Exploring a nanotube dispersion mechanism with gold-labeled proteins via cryo-TEM imaging

The protein gold-labeling technique was employed in a cryo-Transmission Electron Microscopy (TEM) method to study the exfoliation of single walled carbon nanotubes (SWNT) while preserving its unique properties. The dispersion molecule bovine serum albumin (BSA) was labeled by monomer dispersed gold nanoparticles (GNP) having a high electron-density contrast, such that the protein maintained its biological activity. The negative-strain TEM micrograph of the nanotubes dispersed by BSA has a sufficiently high contrast to confirm that BSA is attached to the SWNT. The analysis results show that the majority of the observed BSA-GNP complexes are distributed at distances of 20-80 nm from each other along the individually dispersed SWNTs. A 2-4-nm increase in SWNT height is observed at various points along the nanotubes where the proteins are absorbed and such a change in diameter closely matches the molecular dimensions of unfolded protein.