"Shaken, not stable": dispersion mechanism and dynamics of protein-dispersed nanotubes studied via spectroscopy.

Bundles of nanotubes have been exfoliated in solution by handful of dispersants, such as surfactants, polymers, or proteins, for efficient use in various applications. Common procedures in carbon nanotube exfoliation and dispersion are sonication followed by centrifugation. The dispersion dynamics of single-walled carbon nanotubes (SWNT) by protein were studied by UV-vis spectroscopy (enhanced with chemometric analysis) and low-temperature transmission electron microscopy (cryo-TEM). We studied the effect of both pH and BSA-to-SWNT ratio on SWNT exfoliation dynamics and recovery. We found that, indeed, BSA properties (i.e., electric charge and conformation) affect the exfoliation dynamics in a similar manner as it affects the SWNT recoveries: bulkier protein conformation-->faster exfoliation-->higher SWNT recoveries. Higher BSA-to-SWNT ratio results in lower recoveries and slower dynamics, suggesting that entropic consideration may take part in the exfoliation-stabilization process of SWNT.