10.1021/ja2049594.s001 Sohee Jeong Sohee Jeong Jae Hyo Han Jae Hyo Han Jung-tak Jang Jung-tak Jang Jung-wook Seo Jung-wook Seo Jin-Gyu Kim Jin-Gyu Kim Jinwoo Cheon Jinwoo Cheon Transformative Two-Dimensional Layered Nanocrystals American Chemical Society 2011 TMC Cu ion 2 D TiS 2 nanodiscs interlayer nanochannels Ag 2S MnS chemical reaction toroidal nanocrystals Such 2 D regioselective chemical reactions ion diffusion chemical stimulus edge reaction chemical principles 2011-09-21 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Transformative_Two_Dimensional_Layered_Nanocrystals/2612170 Regioselective chemical reactions and structural transformations of two-dimensional (2D) layered transition-metal chalcogenide (TMC) nanocrystals are described. Upon exposure of 2D TiS<sub>2</sub> nanodiscs to a chemical stimulus, such as Cu ion, selective chemical reaction begins to occur at the peripheral edges. This edge reaction is followed by ion diffusion, which is facilitated by interlayer nanochannels and leads to the formation of a heteroepitaxial TiS<sub>2</sub>–Cu<sub>2</sub>S intermediate. These processes eventually result in the generation of a single-crystalline, double-convex toroidal Cu<sub>2</sub>S nanostructure. Such 2D regioselective chemical reactions also take place when other ionic reactants are used. The observations made and chemical principles uncovered in this effort indicate that a general approach exists for building various toroidal nanocrystals of substances such as Ag<sub>2</sub>S, MnS, and CdS.