Intercalation route to nano-hybrids inorganic/organic-high T(c) cuprate hybrid materials

A systematic application of intercalation techniques to layered superconducting oxides enables us to open a new chapter in the development of nano-hybrids with various functions. Recently we were successful in preparing a new series of inorganic-inorganic nano-hybrids, M-X-Bi₂Sr₂Ca(m- 1)Cu(m)O(y) (M = Hg, Ag, Au; X = Br, I; m = 1-3) and organic-inorganic ones, R₂HgI₄-Bi₂Sr₂Ca(m-1)Cu(m)O(y) (R = organic cation). Our synthetic strategies are based on (1) HSAB (hard-soft acid-base) interactions and (2) interlayer complexation concepts. Since the iodine species in IBi₂Sr₂Ca(m- 1)Cu(m)O(y) are stabilized as I₃ (soft base) with a charge transfer between host and guest, soft Lewis acids like Ag⁺, Au⁺, and Hg²⁺ can be further intercalated into the iodine layers in between the (Bi-O) double layers. On the other hand, new organic-inorganic nano-hybrids (R₂HgI₄-Bi₂Sr₂Ca(m- 1)Cu(m)O(y)) have also been achieved through the intercalative complex-salt formation reaction between preintercalated HgI₂ molecules and R⁺I^- salts in the interlayer space of Bi₂Sr₂Ca(m-1)Cu(m)O(y). Compared to the pure compounds the superconducting transition temperatures of the organic-salt intercalates are little changed even with a large basal increment upon intercalation, indicating a two-dimensional nature of the high-T(c) superconductivity. From the viewpoint of application, the intercalation of large organic molecules provides a new synthetic route to high-T(c) superconducting thin-film and nano-particles by separating superconducting blocks into isolated single sheets.