Micrometer-sized rodlike structure formed by the secondary assembly of cyclodextrin nanotube.

In this work, we report the observation on the self-assembly of beta-CD nanotube induced by 2-phenyl-5-(4-diphenylyl)1,3,4-oxadiazole (PBD) molecule with fluorescence microscopy and transmission electron microscopy (TEM). Micrometer-sized rodlike structure is formed by the secondary assembly of cyclodextrin nanotube driven by the inter-nanotubular hydrogen bonding. The effects of pH value, urea, DMF and NaCl on the formation of the rodlike structure are investigated. Dynamic light scattering (DLS) is applied to further characterize the formation of the PBD-beta-CD nanotube. The effect of light scattering on the measurement of fluorescence anisotropy of PBD in the aqueous solutions of beta-CD is corrected. A new mechanism of cyclodextrin aggregation is proposed for this system.