A Mixed-Extractor Strategy for Efficient Sorting of Semiconducting Single-Walled Carbon Nanotubes

Efficient Sorting of Semiconducting Single-Walled Carbon Nanotubes in Bio-Renewable Solvents Through Main-Chain Engineering of Conjugated Polymers

Conjugated polymer sorting is recognized as an efficient and scalable method for the selective extraction of semiconducting single-walled carbon nanotubes (s-SWCNTs). However, this process typically requires the use of nonpolar and aromatic solvents as the dispersion medium, which are petroleum-based and carry significant production hazards. Moreover, there is still potential for improving the efficiency of batch purification. Here, this study presents fluorene-based conjugated polymer that integrates diamines containing ethylene glycol chains (ODA) as linkers within the main chain, to effectively extract s-SWCNTs in bio-renewable solvents. The introduction of ODA segments enhances the solubility in bio-renewable solvents, facilitating effective wrapping of s-SWCNTs in polar environments. Additionally, the ODA within the main chain enhances affinity to s-SWCNTs, thereby contributing to increased yields and purity. The polymer achieves a high sorting yield of 55% and a purity of 99.6% in dispersion of s-SWCNTs in 2-Methyltetrahydrofuran. Thin-film transistor arrays fabricated with sorted s-SWCNTs solution through slot-die coating exhibit average charge carrier mobilities of 20-23 cm2 V⁻¹ s⁻¹ and high on/off current ratios exceeding 105 together with high spatial uniformity. This study highlights the viability of bio-renewable solvents in the sorting process, paving the way for the eco-friendly approach to the purification of SWCNTs.

High-Performance Semiconducting Carbon Nanotube Transistors Using Naphthalene Diimide-Based Polymers with Biaxially Extended Conjugated Side Chains

Polymer-wrapped single-walled carbon nanotubes (SWNTs) are a potential method for obtaining high-purity semiconducting (sc) SWNT solutions. Conjugated polymers (CPs) can selectively sort sc-SWNTs with different chiralities, and the structure of the polymer side chains influences this sorting capability. While extensive research has been conducted on modifying the physical, optical, and electrical properties of CPs through side-chain modifications, the impact of these modifications on the sorting efficiency of sc-SWNTs remains underexplored. This study investigates the introduction of various conjugated side chains into naphthalene diimide-based CPs to create a biaxially extended conjugation pattern. The CP with a branched conjugated side chain (P3) exhibits reduced aggregation, resulting in improved wrapping ability and the formation of larger bundles of high-purity sc-SWNTs. Grazing incidence X-ray diffraction analysis confirms that the potential interaction between sc-SWNTs and CPs occurs through π-π stacking. The field-effect transistor device fabricated with P3/sc-SWNTs demonstrates exceptional performance, with a significantly enhanced hole mobility of 4.72 cm2 V-1 s-1 and high endurance/bias stability. These findings suggest that biaxially extended side-chain modification is a promising strategy for improving the sorting efficiency and performance of sc-SWNTs by using CPs. This achievement can facilitate the development of more efficient and stable electronic devices.

High-yield and chirality-selective isolation of single-walled carbon nanotubes using conjugated polymers and small molecular chaperones

Single-walled carbon nanotubes (SWCNTs) have potential for a wide range of applications in diverse fields, but the heterogeneous properties of the synthesized mixtures of SWCNT types hinder the realization of these aspirations. Recent developments in extractive purification methods of polychiral SWCNT mixtures have somewhat gradually alleviated this problem, but either the yield or purity of the obtained fractions remains unsatisfactory. In this work, we showed the possibility of simultaneously achieving both the aforementioned goals, commonly considered mutually exclusive, via the enhancement of the capabilities of the conjugated polymer extraction (CPE) technique. We found that combining small molecular species, which alone are unwanted in the system, with a selective poly(9,9'-dioctylfluorenyl-2,7-diyl-alt-6,6'-(2,2'-bipyridine)) polymer increased the concentration of the harvested SWCNTs by an order of magnitude while maintaining near-monochiral purity of the materials. The conducted modeling revealed that the presence of these additives facilitated the folding of conjugated polymers around (6,5) SWCNTs, leading to a substantial increase in the concentration and quality of the SWCNT suspension. The obtained results lay the foundation for the widescale implementation of the CPE of usually scarcely available chirality-defined SWCNTs owing to the molecular chaperones expediting the folding of the conjugated polymers.

Iterative Strategy for Sorting Single-Chirality Single-Walled Carbon Nanotubes from Aqueous to Organic Systems

Significant advancements in electronic devices and integrated circuits have been facilitated by semiconducting single-walled carbon nanotubes (SWCNTs) sorted by conjugated polymers (CPs). However, the variety of CPs with single-chirality selectivity is limited, and the sorting results are strongly dependent on the chiral distribution of the starting materials. To address this, we develop an iterative strategy to achieve single-chirality SWCNT separation from aqueous to organic systems, based on a multistep tandem extraction technique that allows a gentle and nondestructive separation of surfactants from SWCNTs, ensuring an efficient system transfer. In parallel, we refined the iterative sorting process between CPs. Employing two starting materials with narrow diameter distributions, using three CPs, we successfully sorted out five single-chirality SWCNTs of the (9,5), (8,6), (10,5), (8,7), and (11,3) species in organic systems. This strategy bridges the gap between aqueous and organic separation systems, achieving efficient complementarity between them.

Two-component polymer sorting to obtain high-purity s-SWCNTs for all-carbon photodetectors

The advancement of carbon-based electronics is reliant on the development of semiconducting carbon nanotubes with high purity and yield. We developed a new extraction strategy to efficiently sort SWCNTs with superior yields and purity. The approach uses two polymers, poly[N-(1-octylnonyl)-9H-carbazol-2,7-diyl](PCz) and poly(9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole)(PDFP), and two sonication processes to eliminate surface polymer contamination. PCz selectively wraps large-diameter s-SWCNTs, with PDFP added as an enhancing molecule to increase sorting efficiency at 4-fold compared to the efficiency of only PCz alone sorting. The purity of the sorted s-SWCNTs was confirmed to be above 99 % using absorption and Raman spectra. Field-effect transistors and photodetectors made from the sorted s-SWCNTs exhibited excellent semiconductor properties and broad-spectrum detection, with good long-term stability. Furthermore, a photodetector using large-tube diameter s-SWCNTs achieved broad-spectrum detection, which the photoresponsivity is 0.35 mA/W and the detectivity is 4.7×106 Jones. The s-SWCNTs/graphene heterojunction photodetector achieved a photoresponsivity of 3 mA/W and a detectivity of 6.3×106 Jones. This new strategy provides a promising approach to obtain high-purity and high-yield s-SWCNTs for carbon-based photodetectors.

Stabilization of Lithium Metal Interfaces by Constructing Composite Artificial Solid Electrolyte Interface with Mesoporous TiO2 and Perfluoropolymers

The next generation of high-energy-density storage devices is expected to be rechargeable lithium metal batteries. However, unstable metal-electrolyte interfaces, dendrite growth, and volume expansion will compromise lithium metal batteries (LMB) safety and life. A simple drop-casting method is used to create a double-layer functional interface composed of inorganic mesoporous TiO₂ and F-rich organics PFDMA. For high-quality lithium deposition, TiO₂ can provide uniform mechanical pressure, abundant mesoporous channels, and increased ionic conductivity, while PFDMA provides enough F to form LiF in the first cycle and improves Li-electrolyte compatibility. Experiments and simulations are combined to investigate the optimized mechanism of the LiF-rich solid electrolyte interface (SEI). The high binding energy of organic matter and Li demonstrates that Li⁺ preferentially binds with the F atom in organic matter. As a result, the tightly bound double-layer structure can inhibit lithium dendrite growth and slow electrolyte decomposition. Consequently, the symmetric Li||Li cell has a high stability performance of over 800 h. The assembled LiFePO₄ ||Li cell can sustain 300 cycles at a 1 C rate and has a reversible capacity of 136.7 mAh g^-1 .

Separation of Semiconducting Carbon Nanotubes Using Conjugated Polymer Wrapping

In the past two decades, single-walled carbon nanotubes (SWNTs) have been explored for electronic applications because of their high charge carrier mobility, low-temperature solution processability and mechanical flexibility. Semiconducting SWNTs (s-SWNTs) are also considered an alternative to traditional silicon-based semiconductors. However, large-scale, as-produced SWNTs have poor solubility, and they are mixtures of metallic SWNTs (m-SWNTs) and s-SWNTs, which limits their practical applications. Conjugated polymer wrapping is a promising method to disperse and separate s-SWNTs, due to its high selectivity, high separation yield and simplicity of operation. In this review, we summarize the recent progress of the conjugated polymer wrapping method, and discuss possible separation mechanisms for s-SWNTs. We also discuss various parameters that may affect the selectivity and sorting yield. Finally, some electronic applications of polymer-sorted s-SWNTs are introduced. The aim of this review is to provide polymer chemist a basic concept of polymer based SWNT separation, as well as some polymer design strategies, influential factors and potential applications.

Solution-Processing of High-Purity Semiconducting Single-Walled Carbon Nanotubes for Electronics Devices

High-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) are of paramount significance for the construction of next-generation electronics. Until now, a number of elaborate sorting and purification techniques for s-SWCNTs have been developed, among which solution-based sorting methods show unique merits in the scale production, high purity, and large-area film formation. Here, the recent progress in the solution processing of s-SWCNTs and their application in electronic devices is systematically reviewed. First, the solution-based sorting and purification of s-SWCNTs are described, and particular attention is paid to the recent advance in the conjugated polymer-based sorting strategy. Subsequently, the solution-based deposition and morphology control of a s-SWCNT thin film on a surface are introduced, which focus on the strategies for network formation and alignment of SWCNTs. Then, the recent advances in electronic devices based on s-SWCNTs are reviewed with emphasis on nanoscale s-SWCNTs' high-performance integrated circuits and s-SWCNT-based thin-film transistors (TFT) array and circuits. Lastly, the existing challenges and development trends for the s-SWCNTs and electronic devices are briefly discussed. The aim is to provide some useful information and inspiration for the sorting and purification of s-SWCNTs, as well as the construction of electronic devices with s-SWCNTs.

Microwave-Assisted Regeneration of Single-Walled Carbon Nanotubes from Carbon Fragments

Direct growth of chirality-controlled single-walled carbon nanotubes (SWNTs) with metal catalyst free strategy, like cloning or epitaxial growth, has suffered from the low efficiency. The underlying problem is the activation of seed edge. Here an unexpectedly efficient microwave-assisted pathway to regenerate SWNTs from carbon fragments on SiO₂ /Si substrate is demonstrated via Raman spectroscopy and atomic force microscope (AFM) characterization. In this attempt, microwave irradiation provides fast heating to remove polar groups bonded to carbon nanotubes and reduce the spontaneous closure of tubes' open ends. The survived SWNT and carbon fragments connected to it after plasma treatment are simply microwaved and then they serve as the template for regeneration. Scanning electron microscope and AFM characterizations indicate that the efficiency of the regeneration can reach 100%. And the regenerated SWNT has been proved without any change in chirality compared to the original SWNT. Electrical measurements on regenerated carbon nanotube films indicate 1 and 2 times increase in on/off ratio and on-state current respectively than original carbon nanotube films obtained from solution-phase separation, confirming the improvement of SWNT's quality. The microwave-assisted regeneration is found to be highly effective and would be applied to improve the cloning efficiency of carbon nanotubes potentially.

Recycling Strategy for Fabricating Low-Cost and High-Performance Carbon Nanotube TFT Devices

High-purity semiconducting single-walled carbon nanotubes (s-SWNTs) can be obtained by conjugated polymer wrapping. However, further purification of sorted s-SWNTs and high costs of raw materials are still challenges to practical applications. It is inevitable that a lot of polymers still cover the surface of s-SWNTs after separation, and the cost of the polymer is relatively higher than that of SWNTs. Here, we demonstrated a facile isolated process to improve the quality of s-SWNT solutions and films significantly. Compared with the untreated s-SWNTs, the contact resistance between the s-SWNT and the electrode is reduced by 20 times, and the thin-film transistors show 300% enhancement of current density. In this process, most of the polymers can be recycled and reused directly without any purification, which can greatly decrease the cost for s-SWNT separation. The results presented herein demonstrate a new scalable and low-cost approach for large-scale application of s-SWNTs in the electronics industry.