Length Distribution of Single-Walled Carbon Nanotubes in Aqueous Suspension Measured by Electrospray Differential Mobility Analysis

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 5; no. 24; pp. 2894 - 2901
• Main Authors: Pease III, Leonard F., Tsai, De-Hao, Fagan, Jeffery A., Bauer, Barry J., Zangmeister, Rebecca A., Tarlov, Michael J., Zachariah, Michael R.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 18-12-2009; WILEY‐VCH Verlag
• Subjects: Aqueous solutions; aqueous suspensions; carbon nanotubes; Crystallization - methods; Dispersion; Electronics; electrospray differential mobility analysis; length distribution; Light scattering; Macromolecular Substances - chemistry; Materials Testing; Molecular Conformation; Nanocomposites; Nanomaterials; Nanostructure; Nanotechnology - methods; Nanotubes, Carbon - chemistry; Nanotubes, Carbon - ultrastructure; Nephelometry and Turbidimetry - methods; Particle Size; scanning mobility; Single wall carbon nanotubes; Spectrometry, Mass, Electrospray Ionization - methods; Surface Properties; Suspensions
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.200900928

The first characterization of the length distribution of single‐walled carbon nanotubes (SWCNT) dispersed in a liquid by electrospray differential mobility analysis (ES‐DMA) is presented. Although an understanding of geometric properties of SWCNTs, including length, diameter, aspect ratio, and chirality, is essential for commercial applications, rapid characterization of nanotube length distributions remains challenging. Here the use of ES‐DMA to obtain length distributions of DNA‐wrapped SWCNTs dispersed in aqueous solutions is demonstrated. Lengths measured by ES‐DMA compare favorably with those obtained from multiangle light scattering, dynamic light scattering, field flow fractionation with UV/vis detection, and atomic force microscopy, validating ES‐DMA as a technique to measure SWCNTs of <250 nm in length. The nanotubes are previously purified and dispersed by wrapping with oligomeric DNA in aqueous solution and centrifuging to remove bundles and amorphous carbon. These dispersions are particularly attractive due to their amenability to bulk processing, ease of storage, high concentration, compatibility with biological and high‐throughput manufacturing environments, and for their potential applications ranging from electronics and hydrogen‐storage vessels to anticancer agents.
Complete length distributions of carbon nanotubes in aqueous dispersion are obtained using differential mobility analysis (DMA). Electrospray is used to sample the suspension, enabling direct and rapid read‐out of the particle size distribution (see image). DMA detects nanometer‐scale changes in the nanotube mobility distribution with length averages comparable to those from other techniques. Colloidal suspensions of nanotubes are particularly attractive due to their amenability to bulk processing and compatibility with biological and manufacturing environments.