Bottom-up-then-up-down Route for Multi-level Construction of Hierarchical Bi(2)S(3) Superstructures with Magnetism Alteration

A bottom-up-then-up-down route was proposed to construct multi-level Bi(2)S(3) hierarchical architectures assembled by two-dimensional (2D) Bi(2)S(3) sheet-like networks. BiOCOOH hollow spheres and flower-like structures, which are both assembled by 2D BiOCOOH nanosheets, were prepared first by a “bottom-up” route through a “quasi-emulsion” mechanism. Then the BiOCOOH hierarchical structures were transferred to hierarchical Bi(2)S(3) architectures through an “up-down” route by an ion exchange method. The obtained Bi(2)S(3) nanostructures remain hollow-spherical and flower-like structures of the precursors but the constructing blocks are changed to 2D sheet-like networks interweaving by Bi(2)S(3) nanowires. The close matching of crystal lattices between Bi(2)S(3) and BiOCOOH was believed to be the key reason for the topotactic transformation from BiOCOOH nanosheets to 2D Bi(2)S(3) sheet-like nanowire networks. Magnetism studies reveal that unlike diamagnetism of comparative Bi(2)S(3) nanostructures, the obtained multi-level Bi(2)S(3) structures display S-type hysteresis and ferromagnetism at low field which might result from ordered structure of 2D networks.