Monodisperse single-walled carbon nanotube populations and related methods for providing same

Abstract

The present teachings provide methods for providing populations of single-walled carbon nanotubes that are substantially monodisperse in terms of diameter, electronic type, and / or chirality. Also provided are single-walled carbon nanotube populations provided thereby and articles of manufacture including such populations.

Description

[0001]This application claims priority to and the benefit of the filing date of U.S. Provisional Application Ser. No. 60 / 840,990, filed on Aug. 30, 2006, the entire disclosure of which is incorporated by reference herein.[0002]The United States Government has certain rights to this invention pursuant to Grant Nos. EEC-0118025 and DMR-0134706 from the National Science Foundation and Grant No. DE-FG02-00ER54810 from the Department of Energy, all to Northwestern University.INTRODUCTION[0003]Carbon nanotubes have recently received extensive attention due to their nanoscale dimensions and outstanding materials properties such as ballistic electronic conduction, immunity from electromigration effects at high current densities, and transparent conduction. However, as-synthesized carbon nanotubes vary in their diameter and chiral angle, and these physical variations result in striking changes in their electronic and optical behaviors. For example, about one-third of all possible single-wall...

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Benefits of technology

[0022]In some embodiments, the method can include treatment of the enriched population to provide bare single-walled carbon nanotubes. In some embodiments, the method can include centrifuging the mixture of semiconducting single-walled carbon nanotubes and metallic single-walled carbon nanotubes. In certain embodiments, the method can provide a population of single-walled carbon nanotubes that includes at least 50% metallic single-walled carbon nanotubes. In addition to providing a population enriched with metallic single-walled carbon nanotubes, the method can further enrich the substantially metallic population with a predetermined range of nanotube diameter dimensions and / or chiralities. In some embodiments, single-walled carbon nanotubes in the mixture can independently have diameter dimensions up to about 20 Å or more. In certain embodiments, dimensions can range from about 7 Å to about 11 Å, while in certain other embodiments, dimensions can be greater than about 11 Å (for example, ranging from about 11 Å to about 20 Å or from about 11 Å to about 16 Å).

Problems solved by technology

However, as-synthesized carbon nanotubes vary in their diameter and chiral angle, and these physical variations result in striking changes in their electronic and optical behaviors.

The unavoidable structural heterogeneity of the currently available as-synthesized SWNTs prevents their widespread application as high-performance field-effect transistors, optoelectronic near-infrared emitters / detectors, chemical sensors, materials for interconnects in integrated circuits, and conductive additives in composites.

Accordingly, the utilization of SWNTs will be limited until large quantities of monodisperse SWNTs can be produced or otherwise obtained.

While several SWNT purification methods have been recently demonstrated, no pre-existing technique has been reported that simultaneously achieves diameter and band gap selectivity over a wide range of diameters and band gaps, electronic type (metal versus semiconductor) selectivity, and scalability.

Furthermore, most techniques are limited in effectiveness, and many are only sensitive to SWNTs that are less than about 11 Å in diameter.

This is a significant limitation because the SWNTs that are most important for electronic devices are generally ones that are larger in diameter, since these form less resistive contacts (i.e. reduced Schottky barriers).

The methods of dielectrophoresis and controlled electrical breakdown are both limited in scalability and are only sensitive to electronic type (not diameter or band gap).

Furthermore, the selective chemical reaction of diazonium salts with metallic SWNTs has only been demonstrated for SWNTs in the 7-12 Å diameter range, and this approach does not provide diameter and band gap selectivity.

More problematically, the chemistry also results in the covalent degradation of the nanotube sidewalls.

In addition, the use of amine-terminated surfactants in organic solvents is limited to the production of samples that are only 92% semiconducting, and the technique has been successfully applied only to SWNTs having a diameter of less than or about 10 Å. Similarly, while diameter and electronic type selectivity have been observed using anion exchange chromatography, such approach has only been demonstrated for SWNTs wrapped by specific oligomers of DNA ranging from 7-11 Å in diameter.

As previously mentioned, current methods for separating metallic single-walled carbon nanotubes from an electronically heterogeneous mixture were reported to cause degradation of the nanotube sidewalls.

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