Morphosynthesis Of Inorganic Materials Assisted By Organic Additives

Biological systems are able to generate crystalline materials with complex morphologies and specific functions via the processes of biomineralization and these processes are elaborately controlled by some biomacromolecules. Controlled synthesis of inorganic and inorganic/organic hybrid materials of specific morphology, orientation, organization, complex form, and hierarchical structure has drawn a lot of attention in materials science. The strategy of using organic templates or modifiers with complex functionalization patterns to control the nucleation, growth, and alignment of crystals has been widely adapted for the biomimetic synthesis of a variety of inorganic materials with complex forms. This dissertation focuses on the morphosynthesis of some inorganic materials assisted by organic additives, and contains seven parts.In the first two parts, controlled synthesis of CaCO₃ and PbS was studied in a mixed systems of poly-(styrene-alt- maleic acid) (PSMA) and cetyltrimethylammonium bromide (CTAB), and the results showed that the mixed PSMA-CTAB system was a very effective crystal growth modifiers to direct the growth of CaCO₃ and PbS crystals to various morphologies. The concentrations of PSMA and CTAB in the mixed system exerted great influence on the crystal growth of CaCO₃ and PbS. Peanut-like CaCO₃ and star-like PbS crystals were synthesized, and the formation mechanism was related to the selective interaction between the organic-inorganic interfaces, which resulted in preferential growth along some specific crystallographic directions. Moreover, we successfully prepared micrometer sized CaCO₃ hollow spheres in the mixed PSMA-CTAB system, and the formation of hollow structured CaCO₃ was ascribed to the templating of polymer-surfactant mixed micelle.In the third part, crystallization of PbS was studied in another polymer-surfactant mixed system: poly(methacrylic acid)-cetyltrimethylammonium bromide (PMAA-CTAB). We found that the presence of a single organic additive, i.e. PMAA or CTAB, could alter the crystal habit of PbS. Moreover, the PMAA-CTAB mixed system could induce self-assembly of PbS nanocrystals to spherical and coral-like aggregates by virtue of the interaction between the adsorbed PMAA and CTAB on different crystalline building blocks.The hydrothermal synthesis of PbWO4 crystals in the presence of PMAA was studied in the forth part. The concentration of PMAA, [pb²⁺]/[WO₄^2-] molar ratio (R), pH value, and ageing temperature exhibited great effect on the crystal morphology of PbWO₄. Novel needle-like PbWO₄ single crystals of micrometer size were prepared. The length and photoluminescence intensity of PbWO₄ microneedles increased with raising ageing temperature. A nonclassical crystallization mechanism was proposed to elucidate the formation of needle-like structure of PbWO4 and the related experimental results.In the fifth part, we demonstrated the morphosynthesis of pitted or patterned copper oxalate polycrystalline tablets by a precipitation reaction between copper sulfate and oxalic acid solutions. The formation of the pit or pattern on the surfaces of the tablets could be due to the etching or partial dissolution at the central region of the tablets during ageing. Because the etching of copper oxalate depends on the coexisted poly(ethylene glycol) (PEG), acidity of the reaction mixture and ageing temperature, the morphology of copper oxalate could be facilely tailored by regulating these experimental parameters.In the sixth part, we presented a facile route to hollow structured metal tungstate and molybdate particles via precipitation reactions at the ambient temperature in the presence of PMAA. A "polymer-M in situ template" reaction model was established to elucidate the formation of these hollow structures. Moreover, hollow structured WO₃ was achieved using the hollow structured SrWO₄ or BaWO4 particles as the precursors, which were treated by nitric acid and calcinations sequentially. In the procedure, BaWO₄ or SrWO₄ was turned to WO₃, whereas the original hollow structures of the precursors were perfectly maintained.In the last part, micrometer and submicrometer sized monodispersed particles of polycrystalline BaSO₄ were produced by a simple precipitation reaction in the presence of PMAA at the ambient temperature. The "polymer-M in situ template" model was also available in explanation of formation process of such polycrystalline BaSO₄ particles.