METAL/SEMICONDUCTOR SORTING OF LARGE DIAMETER SINGLE-WALLED CARBON NANOTUBES BY NOVEL LIQUID CHROMATOGRAPHY METHODS.

Abstract

The growth of the semiconductor industry has been dependent upon the continuous miniaturization of silicon-based transistors over the past five decades. Currently, the dimensions of such transistors are reaching to the sub 10-nm regime wherein quantum physical laws set limits to further miniaturization of silicon-based materials. As a result, new materials that properly function at such reduced dimensions are highly sought. Single-walled carbon nanotubes (SWCNTs) are considered as the most promising nanomaterials in this regard due to their exceptional electronic properties. The upstream synthesis methods used for SWCNT production result in the generation of complex mixtures of both metallic and semiconducting forms. However, the application of SWCNTs as electronic transistors requires fractions that are highly enriched in the semiconducting forms. The use of SWCNTs as highly selective sensors, components of synthetic skin that preserve a sense of touch, and other new technologies also require the use of purified fractions containing single chiral forms. To address this, we have investigated multiple aqueous-based separation techniques that yield high purity fractions of a single electronic type. Our results demonstrate that various modes of liquid chromatography under optimized conditions yield efficient separations of semiconducting and metallic SWCNTs. We believe that the knowledge acquired, and the techniques developed in this work give strong evidence of the important role of liquid chromatography in the future of the nanotechnology, in general, and the semiconducting industry, in particular.