Physical chemical characterization of DNA–SWNT suspensions and associated composites

Suspensions of DNA–SWNT composites have been prepared as part of an ongoing study of individualized single-walled carbon nanotubes (SWNTs) using chemically modified or unmodified single-stranded DNA as the surfactant. We report optical absorption, photoluminescence (PL) and Raman spectra which are used to distinguish the types of carbon nanotubes (CNTs) present in the suspensions. Pyrenyl groups appended to the DNA affect the appearance of absorption and photoluminescence spectra. Furthermore, TEM has been used to characterize DNA–SWNT composites deposited on grids and flushed with a volatile aqueous buffer. Electron micrographs provide preliminary evidence for helical wrapping of single strand DNA (ssDNA) around individual CNTs and thin ropes of CNTs.