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

In this work, we report the observation on the self-assembly of β-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–β-CD nanotube. The effect of light scattering on the measurement of fluorescence anisotropy of PBD in the aqueous solutions of β-CD is corrected. A new mechanism of cyclodextrin aggregation is proposed for this system.

Graphical abstractDescription: High-resolution TEM micrograph of the micrometer-sized rodlike structure formed by the secondary assembly of PBD–β  -CD nanotubes. [PBD]=1×10−5 M[PBD]=1×10−5 M, [β-CD]=10 mM[β-CD]=10 mM.Figure optionsDownload full-size imageDownload as PowerPoint slide