Measuring the Adsorbed Interfacial Layer on Dispersed Carbon Nanotubes

J.A. Fagan
NIST,
United States

Keywords: cellulose, chitin, CNT, nanotube

Summary:

For dispersed carbon nanotubes (CNTs) relevant to fluid phase processing and biological applications the nature and structure of the interfacial layer of adsorbed dispersant is typically the key parameter that controls dispersion stability, processability and any interactions with its media. However, measurement of these interfacial layers is a significant challenge for many nanoparticles, and this challenge is exacerbated by the polydispersity and anisotropy of CNTs. Ideally a metrology technique will enable discrimination of the interfacial layer size and density even in the presence of CNT polydispersity and be able to report parameters necessary to enable quality control of produced materials. In this presentation I will show that analytical ultracentrifugation (AUC), a technique that allows optical monitoring of particle sedimentation in situ in a media, can accomplish these goals for single-wall carbon nanotubes with a variety of dispersants and nanotube structures. Utilizing AUC we can characterize and monitor changes to the quantity of bound dispersant and hydration of dispersed SWCNTs and even measure the length distribution of the SWCNT populations. The information from these measurements on different populations and with modified dispersant chemistries and solution environments are providing the basis to analyze samples in complex or biological media, with applications for process quality control and resolution of environmental driven changes to the interfacial structure.