Intercalative route to heterostructured nanohybrids

We have successfully synthesized inorganic-inorganic, organic-in organic and bio-inorganic nanohybrids by applying an intercalation technique systematically to layered titanate, molybdenum disulfide (MoS2), Bi-based cuprate superconductors (Bi2Sr2Cam-1CumOy (m = 1, 2, and 3; BSCCO)), and to layered double hydroxides (LDHs), those which are of high importance in terms of basic understanding of intercalation reactions and of their practical applications. The inorganic-inorganic systems such as TiO2-pillared titanate, TiO2-pillared MoS2, and CdS-MoS2 hybrids were synthesized by exfoliation-restacking method. A novel pillaring process using an osmotic swelling was developed to prepare TiO2-pillared layered titanate with a large surface area, high thermal stability, and enhanced photocatalytic activity. And the intercalation of TiO2 and/or US nanocluster into the two dimensional MoS2 lattice could be also realized by exfoliating and reassembling the lithiated molybdenum disulfide (LiMoS2) in the presence of cationic TiO2 and/or US nanocluster in an aqueous solution, respectively, to obtain the semiconductor-semiconductor hybrids. On the other hands, the organic-inorganic hybrids were achieved via intercalative complexation of iodine intercalated BSCOO with organic salt of Py-CnH2n+1I (Py = pyridine). The high-T-c superconducting intercalate with its remarkable lattice expansion can be applied as a precursor for superconducting colloids when dispersed in an appropriate solvent. This superconducting hybrid material had an unique structural feature of a superconducting-insulating-superconducting multilayer with atomically clean interfaces. Especially, this organic-inorganic nanohybrid is expected to be a promising precursor for preparing the superconducting colloidal suspension, which could be applied to the fabrication of superconducting films or wires. Recently, we were very successful in demonstrating in which the formation of bio-morganic hybrids stabilized in the interlayer space of LDH retain their chemical and biological integrity. If necessary, LDH, as a reservoir, can be intentionally removed by dissolving it in an acidic media in such a way the interlayer biomolecules can be recovered or the intercalated biomolecules can be released from the LDH via ion-exchange reaction in electrolyte. It is, therefore, concluded that the inorganic LDH can play a role as a gene reservoir or carrier for various unstable organic or bio-molecules such as drugs and genes. (C) 2002 Elsevier Science B.V. All rights reserved.