Determinants of crystal structure transformation of ionic nanocrystals in cation exchange reactions

Shape and nanocrystal transformations Cation exchange reactions that change the composition of a nanocrystal (NC) under mild conditions usually preserve the sublattice of the larger anions. Li et al. found that the shape of roxbyite (Cu 1.8 S) nanocrystals, which have a distorted, hexagonal, close-packed sulfide anion sublattice, affected the outcome of exchange reactions with cobalt ions. Flat nanoplates retained the anion lattice and formed cobalt sulfide, but tall nanorods transformed into Co 9 S 8 nanocrystals with a cubic, close-packed structure. Facile crystal plane sliding in the taller nanocrystals appears to have driven the different layer stacking of sulfide anions. Science , abh2741, this issue p. 332