| Inorganic layered compounds can accommodate a great diversity of guest molecules (including organic, inorganic and organometallic compounds) due to their ionic exchange capacity and the expandability of their interlayer spaces while maintaining other structural features unalterable. The design of layered nanocomposites by the intercalation techniques is based on the interconnection and compatibility between the chemical, optical, electrical and magnetic properties of the guest molecule with the structural, mechanical and thermal stability of the host material, which has been considered as one of the most promising methods for the fabrication of nanocomposites. Layered nanocomposites offered novel material systems for the design of optoelectronic nanodevices, chemical sensors and biosensors, with potential applications in the fields of molecular recognition and catalysis.In this dissertation, the cationic inorganic layered compounds (niobate, titanate, titanoniobate and a-zirconium phosphate) were chosen as host materials. By using water-soluble metalloporphyrins, conducting polymers and pigments as guest molecules, several novel layered nanocomposites have been successfully prepared. The sturcture, morphology and properties of the obtained nanocomposites have been characterized by XRD, IR, elemental analysis, UV-vis, et al. Furthermore, the applications of these nanocomposites in the fields of electrocatalysis, chemical catalysis, luminescence and photocatalysis have been investigated.The water-soluble metalloporphyrins cations MtTMPyP (Mt=Mn, Fe, Co) have been successfully inserted into the interlayer spacing of layered semiconductor compounds (K4Nb6O17, K2TiO9and KTiNbO5). Based on XRD analysis and the molecular dimension of metalloporphyrins, it has been speculated that the guest molecules are closely packed with the monolayer tilted against the host nanosheets. By simple dip-coating, the layered nanocomposited modified glassy carbon electrodes were prepared. The cyclic voltammetry tests revealed that the modified electrodes exhibit good electrochemical activity and can effectively electrocatalyze oxygen reduction in neutral buffer solution.The catalytic performance of the as-prepared metalloporphyrins intercalated nanocomposites for the epoxidation of cyclohexene was studied. Although in heterogeneous systems the conversion rate of substrate was lower than that of homogeneous systems, the selectivity is obviously higher. The oxidation can proceed selectively by means of the unique two dimensional reaction field provided by the host layers. Among the nine layered nanocomposites, MnTMPyP-Nb6O17and CoTMPyP-Nb6O17exhibited the best catalytic performance. And both catalysts showed no appreciable decrease in activity after several reaction cycles.Polyaniline intercalated titanoniobate (PANI-TiNbO5) and polypyrrole intercalated niobate (PPy-Nb6O17) nanocomposite have been successfully prepared by in-situ polymerization method. Accordingly to the XRD results, the arrangement of monomers in the interlayer spacing as well as the polymerization mechanism has been proposed. In HCl solution, the cyclic voltammetry curves of PANI-TiNbO5modified electrode showed two pairs of redox peaks, corresponding to the conversion of Leucoemeraldine state to Emeraldine salt and Emeraldine salt to Pernigraniline state, respectively. In LiClO4aqueous solution, the CV curves of PANI-TiNbO5modified electrode showed one reversible redox wave, corresponding to [PPy+,ClO4-]/PPy couples. In the preparation process of polyaniline/α-zirconium phosphate composite, monomer was inserted between the nanosheets, while the polyerization occurred in the outer space.Rhodamine6G (R6G), a well-known fluorescent dye, has been intercalated into layered potassium titanoniobate through a guest-guest exchange method. It is postulated here that R6G forms monolayer coverage with its long molecular axis being oriented perpendicular with respect to titanoniobate nanosheets. TG-DSC analysis revealed that in comparison with pure dye, the intercalation of dye molecules in solid inorganic host material enhances thermostability of the dye. We are delight to find that R6G cations in thin film are highly fluorescent even at a high dye concentration (34.8wt%).Finally, Fe2O3pillared titanate nanocomposite was fabricated. The photocatalytic degradation performance of the nanocomposite toward methyl orange was studied. It was found that the photocatalytic activity of the nanocomposite was higher than the single host and guest material. The intercalation assembly structure may favor the electron transfer between the host and the guest and increase the lifetime of transient electrons. And the enhanced photocatalytic acvitiy may also be related to the new energy match formed between the host and guest. |
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