The utility of this invention is to extract metals (semi-metals) or semiconductors from bulk nanotube samples. The bulk material is a mixture of the two. These materials can then be used to clone a particular type of nanotube, place a particular type in a device, generate smart materials, or make sensing elements.

Raw carbon nanotubes are dispersed as individuals in a surfactant water mixture. Once the dispersion is obtained, the material is either selectively functionalized or heavily functionalized with diazonium salts. The selective functionalization is used to place polar or nonpolar groups on a particular type of nanotube. Once the nanotubes are selectively functionalized with an appropriate functional group, the sample is then reacted the rest of the way with the opposite functional group; i.e., if polar groups are used for the selective work, then nonpolar groups are used to react the sample to its greatest extent.

After completion of the reaction, the sample is isolated and cleaned. For bulk separation, the purified nanotube sample is then dispersed in a minimum of o-dichlorobenzene (ODCB). Flash chromatography is then performed with silica gel as the stationary phase and ODCB as the mobile phase. After the nonpolar portion of the nanotube elutes from the column, the column is then washed with N,N-dimethylformamide (DMF) to elute the polar component. This constitutes separation of the bulk nanotube sample into two portions: polar and nonpolar components.

When this separation is performed on a sample that has nonpolar groups attached to the semi-metal type nanotubes or a heavily functionalized sample, the nonpolar component is greatly enriched in semi-metals; therefore, this constitutes a bulk separation of nanotubes by type.

This work was done by James M. Tour and Christopher A. Dyke of Rice University for Johnson Space Center. MSC-24069-1

NASA Tech Briefs Magazine

This article first appeared in the October, 2014 issue of NASA Tech Briefs Magazine.

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