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 (NH2 SWNT), and carboxyl group (COOH
SWNT) showed individual specific features in AFM images. Although NH2 SWNT is typically soluble in organic
solvents, uniform distribution was observed when DNA molecules were mixed with NH2 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.
The surface structures of Coscinodiscus granii frustules were investigated before and after liquid phase deposition (LPD)
treatment. Scanning electron microscopy (SEM) images showed that the outer surface of the frustules was rapidly
covered with a TiO2 layer within 6 h although the inner surface was not fully covered under the same condition.
Comparison between the un-coated samples and the samples coated with metal prior to SEM observation provided
valuable results to facilitate the understanding of the differences between the surface properties of the inner and outer
frustule structures. Additionally, useful topographical information about the inner frustule surfaces was obtained by
AFM imaging. The results of this investigation provide fundamental information about the process of LPD treatment
onto frustule surfaces.
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