Adsorption of streptavidin onto single-walled carbon nanotubes: application in fluorescent supramolecular nanoassemblies

We report the solubilization of full-length single-walled carbon nanotubes into a physiological buffer by sonication in presence of streptavidin. Transmission electron microscopy showed that the resultant dispersion was enriched of individual/small ropes of nanotubes. By the analysis of the crystal structure of tetrameric streptavidin and of the tryptophan emission of adsorbed proteins we hypothesized that proteins adsorbed onto SWNT sidewalls through their amine functionalities. Our results suggested using streptavidin as an interlinker between carbon nanotubes and semiconducting nanocrystals. We fabricated a supramolecular luminescent nanoassembly composed of individual or small ropes of full-length single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots. The luminescent nanoassembly was stably dispersed under physiological conditions and was readily visible by optical fluorescent microscopies.