Fig. 2. Chiral switching of hierarchically organized vaterite suprastructures induced by a single chiral enantiomer of amino acid.

(A) SEM image of an initial vaterite helicoid with right-handed (counterclockwise), inclined spiraling chirality (green) as grown in the presence of l-Asp for 24 hours. (B) Achiral vaterite helicoid with straight-radiating (relative to the centroid, blue) vertical vaterite platelets formed after 3 days of growth. (C) With time, chiral switching appears first as a left-handed (clockwise, yellow) spiraling vaterite helicoid consisting of vertical vaterite platelets after 1 week of growth. (D) Again, with more time (2 weeks), achiral vaterite helicoids are formed having horizontal-surrounding vertical platelet orientation (relative to the centroid, blue). (E) Right-handed (counterclockwise, green) vaterite helicoids are found at 1 month with interlacing vertical platelets assembled into the helicoidal suprastructure (F). All platelets have nanoparticle subunit structure [inset in (F)].