Nanobelts of hexagonal columnar crystal lattice through ionic self-assembly

Well-organized nanobelts from the complexes of p-aminoazobenzene hydrochloride (AzoHCl) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) have been constructed through the non-covalent forces such as electrostatic, hydrophobic, and pi-pi interactions. The nanobelt morphologies were characterized by optical microscope (OM) and scanning electronic microscope (SEM). The nanobelts with the length up to hundreds of micrometers were stacked layer by layer. Their crystal structures were analyzed by small-angle X-ray scattering (SAXS) and X-ray power diffraction (XRD) measurements. The obtained results indicated that the nanobelts of a hexagonal lattice were self-assembled from the columns of complex aggregates with azobenzene groups in the core and hydrocarbon tails of AOT outside. The H-type aggregation state of azobenzene groups here lead to a fluorescence quenching of AzoHCl. The differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) measurements demonstrated the thermostability and crystal nature for these nanobelts. Such a versatile route of self-assembly should shed light on ordered functional materials preparation, with the use of economical surfactants and organic functional molecules.