Formation Mechanism Of Naiiotubes Via Self-assembly Of A Small Molecule

In recent years,nanomaterials have become a hot topic because of their unique properties in physics and chemistry.Organic nanotubes are particularly noticeable due to their high aspect ratio and the available outer surfaces,inner surfaces and hollow spaces.Molecular self-assembly has become an important method for the preparation of organic nanotubes.Although the preparation method and application of nanotubes are developing rapidly,the formation mechanism of nanotubes is still controversial.At present,there are two main mechanisms for self-assembly to form organic nanotubes: One is self-assembly via helical intermediates,another is the "rolling-up" mechanism.We have previously reported that ABA11 self-assembled into nanotubes starting from nanosheets and experiencing a meta-state of helical ribbons in DMSO solution.Herein,we found that changing the solvent can affect the self-assembly pathway of ABA11 to nanotubes.When DMSO was replaced by ethanol,the process of ABA11 forming nanotubes conforms to the "rolling-up" mechanism instead of the helical intermediates.Time-varying transmission electron microscopy(TEM)images,section analysis of atomic force microscopy(AFM)image,and the result of X-ray diffraction(XRD)indicated that the ABA11 molecules initially self-assembled into bimolecular nanosheets in ethanol.And then ABA11 either directly scrolled up to form nanotubes at low concentration,or stacked up to form nanobricks at higher concentration.In addition,increasing the water content in ethanol can significantly accelerate the formation of the nanostructures.Based on the experimental results,it can be concluded that the solvent plays an important role in the formation of nanotubes.