Two-dimensional folded nanosheets lead to an unusual circular dichroism effect in aqueous solution

We found that two-dimensional (2D) folded nanosheets with crystalline structure in aqueous solution could induce an unusual time-dependent circular dichroism (CD) effect in the CD measurements after shaking or stirring the solution. In addition, a critical damping curve was observed in the CD spectrum after stop of stirring the solution. The apparent CD effect actually originates from linear dichroism (LD) changes in the oscillations of two-dimensional folded nanosheets and the inherent optical imperfections of the CD instruments. The oscillations of the folded nanosheets should induce this CD effect by the conformational change. Although an unusual apparent CD effect in alignment of one-dimensional (1D) dye-containing supramolecular nanofibers has been documented, this study reports for the first time that 2D folded nanosheets can lead to such a CD effect. It is anticipated that the method may provide a way to spectroscopically visualize the dynamic conformational change of self-assemblies in solutions.