Molecular characterization of macroscopic aerogels of single-walled carbon nanotubes

TL;DR

This study uses Raman spectroscopy and electron microscopy to analyze the molecular structure of SWCNT aerogels, revealing detailed distributions of chiral angles and electronic types, aiding in the development of controlled SWCNT fibers.

Contribution

It provides a comprehensive characterization method combining spectroscopy and microscopy to analyze SWCNT aerogels without full aggregation, enabling better control of molecular structure.

Findings

Revealed the presence of both semiconducting and metallic SWCNTs in aerogels.

Matched chiral angle distribution with electron microscopy data.

Discussed effects of bundling on Raman spectral features.

Abstract

Single-walled carbon nanotubes (SWCNT) can be assembled into various macroscopic architectures, most notably continuous fibers and films, produced currently on a kilometer per day scale by floating catalyst chemical vapor depositionand spinning from an aerogel of CNTs. An attractive challenge is to produce continuous fibers with controlled molecular structure with respect to the diameter, chiral angle and ultimately(n,m)indices of the constituent SWCNT molecules. This work presents an extensive Raman spectroscopy and high resolution transmission electron microscopy study of SWCNT aerogels produced by the direct spinning method. By retaining the open structure of the SWCNT aerogel, we reveal the presence of both semiconducting and metallic SWCNTs and determine a full distribution of families of SWCNT grouped by optical transitions. The resulting distribution matches the chiral angle distribution obtained by electron microscopy and electron diffraction. The effect of SWCNT bundling on the Raman spectra, such as the G line shape due to plasmons activated in the far-infrared and semiconductor quenching, are also discussed. By avoiding full aggregation of the aerogel and applying the methodology introduced, rapid screening of molecular features can be achieved in large samples, making this protocol a useful analysis tool for engineered SWCNT fibers and related systems.