Figure 2: Dynamic material with switchable CD.

(a) Theoretical (grey curve) and experimental (black curve) CD spectra for L-NHs dispersed in solution. (b) Theoretical CD spectra of L-NHs oriented parallel (red curve) and perpendicular (blue curve) to the incident beam. (c) Experimental CD spectra (top) and scheme of orientation state (bottom) of the L-NHs. The light beam penetrates the quartz substrate perpendicular to its surface plane. Measurements shown were performed with the same ensemble of L-NHs and in the displayed order. L-NHs stood upright if dispersed in solution and were hence aligned parallel to the incoming light beam. The expected transverse CD_z was observed in this case. After removal of the buffer and drying of the surface, the L-NHs laid flat on the substrate and were thus oriented perpendicular to the incoming light beam. Here, the expected longitudinal CD_xy was measured. The cuvette was re-filled with buffer, which led to re-alignment of the L-NHs parallel to the light beam. Again the transverse CD_z was obtained. The sample was dried again and the longitudinal CD_xy reappeared.