Flexible light-emitting devices based on chirality-sorted semiconducting carbon nanotube films

Controllable etching-induced contact enhancement for high-performance carbon nanotube thin-film transistors

Semiconducting single-walled carbon nanotubes (s-SWNTs) show great promises in advanced electronics. However, contact resistance between the nanotubes and metal electrode has long been a bottleneck to the development of s-SWNTs in high-performance electronic devices. Here we demonstrate a simple and controllable strategy for enhancing the electrode contact and therefore the performance of s-SWNT thin film transistors by plasma etching treatment, which effectively removes the polymer residues, including the photoresist and the conjugated molecules, adsorbed on the surface of s-SWNTs. As a result, the contact resistance is reduced by 3 times and the carrier mobility rises by up to 70%. Our method is compatible with current silicon semiconductor processing technology, making it a viable effective approach to large-scale application of s-SWNTs in the electronics industry.

Controllable plasma etching induced contact enhancement for high-performance carbon nanotube thin-film transistors and analysis of the mechanism.

Universal Selective Dispersion of Semiconducting Carbon Nanotubes from Commercial Sources Using a Supramolecular Polymer

Selective extraction of semiconducting carbon nanotubes is a key step in the production of high-performance, solution-processed electronics. Here, we describe the ability of a supramolecular sorting polymer to selectively disperse semiconducting carbon nanotubes from five commercial sources with diameters ranging from 0.7 to 2.2 nm. The sorting purity of the largest-diameter nanotubes (1.4 to 2.2 nm; from Tuball) was confirmed by short channel measurements to be 97.5%. Removing the sorting polymer by acid-induced disassembly increased the transistor mobility by 94 and 24% for medium-diameter and large-diameter carbon nanotubes, respectively. Among the tested single-walled nanotube sources, the highest transistor performance of 61 cm²/V·s and on/off ratio >10⁴ were realized with arc discharge carbon nanotubes with a diameter range from 1.2 to 1.7 nm. The length and quality of nanotubes sorted from different sources is compared using measurements from atomic force microscopy and Raman spectroscopy. The transistor mobility is found to correlate with the G/D ratio extracted from the Raman spectra.

Spiral Countercurrent Chromatography Enrichment, Characterization, and Assays of Carbon Nanotube Chiralities for Use in Biosensors

Single-walled carbon nanotubes (SWCNTs) are synthetic materials that hold great promise for electronics that are smaller and more versatile than the current silica-based technologies. But as-produced SWCNTs are generally a mixture of nanotubes with different structures that have vastly different properties. Separating these SWCNTs from multiwalled and metallic carbon nanotubes is vital to explore their individual properties and commercial utility ranging from optics to semiconductors. Compounding the problem of commercial investigation is that the semiconducting SWCNTs are also a mixture of different diameters and/or chiralities with different properties. Analyzing properties of enriched semiconducting SWCNT chiralities has only recently been possible through separation techniques such as aqueous two-phase solvent systems. Our study illustrates a semipreparative spiral countercurrent chromatography (CCC) separation of a commercial mixture of SWCNTs into distinct enriched fractions. A new mixer-settler spiral disk rotor was applied in this study, in which we compare the enriched SWCNTs for their effectiveness in biosensors with a high-throughput model assay, followed by antibody-mediated detection of Escherichia coli. Our results demonstrate that CCC-enriched responsive SWCNTs for biosensors can be used in our model assay, as well as for the detection of E. coli. To date, we believe that this is the first study along with Liu et al. [Chirality-controlled synthesis of single-wall carbon nanotubes using vapour-phase epitaxy. Nat. Commun.2012, 3, 1199] to demonstrate a specific utility of separated SWCNT species.

Carbon black functionalized stretchable conductive fabrics for wearable heating applications

There is an increasing interest on robust electrically conductive textiles with light weight and flexibility to meet the applications in wearable electronics.

(n,m) Assignments of Metallic Single-Walled Carbon Nanotubes by Raman Spectroscopy: The Importance of Electronic Raman Scattering

In this work, we report an accurate and convenient method that can be used to assign the chirality of all metallic single-walled carbon nanotubes (M-SWNTs). This method is designed based on the electronic Raman scattering (ERS) features, which are resonantly enhanced at the corresponding excitonic transition energies (M_ii⁺ and M_ii^-). Using this method, we are able to accurately determine the electronic property M_ii with the resolution of a vibrational Raman spectroscopy (∼0.3 meV), which is significantly higher than that of the electronic spectroscopies (∼3 meV). We use the M_ii splitting value, which is found insensitive to environmental changes, as a universal criteria for (n,m) assignments in various environments. As an illustrative example, simply using a commercialized Raman spectrometer with two laser lines (1.959 and 2.330 eV), we are able to unambiguously assign 18 metallic chiralities with M₁₁ in the 1.6-2.3 eV range in our samples. This method provides an accurate database of M_ii's in a similar way as photoluminescence excitation spectroscopy does for S_ii's. It can facilitate further systematic studies on the properties of M-SWNTs with defined chirality.