Structures of hybrids of DNA and carbon nanotubes in air and in liquids

摘要

We investigated single-walled carbon nanotubes (SWNT) and DNA-SWNT hybrids by atomic force microscopy (AFM). From the AFM observation of several different types of SWNTs and DNA-SWNT hybrids in air, we found several specific differences in morphology among the samples. Longer SWNT molecules were observed when the SWNT was dispersed using a bath type sonicator. When a probe type sonicator was used, the SWNT became short obviously. The phenomenon was common in all of our experiments, thus, the phenomenon was independent on the types SWNTs. SWNT functionalized with polyethyleneglycol (PEG SWNT), amino group (NH_2 SWNT), and carboxyl group (COOH SWNT) showed individual specific features in AFM images. Although NH_2 SWNT is typically soluble in organic solvents, uniform distribution was observed when DNA molecules were mixed with NH_2 SWNT. Finally, we observed DNA-SWNT hybrids by AFM in liquids for the first time. DNA-SWNT hybrids were significantly swollen in the aqueous solution even though the sample was dried once. This is helpful information for considering biological applications of the DNA-SWNT hybrids.