Self-Assembled Ultralong Chiral Nanotubes and Tuning of Their Chirality Through the Mixing of Enantiomeric Components

Enantiomeric L- or D-glutamic acid based lipids were designed and their self-assembly was investigated. It was found that at a certain concentration, either L- or D-enantiomeric derivatives could self-assemble in absolute alcohol to form a white organogel, which was composed of ultralong nanotubes with an aspect ratio higher than 1000. Further investigations revealed that these nanotubes were in chiral forms. The chirality of the nanotubes was determined by that of the enantiomers employed. In addition, when D and L enantiomers were mixed in different ratios, the nanotube could be tuned consecutively from nanotubes with a helical seam to nanotwists, the chirality of which being determined by the excess enantiomer in the mixed systems. In the case of an equimolar mixture of the enantiomers, flat nanoplates instead of helical nanotubes or nanotwists were obtained. The FTIR vibrational data and XRD layer-distance values showed a consecutive change as a function of the enantiomeric excess. It was further revealed that the slightly stronger interaction between D-L enantiomeric pairs than that between D-D or L-L pairs was responsible for the formation of the diverse self-assembled nanostructures.