elute using a single surfactant system, allowing for multiple iterations. Iterative processing enables a far more rapid path to achieving the level of purities needed for high performance computing. After a single iteration, the metallic peak in the absorption spectra is completely attenuated. Although absorption spectroscopy is typically used to characterize CNT purity, it is found to be insufficient in quantifying solutions of high purity (>98 to 99%) due to low signal-to-noise in the metallic region of ultrahigh purity solutions. Therefore, a high throughput electrical testing method was developed to quantify the degree of separation by characterizing ∼4000 field-effect transistors fabricated from the separated nanotubes after multiple iterations of the process. The separation and characterization methods described here provide a path to produce the ultrahigh purity semiconducting CNT solutions needed for high performance electronics.

All‐Carbon Thin‐Film Transistors as a Step Towards Flexible and Transparent Electronics

“…At least 13 chiralities of CNTs were purified after two successive separations, and 99.9% semiconducting CNT inks were obtained after three iterations of the process. [166,167] Semiconducting CNTs with a large diameter (>1.4 nm) have a low interaction with the gel, and are almost insensitive it, so that they are difficult to separate, and thus remain in the bottom column in the multi-column version.…”

“…[89] In terms of their use as a channel material, the absence of a bandgap makes graphene difficult to use as a channel in TFTs with a high on/off current ratio, and the different electrical properties of CNTs, depending on their chirality, inevitably leads to device-to-device performance variation. Although semiconductor-enriched CNT inks are commercially available, chirality-specific purification techniques such as ion-exchange chromatography [164,165] and gel chromatography [166,167] are very important to produce uniform channels. High-purity sorting of more than 99.9% semiconducting CNTs can be achieved by using charge sign reversal sorting [168] and recyclable conjugated polymer sorting [172] techniques.…”

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

“…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.…”

Variability and reliability analysis in self-assembled multichannel carbon nanotube field-effect transistors

“…The NMPI containing a hydroxamic acid group selectively binds to the HfO 2 surface but does not stick to SiO 2 . 13,15 An aqueous CNT solution in SDS with a high semiconducting purity was prepared via column chromatography 16 and was applied on the patterned substrate for 1 h. The iodide of NMPI was exchanged with the anionic surfactant wrapped around CNTs, leading to a strong coulombic attraction between the negatively charged CNTs and the positively charged monolayer. This process results in deposition of the CNTs in the HfO 2 trenches, but not onto the SiO 2 field oxide.…”